Production of CO-rich hydrogen gas from glycerol dry reforming over La-promoted Ni/Al2O3 catalyst

Dry reforming of glycerol has been carried out over alumina-supported Ni catalyst promoted with lanthanum. The catalysts were characterized using EDX, liquid N₂ adsorption, XRD technique as well as temperature-programmed reduction. Significantly, catalytic glycerol dry reforming under atmospheric pressure and at reaction temperature of 1023 K employing 3 wt%La–Ni/Al₂O₃ catalyst yielded H₂, CO and CH₄ as main gaseous products with H₂:CO < 2.0. Post-reaction, XRD analysis of used catalysts showed carbon deposition during glycerol dry reforming. Consequently, BET surface area measurement for used catalysts yielded 10–21% area reduction. Temperature-programmed gasification studies with O₂ as a gasification agent has revealed that La promotion managed to reduce carbon laydown (up to 20% improvement). In comparison, the unpromoted Ni/Al₂O₃ catalyst exhibited the highest carbon deposition (circa 33.0 wt%).     

Influence of promoting Ni-based catalysts with ruthenium in the dry reforming of polypropylene plastics for syngas production

The catalytic dry reforming of plastic waste is conducted in two-stage fixed bed reactors. The pyrolysis of polypropylene plastics occurs in the first reactor, and the pyrolyzed gases undergo a reforming reaction with carbon dioxide over a catalyst in the second reactor. The wet impregnation method is used to synthesize Ru–Ni/Al₂O₃ catalysts, which are then calcined and reduced at 800 °C. The results show that as the nickel loading increases, the syngas production increases. Promoting the catalyst with a small quantity of ruthenium significantly improves the plastic conversion into syngas. The dry reforming of polypropylene over 1Ru15Ni/Al₂O₃ catalyst resulted in the maximum syngas yield (159 mmol_syngas/g_PP) at a 2:1 plastic to catalyst ratio. The catalytic dry reforming of plastics is promising for the production of synthesis gas.     

Preparation and improvement of the mesoporous nanostructured nickel catalysts supported on magnesium aluminate for syngas production by glycerol dry reforming

Dry reforming of glycerol is an interesting method for syngas production due to its H₂/CO ≈ 1 that is suitable for FT synthesis. In this study, the performance of the Ni/MgO.Al₂O₃ catalysts with different nickel contents was investigated in glycerol dry reforming. The MgO.Al₂O₃ 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 CO₂/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.Al₂O₃ catalysts possessed the highest catalytic performance (52% of glycerol conversion at 750 °C) due to the high dispersion of nickel on the prepared carrier.     

Plasma-assisted CO2 reforming of methane over Ni-based catalysts: Promoting role of Ag and Sn secondary metals

Carbon dioxide (CO₂) and methane (CH₄) are the primary greenhouse gases (GHGs) that drive global climate change. CO₂ reforming of CH₄ or dry reforming of CH₄ (DRM) is used for the simultaneous conversion of CO₂ and CH₄ into syngas and higher hydrocarbons. In this study, DRM was investigated using Ag–Ni/Al₂O₃ packing and Sn–Ni/Al₂O₃ packing in a parallel plate dielectric barrier discharge (DBD) reactor. The performance of the DBD reactor was significantly enhanced when applying Ag–Ni/Al₂O₃ and Sn–Ni/Al₂O₃ due to the relatively high electrical conductivity of Ag and Sn as well as their anti-coke performances. Using Ag–Ni/Al₂O₃ consisting of 1.5 wt% Ag and 5 wt% Ni/Al₂O₃ as the catalyst in the DBD reactor, 19% CH₄ conversion, 21% CO₂ conversion, 60% H₂ selectivity, 81% CO selectivity, energy efficiency of 7.9% and 0.74% (by mole) coke formation were achieved. In addition, using Sn–Ni/Al₂O₃, consisting of 0.5 wt% Sn and 5 wt% Ni/Al₂O₃, 15% CH₄ conversion, 19% CO₂ conversion, 64% H₂ selectivity, 70% CO selectivity, energy efficiency of 6.0%, and 2.1% (by mole) coke formation were achieved. Sn enhanced the reactant conversions and energy efficiency, and resulted in a reduction in coke formation; these results are comparable to that achieved when using the noble metal Ag. The decrease in the formation of coke could be correlated to the increase in the CO selectivity of the catalyst. Good dispersion of the secondary metals on Ni was found to be an important factor for the observed increases in the catalyst surface area and catalytic activities. Furthermore, the stability of the catalytic reactions was investigated for 1800 min over the 0.5 wt% Ag-5 wt% Ni/Al₂O₃ and 0.5 wt% Sn-5 wt% Ni/Al₂O₃ catalysts. The results showed an increase in the reactant conversions with an increase in the reaction time.     

