An innovative green process of producing ε-caprolactam was proposed by integrating ammoximation and Beckmann rearrangement effectively. As a first part of the new process, TS-1 molecular sieve-catalyzed synthesis of ...An innovative green process of producing ε-caprolactam was proposed by integrating ammoximation and Beckmann rearrangement effectively. As a first part of the new process, TS-1 molecular sieve-catalyzed synthesis of cyclohexanone oxime from cyclohexanone, ammonia and hydrogen peroxide was carried out in a batch plant. Cyclohexane was used as the solvent in the three-phase reaction system. The influences of essential process parameters on ammoximation were investigated. Under the reaction conditions as catalyst content of 2.5% (by mass); H 2 O 2 /yclohexanone molar ratio of 1.10; NH 3 /cyclohexanone molar ratio of 2.20; reaction temperature of 343 K; reaction time of 5 h, high conversion of cyclohexanone and selectivity to oxime (both>99%) were obtained. Thus, the three-phase ammoximation process showed equal catalytic activity as TS-1 but much more convenient and simpler for the separation of catalyst in comparison to the industrial two-phase system with t-butanol used as solvent.展开更多
An intrinsic kinetics of cyclohexanone ammoximation in the liquid phase over titanium silicate molecular sieves is investigated in an isothermal slurry reactor at different initial reactant concentrations, catalyst lo...An intrinsic kinetics of cyclohexanone ammoximation in the liquid phase over titanium silicate molecular sieves is investigated in an isothermal slurry reactor at different initial reactant concentrations, catalyst loading, and reaction temperature. The rate equations are developed by analyzing data of kinetic measurements. More than 10 side reactions were found. H2O2 decomposition reaction must be considered and other side reactions can be neglected in the kinetic modeling. The predicted values of reaction rates based on the kinetic models are almost consistent with experimental ones. The models have guidance to the selection of reactor types and they are useful to the design and operation of reactor used.展开更多
Mesoporous titanium silicalite-1(TS-1)was hydrothermally synthesized with the addition of triethanolamine(TEA)in the conventional process, and used in the cyclohexanone ammoximation in a continuous slurry reactor. The...Mesoporous titanium silicalite-1(TS-1)was hydrothermally synthesized with the addition of triethanolamine(TEA)in the conventional process, and used in the cyclohexanone ammoximation in a continuous slurry reactor. The as-prepared TS-1 was characterized with X-ray diffraction(XRD), scanning electron microcopy(SEM), N_2 adsorption-desorption, Fourier transform infrared(FT-IR)spectroscopy, UV-Visible(UV-Vis)diffuse reflectance spectra and UV Raman spectroscopy. The results indicated that the addition of TEA resulted in the formation of mesopores and the slight increase of framework titanium in TS-1. TS-1 synthesized with the addition of TEA exhibited a higher stability in the cyclohexanone ammoximation than that without the addition of TEA, attributing to the increase of mesopore volumes and the slight increase of the framework titanium in TS-1. However, when the addition of TEA was up to TEA/SiO_2 ratio of 0.24, the crystallinity and framework titanium of TS-1 decreased markedly, and the average crystal sizes of TS-1 increased, with the catalyst stability becoming poor.展开更多
The liquid phase direct ammoximation of 5-isooctyl salicylaldehyde with ammonia and hydrogen peroxide was studied using titanium silicalite-1(TS-1)catalyst.The effect of reaction parameters on the yield of the product...The liquid phase direct ammoximation of 5-isooctyl salicylaldehyde with ammonia and hydrogen peroxide was studied using titanium silicalite-1(TS-1)catalyst.The effect of reaction parameters on the yield of the product was studied,which include reaction temperature,reaction time,molar ratio of ammonia to aldehyde as well as hydrogen peroxide to aldehyde.The influence of the amount of catalyst on the reaction results was also investigated.The maximum 5-isooctyl salicylaldoxime yield of 98.76%was achieved under the following optimal reaction conditions:the molar ratio of 5-isooctylaldehyde to hydrogen peroxide and ammonia of 1:1.4:1.6,the reaction temperature of 70℃,the amount of TS-1 of 17.5 g·mol^(-1)(5-isooctyl salicylaldehyde),and the feeding time of 2 h.This method has the mild reaction conditions and avoids the shortcomings of traditional methods.Moreover,useless inorganic salts by-products are avoided,and there is no environmental pollution.展开更多
