US2180001A - Purification of hardwood oils - Google Patents

Description

Patented Nov. 14, 1939 UNITED STATES PATENT OFFICE PURIFICATION OF HARDWOOD OILS No Drawing. Application March 1, 1938,

Serial No. 193,306

4 Claims.

This invention relates to the purification of oils derived from the destructive distillation of hardwood, and particularly to the purification of those oils known as neutral oils, such, for instance, as

5 the light acid oil and washed alcohol oil, described in my United States Patents 1,975,090 and 1,975,091. These oils are called neutral oils in contradistinction to caustic-soluble wood oils.

It is well known that these neutral oils contain, as impurities, phenolic derivatives and complex unsaturated compounds in varying amounts. These impurities bring about darkening .of the wood oils when they are exposed to light and air, or stored in iron containers. The darkening is accelerated by heat.

The impurities also bring about corrosion of the iron containers. In United States Patent 2,095,857, of Carter and Fig'g, we have described a method by which the amount of these impurities may be reduced to such an extent that the oils are no longer corrosive to ferrous containers, and that their stability to light and to metals is improved. The Carter and Figg treatment consists in distilling the wood oils through a column packed with steel wool or other form of iron presenting a large surface relative to its mass. While the Carter and Figg method produces an oil which is non-corrosive to ferrous containers, the oil so purified is not entirely stable as to color when exposed to light and air, and particularly when stored in ferrous containers and exposed to heat.

I have discovered that hardwood neutral oils can be purified, and their stability to light, air, and metals greatly increased by extraction with ethylene diamine, followed by removal of the residual ethylene diamine. If the residual ethylene diamine is not removed, thecolor will not be stable. I give below various illustrations of the way in which my invention may be carried out.

Example 1.Neutral oil was distilled, the frac. tion distilling below 180 C. at atmospheric pressure being taken. The usual acid content in this fraction is 50-7 .0 grams per 100 cc., calculated as acetic acid. The oil fraction was shaken thoroughly with 20% by volume of ethylene diamine. A vigorous reaction took place. The mixture was allowed to settle, and the ethylene diamine layer was drawn off. The oil was distilled through steel wool, as described in patent 2,095,857. The distillate 'came over colorless up to the last 5-10%. A heavy, stifi, tarry residue was left in the base heater of the distilling apparatus. The distillation range of the vapors was 30-120 C. The distillate was washed twice with two parts of water. The color of the washed distillate was a a very, very light greenish yellow, which turned to a clear, reddish color after the oil had stood cold for a few days. It was much more stable as to color than a portion of the same oil fraction which had merely been distilled through steel wool.

Example 2.-Neutral oil was distilled, the fraction distilling below 180 ,C. at atmospheric pressure being taken. The oil fraction was'shaken thoroughly with 20% by volume of ethylene diamine. The mixture was allowed to settle for one-half hour, and the ethylene diamine layer was drawn oil. The oil layer was washed twice with two parts of water, and distilled through steel wool. The distillate was washed twice with two parts otwater, shaken again with 20% by volume of ethylene diamine, and separated immediately after settling. The oil layer was distilled through steel wool, and the distillate washed twice with two parts of water. The oil thus purified turned only slightly off color in 24 hours of storage at C. in steel. Its saponiflcation number was 5.01, the low saponification number indicating a high degree of stability.

Example 3.-Neutral oil was distilled, the fraction distilling below 180 C. being taken. The oil was washed twice with two parts of water. It was then agitated twice with two parts of a 2% solution of 50% caustic soda at 50 C. for two hours, cooled, separated, and distilled through steel wool. The distillate was shaken thoroughly with 20% by volume of ethylene diamine, allowed to settle and the oil separated. The oil was washed twice with two parts of water and separated. It was then distilled through steel wool and again washed with two parts of water. The color of the purified oil was a clear light yellow. Its saponification number was 3.06, indicating great stability. It turned only slightly off color in two days of storage at 75 C. in steel. Even when stored in an open steel vessel and placed in the Fadeometer for 48 hours it showed only very slight discoloration.

Example 4.Neutral oil is distilled under vacuum without fractionation, the entire distillate that comes over at 25" vacuum and lbs. steam being collected. 5% to 20% of ethylene diamine is added to the distillate, the mixture is agitated thoroughly and allowed to settle, and the ethylene diamine layer is separated from the oil layer. The oil layer is washed, either with an equal part of water or with an equal part of a 1.0% solution by volume of sulfuric acid. The washed oil is vacuumdistilled through a column packed with steel wool, a rectifying column, dephlegmator and condenser, and the distillate that comes over at C. and 25" vacuum is collected. Finally, the distillate is washed with an equal part of a 1.0% solution by volume of sulfuric acid and then with an equal part of water. The ethylene diamine from the original ethylene diamine layer can be regenerated by washing with water or a weak alkaline solution, decanting, and separating the ethylene diamine from water by'fractional distillation.

It will be understood that purification by means of ethylene diamine can be applied to light acid oil alone, washed alcohol oil alone, or to any other neutral oil or combination of neutral oils derived from the destructive distillation of hardwood. It will also be understood that ethylene diamine treatment, followed by removal of the residual ethylene diamine, may be used alone or in combination with other methods of purifying wood oils. It need not be used only in connection with distillation through steel, wool, although I have discovered that the combination of ethylene diamine treatment and distillation through steel wool gives a purer and more stable wood oil than any other treatment or combination of treatments which I have investigated. It will be understood that iron in other forms presenting a large surface relative to its weight may be used in place of steel wool. The wood oils purified by my novel process are useful as alcohol denaturants.

what I claim as my invention and desire to be secured by Letters Patent of the United States is:

1. A process of purifying and stabilizing "neutral oils derived from the destructive'distillation of hardwood, comprising extraction of impurities therefrom with ethylene diamine and removal of the residual ethylene diamine from the wood oil.

2. A process of purifying and stabilizing neutral" oils derived from the destructive distillation of hardwood, comprising extracting impurities therefrom with ethylene diamine and washing out the residual ethylene diamine from the wood oil.

3. A process of purifying and stabilizing neutral"'oils derived from the destructive distillation of hardwood, comprising extracting impurities therefrom with ethylene diamine, distilling the wood oil through iron in a form presenting a large surface relative to its mass, and washing out the residual ethylene diamine from the'wood oil.

4. A process of purifying and stabilizing "neutralfoils derived'from the destructive distillation of hardwood, comprising extracting impurities therefrom with ethylene diamine, distilling the wood oil through steel wool, and washing out the residual ethylene diamine from the wood oil.

LOUIS J. FIGG. JR.