Process for the production of unsymmetrical tert-dialkyl ethers

A method for preparing unsymmetrical dialkyl ethers and derivatives thereof. The ethers are prepared by reacting a C.sub.1 to C.sub.3 aliphatic alcohol with a tertiary alcohol in the presence of a novel catalyst comprised of a transition metal pillared interlayered clay having generally separated layers wherein the interlayer distances are substantially greater than a precursor of the same but non-separated clay and wherein the product includes multimetallic pillars comprised of a cationic polymeric complex of the formula: EQU Al.sup.iv (Al.sub.12-x M.sub.x).sup.vi O.sub.4 (OH).sub.24.sup.a+ where x is a number from 1 to 6; a depends on the selection of M and N; N is selected from Al.sup.3+, Si.sup.4+, Ga.sup.3+, Ge.sup.4+, As.sup.5+, P.sup.5+, Cr.sup.3+, Fe.sup.3+, V.sup.5+, Ru.sup.3+, Ru.sup.4+, N.sup.3+ ; and M is selected from a metal from Groups 5B, 6B, 7B and 8 of the 4th, 5th and 6th Periods of the Periodic Table of the Elements.

FIELD OF THE INVENTION 
The present invention relates to the preparation of unsymmetrical dialkyl 
ethers and derivatives thereof. The ethers are prepared by use of a novel 
catalyst comprised of a transition metal pillared interlayered clay. 
BACKGROUND OF THE INVENTION 
Motor gasoline formulations are expected to change in order to meet ever 
restrictive governmental regulations and competition from alternative 
fuels, such as methanol. One requirement of these reformulated gasolines 
is that they be substantially reduced in aromatics compounds, such as 
benzene. Furthermore, it is expected that governmental regulations will 
also substantially restrict the amount of light hydrocarbons which can be 
present, thus establishing the requirement that the gasoline be low in 
emissions. 
While the removal of aromatics from gasolines is beneficial from an 
environmental point of view, their removal represents a substantial debit 
on motor octane number. This leaves the refiner in a position of finding a 
suitable substitute for aromatics from an octane number point of view, but 
which also meets the low emissions requirement. 
One class of compounds which have been proposed for reformulated gasolines 
are oxygenates, such as the unsymmetrical dialkyl ethers, particularly 
methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and 
tert-amyl methyl ether (TAME). If such compounds are to be extensively 
used in reformulated gasolines, then new and improved methods of their 
manufacture will be needed. 
Conventional methods of manufacture of such ethers are typically based on 
liquid-phase reactions, such as the reaction of iso-butylene with methanol 
over cation-exchanged resins (e.g. Amberlyst 15. See Hydrocarbon 
Processing, Oct. 1984, p. 63). Metal exchanged conventional clays have 
been used to make ethers, such as the reaction of 1-alkenes to 
bis-sec-alkyl ethers (Adams, et al., J. Catalysis, 58, p. 252 (1979)); the 
reaction of ethanol with hex-1-ene (Ballantine et al., J. Mol. Catalysis, 
26, p. 37 (1984)). However, in a comparison of ether formation from 
pentanol over exchanged and pillared clays, the pillared clays were much 
less active than the non-pillared clay catalysts (Diddams, et al., J. 
Chem. Soc. Chem. Commun., p. 1340 (1984)). The projected shortage of 
isobutylene, and other C.sub.4 and C.sub.5 unsaturates as raw materials, 
provides an incentive for finding alternative reactions for producing such 
ethers. 
One such alternative method is taught in U.S. Pat. No. 4,503,263 wherein an 
olefin and water in the gas phase, are reacted over a solid heterogeneous 
C.sub.10 to C.sub.18 perfluorinated alkanesulfonic acid superacid in the 
olefin and the water in the gas phase, but below about 120.degree. C. 
Other alternative approaches can be found in U.S. Pat. Nos. 4,822,921 and 
4,827,048 wherein tertiary butyl alcohol is reacted with methanol. In 
accordance with the '921 patent, these alcohols are reacted in the 
presence of a catalyst comprised of an inert support, such as titania, 
having a phosphoric acid impregnated thereon. The catalyst of the '048 
patent is a heteropolyacid, such as 12-tungstophosphoric acid or 
12-molybdophosphoric acid, on an inert support, such as titania. 
