Separation Of Cyclopentadiene From C₅ Fraction Of Steam Cracking Products And The Synthesis Of Polypropylene Nucleating Agents

The issue of efficient separation and reasonable utilization of C5 fraction, obtained from steam cracking process, is the key to improve the efficiency utilization of petrochemicals resource, reducing ethylene production costs and increasing economic efficiency of petrochemical plants. Cyclopentadiene (CPD) is an unsaturated cyclic hydrocarbon with a high chemical activity. At room temperature, it could dimerize into dicyclopentadiene (DCPD).CPD and DCPD could easily react with unsaturated compounds to produce a large number of cyclic compounds. CPD containing active methylene group, which could react with aldehydes and ketones, and it is one of important chemical raw materials. Convensional separation method of CPD from steam cracking C5 cuts has many disadvantages, such as low CPD yield, low purity and coke blocking of reaction pipe. It leads tot the difficultes of further exploitation and utilization of CPD and DCPD.An intergrated process, including thermal dimerization-distillation-depolymerization or cracking methods, was developed to obtain high purity CPD or DCPD. At the beginning, the light components were removed by distillation method, which could reduce the side reaction happened in the following process. Then, thermal dimerization was investigated to improve the conversion rate of CPD to DCPD, the optimal reaction temperature is 100℃. The CPD conversion and selectivity could reach 88% and 98%, respectively, while the yield was 86%, after 3h reaction.4.5 h reaction could give the 97% CPD conversion with 95% selectivity and 92% yield. Reducing the reaction temperature gave a high selectivity but increase the reaction time. High temperature reduces the selectivity, and this causes separation process complicated. Therefore, separation of DCPD by vacuum distillation was.carried out to lower the distillation column bottom temperature. It could prevent the DCPD depolymerization. At the negative pressure 0.098MPa, tower reactor temperature of 98℃, 86% purity DCPD was obtained and DCPD yield was 91%. On this basis, the work studies the liquid phase cracking of DCPD in a tank reactor. Dodecane diluent, inhibitor compounds and other methods were also studied and effectively reduce the oligermiraztion of DCPD and other olifines in the liquid phase.Liquid phase cracking of DCPD by reactive distillation and gas phase crackingof DCPD using hydrogen as carrier gas were studied in order to intensify the cracking process of DCPD. Using diluents and inhibitors could alleviate the formation of oligomers during the cracking process. Reactive distillation results demonstrate that it could enforce the cracking of DCPD and prohibit oligomerization reactions simultaneously. Hence, the yield and purity of cyclopentadiene reach 90 and 98 wt%, respectively. Reactive distillation greatly alleviates the forming of oligomers compared with conventional processes. Using H2 carrier gas, the cracking reaction pressure is not so high,0.12MPa. The process can prevent coke formation during the DCPD cracking, but also avoid the dehydration process of the products, which simplify the process of preparation of CPD. At optimal conditons, DCPD conversion rate reached 98%, and yield reached 97%. Using further distillation of cracking products could give CPD purity of 99%. Simulation of 150000 tons per year of C5 fraction was investigated to separate CPD by Aspen Plus. Results showed that the intergrated process could produce 99% purity CPD with 85% yield.The purity of 99% CPD obtained form above processes was used to synthesis norbornene anhydride, and then norbornene anhydride was synthesized into six norbornene dicarboxylate salt nucleating agent. In the six nucleating agent, norbornene dicarboxylic acid aluminum salt improves the transparency of polypropylene, rigid and intensity most prominently, and appropriate norbornene dicarboxylic acid concentration of aluminum was 0.2%. At the concentraction, PP has good tensile properties, bending properties, haze and impact strength. The DCS results showed that the aluminum salt can significantly increase aluminum crystallization temperature of PP. With the increasing concentration, crystallization temperature rises. Caze method used by the different concentration of the nucleation of polypropylene non-isothermal crystallization kinetics results show that the nucleating agent can significantly reduce the half life-time of crystallization of PP, PP nucleation Avrami index increases with the concentration. At low concentrations, the result indicates that the crystal growth pattern of nucleated PP is heterogeneous nucleation followed by three-dimension spherical growth; At high concentrations, heterogeneous nucleation goes under the multi-dimensional crystal growth mode. The nucleating agent can increase the crystallization temperature of polypropylene and promot polypropylene crystal growth. However, it also leads to the increase of the activation energy of crystallization of polypropylene, which is due to the crystal nucleating agent interaction with the PP chain. The presence of the interaction impeded the migration of the PP chain and reduced the growth rate of PP, which results in higher activation energy of nucleation of polypropylene.