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
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
E xisting methods for synthesizing p -benzoquinone have drawbacks with respect to environmental protection, production scale, or industrial value. Therefore, it is imperative that a simple and environmentally friendly...E xisting methods for synthesizing p -benzoquinone have drawbacks with respect to environmental protection, production scale, or industrial value. Therefore, it is imperative that a simple and environmentally friendly alternative be developed. The approach that involves preparing p -benzoquinone by the catalytic oxidation of benzene with hydrogen peroxide (H 2 O 2 ) over copper-modi ed titanium silicalite-1 (Cu/TS-1) has a certain superiority due to its green synthesis and mild reaction condi- tions. In this study, Cu/TS-1 catalyst was prepared by the wet impregnation of TS-1 with an aqueous solution of Cu(NO 3 ) 2 and then characterized by X-ray di raction, Fourier transform infrared spectroscopy, di use re ectance UV Vis spectros- copy, scanning electron microscopy, inductively coupled plasma mass spectrometry, X-ray uorescence, and analysis of the N 2 adsorption desorption isotherms. The results reveal that Cu species exist mainly in the form of amorphous CuO that is well dispersed on the surface of catalysts, with no major change in the molecular sieve framework. After optimizing the reaction conditions, a desirable p -benzoquinone selectivity (88.4%) and benzene conversion (18.3%) were obtained when the doping of Cu in Cu/TS-1 is 1.95 wt%. In addition, Cu/TS-1 can be conveniently regenerated, showing a slight decrease in catalytic capability after initial use, which then stabilizes in subsequent circulations. The satisfactory stability and low cost of synthesizing Cu/TS-1 give this method considerable potential for further industrialization.展开更多
The catalytic performances over propylene epoxidation with H_(2)and O_(2)(HOPO process)are significantly affected by the properties(e.g.,surface properties,Ti coordination,morphology)of titanosilicate zeolite.Introduc...The catalytic performances over propylene epoxidation with H_(2)and O_(2)(HOPO process)are significantly affected by the properties(e.g.,surface properties,Ti coordination,morphology)of titanosilicate zeolite.Introducing urea into zeolite synthesis is a simple and convenient method to modify these properties of titanosilicate zeolite.Uncalcined pore-blocked titanium silicalite-1(TS-1,i.e.,TS-1-B)with the lower urea dosage possesses more defective structure and unsaturated coordinated Ti sites verified by 29Si nuclear magnetic resonance(NMR)and X-ray photoelectron spectroscopy(XPS)analysis,which results in a high initial activity and hydrogen efficiency;while the high surface acidity generated by these Ti species leads to a continuous decrease in the activity and the propylene oxide(PO)selectivity during the reaction.As the amount of urea gradually increases,the TS-1-B samples present the reduced surface defects and defective and unsaturated Ti species.Specially,TS-1-B-0.30U presents the weaker PO adsorption on PO-diffusion reflectance infrared Fourier transform spectra(DRIFTS),thus results in the high stable PO formation rate and selectivity over its Au catalyst.Furthermore,a flat-plate-like shape with a shorter thickness of 100 nm along the b-axis direction is observed on the urea-modified TS-1.Compared with the conventional ellipsoidal TS-1 with crystal sizes of 200 and 500 nm,the flat-plate-like TS-1-0.30U displays the less surface defects,unsaturated Ti species,the weaker Lewis acid,which is favorable for the desorption and intracrystalline diffusion of PO,thus reduces the occurrence of side reactions for the improved selectivity and stability.This work may provide a reference for developing titanium-containing materials with high activity and stability over HOPO reaction.展开更多
以无助剂的二氧化硅溶胶为胶液,通过离心喷雾干燥制备球径可控的微米钛硅分子筛催化剂(TS-1)微球。考察了成型过程中进料速度、喷雾成型温度等工艺参数对分子筛成球、球径以及球形度的影响,并初步探讨了成球机制。结果表明,成型温度为17...以无助剂的二氧化硅溶胶为胶液,通过离心喷雾干燥制备球径可控的微米钛硅分子筛催化剂(TS-1)微球。考察了成型过程中进料速度、喷雾成型温度等工艺参数对分子筛成球、球径以及球形度的影响,并初步探讨了成球机制。结果表明,成型温度为170℃、进料速度为8 m L/min时可制备出球形度良好、球径集中分布于55μm的钛硅分子筛微球。将其用于环己酮氨肟化反应中,在环己酮空速为12 h-1催化反应中,寿命为28 h(转化率>90%)。优异的催化性能归因于分子筛微球高的比表面积、丰富的孔结构以及微球中含硅非活性成分抑制了钛硅分子筛骨架钛流失。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.
