Isopropyl tert-butyl ether from crude acetone streams
John F. Knifton,* Pei-Shing E. Dai and John M. Walsh
Received (in Bloomington, IN) 19th March 1999, Accepted 22nd June 1999
Table 1 Typical properties of fuel ethersa
MTBE ETBE TAME IPTBE
Isopropyl tert-butyl ether may be prepared from crude
acetone streams through a combination of selective hydro-
genation and tert-butyl alcohol etherification.
Octane blending value (R + M)/2
Oxygen content (wt%)
Vapor pressure neat Rvp (37.8 °C)
110
18.2 15.7
7.8 4.0
112
105
15.7
2.5
113
13.8
2.5
Methyl tert-butyl ether (MTBE) has in recent years been under
severe environmental pressure and refiners have been examin-
1
ing alternative gasoline blending stocks, including tert-amyl
methyl ether (TAME), ethyl tert-butyl ether (ETBE), etc.2 Of
the fuel ethers seriously being considered, isopropyl tert-butyl
a
Data taken from references 2 and 3.
,3
3
ether (IPTBE) has the triple advantages (see Table 1) of (i)
liquid hourly space velocities (LHSVs) of 0.5, with IPA as the
major product. Selectivity to IPA is typically in the range of
highest octane blending values, (ii) lowest oxygen content and
(
iii) low vapor pressure. However, until now the only route to
7
6–80 mol%. Critical features of this selective hydrogenation
IPTBE was through the acid-catalyzed etherification of iso-
are (i) catalyst activity may be sustained for extended periods
without loss of performance and (ii) any ATBP or tert-butyl
hydroperoxide fractions present in this crude acetone feed are
quantitatively converted to more innocuous alcohols, e.g. tert-
butyl alcohol, without causing catalyst deactivation.
butene (oftentimes in short supply) with isopropyl alcohol
,5
(
propan-2-ol, IPA) [eqn. (1)].4 We have developed an
alternative route to IBTBE from crude acetone streams, making
it a co-product of propylene oxide (PO) manufacture. Propylene
epoxidation with tert-butyl hydroperoxide produces PO plus
tert-butyl alcohol commercially [eqn. (2)], with significant
Etherification of the IPA intermediate with added tBA to give
IPTBE [eqn. (4)] has also been demonstrated in continuous,
6
quantities of acetone as a secondary by-product. We have
upflow, reactor systems using three classes of acidic, large-
7
demonstrated, and report herein, that IPTBE can be made in
pore, zeolites:7 Zeolite Beta, transition metal-modified b-
good yield via (i) selective hydrogenation of the crude acetone
zeolites, and dealuminized Y-zeolites.
(
(
2
Me CO) by-product stream to give isopropanol [eqn. (3)] and
ii) isopropyl alocol etherification with the tert-butyl alcohol co-
IPTBE is typically generated in near quantitative molar
selectivities (on the basis of IPA converted) in the crude liquid
products under mild etherification conditions. Fig. 1 illustrates
IPTBE syntheses from the crude IPA stream of Table 2, plus
added tBA (IPA+tBA mole ratio 1+1.6), using an acidic b-
product to yield IPTBE plus water [eqn. (4)].
1
zeolite catalyst (80% Beta, 20% alumina binder, in ⁄16B diameter
extruded form), over a reactor temperature range of 40 to 100
°
C. At 60–80 °C the estimated IPA conversion level is moderate
(ca. 12%) and the crude liquid effluent comprises 7–8 wt%
IPTBE. However, IPTBE molar selectivity on the basis of tBA
converted is below 50% with this crude feedstock, due to
Typically, low-value acetone by-product streams from pro-
pylene oxide manufacture comprise 20–80% Me
contain significant quantities of MeOH, tert-butyl alcohol
tBA), and allyl tert-butyl peroxide (ATBP), as well as
detectable quantities of HCO H, AcOH, plus their ester
2
CO, but also
(
2
6
derivatives, such as tert-butyl formate (tBF). Selective hydro-
genation of a 61.7% acetone stream in a continuous, upflow,
reactor system containing a nickel, copper, chromium bulk-
metal catalyst (72% Ni), at 160 °C, is illustrated in Table 2. Near
quantitative (99%) acetone conversion levels are achieved at
Fig. 1 Crude IPA etherification to IPTBE with tBA. IPTBE molar
selectivity basis IPA and tBA converted.
Table 2 Crude acetone hydrogenation to isopropyl alcohol
Composition (%)
Catalyst
Ni-2715
T/°C
LHSV
0.5a
Sample
Me
2
CO
IPA
MeOH
tBA
tBF
ATBP
Feed
Product
61.7
0.8
0.1
48.3
13.9
15.8
16.7
30.8
0.1
< 0.1
3.3
< 0.1
b
160
a
Hydrogen feed rate, 90 l h21; total pressure, ca. 35 bar. b Product composition maintained for 200 h.
Chem. Commun., 1999, 1521–1522
1521