Molecular sieve abstract
Compositions comprising certain metal-containing materials distributed
interactively on a deboronated HAMS-1B crystalline borosilicate
molecular sieve which are useful for catalytically oxidizing or
oxidatively dehydrogenating organic compounds such as alkanes, aromatics,
and alkyl-substituted aromatics are described. Alkanes are oxidatively
dehydrogenated to olefins, and an aromatic compound such as benzene
can be oxidized by nitric and/or nitrous oxide to largely phenol
or largely nitrobenzene depending upon the oxidation temperature.
When the compound is a methylaromatic, oxidation produces an aromatic
aldehyde. Alkyl groups larger than methyl oxidatively dehydrogenate
to alkenyl groups. The compositions can be used in a process to
separate p-xylene from a mixture of its isomers based upon the ability
of the compositions, which preferably comprise a iron molybdenum
material interactively distributed on a deboronated HAMS-1B crystalline
borosilicate molecular sieve, to selectively oxidize the p-xylene
to an aldehyde or dialdehyde while not substantially oxidizing the
ortho and metaxylene isomers. Such partially oxidized mixtures of
p-xylene are useful to make TPAA or as feeds to a water-based, further
oxidation to make terephthalic acid. Carbon dioxide used as a carrier
gas with a methylaromatic feed to the oxidation catalyst is shown
to have a beneficial effect on yield and selectivity.
Molecular sieve claims
That which is claimed is:
1. A composition comprising a minor amount of a material consisting
of a first component which is a compound of an element selected
from the group consisting of Fe(III), Zn(II), Zr(IV), Nb(V), In(III),
Sn(IV), Sb(V), Ce(III) and Bi(III), and a second component which
is a compound of an element selected from the group consisting of
V(V), Mo(VI) and W(VI), which first and second components are interactively
distributed on a major amount of deboronated HAMS-1B crystalline
borosilicate molecular sieve containing less than about 0.1 weight
percent as the element of boron.
2. The composition of claim 1 wherein the total metals in the minor
amount of material is in a range form about 0.5 to about 15 weight
percent of the total weight of the composition.
3. The composition of claim 2 wherein the minor amount of a material
consisting of a first component which is a compound of an element
selected from the group consisting of Fe(III), Zn(II), Sb(V), and
Bi(III), and a second component which is a compound of an element
selected from the group consisting of Mo(VI) and W(VI).
4. The composition of claim 2 wherein the first component is a
compound of Fe(III) and the second component is a compound of Mo(VI),
and the minor amount of iron-molybdenum material having a molybdenum
to iron ratio in a range from about 1.5 to about 2.5 distributed
on a major amount of deboronated HAMS-1B crystalline borosilicate
molecular sieve containing less than about 0.1 weight percent as
the element of boron.
5. The composition of claim 2 made by a process comprising:
depositing a volatile iron compound on a HAMS-1B crystalline borosilicate
molecular sieve containing at least about 0.4 weight percent as
the element of boron or a predeboronated HAMS-1B crystalline borosilicate
molecular sieve containing less than about 0.1 weight percent of
boron as the element from the vapor phase to form an iron-containing,
deboronated HAMS-1B crystalline borosilicate molecular sieve;
washing and drying said iron-containing deboronated HAMS-1B crystalline
borosilicate molecular sieve;
depositing a volatile molybdenum compound on said washed and dried
iron-containing deboronated HAMS-1B crystalline borosilicate molecular
sieve from the vapor phase to form an iron-molybdenum-containing
deboronated HAMS-1B crystalline borosilicate molecular sieve; and
heating said iron-molybdenum-containing deboronated HAMS-1B crystalline
borosilicate molecular sieve to form a composition comprising a
minor amount of an iron molybdenum material having a molybdenum
to iron ratio between about 1.5 and about 2.5 distributed on a major
amount of deboronated HAMS-1B crystalline borosilicate molecular
sieve containing less than about 0.1 weight percent as the element
of boron.
Molecular sieve description
BACKGROUND OF THE INVENTION
This invention relates to compositions containing a pair of metal
compounds distributed interactively on a deboronated HAMS-1B crystalline
borosilicate molecular sieve (DBH) and a process of using such compositions
as oxidation or oxidative dehydrogenation catalysts. More particularly,
this invention relates to an improved process and composition for
the alkyl group oxidation or oxidative dehydrogenation of an alkyl-substituted
aromatic using a novel metal-compound-containing composition based
upon a deboronated HAMS-1B crystalline borosilicate molecular sieve.
