Development Of TS-1 Monolithic Catalyst And Evaluation, Simulation Of Continuous Cyclohexanone Ammoximation Reaction

Because of the resources shortage and environment pollution, the green chemical process has been becoming more and more importment in chemical industry in future. As a raw material of the engineering plastics, caprolactam is produced by the key intermediate — cyclohexanone oxime. Cyclohexanone oxime can be directly synthesized by cyclohexanone, hydrogen peroxide and ammonia on titanosilicate-1 (TS-1) zeolite. In this new industrial process, the conversion of cyclohexanone and the selectivity of oxime are close to 100%, almost reach the highest utilization in atomic theory. And only a by-product of water which is friendly to the environment appears during the ammoximation reaction. The new ammoximation process is taken as a model of green chemistry and improves the chemical industry to an extreme. But its development is hindered by the fast deactivation of TS-1 zeolite catalyst caused by coke formation and framework collapse, which can cause safety problems. And the introduction of solvent tert-butanol (TBA) causes the increase of the cost of subsequent separation. So reduction in use of organic solvent in reaction and adoption of new type reactor may improve the ammoximation reaction such as the intensification of the reaction process and prolongation of the catalyst lifetime.This thesis investigated the preparation of the TS-1 zeolite crystal layer immobilized on the monolithic honeycomb cordierite by the dip-coating method and directly hydrothermal synthesis. The adhesiveness of immobilized layer of TS-1 zeolite crystal was investigated by the experiments.The growth of monolithic TS-1 crystal layer prepared by directly hydrothermal synthesis was experimentally studied, and the results showed that the morphology, grain size and thickness of TS-1 layer depended on the concentration of TS-1 precursor solution and the crystallization time. Based on the phase analysis of ammoximation reaction, the TS-1 monolithic catalyst as the monolithic reactor was applied to cyclohexanone ammoximation reaction in liquid phase.We used the monolithic reactor instead of slurry bed reactor to offset poor mass transfer without solvent TBA and to intensify ammoximation reaction. The activity and lifetime of the TS-1 monolithic catalyst with TBA were compared with that without TBA in continuous ammoximation reaction. And the characteristic of TS-1 monolithic catalyst intensifying ammoximation reaction was major investigated in experiment.When the solvent TBA was not used in ammoximation reaction, cyclohexanone had a poor solubility in the liquid phase of hydrogen peroxide and ammonia water. So the reactants would form liquid/liquid/solid three phases, and the rate of mass transfer droped. When the temperature of reaction was about 70 ℃ and weight hour space velocity (WHSV) was lower than 10h-1, the conversion of cyclohexanone and the selectivity of oxime approached to higher than 0.96 in continuous ammoximation reaction due to the intensification of the narrow channels in the monolithic reactor and the elimination of the diffusion in thin film of the monolithic catalyst. The unreacted cyclohexanone completely dissolved into the solution to form a single phase, and the product cyclohexanone oxime was crystalized with a great degree of supersaturation.The fresh catalyst and the deactivated catalyst during ammoximation reaction with TBA or without TBA were characterized by SEM-EDX, XRD, FT-IR, UV-vis, BET and TGA. From the results of the characterization, it was found that the solvent TBA accelerated the deactivation of the monolithic TS-1 catalyst in ammoximation reaction. The reasons for the faster deactivation were coking from TBA and the collapse of the framework —Si—O—Si—/—Si—O—Ti—. If the concentration of oxime was effectively reduced in the reaction system by cooling, the rate of carbon deposition was slowed down and the lifetime of the catalyst was extended.A one dimensional model for the monolithic catalytic reactor was established, and the simulation results could better confirm the experimental data from continuous ammoximation reaction. The channel size of the monolithic catalyst such as hydraulic diameter and the operational conditions such as WHSV and external flow rate were the characteristic parameters for ammoximation reaction in the monolithic catalytic reactor. In addition, the simulation results aslo indicated that apparent dimensionless WHSVDh3QC-1 parameter would effectively predict the catalytic ammoximation performance in the monolithic reactor and guide the design of the monolithic catalytic reactor, as well as the optimization of reactor operation.