A novel method, based on acoustic emission (AE) techniques, for detecting agglomeration in fluidized beds is presented. Particle size characteristics are determined based on the principle that AE signals with differen...A novel method, based on acoustic emission (AE) techniques, for detecting agglomeration in fluidized beds is presented. Particle size characteristics are determined based on the principle that AE signals with different frequency band energies are emitted when particles of different sizes impact an internal wall. By applying chaotic analysis to the AE signals, the malfunction coefficients are well defined. Agglomeration in the fluidized bed can then be detected by the sudden variation of malfunction coefficients. AE signals were investigated in a laboratory scale heated fluidized bed and an industrial polyethylene fluidized bed. Experimental data showed that the malfunction coefficients increased with the growth of agglomeration. The results indicated that agglomeration in fluidized beds can be predicted and diagnosed effectively and precisely using AE techniques based on chaotic analysis.展开更多
A novel central hole-expansion phenomenon is identified, in which the cation-exchange resin is pyrolyzed in a mixed atmosphere of nitrogen and oxygen at 400–500 ℃. In this reaction, the reaction path is predictable ...A novel central hole-expansion phenomenon is identified, in which the cation-exchange resin is pyrolyzed in a mixed atmosphere of nitrogen and oxygen at 400–500 ℃. In this reaction, the reaction path is predictable and always starts from the center of the resin particle to form a central hole, then continues and expands around the hole, finally forming a uniformly distributed hole group;the particle surface remains intact. Analysis shows that this formation mode is due to the different reaction paths of sulfonic groups between the surface and interior of the particle, caused by the temperature difference. On the surface, transformation reactions happen at high temperatures(410–500 ℃) to form stable organic sulfur structures, while decomposition occurs inside the particle at a relatively low temperature(<410 ℃) and promotes complete pyrolysis of the copolymer matrix to form holes.展开更多
A co-reaction of methane with methanol over zeolite catalysts has emerged as a new approach to the long-standing challenge of methane transformation.However,the effect of catalyst acid properties on the co-reaction ha...A co-reaction of methane with methanol over zeolite catalysts has emerged as a new approach to the long-standing challenge of methane transformation.However,the effect of catalyst acid properties on the co-reaction has been rarely studied.In this study,a series of HZSM-5 zeolites with comparable diffusion abilities and various acidities were synthesized directly through steaming with 100%water vapor at 693 K.The co-reaction of methane and methanol was subsequently evaluated.Br?nsted acidity at 0.262 mmol/g was detected to reach the maximum methane conversion of 5.42%at 673 K,which was also the odd point in the relationship between acid concentration and C4 hydrogen transfer index.Moreover,the influence of methanol feed was investigated over parent and steamed ZSM-5 catalyst,with results showing that excessive acid sites or methanol molecules reduce methane conversion.It is proposed that acid sites adsorbed with methanol molecules construct the methane activation sites.Hence,a proper design of zeolite acidity should be achieved to obtain higher methane conversion in the co-reaction process.展开更多
In this study, a series of aryloxy-aluminoxanes originated directly from the hydrolysis of reaction products of A1Me3 and phenols were synthesized, which could serve as effective polymer-retarding activators for the i...In this study, a series of aryloxy-aluminoxanes originated directly from the hydrolysis of reaction products of A1Me3 and phenols were synthesized, which could serve as effective polymer-retarding activators for the iron-catalyzed ethylene oligomerization. The molar ratios of [PhOH]/[AlMe3] and [H2O]/[Al] during the preparation were explored and their impacts on the oligomerization activity and product distribution were discussed. To obtain the effective activators with good polymer-retarding effect and relatively high activity, the optimized conditions were proposed to be [PhOH]/[AlMe3] = 0.5 and [H2O]/[Al] = 0.7. Various aluminoxanes with different [-OH] sources confirmed the importance of using phenols in preparing the effective polymer-retarding activators. By utilizing these aryloxy-aluminoxanes, the mass fraction of polymers in the total products could be reduced to lower than 1.0 wt%, which is much lower than that of the MAO-activated systems (〉 30 wt%). This is a potential benefit for the industrial application of the iron-catalyzed oligomerization process.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos. 20676114 and 20736011)the National Hi-Tech Research and Development Program (863) of China (No. 2007AA04Z182)
文摘A novel method, based on acoustic emission (AE) techniques, for detecting agglomeration in fluidized beds is presented. Particle size characteristics are determined based on the principle that AE signals with different frequency band energies are emitted when particles of different sizes impact an internal wall. By applying chaotic analysis to the AE signals, the malfunction coefficients are well defined. Agglomeration in the fluidized bed can then be detected by the sudden variation of malfunction coefficients. AE signals were investigated in a laboratory scale heated fluidized bed and an industrial polyethylene fluidized bed. Experimental data showed that the malfunction coefficients increased with the growth of agglomeration. The results indicated that agglomeration in fluidized beds can be predicted and diagnosed effectively and precisely using AE techniques based on chaotic analysis.