Still more particularly, this invention relates to improved process
for the methyl group oxidation of a methyl-substituted aromatic,
such as p-xylene, to an aromatic mono and/or dialdehyde using a
catalytic amount of a novel composition containing an iron molybdenum
material distributed interactively on a deboronated HAMS-1B crystalline
borosilicate molecular sieve.
U.S. Pat. No. 3597485 discloses a process for preparation of
terephthalaldehyde (referred to herein as TPAA) which comprises
subjecting p-xylene to a vapor phase oxidation in the presence of
a catalyst mixture consisting of tungsten and molybdenum compounds.
U.S. Pat. No. 3845137 describes a process for preparation of
TPAA in which p-xylene is oxidized in the vapor phase in the presence
of a supported catalyst mixture of oxides of tungsten and molybdenum
and at least a third metal or oxide selected from the group consisting
of calcium, barium, titanium, zirconium, hafnium, thallium, niobium,
zinc, and tin. According to this patent, the three component catalyst
composition processes have improved catalyst life when compared
to the catalyst described in U.S. Pat. No. 3597485. However, in
both of these patents the conversion of p-xylene to TPAA is low.
U.S. Pat. No. 4017547 describes an improved process for making
TPAA which uses a mixture of molybdenum oxide and silico-tungstic
acid in combination with bismuth oxide. Catalyst lifetime and conversion
to TPAA are both said to be improved over the prior art techniques.
Not only is the conversion of p-xylene to TPAA said to be increased
substantially by the use of the oxide of bismuth, but catalyst life
is also said to be improved considerably, thereby permitting the
operation of the oxidation process for longer periods of time before
catalyst regeneration is required.
In an article entitled "Polymer Applications of Some Terephthalaldehyde
Derivatives" in Ind. & Eng. Chem., Prod. Res. Dev. 15 (1)
83-88(1976), the authors use a tungsten-molybdenum catalyst in a
ratio of about 9:1 deposited in an amount of ten percent or less
on an alumina support to oxidize a mixture of air and p-xylene at
475.degree. C. to 575.degree. C. to a mixture of tolualdehyde (TAL)
and TPAA. A 40-60% yield of TPAA with a minor production of byproducts
is reported. The lifetime of the catalyst however appears to be
poor.
Two catalyst properties are of primary importance for the operation
of a continuous oxidation or oxidative dehydrogenation process which
converts alkanes, aromatics or alkyl aromatics on a commercial scale.
The first is yield of the desired oxidation product and the second
is catalyst lifetime.
Now it has been discovered that metal-compound-containing compositions
based on a deboronated HAMS-1B crystalline borosilicate molecular
sieve having the MFI crystal structure can be very selective in
oxidation and oxidative dehydrogenation reactions while having a
long lifetime. For example, the alkyl group oxidation of an alkyl-substituted
aromatic in the presence of a catalytic amount of a composition
which is an iron molybdenum material distributed interactively on
a deboronated HAMS-1B crystalline molecular sieve can yield aromatic
aldehydes where the alkyl substituent is methyl and alkenyl-substituted
aromatics when the alkyl substituent is larger than methyl. (oxidative
dehydrogenation). The compositions give a combination of both good
yield and good catalyst lifetime for the production of aromatic
aldehydes or alkenyl aromatic products with reduced amounts of burning
to fully oxidized products. In addition, the compositions show a
selectivity in the oxidation of xylene and dialdehydes which can
serve as the basis for a process for separating p-xylene from the
other xylene isomers by selectively oxidizing p-xylene. Products
of such selective p-xylene and dialdehyde oxidation are suitable
intermediates for a variety of novel and specialty polymer applications
including liquid crystals, engineering polymers, and optical brighteners.
These oxidation products are also useful in synthesis of alcohols
such as cyclohexanedimethanol. A particularly useful product of
this invention is p-tolualdehyde which is useful as a feed to a
water-based oxidation process to make purified terephthalic acid.
