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Steam reforming of glycerol (GSR) to produce hydrogen has been considered a sustainable and low-cost route for hydrogen production. The selection of a suitable catalyst support is crucial for achieving efficient hydrogen production at lower temperatures. CeO 2 has been widely used in heterogeneous catalysis and exhibits excellent low-temperature catalytic performance. However, different calcination mode may influence catalyst performance. In this study, the Ni/CeO 2 catalyst prepared by rapid calcination mode (Ni/CeO 2 -RC), was used for hydrogen production from GSR, and the Ni/CeO 2 catalyst with the conventional programmed-heating calcination method (Ni/CeO 2 -PC) was applied for comparison. The effect of different calcination modes on the physico-chemical properties of the catalysts was investigated through multiple characterizations such as N 2 adsorption-desorption, X-ray diffraction, hydrogen temperature programmed reduction, transmission electron microscopy, X-ray photoelectron spectroscopy, H 2 chemisorption, CO-oxygen storage capacity and conversion, temperature programmed oxidation, and Raman spectroscopy. The rapid calcination mode promoted stronger metal-support interactions in Ni/CeO 2 -RC, inducing the formation of nickel species highly susceptible to reduction due to the electronic effect. Additionally, rapid calcination facilitated the increased incorporation of nickel particles into the cerium dioxide lattice, leading to lattice distortions, thereby contributing to the formation of more oxygen vacancies. The abundant oxygen vacancies promoted the activation of water, thus realizing the high H 2 selectivity of Ni/CeO 2 -RC. Moreover, the strong oxygen storage-release ability of Ni/CeO 2 -RC facilitated the oxidative effect of carbon deposition and the strong Ni–CeO 2 interaction effectively inhibit sintering of nickel nanoparticles on Ni/CeO 2 -RC. Therefore, Ni/CeO 2 -RC exhibited outstanding catalytic stability, remaining active for 35 h without deactivation, whereas Ni/CeO 2 -PC rapidly deactivated after 25 h of reaction. [Display omitted] • Ni/CeO 2 catalyst with rapid calcination enhances catalytic stability of the catalyst. • Nickel-ceria interaction modulates active nickel and oxygen vacancies. • Strong nickel-ceria interaction is achieved through rapid calcination. • Ni/CeO 2 catalyst with rapid calcination inhibits the formation of carbon deposition. [ABSTRACT FROM AUTHOR]

Ni catalysts impregnated on CaO–Al2O3 with various Al/Ca molar ratios were synthesized, and employed in the glycerol steam reforming process to investigate the effect of calcium content on the catalyst efficiency. The prepared catalysts were characterized by XRD, BET, H2-TPR, CO2-TPD and SEM analyses. According to the preliminary tests, the characteristic features of the catalysts were directly affected by the Al/Ca molar ratio. The specific surface area and total pore volume increased with increasing in Al2O3 content. Meanwhile, the higher CaO content increased the catalyst reducibility and also the concentration of basic sites. The sample with Al/Ca of 2 had the best performance with glycerol conversion of 99.4% and H2 yield of 99.9% at 700 °C. Moreover, the results revealed that the catalyst calcined at 500 °C, and reduced at 700 °C possessed a glycerol conversion of 99.4% and this catalyst was selected as the best sample among the studied catalysts. [ABSTRACT FROM AUTHOR]

Ni catalysts impregnated on CaO–Al2O3 with various Al/Ca molar ratios were synthesized, and employed in the glycerol steam reforming process to investigate the effect of calcium content on the catalyst efficiency. The prepared catalysts were characterized by XRD, BET, H2-TPR, CO2-TPD and SEM analyses. According to the preliminary tests, the characteristic features of the catalysts were directly affected by the Al/Ca molar ratio. The specific surface area and total pore volume increased with increasing in Al2O3 content. Meanwhile, the higher CaO content increased the catalyst reducibility and also the concentration of basic sites. The sample with Al/Ca of 2 had the best performance with glycerol conversion of 99.4% and H2 yield of 99.9% at 700 °C. Moreover, the results revealed that the catalyst calcined at 500 °C, and reduced at 700 °C possessed a glycerol conversion of 99.4% and this catalyst was selected as the best sample among the studied catalysts. [ABSTRACT FROM AUTHOR]

In this work, a sol-gel Ni–Mo 2 C–Al 2 O 3 catalyst is employed for the first time in the glycerol steam reforming for syngas production. Catalyst stability and activity are investigated in the temperature range of 550 °C–700 °C and time on stream up to 30 h. As reaction temperature increases, from 550 °C to 700 °C, H 2 yield boosts from 22% to 60%. The stability test, carried out at milder conditions (600 °C and Gas-Hourly Space-Velocity (GHSV) of 50,000 mL h−1.g cat −1), shows high catalyst stability, up to 30 h, with final conversion, H 2 yield, and H 2 /CO ratio of 95%, 53% and 1.95, respectively. Both virgin and spent catalysts have been characterized by a multitude of techniques, e.g. , Atomic-Absorption spectroscopy, Raman spectroscopy, N 2 -adsorption-desorption, and Transmission Electron Microscopy (TEM), among others. Regarding the spent catalysts, carbon deposits' morphology becomes more graphitic as the reaction temperature increases, and the total coke formation is mitigated by increasing reaction temperature and lowering GHSV. • Compared to the literature increased activity and stability were observed herein. • A high surface area carbide-containing catalyst was synthesized by sol-gel technic. • Coke-related catalyst deactivation was reduced in the stability test (30 h). • H 2 yield and stability increase with temperature and decrease with GHSV. • More graphic and less harmful coke is produced at higher temperatures. [ABSTRACT FROM AUTHOR]

A new thermally coupled microreactor, which simultaneously produces hydrogen and aniline, is simulated. It is suggested that the nitrobenzene hydrogenation process, the heat source, occurs in the tube section, thereby providing the requisite energy for the reactor system. Conversely, the shell section contains the steam reforming of glycerol coolant for the exothermic reaction. The results are evaluated in the two flow directions, namely, cocurrent and countercurrent. The furnace and cooling system, vital for the conventional steam reforming and aniline production processes, are eliminated, respectively, having accurately implemented the sensitivity analysis. Optimization of the most effective parameters is performed via genetic algorithm. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crystal-phase-depended SMSI structure on Ni/TiO 2 catalyst. • An induction period phenomenon in glycerol steam reforming reaction. • Dynamic weakening of the SMSI structure is a direct cause of the induction period. • SMSI structure inhibits sintering of active Ni0 sites. • Outstanding catalytic performance is achieved after the induction period. The dynamic relationship of TiO 2 crystal phase and strong metal-support interactions (SMSI) of Ni/TiO 2 catalyst was investigated to reveal the induction period of glycerol steam reforming. Comprehensive investigations confirmed that the SMSI between Ni0 and anatase TiO 2 was formed by anatase TiO 2 encapsulated Ni0 after H 2 reduction at 500 °C for the Ni/TiO 2 catalyst calcined at 500 °C (Ni/Ti-500R), which inhibited the contact of Ni0 active sites with reactants and led to the low hydrogen yield in the initial stage of the reaction. Interestingly, the dynamic conversion of anatase to rutile during the GSR process at 600 °C caused the TiO 2 overlayers on the Ni0 particles to gradually fade, exposing more Ni0 sites, resulting in a gradual increase in hydrogen yield to 5.93 mol H2 /mol glycerol. In addition, Ni/Ti-500R with a dynamic SMSI inhibited Ni0 particles sintering and encapsulated carbon deposition, resulting in relatively better stability (21 h) after induction period. In comparison, the designed Ni/TiO 2 catalyst calcined at 600 °C (Ni/Ti-600R) with rutile TiO 2 as the main component inhibited the formation of the classical SMSI, even after 600 °C H 2 reduction, and no excessive TiO 2 encapsulated Ni0 particles were observed, so no obvious induction period occurred. This study provides new insights into the relationship of SMSI with crystal phases and the induction period in multiphase catalysis, also a new strategy for designing efficient catalysts. [ABSTRACT FROM AUTHOR]

