A two-phase dynamic model, describing gas phase propylene polymerization in a fluidized bed reactor, was used to explore the dynamic behavior and process control of the polypropylene production rate and reactor temper...A two-phase dynamic model, describing gas phase propylene polymerization in a fluidized bed reactor, was used to explore the dynamic behavior and process control of the polypropylene production rate and reactor temperature. The open loop analysis revealed the nonlinear behavior of the polypropylene fluidized bed reactor, jus- tifying the use of an advanced control algorithm for efficient control of the process variables. In this case, a central- ized model predictive control （MPC） technique was implemented to control the polypropylene production rate and reactor temperature by manipulating the catalyst feed rate and cooling water flow rate respectively. The corre- sponding MPC controller was able to track changes in the setpoint smoothly for the reactor temperature and pro- duction rate while the setpoint tracking of the conventional proportional-integral （PI） controller was oscillatory with overshoots and obvious interaction between the reactor temperature and production rate loops. The MPC was able to produce controller moves which not only were well within the specified input constraints for both control vari- ables, but also non-aggressive and sufficiently smooth for practical implementations. Furthermore, the closed loop dynamic simulations indicated that the speed of rejecting the process disturbances for the MPC controller were also acceotable for both controlled variables.展开更多
In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and h...In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and heat transfer between the solid particles and the surrounding gas in the emulsion phase is developed in this work to include site activation reaction. This model developed in the present study is subsequently compared with well-known models, namely, the bubble-growth, well-mixed and the constant bubble size models for porous and non porous catalyst. The results we obtained from the model was very close to the constant bubble size model, well-mixed model and bubble growth model at the beginning of the reaction but its overall behavior changed and is closer to the well-mixed model compared with the bubble growth model and constant bubble size model after half an hour of operation. Neural-network based predictive controller are implemented to control the system and compared with the conventional PID controller, giving acceptable results.展开更多
The estimation of the amount of reactive impurities in a loop reactor is of strategic importance to the propylene polymerization industry. It is essential to investigate the level of impurities in order to develop rel...The estimation of the amount of reactive impurities in a loop reactor is of strategic importance to the propylene polymerization industry. It is essential to investigate the level of impurities in order to develop reliable monitoring and control strategies. This paper described one approach based on generation function technique with the following two steps. First, a new mechanism for propylene polymerization was proposed by considering the effects of the reactive impurities in the material on the propylene polymerization. Second, a series of equations of population balance for the propylene polymerization in loop reactors were established based on the proposed mechanism. Accordingly, the equations were transformed into the mathematic matrix through the generation function technique to investigate the effects of the reactive impurities on the propylene polymerization. Significant effects of the reactive impurities were analyzed through computational simulation. The results show that the concentration of active centre on catalysts and the polymerization conversion both decrease with the increase of the initial concentration of any reactive impurity; hydrogen concentration decreases with the increase of the initial concentration of ethylene or butylenes, whereas, it increases with the increase of the initial concentration of propadiene; the simulated weight average molecular weight and the molecular weight distribution index of polymer resins both increase with the increase of the initial concentration of ethylene or butylenes. They decrease with the increase of the initial concentration of propadiene.展开更多
Monodisperse micron-sized polyacrylamide （PAM） particles with a regular shape have been successfully prepared through dispersion polymerization of the monomer using a rotary reactor. FTIR and NMR spectroscopic resul...Monodisperse micron-sized polyacrylamide （PAM） particles with a regular shape have been successfully prepared through dispersion polymerization of the monomer using a rotary reactor. FTIR and NMR spectroscopic results demonstrated the formation of PAM. POM and TEM observations revealed that PAM particles had a regular shape and good dispersity. A thick layer of surfactant （PVP） still existed on PAM particles after multiple centrifugation and ultrasonic re-dispersion in ethanol, which indicates a strong interaction between PVP and PAM. The effects of various polymerization factors on the average size of PAM particles have also been studied.展开更多
