Research Of Methanol Synthesis Catalysts Prepared By Micro-channel Reactor

Nowadays, people pay more and more attention to energy, methanol is one of clean and renewable energy. So it is meaningful to study methanol synthesis process. The research of methanol synthesis was mainly focused on the catalysts used in the process, micro-channel reactor was used to prepare the catalysts for the first time, and studied some parameters to find a better method to prepare catalysts of high catalytic activity.To study the effect of various factors during the preparation of the catalyst on the catalytic properties of the catalyst, the internal diffusion effect should be fisrt studied. Therefore, Co-precipitation method was used to prepare Cu/ZnO/Al2O3catalysts, and the influence of internal diffusion on the process was researched by varied pelleting force, binder type and particle size of catalysts. The results showed that the restriction of internal diffusion increased with the increase of pelleting force, which caused the decrease of CO conversion and increase of methanol selectivity. Via analysis of reaction mechanism and comparison of the mean free paths of CO and H2under the reaction condition, it was found that the diffusion type of CO and H2is different, the change of pore properties had different influences on CO and H2, and the effect on each reaction route was different when the H2concentration near active sites decreased, therefore the decrease ratio of reaction rates were different, that caused the change of methanol selectivity.Then, Cu/ZnO catalysts was prepared via micro-channel reactor, the catalysts were characterized by TEM, HRTEM, BET, XRD and so on. The results showed that, the lower the nucleation speed, the better the catalytic performance of the catalys, high nucleation speed led to too much crystal nucleus which could restrain the growth of the crystal; Ageing was the process in which the catalysts began to generate crystal structure, and this process needed some time to complete, suitable pH and ageing temperature could increase copper structure in the catalysts and make the copper more dispersive. The particles had grown to a stable size before ageing could be benefit to the performance of the catalysts, because that avoided the formation of bigger particles, the crystal could grow well.Next, the catalysts prepared by micro-channel reactor and traditional method were compared, the results demonstrated that the catalysts prepared by micro-channel reactor had smaller particle size and a narrow distribution, a higher degree of crystallization, more copper structures, and higher methanol yield. This is because the mixing effect of traditional co-precipitation was limited, some reactions were inevitably happened at extremely high or low pH, and the back mixing was serious, new particles would grow upon the old ones, that caused large particles and agglomeration, these were not conducive to the formation of crystal structure, so that the catalysts prepared by traditional co-precipitation had lower methanol catalyst activity.Last, the author summarized the whole thesis, and puts forward some views on the direction of follow-up study, hope to be able to play little role of the later research.