We study silver-zinc oxide type catalysts with and without the addition of alumina and perform structural analysis and activity tests for the hydrogenation of carbon dioxide. Adding alumina has a dispersing effect on the zinc oxide without structurally altering the silver phase. An alumina-surface enriched ZnO/Al2O3 phase is observed with an increased surface reducibility. Ag/ZnO has a high selectivity towards carbon monoxide (63 ± 12 %) and methane (24 ± 3 %) and low selectivity towards methanol (13 ± 0.5 %). Operando infrared (SSITKA-FTIR) and mass spectrometric product detection indicate methane formation via an adsorbed carbon monoxide (COads) intermediate. The selectivity changes gradually with increasing alumina content, up to 80 ± 3 % toward methanol, and 20 ± 4 % carbon monoxide without methane detection, combined with a tripling of the space time yield to 0.65 ± 0.02mmolMeOH*gcat-1*h−1 at 250 °C and 30bar. Kinetic analysis suggests that the selectivity change originates from hindering the CO-pathway, while the formate pathway leading to methanol remains active.

中文翻译：

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氧化铝对 Ag/ZnO 基二氧化碳加氢催化剂性能的影响


我们研究添加和不添加氧化铝的银-锌氧化物型催化剂，并对二氧化碳的加氢进行结构分析和活性测试。添加氧化铝对氧化锌有分散作用，而不会改变银相的结构。观察到富含氧化铝表面的 ZnO/Al2O3 相，表面还原性增加。Ag/ZnO 对一氧化碳 （63 ± 12%） 和甲烷 （24 ± 3%） 具有高选择性，对甲醇 （13 ± 0.5%） 具有低选择性。原位红外 （SSITKA-FTIR） 和质谱产品检测表明甲烷是通过吸附一氧化碳 （COads） 中间体形成的。选择性随着氧化铝含量的增加而逐渐变化，对甲醇的选择性高达 80 ± 3%，对一氧化碳的选择性高达 20 ± 4%，无需甲烷检测，在 250 °C 和 30 bar 下，时空产率增加两倍，达到 0.65 ± 0.02 mmolMeOH*gcat-1*h-1。动力学分析表明，选择性变化源于阻碍 CO 通路，而导致甲醇的甲酸盐通路保持活性。