SUMMARY OF THE INVENTION
In one aspect, the invention is a composition comprising a minor
amount of a material made from a first component which is a volatile
compound of a element selected from the group consisting of Fe(III),
Zn(II), Zr(IV), Nb(V), In(III), Sn(IV), Sb(V), Ce(III) and Bi(III)
and a second component which is a volatile compound of an element
selected from the group consisting of Mo(VI), W(VI) and V(V) which
first and second components are interactively distributed on a major
amount of deboronated HAMS-1B crystalline borosilicate molecular
sieve containing less than about 0.1 wt % of boron as the element.
Advantageously, total metals in the minor amount of material is
in a range form about 0.5 to about 15 weight percent of the total
weight of the composition.
Preferred compositions include minor amount of a material consisting
of a first component which is a compound of an element selected
from the group consisting of Fe(III), Zn(IV), Sb(V), and Bi(III),
and a second component which is a compound of an element selected
from the group consisting of Mo(VI) and W(VI).
In a second aspect, the invention described herein is a composition
comprising a minor amount of iron molybdenum material with an atomic
ratio of molybdenum to iron in a range from about 1.5 to about 2.5
distributed on a major amount of deboronated HAMS-1B crystalline
borosilicate molecular sieve containing less than about 0.05 wt
% as the element of boron.
In another aspect, the invention embraces a methyl-group oxidation
process comprising combining a feed containing a methyl aromatic
compound with an oxygen-affording substance at oxidation conditions
over a composition comprising a minor amount of an iron molybdenum
material with an atomic ratio of molybdenum to iron in a range from
about 1.5 to about 2.5 distributed on a major amount of deboronated
HAMS-1B crystalline borosilicate molecular sieve containing less
than about 0.1 wt % as the element of boron.
In still another aspect, the invention embraces a composition made
by a process comprising:
depositing an iron compound on a HAMS-1B crystalline borosilicate
molecular sieve containing at least about 0.4 wt % as the element
of boron or a predeboronated HAMS-1B crystalline borosilicate molecular
sieve containing less than about 0.1 wt % as the element of boron
from the vapor phase to form an iron-containing deboronated HAMS-1B
crystalline borosilicate molecular sieve;
washing and drying said iron-containing deboronated HAMS-1B crystalline
borosilicate molecular sieve;
depositing a molybdenum compound on said washed and dried iron-containing
deboronated HAMS-1B crystalline borosilicate molecular sieve from
the vapor phase to form an iron-molybdenum-containing deboronated
HAMS-1B crystalline borosilicate molecular sieve; and
heating said iron-molybdenum-containing deboronated HAMS-1B crystalline
borosilicate molecular sieve to form a composition comprising a
minor amount of an iron molybdenum material having an atomic ratio
of molybdenum to iron in a range from about 1.5 to about 2.5 distributed
on a major amount of deboronated HAMS-1B crystalline borosilicate
molecular sieve containing less than about 0.1 wt % as the element
of boron.
In still another aspect the invention is a separation process for
a feed comprising primarily xylenes including p-xylene comprising:
contacting said feed in an oxidation stage at oxidation conditions
with an oxygen-affording substance over a composition comprising
a minor amount of iron molybdenum material having a molybdenum to
iron ratio between about 1.5 and about 2.5 distributed on a major
amount of deboronated HAMS-1B crystalline borosilicate molecular
sieve containing less than about 0.1 wt % as the element of boron
to form an oxidized product;
separating said oxidized product into a primarily aromatic aldehyde-containing
product and a primarily xylene-containing product;
sending said primarily xylene-containing product to an isomerization
stage; and
recycling the isomerized product of said isomerization stage to
said oxidation stage.
In still another aspect the invention is an oxidative dehydrogenation
process comprising combining a feed containing at least one C.sub.2
to C.sub.5 alkyl aromatic and/or C.sub.2 to C.sub.6 alkane hydrocarbon
compound with an oxygen-affording substance at oxidative dehydrogenation
conditions over a composition comprising a minor amount of an iron
molybdenum material having an atomic ratio of molybdenum to iron
in a range from about 1.5 to about 2.5 distributed on a major amount
of deboronated HAMS-1B crystalline borosilicate molecular sieve
containing less than about 0.1 wt % as the element of boron to form
a C.sub.2 to C.sub.5 alkenyl aromatic compound and/or C.sub.2 to
C.sub.6 alkene hydrocarbon compound. Typically, oxidative dehydrogenation
is carried out at temperatures above about 225.degree. C., preferably
in a range from about 250.degree. C. to about 550.degree. C.
