Magnesium-containing catalyst activated under vacuum, in nitrogen, or in air, and use in an ortho-alkylation process

A catalyst precursor comprising a magnesium compound or material, optionally also containing other metal compounds, is activated for use by calcining at an elevated temperature in the presence of air or nitrogen, or under vacuum. The active catalyst which results may be used in processes for the ortho-alkylation of phenolic compounds, with good yields of and selectivity to the ortho-alkylated end product.

BACKGROUND OF THE INVENTION 
Phenolic compounds which have an alkyl substituent in the ortho position on 
the ring are known to be useful as starting materials for the preparation 
of polyphenylene oxide (ether) resins. In general, such compounds are made 
by processes involving the vapor phase reaction of a phenolic compound and 
an alkyl alcohol in the presence of a catalyst. Various catalysts have 
been described in the patent literature. 
For instance, processes for the ortho-methylation of a phenolic compound 
using magnesium oxide as a catalyst are disclosed by Hamilton in U.S. Pat. 
Nos. 3,446,856 and 3,479,410. Hamilton teaches that the magnesium oxide 
can be derived by the thermal decomposition of magnesium carbonate, basic 
magnesium carbonate or magnesium hydroxide. Van Sorge in U.S. Pat. No. 
3,972,828, describes a catalyst consisting of powdered magnesium oxide in 
combination with an inert polymeric binder. 
Still other catalysts are disclosed elsewhere in the patent literature. 
U.S. Pat. No. 3,873,628 describes a catalyst prepared by forming a mixture 
of magnesium oxide and manganese sulfate, heating to nearly complete 
dryness, and calcining at an elevated temperature to achieve activation. 
The mixture can be prepared using finely divided powders of the two 
compounds, or from an immersion of the magnesium oxide in an aqueous 
solution of manganese sulfate. Both U.S. Pat. Nos. 3,972,836 and 3,974,229 
(also to Van Sorge) describe ortho-alkylation processes in which the 
catalyst comprises a mixture of magnesium and manganese oxides. In a 
preferred procedure, the catalyst is activated for use by heating it in 
the reactor in the presence of methanol vapor, prior to commencement of 
the alkylation reaction. 
More recently, an ortho-alkylation process has been disclosed in which a 
catalyst comprising a magnesium compound is activated by calcining at an 
elevated temperature, in situ, in the presence of a feed stream of the 
alkylation reaction mixture. This is described in U.S. application Ser. 
No. 303,567, filed Sept. 18, 1981, belonging to the same assignee as 
herein. 
INTRODUCTION TO THE INVENTION 
The present invention is based on the discovery that a catalyst precursor 
comprising a source of magnesium, optionally also containing other 
catalytic metal or metal compounds, can be activated for subsequent use in 
ortho-alkylation reactions by a treatment comprising calcining at an 
elevated temperature in air or an inert gas such as nitrogen, or in a 
vacuum. The calcination can be performed outside the reactor, or in situ 
in the reactor prior to contacting with an alkylation feed mixture. 
Alkylation reactions carried out in the presence of these catalysts result 
in a better yield of ortho-alkylated product, or alternatively, in better 
selectivity to the ortho-alkylated product, in comparison with a catalyst 
which has been calcined in situ in the presence of an alkylation feed. 
Thus, one aspect of the invention comprises catalysts formed in the manner 
prescribed, and another aspect comprises use of the catalysts in a process 
for the ortho-alkylation of phenolic compounds. These aspects are more 
fully described as follows. 
DESCRIPTION OF THE INVENTION 
The catalyst precursor is generally provided in the form of a 
magnesium-containing material or compound, which may be used alone or in 
admixture with one or more additional metals or metal compounds that serve 
as co-catalytic ingredients. 
Suitable magnesium compounds include magnesium carbonate and magnesium 
hydroxide, but other magnesium compounds capable of being converted to 
magnesium oxide at an elevated temperature without fusing or sintering may 
also be employed. 
Suitable manganese-containing materials include basic magnesium carbonate. 
The term "basic magnesium carbonate" refers to materials represented by 
the formula 
EQU xMgCO.sub.3 .multidot.Mg(OH).sub.2 .multidot.xH.sub.2 O 
in which each x is independently a number average from about 3 to about 5. 
In the preferred embodiments, the source of magnesium for the catalyst is 
basic magnesium carbonate, especially in the form of finely divided 
particles. 
