Experimental Study on Catalyst Deactivation by Nitrogen Compounds in a Hydroprocessing Reactor

The present work was devoted to study the effect of nitrogen compounds on hydrodesulfurization (HDS) activity of straight-run heavy naphtha loaded with thiophene, as a sulfiding model, onto a commercial in a fixed bed reactor. Parameter evaluation of ideal flow behavior in the reactor revealed that a catalyst bed packed with a particle diameter helps to eliminate wall, poor wetting and back-mixing effects. Results showed that sulfur removal would be enhanced by increasing temperature, and pressure, while liquid flow rate gives a different trend. The effect of nitrogen compounds on reaction rate constant was investigated (at temperature 320-380, pressure 30 bar, particle diameter , and ) with different concentrations of carbazole and pyridine, and a mixture with equal weight proportions of them. The experimental results were fitted to a first-order kinetics with correlation coefficients higher than 0.98. The experimental results confirmed that addition of nitrogen compounds does not affect the order of HDS reaction. Hydrodesulfurization efficiency was decreased from 93.4 to 73.3, 66.5, and 63.3% as the concentration of carbazole, pyridine, and a mixture of them increased from 0 to 100 ppmw, respectively. As observed from experimental results, the inhibiting effect of nitrogen compounds on HDS activity increased as the nitrogen concentration increased. The inhibition behavior was found to be highly nonlinear.