Catalytic methanation reaction over alumina supported cobalt oxide doped noble metal oxides for the purification of simulated natural gas

A series of alumina supported cobalt oxide based catalysts doped with noble metals such as ruthenium and platinum were prepared by wet impregnation method.The variables studied were difference ratio and calcination temperatures.Pt/Co(10∶90)/Al2O3 catalyst calcined at 700 ℃ was found to be the best catalyst which able to convert 70.10% of CO2 into methane with 47% of CH4 formation at maximum temperature studied of 400 ℃.X-ray diffraction analysis showed that this catalyst possessed the active site Co3O4 in face-centered cubic and PtO2 in the orthorhombic phase with Al2O3 existed in the cubic phase.According to the FESEM micrographs,both fresh and spent Pt/Co(10∶90)/Al2O3 catalysts displayed small particle size with undefined shape.Nitrogen Adsorption analysis showed that 5.50% reduction of the total surface area for the spent Pt/Co(10∶90)/Al2O3 catalyst.Meanwhile,Energy Dispersive X-ray analysis(EDX) indicated that Co and Pt were reduced by 0.74% and 0.14% respectively on the spent Pt/Co(10∶90)/Al2O3catalyst.Characterization using FT-IR and TGA-DTA analysis revealed the existence of residual nitrate and hydroxyl compounds on the Pt/Co(10∶90)/Al2O3 catalyst.

Studies on the Reaction Mechanism of CO_2-Reforming of Methane over Co/γ-Al_2O_3 Catalyst

TPPR and XPS characterizations were combined to study the reaction mechanism of CO2reforming of methane to syngas over Co/γ-Al2O3 catalysts. CH4 shows a tendency to form surface carbons by deep dissociation at high temperatures. CO2 dissociation reaction also occurs at >673K. It is believed that carbide carbons are active species to generate CO by rcacting with o atoms dissociated from CO2. In the reaction,Co(0) particles are responsible for dissociating CH4 to form active C. abstracting an O atom from CO2 molecule, and transferring O atom to C to form CO.

Synthesis of atomically dispersed cationic nickel-confined mesoporous ZSM-48(ANMZ-48)directed by metal complexes in amphiphilic molecules

The synthesis of mesoporous zeolite-anchored atomically dispersed metal catalysts(ADCs)is a considerable challenge in chemistry and materials science.Here we report the synthesis of atomically dispersed cationic nickel-confined mesoporous ZSM-48(ANMZ-48)by in situ hydrothermal reaction employing a designed tri-functional metal complex template,by which the triquaternary ammonium groups in the hydrophilic region direct the formation of ZSM-48 zeolite;the aromatic groups in the hydrophobic tail generate the mesopores through π-π stacking;and the complexes formed by nickel ions coordinated with terpyridyl groups generate atomically dispersed Ni2+confined in zeolite frameworks due to the strong sintering resistance generated by the strong coordination interaction.The ANMZ-48 is consisting of stacking of sheet-like ZSM-48 domains connected by multiply crystal twinning sharing the common(011)plane,generating abundant of imbedded mesopores with the uniform thickness of~2.4 nm and with the width of 10-50 nm.The excellent catalytic activity and stability of ANMZ-48 were also reflected in the dry reforming of methane(DRM)reaction.

Design of a multi-inlet solar thermochemical reactor for steam methane reforming with improved performance

Reactor structure design plays an important role in the performance of solar-thermal methane reforming reactors.Based on a conventional preheating reactor,this study proposed a cylindrical solar methane reforming reactor with multiple inlets to vary the temperature field distribution,which improved the temperature of the reaction region in the reactor,thereby improving the reactor performance.A multi-physical model that considers mass,momentum,species,energy conservation,as well as thermochemical reaction kinetics of methane reforming,was applied to numerically investigate the reactor performance and analyze the factors that affect performance improvement.It was found that compared with a conventional preheating reactor,the proposed cylindrical reac-tor with inner and external inlets for gas feeding enhanced heat recovery from the exhausted gas and provided a more suitable temperature field for the reaction in the reactor.Under different operating conditions,the methane conversion in the cylindrical reactor with multi-inlet increased by 9.5%to 19.1%,and the hydrogen production was enhanced by 12.1%to 40.3%in comparison with the conventional design,even though the total reaction catalyst volume was reduced.

Selective oxidation of methane and carbon deposition over Fe_2O_3/Ce_(1-x)Zr_xO_2 oxides

A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron microscope（TEM）, and H2-temperature-programmed reduction（H2-TPR） techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity（ca. 97 %） for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation.