Chemistry Reference
In-Depth Information
electrochemical process for the production of
adiponitrile (2.7 ¥ 10
5
t year
-1
) by electrohy-
drodimerisation of acrylonitrile was developed and
commercialised by Monsanto [11]. How much
energy is required to run the operation? Is the source
of that energy a coal-fired power plant or a hydro-
electric facility? Manufacture of the acrylonitrile
used as a starting material also generates large
amounts of a salt as a by-product that must be dis-
posed of. Each of these questions again links directly
to the overall economics and the resulting cost to the
industry. Long term, the clearest quantitative goal for
green technology in the chemical industry may be
that of Pereira: develop processes having 100% raw
materials utilisation or zero waste [1].
Questions such as these surrounding industrial
adoption of green process technology clearly high-
light the need to incorporate more life-cycle analy-
sis [12] (see also Chapter 5) for the evaluation of any
supposed 'environmentally friendly' routes [13]. In
the context of life-cycle analysis, some have pro-
posed that green technology eventually must
provide a cradle to grave service for a product, e.g.
in the photocopier industry where the makers of
toner cartridges are also their primary recyclers [14].
Research also provides answers. Improvements in
the synthesis of H
2
O
2
have been developed that could
lower its cost and make it more attractive as a green
oxidant from an energy viewpoint [15].
fragments in the final product. Catalysis thus
embodies the goal of eliminating the stoichio-
metric reagent and its associated waste from
chemical manufacturing. Catalysis also encom-
passes efficient organic synthesis as a subset,
because conversions of high atom economy fre-
quently employ catalytic steps to carry out given
transformations [16]. This field of research con-
tinues to develop within the chemical industry,
with 80-90% of all chemical processes involving
at least one catalytic step [17].
(2)
Biocatalysis/bioprocessing
. Biocatalysis is closely
related to non-biological catalysis and possesses
many of the same features and benefits. In addi-
tion, bioprocesses proceed under very mild con-
ditions, frequently in aqueous reaction media,
and can use renewable feedstocks as starting
materials. However, issues of separation,
expense, productivity, maintenance of organ-
isms and new capital investment so far have
limited the use of bioprocesses in the chemical
industry, except where no other alternatives are
available [18].
(3)
Renewables as chemical feedstocks
. The USA pos-
sesses sufficient renewable resources to supply
all domestic organic chemical needs without sac-
rificing traditional applications of renewables in
the production of food, feed and fibre. Yet, apart
from a few exceptions, the chemical industry
has not embraced renewables on a large scale.
Renewables will play an important role in the
future evolution of the chemical industry.
Progress in the use of conventional chemical
processing and catalysis for the conversion of
renewables to products are areas that will see
significant growth as the world turns its atten-
tion to new carbon sources as non-renewable
crude oil feedstocks diminish.
3 Overview
Against this backdrop, this chapter will attempt to
review green technologies that, apparently, have
surmounted all the life-cycle and economic barriers
and currently are being practiced by industry for the
commercial manufacture of products. The green
technologies that have been employed most widely
by the industry comprise three major categories. It is
interesting to note that over 85% of the technolo-
gies described in a recent review of winners of the
EPA Presidential Green Chemistry award also fall
into these categories [3]:
A review of this size cannot be exhaustive. The
chapter will not discuss reactor, separation or engi-
neering technology. Although widespread in the
industry [1], there will be no description of end-of-
pipe strategies. Where possible, the examples are
limited to newer technologies reported in the last
few years, with well-known industrial processes
mentioned only briefly. Moreover, an attempt has
been made to limit coverage to those processes cur-
rently being used in industry at a reasonable pro-
duction scale (e.g. bulk and commodity chemicals),
(1)
Catalysis
. Catalysis is proving to be a most pow-
erful technology for the greening of the chemi-
cal industry. Most simply, catalysis is employed
because of its ability to promote reactions by
adding one molecular fragment to another, with
incorporation of most or all of the atoms in both