For simulating the real deactivation of hollow titanium silicalite(HTS) zeolite in commercial ammoximation process, HTS was treated by 10% NH_3·H_2O solution at 120 ℃ in stirred autoclave. It is found that a par...For simulating the real deactivation of hollow titanium silicalite(HTS) zeolite in commercial ammoximation process, HTS was treated by 10% NH_3·H_2O solution at 120 ℃ in stirred autoclave. It is found that a part of HTS zeolite crystals dissolved in the hot NH_3·H_2O solution, and the specific surface area and pore volume continuously decreased with the increase in NH_3 hydrothermal treatment time. Meanwhile, the transformation of framework Ti species into extraframework Ti species was detected by the spectroscopic methods. However, the extraframework Ti species were still in a highly dispersed state after the hydrothermal and thermal treatments as shown by TEM images, while the formation of new acid sites was not detected. Upon combining the results of characterization with catalytic performance of HTS, the main deactivation reason for this material had been determined, which might be attributed to the reduction of specific surface area and active centers after basic treatment and calcination of HTS samples. And then the possible mechanism of simulated deactivation of HTS zeolite was proposed, which could describe the elemental reaction steps much more visually and directly.展开更多
Titanium silicalite-1 （TS-1） has been hydrothermally synthesized with tetrapropylammonium hydroxide （TPAOH） as the template in the presence of various amounts of Na＋, characterized by inductively coupled plasma, ...Titanium silicalite-1 （TS-1） has been hydrothermally synthesized with tetrapropylammonium hydroxide （TPAOH） as the template in the presence of various amounts of Na＋, characterized by inductively coupled plasma, X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and ultro-violet-visible spectroscopy and studied in cyclohexanone ammoximation. The characterization results show that with the increase of Na＋ concentration in the synthesis, both the crystal sizes of TS- land extra framework Ti increase but framework Ti decreases. The addition of Na＋ below 3 mol-% of TPAOH in the synthesis does not influence the catalytic properties with above 98% conversion of cyclohexanone and 99.5% selectivity to cyclohexanone oxime. However, at the concentrations of Na＋≥3mol-% of TPAOH in the synthesis, the catalysts are deactivated faster with the increase of Na＋ addition, which can be attributed to more high molecular weight byproducts deposited in the large TS-1 particles and the loss of the frame-work titanium. The results of this work are of great importance for the industry.展开更多
Small-crystal TS-1 was synthesized via a seed-induced approach using ammonia as the alkali source and tetrapropylammonium bromide as an auxiliary structure-directing agent. The TS-1 samples were characterized using X-...Small-crystal TS-1 was synthesized via a seed-induced approach using ammonia as the alkali source and tetrapropylammonium bromide as an auxiliary structure-directing agent. The TS-1 samples were characterized using X-ray diffraction, N2 adsorption-desorption, Fourier-transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscopy, scanning electron microscopy, and ultraviolet-visible spectroscopy. The use of the colloidal seed reduced the crystal size, and an appropriate amount of silicalite-1 seed assisted Ti incorporation into the TS-1 framework. This method reduces the cost of TS- 1 synthesis because a significantly smaller amount of tetrapropylammonium hydroxide is used. The catalytic performance of the synthesized small-crystal TS-1 samples in cyclohexanone ammoximation was better than that of bulk TS-1 as a result of improved diffusion and a larger number of active tetrahedral Ti centers.展开更多
TS-2 microspheres,consisting of intergrown primary nanocrystals,was prepared by controlling the synthetic parameters.The effects of the amount of quaternary ammonium cations as structure-directing agent,H2O/Si ratio,t...TS-2 microspheres,consisting of intergrown primary nanocrystals,was prepared by controlling the synthetic parameters.The effects of the amount of quaternary ammonium cations as structure-directing agent,H2O/Si ratio,the presence of alcohol and the temperature were carefully investigated on the crystallization process.The high alkalinity was proved to be highly important for the preservation of the microsphere morphology initially formed,due to the unique intergrown stacking style.An alkali treatment with the aqueous solution of structure-directing agent,organic amine and ammonium salt and subsequent Na+ion-exchange were performed to enhance the catalytic activity of TS-2 microsphere in the cyclohexanone ammoximation reactions,with both the conversion and selectivity higher than 99%.In the continuous reaction,the TS-2 microspheres exhibited to be durable catalyst with potential application in industrial ammoximation processes.展开更多
