Preparation of tertiary butyl alcohol using promoted cycloalkenyl iron catalyst

A method for preparing tertiary butyl alcohol wherein a solution of a tertiary butyl hydroperoxide feedstock comprising a solution of tertiary butyl hydroperoxide in tertiary butyl alcohol is charged to a hydroperoxide decomposition reaction zone containing a catalytically effective amount of a hydroperoxide decomposition catalyst consisting essentially of a mixture of a soluble cycloalkenyl iron compound with a soluble ruthenium compound, and is brought into contact with the catalyst in liquid phase with agitation under hydroperoxide decomposition reaction conditions to convert the tertiary butyl hydroperoxide to decomposition products, principally tertiary butyl alcohol.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the catalytic decomposition of tertiary butyl 
hydroperoxide (THHP). More particularly, this invention relates to a 
method for the preparation of tertiary butyl alcohol (TBA) by the 
catalytic decomposition of tertiary butyl hydroperoxide. Still more 
particularly, this invention relates to a method wherein a soluble 
cycloalkenyl iron compound promoted with a soluble ruthenium co-catalyst 
is used to catalyze the decomposition of tertiary butyl hydroperoxide to 
tertiary butyl alcohol. 
2. Prior Art 
It is known to react isobutane with oxygen, either thermally or 
catalytically, to form a peroxidation reaction product wherein the 
principal peroxide that is formed is tertiary butyl hydroperoxide. It is 
also known to thermally or catalytically decompose the tertiary butyl 
hydroperoxide to form tertiary butyl alcohol. 
In the text entitled "Organic Peroxides" edited by Daniel Swern (Wiley 
Interscience, a Division of John Wiley & Sons, New York), in Vol. II on 
page 157 it is stated that the metal-ion-catalyzed decomposition of 
primary hydroperoxides yields mainly alcohols, aldehydes and carboxylic 
acids, citing as an example the decomposition of hydroxymethyl 
hydroperoxide with aqueous ferrous sulfate to provide formaldehyde, formic 
acid and water. 
Quin U.S. Pat. No. 2,854,487 discloses the hydrogenation of hydrocarbon 
peroxides in the presence of hydrogen and palladium on activated alumina 
to provide carbinols. 
In Massie U.S. Pat. No. 3,775,472 a process is disclosed wherein alkyl 
substituted aromatic hydrocarbons are oxidized to products such as 
aromatic alcohols, aldehydes and carboxylic acids in the presence of 
ruthenium compounds. 
Grane U.S. Pat. No. 3,474,151 discloses that tertiary butyl alcohol starts 
to dehydrate at 450.degree. F. and to decompose at a "rapid rate" at 
temperatures above 475.degree. F. Grane discovered, however, that residual 
quantities of hydroperoxide contaminants present in tertiary butyl alcohol 
could be thermally decomposed by heating the contaminated tertiary butyl 
alcohol at a temperature of 375.degree. to 475.degree. F. for about 1 to 
10 minutes. 
Grane et al. U.S. Pat. No. 4,294,999 discloses a process wherein isobutane 
is oxidized in a pressured reactor in the presence of a solubilized 
molybdenum catalyst to provide a mixture of tertiary butyl alcohol, 
tertiary butyl hydroperoxide, methanol, acetone, and other 
oxygen-containing compounds. The tertiary butyl hydroperoxide is thermally 
decomposed under pressure at about 280.degree. F. to provide a tertiary 
butyl alcohol product containing only residual quantities of tertiary 
butyl hydroperoxide which are then decomposed in accordance with Grane 
U.S. Pat. No. 3,474,151 by heating the tertiary butyl alcohol at 
375.degree. to 475.degree. for about 1 to 10 minutes. Heating tertiary 
butyl alcohol containing small amounts of peroxides at high temperatures 
for even short periods of time to remove the peroxides produces 
undesirable products such as isobutylene. 
Grane et al. U.S. Pat. No. 4,296,262 discloses a related process wherein 
isobutane is reacted with oxygen in a reaction zone for a residence time 
of about 1 to 10 hours at a temperature of about 240.degree. to about 
340.degree. F. and a pressure of about 100 to about 1000 psig. in the 
presence of a catalytically effective amount of a soluble molybdenum 
catalyst. A liquid stream comprising tertiary butyl alcohol is recovered 
from the reaction mixture and fed to a decomposition zone wherein the 
tertiary butyl hydroperoxide contained therein is decompose by "hot aging" 
at 250.degree.-350.degree. F. at a pressure lower than the pressure in the 
oxidation zone. The tertiary butyl alcohol can be further subjected to a 
clean-up treatment at 375.degree.-475.degree. F. for 1 to 10 minutes. 
