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Catalysts used in polymerization systems are sensitive to the purity of raw materials. Proper knowledge transfer from purification technology providers is key to meeting these high-purity requirements.

Polymerization reactions that use high-activity catalysts require raw materials with high purities. The ability of the polymerization reaction system to produce high-quality polymer resins largely depends on the purity of the raw materials. Polymer producers license purification schemes from technology providers to ensure that raw materials meet certain purity standards before polymerization.

Polyethylene and polypropylene are by far the two largest thermoplastics produced by volume. Low-density polyethylene (LDPE) was discovered and commercialized in the 1930s. Shortly after, cutting-edge technologies were pioneered in the 1950s to produce high-density polyethylene (HDPE) and homopolymer polypropylene. Since the development of these new products, the industry has focused on improving polymerization catalyst activity (or productivity), and improving process technology to match higher catalyst productivity and increase energy efficiency.

Process technology improvements mainly focus on increasing the heat and mass transfer capacities of reactors. The reactor must satisfy the basic prerequisites of polymerization reactions: quick removal of exothermic heat of polymerization, efficient mixing, and short residence times to meet desired product properties. These factors have contributed to an increase in single-line capacities. Currently, the single-line capacity of most polyethylene and polypropylene plants is approximately 400鈥�600 kilometric tons per annum.

This article describes the purification of raw materials that is required to meet the demand of high-activity catalyst systems used in high-capacity polymerization reactor systems. The article outlines the principles and design of purification schemes for ethylene and propylene, among other raw materials.