Catalytic Steam Reforming of Propane over Ni/LaAlO3 Catalysts: Influence of Preparation Methods and OSC on Activity and Stability

Support Effects on the Activity of Ni Catalysts for the Propane Steam Reforming Reaction

The catalytic performance of supported Ni catalysts for the propane steam reforming reaction was investigated with respect to the nature of the support. It was found that Ni is much more active when supported on ZrO₂ or YSZ compared to TiO₂, whereas Al₂O₃₋ and CeO₂-supported catalysts exhibit intermediate performance. The turnover frequency (TOF) of C₃H₈ conversion increases by more than one order of magnitude in the order Ni/TiO₂ < Ni/CeO₂ < Ni/Al₂O₃ < Ni/YSZ < Ni/ZrO₂, accompanied by a parallel increase of the selectivity toward the intermediate methane produced. In situ FTIR experiments indicate that CH_x species produced via the dissociative adsorption of propane are the key reaction intermediates, with their hydrogenation to CH₄ and/or conversion to formates and, eventually, to CO, being favored over the most active Ni/ZrO₂ catalyst. Long term stability test showed that Ni/ZrO₂ exhibits excellent stability for more than 30 h on stream and thus, it can be considered as a suitable catalyst for the production of H₂ via propane steam reforming.

Effect of Ce Doping of a Co/Al2O3 Catalyst on Hydrogen Production via Propane Steam Reforming

We synthesized cerium-doped cobalt-alumina (CoxCey/Al2O3) catalysts for the propane steam reforming (PSR) reaction. Adding cerium introduces oxygen vacancies, and the oxygen transfer capacity of the Ce promoter favors CO to CO2 conversion during PSR, inhibiting coke deposition and promoting hydrogen production. The best PSR activity was achieved at 700 °C using the Co0.85Ce0.15/Al2O3 catalyst, which showed 100% propane (C3H8) conversion and about 75% H2 selectivity, and 6% CO, 5% CO2, and 4% CH4 were obtained. In contrast, the H2 selectivity of the base catalyst, Co/Al2O3, is 64%. The origin of the difference in activity was the lower C3H8 gas desorption temperature of the Co0.85Ce0.15/Al2O3 catalyst compared to that of the Co/Al2O3 catalyst; thus, the PSR occurred at low temperatures. Furthermore, more CO was adsorbed on the Co0.85Ce0.15/Al2O3 catalyst, and subsequently, desorbed as CO2. The activation energy for water desorption from the Co0.85Ce0.15/Al2O3 catalyst was 266.96 kJ/mol, higher than that from Co/Al2O3. Furthermore, the water introduced during the reaction probably reacted with CO on the Co0.85Ce0.15/Al2O3 catalyst, increasing CO2 generation. Finally, we propose a mechanism involving the Co0.85Ce0.15/Al2O3 catalyst, wherein propane is reformed on CoxCey sites, forming H2, and CO, followed by the conversion of CO to CO2 by water on CeO2 sites.

Thermodynamic Modeling of Propane Reforming Processes to Quantify Hydrogen and Syngas Production with and without Product Removal

The present study aims to explore the possibility of promoting hydrogen and syngas production capacity and quality by steam (SRP) and oxidative steam (OSRP) reforming of propane with and without H2 and CO2 removal. Conditions studied are temperature range of 600–1,100 K under atmospheric pressure with steam to propane feed ratio (WPR) of 1–18, oxygen to propane feed ratio (OPR) and fractional removal of H2 and CO2 (f) ranging from 0–0.99. The results indicate that SRP with 99% H2 removal produces high H2 yield of 9.93 moles close to theoretical value of 10 moles at relatively low temperature (750 K) than SRP (950 K). Approximately identical results are achieved at 950 K with 99% CO2 removal at same conditions of WPR (12), pressure (1 atm), and complete conversion of propane. Thus, SRP with H2 removal is more energy saving process. In OSRP, lower OPR, higher WPR minimize CO and CH4 production but at the expense of H2 production. However, OSPR process is the most suitable process to provide most favourable H2/CO ratio in syngas. Molar H2/CO ratio in syngas in the range of 1–3 are found at T≥1,000 K, WPR≤6 in SRP, SRP with H2 removal (f=0.4–0.99) and OSRP (OPR=0.2–2). Thermal efficiency is higher than 80% in both SRP with H2 or CO2 removal than SRP(69.39%). The thermal efficiency in OSRP is less than 69%. Hence, propane reforming process in hydrogen selective membrane reactor, provides high quality of hydrogen at relatively lower energy utilization.

Biomass to hydrogen-rich syngas via catalytic steam gasification of bio-oil/biochar slurry

The catalytic steam gasification of bio-oil/biochar slurry (bioslurry) for hydrogen-rich syngas production was investigated in a fixed-bed reactor using LaXFeO3 (X=Ce, Mg, K) perovskite-type catalysts. The effects of elemental substitution in LaFeO3, temperature, water to carbon molar ratio (WCMR) and bioslurry weight hourly space velocity (WbHSV) were examined. The results showed that La0.8Ce0.2FeO3 gave the best performance among the prepared catalysts and had better catalytic activity and stability than the commercial 14 wt.% Ni/Al2O3. The deactivation caused by carbon deposition and sintering was significantly depressed in the case of La0.8Ce0.2FeO3 catalyst. Both higher temperature and lower WbHSV contributed to more H2 yield. The optimal WCMR was found to be 2, and excessive introducing of steam reduced hydrogen yield. The La0.8Ce0.2FeO3 catalyst gave a maximum H2 yield of 82.01% with carbon conversion of 65.57% under the optimum operating conditions (temperature=800°C, WCMR=2 and WbHSV=15.36h(-1)).