Also, copending application, having an Attorney Docket No. of OP-3637, 
entitled "PROCESS FOR THE PRODUCTION OF UNSYMMETRICAL TERT-DIALKYL 
ETHERS", discloses a process for preparing the unsymmetrical tert-dialkyl 
ethers by use of a catalyst comprised of boron trifluoride hydrates on 
porous inorganic supports. 
While such alternative processes for producing ethers, such as MTBE, show 
promise and may have some commercial value, there is still a need in the 
art for other alternative processes for producing this potentially 
important class of ethers. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a process for 
preparing unsymmetrical dialkyl ethers, wherein one of the alkyl groups is 
a tertiary group, which process comprises reacting a C.sub.1 to C.sub.3 
aliphatic alcohol with a tertiary alcohol, in the presence of a catalyst 
comprised of a transition metal pillared interlayered clay having 
generally separated layers wherein the interlayer distances are 
substantially greater than a precursor of the same but non-separated clay. 
An example is one wherein the product includes multimetallic pillars 
comprised of a cationic polymeric complex of the formula: 
EQU N.sup.iv (Al.sub.12-x M.sub.x).sup.vi O.sub.4 (OH).sub.24.sup.a+ 
where N is selected from Al.sup.3+, Si.sup.4+, Ga.sup.3+, Ge.sup.4+, 
As.sup.5+, P.sup.5+, Cr.sup.3+, Fe.sup.3+, V.sup.5+, Ru.sup.3+, Ru.sup.4+, 
Ni.sup.3+ ; and M is selected from Groups 5B, 6B, 7B and 8 of the 4th, 5th 
and 6th Periods of the Periodic Table of the Elements. These metals 
include V, Cr, Mn, Fe, Co, Ni, Nb, Mo, Te, Ru, Rh, Pd, Ta, W, Re, Os, Ir, 
an Pt. The value for "x" may be from 1 to 6 and "a" will depend on the 
nature of the metal substitutions. 
In preferred embodiments of the present invention, N is Al , or Al and Ru, 
and M is selected from V, Cr, Mn, Fe, Co, Ni or a mixture thereof. 
Another form of metal pillared clay is one that is exchanged with a metal 
cation solution after the Al.sub.13 pillar is set. 
Small spacing metal pillared materials have been described in U.S. Pat. No. 
4,465,892 and by Brindley and Yamanaka (Clays and Clay Minerals, vol. 26, 
p.21 (1978); Amer. Mineralogist, vol. 64, p. 830 (1979)). Larger spacing 
metal oxide pillared materials have been described in U.S. Pat. No. 
4,665,044. The many other possibilities in this system have been described 
in a review by Vaughan (Amer. Chem. Soc. Symp. Proc., vol. 368, p. 308 
(1988)). 
It is further recognized that reaction of the forementioned metal modified 
(Al.sub.13-x M.sub.x) clustered at temperatures between 60.degree. and 
120.degree. C. may react to form smaller or larger polymers. Some of these 
may be more representative of hydrocalcite, or gibbsite type fragments 
having compositions in the range of M.sub.(3-x) Al.sub.x (OH).sub.6.sup.+ 
or Al.sub.2 M(OH.sub.6).sup.2+, where M is a divalent metal. Clusters of 
this type, or other clusters of a similar composition and cluster sizes, 
may have pillar spacings in the range of about 5 to 7 .ANG., giving 
pillared clay basal spacings in the range (001)=14.ANG. to 16 .ANG.. 
Alternatively, such reactions may generate larger polymer clusters and 
produce pillar spacings greater than about 8 .ANG. to yield pillared clays 
having basal spacings with (001) greater than about 18 and up to about 30 
.ANG.. 
The reaction can be represented by: 
##STR1## 
where each R is independently a C.sub.1 to C.sub.5 alkyl group; and 
R.sub.1 is methyl, ethyl, propyl or butyl. 
In another preferred embodiment of the present invention, two of the R 
groups are methyl and the third is selected from methyl, ethyl, and 
propyl. 
In yet another preferred embodiment of the present invention, two of the R 
groups are methyl and the third is methyl or ethyl. 
DETAILED DESCRIPTION OF THE INVENTION 
The high octane/low emissions unsymmetrical dialkyl ethers of the present 
invention are those wherein one of the alkyl groups is a tertiary group. 