CeO2 nanosphere-supported nickel catalysts were prepared by the wetness impregnation method and employed for hydrogen production from glycerol steam reforming. The dried catalyst precursors were either reduced by H2 after thermal calcination or reduced by H2 directly without calcination. The catalysts that were reduced by H2 without calcination achieved a 95% glycerol conversion at a reaction temperature of only 475 °C, and the catalytic stability was up to 35 h. However, the reaction temperature required of catalysts reduced by H2 with calcination was 500 °C, and the catalysts was rapidly inactivated after 25 h of reaction. A series of physicochemical characterization revealed that direct H2 reduction without calcination enhanced the concentration of oxygen vacancies. Thus, the nickel dispersion was improved, the nickel nanoparticle size was reduced, and the reduction of nickel was increased. Moreover, the high concentration of oxygen vacancy not only contributed to the increase of H2 yield, but also effectively reduced the amount of carbon deposition. The increased active nickel surface area and oxygen vacancies synergistically resulted in the superior catalytic performance for the catalyst that was directly reduced by H2 without calcination. The simple, direct hydrogen reduction method remarkably boosts catalytic performance. This strategy can be extended to other supports with redox properties and applied to heterogeneous catalytic reactions involving resistance to sintering and carbon deposition. [ABSTRACT FROM AUTHOR]

Bio-glycerol Steam reforming over green and economical Co/sepiolite (SEP) catalysts was a promising strategy to hydrogen production. The activation pretreatment of SEP played a vital role for boosting catalytic behavior of Co/SEP. This work originally explored a full activation of SEP by molten NaOH for tailoring the physicochemical properties of Co-based catalysts prepared by urea precipitation method. Differing from the acid pickling/calcination and molten NaNO 3 activation, the molten NaOH treatment enhanced surface area of SEP by desilicication/dealumination effect and further improved the exposure of framework Si and its surface 'reactivity'. According to the characterization results of N 2 adsorption-desorption, XRD, TEM, H 2 -TPR, CO/CO 2 -TPD and XPS, it was found that the feathered Co-phyllosilicate formed on Co/SEP-NaOH catalyst, which enhanced the metal-support interaction, surface area and basic/metallic sites. In contrast, the molten NaNO 3 treatment facilitated the transformation of SEP into loughlinite and it was adverse to metal dispersion. Therefore, Co/SEP-NaOH catalyst possessed the highest conversion (92%) and H 2 yield (68%) during the activity test at 600 °C and the superior resistance to amorphous coke. Additionally, DFT analysis was introduced to simulate the process of glycerol adsorption and decomposition and demonstrated the Co–CoO interface as the primary reaction sites for the catalytic process. [Display omitted] [ABSTRACT FROM AUTHOR]

In this work, a universal dopamine modification strategy is used to improve the catalytic performance of Ni/Al2O3 for hydrogen production in glycerol steam reforming (GSR). Ni/Al2O3 showed poor catalytic stability with rapid deactivation after 8 h of reaction in GSR. Glycerol conversion and hydrogen selectivity were significantly higher for dopamine‐modified Ni/Al2O3 (by 98 % and 95 %, respectively) and this improved performance was maintained well for 21 h in the stability test. The protective carbon shell derived from dopamine was formed easily on the Ni/Al2O3 surface, the aggregation of Ni nanoparticles was inhibited, and the dispersion of Ni nanoparticles was improved. The electron‐donating effect of amino group to Ni2+ weakened the Ni‐Al2O3 interaction, and then promoted the reduction of the Ni species. In addition, the decrease in the number of strong acidic sites reduced the amount of carbon deposition on dopamine‐modified Ni/Al2O3. The moderate metal‐support interaction was more conducive to the formation of filamentous carbon, which collectively contributed to the increased catalytic stability of dopamine‐modified Ni/Al2O3. The facile dopamine‐modified method significantly improves the catalytic performance and can be generalized to other catalytic reaction that involve sintering and carbon deposition issues. [ABSTRACT FROM AUTHOR]

A comprehensive study was conducted on the performance of M-promoted (M = 1%Ru, 1%Rh, 5%Ni) upgraded slag oxide metallurgical waste catalysts (M-UGSO) for hydrogen production by glycerol steam reforming (GSR). The results confirmed that the tendency of the incorporated metal to interact with Mg/Fe containing species within UGSO plays a key role in the surface availability of the corresponding metal, structural changes after reduction, and catalyst stability. Aside its best stability, 5% Ni-UGSO showed a performance (glycerol conversion to gaseous products of 100% and H 2 yield of 74%) comparable with 1% Rh-UGSO (100% and 78%, respectively) or even surpassing that of 1% Ru-UGSO (94% and 71%, respectively), as noble metal-based catalysts. Synergistic cooperation was achieved by incorporated metals (M) and Fe/Mg containing species within UGSO, resulting in enhanced glycerol and water activation. The weakest results of Ru-UGSO could be justified by lack of propensity for MgO–RuO 2 interaction on UGSO surface. [Display omitted] • Valorization of glycerol and metallurgical UGSO residues for H 2 production. • Metal (Ni, Ru, Rh) surface availability influenced by tendency to react with MgO. • Close ionic radii of Ni+2/Mg+2 results in highly effective Ni incorporation to UGSO. • Synergic cooperation of metal with Fe/Mg oxides by formation of M-Fe x O y and M-MgO. • Ni-UGSO provides higher stability and comparable activity to noble Ru/Rh-UGSO. [ABSTRACT FROM AUTHOR]

The effect of La/AlZn/AlLa oxide supports on Ni-based catalysts performance was assessed for glycerol steam reforming for renewable H 2 production. NiAlLaO x showed the best performance providing a glycerol conversion into gaseous products of 91 % and H 2 yield of 5.40 mol H 2 ·mol G , in ‐ 1 at 700 °C. Additionally, stability experiments lasting up to 24 h were performed at 625 °C, having been observed a stable behavior for NiAlLaO x with low coke formation. The materials' physicochemical properties, determined from different techniques (ICP-OES, N 2 -adsorption at -196 °C, XRD, TEM/EDX, TPR and TPO), allowed to comprehend how these influence their performance and stability. The NiAlLaO x good performance was assigned to the presence of LaAlO 3 perovskite, which was more efficient in preventing coke formation and selective towards H 2 production. Moreover, the harder reducibility of Ni species present in NiAlLaO x suggested the existence of strong interactions between them and the support, which were also responsible for this sample outstanding performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Different types of cobalt-based mixed oxide catalysts (20 wt%Co/MgO, 5 wt%Cu-20 wt% Co/MgO, 20 wt%Co/50%MgO–50%Al 2 O 3) were synthesized by the co-precipitation method and applied for hydrogen production from glycerol steam reforming. The catalysts were characterized using X-ray diffraction (XRD), H 2 -Temperature-programmed reduction (H 2 -TPR), CO 2 -Temperature Programmed desorption, CO-Chemisorption, and CHN techniques. The H 2 -TPR analysis showed the reducibility of cobalt-oxide (5Cu20CM; 5 wt%Cu-20 wt% Co/MgO) was enhanced by the copper, and reduction profiles of cobalt oxide shifted to a lower temperature (<450 °C). Among the catalysts, 5Cu20CM showed a maximum yield of hydrogen (74.6%) with 100% conversion of glycerol to the gaseous phase. The superior catalytic performance of 5Cu20CM for glycerol conversion was attributed to the smaller particle size (7 nm), higher dispersion of cobalt (35.0%), and the higher surface area (56 m2/g) of cobalt metal. Furthermore, Raman spectroscopy of the spent catalysts confirmed that the copper promoted cobalt-magnesium catalyst suppressed the carbon formation, consequently, 5Cu20CM catalyst showed a stable performance up to 30 h. • Co-based catalysts by coprecipitation method were used for glycerol steam reforming. • The addition of pure MgO is encouraged to obtain stable hydrogen yield. • The 5 wt% Cu- 20 wt%Co/MgO reported the highest yield of hydrogen as 74.6%. • Cu addition suppressed coke formation due to smaller particles of Co. [ABSTRACT FROM AUTHOR]

CeO2 nanosphere-supported nickel catalysts were prepared by the wetness impregnation method and employed for hydrogen production from glycerol steam reforming. The dried catalyst precursors were either reduced by H2 after thermal calcination or reduced by H2 directly without calcination. The catalysts that were reduced by H2 without calcination achieved a 95% glycerol conversion at a reaction temperature of only 475 °C, and the catalytic stability was up to 35 h. However, the reaction temperature required of catalysts reduced by H2 with calcination was 500 °C, and the catalysts was rapidly inactivated after 25 h of reaction. A series of physicochemical characterization revealed that direct H2 reduction without calcination enhanced the concentration of oxygen vacancies. Thus, the nickel dispersion was improved, the nickel nanoparticle size was reduced, and the reduction of nickel was increased. Moreover, the high concentration of oxygen vacancy not only contributed to the increase of H2 yield, but also effectively reduced the amount of carbon deposition. The increased active nickel surface area and oxygen vacancies synergistically resulted in the superior catalytic performance for the catalyst that was directly reduced by H2 without calcination. The simple, direct hydrogen reduction method remarkably boosts catalytic performance. This strategy can be extended to other supports with redox properties and applied to heterogeneous catalytic reactions involving resistance to sintering and carbon deposition.