Batch to batch temperature control of a semi-batch chemical reactor with heating/cooling system was discussed in this study. Without extensive modeling investigations, a two-dimensional(2D) general predictive iterativ...Batch to batch temperature control of a semi-batch chemical reactor with heating/cooling system was discussed in this study. Without extensive modeling investigations, a two-dimensional(2D) general predictive iterative learning control(2D-MGPILC) strategy based on the multi-model with time-varying weights was introduced for optimizing the tracking performance of desired temperature profile. This strategy was modeled based on an iterative learning control(ILC) algorithm for a 2D system and designed in the generalized predictive control(GPC) framework. Firstly, a multi-model structure with time-varying weights was developed to describe the complex operation of a general semi-batch reactor. Secondly, the 2 D-MGPILC algorithm was proposed to optimize simultaneously the dynamic performance along the time and batch axes. Finally, simulation for the controller design of a semi-batch reactor with multiple reactions was involved to demonstrate that the satisfactory performance could be achieved despite of the repetitive or non-repetitive disturbances.展开更多
Poly(ethylene glycol)-poly(n-butyl cyanoacrylate)(PEG-PBCA)is a remarkable drug delivery carrier for permeating blood-brain barrier.In this work,a novel high-gravity procedure was reported to intensify Knoevenagel con...Poly(ethylene glycol)-poly(n-butyl cyanoacrylate)(PEG-PBCA)is a remarkable drug delivery carrier for permeating blood-brain barrier.In this work,a novel high-gravity procedure was reported to intensify Knoevenagel condensation-Michael addition polymerization of PEG-PBCA.A series of PEG-PBCA containing different block ratios were synthesized with narrow molecular weight distribution of polydispersity indexes less than 1.1.Furthermore,the reaction time reduced 60%compared to conventional stirred tank reactor process.Chemical structures of as-prepared polymers were characterized.In vitro drug delivery performance was evaluated.The cytotoxicity of PEG-PBCA to brain microvessel endothelial cells(BMVEC)decreases with the extension of the PEG chain and the shortening of the PBCA chain.The polymer cellular uptake to BMVECs was better after improving hydrophilicity by PEG block.Results of bloodbrain barrier permeability demonstrated that medium length of PBCA chain and short PEG chain are favorable for hydrophobic Nile red permeation,while long PEG chain and short PBCA chain are beneficial to delivery water-soluble doxorubicin hydrochloride(Dox).The average apparent permeability coeffi-cient increased 1.7 and 0.25 times than that of raw Nile red and Dox,respectively.High-gravity intensi-fied condensation polymerization should have great potential in brain drug delivery system.展开更多
The aerobic granular sludge was cultivated in a pilot-scale sequencing batch reactor （SBR）, and some of the granules were stored at 8 ℃ for 150 d. Extracellular polymeric substances （EPS） of sludge samples were e...The aerobic granular sludge was cultivated in a pilot-scale sequencing batch reactor （SBR）, and some of the granules were stored at 8 ℃ for 150 d. Extracellular polymeric substances （EPS） of sludge samples were extracted and analyzed during the granulation and storage process. The results show that the contents of protein and EPS increase along with the granulation process, while polysaccharides remain almost unchanged. The content of protein in EPS is almost two-fold larger than that of polysaccharides in granular sludge cultivated with municipal wastewater. Moreover, some of the granules disintegrate during storage, corresponding to the decrease of protein contents in EPS. Three peaks are identified in three-dimensional excitation emission matrix （EEM） fluorescence spectra of the EPS in the aerobic granules. Two peaks （A and B） are attributed to the protein-like fluorophores, and the third （peak C） is related to visible fulvic-like substances. Peak A gradually disappears during storage, while a new peak related to ultraviolet fulvic acid （peak D） is formed. The formation and the stability of aerobic granules are closely dependent on the quantity and composition of EPS proteins. Peak C has no obvious changes during granulation, while the fulvic-like substances present an increase in fluorescence intensities during storage, accompanied with an increase in structural complexity. The fulvie-like substances are also associated with the disintegration of the aerobic granules.展开更多