They are synthesized from alcohols, instead of iso-butylene aliphatic 
alcohol mixtures. The synthesis of these ethers is accomplished using a 
unique catalyst system with two classes of alcohols. One class of alcohol 
is an aliphatic alcohol represented by R.sub.1 OH, where R.sub.1 is a 
C.sub.1 to C.sub.3 aliphatic alkyl group, preferably a methyl or ethyl 
group, more preferably a methyl group. The other class of alcohols are 
tertiary alcohols represented by: 
##STR2## 
where each R is independently a C.sub.1 to C.sub.5 alkyl group, with the 
proviso that the total number of carbons not exceed about 7. Preferred is 
when two of the R groups is methyl and the other is selected from the 
group consisting of methyl, ethyl, propyl, or butyl. More preferred is 
when the other R group is a methyl or ethyl group. 
The catalysts used in the synthesis of the ethers of the present invention 
are prepared from naturally occurring and synthetic smectites which may be 
visualized as a sandwich comprising two outer layers of silicon tetrahedra 
and an inner layer of aluminum octahedral. These clays are generally 
represented by the general formula: 
EQU (Si.sub.8).sup.iv (Al.sub.4).sup.vi O.sub.20 (OH).sub.4 
where the iv designation indicates an ion coordinated to four other ions, 
and the vi designates an ion coordinated to six other ions. The iv 
coordinated ion is commonly Si.sup.4+, Al.sup.3+, or Fe.sup.3+, but could 
also include several other four-coordinate ions, e.g., P.sup.5+, B.sup.3+, 
Ga.sup.3+, Cr.sup.3+, Ge.sup.4+, Be.sup.2+, et. The vi coordinated ion is 
typically Al.sup.3+ or Mg.sup.2+, but could also include many other 
possible hexacoordinate ions, e.g., Fe.sup.3+, Fe.sup.2+, Ni.sup.2+, 
Co.sup.2+, Li.sup.+, Cr.sup.3+, V.sup.2+, etc. The charge deficiencies 
created by substitutions into these cation positions are balanced by one 
or more cations located between the structure's platelets. Water may be 
occluded between the layers and either bonded to the structure itself or 
to the cations as a hydration shell. Commercially available clays of this 
type include bentonite, montmorillonite, hectorite, beidellite, 
nontronite, and a host of other smectite materials, from hundreds of 
localities, often having local names and specific compositions. 
Normally, the clay structure yields repeating plates every 9 .ANG. or 
thereabouts. Much work has been done to demonstrate that these platelets 
may be separated further, i.e., interlayered, by insertion of various 
polar molecules such as water, ethylene glycol, various amines, etc,. and 
that the platelets can be separated by as much as 30 to 40 .ANG.. 
The catalyst of the present invention may be obtained by reacting smectite 
type clays with polymeric cationic multimetal complexes. Such compositions 
are extensively discussed in U.S. Pat. No. 4,666,877 which is incorporated 
herein by reference. 
The pillared interlayered clays of the present invention possess an 
internal microstructure which may be established by introducing discrete 
and non-continuous inorganic oxide particles or pillars having a length 
between about 5 and 20 .ANG., between the clay layers. These pillars serve 
to hold the space between the clay layers open after removal of included 
water and serve to form an internal interconnected micropore structure 
throughout the inner layer in which the majority of the pores are less 
than about 30 .ANG. in diameter. The product interlayered clay may be 
produced by reacting a naturally occurring or synthetic smectite type clay 
with a polymeric cationic hydroxy multimetal complex, the complex being 
produced by reacting certain metal-containing compounds with materials 
such as aluminum chlorohydroxide complexes ("chlorhydrol", Reheis Chemical 
Co.), and heating to convert the hydrolyzed polymer complex into an 
inorganic multimetal oxide. The polymeric cationic hydroxy multimetal 
complex may be, of course, produced in a variety of other ways, including 
introducing additional metals into the initial aluminum solutions used in 
the polymer synthesis. 
