Search Results (10)

The mixed oxides of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and Ni-Ba-Ca/ZrO₂ were prepared using the co-precipitation method at a pH of precisely 8.3. The catalytic mixed oxides of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and Ni-Ba-Ca/ZrO₂ were characterized using x-ray diffraction XRD, Brunauer Emmett Teller (BET), scanning electron microscopy (SEM), and metal dispersion for the screening of phase purity, surface area, and morphology. The mixed oxides are subjected to CO₂-TPD to quantify the basicity of every composition. The mixed oxide catalysts of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and Ni-Ba-Ca/ZrO₂ were screened for oxythermal reforming of CH₄ with CO₂ in a fixed bed tubular reactor at 800 °C. Among all catalysts, the Ba- and Ca- loaded Ni-Ba-Ca/ZrO₂ showed high conversion by the decomposition of methane and CO₂ disproportionation throughout the time on stream of 29 h. The high activity with stability led to less coke formation over Ni-Ba-Ca/ZrO₂ over the surface. The stable syngas production with an active catalyst bed contributed to the improved bimetallic synergy. The high surface basicity of Ni-Ba-Ca/ZrO₂ may keep actively gasifying the formed soot and allow for further stable reforming reactions. Full article

The aim of this work is the development of a structured catalyst for the dry reforming of biogas to be used as a pre–reformer in the indirect internal reforming configuration (IIR) of solid oxide fuel cells (SOFCs). The structured catalyst is based on NiCrAl foams coated with ruthenium (nominal loading 3.0 wt%) supported on a CaZr_0.85Sm_0.15O_3−δ (CZS) perovskite oxide. The powder is produced by solution combustion synthesis and deposited on metallic foams by the wash–coating method. Catalytic tests for the dry reforming of methane (DRM) reaction are carried out at 850 °C, 700 °C and 550 °C for an overall 50 h with CH₄/CO₂ = 1 and p = 1.3 bar at different gas hourly space velocities (GHSVs). The final goal is a proof–of–concept: a laboratory validation of an IIR–SOFC fed by biogas. The carbon amount on spent structured catalysts is evaluated by thermogravimetric analysis and microstructural/compositional investigation. Full article

H₂ production can be used as a clean and renewable energy source for various applications, including fuel cells, internal combustion engines, and chemical production. Using nickel-based catalysts for steam reforming biomass tar presents challenges related to catalyst deactivation, poisoning, heterogeneous composition, high process temperatures, and gas impurities. To overcome these challenges, adopting a nickel-based catalyst with selected oxide support and MgO and CaO promoter is a promising approach for improving the efficiency and sustainability of steam reforming for hydrogen production. The majority of studies conducted to date have focused on the steam reforming of particular tar compounds, most commonly benzene, phenol, toluene, or naphthalene, over a range of support catalysts. However, the actual biomass tar composition is complex, and each component impacts how well steam reforming works. In this research, a multi-compound biomass tar model including phenol, toluene, naphthalene, and pyrene underwent a steam reforming process. Various types with 10 wt.% of nickel-based catalysts were generated by the co-impregnation technique, which included 90 wt.% different oxide supports (Al₂O₃, La₂O₃, and ZrO₂) and 10 wt.% of combination alkaline oxide earth promoters (MgO and CaO). Thermogravimetric analysis, Brunauer–Emmett–Teller (BET) method, N₂ physisorption, temperature-programmed reduction (H₂-TPR), temperature-programmed desorption (CO₂-TPD), and X-ray diffraction (XRD) of ni-based catalyst characterized physiochemical properties of the prepared catalyst. The reaction temperature used for steam reforming was 800 °C, an S/C ratio of 1, and a GHSV of 13,500 h⁻¹. Ni/La₂O₃/MgO/CaO (NiLaMgCa) produced the most carbon to-gas conversion (86.27 mol%) and H₂ yield (51.58 mol%) after 5 h of reaction compared to other catalysts tested in this study. Additionally, the filamentous carbon coke deposited on the spent catalyst of NiLaMgCa does not impact the catalyst activity. NiLaMgCa was the best catalyst compared to other catalysts investigated, exhibiting a stable and high catalytic performance in the steam reforming of gasified biomass tar. In conclusion, this study presents a novel approach by adding a combination of MgO and CaO promoters to a ni-based catalyst with various oxide supports, strengthening the metal-support interaction and improving the acid-base balance of the catalyst surface. The mesoporous structure and active phase (metallic Ni) were successfully developed. This can lead to an increase in the conversion of tar to H₂ yield gas and a decrease in the production of undesired byproducts, such as CH₄ and CO. Full article