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.
基金supported by the National Natural Science Foundation of China (No. 21376163)
文摘E xisting methods for synthesizing p -benzoquinone have drawbacks with respect to environmental protection, production scale, or industrial value. Therefore, it is imperative that a simple and environmentally friendly alternative be developed. The approach that involves preparing p -benzoquinone by the catalytic oxidation of benzene with hydrogen peroxide (H 2 O 2 ) over copper-modi ed titanium silicalite-1 (Cu/TS-1) has a certain superiority due to its green synthesis and mild reaction condi- tions. In this study, Cu/TS-1 catalyst was prepared by the wet impregnation of TS-1 with an aqueous solution of Cu(NO 3 ) 2 and then characterized by X-ray di raction, Fourier transform infrared spectroscopy, di use re ectance UV Vis spectros- copy, scanning electron microscopy, inductively coupled plasma mass spectrometry, X-ray uorescence, and analysis of the N 2 adsorption desorption isotherms. The results reveal that Cu species exist mainly in the form of amorphous CuO that is well dispersed on the surface of catalysts, with no major change in the molecular sieve framework. After optimizing the reaction conditions, a desirable p -benzoquinone selectivity (88.4%) and benzene conversion (18.3%) were obtained when the doping of Cu in Cu/TS-1 is 1.95 wt%. In addition, Cu/TS-1 can be conveniently regenerated, showing a slight decrease in catalytic capability after initial use, which then stabilizes in subsequent circulations. The satisfactory stability and low cost of synthesizing Cu/TS-1 give this method considerable potential for further industrialization.
基金the funds from the Research Fund for National Key Research and Development Program of China(No.2021YFA1501403)the National Natural Science Foundation of China(Nos.21922803 and 22038003)+1 种基金Shanghai Rising-Star Program(No.17QA1401200)the Innovation Program of the Shanghai Municipal Education Commission(No.17ZR1407300).
文摘The catalytic performances over propylene epoxidation with H_(2)and O_(2)(HOPO process)are significantly affected by the properties(e.g.,surface properties,Ti coordination,morphology)of titanosilicate zeolite.Introducing urea into zeolite synthesis is a simple and convenient method to modify these properties of titanosilicate zeolite.Uncalcined pore-blocked titanium silicalite-1(TS-1,i.e.,TS-1-B)with the lower urea dosage possesses more defective structure and unsaturated coordinated Ti sites verified by 29Si nuclear magnetic resonance(NMR)and X-ray photoelectron spectroscopy(XPS)analysis,which results in a high initial activity and hydrogen efficiency;while the high surface acidity generated by these Ti species leads to a continuous decrease in the activity and the propylene oxide(PO)selectivity during the reaction.As the amount of urea gradually increases,the TS-1-B samples present the reduced surface defects and defective and unsaturated Ti species.Specially,TS-1-B-0.30U presents the weaker PO adsorption on PO-diffusion reflectance infrared Fourier transform spectra(DRIFTS),thus results in the high stable PO formation rate and selectivity over its Au catalyst.Furthermore,a flat-plate-like shape with a shorter thickness of 100 nm along the b-axis direction is observed on the urea-modified TS-1.Compared with the conventional ellipsoidal TS-1 with crystal sizes of 200 and 500 nm,the flat-plate-like TS-1-0.30U displays the less surface defects,unsaturated Ti species,the weaker Lewis acid,which is favorable for the desorption and intracrystalline diffusion of PO,thus reduces the occurrence of side reactions for the improved selectivity and stability.This work may provide a reference for developing titanium-containing materials with high activity and stability over HOPO reaction.
文摘以无助剂的二氧化硅溶胶为胶液,通过离心喷雾干燥制备球径可控的微米钛硅分子筛催化剂(TS-1)微球。考察了成型过程中进料速度、喷雾成型温度等工艺参数对分子筛成球、球径以及球形度的影响,并初步探讨了成球机制。结果表明,成型温度为170℃、进料速度为8 m L/min时可制备出球形度良好、球径集中分布于55μm的钛硅分子筛微球。将其用于环己酮氨肟化反应中,在环己酮空速为12 h-1催化反应中,寿命为28 h(转化率>90%)。优异的催化性能归因于分子筛微球高的比表面积、丰富的孔结构以及微球中含硅非活性成分抑制了钛硅分子筛骨架钛流失。
