DE2716035A1 - PROCESS FOR THE SELECTIVE ORTHO-ALKYLATION OF A PHENOL IN THE PRESENCE OF A COPPER-CHROMOXIDE CATALYST - Google Patents

Description

Process for the selective ortho-alkylation of a phenol in the presence of a copper-chromium oxide catalyst

The invention relates to a process for the selective ortho-alkylation of a phenolic compound, the reaction comprising the phenolic compound with an alkanol in the presence of a copper-chromium oxide catalyst.

It is widely known to alkylate phenols with at least one unsubstituted ortho position. Many known processes have been described as being non-selective and non-selective with respect to the type of products formed are distinctive. Winkler et al. describes e.g. in

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U.S. Patent 2,448,942 discloses a process for making pentasubstituted Phenols. In the Winkler et al. it is mentioned that one can use 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, magnesium oxide, calcium oxide, etc. can apply as a catalyst. Alumina is the preferred catalyst. The Winkler process et al. however, it is somewhat indistinguishable and lacks specification for ortho-alkylation with regard to the relative Exclusion of alkylation in the meta and para positions.

Winkler et al. indicate that the reaction occurs at superatmospheric pressures is carried out at temperatures ranging from 300 ° C to about 450 ° C. However, it was indicated, e.g. by Hamilton in US Pat. No. 3,446,856 states that temperatures above 430.degree. C. result in a decrease in the yield of the alkylated product cause. When phenol and methanol are reacted at temperatures above 450 ° C., Hamilton teaches that the production favored by hexamethylbenzene, a non-phenolic product will. For reactions of methanol with phenol, xyIenol or cresol, Hamilton indicates that a temperature of about 350 to 430 ° C is favorable to high yields of alkylated To obtain product, while temperatures below 350 C increase the yield of ether by-products. Temperatures Above 50 ° C. and atmospheric pressures cause decomposition of the reaction constituent and promote it the generation of undesirable materials. The Hamilton method was based on the experimental result that magnesium oxide was a selective ortho-alkylation catalyst, the was useful at atmospheric pressure in a defined temperature range.

U.S. Patents 3,707,569 and 3,751,488 are each based accordingly based on the results that certain tellurium-containing compounds and molybdenum acid salts act as selective ortho-

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Alkylation catalysts are useful. Furthermore, in the U.S. Patent 3,764,630 discloses a process for selectively alkylating a phenolic compound with an alkanol in the presence of Water and a catalytically active compound such as molybdenum oxide and alkali metal, alkaline earth metal, lead, bismuth and ammonium salts of molybdic acid in admixture with magnesium oxide. Also in U.S. Patent 3,843,606 a Catalyst described, the porous magnesium oxide powder is bound with an inert organic cellulosic polymer binder for use in selective alkylation of phenols. Finally, US Pat. No. 3,873,628 describes mixtures of magnesium oxide and manganese sulfate as useful catalysts for the ortho-alkylation of phenols. These patents are incorporated herein by reference the present description added.

Ortho-alkylated phenols have valuable properties. They are particularly useful as a starting material for the production of polyarylene ethers, such as polyphenylene oxide, a valuable thermoplastic resin that is e.g. in U.S. Patent 3,306,875 to A.S. Hay is described and claimed.

It has now been found that a copper-chromium oxide composition can act as a catalyst for alkylation at relatively low temperature can be used, the high selectivity with respect to the substitution in the ortho position in the reaction of phenols and alkanols. The high selectivity and the relatively gentle conditions this method leave the method in terms of solving the problems of unsatisfactory alcohol use and short catalyst life, which the known procedures appear to be promising.

According to the present invention, a selective process for the ortho ^ lkylation of a phenolic ver-

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binding the general formula

created in which each R is a monovalent substituent, selected from the group consisting of hydrogen, alkyl of 1 to 12 carbon atoms, aryl of 6 up to 12 carbon atoms and alkaryl with 7 to 12 carbon atoms, the process comprising reacting the phenolic compound with a lower alkanol in the presence a copper-chromium oxide catalyst. Examples of these substituents include methyl, ethyl, n-propyl, Phenyl, o-methylphenyl, p-methylphenyl, 2,6-xylyl and the like. Particularly useful starting materials are phenol, o-cresol, m-cresol, p-cresol, o-phenylphenol and 3,5-xylenol. The preferred embodiment of the method is made using phenol, ortho-cresol, or a mixture of the two as the phenolic starting material carried out.

