US1858022A - Method of preventing the decomposition of carbon tetrachloride and product thereof - Google Patents

Description

Patented May 10, 1932 UNETED STATES rara'r FFEQE LAWRENCE F. MARTIN AND ARTHUR A. ELSTQN, OF MIDLAND, MICHIGAN, ASSIGNORS TO THE DOW CHEMICAL COMPANY, OF MIDLAND, MICHIGAN, A CORPORATION OF MICHIGAN METHOD OF PREVENTING THE DECOMPOSITION OF CARBON TETRQACHLORIDE' AND PRODUCT THEREOF No Drawing. Application filed May 3, 1929, Serial No. 360,310. Renewed March 7, 1931.

which, when present in only relatively small amount, have the property of inhibiting such decomposition. More particularly, it is concerned with the preservation of chlorinated or brdminated derivatives of the saturated or unsaturated aliphatic series of hydrocarbons which have a tendency to decompose under the influence of air, moisture, heat or light, or a combination of such factors, with the consequent formation of corrosive chloroor bromo-compounds. Examples of such halogenated hydrocarbons are carbon tetrachloride, CCh, chloroform, CHCl trichlorethylene, 0 1101 tetrachlorethylene, C2Cl and the like.

A source of trouble connected with the use of the aforementioned halogenated hydrocarbons is the corrosion of metal surfaces exposed thereto, either in the liquid, gaseous or combined phases, and especially in the presence of water. The problem may be subdivided into two principal factors, (1) corrosion of metal containers with which the liquid comes in contact and (2) deterioration of the fluid itself, due to the presence of decomposition products. Of the aforementioned factors influencing the decomposition of halogenated aliphatic hydrocarbons, i. e., air, moisture, light and heat, moisture plays the greatest part in the present problem, the others being of lesser importance. If water is absent, the corrosion of metallic surfaces produced as a result of the action of the decomposition products of the halogenated hydrocarbon, e. g. carbon tetrachloride, is negligible.

It is known that certain compounds, such as benzaldehyde, tend to prevent corrosion of metals by carbon tetrachloride, as shown by Ferguson in U. S. Patent 1,151,255, thus making the carbon tetrachloride more suitable for use in metallic fire-extinguisher containers. We have now discovered that in the presence of considerable moisture decomposition of carbon tetrachloride or like halogenated aliphatic hydrocarbon may be in hibited, or, at least, largely prevented by the addition thereto of a hydrogenated aromatic hydrocarbon, such a cyclohexane. It is known that cyclohexane forms an azeotropic mixture with carbon tetrachloride, hence the former is carried alon with the latter when the mixture is subjected to distillation. Such formation of a constant boiling mixture is particularly advantageous in the present case because no material separation of the effective inhibitory agent occurs when the mixture is distilled for the purpose of purification after use, e. g. in dry-cleaning. Furthermore, the protective or preservative effect is exerted in the vapor phase to an equal degree as in the liquid phase. To the accomplishment of the foregoing and related ends, the invention, then, consists of the steps and new products hereinafter fully described and particularly pointed out in the claims, the following description setting forth but several of the various ways in which the principle of the invention may be employed.

Of various preservative compounds that We have tested, we have found cyclohexane to be the mosteffective in reducing the decomposition of carbon tetrachloride in the presence of moisture. The following detailed examples will serve to demonstrate the beneficial effect of the admixture of the former with the latter compounds forreducing the corrosion of metals exposed to the action of the mixture when water is present.

Ewample In a set of comparative tests, strips of lead and nickel of known weight were suspended above the surface of the liquid boiling under reflux for a period of ten days, the metal surfaces being exposed to the vapors and restrips, as shown in the following table Loss in weight, grams (100 cm!) day Metal 0, C1 1 C H oo14+1o% H20 (81-0 1 6: @3

Nickel o. 0057 o. 0013 Lead o. 0157 o. 0011 Inspection of the above table shows conclusively that the presence of cyclohexane has the eifect of greatly reducing the corrosion of the metallic samples under the conditions of the tests. It, therefore, becomes apparent that decomposition of the carbon tetrachloride due to the action of water-has been repressed or prevented to a corresponding degree by the addition thereto of a minor proportion of cyclohexane. Thereby a simple means is afforded of limiting or preventing the deleterious action of water upon carbon tetrachloride.

The present method has not only the advanta es of ease of application and cheapness ailong with attainment of preservative results, but the use for the purpose in question of a material forming an azeotropic solution with carbon tetrachloride is especially desirable because such material is not separated from the mixture in case repurification thereof by distillation becomes necessary. Regardless of such contingency the two components of the mixture are maintained at all times in approximately their original proportions.

We have found that the extent to which the decomposition of carbon tetrachloride is repressed or inhibited varies somewhat with the amount of preservative added. HOW- ever, when the cyclohexane is present in from five to forty per cent by volume of the mixture, the decomposition is inhibited sufficiently for practical use. Although cyclohexane by itself is inflammable, the above mixture is non-inflammable, and is outside of the limits within which combustion can be spontaneously maintained.

Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

We therefore particularly point out and distinctly claim as our invention corresponding to from five to forty per cent by volume of the resultant mixture.

5. 'As a composition of matter, a halogenated aliphatic hydrocarbon having dissolved therein cyclohexane.

6. As a composition of matter, a halo enated aliphatic hydrocarbon having disso ved therein cyclohexane in amount from five to forty per cent by volume of the resultantmixture.

7. As a composition of matter, carbon tetrachloride having dissolved therein cyclohexane.

8. As a composition of matter, carbon tetw rachloride having dissolved therein cyclohexane in amount from five to forty percent by volume of the resultant mixture.

9. Themethod of preventing the decomposition of a chlorinated methane which com-,

prises adding thereto cyclohexane.

10. As a composition of matter, a. chlori-;v nated methane having dissolved therein cyv clohexane.

11. As a composition of matter, chloroform having dissolved therein cyclohexane. Signed by us this 27 day of April, 1929.

LAXVRENOE F. MARTIN. I ARTHUR A. ELSTON.