US2171202A - Method of recovering fatty acids - Google Patents

Description

Aug. 29,` 1939. o. Ml. URBAIN ET A1. 2,171,202

. V METHOD 0F RECOVERING FATTY ACIDS Filed Feb. 13, 1937 Patented Aug. 29, 1939 UNITED STATES PATENT oFFicE Oliver M. Urbain and William R. Sternen, Co-

lumbus, Ohio, assignors to Charles H. Lewis,

Harpster, Ohio Application February 13, 1937, Serial No. 125,670

8 Claims.

This invention relates to a process for recovering fatty acids from solutions containing the same. In its more specic aspect, the invention contemplates the recovery of the fatty acids present in the soaps discharged in waste waters from laundries and the like.

It is well-known that the wash waters or suds employed in laundering operations contain from 0.25 gram to 5.0 grams of fatty acids per liter;

'I'hese fatty acids are, of course, present in the form of sodium and potassium salts, that is, in the form of soaps. In addition to soaps, the laundry wastes contain so-called soap builders, free alkali, dirt, dyes, greases, starch', carbohy- 1'5 drates, lint, and other cellulosic materials as well as various forms of bacteria.

The present process is primarily concerned with the steps of freeing the fatty acids from the soaps and recovering the same from the Waste 20 solution. The fatty acids may be released from the soap by effecting hydrolysis thereof through the addition of a dilute acid such as dilute hydrochloric to the waste.

When dilute hydrochloric acid is added to 25 laundry waste or the like, the fatty acids are released from the soaps according to the following general reaction:

R.COO.Nal-HClR.COOH-}Na0l Soap Fatty acid A specific example of the general reaction above is given .as follows:

Sodium stearate Stearic acid 35 The above reactions take place at all pHs below pH '7.0, but evenl at pHs above pH 7.0 the soaps hydrolyze according to the following general reaction:

40 Soap Fatty acid It should be noted that this reaction is of the reversible type. If the fatty acid formed on the right is removed, the hydrolysis of the soap will proceed to completion. In other Words, .as long as the pressure is eliminated from the right side of the reaction, it will continue to move to the right. f

A speciflcexample of the hydrolysis of a soap is given in the folloWi-ng reaction: y

Sodium palmitate Palmitic acid Coming now to a description` of the present process, reference Will be hadA to the accompany- 55 in'g drawing' for clarification, wherein:

be retained on a twenty-mesh screen.

Figure 1 is a diagrammatic ow chart representing the various steps in the process; and

Figure 2 is a more or less diagrammatic illustration of a suitable filter structure for employment in removing the fatty acids. 5

Referring to the drawing, the waste containing the recoverable fatty acids is rst passed through a screening unit to free the same of entrained solids .and thence preferably passed through a coarse sand filter to remove such sol- 10 ids as might otherwise foul the subsequent chemical lter unit. There is added to the Waste a dilute acid, such as hydrochloric acid, to induce hydrolysis of the contained soaps. The solution is then passed into a filter for removing fatty acids.

The nature of the ltering medium employed for removing the fatty acids constitutes an important feature of the present invention. In the present process, the ltering medium for eiecting removal of the fatty acids released from the soaps as a result of hydrolysis due to the addition of the dilute acid comprises a material, the active reagent of which is titania (TiOz). The term titania as herein employed is intended to be used in a generic sense and to be inclusive of the three numerals in which titania occurs in nature, namely, rutile, brookite, and anatase, as well as inclusive of an inert granular carrier impregnated with T102.

The minerals rutile, brookite, and antase are Very insoluble and are all suitable, after being granulated to the proper mesh, for use as a ltering medium. Where one of these minerals as such is used, it should be reduced to a size such that it will pass through a five-mesh screen and When a carrier impregnated with TiO2 is employed in lieu of the mineral, we may use as the carrier either hard coke or magnesia silicate brick reduced to granules which likewise pass a live-mesh screen and are retained on a twenty-mesh screen.

If a filtering medium composed of an inert carrier impregnated with TiOz is to be prepared, we can use any of the soluble salts; of titania for the purpose of impregnating the carrier. For example the granulated carrier material is pickled ina concentrated solution of the titanium salt, such, for instance, as TiCl4. The excess solution is drawn off, and. the granulated mass is then treated by passing therethrough a Warm current of moist air. After the material is dried, it is ignited at a temperature ranging from 600 C. to 900" C. By following` this procedure, the relatively inert carrier is thoroughly impregnated l with titania (TiOz), and the material is ready for use.

It will thus be observed that the filtering agent employed is made up of a granular mass comprising either a mineral carrying titania or a granular carrying agent impregnated with titania. We are not certain as to the precise manner in which the titania filtering medium effects removal of fatty acids from the Waste containing the same. 'I'he reagent carries no ions for effecting an anion exchange and is furthermore relatively unreactive. The reagent, that is, titania, nevertheless does effectively remove fatty acids With great rapidity. We additionally are able to regenerate the titania carrying filter medium by passing therethrough superheated steam which acts to free the fatty acids from the filtering medium so that they are carried over with the steam. We are of the opinion that the fatty acids are removed through the medium of titania purely by sorption. We do know that the titania has an enormous Capacity for the fatty acids. In our view, this is a phenomenon of physical chemistry, namely selective adsorption.

