US2066951A - Hydroquinone manufacture - Google Patents

Description

Patented Jan. 5, 1937 UNITED STATES PATENT OFFICE HYDROQUINONE MANUFACTURE Joseph Schumacher, Peru, Ill., assignor to Garus Chemical Company, a corporation of Illinois No Drawing. Application May 9, 1936,

Serial No. 78,921

9 Claims.

product from the borings and turnings' of cast iron cylinder blocks and other castings from the automotive industry. The recent tendency in this field is to use alloyed irons and there is also an increasing tendency to use scrap irons in such castings. This scrap iron often brings into the castings such elements as vanadium, molybdenum, chromium, manganese, copper, etc. Iron dust from such castings used in the reduction of quinones, or as a source of ferrous salts in such reductions introduces some of these elements into the hydroquinone solutions. Many of these elements facilitate the absorption of atmospheric oxygen and such solutions detericrate rapidly. Hydroquinones crystallizing from such solutions are brown and have to be recrystallized. Even the color of the recrystallized product and the keeping properties of the finished crystals leave much to be desired. Developing solutions made from such a product containing even traces of some of these elements have poor stability and exhaust prematurely.

It has now been found that the reduction to the hydroquinone stage may be readily made with zinc powder in a substantially neutral solution without the difliculties due to t e. introduction of these objectionable elements into the finished crystal. In such a neutral solution the resulting zinc-hydroxide is insoluble, and the products are not contaminated by a zinc salt. Hydroquinone crystals of sparkling whiteness, excellent keeping qualities, from which developing solutions having longer life may be prepared, are more readily obtainable by the use of such method.

The reduction may be carried out in the presence of only water, powdered zinc and the quinone or quinhydrone. The reaction proceeds much more readily, however, in the presence of a small amount of a soluble salt or acid whose anion when combined with zinc produces a salt of appreciable solubility. The use of large amounts of such salts is normally to be avoided in order to prevent inclusion of large amounts thereof in the hydroquinone mother liquor.

Instead of forming the customary light, flocculent, fioury zinc oxide, the zinc is oxidized during the reaction to a dense zinc hydroxide which may be readily filtered off, together with any excess of unreacted zinc, giving an exceptionally pure hydroquinone solution. The hydroxide itself is of unusual density and may be washed, dried and sold or reclaimed.

Instead of powdered zinc, a powder from a predominantly zinc alloy such as Zinc and alumi- 1 num, zinc and magnesium or any reactive high zinc alloy relatively free from objectionable elements may be employed. The blue powder, which is produced in the smelting of zinc, may

likewise be used. This powder consists of condensed fumes which were distilled ofi during the smelting operation and contains appreciable quantities of finely divided zinc metal together with zinc oxide.

It has also been discovered that the reduction may be carried out in the presence of a soluble salt whose cation is capable of having more than one valence, providing the higher valent cation is reducible by the zinc, and the lower valent cation is oxidizable by the quinone or quinhydrone. For example, a small amount of a soluble iron salt; such as a ferrous salt, may be added to the reaction mixture. When this is done, the ferrous salt in solution will act on the quinone or quinhydrone and. the metallic zinc. The ferric salts produced by the reaction are then reduced by the zinc and the cycle is repeated. Other polyvalent metals such as tin may likewise be employed.

The following examples will serve further to illustrate my invention:

Example I 80 parts of finely divided zinc and four parts of potassium chloride are added to a vessel equipped with agitator and containing 2000 parts of water. The contents of the vessel are heated to 75 centrigade and agitated. To this 220 parts of quinhydrone are added gradually during the course of an hour. The color of the solution is first brown but when the reduction has been completed it has become almost colorless. When this has occurred, the solids are filtered off and the hydroquinone solution is then treated in the usual way for crystal recovery. The yield is almost theoretical.

Example 11 160 parts of blue powder containing 50% finely divided zinc metal and 4 parts of ferrous chloride are added to 2000 parts of water, heated to C., agitated, and parts of benzoquinone added as in Example I. After reduction, the solids are filtered off and the hydroquinone recovered in the usual manner.

While the foregoing examples serve to illustrate the procedure and quantities used, it is understood that toluquinones, and other substituted quinones ortheir quinhydrones in proportionate amounts can be similarly reduced and that instead of adding these compounds in their solid form they can be added in solution or they can be introduced in a vapor form to -a cooled hydroquinone solution as described in Patent No. 1,987,148 and the resulting solution or mixture reduced with the zinc suspended therein. Also, I do not limit myself to the temperature given but lower or higher temperatures may be used, as varying the temperatures merely affects the speed of the reaction.

Where a salt is added to the solution to: speed up the reaction, any salt or acid may be used whose anion when joined to zinc will give an appreciably soluble zinc salt. For example, hydrochloric acid, sodium chloride, or magnesium sulphate may be employed.

Either quinone or quinhydrone may be employed in connection with the zinc, although it is preferred to carry out the reduction with quinhydrone. When quinone is employed, it is believed that the hydroquinone first formed units with the quinone to form quinhydrone and thereafter the reaction proceeds on the quinhydrone.

Theforegoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible in view of the prior art.

I claim:

1. The process which comprises reducing a compound of the class consisting of quinone and quinhydrone in a substantially neutral aqueous solution to its corresponding hydroquinone in the presence of metallic zinc particles.

2. The method as set forth in claim 1 in which the compound is benzoquinhydrone.

3. The method as set forth in claim 1 in which the solution also contains anions whose zinc salt is soluble.

4. The process which comprises reducing a compound of the class consisting of quinone and quinhydrone in a substantially neutral aqueous solution to its corresponding hydroquinone in the presence of metallic zinc particles and a small proportion of a soluble zinc salt.

5. The method as set forth in claim 1 in which the zinc particles are in the form of blue powder.

6. The method as set forth in claim 4 in which the zinc particles are in the form of blue powder.

7. The method as set forth in claim 1 in which the zinc particles include predominantly zinc alloys containing other metals of the order of reactivity of the zinc.

'8. The process which comprises condensing quinone vapors in a substantially neutral aqueous hydroquinone solution in the presence of metallic zinc particles and reducing the solution to hydroquinone.

9. The process which comprises reducing a compound of the class consisting of quinone and quinhydrone in a substantially neutral aqueous solution to its corresponding hydroquinone in the presence of metallic zinc and a soluble salt of a polyvalent material, the reduced form of which is oxidized by the compound and the oxidized form of which is reduced by the zinc.

JOSEPH SCHUMACHER.