Integrated Process Of H₂O₂ Generation Through Anthraquinone Hydrogenation-Oxidation Cycles And The Ammoximation Of Cyclohexanone

The ammoximation of cyclohexanone to cyclohexanone oxime with hydrogen peroxide and ammonia catalyzed by TS-1 is an environmentally benign process. However, the profitability of this process depends on the cost of H2O2. If the H2O2 production process and the ammoximation reaction can be integrated, the production cost will be significantly decreased. In the present work, the integration of the processes of H2O2 generation through the anthraquinone hydrogenation-oxidation cycles and cyclohexanone oxime production through the direct ammoximation of cylohexanone has been studied. Some problems concerning the mechanism of ketone ammoximation have also been studied. Finally, TS-1 was used for the ammoximation of acetophenone and the reaction conditions were optimized. Firstly, integrated process of H2O2 generation through the anthraquinone hydrogenation-oxidation cycles and cyclohexanone oxime production through the direct ammoximation of cylohexanone was studied. The extraction of H2O2 with an aqueous methanol solution was simulated on the basis of the liquid-liquid-phase equilibrium of a five-component system of methanol-water-H2O2-TMB-TOP at 40?C. When the feed ratio of anthraquinone working solution to extractant is less than 30:1, the theoretical plate number is more than 10 and the concentration of methanol in extractant is less than 60 wt %, the concentration of H2O2 in raffinate can be kept below 200ppm which can meet the requirement of H2O2 production and the extracted H2O2 solution can meet the requirement of ammoximation reaction. As the anthraquinone working solution recycles in the process, the concentrations of methanol and water in it are 3.81 wt % and 0.48 wt %, respectively, which do not affect the hydrogenation of anthraquinone. The concentrations of TMB and TOP in H2O2 solution are 0.63 wt % and 0.04 wt %, respectively. In the ammoximation of cyclohexanone the optimal temperature is 80 ?C and the upper limit of the methanol content in reaction solution is 27.07 wt %. All of the impurities in the H2O2 solution obtained with an aqueous methanol solution as the extractant from the H2O2 generation process as well as the stabilizers and corrosion inhibitors that should be added in the H2O2 solution did not appreciably affect the direct ammoximation of cyclohexanone with NH3 and H2O2 catalyzed by TS-1. The results indicated that the processes of H2O2 generation through the anthraquinone hydrogenation-oxidation cycles and cyclohexanone oxime production through the direct ammoximation of cylohexanone could be integrated.Secondly, some problems concerning the mechanism of ketone ammoximation were studied. Absorbed amounts of ketones on TS-1 were determined by the liquid-phase-adsorption experiment, and then the TS-1 samples after absorption were analyzed by TGA. The ammoximation of these ketones catalyzed by TS-1 was then investigated. After the reactions, the used catalysts were also analyzed by TGA. The results showed that the reaction might precede through first the formation of hydroxylamine and then oximation of ketones outside TS-1 by hydroxylamine; the hydroxylamine formed in oxidation of NH3 by H2O2 did not decompose appreciably during the diffusion out of the pores of TS-1. Thirdly, the ammoximation of acetophenone catalyzed by TS-1 was studied. The influence of the solvents, temperature, the co-catalysts (Al2O3 and ammonium acetate), the mole ratios of NH3 to acetophenone, and H2O2 to acetophenone on the reaction were investigated. The results showed that the best solvent is ethanol, the optimal reaction temperature is 80?C and ammonium acetate can promote the formation of acetophenone oxime. In order to achieve the high yield, the mole ratios of NH3 to acetophenone and H2O2 to acetophenone should be kept above 2.00 and 1.27, respectively.