Suitable alkanols can have the formula: R ₁ - OH

where R _{1 is} a saturated straight chain or branched chain alkyl of up to about 12 carbon atoms. Examples of alkanols are those in which R 1 is methyl, ethyl, n-propyl, i-propyl, n-butyl, hexyl, octyl, 2-ethylhexyl, decyl, dodecyl. Preferred alkanols are lower primary and secondary alkanols, ie those in which R- contains 1 to 6 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl and hexyl alcohols. Methanol is the preferred alkanol.

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To get the maximum yield of ortho-alkylated products It is preferred to use at least 0.5 moles of alkanol and preferably 1 to 3 moles of alkanol for each hydrogen to be used in the ortho position in the phenolic compound to be alkylated. For example, when phenol are methylated If, in order to produce a maximum yield of 2,6-xylenol (2,6-dimethylphenol), it is preferred to at least To use 2 moles and more preferably 2 to 6 moles of methanol for each mole of phenol. If the phenolic compound is already mono-substituted in one of the ortho positions, maximum yields with at least one Moles of alkanol, e.g., methanol, are obtained per mole of phenolic compound, e.g., ortho-cresol.

The catalysts useful in the present process are copper-chromium oxide compositions containing mixed amorphous oxides or crystalline copper-chromite substances such as those described by H. Charcosset et al. in Compt. Rend. 254, 299O-2 (1962), or mixtures of the amorphous and crystalline substances can be. The copper ⁷ chromium ratio can be varied from about 0.05 to about 10 parts copper per part chromium. In a preferred embodiment, the effect of the copper-chromium oxide compositions is increased or improved by the presence of a component selected from oxides and hydroxides of group I, II or III metals, of manganese, iron and mixtures thereof. These promoters can constitute from about 3 to about 95 percent of the catalyst composition.

The catalysts can be prepared by a number of different processes, such as, for example, the la US Pat. No. 3,899,446 are described, which is incorporated into the present description by this reference. is taken. In an example in this patent, the

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It

Preparation of a mixed copper-chromium-zinc oxide composition described which is effective after reduction to the selective ortho-methylation of phenol and ortho-cresol by methanol at substantially lower temperatures than in the cases of known catalysts. Alternatively, standard copper chromite or Copper chromite precursor compositions by impregnation with suitable metal oxides, hydroxides, carbonates, Formats and the like and heating on the spot can be activated. Another method can use copper and Chromium oxides can be precipitated along with such other promoters as zinc oxide, barium oxide, manganese oxide, cadmium oxide, magnesium oxide and the like.

In another modification, the catalyst may be composed of mixed types of pellets. It can e.g. a bed of copper chromite pellets mixed with magnesium oxide or zinc oxide pellets can be used.

The catalyst is preferably used in the form of a bed through which the reaction components are passed in the vapor phase. Preferred pressures are in the range from about atmospheric pressure to about 5 atmospheres.

The process is carried out at a temperature of at least 185 ° C. The optimal alkylation temperature is in the range of 185 ° C to about 350 ° C.

The process can be carried out using different reactors with varying flow rates of the reaction components, the vapor volume velocities (space velocities) of the reaction components and the length of the catalyst bed can be varied. Tubular reactors like a glass or metal pipe that filled with a bed of the catalyst can be used. The reactor is operated by conventional means either by surrounding the reactor with an elec-

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tric heater, a heated gas or a molten salt bath, liquid metal, etc., which is convenient is maintained at the reaction temperature by the use of immersion type electric heaters. Alternatively a fluidized bed or fluidized bed reactor can be used for this purpose. The alkylation reaction is exothermic and therefore the heat of reaction can be used to maintain the catalyst bed at the correct reaction temperature.

The methods are conventional and known per se, and it reference is made to the patents cited above.

When carrying out an alkylation according to the invention any of the or a mixture of phenols with an ortho-hydrogen can be vaporized together with an alkenol and passed through a reactor which is on is heated to a temperature of at least 185 ° C and contains the copper-chromium catalyst of the invention. The alkanol can be mixed with the phenol to form a solution which is then evaporated, or separate streams can be used me of the two reaction components to the same or separate evaporators and then fed to the reactor. The reaction constituents can also, for example, with a water Substance carrier gas are passed through the catalyst bed.

The vapors emanating from the reactor are condensed in the usual way and the products in the usual way Separately, e.g. by crystallization, distillation, etc.

