Page 174 - CW E-Magazine (9-1-2024)

Special Report

Acrylonitrile – A techno-commercial profi le

INTRODUCTION ACN plants. In addition, INEOS manu- which is offset against the lower price
crylonitrile (ACN) (formula: factures and markets ACN catalysts. of propane compared to propylene. In
C H N) is one of the leading The INEOS process and catalysts are addition, there is about 2.5 times as
3
3
Achemicals with a worldwide recognized as delivering highest con- many by-products by weight produced
production of about 8-mt. The most versions of raw materials to useful in the propane-based process.
important applications of ACN are products, while maintaining on-stream
acrylic fi bres; thermoplastics such as plant reliability factors in excess of The key competitive element is
styrene-ACN (SAN), ACN butadiene 98%. Primary attributes of INEOS’ the availability of a suitable catalyst.
styrene (ABS), and ACN styrene acry- ACN catalyst technology include: Despite intensive research the perfor-
late (ASA); synthetic rubbers such as  High ACN yields; mance of today’s catalysts remains
ACN butadiene (NBR); adiponitrile; as  High co-product hydrogen cyanide rather modest.
well as speciality polymers. (HCN) yield;
 High propylene conversion; Because of the recycle of uncon-
ACN is currently the second largest  Over 50 years of demonstrated verted propane and larger spectrum of
outlet for propylene (after polypropylene). R&D success; by-products, the advantage of lower
 New catalyst developments com- price seems to be not suffi cient for a
Manufacturing patible with all ACN plants; and technological breakthrough.
At one time the predominant com-  Stable performance and operational
mercial route to ACN was the addition fl exibility. A few propane ammoxidation plants
of hydrogen cyanide to acetylene. But have, however, been set up. In 2012,
this route has been completely replaced Propane ammoxidation PTT Asahi Chemical – a joint venture
by the ammoxidation of propylene, and An economic analysis can show between Thailand’s PTT and Japan’s
now about 90% of the worldwide ACN that the most effective factor in reduc- Asahi Kasei – started up a 200-ktpa
is manufactured by the latter process, as ing the manufacturing costs could be propane ammoxidation plant in Map Ta
described by the reaction: replacing the propylene by propane, Phut, Thailand. INEOS experimented
which is ~30% cheaper. with a propane demonstration unit in
CH =CH-CH + NH + 3/2O Green Lake (Texas, US), but found it
3
2
3
2
CH =CH-CN + 3H O A key difference in process opera- was not cost effective.
2
2
tion between the propane- and propy-
INEOS’ patented ACN process lene-based route is the lower reaction Applications
technology is the established world yield of ACN from propane compared
leader, used in over 95% of the world’s with that obtained from propylene, Acrylic fi bre
ACN is used mainly as a monomer
or co-monomer in the production of
synthetic fi bres – i.e., acrylic fi bre,
which is used to make clothing and
carpeting. Acrylic fi bre is an economi-
cal substitute for expensive wool, and
has a variety of applications in apparel,
house-hold and industrial areas.

The growth in the acrylic fi bre mar-
ket has declined compared to other uses
of ACN. Much of the acrylic fi bre manu-
facturing capacity has moved from the
US and Europe to Asia, particularly to
China.
Fig. 2.1: Simplifi ed process fl ow diagram of the commercial propylene ammoxidation process
a) Fluidized bed reactor; b) Counter-current absorber; c) Recovery column; d) Second recovery
column; e) Fractionation columns Acrylic fi bre is composed of at least

174 Chemical Weekly January 9, 2024

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