Worrell et al. in U.S. Pat. No. 4,296,263 disclose a related process 
wherein the feedstock is a mixture of normal butane with isobutane and 
wherein the oxidation catalyst is a soluble form of chromium, cobalt, 
nickel, manganese, molybdenum, or a mixture thereof. 
BACKGROUND INFORMATION 
In U.S. Pat. No. 3,505,360, Allison et al. disclose a method wherein an 
alkenyl hydroperoxide is decomposed in the presence of a catalyst based on 
a compound of a Group IV-A, V-A or VI-A metal. Taylor et al., in U.S. Pat. 
No. 4,508,923 disclose the use of a catalyst system comprising ruthenium 
and chromium for decomposing organic hydroperoxides. The use of a cobalt 
borate catalyst for the decomposition of hydroperoxides is disclosed in 
Sanderson et al. U.S. Pat. No. 4,547,598. 
Taylor et al. U.S. Pat. No. 4,551,553 is directed to a process for the 
formation of alcohols such as tertiary butyl alcohol by the catalytic 
decomposition of an organic hydroperoxide such as tertiary butyl 
hydroperoxide using a binary catalyst composed of a mixture of a ruthenium 
compound with a chromium compound. It is stated that the use of the binary 
catalyst eliminates the need for stabilizing ligands. 
Sanderson et al. disclose the use of a variety of catalysts for the 
decomposition of tertiary butyl hydroperoxide in a series of U.S. patents, 
including a catalyst composed of unsupported nickel, copper, chromia and 
iron (U.S. Pat. No. 4,704,482), a catalyst composed of iron, copper, 
chromia and cobalt (U.S. Pat. No. 4,705,903), a catalyst composed of a 
base treated hydrogenation catalyst from groups VIB or VIIIB of the 
Periodic Table (U.S. Pat. No. 4,742,179), a catalyst consisting 
essentially of nickel, copper, chromium and barium (U.S. Pat. No. 
4,873,380), a catalyst composed of a metal phthalocyanine promoted with a 
rhenium compound (U.S. Pat. No. 4,910,349), a catalyst composed of a base 
promoted metal phthalocyanine compound (U.S. Pat. No. 4,912,269), a 
catalyst composed of a soluble ruthenium compound promoted with a 
bidentate ligand (U.S. Pat. No. 4,912,033), a catalyst composed of a metal 
porphine such as iron (III) or manganese (III) promoted with an alkyl 
thiol or an amine, a catalyst composed of an imidazole promoted metal 
phthalocyanine compound (U.S. Pat. No. 4,912,266), (U.S. Pat. No. 
4,922,034), or a catalyst composed of a metal phthalocyanine promoted with 
a thiol and a free radical inhibitor (U.S. Pat. No. 4,922,035), a catalyst 
composed of a borate promoted metal phthalocyanine (U.S. Pat. No. 
4,922,036). 
Sanderson et al. also disclose that a catalyst composed of a soluble 
ruthenium compound and an iron compound such as a ferrous or ferric salt 
of an organic carboxylic acid (e.g., an acetate, a borate, a bromide, a 
chloride, a 1,3-propanedionate, a 2-ethylhexanoate, an iodide, a nitrate, 
a 2,4-pentanedionate, a perchlorate or a sulfate) in their U.S. Pat. No. 
5,025,113. 
When isobutane is reacted with molecular oxygen, the principal products of 
the reaction are tertiary butyl alcohol and tertiary butyl hydroperoxide. 
However, minor amounts of other contaminants are also formed. 
In addition, a minor amount of water will be formed, which will normally 
amount to about 0.5 to 1 wt. % of the reactor effluent. The amount of 
byproduct water that is produced is a function of the severity of the 
reaction conditions employed and will tend to increase as the severity of 
the reaction conditions is increased. 
A listing of the components present in a representative reaction product, 
and their nominal boiling points (NBP) is given in Table A. 
TABLE A 
______________________________________ 
Component NBP (.degree.C.) 
