Study Of Kinetics Of Hydrotreating Catalyst Presulfiding

The intrintic kinetics and macro-kinetics of hydrotreating catalyst presulfiding were studiedusing method of fixed-bed breakthrough. The leaving concentration of H2S under differentconditions was measured by TCD and titration. The unreacted shrinking reaction core model wasused for catalyst particle, the materiel balance was used in the bed and then the mathematicalmodels were established. The computing expression of leaving concentration of H2S wasdeduced through the difference method of Crank-Nicholson which was steady. The least squareof the difference of calculated concentration of H2S and experimental concentration of H2S wasenacted the end-function and then the parameters were computed and optimized. The salience ofthe models was tested at last. Besides the effect of temperature, time, concentration of H2S,catalyst particle scales etc. on reaction was discussed.The results of intrintic kinetics showed that the process of sulfiding was unsteady, and therate of the reaction was changed with time;the value of E was high;the reaction was first orderin concentration of H2S;the unreacted shrinking reaction core model could be used to describethe process of presulfiding;and the prediction of the model was excellent. The effect of solidgrain diffusion was reflected by f0. The core diffusion could be excluded by minishing theparticle scales, but the solid grain diffusion could not.The results of macro-kinetics showed that the effective diffusion coefficient De increasedwith temperature, and De was an exponential function of temperature;the order of De was10-17～10-25 and the diffusion resistance of H2S in the production layer was great;and theprediction of the macro-kinetics model was also excellent. The reaction rate was mainlyinfluenced by temperature but nearly uninfluenced by concentration of H2S and particle scaleswhen they were small. Comparing the results of intrintic kinetics and macro-kinetics, reactionpower was smaller than diffusion power.