CATEGORY: DEHYDROGENATION
PATENT
Dehydrogenation Processes and Phenol Compositions
(ExxonMobil Chemical Patents Inc)
United
States Patent Application 20130296614
Inventors:
Kuechler, Keith H. (Friendswood, TX, US)
Benitez, Francisco M. (Cypress, TX, US)
Application Number:
13/814873
Publication Date:
11/07/2013
Assignee:
ExxonMobil Chemical Patents Inc. (Baytown, TX, US)
Abstract:
Described herein is a process for producing
phenol in which (a) benzene and hydrogen are contacted with a hydroalkylation
catalyst under hydroalkylation conditions to produce cyclohexylbenzene; (b) the
cyclohexylbenzene is contacted with an oxidation catalyst under oxidation
conditions to produce cyclohexylbenzene hydroperoxide; (c) the
cyclohexylbenzene hydroperoxide is contacted with a cleavage catalyst under
cleavage conditions to produce a cleavage effluent comprising phenol and
cyclohexanone; (d) the cyclohexanone is contacted with a dehydrogenation
catalyst under dehydrogenation conditions to produce a dehydrogenation effluent
having at least a portion of the cyclohexanone and a first contaminant; and (e)
the first contaminant is contacted with an acidic material under contaminant
treatment conditions to convert at least a portion of the first contaminant
into a converted first contaminant. Phenol compositions made from the
above-described process are also described herein.
FIELD
The present invention relates to methods for dehydrogenating cyclohexanone to
produce phenol, and compositions produced from same.
BACKGROUND
Phenol is an important product in the chemical industry and is useful in, for
example, the production of phenolic resins, bisphenol A, ε-caprolactam, adipic
acid, and plasticizers.
Currently, the most common route for the production of phenol is the Hock
process. This is a three-step process in which the first step involves
alkylation of benzene with propylene to produce cumene, followed by oxidation
of the cumene to the corresponding hydroperoxide and then cleavage of the
hydroperoxide to produce equimolar amounts of phenol and acetone.
However, the various steps involved in the production of phenol and acetone
from cumene can produce various contaminants that are difficult to separate
from the desired phenol and acetone products. Examples of these contaminants
may include hydroxyacetone, mesityl oxide, 2-methylbenzofuran, acetophenone,
alpha-methylstyrene, cumene, 2-phenylpropanal.
These contaminants, if left in the phenol product, may cause difficulties in
downstream processing, or render the phenol unusable for such downstream
processing, for example in the subsequent production of bis-phenols and
polycarbonates. Therefore, techniques have been proposed to remove those
contaminants involving certain treatments. For example, U.S. Pat. No. 5,064,507
discloses obtaining high purity phenol from cleavage of cumene hydroperoxide
through one or more amine treatment steps. The phenol mixture includes at least
0.5 wt % to no greater than 10 wt % of alpha-methylstyrene, and further
includes acetol, 2-phenyl-propionaldehyde (2PPA), methyl-benzofuran (MBF),
mesityl oxide (MO) and carbonyl impurities. In addition, U.S. Pat. No.
3,322,651 discloses a method of producing phenol made by decomposition of
cumene hydroperoxide. The phenol is purified by contacting the carbonyl
compounds with a nitrogen compound.
The production of phenol from cyclohexylbenzene is an emerging technology,
interesting in that it co-produces cyclohexanone rather than acetone.
Cyclohexylbenzene can be produced, for example, by direct alkylation of benzene
with cyclohexene, or as disclosed in U.S. Pat. No. 6,037,513, by contacting
benzene with hydrogen in the presence of a catalyst. The cyclohexylbenzene can
then be oxidized to the corresponding hydroperoxide and the peroxide cleaved to
phenol and cyclohexanone using an acidic cleavage catalyst.
One problem of producing phenol by way of the cleavage of cyclohexylbenzene hydroperoxide
is that the cyclohexanone and phenol produce an azeotropic mixture composed of
28 wt % cyclohexanone and 72 wt % phenol. Thus, any attempt to separate the
cleavage effluent by simple distillation results in this azeotropic mixture. To
obviate this problem it has been proposed to integrate the cyclohexylbenzene
oxidation and cleavage process with a dehydrogenation step whereby at least
part of the cyclohexanone is converted to additional phenol (see International
Patent Publication No. WO2010/024975). Such a dehydrogenation step is generally
achieved by contacting the cyclohexanone with a supported metal catalyst at a
temperature of about 250° C. to about 500° C.
