Autothermal Reforming of Acetic Acid to Hydrogen and Syngas on Ni and Rh Catalysts

The autothermal reforming (ATR) of acetic acid (HAc) as a model bio-oil compound is examined via bench scale experiments and equilibrium modelling to produce hydrogen and syngas. This study compares the performance of nickel (Ni-Al, Ni-CaAl) vs. rhodium (Rh-Al) for particulate packed bed (PPB), and of Rh-Al in PPB vs. Rh with and without Ceria for honeycomb monolith (‘M’) catalysts (R-M and RC-M). All PPB and M catalysts used Al2O3 as main support or washcoat, and when not pre-reduced, exhibited good performance with more than 90% of the HAc converted to C1-gases. The maximum H2 yield (6.5 wt.% of feed HAc) was obtained with both the Rh-Al and Ni-CaAl catalysts used in PPB, compared to the equilibrium limit of 7.2 wt.%, although carbon deposition from Ni-CaAl at 13.9 mg gcat−1 h−1 was significantly larger than Rh-Al’s (5.5 mg gcat−1 h−1); close to maximum H2 yields of 6.2 and 6.3 wt.% were obtained for R-M and RC-M respectively. The overall better performance of the Ni-CaAl catalyst over that of the Ni-Al was attributed to the added CaO reducing the acidity of the Al2O3 support, which provided a superior resistance to persistent coke formation. Unlike Rh-Al, the R-M and RC-M exhibited low steam conversions to H2 and CH4, evidencing little activity in water gas shift and methanation. However, the monolith catalysts showed no significant loss of activity, unlike Ni-Al. Both catalytic PPB (small reactor volumes) and monolith structures (ease of flow, strength, and stability) offer different advantages, thus Rh and Ni catalysts with new supports and structures combining these advantages for their suitability to the scale of local biomass resources could help the future sustainable use of biomasses and their bio-oils as storage friendly and energy dense sources of green hydrogen.

Numerical modeling of hydrogen-rich gas production from gasoline autothermal reforming in a plug flow reactor for electric vehicles

Due to the increase in the greenhouse effect, lowering emissions is becoming a certain issue all over the world. It is a concern to develop alternative options to minimize the spread of exhaust gases. For this purpose, in this study, the plug flow reactor in the system consisting of solid oxide fuel cell (SOFC), reactor, electric motor, battery, burner, and the heat exchanger is considered. Numerical modeling of hydrogen gas generation in a plug flow reactor is studied. The reactor indicated on-board hydrogen gas generation for an electric motor automobile has not been modeled in the literature yet. Autothermal reforming of isooctane is simulated in the COMSOL multi-physics software program in the reactor particularly. Conversion of isooctane and H2O are examined at different overall heat transfer coefficients, input temperatures, and steam/carbon ratios. Also, there are certain differences between adiabatic and non-adiabatic conditions. The produced synthesis gas of hydrogen drastically increases in the non-adiabatic case. The obtained results from the model are compared with experimental data obtained from the literature. H2 production at the end of the autothermal reforming process indicates the power provided from the reactor can operate a motor of an automobile. In the study, the achieved power is 65.8 kW (88 HP) is sufficient for an automobile. Simulation results show that the reactor volume of 75 L supplies 0.18 mols−1 of H2 and 0.08 mols−1 of CO in the non-adiabatic case.

Hydrogen Production through Autothermal Reforming of Ethanol: Enhancement of Ni Catalyst Performance via Promotion

Autothermal reforming of bioethanol (ATR of C2H5OH) over promoted Ni/Ce0.8La0.2O1.9 catalysts was studied to develop carbon-neutral technologies for hydrogen production. The regulation of the functional properties of the catalysts was attained by adjusting their nanostructure and reducibility by introducing various types and content of M promoters (M = Pt, Pd, Rh, Re; molar ratio M/Ni = 0.003–0.012). The composition–characteristics–activity correlation was determined using catalyst testing in ATR of C2H5OH, thermal analysis, N2 adsorption, X-ray diffraction, transmission electron microscopy, and EDX analysis. It was shown that the type and content of the promoter, as well as the preparation mode (combined or sequential impregnation methods), determine the redox properties of catalysts and influence the textural and structural characteristics of the samples. The reducibility of catalysts improves in the following sequence of promoters: Re < Rh < Pd < Pt, with an increase in their content, and when using the co-impregnation method. It was found that in ATR of C2H5OH over bimetallic Ni-M/Ce0.8La0.2O1.9 catalysts at 600 °C, the hydrogen yield increased in the following row of promoters: Pt < Rh < Pd < Re at 100% conversion of ethanol. The introduction of M leads to the formation of a NiM alloy under reaction conditions and affects the resistance of the catalyst to oxidation, sintering, and coking. It was found that for enhancing Ni catalyst performance in H2 production through ATR of C2H5OH, the most effective promotion is with Re: at 600 °C over the optimum 10Ni-0.4Re/Ce0.8La0.2O1.9 catalyst the highest hydrogen yield 65% was observed.