关键词: 多壁碳纳米管, Ni-修饰多壁碳纳米管, Ni修饰碳纳米管促进的Cu基催化剂, 甲醇合成

By using chemical reduction-deposition method, a nickel-modified multi-walled carbon nanotube material, symbolized as y%Ni/MWCNT, was prepared. The H₂-TPD measurement showed that the modification of metallic nickel to the MWCNT could significantly enhance its capability of dissociatively adsorbing hydrogen. With the y%Ni/MWCNT as promoter, highly active y% Ni/MWCNT-promoted Cu-ZnO-Al₂O₃ catalysts, symbolized as Cu₆Zn₃Al₁-x% (y%Ni/MWCNT), were prepared by co-precipitation method. It was experimentally found that appropriate incorporation of a minor amount of the y%Ni/MWCNT into the Cu₆Zn₃Al₁ could significantly enhance the catalyst activity for methanol synthesis. Under the reaction conditions of 2.0 MPa, V(H₂):V(CO):V(CO₂):V(N₂)=62:30:5:3, GHSV=2700 mL(STP)·h^-1·(g-cat.)^-1, the observed CO-conversion over the Cu₆Zn₃Al₁-12.5% (8%Ni/MWCNT) catalyst reached 34%, with the corresponding methanol-STY at 442 mg·h^-1·(g-cat.)^-1, which was about 38% and 17% higher than those over the Cu₆Zn₃Al₁ and Cu₆Zn₃Al₁-12.5% MWCNT catalysts as contrast, respectively, at the respective optimal operation temperature, 513 K and 503 K. Characterization of the catalyst revealed that the pre-reduced Cu₆Zn₃Al₁-12.5%(8%Ni/MWCNT) system could reversibly adsorb a considerably greater amount of hydrogen under atmospheric pressure at temperatures ranging from room temperature to ～573 K. This unique feature would be beneficial to generating microenvironments with relatively high stationary-state concentration of active hydrogen-adspecies on surface of the functioning catalyst, thus being favorable to increasing the rate of the CO hydrogenation reactions.

Key words: MWCNT, Ni-modified MWCNT, Cu_iZnjAl_k-x%(y%Ni/MWCNT)catalyst, methanol synthesis