Controllable Synthesis Of Mordenite Zeolites And Their Catalytic Performance On Dimethyl Ether Carbonylation

Ethanol,as an important basic chemical and fuel additive,has a broad market prospect.Considering the characteristics of the energy structure of our country,developing a new process for producing ethanol from syngas is in line with the country’s energy strategy that aims at the development of energy diversification and clean utilization.Carbonylation of dimethyl ether to methyl acetate followed by hydrogenation of methyl acetate to ethanol is a promising synthesis route that has attracted wide attention in recent years,owing to its superior atom economy,wide source of raw materials and mild reaction conditions.In terms of carbonylation of DME to MA reaction,mordenite(MOR)is considered to be the most promising catalyst so far.Focusing on the two objectives of "preparing MOR catalysts with high efficiency" and "efficiently preparing MOR catalysts",this thesis studied the synthesis and regulation of MOR from the spatial and time dimensions.The strategies for morphology control and efficient preparation were proposed and the obtained catalysts showed great performance for DME carbonylation.Based on understanding the crystallization mechanism of MOR,a facile method to tailor the morphology of MOR is proposed.Cetyltrimethylammonium bromide(CTAB)was employed as a growth modifier to alter the anisotropic growth rates of MOR,resulting in controllable morphology of nanosheets-assembled,bundles-like and flowers-like nanorods clusters.XRD,Ar physisorption,ICP-OES,27 Al MAS NMR,NH3-TPD,and FTIR were used to analyze the effect of CTAB addition on the physicochemical properties of MOR.Taking TG-DTG characterization together with DFT calculations,we revealed the morphology regulation mechanism,and CTAB was demonstrated to play two roles in the crystallization of MOR: i.e.growth modifier and structure-directing agent.The optimized MOR catalysts were proved to have better diffusion performances.As a consequence,they showed better catalytic activity in DME carbonylation with an enhanced DME conversion from 49% to 67%.Fast synthesis of MOR on the order of minutes was achieved in a stainless steel tubular reactor at high temperature with a rapid heating rate.Characterization results demonstrated that the fast synthesis method significantly reduced the crystallization time without any negative impact on acidic properties of the synthesized MOR.Compared with the counterpart synthesized by traditional method for 72 hours,the MOR catalyst synthesized in 45 minutes by fast synthesis exhibited better catalytic activity in DME carbonylation.It proves that this method is an efficient way for preparation of MOR catalyst for DME carbonylation.