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用热重法(TGA)和程序升温脱附法(TPD)考察了几种不同孔道结构的沸石——毛沸石(HE),类毛—菱钾沸石(HSW),Fu-1,ZSM-5,ZSM-11,丝光沸石(HM)和Y 型沸石——在甲醇转化为烃时的积炭行为。认为甲醇在沸石上转化为烃时的积炭倾向不仅与沸石的孔道结构有关,而且也与其强酸部位(即TPD 谱的峰Ⅱ)的酸量有着密切关系。甲醇在所考察过的七种沸石上的积炭初速度有着如下排列顺序:HE>(HSW,HY)>HM>(HF,HZSM-5,HZSM-11);其除炭初速度的大小有着与积炭初速度一致的顺序。采用往ZSM-5沸石上添加磷或镁等化合物以改质的方法,可以调节沸石的酸性和孔道尺寸,使得沸石的抗积炭能力增强,有利于改善沸石催化剂的稳定性和选择性。甲醇在改质沸石催化剂上转化为烃时的积炭初速度有着下列顺序,Zn ZSM-5》HZSM-5>Mg ZSM-5>PZSM-5>MnZSM-5。
Several kinds of zeolites - erionite (HS), hair wool-offretite (HSW), Fu-1 and ZSM-5 have been investigated by thermogravimetric method (TGA) and temperature programmed desorption (TPD) , ZSM-11, Mordenite (HM) and Y-type zeolite - the carbon deposition behavior when methanol is converted to hydrocarbons. It is believed that the tendency of carbon deposition on the conversion of methanol on zeolites is not only related to the pore structure of the zeolite, but also to the acidity of the strong acid sites (ie, peak II of the TPD spectrum). The initial rate of carbon deposition on the seven zeolites examined by methanol has the following sequence: HE> (HSW, HY)> HM> (HF, HZSM-5 and HZSM-11) Consistent with the initial rate of coke deposition order. Adopting the method of adding phosphorus or magnesium compound to zeolite ZSM-5 for modification can adjust the acidity and pore size of the zeolite so as to enhance the anti-carbon deposition capability of the zeolite and improve the stability and selectivity of the zeolite catalyst. The initial rate of carbon deposition of methanol upon conversion into hydrocarbons on a modified zeolite catalyst has the following sequence, Zn ZSM-5 "HZSM-5> Mg ZSM-5> PZSM-5> MnZSM-5.