One method of obtaining the novel pillared interlayered clay catalysts of 
the present invention is to use the following general procedure: 
(1 ) a cationic polymer of the type believed to be (Al.sub.13 O.sub.4 
(OH).sub.24).sup.7+, having a globular structure as first described by 
Johansen, Acta. Chem. Scand., v. 14 (1960), p. 771, is reacted in aqueous 
solution with a 4th, 5th or 6th period transition metal salt. These will 
primarily be from Groups 5B, 6B, 7B and 8 of the Periodic Table. The base 
multiatomic complex is thought to be of the type: 
EQU Al.sup.iv Al.sub.12.sup.vi O.sub.4 (OH).sub.24).sup.7+ 
In one form of the present invention, one or more of the noted elements may 
be substituted into either or both of the iv or vi coordinate Al sites in 
this molecular cluster. The general formula for the substituted molecule 
may be represented as: 
EQU N.sup.iv (Al.sub.12-x M.sub.x).sup.vi O.sub.4 (OH).sub.24.sup.+a 
where N is selected from Al.sup.3+, Si.sup.4+, Ga.sup.3+, Ge.sup.4+, 
As.sup.5+, P.sup.5+, Cr.sup.3+, Fe.sup.3+, V.sup.5+, Ru.sup.4+, Ni.sup.3+ 
; and M is selected from one or more of the elements of Groups 5B, 6B 7B, 
and 8 of the 4th, 5th, or 6th Periods of the Periodic Table (see 
Kirk-Othmer Encyclopedia of Chemical Technology, 2nd Ed., vol. 8, (1965) 
for complete definition). The value for "x" may be from about 1 to about 
6. The value for "a" depends upon the nature of the metal substitutions. 
Representative multimetal cationic polymer complexes include: 
EQU (Fe.sup.iv (Al.sub.10 Cr.sub.2).sup.vi O.sub.4 (OH).sub.24).sup.7+ 
EQU (Al.sup.iv (Al.sub.9 Fe.sub.3).sup.vi O.sub.4 (OH).sub.24).sup.7+ 
EQU (Al.sup.iv (Al.sub.10 Ni.sub.2).sup.vi O.sub.4 (OH).sub.24).sup.5+ 
Obviously, such substitutions may change the charge on the polymer 
molecules. Depending upon the pH of the solution, such multimetallic 
molecules may be hydrolyzed to produce lower charged species as indicated 
by Vaughan et al, Proc. 5th Intl. Zeolite Confi, (1980), p. 94. 
Another method for producing (Al.sub.13).sup.7+ substituted derivatives is 
discussed below and may be used as an alternative to beginning with a 
commercial solution of lower aluminum chlorhydrol. 
(2) A smectite clay is mixed with the aqueous solution of polymeric 
cationic hydroxy multiatomic complex formed in step (1), in amounts so 
that the weight ratio of clay to metal complex solution is from about 1:2 
to 1000. The metal complex solution will preferably contain from about 1 
to about 40%, by weight, of solids in a suitable liquid medium such as 
water. 
(3) The mixture of clay and metal complex is maintained at a temperature of 
about 5.degree. C. to about 200.degree. C. for a period of 0.1 to 4.0 
hours. 
(4) The reacted clay solids are recovered and heated at a temperature of 
from about 200.degree. to about 700.degree. C. to decompose the hydrolyzed 
metal complex to a pillar believed to be of multiple metallic oxides or 
hydroxides. 
Depending on the nature of the reactant metal salts, the reactant 
concentrations and aging temperatures and pressures, alternative complexes 
may be formed in this reaction system to yield either larger or smaller 
metallic or multimetallic clusters. 
After "setting" the pillar by calcination, it is possible to further 
increase the metal concentration between the layers of the pillared clay 
by exchanging said pillared clay with a solution containing cations of the 
metal to be exchanged. For example, by exchanging said pillared clay with 
a one tenth molar solution of CrC.sub.13, the chromium content of said 
pillared clay could be increased. Such post-exchange is also a way to 
control the residual acidity of the catalyst, as the metal cation will be 
titrating residual acidic protons in the pillared clay catalyst 
interlayer. 
The pillared clay catalysts of the present invention may also be treated 
with a solution of BF.sub.3 .cndot.xH.sub.2 O, where x is 1 or 2. The 
pillared clay is treated with an aqueous solution of the above boron 
trifluoride hydrate by any suitable impregnation technique at an effective 
temperature and time which results in the desired degree of impregnation. 
Typical temperatures will range from about 0.degree. C. to about 
70.degree. C., preferably from about 20.degree. C. to about 35.degree. C. 
Typical times will range from about 5 minutes to about 300 minutes, 
preferably from about 10 minutes to about 30 minutes. 
The ethers of the present invention can be produced by first preparing a 
mixture of the tertiary alcohol and aliphatic alcohol. The alcohol mixture 
is then introduced into a suitable reaction vessel containing the catalyst 
wherein the reaction is conducted at a temperature from about ambient 
temperature (about 22.degree. C.) to about 200.degree. C., preferably from 
about 80.degree. to 140.degree. C., and a pressure from about 0 psig to 
about 1000 psig, preferably from about 150 psig to about 350 psig. A 
preferred type of reaction vessel is a tubular reactor. The reaction is 
conducted at an effective liquid hourly space velocity (LHSV). Such space 
velocities will normally range from about 0.5 to 10 LHSV, preferably from 
about 1 to 4 LHSV.

