摘要
本文用NH_3-TPD(氨的程序升温脱附)和FT-IR研究了三种不同硅铝比的超稳Y沸石的酸性质,并以正十六烷为探针反应研究了它们的催化性能。NH_3-TPD 结果表明:随着深床焙烧脱铝程度的加深,两种强弱不同的酸中心均同时逐步减小。弱酸中心的强度不随硅铝比而改变,但强酸中心的强度随硅铝比增加而逐渐变弱,说明提高焙烧温度和增加焙烧次数有利于与强酸位相应的骨架铝的脱除。IR 结果表明,与铝关联的羟基随着脱铝明显减少;相反,Si-OH 则随着脱铝而逐渐增强。在高硅铝比的样品中,与此波数相应的羟基中有一部分具有酸性。另外,随着脱铝的增加,B 酸浓度明显地减小,而 L 酸的浓度略有增加;说明在超稳化过程中,脱羟基在脱铝和脱羟基两者之中占主导地位。低硅铝沸石的 B 酸约占总酸的85%,而在高硅沸石中 B 酸和 L 酸各占50%。在酸强度方面各样品的 B 酸和 L 酸的强度是均匀的,高硅铝比的 B 酸较低硅铝比的强。各样品的 B酸的酸强度较 L 酸弱。正十六烷裂解反应的结果表明,脱铝程度的增加有利于稀烃和芳烃的形成和液收的提高。
The acidity of USY with different SIO_2/Al_2O_3 ratios was studied by NH_3-TPD and FT-IR,and the cracking of n-hexadecane was chosed as a probe rea- ction.The results of NH_3-TPD show that with the increase of the extent ofdealumination the number of strong and weak acid sites simultaneously decre-ase and the strength of weak acid site is unchanged,but that of strong acidsites' gradually decreases.It also indicate that by increasing the temperatureand frequency of deep-bed calcination,the framework aluminium relating tothe strength of acid sites are removed first.IR results show that the Br(?)ns-ted acid sites are obviously decreased and Lewis acid sites are slightly increa-sed with the dealumination.It suggests that the reaction of dehydroxylationis more prevailing than that of dealumination during deep-bed calcination.Inaddition,the strength of Br(?)nsted acid sites are weaker than that of Lewisacid sites,and the strength of Br(?)nsted acid sites of the high SiO_2/Al_2O_3 ratioUSY are stro(?)ger than that of low SiO_2/Al_2O_3 ratio USY.The results of cra-cking of n-hexadecane illustrate that the increase of the extent of dealumina-tion is benefieial to the production of olefins and aromatics and to the liquidyield.
出处
《石油炼制》
CSCD
1991年第2期27-32,共6页
基金
国家自然科学基金
抚顺石油化工研究院资助
