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Calcium aluminate (CaAl 4 O 7 or CA2) prepared by a surfactant assisted (PEG-PPG-PEG, MW:5800) co-precipitation method were employed as catalyst support for potassium modified (1–3% wt.%) 7 wt% nickel catalysts in reforming of methane with carbon dioxide. The X-ray diffraction (XRD), nitrogen adsorption analysis, H 2 chemisorption, temperature programmed reduction (TPR) and oxidation (TPO) and scanning electron microscopy (SEM) techniques were used to charactrize the fresh and spent catalysts. The catalytic activity results revealed relatively high conversions (CH 4 and CO 2) and stability for all the K 2 O modified catalysts. About 2–6% decrease of CH 4 conversion was observed after promotion of 7%Ni/CA2 with K 2 O. The decrease was attributed to increase in Ni particle size or decrease in Ni dispersity, which caused reduction of available active site for the DRM reaction. Among the promoted catalysts 7%Ni–1%K 2 O catalyst with 62% CH 4 conversion at 700 °C showed highest catalytic activity. K 2 O promoter increased CO 2 affinity, coke resistance and CO 2 coke gasification rates of catalysts. After 5 h on stream the TPO analysis of spent catalysts revealed lower carbon deposition with increase of K 2 O loading from 1 to 3%. 7%Ni–3% K 2 O showed 45 % decrease in carbon deposition compared to unmodified catalyst. TPO analysis detected atomic, fibrous and graphitic carbon deposition over spent catalysts, with filamentous type as the major type. SEM results only detected fibrous carbon for modified and unmodified spent catalysts. • Ni–K 2 O/CaAl 4 O 7 catalysts with different K 2 O amount were introduced for DRM. • The coke deposition decreased with addition of K 2 O promoter to Ni/CaAl 4 O 7. • 7%Ni–1%K 2 O revealed highest catalytic activity among the promoted catalysts. • 7%Ni–3%K 2 O showed lowest carbon deposition. • Promoted catalysts performed great stability after 5 h on stream. [ABSTRACT FROM AUTHOR]

In the present study, an easily-prepared binary metal supported on a magnetic nanocomposite of graphene oxide was synthesized with a particular focus on the sequence of metal introduction. Specifically, the Co/Ni/Fe 3 O 4 @GO, Ni/Co/Fe 3 O 4 @GO, and CoNi/Fe 3 O 4 @GO samples were synthesized, and subjected to a comprehensive characterization. Following the incorporation of nickel into the cobalt-based catalyst, the surface areas of the samples and the dispersion of the particles were notably enhanced. The positive effect of nickel introduction was found to be more pronounced in the CoNi/Fe 3 O 4 @GO nanocatalyst, which was synthesized via the simultaneous impregnation-reduction of cobalt and nickel nanoparticles. The prepared catalysts were found to be efficient catalysts in the sodium borohydride hydrolysis/methanolysis/ethanolysis process. Notably, the results revealed that the CoNi/Fe 3 O 4 @GO exhibited superior performance in the methanolysis reaction compared to the other catalysts. Impressively, this catalyst yielded a high hydrogen generation rate of 8200 mL/min.g cat. A thorough kinetic analysis of the catalyzed methanolysis reaction revealed a remarkably low activation energy of 21.45 kJ/mol. Furthermore, a thermodynamic study yielded an activation entropy (ΔS) of −97.75 J/K, which is indicative of a Langmuir-Hinshelwood-type mechanism for the methanolysis of sodium borohydride. [Display omitted] • Successful synthesis of CoNi/Fe 3 O 4 @GO was acheived by the impregnation-reduction method. • The simultaneous synthesis of CoNi/Fe 3 O 4 @GO displayed the best performance. • Addition of nickel nanoparticles in the Co/Fe 3 O 4 @GO structure improved the catalyst activity. • Low E a of 21.45 kJ/mol and high H 2 generation rate of 8200 mL/min.g cat were achieved. [ABSTRACT FROM AUTHOR]

The process of hydrolysis of sodium borohydride is a new and clean method for the production of hydrogen. In this study, cobalt nanoparticles were synthesized by the mechanochemical and chemical reduction methods, and their catalytic performance was compared. The effect of using different cobalt precursors and reducing agents was investigated for the sample prepared via the chemical reduction method. The results showed that the cobalt catalysts synthesized through the chemical reduction method possessed better catalytic performance. Also, the sample prepared using cobalt nitrate and sodium borohydride had a higher hydrogen generation rate (HGR), which was equal to 3272.7 ml min−1g−1. The kinetics of the cobalt catalyst in the process have also been investigated, revealing that the rate of hydrogen production is dependent on the concentrations of sodium borohydride and sodium hydroxide, the catalyst dosage, and the process temperature. The crystal size of this catalyst was 21.6 nm with spherical agglomerated particles. The BET area of the best sample and its activation energy was equal to 11.18 m2g-1 and 22.3 kJmol-1, respectively. This catalyst was also stable in successive cycles. [Display omitted] • Cobalt catalysts were synthesized via the mechanochemical and chemical reduction methods. • The catalytic performance of the cobalt catalyst in the hydrolysis of NaBH 4 was high. • The hydrogen generation rate of the Co–B catalyst was 3272.7 mLmin−1g−1 at 30 °C. • The activation energy of the Co–B catalyst is lower compared to that of other cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

Underground hydrogen storage (UHS) plays a critical role in ensuring the stability and security of the future clean energy supply. However, the efficiency and reliability of UHS technology depend heavily on the careful and criteria-driven selection of suitable storage sites. This study presents a hybrid multi-criteria decision-making framework integrating the Analytical Hierarchy Process (AHP) and Preference Ranking Organisation Method for Enrichment of Evaluations (PROMETHEE) to identify and select the best hydrogen storage sites among depleted gas reservoirs in the UK. To achieve this, a new set of site selection criteria is proposed in light of the technical and economic aspects of UHS, including location, reservoir rock quality and tectonic characteristics, maximum achievable hydrogen well deliverability rate, working gas capacity, cushion gas volume requirement, distance to future potential hydrogen clusters, and access to intermittent renewable energy sources (RESs). The framework is implemented to rank 71 reservoirs based on their potential and suitability for UHS. Firstly, the reservoirs are thoroughly evaluated for each proposed criterion and then the AHP-PROMETHEE technique is employed to prioritise the criteria and rank the storage sites. The study reveals that the total calculated working gas capacity based on single-well plateau withdrawal rates is around 881 TWh across all evaluated reservoirs. The maximum well deliverability rates for hydrogen withdrawal are found to vary considerably among the sites; however, 22 % are estimated to have deliverability rates exceeding 100 sm3/d, and 63 % are located within a distance of 100 km from a major hydrogen cluster. Moreover, 70 % have access to nearby RESs developments, with an estimated cumulative RESs capacity of approximately 181 GW. The results highlight the efficacy of the proposed multi-criteria site selection framework. The top five highest-ranked sites for UHS based on the evaluated criteria are the Cygnus, Hamilton, Saltfleetby, Corvette, and Hatfield Moors gas fields. The insights provided by this study can contribute to informed decision-making, sustainable development, and the overall progress of future UHS projects within the UK and globally. [Display omitted] • A novel multi-criteria site selection framework is proposed for UHS in gas fields. • Eight selection criteria are proposed to capture the most essential UHS technical and economic aspects. • The model integrates the AHP and PROMETHEE methods for decision-making. • 71 gas reservoirs in the UK are ranked based on their suitability for conversion to UHS assets. [ABSTRACT FROM AUTHOR]

The preparation of catalysts with adequate stability for the n -hexane hydroisomerization reaction is always a challenge in refineries. Therefore, in this work, the metal-organic framework UiO-66, heteropoly phosphomolybdic acid (HPMo), and bifunctional (Pd + Pt)/HPMo/UiO-66 samples were synthesized, characterized by experimental techniques, and tested in the n-hexane hydroisomerization reaction. As a result, the microporous (0.2%Pd+0.3%Pt)/30%HPMo/UiO-66 bifunctional catalyst exhibited an iso-hexane selectivity of 86% and n -hexane conversion of 72.1% after 36 h of reaction time. In addition, the Langmuir-Hinshelwood model was used to examine the kinetics of this reaction due to the inhibitory effect of hydrogen. The results provided an acceptable fit to the experimental data and allowed the determination of the kinetic parameters. Accordingly, the apparent activation energy of this bifunctional catalyst and the adsorption heats of hydrogen and n -hexane were calculated at 26.27, −16.12, and −7.82 kJ mol−1, respectively. [Display omitted] • Hydroisomerization of n-hexane was performed over (Pd + Pt)/HPMo/UiO-66 sample. • Bifunctional catalyst (0.2%Pd+0.3%Pt)/30%HPMo/UiO-66 exhibited 75% nC 6 conversion. • The highest iC 6 selectivity was achieved at 90.1%. • Kinetic study was carried out using the Langmuir-Hinshelwood model. • The apparent activation energy was obtained at 26.27 kJ mol−1. [ABSTRACT FROM AUTHOR]

