Simulation And Experiment Of Bimodal Polyethylene Products By Operation Parameters Oscillation

Bimodal polyethylene is a kind of polyolefin which has bimodal molecular weight distribution. It has little chain branch in low molecular weight part, and many chain branches in high molecular weight part. Bimodal polyethylene has good mechanical properties and processing properties because of this structure. Now bimodal polyethylene has been the important research aspect of high-powered polyolefin. There are three methods producing bimodal polyethylene: (1) melting mixture, which can't produce homogeneous polymer;(2) multistage polyolefin process, which has complex process and high price, (3) one stage polyolefin process, which don't need change process. So this research paper proposed a new technology that produces bimodal polyethylene in a single reactor. The main innovative work in this paper is:(1) For the industrial fluidized bed gas-phase polyethylene production process, a new technology that produces bimodal polyethylene in a single reactor by oscillating the operation parameters is proposed firstly. An experiment that produces bimodal polyethylene in a single reactor by oscillating hydrogen flow rate is operated firstly to do a further research on the new technology. In the experiment, APE-1 type metallocene catalyst is used to catalyze polymerization and hydrogen is used as chain transport. The effect of the press of hydrogen and the periods of hydrogen on the polymers' Mw and MWD is studied. The polymers' broad molecular distribution proves the feasibility of the new technology.(2)A Monte Carlo method has been firstly applied to simulate the experiment that produces bimodal polyethylene in a single reactor by oscillating hydrogen flow rate. A new Monte Carlo algorithm for dynamic operation in polymerization has been developed for the first time. The conclusion of Monte Carlo simulation is similar to the experiment result and different from the conclusion of theoretic simulation. The main reason is that in the experiment oscillation and diffusion needs time, the polymerization is operated in the intergradations, not in the perfect state.