Study On Preparation Of Environmental Friendly Plasticizers Di(2-ethylhexyl)-1,2-cyclohexane Dicarboxylate

With the improvement environmental protection as well as health and safety requirements on plastics, the study of environmentally friendly plasticizers have been concerned by more and more people for its environmental and practical significance. In this paper two synthesis routes of environmental friendly plasticizers cyclohexane-1,2-dimethyl dioctyl were studied, and suitable reaction conditions were investigated to provide theoretical and experimental basis for industrial production.Cyclohexane-1,2-dimethyl dioctyl can be prepared by catalytic hydrogenation of diisooctyl phthalate(DOP), and can also be synthesized by esterification and hydrogenation of tetrahydrophthalic anhydride(THPA) with iso-octanol, or by direct esterification of hexahydrophthalic anhydride(HHPA) with iso-octanol at the presence of catalyst.Raney Ni was used as the catalyst of direct hydrogenation of DOP, and the effects of Raney Ni types and the reaction conditions on hydrogenation performance were studied. The prefered catalyst was selected from five types of nickel-aluminum alloys with different components through catalysts characterization and their differences of DOP hydrogenation activity. As can be seen from the results, the Raney Ni from amorphous Ni Al binary alloy has preferable DOP hydrogenation activity for its larger surface area and pore volume resulting from the higher content of NiAl3 phase which can provide active nickel. Higher catalyst amount, reaction temperature and pressure have advantages to DOP hydrogenation and the product yield. The addition of NaOH into the reaction system can result in DOP decomposition and greatly reduce the conversion rate. The effects of reaction conditions on the DOP hydrogenation were investigated in detail. According to the experimental results, DOP conversion and product yield were both more than 99% at the following conditions: isooctanol as solvent, reaction temperature at 100℃, hydrogen pressure at 4.0MPa and catalyst amount at 3%.For esterification and hydrogenation of THPA(or HHPA), the effects of tetrabutyl tianate catalyst and reaction conditions were chiefly studied, as well as the suitable hydrogenation conditions of THPA and its esterification product tetrahydro-iso-octyl phthalate catalyzed over Raney Ni catalyst. The esterification results showed that esterification product yields of THPA(or HHPA) increased with the increasing of the catalyst amount, reaction temperature and the mol ratio of isononyl alcohol to anhydride. The optimum conditions determined by the single factor experiments were as follows: the mol ratio of isononyl alcohol to anhydride at 2.4, reaction temperature at 210℃, catalyst amount at 2%. In addition, the supported tetrabutyl tianate catalyst was prepared for the sake of esterification catalyst separation and reuse, and the esterification product yield was still over 97% after using seven times. The hydrogenation results indicated that the hydrogenation of THPA and tetrahydro-iso-octyl phthalate were more easy than that of DOP. The product yield of THPA hydrogenation could exceed 98% at temperature 65℃, hydrogen pressure 2MPa and catalyst dosage 2%, and the product yield of tetrahydro-iso-octyl phthalate hydrogenation could exceed 99% at temperature 70℃, hydrogen pressure 2MPa catalyst dosage 3%.