Design Of Solid Base Catalysts And Their Technological Process For Propylene Dimerization To Produce 4-methyl-1-pentene

Propylene dimerization is an important way to produce fine chemicals,and its dimerization products include 4-methyl-1-pentene,1-hexene and 2,3-dimethy-1-butene.Both4-methyl-1-pentene and 1-hexene can be copolymerized with ethylene to form linear low-density polyethylene with excellent performance.In addition,poly 4-methyl-1-pentene（TPX）is a new type of polyolefin resin with excellent light transmittance and heat resistance.The industrialization of 4-methyl-1-pentene has not been realized in China now,so the development of high-efficiency catalysts,the optimization of reaction process conditions and the design of product separation process for the reaction of propylene dimerization to4-methyl-1-pentene are very important to lay the foundation for its realization of industrial production.Preparation of solid base catalyst by melting method to catalyze propylene dimerization and screen the active components,carriers and additives of the catalyst.It is determined that the K-Cu/K₂CO₃ catalyst composed of alkali metal element K as the active component,K₂CO₃ as the carrier,and transition metal Cu as the auxiliary agent has the best propylene dimerization catalytic effect.The effects of temperature and reaction time on the performance of the catalyst are investigated,and it is proved that the suitable temperature window of the catalyst is narrow and the isomerization reaction of the target product 4-methyl-1-pentene is also greatly affected by the reaction time.It is finally determined that 1.5 g catalyst has the best effect after catalyzing the dimerization of propylene in a tank reactor at a temperature of160℃and a pressure of 6 MPa for 16 h,and the single-pass conversion rate of propylene and the selectivity of 4-methyl-1-pentene are 64.3 wt.%and 80.6 wt.%respectively.In addition,the method of directly adding Cu powder with a particle size of about 40μm is considered to be the best way.By performing hydrogen reduction treatment on the catalyst after the reaction,the unsaturated polymerized hydrocarbons adsorbed on the surface can be removed and the life of the catalyst can be prolonged.Using Aspen Plus software,a propylene dimerization reaction product separation and propylene raw material recovery process simulation model is established,on the basis of meeting product separation requirements and the principle of energy saving at the top and bottom of the tower,sensitivity analysis is used to investigate the influence of the feed position and reflux ratio on each rectification tower.After optimization,the operating conditions of the propylene recovery tower（T-1）,the 4-methyl-1-pentene separation tower（T-2）,the 4-methyl-2-pentene separation tower（T-3）and the heavy component separation tower（T-4）are as follows:T-1:The number of theoretical plates is 22,the best feed position is the 10th plate,and the best reflux ratio is 0.375.T-2:The number of theoretical plates is 142,the best feed position is the 65th plate,and the best reflux ratio is 31.T-3:The number of theoretical plates is 72,the best feed position is the 33rd plate,and the best reflux ratio is 14.T-4:The number of theoretical plates is 12,the best feed position is the sixth plate,and the best reflux ratio is 0.7.The simulation calculation results can provide a reference for the design and actual operation of the industrial process for preparing 4-methyl-1-pentene by propylene dimerization.