Ammoximation Of Cyclohexanone Catalyzed By Titanium Silicalite-1

Cyclohexanone oxime is an important chemical material. Conventionally, it is manufactured by the oximation of cyclohexanone with a mineral salt of hydroxylamine. However, this process has serious disadvantages because it involves several steps, requires a large amount of energy, uses many environmentally unfavorable chemicals and produces a large amount of ammonium sulfates as by-product. TS-1 has an excellent catalytic performance in the reaction of cyclohexanone ammoximation to cyclohexanone oxime with NH3 and H2O2. This process has many advantages, for example, mild conditions, simple process, high selectivity and using environmentally-friendly materials. Therefore, the ammoximation of cyclohexanone shows good prospect for industrial application.In this dissertation, TS-1 powder was hydrothermally synthesized and the effects of the reaction temperature, ammonia concentrations and hydrogen peroxide concentrations on the catalytic properties in the ammoximation in a continuous slurry reactor were investigated. TS-1 was treated with triethylamine, and the effects of the treatment conditions on the catalytic stabilities were also studied. The major reason of the catalyst deactivation and the regeneration of the spent catalysts were studied.Tetrapropylammonium bromide was used to partially replace tetrapropylammonium hydroxide in the synthesis of TS-1. Finally, glass beads-supported TS-1 was prepared and the catalytic performance was studied for the cyclohexanone ammoximation in a fixed bed reactor.The results showed that the reaction conditions had great effects on the catalyst stability. The optimal reaction conditions were: temperature, 76 ? C;H2O2/cyclohexanone = 1.1:1(mol); NH3/cyclohexanone = 1.7:1(mol).After treated with triethylamine, many irregular hollow cavities were formed in the TS-1 crystals, and the amount of the framework Ti atoms decreased. The diffusional resistance of TS-1 was significantly reduced by the formation of the hollow cavities and more deposit could be accommodated in these cavities, and thus,the catalytic stability was greatly prolonged. The catalytic stability was improved with the increase of the volume of the hollow cavities, but when it comes to a certain value,the catalytic stability decreased with further increasing the volume of the hollowcavities due to the significant loss of the framework Ti species. The main reason of the deactivation of TS-1 in the ammoximation is the coke deposit formed in the channels of TS-1. After the reaction, the deactivated TS-1 can be effectively regenerated through calcination in air.The crystal sizes of TS-1 could be reduced with the addition of tetrapropylammonium bromide in the synthesis solutions, and tetrapropylammonium bromide could partly replace tetrapropyl ammonium as the template in the synthesis of TS-1 without the decrease of the catalytic performance of TS-1 in the ammoximation.Glass beads could be used as the support to synthesize the supported TS-1 after modified with chitosan. After third growth, TS-1 crystals with the crystal sizes between 300 and 400 nm could be uniformly coated on the glass beads.The supported TS-1 were studied in the cyclohexanone ammoximation in a fixed bed reactor, and the catalysts exhibited good catalytic performance.