The Study Of The Preparation And Catalyst For The Gas Phase Synthesis Of Vinylacetate From Acetylene And Acetic Acid

The feasibility of different bamboo-derived activated carbon act as the catalyst carrier for the gas phase synthesis of vinyl acetate from acetylene and acetic acid was discussed,and the effects of modification of carrier on catalyst activity and stability were studied.Subsequently,the reasons of catalyst deactivation were analyzed and summarized.Based on the physicochemical properties and adsorption property to zinc acetate of bamboo-derived activated carbon prepared by phosphoric acid activation and by physical activation,the feasibility of bamboo-derived activated carbon act as the catalyst carrier for the gas phase synthesis of vinyl acetate from acetylene and acetic acid was studied.The results can be described as follow,the average pore size of the bamboo-derived activated carbon prepared by phosphoric acid activation is 2.72 nm and its specific surface area is 1411.82m2/g,similar to the activated carbon prepared from coconut shell,which is often used as the catalyst carrier.The effective loading amount of zinc acetate onto the surface of the carrier calculated with the theory of spontaneous monolayer dispersion of oxides and salts on supports and the close-packed model is 18.26%,and value measured by thermogravimetric analysis is21.66%,close to the loading amount on activated carbon prepared from coconut shell.So the bamboo-derived activated carbon prepared by phosphoric acid activation is qualified as catalyst support.But the bamboo-derived activated carbon prepared by physical activation doesn't possess these superior situations.The effects of ultrasonic treatment,high-temperature heat treatment and nitric acid treatment on surface structure of bamboo-derived activated carbon and production capacity of the catalyst were studied.The results can be shown like this,ultrasonic treatment of carrier makes the volume of mesopore and micropore increase and the surface area decrease,and the optimum time is from 60 to 90 minutes.The productive capacity of the catalyst is increased by 23% under the best conditions.The high-temperature heat treatment under CO2 protected condition and under N2 protected condition have different effect on surface area and the pore-size distribution,even though they have the same optimum temperature,which is about 600?.The production capacity of the catalyst prepared from carrier after high temperature treatment under N2 protected condition reaches 1.185g/(d·ml)and is increased by 14%.While the production capacity of the catalyst prepared from carrier after treatment under CO2 protected condition reaches 1.252g/(d·ml)and is increased by 20%,that can even be up to 73% of the production capacity of the catalyst prepared from coconut shell activated carbon.The surface area and the pore size of carrier after nitric acid treatment are decreased and the loading amount of zinc acetate is increased.The production capacity shows no improvement and nitric acid treatment at high concentration even makes the capacity be decreased.The stability of the catalyst and the reasons of catalyst deactivation were studied.The results show that the content of zinc acetate decreases as the reaction progress.The catalyst after reaction is characterized by a large number of polymer coating on the surface,the decrease of the oxygenic groups,the blockage and destroy of the micropores,and the reduce of the specific surface area,which are the main causes for deactivation of catalyst.The stability test proves that the catalyst with bamboo-derived activated carbon as carrier has very good stability,and the modifying of the matrix makes the activity of the catalyst remain satisfactorily high after the reaction for a while.