Study On Isomerization Reaction Of Endo-TCD Over AlCl₃/MCM-41 Catalyst

Both the adamantine(ADH) and exo-tricyclodecane(exo-TCD) are important fine chemical intermediates which can be prepared by endo-tricyclodecane(endo-TCD) isomerization. Exo-TCD is successfully used as high-density liquid fuels while adamantane is widely applied in the fields such as medicines, functional materials and fine chemical industry. Nowadays, they are mostly produced traditionally through the isomerization of endo-TCD using AlCl3 and modified zeolites as catalysts, which brought environmental pollution or high cost. In this thesis, immobilized AlCl3 on MCM-41 was used to catalyze the isomerization of endo-TCD to the formation of adamantane and exo-TCD. It focuses on the effect of the support properties on catalytic performance, and the effect of reaction conditons on the selectivity of adamantane and exo-TCD. The main results are as follows:(1) The catalytic activity of AlCl3 immobilized on MCM-41 for the isomerization of endo-TCD to exo-TCD was compared with that of AlCl3 immobilized on SiO2. At 180℃, both the catalysts exhibit high activity, but the selectivity of exo-TCD and ADH is different.＞95.0% exo-TCD selectivity was obtained over AlCl3/MCM-41, while this was only 86.3% over AlCl3/SiO2. The catalysts were characterized by N2 adsorption, Hammett titration, Fourier transform infrared spectroscopy, and chemical analysis techniques. The weaker acidity and smaller straight channels of AlCl3/MCM-41 gave it the higher exo-TCD selectivity.(2) The Si/Al ratio of MCM-41 and the preparation temperature of catalysts influence the acid strength of the immobilized AlCl3 catalysts. It is found that the catalyst with purely siliceous MCM-41 support and lower immobilization temperature (200℃) is of stronger acid, which is beneficial to increase ADH selectivity. The optimal reaction conditions are as follows:endo-TCD 0.5 g, catalyst dosage 0.2 g [-O-AlCl2], cyclohexane 20 ml,N2 pressure 2.2 MPa, reaction temperature 180℃, and reaction time 4 h, endo-TCD conversion and ADH selectivity are 97.6% and 19.89%, respectively.(3) The pore size of MCM-41 supports influence the product distribution of endo-TCD isomerization. With the increase of pore size, ADH selectivity increases, and the exo-TCD selectivity decreases.