______________________________________ 
Isobutane -11.7 
Methyl formate 31.8 
Acetone 56.3 
Isobutylene oxide 60.0 
Isobutyraldehyde 64.1 
Methanol 64.7 
Methyl-t-butyl peroxide 
74.2 
Isopropyl alcohol 82.3 
Tertiary butyl alcohol 
82.4 
Ditertiary butyl peroxide 
111.0 
t-butyl-i-pr-peroxide 
124.0 
Tertiary butyl formate 
163.8 
______________________________________ 
The minor by-products are: sometimes difficult to remove. For example, 
tertiary butyl formate has a higher boiling point than ditertiary butyl 
peroxide but tends to distill overhead, which suggests that it forms a 
minimum boiling azeotrope with another component or components. 
As indicated, tertiary butyl hydroperoxide is useful as a raw material for 
the manufacture of tertiary butyl alcohol. The tertiary butyl alcohol can 
be formed by catalytic decomposition of the tertiary butyl hydroperoxide. 
In the Williams et al. process disclosed in U.S. Pat. No. 3,472,876, an 
oxygen-containing gas was charged to a reactor containing isobutane and an 
oxidation catalyst to provide a reaction mixture comprising tertiary butyl 
alcohol, tertiary butyl hydroperoxide, acetone, and tertiary butyl ether. 
The reported results in the patent indicate that there was a comparatively 
low rate of conversion and a comparatively poor selectivity of the 
reaction to tertiary butyl alcohol. 
SUMMARY OF THE INVENTION 
A feedstock for the present invention is suitably one formed by the 
oxidation of isobutane with molecular oxygen to provide an oxidation 
reaction product containing a solution of tertiary butyl hydroperoxide and 
tertiary butyl alcohol in unreacted isobutane. The feedstock for the 
present invention may comprise tertiary butyl hydroperoxide dissolved in 
tertiary butyl alcohol and is recovered from the isobutane oxidation 
reaction product by distillation. The feedstock is charged to a catalytic 
decomposition zone wherein the tertiary butyl hydroperoxide is decomposed 
in the presence of a soluble cycloalkenyl iron compound to provide a 
decomposition reaction product characterized by a high conversion rate and 
a high selectivity of tertiary butyl hydroperoxide to tertiary butyl 
alcohol. 
The tertiary butyl alcohol will not be the only decomposition product that 
is formed. Minor amounts of other oxygen-containing materials such as 
those listed above will also be formed. 
The tertiary butyl alcohol that is recovered from the decomposition 
reaction mixture will be contaminated with the oxygenated impurities. 
DESCRIPTION OF THE PROCESS OF THE PRESENT INVENTION 
The starting materials for the process of the present invention are a 
tertiary butyl hydroperoxide feedstock and a catalyst system composed of a 
soluble cycloalkenyl iron compound promoted with a soluble ruthenium 
compound. 
The Tertiary Butyl Hydroperoxide Feedstock 
The feedstock to be used in accordance with the present invention is a 
tertiary butyl alcohol solution of tertiary butyl hydroperoxide that 
preferably contains from about 5 to about 30 wt. % of tertiary butyl 
hydroperoxide. As indicated, the feedstock is suitably prepared by the 
oxidation of isobutane to form an oxidation product from which a feedstock 
of the present invention can be recovered by distillation. 
The Catalyst System 
The catalyst system to be used in accordance with the present invention is 
a hydroperoxide decomposition catalyst consisting essentially of a soluble 
cycloalkenyl iron compound promoted with a soluble ruthenium compound. 
The soluble cycloalkenyl iron compound may suitably consist essentially of 
an alkylcycloalkadienyl iron compound or a cycloalkenyl iron carbonyl. 
Soluble alkylcycloalkadienyl iron compounds include compounds such as 
bis(pentamethylcyclopentadienyl) iron, a compound having the formula: 
##STR1## 
Soluble cycloalkenyl iron carbonyl compounds include dimers such as 
cyclopentadienyl iron dicarbonyl dimer having the formula: 
##STR2## 
Also included cylcoalkenyl iron tricarbonyls such as cyclohexadiene iron 
tricarbonyl and cyclooctatetraene iron tricarbonyl. The formula for 
cyclohexadiene iron tricarbonyl is: 
##STR3## 
The formula for cyclooctatetraene iron tricarbonyl is: 
##STR4## 
The Soluble Ruthenium Compound 
The soluble ruthenium compounds to be used in accordance with the present 
invention are selected from the group consisting of ruthenium salts of 
mineral acids and organic carboxylic acids. For example, the ruthenium 
compound may be a salt of a mineral acid, such as ruthenium (III) chloride 
hydrate, ruthenium (III) bromide, ruthenium (III) iodide, 
tricarbonylruthenium nitrate, or as a salt of a suitable organic 
carboxylic acid such as, for example, ruthenium (III) acetate, ruthenium 
naphthenate, ruthenium valerate and ruthenium complexes with 
carbonyl-containing ligands such as ruthenium(III) acetylacetonate. 