In a still further aspect the invention is a process comprising
combining a benzene feed with nitric acid or nitrous oxide at oxidizing
conditions above about 350.degree. C. over a composition comprising
a minor amount of a material made from a first component which is
a volatile compound of an element selected from the group consisting
of Fe(III), Zn(II), Zr(IV), Nb(V), In(III), Sn(IV), Sb(V), Ce(III)
and Bi(III), and a second component selected from the group consisting
of Mo(VI), W(VI) and V(V), which first and second components are
interactively distributed by vapor deposition on a major amount
of deboronated HAMS1-B crystalline borosilicate molecular sieve
containing less than about 0.1 wt % as the element of boron to form
primarily phenol.
In a still further aspect, the invention is a crystalline borosilicate
molecular sieve containing some lattice boron but less than about
0.05 wt % and more than about 20 wt % silanol groups.
DETAILED DESCRIPTION OF THE INVENTION
The compositions of this invention may be made directly from a
AMS-1B crystalline borosilicate molecular sieve in the hydrogen
form, HAMS-1B, or indirectly from a deboronated variation of such
sieve. The preparation of such a sieve is set out in detail in U.S.
Pat. Nos. 4268420; 4269813; and 4285919. A description of
a particularly useful, essentially sodium-free variant of HAMS-1B
molecular sieve may be found in U.S. Patent No. 5053211. All of
such patents are specifically incorporated herein by reference.
Such HAMS-1B sieves contain characteristically between about 0.4
and about 1.1 wt % of lattice boron (about 2% of total boron) measured
as the element. However, they may have a larger total boron content
as not all the boron need be present as lattice boron.
In the direct procedure described below for making deboronated
sieve, the HAMS-1B sieve is first preferably aqueous ammonia exchanged
and then calcined between about 300.degree. C. and 700.degree. C.
for a short period of time before deposition of the metal compounds
from the vapor phase. Only a small loss of boron is noted in this
preliminary aqueous exchange and subsequent heating. If the deboronated
sieve is made indirectly (predeboronated HAMS-1B sieve) as is also
described below, it may also be calcined in the same temperature
range before extracting the boron and depositing the metal compounds
from the vapor phase.
The deboronated HAMS-1B crystalline borosilicate molecular sieve
of the invention may be made directly, and preferably, by depositing
the metal compounds from the vapor state on HAMS-1B sieve, a process
which is involved in reducing the lattice boron content of the sieve
during the deposition process. The boron can then be water extracted
from the sieve. The sieve can also be made indirectly by extracting
a HAMS-1B sieve with deionized hot water or dilute acid prior to
vapor deposition of the metals. Preferably, the boron content of
the sieve is reduced to less than about 0.01 wt as the element,
more preferably, less than about 0.05 wt %, and most preferably,
less than about 0.02 wt %, when the deboronated sieve is made using
either method. Made by either method, a small amount of boron remains
in the sieve along with some aluminum present as an impurity.
The sieve retains the MFI structure of the original HAMS-1B sieve
and may be considered a high-silanol-containing silicalite. It is
believed that when the boron atoms are removed from the HAMS-1B
sieve after the vapor deposition process or the aqueous deboronation
process, silanol-rich reactive sites are left behind which are able
to capture effectively the metal compounds to form interactively
catalytically active sites. The silanol content of the deboronated
HAMS-1B crystalline borosilicate molecular sieve prior to vapor
deposition, as determined by magic angle spinning NMR, is preferably
above about 15 wt %, more preferably, above about 18 wt %, and most
preferably, above about 20 wt % of the total weight of the silicon
atoms present in the sample. Weight percent silanol in a sample
is determined by the ratio of the area under the peak corresponding
to the HOSi(OSi).sub.3 NMR signal to the total areas of the peaks
corresponding to the Si(OSi).sub.4 and HOSi(OH).sub.3 signals.
Metal ions whose volatile compounds are particularly useful in
making the metal materials of this invention include Fe(III), Bi(III),
Zr(IV), Sn(IV) and Sb(V) as the first component. As the second component,
the metals whose compounds are particularly useful include Mo(VI),
W(VI) and V(V). After vapor depositing the two metal components
on the sieve, the result is heated to interact the compounds with
each other and the sieve. Depending upon the nature of the first
and second component, it may be desirable to switch the order of
their depositing on the sieve. For example, preferred Fe-Mo-DBH
catalysts are obtained by distribution of an iron compound followed
by molybdenum compounds, however, preferred Sb-Mo-DBH catalysts
are obtained by distribution of an molybdenum compound followed
by antimony compounds.
