Evaluation of molecular sieves in the purification of propylene used in the production of polypropylene
Keywords:
Polypropylene (PP), molecular sieves, Ziegler-Natta catalysis, methanolAbstract
The polymerization of propylene is a reaction that requires high quality feed streams, making it necessary to remove all traces of contaminants, such contaminants can be: H2O, H2S, CO2, COS, NH3, PH3 and other hydrocarbons oxygenates such as alcohols, ketones and ethers, etc.. Separation technology and cost effective for the removal of these contaminants is the use of selective adsorbents. In the process, the propylene feed is purified in a fixed-bed adsorption (D-1 A / B) to remove the moisture present in the propylene, which is used as a molecular sieve adsorbent material used in plant propylene 4A. The propylene comes from a process of pyrolysis of ethane and propane which contains impurities such as H2O, methanol, methyl mercaptan, etc.. In the present study evaluates the molecular sieves 4A, 13X, OG-941 and F9, for the purification of PP used for the production of polypropylene. Scaling was performed adsorber used industrial and designed a pilot-scale adsorber through a selected scaling factor (0.005) maintaining the same ratio of length and diameter. Propylene samples were purified with molecular sieves, was determined by chromatography main impurities before and after passing through molecular sieves. After polymerization was tested in a pilot scale reactor which evaluated the performance of the catalyst activity with molecular sieves and compared with data from crop and then set the final industry-wide replacement. Characterized the product generated in the reactor to determine whether there is any difference in the main properties and isotactic index (II), flow index (FI), particle size distribution (DTP), average molar mass Viscosimetric (Mv). The results of catalyst performance show that molecular sieves 13X and F9 are most effective for the removal of major pollutants present in the propylene. The industrial test performed with the purified propylene sieve 13X reported values of activity 10% higher than typical values registered with the sieve 4A.
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