Note: Descriptions are shown in the official language in which they were submitted.
.~l~9(1~
8CH-2415
This invention is directed to a process for selectively ortho-
~lkylating 8 phenolic compound which comprises re~cting the phenolic
compound with sn alkanol in the presence of a copper-ehromium cstalyst.
Background of the Invention
It is well known in the art to alkyl~te phenols having Rt lea8t
one unsubstituted ortho position. Many prior art processes have been
disclosed as being non-selective and indiscrim~nate in regard to the nsture
of the products that are formed. Winkler et al, U.S. 2,448,942, for
example, discloses a process for the preparation o~ penta-substituted
phenols. The Winkler et al patent mentions that one may employ either
alcohol or methyl ether in the vapor phase using various metal oxides such
as aluminum oxide, thorium oxide, zirconium oxide, zinc oxide, iron oxide,
chromium oxide, barium oxide, manganese oxide, magneaium oxide, calcium
oxide, etc. as the catalyst. Alumin~ is the preferred catalyst. The
WLnkler et 81 process, however, i8 somewhat indiscrimlnate snd lacks
specificity for ortho-alkylatlon to the relative exclusion of alkylstion
in the meta- and para- positionæ.
Winkler et al teach that the reaction is carried out at super
l atmospheric pressures at temperatures in the range of 300C. to about
450C. However, temperatures of above 430C. have been noted, e.g., in
Hsmilton, U.S. 3,446,856, to cause 8 decrease in the yield of alkylated
product. When phenol and methanol are reacted at temperatures above 450 C.,
Hamilton ~eaches that the production of hexsme~hyl benzene, a non-phenolic
product, is favored. For reactions of methanol with phenol, xylenol or
¦ cresol, Hamilton stated that a temperature of about 350 to 430C. is
I -1-
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109~
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favored in order to obtain high yields of alkylated p~oduct, while
temperatures below 350C increase the yield of ether by-products.
Temperatures of above 450 C. snd superatmospheric pre~sures cause decom-
position of the resctant and fsvor the production of unw~nted msterials.
The Hamilton process w88 based on the discovery that magneslum oxide wss
a selective ortho-alkylation catalyst that was useful st at~ospheric
pressure at a defined temperatura range.
U S. Patents 3,707,569 and 3,751,488 are ba~ed respectively,
on the discoveries that certain tellurium-cont~ining compounds and molybdic
acid salts are useful as selective ortho-alkylation catslysts. Further,
U.S. Patent 3,764,630 describeS a method for selectively alkylating a
- phenol compound with an alkanol in the presence of wster and a catalytically
active compound such as molybdenum oxide and alkali metal, alkaline ear~h
metal, lead,bismuth and ammonium salts of molybdic acid in admixture with
i magnesium oxide. Also, U.S. Patent 3,843,606 discloses a catalyst which
is porous magnesium oxide powder bonded with an inert organic cellulosic
polymeric binder ior use in selective alkylation of phenols. L~stly,
U.S. Patent 3,873,628 discloses mixtures of magne~ium oxide and manganese
sulfate as useful catalysts for ortho-alkyla~ion of phenols.
!
Ortho-alkylated phenols have valuable properties. They are
particularly useful as the starting material for the manufacture of
polysrylene ethers such as polyphenylene oxide, a valuable thermoplastic
Il resin disclosed and claimed, for example, in A. S. Hay's U.S. Patent
1 3,306,875.
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Description of the In~Lntion
.
It has now been discovered that a copper-chromium composition
may be used aa a relatively lo~ temperature alkylation catalyst ~hat
provides high selectivlty with respect to substltution in the ortho
position in the reaction of phenols and alkanols. The high selectivity and
the relatively mild conditions of this process make it a promising approach
toward solving the problems of unsatisfactory alcohol utilization and
short catalyst life associated with prior art methods.
According to this invention, there is provided a selective process
for the ortho-alkylation of a phenolic compound of the general formula:
R~ R
wherein each R is a monovalent substituent selected from the group consist-
ing of hydrogen, alkyl of 1 to 12 carbon atoms, aryl of 6 to 12 carbon
atoms and alkaryl of 7 to 12 carbon atoms, the process comprising reacting
said phenolic compound with a lower alkanol in the presence of a copper~
chromium catalyst. Examples of these substituents include methyl, ethyl,
n-propyl, phenyl, o-methylphenyl, p-methylphenyl, 2,6-xylyl, and the like.
Especially useful starting materials are phenol, o-cresol, m~cresol,
p-cresol, o-phenylphenol and 3,5-xylenol. The preferred embodiment of the
process is carried out using phenol, ortho cresol, or a mixture of the two
as the phenolic~starting material.