The preferred combination of metal compounds forms an iron molybdenum
material which is made by vapor-depositing a volatile iron compound
on the sieve followed by vapor-depositing a volatile molybdenum
compound on the sieve and calcining the result to promote the interaction
of the iron and molybdenum compounds with each other and the sieve.
The process for making the catalytic compositions of the invention
is illustrated below using the preparation of a Fe-Mo-DBH composition.
In preparing the iron molybdenum material deboronated HAMS-1B composition,
the aqueous exchanged and calcined HAMS-1B sieve or calcined, predeboronated
HAMS-1B sieve is treated with a volatile iron compound such as iron
(III) chloride to deposit the iron compound on the sieve. The amount
of iron compound deposited on the surface of the sieve depends on
the amount of iron molybdenum material desired in the final composition.
Preferably, the iron-containing sieve is then washed to remove boron
and chlorine, and then it is calcined at a temperature between about
200.degree. C. and 400.degree. C. It has been found particularly
advantageous to the catalytic properties of the compositions to
vapor-deposit the iron compound on the sieve prior to vapor deposition
of the molybdenum compound.
The iron-containing sieve is then treated with a volatile molybdenum
compound such as MoO.sub.2 Cl.sub.2 MoOCl.sub.4 MoCl.sub.5 etc.
to vapor deposit the molybdenum compound on the sieve. Care should
be taken to lay down an amount of molybdenum to provide an atomic
ratio molybdenum to iron in a range upward from 1.5 which roughly
corresponding to the stoichiomety of the formula of iron molybdate,
Fe.sub.2 (MoO4).sub.3. Another calcination carried out at temperatures
in a range from about 300.degree. C. to about 700.degree. C. is
believed to promote interactions of iron and molybdenum compounds,
with each other and the sieve, to form primarily iron molybdate.
It is preferred not to have an excess of iron over that corresponding
to the iron molybdate formula given above, as the presence of excess
of iron appears to produce more hydrocarbon burning during use of
the composition as an catalyst. The major amount of the iron molybdenum
material seems to be in the form of finely divided iron molybdate,
Fe.sub.2 (MoO.sub.4).sub.3 and molybdenum trioxide, MoO.sub.3.
It is preferred to have an excess of molybdenum over that required
for the iron molybdate formula of 3 molybdenum atoms for each 2
Fe atoms. Preferably, the molybdenum to iron atomic ratio of the
deboronated HAMS-1B compositions lies between about 1.5 to about
2.5 more preferably, between about 1.6 and 2.4 and most preferably
between about 1.6 and 2.3.
More generally, the atom ratio of the second component metal to
the first component metal of the metal material on the deboronated
HAMS1-B crystalline borosilicate molecular sieve is about 0.2 to
1 to about 3 to 1 more preferably, it is about 0.5 to 1 to about
2.5 to 1 and most preferably, it is about 1 to 1 to about 2.5 to
1.
Generally, the total metals content of the interacted metal materials
on the deboronated sieves should be between about 0.5 and about
20 wt % of the total composition. More specifically, the total metals
in the iron molybdenum material distributed on the deboronated HAMS-1B
sieve is desirably between about 0.5 and about 15 wt % based on
the total composition weight. More preferably, the total metals
in the iron molybdenum material distributed on the deboronated HAMS-1B
sieve lies between about 1 and about 12 wt %, and most preferably,
the total metals in the iron molybdenum material distributed on
the sieve lies between about 2 and about 10 wt %.
The oxidants useful in this invention for oxidation and oxidative
dehydrogenation are oxygen-affording substances such as air or mixtures
of oxygen with other gases such as nitrogen, argon, helium, carbon
dioxide, and the like. Use of carbon dioxide, as a carrier gas and/or
oxygen-affording substance alone or in combination with additional
oxygen-affording substances, appears to promote the conversion and
selectivity of the oxidation of p-xylene to aldehyde products and
also suppress substrate burning. Nitric acid and nitrous oxide are
also useful as oxidants for benzene in this invention.
