NaBH4处理LaCuZnX(X=Zr、Al、Zr+Al)(类)钙钛矿型催化剂及其CO2加氢合成甲醇性能的研究

采用共沉淀法分别制备了不同F-T组分(Fe、Co、Ni)改性的KCuZrO_2催化剂,并用于催化CO加氢合成异丁醇。通过BET、XRD、TEM、XPS、H_2-TPR、CO-TPD以及in-situ DRIFTS对催化剂进行了表征。结果显示,F-T组分的加入促进了乙醇和丙醇的形成,但是对异丁醇选择性影响不同。结果表明,Fe促进了催化剂中各组分的分散,活性组分Cu在催化剂表面发生了富集,提高了H_2/CO活化吸附;另外,KFeCuZrO_2的催化剂表面含有较多的C_1物种,有利于乙醇和丙醇进一步发生β-加成反应得到异丁醇,而Co和Ni改性的催化剂上缺少足够的C_1物种,因此,异丁醇的选择性并未明显增加。Co的引入对催化剂结构以及Cu的分散影响不大,但是Co改性后催化剂性能有所下降,其原因是催化剂发生了失活;Ni添加后催化剂比表面积有所减小,且催化剂表面Cu/Zr物质的量比也降低到0.19,催化剂粒径增大,Cu-Zr之间相互作用减弱,异丁醇选择性降低。

LaCuZnX (X=Al,Zr, Al+Zr) perovskite-like catalysts treated by NaBH4 and their catalytic performance for CO2 hydrogenation to methanol

La:Cu:Zn:X (X=Zr, Al, Al+Zr) perovskite-like catalysts were prepared by coprecipitation method followed by liquid phase reduction by NaBH₄. The physicochemical properties of the catalysts were tested by a series of characterization methods, and the catalysts were tested for methanol synthesis from CO₂ hydrogenation in a fixed-bed reactor. The results showed that the as-prepared catalysts were mainly composed of La₂CuO₄ perovskite-like crystal structure and doping of elements led to the spatial distortion of the perovskite-like structure. After reduction by NaBH₄, metal copper species and some high-valence copper species were found, which could be further reduced during the reaction. The CO₂ conversion was positively correlated with the Cu surface area, the dispersion of Cu, and the (Cu^α++Cu⁰)/Cu_total of the catalyst. The higher methanol selectivity was obtained when Cu^α+ binding energy was farther away from Cu⁺ binding energy. LCZA had the highest CO₂ conversion, LCZ catalyst possessed the highest methanol selectivity, and LCZZA catalyst presented the optimal methanol space time yield.