This study conducted the CO 2 methanation reaction over the nickel-based catalysts supported on CaO.Al 2 O 3 with different CaO/Al 2 O 3 molar ratios. The catalyst support was synthesized with the mechanochemical method, and the influence of nickel loading was investigated on the selected catalyst support with an appropriate CaO/Al 2 O 3 molar ratio. According to the results, incorporating Al 2 O 3 into the CaO increased the BET area from 5 to 196 m2 g−1. Also, the S BET of the calcined catalysts decreased with the augmentation of nickel oxide percentage from 5 to 15 wt% due to the pore blocking of the support after metal addition. Moreover, the activity of catalysts enhanced with the increment of CaO/Al 2 O 3 molar ratio and NiO percentage, ascribed to the improvement in the reducibility of the catalysts. However, the excessive addition of CaO and nickel oxide reduced the CO 2 conversion because of a significant decrease in surface area. Therefore, 10 wt% NiO/CaO.2Al 2 O 3 catalyst possessed superior CO 2 conversion (79.1%) and CH 4 selectivity (98.1%) in CO 2 methanation reaction at 450 °C, H 2 /CO 2 = 4 and GHSV = 18,000 ml h−1.g−1 cat. The selected sample illustrated great stability for 11 h without any remarkable change in its initial catalytic activity. The impact of GHSV on the catalytic performance of the selected catalyst was evaluated, and the outcomes exhibited that decrement in GHSV value enhanced CO 2 conversion. With the increment of feed ratio (H 2 /CO 2) from 2 to 5, CO 2 conversion reached 93.3%, ascribed to the existence of adequate hydrogen to react with CO 2. [Display omitted] • The CaO–Al 2 O 3 supports were synthesized by the mechanochemical method. • Effect of CaO:Al 2 O 3 with different molar ratios was evaluated in the CO 2 methanation process. • Various nickel loadings were investigated over the selected CaO–Al 2 O 3 powder. • 10 wt% NiO/CaO.2Al 2 O 3 showed the highest CO 2 conversion and CH 4 selectivity in this process. [ABSTRACT FROM AUTHOR]

In this study, cobalt nanocatalysts supported on the Fe 3 O 4 @GO were synthesized for boosting hydrogen generation upon hydrolysis of sodium borohydride. Co/Fe 3 O 4 @GO catalysts were synthesized through a facile co-precipitation method followed by a chemical reduction step. The prepared samples were characterized using various techniques including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM), Vibrating sample magnetometer (VSM), and Nitrogen adsorption–desorption (BET). Benefiting from the high crystallinity, good dispersion of Co nanoparticles over the Fe 3 O 4 @GO, and the synergistic effect between Co nanoparticles and Fe 3 O 4 @GO support, Co/Fe 3 O 4 @GO catalysts with 30 wt% cobalt loading showed the highest catalytic activity with high hydrogen generation rate of 4000 mL/min.g cat and relatively good stability. To investigate the effect of the parameters on hydrogen generation rate and optimal reaction conditions, the Box-Behnken design under response surface methodology (RSM) was applied. ANOVA results denoted that the temperature with the highest F-value and lowest P-value had the most effect on the hydrogen generation rate. Under the optimum conditions including a temperature of 39.83 °C, 17.74 mg of catalyst, and 5.135 wt% NaBH 4 concentration, Co(30%)/Fe 3 O 4 @GO exhibited a superior H 2 generation rate of 6005 mL/min.g cat and low activation energy of 44.4 kJ/mol. Therefore, the Co/Fe 3 O 4 @GO is a promising catalyst for NaBH 4 hydrolysis due to its easy preparation and separation method, high hydrogen generation rate, and low activation energy. [Display omitted] • Fe 3 O 4 /GO was synthesized as a support to promote the Co-based catalyst activity and reusability. • The highest performance was obtained over a catalyst containing 30 wt% of Co nanoparticles. • Response surface methodology (RSM) was carried out to optimize the hydrogen-generation rate reaction conditions. • Over the Co(30%)/Fe 3 O 4 @GO, the activation energy was calculated to be as low as 44.4 kJ/mol. • The maximum hydrogen generation rate (HGR) obtained at optimun condition was 6005 mL/min.g cat. [ABSTRACT FROM AUTHOR]

Grid-scale underground hydrogen storage (UHS) is essential for the decarbonization of energy supply systems on the path towards a zero-emissions future. This study presents the feasibility of UHS in an actual saline aquifer with a typical dome-shaped anticline structure to balance the potential seasonal mismatches between energy supply and demand in the UK domestic heating sector. As a main requirement for UHS in saline aquifers, we investigate the role of well configuration design in enhancing storage performance in the selected site via numerical simulation. The results demonstrate that the efficiency of cyclic hydrogen recovery can reach around 70% in the short term without the need for upfront cushion gas injection. Storage capacity and deliverability increase in successive storage cycles for all scenarios, with the co-production of water from the aquifer having a minimal impact on the efficiency of hydrogen recovery. Storage capacity and deliverability also increase when additional wells are added to the storage site; however, the distance between wells can strongly influence this effect. For optimum well spacing in a multi-well storage scenario within a dome-shaped anticline structure, it is essential to attain an efficient balance between well pressure interference effects at short well distances and the gas uprising phenomenon at large distances. Overall, the findings obtained and the approach described can provide effective technical guidelines pertaining to the design and optimization of hydrogen storage operations in deep saline aquifers. [Display omitted] • Cyclic storage performance is found by injection at the highest achievable rates. • The storage capacity, deliverability, and recovery efficiency increase cycle-wise. • Co-production of water during hydrogen withdrawal from the aquifer is marginal. • Pressure interference and gas up-rising emerge as main challenges in well planning. • The need for using additional wells can be avoided by optimizing the well distance. [ABSTRACT FROM AUTHOR]

CH 3 OH steam reforming is an attractive way to produce hydrogen with high efficiency. In this study, CuO.xAl 2 O 3 (x = 1, 2, 3, and 4) were fabricated based on the solid-state route, and the calcined samples were employed in methanol steam reforming at atmospheric pressure and in the temperature range of 200–450 °C. The results revealed that all samples have a high BET area (173–275 m2 g−1), and their crystallinity was reduced by increasing the alumina content in the catalyst formulation. The catalytic activity tests showed that the CH 3 OH conversion and H 2 selectivity decreased by rising the Al 2 O 3 ·CuO molar ratio. The methanol conversion enhanced from 13% to 85% by increasing the reaction temperature from 200 °C to 450 °C over the CuO·Al 2 O 3 catalyst, due to the higher reducibility of this catalyst at lower temperatures compared to other prepared samples. The influence of calcination temperature (300–500 °C), GHSV (28,000–48000 ml h−1. g−1 cat), feed ratio (C:W = 1:1 to 1:9), and reduction temperature (250–450 °C) was also determined on the yield of the chosen sample. The results revealed that the maximum methanol conversion decreased from 90 to 79% by raising the calcination temperature from 300 to 500 °C due to the reduction of surface area and sintering of species at high calcination temperatures. [Display omitted] • The CuO–Al 2 O 3 catalysts were synthesized by the mechanochemical method. • Various molar ratios of CuO:Al 2 O 3 were used in methanol steam reforming. • The CuO–Al 2 O 3 (CuO:Al 2 O 3 = 1:1) possessed the best performance in this process. • The influence of calcination temperature and processing conditions were studied on the catalyst efficiency. • The high reducibility degree of the sample with an equimolar ratio of particles is the main reason for its better activity. [ABSTRACT FROM AUTHOR]

This study examines the sensitivity of the levelised cost of hydrogen (LCOH), produced from solar photovoltaic (PV) electricity, to four factors that strongly influence the economics of green hydrogen: electrolyser efficiency, PV capacity factor, nominal interest rate and inflation rate. The authors' aim was not to calculate an absolute value for the LCOH, which varies according to location and economic circumstances, but to examine its sensitivity to these critical parameters of the economic model. This approach facilitates comparisons between potential solar hydrogen projects to select the location with the lowest LCOH. Direct coupling of a PV power plant to proton exchange membrane (PEM) electrolysis, without storage, was assumed, along with a base-case scenario with nominal interest rate 7%, inflation rate 2%, electrolyser efficiency 75% and PV capacity factor 22%. To account for the rapidly evolving electrolyser market, a learning-rate model was employed to estimate for the cost of routine end-of-life replacement of the electrolyser. Finally, the effect of grid-assisted operation on the LCOH was considered. The results demonstrated clearly the importance of careful site selection to achieve high PV capacity factor, which was more influential than foreseeable increases in electrolyser efficiency. Moreover, examination of the mutual sensitivities between the four critical parameters showed that high capacity factor is a good hedge against high inflation rates. • Sensitivity of levelised cost of hydrogen to influential factors examined, singly and in pairs. • PV capacity factor, electrolyser efficiency, interest rate and inflation rate considered. • Learning rate model applied to electrolyser replacement cost. • High PV capacity factor is more beneficial than increased electrolyser efficiency. • High PV capacity factor is a good hedge against high inflation rates. [ABSTRACT FROM AUTHOR]

