Methanol-to-olefins(MTO)is industrially applied to produce ethylene and propylene using methanol converted from coal,synthetic gas,and biomass.SAPO-34 zeolites,as the most efficient catalyst in MTO process,are subject...Methanol-to-olefins(MTO)is industrially applied to produce ethylene and propylene using methanol converted from coal,synthetic gas,and biomass.SAPO-34 zeolites,as the most efficient catalyst in MTO process,are subject to the rapid deactivation due to coke deposition.Recent work shows that steam regeneration can provide advantages such as low carbon dioxide emission and enhanced light olefins yield in MTO process,compared to that by air regeneration.A kinetic study on the steam regeneration of spent SAPO-34 catalyst has been carried out in this work.In doing so,we first investigated the effect of temperature on the regeneration performance by monitoring the crystal structure,acidity,residual coke properties and other structural parameters.The results show that with the increase of regeneration temperature,the compositions of residual coke on the catalyst change from pyrene and phenanthrene to naphthalene,which are normally considered as active hydrocarbon pool species in MTO reaction.However,when the regeneration temperature is too high,nitrogen oxides can be found in the residual coke.Meanwhile,as the regeneration temperature increases,the quantity of residual coke reduces and the acidity,BET surface area and pore structure of the regenerated samples can be better recovered,resulting in prolonging catalyst lifetime.We have further derived the kinetics of steam regeneration,and obtained an activation energy of about 177.8 kJ·mol^(-1).Compared that with air regeneration,the activation energy of steam regeneration is higher,indicating that the steam regeneration process is more difficult to occur.展开更多
Producing methanol from coke oven gas(COG) is one of the important applications of COG. Removal of sulfur from COG is a key step of this process. Conversion and reaction kinetics over a commercial Fe-Mo/Al2O3 catalyst...Producing methanol from coke oven gas(COG) is one of the important applications of COG. Removal of sulfur from COG is a key step of this process. Conversion and reaction kinetics over a commercial Fe-Mo/Al2O3 catalyst(T-202) were studied in a continuous flow fixed bed reactor under pressures of 1.6-2.8 MPa, space time of 1.32-3.55 s and temperatures of 240-360 °C. Though the COG contains about 0.6 mol/mol H2, hydrogenation of CO and CO2 is not significant on this catalyst. The conversions of unsaturated hydrocarbons depend on their molecular structures. Diolefins and alkynes can be completely hydrogenated even at relatively low temperature and pressure. Olefins, in contrast, can only be progressively hydrogenated with increasing temperature and pressure. The hydrodesulfurization(HDS) of CS2 on this catalyst is easy. Complete conversion of CS2 was observed in the whole range of the conditions used in this work. The original COS in the COG can also be easily converted to a low level. However, its complete HDS is difficult due to the relatively high concentration of CO in the COG and due to the limitation of thermodynamics. H2 S can react with unsaturated hydrocarbons to form ethyl mercaptan and thiophene, which are then progressively hydrodesulfurized with increasing temperature and pressure. Based on the experimental observations, reaction kinetic models for the conversion of ethylene and sulfur-containing compounds were proposed; the values of the parameters in the models were obtained by regression of the experimental data.展开更多
The kinetics of coke solution loss reaction with and without sodium carbonate were investigated under the reaction atmosphere of carb on dioxide. The variables of gas flow rate and coke particle size were explored to ...The kinetics of coke solution loss reaction with and without sodium carbonate were investigated under the reaction atmosphere of carb on dioxide. The variables of gas flow rate and coke particle size were explored to eliminate the external and inteirial diffusion, respectively. Then, the improved method combining with the least square and the genetic algorithm was proposed to solve the homogeneous model and the shrinking core model. It was found that the improved genetic algorithm method has good stability by studying the fitness function at each generation. In the homogeneous model, the activation energy with and without sodium carbonate was 54.89 and 95.56 kJ/mol, respectively. And. the activation energy with and without sodium carbonate in the shrinking core model was 49.83 and 92.18 kJ/mol, respectively. Therefore, it was concluded that the sodium carbonate has the catalytic action. In addition, results showed that the estimated conversions were agreed well with the experimental ones, which indicated that the calculated kinetic parameters were valid and the proposed method was successfully developed.展开更多
