Catalytic ethanol dehydration to diethyl ether over palladium-modified phosphorus gamma alumina catalysts

Abstract

The gamma alumina (γ-Al2O3) catalyst was modified with phosphorous (P) by acid activation technique and palladium (Pd) by the incipient wetness impregnation technique. The obtained catalysts were characterized with various techniques including X-ray diffraction (XRD), inductively coupled plasma (ICP), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX), N2 physisorption, ammonia temperature-programmed desorption (NH3-TPD), and thermogravimetric analysis (TGA). In addition, these modified catalysts were tested in ethanol dehydration reaction in a fixed-bed microreactor to determine ethanol conversion and product yield at the atmospheric pressure with temperatures ranging from 200-400oC. From the results, the phosphorous modification diminished the amount of moderate to strong acid sites leading to increased amount of weak acid sites. The phosphorous modified catalyst exhibited the highest diethyl ether yield of 38.41% at the temperature of 350°C. Furthermore, the phosphorous addition on catalyst significantly decreased the amount of coke deposition on the catalyst surface. The Pd-modified catalyst likely acted as the chemical promoter of catalyst resulting in increased ethanol conversion at low temperature. Nevertheless, the presence of Pd on catalysts enhanced the dehydrogenation reaction to produce acetaldehyde as a major product at low temperature ca. 200°C.