基金Supported by the National Natural Science Foundation of China and Sinopec (20736009)
文摘An innovative green process of producing ε-caprolactam was proposed by integrating ammoximation and Beckmann rearrangement effectively. As a first part of the new process, TS-1 molecular sieve-catalyzed synthesis of cyclohexanone oxime from cyclohexanone, ammonia and hydrogen peroxide was carried out in a batch plant. Cyclohexane was used as the solvent in the three-phase reaction system. The influences of essential process parameters on ammoximation were investigated. Under the reaction conditions as catalyst content of 2.5% (by mass); H 2 O 2 /yclohexanone molar ratio of 1.10; NH 3 /cyclohexanone molar ratio of 2.20; reaction temperature of 343 K; reaction time of 5 h, high conversion of cyclohexanone and selectivity to oxime (both>99%) were obtained. Thus, the three-phase ammoximation process showed equal catalytic activity as TS-1 but much more convenient and simpler for the separation of catalyst in comparison to the industrial two-phase system with t-butanol used as solvent.
文摘An intrinsic kinetics of cyclohexanone ammoximation in the liquid phase over titanium silicate molecular sieves is investigated in an isothermal slurry reactor at different initial reactant concentrations, catalyst loading, and reaction temperature. The rate equations are developed by analyzing data of kinetic measurements. More than 10 side reactions were found. H2O2 decomposition reaction must be considered and other side reactions can be neglected in the kinetic modeling. The predicted values of reaction rates based on the kinetic models are almost consistent with experimental ones. The models have guidance to the selection of reactor types and they are useful to the design and operation of reactor used.
基金Supported by the National Natural Science Foundation of China(No.21276183)
文摘Mesoporous titanium silicalite-1(TS-1)was hydrothermally synthesized with the addition of triethanolamine(TEA)in the conventional process, and used in the cyclohexanone ammoximation in a continuous slurry reactor. The as-prepared TS-1 was characterized with X-ray diffraction(XRD), scanning electron microcopy(SEM), N_2 adsorption-desorption, Fourier transform infrared(FT-IR)spectroscopy, UV-Visible(UV-Vis)diffuse reflectance spectra and UV Raman spectroscopy. The results indicated that the addition of TEA resulted in the formation of mesopores and the slight increase of framework titanium in TS-1. TS-1 synthesized with the addition of TEA exhibited a higher stability in the cyclohexanone ammoximation than that without the addition of TEA, attributing to the increase of mesopore volumes and the slight increase of the framework titanium in TS-1. However, when the addition of TEA was up to TEA/SiO_2 ratio of 0.24, the crystallinity and framework titanium of TS-1 decreased markedly, and the average crystal sizes of TS-1 increased, with the catalyst stability becoming poor.
基金the National Natural Science Foundation of China(21376269)the Hunan Provincial Science and Technology Plan,China (2016TP1007)the independent exploration and innovation project for graduate students of Central South University(2020zzts403)
文摘The liquid phase direct ammoximation of 5-isooctyl salicylaldehyde with ammonia and hydrogen peroxide was studied using titanium silicalite-1(TS-1)catalyst.The effect of reaction parameters on the yield of the product was studied,which include reaction temperature,reaction time,molar ratio of ammonia to aldehyde as well as hydrogen peroxide to aldehyde.The influence of the amount of catalyst on the reaction results was also investigated.The maximum 5-isooctyl salicylaldoxime yield of 98.76%was achieved under the following optimal reaction conditions:the molar ratio of 5-isooctylaldehyde to hydrogen peroxide and ammonia of 1:1.4:1.6,the reaction temperature of 70℃,the amount of TS-1 of 17.5 g·mol^(-1)(5-isooctyl salicylaldehyde),and the feeding time of 2 h.This method has the mild reaction conditions and avoids the shortcomings of traditional methods.Moreover,useless inorganic salts by-products are avoided,and there is no environmental pollution.
