Chemistry Reference
In-Depth Information
7
Materials and Resources for Phosgenation
Reagents
Most of the phosgene equivalents and substitutes are commercially available, albeit
at widely varying costs, whereas phosgene itself is subject to restrictions. For those
phosgene substitutes that are not available, procedures or references for their
preparation are given herein. In some phosgenation reactions, the role of phos-
gene is played by rather simple, ordinary chemicals, which can be found in any
catalogue of fine chemicals and hence need not be mentioned further in this
chapter.
7.1
Sources of Phosgene
Phosgene is nowadays produced in two ways, in stationary plants or special facili-
ties that operate continuously producing 100s of kilograms up to 1,000s of tons a
day, and in rather small amounts on a scale of grams to kilograms a day in bottles,
lecture bottles, or dissolved in toluene. Recently, a process whereby phosgene is
evolved from a safe precursor has been developed [1], which has also been applied
in the form of cartridges for safe phosgenations [2].
7.1.1
Industrial Plants
Most of the annual worldwide consumption of 5-6 million tons of phosgene is
produced from carbon monoxide and chlorine in the presence of a catalyst based
on activated carbon (charcoal) in special plants. The process, the tetrachloro-
methane problem associated with it, and the approaches to solve it, are described
in Section 2.1.
To provide phosgene on the demand of consumer by producing it on location,
Modular Phosgene Generators are offered by Davy Process Technology (DPT), Swit-
zerland [3], in seven output sizes ranging from 3 kg/h up to 10,000 kg/h (Table
7.1). These Modular Generators produce phosgene from carbon monoxide and
chlorine and consist of two sections, the intrinsic phosgene generator (see Scheme
2.3, Section 2.1) and a safety absorption module.