Effect of ZrO2 addition on Ni/Al2O3 catalyst to produce H2 from glycerol

In this work, ZrO₂ was employed as support and as Al₂O₃ modifier of Ni based catalysts due to its special interesting characteristics. The catalytic activity of these systems was studied in steam reforming of glycerol to produce H₂. As the activity results at 773 K and 873 K showed, the NiZ catalyst allowed low glycerol conversion and H₂ production when compared to the NiγA catalyst. Moreover, the NiZ catalyst was not able to reform intermediate liquid products into gaseous products.     

Catalytic gasification of food waste in supercritical water over La promoted Ni/Al2O3 catalysts for enhancing H2 production

Ni/Al₂O₃ catalyst is the one of promising catalysts for enhancing H₂ production from supercritical water gasification (SCWG) of biomass. However, due to carbon deposition, the deactivation of Ni/Al₂O₃ catalyst is still a serious issue. In this work, the effects of lanthanum (La) as promoter on the properties and catalytic performance of Ni/Al₂O₃ in SCWG of food waste were investigated. La promoted Ni/Al₂O₃ catalysts with different La loading content (3–15 wt%) were prepared via impregnation method. The catalysts were characterized using XRD, SEM, BET techniques. The SCWG experiments were carried out in a Hastelloy batch reactor in the operating temperature range of 420–480 °C, and evaluated based on H₂ production. The stability of the catalysts was assessed by the amount of carbon deposition on catalyst surface and their catalytic activity after reuse cycles. The results showed that 9 wt% La promoter is the optimal loading as Ni/9La–Al₂O₃ catalyst performed best performance with the highest H₂ yield of 8.03 mol/kg, and H₂ mole fraction of 42.46% at 480 °C. La promoted Ni/Al₂O₃ catalysts have better anti-carbon deposition properties than bare Ni/Al₂O₃ catalyst, resulting in better gasification efficiency after reuse cycles. Ni/9La–Al₂O₃ catalyst showed high catalytic activity in SCWG of food waste and had good stability as it was still active for enhancing H₂ production when used in SCWG for the third time, which indicated that La promoted Ni/Al₂O₃ catalysts are potential additive to improve the SCWG of food waste.     

Turning glycerol surplus into renewable syngas through glycerol steam reforming over a sol-gel Ni–Mo2C-Al2O3 catalyst

In this work, a sol-gel Ni–Mo₂C–Al₂O₃ 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, H₂ 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, H₂ yield, and H₂/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, N₂-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.     

Hydrogen production by steam reforming of dimethyl ether over ZnO–Al2O3 bi-functional catalyst

A series of ZnO–Al₂O₃ catalysts with various ZnO/(ZnO + Al₂O₃) molar ratios have been developed for hydrogen production by dimethyl ether (DME) steam reforming within microchannel reactor. The catalysts were characterized by N₂ adsorption-desorption, X-ray diffraction and temperature programmed desorption of NH₃. It was found that the catalytic activity was strongly dependent on the catalyst composition. The overall DME reforming rate was maximized over the catalyst with ZnO/(ZnO + Al₂O₃) molar ratio of 0.4, and the highest H₂ space time yield was 315 mol h⁻¹·kg_cat⁻¹ at 460 °C. A bi-functional mechanism involving catalytic active site coupling has been proposed to account for the phenomena observed. An optimized bi-functional DME reforming catalyst should accommodate the acid sites and methanol steam reforming sites with a proper balance to promote DME steam reforming, whereas all undesired reactions should be impeded without sacrificing activity. This work suggests that an appropriate catalyst composition is mandatory for preparing good-performance and inexpensive ZnO–Al₂O₃ catalysts for the sustainable conversion of DME into H₂-rich reformate.     

