Preparation Of LDO Bifunctional Catalysts And The Reaction Performance Of The Sidechain Alkylation Of Toluene To Styrene

As an important raw material in the petrochemical industry,styrene was mainly produced by a two-step process of dehydrogenation after the alkylation of benzene and ethylene to form ethylbenzene.Compared with the traditional technology,one-step synthesis of styrene by the side-chain alkylation of toluene and methanol had the advantages of energy saving,consumption reduction,short process route and low raw material cost.For the reaction of side-chain alkylation of toluene to styrene,it has been confirmed that this reaction requires the catalyst to have suitable acid-base sites and space structure.Layered double oxides（LDO）possessed acid-base bifunctional properties and a layered two-dimensional structure,which are suitable for the side-chain alkylation of toluene.In this paper,a series of Cs/CuAl-LDO@X catalysts were prepared by using X zeolite as the support,copper nitrate and aluminum nitrate as the Cusource and the Al source.On this basis,a series of different acid components were introduced to prepare a series of modified Cs/CuAl-LDO@X catalysts;the morphology,texture and acid-base properties of the catalysts were characterized to provide a basis for the reaction;the reaction was carried out in the self-made fixed bed.The reaction performance for the side-chain alkylation of toluene and methanol to styrene was explored in the reactor,and the side-chain alkylation conditions were optimized.The research contents started from the following:（1）The Cs/CuAl-LDO@X catalysts were prepared by co-precipitation method using X zeolite as the support to grow CuAl-LDH on its surface,impregnated with Cs and then calcined.The CuAl-LDO in the catalysts were uniformly coated on the surface of the zeolite in a lamellar structure,with good crystal structure,large surface area and rich pore space structure.The acid-base sites in the catalysts were evenly dispersed and the acid-base strength is appropriate,which had good side-chain alkylation performance of toluene;The reaction properties of catalysts with different LDO contents and different Cs impregnation amounts were evaluated,and the side-chain alkylation conditions were optimized.When the conversion of toluene was 4.78%,the selectivity of styrene was 46.91%,the total yield of styrene and ethylbenzene was 4.43%.（2）The modified Cs/CuAl-LDO@X catalysts were prepared by impregnating different acid components in equal volume.The number and distribution of acid-base sites in the BPO₄-modified catalysts were further adjusted,and the proportion of medium and strong base sites increases.At this time,the strength of acid-base sites in the catalyst was more suitable.The performance of catalysts with different BPO₄ contents and different reaction conditions were investigated.When the BPO₄ contents were 7 wt%,the performance was the best.Under the optimal side-chain alkylation conditions,the conversion of toluene was increased to 8.53%,the selectivity of styrene was increased to 75.78%,and the total yield of styrene and ethylbenzene was 8.17%.