In this research, inexpensive transition metals are used for electrocatalytic oxygen evolution reactions. Nickel foam was modified as a substrate using spindle-like Co–Fe LDH. XRD, FE-SEM, EDS, and elemental mapping techniques are used for characterization. Based on LSV results, overpotentials of 280 and 355 mV were obtained at 10 and 100 mA cm−2, respectively. To evaluate the stability of electrocatalyst, cyclic voltammetry, chronoamperometry (at constant potentials of 1.55 and 1.65 V vs. RHE), and chronopotentiometry (at applied current densities of 10 and 100 mA cm−2) methods are used. All stability tests were performed consecutively using one electrode. Current density increased by 0.05% after performing 500 CV cycles. The catalytic performance was enhanced during the chronoamperometry analysis. However, the potential decreased slightly by less than 0.44% after 7200 s at 100 mA cm−2 in chronopotentiometry analysis. The high durability and current density ensure the efficient performance of the as-prepared electrocatalyst in water splitting process. [Display omitted] • Co–Fe LDH nanosheets were synthesized via a one-pot self-templating method. • The designed Co–Fe LDH/NF electrode exhibits excellent catalytic performance. • Co–Fe LDH shows an overpotential of 280 mV at 10 mA cm−2 for water oxidation. • MIL-88 was used as a framework and precursor in Co–Fe LDH synthesis procedure. • The Co–Fe LDH electrode keeps its initial catalytic property after 500 CV cycles. [ABSTRACT FROM AUTHOR]

In this work, hydrate based separation technique was combined with membrane separation and amine-absorption separation technologies to design hybrid processes for separation of CO 2 /H 2 mixture. Hybrid processes are designed in the presence of different types of hydrate promoters. The conceptual processes have been developed using Aspen HYSYS. Proposed processes were simulated at different flow rates for the feed stream. A comprehensive cost model was developed for economic analysis of novel processes proposed in this study. Based on the results from process simulation and equipment sizing, the amount of total energy consumption, fixed cost, variable cost, and total cost were calculated per unit weight of captured CO 2 for various flow rates of feed stream and in the presence of different hydrate promoters. Results showed that combination of hydrate formation separation technique with membrane separation technology results in a CO 2 capture process with lowest energy consumption and total cost per unit weight of captured CO 2. As split fraction and heat of hydrate formation increases, the share of hydrate formation section in total energy consumption increases. When TBAB is applied as hydrate promoter, due to its higher hydrate separation efficiency, more amount of CO 2 is captured in hydrate formation section and consequently the total cost for process decreases considerably. Hybrid hydrate-membrane process in the presence of TBAB as hydrate promoter with 29.47 US$/ton CO 2 total cost is the best scheme for hybrid hydrate CO 2 capture process. Total cost for this process is lower than total cost for single MDEA-based absorption process as the mature technology for CO 2 capture. • Hydrate-based separation was combined with membrane and chemical absorption technologies to purify CO 2 /H 2 mixture. • The processes were designed and simulated in the presence of different hydrate promoters. • Techno-economic study was performed to estimate energy consumption, operating cost, and fixed cost of proposed processes. • Hybrid hydrate-membrane process in the presence of TBAB has the lowest total cost as 29.47 US$/ton CO 2. [ABSTRACT FROM AUTHOR]

Bubble reactors using molten metal alloys (e.g, nickel-bismuth and copper-bismuth) with strong catalytic activity for methane decomposition are an emerging technology to lower the carbon intensity of hydrogen production. Methane decomposition occurs non-catalytically inside the bubbles and catalytically at the gas-liquid interface. The reactor performance is therefore affected by the hydrodynamics of bubble flow in molten metal, which determines the evolution of the bubble size distribution and of the gas holdup along the reactor height. A reactor model is first developed to rigorously account for the coupling of hydrodynamics with catalytic and non-catalytic reaction kinetics. The model is then validated with previously reported experimental data on methane decomposition at several temperatures in bubble columns containing a molten nickel-bismuth alloy. Next, the model is applied to optimize the design of multitubular catalytic bubble reactors at industrial scales. This involves minimizing the total liquid metal volume for various tube diameters, melt temperatures, and percent methane conversions at a specified hydrogen production rate. For example, an optimized reactor consisting of 891 tubes, each measuring 0.10 m in diameter and 2.11 m in height, filled with molten Ni 0·27 Bi 0.73 at 1050 °C and fed with pure methane at 17.8 bar, may produce 10,000 Nm3.h−1 of hydrogen with a methane conversion of 80% and a pressure drop of 1.6 bar. The tubes could be heated in a fired heater by burning either a fraction of the produced hydrogen, which would prevent CO 2 generation, or other less expensive fuels. [Display omitted] • Faster superficial gas velocity increases gas-liquid interfacial area and gas holdup. • Larger diameter tubes lower the total melt volume in multitubular reactor designs. • Liquid metal volume increases faster than exponentially with decreasing temperature. • 14.8 m3 of Ni 0·27 Bi 0.73 melt at 1050 °C produces 10,000 Nm3.h−1 of H 2 at 80% CH 4 conversion. • Molten Cu–Bi alloy results in smaller reactors (shorter tubes) than Ni–Bi alloy. [ABSTRACT FROM AUTHOR]

This study seeks to enhance the site selection procedure for decision-makers to select the most effective wind-powered hydrogen refueling station via the aid of Fuzzy Multi-criteria Decision-making (FMCDM) approaches. To accomplish the purpose of the study, technical, economic, environmental, geographical, and social aspects constitute the influential criteria for prioritizing the eight aptest cities of Iran. Then, the Fuzzy Multi-criteria Optimization and Compromise Solution (FVIKOR) is employed to ascertain which alternative should be chosen as the most efficient one with respect to the criteria. In addition to several non-fuzzy MCDM techniques, the Fuzzy Technique for Order of Preference by Similarity to Ideal Solution (FTOPSIS) and a novel integrated method are applied for validation. Moreover, an FMCDM approach coupling FTOPSIS and FVIKOR has been introduced for the prioritization of different alternatives while many conflicting criteria exist. The simulation results of fuzzy and non-fuzzy approaches suggest that Manjil is the best option for the purpose of study. The numerical findings also imply utilizing a 100-kW turbine in Manjil generates 548,376 kWh of electricity, resulting in the prevention of 109,675 kg of CO 2 emissions and in the production of 8876 kg of hydrogen annually. • Enhancing the wind powered H 2 station selection procedure. • Utilization of MCDM approaches with 10 conflicting criteria. • Benchmarking the integrated method of FVIKOR-based FTOPSIS. • Sensitivity analysis of the nominated criteria. [ABSTRACT FROM AUTHOR]

Glycerol is the main by-product in the biodiesel process and can be considered as a promising and renewable source for hydrogen generation through the reforming process. In this work, catalysts with 15 wt% Ni supported on 3 wt% M − Al 2 O 3 (M = MgO, CaO, SrO, and BaO) were prepared and employed in the glycerol dry reforming (GDR) reaction to produce hydrogen and carbon monoxide. The textural characteristics of the fresh and spent catalysts were determined using the ICP, BET, TPR, TPO, and SEM analyses. Based on the obtained results, the catalyst promoted by SrO had the highest catalytic activity. The results indicated that adding various alkaline-earth oxides into the catalyst support decreased the Ni crystalline size from 17.2 nm to 7.4–10.9 nm. Moreover, all promoted catalysts showed better catalytic performance and the promoted sample with 3 wt% SrO possessed higher stability than unpromoted catalyst during 20 h on stream. • 15 wt%. Ni catalysts supported on 3 wt%MO-Al 2 O 3 (M = Mg, Ca, Sr, and Ba) were prepared. • The catalysts were employed in glycerol dry (CO 2) reforming. • The crystallite sizes of the catalysts were in the range of 7.4–10.9 nm. • 15 wt%Ni/3 wt%SrO–Al 2 O 3 catalyst had the highest performance in glycerol dry reforming. • The addition of promoters resulted in a lower amount of deposited carbon. [ABSTRACT FROM AUTHOR]