The following examples are given to further illustrate the principle and practice of this invention to those skilled in the art. Unless otherwise stated when mentioned, parts or percentages are parts by weight or percentages by weight.

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Example 1

This example is given to address the limited applicability of a copper chromite catalyst which does not contain an alkylation component has been incorporated to show in ortho-methylation of phenols.

A vertical hot tube reactor (16 in internal diameter x 70 cm effective length) was made of thick-walled glass and provided with 24'40 core and sleeve connections. Vigreaux points were indented just above the core connector to support catalyst pellets. It Thermocouple leads were attached to three other vigreae indentations at points along the length. Three 1.2 m χ 2.54 cm (4 ft. Χ 1 in.) Briskheat-glass insulated ——— Heating tapes were wound on the pipe, covered with glass wool and glass tape, and with separate regulating transformers tied together. The pipe outlet was through a (also heated) S-bend with an effective Condenser and a collecting vessel connected. A three-necked flask served as an evaporator, taking the reaction ingredients were added through a side neck by a syringe pump.

The reactor was loaded with 193 grams (130 ml) of copper chromite catalyst (Girdler G-13 3 / lfi χ 3'lfi in. Tablets made from 40% Cu, 25.5% Cr and the remainder composed of oxide oxygen goods). The bed was activated by heating under a stream of hydrogen-nitrogen, with the exothermic balance was carefully controlled (maximum temperature 300 ° C).

The reactor temperature was kept at 250 ° C., while a methanol-phenol mixture (5: 1 molar ratio) at 36 ml / h (LHSV = 0.28) with a 130 ml / min. Waaserstoffträ'ger was introduced into the evaporator. The condensed effluent contained some methylation products _v

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and analysis by gas-liquid separation chromatography (glpc) showed the presence of o-cresol (about 5% conversion) along with small amounts (about 1% conversion) of anisole and p-cresol and a trace of 2,6-xylenol. Gas evolution by decomposition of the methanol was vigorous.

As the reactor temperature was increased to 275, 300 and 325 ° C, the phenol conversion increased to levels of, respectively about 10%, 20% and 25%. The selectivity to o-cresol and 2,6-xylenol remained relatively weak. At 325 ° C., in particular, the ethanol decomposition was almost complete.

Example Il

This example is given to demonstrate the effect of using an alkylation co-catalyst in conjunction with to show the copper chromite in the methylation process.

The reactor described in Example 1 was mixed with equal volumes (70 ml each) of the copper chromite (Girdler G-13) and magnesium oxide (Harshaw Mg 0601, 1/8 in. Tablets). After activating the bed were the 5: 1 methanol-phenol / and hydrogen carrier passed through as in Example 1, initially at 250.degree. Analysis of the leakage showed that an effective conversion had taken place in o-cresol and 2,6-xylenol. The phenolic composition (mole percentages) of the condensate under steady-state operating conditions at different temperatures is summarized in Table 1.

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Table 1

Methylation of phenol using copper chromite and magnesium oxide co-catalysts.

T, ° C Phenol, % o-cresol, % 2,6-xylenol, % Mesitol, % 250 60.7 30.4 8.9 - 300 40.3 34.9 24.6 0.2 325 31.1 37.3 31.1 0.5 Example 1 III

The reactor and catalyst bed described in Example II were operated with a liquid feed stream consisting of methanol and o-cresol in proportion 2: 1 and was introduced into the evaporator at 36 ml / h. The phenolic product composition of the condensate in steady-state operation at different temperatures is summarized in Table 2 .

Table 2

Methylation of o-cresol using copper chromite and magnesium oxide co-catalysts.

Phenolic composition T, ⁰ C o-cresol, % 2,6-xylenol, % mesitol, %

0.5 1.5

250 78 , 0 22nd , 0 300 58 ,1 41 , 4 325 51 , 4 47 ,1 Example IV

This example is given to show the influence of incorporation an alkylating component in the copper chromite catalyst in the methylation process.

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The Girdler G-13 copper chromite was impregnated with 10% by weight zinc formate using an aqueous solution of the formate and a rotary evaporation process. The reactor described in Example I was charged with 130 ml of the impregnated catalyst. Activation in hydrogen at 250 ° produced a catalyst containing zinc oxide (about 5 wt -.% _T based on the initial copper chromite, generated by decomposition of the zinc formates).

