High-temperature treatment is key to the preparation of zeolite catalysts.Herein,the effects of hightemperature treatment on the property and performance of HZSM-5 zeolites were studied in this work.X-Ray diffraction,...High-temperature treatment is key to the preparation of zeolite catalysts.Herein,the effects of hightemperature treatment on the property and performance of HZSM-5 zeolites were studied in this work.X-Ray diffraction,N2physisorption,27Al magic angle spinning nuclear magnetic resonance(MAS NMR),and temperature-programmed desorption of ammonia results indicated that the hightemperature treatment at 650℃ hardly affected the inherent crystal and texture of HZSM-5zeolites but facilitated the conversion of framework Al to extra-framework Al,reducing the acid site and enhancing the acid strength.Moreover,the high-temperature treatment improved the performance of HZSM-5 zeolites in n-heptane catalytic cracking,promoting the conversion and light olefins yield while inhibiting coke formation.Based on the kinetic and mechanism analysis,the improvement of HZSM-5 performance caused by high-temperature treatment has been attributed to the formation of extra-framework Al,which enhanced the acid strength,facilitated the bimolecular reaction,and promoted the entropy change to overcome a higher energy barrier in n-heptane catalytic cracking.展开更多
The catalytic conversion of polystyrene (PS) was studied in the presence of the materials type HZSM-5, CeO<sub>2</sub>, 10% CeO<sub>2</sub>/HZSM-5 and 20% CeO<sub>2</sub>/HZSM-5, wh...The catalytic conversion of polystyrene (PS) was studied in the presence of the materials type HZSM-5, CeO<sub>2</sub>, 10% CeO<sub>2</sub>/HZSM-5 and 20% CeO<sub>2</sub>/HZSM-5, which were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and nitrogen adsorption at 77K. The catalytic tests were performed via thermogravimetric analysis (TG) at heating rates of 5, 10 and 20˚C min<sup>−1</sup> in a temperature range from 30˚C to 900˚C. For the tests, a ratio of 30% by mass of each catalytic material mixed with PS was used and the activation energy of the degradation process was determined by the Vyazovkin method. The obtained results showed that the addition of the catalyst to the PS in general reduced its degradation temperature. The 10% CeO<sub>2</sub>/HZSM-5 catalyst showed greater efficiency, as it resulted in lower activation energy for PS degradation. Thus, the combination of CeO<sub>2</sub> with HZSM-5 resulted in materials with potential for application in the catalytic degradation of polystyrene and the results indicate that the production of a composite material can be a good strategy to generate an increase in catalytic activity and a decrease in energy process activation.展开更多
通过调控铝源合成了四种HZSM-5分子筛,并将其应用于催化甲缩醛(DMM)气相羰基化合成甲氧基乙酸甲脂(MMAc)反应。结果表明,改变合成凝胶体系中的铝源种类,可以制备出织构性质、酸性特征相近,但骨架铝分布不同、催化羰基化性能迥异的HZSM-...通过调控铝源合成了四种HZSM-5分子筛,并将其应用于催化甲缩醛(DMM)气相羰基化合成甲氧基乙酸甲脂(MMAc)反应。结果表明,改变合成凝胶体系中的铝源种类,可以制备出织构性质、酸性特征相近,但骨架铝分布不同、催化羰基化性能迥异的HZSM-5分子筛。其中,使用硝酸铝与硫酸铝作为铝源制备的分子筛HZ-N与HZ-S表现出更为优异的催化活性,HZ-N对应的DMM转化率与MMAc选择性分别为25.3%与58.9%,HZ-S对应的DMM转化率与MMAc选择性分别为28.7%与64.6%。采用Co-ZSM-5的UV-vis-DRS与27 Al MAS NMR等表征手段详细分析证实,硝酸铝与硫酸铝作为铝源时,更多的骨架铝优先落位于HZSM-5分子筛交叉孔道,其在催化DMM羰基化反应过程中起主导作用,落位比例高,更有利于反应的进行,反之可能导致较低的DMM转化率以及更高的副产物选择性。展开更多