I
Suitable alkanols ~ay be represented by the formula:
Rl - OH
. . .
~ _3_
.: .
'...:"
. . . _.._ __. .
I ~ 30~
I
,
8CH-2415
whereln Rl is a saturated alkyl of up to about 12 carbon atoms, straight
chain or branched chain. Illustra~ive alkanols are those wherein Rl i~
i methyl, ethyl, n-propyl, i-propyl, n-butyl, haxyl, octyl, 2-ethylhexyl,
i decyl, dodecyl. Preferred alkanols are lower primary and secondary
5 1 alkanols, i.e., those in which Rl contains from 1 to 6 carbon atoms such
as me~hyl, ethyl, propyl, isooropyl, butyl, isobutyl, amyl and hexyl
alcohols. Methanol is the preferred alkanol.
In order to obtain the maximum yield of ortho-alkylated products,
it is preferred to use at least 0.5 mole of alkanol, and preferably from
1 to 3 moles of alkanol for each ortho ~osition hydrogen in the phenolic
compound to be alkylated. For example, if phenol is to be methylated
to produce a maximum yield of 2,6-xylenol (2,6-di~ethylphenol), it is
¦ preferred to use at least 2 moles and especially preferred to use from
¦ 2 to 5 moles of methanol for each mole of phenol. 0f course, if the
phenolic compound is already mono-substituted in one of the ortho-
positions, maximum yields will be obtained with at least one mole of
alkanol, e.g., methanol, per mole of phenolic compound, e.g., ortho-
cresol.
The catslysts of the instant invention are copper-chromium oxide
COmpQSitions~ either as amorphous mixed oxides, or as crystalline copper
chromite sub~tances such as those described in ~. Charcosset et al, Co~
Rend: 254, 2990-2 (1962), or ~s mixtures of the amorphous and crystalline
substances. The copper-Ghromium catalysts of the ins~ant invention can
be varied in composi~ion from about 0.05 parts to about 10 parts of copper
per part of ~hromium. In a preferred embodiment, the copper-chromium
; oxide compositions are promoted by the presence of a component selected
¦ from the oxides and hydroxides of the Group I, II or lII metals,
~¦ manganeseS iron and mixtures thereof. These promoters can constitute
.,
Il - 4 -
li ':
~ ~ 8CH-2415
from about 3 to about 95~ of the catalyst composition.
The catalysts of the instant invention may be prepared
by a number of different methods, such as those described in
U.S. 3,899,~46, for example. An Example in this Patent describes
the preparation of a copper-chromium-zinc mixed oxide composition,
which after reduction is effective in bringing about the
selective ortho methylation of phenol and ortho cresol by
methanol at substantially lower temperatures than in the cases
of the prior art catalysts. Alternatively, standard copper
chromite or copper chromite precursor compositions can be promoted
by impregnation with suitable metal oxides, hydroxides, carbonates,
formates and the like and heating in place. In another method,
copper and chromium oxides can be coprecipitated with such
other promoters as zinc oxide, barium oxide, manganese oxide,
cadmium oxide, magnesium oxide and the like.
In another variation, the catalyst of the instant
invention can be composed of mixed pellet types. For example,
a bed of copper chromite pellets mixed with magnesium oxide or
zinc oxide pellets can be employed.
The catalyst is preferably used in the form of a bed
through which the reactants are passed in the vapor phase.
Preferred pressures are in the range from about atmospheric to
about 5 atmospheres.
The instant process is carried out at a temperature
of at least 185C. The optimum alkylation temperature is in the
range of from 185C. to about 350C.
The instant process may be carried out
using a variety of reactors with varying flow
rates of the reactants, varying vapor space
8CH-2415
velocities of the reactants and length of the catalyst bed. Tubular
reactors, such as a glass or a metal tube filled ~ith a bed of the
catalyst may be employed. The reactor is heated with conventional means
either by surrounding the reactor with an electrical heater, a heated
¦ gas, or a fused salt bath, liquid metal, etc., which can be conveniently
maintained at reaction temperature by the use of immersion type
electrical heaters. Altern~tively, a fluid bed reactor may be used. The
alkylation reaction is exothermic and, therefore, the heat of reaction
l can be utilized to maintain the catalyst bed at the proper reactiDn
lO ¦ temperature.
¦ The techniques are conventional and reference is made to the
above-mentioned patents.
