Catalytic Activity Of Ni-based Catalyst For Producing Syngas By CO₂ Reforming Of CH₄

Responsible for series of environmental problems like global warming,melting iceberg,rising sea level and so forth,methane and carbon dioxide are two major green house gases released during human's living and producing activities and natural process.They are also an important hydrocarbon raw material,key to exploitation and application of new source of energy.One effective way to reduce emissions of both gases is by synthesizing syngas using methane and carbon dioxide through reforming reaction.At the moment,research and development of new catalysts for carbon dioxide reforming of methane has become a hotspot in the field.This work focuses mainly on the catalytic activity of Ni-based catalyst for producing syngas by reforming CH₄ and CO₂.In this paper,nickel was chosen as the active component,by carrier screening,addition of a second active component Rhodium and other methods several improved Ni-based catalysts were synthesized.With the assistance of characterization techniques including SEM,XRD,BET,FT-IR and TG,effects of factors like preparation method,reaction conditions etc.on the as-prepared catalysts were discussed and the conclusions followed:1?The thermodynamic simulation of the reaction system suggests that in certain range,rising temperature and reducing pressure promotes the efficiency notably.2?The carrier had a significant effect on the catalytic activity,the catalytic activity tests of catalysts on different carrier under the same condition suggested that ?-Al2O3,compared to other carriers,was most suitable for the reforming catalyst for its big specific surface area and high thermal stability.3?Catalytic activity tests of catalysts with different Ni loading and the XRD profiles showed that the optimal Ni loading was 10%since it was the maximum capacity for monolayer-dispersed nickel on the ?-Al₂O₃ carrier.4?The optimal reaction condition for the reaction was 600?,1 atm,space velocity of 4500 h-1,and CH₄/CO₂ molar ratio of 1.In the perspective of thermodynamics and kinetics,further analysis on the reaction system was also presented in the paper.5?Under the optimal condition,catalytic activity tests showed that the Rh-Ni/?-Al₂O₃ catalyst remained highly effective for 72 hours;CH₄ and CO₂ conversions over 90%,together with stable yields of H₂ and CO at a molar ratio of about 1 were obtained at the same time.6?Addition of rhodium as a second active component greatly enhanced the catalytic activity;the best catalytic performance was obtained when the dosage was 0.1%.The reason for the promotive effect might be that,based on the BET and TG profiles of the catalysts,rhodium on the carrier's surface could improve the distribution of the nickel,the formation of Ni-Rh double alloy could significantly improved the catalyst's stability and resistance to carbon deposition.