The formation of methane hydrate was undertaken in this research. The purpose of this work was to model the methane hydrate formation with a hydrate-water–methane system in a semi-batch reactor under steady–state, i...The formation of methane hydrate was undertaken in this research. The purpose of this work was to model the methane hydrate formation with a hydrate-water–methane system in a semi-batch reactor under steady–state, isothermal and isobaric conditions. Obtained results were validated with experiments conducted in a semi-batch spray reactor at low temperatures and high pressures. The investigated formation of gas hydrate from pure methane required physical constants of these materials which were determined through experimental data. The experiments hence, the theoretical calculations were conducted with pure methane and carried out in a spray reactor at 273.95K and 8705kPa to determine the actual amount of hydrate formation in such reactor. Ultimately;the comparison of the results generated from the developed mathematical model with those of experimental data of others indicated a very satisfactory agreement obtained.展开更多
Spherical polyethylene/polypropylene (PE/PP) in-reactor blend granules with various ethylene/propylene molar ratios and high porosity were synthesized using a high yield TiCVMgCl2 supported catalyst. A solution of ben...Spherical polyethylene/polypropylene (PE/PP) in-reactor blend granules with various ethylene/propylene molar ratios and high porosity were synthesized using a high yield TiCVMgCl2 supported catalyst. A solution of benzoyl peroxide (BPO)/maleic anhydride (MAH)/xylene (interfacial reagent) or BPO/MAH/St (comonomer) was absorbed onto the PE/PP in- reactor blend granules, and solid phase graft polymerization of MAH on PE/PP was conducted. The amount of grafted MAH on PE/PP was measured through chemical titration. The results showed that solid phase graft polymerization of MAH in PE/PP in-reactor blend granules produced graft copolymer with high amount of grafted MAH, and the amount of grafted MAH was raised slightly when St was introduced as comonomer. The graft in-reactor blend was fractionated into five fractions through temperature-gradient extraction fractionation (TGEF), and the fractions were analyzed by FTIR. The results revealed that MAH is mainly grafted on the PE segments, whereas MAH was predominantly grafted on the PP segments when St was present in the graft polymerization system. In addition, the final product is still in the form of regular spherical granules, which is beneficial for industrial processing.展开更多
A starved feed reactor (SFR) is a semi-batch polymerization reactor where initiator and monomer are fed slowly into a fixed amount of solvent. The polymerization is carried out isothermally at elevated temperatures. T...A starved feed reactor (SFR) is a semi-batch polymerization reactor where initiator and monomer are fed slowly into a fixed amount of solvent. The polymerization is carried out isothermally at elevated temperatures. The added initiator decomposes instantaneously and the added monomer polymerizes immediately. The molecular weight (MW) and molecular weight distribution (MWD) of the product polymer can be effectively controlled by the feed ratio of monomer to initiator. This paper presents a study on the MWD of styrene polymerization in a SFR. The MWD model parameters are regressed with experimental data. Although the solids fraction in the SFR is high (higher than 50%), viscosity is not too high and the 'gel effect' is weak due to the low molecular weight of the products. It is found that the termination rate constant is a power function of molecular weight, radicals terminate via 100% combination, the thermal initiation can be neglected even at high reaction temperature studied. And calculated results indicate that in the SFR, the validity of the long chain assumption becomes doubted. It appears that other alterative assumption should be found for an improved model.展开更多
This study reports the development and performance of a pilot-scale barrel atmospheric plasma reactor for the atmospheric plasma activation treatment of polymer particles. The polymer particles treated included acrylo...This study reports the development and performance of a pilot-scale barrel atmospheric plasma reactor for the atmospheric plasma activation treatment of polymer particles. The polymer particles treated included acrylonitrile butadiene styrene(ABS) and polypropylene(PP). These particles had diameters in the range of 3–5 mm. The initial studies were carried out using a laboratory-scale barrel reactor designed to treat polymer particle batch sizes of 20 g. A pilot-scale reactor that could treat 500 g particle batch sizes was then developed to facilitate pre-industrial-scale treatments. The effect of operating pulse density modulation(PDM) in the range 10%–100% and plasma treatment time on the level of activation of the treated polymers were then investigated. ABS revealed a larger decrease in water contact angle compared with PP after plasma treatment under the same conditions. The optimal treatment time of ABS(400 g of polymer particles) in the pilot-scale reactor was 15 min. The plasma-activated polymer particles were used to fabricate dog-bone polymer parts through injection molding.Mechanical testing of the resulting dog-bone polymer parts revealed a 10.5% increase in tensile strength compared with those fabricated using non-activated polymer particles.展开更多
