Synthesis of dimethyl ether from methanol over aluminium phosphate and silica–titania catalysts

Abstract

A series of solid–acid catalysts with different content of components were prepared by co-precipitation (sol–gel) method. These samples comprised silica–titania and modified γ-Al 2O 3 with phosphorus. To determination of optimum ones, the effects of various contents of phosphorus have been investigated. Dehydration of methanol to dimethyl ether (DME) on solid–acid catalysts was studied in a fixed-bed reactor at a temperature of 300 °C under atmospheric pressure and a GHSV of 15,600 h −1. The catalysts have been characterized using BET, XRD, FT-IR, NH 3–TPD and elemental analysis techniques and also the results were reported. According to the experimental results, silica–titania catalysts have exhibited low activity for DME synthesis. Phosphorus-modified catalysts have shown better performance compared to the untreated γ-Al 2O 3. It was found that surface areas increase with increasing in the molar ratio of aluminium-to-phosphorus at aluminium phosphate catalysts. Also, by modifying alumina with phosphorus, it was observed that the surface acidity of aluminium phosphate catalysts decrease with increasing in the molar ratio of Al/P at aluminium phosphate catalysts. The sample of non-stoichiometric aluminium phosphate (molar ratio of Al/P = 2) have exhibited the best conversion without any by-product.