Effects Of Different Pore Structures And Acidity Zeolites On The Alkylation Of Isobutane/butene

Alkylated gasoline produced by alkylation of isobutane and butene is a clean and environment-friendly gasoline blending component.This alkylated gasoline is mainly composed of trimethylpentane（TMPs）.Traditional liquid acid catalysts include concentrated sulfuric acid and hydrofluoric acid.These two strong acid catalysts have problems such as corrosion of equipment and environmental pollution,so their industrial application is limited.The use of solid acid catalyst can solve this problem.Among many solid acid catalysts,Beta and Y zeolites have attracted extensive attention from scholars at home and abroad because of their unique pore structure and acidity that can meet the requirements of isobutane/butene alkylation reaction.The current research focuses on the effects of molecular sieves with different topologies and acid properties,but the influence of pore shape selection and acid properties on the product distribution is not clear.In addition,there are few studies on the difference between liquid phase feed and gas phase feed,as well as the comprehensive influence of the acidity of different Si/Al zeolite on their catalytic alkylation stability.In this work,Beta zeolites and Y zeolites with different acidity and pore structure were selected,and their catalytic properties in Isobutane/butene alkylation were studied.The physicochemical properties of molecular sieves were characterized by XRD,SEM,N₂adsorption-desorption,NH₃-TPD and Py-IR measurement.At the same time,the pore structure and surface acidity of the catalyst are combined with the catalytic performance of alkylation reaction.The concrete research contents are as follows:（1）Beta zeolites with Si/Al of 8 was selected to calculate the bubble point temperature of Isobutane/butene C₄mixed raw materials at 1 MPa and 2 MPa respectively.Under a certain pressure,the alkylation performance below the bubble point（liquid phase feed）and above the bubble point（gas feed phase）was explored by changing the reaction temperature and sampling 30 min after the reaction.The optimum process conditions of Isobutane/butene alkylation were determined.The reaction temperature was 80 ^oC.The reaction pressure was 1MPa.The WHSV was 1 h^-1.The alkylation C₈yield and the selectivity of the target product TMP of mesoporous Beta zeolites with Si/Al of 10,13 and 17 were investigated.The comprehensive effects of acid properties and pore shape selection of the molecular sieves were studied.The catalytic results showed that the initial yield of C₈and the initial selectivity of TMP decreased with the increase of Si/Al.With the increase of reaction time,the C₈yield and TMP selectivity of different Si/Al zeolite decreased gradually.The greater the ratio of medium strong B/L acid and the greater the concentration of medium strong（strong）B acid center,the higher the stability of zeolite.Under the comprehensive influence of less acid amount and mesoporous,the catalytic effect and stability of zeolite were the worst.（2）Industrial NaY zeolite were modified by three post-treatment methods to obtain Y zeolite with different acidity and pore structure.The characterization results showed that Y-1and Y-3 are microporous zeolite,and Y-2 had many mesopores.The total acid content of Y-1and Y-2 was much greater than that of Y-3;Under the conditions of 80 ^oC,1 MPa,isobutane/butene molar ratio of 37.8,WHSV of 1 h^-1and 30 min,the yield of target product C₈under the action of Y-1,Y-2 and Y-3 decreased successively.The effects of acid properties and pore shape selection on product distribution were explored.The catalytic results showed that the increase of total acid content was conducive to the formation of target products for Y zeolite with similar pore structure.For the Y zeolite with similar total acid content,the zeolite with more mesopores and large external specific surface area was not conducive to the shape selection of reactant molecules,so the yield of the target product was low.Relative to the pore properties,the regulation of acid centers of zeolite was the key factor affecting the distribution of reaction products.