Poisoning effect of nitrogen compounds on the transformation of model hydrocarbons and real feed under catalytic cracking conditions

Abstract

The effect of the content and nature of nitrogen compounds on the distribution of target products in transforming model hydrocarbons under cracking conditions over equilibrium zeolite-containing catalyst was studied. Using cracking of n-undecane as an example, a nearly 50% drop in the conversion and in yields of propane-propene (PPF) and butane-butene fractions (BBF) was observed when the pyrrol content in the feed was raised to 3000 ppm of nitrogen. Increasing the nitrogen content in the feed led to a nonlinear reduction in the rate constants of n-undecane cracking. It was found that the dependence of the yields of PPF, BBF, and isobutane in BBF on the conversion remained constant upon the cracking of n-undecane with various of nitrogen compounds; poisoning was likely to proceeds only because the acidic sites of the catalyst were blocked. The high poisoning effect of pyrrol and indole upon the cracking of n-undecane and decalin (strong proton donors) was observed along with the formation of ammonia. Quinoline exhibited high poisoning ability in the catalytic cracking of cumene with low [H]-donor activity. Quinoline poisoned catalysts to a greater degree than indole, during the catalytic cracking of non-hydrofined vacuum gasoil with a high content of aromatic structures. Indole exhibited the highest poisoning ability in processing heavy hydrocracking residue which was rich of paraffin-naphthene hydrocarbons.