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Highly active Cu/ZnO–Al catalyst for methanol synthesis: effect of aging on its structure and activity

机译：用于甲醇合成的高活性Cu / ZnO-Al催化剂：老化对其结构和活性的影响

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The influence of aging of precipitates on the physical and catalytic properties of a copper/zinc oxide-aluminium (Cu/ZnO–Al) catalyst with an optimized composition (low Al concentration, Cu/Zn/Al = 68/29/3) prepared using co-precipitation has been investigated in detail. The change in the structure of precipitates with aging (from amorphous zincian georgeite to crystalline zincian malachite) strongly influences the micro- and nano-structure (Cu and ZnO crystallite size, exposed copper surface area, Cu–ZnO interactions and stability of ZnO) of the final Cu/ZnO–Al catalysts obtained after calcination and reduction of the precipitates. The results of catalytic activity in methanol synthesis from syngas show the higher intrinsic activity of the catalysts derived from aged zincian malachite precipitates as consequence of the increase in the exposed copper surface area and the Cu–ZnO contacts. The stability of catalysts under the reaction conditions was also improved in the catalysts derived from precipitates aged after crystallization of malachite. The catalyst derived from the precipitate removed close to the point of crystallization of malachite shows very poor activity in the methanol synthesis as consequence of its segregated large Cu crystallites in low contact with ZnO derived from the absence of carbonate retention after calcination of the precipitate and the presence of sodium species after conventional washing which favour the strong sintering and crystallization of Cu during reduction.
机译：沉淀物的老化对具有最佳组成（低铝浓度，Cu / Zn / Al = 68/29/3）的铜/氧化锌铝（Cu / ZnO-Al）催化剂的物理和催化性能的影响使用共沉淀已被详细研究。随着时间的推移，沉淀物结构的变化（从无定形的锌矿乔治山石到结晶的锌绿孔雀石）会强烈影响合金的微观和纳米结构（Cu和ZnO的晶粒尺寸，暴露的铜表面积，Cu-ZnO相互作用和ZnO的稳定性）。煅烧和沉淀物还原后获得的最终Cu / ZnO-Al催化剂。由合成气合成甲醇的催化活性结果表明，由于暴露的铜表面积和Cu-ZnO接触面积的增加，衍生自老化的锌基孔雀石沉淀的催化剂具有更高的固有活性。在孔雀石结晶后老化的沉淀物中衍生的催化剂中，催化剂在反应条件下的稳定性也得到了改善。从孔雀石结晶点附近移出的沉淀物得到的催化剂在甲醇合成中显示出非常差的活性，这是由于其分离出的大的铜微晶与ZnO接触程度低，这是由于沉淀物煅烧后没有碳酸盐残留而导致的。常规洗涤后存在钠物质，这有助于还原过程中铜的强力烧结和结晶。

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