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In this study, zirconia-modified alumina support (S) was used to investigate Ga-promoted Ni catalysts for dry reforming of methane (DRM). The catalysts (Ni + (0–3) wt% Ga/S) were prepared using the wet impregnation method and calcined at 700 °C for 3 h. The inclusion of Ga enhanced the surface area, basicity, and metal-support interaction of the Ni-Ga/S catalysts. Smaller Ni particles containing Ga were seen in the TEM. The most active and stable catalyst was Ni + 2.0 Ga/S, having a conversion of 35% CO2 and 28% CH4 at 600 °C and displaying less (17%) carbon deposition. Furthermore, the DRM process was optimized by a mathematical model. The model determined the optimal conditions as follows: temperature (800 °C), gas flow rate (GHSV—30,000 ml h−1gcat−1), and methane to carbon dioxide ratio (1:1). The model predicts CH4 and CO2 conversions of 76.76% and 82.0%, respectively, and an H2/CO ratio of 1.02, compared to experimental results showing CH4 conversion at 74.56%, CO2 conversion at 83.25%, and an H2/CO ratio of 1.01. The model demonstrates excellent agreement with the experimental observations, exhibiting less than 3% error. [ABSTRACT FROM AUTHOR]

The catalytic partial oxidation of methane (POM) is aimed at the mitigation of CH4 (a highly potent greenhouse gas) from the environment and the synthesis of syngas with a high H2/CO ratio. Herein, to enhance the POM reaction, Ni‐supported phosphate‐modified‐zirconia were synthesized with promotor "Ce" to achieve high H2/CO ratio (2.4–3.2). The catalysts were characterized by surface area and porosity, X‐ray diffraction, RAMAN, temperature‐programmed experiments (TPR, CO2‐TPD, and TPO), and TEM. Increasing the ceria addition over 10Ni/PO4 + ZrO2 resulted in lower crystallinity, higher dispersion of active sites, and enhanced the surface area of catalyst. The unique and prominent reducibility and basicity of NiO‐species and surface oxide ions, respectively, are particularly notable at 4 wt.% ceria loading. At a reaction temperature of 600°C, the highest concentration of active sites and a unique concentration of moderate strength basic sites can be achieved with 4 wt.% ceria loading over 10Ni/PO4 + ZrO2. This leads to 44% conversion of CH4, 36% yield of H2, 35% yield of CO2, and H2/CO ratio of 3.16 for the POM reaction. The cyclic H2TPR‐O2TPO‐H2TPR experiment confirms the reorganization of the active site towards high temperature under oxidizing gas O2 and reducing gas H2 gas stream during the POM reaction. [ABSTRACT FROM AUTHOR]

Preparing catalysts from cheap metal precursors in a single pot are an appealing method for reducing catalytic preparation costs, minimizing chemical waste, and saving time. With regards to the catalytic conversion of dry reforming of methane, it offers the prospect of significantly reducing the cost of H2 production. Herein, NiO-stabilized metal oxides like Ni/TiO2, Ni/MgO, Ni/ZrO2, and Ni/Al2O3 are prepared at two different calcination temperatures (600 °C and 800 °C). Catalysts are characterized by X-ray diffraction, Raman spectroscopy, surface area-porosity analysis, Temperature program experiments, infrared spectroscopy, and thermogravimetry analysis. The MgO-supported Ni catalyst (Ni/MgO-600), ZrO2-supported Ni catalyst (Ni/ZrO2-600), and Al2O3-supported Ni (Ni/Al2O3-600) catalyst calcined at 600 °C show initial equal H2 yields (~ 55%). The population of CH4 decomposition sites over ZrO2-supported Ni catalyst remains highest, but H2-yield drops to 45% against high coke deposition. The catalytic activity remains constant over the Ni/MgO-600 catalyst due to the enrichment of "surface interacted CO2-species". MgO-supported Ni catalyst calcined at 800 °C undergoes weak interactions of NiO-M′ (M′ = support), serious loss of CH4 decomposition sites and potential consumption of H2 by reverse water gas shift reaction, resulting in inferior H2 yield. H2-yield remains unaffected over an Al2O3-supported Ni catalyst even against the highest coke deposition due to the formation of stable Ni (which exsolves from NiAl2O4) and proper matching between carbon formation and rate of carbon diffusion. [ABSTRACT FROM AUTHOR]