Preparation and characterization of Ni catalysts supported on pillared nanoporous bentonite powders for dry reforming reaction

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 CO₂.     

H2-rich syngas from glycerol dry reforming over Ni-based catalysts supported on alumina from aluminum dross

The performance of Ni-based catalyst supported on γ-Al₂O₃ for glycerol dry reforming (GDR) reaction was investigated in the current study. γ-Al₂O₃ was prepared from aluminum dross (AD) before use as catalyst support. Al₂O₃ was extracted using three different techniques assisted with ultrasonication: acid leaching with ammonia precipitation, acid leaching with re-precipitation of HCl, and alkaline leaching with ammonium hydrogen carbonate. The results show that extracted γ-Al₂O₃ 3 (EGA3) with the highest purity and the surface area of 267.5 m² g⁻¹ was produced from acid leaching with ammonia precipitation technique at a calcination temperature of 800 °C. A series of Ni/EGA3 (5%, 10%, 15% and 20%) catalysts were tested and it was found that the catalytic activity was increased in the order of 5%Ni/EGA3 < 10%Ni/EGA3 < 20%Ni/EGA3 < 15%Ni/EGA3. 15%Ni/EGA3 catalyst has the highest catalytic activity due to the excellent distribution of Ni on the EGA support, high specific surface area of the support and high catalyst's basicity. In addition, the strong Ni-EGA3 interaction of the 15%Ni/EGA3 catalyst suppressed the carbon formation with the catalyst having the lowest carbon deposition value of 25.51% during the GDR reaction carried out for 8 h. Studies on the GDR reaction catalytic activities revealed that 15%Ni/EGA3 achieved the maximum catalytic activity with 56.7% glycerol conversion, 44.7% H₂ yield, and 40.6% CO yield at 800 °C and CGR of 1:1. The H₂:CO ratio obtained in this study was approximately 1.2–1.5 throughout the reaction, depicting a relatively rich H₂ syngas product. Overall, the strong interaction between Ni and EGA3 ensured stable Ni particles that can mitigate carbon deposits, thereby enhancing the catalytic activity.     

Preparation and characterization of Ni based catalysts for the catalytic partial oxidation of methane: Effect of support basicity on H2/CO ratio and carbon deposition

The catalytic partial oxidation of methane (CPOM) was studied on Ni based catalysts. Catalysts were prepared by wet impregnation method and characterized by using AAS, BET, XRD, HRTEM, TPR, TPO, Raman Spectroscopy and TPSR techniques. The prepared catalysts showed nearly 95% CH₄ conversion and nearly 96% H₂ selectivity under the flow of 157,500 (L kg⁻¹ h⁻¹) with the ratio of CH₄/O₂ = 2 by using air as an oxidant at 1 atm and 800 °C. Support basicity greatly influenced the H₂/CO ratio and carbon deposition. It was found that the lowest carbon deposition occurred on Ni impregnated MgO catalyst. Considering the results, it was found that Ni/MgO catalyst with 10% Ni content would be the best catalyst amongst Ni/Al₂O₃, Ni/MgO/Al₂O₃, Ni/MgAl₂O₄ and Ni/Sorbacid for the CPOM only under more reductive conditions. Under optimum conditions, Ni/MgO showed poor performance and therefore Ni/Sorbacid would be the ideal catalyst because of its greater carbon resistance than the other catalysts.     