As indicated, the magnesium containing material or compound may be used in 
conjunction with additional metals or metal compounds in the catalyst 
precursor. These are selected from among compounds of other metals besides 
magnesium which, after calcining, exhibit co-catalytic activity with 
magnesium oxide. Compounds of manganese, copper, titanium and zinc are 
representative. Examples include manganese nitrate, manganese sulfate, 
manganese acetate, manganese bromide, manganese chloride, metallic copper, 
cupric nitrate, cuprous oxide, zinc nitrate, zinc oxide and titanium 
dioxide. The precursor may be prepared by mixing together dry powders of 
the respective metals or metal compounds, or if desired with use of more 
sophisticated techniques such as by precipitation of a compound of one of 
the metals, e.g., manganese hydroxide, in the presence of a suspension or 
slurry of the other, e.g., magnesium carbonate. 
By way of further illustration, in one procedure a sequence is followed in 
which an aqueous solution of a manganese compound is added to a suspension 
of a magnesium compound in water, the two are mixed together, and a base, 
e.g., sodium hydroxide or ammonium hydroxide, is added gradually to cause 
precipitation of manganese hydroxide. In another procedure, which is also 
suitable, the aqueous mixture of magnesium and manganese compounds is 
heated to an elevated temperature to induce precipitation of the manganese 
compound without the use of a base. 
Depending on how the catalyst precursor has been prepared, it may be 
desirable to dry it before calcination, to drive off any volatiles and to 
remove most of any moisture which may be present. Drying may be effected 
in any convenient manner, such as by blowing hot air over the particles, 
by heating in the presence of an applied vacuum, and so forth. In a 
preferred procedure, the particles of the precursor are placed in an open 
tray and heated in an oven at a temperature of from 100.degree. to about 
110.degree. C., until less than about 2 percent by weight of volatiles 
remain. 
Afterwards, the precursor is preferably treated to convert the particles to 
a free-flowing, finely divided form. This may be done, for instance, by 
grinding the particles through a wire mesh screen, for example, 16 to 20 
mesh, U.S. Standard Sieve. 
The finely divided precursor particles are then shaped into the desired 
physical form, which may be done using any suitable method or device. 
Illustratively, and preferably, the particles are shaped into tablets on a 
press, using standard tabletting equipment and procedures. If desired, 
however, the particles can be processed into cylinders, pellets or 
virtually any other shape known to those skilled in the art. 
One or more supplementary materials which function as shaping aids or 
binders for the particles may also be added. In one procedure, a 
polyphenylene ether resin, such as described by Hay in U.S. Pat. Nos. 
3,306,874 and 3,306,875, is compounded as a binder with the particles in 
an amount from about 0.1 up to about 20% by weight. Special mention is 
made of poly (2,6-dimethyl-1,4-phenylene ether)resin for this purpose. A 
polyphenylene ether copolymer may also be used instead. This is followed 
by the addition of a small amount, for instance, from 0.1 to 3.0% by 
weight, of powdered graphite as a shaping aid. The mixture is then 
tabletted. 
After being shaped, the precursor is activated for use by a calcining 
treatment in which the particles are heated at an elevated temperature in 
air or nitrogen gas, or under vacuum. A temperature of at least 
300.degree. C., and preferably between about 350.degree. and about 
500.degree. C., for a period of up to about 24 hours is usually 
sufficient, but temperatures as high as 550.degree. C., may be used. The 
calcination may be and preferably is carried out before the catalyst is 
loaded into the reactor. Alternatively, calcination may be conducted in 
situ in the reactor after the catalyst precursor has been loaded and 
before the reaction is initiated. 
The manner in which the precursor particles are heated is not critical. 
Thus, heat may be applied directly to the particles, as in an oven or upon 
contact with the heated walls of the reactor chamber, or through 
convection by contacting with air or nitrogen which has been preheated to 
the temperature of catalyst activation. 
During calcination, minute pores form in the catalyst composite, thereby 
exposing more surface area. A surface area of least 25 and especially from 
25 to 450 square meters per gram of catalyst is desirable and will 
normally be achieved using the conditions described above. 