The following examples are presented for illustrative examples and are not 
to be considered as limiting the scope of the present invention in any 
way. 
EXAMPLE 1 
A chromium aluminum pillared clay was prepared from a commercial smectite 
clay (Bentolite L, Georgia Kaolin Co.). After first dissolving 53.2 gm 
(0.2 mole) CrCl.sub.3 .cndot.6H.sub.2 O in 42 gm H.sub.2 O then adding 42 
gm of a commercial 50 wt. % solution of the [Al.sub.13 ].sup.7+ polymer 
("chlorhydrol" Reheis Chemical Co.), followed by aging at room temperature 
for three days, 125 gm of the resulting blue solution was reacted with 5 
gm Bentolite L at room temperature for 18 hours, at which time the product 
was vacuum filtered, and the filter coke washed with deionized water until 
the filtrate was colorless. This product was then freeze dried, then 
calcined at 450.degree. C. X-ray diffraction analysis showed that the 
larger spacing (001) was 14.8 .ANG.. To a 100 ml stirred batch reactor was 
added 200 mg of the Cr--Al pillared clay together with 5.51 gm (0.063 
mole) tert-amyl alcohol and 3.96 gm (0.124 mole) methanol. After reacting 
the contents at 140.degree. C. for 1 hour with stirring, the products were 
removed and analyzed by gas chromatography. The results are given in Table 
I below, showing moderate selectivity for TAME production and high 
selectivity for 2-methyl butenes at very high conversions for tert-amyl 
alcohol. 
EXAMPLE 2 
A cobalt-alumina pillared clay catalyst was made using the general method 
of Example 1 above, but using 46 gm CoCl.sub.2 .cndot.6H.sub.2 O dissolved 
in 46 gm H.sub.2 O in place of the CrCl.sub.3 solution. X-ray diffraction 
analysis showed the main basal reflection (001) to be a strong broad peak 
with a position at half maximum at 18.8 .ANG.. Chemical analysis gave a 
composition of 72.2 wt. % SiO.sub.2 ; 25.21 wt. % Al.sub.2 O.sub.3 and 
0.31 wt. % CoO compared to a base Bentolite L composition of 76.66 wt. % 
SiO.sub.2 and 16.77 wt. % Al.sub.2 O.sub.3 (all dry basis values). This 
represents an Al/Co ratio of about 35 in the pillar. Reacting 200 mg of 
this catalyst as described in Example 1 yielded the products shown in 
Table I, indicating high conversions and good selectivity for TAME. 
EXAMPLE 3 
A nickel-aluminum pillared clay catalyst was made using the general method 
of Example 1, but using 47.4 gm NiCl.sub.2 .cndot.6H.sub.2 O dissolved in 
42 gm H.sub.2 O in place of the CrCl.sub.3 solution. X-ray diffraction 
analysis of the product showed a very broad strong peak between 20 .ANG. 
and 14.8 .ANG., with the position at half maximum at 16.4 .ANG.. Chemical 
analysis gave 72.97 wt. % SiO.sub.2, 23.39 wt. % Al.sub.2 O.sub.3 and 1.29 
wt. % NiO, representing an Al/Ni ratio of 8.4 in the pillar. Reacting this 
catalyst in the identical manner to those in Examples 1 and 2 above 
yielded the results shown in Table I below, showing very high conversion 
and good TAME selectivity. 
EXAMPLE 4 
54 gm. FeCl.sub.3 .cndot.6H.sub.2 O were dissolved in 42 gm H.sub.2 O; the 
solution was filtered then added to 42 gm 50 wt. % Al.sub.13 chlorhydrol 
solution (Reheis Chemical Co.) and aged for 90 minutes at room 
temperature. To the resultant soft gel were added 42 gm H.sub.2 O with 
vigorous homogenization, then 5 gm Bentolite L. This was then freeze 
dried, yielding a catalyst having no X-ray diffraction peaks. Such a 
material comprises a highly delaminated clay admixed with an iron-aluminum 
oxide colloid. Such materials are said to have a "house-of-cards" 
structure, with little microporosity characteristic of pillared clays, and 
appreciable mesoporosity. Reacting this catalyst (Fe-clay) in the reaction 
described in Example 1 showed it to have low activity and poor selectivity 
(Table I below), confirming that the microporous properties of the metal 
pillared clay is important for improved catalytic performance. 