The existence of acid gas and tar in syngas of municipal solid waste gasification limits its downstream utilization as a clean energy source. Here, we investigated the catalytic removal of HCl and tar. The key parameters affecting the catalytic reaction, including space velocity, temperature, the amounts of active metals in the catalyst and the carrier material, were studied, targeting optimized operating conditions for enhanced syngas purification. The morphology, mineral phases, surface area and pore size before and after the reaction were investigated to understand the mechanism to dominate the reaction. The results showed that the removal rate of CaO adsorbent and HCl reached 96% at 400 °C. When the space velocity ratio was 1.0 and the temperature was 400 °C, HCl removal (97%) by NaAlO₂ was even better. Nevertheless, clogging was observed for NaAlO₂ via the BET test after reaction to jeopardize its durability. A level of 25% Ni doping on Zr_1-x(Ce_x)O₂ support provides high stability for tar removal. This is because the Zr_1-x(Ce_x)O₂ carrier has higher carbon deposition resistivity than the Al₂O₃ carrier. The EDX results confirmed that a large amount of C (79.3%) was accumulated on the commercial catalyst surface supported by Al₂O₃ (25% Ni-based). As for the temperature, a temperature higher than 800 °C could not enhance the efficiency of tar removal, likely due to catalyst deactivation. Carbon deposition and agglomeration are the two main causes of catalyst deactivation. At 800 °C, 25% Ni-based synthetic catalyst can convert 48.5 ± 19.4% tar to low molecular weight organic compounds. By contrast, such a conversion rate under the same temperature only accounted for 5.0 ± 6.8% based on a commercial catalyst. These insights point to the important role of catalyst support materials. Full article

The present work is focused on the fabrication of NiO-ZrO₂/FTO and NiO-Y₂O₃/FTO thin films via a simple dip-coating method. The films are deposited from precursor solutions of Ni(CH₃COO)₂·2H₂O, Zr(CH₃COO)₄, Y(CH₃COO)₃·H₂O in methanol. The synthesized films, after proper characterization, are employed for electrochemical oxidation of methanol. The analytical techniques such as X-ray diffraction (XRD), Raman, and Infrared (IR) spectroscopy reveal the successful formation of crystalline thin films of mixed metal oxide without any additional impurities. Further, X-ray photoelectron spectroscopy (XPS) results, confirm the composition and oxidation state of all the elements present in thin films. The field emission scanning electron microscopy (FESEM) further aided to identify the uniformity and porous nature of composite thin films while the energy-dispersive X-ray spectroscopy (EDS) confirms the targeted elemental composition of the prepared thin films is in good agreement with precursors. The electrochemical oxidation of methanol results reveals that NiO-Y₂O₃/FTO and NiO-ZrO₂/FTO thin films showed current densities of 6.2 mA/cm² and 10 mA/cm² at 0.65 V, respectively, against Ag/AgCl/3M KCl using 0.6 M methanol solution. Furthermore, Chronoamperometric (CA) results show good stability of NiO-ZrO₂/FTO and NiO-Y₂O₃/FTO thin films with observed current decay of 10% and 6.8% of the initial current density, respectively. Moreover, the effect of scan rate and concentration of metals in a catalyst was also investigated. The Electrochemical impedance studies (EIS) further support electrochemical results, where the lower charge transfer resistance (R_ct) values are recorded for composite thin films as compared to the pure metal oxide thin films (NiO/FTO, ZrO₂/FTO, and Y₂O₃/FTO). Full article

The kinetics for crude glycerol autothermal reforming was studied over S/C ratio of 2.6 and O₂/C ratio of 0.125 using 5% Ni/CeZrCa catalyst. Both power law and mechanistic kinetic models were studied. The overall power law model for crude glycerol autothermal reforming was investigated with a pre-exponential factor of 4.3 × 10¹⁰ mol/g_cat·min and activation energy of 8.78 × 10⁴ J/mol. The reaction orders with respect to crude glycerol, water and oxygen are 1.04, 0.54 and 1.78 respectively. The power law model presented an absolute average deviation of 5.84%, which showed a good correlation between the predicted and experimental rate. Mechanistic models were developed for crude glycerol autothermal reforming. For steam reforming, the Eley–Rideal approach best described the reaction rate with the surface reaction being the rate-determining step (AAD < 10%). The kinetics of the total oxidation reaction was best described by the power law model with an AAD of less than 1%, whereas for the TOR process, the molecular adsorption of crude glycerol with an AAD of 14.6% via Langmuir Hinshelwood Hougen-Watson approach was best. CO₂ methanation resulted in an AAD of 5.8% for the adsorption of carbon dioxide (CO₂) by the Eley–Rideal mechanism. Full article

