Study On Inhibition Of Dienes Compounds In Cracking C₅

Cracking C₅ had become an important way for making the best of petroleum resources and decreasing the cost of producing ethane, and it had been taken into account in world. The method combined azeotropic distillation and extractive distillation was taken to separate cracking C₅. The method had the advantages of minor amount of the solvent, and lower operation temperature in the separation process, and pentane could be produced .In the process of yielding IP from cracking C₅, polymeric compound was generated by IP easily polymerized. Therefore some problems, such as efficiency of heat transfer decreasing and period of running shortening and so on might be caused easily. In order to avoid these problems, inhibitor was added to raw material to slow the rate of polymerization. The inhibitors for IP were filtered and the influencing factors such as reactor temperature , reactor time, the ONP concentration and so on, for the isoprene polymerization were researched. The experimental results showed that:1. Cracking C₅ from Yangzi Petrochemial Ltd as the materials, the inhibiting performance of o-nitrophenol (ONP) was better than the others.2. At the temperature 85℃, n-pentane as the solvent, containing 0.2% ONP and 50% to 90% IP, reacting 48h, the relationship between losses of IP and concentration of IP was approximately linear. The loss rate of IP when the time was 48h was faster than the loss rate of IP when the time was 2h.3. At the temperature 90℃, containing 0.2% ONP and 20% IP, reacting 48h, different solvents had no obvious effect on IP polymerization. But others dienes (CPD or PD) in materials would accelerate the IP self-polymerizing.4. At the temperature 90℃, n-pentane as the solvent, containing 20% IP, reacting 48h, there was a range of ONP concentration in which the polymerization of IP was least. The performance of inhibiting polymerization was better when the ONP concentration was 0.2%¹.3%. So, in order to keep the concentration of ONP in the range of good inhibiting performance, ONP should be supplied.5. Used n-pentane as the solvent, containing 0.2% ONP, and 20% IP, the rate of reaction would accelerate with the rising of temperature from 30 °C to 85 °C. The loss rate of IP would increase slowly when the reaction time was less than lOh, but it would accelerate sharply when the reaction time was more than 20h.6. At the temperature 70°C, n-pentane as the solvent, containing 0.2% ONP and 20% IP, reaction time also had affected the performance of polymerization inhibiting. The loss rate of IP would increase slowly when the reaction time was less than 20h, but it would accelerate sharply when the reaction time was more than 25h. So, the IP should be separated in shorted time in the process of commercial production.Secondly the relationship between the concentration of ONP and reaction time was researched. Used n-pentane as the solvent, containing 0.2% ONP and 20% IP, at the temperature 60°C to 95 °C, the relationship could be expressed by quadratic curve:Used n-pentane as the solvent , containing 0% or 0.2% ONP, both the polymerization reaction rate of IP were researched, containing 0% ONP and containing 0.2% ONP, could be expressed by second order reaction. The activity energy containing 0.2% ONP was larger than containing 0% ONP.Lastly, the influencing factors such as concentration of ONP, temperature and reaction time and so on for the isoprene and other dienes in cracking C5 were researched. The experimental results showed that: all factors had the same influencing trends on IP polymerization in cracking C5 as IP in inert solvents. ONP had no effect on other dienes polymerization.