Ni-based catalysts (Ni, Ni–La 2 O 3 , and Ni–La 2 O 3 –CeO 2) on mesoporous silica supports (SBA-15 and KIT-6) were prepared by an incipient wetness impregnation and tested in glycerol steam reforming (GSR) for hydrogen-rich gas production. The catalysts were characterized by the N 2 -physisorption, TPD, X-ray diffraction (XRD), SEM-EDS, and TEM techniques. N 2 -physisorption results of calcined catalysts highlight that adding of La 2 O 3 increased surface area of the catalyst by preventing pore mouth plugging in SBA-15, which was frequently observed due to the growth of NiO crystals. A set of GSR experiments over the catalysts were performed in an up-flow continuous packed-bed reactor at 650 °C and atmospheric pressure. The highest hydrogen concentration of 62 mol% was observed with a 10%Ni–5%La 2 O 3 –5%CeO 2 /SBA-15 catalyst at a LHSV of 5.8 h−1. Adding of CeO 2 to the catalyst appeared to increase catalytic stability by facilitating the oxidative gasification of carbon formed on/near nickel active sites of Ni–La 2 O 3 –CeO 2 /SBA-15 and Ni–La 2 O 3 –CeO 2 /KIT-6 catalyst during the glycerol steam reforming reaction. Image 1 • Ni-based catalysts on mesoporous silica were prepared for GSR reaction. • Adding of La 2 O 3 to Ni/SBA-15 catalyst suppressed crystalline growth of Ni. • Adding of CeO 2 to Ni–La 2 O 3 /SBA-15 catalyst facilitate carbon removal. • 10% Ni–5%La 2 O 3 –5%CeO 2 /SBA-15 catalyst showed the highest hydrogen yield. [ABSTRACT FROM AUTHOR]

Steam reforming of glycerol was carried out using Si-based mesoporous SBA-15 catalysts. Different mesoporous catalysts- Co-SBA-15, Ni-SBA-15, Co–MgO-SBA-15, Ni–MgO-SBA-15, and Co–Ni-SBA-15 were prepared using a one-pot hydrothermal method. An incipient wetness impregnation method was used only for the bimetallic Co–Ni-SBA-15 catalyst (catalyst designated as Co–Ni-SBA-15-IMPG) to compare its activity to that prepared by the one-pot method. The catalysts were characterized using XRD, TPR, TEM, TGA-DSC, ICP-OES and N 2 adsorption-desorption analytical techniques. A high surface area in the range of 540–750 m2/g was observed depending on the catalyst composition. The glycerol steam reforming (GSR) activity of the catalysts was studied in the reaction temperature range of 450 °C–700 °C for hydrogen production. Results from the GSR studies for continuous 40 h showed that both Co–Ni-SBA-15-IMPG (impregnation) and Co–Ni-SBA-15 (one-pot) were resistant to deactivation, and both yielded 100% glycerol conversion for the entire 40 h. 10%Co–5%Ni-SBA-15 and 10%Co–5%Ni-SBA-15-IMPG produced (70–78) % and (60–78) % H 2 selectivity, respectively. Addition of MgO to Co-SBA-15 and Ni-SBA-15 increased the activity and stability of the catalysts. The catalyst stability performance followed the trend 10%Co–5%Ni > 10%Co–5%MgO >10%Co–5%Ni-IMPG. > 15%Co > 10%Ni–5%MgO >15%Ni-SBA-15. Thermal analyses of the spent catalyst showed a substantial amount of coke deposition which could be the major factor responsible for catalysts deactivation. Bimetallic catalysts prepared by one-pot method (10%Co–5%Ni-SBA-15) and incipient wetness impregnation (10%Co–5%Ni-SBA-15-IMPG) exhibited remarkable GSR activity compared to their monometallic counterparts. The GSR activity was observed in the order: 10%Co–5%Ni-IMPG ≥ 10%Co–5%Ni > 10%Co–5%MgO >15%Co > 15%Ni > 10%Ni–5%MgO. • M-SBA-15, M-MgO-SBA-15 (M = Co, Ni) and Co–Ni-SBA-15 were prepared by one-pot method. • XRD confirmed the presence of active NiCo 2 O 4 spinel crystal phase in the catalysts. • Bimetallic catalysts were more active toward glycerol reforming at as low as 450 °C. • Cobalt exhibited better GSR activity and higher stability than nickel catalysts. • MgO addition to Ni-SBA-15 decreased carbon deposition on the catalyst by 66%. [ABSTRACT FROM AUTHOR]

In the study presented herein, the catalytic activity and stability of a Ni catalyst supported on Y 2 O 3 –ZrO 2 was examined for the first time in the glycerol steam reforming reaction and compared with a Ni/ZrO 2. The addition of Y 2 O 3 stabilized the ZrO 2 tetragonal phase, increased the O 2 storage capacity of the support and the medium strength acid sites of the catalyst, and although the Ni/Zr catalyst had a higher concentration of basic sites, the Ni/YZr presented more stable monodentate carbonates. Moreover, the Ni/YZr had substantially higher Ni surface concentration and smaller Ni particles. These properties influence the gaseous products' distribution by increasing the H 2 yield and selectivity and preventing the transformation of CO 2 to CO, by inhibiting the reverse water gas shift (RWGS) reaction from taking place. For both catalysts the main liquid products identified were allyl alcohol, acetaldehyde, acetone, acrolein, acetic acid and acetol; these were subsequently quantified. The time-on-stream experiments showed that the Ni/YZr was more stable during reaction and had a higher H 2 yield after 20 h (2.17 in comparison to 1.50 mol H 2 /mol C 3 H 8 O 3 , for the Ni/Zr). Extensive investigation of the carbon deposits showed that although lower amounts of coke were deposited on the Ni/Zr catalyst, these structures were more graphitic in nature and had fewer defects, which means they were harder to oxidize. Moreover, transmission electron microscopy (TEM) analysis showed that sintering of Ni nanoparticles during the reaction was significant for the Ni/Zr catalyst, as the mean particle diameter increased from an initial value of 48.2 to 67.9 nm, while it was almost absent on the Ni/YZr catalyst (the mean particle diameter increased from 42.1 to 47.4 nm). • Y 2 O 3 stabilizes the tetragonal ZrO 2 and improves reducibility. • Y 2 O 3 leads to higher Ni surface concentration and smaller Ni particles. • Y 2 O 3 prevents Ni sintering and forms carbon with low crystallinity. • Ni/YZr reveals increased H 2 yield, CO 2 selectivity and high H 2 /CO ratio. • Ni/YZr more resistant to deactivation in comparison with the Ni/Zr. [ABSTRACT FROM AUTHOR]

In order to improve the hydrogen production efficiency by glycerol steam reforming, a membrane-assisted fluidized bed reactor with carbon dioxide sorption is developed to enhance the reforming process. Low-temperature operation in a membrane reactor is necessary considering the thermal stability of membrane. In this work, the sorption-enhanced glycerol steam reforming process in a fluidized bed membrane reactor under the condition of low temperature is numerically investigated, where the hydrotalcite is employed as CO 2 sorbents. The impact of operating pressure on the reforming performance is further evaluated. The results demonstrate that the integration of membrane hydrogen separation and CO 2 sorption can effectively enhance the low-temperature glycerol reforming performance. The fuel conversion above 95% can be achieved under an elevated pressure. • Low-temperature glycerol reforming is investigated considering membrane stability. • Fuel conversion above 95% is achieved under high pressure condition. • Capacity of hydrotalcite as low-temperature sorbents is examined. • Concentration polarization by membrane separation in a fluidized bed is analyzed. [ABSTRACT FROM AUTHOR]

