Performance For CO2 Reforming Research Articles

A study of CO2 reforming of CH4 for coal delivered gases over Ni-based catalysts

NiCo-Mg/Al-1.7, Ni-Mg/Al-1.6, Ni-Mg/Al-0, and NiCo-Mg/Al-0.3 Ni-based catalysts were used to test their performance in CO2 reforming of CH4 reaction for a coal gas feed mainly containing CO and H2 as well as CO2 and CH4 at 900°C and the ambient pressure. Compared to the performance in ideal feed of CO2 and CH4 balanced with N2, the smaller reaction rate in the coal gas observed over all the catalysts was barely due to the lower concentration of CO2 and CH4 in the feed. NiCo-Mg/Al-1.7 catalyst showed the highest activity and stability among the four catalysts owing to its right metallic NiCo alloy sites to activate CH4 and the strong basic sites to activate CO2. The TPO of the spent catalyst after 24h TOS showed no carbon formation. The other three catalysts facilitated more or less various formats of carbon formation depending on different surface properties, leading to the decay of catalytic activity along the TOS. The coal gas feed that contains very small amount of O2 helped mitigate the formation of the inactive graphitic carbon, possibly because O2 burned the carbon of this kind. This study will improve the efficiency of using coal gas by converting its to-be-emitted CO2 and CH4 into valuable CO and H2.

CO2 reforming of CH4 over a highly active and stable Ni[sbnd]Mg[sbnd]Al catalyst

Although the catalytic systems containing the NiOMgO solid solution possess excellent catalytic performance in CO2 reforming of CH4 reaction, a serious drawback was that the higher than 10 wt% Ni loadings would increase the burden on the environment and finance. A NiMgAl catalyst with 3 wt% Ni loadings derived from a hydrotalcite precursor was prepared in order to study the CO2 reforming of CH4 reaction. For comparative purpose, a NiOMgO catalyst and a Ni/γ-Al2O3 catalyst containing NiAl2O4, were also synthesized. Analysis showed that the NiMgAl catalysts had high catalytic activity due to the improved reducibility which was caused by the presence of Al3+ ions in the NiOMgO cubic lattice. Moreover, the NiMgAl catalyst showed ultra-stability without carbon formation for 320 h period due to the small Ni particles and the suitable Ni-support interaction which effectively prevented the sintering of Ni particles.

Cr‐Doped La‐Ni‐O Catalysts Derived from Perovskite Precursors for CH4‐CO2 Reforming under Microwave Irradiation

AbstractThe nickel catalysts derived from Cr‐doped LaNiO3 perovskite‐like precursors were characterized by X‐ray diffraction, high‐resolution transmission electron microscopy, temperature‐programmed oxidation, temperature‐programmed reduction, and X‐ray photoelectron spectroscopy. Their catalytic performance in CO2 reforming of methane under microwave irradiation was investigated. It was found that the structure and morphology of the oxide composites in this research were influenced by the ratio of Ni and Cr, and the mismatch of La3+, Ni3+, and Cr3+ may cause phase segregation. The catalytic performance of the Ni catalysts is dependent on the oxygen mobility of the perovskite oxide matrix, the content of the reduced Ni0, and the content of the remaining perovskite structure. The mobile oxygen in the perovskite matrix in the catalyst may enhance the conversion of CO2 during the reaction.

Effects of α- and γ-cyclodextrin-modified impregnation method on physicochemical properties of Ni/SBA-15 and its catalytic performance in CO2 reforming of methane

Organic compounds containing multiple hydroxyl groups, namely α-cyclodextrin and γ-cyclodextrin, were used as additives for promoting Ni dispersion on supported Ni/SBA-15 catalysts. Catalysts prepared using modified and unmodified impregnation methods were characterized using N2 adsorption-desorption isotherms, X-ray diffraction, transmission electron microscopy, temperature-programmed reduction, and thermogravimetric analysis, and their catalytic performance in the CO2 reforming of methane (CRM) to syngas was evaluated. The results show that compared with Ni/SBA-15 prepared using a conventional impregnation method, the cyclodextrin-modified catalysts had smaller NiO particles. They also exhibited higher catalytic activity and had stronger ability to resist carbon deposition in the CRM. Mechanistic studies showed that for the unmodified catalysts, Ni2+ could migrate into the channels of SBA-15 as a result of concentration differences, and the Ni species were sintered during the following thermal treatment processes, and could not be well dispersed. In contrast, various types of complex were formed between Ni(NO3)2 and the cyclodextrins, and this would be favorable for Ni2+ being taken into the channels of the SBA-15. The presence of cyclodextrins was beneficial to the mutual isolation of Ni species, and finally resulted in better dispersion of Ni species.

Promoting effect of glucose and β-cyclodextrin on Ni dispersion of Ni/MCM-41 catalysts for carbon dioxide reforming of methane to syngas

Mesoporous silica MCM-41 supported Ni-based catalysts were prepared by glucose (Glu) and β-cyclodextrin (βCD) modified impregnation method, respectively. The physicochemical properties of the catalysts (Ni/MCM-41-βCD and Ni/MCM-41-Glu) were characterized with BET, XRD, H2-TPR and TEM techniques, and their catalytic performance in CO2 reforming of methane to syngas was evaluated. The results revealed that the prepared catalysts remained the ordered mesoporous structures of MCM-41, and no obvious NiO particles could be viewed on catalysts prepared with β-cyclodextrin or glucose modified method. In contrast, on the catalyst prepared with the conventional impregnation method (Ni/MCM-41), large NiO particles could be observed. In the reaction of CO2 reforming of methane to syngas, compared with Ni/MCM-41, Ni/MCM-41-βCD and Ni/MCM-41-Glu exhibited higher catalytic activities and better catalytic stabilities.