In carrying out an alkylation in accordance with the invention,
a~y one or a mixture of phenols having an ortho hydrogen together with
lS an alkanol may be vaporized and passed through a reactor heated to a
temperature of st least 185C. containing the copper-chromium catalyst
of the invention. The alkanol can be mixed with the phenol to form a
solution which is then vaporized or separate streams of the two reactants
l may be fed to the same or separate vaporizers and then to said reactor.
Also, the reactants may be passed through ~he catalyst bed with a hydrogen
carrier gas, for example.
The vapors issuing from tbe reactor are condensed in the usual
fashion and the products ~eparated in the usual fashion, for example, by
¦ crystallizatio~, distillation, etc.
. ' 11 ,.
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Description oi the Preferred Embodi ent
The following example~ are set forth to illustrate mora clearly
the principle and prac~ice of this invention to thoae skilled in the art.
Unless otherwise specified, where parts or percents are mentioned, ~hey
-5 are par~s or percents by weight.
EXAMPLE I
_ '
This example is presented to demonstrate the llmited ut~lity
in orthomethylation of phenols of a copper chromit~ cataly6t in which
l no alkylating component has been incorporated.
A vertical hot tube reactor (16 mm ID x 70 cm effective length)
was constructed from hesvy wall glsss, with 24/40 male and female ~OintB.
Vigreaux points were indented just above the male ~oint to support
catalyst pellets. Thermocouple leads were fastened into three other
Vigreaux indentations at points along the length. Three 4 ft. x 1 in.
15 ~ Bris~heat gl8ss insulating he~ting tapes were wound on~o the tube, covered
with glass wool and glass tape, and connected to ~eparate variable trans-
formers. The tube exit was connected by a gooseneck (also heated~ to an
efficient condenser and collection vessel. A three-necked flask served
as the evaporator, with the reactants sdded through a side neck by a
syringe pump.
The reactor wa8 charged with 193 grams (130 ml.) o~ copper
chromite catalyst (Girdler G-13 3/16 x 3/16 in. tablets co~posed of 40%
Cu, 25.5% Cr and the remainder oxide oxygen). The bed was sctivated by
heating under a hydrogen-nitrogen stream, with care taken to control the
Z5 ¦ eYotherm mxim~m eemperat~re 30 ~C ).
L : ~
. ..
1090~
8CN-2415
The reactor temperature was maintsined at 250C. while a
methanol-phenol mixture (5:1 molar ratio) was psssed into the evsporator
at 36 ml/hr. (L~SV=0.28) with a 130 ml/min. hydrogen carrier. The
cond~nsed effluent contained some methylation products -- analysis by
gas-liquid partition chromatography (glpc) showed the presence of
o-cresol (about 5% conversion) along with ~mall amounts (about 1% con-
version) of anisole and p-cresol, and a trace of 2,6-xylenol. Gas
evolution by decomposition of the methsnol was substantial.
On raising the reactor tempersture to 275, 300 and 325C.,
the phenol conversion increased to levels of abou~ lO~h, 20% and 25%,
respectively. The selectivity to o-cresol and 2,6-xylenol remained
relatively poor. At 325C. psrticularly the methanol decompositlon wa~
nearly complete.
I EXAMPLE II
¦ This example is presented to demonstrate the efiect of using
an alkylating co-catalyst in conjunction with the copper chromite in
the methylation process.
The reactor described in Example I was charged with mixed equal
volumes (70 ml. esch) af the copper chromite (Girdler G-13) snd magnesium
. ~r1
oxide (E~rshsw Mg 06019 1/8 in. t~blets). After activatlon of the bet
the 5:1 methanol-phenol and hydrogen carrier were passed through as in
Example I, initially at 250C. Analysi3 of the effluent showed that an
efficient conversion to o-cresol and 2,6-~ylenol had been effected. The
phenolic composition (mole percentages) of the condensate on steady state
~5 operation at several temperatures is summarized in Table 1.
-8-
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8CH-2415
T~ble 1.
Methylation of Phenol Using Copper Chromite
- and Magnesis o-Catalysts
T. C. Phenol~ /0 o-CresoL J0 2~,6-Xylenol, % Mesitol. %
250 60.7 30.4 8.9
300 40.3 34.9 24.6 0.2
325 ~1.1 37.3 31,1 0.5
l .
EXAMPLE III
l The reactor and catalyst bed described in Example II wa~
¦ operated with a liquid feed composed of methanol and o-cresol in 2:1
ratio passed into the evapor2tor at 36 ml/hr. The phenolic product
composition of the condensate on steady state operation at several
temperatures is summarized in Tsble 2.
~able 2.
