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Abstract Hydrogen is a clean fuel and potential alternative for fossil fuels, and many efforts have been devoted to low-carbon hydrogen production. Highly dispersed and robust Ni/carbon catalysts can be handily prepared in situ for catalytic methane decomposition (CMD) by selective steam gasification of pine sawdust. Effect of the gasification conditions (temperature, mass ratio of PS:Ni, steam flow rate and gasification reaction time) was investigated on the nickel species, activity and stability of the Ni/carbon catalyst in CMD. Besides hydrogen-rich gas released from the gasification process, co-production of hydrogen and carbon fibers can be obtained on the optimized catalyst with high and stable methane conversion (up to higher than 90% at 850 °C) in the 600-min CMD reaction. The implementation of such selective biomass gasification and CMD could be one promising approach towards process intensification for highly cost-effective hydrogen production, and enables it possible to yield a high metal efficiency as well. Highlights • Robust Ni/carbon catalysts are prepared by selective gasification of pine sawdust. • The gasification residue is used for catalytic methane decomposition. • Highly dispersed and robust Ni/carbon catalysts can be handily prepared in situ. • Co-production of H 2 and carbon fibers can be obtained by methane decomposition. [ABSTRACT FROM AUTHOR]

The relationship between chemical looping CH 4 CO 2 reforming performance and the microstructure of oxygen carrier (OC) is very important for the rational design of OC. In this paper, we studied the structural evolution of La Fe Al (LFA-t, t = 900–1200 °C) OCs as thermal treatment and ten periodic CH 4 /CO 2 redox cycles, and correlated to their reactivity and stability for syngas production. Different calcination temperature brought about great discrepancy in phase composition of LFA OCs: LaFeO 3, Fe 2 O 3 , and α-Al 2 O 3 at 900 °C, LaFe x Al 1-x O 3 and La-hexaaluminate at 1000 °C, and monophasic La-hexaaluminate at 1100–1200 °C. During the CH 4 /CO 2 redox process, the repeated phase separation occurred over LFA-900 and LFA-1000 accompanied by the appearance of metallic Fe and FeAl 2 O 4 , which resulted in serious CH 4 pyrolysis. La-hexaaluminate showed good phase stability during CH 4 /CO 2 redox process via the charge compensation mechanism. The large hexaaluminate crystalline of LFA-1200 inhibited the oxygen transport from the bulk to surface, which led to carbon deposition. LFA-1100 hexaaluminate OC with moderate crystal size exhibited excellent reactivity and stability for producing syngas with desirable H 2 /CO ratio (∼2) during ten CH 4 /CO 2 redox cycles thanks to high oxygen mobility and the reservation of hexaaluminate structure during redox process. [ABSTRACT FROM AUTHOR]

Methane decomposition was conducted by using K 2 CO 3 /carbon hybrids as the catalysts, and hydrogen-rich gas (with hydrogen content of about 87%) and fibrous carbons can be simultaneously obtained together with high and stable methane conversion (up to about 90% at 850 °C). Effects of K 2 CO 3 on methane conversion, hydrogen content and fibrous carbons were investigated by changing the reaction temperature and space velocity. The results indicate that K 2 CO 3 can greatly promote methane activation and conversion, taking responsibility for the continuous formation of CO and a trace of CO 2 . The oxygen transfer from K 2 CO 3 probably provides convenience for the formation and growth of fibrous carbons. [ABSTRACT FROM AUTHOR]

The objective of the study is to investigate the catalytic performance of Cr-promoted Ni/char in CO2 reforming of CH4 at 850 °C. The char obtained from the pyrolysis of a long-flame coal at 1000 °C was used as the support. The catalysts were prepared by incipient wetness impregnation methods with different metal precursor doping sequence. The characterization of the composite catalysts was evaluated by XRD, XPS, SEM-EDS, TEM, H2-TPR, CO2-TPD, CH4-TPSR, and CO2-TPO. The results indicate that the catalyst prepared by co-impregnation of Ni and Cr possess higher activity than those by sequential impregnation. The optimal loading of Cr on 5 wt% Ni/char is 7.8 wt‰. Moreover, the molar feed ratio of CH4/CO2 has a considerable effect on both the stability and the activity of Cr–Ni/char. The main effect of Cr is the great enhance of the adsorption to CO2. It is interesting that the conversions of CH4 and CO2 over Cr-promoted Ni/char and Ni/char decrease initially, following by a steady rise as the reaction proceeds with time-on-stream (TOS). In addition, cyclic tests were conducted and no distinct deterioration in the catalytic performance of the catalysts was observed. On the basis of the obtained results, nickel carbide was speculated to be the active species which was formed during the CO2 reforming of CH4 reaction. [ABSTRACT FROM AUTHOR]