Effect of surface hydroxyls on dimethyl ether synthesis over the γ-AlO in liquid paraffin: A computational study

In a recent paper (Zuo et al., Appl Catal A 408:130-136, 2011), the mechanism of dimethyl ether (DME) synthesis from methanol dehydration over γ-AlO (110) was studied using density functional theory (DFT). Using the same method, the effect of surface hydroxyls on γ-AlO in liquid paraffin during DME synthesis from methanol dehydration is investigated. It is found that DME is mainly formed from two adsorbed CHO groups via methanol dehydrogenation on both dehydrated and hydrated γ-AlO in liquid paraffin. No close correlation between catalytic activity and acid intensity was found. Before and after water adsorption at typical catalytic conditions (e.g., 553 K), the reaction rate is not obviously changed on γ-AlO (100) surface in liquid paraffin, but the reaction rate decreases by about 11 times on the (110) in liquid paraffin. Considering the area of the (110) and (100) surfaces under actual conditions, the catalytic activity decreased mainly because the Al3 sites on the (110) surface gradually become inactive. Catalytic activity decreased mainly due to surface hydrophilicity. The calculated results were consistent with the experiment. © 2013 Springer-Verlag Berlin Heidelberg.