Hydrogen production from waste glycerol, mainly producible as a by-product of biodiesel synthesis, is investigated as an attractive opportunity for exploiting renewable energy sources for further applications. Glycerol steam reforming using membrane technology was modeled by taking into accounts the maim transport phenomena, thermodynamic criteria and chemical process kinetics. A sensitivity analysis of operating conditions was made for key performance metrics such as glycerol conversion, hydrogen yield and hydrogen recovery. Glycerol conversion intensifies with enhancement of operating pressure and temperature, whereas high feed molar ratio and sweep ratio have limiting effect. Hydrogen permeation and subsequently, hydrogen recovery facilitates with increasing sweep gas ratio and sweep gas temperature. Hydrogen recovery enhances from 70% to 99% with increasing temperature from 350 to 500 °C at feed molar ratio of 3. Also, hydrogen recovery improves from 50% to 71% with increasing sweep ratio from 0 to 20 at 350 °C and 1 bar. • Conversion of waste glycerol to hydrogen has been studied. • Membrane technology has been used to improve the process performance. • A detailed model has been constructed and validated to describe the process. • The impact of operating variables have been evaluated. [ABSTRACT FROM AUTHOR]

• Hybrid material, Ni/Al 2 O 3 /Li 2 CuO 2 , was synthesized by wet impregnation method. • High purity H 2 was produced via sorption-enhanced glycerol steam reforming (SEGSR). • 100 % glycerol conversion and 93 % pure H 2 production was achieved at 700 °C. • Hybrid material exhibited a remarkable adsorption capacity of 3.9 mmol CO 2 /g. • It displayed appreciable multi-cycle stabilSUPPity for 13 cycles. We investigated the production of high-purity H 2 through sorption-enhanced glycerol steam reforming (SEGSR) using lab-made bifunctional materials consisting of nickel, Al 2 O 3 , and Li 2 CuO 2. Different bifunctional materials were prepared with 10 wt % Ni loading but varying wt % of Al 2 O 3 and Li 2 CuO 2 , and their catalytic activity was evaluated in a continuous fixed-bed down-flow reactor. HM-50, which had an equal wt % of Al 2 O 3 and Li 2 CuO 2 , showed the highest performance. The conversion of glycerol and the purity of H 2 were examined with respect to temperature, feed flow rate, and steam-to-carbon molar ratio (S/C). At the optimum reaction conditions (temperature = 700 °C, feed flow rate = 0.5 ml/min, and S/C = 6), glycerol conversion and H 2 purity were 100 % and 94 mol %, respectively. The adsorption capacity of HM-50 was found to be 3.9 mmol CO 2 per gram. With a breakthrough time of 15 min, the substance was stable for 13 adsorption-desorption cycles. The material was regenerated by substituting the feed with a N 2 and steam mixture heated to 700 °C for 30 min. A most likely reaction mechanism suggested that glycerol was catalytically converted to acetaldehyde, which was then quickly decomposed to CO and CH 4. We are the first research team to investigate the use of Li 2 CuO 2 in any steam reforming process. Glycerol steam reforming (GSR) is an exothermic reaction where glycerol is catalytically converted to H 2 and CO 2. High purity H 2 is obtained by downstream removal of CO 2 in the 2nd step. C 3 H 8 O 3 + 3H 2 O ⇌ 3CO 2 + 7H 2 , ΔHo 298K = + 128 kJ mol–1 Sorption-enhanced glycerol steam reforming (SEGSR): Lab-made hybrid material, Ni/Al 2 O 3 /Li 2 CuO 2 simultaneously catalyzes the steam reforming of glycerol and in-situ chemisorbs CO 2 to give high purity H 2 in a single step. It eliminates downstream processing and reduces the cost. [Display omitted] [ABSTRACT FROM AUTHOR]

Steam reforming of glycerol to produce hydrogen is considered to be the very promising strategy to generate clean and renewable energy. The incipient-wetness impregnation method was used to load Ni on the reducible carrier TiO2 (P25). In the process of catalyst preparation, the interaction and electronic effect between metal Ni and support TiO2 were adjusted by changing the calcination temperature, and then the activity and hydrogen production of glycerol steam reforming reaction (GSR) was explored. A series of modern characterizations including XRD, UV-vis DRS, BET, XPS, NH3-TPD, H2-TPR, TG, and Raman have been applied to systematically characterize the catalysts. The characterization results showed that the calcination temperature can contribute to varying degrees of influences on the acidity and basicity of the Ni/TiO2 catalyst, the specific surface area, together with the interaction force between Ni and the support. When the Ni/TiO2 catalyst was calcined at 600 °C, the Ni species can be produced in the form of granular NiTiO3 spinel. Consequently, due to the moderate metal–support interaction and electronic activity formed between the Ni species and the reducible support TiO2 in the NiO/Ti-600C catalyst, the granular NiTiO3 spinel can be reduced to a smaller Ni0 at a lower temperature, and thus to exhibit the best catalytic performance.

Nickel based catalysts were prepared by incipient wetness impregnation method using CeO 2 with morphologies of nanorods and nanoparticles as supports. Nickel nitrate in catalyst precursors was decomposed either by thermal calcination or glow discharge plasma treatment. The effects of plasma treatment and CeO 2 morphologies on the catalytic performance of glycerol steam reforming were investigated. Characterization and catalytic results showed that Ni/rCeO 2 -P catalyst, supporting on CeO 2 nanorods and treated by glow discharge plasma, had higher nickel dispersion, higher nickel reducibility, more acid sites as well as more amounts of surface oxygen vacancies and Ce3+. These features were beneficial for the formation of more active Ni0 sites, the stabilization of nickel particles from sintering, and hindering the coke deposition during reaction. This catalyst thus showed the best catalytic performance in glycerol steam reforming reaction, including high activity, high selectivity to hydrogen, and good stability in 8 h of reaction. Unlabelled Image • Glow discharge plasma technique was applied to decompose the Ni-based precursor. • Effects of CeO 2 morphology and plasma treatment were investigated. • Plasma treatment significant enhanced both the nickel dispersion and reducibility. • Plasma treatment improved the amount of surface Ce3+ and oxygen vacancies. • Plasma treated Ni/CeO 2 nanorods catalyst showed the best catalytic performance. [ABSTRACT FROM AUTHOR]

In this work, a three-dimensional simulation of the sorption-enhanced glycerol reforming (SEGR) process for hydrogen production in a membrane-assisted fluidized bed reactor is carried out by means of the multi-fluid model coupling with chemical kinetics model and membrane separation model. The mutual interaction mechanism of the two enhancing methods including membrane hydrogen separation and carbon dioxide sorption is revealed. The results indicate that the carbon dioxide sorption can hinder the concentration polarization resistance and improve the hydrogen permeation rate while the scope of densified zones is enlarged. Meanwhile, the increase of hydrogen separation degree is also beneficial to the carbon dioxide sorption performance. In addition, the utilization of bi-functional sorbent-catalyst particles can further promote the sorption-enhanced reforming process compared to the conventional two-pellet design. • SEGR process in a membrane-assisted fluidized bed reactor is simulated. • Impact of carbon dioxide sorption on concentration polarization is examined. • Capability of bi-functional catalyst-sorbent particles is evaluated. • Effect of membrane parameters on SEGR process is analyzed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Glow discharge plasma technique was applied to decompose the Ni-based precursor. • Plasma treatment maintained the high nickel dispersion during reaction. • Plasma treatment remarkably decreased the coke-deposition rate. • Catalyst prepared by nickel chloride tended to form carbon more in amorphous form. Abstract CeO 2 nanorods supported nickel catalysts were prepared by wetness impregnation method, using nickel nitrate and nickel chloride as nickel sources. The dried catalyst precursors were decomposed either by thermal calcination or glow discharge plasma technique. The effects of precursor decomposition methods and nickel sources on the catalytic performance of glycerol steam reforming were then investigated. Characterization and catalytic results showed that glow discharge plasma treatment instead of thermal calcination enhanced the nickel dispersion, improved the Ni-Ce interaction and led to the formation of Ni-O-Ce composite, which could both enhance the H 2 selectivity and restrain the coke deposition during reaction. Thus, no deactivation was observed on the two plasma treated catalysts throughout the tests. Nickel source may influence both rate of particle sintering and carbonaceous deposition during reaction; fast nickel sintering but slower coke deposition was found on the catalysts prepared from nickel chloride, and coke deposition was more detrimental to active sites decrease than nickel sintering. [ABSTRACT FROM AUTHOR]

