锆助剂对低温液相合成甲醇用铜铬硅催化剂性能的影响

Effects of zirconium on the performance of Cu-Cr-Si-O for low-temperature methanol synthesis in liquid phase

考察了含锆的铜铬硅催化剂低温液相合成甲醇性能,并进行了BET、TPR-H2、TPD-H2、TPD-CO、XRD和XPS表征。结果表明,锆作为结构助剂及电子助剂对催化剂在低温液相合成甲醇反应中具有显著的促进作用,反应活性可提高32.25%。锆助剂能有效提高催化剂的比表面积,促进催化剂中铜铬组分的分散及表面富集。ZrO2加入在催化剂表面产生的Cu+与催化活性的改善密切相关,Zr4+、Cr3+、Cu+可形成复合中心,为价态的稳定性提供微环境,在H2活化及C-O键的断裂等反应步骤中起重要作用。

The low-temperature methanol synthesis from syngas was studied in a semi-continuous slurry reactor using Cu-Cr-Si-O catalysts promoted by zirconia. The catalysts were characterized by BET, TPR-H2, TPD-H2, TPD-CO, X-ray diffraction spectroscopy and X-ray photoelectronic spectroscopy. The results,showed that zirconia plays an important role in the catalytic performance improvement. With the promotion of zirconia, the reaction activity increases by 32.5 %, the selectivity of methanol reaches a maximum of 96.2%, and the reaction stability improves obviously. Zirconia acts as an effective structural promoter. It gives an enhancement in surface area of catalysts, promots the copper dispersion on surface and brings about an enrichment of copper and chromium on surface. Meanwhile, zirconia acts as an electronic promoter and Cu^＋ exists steadily on surface. It could be concluded from the reaction and characterization results that the excellent performance of catalysts relates directly to the presence of Cu^＋ on the catalyst surface and an increase of surface area of catalysts, which is promoted by zirconia. On the catalysts surface, more complex active sites composed of Zr^4＋ , Cr^3＋ and Cu^＋ provides the micro surroundings for the valence stability, which is a key factor for the activation of H-H bond and carbon-oxygen bond.