Chemistry Reference
In-Depth Information
Temperature and time of activation will depend on
the Envirocat: EPZ10, and EPZE can be activated at
280-300°C for 18 h but, EPZG can be activated at
300°C for 5-10 min under N
2
. However, these con-
ditions can be used only rarely in an industrial
process and therefore it is possible to activate these
catalysts at 100-120°C for 1 h under a vacuum,
releasing the vacuum with dry N
2
. It should be noted
that thermal activation usually leads to active sites
that are highly sensitive to moisture. Exposure to the
atmosphere will result in permanent deactivation of
the catalyst.
When using Envirocat EPIC in an esterification it
is not necessary to use these methods of activation
prior to use. Simply suspend the catalyst in the reac-
tion mixture and begin azeotropic drying.
In general, failure to activate the Envirocat will
result in little or no activity. Envirocat EPAD,
however, does not require activation prior to use.
7 Commercial Applications of Envirocats
7.1 Benzoylations
This catalyst can be used to catalyse the production
of benzophenones, which are used as starting ma-
terials for pharmaceuticals, flavours, fragrances and
sunscreens. As a general rule, EPZG will not catalyse
the benzoylation of deactivated substrates, e.g.
nitrobenzene, and cannot activate benzoyl chlorides
that contain electron-donating groups, e.g.
4-
methoxybenzoyl chloride. Envirocat EPZG will not
catalyse Fries rearrangements to form hydroxy-
benzophenones.
4-Chlorobenzophenone is an intermediate for a
variety of pharmaceutical products [31] and this
product was produced successfully using Envirocat
technology at CCL (see Scheme 13.1). Typically, the
yields for this process were 70% and no scrambling
of the aromatic chlorine was observed (cf. anhydrous
AlCl
3
).
Another application of EPZG is in the production
of 2-chloro-5-nitrobenzophenone (see Scheme
13.2), which is a precursor to the benzodiazepine
drugs. In this particular example, an isolated yield of
85% was attained with a gas chromatography (GC)
assay of >99%.
6 General Methods for Using Envirocats
6.1 Catalyst concentration
For Envirocats EPZG, EPZE, EPZ10 and EPIC there
is a very simple rule of thumb: 10 g catalyst
mol
-1
reagent. In the esterification of benzoic acid,
for example, 10 g of EPIC would be used to catalyse
the esterification. However, the esterification of
adipic acid would require 20 g of EPIC. Envirocat
EPAD requires significantly lower catalyst concen-
trations, typically 1% (w/w) suspension in the neat
substrate.
7.2 Acylations
Although it is possible to use EPZG to catalyse the
production of alkylphenones, the number of appli-
COCl
O
6.2 Reaction temperature
140ºC / 24h
+
EPZG
This will vary depending on the reaction type and
substrates used. Benzoylations and sulfonylations
require a minimum reaction temperature of 80°C
but more usually 130-160°C. The reason for these
high temperatures is to make sure that any complex
formed between the product and the active site can
be broken down, allowing the catalytic cycle to con-
tinue. Alkylations are performed over a very wide
temperature range of 20-140°C. Typically, benzoyla-
tions can be performed at ambient temperatures,
whereas some olefin alkylations require tempera-
tures of up to 140°C. Oxidations catalysed by Envi-
rocat EPAD usually are performed at the boiling
point of the substrate.
Cl
Cl
Scheme 13.1
COCl
O
Cl
Cl
135ºC / 6h
EPZG
+
O
2
N
NO
2
Scheme 13.2
