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Study On The Deactivated Mechanism And Improvement Of Stability Of Catalyst For Hydration Of Cyclohexene To Cyclohexanol

Posted on:2013-05-01Degree:MasterType:Thesis
Country:ChinaCandidate:S L WangFull Text:PDF
GTID:2231330371476088Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
The deactivation of catalyst brings very adverse impact on industrial production. So, the catalytic researchers need to solve the problems that study the reason of catalyst deactivation, how to prevent the catalyst deactivation, improve the stability of catalyst and keep good catalytic performance.This paper is on the basis of the achievements that the larger particle of HZSM-5catalyst is synthesized successfully in our laboratory. It solves the difficulty with separation of catalyst, loss of catalyst, recovery of catalyst and so on. Moreover, it avoides the above bad factors to research the coke, particle size, dealuminum, using time and regeneration numbers which exert influences on the stability of catalyst. At the same time, the improvement of stability of catalyst is also studied.Firstly, the deactivation behavior and reason of HZSM-5catalyst were studied in a slurry reactor, and the organic coke was main reason for organic coke to cause deactivation of HZSM-5catalyst. The deactivation catalyst and organic coke on the catalyst were characterized by FT-IR, NH3-TPD, TG-DTG, GC-MS and so on, and the main composition of coke contained dicyclohexyl ether and dicyclohexene probably. In addition, the reason of catalyst deactivation was also analyzed from the thermodynamics and kinetics of hydration reaction.Secondly, the stability of four kinds of particle size catalysts were investigated including two commercial catalysts(NK, JP), two catalysts prepared in our laboratory (small particle, large particle). We found that the larger particle of catalyst prepared in our laboratory still had remained better stability after300h reaction. Subsequently, it was continued for the1200h stability, and found that as time use increased, life use shortened, regeneration frequency increased and the rate of deactivation markedly accelerated. What was more, the reason of catalyst deactivation was analyzed from microscopic structural changes of different reaction time and it was found that the strong acid with the hydration occurrence of clohexene gradually reduced due to the shedding of framework aluminum, further speeding up the catalyst deactivation. So, it was probable for non-renewable deactivation. Thirdly, the shedding and complement of aluminum of framework were also studied which had the effects on the stability of catalyst. While the hydrothermal treatment time increased, aluminum fell out of framework constantly, Bronsted acid reduced sharply, and the activity and selectivity also reduced obviously, but its crystal structure was intact basically. The activity was not restored by its own aluminum source for complement because the aluminum source was insufficient possibly. However, the activity had been basically restored by extra aluminum source for complement because the aluminum source was sufficient so that Bronsted acid got basic recovery. The catalyst still had very high activity after100h running, indicating that the extra aluminum source could be added into framework of molecular sieve and showed better stability.At last, the improvement of stability of catalyst was studied by using different non-metal elements, and found that with trace oron element into the framework of molecular sieve, the activity and selectivity changed small. In particular, it had better separation and sedimentation performance.
Keywords/Search Tags:cyclohexene, cyclohexanol, HZSM-5, coke, deactivation, stability
PDF Full Text Request
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