Zsm-5 Zeolite Catalyzed Methanol To Propylene Process Research

Propylene is one of the most basic organic chemical materials, global propylene demand is increasing. Because oil is the main raw material for propylene production by now, which is very limited over the world. There is lots of concern about methanol as raw materials for preparation of propylene, that is MTP technology(Methanol to Propylene). The focus of MTP technology is development of catalysts which has good performance on methanol to propylene. It is mainly based on the modification of ZSM-5 used as catalyst. Therefor, ZSM-5 zeolite was used as catalyst, the impact of silica alumina ratio and the various elements on the catalytic properties were studied, and optimum process conditions were determined.First, We investigated the effect of silica alumina ratio on the performance of catalytic activities. It was found that silica alumina ratio had a greater impact on the selectivity of propylene, and different silica alumina ratio corresponded to different optimum reaction temperature. Such as ZSM-5 zeolites with Si/Al ratio 50 and 200,reaction temperature 400℃and 450℃.ZSM-5 zeolites with silica alumina ratio 50 and 200 were modified using non-metallic elements P, transition metals Zn, Cu, Co, Ag, rare earth elements Ce, La, alkali and alkaline earth metals Mg, K respectively The experimental results shown that under the evaluation conditions of the catalyst, K-modified ZSM-5 catalyst with silica alumina ratio of 200 had the best yield of propylene. The effect of the concentration of K on the modification of the catalyst studied as well, the mass fraction of 2% of the K-modified Si-Al-ZSM-5 with silica alumina ratio 200 catalysts is the best candidate for the reaction of methanol to propylene catalysts, the methanol conversion rate was 98.6%,43.93% selectivity of propene was selectivity. Meanwhile the catalyst stability of catalyst modified by K was investigated using thermogravimetric method, the test found that the catalyst stability of catalyst was improved. At the same conditions, the coke deposition on the surface of the modified catalyst was less than that of the original catalyst, the active sites on the surface of the modified catalyst was suffered less effect, thereby increasing the life of the catalyst.The influences of reaction temperature, feed space velocity, material composition and other factors on performance of modified catalyst were researched based on 2% K-modified ZSM-5 zeolite catalyst. We found that high temperature was beneficial to enhance the methanol conversion rate and selectivity of propylene, but high temperature resulted the catalyst coking deactivation at the same time. Increasing space velocity was harmful to the methanol conversion and yield of propylene, this trend was intensified with the space velocity more than 3Kg (Methanol)/Kg (cat.)-h. At the same time increasing the proportion of water in the raw material leaded to the decreasing rate of methanol conversion and yield of propylene, and the water can be used as heat carrier would promptly remove the reaction heat, ensuring a longer life of the catalyst. The optimum conditions for methanol to propylene were as follows:reaction temperature 450℃, raw material feed space velocity 3Kg (methanol)/ Kg (cat.)·h, pure methanol feed at the same time. Isobutylene represents carbon 4 olefins, which was used for backing to the reactor during the methanol to propylene process, the activity of 2%K modified catalyst was investigated under reaction temperature 450℃, feed space velocity 3h-1, atmospheric pressure, The results showed that, when the molar ratio of isobutylene and methanol was 1:10, the selectivity of propylene could reach 44.5% when the methanol conversion rate was 98.7%.