Hydrogen production by glycerol steam-reforming over nickel and nickel-cobalt impregnated on alumina

Hydrogen is a clean energy carrier, and its utilization will reduce environmental problems related to fossil fuels one. Biomass is an inexhaustible renewable source to generate biocompounds. Glycerol, obtained from a crescent biodiesel industry, is an abundant bio-substrate to produce hydrogen. The steam reforming of glycerol was studied employing 4Ni/Al₂O₃, 4Co–4Ni/Al₂O₃, and 12Co–4Ni/Al₂O₃ catalysts at 300, 500, and 700 °C, 1 atm, 10 h⁻¹ WHSV, 6:1 water:glycerol molar ratio (WGMR), 0.17 ml min⁻¹ glycerol solution feed flow rate and time-on-stream 8 h. The main product obtained was H₂, followed by CO₂, CO, and CH₄ in smaller proportion. Co promotes H₂ production and unfavors CO₂ generation when temperature decreases; CH₄ formation is observed at higher temperature. A low Co loading produces the largest H₂ and CO₂ amounts at the lowest temperature. A high Co loading improves H₂ production at lower temperature, but this does not occur at high temperature.     

Enhanced hydrogen production via staged catalytic gasification of rice husk using Ca(OH)2 adsorbent and Ce–Ni/γAl2O3 catalyst in a fluidized bed

Hydrogen production from rice husk was carried out via a two-stage system combining CLG (calcium looping gasification) using Ca(OH)₂ adsorbent in a bubbling fluidized bed and catalytic reforming with Ce–Ni/γAl₂O₃ catalyst in a connected fixed bed. The results show that the maximum H₂ concentration (69.16 vol%) and H₂ yield (11.86 mmol g⁻¹rice husk) are achieved at Ca/C (Ca(OH)₂ to carbon molar ratio) = 1.5, H₂O/C (H₂O to carbon molar ratio) = 1.5, T_g (gasification temperature) = 500 °C, T_c (catalytic temperature) = 800 °C. The supplementation of fresh Ca(OH)₂ at Ca/C of 0.5 during calcination helps to activate the regenerated CaO by hydration, maintaining its carbonation activity and CO₂ adsorption. Ce–Ni/γAl₂O₃ catalyst promotes water gas shift (WGS), steam methane reforming (SMR), and C₂–C₃ hydrocarbons reforming, also exhibits excellent activity stability to maintain H₂ concentration and H₂ yield above 67.21 vol% and 11.67 mmol g⁻¹_{rice husk}, respectively, during 5 lifetime tests.     

Biohydrogen production by gas phase reforming of glycerine and ethanol mixtures

In this paper the steam reforming of bioalcohols over Ni and Pt catalysts supported on bare Al₂O₃ and La₂O₃ and CeO₂-modified Al₂O₃ to produce H₂ was studied. Catalytic activity results showed that the glycerine and the intermediate liquid products may hinder the ethanol adsorption on metal active sites of the catalysts, especially at temperatures below 773 K. In fact, ethanol conversion was lower than glycerine conversion in the steam reforming reaction at low temperatures. H₂ chemisorption revealed that La₂O₃ doping of the Ni/Al₂O₃ catalyst improved the metal dispersion providing a better behaviour to the Ni/Al₂O₃-O2 catalyst towards H₂ production. In the case of Pt catalysts, the good reducibility and the H₂ spillover effect provided to the Pt/Al₂O₃-O1 catalyst the capacity to produce higher H₂ yields.     

