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SUMMARY OF DATA FOR CHEMICAL SELECTION

METHYL TERT-BUTYL ETHER

CHEMICAL IDENTIFICATION:

CAS Registry Number: 1634-04-4

Name: Methyl tert-butyl ether

Chem. Abstr. Name: 2-Methoxy-2-methylpropane (9CI)

Synonyms: MTBE; tert-butyl methylether (8CI); methyl 1,1-dime-
thylethyl ether

Structure, Molecular Formula and Molecular Weight:

CH3
|
CH3-CH2-O-CH3
|
CH3

C5H12O Mol. wt.: 88.15

Chemical and Physical Properties:

Description: Colorless liquid (1)

Melting Point: -109 C (2)

Boiling Point: 55.2 C (2)

Density: 0.745 (2)

Solubility: Soluble in ether and ethanol (2); slightly soluble in water
(4.8 g/1 at 25 C) (3); MTBE in water 4.8 weight% (6); water
in MTBE 1.5 weight% (4).

Technical Products and Impurities:

MTBE is available from US manufacturers typically in 97.0-97.45 weight % compo-
sitions. Specifications for the minimum concentration of MTBE range from 95.0
-97.0 weight % (4,1). Methanol is allowed in concentrations not to exceed 0.5%
(1) or 0.7% (4). Water may be present in less than 0.15% concentration by
weight (4,1). Other typical contaminants include diisobutylene, triisobutylene
and t-butyl alcohol (0.56%); C4 hydrocarbons (1.10%) and C5 hydrocarbons (0.35%)
by weight (1).

Basis of Nomination to the CSWG:

Methyl tert-butyl ether was nominated in joint discussions between NCI, TJ, and
TRI personnel at a CSPG meeting (5/7/85). The nomination was based on the
extensive production of the compound, its increasing use as a blending component
in high octane gasoline, its recent application in the dissolving of gallstones,
and the lack of carcinogenicity testing information.

Methyl tertiary-butyl ether (MTBE) was submitted to the CSWG for review on the
basis of the extensive productin of the compound, its increasing use as a blen-
ding component in hgh octane gasoline, its recent application in the dissolving
of gallstones, and the lack of carcinogenicity testing information. It was
noted that MTBE is used as an additive in unleaded gasoline in amounts up to 11%
. Although the major human exposure was considered as occurring in people work-
ing in gas stations, it was recognized that the possibility of general populat-
ion exposure is very high. It was noted that in rats, MTBE is exhaled mostly
intact with small amounts of formic acid and methanol being excreted in the
faces and urine. [API has also reported the identification of t-butyl alcohol
and formaldehyde as metabolites of MTBE]. In addition, the CSWG considered
that the compound has not been tested for carcinogenicity and that the mutagen-
icity data available is limited and does not permit meaningful assessment of the
mutagenicity potentials of MTBE. The group unanimously recommended that MTBE be
tested for carcinogenicity.

EXPOSURE INFORMATION

Commercial Availability:

Production Procedures:

Methyl t-butyl ether (MTBE) was introduced into the US market by phillips chemi-
cal in 1979 (5). Since that time, there has been a dramatic increase in MTBE
production, as represented by eight major US manufacturers (6).

MTBE Producer Production Capacity
-------------- ---------------------

Arco 855
Champlin 150
Charter International 135
Exxon 230
Petro-Tex 620
Phillips 265a
Texaco 600
Texas Petrochemical 55
------
2910

* Capacity in millions of lbs. as of July 1985 (6)
No longer available as of May 1985 (7)

U.S. PRODUCTION OF MTBE (8)
(millions of lbs)

1980 1981 1982 1983 1984
---- ---- ---- ---- ----

705.7 760.0 824.0 838.7 1,469.5

The Arco chemical company plans to expand its MTBE capacity to a total of 950
million lbs. (6). Amoco is preparing to place on-stream two MTBE plants with
a combined capacity of 3078 million lbs. In addition, Cosden plans to open
a facility in 1986 with a 66 million lb capacity, and Exxon will add to its
MTBE production capability in 1987 (9). The total US production capacity of
MTBE in 1986 is projected to be 3.38 billion lbs. Recent correspondence with
the phillips chemical company indicates that MTBE is no longer commercially
available from that firm (7).

The US International Trade Commission (8) reported the production of 1.47 bill-
ion lbs. of MTBE by US producers in 1984. This represents 42% increase over the
previous year's total, and ranked MTBE production among the top 50 industrial
chemicals manufactured in the US (10). Consumption of MTBE in 1984 was estima-
ted at between 1.49 and 1.52 billion lbs., with demand expected to increase by
10% in 1985 (6). Import/export figures for this compound are not available (11)

MTBE is produced commercially by reacting methanol with isobutylene contained in
mixed C4 stream and passing the mixture over a fixed bed ctalyst (1,6,12). Dif-
fering technologies for this process have been utilized by Neochem, Arco, Phill-
ips, and Texaco in the US, Huels in Germany, and Snamprogetti in Italy (13).