Hydroisomerization Of N-Heptane Over Al-MCM-41Catalysts Modiifed By Rare Earth

Alkanes isomerization is one of important processes in petrorefining industry. In therecent years, this process has faced great demand for middle distill and the more stringentenvironmental protection. As a means to increase the gasoline octane number, theisomerization of n-alkanes into the corresponding isomers has attracted wide attention. Thetypical zeolite containing catalyst used in paraffins hydroconversion have high crackingactivivty confined pore structure, which restricted the effective conversion of heavy paraffinsinto middle distillates. Therefore research and development with the open pore, high activityand high stability of paraffin isomerization catalyst for improving the quality of gasoline,reduce environmental pollution and improve the human environment are significant.Mesoporous molecular sieves （Al-MCM-41） with high surface area, mild acidity andadjustable pore size in the rang of2⁵0nm, provide a new chance to design heterogeneouscatalyst with high metal dispersion and fast mass transfer of the reactants and product.The catalysts were prepared by incorporating Ni and HPMo₁₂into Re-MCM-41whowere modified with rare earth element by ionexchange method. And these catalyst were usedin n-heptane isomerization reactions, and they show a good activity. The primary andsecondary impact order of main factors that influence the reaction was tested throughorthogonal experimental design. The order that influence the selectivity for i-C7is reactiontemperatureâ†'the content of metal elements Niâ†'the flow of H2â†'the content ofmolybdophosphoric acidâ†'reduction temperatureâ†'rare earth. The order that influence then-C7conversion is reaction temperatureâ†'rare earthâ†'the flow of H2â†'the content ofmolybdophosphoric acidâ†'the content of metal elements Niâ†'reduction temperature. Andwith the orthogonal experiment according to the result of successive to each factor toinfluence the reaction n-heptane isomerization makes a thorough investigation. Then theimportance of experimental design factors, select a catalyst for n-heptane isomerization ratioof the best prepared and best reaction conditions. The catalyst doped with La was found toexhibit a higher catalytic conversion and much higher isomerization selectivity than thecatalyst without the dopant. The result showed that when Ni content is at5%and HPMo₁₂content is at20%, the activity of Ni/HPMo₁₂/La-MCM-41is best. Isomerization selectivity toi-heptane can reach72%at a higher conversion of n-heptane.