Silica-supported model copper catalysts were prepared by supporting bis(1,5-diphenyl-1,3,5-pentanetrionato)dicopper(II), Cu₂(dba)₂, on Cab-O-Sil by a batch impregnation technique. This metal complex showed a strong affinity for the silica support, developing monolayer coverages near the value predicted from a consideration of the size and shape of the planar metal complex (2.6 wt % Cu). The supported catalysts were subsequently activated by decomposing the organic ligands at 400 °C in air followed by reduction with 2% H₂/He at 250 °C. One sample was prepared having a loading of 3.70 wt % Cu₂(dba)₂/silica catalyst, and it was examined for the methanol synthesis reaction under the following conditions: 250 °C with an equimolar gas mixture of CO and H₂ in a high-pressure batch reactor. Kinetic data over the model catalyst were fit to a rate equation, second order in the limiting reactant (H₂), with a pseudo-second-order rate constant k₂[CO]_o[H₂]_o = 0.0957 [h-g total Cu]⁻¹. A control experiment using a commercial catalyst, Cu/ZnO/Al₂O₃ with a copper loading of 41.20 wt %, showed a value of k₂[CO]_o[H₂]_o = 0.793 [h-g total Cu]⁻¹. A fresh sample of Cu₂(dba)₂/silica was examined for methanol decomposition reaction at 220 °C. The model catalyst shows a methanol decomposition first-order rate constant greater than that of the commercial Cu/ZnO/Al₂O₃catalyst: 1.59 × 10^–1 [min-g total Cu]⁻¹ versus 9.6 × 10^–3 [min-g total Cu]⁻¹. X-ray diffraction analyzes confirm the presence of CuO particles in both catalysts after calcinations. Copper metal particles were found in both catalysts (fractional Cu dispersions were 0.11 and 0.16 on commercial and model catalysts, respectively) after the reduced catalysts were used in both the methanol synthesis and decomposition reactions. Using the values of copper dispersion found in these samples, we recalculated the rate constants for the two reactions per unit surface copper. These refined rate constants showed the same trends as those reported per total amount of Cu. One role of the promoter(s) in the commercial catalyst is the inhibition of the methanol decomposition reaction, thus allowing higher MeOH synthesis reaction rates in those regimes not controlled by thermodynamics.

中文翻译：

---

双（1,5-二苯基-1,3,5-戊烷三酮）二铜（II）/二氧化硅制备的模型催化剂催化的甲醇合成和分解反应

通过分批浸渍技术在Cab-O-Sil上负载双（1,5-二苯基-1,3,5-戊烷三酮）二铜（II），Cu ₂（dba）₂来制备二氧化硅负载的模型铜催化剂。该金属络合物显示出对二氧化硅载体的强亲和力，在考虑到平面金属络合物（2.6wt％Cu）的尺寸和形状所预测的值附近发展出单层覆盖率。随后通过在400℃下在空气中分解有机配体，然后在250℃下用2％H ₂ / He还原来活化负载的催化剂。制备一个样品，其负载量为3.70 wt％Cu ₂（dba）₂/二氧化硅催化剂，并在以下条件下检查甲醇的合成反应：在高压间歇反应器中，在250°C下用等摩尔的CO和H _2的气体混合物。模型催化剂上的动力学数据拟合至速率方程，在限制反应物（H ₂）中为_二级，其拟_二级速率常数为k ₂ [CO] _o [H ₂ ] _o = 0.0957 [hg总铜] ^-1。使用市售催化剂Cu / ZnO / Al ₂ O ₃的铜负载量为41.20 wt％的对照实验显示k ₂ [CO] _o [H ]的值₂ ] _o＝ 0.793 [hg总Cu] ^-1。在220℃下检查新鲜的Cu ₂（dba）₂ /二氧化硅样品的甲醇分解反应。模型催化剂显示的甲醇分解一级速率常数大于商用Cu / ZnO / Al ₂ O ₃催化剂：1.59×10 ^–1 [min-g总Cu] ^-1对9.6×10 ^–3 [min -g总Cu] ^-1。X射线衍射分析证实煅烧后两种催化剂中都存在CuO颗粒。在将还原的催化剂用于甲醇合成和分解反应后，两种催化剂中均发现了铜金属颗粒（在商业催化剂和模型催化剂上，Cu的分数分散度分别为0.11和0.16）。使用这些样品中发现的铜分散值，我们重新计算了每单位表面铜的两个反应的速率常数。这些精制的速率常数显示出与报告的每单位铜含量相同的趋势。助催化剂在市售催化剂中的作用之一是抑制甲醇分解反应，从而在不受热力学控制的那些条件下允许更高的甲醇合成反应速率。