Since paraffins catalytic cracking was of significant importance to light olefins and aromatics production,this work was intended to gain insights into the feature and model of coke formation and catalyst deactivation...Since paraffins catalytic cracking was of significant importance to light olefins and aromatics production,this work was intended to gain insights into the feature and model of coke formation and catalyst deactivation in n-heptane catalytic cracking over HZSM-5 zeolites. 18 tests of n-heptane catalytic cracking were designed and carried out over HZSM-5 zeolites in a wide range of operating conditions. A particular attention was paid to the measurement of the conversion, product distribution, coke content, and the porosity and acidity of the fresh and spent HZSM-5 zeolites. It was found that alkene and aromatic promoted coke formation, and it reduced the pore volume and acid site of HZSM-5 zeolites, tailoring its performance in n-heptane catalytic cracking. The specific relationship between HZSM-5 zeolites, n-heptane conversion, product distribution and coke formation was quantitively characterized by the exponential and linear function. Based on the reaction network, the coupled scheme of coke formation and catalyst deactivation were specified for n-heptane catalytic cracking. The dual-model was proposed for the process simulation of n-heptane catalytic cracking over HZSM-5 zeolites. It predicted not only the conversion and product distribution but also coke content with the acceptable errors.展开更多
Toluene methylation with methanol to produce para-xylene has been extensively and intensively studied.However,the methanol-to-hydrocarbons(MTH)side reaction in this reaction is difficult to be inhibited,which will cau...Toluene methylation with methanol to produce para-xylene has been extensively and intensively studied.However,the methanol-to-hydrocarbons(MTH)side reaction in this reaction is difficult to be inhibited,which will cause a mass of carbon deposition and cover the catalyst surface,resulting in catalyst deactivation.Here,a dual-functional Ru@HZSM-5 catalyst with high para-selectivity and low carbon deposition was prepared by encapsulating Ru metal with HZSM-5.According to catalytic performance studies,the Ru@HZSM-5 catalyst produced xylene selectivity of 98%and para-xylene selectivity of 96%.Meanwhile,we find that carbon precursors(e.g.ethylene)were very little when Ru catalyst was used,but the results of HZSM-5 catalyst were completely opposite.Ru@HZSM-5 catalyst achieves a lower carbon deposition rate of only 6%of HZSM-5.The main possible reason for this is that the initial C-C bond between methanol and the olefin is difficult to form.展开更多
基金the financial support from the National Natural Science Foundation of China(21908010)Jilin Provincial Department of Science and Technology(20220101089JC)the Education Department of Jilin Province(JJKH20220694KJ)。
文摘High-temperature treatment is key to the preparation of zeolite catalysts.Herein,the effects of hightemperature treatment on the property and performance of HZSM-5 zeolites were studied in this work.X-Ray diffraction,N2physisorption,27Al magic angle spinning nuclear magnetic resonance(MAS NMR),and temperature-programmed desorption of ammonia results indicated that the hightemperature treatment at 650℃ hardly affected the inherent crystal and texture of HZSM-5zeolites but facilitated the conversion of framework Al to extra-framework Al,reducing the acid site and enhancing the acid strength.Moreover,the high-temperature treatment improved the performance of HZSM-5 zeolites in n-heptane catalytic cracking,promoting the conversion and light olefins yield while inhibiting coke formation.Based on the kinetic and mechanism analysis,the improvement of HZSM-5 performance caused by high-temperature treatment has been attributed to the formation of extra-framework Al,which enhanced the acid strength,facilitated the bimolecular reaction,and promoted the entropy change to overcome a higher energy barrier in n-heptane catalytic cracking.
