Isopropyl tert-butyl ether from crude acetone streams

Article abstract of DOI:10.1039/a902458a

Isopropyl tert-butyl ether may be prepared from crude acetone streams through a combination of selective hydrogenation and tert-butyl alcohol etherification.

Full text of DOI:10.1039/a902458a

Isopropyl tert-butyl ether from crude acetone streams
John F. Knifton,* Pei-Shing E. Dai and John M. Walsh
Shell Chemical Company,PO Box 1380, Houston, TX 77251-1380, USA. E-mail: jfknifton@shellus.com
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

Table 3 Isopropyl alcohol etherification to isopropyl tert-butyl ether
Composition (%)
IPTBE MTBE
Catalyst
T/°C
LHSV
Sample
IPA
tBA
MeOH
C4H8
C8H16
Feed
#1
#2
Feed
#1
#2
0.1
4.2
5.9
11.3
9.3
9.1
11.3
9.3
9.5
81.2
68.3
61.1
82.2
67.7
60.6
3.4
1.3
0.8
2.1
1.2
0.7
Pt/Beta zeolite
Pd/Beta zeolite
60
0.25
0.25
5.9
5.5
6.6
10
0.5
2.9
8
0
6
8
0
0
0.25
0.25
6.1
5.4
4.3
6.2
6.7
9.7
0.6
3
a
Designations as per Table 2.
Table 4 Standard enthalpy and entropy changes for IPTBE syntheses
Table 2, but adding additional tBA (IPA:tBA molar feed ratio
1
+5.8). The transition metal-modified b-zeolites were selected
DH/kcal mol2
1
DS/cal mol21 K21
217.1a
IPTBE Synthesis Route
IPA + iso-C ? IPTBE
for study here, on the basis of our earlier observations that they
provide superior performance in related service, e.g. MTBE
production from Bu OH–MeOH mixtures, as well as in ETBE
a
H
4 8
26.1
t
8
b
b
2
5.5
214.4
9
c
27.0c
synthesis. Significantly poorer etherification performance was
IPA + tBA ? IPTBE + H
a
2
O
20.4
generally realized with the dealuminized Y-zeolites.7
From reference 4. b From reference 5. c This work, ideal gas conditions
Liquid-phase IPTBE synthesis from IPA–tBA mixtures [eqn.
(298 K, 1.0 atm).
(
4)] is essentially thermoneutral—see Table 4—in contrast to
4,5
IPTBE from isobutene [eqn. (1)]. Isolating and purifying
99%) the intermediate IPA from Table 2, and running
(
etherification with close to stoichiometric quantities of tBA,
provides measurably higher IPTBE selectivities over this
temperature range (see Fig. 2, IPA+tBA feed ratio 1+1.6) and
fewer competing reactions. However, etherifications conducted
much above 100 °C lead to the formation of diisopropyl ether as
a dominant product.10
Continuing improvements in this technology are under
investigation, particularly in the area of an integrated, one-step,
1
1
route to C-3 ethers from crude acetone streams plus tBA.
The authors wish to thank Mr Melvin Stockton for experi-
mental excellence.
Notes and references
1
See: Chem. Eng. News, May 5, 1997, 54; ibid., Dec. 2, 1996, 14; ibid.,
Nov. 23, 1998, 30.
2
3
4
W. J. Piel, Fuel Reformulation, March/April 1994, 4, 28.
W. J. Piel, Fuel Reformulation, November/December 1992, 2, 34.
J. A. Linnekoski, A. O. I. Krause, A. Holman, M. Kjetsa and K. Moljord,
Appl. Catal., 1998, 174, 1.
Fig. 2 Pure IPA etherification to IPTBE with tBA.
5
A. Calderon, J. Tejero, J. F. Izquierdo, M. Iborra and F. Cunill, Ind. Eng.
Chem. Res., 1997, 36, 896.
competing tBA dehydration and oligomerization to isobutene
and diisobutene, as well as the formation of smaller quantities of
MTBE through etherification. It is noteworthy, nevertheless,
that the b-zeolite catalyst does maintain etherification activity
and good IPTBA molar selectivity with this crude hydrogenated
6 Stanford Research Institute PERP Report 2E, ‘Propylene Oxide’,
August 1994.
7
8
9
J. F. Knifton, E. L. Yeakey and P. E. Dai, US Patent 5449838, 1995.
J. F. Knifton and P. E. J. Dai, US Patent 5364981, 1994.
P. E. Dai, R. J. Taylor, J. F. Knifton and B. R. Martin, US Patent
Me
2
CO feedstock for extended periods.7
5
476972, 1995.
Very similar product distributions were realized when using
transition metal-modified b-zeolite catalysts—particularly b-
zeolites modified with platinum, palladium, and nickel. These
data are illustrated in Table 3 for the non-aqueous product
fraction, when starting with the same crude IPA feed stream of
1
1
0 J. F. Knifton and P. E. Dai, Catal. Lett., 1999, 57, 193.
1 R. J. Taylor, P. E. Dai, J. F. Knifton and B. R. Martin, US Patent
5
637778, 1997.
Communication 9/02458A
1522
Chem. Commun., 1999, 1521–1522