Research On The Structural Properties And Reaction Behavior Of ZSM-5 Catalyst In The Multi-period Reaction Of Methanol To Propylene

Methanol to propylene process is an important method of non-oil route for increasing propylene production.It is not only a key step to combine our country resource condition of more coal and less oil with demand of basic chemical raw materials,but also has important significance on the future of China's chemical industry structure.Deactivation of ZSM-5 catalyst inevitably occurs in the MTP industrial plant,and multiple period of reaction-regeneration is necessary to ensure long life of the catalyst.How to effectively control the state of the catalyst and prolong the service life of the catalyst is an important scientific proposition.In this paper,the relationship between the structural properties and the reaction behavior of the catalyst in the multi cycle reaction-regeneration operation of MTP industrial plant is studied.The relationship between the change of catalyst state and the behavior of multi cycle MTP reaction was determined by studying the difference of the structural properties and the variation rules of the specific structure parameters in the multi cycle.With the help of high temperature water vapor treatment method,different degree of aluminum removal of ZSM-5 catalyst samples were prepared,and they were used to explore dealumination deactivation effect on structure properties of ZSM-5 catalyst and MTP reaction rules.Moreover,method of matching to simulate multi cycle samples by steam treatment operation of key variables in catalyst properties was proposed.The process of coke deposition on the catalyst deactivation in the single period was studied,and the difference of the coke deposition behavior in multi period sample was also investigated.Based on the former research,the intrinsic regeneration dynamics of multi cycle deactivation of catalyst was further established.And the key parameters in the dynamics of the catalyst are finely associated with the structural properties of catalyst samples.The main research contents are as follows:1.By means of a series of characterization methods,such as XRD?NH3-TPD,the changes of the properties of the catalysts,especially the pore structure and acid properties of the catalysts were investigated.And the behavior ofreaction on the multi period samples was further studied.The results showed that the skeleton structure of the catalyst is destroyed gradually with the development of multi cycle,some framework aluminum lost and the relative crystallinity decreased obviously,also the acidity.However,more 8-12nm mesopore was produced.The activity of the catalyst decreased with the multi cycle,and the selectivity of propylene was also gradually decreased.2.The method of rapid deactivation was established by means of hydrothermal treatment and the changes of catalyst properties before and after the treatment of water vapor were investigated.What is more,the effect of water treatment on the properties of catalysts was elucidated by means of characterization.The results showed that the skeleton structure was dramatically destructed under the high temperature vapor treatment of 600?.It led to rapid destruction of the catalyst,the crystallinity decreased,and total acid decreased.At the same time,the catalyst pore structure destruction degree is smaller,the most obvious change is the distribution of pore size of 3.5nm-4nm.Standing on the angle of dealumination,a method for simulating the actual multi period samples is proposed by the comparison of the properties of water vapor treatment samples and industrial multi cycle catalysts.3.The process of coke deposition on catalyst in single cycle MTP reaction was investigated.The reasonable catalyst samples of different reaction time in a single reaction period were designed and prepared.Through the analysis of various properties of coke samples,including coke content,coke species,coke distribution and changes in the catalyst acid center and skeleton structure,the growth procedure of coke in a single period MTP reaction was revealed.Furthermore,the coke behavior of catalysts in multi periods were explored and contrasted,and these were well linked to the acidity of the catalyst center changes.4.Thermogravimetric analyzer was used to examine the effects of different conditions on the regeneration of catalyst regeneration.And the intrinsic kinetics of coke burning of multi period catalyst was established.Effective correlation between the dynamics model parameters and the pore structure and acidity of the catalyst was put forward.And a prediction model for coke burning dynamics was constructed.