The release of the fatty acids from the filtering medium by the application of steam is done without impairing the capacity of the titania for further use. In fact it is possible to reuse the titania filtering medium for several months without substantial loss or impairment of the effectiveness of this reagent.

The apparatus instrumentalities employed in carrying out the process of the present invention are more or less conventional and relatively unimportant to the process. It is accordingly not believed necessary that they be specifically i1- lustrated. The screening unit is employed to remove the heavy suspended matter from the waste. Such screens are self-discharging, and the solids removed by the screens may be flushed directly into a suitable sewer or the like.

The mechanical sand filter is employed to remove such suspended matter as passes the screens and to insure that no suspended matter Will pass into and foul the fatty acid recovery unit. The sand filter can, of course, be equipped with a conventional back-wash through the medium of which it may be back-washed with clear water after each days run. The back-wash Water will, of course, carry the solids from the sand filter and may be likewise discharged into a suitable sewer or the like.

A suitable construction for the fatty acid recovery unit is illustrated in Figure 2 wherein the filtering chamber is designated generally at I and constitutes a suitable sheet metal container since it is not required to withstand excessive pressure or temperature conditions. The chamber I is provided with a filtering medium carrying grate 2 suitably supported on members 3, the filtering agent diagrammatically illustrated at 4, and the line 5 through which the solution containing the fatty acids to be recovered is introduced to the filtering chamber.

The filtrate leaves the bottom of the chamber through the line 6 and may be discharged through branch line 'I controlled by the valve 8 for further treatment or into a sewer as may be desired. A steam line 9 extends into the bottom of the chamber I and is provided with a perforated extension I for delivering steam below the filtering medium for the purpose of driving off the fatty acids from the filter. v'Ihe steam carrying its fatty acid content leaves the top of the filter through line II controlled by valve I2 and passes to the condenser I3. The condensate is then delivered through line I4 to a suitable evaporating unit I wherein the water is driven off through the line I6 and the fatty acids are recovered.

Oftentimes during the introduction of steam to the filtering chamber I, condensation occurs in the filtering medium, and the condensate carrying some of the fatty acids passes out through the line 6. In this case the valve can be closed and this condensate passed through the by-pass line I1 controlled by the valve I8 and introduced to the line I4' to flow with the condensate from the condenser I3 to the evaporator I5.

It will be understood that the process is not dependent upon this particular form of apparatus, nor is the invention to be limited by the foregoing description beyond the scope of the subjoined claims.

Having thus described our invention, what we claim is:

l. In a process for recovering fatty acids from solutions containing the same, the steps comprising effecting chemical removal of fatty acids by passing such solution through a lter containing a substantial quantity of titania (TiO2) and thereafter effecting recovery of said fatty acids by treatment of the titania filter.

2. In a process for recovering fatty acids from solutions containing the same, the steps cornprising effecting chemical removal of fatty acids by passing such solution through a filter containing a substantial quantity of the mineral rutile and thereafter Aeffecting recovery of said fatty acids by treatment of the rutile filter.

3. In a process for recovering fatty acids from solutions containing the same, the steps comprising effecting chemical removal of fatty acids by passing such solution through a filter containing a substantial quantity of the mineral brookite and thereafter effecting recovery of said fatty acids by treatment of the brookite filter.

4. In a process for recovering fatty acids from solutions containing the same, the steps comprising effecting chemical removal of fatty acids by passing such solution through a filter containing a substantial quantity of the mineral anatase and thereafter effecting recovery of said fatty acids by treatment of the anatase filter.

5. A process for the recovery of fatty acids from solutions containing the same, comprising effecting chemical removal of fatty acids by passing the solution through a lter charged with titania (T102), thereafter passing steam through the filter to free the fatty acids from the filter and carry them over to a condenser, and finally evaporating the water from the resulting condensate and recovering the fatty acids as a product of the process.

6. A process for recovering fatty acids from soap solutions comprising adding a dilute acid to the soap solution to release the fatty acids from the soap by hydrolysis, passing the solution through a filter charged with titania (T102) to chemically remove the fatty acid product of the hydrolysis reaction, and finally recovering the fatty acids: from the filter.

'7. A process for recovering fatty acids from laundry Waste comprising adding to the waste a quantity of HC1 to effect hydrolysis of the soap solution and release of'the fatty acids, removing the fatty acids asv released by effecting the hydrolysis in the presence of a titania (TiOz) carrying reagent which chemically effects removal of said acids, and finally recovering the fatty acids from said titania (T102) carrying reagent.

8. In a process for recovering fatty acids from solutions containing the same, the steps comprising eifecting chemical removal of fatty acids by passing the fatty acid solution through a lter composed of substantially inert granular material impregnated With titania (T102) and thereafter eiecting recovery of said fatty acids by treatment of the titania filter.

OLIVER M. URBAIN. WILLIAM R. STEMEN.

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