基金Project supported by the National Natural Science Foundation of China(No.20490200)the National Key Technology R&D Program of China(Nos.85-516-06-03,2001BA305B03,and 2007BAF22B08)+1 种基金the National High-Tech R&D Program(863 Program)of China(No.2007AA04Z182)the SINOPEC Technology Project(No.406005),China
基金supported by the National Natural Science Foundation of China(No.91434205)the National Science Fund for Distinguished Young Scholars(No.21525627)+1 种基金the Zhejiang Provincial Natural Science Foundation of China(No.LR14B060001)the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20130101110063)
基金supported by the Joint Funds of the National Natural Science Foundation of China (No. U21B2095)the Major Research Project of National Natural Science Foundation of China (No. 91834303)the Science Fund for Creative Research Groups of National Natural Science Foundation of China (No. 61621002)。
文摘A novel central hole-expansion phenomenon is identified, in which the cation-exchange resin is pyrolyzed in a mixed atmosphere of nitrogen and oxygen at 400–500 ℃. In this reaction, the reaction path is predictable and always starts from the center of the resin particle to form a central hole, then continues and expands around the hole, finally forming a uniformly distributed hole group;the particle surface remains intact. Analysis shows that this formation mode is due to the different reaction paths of sulfonic groups between the surface and interior of the particle, caused by the temperature difference. On the surface, transformation reactions happen at high temperatures(410–500 ℃) to form stable organic sulfur structures, while decomposition occurs inside the particle at a relatively low temperature(<410 ℃) and promotes complete pyrolysis of the copolymer matrix to form holes.
基金Project supported by the National Natural Science Foundation of China(No.U1663222)。
文摘A co-reaction of methane with methanol over zeolite catalysts has emerged as a new approach to the long-standing challenge of methane transformation.However,the effect of catalyst acid properties on the co-reaction has been rarely studied.In this study,a series of HZSM-5 zeolites with comparable diffusion abilities and various acidities were synthesized directly through steaming with 100%water vapor at 693 K.The co-reaction of methane and methanol was subsequently evaluated.Br?nsted acidity at 0.262 mmol/g was detected to reach the maximum methane conversion of 5.42%at 673 K,which was also the odd point in the relationship between acid concentration and C4 hydrogen transfer index.Moreover,the influence of methanol feed was investigated over parent and steamed ZSM-5 catalyst,with results showing that excessive acid sites or methanol molecules reduce methane conversion.It is proposed that acid sites adsorbed with methanol molecules construct the methane activation sites.Hence,a proper design of zeolite acidity should be achieved to obtain higher methane conversion in the co-reaction process.
基金support and encouragement of the National Natural Science Foundation of China(Nos.U1663222 and 21176208)
文摘In this study, a series of aryloxy-aluminoxanes originated directly from the hydrolysis of reaction products of A1Me3 and phenols were synthesized, which could serve as effective polymer-retarding activators for the iron-catalyzed ethylene oligomerization. The molar ratios of [PhOH]/[AlMe3] and [H2O]/[Al] during the preparation were explored and their impacts on the oligomerization activity and product distribution were discussed. To obtain the effective activators with good polymer-retarding effect and relatively high activity, the optimized conditions were proposed to be [PhOH]/[AlMe3] = 0.5 and [H2O]/[Al] = 0.7. Various aluminoxanes with different [-OH] sources confirmed the importance of using phenols in preparing the effective polymer-retarding activators. By utilizing these aryloxy-aluminoxanes, the mass fraction of polymers in the total products could be reduced to lower than 1.0 wt%, which is much lower than that of the MAO-activated systems (〉 30 wt%). This is a potential benefit for the industrial application of the iron-catalyzed oligomerization process.