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Abstract:
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The kinetics of vapour phase hydrodenitrogenation of pyridine over a catalyst containing 0.5% platinum supported in alumina was studied using a fixed-bed catalytic reactor. The effect of process variables such as total reactor pressure, reaction temperature and space time on the conversion of pyridine, organic product distribution, yield of hydrocarbons and selectivity for hydrocarbons was studied. The effect of pressure is more than that of temperature and space time. When the pressure was doubled, the conversion of pyridine increased by 1.3 to four times and the yield and selectivity for hydrocarbons increased many folds. The reaction is believed to proceed via hydrogenation of pyridine to piperidine followed by the ring rupture of piperidine to pentylamine and finally the formation of pentane and ammonia. Pentyl piperidine was a major intermediate found. At higher pressure, ethyl piperidine and traces of cyclopentane were found to be other products. Dipentylamine was another intermediate found at higher pressure. At low pressure, dipentylamine, ethyl piperidine and cyclopentane were not detected. Many rate equations were tried to fit the kinetic data of the hydrodenitrogenation of pyridine. A Langmuir-Hinshelwood type rate expression with a pseudo order rate constant fitted the data best. From the Arrhenius plot of the pseudo rate constants using a lumped parameter theoretical model, the activation energy was estimated to be 19.89 kcal/mol. From the mechanistic model, the ring rupture of piperidine to pentylamine was found to be the rate determining step in the hydrodenitrogenation of pyridine. |
