Preparation Of Acid-Base Dual-Function Magnetic Nucleus Catalyst And Its Performance Of Toluene Side Chain Alkylation To Styrene

Styrene is an important petrochemical resource,and my country’s styrene industry is still in a period of rapid development.Common methods currently used for synthesizing styrene are ethylbenzene dehydrogenation,which uses benzene and ethylene as raw materials to obtain styrene through a two-step reaction.Toluene side chain alkylation can obtain styrene through one-step reaction,but this method requires the catalyst to have dual functions of acid and base and a certain spatial structure.The layered composite oxide（LDO）obtained by calcination of layered hydroxide)has a two-dimensional layered structure and acid-base sites to meet the requirements of this reaction.In this paper,Co Al-LDH was grown in situ on X molecular sieve by co-precipitation method,and the final Cs/Co Al-LDO@X catalyst was obtained after Cs OH modification and calcination,which was used for the side chain of toluene with methanol for gas-solid alkylation.The catalyst preparation conditions and reaction factors were tested and optimized.Besides,Fe₃O₄ was prepared,and coated with a layer of protective Al₂O₃ to synthesize Al₂O₃@Fe₃O₄ as a carrier,and the obtained Al₂O₃@Fe₃O₄ was used as a carrier.Then loaded with Co Al-LDH,and then impregnated with Cs OH and calcined to obtain Cs/Co Al-LDO@Al₂O₃@Fe₃O₄ magnetic catalyst,which was used for the reaction that side chain of toluene with methanol for liquid-solid alkylation.The following results were achieved:Using X molecular sieve as carrier,cobalt nitrate as cobalt source and aluminum nitrate as aluminum source,Co Al-LDH with layered structure was synthesized on the surface of X molecular sieve,which was impregnated with Cs OH and calcined at 450℃for 4 h to obtain Cs/Co Al-LDO@X catalyst.The characterization results show that LDO is distributed on the surface of the X molecular sieve in the form of nanosheets.The diameter of the nanosheets is between 100-200 nm and the thickness is between 10-20 nm.The catalyst has both weak acid and medium acid,medium base and strong base sites.The catalyst was used in the reaction of toluene side chain methanol alkylation.The catalyst showed the best catalytic performance when the Cs content was15 wt%and the Co Al-LDO content was 6 wt%,and the toluene conversion rate is 4.92%,and the styrene yield reaches 1.97%.In order to further improve the toluene conversion rate,a new alkaline earth metal component Ca was introduced through calcium nitrate,and prepared the two-component modified catalyst Ca-Cs/Co Al-LDO@X that used to toluene side chain methanol alkylation reaction.When the Ca content is 3 wt%,the catalyst has the best catalytic activity,the toluene conversion rate is 8.22%,and the styrene yield reaches 2.55%.At this time,the styrene selectivity and side chain The selectivities are 31.07%and 94.93%,respectively.First,Fe₃O₄ was synthesized as the magnetic core,and then a layer of Al₂O₃ was wrapped to protect the magnetic core,and the obtained Al₂O₃@Fe₃O₄ was used as the catalyst carrier.Then the Co Al-LDH active component was synthesized on the catalyst carrier using cobalt nitrate and aluminum nitrate as raw materials,and the Cs/Co Al-LDO@Al₂O₃@Fe₃O₄magnetic catalyst was obtained by alkali modification and calcination treatment.The characterization results show that the magnetic core Fe₃O₄ is distributed in spherical shape,the diameter of a single particle is about 100 nm,and LDO grows vertically on the surface of the magnetic core in the form of nanosheets with a thickness of about 20 nm.The catalyst was used in the liquid-solid alkylation of toluene side-chain formaldehyde,and the optimal Cs content and LDO content of the catalyst were 15 wt%and 20 wt%,respectively.After the reaction conditions were optimized,the toluene conversion and styrene yield reached 3.14%and 2.3%,the styrene selectivity was 73.3%.