Study On Toluene Adsorption Performance Of Metal Modified Zeolite Molecular Sieve

The problem of air pollution caused by automobile exhaust emissions has become increasingly severe with the increasing number of automobiles.The low-temperature emission control of hydrocarbon(HC)components in exhaust gas has always been a major technical problem in vehicle exhaust gas treatment.With the escalation of emission regulations and increasingly stringent emission control requirements,this technical problem is even more prominent.HC capture technology is an effective measure to reduce HC emissions control during cold start of automobiles.In this study,toluene,which contributes the most to the total hydrocarbon(THC)emission value of HC compounds at cold start,is used as a research substance,and explore molecular sieve materials with excellent low temperature adsorption properties of toluene.The main work of the thesis is as follows:1.Seven different molecular sieve materials were selected.By testing their toluene saturated adsorption capacity,desorption temperature and toluene adsorption performance after aging,it was found that the adsorption characteristics of different types of molecular sieves were different.The results show that the saturated adsorption capacity of several molecular sieves is from large to small: NaY > USY > β > 5A >13X > MOR > ZSM-5,and the toluene desorption temperature is from high to low:USY > β > ZSM-5 > MOR > 5A > 13 X > NaY.In contrast,USY and ZSM-5 molecular sieves have better heat aging properties.2.The molecular sieves were modified by Ce and Pd,andit was found that metal modification had a great influence on the adsorption performance of molecular sieves.The modification of Ce and Pd had different effects on different molecular sieves.The adsorption capacity of toluene in several molecular sieves increased after Ce modification.After Pd modification,the adsorption capacity of toluene in othermolecular sieves except 5A increased.The modified USY molecular sieve has very good toluene adsorption performance.The toluene saturated adsorption capacity of Ce/USY can reach 258.9 mg/g,the desorption temperature is 260℃,and the toluene saturated adsorption capacity of Pd/USY can reach 239.7 mg/g,the maximum desorption temperature can reach 300℃.3.By comparing the adsorption performance of USY molecular sieve under different modification conditions,the optimal conditions for obtaining Pd/USY molecular sieve are: the loading of Pd was 1wt%,the pH was 8,and the calcination temperature was450℃.The USY molecular sieves were modified by different metal combinations.The results show that the addition of different metal ions changes the microstructure of the USY molecular sieve,and each metal is highly dispersed in the molecular sieve in the form of oxide.The ruthenium-modified Pd/USY molecular sieve has a certain effect on the adsorption performance of toluene.Among them,Ce-Zr has the best effect on Pd/USY molecular sieve.The adsorption capacity of Pd/Ce/Zr-USY is up to 290.7mg/g,and the temperature of toluene can reach 290~360℃.