水凝胶法制备Ni/ZrO_2催化剂及催化CO_2加氢甲烷化性能

Catalytic Performance of the Ni/ZrO_2 Catalysts Prepared with the Hydrogel Method in Methanation of CO_2

采用水凝胶法制备出一系列Ni／ZrO2催化剂，使用X射线衍射（XRD），比表面积（BET）测试，透射电子显微镜（TEM）和氢气程序升温还原（H2-TPR）对其结构进行了表征，并考察了在CO2加氢甲烷化反应中的催化活性．研究结果表明，经过450℃焙烧的催化剂中ZrO2呈无定形结构，NiO均匀分散在ZrO2表面上；在400℃时H：还原过程中，部分无定形ZrO2转变为四方晶相结构并使Ni再次分散，Ni与ZrO2之间的电子作用抑制了Ni晶粒的生长和ZrO2晶型的转变；与无定形ZrO2和四方相ZrO2产生电子作用的NiO对催化剂活性起决定性作用，当Ni／Zr摩尔比为0．707时，催化剂活性最高．在H2／CO2体积比为4，空速为1×10^4h^-1，压力为0．5MPa，反应温度为200℃时，CO2转化率达到27％以上，当反应温度上升至280—320℃时，C02转化率达到99％以上，CH4选择性大于92％．

A series of Ni/ZrO2 catalysts was prepared by the hydrogel method and characterized by X-ray diffraction （ XRD）, Brunauer-Emmett-Tetter （ BET）, transmission electron microscopy （ TEM ） and H2 tempera- ture programmed reduction（ HE-TPR）, and their catalytic activities for the methanation of carbon dioxide were investigated. The results show that ZrO2 presents an amorphous structure in the Ni/ZrO2 catalysts after calcination at 450℃. During the Ha reduction at the temperature of 400℃, the amorphous ZrO2 carrier was partly transformed into tetragonal phase and Ni species were re-dispersed on the surface of ZrO2. The metal-support interaction restrains the growth of NiO and ZrO2 , and electron cavity on amorphous ZrO2 carrier favors the dispersion of Ni species. The NiO species interacted with amorphous ZrO2 and tetragonal ZrO2 has a definitive effect on the catalytic performance of the Ni/ZrO2 catalysts. The highest catalytic activity was obtained on the Ni/ZrO2catalyst with a Ni/Zr molar ration of 0. 707. Under the reaction condition, V（ CO2 ）/V（ H2 ）= 1/4, gaseous hourly space velocity（GHSV） = 1×10^4 h^-1 , P=0. 5 MPa, 27% CO2 conversion was obtained at a low temperature of 200 ℃. The conversion of COa reached above 99% with the selectivity of CH4 above 92% when the reaction temperature was improved to 280--320 ℃.