络合法制备Ce-Zr-O固溶体作为CO_2重整CH_4催化剂载体的研究

Ceria-zirconia solid solutions prepared by complex-decomposition method as supports for Ni catalysts for CH_4 reforming with CO_2

以草酸、柠檬酸、甘氨酸、聚乙烯吡咯烷酮(PVP)为络合剂,采用络合分解法制备Ni-Ce-ZrO2催化剂,考察了所制备Ni-Ce-ZrO2催化剂的CO2重整CH4催化性能,并对所得催化剂进行了XRD、BET和H2-TPR表征。实验结果表明,不同络合剂对催化剂的晶型结构有很大影响,以PVP为络合剂更有利于形成均匀的Ce-Zr-O立方固溶体,且催化剂PVP-NiCeZr具有较大的比表面积、孔容和孔径,在反应中也具有最高的CH4和CO2转化率,其初始转化率分别为83.3%和87%,合成气中H2/CO接近于1。PVP-NiCeZr表现出良好的反应稳定性,反应后100h其热失重率仅为1.8%,这归因于Ce-Zr-O立方固溶体结构更有利于活性氧的移动,增加了催化剂表面积炭与氧的接触,提高了催化剂的抗积炭性能,也有利于提高Ni活性组分的抗烧结团聚能力。

The Ni-Ce-ZrO2 catalyst was prepared with the complex-decomposition method using oxalic acid(OA),citric acid(CA),glycine(GA)and polyvinyl pyrrolidone(PVP)as the complexing agent.The catalytic performance of the catalysts for the CO2 reforming of CH4 reaction was measured.Theose catalysts were characterized by XRD,BET and H2-TPR.The results showed that the complexing agent had a greater impact on the crystalline structure of catalysts.PVP was more beneficial to the formation of homogeneous cubic Ce-Zr-O solid solution.As-prepared catalyst PVP-NiCeZr had higher surface area,pore volume and pore size.The results indicated that catalyst prepared by PVP exhibited higher catalytic activity for CH4 reforming with CO2.The original conversion rate of CH4 and CO2 were 83.3% and 87%;a syngas with a H2/CO molar ratio of about 1could be obtained on catalyst PVP-NiCeZr.The catalyst of PVP-NiCeZr exhibited good reaction stability.The four catalysts after reaction were characterized by TG.The weight loss rate of PVP-NiCeZr after reaction 100 hwas only 1.8%.Due to the cubic Ce-Zr-O solid solution was more beneficial to the shift of active oxygen,the contact chance of carbon species on the catalysts surface and active oxygen was improved.The resistance to carbon formation and accumulation was greatly enhanced for the catalyst PVP-NiCeZr.The cubic Ce-ZrO solid solution could also improve the anti-sintering and high temperature stability of the active Ni.Combined XRD,BET,TPR,TG with catalytic performance,it showed that the better activity and stability of PVP-NiCeZr was related to the homogeneous cubic Ce-Zr-O solid solution and the higher surface area.