| Summary: | 碩士 === 國立清華大學 === 化學工程學系 === 88 === Abstract
Since the mismatch between the supply and demand of the C8 aromatics, various catalysts and processes have been developed to isomerize meta-and ortho-xylenes to para-xylene. The key criterion of the process is to minimize the xylene loss with highest possible ethylbenzene conversion during the transformation. The purpose of this study is to minimize the side reactions, which are responsible for the xylene loss cause by the inactivation of the external sites of the catalyst. On the other hand, the demand in lifting the ethylbenzene conversion level is desirable.
The curves present the characters of the catalyst were discovered in the consequence of repeated Si-CVD treatment. Our results show that these curves are changed when Pt is loaded on the catalyst. Saturation effect was observed when the Si-CVD treatment is prolonged more than two hours.
Unlike Si-CVD treatment, poisoning of external active sites by beta-naphthoquinoline tend to retain the xylene loss more effectively, however, this is achieved at the cost of lower initial ethylbenzene conversion. It is found that the addition of Pt hydrogenates the excess poisoning agent, and gradually recovers the ethylbenzene conversion.
It is concluded that the H-MFI-25 containing 0.5 wt.% Pt has best catalytic performance after twice in-situ chemical vapor deposition of Si (Si-CVD) and poisoning using b-naphthoquinoline as N-containing poisoning agent. Under the reaction condition of 390 ℃, 400 psi, WHSV= 10 h--1, H2/H.C.= 2, less than 1 wt.% xylene loss and up to 60 wt.% ethylbenzene conversion was obtained.
|
|---|