The catalyst prepared in the aforementioned manner may be employed to 
effect or facilitate the ortho-alkylation of phenolic compounds, such as 
those having the formula 
##STR1## 
in which each R, independently, is a monovalent substituent selected from 
the group consisting of hydrogen, alkyl (preferably, C.sub.1 to C.sub.12 
alkyl), phenyl, and alkyl substituted phenyl (preferably, C.sub.1 to 
C.sub.12 alkyl substituted phenyl). 
The alkyl alcohol which is a co-reactant in the process is desirably a 
branched or linear saturated alcohol having up to about 16 carbon atoms, 
such as, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, 
tert.-butyl, amyl, isoamyl, hexyl, heptyl, octyl, nonyl, decyl, lauryl, 
cetyl, cyclohexyl, and the like. Especially preferred are alcohols having 
up to 6 carbon atoms, with methanol being the most preferred. 
By way of illustration, a reaction feed mixture comprising the phenolic 
compound or compounds and an alkyl alcohol is vaporized and passed through 
a reactor heated to a temperature of at least 300.degree. C., preferably 
from about 400.degree. to about 500.degree. C., which contains a catalyst 
prepared as described. For best results, it is advisable to use at least 
one mole of the alkyl alcohol, and preferably from one to three moles, for 
each ortho position on the phenol to be alkylated. For example, if phenol, 
which has two ortho hydrogens per molecule, is to be methylated to produce 
2,6-xylenol, it is desirable to employ from two to six moles of methanol 
for each mole of phenol, the larger yields being obtained with use of 
higher ratios of methanol to phenol. 
The ortho alkylation process can be carried out under a variety of reaction 
conditions of temperature, pressure, flow rate of reactants, vapor space 
velocity of reactants over catalyst, contact time of reactants with 
catalyst, length of catalyst feed, and so forth. Above a temperature of 
500.degree. C., however, decomposition of the reactants or products often 
becomes a problem, and such temperatures should be avoided. 
Generally, the reaction conditions are regulated to minimize the amount of 
unreacted feed materials which must be recovered and reused, and to 
maximize the percentage of selectivity to the desired ortho-alkylated end 
product, that is, phenolic compounds having an alkyl substituent in the 
"2" or both the "2" and "6" positions on the ring. 
While the reaction proceeds at atmospheric pressure, which is preferred, 
superatmospheric pressures or subatmospheric pressures can be used if 
desired. 
The vapors issuing from the reactor are condensed, and the products are 
separated by conventional methods, such as crystallization or 
distillation.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS 
The invention is illustrated in the examples which appear below. A 
comparison with another catalyst type is included. 
EXAMPLE 1 
This example illustrates the preparation of a catalyst precursor and 
activation of the precursor by calcining under various conditions, 
including those in accordance with this invention. 
In a vessel equipped with temperature measurement and stirring means, 518.9 
grams of basic magnesium carbonate were added to 2000 milliliters of 
distilled water, with continuous mixing, to form a slurry. To this was 
added a 20 percent (by weight) solution of manganese nitrate in water, 
with the addition being carried out gradually over a period of 90 minutes. 
The resulting mixture, still comprising a suspension of basic magnesium 
carbonate particles, was stirred under a blanket of nitrogen, for 3 hours, 
with the temperature of the mixture being maintained at 80.degree. C. for 
the entire period, during which a precipitate of manganese hydroxide 
formed. At the end of the period, the reation mixture was centrifuged to 
separate the solids. The solids were dried, then blended with 
poly(2,6-dimethyl-1,4-phenylene ether)resin (PPO.RTM., General Electric 
Company) in a 90:10 weight ratio. Powdered graphite in an amount of 0.5 
percent by weight was added, and the resulting blend was tabletted on a 
press to form tablets having a dimension of 3/16 inch by 1/8 inch. This 
constituted the catalyst precursor. 
The tablets were divided into four equal portions. One portion was not 
calcined, a second was calcined by heating at 500.degree. C. overnight in 
air, a third was calcined by heating at 500.degree. C. overnight in 
nitrogen, and the fourth was calcined by heating at 500.degree. C. 
overnight in a vacuum. 
EXAMPLE 2 
The activated and non-activated catalysts prepared as described in Example 
1 were evaluated in a process for the ortho-methylation of phenol and 
ortho-cresol to form 2,6-xylenol, using the reactor described below. 