The coke deposition on HZSM-5/SAPO-34 composite catalysts has been studied in the conversion of ethanol to propylene. The HZSM-5/SAPO-34 composite catalysts were synthesized by hydrothermal method（ZS-HS） and fully b...The coke deposition on HZSM-5/SAPO-34 composite catalysts has been studied in the conversion of ethanol to propylene. The HZSM-5/SAPO-34 composite catalysts were synthesized by hydrothermal method（ZS-HS） and fully blending（ZS-MM）. The used catalysts were characterized by XRD, N;adsorption–desorption, TGA, TPO, elemental analysis, FTIR and XPS. The coking kinetics on both ZS-HS and ZS-MM has been investigated and their coking rate equations were obtained. The used ZS-MM catalyst had higher amount of coke and lower nC:nHthan the used ZS-HS. 90% of the coke was deposited in the micropores of ZS-HS, while almost 45% of the coke located in the micropores of ZS-MM. The coke deposited on ZS-HS catalyst was mainly graphite-like carbon species, whereas dehydrogenated coke species was the major on ZS-MM. The coking activation energy of ZS-MM was lower than that of ZS-HS, and the coking rate on ZS-MM was faster than on ZS-HS. In addition, the regeneration of ZS-MM catalyst showed that it had a good hydrothermal stability. The differences on coking behaviors on the two catalysts were due to their different acidic properties and textures.展开更多
In industrial catalytic processes,coke deposition can cause catalyst deactivation by covering acid sites and/or blocking pores.The regeneration of deactivated catalysts,thereby removing the coke and simultaneously res...In industrial catalytic processes,coke deposition can cause catalyst deactivation by covering acid sites and/or blocking pores.The regeneration of deactivated catalysts,thereby removing the coke and simultaneously restoring the catalytic activity,is highly desired.Despite various chemical reactions and methods are available to remove coke,developing reliable,efficient,and economic regeneration methods for catalytic processes still remains a challenge in industrial practice.In this paper,the current progress of regeneration methods such as oxidation(air,ozone and oxynitride),gasification(carbon dioxide and water steam),and hydrogenation(hydrogen)is reviewed,which hopefully can shed some light on the design and optimization of catalysts and the related processes.展开更多
Carbon deposition via coke formation is one of the critical problems causing catalyst deactivation during the reforming of hydrocarbons. An effort was made to regenerate the catalyst （Ni/γ-alumina） by oxidation met...Carbon deposition via coke formation is one of the critical problems causing catalyst deactivation during the reforming of hydrocarbons. An effort was made to regenerate the catalyst （Ni/γ-alumina） by oxidation methods. Two approaches were carded out for the regeneration of the deactivated catalyst. The first one involves the plasma treatment of the deactivated catalyst in the presence of dry air over a temperature range of 300-500℃, while the second one only the thermal treatment in the same temperature range. The performance of the regenerated catalyst was evaluated in terms of C4H10 and CO2 conversions and the physicochemical characteristics were examined using a surface area analyzer, an elemental analyzer, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. It was observed that the carbon deposit （coke） on the catalyst was about 9.89 wt% after reforming C4H10 for 5 h at 540℃. The simple thermal treatment at 400 ℃ reduced carbon content to 6.59 wt% whereas it was decreased to 3.25 wt% by the plasma and heat combination. The specific surface area was fully restored to the original state by the plasma-assisted regeneration at 500℃. As far as the catalytic activity is concerned, the fresh and regenerated catalysts exhibited similar C4H10 and CO2 conversion efficiencies.展开更多
The aim of this study is to generate operational data that can be used to improve the production capacity in the Fluid Catalytic Cracking Unit (FCCU) in a Refinery and Petrochemical Company. This will aid in tackling ...The aim of this study is to generate operational data that can be used to improve the production capacity in the Fluid Catalytic Cracking Unit (FCCU) in a Refinery and Petrochemical Company. This will aid in tackling the daunting challenge of unavailability of operational data that can be used to better understand and improve production capacity and ensure maximizing catalyst utilization. In addition, it addresses the challenges of analysis and control of the FCCU process due to its very complicated and little-known hydrodynamics, complex kinetics of both reactions of cracking and coke burning, strong interaction between the reactor and regenerator, and numerous operating constraints. Aspen HYSYS version 8.0 was used in modeling the cracking process using parameters extracted from the operating manual of the FCCU in the refinery. The operational data was used to compare the simulated effect of stepwise input in feed and reactor plenum temperatures as well as stepwise increase in reactor length on yield, catalyst-to-oil-ratio and catalyst regeneration. An optimum flow in naphtha was obtained by the interaction of the inlet crude flow rate, riser height, and temperature this optimum was supported by the study of the interaction of these parameters when, catalyst to oil ratio was set as the dependent parameter. The inferences drawn from the results are that the reactor plenum temperature of 560℃and a riser length of 27 m are recommended for optimum performance that ensures lasting effect of an efficient catalyst activity.展开更多