Dry reforming of glycerol is an interesting method for syngas production due to its H 2 /CO ≈ 1 that is suitable for FT synthesis. In this study, the performance of the Ni/MgO.Al 2 O 3 catalysts with different nickel contents was investigated in glycerol dry reforming. The MgO.Al 2 O 3 carrier was prepared by a simple sol-gel method and the nickel-based catalysts were synthesized by the wet impregnation method. The prepared catalysts possessed high BET surface area and pore volume. The TPR analysis showed a strong interaction between Ni and the catalyst support. The results demonstrated that the glycerol conversion decreased by increasing in CO 2 /glycerol (GRR) molar ratio. All the prepared samples showed high stability in glycerol dry reforming during 25 h of reaction, indicating the high resistance of the catalysts against carbon formation. Also, 10 wt%Ni/MgO.Al 2 O 3 catalysts possessed the highest catalytic performance (52% of glycerol conversion at 750 °C) due to the high dispersion of nickel on the prepared carrier. • Dry reforming of glycerol was investigated over Ni/MgO.Al 2 O 3 catalysts. • The catalyst support was prepared by a simple sol-gel method. • The catalyst support possessed a high BET surface area. • The prepared catalysts exhibited high stability in glycerol dry reforming reaction. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the economic prospects of producing electricity and hydrogen using wind energy under different scenarios. For this, the most essential criteria to investors including Levelized Cost of Wind-generated Electricity (LCOWE), Levelized Cost of Wind-based Hydrogen (LCOWH), payback period, and rate of return are examined. Technical and environmental impacts are factored into the LCOWE formulation to obtain comprehensive insight. Owing to the uncertain nature of future, five degradation rates concerned with wind turbine performance and five likely rates as to the future value of money are investigated under the scenarios of I) utilizing wind electricity to replace fuel oil electricity, II) to replace natural gas electricity and III) without considering environmental penalties. The results indicate that LCOWE would be in the range of 0.0325–0.0755 $/kWh, while the corresponding LCOWH being in the range of 1.375–1.59 $/kg. Moreover, payback period of the related LCOWE and LCOWH would be in the range of 2.55–9.48 yr during the lifetime of wind power plant and 3.91–8.41 yr during that of hydrogen production system, respectively. The corresponding rate of return pertinent to the above-mentioned ones would be respectively in the range of 14.15–23.54% and of 9.87–21.55%. • Wind-based electricity and hydrogen generation in the city of Lutak is investigated. • Scenarios of replacement for fuel oil electricity and natural gas electricity are examined. • LCOWE for different scenarios would be in the range of 32.5–75.5 $/MWh. • LCOWH for different scenarios would vary from 1.375 to 1.59 $/kg. [ABSTRACT FROM AUTHOR]

This study focuses on the utilization of activated carbon (AC) as a catalyst support after undergoing treatment with HNO 3. The treated AC exhibited a microporous structure and a high specific surface area (S BET) of 1483.8 m2 g−1. In this study, supported nickel-based catalysts were synthesized using the wet impregnation method with varying amounts of NiO (2.5, 5, 7.5, 10, 12.5, and 15 wt%). The calcined catalyst samples were then evaluated for their performance in the dry reforming of methane (DRM). Characterization of the catalysts was conducted through FESEM, TPO, H 2 -TPR, XRD, and N 2 adsorption-desorption (BET) analyses. The results revealed that catalytic efficiency increased with an increase in the nickel loading percentage, up to 12.5 wt%. The NiO (12.5)/AC catalyst demonstrated the highest CH 4 (60%) and CO 2 (68%) conversions and exhibited good stability at 700 °C during 10 h of reaction. Additionally, the catalyst's efficiency decreased with an increase in the calcination temperature from 400 to 600 °C. However, alterations in the CH 4 /CO 2 molar ratio from 0.5 to 1.5 indicated that CH 4 and CO 2 conversions decreased from 85% to 40% and increased from 63% to 74% at 700 °C, respectively. Moreover, the findings demonstrated that elevating the gas hourly space velocity (GHSV) from 12,000 to 18,000 ml h−1.g−1 cat resulted in a decline in catalytic efficiency at a temperature of 700 °C. Moreover, the catalytic efficiency declined with an increase in the reduction temperature from 500 to 600 °C. [Display omitted] • AC treated with HNO 3 exhibited a high surface area (1483.8 m2/g), making it an ideal catalyst support. • The NiO (12.5)/AC catalyst showed high performance, achieving conversions of CH 4 (60%) and CO 2 (68%) at 700 °C in DRM. • Higher T calcination altered the catalyst's morphology and increased the size of nickel particles. [ABSTRACT FROM AUTHOR]

The identification of site location is one of the critical tasks in developing or expanding any supply chain system including the construction of renewable power generation plants. The accurate identification of a plant site can considerably reduce unforeseen risks and costs and also raise productivity and efficacy. As such, this study sought to thoroughly evaluate all capital cities of a developing country for the establishment of a hybrid wind/solar power plant to produce hydrogen while considering the most influential and conflicting criteria. For this, 14 criteria including daily solar radiation, wind power density, clearness index, altitude, population, average sunny hours in a year, unemployment rate, average air temperature, average air humidity, average yearly precipitation, natural disasters, the distance between the site and the main road, average dusty days per year, and land price constituted the set of vital factors. To prioritize alternatives, a Fuzzy Multi-Criteria Decision Making approach named FVIKOR (Fuzzy Multi-Criteria Optimization and Compromise Solution) was used. The results indicated that among 31 capital cities, the city of Yazd with a wind power density of 309.5 W/m2 and daily solar radiation of 5.4 kWh/m2 would be the best location for the purpose of this study. To validate the findings, FTOPSIS (Fuzzy Technique for Order Preference by Similarity to Ideal Solution) method was utilized and it also ranked Yazd as the first option. Then, a sensitivity analysis was conducted to discern the behavior of each criterion and their impact on the ranking of the cities. Finally, for hydrogen generation, an autonomous hybrid wind/solar system was techno-economically assessed using HOMER software. According to the analysis outcome, the proposed system showed a payback period of 7 years with levelized cost of 4.75 $/kg for hydrogen. • Utilizing Fuzzy VIKOR for accurate location planning of a stand-alone hybrid wind/solar site. • Proposing crucial and conflicting criteria for the process of prioritization. • Validating the results of ranking via FTOPSIS. • Investigating all 31 capital cities of Iran. [ABSTRACT FROM AUTHOR]

The coupled ZnO–NiO nano-composite (NC) was prepared and identified by powder X-ray diffraction (PXRD), scanning electron microscope (SEM), UV–Vis diffuse reflection spectroscopy (DRS) and Fourier transformation infrared spectroscopy (FTIR) characterization techniques. The crystallite sizes of about 6.7, 36.7 and 29.5 nm were obtained for the NiO, ZnO, and ZnO/NiO samples by the Williamson-Hall equation, and about of 33.5, 33.8 and 39.8 nm by the Scherrer equation, respectively. The energy dispersive X-Ray analysis (EDX) showed a NiO:ZnO mole ratio of 3.1 for the composite. The band gap energies of 3.49, 3.19, and 3.02 eV were estimated for the NiO, ZnO, and ZnO–NiO samples by using the absorption edge wavelengths of 355, 388, and 410, respectively. The pHpzc values of 9.3, 8.8, and 7.6 were also estimated for the NiO, ZnO, and ZnO–NiO samples respectively. At initial steps of the work about 42%, 60%, and 87% of a 10 mg/L SZ solution were degraded by the ZnO and NiO NPs and the ZnO–NiO NC, respectively. The best photocatalytic activity was obtained at pH 6.5 (near the pHpzc: 7.6), 0.7 g/L of the catalyst, and 7 mg/L sulfasalazine (SZ). The rate constants of 0.0904 min−1 (t 1/2 = 7.66 min) and 0.0915 min−1 (t 1/2 = 7.57 min) were obtained for the SZ photodegradation and mineralization processes, respectively. The frequency factor of 2.131 × 104 min−1 and the activation energy of 15.87 kJ/mol were obtained for the process by the Arrhenius equation. A negative activation ΔS (−0.22 kJ/mol) with the positive ΔH and ΔG values obtained for the SZ photodegradation by the ZnO–NiO composite. Image 1 • Enhance in bang-gap energy of NiO–ZnO by coupling of semiconductors. • Best photoactivity of the composite at pH 6.5 near to its pH pzc of 7.6. • Increased activity with temperature confirms vital role of collision probability. • Equal rate of SZ-mineralization and photodegradation. • Positive ΔH and ΔG obtained while a less negative ΔS. [ABSTRACT FROM AUTHOR]

Production and storage of hydrogen from biomass component by using efficient catalysts, it can finely maintain the future energy of the world and reduce human dependence on fossil fuels. Hydrogen production mechanism via formic acid decomposition on the TiO 2 anatase (101) and Pt–TiO 2 surfaces in the solvent (water) and gaseous conditions performed by density functional theory (DFT) calculation. Regarding to the proposed routes, decomposition reaction of formic acid on TiO 2 surface incline to be followed by second route in the water which is acceptable in terms of energy. Decomposition reaction of formic acid on Pt–TiO 2 surface prefers to do it via first route (rotation around C O bond of formic acid) in solvent conditions. Furthermore, adsorption energy and geometric changes of formic acid on TiO 2 anatase (101) and Pt–TiO 2 surface in gaseous and solvent conditions were clearly studied. • Decomposition of formic acid on TiO 2 and Pt-doped TiO 2 surfaces was investigated. • The reaction mechanism was studied in both gas phase and solvent phase. • Different modes was considered for formic acid adsorption on TiO 2 surfaces. • Activation energy on TiO 2 surface is lower than Pt-TiO 2 surface. [ABSTRACT FROM AUTHOR]

