Study On Kinetics Of Pine Gum Catalytic Disproportionation

The kinetics of catalytic disproportionation reaction of pine gum as rawmaterial in a agitated autoclave(type CQF-2) were investigated.On-line trackinganalysis for the changes of major chemical components during catalyticdisproportionation of pine gum were study. And the optimal process conditionsfor preparation of disprotionated rosin and p-cymene from pine gum weresearched. Main chemical components of disproportionated products weredetermines. And the kinetic model of catalytic disproportionation from pine gumwere discussed. The main contents as follows:The article chooses gas chromatography to analyse the components indisproportionated pine gum.The settled conditions of chromatogram wereshowed as: BP-5 capeillary column of chromatogram;carrier gas and its flowrate:nitrogen gas,70 mL·min^-1; hydrogen gas flow rate: 17 mL·min^-1;air flow rate:160 mL·min^-1;pressure before columniation: 0.07MPa; temperature of checkmachine:523.15K;temperature of boil room:523.15K;split stream ratio: 50: 1;sample volume: 0.2μL;range: 8; raising temperature by three steps program:55℃(?)90℃(?)200℃(?)250℃(2min)The process for preparation of high content dehydroabietic acid ofdisprotionated and p-cymene from masson pine gume on Pd/C catalyst wasinvestigated.The effects of reaction temperature, the amount of catalyst,agitating velocity and reaction time on the conversation of dehydroabietic acid have examined with the experimental method of Uniform Design.At last, theoptimal process conditions for preparation of disprotionated rosin and p-cymenefrom masson pine gum were obtained as follows: Pd/C catalyst content 0.28ï¼…(based on pine gum weight), reaction temperature 260℃, reaction time 180 min,agitating velocity 500 r/min.An experiment was made to validate the besttechniques condition and the quantitative analysis of product disproportionatedwere carried out by capillary gas chromatography, the content of dehydroabieticacid was 88.6ï¼…(wtï¼…), the content of p-cymene was 63.0ï¼…(wtï¼…).The kinetics of catalytic disproportionation of pine gum on Pd/C catalystwere investigated at temperature 483.15K～523.15K.The kinetic modelparameters in Arrhenims equation were also determined, and pre-exponentialparameters were k₀₁=3.8789×10¹¹min^-1, k₀₂=1.2181×10⁸min^-1, k₀₃=7.6476×10¹³L·mol^-1·min^-1, k₀₄=3.3234×10¹² L·mol^-1·min^-1, k₀₅=2.533×10¹³ L·mol^-1·min^-1,and the activation energies were Ea₁=130.4 KJ·mol^-1, Ea₂=100.11KJ·mol^-1, Ea₃=143.16 KJ·mol^-1, Ea₄=133.95 KJ·mol^-1, Ea₅=141.44KJ·mol^-1, and the rate constants were k₁=3.8789×10¹¹exp(-15684/T),k₂=1.2181×10⁸exp(-12041/T), k₃=7.6476×10¹³exp(-17219/T),k4=3.3234×10¹²exp(-16111/T), k₅=2.533×10¹³exp(-17012/T) for themonoterpene hydrogenation and dehydrogenation, abietic-type acidhydrogenation and dehydrogenation and pimaric-type resin acid hydrogenationrespectively. The final results demonstrated that k increase with temperatureincreasing. In the scope of temperature monoterpene hydrogenation and dehydrogenation can be regarded as the first order (α₁≈α₂≈1),the abietic-typeresin hydrogenation and dehydrogenation can be regarded as the second order(α₃≈α₄≈2), and pimaric-type resin acid hydrogenation can be regarded as thesecond order (α₅≈2) , the results showed that concentration influence the rate ofdisproportionated rosin action. The models were verified according to the kineticmodel and parameters. The experimental and calculated results showed thatkinetic model tally with experimental data.