沉淀法ZrO2-Al2O3复合载体的制备及其甲烷化催化性能初探

Preparation of ZrO2-Al2O3 composite carrier by precipitation method and preliminary study on its catalytic performance in methanation

以氧氯化锆和硝酸铝混合溶液为前驱体,氨水为沉淀剂,PEG-6000为分散剂,通过沉淀法合成多孔Zr O2-Al2O3复合载体。利用正交实验考察了氧氯化锆和硝酸铝混合溶液浓度、锆铝摩尔比、分散剂质量、焙烧时间等因素对Zr O2-Al2O3复合载体比表面积的影响,得到合成多孔Zr O2-Al2O3复合载体的最佳工艺条件:氧氯化锆和硝酸铝混合溶液浓度为0.4 mol/L、锆铝摩尔比为3∶7、分散剂PEG-6000的质量为1 g、焙烧时间为6 h。对该条件下合成的多孔Zr O2-Al2O3复合载体进行BET、SEM、XRD和粒度表征。结果发现,合成的多孔Zr O2-Al2O3复合载体粒度小、分布均匀、表面疏松、比表面积大,适合做负载型催化剂载体的材料。通过浸渍法载镍制得Ni/Zr O2-Al2O3催化剂,初步检测了其甲烷化催化活性,结果发现,CO转化率随温度单调增大,在470℃高达89%,之后有所减低;CH4选择性最高可达98%。

A porous ZrO2-Al2O3 composite carrier is synthesized by a precipitation method using a mixed solution of zirconium oxychloride and aluminum nitrate as a precursor,ammonia as a precipitant and PEG-6000 as a dispersant.The effects of the concentration of mixed solution,the molar ratio of zirconium to aluminum,the dosage of dispersant and the roasting time on the specific surface area of porous ZrO2-Al2O3 composite carrier are investigated by orthogonal experiment.The optimal process conditions for the synthesis of porous ZrO2-Al2O3 composite carrier are obtained by orthogonal analysis as follows:the concentration of mixed solution is 0.4 mol·L-1,the molar ratio of zirconium to aluminum is 3∶7,the dosage of dispersant(polyethylene glycol-6000)is 1 g,and the roasting time is 6 hours.ZrO2-Al2O3 composite carrier synthesized under the optimum conditions is characterized by BET,SEM,XRD and particle size analysis.The results show that the synthesized ZrO2-Al2O3 composite carrier has small particle size,uniform particle size distribution,loose surface and large specific surface area,and is suitable as a carrier for supporting catalysts.Ni/ZrO2-Al2O3catalyst is prepared through impregnation method by loading Ni and its catalytic activity for methanation is preliminarily detected.It is found that the conversion rate of CO over the catalyst increases monotonically with increasing temperature,reaching 89% at 470℃,and decreases then.CH4 selectivity also has a similar variation pattern,reaching 98% at 470℃.