TABLE I 
______________________________________ 
Products Produced from the Reaction of 
Tert-Amyl Alcohol and Methanol 
Tert-amyl 
TAME 2-Me-Butenes 
Alcohol 
Example 
Catalyst (Mol %) (Mol %) Conversion 
______________________________________ 
1 Cr-PILC* 18.9 77.0 95.9 
2 Co-PILC 28.2 40.0 68.2 
3 Ni-PILC 30.1 46.6 76.7 
4 Fe-Clay 18.1 22.4 40.5 
______________________________________ 
*PILC = pillared clay 
EXAMPLE 5 
To a 100 mL stirred batch reactor is added either the Ni-PILC, made as 
described in Example 3, or a post-exchanged Ni-pillared clay [Ni(PILC)] 
made by exchanging 5 gm Al-PILC (typical of U.S. Pat. No. 4,271,043) with 
a solution of 2 gm NiO.sub.2 .cndot.6H.sub.2 O dissolved in 40 gm H.sub.2 
O for 10 minutes at room temperature, followed by calcination for 1 hour 
at 400.degree. C. X-ray diffraction analysis showed this to have a larger 
spacing (001) of 18.5 .ANG.. (0.200 g), tert-amyl alcohol (5.51 g, 0.063 
mol) and methanol (3.96 g, 0.124 mol). The contents are then sealed and 
heated to 140.degree. C. with stirring for 1 hr. The exchanged Ni-PILC of 
Example 3 enhances tert-amyl alcohol conversion and TAME production (see 
Table II below). This implies that the pre-exchanged transition-metal 
pillared clays are more acidic than their post-exchanged counterparts, 
indicating that the Ni.sup.2+ post exchange titrates residual proton sites 
with Ni.sup.2+. 
TABLE II 
______________________________________ 
Effect of Transition-Metal Pillaring Preparation 
2-Me- Tert-amyl 
TAME Butenes 
Alcohol 
Catalyst 
Preparation (Mol %) (Mol %) 
Conversion 
______________________________________ 
Ni-PILC Pre-exchanged 
30.1 46.6 76.7 
Ni(PILC) 
Post-exchanged 
11.6 22.4 34.0 
______________________________________ 
EXAMPLE 6 
In a 100 mL stirred batch reactor the Cr-PILC, made as described in Example 
1 (0.200 g), was reacted with various ratios of methanol/tert-amyl 
alcohol. The C.sub.5 carbocation is more likely to undergo attack by MeOH 
compound. Thus TAME yields increase (nucleophilic pathway) while the 
formation of 2-Me-butenes decrease (elimination pathway) without loss in 
overall conversion (see Table III below). 
TABLE III 
______________________________________ 
Increased MeOH/Tert-Amyl Alcohol Ratio 
Increases TAME Selectivity with the CR-PILC 
Tert-amyl 
MeOH/Tert-amyl Alcohol 
TAME 2-Me-Butenes 
Alcohol 
(eq) (Mol %) (Mol %) Conversion 
______________________________________ 
2 18.9 77.0 95.9 
5 40.0 53.2 93.2 
10 47.4 43.9 91.3 
______________________________________ 
EXAMPLE 7 
To a 100 mL stirred batch reactor is added the Cr-PILC, made as described 
in Example 1 (0.200 g), tert-amyl alcohol (5.51 g, 0.063 mol) and methanol 
(3.96 g, 0.124 mol). The contents are then sealed and heated at various 
temperatures with stirring for 1 hr (see Table IV below). As the 
temperature increases, the C.sub.5 carbocation is less stable and more 
prone to elimination pathways producing more 2-Me-butenes. Although lower 
reaction temperatures favors TAME selectivity, tert-amyl alcohol 
conversion decreases. Longer reaction times at lower temperatures should 
show greater conversion and increased TAME selectivities. 
TABLE IV 
______________________________________ 
TAME Selectivity Increases as 
Temperatures Decreases with the Cr-PILC 
Tert-amyl 
TAME 2-Me-Butenes 
Alcohol 
Temperature 
(Mol %) (Mol %) Conversion 
Selectivity 
______________________________________ 
90 10.1 6.1 16.1 62.7% 
120 40.1 36.4 76.5 52.4% 
140 18.9 77.0 95.9 19.7% 
______________________________________