Targeted Regulation Of Br?nsted Acid In 8-MR Channels Of Mordenite Catalyst For Dimethyl Ether Carbonylation

Ethanol is an important basic chemical raw material,and can also be used as green fuel and oil additive.Based on the energy structure of“poor oil,less gas and relatively rich coal”,developing a new route for producing ethanol from syngas is is helpful to alleviate the shortage of Chinese energy and guarantee the energy security of our country.The synthesis of methyl acetate（MA）from syngas by the carbonylation of dimethyl ether（DME）,and further hydrogenation to ethanol has many advantages,such as wide source of raw materials,mild reaction conditions,strong atomic economy,and high product selectivity.At present,this route is mainly subject to the core process step of carbonylation of DME to MA.Mordenite（MOR）is the most promising candidate catalyst for this reaction,but its activity and stability need to be further improved.This thesis focuses on the directional regulation of Br?nsted acid in microsized and nanosized MOR zeolites.The obtained MOR zeolite exhibits excellent catalytic performance in the carbonylation reaction of DME.A series of micronsized MOR with controlled acid distribution were prepared by hydrothermal synthesis using aniline or p-phenylenediamine as additives.The physical structure of the MOR catalyst synthesized with the addition of additives is similar to that of the HM parent.The quantitative analysis of acidity in different channels of HMOR shows that the number of Br?nsted in the 8-member ring（8-MR）of MOR zeolites synthesized with aniline as the additive can increase by up to 1.8 times compared with the HM parent.The number of Br?nsted in MOR zeolites 8-MR synthesized with p-phenylenediamine as additive can be increased by up to 2.2 times.Using aniline or p-phenylenediamine as additives,Br?nsted acid can be directionally enriched into 8-MR,significantly increasing the active site of the catalyst,and increasing the DME conversion from 23.2%to 60.3%.The sample modified by pyridine still exhibits high activity and stability after 40 h of reaction.Nanosized MOR zeolite with controllable acid distribution was successfully synthesized by introducing cetyltrimethylammonium hydroxide（CTAOH）into the hydrothermal synthesis system.CTAOH can significantly increase the total Br?nsted acid content of MOR zeolites,up to more than twice the amounts of MOR-N samples,and can selectively enrich Br?nsted acid to 8-MR,where the proportion of Br?nsted acid content to the total Br?nsted acid content increases from 55%to 66%.Meanwhile,MOR zeolites with prismatic,nanosheet,and petal morphologies can be obtained.The thickness of the nanosheets MOR is only 10–30 nm,greatly reducing the pore length of the 8-MR side bag,reducing the material transport distance,and reducing the formation of carbon deposits.By analyzing the evolution of structure and morphology during the crystallization process of the nanosheets MOR,the crystallization mechanism was revealed.The steady-state conversion and STY_MA of DME on nanosheet MOR zeolites can be up to three times as high as traditional MOR zeolites.In this thesis,the effect of acid distribution on carbonylation of DME was investigated by directional enrichment of Br?nsted acid on zeolite at micron and nano scale.This study provides an idea for the design of high activity zeolites and an effective method for the development of efficient and green ethanol synthesis.