Highlights • Performing integrated analysis of glycerol steam reforming for H 2 production. • Obtaining ranges of unit H 2 production cost and B/C ratio from uncertainty analysis. • Economic viability for glycerol steam reforming in distributed H 2 refueling station. Abstract In this paper, we report an integrated techno-economic analysis of glycerol steam reforming (GSR) targeting distributed H 2 refueling stations for a H 2 production capacity of 700 m3 h−1. A process simulation based on mass and energy balances was performed to identify the product yield at effect of temperature and water/glycerol ratio. The results show that temperature of 900 K and a water/glycerol ratio of 9 are optimal to techno-economically operate a GSR process. An economic analysis using itemized cost estimation, sensitivity analysis (SA), and profitability analysis (PA) was carried out to investigate the economic feasibility of GSR for distributed H 2 refueling stations. The unit H 2 production cost was 4.46 $ kgH 2 −1 at the optimum conditions identified in the process simulation, and the most influential economic key factor was the reactant from the SA. Meaningful economic indicators such as net present value, discounted payback period, present value ratio, and rate of return on investment were obtained from the PA through a discounted cash flow diagram. Moreover, a cumulative probability analysis based on an uncertainty analysis using a Monte-Carlo simulation method was applied to unit H 2 production cost and B/C ratio calculations to quantify the risk of a proposed GSR process as premature technology providing crucial guidelines to decision-makers. [ABSTRACT FROM AUTHOR]

Abstract In the present paper, a CFD modeling of palladium membrane reactor, in which hydrogen produced through glycerol steam reforming, is presented. A comprehensive and precise kinetic and permeation model was used. On the basis of the equations and assumptions, an excellent agreement between model prediction and experimental data was achieved. Pressure, velocity and concentration distribution of various component within the Membrane Reactor (MR) were predicted. Moreover, the performance of both a Traditional Reactor (TR) and a MR was compared in various condition. The effects of some operating conditions such as temperature, pressure, feed flow rate and flow pattern on the glycerol conversion, hydrogen recovery and CO selectivity were evaluated. The most effective parameter was pressure: increasing it from 1 to 10 bar in co-current MR, the glycerol conversion, H2 recovery and CO selectivity were shifted from 46%, 17% and 6.6%–81%, 56% and 0.8%, respectively. The CFD model indicates that the performance of glycerol steam reforming improves when MR is used instead of TR. At various operating conditions the glycerol convertion enhanced 10–64% and CO selectivity reduced 7.5–99.0% in the MR when compared with the TR. Graphical abstract Image 1 Highlights • The Glycerol steam reforming was modeled in the Pd Ag membrane reactor (MR). • The CFD based model was applied for evaluation of Pd Ag MR performance during glycerol steam reforming. • The Pd Ag MR performance was investigated by varying the operating parameters for hydrogen production. [ABSTRACT FROM AUTHOR]

Abstract A comparative study of the GSR performance for Ni/CaO-MgO-Al 2 O 3 and Ni/Al 2 O 3 catalysts is reported. Catalysts were synthesized applying the wet impregnation method at a constant metal loading (8 wt %). Synthesized samples were characterized by N 2 adsorption/desorption, ICP, BET, XRD, NH 3 -TPD, CO 2 -TPD, H 2 -TPR, XPS, TEM, STEM-HAADF and EDS. The carbon deposited on their surface under reaction conditions was characterized by TPO, Raman and TEM. It was proven that the use of CaO-MgO as alumina modifiers leads to smaller nickel species crystallite size, increased basicity and surface amount of Ni0 phase. Thus, it increases the conversion to gaseous products favoring H 2 and CO 2 production to the detriment of CO formation, by enhancing the water gas-shift (WGS) reaction. No liquid products were produced by the Ni/modAl catalyst over 550 °C, whereas time on stream results confirmed that deactivation can be prevented, as apart from decreasing the amount of coke deposition the nature of carbon was altered towards less graphitic and more defective structures. Highlights • Ni on CaO-MgO-Al 2 O 3 highly selective and stable for H 2 production via GSR reaction. • Presence of CaO and MgO leads to significantly increased amount of Ni0 active phase. • Higher conversion to gaseous products for Ni/modAl by favoring H 2 and CO 2 production. • No liquid products produced by Ni/modAl over 550 °C, 100 °C lower than Ni/Al. • Less amount and more defective structures of deposited coke for the modified sample. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • SiO 2 stabilizes monoclinic ZrO 2 , restricts sintering, strengthens Ni-support interaction. • Ni/SiZr reveals increased H 2 yield (close to thermodynamic) and CO 2 selectivity. • High H 2 /CO ratio and a negligible CO/CO 2 can be achieved by the Ni/SiZr. • At 750 °C acetone, acetaldehyde main products for Ni/Zr and allyl alcohol for Ni/SiZr. • Ni/SiZr (half of carbon) more resistant to deactivation in comparison with the Ni/Zr. Abstract The glycerol steam reforming (GSR) reaction for H 2 production was studied comparing the performance of Ni supported on ZrO 2 and SiO 2 -ZrO 2 catalysts. The surface and bulk properties were determined by ICP, BET, XRD, TPD, TPR, TPO, XPS, SEM and STEM-HAADF. It was suggested that the addition of SiO 2 stabilizes the ZrO 2 monoclinic structure, restricts the sintering of nickel particles and strengthens the interaction between Ni2+ species and support. It also removes the weak acidic sites and increases the amount of the strong acidic sites, whereas it decreases the amount of the basic sites. Furthermore, it influences the gaseous products' distribution by increasing H 2 yield and not favouring the transformation of CO 2 in CO. Thus, a high H 2 /CO ratio can be achieved accompanying by negligible value for CO/CO 2. From the liquid products quantitative analysis, it was suggested that acetone and acetaldehyde were the main products for the Ni/Zr catalyst, for 750 °C, whereas for the Ni/SiZr catalyst allyl alcohol was the only liquid product for the same temperature. It was also concluded that the Ni/SiZr sample seems to be more resistant to deactivation however, for both catalysts a substantial amount of carbon exists on the catalytic surface in the shape of carbon nanotubes and amorphous carbon. [ABSTRACT FROM AUTHOR]

Flame spray pyrolysis was used to produce nanosized Ni-based catalysts starting from different mixed oxides. LaNiO3 and CeNiO3 were used as base materials and the formulation was varied by mixing them or incorporating variable amounts of ZrO2 or SrO during the synthesis. The catalysts were tested for the steam reforming of glycerol. One of the key problems for this application is the resistance to deactivation by sintering and coking, which may be increased by (1) improving Ni dispersion through the production of a Ni-La or Ni-Ce mixed oxide precursor, and then reduced; (2) using an oxide as ZrO2, which established a strong interaction with Ni and possesses high thermal resistance; (3) decreasing the surface acidity of ZrO2 through a basic promoter/support, such as La2O3; and (4) adding a promoter/support with very high oxygen mobility such as CeO2. A further key feature is the use of a high temperature synthesis, such as flame spray pyrolysis, to improve the overall thermal resistance of the oxides. These strategies proved effective to obtain active and stable catalysts at least for 20 h on stream with very limited coke formation.

