Essay on Chemical Engineering

3238 Words Dec 13th, 2012 13 Pages
ACETIC ACID BY THE CHIYODA/UOP ACETICA™ PROCESS

Aspen Model Documentation

Index

• Process Summary

• About This Process

• Process Definition

• Process Conditions

• Physical Property Models and Data

• Chemistry/Kinetics

• Key Parameters

• Selected Simulation Results: Blocks
Streams

• References

PEP Process Module 1 19 Aug 1999
SRI Consulting

Process Summary

This Aspen Plus model simulates the production of acetic acid by low pressure methanol carbonylation in the presence of a heterogeneous rhodium (Rh) catalyst and the promoter methyl iodide. It is intended to resemble the Chiyoda/UOP Acetica™ process, a novel heterogeneous methanol process for the production of acetic acid. This
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Under reaction conditions, the Rh is converted to its catalytically active anionic form. The nitrogen atoms of the resin pyridine groups become positively charged after quarternization with methyl iodide. Subsequently, strong ionic bonds between the pyridine nitrogen groups and the Rh complex result in catalyst immobilization (see below). Because the ion exchange equilibrium favors the solid phase, almost all Rh in the reaction mixture is immobilized.1
RHODIUM IMMOBILIZATION

CH3
I–

[Rh2(CO2)2I2]

CH3

+ N

+ [Rh2(CO2)2I2]

+ N

+ I–

Vinylpyridine Resin Active form of Rh at high
CO partial pressure

Rh Immobilized Catalyst

The amount of Rh in the catalyst is preferably 0.1– 1 wt%, based on the weight of the insoluble, pyridine- containing polymer (560989). The catalyst is presumably used in an amount of at least 400 ppmw in terms of elemental Rh based on the weight of the solution in the reaction zone (560988). The pyridine ring of the polymer may be in the free base or N-oxide form or quartenized form. The polymer is also preferably in a spherical form, 0.25– 0.7 mm in diameter (560988). Commercially available pyridine-containing polymers such as Reillex-425 (a product of Reilly Tar and Chemical) and KEX-316, KEX-501, and KEX-212 (products of Koei Chemical Co.) are suitable for the purpose of this technology.

1 A commercial catalyst stability had been tested at normal

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