Industrial-scale implementation of liquid metal bubble reactors (LMBRs) to produce hydrogen by methane decomposition will require large gas holdups (e.g., 20–30 vol%) and elevated gas pressures (>20 bar) to allow for practical reactor sizes. A realistic reactor design must account for the coupling between reaction kinetics and hydrodynamic effects. The gas holdup is predicted from the superficial gas velocity with a drift flux model that was experimentally corroborated in gas-molten metal mixtures. Large superficial gas velocities (>0.40 m s−1) are required to achieve gas holdups of about 25 vol% in liquid metal baths (LMBs). A noncatalytic kinetic model is developed to provide thermodynamically consistent decomposition rates at methane conversions approaching equilibrium. The coupled model optimizes the LMB dimensions (diameter and length) and the inlet pressure to minimize the volume of liquid metal when the hydrogen production rate, bath temperature, methane conversion, metal composition, and maximum gas holdup are specified. For example, 200 kt a−1 of hydrogen can be produced in an LMBR containing at least 96.5 m3 of molten tin held at 1100 °C in a bath measuring 3.50 m in diameter and 14.3 m in length, with an inlet methane pressure of 57.8 bar resulting in an average gas holdup of 29.7 vol% and a methane conversion of 65%. Image 1 • Gas holdups ≈25% in liquid metal baths need superficial gas velocities >0.40 m/s. • Practical industrial reactor size sets minimum liquid metal temperature ≈1100 °C. • Producing 200 kt/a H 2 requires 96.5 m3 molten Sn at 1100 °C at 65% CH 4 conversion. • Higher temperature decreases required liquid metal volume considerably. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of CO 2 to value-added products is one of the useful approaches to reducing the effects of global climate change. Herein, a novel electrocatalyst consisting of platinum nanoparticles on histamine-reduced graphene oxide plates (Pt@His-rGO) supported by a glassy carbon (GC) substrate for the electrochemical conversion of CO 2 to methanol has been developed. The nanocomposite was optimized in terms of pH, applied potential, CO 2 purging time and platinum loading for the highest current densities and faradaic efficiencies toward methanol production. The best results were obtained in a solution containing KNO 3 0.1 mol L−1 at the pH of 2.0, the applied potential of −0.3 V vs Ag/AgCl (KCl sat), CO 2 purging duration of 30 min and Pt loading of 5.17 × 10−7 mol cm−2. The faradaic efficiency of 37% was obtained for methanol production. The prepared nanocomposite requires a lower applied potential and serves as an intermediate stabilizer through the production of methanol. Image 1 • Pt@histamine-reduced graphene oxide is synthesized by oxidative diazonium reaction. • The prepared nanocomposite efficiently reduces CO 2 to methanol. • Histamine stabilizes CO 2 on the electrode surface for the optimized reduction. • A quite low applied potential is required for CO 2 electrolysis. [ABSTRACT FROM AUTHOR]

The Ni/pillared-bentonite catalysts with high BET area were synthesized and used in dry reforming reaction. The effects of different parameters such as calcination temperature, OH−/Al3+ ratio, temperature and time of pillaring process and the content of nickel on the textural and catalytic properties of the synthesized catalysts were studied. The results indicated that the 15 wt% Ni catalyst supported on pillared bentonite prepared under specified conditions (OH−/Al3+ = 2.2, pillaring temperature of 40 °C and pillaring time of 3 h) possessed the highest BET area (90.80 m2/g). Also, this catalyst possessed higher catalytic activity and stability with lower amount of deposited carbon in comparison to other prepared catalysts in methane reforming with CO 2. • The Ni/pillared-bentonite catalysts were synthesized and used in dry reforming reaction. • The effects of OH−/Al3+ ratio, temperature and time of pillaring process were studied. • 15 wt% Ni catalyst supported on pillared bentonite possessed the highest BET area (90.80 m2/g). • 15 wt% Ni catalyst possessed higher activity and stability with low amount of deposited carbon. [ABSTRACT FROM AUTHOR]

Significant attention has been directed towards the direct reduction of iron oxide (DRI) due to its potential for reducing carbon dioxide emissions compared to the blast furnace. The DRI furnace, known as a shaft furnace, operates as a multi-scale reactor with a moving bed and counter-current flow. The mesoscale modeling of iron ore pellets involves deriving the reaction rate equation, while closure is achieved for mass, energy, and Ergun equations at the macro-modeling scale. Despite various studies, the impact of pellet shape and pressure profile on the process has not been explored extensively. In this research, the developed model, based on the unreacted shrinking core model (USCM), employs a non-isothermal, non-isobaric, steady-state, and heterogeneous approach. The investigation considers Leva's shape factor in three scenarios: 100% non-spherical, 20% non-spherical, and 10% non-spherical pellets, revealing their influence on metallization degree (MD). Additionally, pressure variations, increased or decreased by 50 kPa, are examined for the first time, revealing their effects on conversion and temperature profiles in both gas and solid phases. A 50 kPa increase in inlet pressure achieves 100% MD approximately 0.95 m before the reduction zone's end. Moreover, the effects of sponge iron production rate and H 2 /CO on MD are investigated. [Display omitted] • The first shaft furnace model with pellet shape effects is developed. • Enhanced metallization seen with pellet shape deviations is demonstrated. • Pressure's impacts on temperatures, metallization, and gas compositions are illustrated. • Effects of production rate and H 2 /CO ratio on metallization are elaborated. [ABSTRACT FROM AUTHOR]

The study aimed to explore synergies resulting from the combination of dry reforming and partial oxidation of methane, using 10%Ni/Al 2 O 3 –CeO 2 catalysts with varying CeO 2 proportions (10, 30, 50, and 70 wt%). The manufacturing involved mechanochemical and impregnation methods for supports and catalysts, respectively. The inclusion of 10 wt% CeO 2 played a crucial role in enhancing nickel dispersion and reinforcing interaction with the support. Particularly noteworthy was the exceptional performance of the 10%Ni/Al 2 O 3 –10%CeO 2 catalyst, achieving an impressive 83% methane conversion at 700 °C, surpassing other prepared nickel-based catalysts. The introduction of a small quantity of O 2 during methane dry reforming, inferred from TPO and FESEM analyses, effectively mitigated carbon deposition. Demonstrating remarkable endurance, the catalyst 10%Ni/Al 2 O 3 –10%CeO 2 maintained efficacy for 440 min at 700 °C, yielding CH 4 and CO 2 conversion rates of 93% and 34%, respectively. Higher calcination temperatures led to nickel particle aggregation, causing a decline in catalytic efficiency. • Dry reforming and partial oxidation of methane were done on Ni/Al 2 O 3 –CeO 2 catalyst. • The Ni/Al 2 O 3 –10CeO 2 possessed the best efficacy among the investigated samples. • Introducing oxygen during reforming significantly reduced carbon formation. • Higher reduction temperature boosts stability and performance. • Higher T calcination reduces BET area, lowering performance via particle sintering. [ABSTRACT FROM AUTHOR]

In this article mesoporous nanocrystalline 5 wt%M-95 wt%MgAl 2 O 4 (M: CeO 2 , ZrO 2 , La 2 O 3) powders were prepared by a novel on-step sol-gel process and employed as a support for the synthesis of 5 wt%Ni catalysts for synthesis gas production via dry reforming. The magnesium aluminate spinel prepared with this sol-gel method possessed a high BET area of 264 m2 g−1 with a high pore volume of 0.436 cm3 g−1. The results indicated that the addition of promoters (CeO 2 , ZrO 2 , La 2 O 3) to magnesium aluminate improved the BET area and pore volume and also decreased the crystallite size. Among the prepared powders and catalysts, 5 wt%La 2 O 3 -95 wt%MgAl 2 O 4 and 5 wt%Ni/5 wt%CeO 2 -95 wt%MgAl 2 O 4 exhibited the highest BET area of 306 m2 g−1 and 263 m2 g−1, respectively. The catalytic results indicated that the 5 wt%Ni/5 wt%CeO 2 -95 wt%MgAl 2 O 4 catalyst exhibited the highest activity and the lowest carbon formation among the prepared catalysts with the same content of the promoter. The influence of the CeO 2 content on the textural and catalytic performance was also investigated and the results illustrated that the increment in CeO 2 content improved the methane conversion and reduced the amount of deposited carbon, which could be related to the redox properties of the catalyst support. • Dry reforming over 5% Ni/M-MgAl 2 O 4 (M: CeO 2 , ZrO 2 , La 2 O 3) catalysts was studied. • 5 wt%La 2 O 3 -95 wt%MgAl 2 O 4 powders showed the highest BET area. • The prepared catalysts exhibited mesoporous structure with high BET area. • 5%Ni/5%CeO 2 –95%MgAl 2 O 4 exhibited the highest activity and the lowest carbon formation. • The increment in CeO 2 content improved the activity and reduced the amount of deposited carbon. [ABSTRACT FROM AUTHOR]

