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-Al2O3 (110) was studied using density functional theory (DFT). Using the same method, the effect of surface hydroxyls on γ-Al2O3 in
liquid paraffin during DME synthesis from
methanol dehydration is investigated. It is found that DME is mainly formed from two adsorbed CH3O groups via
methanol dehydrogenation on both dehydrated and hydrated γ-Al2O3 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-Al2O3(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.