Polyethylene catalysts development

Exxpol [Exxon polymerization] A gas-phase process for making polyethylene from ethylene. The process uses single-site catalysis (SSC), based on a zirconium metallocene catalyst. Developed by Exxon Chemical Company in 1990 with plans to be commercialized in 1994. 

The unique nature of the alkyl attached to titanium in a polyethylene catalyst has been indicated by Gray (80). Methyltitanium trichloride has an infrared spectrum which is unique and different from the bridged or unbridged methyl of methylaluminum chlorides. Although methyltitanium trichloride is not an effective catalyst to polymerize ethylene, this unique character is an indication of a difference which is developed further in the effective polyethylene catalysts. 

Various aspects of organocatalysis with larger molecules are also covered in this book. Possible benefits from immobilization approaches for organic catalysts are pointed out by M. Benaglia. Apart from catalyst recycling or simplified workup procedures, catalyst immobilization can be additionally advantageous in terms of catalyst development and optimization. The use of soluble supports, such as polyethylene glycol, often allows the direct transfer and application of already optimized reaction conditions. 

Evolue Also written Evolue. A gas-phase process for making linear low-density polyethylene using higher a-olelin co-monomers and a metallocene catalyst. Developed by Mitsui Chemicals and Idemitsu Kosan, and now manufactured in Japan by Prime Polymer, a joint venture of these two companies. 

In the early 1950 s, Ziegler found that in the presence of ZrCl + AIR3 ethylene can be polymerized at low temperature and pressure into linear, high density polyethylene (HOPE). The catalysts developed by Ziegler, and later by Natta become known as Ziegler-Natta, or Z-N catalysts. These can be defined as polymerization initiators created from a catalyst (1) and co-catalyst... 

PP known as polypropene, is one of those most versatile polymers available with applications, both as a plastic and as a fibre, in virtually all of the plastics end-use markets. Professor Giulio Natta produced the first polypropylene resin in Spain in 1954. Natta utilised catalysts developed for the polyethylene industry and applied the technology to propylene gas. Commercial production began in 1957 and polypropylene usage has displayed strong growth from this date. PP is a linear hydrocarbon polymer, expressed as... 

Particles are the bed material employed in fluidized bed reactors and can be reactants (e.g., coal and limestone), products (e.g., polyethylene), catalysts, or inert. The choice of particle size, in general, affects the hydrodynamics, transport processes, and hence the extent of reactor conversion. Particles experience particle particle collisions, friction between particles and walls or internals, and cyclones. In some cases, the catalyst material is inherently susceptible to attrition, and special preparation to enhance the attrition resistance is required. For example, the vanadium phosphate metal oxide (VPO) catalysts developed for butane oxidation... 

Catalyst developments for the manufacture of polyethylene with Ti-based catalysts can be best described as based on two different types of catalysts, which are broadly defined as first and second generation catalysts. 

Catalyst developments for the polyethylene industry in the near future will continue to expand the types of molecular structures available for future commercial applications. These catalyst developments can be classified as follows ... 

Because licensees of the Ziegler catalyst developed their own proprietary process technology, DuPont Sclair provides an excellent example how a Ziegler licensee developed and expanded both the process, catalyst and product technology, developing new markets and applications for low-pressure polyethylene. 

This chapter will discuss the equipment necessary to set up a catalyst development laboratory and the analytical instrumentation required to characterize the polyethylene produced with experimental catalysts. The introduction of high throughput research methods since the 1990s has improved the potential productivity of such a laboratory. In addition, utilization of designed experiments in which the effect of several variables on the properties under investigation can be screened in a more efficient manner is also necessary to discover new technology for commercialization. 

With the publication of this report by IKC researchers on the discovery of SPS, a flurry of activity was set in motion in several laboratories around the world in an effort to find the catalysts used. In a coincidence of timing, researchers at The Dow Chemical Company (TDCC) had been investigating MAO counterions for polyethylene catalyst research. Researchers there also had a renewed interest in IPS based on the ability to produce very high purity styrene monomer for anionic polymerization at a large commercial scale. By December of 1986, Dow had been able to independently replicate the IKC discovery. At that time, Dow was the largest commercial manufacturer of both styrene monomer and atactic polystyrene in the world, and a decision was made to pursue research and development of this new polymer. At the same time, an intense research and development effort was in progress at Idemitsu and this had in fact already been ongoing for almost 2 years. 

Energx A process for making linear low-density polyethylene (LLDPE). Developed by Eastman Chemical in the 1990s and used at its plant in Longview, TX. Licensed to Chevron Chemical in 1999 for use at its plant in Baytown, TX. By 2002, licenses had been granted in Europe, North America, and Asia. A variation, Energx DCX, uses a supported catalyst (Sylopol DCX) made by W.R. Grace. The polyethylene products have the trade name Hifor. 

IntegRex A process for making polyethylene terephthalate, developed by Eastman Chemical, announced in 2004. It integrates the PX-PTA process with the PTA-PET process. It uses an aqueous solution of tere-phthalic acid instead of the solid acid. Johnson Matthey has developed a special catalyst for it. The first plant was built in S. Carolina in 2006. There was a patent dispute between Eastman Chemical and Wellman regarding the resin product, trade named ParaStar. The process was sold to DAK Americas in 2011 who licensed it to Alpek in 2013. 

The characterization methods described in Chapter 2 are limited in what they can tell us about structure in the absence of any information about how a sample was made. Chapter 3 surveys the various types of reaction systems used in polymerization and describes the molecular structures that can be produced by each. Anionic and living free-radical polymerizations are used in the laboratory to prepare samples having ideal structures, while processes used in industry produce materials that more complex in structure. The commercial polymer with the most complex structure is low-density (highly branched) polyethylene. The development of single-site catalysts has led to the commercial production of polymers that, while they do not have the homogeneity of ideal samples, do have structures that are reproducible and simply described. 

The first commercial process for making LLDPE was the Sclair technology developed by Dupont Canada and now implemented by NOVA Chemicals. This process involves high-temperature solution polymerization. Much LLDPE is now made in gas-phase reactors with butene or hexene as the co-monomer. The constrained-geometry catalyst (CGC) is a metallocene catalyst developed by Dow Chemical for the manufacture of linear, very-low density polyethylene resins by solution polymerization with octene as the comonomer. For a given co-monomer content, the solid-state density is lower for octene than for lower a-olefins. 

Worldwide demand for polypropylene was still only about 1-6 million tones year during the period from 1970 to 1980. As demand began to increase, more efficient catalysts, based largely on a successful range of supported polyethylene catalysts, were developed. 

High density polyethylene (HDPE) is defined by ASTM D1248-84 as a product of ethylene polymerisation with a density of 0.940 g/cm or higher. This range includes both homopolymers of ethylene and its copolymers with small amounts of a-olefins. The first commercial processes for HDPE manufacture were developed in the early 1950s and utilised a variety of transition-metal polymerisation catalysts based on molybdenum (1), chromium (2,3), and titanium (4). Commercial production of HDPE was started in 1956 in the United States by Phillips Petroleum Company and in Europe by Hoechst (5). HDPE is one of the largest volume commodity plastics produced in the world, with a worldwide capacity in 1994 of over 14 x 10 t/yr and a 32% share of the total polyethylene production. 

---