Abstract Wind power potential by itself is not a good indicator of the suitability of a region for wind power generation for different purposes. Economic attractiveness is a better indicator in this regard as it stimulates the involvement of private businesses in this sector. Naturally, the shorter is the payback period or the time required to reach profitability, the more attractive will be the project. Considering the high wind energy potential of some regions of Iran, this study evaluates the wind energy available for generating electricity as well as hydrogen by industrial and agricultural sectors in four cities of Ardebil province, namely Ardebil, Khalkhal, Namin, and Meshkinshahr, and then conducts an econometric analysis accordingly. Wind power potentials are evaluated using the energy pattern factor and Weibull distribution function based on 5-year meteorological data of the studied regions. Economic evaluations are performed based on the present worth of incomes and costs, which are estimated for two models of wind turbines with 3.5 and 100 KW rated power. Results indicate that the cities of Namin and Ardebil with wind power densities of respectively 261.68 and 258.99 W/m2 have the best condition. The economic analysis conducted for turbines shows that for Ardebil, installation of the 3.5 KW and 100 KW turbines will have a payback period of 13 and 5 years, respectively. For Khalkhal, Namin, and Meshkinshahr, the only feasible option is installation of the 100 KW turbine, which would result in a payback period of respectively 10.2, 6.1 and 8.7 years. Then it is investigated how much hydrogen can be gained if these private sectors invest in producing hydrogen using nominated wind turbines. Highlights • Hydrogen production by renewable wind energy was investigated. • Feasibility of hydrogen energy for agricultural and industrial sectors was performed. • Economic evaluation was done for four cities of Ardebil province in Iran. • It was found that these sectors can produce 25% of their own need to electricity. • Yearly hydrogen of 5253 kg would be produced in Ardebil City. [ABSTRACT FROM AUTHOR]

Abstract The objective of this study is to socially and economically investigate installation of wind turbines in Iran in order to produce hydrogen using its electricity. Due to adequate condition of wind blow in Manjil, Zabol, and Ardebil, these cities were chosen as the case studies and sample society. To scrutinize the acceptance of wind power among the sample members, first, data was gathered through questionnaires and analyzed by Partial Least Squares (PLS) approach to Structural Equations Modeling (SEM). The results showed that the first hypothesis (H1), positive effect of financial condition of households on wind power acceptance, was rejected with the coefficient of 1.184. On the other hand, the second hypothesis (H2) was approved with a meaningful coefficient of 3.159, that is, the social awareness of wind energy has a positive effect on its acceptance as an electricity generating source. Costs and Incomes Chart was utilized to estimate the payback period of investing in the wind power site project. Five wind turbines with different nominal capacities were tested and the results showed that the payback period for Manjil is shorter than that of others' in a way that for turbines with 5, 30, 50, 60 and 100 kW nominal capacity is 3.1, 2.4, 2.3, 1.9, 2.6 years respectively. Finally, Hummer H25.0–60 KW wind turbine was selected due to its payback time which was less than other turbines to estimate the amount of hydrogen produced. The results showed that with installing one set of this turbine in Manjil, Zabol, and Ardebil 7.12, 5.82 and 5.72 ton hydrogen per year will be produced, respectively. Highlights • Investigation of wind energy social acceptance using PLS approach to SEM. • Economically assessment of installing wind turbines using Costs and Incomes Chart. • Estimating yearly hydrogen production via a wind-powered hydrogen generation system. • Evaluating energy efficiency of the wind-to-hydrogen energy conversion system. [ABSTRACT FROM AUTHOR]

Abstract Nanocrystalline Ni/CeO 2 catalysts with various loadings of Ni (10, 15, 20, and 25%) were synthesised by a facile solvent deficient precipitation method for methane autothermal reforming process. The characterisation techniques such as XRD, BET, TPH, H 2 -TPR were carried out on fresh and spent samples to investigate the catalytic properties of the Ni/CeO 2. On the basis of characterisation results, the 20% Ni/CeO 2 performs the best activity among the catalysts with different Ni contents. The optimal reaction conditions for autothermal methane reforming has been investigated by evaluating the effect of reaction parameters including the reactivity temperature, the gas hourly space velocity (GHSV) and H 2 O/CH 4 (S/C) and O 2 /CH 4 (O/C) molar ratios. The stability of 20 wt% Ni/CeO 2 catalyst at 700 °C is examined for 20 h on-stream reaction. It reveals that the methane conversion starts a graduate decrease trend from the second 10 h, which is found to be because of the sintering of Ni nanoparticles by TPH and BET analysis. Graphical abstract Image 1 Highlights • Nanocrystalline Ni/CeO 2 catalysts were studied for autothermal reforming reaction. • 20 wt% Ni/CeO 2 with the large surface area and good reducibility exhibited the highest catalytic performance. • 20 wt% Ni/CeO 2 shown excellent thermal stability at 700 °C for 20 h on-stream reaction. • Carbon depositions were determined to occur on the surface of the samples with high Ni loading. [ABSTRACT FROM AUTHOR]

Abstract In this study, a microchannel reactor was designed, its catalytic performance in dry methane reforming (DRM) was assessed, and the results were compared with those observed in a conventional fixed bed reactor. The catalyst was prepared in two forms, including catalyst pellets and catalyst-coated plate. The microchannel reactor had thin films of Ni/Al 2 O 3 coated on stainless steel substrate via radio frequency (RF) magnetron sputtering method in various sputtering times. The fall-off rate of the catalyst-coated plates can be neglected after putting the plates under the high-temperature DRM reaction, due to the formation of firm active catalyst coatings. The performance of the samples was evaluated at different temperatures from 700 to 800 °C, at P = 1 atm, with a CH 4 :CO 2 ratio of 1. The results of XRD showed that with increasing the sputtering time, there was an increase in crystallinity. As observed in FESEM images, the sample prepared with 5 min of sputtering was dense and uniform. The results of EDX not only proved the dispersion of the samples observed in XRD and FESEM analysis, but also verified the presence of the utilized elements. The temperature of 800 °C and the sample with 5 min sputtering time were selected as the optimum condition that provided the best performance. Catalytic performance was investigated in fixed bed reactor at the same GHSV; based on the results there were no significant conversions in the fixed bed reactor. The results of the stability test in the microchannel reactor showed a good performance during 30 h on stream. Therefore, Ni/Al 2 O 3 thin films had a satisfactory performance in the designed microchannel. Our study shows that this type of reactor has many advantages in terms of performance, compactness, and economic concerns. Highlights • A microchannel reactor designed for DRM with a replaceable catalytically coated plate. • A new method utilized to prepare a metal-ceramics complex substrate as the catalyst support. • Microchannel reactor was compared with that of a conventional fixed bed reactor. • Microchannel reactor showed similar catalytic activity using much less catalyst. [ABSTRACT FROM AUTHOR]

Abstract A series of nanocrystalline mesoporous Ni/Al 2 O 3 SiO 2 catalysts with various SiO 2 /Al 2 O 3 molar ratios were prepared by the sol-gel method for the carbon dioxide methanation reaction. The synthesized catalysts were evaluated in terms of catalytic performance and stability. The catalysts were studied using XRD, BET, TPR and SEM. The BET results indicated that the specific surface area of the samples with composite oxide support changed from 254 to 163.3 m2/g, and an increase in the nickel crystallite size from 3.53 to 5.14 nm with an increment of Si/Al molar ratio was visible. The TPR results showed a shift towards lower temperatures, indicating a better reducibility and easier reduction of the nickel oxide phase into the nickel metallic phase. Furthermore, the catalyst with SiO 2 /Al 2 O 3 molar ratio of 0.5 was selected as the optimal catalyst, which showed 82.38% CO 2 conversion and 98.19% CH 4 selectivity at 350 °C, high stability, and resistivity toward sintering. Eventually, the optimal operation conditions were specified by investigating the effect of H 2 /CO 2 molar ratio and gas hourly space velocity (GHSV) on the catalytic behavior of the denoted catalyst. Highlights • Nanocrystalline mesoporous Ni/Al 2 O 3. SiO 2 catalysts were prepared by sol-gel method. • Ni/Al 2 O 3.0.5SiO 2 exhibited mesoporous structure with a high BET area of 281 m2 g−1. • Ni/Al 2 O 3.0.5SiO 2 possessed the highest catalytic activity and stability in CO 2 methanation. • The increase of Si/Al molar ratio decreased the BET area from 254 to 163.3 m2 g−1. • The nickel crystallite size increased from 3.53 to 5.14 nm with an increment of Si/Al molar ratio. [ABSTRACT FROM AUTHOR]

