Elimination of the negative effect of nitrogen compounds by CO2–water in the hydrocracking of anthracene

Abstract

Development of green and efficient methods to eliminate the negative effect of the nitrogen compounds in the hydrocracking of heavy oils is of great importance, and model compounds (e.g. anthracene) are often used to get the related chemical knowledge. In this work, we studied the effect of CO2 and/or water on the hydrocracking of anthracene catalyzed by NiFe + HZSM-5 in the presence of nitrogen compounds. Using 2-methylimidazole as the nitrogen compound, the influences of different factors, such as the amount of water, amount of the nitrogen compound, and the Si/Al molar ratio of HZSM-5 on the reaction were investigated. It was demonstrated that without water and CO2 the nitrogen compound had significant negative effect on the hydrocracking by poisoning the catalyst. Water or CO2 could reduce the negative effect to a considerable degree. Interestingly, CO2–water mixture could eliminate the negative effect completely, and the yields of the products could be even higher than that in the absence of the nitrogen compound. Further study indicated that some other nitrogen compounds like pyrrole, pyridine and 2-methylpyrazine also had a positive effect on the hydrocracking in the presence of CO2–water mixture. The reason for this phenomenon was discussed.