基金the National Natural Science Foundation of China(91834302)。
文摘Methanol-to-olefins(MTO)is industrially applied to produce ethylene and propylene using methanol converted from coal,synthetic gas,and biomass.SAPO-34 zeolites,as the most efficient catalyst in MTO process,are subject to the rapid deactivation due to coke deposition.Recent work shows that steam regeneration can provide advantages such as low carbon dioxide emission and enhanced light olefins yield in MTO process,compared to that by air regeneration.A kinetic study on the steam regeneration of spent SAPO-34 catalyst has been carried out in this work.In doing so,we first investigated the effect of temperature on the regeneration performance by monitoring the crystal structure,acidity,residual coke properties and other structural parameters.The results show that with the increase of regeneration temperature,the compositions of residual coke on the catalyst change from pyrene and phenanthrene to naphthalene,which are normally considered as active hydrocarbon pool species in MTO reaction.However,when the regeneration temperature is too high,nitrogen oxides can be found in the residual coke.Meanwhile,as the regeneration temperature increases,the quantity of residual coke reduces and the acidity,BET surface area and pore structure of the regenerated samples can be better recovered,resulting in prolonging catalyst lifetime.We have further derived the kinetics of steam regeneration,and obtained an activation energy of about 177.8 kJ·mol^(-1).Compared that with air regeneration,the activation energy of steam regeneration is higher,indicating that the steam regeneration process is more difficult to occur.
文摘Producing methanol from coke oven gas(COG) is one of the important applications of COG. Removal of sulfur from COG is a key step of this process. Conversion and reaction kinetics over a commercial Fe-Mo/Al2O3 catalyst(T-202) were studied in a continuous flow fixed bed reactor under pressures of 1.6-2.8 MPa, space time of 1.32-3.55 s and temperatures of 240-360 °C. Though the COG contains about 0.6 mol/mol H2, hydrogenation of CO and CO2 is not significant on this catalyst. The conversions of unsaturated hydrocarbons depend on their molecular structures. Diolefins and alkynes can be completely hydrogenated even at relatively low temperature and pressure. Olefins, in contrast, can only be progressively hydrogenated with increasing temperature and pressure. The hydrodesulfurization(HDS) of CS2 on this catalyst is easy. Complete conversion of CS2 was observed in the whole range of the conditions used in this work. The original COS in the COG can also be easily converted to a low level. However, its complete HDS is difficult due to the relatively high concentration of CO in the COG and due to the limitation of thermodynamics. H2 S can react with unsaturated hydrocarbons to form ethyl mercaptan and thiophene, which are then progressively hydrodesulfurized with increasing temperature and pressure. Based on the experimental observations, reaction kinetic models for the conversion of ethylene and sulfur-containing compounds were proposed; the values of the parameters in the models were obtained by regression of the experimental data.
基金the National Natural Science Foundation of China(21476001)Key Project of Anhui Provincial Department of Education(KJ2017A045)are gratefully acknowledgedOpen Fund of Shaanxi Key Laboratory of Energy Chemical Process Intensification(No.SXECPI201601).
文摘The kinetics of coke solution loss reaction with and without sodium carbonate were investigated under the reaction atmosphere of carb on dioxide. The variables of gas flow rate and coke particle size were explored to eliminate the external and inteirial diffusion, respectively. Then, the improved method combining with the least square and the genetic algorithm was proposed to solve the homogeneous model and the shrinking core model. It was found that the improved genetic algorithm method has good stability by studying the fitness function at each generation. In the homogeneous model, the activation energy with and without sodium carbonate was 54.89 and 95.56 kJ/mol, respectively. And. the activation energy with and without sodium carbonate in the shrinking core model was 49.83 and 92.18 kJ/mol, respectively. Therefore, it was concluded that the sodium carbonate has the catalytic action. In addition, results showed that the estimated conversions were agreed well with the experimental ones, which indicated that the calculated kinetic parameters were valid and the proposed method was successfully developed.