Aqueous-phase reforming of n-BuOH over Ni/Al2O3 and Ni/CeO2 catalysts

The aqueous-phase reforming (APR) of n-butanol (n-BuOH) over Ni(20 wt%) loaded Al₂O₃ and CeO₂ catalysts has been studied in this paper. Over 100 h of run time, the Ni/Al₂O₃ catalyst showed significant deactivation compared to the Ni/CeO₂ catalyst, both in terms of production rates and the selectivity to H₂ and CO₂. The Ni/CeO₂ catalyst demonstrated higher selectivity for H₂ and CO₂, lower selectivity to alkanes, and a lower amount of C in the liquid phase compared to the Ni/Al₂O₃ sample. For the Ni/Al₂O₃ catalyst, the selectivity to CO increased with temperature, while the Ni/CeO₂ catalyst produced no CO. For the Ni/CeO₂ catalyst, the activation energies for H₂ and CO₂ production were 146 and 169 kJ mol⁻¹, while for the Ni/Al₂O₃ catalyst these activation energies were 158 and 175 kJ mol⁻¹, respectively. The difference of the active metal dispersion on Al₂O₃ and CeO₂ supports, as measured from H₂-pulse chemisorption was not significant. This indicates deposition of carbon on the catalyst as a likely cause of lower activity of the Ni/Al₂O₃ catalyst. It is unlikely that carbon would build up on the Ni/CeO₂ catalyst due to higher oxygen mobility in the Ni doped non-stoichiometric CeO₂ lattice. Based on the products formed, the proposed primary reaction pathway is the dehydrogenation of n-BuOH to butaldehyde followed by decarbonylation to propane. The propane then partially breaks down to hydrogen and carbon monoxide through steam reforming, while CO converts to CO₂ mostly through water gas shift. Ethane and methane are formed via Fischer-Tropsch reactions of CO/CO₂ with H₂.     

A highly active and stable Pt modified molybdenum carbide catalyst for steam reforming of dimethyl ether and the reaction pathway

To improve the stability of molybdenum carbide catalysts in dimethyl ether steam reforming (DSR), the inactivation mechanism and the performance of Pt modified catalyst has been investigated. The Mo₂C oxidation induced by H₂O is verified to be the main reason of catalytic deactivation. After modified with Pt, the H₂ production rate and selectivity are greatly enhanced, reaches 1605 μmol min⁻¹·g_cat⁻¹ at 350 °C, in comparison to that of the Mo₂C/Al₂O₃ catalyst. Moreover, the 2%Pt–Mo₂C/Al₂O₃ catalyst is more stable with only 20% activity loss after 50 h on stream compares to the 73% activity loss in 12 h with Mo₂C/Al₂O₃ catalyst. By means of in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the enhancement brought by Pt is ascribed to the consumption acceleration of intermediate oxygen species on catalyst surface and the decline of onset temperature of DSR reaction. It is expected that these findings can lead us to more practical molybdenum carbide catalysts in DSR.     

Hydrogen production by biomass gasification in supercritical water over Ni/γAl2O3 and Ni/CeO2-γAl2O3 catalysts

Hydrogen production by supercritical water gasification (SCWG) is a promising technology for wet biomass utilization. Ni catalyst can realize the high gasification efficiency of biomass near the critical temperature of water. In this paper, Ni/γAl₂O₃ and Ni/CeO₂-γAl₂O₃ catalysts were prepared by an impregnation method. The catalyst performance for glucose gasification in supercritical water was tested in autoclave reactor. All experiments were carried out in the autoclave at 673 K, 24.5 MPa, and the concentration of glucose was 9.09 wt.%. The catalysts before and after reaction were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET specific surface area measurements, X-ray fluorescence spectrum (XRF) and Thermo-gravimetric analyses (TGA) in order to investigate on the chemical property and catalytic mechanism. The experimental results showed that hydrogen yield and hydrogen selectivity increased sharply with addition of Ni/γAl₂O₃ and Ni/CeO₂-γAl₂O₃ catalysts. The catalytic activity and H₂ selectivity of Ni/CeO₂-γAl₂O₃ was higher than that of Ni/γ-Al₂O₃ catalyst. The results revealed that carbon deposition and coking led to the deactivation of the catalysts. Ce in the Ni/CeO₂-γAl₂O₃ catalyst had a certain role in the inhibition of carbon deposition and coking.     

