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Study On The Behaviors Of Catalyst Deactivation And Regeneration In Synthesis Of Pyridine Bases

Posted on:2004-09-10Degree:MasterType:Thesis
Country:ChinaCandidate:Y N OuFull Text:PDF
GTID:2121360092981242Subject:Chemical Engineering
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Pyridine bases are widely used in Chemical industry since the industrialization of their synthetic technology in the 1950's. There are two main sources about pyridine bases: One is distilling from coal tar, the other is chemical synthesis. With the rapid development of chemical industry and feedstuff industry in our country, the demand of pyridine bases is expanded increasingly. As far as the independent property for synthetic technology and the manufacture equipment in our country are concerned, it's a blank in this area. Then it is exigent and necessary to exploit our own technology to produce pyridine bases. Further research has been experimented on catalysts and the technical conditions of synthesis, which used formaldehyde . acetaldehyde and ammonia as raw material since 1999 to improve the activity of catalysts. Based on the easily deactivation and the rapidly regeneration of this kind of catalyst which can be used times, more attentions were paid on the factors in order to provide theoretical and practical guidance for catalysts' further improvement.The experiments on catalyst's deactivation showed that the more ratio of the ammonia in the gas of raw material, the more yield of pyridine and the less that of 3-picoline. The catalyst was prone to deactivation when the proportion of ammonia in the raw materials was large. The content of water in the raw materials can restrains the catalyst's deactivation because of keeping the catalyst cleanly. At the same time, the results of experiments indicated that the catalyst's deactivation was made up of two parts: one was caused by ammonia called poisoning-deactivation, the other was caused by formaldehyde . acetaldehyde ,called coking. But the latter was the main reason for catalyst's deactivation. The connected equation of accumulated carbon with the deactivated time was: Cc=0.01684 t062644.After a series of experiments on the behavior of catalyst's regeneration, the optimum conditions were obtained: the optimum temperature of regeneration was between 770 K and 800 K; the optimized space-velocity of regeneration was about 3000 h-1, and the influence of the regeneration space-velocity was significant. On these conditions, more than 99 percent of the original accumulated carbon could be burnt out, the activity of catalyst could be restored mostly, and it could be satisfied to the need of industry. Finally, when the temperature of regeneration was between 725K and 800K, the regeneration equation for this deactivated catalyst was shown as following:On considering the environment and the integration of process, more carbon monoxide is expected in the waste gas during catalyst's regeneration, but carbon dioxide is on the contrary. For this destination, elevating the reaction temperature and reducing the space-velocity were adopted.inBased on summarizing the literature, this thesis has researched the alteration of catalyst also. The results showed that catalyst dipped with vanadium or zirconium could improve the total yields of pyridine bases remarkably. At the same time, the catalyst dipped with vanadium element was more propitious to the manufacture of 3-picoline. The total yields of pyridine and 3-picoline was improved by from 15 percent to 20 percent through the alteration of catalysts with zirconium or vanadium element. Moreover, the results of experiments exhibited that the catalyst dipped with vanadium has much higher activity, while the catalyst mended with zirconium exhibited long-term stabilities.
Keywords/Search Tags:pyridine bases, catalyst deactivation, catalyst regeneration, regeneration dynamics, catalyst alteration
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