DE2205806A1 - METHOD FOR MANUFACTURING ALPHA-TETRALON - Google Patents

Description

FARBENFABRIKEN BAYER AG

LEVERK US EN-Bayerwerk Central area Patents, trademarks and licenses

^{Zg / Rä} _L Feb. 7, 1972

Process for the production of <= C-Tetraion

The invention relates to a new process for the production of <£ -Tetraion "

Processes for the production of O ( -Tetraion are already known:

For example, OC- tetraion is obtained by Friedel-Crafts reaction from benzene and ^ T-butyrolactone (Am. Soc. 74, 4721 (1952)) or from Jf-phenylbutyric acid chloride (Org, Synth. Coll. Vol. II, 569 (1943 )). It can also be obtained by splitting off water with ring closure from (/ "- ^ - pheny! Butyric acid;

dehydrating agents are used, e.g. polyphosphoric acid (Angew. Chem. 79, 1100 (1967); Am. Soc. 72, 2966, 2967 (195O)), phosphoric acid on charcoal (Ann. 596, 220 (1955)), hydrogen fluoride (Am. Soc. 61, 1278 (1939)) or Sulfuric acid (Ber. 56, 624 (1923)). However, these processes have serious disadvantages for industrial production; Not only is the production of the starting products cumbersome, the greater disadvantage lies in the use of expensive and corrosive condensing agents such as anhydrous aluminum chloride, anhydrous hydrofluoric acid, polyphosphoric acid and others.

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A technically more interesting route is the oxidation of tetralin, which leads via the hydroperoxide to the tetraion and can be carried out in the presence of catalytically active metal salts with air or oxygen. Because of the instability of the intermediate tetralin hydroperoxide, one works in expensive solvents, e.g. lower aliphatic carboxylic acids (French patent specification 1 095 348) or hydrocarbons, possibly the tetralin itself, and the subsequent decomposition of the hydroperoxide is carried out in a second reaction step with an aqueous metal salt solution ( See U.S. Patent 2,462,102). In most cases, however, the output is only about 50 % of theory; in addition, the conduct of the reaction at relatively high hydroperoxide contents (about 25 %) is not harmless and, due to the subsequent separation of the reaction mixtures by distillation, is expensive.

The catalytic hydrogenation ofoC-naphthol to cC- tetraion is also described (DRP 352 720), but a yield of about 60% is not of interest for the technical production ofoC-tetralone. The particular difficulty of this process, however, is still the separation of the oC-tetralone from the simultaneously formed oC-tetralol, since the mixture cannot be separated by distillation. For separation, the procedure according to DRP 709 322 is such that the mixture is stirred with powdery, anhydrous calcium chloride and the solid calcium chloride compound of the oC tetralons which is deposited is separated off and then decomposed with water.

In view of the described difficulties and disadvantages of the known processes for the production of oC-tetralone direct, one-step route from tetralin oroC-naphthol it is more advantageous to start the production from the "^ -naphthol to be carried out in two stages by hydrogenating ^ -naphthol in a first stage to formoC-tetralol and then hydrogenating this

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dehydrogenated to c-tetralone in the second stage * The hydrogenation of C-naphthol is known and, according to our own experience, gives a yield of 78 - 80%.

Surprisingly, it has now been found that manoC tetralone is easy to use Way in excellent yields and with high purity when manoC-Tetralol is obtained at temperatures between Catalytically dehydrogenated at 200 and 400 ° C over zinc oxide catalysts.

Preferably one works at temperatures between 300 and 360 ° C, especially between 320 and 340 ° C.

The zinc oxide catalysts of the invention are generally manufactured as follows:

By annealing thermally unstable zinc compounds, for example hydroxide, carbonate, nitrate, acetate or oxalate, but preferably basic zinc carbonate in a generally oxygen-containing atmosphere, an active zinc oxide is obtained, which is then obtained in a manner known per se by pressing, tabletting, briquetting or in is otherwise shaped into spheres, pills, tablets, briquettes or other shapes, it is essential to the invention that the catalyst thus produced has a specific surface area (measured according to BET (J.Amer. Chem. Soc. 60 (1938, 309)) by 10-30 m ² / g, in particular 15-25 m / g.

It is also possible to apply the zinc compound by impregnation or cementation to commercially available carrier materials, preferably fC-aluminum oxide, and then to anneal it, but this catalyst preparation is generally more laborious and offers no advantage.

It is possible and can be advantageous to carry out the dehydrogenation reaction continuously.

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In general, the process is carried out in such a way that the preheated, liquid 6-tetralol is applied directly to the catalyst there, but it can also be done with steam or another inert diluent gas, e.g. nitrogen or hydrogen or high-boiling hydrocarbons, e.g. tetralin, diluted through the contact zone. However, it offers a dilution generally no advantage, since the space-time yield is correspondingly lower.

The dehydrogenation reaction can be carried out at normal pressure, lower or higher pressure; because the pressure in general has no influence on the degree of conversion or the yield, this reaction parameter can be chosen freely and according to other considerations, e.g. design of the equipment and the costs of the process.

In addition to the temperature, the load on the catalyst is an essential reaction parameter. It is generally up to 3 moles per liter of catalyst per hour, preferably between ΐ, Ο and 2.0, in particular between 1.2 and 1.8 mol per liter of catalyst per hour.

A particularly surprising advantage of the process according to the invention is that the oC tetraion formed is not aromatized to give ° G -naphthol and the dehydration to 1,2-dihydronaphthalene occurs only to a very small extent and remains below 2% by weight. It was to be expected that oC-tetralol, which is structurally comparable to 1-phenyl-ethanol- (1), would be easily dehydrated to 1,2-dihydronaphthalene, since it is known that 1-phenyl-ethanol- ( 1) is dehydrated to styrene even at temperatures below 100 ° C, in particular also on zinc oxide.