The compositions of this invention are particularly useful as oxidation
and oxidative dehydrogenation catalysts, more particularly for the
oxidation of aromatic and methyl aromatic compounds and the oxidative
dehydrogenation of alkanes and alkyl aromatics, where the alkyl
group is larger than methyl. They can be used with nitric acid or
nitrous oxide as oxidants to oxidize benzene to phenol or nitrobenzene,
depending upon the reaction temperature. For example, methyl-substituted
aromatics such as methyl-naphthalenes, methylbiphenyls and methylbenzenes
are conveniently oxidized to aldehydes. Toluene, mixed xylenes and
p-xylene are particularly useful feeds. In the case of p-xylene,
for example, both p-tolualdehyde (TAL) and TPAA are formed. The
compositions are also useful in oxidizing ethylaromatics selected
from the group consisting of ##STR1## in which X is H, OCH.sub.3
NO.sub.2 OH, F, Cl, Br, COOH, COCl, R, COOR and COR where R is
a C.sub.1 to C.sub.4 alkyl group. The products of the oxidation
are aldehydes.
The compositions may also be used to oxidatively dehydrogenate
alkanes, or mixtures of alkanes, such as ethane, propane, butane,
isobutane, pentane, hexane and the like to the corresponding olefin
or olefins, and C.sub.2 -C.sub.5 alkyl aromatics to aromatic alkenyl
derivatives. The t-butyl group of course is not included as it is
not subject to partial oxidation to an alkenyl group. For example,
ethane is oxidatively dehydrogenated to ethylene, ethylbenzene is
oxidatively dehydrogenated to styrene, p-diethylbenzene to divinylbenzene,
and cumene is converted to isopropenylbenzene.
It has been found the Fe-Mo-DBH compositions of this invention
are poor at catalyzing the oxidation of o-xylene and m-xylene to
their respective aldehydes and dialdehydes whereas the compositions
are quite effective in catalyzing the oxidation of p-xylene to its
respective aldehyde and dialdehyde. This difference believed to
be a unique property of the Fe-Mo-DBH compositions of this invention
which may, in part, be the result of the pore structure of the deboronated
HAMS-1B sieve, allows the oxidation process to be used to effect
a separation of the isomers of xylene or mixtures of xylene isomers
with other hydrocarbons such as ethylbenzene, and C.sub.9 paraffins
and naphthenes by preferentially forming para-tolualdehyde and TPAA
from the p-xylene. Ethylbenzene can be oxidatively dehydrogenated
in the process to styrene. Reaction conditions of oxidation over
Fe-Mo-DBH compositions of this invention can readily be selected
to limit dehydrogenation reaction of ethylbenzene. The mixture of
aldehydes is easily separated from the unreacted xylenes by distillation,
for example, and can be further purified to remove the small amount
of the aldehydes and dialdehydes of o-xylene and m-xylene which
are formed in the oxidation process. The purified mixture of p-tolualdehyde
and TPAA can then be used to make pure TPAA or as intermediate for
various applications described herein above, for example, advantageously
as a feed to a water-based oxidation process for the preparation
of terephthalic acid. The unreacted xylenes from the oxidation stage
after separation from the aldehydes can be recycled to the alkyl
group oxidation unit after first being isomerized in a unit in which
the amount of p-xylene is augmented. In this manner, a feed of mixed
xylenes can be continuously converted to p-xylene oxidation products
to form TPAA or to form an appropriate feed for a water-based procedure
for the preparation of terephthalic acid. The details of a similar
process using a cobalt boron and oxygen catalyst to partially oxidize
p-xylene and the use of the p-xylene oxidation products in a water-based
terephthalic acid process is taught in U.S. Pat. No. 4863888 which
is specifically incorporated herein by reference.
The Fe-Mo-DBH compositions are also useful for the vapor or liquid
phase oxidation of benzene using nitric acid or nitrous oxide as
the oxidant. With these oxidants the product of the reaction is
temperature sensitive. Above about 350.degree. C. the oxidation
produces primarily phenol, and below about 400.degree. C. the oxidation
produces primarily nitrobenzene.
The metal compound material distributed on deboronated HAMS-1B
crystalline borosilicate molecular sieve compositions useful in
this invention can be admixed with, or incorporated in, a silica
or other oxide, such as alumina, silica-alumina, thoria, titania,
magnesia, a spinel, a perovskite, bentonite and the like, as a binder.
