Zn改性纳米ZSM-5分子筛的物化性能及催化甲醇制汽油反应性能研究

以晶种引导法合成的纳米ZSM-5分子筛为母体,采用液相沉积法制备了系列不同Zn担载量的改性纳米ZSM-5分子筛催化剂,分别采用SEM、N2物理吸附、H2-TPR、NH3-TPD和Py-IR等手段对催化剂进行了表征,并考察了Zn改性前后的ZSM-5分子筛的物化性质及用于甲醇制汽油(MTG)的催化反应性能。结果表明,随着Zn担载量的增大,改性分子筛的孔容和比表面积减小,由Br准nsted酸提供的强酸位的强度减弱、强酸量减少,由Lewis酸提供的弱酸位的酸量减少、中强酸性位的强度增强、酸量增加,由Zn活性物种形成了新的更强的酸性位。Zn O担载量为2.0%(wt)的改性纳米ZSM-5分子筛2.0Zn NZ5是最适宜的MTG反应催化剂,当甲醇转化率为98.2%时汽油的选择性高达64.7%。     

无粘结剂ZSM-5催化剂改性及其甲苯与乙烯择形烷基化反应的催化性能

利用甲苯与乙烯的烷基化反应制备对甲乙苯,是一条具有技术经济性的合成工艺路线。本工作对无粘结剂ZSM-5分子筛催化剂颗粒进行了聚苯甲基硅氧烷(PPMS)修饰剂化学液相沉积(CLD)改性处理研究,考察了其对催化剂物化性质与择形烷基化反应性能的影响。在CLD改性过程中形成的SiO2使ZSM-5孔口收窄、外表面酸性位点钝化,这可以有效阻止对甲乙苯异构化为间甲乙苯或邻甲乙苯。经过重复3次改性的无粘结剂ZSM-5可将对甲乙苯的择形选择性提高至97%以上,与改性的常规含粘结剂ZSM-5催化剂颗粒相比,CLD改性的无粘结剂ZSM-5催化剂颗粒具有更好的烷基化活性和反应稳定性。     

改性HZSM-5分子筛催化剂芳构化性能研究

制备Ni改性及水热改性HZSM-5分子筛催化剂,并在固定床连续微型反应装置上考察对正辛烷芳构化反应的催化性能。采用低温氮吸附、NH₃-TPD和FT-IR等方法对催化剂进行表征。结果表明,随着Ni含量的增加,催化剂B酸逐渐减少,L酸逐渐增多,总酸呈现出先减少后增多的趋势,适宜的Ni含量能够促进芳构化反应。随着水热温度的提高,B酸减少,总酸增多,催化剂的芳构化活性逐渐降低。催化剂活性与表面酸性有关,尤其是与强酸量有关,强酸量下降,芳构化能力下降。     

Selective catalytic reduction of NO by ammonia using mesoporous Fe-containing HZSM-5 and HZSM-12 zeolite catalysts: An option for automotive applications

Mesoporous and conventional Fe-containing ZSM-5 and ZSM-12 catalysts (0.5–8 wt% Fe) were prepared using a simple impregnation method and tested in the selective catalytic reduction (SCR) of NO with NH₃. It was found that for both Fe/HZSM-5 and Fe/HZSM-12 catalysts with similar Fe contents, the activity of the mesoporous samples in NO SCR with NH₃ is significantly higher than for conventional samples. Such a difference in the activity is probably related with the better diffusion of reactants and products in the mesopores and better dispersion of the iron particles in the mesoporous zeolite as was confirmed by SEM analysis. Moreover, the maximum activity for the mesoporous zeolites is found at higher Fe concentrations than for the conventional zeolites. This also illustrates that the mesoporous zeolites allow a better dispersion of the metal component than the conventional zeolites. Finally, the influence of different pretreatment conditions on the catalytic activity was studied and interestingly, it was found that it is possible to increase the SCR performance significantly by preactivation of the catalysts in a 1% NH₃/N₂ mixture at 500 °C for 5 h. After preactivation, the activity of mesoporous 6 wt% Fe/HZSM-5 and 6 wt% Fe/HZSM-12 catalyst is comparable with that of traditional 3 wt% V₂O₅/TiO₂ catalyst used as a reference at temperatures below 400 °C and even more active at higher temperatures.     

焙烧温度对HZSM-5分子筛催化1-丁烯齐聚性能的影响

考察焙烧温度对HZSM-5分子筛催化剂结构及1-丁烯齐聚性能的影响,采用XRD、SEM和NH3-TPD对催化剂进行表征。结果表明,升高焙烧温度,对HZSM-5分子筛催化剂的晶相和晶粒尺寸没有影响,催化剂中弱酸与强酸的酸强度和酸量均随焙烧温度的升高逐渐减弱。在催化剂晶粒尺寸一定条件下,催化剂酸性对催化剂的齐聚性能有较大影响,焙烧温度500℃时,C5+收率和C10+选择性最佳。     

Selective catalytic reduction of NO by ammonia using mesoporous Fe-containing HZSM-5 and HZSM-12 zeolite catalysts: An option for automotive applications

Mesoporous and conventional Fe-containing ZSM-5 and ZSM-12 catalysts (0.5–8 wt% Fe) were prepared using a simple impregnation method and tested in the selective catalytic reduction (SCR) of NO with NH₃. It was found that for both Fe/HZSM-5 and Fe/HZSM-12 catalysts with similar Fe contents, the activity of the mesoporous samples in NO SCR with NH₃ is significantly higher than for conventional samples. Such a difference in the activity is probably related with the better diffusion of reactants and products in the mesopores and better dispersion of the iron particles in the mesoporous zeolite as was confirmed by SEM analysis. Moreover, the maximum activity for the mesoporous zeolites is found at higher Fe concentrations than for the conventional zeolites. This also illustrates that the mesoporous zeolites allow a better dispersion of the metal component than the conventional zeolites. Finally, the influence of different pretreatment conditions on the catalytic activity was studied and interestingly, it was found that it is possible to increase the SCR performance significantly by preactivation of the catalysts in a 1% NH₃/N₂ mixture at 500 °C for 5 h. After preactivation, the activity of mesoporous 6 wt% Fe/HZSM-5 and 6 wt% Fe/HZSM-12 catalyst is comparable with that of traditional 3 wt% V₂O₅/TiO₂ catalyst used as a reference at temperatures below 400 °C and even more active at higher temperatures.     