Renewable hydrogen production via steam reforming of simulated bio-oil over Ni-based catalysts

The production of hydrogen via steam reforming (SR) of simulated bio-oil (glycerol, syringol, n-butanol, m-xylene, m-cresol, and furfural) was investigated over Ni/CeO₂-Al₂O₃ and Me-Ni/CeO₂-Al₂O₃ (Me = Rh, Ru) catalysts. Monometallic (Ni) and bimetallic (Rh-Ni and Ru-Ni) catalysts were prepared by the wetness impregnation technique of the CeO₂-Al₂O₃ support previously synthesized by the surfactant-assisted co-precipitation method. The as-prepared powders were systematically characterized by N₂-physisorption, XRD, H₂-TPR, and TEM measurements to analyze their structure, morphology, and reducibility properties. Experiments were performed in a continuous fixed-bed reactor at atmospheric pressure, temperature of 800 °C, steam to carbon (S/C) ratio of 5, and WHSV of 21.15 h⁻¹. Then, the temperature was decreased to 700 °C and increased afterwards to 800 °C. After the experiments TPO and TEM analysis were performed on the spent catalysts to check any evidence of catalyst deactivation. The results showed that the incorporation of noble metal (Ru or Rh) promoter positively affected the activity of the Ni/CeO₂-Al₂O₃ catalysts by enhancing the reducibility of Ni²⁺ species. Ni-based catalyst deactivated under the studied conditions, whereas Ru- and mainly Rh-promoted systems showed increased resistance to carbon deposition by favouring the gasification of adsorbed carbon species. Between all tested catalysts, the Rh-Ni/CeO₂-Al₂O₃ provided the highest H₂ yield and coking-resistance in SR of simulated bio-oil.     

Highly dispersed Fe-decorated Ni nanoparticles prepared by atomic layer deposition for dry reforming of methane

Dry reforming of methane (DRM) is a sustainable chemical process that can simultaneously transform methane and carbon dioxide, which are generally considered greenhouse gases, into syngas with H₂/CO ratio close to 1. The deposition of carbon on the active sites during long-period DRM tests will lead to severe deactivation of Ni-based catalysts. Thus, in this work, we proposed a series of uniformly dispersed Fe-decorated Ni/Al₂O₃ catalysts via atomic layer deposition (ALD) to solve this key issue. Modification with trace amounts of Fe (0.3–0.6%) had multiple effects on facilitating the CH₄ dissociation on Ni⁰, improving the low-temperature catalytic activity, moderating the carbon species and accelerating coke oxidation. The sample denoted as 0.3%Fe/Ni/Al₂O₃ exhibited almost no activity loss in the 72 h test at 650 °C. The Fe-decorated Ni/Al₂O₃ structure achieved a balance between the enhancement of CH₄ cracking and the elimination of coke. Furthermore, this advanced ALD approach of preparing uniform secondary metal nanoparticle-decorated catalysts provided guidance to other bimetallic systems, such as Pt/Ni, Mn/Ni, and Cu/Ni.     

Performance characteristics of Mo–Ni/Al2O3 catalysts in LPG oxidative steam reforming for hydrogen production

A 1:1 propane–butane mixture was used to study the effect of promoting 15 wt.% Ni/Al₂O₃ (15Ni) catalyst with small amounts of Mo (0.05, 0.1, 0.3, and 0.5 wt.%) for H₂ production during LPG oxidative steam reforming. Stability tests at 450 °C showed that lower Mo loadings (0.1 and 0.05 wt.%) had higher conversions and H₂ production rates than the non-promoted catalyst and a stable performance for the whole 18-h test period. TPO results showed that slightly more Ni sites were available for whisker formation over the Mo catalyst with 0.1 wt.% loading, the types of carbon resulting from cracking were the same on both promoted and non-promoted catalysts. Higher Mo loaded catalysts (0.3 and 0.5 wt.%) showed higher H₂ yields than the non-promoted catalysts, but lower feed-fuel conversions. XRD revealed that the loss in activity was due to oxidation of active Ni species to inactive Ni and Ni–Mo.