基金Supported by the Research Grants of the Research Council of Malaya
文摘A two-phase dynamic model, describing gas phase propylene polymerization in a fluidized bed reactor, was used to explore the dynamic behavior and process control of the polypropylene production rate and reactor temperature. The open loop analysis revealed the nonlinear behavior of the polypropylene fluidized bed reactor, jus- tifying the use of an advanced control algorithm for efficient control of the process variables. In this case, a central- ized model predictive control （MPC） technique was implemented to control the polypropylene production rate and reactor temperature by manipulating the catalyst feed rate and cooling water flow rate respectively. The corre- sponding MPC controller was able to track changes in the setpoint smoothly for the reactor temperature and pro- duction rate while the setpoint tracking of the conventional proportional-integral （PI） controller was oscillatory with overshoots and obvious interaction between the reactor temperature and production rate loops. The MPC was able to produce controller moves which not only were well within the specified input constraints for both control vari- ables, but also non-aggressive and sufficiently smooth for practical implementations. Furthermore, the closed loop dynamic simulations indicated that the speed of rejecting the process disturbances for the MPC controller were also acceotable for both controlled variables.
文摘In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and heat transfer between the solid particles and the surrounding gas in the emulsion phase is developed in this work to include site activation reaction. This model developed in the present study is subsequently compared with well-known models, namely, the bubble-growth, well-mixed and the constant bubble size models for porous and non porous catalyst. The results we obtained from the model was very close to the constant bubble size model, well-mixed model and bubble growth model at the beginning of the reaction but its overall behavior changed and is closer to the well-mixed model compared with the bubble growth model and constant bubble size model after half an hour of operation. Neural-network based predictive controller are implemented to control the system and compared with the conventional PID controller, giving acceptable results.
基金This work was financially supported by the National Natural Science Foundation of China (No. 20406016)Fujian Petrochemical Company of SINOPEC (No. MS/FJ-08-JS-15-2005-01)
文摘The estimation of the amount of reactive impurities in a loop reactor is of strategic importance to the propylene polymerization industry. It is essential to investigate the level of impurities in order to develop reliable monitoring and control strategies. This paper described one approach based on generation function technique with the following two steps. First, a new mechanism for propylene polymerization was proposed by considering the effects of the reactive impurities in the material on the propylene polymerization. Second, a series of equations of population balance for the propylene polymerization in loop reactors were established based on the proposed mechanism. Accordingly, the equations were transformed into the mathematic matrix through the generation function technique to investigate the effects of the reactive impurities on the propylene polymerization. Significant effects of the reactive impurities were analyzed through computational simulation. The results show that the concentration of active centre on catalysts and the polymerization conversion both decrease with the increase of the initial concentration of any reactive impurity; hydrogen concentration decreases with the increase of the initial concentration of ethylene or butylenes, whereas, it increases with the increase of the initial concentration of propadiene; the simulated weight average molecular weight and the molecular weight distribution index of polymer resins both increase with the increase of the initial concentration of ethylene or butylenes. They decrease with the increase of the initial concentration of propadiene.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50403017).
文摘Monodisperse micron-sized polyacrylamide （PAM） particles with a regular shape have been successfully prepared through dispersion polymerization of the monomer using a rotary reactor. FTIR and NMR spectroscopic results demonstrated the formation of PAM. POM and TEM observations revealed that PAM particles had a regular shape and good dispersity. A thick layer of surfactant （PVP） still existed on PAM particles after multiple centrifugation and ultrasonic re-dispersion in ethanol, which indicates a strong interaction between PVP and PAM. The effects of various polymerization factors on the average size of PAM particles have also been studied.
