Possible Directions of by-Products Formation at the Epoxidation Stage in Cumene Technology for Propylene Oxide Production

The information on the composition of the dimethylphenylcarbinol fraction given in the security documents protecting the methods of hydrogenation treatment of the fraction within the Sumitomo technology is summarized. The main components in the composition of the fraction are isopropylbenzene and dimethylphenylcarbinol, the amount of which varies in the range of 20-60 % wt.; the main impurities are products of non-targeted decomposition of isopropylbenzene hydroperoxide (acetophenone, phenol) and intramolecular dehydration of dimethylphenylcarbinol (alpha-methylstyrene). The presence of aromatic ring hydrogenation products (isopropylcyclohexane, cyclohexanol) can be associated both with the organization of the reactor unit (cascade of reactors) and with partial recirculation of the hydrogenation products. The presence of isopropylbenzene hydroperoxide (up to 0,4 % wt.) in the fraction indicates that its conversion does not reach 100 % at the epoxidation stage. The qualitative (method of chromato-mass-spectrometry) and quantitative (method of gas-liquid chromatography, internal normalization with calibration coefficients) composition of the dimethylphenylcarbinol fraction isolated from the products of epoxidation of propylene with isopropylbenzene hydroperoxide in the presence of isopropanol and homogeneous molybdenum catalysts has been established. In contrast to the composition of objects given in security documents, the investigated system is characterized by the presence of interaction products of isopropyl alcohol with propylene oxide (1-isopropoxy-2-propanol and 2-isopropoxy-1-propanol in total 0,509 % wt.) and alpha-methylstyrene ((1-isopropoxy-1-methylethyl)benzene 0,221 % wt.). According to an estimated calculation, for a propylene oxide production of 70000 tons/year, the total production of 1-isopropoxy-2-propanol and 2-isopropoxy-1-propanol is about 4000 tons/year. Experiments on a model compound (1-methoxy-2-propanol) showed that in the temperature range of 150-170°С in the presence of a catalyst with an acid function, the ester does not undergo hydrolysis, thus when developing a technological scheme of the process, one can consider the location of the separation unit for 1-isopropoxy-2-propanol and 2-isopropoxy-1 propanol after the stage of hydrogenolysis of the dimethylphenylcarbinol fraction.