Preparation Of Industrial MTO Catalyst In The Solid Phase System

Ethylene and propylene are not only the important raw materials of organic chemical industry,but also their production is closely related to the energy and resource security in china.In our country,the methanol to olefins(MTO,the first industrialization in China)is a reasonable and effective means to supplement ethylene and propylene resources.MTO catalyst is the core and key in the optimization of MTO process.In recent years,there are more than 30-40 large coal or energy companies to set up MTO projects in China,and the new industry projects are in urgent need of a new generation of MTO catalysts with high efficiency and low consumption.It is one of the most important subjects in the field of energy and chemical industry that the preparation of MTO catalysts with high performance can be satisfied with the requirement is characterized by green chemistry.Synthesis of molecular sieves in solid phase is a recently developed new method,and it is expected to provide an efficient and environmentally friendly high technique for the production MTO catalyst in industrial scale.In this subject,the following points should be given more attention.First,SAPO-34 molecular sieve is an important component in MTO catalysts.However,SAPO-34 is easily deactivated by carbon deposition and has a obvious induction period in MTO reaction.How to shorten the induction period of the catalyst in the reaction process,prolong the catalytic life and improve the selectivities to ethylene and propylene has always been a key problem for domestic and international researchers.Second,at present,SAPO-34 is synthesized by hydrothermal method in industry.In this method,the synthesis system contain a large amount of water as the solvent and other organic medium,which leads to low utilization rate of unit reactor volume and high synthesis cost,but also produces a large number of liquor containing a lot of organic amine and un-reacted raw materials.Although the mother liquor can be reused,a limited number of cycles still inevitably cause the emission of large amount of waste liquor.So the present production method of SAPO-34 cannot satisfy the requirement of clean production.Third,a large amount of waste MTO catalyst powder will be produced in MTO plant operation.The fine powders have been unable to meet the requirements of industrial reaction according to the point of view of the size,strength as well as catalytic activity,but they still retains a part of catalytic activity of SAPO-34.Therefore,as how to upgrade and reuse the waste MTO catalyst powder is the current problem to be sloved urgently.In view of the above problems,this paper with practical application as starting point and the solid phase synthesis as main line did some works on the two aspects: industrial preparation of SAPO-34 in a green method and upgrading the quality of the waste MTO catalyst.The main contents are as follows:First,in the solid phase synthesis system,the SAPO-34 with layered morphology was prepared by using the seed solution directing agent,when the SAPO-34 with layered morphology shorten the diffusion path of the reactant and the product effectively in the MTO reaction,and improves the catalytic selectivity and prolongs the catalyst life.At the same time,the scale-up experiments were carried out on the scale of 10 L and 100 L,and the key factors in the scale-up production of SAPO-34 via the the solid phase synthesis were preliminarily explored,which laid the foundation for the realization of green and clean production of SAPO-34 molecular sieves.Second,silicon aluminum phosphate ingredients containing in the waste liquor produced by hydrothermal synthesis of SAPO-34 were simply and efficiently recovered through a combination of flocculation method.The recovered materials after being dried and broken into powder can be used as a part of raw material for the solid phase synthesis of new SAPO-34 with a multi layer structure.This method does not reproducethe second mother liquor and realizes the complete utilization of the waste liquor.Third,a new green and environmentally friendly method for synthesis of SAPO-34 with rich nano crystalline mesoporous MTO catalyst was explored.In addition,the waste MTO catalyst fine powder can be re-bonded by the binder ofthe raw material of aluminum silicon phosphorus and after the re-bonded waste catalyst was regenerated by solid phase conversion,a new fresh MTO catalyst with high performance can beobtained.The solid phase regeneration process not only simplifies the SAPO-34 regeneration process,but organic amine template can be easily recovered and no waste liquor was generated.It is a green process route for waste MTO catalyst reutilization.On the basis of laboratory experiment and pilot experiment,the author and the team together have realized industrialization on the SAPO-34 solid phase synthesis for the first time and the prepared MTO catalysts showed comparable catalytic performance to the present commercial MTO catalysts.This result demonstrates that synthesis of SAPO-34 in solid phase synthesis is a new green and environmentally friendly route for preparation of efficient MTO catalysts.