Titanium silicalite (TS-1) without and with extra-framework titanium have been prepared and TiO_2 is also prepared under the same conditions.All the samples are characterized with XRD,FT-IR,and UV–Vis.The effects of ...Titanium silicalite (TS-1) without and with extra-framework titanium have been prepared and TiO_2 is also prepared under the same conditions.All the samples are characterized with XRD,FT-IR,and UV–Vis.The effects of extra-framework titanium in TS-1 on the ammoximation of cyclohexanone have been studied in a continuous slurry reactor.The characterization results reveal that the extra-framework titanium exists as anatase.The catalytic evaluation results show that the anatase has a positive effect on the ammoximation of cyclohexanone by extending the catalytic life because it also exhibits some activity,while the conversion of cyclohexanone and the selectivity to cyclohexanone oxime are not influenced.The anatase TiO_2 does not catalyze H_2O_2 decomposition appreciably compared with TS-1 without extra-framework titanium.The results are very useful in guiding the TS-1 production.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
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
基金was supported by the National Basic Research Program of China(‘‘973’’Program,No.G2000048005)the National Natural Science Foundation of China(No.21276183)
文摘Titanium silicalite (TS-1) without and with extra-framework titanium have been prepared and TiO_2 is also prepared under the same conditions.All the samples are characterized with XRD,FT-IR,and UV–Vis.The effects of extra-framework titanium in TS-1 on the ammoximation of cyclohexanone have been studied in a continuous slurry reactor.The characterization results reveal that the extra-framework titanium exists as anatase.The catalytic evaluation results show that the anatase has a positive effect on the ammoximation of cyclohexanone by extending the catalytic life because it also exhibits some activity,while the conversion of cyclohexanone and the selectivity to cyclohexanone oxime are not influenced.The anatase TiO_2 does not catalyze H_2O_2 decomposition appreciably compared with TS-1 without extra-framework titanium.The results are very useful in guiding the TS-1 production.
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.