While maintaining the operating temperature at 250 ° C, the 5: 1 methanol ^ -Senby at 36 ml / h with the 130 ml / min. Hydrogen carriers initiated. A steady state was reached after about 6 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 effectiveness remained essentially the same over 200 hours of operation.

Example V

The catalyst bed described in Example IV was kept at 270 ° C. while a mixture of methanol, phenol and o-cresol in 4.0: 0.6: 0.4 molar proportions (and 3% by weight) was added to the hydrogen carrier gas was passed through at 72 ml / h (LHSV - 0.55). Analysis of the steady-state leak under these conditions showed a phenolic composition of 30.7% phenol, 4.9% o-cresol and 23.4 % 2,6-xylenol. Analysis of the uncondensed spill showed the presence of carbon dioxide and carbon monoxide in the ratio of 1.7: 1, a trace of methane and the hydrogen which was present as a carrier and as a methanol decomposition product.

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Examples VI to IX

Copper chromite catalysts improved with metal hydroxide (about 5% by weight ) were produced by impregnating the copper chromite tablets with the corresponding metal formates (magnesium formate, sodium formate, calcium formate and lithium formlate) and pyrolysing the catalysts on the spot were (maximum temperature 3OO ° C) during activation under hydrogen. The catalyst bed was then kept at 250 ° C. in each case while the 5: 1 methanol-phenol mixture was introduced at 36 ml'h together with the hydrogen carrier gas. The phenolic composition in the effluent was determined by glpc analysis at the one hour point for each catalyst. The results are shown in Table 3. In each case the catalyst activity gradually decreased and reached relatively low values within 24 hours of operation.

Table 3

Methylation of phenol using copper chromite catalysts, impregnated with metal hydroxide.

at Impregnation Phenolic composition o-cresol,% 2 , 6-xylenol , 5 ,% Mesitol,% game funds Phenol, % 29.8 9 - 5 Mg (OH) ₂ 58.7 34.6 10, , 2 - 6th NaOH 54.5 32.2 43, 1.8 7th Ca (OH) ₂ 22.8 9.6 66 19.4 8th LiOH 5.0 Example X

The 5: 1 methanol-phenol feed was introduced into the reactor, the 130 ml with Harshaw barium oxide "stabilized" Copper chromite Cu 1107 (1/8 in. Tablets containing 33% CuO, 38%

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Cr ₀ O ₀ and 9% BaO) was charged as in the above examples, the bed temperature being kept at 250 ° C. The phenolic composition of the steady-state effluent was 69.8% phenol, 26.5% o-cresol and 3.7% 2,6-xylenol. Small amounts of anisoles and ring hydrogenated products (about 3% total) were also detected.

Example XI

A catalyst was prepared by impregnating copper chromite (Girdler G-13, see Example I) with 10% by weight aluminum isopropoxide using an isopropanol solution of the impregnant and a rotary evaporation process. The dried catalyst was voided with hydrogen in place. Site activated as in the examples above, then converted to an "alumina" modified form by treatment with a 5: 1 methanol-phenol feed containing 5% by weight water, introduced at 36 ml / h with the hydrogen carrier gas, the operating temperature was kept at 250 °. The phenolic composition of the discharge in stationary operation 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 216 g (130 ml) of a catalyst composed of 52% Zn, 5.7% Cu, 13% Cr and the remainder was composed of oxide oxygen (Girdler T-359, pieces on average about 3/16 χ 3'1G in.). After activation under hydrogen it became Bed held at 280 ° C while the 5: 1 methanol-phenol feed was initiated at 36 ml / h. The steady state phenolic composition was in the spout 60.6% phenol, 34.4% o-cresol and 5.0% 2,6-xylenol.

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it »

Example XIII

The 5: 1 methanol-phenol feed was in a bed of 206 Introduced grams (130 ml) of catalyst containing 16% Cu, 32% Cr and 25% Cd as the oxides before activation (Girdler T 988, 3 / lfi 3Ί6 in. Pellets). The methylation process was slow at 250 ° C; about 2% o-cresol was formed in the LHSV of 0.28. At 325 ° the phenolic composition in the spout was 49.2% phenol, 32.7% o-cresol and 18.1% 2,6-xylenol.

Example XIV

The reactor described in Example I was charged with 130 ml of Girdler G-89 catalyst with a nominal composition of 38% Cu, 31% Cr and 3% Mn as oxides. After activation, the 5: 1 methanol-phenol mixture was passed in at 36 ml ^/ h with hydrogen as in the above examples. The results of the steady-state operation at various temperatures are shown in Table 4.

