Synthesis And Characterization Of NiAPSO-34 Molecular Sieves And Its Catalytic Performance On Dehydration Of Ethanol To Ethylene

Ethylene is an important material for the organic chemistry industry. Catalytic dehydration of ethanol to ethylene was studied in this thesis. A series of NiAPSO-34 catalysts were home-made by hydrothermal method and tested for dehydration of ethanol using fixed bed reactor. The catalyst samples were characterized by XRD,FT-IR,NH3-TPD,H2-TPR,ESR,BET,TG-DTG,SEM and XPS respectively. Reaction thermodynamics and kinetics were researched.Research showed that among the catalysts prepared by hydrothermal method, the Ni0.015 sample showed the best activity, whose preparation condition was as follow: 30wt% colloidal silica and pseudoboehmite were used as the sources of silicon and aluminum respectively; the molar ratio of the starting gel was P/Al=1, Si/Al=1, Ni/Al=0.015, R/Al=2; the crystallization temperature was 200°C and the crystallization time was 60h. Moreover, NiAPSO-34 catalyst showed better stability compared with HZSM-5 catalyst.Central composite experimental design was applied in catalytic dehydration of ethanol to optimize the reaction condition. The mathematical relationship of ethanol conversion and ethylene selectivity on the reaction temperature, residence time through catalyst bed, ethanol partial pressure can be approximated by polynomial models. Predicted values were found to be in good agreement with experimental values (R-Sq of 99.8% and R-Sq (adj) of 99.7% for ethanol conversion; R-Sq of 100% and R-Sq (adj) of 99.9% for ethylene selectivity). The result of optimization predicted by the model showed that ethylene selectivity presented the maximal result 99.3% at the optimal condition of reaction temperature 385°C, contact time with catalyst 3.3s, ethanol partial pressure 0.57atm, when ethanol conversion reached to 98.4%.Thermodynamics analysis for the reaction system showed that high-temperature was favorable to produce ethylene, but byproduct diethyl ether yield increased under low-temperature. Based on the kinetics research, dehydration of ethanol was parallel-consecutive reaction mechanism and the intrinsic kinetic models of dehydration of ethanol to ethylene and diethyl ether were gained. Kinetic parameters for dehydration of ethanol were calculated through tabu-hierarchy genetic algorithm. Activation energies of ethanol to ethylene, ethanol to diethyl ether, diethyl ether to ethylene and heats of adsorption of ethanol, water, diethyl ether were obtained.