The current paper presents an innovative model for a polygonation purpose based on glycerol steam reforming for the first time. This model uses an innovative thermal integration, wherein the flue gas leaving the reforming unit as well as the output syngas are considered for producing electricity, low-pressure steam, chilled water, freshwater, and methanol. This model consists of glycerol steam reforming unit, transcritical-carbon dioxide (CO 2) cycle, chilled water unit, water desalination unit, steam power plant, and methanol production unit. This system was simulated using the Aspen HYSYS program, and its performance under steady-state operating circumstances was assessed using a thorough 4E analysis. The total exergy and energy efficiency are found to be 68.81 % and 35.57 %, respectively, according to the exergetic and energetic analyses. Moreover, the total rate of exergy destruction is measured at 202841 kW. Considering the environmental aspect, the system exhibits a total CO 2 emission of 154,306.82 kg/h and a CO 2 footprint of 0.1943 kg CO2/kgMeOH. Besides, the economic analysis exhibits that the methanol production unit has the maximum capital cost (38,298,289 $) among the equipment, contributing to 82 % of the total value. In addition, the production cost of electricity, low-pressure steam, chilled water, freshwater, and methanol is obtained at 0.088 $/kWh, 0.4 $/kg steam , 0.026 $/kg CW , 0.12 $/kg FW , and 0.214 $/kg MeOH , respectively. • Glycerol steam reforming toward a novel polygeneration arrangement • Combined power cycles, desalination, chiller, and methanol synthesis are integrated. • Use of Aspen Hysys for simulation along with a coherent 4E study • Overall exergy efficiency and methanol cost are 68.81 % and 0.214 $ kg MeOH , respectively. • CO 2 emission and CO 2 footprint are 154306.82 kg h and 0.1943 kg CO 2 MJ , respectively. [ABSTRACT FROM AUTHOR]

A promising route for the energetic valorisation of the main by-product of the biodiesel industry is the steam reforming of glycerol, as it can theoretically produce seven moles of H2 for every mole of C3H8O3. In the work presented herein, CeO2–Al2O3 was used as supporting material for Ir, Pd and Pt catalysts, which were prepared using the incipient wetness impregnation technique and characterized by employing N2 adsorption–desorption, X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR), Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The catalytic experiments aimed at identifying the effect of temperature on the total conversion of glycerol, on the conversion of glycerol to gaseous products, the selectivity towards the gaseous products (H2, CO2, CO, CH4) and the determination of the H2/CO and CO/CO2 molar ratios. The main liquid effluents produced during the reaction were quantified. The results revealed that the Pt/CeAl catalyst was more selective towards H2, which can be related to its increased number of Brønsted acid sites, which improved the hydrogenolysis and dehydrogenation–dehydration of condensable intermediates. The time-on-stream experiments, undertaken at low Water Glycerol Feed Ratios (WGFR), showed gradual deactivation for all catalysts. This is likely due to the dehydration reaction, which leads to the formation of unsaturated hydrocarbon species and eventually to carbon deposition. The weak metal–support interaction shown for the Ir/CeAl catalyst also led to pronounced sintering of the metallic particles.

Abstract The attapulgite supported transition metals (Ni, Cu, Co or Fe) catalysts were prepared by precipitation method at constant loading (10 wt%) and investigated in the glycerol steam reforming reaction for H 2 production under 400–750 °C, water/glycerol (W/G) = 3, N 2 flow ratio = 0.16 L/min and WHSV = 6.46 h−1. The as-prepared catalysts were characterized by N 2 adsorption-desorption, XRD, H 2 -TPR and TEM-EDS. The results shown different active metals presented various crystalline sizes and reduction properties. The experimental results revealed Ni/ATP and Co/ATP catalysts had more active for glycerol steam reforming than Cu/ATP and Fe/ATP catalysts, due to the fact that active metal Ni and Co have superior capacity to promote the necessary C C rupture and facilitate the water gas shift reaction. In addition, the results revealed that CH 4 production was favored at low temperatures while CO production was presented at high temperatures, which were induced by the different reaction networks over catalysts. In addition, the stability test shown all catalysts had different various degrees of inactivation, resulting from the sintering of active metals and carbon deposition. The characterizations of XRD, TEM and TG-DTG for spent catalysts revealed the smallest amount of carbon deposited for Cu/ATP, which was attributed to the lowest Cu particle size. Additionally, two different types of carbon was found, namely filamentous carbon for Ni and Co/ATP and encapsulating carbon for Cu and Fe/ATP. Highlights • M/ATP (M = Ni, Cu, Co and Fe) catalysts were prepared by precipitation method. • The catalytic performance of all catalysts was investigated in GSR reaction. • Ni/ATP and Co/ATP presented the higher glycerol conversion and H 2 yield. • Active metals of Ni and Co revealed the superior C C breakage and enhanced WGSR. • The deactivation mechanism is encapsulating carbon blocks active mental sites. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen production via the steam reforming of glycerol, the main by-product of biodiesel production, and the pyrolysis/gasification route of biomass are two processes that have drawn considerable attention by the scientific community due to their potential in reducing our dependence on fossil based sources and in mitigating the effects of greenhouses gases on our planet. However, the commercial exploitation of the processes depends on the development of cheap, active and stable catalysts. In the present review, the key literature on the glycerol and phenol steam reforming reactions is presented and discussed. The impact of crucial variables for both the reactions at hand are discussed, such as active metal nature, metal loading, support, reaction temperature, method of preparation, poisoning resistance and coking tolerance. For catalytic systems design purposes the aspect of how the catalyst physicochemical characteristics affect the catalytic performance is addressed. Particular attention is given at the issue of coke resistance of the catalysts due to its detrimental effect for the reactions at hand. Natural materials, such as calcites, dolomites and olivines, utilized for the phenol steam reforming reaction are discussed. Highlights • SR of OH-containing molecules is a promising technology for H 2 -rich gas production. • Poisoning resistance and coking tolerance are critical for phenol and glycerol SR. • Me0 nature, loading, support, synthesis method crucial for PhOH and GLY SR catalysts • Natural ores (e.g. olivines, dolomites) CO 2 sorption along with SR activity • Open challenge in SR is catalyst engineering towards lower susceptibility to coke. [ABSTRACT FROM AUTHOR]

Abstract Membrane hydrogen separation can effectively promote fuel conversion and hydrogen yield by means of altering chemical equilibrium of reforming reactions. In this work, the enhancing process of glycerol steam reforming via a fluidized bed membrane reactor is numerically investigated. Under the framework of the Euler-Euler method, chemical kinetic model is implemented and the reforming performance with and without membrane separation is compared. The effect of densified zones caused by membrane separation is examined. Meanwhile, the impacts of operating parameters including hydrogen partial pressure on the permeate side and fuel gas velocity on densified zones and hydrogen yield are evaluated. The results demonstrate that the excessive reduction of hydrogen partial pressure on the permeate side and the increase of feed gas velocity are detrimental to fuel conversion and hydrogen yield. Highlights • Enhancement of glycerol reforming via a fluidized bed membrane reactor is studied. • Effect of densified zones formation on reforming performance is evaluated. • Influence of operating parameters on membrane enhancing effects is investigated. [ABSTRACT FROM AUTHOR]

In order to investigate the hydrogen separation enhancing effect on glycerol steam reforming performance, the simulation is carried out via a packed bed membrane reactor, where the porous media model is employed to model the distribution of catalyst and the non-isothermal environment in the reactor is considered. The reforming performances with and without membranes are compared. The results indicate that the membrane separation can promote the hydrogen production at a low temperature. The impacts of operating parameters including catalyst load, fuel gas temperature, sweep gas velocity and sweep gas temperature on the enhancement of the reforming performance are analyzed. The results reveal that the membrane separation is very sensitive to the temperature variation under different operating conditions. It is essential to properly control the operating parameter so as to achieve the promotion of hydrogen yield with low cost of energy. [ABSTRACT FROM AUTHOR]

