CA1253135A - Production of phenols and catalyst therefor - Google Patents

Abstract

ABSTRACT

Multicomponent catalysts comprising (1) copper, (2) vanadium, chromium, manganese, iron, cobalt, nickel or zinc; and (3) phosphate are employed for oxidizing an aromatic carboxylic acid to the corres-ponding phenol, e.g., benzoic acid to phenol.

Description

L2~S3~35 PRODUCTION OF P~ENOLS
AND CATALYST THEREFOR

This invention concerns the production o~
phenols, and more particularly the oxldation of aro-matic carboxylic acids to phenols and catalyst there-for.

In U.S. Patents 2,737,026 and 2,852,567, there are described processes for producing phenols from aromatic carboxylic acids which employ a catalyst including copper oxide. The present invention is directed to an improved process and catalyst for oxi-dizing an aromatic carboxylic acid to a phenol.

In accordance with one aspect of the present invention, there is provided a multicomponent catalyst which comprises copper, phosphorus present in the form of phosphate, and vanadium, chromium, manganese, iron, cobalt, nickel or zinc. A preferred ca-talyst is com-prised of copper, zinc and phosphate.

In accordance with another aspect of -the pres-ent inven-tion, there is provided an improved ca-talytic 29,800-F -1-~,

-2~ 3~3~

process for oxidizing an aromatic carboxylic acid having at least one carboxyl group subs-tituted on the aromatic nucleus -to the corresponding phenol in which the cata-lyst is comprised of the above-described multicomponen-t catalyst.

The copper and other metal components of the catalyst are presen-t in an oxidation s-tate suitable for catalyzing the reaction of an aromatic carboxylic acid to a phenol. Preferably, the copper and remaining metals are present in an oxidized form, e.g., either as phos-phates or oxides.

Further preferred are such multicomponent catalysks that additionally comprise alkali metals or alkaline earth metals, also present in an oxidized state. A highly preferred multicomponent ca-talyst com-prises five components: copper, zinc, lithium, magne-sium and phosphate, all metals being present either as phosphate salts or as oxides.

Particularly preferred is the above mul-ticom-ponent catalyst wherein the molar ratio Cu/Zn/P/Li/Mg isin the range of 1.0/0.1/0.1/0.1/0.1 to 1.0/4.0/4.0/4.0/6.0, and preferably within the range of 1.0/1.0/l.0/l.0/1.0 to 1.0/3.0/3.0/3.0/4Ø

The multicomponent catalys-t of the invention can be employed in the absence or presence of a suitable suppor-t material. Thus, for example, -the ca-talys-t may he in the form of pellets or extruda-tes, or supported on a suppor-t material. Suitable support materials include alumina, silica, magnesium oxide, zirconium oxide, sili-con carbide and diatomaceous earth.

29,800-F -2-

-3- ~53~3~

The catalyst may be prepared by a variety of procedures known in the art. Thus, for exarnple, sup-ported catalysts may be prepared by impregnation or spray drying. Al-ternatively, the catalyst components can be mixed and compacted in the form of pelle-ts, extrudates, or other known forms.

In an example illustrating the prepara-tion of a supported catalyst by impregnation, water-soluble salts of the metals, such as the nitrates, are flrst dissolved in concentrated phosphoric acid or a mixture of concen-trated phosphoric and nitric acids. The solutions are then employed to impregnate a suitable support, such as alpha-alumina. The impregnated support may then be dried and calcined to oxidize the metals. The technique is more fully described in the examples that follow.

Af-ter their preparation, -the catalysts of the invention are particularly suitable for use as catalysts in the oxidation of an aroma-tic carboxylic acid to the corresponding phenol. Suitable aromatic carboxylic acids have at least one carboxyl group substituted on the aro-matic nucleus, which is generally a benzene or naphthalene nucleus. Other ring substituent groups, such as alkyl, halo, and others, may also be present. The preferred starting materials are monocarboxylic acids such as benzoic and alkyl-substituted benzoic acids. A most preferred aroma-tic carboxylic acid is benzoic acid.

The oxidation is effected with molecular oxy-gen which can be provided as such or in admixture with other gases, e.g., as air. The oxygen is employed in at least stoichiometric proportions, however, lesser or grea-ter amounts could be employed. In general, oxygen 29,800-F -3-_4~ 3~35 is employed in an amount to provide an oxygen to car-boxyl group mole ratio of from about 1:1 to 10:1, and preferably from 1.5:1 -to 5:1.

The reaction is generally effected in the vapor phase in the presence of steam as a diluent. The steam also functions to minimize the production of esters that result from the reaction of the carboxylic acid and the product phenol. The steam is generally provided in an amount corresponding to a water/carboxyl group mole ratio of 5:1 to 500:1 and preferably 10:1 to 100:1. Additional diluents such as nitrogen may also be present.

