IL24162A - Process and catalyst for the production of aromatic nitriles - Google Patents

Description

SPECIFICATION Process and catalys for the production of aromatic nitriles I- (we) HALCOU IftTERHATIQNAL, INC. , a corporation organized and existing under the laws of the State of Delaware, of 2 Park Avenue, New York, N,Y. 1G016, U.S.A., do hereby declare the nature of this invention and in :what manner the' same is to be performed, to be particularly described and ascertained in and by the following statement :- .GH#MI M.:ERO.eESS- This invention relates .to a new and improved method for the production of aromatic nitriles from alkyl and alkenyl aromatic compounds and, particularly, to a catalyst for such processes. More specifically, the instant invention teaches the use of a catalyst containing vanadium and an-timony.

The conversion of alkyl or alkenyl aromatics to aromatic nitriles by the simultaneous reaction with ammonia and oxygen has been known since 1950. The reaction is generally performed in the vapor phase in the presence of a catalyst. An example of this ammoxidation is the conversion of para-xylene to terephthalonitrile. This process, while advantageous as contrasted to the two-step route, i. e. , the oxidation of the aromatic alkyl and alkenyl to the acid followed by amidation and dehydration of the amide, results in nltrile eelectivlties of only about 70%.

In accordance with the instant invention, it has bee discovered mixed that the use of a ©^-catalyst comprising vanadium and antimony re suit 3 in selectivitles approaching 80%. This sharp incre se in select vity is particularly surprising especially when contrasted to the results obtained by using a single metal catalyst or other combination of metals.

The aromatic compounds suitable for conversion into the nitriles by the process of this invention may be represented by the formula: - /- X— G— R' where R represents — H or an alkyl or an alkenyl radical, R* and R" represents -- H, --OH or ««0 or an alkyl or an alkenyl radical, and X represents the un-" substituted phenyl radical or the phenyl radical substituted in any of the 2 to 6 positions b — F, —CI, — Br, or the radical or represents the phenyl radical condensed with no more tha one benzene ring Where in the above formula R, R* and R" represent hydroge or an alkyl or an alkenyl radical and X represents the un substituted henyl' radical ' or such radical condensed with no more than one benzene ring, the aromatic compounds are alkyl substituted or alkenyl substituted benzene and naphthalene hydrocarbons. Alcohols, aldehydes or ketones which are intermediate oxidation products of such hydrocarbons contain the oxygen linked directly to acyclic carbon with no oxygen atom being directly linked to more than one of the acyclic cajrbon atoms and no acyclic carbon atom being directly linked to oxygen by more than two of its valences.

To illustrate the nitrile compounds formed, reference is made to the following table; , TABLE 1 ' ' '·'' ■ Alkyl or Alkenyl Aromatic Nitrile 1. Toluene Benzonitrile 2. Para-xylene p-toluniHiJliee and terephthalonitrile TABLE 1 (continued) 4. Ortho-xylene o-tolunitWL-rdp, phthalonitrile and . phthalimide . esitylene trime sic acid trinitrile 6. Ethylbenzene benzonltrlle 7. p- Cymene ip^'blun'ttr-ile^* p-isopropyl benzo- nitrile and terephtholonitrile 8. Chlorotoluene chlorobenzonitrile 9. Alph- methyl naphthalene alpha-oyano naphthalene and phthalonitrile The types of compounds which may be used to form the finished cotolyat oro as followo: Antimony halides such as antimony trichloride and antimony tri- ; bromid and antimony oxides such as antimony trioxld© and antimony pent-oxide, to supply the antimony component. The antimony compounds may be dissolved with water and concentrated hydrochloric acid.

The vanadium catalyst may be introduced conveniently as va^: nadium pentoxide and ammonium metavanadate. The vanadium compounds are reduced to the V*4 state in water or concentrated hydrochloric acid with oxalic acid or sulphur dioxide to give a homogeneous solution.

The catalyst support is preferably alumina with a surface area of about 0.5 m2/gm. Other supports such as silicon carbide, pumice and zirconia may be used. antimony trloxide, broadly la present from 0.5 to 20 wt. %, preferably from 4 to 10 wt. %. The vanadium compound, expressed as vanadium pentoxide, is present from 0.1 to 20 wt. %, preferably from 0.5 to 3 wt. %. ' The solution of the metals are mixed and contacted with the support. Thereafter they are dried, preferably in a rotary evaporator, and finally calcined at a temperature from 300 to 550eC.

In performing the reaction the nltrile precursor is Intermixed with an oxygen-containing gas and ammonia or a substance yielding ammonia. Most generally, the oxygen- containing gas is air, but, of course, pure oxygen may be employed. As a general rule, it is desirable that the feed contain from 8 to 20% oxygen.

The ammonia level in the feed may range broadly from 2 to 20%, to 8% is preferred. Generally, ammonia is added; however, compounds which yield ammonia under the reaction conditions, e.g. , ammonium carbonate, may be substituted. ? The amount of the alkyl or alkenyl aromatic s compounds may vary over a broad range and depends on the particular compound employed.

Generally, less than 10% of the aromatic compounds is present, preferably, from 0.5 to 5%.

