Theoretical Study Of The Ziegler-natta Catalysts For Olefin Polymerization Reaction

The olefin polymerization lies in the important position in chemical industry. The polyethylene and polypropylene are known by most people , and the extensive one is applied to each field in life, α- olefin refers to the alkene in the molecule end of one pair of keys, it is regarded as comonomer for linear low density polyethylene (LLDPE), intermediates of the syntheses for surfactant, plasticizer, lubricating oil and other additives in fine chemicals and petroleum to transport and reduce and hinder the pharmaceutical etc. to apply to a lot of fields extensively, it is a kind of important raw materials in the petrochemical industry. Since the Ziegler-Natta catalyst of 1953 come out, it has made inestimable contribution to development of polyolefin industry. People have carried on a large amount of research on the experiment and theory, and make Ziegler-Natta catalyst gain enormous development. For a long time, people have been attempting to explain the catalytic polymerization mechanism of Ziegler-Natta catalyst theoretically all the time . The mechanism proposed by Cossee-Arlman that alkyl migration to coordinated olefin and proposed by Green-Rooney that a hydrogen atom on the a-carbon of the growing polymer chain interacts with metal center throughout the catalytic cycle have been accepted widely. But they can't explain the catalytic polymerization mechanism of Ziegler-Natta catalyst perfectly.According to the above situation, this paper passes B3LYP method of DFT, have carried on the whole parameter to optimize (not add limiting to the reactant, product, intermediated complex of different possibility and transition state symmetrically) on 6-31G* level, have carried on vibration frequency analysis to some of all staying the potential energy on the same theoretical level, and report and reflect the coordinate (IRC) to calculate from the transition state while going on toward reactant and product. We have received a series of results.1. Through studying the first and the second generations of and the third generation of Ziegler-Natta catalyst, we confirmed the steady type of the catalyst basically, and found intermediated complex , transition state and product which...