Monometallic Ni and bimetallic Ni-Co, Ni-Cu, and Ni-Zn catalysts supported on attapulgite (ATP) were prepared by chemical precipitation method and evaluated in the glycerol steam reforming (GSR) reaction under the following conditions W/G = 9, N 2 flow ratio = 0.16 L/min and GHSV = 9619 h −1 . The prepared calcined and/or reduced samples were characterized by ICP-OES, N 2 adsorption-desorption, XRD, TEM, FT-IR, XPS and H 2 -TPR. The analysis results showed the addition of second metals obviously decreased the crystal size and suppressed the reducibility of active metal, by improving the metal-support interaction. These were optimized characters could promote the steam reforming reaction and water-gas shift reaction (WGSR) to improve the catalytic performance. The experimental results of catalytic activity revealed the glycerol conversions and H 2 yields over bimetallic catalysts were significantly higher than those over Ni/ATP catalyst. Among them, the Ni-Cu/ATP exhibited the highest the highest glycerol conversions and H 2 yield in GSR reaction, while it had larger particle size (12.2 nm) than Ni-Co/ATP (8.6 nm) and Ni-Zn/ATP (10.3 nm), and the higher reducibility than other two bimetallic catalysts. It may be deduced that the crystal size and reducibility of catalyst all showed pivotal to impart suitable catalytic activity, while these characteristics should have an optimal proportion for obtaining the outstanding catalytic performance. The effect of temperature on catalytic performance over all catalysts was also investigated. It was found that increasing temperature was favorable for glycerol conversions and H 2 yield, while the increase rate of H 2 /CO ratio was suppressed and CO/CO 2 ratio were increased for all catalysts at high temperature range of 600–700 °C. It was attributed to that increasing temperature although improved the breakage of C C, C H, and C O bonds in glycerol, the WGSR mainly side-reaction for producing H 2 was suppressed. The long-term experiments (30 h) were also conducted over all catalysts at W/G = 9, T = 600 °C, N 2 flow ratio = 0.16 L/min and GHSV = 9619 h −1 . The results demonstrated the outstanding stability was obtained over Ni-Zn/ATP catalyst. In order to account for the causes resulted in catalyst deactivation, all spent catalysts were characterized by XRD, TEM, TPO and TG-DTG. The results shown catalyst deactivation was mainly affected by the sintering of active species and coke formation on catalyst surface. The Ni-Zn/ATP bimetallic catalyst showed the outstanding stability attributed to the excellent anti-sintering and carbon deposition, which resulted from the formation of unique metal-support interaction. [ABSTRACT FROM AUTHOR]

Crude glycerol excess as a by-product of biodiesel industry has given rise to the need to valorize glycerol, e.g. its conversion to hydrogen by steam reforming. While many studies have been made towards catalyst development and their performance, catalyst selectivity and stability continue to be issues of further investigation. In this work, ruthenium doped nickel-alumina-ceria catalyst has been studied. The catalyst was prepared by wet impregnation method. Characterization was done with BET surface area, SEM, temperature programmed reduction, temperature programmed oxidation and pulse hydrogen chemisorption techniques. Performance test experiments were carried out in a packed bed reactor with aqueous glycerol feed, in water to glycerol mole ratio 12:1, at temperatures 550 °C to 800 °C, weight hourly space velocity of 10 h − 1 and atmospheric pressure. It was found that 10Ni-1Ru/Al 2 O 3 /5CeO 2 catalyst showed superior catalytic performance and stability, compared to 10Ni/Al 2 O 3 and 10Ni/Al 2 O 3 /5CeO 2 . Hydrogen selectivity of 88.6% was obtained versus a thermodynamic value of 95.9% at 650 °C. The catalyst was also stable for 24 h on stream. From the kinetic study, overall activation energy was found to be 70.82 kJ/mol and order of reaction with respect to glycerol and steam were 0.31 and 0.52 respectively. [ABSTRACT FROM AUTHOR]

The present work investigates the catalytic potential of a Ni-promoted Fe/Mg containing metallurgical waste for sustainable hydrogen production by glycerol steam reforming (GSR). The catalyst (Ni-UGS) was prepared through solid-state impregnation of Ni into the structure of metallurgical residue. Ni incorporation led to the formation of (Ni,Mg)O solid solution, (NiFe 2 O 4 ) and/or a nickel iron mixed oxide (Ni x Fe 1-x O). GSR performed in a fixed bed reactor at T = 580 °C, P = 1 atm, steam to carbon ratio (S/C) of 3, and gas hourly space velocity (GHSV) of 20,600 cm 3 (STP) g cat −1 h −1 led to a glycerol conversion to gaseous (X g ) of 87%, H 2 yield (Y H2 ) of 79%, and H 2 /CO molar ratio of 5.5. The catalytic performance of Ni-UGS containing 11.7 wt.% Ni was found to be superior to that of an alumina supported Ni-based commercial steam reforming catalyst with higher Ni content (29.8 wt.%): X g = 86%, Y H2 = 71%, and H 2 /CO molar ratio of 4.1. A stable performance during 48 h on stream was also obtained by using the Ni-UGS catalyst. Characterization of the used catalyst confirmed the low formation rate (∼2.7 mg coke g cat −1 h −1 ) of filamentous type carbon. The promising obtained results were mainly attributed to (i) superior dispersion of Ni particles due to the formation of (Ni,Mg)O solid solution and (ii) the presence of active magnesium and iron oxide species (e.g., MgO, Fe 3 O 4, MgFe 2 O 4 and (MgO)(FeO) solid solution) in the Ni-UGS catalyst which stimulate the water gas shift reaction and coke gasification. Regeneration by an oxidative treatment of the used catalyst in air was examined and analysis of the regenerated catalyst revealed complete coke removal together with recovery of initial crystalline phases. [ABSTRACT FROM AUTHOR]

In this study, a critical comparison between two low metal (Ni) loading catalysts is presented, namely Ni/Al2O3 and Ni/AlCeO3 for the glycerol steam reforming (GSR) reaction. The surface and bulk properties of the catalysts were evaluated using a plethora of techniques, such as N2 adsorption/desorption, Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP−AES), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDX, Transmission Electron Microscopy (TEM), CO2 and NH3− Temperature Programmed Desorption (TPD), and Temperature Programmed Reduction (H2−TPR). Carbon deposited on the catalyst’s surfaces was probed using Temperature Programmed Oxidation (TPO), SEM, and TEM. It is demonstrated that Ce-modification of Al2O3 induces an increase of the surface basicity and Ni dispersion. These features lead to a higher conversion of glycerol to gaseous products (60% to 80%), particularly H2 and CO2, enhancement of WGS reaction, and a higher resistance to coke deposition. Allyl alcohol was found to be the main liquid product for the Ni/AlCeO3 catalyst, the production of which ceases over 700 °C. It is also highly significant that the Ni/AlCeO3 catalyst demonstrated stable values for H2 yield (2.9−2.3) and selectivity (89−81%), in addition to CO2 (75−67%) and CO (23−29%) selectivity during a (20 h) long time-on-stream study. Following the reaction, SEM/EDX and TEM analysis showed heavy coke deposition over the Ni/Al2O3 catalyst, whereas for the Ni/AlCeO3 catalyst TPO studies showed the formation of more defective coke, the latter being more easily oxidized.

The aim of the work was to investigate the influence of support on the catalytic performance of Ni catalysts for the glycerol steam reforming reaction. Nickel catalysts (8 wt%) supported on AlO, ZrO, SiO were prepared by the wet impregnation technique. The catalysts' surface and bulk properties, at their calcined, reduced and used forms, were determined by ICP, BET, XRD, NH-TPD, CO-TPD, TPR, XPS, TEM, TPO, Raman, SEM techniques. The Ni/Si sample, even if it was less active for T <600 °C, produces more gaseous products and reveals higher H yield for the whole temperature range. Ni/Zr and Ni/Si catalysts facilitate the WGS reaction, producing a gas mixture with a high H/CO molar ratio. Ni/Si after stability tests exhibits highest values for total (70%) and gaseous products (45%) glycerol conversion, Y (2.5), S (80%), S (65%), H/CO molar ratio (6.0) and lowest values for S (31%), S (3.1%), CO/CO molar ratio (0.48) among all samples. The contribution of the graphitized carbon formed on the catalysts follows the trend Ni/Si ( I / I = 1.34) < Ni/Zr ( I / I = 1.08) < Ni/Al ( I / I = 0.88) and indicates that the fraction of different carbon types depends on the catalyst's support nature. It is suggested that the type of carbon is rather more important than the amount of carbon deposited in determining stability. It is confirmed that the nature of the support affects mainly the catalytic performance of the active phase and that Ni/SiO can be considered as a promising catalyst for the glycerol steam reforming reaction. [ABSTRACT FROM AUTHOR]

Platinum supported catalysts are promising systems to a wide range of catalytic reactions involved in the hydrogen production chain. The performance of these catalysts can be enhanced by designing properly their nature, composition and structure. In this context, the addition of a second metal oxide on a catalyst composed of a well dispersed Pt phase over a high surface area support may be a powerful strategy. In this work we impregnated VO x species over Pt/Al 2 O 3 and evaluated the catalysts performance for water-gas shift (WGS) and glycerol steam reforming (GSR) reactions. The catalysts characterization showed that VO x species formed over the Pt/Al 2 O 3 surface were not deeply affected by the loading in the range of 0.5–2.0 V atoms per nm 2 and were reduced at mild temperatures. In situ measurements during catalysts activation and WGS reaction showed that VO x species presented mixed valence (V 3+ /V 4+ ) while Pt was in metallic state. The addition of vanadium increased Pt/Al 2 O 3 WGS activity; however, the improvement did not linearly correlate with the loading. Under GSR, the results indicated that the WGS step was favored by the presence of vanadium but the selectivity to H 2 decreased, which could be attributed to the parallel reactions enhanced by the acidic nature of the VO x sites. [ABSTRACT FROM AUTHOR]