基金financially supported by the National Basic Research Program of China(973 Program,2006CB202508)the China Petrochemical Corporation(SINOPEC Group 20673054)
文摘For simulating the real deactivation of hollow titanium silicalite(HTS) zeolite in commercial ammoximation process, HTS was treated by 10% NH_3·H_2O solution at 120 ℃ in stirred autoclave. It is found that a part of HTS zeolite crystals dissolved in the hot NH_3·H_2O solution, and the specific surface area and pore volume continuously decreased with the increase in NH_3 hydrothermal treatment time. Meanwhile, the transformation of framework Ti species into extraframework Ti species was detected by the spectroscopic methods. However, the extraframework Ti species were still in a highly dispersed state after the hydrothermal and thermal treatments as shown by TEM images, while the formation of new acid sites was not detected. Upon combining the results of characterization with catalytic performance of HTS, the main deactivation reason for this material had been determined, which might be attributed to the reduction of specific surface area and active centers after basic treatment and calcination of HTS samples. And then the possible mechanism of simulated deactivation of HTS zeolite was proposed, which could describe the elemental reaction steps much more visually and directly.
基金Acknowledgements This work has been supported by the National Natural Science Foundation of China （Grant No. 21276183） and Program of Introducing Talents of Discipline to Universities （No. B06006）.
文摘Titanium silicalite-1 （TS-1） has been hydrothermally synthesized with tetrapropylammonium hydroxide （TPAOH） as the template in the presence of various amounts of Na＋, characterized by inductively coupled plasma, X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and ultro-violet-visible spectroscopy and studied in cyclohexanone ammoximation. The characterization results show that with the increase of Na＋ concentration in the synthesis, both the crystal sizes of TS- land extra framework Ti increase but framework Ti decreases. The addition of Na＋ below 3 mol-% of TPAOH in the synthesis does not influence the catalytic properties with above 98% conversion of cyclohexanone and 99.5% selectivity to cyclohexanone oxime. However, at the concentrations of Na＋≥3mol-% of TPAOH in the synthesis, the catalysts are deactivated faster with the increase of Na＋ addition, which can be attributed to more high molecular weight byproducts deposited in the large TS-1 particles and the loss of the frame-work titanium. The results of this work are of great importance for the industry.
基金supported by the National Natural Science Foundation of China(21403070 and 21373088)Innovation Program of Shanghai Municipal Education Commission(13zz038)+2 种基金Key Project of the Shanghai Committee of Science and Technology(12JC1403600)National Key Technology R&D Program(2012BAE05B02)Shanghai Leading Academic Discipline Project(B409)~~
文摘Small-crystal TS-1 was synthesized via a seed-induced approach using ammonia as the alkali source and tetrapropylammonium bromide as an auxiliary structure-directing agent. The TS-1 samples were characterized using X-ray diffraction, N2 adsorption-desorption, Fourier-transform infrared spectroscopy, inductively coupled plasma atomic emission spectroscopy, scanning electron microscopy, and ultraviolet-visible spectroscopy. The use of the colloidal seed reduced the crystal size, and an appropriate amount of silicalite-1 seed assisted Ti incorporation into the TS-1 framework. This method reduces the cost of TS- 1 synthesis because a significantly smaller amount of tetrapropylammonium hydroxide is used. The catalytic performance of the synthesized small-crystal TS-1 samples in cyclohexanone ammoximation was better than that of bulk TS-1 as a result of improved diffusion and a larger number of active tetrahedral Ti centers.
文摘TS-2 microspheres,consisting of intergrown primary nanocrystals,was prepared by controlling the synthetic parameters.The effects of the amount of quaternary ammonium cations as structure-directing agent,H2O/Si ratio,the presence of alcohol and the temperature were carefully investigated on the crystallization process.The high alkalinity was proved to be highly important for the preservation of the microsphere morphology initially formed,due to the unique intergrown stacking style.An alkali treatment with the aqueous solution of structure-directing agent,organic amine and ammonium salt and subsequent Na+ion-exchange were performed to enhance the catalytic activity of TS-2 microsphere in the cyclohexanone ammoximation reactions,with both the conversion and selectivity higher than 99%.In the continuous reaction,the TS-2 microspheres exhibited to be durable catalyst with potential application in industrial ammoximation processes.