Preferably, a support which is neutral to weakly basic or weakly
acidic is desirable. Typically, the compositions are incorporated
within the binder by blending with a sol of the oxide material and
gelling the resulting mixture. These supported compositions are
then dried at temperatures in a range from about 100.degree. C.
to about 200.degree. C. and thereafter generally calcined at temperatures
in a range from about 500.degree. C. to about 700.degree. C.
If supported, the iron-molybdenum-material-loaded deboronated HAMS-1B
sieve (Fe-Mo-DBH) content of the supported compositions can vary
anywhere from about 5 to about 60 wt % of the total supported composition.
Preferably, they form about 10 to about 60 wt % of the total supported
composition, and more preferably, form about 10 to about 40 wt %
of the total supported composition.
Oxidation or oxidative dehydrogenation in the presence of the above-described
compositions is effected by contact of the organic compound either
in the liquid or vapor phase at temperatures ranging from about
50.degree. C. to about 1000.degree. C. Generally, an oxygen-containing
gas is used as the oxidant. Air can be used or synthetic mixture
of an inert or other gas and the oxygen level adjusted to the desired
amount. The reaction takes place at atmospheric pressure, but the
pressure may be within the range of about 0 psig to about 2000 psig.
Reaction is suitably accomplished using a weight hourly space velocity
of between about 0.01 hr.sup.-1 and about 100 hr.sup.-1. For some
compounds reaction in the liquid phase is preferred. Reactions in
the liquid phase typically are carried out at temperatures in a
range from about 50.degree. C. to about 300.degree. C., preferably
from about 100.degree. C. to about 260.degree. C. and most preferably
from about 100.degree. C. to about 200.degree. C., with pressures
in a range from about 0 to about 300 psig, preferably from about
60 psig to about 250 psig at space velocities in a range from about
0.02 hr.sup.-1 to about 5 hr.sup.-1 preferably from about 0.08
hr.sup.-1 to about 2 hr.sup.-1. Liquid phase reactions can be carried
out in a trickle bed configuration, catalytic distillation configuration
or slurry bed configuration, for example. In the gas phase, reactions
typically are carried out at temperatures in a range from about
250.degree. C. to about 1000.degree. C., preferably from about 300.degree.
C. to about 600.degree. C. and most preferably from about 400.degree.
C. to about 550.degree. C., with pressures in a range from about
0 to about 300 psig, and space velocities in a range from about
0.01 hr.sup.-1 to about 100 hr.sup.-1 preferably from about 0.5
hr.sup.-1 to about 50 hr.sup.-1. Gas-phase reactions can be carried
out in a fluid bed, stirred bed, fixed bed or other suitable reactor
configuration.
Heat generated in the highly exothermic liquid-phase partial oxidation
is typically dissipated at least partially by vaporization of unreacted
aromatic reactant and, if used, solvent, in the partial oxidation
reactor. The resulting vapor and excess oxygen-containing gas are
withdrawn from the partial oxidation reactor through a vent above
the liquid level in the partial oxidation reactor. The withdrawn
aromatic reactant is then condensed in a condenser and recycled
to the partial oxidation reactor
The oxidation or oxidative dehydrogenation of the method of this
invention can be performed in either a batch or semi-continuous
mode. In the batch mode, the aforesaid aromatic reactant, catalyst
and, if used, solvent are initially introduced batchwise into the
reactor, and the temperature and pressure of the reactor contents
are then raised to the desired levels therefor for the commencement
of the oxidation reaction. An oxygen-containing gas or vapor is
introduced continuously into the reactor. After commencement of
the oxidation reaction, the temperature of the reactor contents
is raised to the desired reaction temperature. In the semi-continuous
mode, the catalyst and, if used, solvent are initially introduced
batchwise into the reactor, and then the aromatic reactant and air
are introduced continuously into the reactor. After commencement
of the oxidation reaction, the temperature of the reactor contents
is raised to the desired reaction temperature. Preferably, the continuous
mode is employed for the vapor or liquid phase oxidation or oxidative
dehydrogenation method of this invention.
If the partial oxidation of the method of this invention is performed
semicontinuously, the space velocity in the range of from about
0.02 hr.sup.-1 preferably from about 0.08 hr.sup.-1 to about 5
hr.sup.-1 preferably to about 2 parts of the aromatic reactant
per part of the catalyst particles by weight per hour is employed.