The potential dry reforming of methane technology allows for the synthesis of syngas from methane and carbon dioxide. Numerous investigations have been conducted on developing catalysts with exceptional activity and stability. Carbon deposition causes severe deactivation in typical nickel‐based catalysts, which is one of the most prevalent and important problems. In this study, methane was dry‐reformed over 5 wt.% Ni+xSr‐9La+Zr (x = 0–4 wt.%) catalysts for 7.5 h at 700°C and ambient pressure in a tubular fixed‐bed reactor. According to the weight percent of Sr loading, the features of the material's texture, morphology, and catalysis were investigated. N2‐physisorption, H2‐temperature programmed reduction, X‐ray diffraction, Raman, and TEM were used to evaluate the physicochemical characteristics of the catalysts. N2‐physisorption research revealed that changing the weight percentage loading of the Sr promoter had little effect on the textural qualities. The overall number of reducible NiO‐interacting species over the catalyst surface increased with increasing Sr loading. The 5Ni+2Sr‐9La+Zr catalyst exhibited the optimum CH4 and CO2 conversions of 62.9%–65.9% and 69.1%–70.3%, respectively, and the lowest deactivation factor of 4.7. [ABSTRACT FROM AUTHOR]

Carbon dioxide reforming of methane (CRM) converts CH4 and CO2 greenhouse gases into syngas over nickel-based catalysts. We performed CRM in a tubular microreactor at 700 °C by using 5.0 wt.% NiO catalyst, supported over mixtures of γ-Al2O3 + x MgO (x = 20, 30, 63, and 70 wt.%). The process of impregnation was used to prepare the catalysts. For characterization, N2-physisorption, XRD, H2-TPR, TGA, and Raman spectroscopy techniques were employed. Among the examined catalysts, 5Ni/Al2O3 + 63%MgO was found the most active, where it showed ≅ 72% CH4 conversion, 73% CO2 conversion, and 0.82 H2/CO mole ratio over 7 h of reaction. The MgO modifier was the primary component, which favorably affected both Ni dispersion and stability, for the good interaction between NiO and γ-alumina. The mono-supported samples displayed the lowest total hydrogen consumption. In TGA, the 5Ni/Al2O3 + 63%MgO exhibited a significant weight decrease (40%), reflecting its activity. Furthermore, the Raman spectroscopy analysis showed that the crystallinity of the carbon over this catalyst was more pronounced than the others. [ABSTRACT FROM AUTHOR]

Dry reforming of methane (DRM) is gaining global attention due to its capacity to convert two greenhouse gases together. It proceeds through CH4 decomposition over active sites (into CH4−x) followed by CH4−x oxidation by CO2 (into syngas). Furthermore, CH4−x oligomerization into coke cannot be neglected. Herein, xNi(5−x)Co/Pd+Al2O3 (x = 5, 3.75, 2.5, 1.25, 0) catalysts are prepared, investigated for DRM, and characterized with X-ray diffraction, UV-Vis, transmission electron microscopy, temperature-programmed reduction/desorption techniques, and thermogravimetry. Fine-tuning among stable active sites, graphitic carbon deposits, and catalytic activity is noticed. The total reducibility and basicity are found to decrease upon increasing the Co proportion up to 2.5 wt% in the Ni-Co bimetallic Pd+Al2O3-supported catalyst. The active sites derived from strong metal–support interaction species (NiAl2Ox or dispersed CoOx) are found to be promising in higher levels of activity. However, activity is, again, limited by graphitic carbon which is increased with an increasing Co proportion in the Ni-Co bimetallic Pd+Al2O3-supported catalyst. The incorporation of 1.25 wt% Co along with 3.75 wt% Ni over Pd+Al2O3 results in the generation of fewer such active sites, extensive oxidizable carbon deposits, and inferior catalytic activity compared to 5Ni/Pd+Al2O3. The 2.5Ni2.5Co/Pd+Al2O3 catalyst has lower crystallinity, a relatively lower coke deposit (than the 3.75Ni1.25Co/Pd+Al2O3 catalyst), and a higher number of stable active sites. It attains a 54–51% H2 yield in 430 min TOS and 0.87 H2/CO (similar to 5Ni/Pd+Al2O3) [ABSTRACT FROM AUTHOR]