In this paper, a series of mesoporous supported nickel based catalysts on nanocrystalline alumina carrier promoted with various metals (Fe, CO, Zr, La and Cu) were prepared and employed in carbon dioxide methanation reaction. The samples were characterized by XRD, BET, TPR and SEM techniques. The BET results showed that the incorporation of promoters into nickel based catalysts decreased the surface area. The results showed that among the prepared catalysts, 30 wt.%Ni-5 wt.%La/Al 2 O 3 and 30 wt.%Ni-5 wt.%Fe/Al 2 O 3 possessed the highest surface area and the largest pore volume, respectively. Likewise, there was a slight decrease in the pore volume and the average pore diameters of the promoted samples. The TPR results depicted that the incorporation of the promoters enhanced the reducibility of the catalysts and shifted the reduction of NiO species to a lower reduction temperature. The CO 2 conversions of all promoted catalysts except Cu-promoted sample were higher peculiarly at low temperatures compared to those attained for the unpromoted catalyst. 30 wt.%Ni-5 wt.%Fe/Al 2 O 3 catalyst exhibited the best catalytic performance (70.63% CO 2 conversion and 98.87% CH 4 selectivity at 350 °C), high stability and desirable resistance against sintering. [ABSTRACT FROM AUTHOR]

This paper describes a facile method to produce mesoporous nanostructure Ni/Al 2 O 3 , Ni/MgO, and Ni/xMgO.Al 2 O 3 (x: MgO/Al 2 O 3 molar ratio) catalysts prepared by “one-pot” evaporation-induced self-assembly (EISA) method with some modifications for investigating in the thermocatalytic decomposition of methane. Detailed characterizations of the material were performed with X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and N 2 adsorption/desorption, hydrogen temperature-programmed reduction (H 2 -TPR), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and temperature-programmed oxidation (TPO). The characterizations demonstrated that the synthesized catalysts with various MgO/Al 2 O 3 molar ratios possessed mesoporous structure with the high BET area in the range of 216.79 to 31.74 m 2 g −1 . The effect of different surfactants and calcination temperatures on the characterizations and catalytic activity of the catalysts were also examined in details. The experimental results showed that the catalysts exhibited high catalytic potential in this process and the 55 wt.% Ni/2 MgO·Al 2 O 3 catalyst calcined at 600 ο C possessed an acceptable methane conversion (∼60%) under the harsh reaction conditions (GHSV = 48000 (mL h −1 g cat −1 )). [ABSTRACT FROM AUTHOR]

The present research is centralized on designing and optimizing the preparation conditions of the NiO(50)/FeAl 2 O 4 catalyst in the thermocatalytic decomposition of CH 4 (TDM). The mesoporous FeAl 2 O 4 powders were synthesized by various methods, and the supported nickel catalysts were employed in the TDM. The results showed that the catalyst supported on FeAl 2 O 4 synthesized by the modified co-precipitation (MCOP) method possessed the best efficiency, and CH 4 conversion and H 2 yield were 74 and 82% at 675 °C, respectively. Taguchi L 9 statistical experimental design was applied to investigate and optimize the preparation parameters, including surfactant type (CTAB, PVP, P123), pH (9, 10, 11), aging temperature (40, 60, and 80 °C), and aging time (0, 15, 30 h). The obtained outcomes revealed that the optimized sample displayed a mesoporous nanocrystalline structure with an appropriate BET area (72.6 m2 g−1) and pore volume (0.17 cm3 g−1), and its maximum methane conversion was 80.8% at 700 °C. The results indicated that the Taguchi procedure was impressive in the optimization of the synthesis parameters, and the error value between the predicted value and the actual value was lower than 4%. The physicochemical characteristics of the optimized sample were assessed based on the XRD, BET, H 2 -TPR, FTIR, TGA/DTA, FESEM, and TPO analyses. Furthermore, the influence of calcination temperature was investigated on the textural properties and catalytic performance of the selected catalyst. The stability experiment of the samples showed that the NiO(50)/FeAl 2 O 4 catalyst calcined at 600 °C was utterly stable for 300 min time on stream. Also, the effect of the processing parameters (GHSV, feed composition, and reduction temperature) was evaluated on the catalyst stability and amount of the deposited carbon on the catalyst surface of the optimum NiO(50)/FeAl 2 O 4 catalyst. [Display omitted] • Different methods were applied to synthesize the FeAl 2 O 4 with diverse textural features. • The FeAl 2 O 4 -supported nickel catalysts were used in CH 4 thermocatalytic decomposition. • The modified co-precipitation method was the best efficiency in CH 4 decomposition. • The methane conversion reached about 81% at 700 °C over the optimized catalyst. • The accuracy of the obtained results was confirmed according to the Taguchi analysis. [ABSTRACT FROM AUTHOR]

Methanation of carbon monoxide in the H 2 -rich gas stream was performed on a series of the Ni/MgAl 2 O 4 catalysts in a fixed bed micro-reactor. The catalysts were synthesized using wetness impregnation method and the prepared samples were characterized by XRD, BET, SEM, TEM, H 2 -TPR, CO chemisorption and CO-TPD techniques. The catalyst carrier was prepared by a novel sol-gel method using nitrate salts precursors and propylene oxide as a gelation agent. MgAl 2 O 4 as catalyst carrier possessed a high BET area of 340 m 2 g −1 with high pore volume (0.563 cc g −1 ) and small pore size (6.56 nm). The catalysts also showed high BET area, which decreased with the increase in Ni content. These catalysts exhibited mesoporous structure with average nickel crystal size smaller than 20 nm. The catalyst with Ni content of 25 wt% exhibited the maximum CO conversion and CH 4 selectivity and can be considered as a catalyst with high catalytic potential for the selective methanation of carbon monoxide. [ABSTRACT FROM AUTHOR]

This study aims to determine the best location for the construction of a wind-solar hybrid plant in Fars, Iran. For this purpose, seven regions of the Fars province are studied in terms of four criteria of economic, social, and geological conditions as well as natural disasters. First, the most important factors, wind power and solar irradiation, are obtained by using the Weibull distribution function and the Angstrom–Prescott equation based on the long-term 3-hourly data pertaining to 2006–2015 collected from the Iran Meteorological Organization, respectively. The data analysis and ranking are performed with the fuzzy TOPSIS. The results show that Eghlid is the best option for the construction of a wind-solar plant. According to the obtained results, the cities of Firuzabad, Estahban, Safashahr, Bavanat, Izadkhast and Arsanjan hold the next ranks in terms of suitability for the construction of solar-wind hybrid plants. [ABSTRACT FROM AUTHOR]

In this work, cobalt hydroxide nanoparticles are simply synthesized (size is about 50 nm) and deposited on the reduced graphene oxide nanoflake by the hydrothermal method. Then, the ability of glassy carbon electrode modified with this low-cost nanocomposite is examined as a supercapacitor and oxygen evolution electrocatalysts in 2.0 mol L −1 KOH by a three-electrode system. The modified electrode as a pseudocapacitor with potential windows of 0.35 V, exhibits a powerful specific capacitance (235.20 F g −1 at 0.1 A g −1 current density), energy density, stability (about 90% of the initial capacitance value maintain after 2000 cycles at 1.0 A g −1 ) and fast charge/discharge ability. Furthermore, the modified electrode displays a good electrocatalytic activity for oxygen evolution reaction with a current density of 10.0 mA cm −2 at 1.647 V, small Tafel slope of 56.5 mV dec −1 , good onset potential of 1.521 V vs. RHE and suitable durability. [ABSTRACT FROM AUTHOR]

In this study methane autothermal reforming (ATR) was investigated over Ni/Al 2 O 3 and Ni/Al 2 O 3 –CeO 2 catalysts. The catalyst carriers were prepared through a facile one-step method, which produced mesoporous nanocrystalline carriers for Ni catalysts. The samples were characterized by XRD, TPR, BET, TPO and SEM characterization techniques and the catalytic activity and stability were also studied at different conditions (GHSV and feed ratio) in methane ATR. It was found that the nickel catalyst supported on 3 wt.% Ce–Al 2 O 3 exhibited higher activity compared to the catalysts supported on the Al 2 O 3 and promoted Al 2 O 3 with 1 and 6 wt.% Ce. The results also showed that the nickel catalyst supported on 3 wt.% Ce–Al 2 O 3 possessed the highest resistance against carbon deposition in ATR reaction. [ABSTRACT FROM AUTHOR]

Many advantages of renewable energies, especially wind energy, such as abundance, permanence, and lack of pollution has encouraged many industrialized and developing countries to focus more on these clean and economic sources of energy. Identifying a good location that is suitable for the construction of a wind farm is one of the important initial steps in harnessing wind energy which is assessed this study. The purpose of this study is to prioritize and rank 13 cities of Fars province in Iran, in terms of their suitability for the construction of a wind farm. Six important criteria were used to prioritize and rank the cities. Wind power density is the most important criterion among these criteria which is calculated by obtaining the 3-h wind speed data between 2004 and 2013. DEA (Data Envelopment Analysis) method is used for prioritizing and ranking cities, and then AHP (Analytical Hierarchy Process), and FTOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) methods are used to assess the validity of results. It is concluded that Izadkhast city is the suggested location for the construction of wind farm. The utilizing a wind-hydrogen energy conversion system will result in a substantial amount of hydrogen production (averagely 21.9 ton/year) when a 900 kW wind turbine is installed in this location. [ABSTRACT FROM AUTHOR]