If the partial oxidation of the method of this invention is performed
batchwise, the aromatic reactant and catalyst are mixed in a weight
ratio in the range of from about 250 preferably from about 1000
to about 10000 preferably to about 4000 parts of aromatic feed
per part of catalyst by weight, and the reaction time is in the
range of from about 0.5 preferably from about 1 to about 20 preferably
to about 4 hours.
The resulting partially oxidized liquid aromatic product can then
be separated from the solid catalyst particles by any convenient
solid-liquid separation. The aromatic product can also be separated
from any unreacted aromatic reactant by any convenient liquid-liquid
separation, such as distillation, by any convenient gas-liquid separation
if the unreacted aromatic reactant has been vaporized or by any
convenient solid-liquid separation if the temperature is lowered
to a point where the partially oxidized aromatic product but not
the aromatic reactant crystallizes.
An especially convenient means of both effecting the partial oxidation
and separating the partially oxidized, aromatic product from both
the catalyst and unreacted aromatic reactant involves catalytic
distillation. In such a system, a distillation column in the partial
oxidation reactor is packed with a bed of the solid heterogeneous
catalyst and is heated to a temperature in the range of suitable
reaction temperatures for the partial oxidation. In addition, at
least the bottom region of the catalyst bed is maintained at the
temperature of at least the boiling point of the aromatic reactant
and at least the melting point of the partially oxidized aromatic
product but below the boiling point of the partially oxidized, aromatic
product, at the pressure employed in the column. Liquid aromatic
reactant is introduced into the top of the column and passes downwardly
through the column. An oxygen-containing gas is introduced into
the bottom of the column and flows upward through the column. The
liquid aromatic reactant and oxygen react to form the partially
oxidized aromatic product which flows as a liquid downward through
the column. Any remaining unreacted aromatic feed continues to flow
downward through the column until it vaporizes in the bottom region
thereof and then flows upward through the column in the stream of
oxygen-containing gas.
Thus, substantially only partially oxidized, aromatic product passes
downward out of the column as a liquid and thereby is separated
from both the solid catalyst and unreacted aromatic reactant even
before it is withdrawn from the partial oxidation reactor. The resulting
aromatic product withdrawn from the partial oxidation reactor is
substantially free of unreacted aromatic reactant and contains preferably
less than 10 weight percent, more preferably less than 1 weight
percent of unreacted aromatic reactant.
In the alternative, a trickle bed catalyst configuration can be
employed, in which case both unreacted aromatic reactant and partially
oxidized aromatic product pass as a mixture of liquids out of the
catalyst bed. In such case, it would be necessary to separate the
unreacted aromatic reactant from the partially oxidized aromatic
product.
In a preferred embodiment of this invention, the partially oxidized
aromatic product produced from p-xylene or mixed xylenes as described
herein above is completely oxidized to its carboxylic acid derivative
in at least one additional step. Preferably such complete oxidation
to the carboxylic acid derivative occurs in a second reactor using
a suitable oxidation catalyst dissolved or suspended in water solution.
The partially oxidized p-xylene, etc., product of the partial oxidation
method of the present invention is soluble in water as well as in
other common solvents such as low molecular weight carboxylic acids
such as acetic acid. Hence, it a preferred embodiment of the method
of this invention, the partially oxidized aromatic product is introduced
into a second reactor where it is completely oxidized in the liquid
phase by an oxygen-containing gas to its corresponding carboxylic
acid derivative. Either the partially oxidized product is introduced
directly into the second reactor where it dissolves in water or
a mixed solvent already in the second reactor, or the partially
oxidized aromatic product is first dissolved in water or a mixed
solvent and the resulting solution is introduced into the second
reactor. In either case, the weight ratio of partially oxidized
aromatic product introduced into the second reactor-to-water (or
other solvent) is in the range of from about 0.1 preferably from
about 0.2 to about 0.4 preferably to about 0.3 parts of the partially
oxidized aromatic product per part by weight of water.
The following Examples will serve to illustrate certain specific
embodiments of the herein disclosed invention. These Examples should
not, however, be construed as limiting the scope of the novel invention
as there are many variations which may be made thereon without departing
from the spirit of the disclosed invention, as those of skill in
the art will recognize.
GENERAL
All the metal-containing deboronated HAMS-1B sieve compositions
were pressed into 11/8 in diameter tablets at 10000 psig, crushed
and sieved to 20/40 mesh size (ASTME-11) for use in testing of catalytic
activity. |