The oxidation is effected at temperatures of from about 200C to about 400C, and preferably from 260C
to 350C. The oxidation is generally effected at pressures above atmospheric pressure, with the pressure generally being from about 2 to 20 atmospheres (0.2 to 2.0 MPa).

The catalytic oxidation can be readily effected by the use of any one of a wide variety of vapor-solid contact systems, e.g., employing the catalyst as a fixed or fluidized bed or in a transfer line type of contact system. The above means for effecting the reaction and others should be apparent to those skilled in the art from the present teachings.

The particular advantage obtained according to the instant invention is to provide an active cata-lyst for the highly selective oxidation of aromatic carboxylic acids -to phenolic compounds. Additionally, the catalysts of the invention are characterized by reduced loss or migra-tion of copper from the catalyst.
Advantageously, the catalysts produce less metallic contamination of the phenolic product as well as a 29,800-F -4-~253~L35 reduction in disadvantageous effects caused by migrated copper, such as induced electrochemical corrosion of the reactor surface. Consequently, use of special and expen-sive materials for reactor construc-tion in order to avoid corrosion may be avoided thereby yreatly reducing the costs associated with the invented process.

The following examples are provided as further illustrations of the invention and are no-t -to be construed as limiting.

Exam~le 1 - Catalyst Preparation A 180-ml aqueous solution was prepared from 41-54 g of Cu(NO3)2-2l,2H2O, 24.62 g of LiNo3, 53.12 g of Zn(NO3)2 6~2O, 20.0 g of 85.2 percent H3PO4 and 20.0 g of concentrated HNO3. 192.0 g Of Mg(NO3)2 6H20 was ground into fine powder and mixed thoroughly with 50 r O g Instarok~ cement and 120.0 g of powdered diatomaceous earth (available commercially as Filter-Cel~). The solution was added to the solid mixture and a uniform slurry was made. The slurry was extruded to ~" (0.6 cm) diameter cylindrical strands and dried at 150C in air for 24 hours. The extrudates were ground into 50-80 mesh. The particles were pressed into l~ll (0.6 cm) tablets. The tablets were calcined in air a-t 400C for 18 hours. The finished catalysts had 25 average bulk density 0.55 g/cm3, crush s-trength 41.6 lb/in. (7.4 kg/cm) and dimension 1/4" x l/8" (0.6 cm x 0.3 cm).

Example 2 - Catalyst Preparation A 35-ml aqueous solu-tion was prepared from 30 2-51 g of Cu(MO3)2-2l-~I2O, 1.50 g of LiNo3, 3-21 g o~
Zn(NO3)2 6H2O, 10-85 g of Mg(NO3)2 6H2O, 1-24 g of 85-2 29,800-F -5-~253~3~

percent ~13PO4 and 2.00 ml of concentrated HNO3. Diato-maceous earth (Celite 21A, available commercially from Manville Corp.) was ground to 20-40 mesh as catalyst support. To 15.0 g of support, approximately 12 ml of solution was added to wet the surface of the particles.
. The catalyst was dried at 150C for 2 hours and cQoled to room temperature. The wetting and drying procedures were repeated until the solution was used up. The catalyst was finally calcined at 400C in air for 40 hours. The finished catalyst weighed 20.32 g.

Example 3 - Phenol Production Molten benzoic acid at 150C was pressurized by nitrogen through a capillary tube of 316 stainless steel to achieve the appropriate flow rate. Similarly, the calculated amount of water was pressurized to a vaporizer which was controlled at 250C. Ox~gen and ni-trogen or air were mixed with benzoic acid and steam in a 310C preheating zone above the catalys-t bed.

The catalyst of Example 1 (10.0 cm3, 5.52 g) was charged into a 316 stainless steel fixed bed reac-tor (11/16" (0.7 cm) I.D. x 12" (30 cm) length).
Molten benzoic acid at 150C (flow ra-te, 9.7 g/hr) steam at 250C (flow ra-te, 7.7 g/hr water at room temperature), air (flow rate, 37 cm3/min at room tem-perature) and nitrogen (Elow rate, 36.8 cm3/min at roomtemperature) were introduced into the preheating ~one.
The ca-talyst bed was maintained at 310C and the reac-tion was carried out under ambient pressure, about 0-10 psig (103-173 kPa). The products and -the unreacted benzoic acid were condensed and collected underneath the reac-tor.

29,800-F -6-i3~3~;;

The process was run 6 hours each day for 5 days and -the catalysts regenerated after each run for 3 hours at temperatures under 450C in the presence of steam and limited amounts of oxygen.

Table I presents a typical 6-hour run result using the tablet catalyst.

