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Intensified shape selectivity and alkylation reaction for the two-step conversion of methanol aromatization to p-xylene

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中国化学工程学报:英文版 2023年第7期59卷 240-250页

作者： Tingjun Fu Ran Wang Kun Ren Liangliang Zhang Zhong Li State Key Laboratory of Clean and Efficient Coal Utilization College of Chemical Engineering and TechnologyTaiyuan University of TechnologyTaiyuan 030024China

Two-step conversion of methanol to aromatics via light hydrocarbons can significantly improve the conversion stability compared with direct aromatization of methanol,but it remains a challenge to achieve a high p-xylene(PX)selectivity.Herein,silica coating was firstly used to passivate external acid sites of ZSM-5 catalyst for the aromatization of light hydrocarbons by the chemical liquid deposition method.With the increase of SiO_(2) deposition,the density of the external acid sites of the catalyst was decreased from 0.1 to 0.03 mmol·g^(-1),which inhibited the surface secondary reactions and increased the PX/X from 34.6% to 60.0%.In view of the fact that the aromatization process in the second step was partly inhibited as methanol was consumed in advance in the upper methanol-to-light hydrocarbons catalyst layer,part of methanol was directly introduced into the lower aromatization catalyst layer to promote the alkylation process during the aromatization,which decreased the toluene selectivity from 34.5% to 14.3% but increased the xylene selectivity from 40.0%to 55.3%.It was also found that an appropriate external acid density was needed for aromatization catalyst to strengthen the alkylation process and improve the selectivity of xylene under the conditions of methanol introduction.

关键词： methanol to aromatics Two-step conversion Para-xylene Zeolite Silica Catalysis

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Enhancement of catalytic and anti-carbon deposition performance of SAPO-34/ZSM-5/quartz films in MTA reaction by Si/Al ratio regulation

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Chinese Journal of Chemical Engineering 2023年第4期56卷 314-324页

作者： Jiaxin Wu Chenxiao Wang Xianliang Meng Haichen Liu Ruizhi Chu Guoguang Wu Weisong Li Xiaofeng Jiang Deguang Yang School of Chemical Engineering and Technology China University of Mining&TechnologyXuzhou 221116China Key Laboratory of Coal Processing and Efficient Utilization of Ministry of Education Xuzhou 221116China

In order to further improve the catalytic performance of zeolite catalyst for methanol to aromatics(MTA)technology, the double-tier SAPO-34/ZSM-5/quartz composite zeolite films were successfully synthesized via hydrothermal crystallization. The Si/Al ratio of SAPO-34 film was used as the only variable to study this material. The composite zeolite material with 0.6Si/Al ratio of SAPO-34 has the largest mesoporous specific surface area and the most suitable acid distribution. The catalytic performance for the MTA process showed that 0.6-SAPO-34/ZSM-5/quartz film has as high as 50.3% benzene-toluenexylene selectivity and 670 min lifetime. The MTA reaction is carried out through the path we designed to effectively avoid the hydrocarbon pool circulation of ZSM-5 zeolite, so as to improve the aromatics selectivity and inhibit the occurrence of deep side reactions to a great extent. The coke deposition behavior was monitored by thermogravimetric analysis and gas chromatograph/mass spectrometer, it is found that with the increase of Si/Al ratio, the active intermediates changed from low-substituted methylbenzene to high-substituted methylbenzene, which led to the rapid deactivation of the catalyst. This work provides a possibility to employ the synergy effect of composite zeolite film synthesizing anti-carbon deposition catalyst in MTA reaction.

关键词： Composite zeolite film methanol to aromatics Anti-carbon deposition Si/Al ratio Hydrocarbon pool circulation mechanism

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