This paper explores the synthesis by the impregnation method using citric acid and the characterization of bimetallic Nickel-Cobalt (Ni-Co) catalysts, focusing on their application in ethanol steam reforming leveraging the demonstrated improved stability and catalytic activity observed in previous works when Co is introduced into Ni catalysts. The study aims to investigate the effects of the sequence of incorporation of Ni and Co in the catalyst support in order to optimize the catalytic performance. The results indicate that the optimal sequence for introducing Co and Ni significantly enhanced the catalytic performance in ethanol steam reforming and it was associated to a higher Ce+3/Ce+4 ratio and a stronger active site-support interactions that modified the CNT growth mechanism, preventing increasing pressure drop through the reactors. The best catalytic performance corresponded to the system, Co/Ni/MgAl2O4-CeO2, in which Co was incorporated after Ni.

Ni–Co catalysts supported on MgAl2O4–CeO2 were prepared by the sol–gel method. The solids were calcined under a reducing atmosphere to obtain Ni and/or Co active sites. The influence of the cobalt content (1, 3 and 5% w/w) was studied on bimetallic catalysts containing 8% w/w of Ni. The catalysts were characterized by TG, FTIR, SBET, AAS, XRD, TPR, TEM, EELS, EFTEM, TPO and SEM. XRD patterns of the reduced samples did not reveal the presence of Ni nor Co, nor the possible formation of a metallic alloy, which suggests that metallic crystallite sizes are smaller than the detection limit of the technique (5 nm). The catalysts were evaluated in the ethanol steam reforming reaction at 650 °C for 7 h. The results showed that the catalytic activity and the H2 selectivity are favored in bimetallic catalysts. The main reaction products were H2, CO2, CO and, to a lesser amount, CH4, being the hydrogen selectivity being greater than 80%. The best behavior in terms of the activity, stability and tolerance to carbon deposition was observed in Co3Ni/MC system. These results suggest the existence of an optimal Co/Ni ratio in the sample whit 3 wt% Co and 8 wt% Ni.

Co- and Ce-based structured catalysts deposited on FeCrAlloy monoliths have been prepared. A new two-step strategy for coating the monolith is used: (i) first, a MgAl2O4 spinel layer is generated on the FeCrAlloy substrate, and (ii) then, Co and Ce are incorporated in two different molar ratios by the conventional wet impregnation method. The spinel layer is formed from a solution of colloidal alumina and Mg(NO3)(2), with an apparent viscosity of around 3300 mPa s. The results indicate that a homogeneous spinel coating with excellent adherence is obtained after two immersions and a calcination at 700 degrees C. Both structured catalysts are active in the steam reforming of ethanol at 650 degrees C. The system with a Co/Ce molar ratio of 3.7 exhibits the best performance with a high stability. A complete ethanol conversion and a hydrogen selectivity of around 95% are obtained in two reaction cycles of 36 h each with intermediate regeneration. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Nickel catalysts supported over an amorphous carbon were obtained by a one-step synthesis method based on the mineralization of cellulosic paper impregnated with a salt of nickel. The effect of the mineralization temperature on material characteristics was studied. The characterization of samples revealed the formation of nickel nanoparticles well dispersed on the carbonaceous matrix with an average diameter near to 5 nm. The samples showed high surface areas and they retained the original fibrous paper morphology.

The surface properties of Ni/MgAl2O4 catalysts doped with Ce or Pr were analyzed by XPS after treatment in an inert and reductive atmosphere at 400 °C. The Ce‐promoted solids presented the Ce3+/Ce4+ couple on the surface even after treatment in a reductive atmosphere, H2(5%)/Ar. The promotion effect of Ce on these solids could be associated with their participation on the carbon deposition‐removal mechanism. Pr‐doped catalysts showed a very high concentration of Pr3+ under a reductive atmosphere and the redox behavior associated with the carbon removal could be partially inhibited or become slower. The size of the Ni0 particles after both an inert and a reductive atmosphere was estimated by XPS intensity ratio using the model proposed by Davis. The results obtained from the Davis model showed that an important increase occurred in Ni particle size after treatment in H2(5%)/Ar for the Pr‐promoted solids. The metal sintering under reductive atmosphere could be the reason for the higher loss of activity of the Pr‐doped solids under reforming conditions. Copyright © 2014 John Wiley & Sons, Ltd.