基金Projects(61673205,21727818,61503180)supported by the National Natural Science Foundation of ChinaProject(2017YFB0307304)supported by National Key R&D Program of ChinaProject(BK20141461)supported by the Natural Science Foundation of Jiangsu Province,China
文摘Batch to batch temperature control of a semi-batch chemical reactor with heating/cooling system was discussed in this study. Without extensive modeling investigations, a two-dimensional(2D) general predictive iterative learning control(2D-MGPILC) strategy based on the multi-model with time-varying weights was introduced for optimizing the tracking performance of desired temperature profile. This strategy was modeled based on an iterative learning control(ILC) algorithm for a 2D system and designed in the generalized predictive control(GPC) framework. Firstly, a multi-model structure with time-varying weights was developed to describe the complex operation of a general semi-batch reactor. Secondly, the 2 D-MGPILC algorithm was proposed to optimize simultaneously the dynamic performance along the time and batch axes. Finally, simulation for the controller design of a semi-batch reactor with multiple reactions was involved to demonstrate that the satisfactory performance could be achieved despite of the repetitive or non-repetitive disturbances.
基金This work was supported by National Key Research and Development Program of China(2016YFA0201701).
文摘Poly(ethylene glycol)-poly(n-butyl cyanoacrylate)(PEG-PBCA)is a remarkable drug delivery carrier for permeating blood-brain barrier.In this work,a novel high-gravity procedure was reported to intensify Knoevenagel condensation-Michael addition polymerization of PEG-PBCA.A series of PEG-PBCA containing different block ratios were synthesized with narrow molecular weight distribution of polydispersity indexes less than 1.1.Furthermore,the reaction time reduced 60%compared to conventional stirred tank reactor process.Chemical structures of as-prepared polymers were characterized.In vitro drug delivery performance was evaluated.The cytotoxicity of PEG-PBCA to brain microvessel endothelial cells(BMVEC)decreases with the extension of the PEG chain and the shortening of the PBCA chain.The polymer cellular uptake to BMVECs was better after improving hydrophilicity by PEG block.Results of bloodbrain barrier permeability demonstrated that medium length of PBCA chain and short PEG chain are favorable for hydrophobic Nile red permeation,while long PEG chain and short PBCA chain are beneficial to delivery water-soluble doxorubicin hydrochloride(Dox).The average apparent permeability coeffi-cient increased 1.7 and 0.25 times than that of raw Nile red and Dox,respectively.High-gravity intensi-fied condensation polymerization should have great potential in brain drug delivery system.
基金financially supported by the National Natural Science Foundation of China (Nos. 52174340, 51704338)the Basic Science Center of the National Natural Science Foundation of China (No. 72088101)the National Key Research and Development Project of China (No. 2022YFC2904505)。
基金Project(2006AA06Z318) supported by the National High-Tech Research and Development Program of China
文摘The aerobic granular sludge was cultivated in a pilot-scale sequencing batch reactor （SBR）, and some of the granules were stored at 8 ℃ for 150 d. Extracellular polymeric substances （EPS） of sludge samples were extracted and analyzed during the granulation and storage process. The results show that the contents of protein and EPS increase along with the granulation process, while polysaccharides remain almost unchanged. The content of protein in EPS is almost two-fold larger than that of polysaccharides in granular sludge cultivated with municipal wastewater. Moreover, some of the granules disintegrate during storage, corresponding to the decrease of protein contents in EPS. Three peaks are identified in three-dimensional excitation emission matrix （EEM） fluorescence spectra of the EPS in the aerobic granules. Two peaks （A and B） are attributed to the protein-like fluorophores, and the third （peak C） is related to visible fulvic-like substances. Peak A gradually disappears during storage, while a new peak related to ultraviolet fulvic acid （peak D） is formed. The formation and the stability of aerobic granules are closely dependent on the quantity and composition of EPS proteins. Peak C has no obvious changes during granulation, while the fulvic-like substances present an increase in fluorescence intensities during storage, accompanied with an increase in structural complexity. The fulvie-like substances are also associated with the disintegration of the aerobic granules.