Methylation Table 4 ; composition 2,6-xylenol,% mesitol.% ⁰ C phenol, of phenol using Cu-Cr-Mn-
Catalyst. 5.6
22.0
29.7 0.3
40.8 1.2 T, 63.3
35.5
26.0
15.0 Phenolic « 250
275
300
325 % o-cresol,% 31.1
42.5
44.0
42.9

The phenolic products were accompanied by small amounts (about 3% total) of anisoles and ring hydrogenated products. No undecomposed methanol was detected in the spout at 325 ° C.

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rv

Example XV

A barium oxide stabilized copper chromite catalyst (3/16 in. Tablets consisting of 34.0% Cu, 30.7% Cr, and 5.7% Ba composed as oxides) was impregnated with 10 wt% zinc formate and pyrolyzed in place as in Example IV. A mixture of ethanol and phenol (5: 1 molar ratio, content 4% water) was passed through a 130 ml bed of the activated catalyst, which was kept at 250, at 36 ml / h with the usual hydrogen carrier gas. According to the glpc analysis, the steady-state outlet contained acetaldehyde (little), ethanol, Water and the phenolic derivatives of phenol (62.0%), 2-ethylphenol (29.8%) and 2,6-diethylphenol (8.2%) (molar Percentages). Very small amounts (1% or less) of 4-ethylphenol, 2,1-diethylphenol and 2,4,6-triethylphenol were also detected and identified.

Example XVI

The catalyst bed described in Example XV was kept at 300 °, while a 3: 1 molar mixture of allyl alcohol and phenol (and 4.5% water) at 36 ml / h in the Vaporizers have been initiated. Analysis of the leak showed a phenolic composition of 72.4% phenol, 24.6% 2-n-propylphenol and 3.0% 2,6-di-n-propylphenol. There were no allyl phenol or other unsaturated derivatives detected.

Example XVII

A catalyst was prepared by grinding the copper chromite composition described in Example XV, mixing the resulting powder with an equal weight of zinc oxide powder, and tableting the mixture using 5% by weight Dow Methogel HG 65. The pellets were measured at 426.66 ⁰ C (800 ° F) calcinated

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ned, then activated with hydrogen and used with a 3: 1 n-propanol-phenol feed at 300 ° C. and LHSV = 0.3. The steady state phenolic composition was 52.4% phenol, 30.1% 2-n-propylphenol, 15.5% 2,6-di-n-propylphenol, and a total of about 2% p-substituted products .

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Claims (8)

Dr. rer. not. Horst Schüler ^ ⁰⁰⁰ Frankfurt / Main ι 7 λ . ι ₉₇ 7 PATENT Attorney Kai.erstra * se 41 Dr.HS / fci Telephone (0611) 235555 2716035 ^{Τβ | βχ: 0} ^ ^{16759 m} ° P ^{at d} Postal check account: 282420 (502 Frankfurt / M. Bank account: 225/0389 Deutsche Bank AG, Frankfurt / M. 4246-8CH-2415 Patent claims Process for the selective ortho-alkylation of a phenolic compound of the general formula: wherein each R is selected from hydrogen, alkyl of 1 to 12 carbon atoms, aryl of 6 to 12 carbon atoms, and alkaryl of 7 to 12 carbon atoms is selected, characterized in that it is the reaction of the phenolic compound with an alkanol with up to about 12 carbon atoms at a temperature of at least 185 ° C in the presence of a copper-chromium oxide catalyst comprises, which consists of crystalline Copper chromites, mixed amorphous oxides of copper and chromium, and mixtures of the foregoing Substances is selected. 2. The method according to claim 1, characterized in that each R is hydrogen is. 3. The method according to claim 1, characterized in that the alkanol is methanol. 709844/0742 4. The method according to claim 1, characterized that the catalyst is copper chromite. 5. The method according to claim 1, characterized that the catalyst is mixed with a promoter consisting of the oxides and hydroxides of group I, II or III metals, is selected from manganese, iron, or mixtures thereof. 6. The method according to claim 5, characterized That the catalyst is in the form of copper chromite pellets mixed with pellets of oxides from Group I, II or III metals, of manganese and iron, and mixtures thereof is present. 7. The method according to claim 5, characterized in that the promoter zinc oxide is. 8. The method according to claim 1, characterized in that the alkylation at a Tempe
will lead. a temperature of 185 ° C to about 350 C 709844/0742