文摘The catalytic conversion of polystyrene (PS) was studied in the presence of the materials type HZSM-5, CeO<sub>2</sub>, 10% CeO<sub>2</sub>/HZSM-5 and 20% CeO<sub>2</sub>/HZSM-5, which were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and nitrogen adsorption at 77K. The catalytic tests were performed via thermogravimetric analysis (TG) at heating rates of 5, 10 and 20˚C min<sup>−1</sup> in a temperature range from 30˚C to 900˚C. For the tests, a ratio of 30% by mass of each catalytic material mixed with PS was used and the activation energy of the degradation process was determined by the Vyazovkin method. The obtained results showed that the addition of the catalyst to the PS in general reduced its degradation temperature. The 10% CeO<sub>2</sub>/HZSM-5 catalyst showed greater efficiency, as it resulted in lower activation energy for PS degradation. Thus, the combination of CeO<sub>2</sub> with HZSM-5 resulted in materials with potential for application in the catalytic degradation of polystyrene and the results indicate that the production of a composite material can be a good strategy to generate an increase in catalytic activity and a decrease in energy process activation.
文摘通过调控铝源合成了四种HZSM-5分子筛,并将其应用于催化甲缩醛(DMM)气相羰基化合成甲氧基乙酸甲脂(MMAc)反应。结果表明,改变合成凝胶体系中的铝源种类,可以制备出织构性质、酸性特征相近,但骨架铝分布不同、催化羰基化性能迥异的HZSM-5分子筛。其中,使用硝酸铝与硫酸铝作为铝源制备的分子筛HZ-N与HZ-S表现出更为优异的催化活性,HZ-N对应的DMM转化率与MMAc选择性分别为25.3%与58.9%,HZ-S对应的DMM转化率与MMAc选择性分别为28.7%与64.6%。采用Co-ZSM-5的UV-vis-DRS与27 Al MAS NMR等表征手段详细分析证实,硝酸铝与硫酸铝作为铝源时,更多的骨架铝优先落位于HZSM-5分子筛交叉孔道,其在催化DMM羰基化反应过程中起主导作用,落位比例高,更有利于反应的进行,反之可能导致较低的DMM转化率以及更高的副产物选择性。
基金the financial support from the National Natural Science Foundation of China (21908010)the Education Department of Jilin Province (JJKH20220694KJ)。
文摘Since paraffins catalytic cracking was of significant importance to light olefins and aromatics production,this work was intended to gain insights into the feature and model of coke formation and catalyst deactivation in n-heptane catalytic cracking over HZSM-5 zeolites. 18 tests of n-heptane catalytic cracking were designed and carried out over HZSM-5 zeolites in a wide range of operating conditions. A particular attention was paid to the measurement of the conversion, product distribution, coke content, and the porosity and acidity of the fresh and spent HZSM-5 zeolites. It was found that alkene and aromatic promoted coke formation, and it reduced the pore volume and acid site of HZSM-5 zeolites, tailoring its performance in n-heptane catalytic cracking. The specific relationship between HZSM-5 zeolites, n-heptane conversion, product distribution and coke formation was quantitively characterized by the exponential and linear function. Based on the reaction network, the coupled scheme of coke formation and catalyst deactivation were specified for n-heptane catalytic cracking. The dual-model was proposed for the process simulation of n-heptane catalytic cracking over HZSM-5 zeolites. It predicted not only the conversion and product distribution but also coke content with the acceptable errors.
基金financial support from the Hongliu Outstanding Young Talents Funding Program of Lanzhou University of Technology(02/062214)。
文摘Toluene methylation with methanol to produce para-xylene has been extensively and intensively studied.However,the methanol-to-hydrocarbons(MTH)side reaction in this reaction is difficult to be inhibited,which will cause a mass of carbon deposition and cover the catalyst surface,resulting in catalyst deactivation.Here,a dual-functional Ru@HZSM-5 catalyst with high para-selectivity and low carbon deposition was prepared by encapsulating Ru metal with HZSM-5.According to catalytic performance studies,the Ru@HZSM-5 catalyst produced xylene selectivity of 98%and para-xylene selectivity of 96%.Meanwhile,we find that carbon precursors(e.g.ethylene)were very little when Ru catalyst was used,but the results of HZSM-5 catalyst were completely opposite.Ru@HZSM-5 catalyst achieves a lower carbon deposition rate of only 6%of HZSM-5.The main possible reason for this is that the initial C-C bond between methanol and the olefin is difficult to form.
