The UNIPOL Process for Polyethylene and Polypropylene Production

Develop the mathematical model of a modern riser reactor FCC unit and construct its static bifurcation diagram numerically. 

In this section we have presented modeling results for industrial type IV FCC units that produce high octane number gasoline from gas oil. Such units consist of two connected bubbling fluidized beds with continuous circulation of the catalyst between the two vessels, the reactor and the regenerator. The steady-state design equations are nonlinear transcendental equations which can be solved using the techniques described in the earlier chapters of the book. 

The unsteady state is described by ordinary differential equations or IVPs that can be solved routinely via MATLAB s ODE suit of programs. 

The reader should try and reproduce the graphical results of this section by developing her or his own MATLAB algorithms and verifying her or his results versus the results given graphically in this section. 

3Union Carbide, USA company, 1917-4Karl Ziegler, German chemist, 1898-1973 Guilio Natta, Italian chemist, 1903-1979 

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The Unipol process, initially developed for polyethylene production, was later extended to polypropylene manufacture. The process consists of a large fluidized-bed gas-phase reactor for homopolymer and random copolymer production, and a second smaller reactor for impact copolymer production. The second reactor is smaller than the first one because only 20% of the production comes from the second reactor. This reactor typically has a lower pressure rating as copolymerization is usually carried out at lower temperatures and pressures. Condensed mode operation is used in the homopolymer reactor but an inert diluent is not required because propylene is partially fed as a liquid. The copolymerization reactor is operated purely in the gas phase. The Unipol process has a unique and complex product discharge system that allows for very efficient recovery of unreacted monomer, but this does add complexity and capital cost to the process. 

The UNIPOL gas phase fluidized bed reactor for the production of polymers was commercialized by Union Carbide (now Dow Chemical) in 1968. This reactor produced high-density polyethylene (HDPE). The UNIPOL process was extended in 1975 to the production of linear low-density polyethylene (LLDPE) and in 1985 to polypropylene production. In the late 1980s, BP Chemicals began licensing its own gas phase Innovene fluidized bed process in competition with Union Carbide. The UNIPOL process currently holds the lion s share of the market with over 120 reaction lines sold or under construction. The reactor design is similar for all types of polymers and is shown conceptually in Fig. 9. A... 

UNIPOL [Union Carbide Polymerization] A process for polymerizing ethylene to polyethylene, and propylene to polypropylene. It is a low-pressure, gas-phase, fluidized-bed process, in contrast to the Ziegler-Natta process, which is conducted in the liquid phase. The catalyst powder is continuously added to the bed and the granular product is continuously withdrawn. A co-monomer such as 1-butene is normally used. The polyethylene process was developed by F. J. Karol and his colleagues at Union Carbide Corporation the polypropylene process was developed jointly with the Shell Chemical Company. The development of the ethylene process started in the mid 1960s, the propylene process was first commercialized in 1983. It is currently used under license by 75 producers in 26 countries, in a total of 96 reactors with a combined capacity of over 12 million tonnes/y. It is now available through Univation, the joint licensing subsidiary of Union Carbide and Exxon Chemical. A supported metallocene catalyst is used today. 

UNIPOL [UNIon Carbide POLymerization] A process for polymerizing ethylene to polyethylene and propylene to polypropylene. It is a low-pressure, gas-phase, fluidized-bed process, in contrast to the Ziegler-Natta process, which is conducted in the liquid phase. The catalyst powder is continuously added to the bed, and the granular product is continuously withdrawn. A comonomer, such as 1-butene, is normally used. 

UNIPOL process A process used for polymerizing ethylene to polyethylene and also for polymerizing propylene to polypropylene. Unlike the Ziegler-Natta process, it uses a gas phase process at low pressure. The catalyst is continuously added to the process and the granular product withdrawn. A co-monomer is also usually used in the process. 

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