The production of phenol from cyclohexylbenzene also produces various
contaminants that are difficult to separate from the desired products. However,
the nature of those contaminants and the separations involved are significantly
different than those involved in the conventional Hock process for phenol and
acetone. For example, hydroalkylation of benzene produces significant amounts
of, inter alia, cyclohexane and lesser amounts of methylcyclopentane,
cyclohexene, phenylcyclohexene, and phenylcyclohexyldiene. Similarly, the
oxidation of cyclohexylbenzene typically produces peroxide species alien to the
Hock process, such as the desired cyclohexyl-1-phenyl-1-hydroperoxide (CHBHP),
and undesired byproduct hydroperoxides such as
cyclohexyl-1-phenyl-2-hydroperoxide, cyclohexyl-1-phenyl-3-hydroperoxide, and
cyclohexyl-1-phenyl-4-hydroperoxide. Similarly, the cleavage of these various
hydroperoxides produces, as both the product of the undesired hydroperoxides
and the undesired byproducts of the desired CHBHP, a wide variety of
contaminant species are not produced by the chemistry and technology of the
Hock process. Similarly, the dehydrogenation of cyclohexanone to phenol
typically produces various hydrocarbons such as hexanone, cyclohexenol and
methylcyclopentenone.
That said, provided herein are methods for producing phenol and cyclohexanone
from cyclohexylbenzene and dehydrogenating a portion of the cyclohexanone into
phenol. Further described are methods for managing the contaminants that are
generated in the above-described process.
Advantageously, the methods described herein produce high-quality phenol
compositions that are novel, useful and very different from those typically
produced by conventional methods (e.g., the Hock process). The chemistry
associated with cyclohexylbenzene as a starting material in the instant
invention, and further the complete absence of cumene and its conversion
products and byproducts, potentially provides a phenol composition with
contaminants that are of a markedly different type and concentration than the
conventional methods. These contaminants may be less problematic in further
processing, e.g., to phenolic resins. Moreover, the contaminants produced in
the processes described herein have lower volatility compared to contaminants
produced by conventional methods, and therefore may be present in lower
concentrations.
SUMMARY
In one aspect, the invention resides in a process for producing phenol
comprising:
(a) contacting benzene and hydrogen with a hydroalkylation catalyst under
hydroalkylation conditions to produce cyclohexylbenzene;
(b) contacting at least a portion of the cyclohexylbenzene with an oxidation
catalyst under oxidation conditions to produce cyclohexylbenzene hydroperoxide;
(c) contacting at least a portion of the cyclohexylbenzene hydroperoxide with a
cleavage catalyst under cleavage conditions to produce a cleavage effluent
comprising phenol and cyclohexanone;
(d) contacting at least a portion of the cyclohexanone from the cleavage
effluent with a dehydrogenation catalyst under dehydrogenation conditions to
produce a dehydrogenation effluent having at least a portion of the
cyclohexanone converted to phenol, wherein the dehydrogenation effluent further
comprises a first contaminant; and
(e) contacting at least a portion of the first contaminant from the
dehydrogenation effluent with an acidic material under contaminant treatment
conditions to convert at least a portion of the first contaminant into a
converted first contaminant.
In another aspect, the invention resides in a composition comprising:
(a) at least 99 wt % phenol; and
(b) 0.1 wppm to 1000 wppm of at least one of the following components:
bicyclohexane, cyclohexylbenzene, methylcyclopentylbenzene, n-butylbenzene,
n-pentylbenzene, pentenylbenzene, hydroxycyclohexanone, cyclohexenone,
cyclohexanol, cyclohexanone, cyclohexanedione, benzoic acid, hexanal,
methycyclopentanone, hexanone, cyclohexenol and methylcyclopentenone, wherein
the wt % and wppm are based upon the total weight of the composition.
In another aspect, the invention resides in a composition comprising:
(a) at least 99.99 wt % phenol;
(b) at least 0.1 wppm to 10 wppm of at least one of bicyclohexane,
cyclohexylbenzene, methylcyclopentylbenzene, n-butylbenzene, n-pentylbenzene,
and pentenylbenzene; and
(c) at least 0.1 wppm to 3 wppm of at least one of: hydroxycyclohexanone,
cyclohexenone, cyclohexanol, cyclohexanone, cyclohexanedione, benzoic acid,
hexanal, and methycyclopentanone, wherein the wt % and wppm are measured
according to ASTM D6142 and are based upon the total weight of the composition,
and wherein the total amount of the hydrocarbon components and oxygenate
components present in the composition accounts for at least 10 wt % of the
total amount of contaminants present in the composition.
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