TABLE I
Selectivity %
Time Benzolc Acld (hr) Conversion % Phenol Benzene Diphenyloxide 1 52.05 39.613.40 2.74 2 27.29 84.878.75 6.38 3 26.11 84.328.91 6.82

4 24.74 82.9110.35 6.74 25.06 83.2210.14 6.64 6 23.22 83.0710.11 6.82 Example 4 The reaction conditions of Example 3 were substantially repeated employing the catalysts of Exam-ple 1 and Example 2. Table II shows the reaction con-ditions and -the results of the process using the two catalysts. Each was run for five 6-hour cycles at 310C.
The benzoic acid conversion was averaged for each day's run. The amount of copper was analvzed at the beginning and end of the reaction. The da-ta indicated there was no activity decline or Cu loss.

29,800-F -7--8~ 3~3~

TABLE II
Reaction Conditions .
Ben-zoic Acid H20 AirN2 CatalYst S _ Bed vol q/hr /hr ~cm3/min Exam. 1 ~" 10.0 cm~ 9.70 7.70 37.036.8 (0.6 cm) Exam. 2 mesh 8.3 cm 9.70 5.83 36.2 30.2 Results Time % Benzoic Acid Conversion o~ Cu (dav~ 1 _ 2 3 _ 5 fresh used Exam. 1 27.92 29.95 27.69 29.75 27.73 ~.9 4.7 Exam. 2 35.74 41.03 42.~6 43.27 42.65 3.6 3.9 Exam~le 5 The catalyst of Example 2 was compared with a catalyst comprised only of copper, lithium and magnesium in the oxide forms. T~e comparative catalyst was prepared in the following manner. Diatomaceous earth (Celite*408, available commercially from Manville Corp.) was ground into 20-35 mesh as catalyst support. A 100-ml aqueous solution was prepared from 10.44 g of Cu(NO3)2 3H20, 3.0 g o~ LiNo3 and 43.38 g of Mg(NO3)2 5H2O and 5 ml of concentrated HN03. To 60 g of the support, approximately 50 ml of solution was added to wet the surface of the par-ticles. The catalysts were dried at 150C for 2 hours * Trade mark 29,800-F 8-9 5 ~3~35 and cooled to room temperature. The rest of the solu-tion was added to -the surface of the catalyst and the catalyst was again dried at 150C for 2 hours. The catalysts were calcined at 400C in air for 16 hours.
The finished catalyst weighed 70.22 g.

The catalyst of Example 2 was compared under substantially identical reaction condi-tions with -the above prepared comparative catalyst. Table III shows the comparison between the -two catalysts. A decline in benzoic acid conversion over time and a very substantial Cu loss were noticed for the comparative catalyst.

TABLE III
Reaction Conditions Ben-(cm3) zoic Size Bed C Acid H20 2 N2 Catalyst (mesh) Vol Temp g/hr g/hr cm3/min cm3/min Exam. 2 20-40 8.3 310 15.34 9.0 11.0 92.0 Compar.* 20-35 8.3 310 15.34 9.0 11.0 92.0 *Comparative Results % Benzoic Acid Conversion Time(day) 1 2 3 5 7 9 18 Exam. 2 32.20 34.83 33.71 - - 33.31 25 Compar.* 30.04 - - 31.49 23.41 20.93 9.61 *Comparative 29,800-F -9---10- ~253~3~;

After completion of the reaction, the compar-ative catalyst was analyzed for loss of copper during the reaction. It was found that the comparative catalyst contained 3.5 percent weight copper initially, but only 0.6 percent by weight after completion of -the reaction.
Under substantially the same reaction conditions, no loss of copper was observed for the catalyst according to Example 2.

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Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A multicomponent catalyst which com-prises copper, phosphorus present in the form of phos-phate, and vanadium, chromium, manganese, iron, cobalt, nickel or zinc.

2. A catalyst of Claim 1 comprising copper, zinc and phosphate.

3. A catalyst of Claim 2 additionally com-prising an alkali metal or both an alkali metal and an alkaline earth metal.

4. A catalyst of Claim 3 wherein the cata-lyst comprises copper, zinc, lithium, magnesium and phosphate.

5. A catalyst of Claim 4 wherein copper, zinc, phosphorus, lithium and magnesium are present in a ratio from 1/0.1/0.1/0.1/0.1 to about 1/4/4/4/6.

6. A catalyst of Claim 1 additionally com-prising a support material.

7. In a process for catalytically oxidizing an aromatic carboxylic acid to the corresponding phenol, the improvement comprising effecting the oxidation with a catalyst according to Claim 1.

8. The process of Claim 7 wherein the oxi-dation is effected at a temperature from about 200°C to about 400°C.

9. The process of Claim 7 wherein the oxi-dation is effected in the presence of oxygen and steam.

10. The process of Claim 9 wherein the aro-matic carboxylic acid is benzoic acid.

11. The process of Claim 7 wherein the oxygen to carboxyl group mole ratio is from about 1:1 to 10:1.

12. The process of Claim 7 wherein the pressure is from about 2 to 20 atmospheres (0.2 to 2.0 MPa).