Ni-Al mixed metal oxide with rich oxygen vacancies: CO methanation performance and density functional theory study

Ni-Al mixed metal oxides have been successfully prepared by high shear mixer(HSM)and coprecipitation(CP)methods for low temperature CO methanation.In this work,Ni-Al(HSM-CP)catalyst presented small Ni crystallite size and high surface area,which all contribute to the methanation reaction at low temperature conditions.The obtained Ni-Al(HSM-CP)sample exhibited a mass of defective oxygen,thereby accelerating the dissociation of CO and ultimately increasing the activity of the catalyst.Ni-Al(HSM-CP)catalyst offered the best activity with CO conversion=100%and CH_(4) selectivity=93%at 300℃,and the CH_(4) selectivity can reach 81.8%at 200℃.In situ Fourier transform infrared spectroscopy and density functional theory show that CHO and COH intermediates with lower activation energy barriers are produced during the reaction,and hydrogen-assisted carbon–oxygen bond scission is more favorable.

A Novel Al_2O_3-Based Semiconductor Gas Sensor for CO and CH_4 Detection

A new type of semiconductor gas sensor fabricated on an alumina substrate for CO and CH_4 detection has been developed.The alumina substrate was obtained by an anodizing method companying with micromachining to form patterned structure.Gas sensitive material was made of nano-sized SnO_2 powder prepared by a chemical precipitation method.Au (0.048wt.%) and Pd (0.3 wt%) were doped to SnO_2 powder to increase sensitivity to CO and CH_4,respectively.The heating power and sensing performance were measured with an automatic test system.The results show that the sensors have remarkable responses and certain selectivity to the target gases.Our study demonstrates that alumina substrate can be successfully applied in sensor micromachining technology.

La-enhanced Ni nanoparticles highly dispersed on SiC for low-temperature CO methanation performance

For better performances of Ni-based catalysts at low temperatures,Ni/SiC catalyst doped with a little amount of additive La was successfully prepared.The catalytic CO methanation activity tests showed that 3%La-Ni/SiC catalyst was excellent at a low reaction temperature(95.9%CO conversion and 85.1%CH4 selectivity at250℃)with a superior stability compared with Ni/SiC(3.4%CO conversion and 0%CH4 selectivity at 250℃).This can be attributed to that the addition of La can markedly improve the dispersibility of active metal Ni and reduce the particle sizes of Ni nanoparticles or clusters,and can also regulate the interaction between active components and supports.Moreover,the high thermal conductivity and thermal stability could avoid the generation of hot spots in the catalyst bed.These results will promote the development of highly active Ni-based catalysts for the low-temperature methanation reaction.