文摘The formation of methane hydrate was undertaken in this research. The purpose of this work was to model the methane hydrate formation with a hydrate-water–methane system in a semi-batch reactor under steady–state, isothermal and isobaric conditions. Obtained results were validated with experiments conducted in a semi-batch spray reactor at low temperatures and high pressures. The investigated formation of gas hydrate from pure methane required physical constants of these materials which were determined through experimental data. The experiments hence, the theoretical calculations were conducted with pure methane and carried out in a spray reactor at 273.95K and 8705kPa to determine the actual amount of hydrate formation in such reactor. Ultimately;the comparison of the results generated from the developed mathematical model with those of experimental data of others indicated a very satisfactory agreement obtained.
基金This work was supported by the Special Fund for Major State Basic Research Projects (Grant no. G1999064803).
文摘Spherical polyethylene/polypropylene (PE/PP) in-reactor blend granules with various ethylene/propylene molar ratios and high porosity were synthesized using a high yield TiCVMgCl2 supported catalyst. A solution of benzoyl peroxide (BPO)/maleic anhydride (MAH)/xylene (interfacial reagent) or BPO/MAH/St (comonomer) was absorbed onto the PE/PP in- reactor blend granules, and solid phase graft polymerization of MAH on PE/PP was conducted. The amount of grafted MAH on PE/PP was measured through chemical titration. The results showed that solid phase graft polymerization of MAH in PE/PP in-reactor blend granules produced graft copolymer with high amount of grafted MAH, and the amount of grafted MAH was raised slightly when St was introduced as comonomer. The graft in-reactor blend was fractionated into five fractions through temperature-gradient extraction fractionation (TGEF), and the fractions were analyzed by FTIR. The results revealed that MAH is mainly grafted on the PE segments, whereas MAH was predominantly grafted on the PP segments when St was present in the graft polymerization system. In addition, the final product is still in the form of regular spherical granules, which is beneficial for industrial processing.
基金Supported by the State Key Polymerization Reaction Engineering Laboratory of Zhejiang University.
文摘A starved feed reactor (SFR) is a semi-batch polymerization reactor where initiator and monomer are fed slowly into a fixed amount of solvent. The polymerization is carried out isothermally at elevated temperatures. The added initiator decomposes instantaneously and the added monomer polymerizes immediately. The molecular weight (MW) and molecular weight distribution (MWD) of the product polymer can be effectively controlled by the feed ratio of monomer to initiator. This paper presents a study on the MWD of styrene polymerization in a SFR. The MWD model parameters are regressed with experimental data. Although the solids fraction in the SFR is high (higher than 50%), viscosity is not too high and the 'gel effect' is weak due to the low molecular weight of the products. It is found that the termination rate constant is a power function of molecular weight, radicals terminate via 100% combination, the thermal initiation can be neglected even at high reaction temperature studied. And calculated results indicate that in the SFR, the validity of the long chain assumption becomes doubted. It appears that other alterative assumption should be found for an improved model.
基金support of the Enterprise Ireland Innovation Partnership programthe SFI funded Ⅰ-Form Advanced Manufacturing Research Centre 16/RC/3872
文摘This study reports the development and performance of a pilot-scale barrel atmospheric plasma reactor for the atmospheric plasma activation treatment of polymer particles. The polymer particles treated included acrylonitrile butadiene styrene(ABS) and polypropylene(PP). These particles had diameters in the range of 3–5 mm. The initial studies were carried out using a laboratory-scale barrel reactor designed to treat polymer particle batch sizes of 20 g. A pilot-scale reactor that could treat 500 g particle batch sizes was then developed to facilitate pre-industrial-scale treatments. The effect of operating pulse density modulation(PDM) in the range 10%–100% and plasma treatment time on the level of activation of the treated polymers were then investigated. ABS revealed a larger decrease in water contact angle compared with PP after plasma treatment under the same conditions. The optimal treatment time of ABS(400 g of polymer particles) in the pilot-scale reactor was 15 min. The plasma-activated polymer particles were used to fabricate dog-bone polymer parts through injection molding.Mechanical testing of the resulting dog-bone polymer parts revealed a 10.5% increase in tensile strength compared with those fabricated using non-activated polymer particles.