基金support for this work from National Ministry of Education(No.NCET-10-878)Shaanxi Province(No.2011ZKC4-08,2009ZDKG-70)Northwest University(10YSY08)
文摘The coke deposition on HZSM-5/SAPO-34 composite catalysts has been studied in the conversion of ethanol to propylene. The HZSM-5/SAPO-34 composite catalysts were synthesized by hydrothermal method（ZS-HS） and fully blending（ZS-MM）. The used catalysts were characterized by XRD, N;adsorption–desorption, TGA, TPO, elemental analysis, FTIR and XPS. The coking kinetics on both ZS-HS and ZS-MM has been investigated and their coking rate equations were obtained. The used ZS-MM catalyst had higher amount of coke and lower nC:nHthan the used ZS-HS. 90% of the coke was deposited in the micropores of ZS-HS, while almost 45% of the coke located in the micropores of ZS-MM. The coke deposited on ZS-HS catalyst was mainly graphite-like carbon species, whereas dehydrogenated coke species was the major on ZS-MM. The coking activation energy of ZS-MM was lower than that of ZS-HS, and the coking rate on ZS-MM was faster than on ZS-HS. In addition, the regeneration of ZS-MM catalyst showed that it had a good hydrothermal stability. The differences on coking behaviors on the two catalysts were due to their different acidic properties and textures.
文摘In industrial catalytic processes,coke deposition can cause catalyst deactivation by covering acid sites and/or blocking pores.The regeneration of deactivated catalysts,thereby removing the coke and simultaneously restoring the catalytic activity,is highly desired.Despite various chemical reactions and methods are available to remove coke,developing reliable,efficient,and economic regeneration methods for catalytic processes still remains a challenge in industrial practice.In this paper,the current progress of regeneration methods such as oxidation(air,ozone and oxynitride),gasification(carbon dioxide and water steam),and hydrogenation(hydrogen)is reviewed,which hopefully can shed some light on the design and optimization of catalysts and the related processes.
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education,Science and Technology(Grant number 2012-0007231)
文摘Carbon deposition via coke formation is one of the critical problems causing catalyst deactivation during the reforming of hydrocarbons. An effort was made to regenerate the catalyst （Ni/γ-alumina） by oxidation methods. Two approaches were carded out for the regeneration of the deactivated catalyst. The first one involves the plasma treatment of the deactivated catalyst in the presence of dry air over a temperature range of 300-500℃, while the second one only the thermal treatment in the same temperature range. The performance of the regenerated catalyst was evaluated in terms of C4H10 and CO2 conversions and the physicochemical characteristics were examined using a surface area analyzer, an elemental analyzer, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. It was observed that the carbon deposit （coke） on the catalyst was about 9.89 wt% after reforming C4H10 for 5 h at 540℃. The simple thermal treatment at 400 ℃ reduced carbon content to 6.59 wt% whereas it was decreased to 3.25 wt% by the plasma and heat combination. The specific surface area was fully restored to the original state by the plasma-assisted regeneration at 500℃. As far as the catalytic activity is concerned, the fresh and regenerated catalysts exhibited similar C4H10 and CO2 conversion efficiencies.
文摘The aim of this study is to generate operational data that can be used to improve the production capacity in the Fluid Catalytic Cracking Unit (FCCU) in a Refinery and Petrochemical Company. This will aid in tackling the daunting challenge of unavailability of operational data that can be used to better understand and improve production capacity and ensure maximizing catalyst utilization. In addition, it addresses the challenges of analysis and control of the FCCU process due to its very complicated and little-known hydrodynamics, complex kinetics of both reactions of cracking and coke burning, strong interaction between the reactor and regenerator, and numerous operating constraints. Aspen HYSYS version 8.0 was used in modeling the cracking process using parameters extracted from the operating manual of the FCCU in the refinery. The operational data was used to compare the simulated effect of stepwise input in feed and reactor plenum temperatures as well as stepwise increase in reactor length on yield, catalyst-to-oil-ratio and catalyst regeneration. An optimum flow in naphtha was obtained by the interaction of the inlet crude flow rate, riser height, and temperature this optimum was supported by the study of the interaction of these parameters when, catalyst to oil ratio was set as the dependent parameter. The inferences drawn from the results are that the reactor plenum temperature of 560℃and a riser length of 27 m are recommended for optimum performance that ensures lasting effect of an efficient catalyst activity.