Additional examples of ruthenium compounds include ruthenium octonate, 
ruthenium laurate, ruthenium stearate, ruthenium linoleate, ruthenium 
nitrate, triruthenium dodecacarbonyl (i.e., dodecacarbonyl), ruthenium 
sulfate and ruthenium pentacarbonyl. 
From about 0.01 to about 10 parts by weight of soluble ruthenium compound 
should be employed per part of soluble cycloalkenyl iron compound, e.g., 
from about 0.1 to about 3 parts by weight of soluble ruthenium compound 
per part by weight of soluble iron compound and more preferably from about 
0.1 to about 2 parts by weight of soluble ruthenium compound per part by 
weight of soluble iron compound. 
Stated differently, the combination of the soluble cycloalkenyl iron 
compound with the soluble ruthenium compound may be utilized in the weight 
ratio of iron to ruthenium of 0.01:1 to 100:1. Preferably, the 
iron/ruthenium weight ratio is in the range of about 1:1 to about 10:1. 
Stated in a still different manner, the concentration of iron in the 
tertiary butyl hydroperoxide feedstock may vary widely, constituting for 
example, about 0.001 to about 5 wt. % of the weight of the tertiary butyl 
hydroperoxide feedstock and the ruthenium compound may be present in the 
ratio of about 0.1 to about 3 parts by weight of soluble ruthenium 
compound per part of soluble cycloalkenyl iron compound. In general, the 
catalyst system of the present invention may be advantageously present in 
the tertiary butyl hydroperoxide feedstock in an amount, based on the iron 
compound, of about 0.01 to about 5,000 ppm of soluble cycloalkenyl iron 
compound and the ruthenium compound may be present in the ratio of about 
0.1 to about 3 parts by weight of soluble ruthenium compound per part of 
soluble cycloalkenyl iron compound. 
Catalytic Decomposition of Tertiary Butyl Hydroperoxide 
The process of the present invention may be conducted batchwise in kettles 
or by continuously passing the reactants through a tubular reactor. 
The catalytic decomposition of the tertiary butyl hydroperoxide is 
preferably conducted at a temperature within the range of about 25.degree. 
to about 250.degree. C. and, more preferably, at a temperature within the 
range of about 40.degree. to about 150.degree. C. The reaction is 
preferably conducted at autogenous pressure although superatmospheric 
pressures up to about 1000 psig. may be used, if desired. 
Flow rates of the charge solution to the reaction zone should be adjusted 
in order to provide an appropriate contact time within the reactor. In a 
batch process, the holding time may suitably be from about 0.5 to about 10 
hours, and more preferably about 1 to 3 hours. 
In accordance with the most preferred embodiment of the present invention, 
isobutane is reacted with oxygen in an oxidation zone under oxidation 
reaction conditions including a temperature of about 135.degree. to about 
155.degree. C., a pressure of about 300 to about 800 psig., and a holding 
time of about 2 to about 6 hours to provide an initial oxidation reaction 
product comprising unreacted isobutane, tertiary butyl hydroperoxide, 
tertiary butyl alcohol, and oxygen-containing by-products. The oxidation 
reaction product is fractionated in any appropriate manner (e.g., by 
distillation in a distillation zone) to remove the isobutane therefrom for 
recycle and to provide a solution of tertiary butyl hydroperoxide and 
tertiary butyl alcohol which will normally contain from about 5 to about 
30 wt. % of tertiary butyl hydroperoxide. If the tertiary butyl 
hydroperoxide concentration is excessive, additional tertiary butyl 
alcohol may be added. 
The tertiary butyl alcohol solution of tertiary butyl hydroperoxide is then 
charged to a catalytic hydroperoxide decomposition zone where it is 
brought into contact with a co-catalyst consisting essentially of a 
cycloalkenyl iron compound and the soluble ruthenium compound to convert 
the tertiary butyl hydroperoxide to tertiary butyl alcohol with high 
yields and selectivities. 
The reaction product from the tertiary butyl hydroperoxide decomposition 
step may then be fractionated in any suitable manner, such as by 
extractive distillation to recover the tertiary butyl alcohol.