钾-钙双金属改性对HZSM-5分子筛催化甲醇制丙烯的影响

针对甲醇制丙烯反应体系,研究了不同金属、双金属改性的HZSM-5的催化性能。结果表明,钾改性提高了催化剂的稳定性和催化性能,当钾改性液的质量分数为2%时,改性效果最好,在此基础上,以2%K-HZSM-5作为不同钙负载的改性对象。结果表明,钾钙共同改性,具有较好的协同改性效果,大大提高了丙烯的选择性,有效的降低了乙烯和副产物的产率。     

Influence of the post-treatment of HZSM-5 zeolite on catalytic performance for alkylation of benzene with methanol

The porous material HZSM-5 zeolite with micro-mesopore hierarchical porosity was prepared by post-treatment (combined alkali treatment and acid leaching)of parent zeolite and its catalytic performance for benzene alkyl-ation with methanol was investigated.The effect of post-treatment on the textural properties was characterized by various techniques(including ICP-AES,XRD,nitrogen sorption isotherms,SEM,NH3-TPD,Py-IR and TG).The results indicated that the post-treatment could modify the structural and acidic properties of HZSM-5 zeolite.In this procedure,not only additional mesopores were created by selective extraction of silicon but also the acidity was tuned.Consequently,the modified HZSM-5 zeolite showed larger external surface area with less acid sites as compared to the parent zeolite.It was found out that the modified zeolite exhibited a higher benzene conversion and xylene selectivity for alkylation of benzene with methanol as well as excellent life span of the catalyst than conventional ones.This can be explained by the facts that the presence of additional mesopores improved the diffusion property in the reactions.Furthermore,the modified zeolite showed an appropriate Br?nsted acidity for effective suppression of the side reaction of methanol to olefins,thus reduced the accumulation of coke on the HZSM-5 zeolite,which was favorable for the catalyst stability.In comparison with the parent HZSM-5 zeolite, the modified zeolite by alkali treatment and acid leaching showed better performance for the benzene alkylation with methanol.     

水热处理磷改性HZSM-5催化剂的研究

以催化裂化轻汽油馏分为原料,以水热处理磷改性HZSM-5为催化剂,在小型固定床反应装置上考察了水热处理改性方法制备催化剂的催化裂解性能。通过对HZSM-5分子筛催化剂水热处理,调变其酸性,达到多产丙烯的目的。确定催化剂改性最佳条件为：水热处理温度650 ℃,处理时间2 h,处理空速2 h^-1。HZSM-5水热处理后,明显改善催化剂的水热稳定性和活性,提高丙烯选择性。     

On the exceptional time-on-stream stability of HZSM-12 zeolite: relation between zeolite pore structure and activity

ZSM-12 and several other 12-membered ring large-pore zeolites have been tested for the reforming of naphthenic hydrocarbon mixtures. It was found that ZSM-12 possesses a surprisingly higher coking resistance than other large pore zeolites tested such as USY, L-zeolite, mordenite, and β=zeolite for reforming of hydrocarbon mixtures. This superior performance is due to the unique non-interconnecting tubular-like linear channels of ZSM-12, which do not allow trapping/accumulation of coking precursors. ZSM-12 zeolite also demonstrated excellent structural stability even under severe acid dealumination. From this work, we found that the decrease of the aluminum content of a zeolite is not sufficient to ensure low rates of coke deposition. We also concluded that zeolites with channel intersections (cavities) of comparable size with the zeolite apertures do not favor coke formation. For these types of zeolites the strong acid sites carry out other acid-catalyzed reactions, rather than forming coke. In contrast, zeolites with relatively large supercages are inherently favorable to coking reactions, which in turn lead to the fast deactivation. The appropriate combination of the zeolite pore structure and acidity (controlled via dealumination) showed superior TOS behavior (time-stable activity and product selectivities). For zeolites which are susceptible to coking due to pore structure, the increase of the Brønsted acid strength results in fast deactivation. Contrary to what one would commonly expect and previous reports, we found that one-dimensional zeolites, such as, ZSM-12, can exhibit significantly higher tolerance to coking than multidirectional zeolites.     

偏三甲苯在改性HZSM-5分子筛上合成均四甲苯

采用离子交换制备了HZSM-5分子筛催化剂，用氟化铵溶液对其进行改性，并于不同温度下焙烧。研究了偏三甲苯-甲醇烷基化反应合成均四甲苯，考察了原料配比、反应温度和载气流量对烷基化反应的影响。     

分子筛的补铝及其催化性能研究

本文介绍了分子筛的补铝方法及其补铝后分子筛的催化性能｡按所用的补铝溶液性质可分为NaOH等碱性溶液补铝法､AlCl₃和HCl酸性溶液补铝法及含羟基有机酸溶液补铝法,补铝机理涉及晶格缺陷位补铝､非骨架位表面反应以及同晶取代三种｡补铝的分子筛表面酸性质发生了变化,改善了某些催化反应性能｡