Ni catalysts supported on ZnxMg1-xAl2O4 spinel oxide have been prepared by the wet impregnation method with 8 wt.% Ni. The samples were characterized by XRD, BET area, TPR, CO2-TPD, SEM-EDX and TPO and tested in the ethanol steam reforming reaction.The XRD patterns of Ni catalysts supported on ZnxMg1-xAl2O4 with x = 1 or 0.5 revealed a highly crystalline spinel phase (ZnAl2O4 type) and different size particles of NiO center dot MgAl2O4 with a poorer crystallinity and NiO were observed for the catalyst supported with x = 0. The presence of Mg into the support composition decreased the Ni2+ reducibility and increased the basicity and the specific surface area, allowing a high dispersion of metallic particles and an improved resistance to carbon deposition in the ethanol steam reforming reaction. Under the experimental conditions used in this work. Ni/MgAl2O4 was the most active catalyst but showed deactivation by graphitic carbon deposition. (C) 2013 Elsevier B.V. All rights reserved.

Hydrogen production by ethanol steam reforming was studied using Ni catalysts supported over MgAl2O4 doped with Ce or Pr. Ni/MgAl2O4–CeO2 catalyst obtained from nickel nitrate impregnation was selected as the best one (final steady conversion = 95.8 %, carbon formation = 0.4 wt% and activity decay = 6.6 %) under the experimental conditions used in this work.

The hydrogen production from ethanol steam reforming has been studied over Ni/ZnAl2O4-CeO2 catalysts. The influence of calcination atmosphere and nature of catalytic precursor was analyzed. The impregnation of Ni was carried out from two different nickel salts: nitrate (Nt) and acetate (Ac). The catalysts were obtained from the precursor calcination under reductive and oxidative atmospheres. The catalysts obtained from nitrate salt impregnation were the most carbon resistance measured as mmolC/mol reacted C2H5OH, and those obtained under a reductive atmosphere were the most stable, as evidenced by smaller activity losses. The Ni(Nt)/ZnAl2O4-CeO2 obtained under reductive atmosphere was the most active (steady state ethanol conversion = 88%) and stable (activity loss = 14%) under mild reforming conditions (7.8% C2H5OH inlet concentration. H2O:C2H5OH molar ratio = 4.9, reaction temperature = 650 degrees C and W/F= 49 g min mol(C2H5OH-1)). The hydrogen selectivity was 49% and the main C-containing products were CO2, CO and C2H4O. (C) 2011 Elsevier B.V. All rights reserved.

MgAl2O4 spinel oxide-supported Ni catalysts modified with Pr have been prepared by wet impregnation method with 8wt.% Ni and variable loadings of Pr (0–7wt.%). The samples were characterized by ICP, BET, XRD, TPR, SEM, Raman and TG-TPO and they were tested in ethanol steam reforming reaction.

Nickel catalysts supported over ZnAl2O4 modified by Ce or/and Zr addition were studied in the steam reforming of ethanol under more severe reaction conditions such as a lower extent of feed dilution and lower space velocities. The catalysts were stable at 650 C during 35 h in time on stream. The main reaction products were H-2, CO2, CO, C2H4O and small amounts of CH4 and C2H4. The catalyst supported over CeO2-ZnAl2O4 was the most active and showed the highest hydrogen selectivity. The addition of ZrO2 decreased the activity and favored the CO production. The lowest degree of Ni2+ reduction over Ni/ZAZr could explain the worst performance of this system. Otherwise, the highest Ni2+ dispersion and the high oxygen mobility from ceria or from Ni-Ce boundary allowed a higher residual activity and an improved coking resistance. (C) 2010 Elsevier B.V. All rights reserved.

Ethanol steam reforming was studied over CuCoZnAl oxide with the addition of potassium. The catalyst was prepared by the coprecipitation method and characterized by X-ray diffraction, thermogravimetry, Raman spectroscopy, temperature programmed reduction, BET specific surface area and SEM-EDAX. The influence of reaction temperature was examined between 400 and 600 °C with a H2O/C2H5OH molar ratio of 3.8. At 600 °C, the catalyst was very active with an ethanol conversion of 100%. The main products were CO2 and CO and minor amounts of CH4. The hydrogen yield was 5.2 mol of H2 per mol of ethanol, which means a high hydrogen selectivity (87%). Stable activity and selectivity were obtained at 600 °C which could be attributed to the removing of carbonaceous deposits.