Preparation Of Pd/C Catalyst By Hydrosol Method And Its Application In Rosin Disproportionation Reactio

Rosin disproportionation is one of the main ways to modify rosin,and its products have potential application value in medicine,chemistry,food and other industries.In recent years,China has paid more and more attention to the secondary processing and deep treatment of rosin,which essentially improves the utilization rate of rosin resources.The key lies in the selection of catalysts.The catalytic performance of the catalyst largely determines the disproportionation reaction.The industrial production of disproportionated rosin is mostly achieved by Pd/C catalyst,which has the advantages of high activity,strong anti-poisoning ability,low dosage and short reaction time.Studies have shown that the common criteria for high-performance catalysts are narrow size distribution and high dispersion of active components.（1）The effects of different preparation conditions such as palladium precursor,palladium precursor dispersant,reduction conditions and Pd loading on the distribution,size and composition of active components were studied.The catalytic performance of the catalysts prepared under various conditions was investigated,and the optimum preparation conditions of Pd/C catalyst were obtained:Pd/C catalyst with small average particle size（2.42 nm）,high dispersion and Pd loading of 4 wt%was obtained by hydrosol method using palladium nitrate as palladium precursor,sodium borohydride as reducing agent and dispersant.（2）The prepared Pd/C catalyst was used for the disproportionation reaction of Simao pine rosin.When the dosage was 0.03%（mass fraction of raw ro sin）,the yield of dehydroabietic acid in the reaction product could reach 66.20%,which could meet the requirements of the national standard LY/T 1357-2008.（3）When activated carbon is used as a carrier,there are problems such as low strength,single microporous structure and easy plugging.However,γ-Al₂O₃ has high strength and good catalytic activity.Whenγ-Al₂O₃ and Beta molecular sieves are added to the activated carbon carrier to prepare the catalyst,the dispersion reaches the highest when the content ofγ-Al₂O₃ increases to 10%,and the geometric size of abietic acid and other molecules participating in the disproportionation reaction is larger.Therefore,more mesopores of the composite carrier provide more active sites to contact with it,and the catalytic activity is also improved accordingly,so that the content of dehydroabietic acid in the product can reach 68.43%.（4）The Pd/C catalyst was used to investigate the disproportionation reaction conditions of Simao rosin,and the optimum process conditions for disproportionation of rosin were obtained:the reaction temperature was heated to 270°C,the reaction time was 2 h,and the catalyst input was 0.03%（mass fraction of raw rosin）.It shows that the prepared Pd/C catalyst is a catalyst with good catalytic activity for rosin disproportionation,and its performance is improved compared with other Pd/C catalysts.