Methane decomposition is a promising route to synthesize COx‐free hydrogen and carbon nanomaterials (CNMs). In this work, the impregnation method was employed for the preparation of the catalysts. Systematic investigations on the activity and stability of Fe‐based catalysts were carried out in a packed‐bed micro‐activity reactor at 800 °C with a feed gas flow rate of 18 mL/min. The effect of doping Y2O3, MgO, SiO2 and TiO2 over ZrO2 on the catalytic performance was also studied. BET revealed that the specific surface areas and pore volumes are increased after SiO2, TiO2, and Y2O3 are added to ZrO2 while MgO had a negative impact and hence a little decrease in specific surface area is observed. The catalytic activity results showed that the Fe‐based catalyst supported over TiO2‐doped ZrO2 that is, Fe−TiZr, demonstrated the highest activity and stability, with a maximum methane conversion of 81.3 % during 180 min time‐on‐stream. At 800 °C, a maximum initial methane conversion of 73 %, 38 %, 64 %, and 69 % and a final carbon yield of 121 wt. %, 55 wt. %, 354 wt. %, and 174 wt. % was achieved using Fe−MgZr, Fe−SiZr, Fe−TiZr and Fe−YZr catalysts, respectively. Moreover, bulk deposition of uniform carbon nanotubes with a high degree of graphitization and different diameters was observed over the catalysts. [ABSTRACT FROM AUTHOR]

BACKGROUND: Brewer's Spent Grain (BSG), a form of lignocellulosic biomass more commonly known as barley waste was used to synthesize activated carbon (AC) and carbon nanotubes (CNTs). The produced materials were used in water remediation application. RESULTS: A novel approach involving two activation steps; first, with phosphoric acid (designated BAC‐P) and then using potassium hydroxide (designated BAC‐K) was proposed for the production of AC and CNTs from BSG. The AC produced showed a surface area as high as 692.3 m2 g−1 with a pore volume of 0.44 cm3 g−1. This can help aid and facilitate the circular economy by effectively upcycling and valorizing waste lignocellulosic biomass to high surface area AC and subsequently, multi‐walled carbon nanotubes (MWCNTs). Consequently, MWCNTs were prepared from the produced AC by mixing it with the nitrogen (N)‐based material melamine and iron precursor, iron (III) oxalate hexahydrate, where it produced hydrophilic MWCNTs. Both AC and CNT materials were used in heavy metal removal (HMR), where the maximum lead absorption was observed for sample BAC‐K with 77% removal capacity after the first hour of testing. CONCLUSION: This result signifies that the synthesis of these upcycled materials can have an application in the areas of wastewater treatment or other AC/CNT end uses with a rapid cycle time. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Herein, kinetic modelling and kinetic parameters were used to study methanol dehydration to dimethyl ether reaction and revealed that the best model to fit the experimental data was the Bercic model. The dehydration reaction undergoes dissociative adsorption Langmuir-Hinshelwood mechanism of methanol on the alumina catalyst surface, with the calculated value of the activation energy was 136.7 kJ mol−1. Moreover, the effect of different kinetic parameters such as the catalyst weight and methanol concentration or water in the feed on the catalytic performance of η-Al2O3 was examined in a fixed bed reactor under the reaction conditions where the temperature ranged from 180 to 350 °C with a WHSV = 12.1 h−1.Graphical Abstract: [ABSTRACT FROM AUTHOR]