Methylation of o-Cresol Using Copper Chromite
¦ _snd Magnesia Co-Catalysts
¦ Phenolic Composition
j T. C o-Cresol, % 2.6-XYlenol. /0 Mesitol~ %
250 78.0 22.0
300 58.1 41.4 0.5
325 51.4 47.1 1.5
EXAMPLE IV
l .
¦ 'rhls example i8 presented to demon~trate the effect o~ ln-
corporating an alkylating component into the copper chromite catalyst
in the mathylation proces~.
.,
8CH-2415
The Girdler G-13 copper chromite was impregnated with 10%
by weight of zinc formate, using an aqueous ~olution of the fonmate
and a rotary evaporation technique. The re~ctor de~cribed in Example
I was charged with 130 ml. of the impregnated c~talyst. Activ~tion
under hydrogen at 250 produced a catalyst containing zinc oxide
(sbout 5~/O by weight relative to the initial copper chromite, produced
by decomposition of ~he zinc formate).
With the operating temperature m~intained at 250C., the
5:1 methanol-phenol wa~ pacsed in at 36 ml/hr. ~ith the 130 ml/min.
¦ hydrogen carrier. A 6teady state wa~ reached after sbout æix hours,
at which time the phenolic composition of the condensed effluent was
38.7% phenol, 37.3% o-cresol, 23 9% 2,6-xylenol and 0.1% mesitol~ The
efficiency remained at essentislly the same level over 200 hours of
operation.
EX~`~LE V
The catalyst bed described in Example IV was maintained at
270C. while a mixture of methanol, phenol and o-cregol in 4 0 0.6:0.4.
¦ molar proportions (and 3% by weight) was passed through with the
hydrogen csrrier gas at 72 ml/hr. ~LHSV=0.55). Analysis of the steady
state effluent under these conditions indicated a phenolic composition
of 30.7% phenol, 45.9% o-cresol and 23.4% 2,6-xylenol. Analysis of
the unconden3ed effluent revealed the presence of carbon dioxide ~nd
carbon mono~ide in 1.7:1 rstio, a trace of methsne, and the hydrogen
present as the c~rrier snd a~ a methanol decomposition produc~.
EXAMPLES VI-IX
Metal hydroxide-promoted (about 5% by weight) copper chromite
. -10-
~-,
11~'30f:~Z~ ~
8CH-2415
catalysts were prepared by impregnating the copper chromite tablets with
the corresponding metal formates (magnesium formate, aodium ~ormate,
calcium formate and lithium formate) and pyroly~ing the c~taly~ts in place
(maximum temperature 300C ) during activation under hydrogen. The
S catalyst bed in each case was then maintained at 250C while the 5:1
me~hsnol-phenol mixture was passed in at 36 ml/hr. along with the hydrogen
carrier gas. The phenolic composition in the effluent wa~ determlned by
glpc anslysis at the one-hour point with each cflt~lyst. The results are
summari~ed in Table 3. In each case the catalyst activity gradu~lly
¦ decreased, reaching relatively low levels within 24 hours of operation.
Table 3
Methylation of Phenol Using Metal Hydroxide Impregn~ted
Cop~er Chrom~te Catalysts
Phenol ComPOSitiOn
Example Impre~nant Phenol,% o-Cresol,% 2,6-XYlenol.% Mesitol,%
Mg(OH)2 58.729.8 11.5
6 NaOH 54.534.6 10.9
7 Ca(0~)2 22.832.2 43.2 1.8
8 LiOH 5.0 9.6 66 19.4
Exampte X
The 5:1 methanol-phenol feed was passed into the reactor charged
wi~h 130 ml. of Harshaw barium oxide "stabilized" copper chromite Cu 1107
(1/8 in. tablets containing 33% CuO, 38% Cr203 and 9% BaO) as in the sbove
example~ with the bed temperature maintained at 2500C The phenolic
¦ composition of the effluent at a steady state was 69.8% phenol, 26.5%
~ -11-
11
. ~_
¦ 8CH-2415
o-cresol and 3.7% 2,6-xylenol. Small amounts of anisoles and rlng
hydrogenated products (about 3% total) were also detected,
¦ Exsmplle XI
l A ca~alyst was prepared by impregnating copper chromite (Girdler
5 ¦ G-13, see Example I) with 10% by weight of aluminum isopropoxide, using
an isopropanol solution of the impregnant and ~ rotary evaporation
technique. The dried catalyst was activated with hydrogen in place a8 in
the above examples, then was converted to an "alumina"-modified form by
l trestment with 8 5:1 methanol-phenol feed containing 5% oi water by weight,
psssed in at 36 ml/hr. with the hydrogen carrier ga~, the opexating tempera-
ture being maintained at 250. The phenolic composition of the steady
state effluent was 53.5% phenol, 34.6% o-cresol, and 11.9% 2,6-xylenol.
