前体元素含量及物相组成对甲醇合成催化剂性能的影响

Effect of elemental content and phase composition of precursors on performance of catalysts for methanol synthesis

基于共沉淀法制备了不同n(Cu)∶n(Zn)的Cu/ZnO/Al_(2)O_(3)催化剂,采用XRD、FTIR和N2吸附-脱附等手段对二元前体及催化剂进行表征,并将催化剂用于合成气制甲醇反应,研究了二元前体的物相随n(Cu)∶n(Zn)的演变规律,分析了二元前体元素含量及物相组成对催化剂晶粒尺寸、织构性质和活性的影响。实验结果表明,Zn含量增加使得二元前体物相发生由锌孔雀石到锌孔雀石和绿铜锌矿混合相再到绿铜锌矿的结构转变;二元前体的物相组成同时反映了催化剂中Cu/Zn的相对含量,并影响焙烧后催化剂的晶粒大小和织构特征,进而影响催化剂的性能;当二元前体为锌孔雀石和绿铜锌矿混合相且锌孔雀石物相占比较高时,能够获得晶粒较小、比表面积和孔体积较大的催化剂。此时,催化剂的性能最佳,甲醇时空收率达1.45 g/(mL·h),活性衰减率为11.7%,具有较好的应用价值。

A series of Cu/ZnO/Al_(2)O_(3)catalysts with varying n(Cu)∶n(Zn)were prepared via the co-precipitation method and characterized by XRD,FTIR,and N2 adsorption-desorption techniques.The catalysts were tested in the methanol synthesis reaction from syngas,and the evolution of the precursor phase structure with varying n(Cu)∶n(Zn)was studied.The effects of elemental content and phase composition of the precursors on the crystallite size,textural properties,and activity of the catalysts were analyzed.Results indicate that increasing the Zn content causes the precursor phase to transition from zincian malachite to a mixed phase of zincian malachite and aurichalcite,and finally to aurichalcite.The precursor phase composition reflects the relative Cu/Zn content in the catalyst and influences the crystallite size and textural properties after calcination,which in turn affects the catalyst performance.When the precursor is predominantly zincian malachite in a mixed phase with aurichalcite,the resulting catalyst has a smaller crystallite size,larger specific surface area and pore volume.Under these conditions,the catalyst exhibits optimal performance,achieving a methanol space-time yield of 1.45 g/(mL·h)and an activity decay rate of 11.7%,indicating promising potential for industrial application.