THE REACTOR 
The Reactor comprises two stainless steel tubes, both disposed along a 
verticle axis, one of which has length of 15 inches (38.1 centimeters), 
the other of which has length of 24 inches (60.96 centimeters), and both 
of which have an inner diameter of 3/4 inch (1.91 centimeters). The first 
functions as a vaporizer. The second is filled to a depth of two inches 
with glass beads serving as a support for the catalyst, and functions as a 
reactor. Both tubes are partially immersed in a fused salt bath, the first 
to a depth of 8 inches (20.3 cm), the second to a depth of 17 inches (43.2 
cm). The first (vaporizer) and second (reactor) tubes are joined by a 
third tube, consisting of a two-inch long (5.1 cm) steel pipe connected at 
one end to an opening in the first tube 5 inches (12.7 cm) from its 
bottom, and at the other end to an opening in the second tube 14 inches 
(35.6 cm) from its bottom. The connector tube also passes through the 
fused salt bath. 
In practice, a feed stream comprising the reactants is sent from a 
reservoir, through a metering pump, into the first (vaporizer) tube, where 
the feed stream is heated to a temperature high enough to volatilize the 
constituents. The vapors emitting from the vaporizer tube pass through the 
interconnecting pipe, which serves as a preheater to bring the vapors up 
the the temperature of the reactor tube. The vapors are fed from there to 
the reactor tube and the catalyst bed, where reaction takes place. Product 
vapors leave the bottom of the reactor tube through a stainless steel 
outlet tube, having an inner diameter of 3/8 inch (0.95 cm), and are led 
to a water-cooled condenser and receiver where they are liquified and 
recovered. The non-condensible materials are fed to an off-gas meter, 
where they can be measured. 
In each of the present cases, the reactor was charged with 110 milliliters 
of catalyst (or catalyst precursor in one instance, as explained), then 
capped and placed in a 370.degree. C. salt bath, immediately after which a 
stream of nitrogen gas was blown over the catalyst at a rate of 2 standard 
cubic feet per hour (SCFH). After a period of 15 minutes, the feed stream 
was introduced, which consisted of a 4:1 weight ratio of methanol to 
phenolics. The phenolics comprised a 60:40 weight ratio of 
phenol:ortho-cresol, containing about 20% water. A feed rate of 215 
milliliters per hour was used, which was equivalent to a liquid hourly 
space velocity (LHSV) of 1.95. The reaction was conducted using standard 
pressure (1 atmosphere). The temperature was maintained at about 
456.degree. C. for the entire period. Periodically, the product stream was 
sampled and evaluated. The percentages of unreacted phenol and 
ortho-cresol, of 2,6-xylenol (the desired end product) and of 
2,4,6-trimethyl phenol (a byproduct), as well as the selectivity to the 
desired end product were calculated, and the time weighted average results 
are reported below. 
TABLE 
______________________________________ 
COMISON OF CATALYSTS IN 
ORTHO-ALKYLATION PROCESS 
Catalyst Selectiv- 
by Type of 
Wt. % Wt. % Wt.% Wt. % ity to 
Activation 
Phenol o-Cresol 2,6 2,4,6 2,6, % 
______________________________________ 
Vacuum 2.00 17.30 73.89 6.96 10.5 
Nitrogen 
1.75 16.66 73.26 7.23 10.2 
Air 2.63 25.98 66.86 3.92 17.1 
In Situ* 
3.23 21.21 68.16 6.83 10.1 
______________________________________ 
*Prior Art Comparison 
As can be seen, the best selectivity to 2,6-xylenol occurred with use of a 
catalyst which had been activated by calcining in air, in accordance with 
the invention. The selectivities in the other three cases are comparable, 
but the catalysts calcined in nitrogen and under vacuum, respectively, 
also according to the invention, resulted in higher yields of 2,6-xylenol 
than the comparison catalyst, which had been calcined in situ in the 
presence of the alkylation feed mixture. 
All of the patents mentioned above are hereby incorporated herein by 
reference. 
Other modifications and variations of the invention are possible and will 
occur to those skilled in the art in the light of this disclosure. Instead 
of methanol, other lower alkyl alcohols such as ethyl alcohol, propyl 
alcohol, butyl alcohol, or the like, can be used as a co-reactant. Instead 
of calcining outside the reactor, activation can be carried out in situ in 
the reactor, with use of the environments described, that is, vacuum, air 
or nitrogen. It is to be understood, therefore, that changes may be made 
in the particular embodiments shown which are within the scope of the 
invention defined by the appended claims.