Mesoporous nanocrystalline Ni–Al 2 O 3 powders with different Ni loadings were synthesized via ultrasonic-assisted co-precipitation method and employed in methane dry reforming. The synthesized samples were investigated by BET, XRD, TPR, TPO and SEM analyses. The analyses showed that the increase in nickel loading from 15 wt.% to 25 wt.%, increased the surface area from 171.2 to 188 m 2 g −1 and further increase in Ni loading has a negative influence on the surface area. It was seen that increasing in Ni loading from 15 wt.% to 33 wt.% decreased the crystallite size and also improved the reducibility of the catalyst. The TPO analysis exhibited that decreasing in Ni loading decreased the content of accumulated carbon. The catalytic results showed an improvement in catalytic activity by the increase in Ni loading. The activity measurements showed that the 25wt.%Ni–Al 2 O 3 exhibited high catalytic performance in CH 4 dry reforming. [ABSTRACT FROM AUTHOR]

The promotion effect of La, Ce, Sr and Zr on the catalytic and structural properties of nanocrystalline mesoporous γ-Al 2 O 3 supported Ni catalysts was investigated in autothermal reforming of methane. Mesoporous nanocrystalline γ-Al 2 O 3 powder and promoted ones with high specific surface area (>220 m 2 /g) were prepared by solid state reaction method and employed as the support for nickel catalysts. The prepared catalysts were subjected to autothermal reforming reaction and characterized by XRD, BET, DR-UV-Vis, TPR, TPO and SEM techniques before and/or after the reaction. The effect of experimental conditions, such as temperature was investigated on the catalysts. Ce promoted catalyst, containing small amounts of CeO 2 as a separate phase, was found the most effective catalyst between both promoted and unpromoted ones. [ABSTRACT FROM AUTHOR]

Three large mesoporous alumina powders were prepared by microemulsion (ME) method with different microemulsion structures and compositions (various surfactants and oil phases) and employed as catalyst carrier for preparation of mesoporous nanocrystalline Ni/Al 2 O 3 catalysts. The prepared catalysts were used in dry reforming reaction for production of synthesis gas. The samples were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller surface area analysis (BET), temperature programmed reduction (TPR) and scanning electron microscopy (SEM) techniques. The results showed that the prepared γ-Al 2 O 3 with different microemulsion compositions possessed mesoporous structure with high surface area from 239.7 to 277.7 m 2 g −1 . In addition, the prepared 10wt.% Ni/γ-Al 2 O 3 catalysts exhibited high activity and stability in dry reforming reaction. The results also revealed that the microemulsion composition have a significant effect on the textural properties and affected the catalytic performance. [ABSTRACT FROM AUTHOR]

Ni–Pd/Al 2 O 3 catalysts were prepared and employed for the simultaneous production of CO x -free hydrogen and carbon nanofibers via methane thermocatalytic decomposition. The results showed that the palladium addition to nickel catalyst improved the degree of reducibility and catalytic performance. Addition of palladium to nickel creates Ni–Pd alloy, which has the high activity for methane dissociation and increases the catalytic activity. The carbon diffusion in palladium is very faster than the diffusion in nickel. This leads to enhancing the rate of carbon diffusion and preventing the formation of encapsulating carbon, which increases the catalyst lifetime. Moreover, during the methane decomposition over Ni–Pd alloy, carbon nanofibers grow from several facets and form branched structure, which increases the rate of carbon migration and prevents the coverage of active sites. Scanning electron microscopy (SEM) analysis of the spent catalysts showed the formation of the intertwined filaments form carbon. [ABSTRACT FROM AUTHOR]

Mesoporous nanocrystalline γ-Al 2 O 3 powder with high specific surface area (>220 m 2 /g) was prepared by a “solid state” method and employed as the support for nickel catalysts. Ni catalysts supported on this alumina were prepared and investigated in autothermal reforming of methane. The prepared catalysts were characterized by XRD, BET, DR-UV-Vis, TPR and SEM techniques before and after the reaction. The effect of experimental conditions, such as temperature, space velocity, steam to carbon (S/C) and oxygen to carbon (O/C) ratio was investigated on the catalytic performance of the prepared catalysts. Catalyst with 25 wt.% of Ni content revealed high methane conversion (around 86% at 700 °C). The catalytic activity is reduced by calcination at 800 °C, which results in lower surface area and in the formation of bulk Ni aluminate spinel. [ABSTRACT FROM AUTHOR]

The catalytic behavior of iron promoted nickel catalysts supported on nanocrystalline gamma alumina was investigated for the simultaneous production of CO x -free hydrogen and carbon nanofibers via methane thermocatalytic decomposition. The prepared catalysts exhibited mesoporous structure with high surface area from 89.2 to 74.8 m 2 g −1 depending on the iron content. X-ray diffraction (XRD) studies revealed the formation of NiFe 2 O 4 species and Ni–Fe alloys in calcined and reduced catalysts, respectively. Temperature programmed reduction (TPR) analysis showed that the addition of iron to nickel catalyst decreased the degree of reducibility. The results also revealed that addition of iron to nickel catalyst improved the catalytic stability by enhancing the rate of carbon diffusion and preventing the formation of encapsulating carbon. Scanning electron microscopy (SEM) analysis of the spent catalysts with various reaction temperatures showed that generated carbon is in intertwined filaments form and confirmed that the diameter and length of carbon nanofibers decreased by increasing reaction temperature. [ABSTRACT FROM AUTHOR]

High temperature water gas shift reaction is carried out over nanocrystalline chromium free Fe 2 O 3 –Al 2 O 3 –NiO catalysts with and without alkaline earth promoters. Mesoporous catalysts are prepared by coprecipitation method. The prepared catalysts are characterized using N 2 adsorption (BET), temperature-programmed reduction (TPR) and desorption (TPD), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results indicate that alkaline earth promoters improve the catalytic activity and suppress the progress of methanation reaction, which is related to the increment of amount in weakly basic sites through promoter addition. Furthermore, it is found that the Fe 2 O 3 –Al 2 O 3 –NiO catalyst promoted by Ba exhibits the highest catalytic activity and the lowest methanation among the prepared catalysts and the commercial chromium containing one. In addition, the effect of Ba content on the CO conversion is investigated and the results indicate that the catalyst with 3 wt.% Ba possesses high activity and stability without any decrease in CO conversion during 50 h time on stream. [ABSTRACT FROM AUTHOR]

The CuMn samples with various CuO weight percentages were synthesized by the mechanochemical route. The catalytic activity of the prepared samples was determined in the preferential oxidation of CO process (CO-PROX) in the temperature range of 40–250 °C. According to the XRD results, the 5CuMn and 10CuMn samples exhibited the spinel phase in their structures. The spinel phase formation enhanced the CO adsorption active sites and modified the redox properties. The results indicated that the copper incorporation into the manganese oxide modified the catalytic activity and structural properties. The 5CuMn catalyst with the highest BET area (72.1 m2 g−1) possessed 96% CO conversion and 50% CO 2 selectivity at 70 °C (GHSV = 30,000 ml/h.g cat) and significant resistance in the presence of water due to the formation of hydroxyl groups over the catalyst surface. The catalyst activity remained stable for 14 h at 130 °C. Furthermore, the influence of calcination temperature, feed composition, and GHSV value on the catalytic performance of the 5CuMn catalyst was studied. • The Cu–Mn catalyst with 5 wt% Cu exhibited a CO conversion higher than 90% at 70 °C. • 5 wt%. CuO-MnOx showed a Cu 1.5 Mn 1.5 O 4 spinel structure. • 5 wt%. CuO-MnOx catalyst exhibited sufficient stability in the presence of water vapor. [ABSTRACT FROM AUTHOR]

In the present work, a group of nickel-ceria nanocatalysts was synthesized by co-precipitation method and their catalytic performances were considered in CO methanation reaction. The catalysts were characterized by XRD, BET, SEM, TEM, H 2 -TPR, CO chemisorption and CO-TPD techniques. The results showed that addition of nickel content up to 50 wt.% increased both the CO conversion and CH 4 selectivity at low temperatures while further increase in nickel content adversely affected them. The 50%Ni/CeO 2 catalyst revealed an excellent activity in CO methanation due to high surface area (258 m 2 /g), small nickel particle size (below 5 nm) and high metal dispersion (7.31%). In CO selective methanation, CO 2 conversion was completely suppressed until CO conversion reached to a maximum value, which is an important factor from commercial view point where is needed to extend operating temperature window between maximum of CO conversion and suppressing of CO 2 methanation. [ABSTRACT FROM AUTHOR]