Glycerol represents an emerging renewable bio-derived feedstock, which could be used as a source for producing hydrogen through steam reforming reaction. In this review, the state-of-the-art about glycerol production processes is reviewed, with particular focus on glycerol reforming reactions and on the main catalysts under development. Furthermore, the use of membrane catalytic reactors instead of conventional reactors for steam reforming is discussed. Finally, the review describes the utilization of the Pd-based membrane reactor technology, pointing out the ability of these alternative fuel processors to simultaneously extract high purity hydrogen and enhance the whole performances of the reaction system in terms of glycerol conversion and hydrogen yield. [ABSTRACT FROM AUTHOR]

Steam reforming of glycerol to produce syngas or H 2 -enriched streams is a promising route that has caught the attention of many researchers around the world. This reaction is typically carried out over metal-based catalysts supported on stable materials. Herein we report a study on the effect of Sn on the catalytic properties of Pt/C in the aforementioned reaction. A series of Pt-Sn/C catalysts with different Pt:Sn ratios were prepared and characterized using ICP, H 2 -TPR, TEM and XPS techniques, and they were tested in the glycerol steam reforming reaction at 623 K and atmospheric pressure. The best performance was observed for the catalysts with low tin contents. It was found that Sn promoted oxidation reactions and inhibited methanation. Furthermore, the presence of Sn improved the stability of the catalysts when operating at harsher conditions of temperature and glycerol concentration. A promoter effect of Sn hindering platinum sintering and the formation of coke precursors is proposed as the origin of the observed behaviour. [ABSTRACT FROM AUTHOR]

The nickel-based catalysts with shape-specific CeO 2 nanocrystals (hierarchical and spheres) and adjustable impregnation solvents were successfully synthesized. The synthesized Ni-CeO 2 catalysts were used as the model catalyst to study the structure-dependent catalytic behavior and catalytic reaction mechanism for hydrogen production from glycerol steam reforming (GSR). Ni/CeO 2 -HE with the hierarchical structure and ethanol impregnation solvent obtained the strongest metal-support interaction. Electron effects because of the strong interaction between nickel and cerium dioxide promoted the formation of reducible nickel species. High nickel reduction and nickel dispersion contributed to the maximum active nickel exposure surface area, thus Ni/CeO 2 -HE exhibited superior glycerol conversion than other catalysts. The abundant oxygen vacancies generated due to strong Ni-CeO 2 interaction facilitated the dissociation of water, thereby achieving a high yield of H 2 for Ni/CeO 2 -HE. As a comparison, Ni/CeO 2 and Ni/CeO 2 -E showed relatively poor catalytic activity due to lower exposed specific surface area and oxygen vacancy concentration. Moreover, the strong oxygen storage-release ability (CO-OSCC) promoted the oxidation of carbon deposition on Ni/CeO 2 -HE. As a result, Ni/CeO 2 -HE obtained good catalytic stability with no inactivation within 25 h. The study of the modulation role of Ni-CeO 2 interaction on catalytic behavior can provide valuable guidelines for designing efficient catalysts for GSR. [Display omitted] • Nickel-ceria interaction modulated active nickel and oxygen vacancies. • Strong nickel-ceria interaction was achieved through hierarchical structure. • Dual-active interface sites of activated nickel and oxygen vacancy synergistically enhanced catalytic performance. [ABSTRACT FROM AUTHOR]

Currently, global concerns about greenhouse gas emissions, climate changes, and over-consumption of fossil fuels have drawn human attention to the use of environmentally friendly biofuels and renewable energy sources such as biodiesel. Though biodiesel can serve as an alternative source to fossil diesel fuel, it is quite comparatively expensive to produce. This challenge can be nullified by converting glycerol, a main by-product during biodiesel synthesis, into valuable products such as hydrogen. Catalytic steam reforming of bio-glycerol is one of the potential technologies to address this requirement, which is the main subject of this research. However, this process suffers from energy supply and environmental issues due to CO 2 emissions. In an attempt to resolve this problem, an energy self-sufficient approach has been developed to provide the required energy in an eco-friendly way through the combustion of a part of the produced hydrogen. Among the impacts of this novel procedure on environmental and energy resources management, the following can be mentioned: eliminating dependence on hydrocarbon energy resources; non-greenhouse gas emissions; hydrogen production as renewable energy; and syngas production suitable for methanol and GTL synthesis processes. After sensitivity analysis and optimization of thermal efficiency, the highest hydrogen recovery (≅ 70 %) and H 2 : C O ≅ 2 can be achieved at acceptable glycerol conversion (≅ 81 %) and the lowest level of hydrogen consumption (which is 1/5 of the total produced hydrogen). Furthermore, comparing this process with other conventional hydrogen production technologies showed that it was competitive with other ones in terms of thermal efficiency (≅ 50 %) , making it highly promising for commercialization. • Feasibility study of the integration of glycerol steam reforming and catalytic hydrogen combustion processes. • Modeling and optimization of a heat-integrated membrane reactor for glycerol valorization. • Simultaneous production of sustainable syngas and pure hydrogen without any pollutants emission. • The proposed process successfully promotes energy efficiency and suppresses greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

Increased production of biodiesel in recent years has resulted in a surfeit of crude glycerol as by-product. This oversupply has triggered efforts to valorize glycerol to clean fuels such as hydrogen. In the present work, five kinds of nickel–alumina and ceria promoted nickel–alumina catalysts of different nickel and ceria loadings were prepared by wet impregnation method and tested for conversion of 30 wt.% glycerol in water. Characterization of fresh and spent catalysts were carried out with BET surface area, X-ray diffraction and scanning electron microscopy techniques. The reaction was conducted at temperatures from 550 °C to 800 °C, atmospheric pressure and weight hourly space velocity of 6.8–17 h −1 . Thermodynamic simulations were also made for theoretical estimates of conversion and selectivity and for deciding suitable reaction conditions for experiments. Among the tested catalysts, 10Ni/Al 2 O 3 /5CeO 2 was found to be the most efficient and stable for 16 h time on stream. Complete conversion of glycerol and hydrogen selectivity of 85.7% was obtained over this catalyst at 650 °C, against 95.9% thermodynamic value. Kinetic study was also done for this catalyst to get the reaction rate equation. Using power law model, the order of reaction and activation energy were determined to be 0.45 and 62.91 kJ/mol respectively. [ABSTRACT FROM AUTHOR]

In the present study, Ni/Ce-Sm-xCu (x = 5, 7, 10 at.%) catalysts were prepared using microwave radiation coupled with sol-gel and followed by wetness impregnation method for the Ni incorporation. Highly dispersed nanocrystallites of CuO and NiO on the Ce-Sm-Cu support were found. Increase of Cu content seems to facilitate the reducibility of the catalyst according to the H2 temperature-programmed reduction (H2-TPR). All the catalysts had a variety of weak, medium and strong acid/basic sites that regulate the reaction products. All the catalysts had very high XC3H8O3 for the entire temperature (400–750 °C) range; from ≈84% at 400 °C to ≈94% at 750 °C. Ni/Ce-Sm-10Cu catalyst showed the lowest XC3H8O3-gas implying the Cu content has a detrimental effect on performance, especially between 450–650 °C. In terms of H2 selectivity (SH2) and H2 yield (YH2), both appeared to vary in the following order: Ni/Ce-Sm-10Cu > Ni/Ce-Sm-7Cu > Ni/Ce-Sm-5Cu, demonstrating the high impact of Cu content. Following stability tests, all the catalysts accumulated high amounts of carbon, following the order Ni/Ce-Sm-5Cu < Ni/Ce-Sm-7Cu < Ni/Ce-Sm-10Cu (52, 65 and 79 wt.%, respectively) based on the thermogravimetric analysis (TGA) studies. Raman studies showed that the incorporation of Cu in the support matrix controls the extent of carbon graphitization deposited during the reaction at hand.