Dai-Viet N. Vo

Syngas production from methane dry reforming over Ni/Al2O3 catalyst

We evaluated dry reforming of methane in a tubular fixed-bed reactor at various reaction temperatures from 923 to 973xa0K using different reactant compositions over 10xa0% Ni/Al2O3 catalyst prepared by a wet impregnation method. Both NiO and NiAl2O4 phases were formed on the catalyst surface during calcination, and the 10xa0% Ni/Al2O3 catalyst possessed high surface area of 106.36xa0m2xa0g−1 with fine metal dispersion. The low activation energy observed for formation of NiAl2O4 phase during calcination indicated strong interaction between the NiO form and the γ-Al2O3 support. The NiO phase was completely reduced to metallic Ni0 form via H2 reduction. The conversions of CO2 and CH4 increased noticeably with increasing CO2 partial pressure, and the H2/CO ratio was always below unity, regardless of reaction conditions. The yield of H2 was enhanced with growing CO2 partial pressure, approaching a highest value of about 70xa0%. The heterogeneous nature of the deposited carbon was evident from the coexistence of carbon nanofibers and graphitic carbon. In addition, the amount of filamentous carbon appeared to be slightly less than that of graphitic carbon. However, these deposited carbons were completely removed by O2 at below 900xa0K during temperature-programmed oxidation.

Controlling the Shape of Anatase Nanocrystals for Enhanced Photocatalytic Reduction of CO2 to Methanol

Herein, we report a simple thermal-induced synthesis of pyramidal anatase TiO2 nanocrystals with exposed {101} and {001} facets with controlled shapes and truncated particles. Anatase phase of rod-like structures or truncated bipyramidal nanocrystals was prepared by tailoring the temperature or treatment time in a hydrothermal method using peroxotitanic acid as a precursor without using any shape-controlling reagent. The presence of both {101} and {001} facets in the synthesized nanocrystals enhances the separation of electrons and holes and improves the photocatalytic reduction of CO2 to methanol.

Mechanistic investigation of methane steam reforming over Ce-promoted Ni/SBA-15 catalyst

Methane steam reforming experiments were carried out at atmospheric pressure for temperatures between 873 and 1073xa0K and by varying the partial pressure of methane and steam to achieve S:C between 0.5 and 2.5. Mechanistic considerations for Methane steam reforming (MSR) were derived on the basis of Langmuir–Hinshelwood and Eley–Rideal reaction mechanisms based on single- and dual-site associative and dissociative adsorption of one or both reactants. However, discrimination of these models on statistical and thermodynamic grounds revealed that the model representing a single-site dissociative adsorption of methane and steam most adequately explained the data. However, the product formation rates from these experiments were reasonably captured by power-law model. The parameter estimates from the power-law model revealed an order of 0.94 with respect to methane and −0.16 for steam with activation energy of 49.8xa0kJxa0mol−1 for MSR. The negative order with respect to steam for methane consumption was likely due to steam inhibition.

Reforming of glycerol for hydrogen production over Ni based catalysts: Effect of support type

ABSTRACT This current work focuses on hydrogen production that is a component in syngas by glycerol dry reforming over 15% nickel (Ni) loading supported on different oxides, namely CaO, ZrO2, and La2O3. The screening process was conducted in a fixed-bed reactor at 700°C under atmospheric pressure. It was found that 15% Ni/CaO showed the best performance in screening studies. The effect of temperature and the carbon to glycerol ratio (CGR) was then analyzed for this catalyst. From the analysis, it was seen that 15% Ni/CaO has its optimum condition at 800°C and CGR = 1, where it gives the highest glycerol conversion (XG = 37.66%) and hydrogen yield (YH = 32.45%).

Hydrogen Production From Biogas Reforming: An Overview of Steam Reforming, Dry Reforming, Dual Reforming, and Tri-Reforming of Methane

Abstract Green hydrogen can be produced from biogas as a renewable resource using a multistep process, including mainly biogas reforming, water-gas-shift reaction, and hydrogen separation. This chapter is focused on different methane reforming processes: steam reforming, dry reforming, dual reforming, and tri-reforming. In fact, only steam methane reforming (SMR) has been commercialized, but it is well known as a highly energy intensive process. Thus, alternative processes, such as dry, dual, and tri-reforming, are being developed. These solutions are significantly interesting for biogas reforming because of its high carbon dioxide content, which can be used as an oxidant. For each process, different aspects will be presented, including: thermodynamic equilibrium, process at industrial scale or research laboratory development, kinetic models, and mechanistic study.

Syngas Production from CO2 Reforming and CO2-steam Reforming of Methane over Ni/Ce-SBA-15 Catalyst

This study compares the catalytic performance of mesoporous 10 Ni/Ce-SBA-15 catalyst for CO2 reforming and CO2-steam reforming of methane reactions in syngas production. The catalytic performance of 10 Ni/Ce-SBA-15 catalyst for CO2 reforming and CO2-steam reforming of methane was evaluated in a temperature-controlled tubular fixed-bed reactor at stoichiometric feed composition, 1023 K and atmospheric pressure for 12 h on-stream with gas hourly space velocity (GHSV) of 36 L gcat -1 h-1. The 10 Ni/Ce-SBA-15 catalyst possessed a high specific BET surface area and average pore volume of 595.04 m2 g-1. The XRD measurement revealed the presence of NiO phase with crystallite dimension of about 13.60 nm whilst H2-TPR result indicates that NiO phase was completely reduced to metallic Ni0 phase at temperature beyond 800 K and the reduction temperature relied on different degrees of metal-support interaction associated with the location and size of NiO particles. The catalytic reactivity was significantly enhanced with increasing H2O/CO2 feed ratio. Interestingly, the H2/CO ratio for CO2-steam reforming of methane varied between 1 and 3 indicated the occurrence of parallel reactions, i.e., CH4 steam reforming giving a H2/CO of 3 whilst reverse water-gas shift (RWGS) reaction consuming H2 to produce CO gaseous product.