插层结构水滑石前驱体制备Cu/ZnO/Al2O3催化剂及其甲醇合成催化性能

Preparation of Cu/ZnO/Al2O3 catalyst by intercalated hydrotalcite precursor and its catalytic performance in methanol synthesis

  • 摘要: 分别采用共沉淀法、离子交换法和焙烧复原法制备 \rmCu(\rmC_\rm2\rmO_\rm4\rm)_2^2 - 络合阴离子插层ZnAl-LDH水滑石纯物相前驱体,经焙烧得到片层结构的Cu-ZnAl-LDO催化剂。通过XRD、TEM、ICP、H2-TPR、N2O-H2氧化还原滴定及N2物理吸附-脱附等方式对前驱体和催化剂进行表征分析,考察了不同制备方法对插层结构催化剂结构性质及其合成甲醇催化活性及稳定性的影响。结果表明,相比于离子交换法和焙烧复原法,共沉淀法制备的CP-Cu-ZnAl-LDH前驱体具有较完整的水滑石二维层状结构,且插层Cu组分含量最大,焙烧后层间高分散的Cu物种颗粒尺寸较小,与ZnO发生相互作用,表现出很好的催化活性,单位质量Cu的甲醇收率可达3412 mg/(gCu·h);同时,层板对Cu物种的限域作用有效抑制了Cu颗粒的团聚长大,连续反应60 h过程中催化剂未发现失活。

     

    Abstract: The \rmCu(\rmC_\rm2\rmO_\rm4\rm)_2^2 - complexed anion intercalated ZnAl-LDH hydrotalcite pure phase precursors were prepared by co-precipitation, ion exchange and calcination-reconstruction methods; after that, the Cu-ZnAl-LDO catalysts with lamellar structure were obtained by calcination of the precursors. The precursors and catalysts were characterized by XRD, TEM, ICP, H2-TPR, N2O-H2 TPD titrations and N2 physisorption; the effect of preparation method on the confinement degree of intercalated active Cu species and the catalytic activity and stability of Cu-ZnAl-LDO in methanol synthesis was investigated. The results indicate that compared with the ion exchange and calcination-reconstruction methods, the CP-Cu-ZnAl-LDO catalyst prepared by co-precipitation method has a higher interlayer Cu content as well as a stronger confinement effect of layer plate on the Cu species. In addition, the unique ordered layered structure of hydrotalcite can also improve the dispersion of active Cu species between the layers and inhibit the sintering of Cu particles. As a result, the CP-Cu-ZnAl-LDO catalyst prepared by co-precipitation method exhibits excellent performance in methanol synthesis; the space-time yield of methanol reaches 3412 mg/(gCu·h) and basically no deactivation is observed after continuous reaction for 60 h.

     

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