It is preferable also to carry out the reaction in the presence of steam. Amounts up to 60% are advantageous, but preferably, amounts in the range of from 5 to 25% of the feed gas are used. Steam moderates the reaction thereby decreasing CO and C02 make. The reaction conditions are also dependent on the nltrile compounds formed. Consideration of the number of preferably 325 to 500°C. In the case of the preparation of terephthalonitrile, preferred temperatures are 425 to 600°C.

While atmospheric conditions may be satisfactorily employed, pressures up to 100 atmospheres are suitable. Space velocities of 500 to 4000Aour are satisfactory, preferably 1000 to 2500Aour.

To illustrate more fully the instant invention attention is directed to the following example s: EXAMPLE 1.

The catalyst of the instant invention is prepared by adding 20.8 grams of vanadium pentojdde to 100 cc. of concentrated hydrochloric acid. Sulphur dioxide is bubbled through the solution until it becomes clear blue and homogenous. A rsecond solution is prepared by dissolving 202 grams of antimony trichloride in 400 cc. of concentrated hydrochloric acid. The two solutions are mixed and added to 1440 grams of .Alcoa tabular alumina T-71, : 1/4" to 8 mesh and dried in a rotary evaporator. The catalyst is calcined by , heating to 425°C in an oven. This temperature is maintained for 2 hours. The finished catalyst contains 1.3 wt. % of vanadium pentoxide and 8.1 wt. % of antimony trioxide on alumina, . The calcined catalyst is loaded into a Jacketed carbon steel tube (1 inch G.D. x 10 feet) to form a 114 inch bed. A gaseous mixture containing 1% para-xylene, 10% steam, 6% ammonia and 83% air, all percent by volume, pass through the carbon steel tube over the catalyst at a space velocity of 1500/hbur. The tube is heated to 730°F by running molten salt in the Jacket countercurrently to the feed.

With an essentially complete conversion, a terephthalonitrile yield of 82.5 mole percent is obtained.

EXAMPLE ?, Additional runs using different catalysts are performed to show the outstanding results that are obtained by employing the claimed catalyst. The percentage of catalyst components, the salt temperatures employed and the yield of tferephthalonitrile are 3hown in the following tablet V a 0£ Shafts Sn Ox Cr 03 Salt Temp.»C Mol TPN 1. 4.8 — — 432 56.4 2. 1.3 — . 8. 6 — 400 1. 3. 4. 4 — , — 9.6 399 48.9 4. — 8.1 — — 400 0 . .

In run No. 2 the tin in the catalyst is added as stannous chloride dissolved in water. In run No. 3 the chromium is added as chromium trloxide dissolved in water.

The above table clearly shows that the vanadium- antimony catalyst described ih Example 1 is markedly superior to the other catalysts. The next best catalyst, the vanadium-tin, had a selectivity over 10 points less than that obtained by using the instant invention. Surprisingly, the antimony catalyst is completely ineffective per se yet when combined with the vanadium, also^a particularly poor catalyst per se, outstandingly high yields are obtained. This result is particularly surprising and unexpected.

EXAMPL 3 Run No. 1 was repeated except meta-xy ene was employed as the feed. A yield of isophthalonitril© of 65% was obtained. - 7 - 24162/2

Claims (10)

1. A process for the preparation of aromatic nitriles from the corresponsing alkyl or alkenyl aromatic compounds of the formula where R represents —H or an alkyl or an alkenyl radical, R' and R" represents —H, —OH or ==0 or an alkyl or an alkenyl radical, and represents the unsubstituted phenyl radical or the phenyl radical substituted, in any of the 2 to 6 positions by — F , —CI, —Br, or the radical or represents the phenyl radical condensed with no more than one benzene rin twhich comprises subjecting the compounds to ammoxidation with the aid of a mixed catalyst containing vanadium and antimony on a support.

2. A process according to Claim ¾ wherein meta- or para-xylene is used as starting material.

3. A process according to Claim 1, wherein the suppor of the catalyst is alumina preferably having a surface area of less than l i /g,

4. A process according to Claim 1, 2 or 3* wherein the reaction is carried out at a temperature between 425 and 600°C and at a pressure between 1 and 100 atm. - 8 - 24162/2

5. A process for the ammoxidation of alkyl or alkenyl aromatic compounds to the corresponding nitriles, substantially as described herein with reference to tie Examples.

6. An ammoxidation catalyst for use in the process aocording to any of Claims 1 to 5 which comprises vanadium and antimony on a support.'

7. A catalyst according to Claim 6, wherein the support is alumina having a surface area of less than 1 m /g1 «

8. A catalyst according to Claim 7 containing from 0.5 to 20$ preferably from 4 to 10$ of antimony, expressed as antimony trioxide, and 0.1 to 20$ preferably 0.5 to 3$ of vanadium, expressed as vanadium pentoxide, the percentage being by weight of the catalyst mixture including the support.

9. A process for the preparation of an ammoxidation catalyst according to any of Claims 6 to 8 which comprisess preparing an aqueous solution containing soluble vanadium and antimony compounds, contacting the solution with a catalyst support, and drying the mixture,

10. A process according to Claim 9, wherein the solution is prepared in that an antimony hallde or oxide and a vanadium oxide or ammonium vanadate are dissolved in aqueous hydrochloric acid. For the Applicants DR. BEIHHOLD GOHN/A PARTNERS PC/rb