Studies On Novel Pd-Zr And Cu-Zr-Co Catalyst For Direct Transformation Of Ethanol To Ethyl Acetate

Ethyl acetate is a kind of important chemical raw materials and environmental-friendly organicsolvents, which can be widely used in perfume, dyestuff, pharmaceuticals, and paint. One-step synthesis ofethyl acetate from ethanol dehydrogenation has attracted much attention because it can use renewablebioethanol as the raw material and its process is simple, no corrosive and low toxic. This dissertationfocused on the synthesis, characterization and catalytic application of Cu-Zr-Co and Pd/Zr-SBA-15forone-step synthesis of ethyl acetate from ethanol dehydrogenation. It is composed of two parts:In the first part, Cu-Zr-Co catalyst was synthesized by reverse titration coprecipitation method, normaltitration coprecipitation method and sol-gel method, respectively. The influences of different preparationmethod for Cu-Zr-Co catalyst, molar ratio of raw material, calcination temperature, pretreatmenttemperature and reaction conditions on catalytic performance of direct synthesis of ethyl acetate fromethanol dehydrogenation were also investigated. The synthesized catalysts were characterized by means ofXRD, N2physisorption, H₂-TPR and NH₃-TPD. As compared with other samples, the Cu-Zr-Co-O catalystprepared by reverse titration coprecipitation method using Na₂CO₃as the precipitant possessed largerspecific surface area, smaller particle size of Cu⁰and more surface acid sites, which showed good catalyticperformance in the ethanol dehydrogenation. Adding a small amount of CoO could effectively improve thedispersion of CuO on catalyst surface to form small Cu⁰particles, thus a significant increase of catalyticactivity could be achieved. At the same time, the addition of CoO could also increase surface acid sites,which was beneficial for the synthesis of ethyl acetate. The catalyst at a low calcination temperaturepossessed small specific surface area and pore volume, and its catalytic activity was low. However, a hightemperature would lead to a decrease in specific surface area and pore volume, which would bring about anincrease of the particle size of Cu⁰, thus a decrease in catalytic activity could be occurred. The highestcatalytic activity could be obtained on the catalyst calcined at400℃. Preliminary reduction temperature,which exerted a significant effect on the amount of Cu⁰and its distribution on catalyst surface, could playan important role for ethanol conversion and the selectivity of ethyl acetate. The catalyst reduced at300℃exhibited better catalytic performance in synthesis of ethyl acetate from ethanol. Under the optimized reaction conditions of GHSV1.2min-1, reaction temperature200℃，ethanol conversion and ethyl acetateselectivity were up to85.0%，80.2%，respectively.In the second part, a series of Pd/Zr-SBA-15catalysts prepared by the impregnation method wereinvestigated for direct synthesis of ethyl acetate from ethanol dehydrogenation. The synthesized catalystswere characterized by means of XRD, N2physisorption, NH₃-TPD, TEM and TG. As compared with othersupports, the SBA-15synthesized by the hydrothermal method possessed the appropriate pore size, largerspecific surface area, and highly ordered pore structure, which were beneficial for active componentdispersion and inner diffusion of reactants and products, and thus a high catalytic activity could be achieved.Adding a small amount of Zr could remarkably increase the dispersion of Pd species and improve thecatalytic activity. However, a large amount of Zr would block the hole of molecular sieve, resulting in adecline in the specific surface area of the catalyst and its catalytic activity. At the same time, adding a smallamount of Zr could also increase weak acid sites, which was beneficial for the synthesis of ethyl acetate.The highest catalytic activity could be obtained on the catalyst with a Zr content of10wt%. Under theoptimized reaction conditions of amount of catalyst1ml, reaction temperature200℃and GHSV1.8min-1,ethanol conversion and ethyl acetate selectivity were up to76.0%，62.4%，respectively.