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Likewise, the oC-tetralone formed, which is tautomeric with the 3,4-dihydronaphthol- (1), should be easily aromatized to oC -naphthol , since only two hydrogen atoms need to be split off and aromatization is all the easier and with the better yield , the less hydrogen is split off and the more the aromatic system is already mapped out (Soc. 1940 , 1134). The dehydrogenation of oC-tetralone to oC-naphthol, for example, in US Patents 3,340,411, 3,356,743, 3,378,591 and in French. U.S. Patent 1,344,298; suitable catalyst metals are copper, nickel, chromium and platinum. In particular, the French patent describes two types of catalysts, one of which contains as a catalytically active metal nickel, copper, iron, cobalt, chromium or a metal of the platinum group, which are deposited on oxides of the first and second group of the periodic table, preferably inter alia Zinc oxide, the carrier material being assigned a proportion of the effectiveness of the overall catalyst. With regard to the patent cited last, it is particularly surprising that, according to the process of the invention, zinc oxide is suitable as a catalyst for a selective dehydrogenation ofoC-tetralol tooC-tetralone with a yield of about 95%. Because even according to our own experiments and experience, at the reaction temperature of the process according to the invention, dehydration of the oC-tetralol to 1,2-dihydronaphthalene and dehydration to naphthalene and aromatization to - (^ - naphthol, e.g. already on appropriately heated wall surfaces made of stainless steel or Quartz, galvanized iron rings or copper chromite.

-Tetraion is a valuable intermediate product, especially for the synthesis of optical brighteners.

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Example ii

With a pump 1000 is metered g of liquid * C-tetralol crude product (= 940 ml).% Of 5-hydroxy-1,2,3,4-tetrahydronaphthalene of 95 wt.% E £ tetralol, 4 percent, less than 1 wt.% of 1,2-dihydronaphthalene and a trace tetraline consists in a preheater maintained at 190 ° C. From there it reaches the top of a vertically arranged reactor (stainless steel tube 83 cm long and 3.9 cm diameter), the 600 ml reaction space of which is filled with spherical zinc oxide catalyst, the weight of which is 7 ^ 9 g. The reactor and reaction temperature are kept at 330 ° C. by applying appropriate heat. The reaction product leaving the reactor condenses at room temperature to form a dark, fluorescent, easily mobile liquid; as a control, the split off hydrogen is measured using a gas meter. The hourly charge to the reactor is 236 g (225 ml) of C-tetralol crude product,

After the reaction has ended, 990 g of crude tT-Tetrc Lon are obtained obtained, according to gas chromatographic analysis, no ° C-Tetralol contains more and its 1,2-dihydronaphthalene content only has risen to 2%.

The crude product is purified by fractional distillation; as the main fraction (boiling point 98 ° - 101 ° C / 3Torr) are obtained 910 g of distillate which by gas chromatographic analysis ° C tetralone with 98% purity. The yield is therefore 892 g (= 95 % of theory), based on the ^ -tetralol used.

Example 2:

The procedure is analogous to Example 1, but at a reactor and reaction temperature of 280 ° C. 832 g ° C tetralone with a purity determined by gas chromatography of

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95 % obtained, which corresponds to a yield of 798 g (= 84 % of theory).

Example 3;

The procedure is analogous to Example 1, but at a reactor and reaction temperature of 400 ° C. This gives 770 g <£ tetraion with a gas chromatographically determined purity of 93 % , the yield of 716 g (= 82 % of the Theory).

Example 4;

The procedure is analogous to Example 1, but instead of an hourly throughput of 236 g «Ό -Tetralol crude product (= 1.6 mol) with an hourly throughput of 294 g (= 280 ml) oC -Tetralol crude product, which is a catalyst loading of Corresponds to 2.0 moles per liter of catalyst and hour. 882 g of ad tetra-ion are obtained with a purity of 85 % , determined by gas chromatography, which corresponds to a yield of 751 g (= 80 % of theory).

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Claims (10)

Claims; \ XJ) Process for the production of OC-tetralone, characterized in that O (-Tetralol is catalytically dehydrogenated at temperatures between 200 ° and 400 ° C over zinc oxide catalysts. 2.) Process according to claim 1, characterized in that temperatures between 300 ° and 360 ° C are used. 3.) Process according to Claims 1 and 2, characterized in that that one works at ^ temperatures between 320 ° and 340 ° C. 4.) Process according to Claims 1 to 3, characterized in that that the zinc oxide catalyst has a specific surface area (measured according to BET) between 1C and 30 m / g. 5.) Process according to Claims 1 to 4, characterized in that the zinc oxide catalyst has a specific upper area (measured according to BET) of 15-25 m / g. 6.) Process according to Claims 1 to 5, characterized in that the space velocity over the catalyst is up to 3.0 mol per liter of catalyst per hour. 7.) Process according to Claims 1 to 6, characterized in that that the space velocity over the catalyst is between 1.0 and 2.0 mol per liter of catalyst per hour. 8.) Process according to Claims 1 to 7, characterized in that the space velocity over the catalyst is between 1.2 and 1.8 Moles per liter of catalyst per hour. 9.) Process according to claims 1 to 8, characterized-Le A 14 115 - 8 - 309833/109 net that the dehydrogenation is carried out continuously. 10.) Process according to Claims 1 to 9, characterized in that the used ^ C-tetralol with steam or Inert gas diluted. Le A 14 115 - 9 - 309833/1091