The aqueous phase reforming (APR) of glycerol was studied using sonochemically synthesized 10%Ni-x%Ca/ZrO₂ catalysts (where x = 0, 0.5, 3, and 5) for the production of value-added liquid products. The APR reaction was performed in a batch reactor under the following conditions: 20 bar, 230 °C 450 rpm, and 1 h of reaction time. The synthesized catalysts were characterized using XRD, FESEM, BET, and H₂-TPR to observe the effect of Ca doping on the physio-chemical properties of the catalysts. The results revealed that, at higher Ca loading, the catalysts experienced serious particles’ agglomeration, which resulted in a larger particles’ size, smaller surface area, and smaller pore volume owing to uneven distribution of the particles. The characterization results of the catalysts confirmed that the Us catalysts have a slightly higher surface area, pore volume, and pore size, as well as highly reducible and fine crystalline structure, compared with WI catalysts. The catalytic performance of the catalysts shows that 1,3-propanediol (1,3-PDO) and 1,2-propanediol (1,2-PDO) were the two main liquid products produced from this reaction. The highest selectivity of 1,3-PDO (23.84%) was obtained over the 10%Ni/ZrO₂ catalyst, while the highest selectivity of 1,2-PDO (25.87%) was obtained over the 10%Ni-5%Ca/ZrO₂ catalyst. Full article

Coupling of the pre-reforming and partial oxidation was considered for the conversion of liquefied petroleum gas to syngas for the feeding applications of solid oxide fuel cells. Compared with conventional two step steam reforming, it allows the amount of water required for the process, and therefore the energy needed for water evaporation, to be lowered; substitution of high-potential heat by lower ones; and substitution of expensive tubular steam reforming reactors by adiabatic ones. The supposed process is more productive due to the high reaction rate of partial oxidation. The obtained syngas contains only ca. 10 vol.% H₂O and ca. 50 vol.% of H₂ + CO, which is attractive for the feeding application of solid oxide fuel cells. Compared with direct partial oxidation of liquefied petroleum gas, the suggested scheme is more energy efficient and overcomes problems with coke formation and catalyst overheating. The proof-of-concept experiments were carried out. The granular Ni-Cr₂O₃-Al₂O₃ catalyst was shown to be effective for propane pre-reforming at 350–400 °C, H₂O:C molar ratio of 1.0, and flow rate of 12,000 h⁻¹. The composite Rh/Ce_0.75Zr_0.25O_2-δ–ƞ-Al₂O₃/FeCrAl catalyst was shown to be active and stable under conditions of partial oxidation of methane-rich syngas after pre-reforming and provided a syngas (H₂ + CO) productivity of 28 m³·L_cat⁻¹·h⁻¹ (standard temperature and pressure). Full article

In this study, we reported on the effect of promoting Ni/ZrO₂ catalysts with Ce, Ca (two different loadings), and Y for the aqueous-phase reforming (APR) of methanol. We mainly focused on the effect of the redox properties of ceria and the basicity provided by calcium or yttrium on the activity and selectivity of Ni in this reaction. A systematic characterization of the catalysts was performed using complementary methods such as XRD, XPS, TPR, CO₂-TPD, H₂ chemisorption, HAADF-STEM, and EDS-STEM. Our results reveal that the improvement in reducibility derived from the incorporation of Ce did not have a positive impact on catalytic behaviour thus contrasting with the results reported in the literature for other Ce-based catalytic compositions. On the contrary, the available Ni-metallic surface and the presence of weak basic sites derived from Ca incorporation seem to play a major role on the catalytic performance for APR of methanol. The best performance was found for a Ce-free catalyst with a molar Ca content of 4%. Full article

The resistance to sintering of Ni/Al₂O₃ catalysts with different additives for methanation reaction was modeled and predicted by data mining. In the screening, the resistance to sintering of Na, Ca, Ce, Mg, La, Cu, Zn, Zr, In, Mo, and Ti promoted Ni/Al₂O₃ catalyst were measured in terms of the increased rate of the size of the metallic nickel particles. The resistance to sintering of catalysts, described by the increased rate of Ni particle size as well as basic physicochemical properties of the 11 selected elements, was adopted for optimization model construction by data mining. Through regression model prediction and experimental verification, Cs was found to be an additive, and promotes the resistance to sintering mostly for Ni/Al₂O₃ catalysts. This result provides further evidence that data mining techniques can be employed as a highly efficient tool for the discovery of new catalysts in comparison with the traditional experimental method. Full article