Example XII
¦ The reactor described in Example I was charged with 2i6 grams
I (130 ml.) of a catalyst co~posed of 52% Zn, 5.7% Cu~ 13% Cr and the
remainder oxide oxygen (Girdler T-359, pieces averaging about 3/16 x 3/16 in.)
After activation under hydrogen, the bed was maintained at 280C while the
5:1 methanol-phenol feed was passed in at 36 ml/hr. The ste&dy state
¦ phenolic compo~ition in the effluent was 60.6% phenol, 34.4% o-cresol and
1 5.0% 2,6-xylenol.
I'
Example XIII
The 5:1 methanol-phenol feed was pas~ed into a bed of 206 grams
(130 ml.) of catalyst containing, before activation, 16% Cu, 32% Cr and 25%
Cd as the oxide~ (Girdler T 988, 3/16 x 3/16 in. pellets). The methylation
process was slow at 250C; about 2% o-cres~l was formed at Che LHSV of 0.28.
11 ~
8CH-2415
At 325 the phenolic composi~ion in the effluent ~as 49.2% phenol, 32,7%
o-cresol and 18.1% 2,6-xylenol.
Exam,~e XIV
I
l The reactor described in Example I was charged with 130 ml. of
¦ Girdler G-89 ca~alyst having a nominal compositlon oP 38% Cu, 31% Cr
and 3% Mn as oxides. Aftsr activation, the 5:1 methanol-phenol mixture
was passed in at 36 ml/hr~ with hydrogen as in the above examples. The
results with steady state operation at several temperatures are summarized
l in Table 4.
Table 4
¦ Mathylation of Phenol Using Cu-Cr-Mn Catalyst
Phenolic_Com~osition
¦I T, C Phenol, % o-CresDl, % ~2~ 6-XY1 ol,_'~ Mesitol %
Il 250 63,3 31.1 5.6
l 275 35.5 ~2.5 22.0
300 2~.0 44.0 29.7 0.3
325 15.0 42.9 40.8 1.2
The phenolic products were accompsnied by small amounts (about
¦ 3% total) of anisoles and ring hydrogenation products. No undecomposed
¦ methanol was detected in the effluent st 325C.
~ Exsmple XV
¦ A barium oxide-stabilized copper chromite cataly~t (3/16 in.
tsblets composed of 34.0% Cu, 30.7% Cr and 5.7% Ba as oxides) was
impregnated with 10% by welght of 7inc forma~e and pyrolyzed in place as
in Example IV. A mixture of ethanol and phenol (5:1 molar ratio, containing
8CH-2415
4~ water) was passed through a 130 ml. bed of the activated catalyst
maintained at 250 at 36 ml/hr. with ~he usual hydrogen carrier gas. Th~
steady state effluent contained, according to glpc analysis, acetaldehyde
(minor), ethanol, water, and the ph~nolic derivatives phenol (62.0%),
2-ethylphenol (29.8%) and 2,6-diethylphenol (8.2%) (molar percentages).
Very small amounts (1% or less) of 4-ethylphenol, 2,4-diethylphenol and
2,4,6-triethylphenol were also detected and characterized.
Example XVI
The catalyst bed described in Example XV was maintained at 300
¦ while a 3:1 molar mixture of allyl alcohol and phenol (and 4.5% water)
was passed into the evaporator at 36 ml/hr. Analysis of the effluent
indicated a phenolic composition of 72.4% phenol9 24.6% 2-n-propylphe~ol
and 3.0% 2,6-di-n-propylphenol. No allylphenol or other unsaturated
derivatives were detected.
Ij
15 ¦ Example XVII
¦ A catalyst was prepared by grinding the copper-chromite
¦I composition described in Example XV, blending the resultant powder with an
¦~ equal weight of zinc oxide powder, and tableting the blend using 5% by
¦ weight of Dow Methogel HG65. The pellets were calcined at 800F then
activated with hydrogen and used with a 3:1 n-propanol-phenol feed at 300C
and L~SV=0.3. The phenolic composition at a steady state was 52.4% phenol,
30.1% 2-n-propylphenol, 15.5% 2,6-di-n-propylphenol and a total of about
2~ of p-substituted products.
~` ~
3~
8C~-2415
Obviously, other modifications and varia~ions of the present
invention are possible in the light of ~he above teach1ngs. It is therefore
to be under3tood that changes may be made in the particular embodiments
of the invention described which are within ehe full intended scope of the
i~vention ~ef ined by the appended clsis9.
r ~
