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
Titanium silicalite- 1 （TS- 1） treated with triethy- lamine （TEA） solution under different conditions was characterized by X-ray powder diffraction （XRD）, Fourier- transform infrared spectrum （FTIR）, ultraviol...Titanium silicalite- 1 （TS- 1） treated with triethy- lamine （TEA） solution under different conditions was characterized by X-ray powder diffraction （XRD）, Fourier- transform infrared spectrum （FTIR）, ultraviolet-visible diffuse reflectance spectrum （UV-Vis）, nitrogen physical adsorption and desorption, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The characterization results show that many irregular hollows are generated in the TS-1 crystals due to the random dissolution of framework silicon and the volume of the hollow cavities increase with increasing the TEA con- centration, and the treatment temperature and time. The modified TS-1 samples improved in varying degrees the catalyst life for the epoxidation of propylene in a fixed-bed reactor probably due to the generation of the hollows to make it easy for the reactants and products to diffuse out of the channels.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
以正硅酸乙酯为硅源,合成了具有MFI结构的球形和六方片状silicalite-1全硅分子筛,并将其作为载体制备了负载型催化剂用于丙烷脱氢制丙烯反应;采用SEM、XRD、TEM、N_(2)吸附-脱附、Py-FTIR、NH_(3)-TPD、^(29)Si MAS NMR和H_(2)-TPR等方...以正硅酸乙酯为硅源,合成了具有MFI结构的球形和六方片状silicalite-1全硅分子筛,并将其作为载体制备了负载型催化剂用于丙烷脱氢制丙烯反应;采用SEM、XRD、TEM、N_(2)吸附-脱附、Py-FTIR、NH_(3)-TPD、^(29)Si MAS NMR和H_(2)-TPR等方法对两种分子筛载体及负载型催化剂的结构和表面性质进行表征,研究了不同形貌silicalite-1载体对催化剂性能的影响机制。实验结果表明,球形silicalite-1分子筛载体具有更大的外比表面积和更多的表面硅羟基,进而增强了活性组分与载体间的相互作用,提高了活性金属在载体表面的分散度,因此在丙烷脱氢制丙烯反应中球形silicalite-1载体负载的催化剂具有更高的活性。展开更多
Titanium silicalite-1 (TS-1) was easily synthesized using inorganic silicon and titanium source, tetrapropylammonium bromide (TPABr) or TPAOH as templating molecule, NH3H2O, HDA or TEAOH etc. as base sources. In this ...Titanium silicalite-1 (TS-1) was easily synthesized using inorganic silicon and titanium source, tetrapropylammonium bromide (TPABr) or TPAOH as templating molecule, NH3H2O, HDA or TEAOH etc. as base sources. In this system, TPA+ cations (come from TPABr or TPAOH) served as templating agents to direct the MFI structure. NH3H2O, TEAOH or HDA etc. provides the alkalinity necessary for crystallization. X-ray diffraction, UV-Vis, IR spectroscopies, SEM, 29Si MAS NMR showed that the zeolites obtained possessed all the structural characteristics of TS-1, and titanium atoms were introduced into the framework in TS-1. This material was proved to have high crystallinity and high catalytic activity to allyl chloride epoxidation and propylene epoxidation. All the samples synthesized had similar catalytic properties with a standard TS-1 through compared inorganic reactant system with organic synthesis system using propylene epoxidation. The effects of silicon source and TPABr/SiO2 ratio were discussed.展开更多
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.
文摘Titanium silicalite- 1 （TS- 1） treated with triethy- lamine （TEA） solution under different conditions was characterized by X-ray powder diffraction （XRD）, Fourier- transform infrared spectrum （FTIR）, ultraviolet-visible diffuse reflectance spectrum （UV-Vis）, nitrogen physical adsorption and desorption, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The characterization results show that many irregular hollows are generated in the TS-1 crystals due to the random dissolution of framework silicon and the volume of the hollow cavities increase with increasing the TEA con- centration, and the treatment temperature and time. The modified TS-1 samples improved in varying degrees the catalyst life for the epoxidation of propylene in a fixed-bed reactor probably due to the generation of the hollows to make it easy for the reactants and products to diffuse out of the channels.
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.
文摘以正硅酸乙酯为硅源,合成了具有MFI结构的球形和六方片状silicalite-1全硅分子筛,并将其作为载体制备了负载型催化剂用于丙烷脱氢制丙烯反应;采用SEM、XRD、TEM、N_(2)吸附-脱附、Py-FTIR、NH_(3)-TPD、^(29)Si MAS NMR和H_(2)-TPR等方法对两种分子筛载体及负载型催化剂的结构和表面性质进行表征,研究了不同形貌silicalite-1载体对催化剂性能的影响机制。实验结果表明,球形silicalite-1分子筛载体具有更大的外比表面积和更多的表面硅羟基,进而增强了活性组分与载体间的相互作用,提高了活性金属在载体表面的分散度,因此在丙烷脱氢制丙烯反应中球形silicalite-1载体负载的催化剂具有更高的活性。
基金Project (No. 29792070) supported by the National Natural Science Foundation of China.Present address: Department of Chemical Engineering,Xiangtan University, Xiangtan, Hunan 411105, China.
文摘Titanium silicalite-1 (TS-1) was easily synthesized using inorganic silicon and titanium source, tetrapropylammonium bromide (TPABr) or TPAOH as templating molecule, NH3H2O, HDA or TEAOH etc. as base sources. In this system, TPA+ cations (come from TPABr or TPAOH) served as templating agents to direct the MFI structure. NH3H2O, TEAOH or HDA etc. provides the alkalinity necessary for crystallization. X-ray diffraction, UV-Vis, IR spectroscopies, SEM, 29Si MAS NMR showed that the zeolites obtained possessed all the structural characteristics of TS-1, and titanium atoms were introduced into the framework in TS-1. This material was proved to have high crystallinity and high catalytic activity to allyl chloride epoxidation and propylene epoxidation. All the samples synthesized had similar catalytic properties with a standard TS-1 through compared inorganic reactant system with organic synthesis system using propylene epoxidation. The effects of silicon source and TPABr/SiO2 ratio were discussed.
