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
Thermax 700 thermo gravimetric analysis （TGA） instrument is introduced for the investigation of the reaction and deactivation kinetics of Methanol-to-Olefins （MTO） process with SAPO-34 catalyst.By the use of a spe...Thermax 700 thermo gravimetric analysis （TGA） instrument is introduced for the investigation of the reaction and deactivation kinetics of Methanol-to-Olefins （MTO） process with SAPO-34 catalyst.By the use of a special sample basket,the TGA instrument can be viewed as a plug flow fixed-bed reactor,while the weight change of SAPO-34 during reaction can be recorded online.Kinetic data are acquired in the temperature range of 648.2？748.2 K and space velocities of 7.08？35.91 h^-1 （WHSV）.Catalyst activity is expressed with average coke content,and selectivity for different products is related as a function of coke content and temperature.Methane is also introduced into the lumping kinetic model,and power exponent function with first-order reaction is adopted for model deduction.Exponential function is tested to give the best fit for catalyst activity and product selectivity with the highest correlation coefficient.The nicely agreed results between experimental and calculated data suggest that the overall kinetic model would be meaningful in both product distribution prediction and reactor simulation.展开更多
SAPO-34, a silicoaluminophosphate zeolite, has been synthesized by the hydrothermal method with the addition of different molecular weights of polyethylene glycol(PEG), and has been characterized with XRD, SEM,N_2 ads...SAPO-34, a silicoaluminophosphate zeolite, has been synthesized by the hydrothermal method with the addition of different molecular weights of polyethylene glycol(PEG), and has been characterized with XRD, SEM,N_2 adsorption–desorption, FT-IR, and NH_3 temperatureprogrammed desorption(NH_3-TPD). We studied SAPO-34 as a catalyst in the methanol-to-olefins(MTO) reaction, in a fixed-bed reactor. The results show that the chain length of PEG has a great influence on the particle size and morphology of SAPO-34. PEG acts as inhibitor in the crystallization process. With the increase of the chain length of PEG used in the synthesis, from a relative molecular weight of 400-6000, the morphology of SAPO-34 changes gradually from cubic to nanoplate-like and then changes to cubic again. The particle size decreases markedly at first and then increases to some extent. The catalytic stability in the MTO reaction also increases first and then decreases, with all the catalysts having almost the same selectivity to olefins. When the sample is synthesized with PEG800, the particles become nanoplate-like with a thickness of 46 nm on average, and the catalytic stability is appreciably prolonged, which is attributed to the shorter diffusion paths of the reactants in the zeolite.展开更多
SAPO-34 molecular sieves were synthesized directly by hydrothermal method with rice husk ash(RHA)used as the silicon source.The crystal structure,composition,surface morphology and acidity of the synthesized products ...SAPO-34 molecular sieves were synthesized directly by hydrothermal method with rice husk ash(RHA)used as the silicon source.The crystal structure,composition,surface morphology and acidity of the synthesized products weresieves had a high crystallinity,without any impure phase.Compared with the SAPO-34 prepared by the silica sol,RHA-SAPO-34 had similar acid properties in strength.The methanol to olefins(MTO)experiments showed that the SAPO-34molecular sieve synthesized from RHA exhibited both a good catalytic activity and ethylene selectivity.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Thermax 700 thermo gravimetric analysis （TGA） instrument is introduced for the investigation of the reaction and deactivation kinetics of Methanol-to-Olefins （MTO） process with SAPO-34 catalyst.By the use of a special sample basket,the TGA instrument can be viewed as a plug flow fixed-bed reactor,while the weight change of SAPO-34 during reaction can be recorded online.Kinetic data are acquired in the temperature range of 648.2？748.2 K and space velocities of 7.08？35.91 h^-1 （WHSV）.Catalyst activity is expressed with average coke content,and selectivity for different products is related as a function of coke content and temperature.Methane is also introduced into the lumping kinetic model,and power exponent function with first-order reaction is adopted for model deduction.Exponential function is tested to give the best fit for catalyst activity and product selectivity with the highest correlation coefficient.The nicely agreed results between experimental and calculated data suggest that the overall kinetic model would be meaningful in both product distribution prediction and reactor simulation.
基金supported by the National Natural Science Foundation of China(No.21276183)
文摘SAPO-34, a silicoaluminophosphate zeolite, has been synthesized by the hydrothermal method with the addition of different molecular weights of polyethylene glycol(PEG), and has been characterized with XRD, SEM,N_2 adsorption–desorption, FT-IR, and NH_3 temperatureprogrammed desorption(NH_3-TPD). We studied SAPO-34 as a catalyst in the methanol-to-olefins(MTO) reaction, in a fixed-bed reactor. The results show that the chain length of PEG has a great influence on the particle size and morphology of SAPO-34. PEG acts as inhibitor in the crystallization process. With the increase of the chain length of PEG used in the synthesis, from a relative molecular weight of 400-6000, the morphology of SAPO-34 changes gradually from cubic to nanoplate-like and then changes to cubic again. The particle size decreases markedly at first and then increases to some extent. The catalytic stability in the MTO reaction also increases first and then decreases, with all the catalysts having almost the same selectivity to olefins. When the sample is synthesized with PEG800, the particles become nanoplate-like with a thickness of 46 nm on average, and the catalytic stability is appreciably prolonged, which is attributed to the shorter diffusion paths of the reactants in the zeolite.
基金supported by the Cultivation Foundation of Northeast Petroleum University(2017PYYL-03)
文摘SAPO-34 molecular sieves were synthesized directly by hydrothermal method with rice husk ash(RHA)used as the silicon source.The crystal structure,composition,surface morphology and acidity of the synthesized products weresieves had a high crystallinity,without any impure phase.Compared with the SAPO-34 prepared by the silica sol,RHA-SAPO-34 had similar acid properties in strength.The methanol to olefins(MTO)experiments showed that the SAPO-34molecular sieve synthesized from RHA exhibited both a good catalytic activity and ethylene selectivity.