The dry reforming of methane (DRM) process has attracted research interest because of its ability to mitigate the detrimental impacts of greenhouse gases such as methane (CH4) and carbon dioxide (CO2) and produce alcohols and clean fuel. In view of this importance of DRM, we disclosed the efficiency of a new nickel-based catalyst, which was promoted with magnesia (MgO) and supported over gamma-alumina (γ-Al2O3) doped with silica (SiO2), toward DRM. The synthesized catalysts were characterized by H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric analysis (TGA), and Transmission electron microscopy (TEM) techniques. The effect of MgO weight percent loading (0.0, 1.0, 2.0, and 3.0 wt. %) was examined because the catalytic performance was found to be a function of this parameter. An optimum loading of 2.0 wt. % of MgO was obtained, where the conversion of CH4 and CO2 at 800 °C were 86% and 91%, respectively, while the syngas (H2/CO) ratios relied on temperature and were in the range of 0.85 to 0.95. The TGA measurement of the best catalyst, which was operated over a 15-h reaction time, displayed negligible weight loss (<9.0 wt. %) due to carbon deposition, indicating the good resistance of our catalyst system to the deposition of carbon owing to the dopant and the modifier. TEM images showed the presence of multiwalled carbon nanotubes, confirming the TGA. [ABSTRACT FROM AUTHOR]

Catalytic methane decomposition is a promising technology for reducing the reliance on fossil fuels and mitigating the effects of climate change by producing clean hydrogen and value‐added carbon without the emission of greenhouse gases. The aim of the study was to investigate the use of Al2O3‐modified MgO doped iron‐based catalysts for the catalytic decomposition of methane. The catalysts were synthesized using the impregnation method and characterized using various analysis techniques, including Brunauer, Emmett, and Teller, temperature programmed reduction, temperature programmed oxidation, X‐ray diffraction, thermal gravimetric analysis, Raman, scanning electron microscopy, and transmission electron microscopy. The activity of the synthesized catalysts was tested in a packed‐bed reactor with a gas flow rate of 20 mL/min at a temperature of 800°C. The investigation focuses on the influence of incorporating magnesium into alumina catalysts with MgO concentration ranging from (20%–70%), where higher magnesium levels improve catalytic activity by creating more active sites, positively impacting methane decomposition. Enhanced catalyst reducibility and increased particle dispersion lead to improved catalytic properties despite the reduced surface area. The FA70M and FA63M catalysts exhibited almost the same catalytic characteristics and the highest stability and methane conversion among the catalysts investigated, reaching 87% and 85% at 800°C for 120 min. Moreover, both catalysts showed hydrogen yields of 86% and 85%, respectively. The introduction of MgO further increased the total carbon yield from 103% with FA and 39% for FM to 114% and 120% for the respective catalysts (FA70M and FA63M). During the methane decomposition reaction, carbon nanotubes of varying diameters were produced. Higher iron loading resulted in a positive trend. [ABSTRACT FROM AUTHOR]

The stability and catalytic activity of mesoporous Ni/MCM-41 promoted with a Ga loading of (0.0, 1.0, 1.5, 2.0, 2.5, and 3.0 wt %) as an innovative catalyst was examined for syngas production via CO2 reforming of CH4. The objective of present work was to develop a potential catalyst for CO2 reforming of methane. For this purpose different loadings of gallium were used to promote 5% nickel catalyst supported on MCM-41. An incipient wetness impregnation method was used for preparing the catalysts and investigated at 800 °C. Physicochemical characterization techniques—including BET, XRD, TPD, TPR, TEM, and TGA—were used to characterize the catalysts. The addition of small amounts of Ga resulted in higher surface areas with a maximum surface area of 1036 m2/g for 2.5% Ga. The incorporation of Ga to the catalyst decreased the medium and strong basic sites and reduced the amount of carbon deposited. There was no weight loss for 3%Ga+5%Ni/MCM-41. The 2% Ga loading showed the highest CH4 conversion of 88.2% and optimum stability, with an activity loss of only 1.58%. The Ga promoter raised the H2/CO ratio from 0.9 to unity. [ABSTRACT FROM AUTHOR]