Synthesis Of 1,5-dimethyltetralin

1,5-Dimethyltetralin (1,5-DMT) is a intermediate for synthesizing 2, 6-dimethylnaphthalene (2,6-DMN), a raw material used to make polyethylene naphthalate (PEN) which is a high performance engineering plastics with good thermal and mechanical stability. At present,alkylation of o-xylene and 1,3-butadiene is the only method of industrialized production in the world. Namely, o-xylene and 1, 3-butadiene are reacted in the presence of the catalyst to form 5-(o-tolyl) pentene. Then, said 5-(o-tolyl) pentene is cyclized to form 1,5-dimethyltetralin. Subsequently, said 1,5-dimethyltetralin is dehydrogenated to form 1,5-dimethylnaphthalene, and then 1,5-dimethylnaphthalene is isomerized into 2,6-dimethylnaphthalene. In this paper, the cyclization of 5-(o-tolyl) pentene to 1,5-dimethyltetralin was studied.In the experiment, platinum catalysts supported on the zeolite were prepared with and without ultrasonic treatment during impregnation step. The results show that the activity of the supported catalysts prepared with ultrasonic treatment is higher than those without ultrasonic treatment.Effects of ultrasound frequency, ultrasound output, ultrasound time, platinum loading amount, reaction time, reaction temperature on the conversion,yield and selectivity of cyclization have been studied in a wide range.It was found experimentally that the optimal parameters of cyclization are ultrasound frequency of 30kHz, ultrasound output of 40W, ultrasound time of 0.5h, 1% platinum and 2% copper on supported catalysts, the amount of catalyst of 1.5%(mass ratio of catalyst to raw material), reaction temperature of 210℃, reaction time of 3 hours, and it attains that the conversion of OTP is 80.41%, the yield of 1,5-DMT is 64.98% and the selectivity of 1,5-DMT is 80.81%.