Study On The Dehydration Of Methanol To DME Over Zeolite Catalyst And Its Technical Process

Dimethyl ether(DME) is a new pollution-free fuel that can alternate diesel and LPG, it has attracted great attention at home and abroad. At present, one-step synthesis of DME from Syngas with its unique advantage has become the research hot spot at many sythesise methods, the key to this progress is to choose the most proper catalyst for dehydration of methanol to DME. So, searching for a catalyst with high activity at low temperature, high selectivity at wide temperature area and good stability becomes important for the one-step synthesis of DME.This paper aims to seek an excellent catalyst for one-step synthesis-and develop a green chemical process to synthesis of DME, including the choice of the active component and carrier, the preparation of catalyst and the optimization of the reaction process condition. The primary results have been listed as follows:1. Different zeolites with corresponding topology structure have been investigated during the choice of the active component of methanol dehydration reaction. The results have shown that HZSM-23 zeolite presented good activity and selectivity for DME in methanol dehydration reaction at the temperature between 150 and 450℃.Hence, when selecting the HZSM-23 with the ratio of SiO2/Al2O3 equals to 60 as the active component of the catalyst, the final optimization of reaction technique we have obtained listed as follows:the reaction temperature is 300℃,the feed WHSV is 5h^-1, the reaction pressure is 0.1 MPa, and the corresponding methanol conversion is 86.5%, the selectivity of DME is 98.8%.2. In the second part.the catalytic reaction behaviors of applyingγ-Al2O3 SiO2 and P-Al as the catalyst support have been investigated in the methanol dehydration reaction at various temperatures in detail. The results have shown thatγ-Al2O3 presented much high activity and selectivity at low temperature, but producting too much by-products and coke at high temperature.meanwhile, the DME selectivity dropped down sharply.For SlO2 and P-Al, both show very low activity for methanol dehydration reaction, but owning relatively high selectivity at the temperature between 150 and 450℃. Therefore,we selectγ-Al2O3 as support at the low temperature, SiO2 for high temperature.3. In the study of the optimization of reaction prograss conditions, selecting HZSM-23 zeolite as the active component,γ-Al2O3 and SiO2 as support respectively. The result of the study has indicated that the most proper optimization reaction technique namely the componets of catalyst contains the ratio ofγ-Al2O3/HZSM-23(wt) is 6:4, the reaction temperature is 265℃, the feed WHSV is 5h-1, the pressure is 0.1Mpa, when the time on steam last for 12 hours, corresponding methanol conversion is 88.9%, the selectivity of DME is above 99.8%. The life of catalyst also has been investigated, the result show that after reacting continuously for 500 hours with the same catalyst, methanol conversion turn to 77.5% and the selectivity of DME is still above 99.8%, through the research results mentioned above, it presents a good industrial application foreground.