US2739976A - Method of refining crude wax or the like - Google Patents

Description

United States Patent METHOD OF REFININ G CRUDE WAX OR THE LIKE Albert Ferdinand Sundgren and Erkki Emil Ekman, Helsingfors, Finland No Drawing. Application October 2, 1952, Serial No. 312,858

9 Claims. (Cl. 260-423) Many methods have heretofore been proposed and used for refining or bleaching crude wax, which involve treatment with oxidizing agents such as hydrogen peroxide, permanganate, persulfates and chromic acid, the last mentioned oxidizing agent being considered most advantageous in that it can easily be regenerated by means of electrolysis. Thus it has been previously proposed to introduce fairly solid and hard crude wax into 40-50% sulfuric acid which is then heated, in order to effect the melting of said wax, to a temperature of about 70-400 C. depending on the nature of the material being treated. The Wax in molten state is then intimately mixed with the liquid to form an emulsion, and the oxidizing agent, for instance chromic acid, thereafter added, or a previously prepared oxidizing solution, for instance a mixture of chromic acid and sulfuric acid having the same high temperature, i. e. about 70100 C., isemulsified therewith. At the high temperatures employed the reaction during the initial stages of the bleaching process is very violent indeed and diflicult to control. It follows that the strong bleaching agent destroys or deleteriously affects some crude Wax which bleaches readily while those with high bleaching requirements are subjected to less favourable conditions since the concentration of the bleaching agent decreases and the solution thus considerably loses effect as the reaction proceeds.

In order to avoid this unsatisfactory circumstance it has been previously proposed to add very small amounts of 'chromic acid to the hot mixture of crude wax and sulfuric acid, while separating completely or in part the reaction liquid from the wax prior to each new addition of chromic acid. In this process it is necessary to cool the mixture to a temperature below the solidifying point of the material being treated so as to obtain a cake of wax floating on the liquid which is tapped. Introduction of fresh liquid is again followed by heating the mixture and intimately mixing it in order to form the emulsion required prior to the addition of each new charge of oxidiz'ing agent. After the desired bleaching effect has been obtained the same process of cooling, followed by melting must be repeated when the wax is washed, first with acid for destroying traces of oxidizing agent, for instance with expensive chromic acid, and then with Water for removal of acid.

In a refining process of the kind described .the liquid amount, consequently, weighs from 8 to 10 times that of crude wax, while the amount of oxidizing agent, for instance chromic acid, corresponds to 100-200% of the weight of the crude wax. It is obvious that in the subse quent electrolysis process such substantial amounts of liquid as this hamper exceedingly the regeneration of chromic acid from the reaction and washing liquids separated from the refined wax and containing sulfuric acid, chrome sulfate, and partly unused chromic acid.

A marked improvement in the hereinabove described respect is attained on subjecting, according to a known method, the crude wax while in the form of a solution or emulsion to the anodic action of an electric current in the presence of electrolytes and oxygen carrying agents, preferably sulfuric acid and chrome sulfate. Even according to this method the temperature of the solution of chrome sulfate and sulfuric acid must be raised to about C. prior to "the introduction of wax, and then the temperature of the mixture raised to over C. while intimately mixing the same in order to form the emulsion of minute particles of Wax in the liquid necessary for carrying out the reaction.

However,'the electrolytic refining method as well as the first refining method hereinabove described are unsatisfactory in that the high temperatures employed have a deleterious effect on easily bleached waxes specifically, and a poor yield is obtained as a result of losses due to oxidation carried too far. Moreover it is necessary to resort to exceedingly vigorous stirring in order to maintain the necessary emulsion andprevent the molten 'wax particles from uniting.

According to the present invention the defects hereinabove mentioned can be obviated by treating the crude wax to be refined or bleached at a temperature below the melting point of the wax, and this bleaching process can be accomplished by means of substances adapted to liberate oxygen dissolved in an aqueous bleaching solution containing waxes suspended therein in finely divided and solid form. According to the present method it is unnecessary to melt the wax, and further it is possible to so control the bleaching process in the initial stages of the reaction that even on employing concentrated bleaching solutions no damage whatever is done to the materials treated, and furthermore it is possible to increase the bleaching action of the agents despite the fact that the original concentration of bleaching agents decreases with advancing reaction thereby ensuring an even and good bleach in the course of 'the Whole bleaching process. In order to accomplish this endit is only necessary to regulate the temperature during the reaction so that in the initial stages of the refining 'process the exceptionally violent reaction otherwise occurring at high temperatures is avoided by employing a low temperature. As concentration decreases in the bleaching solution during the reaction the temperature is increased accordingly, and the surplus heat created during the reaction can always be conducted away, when necessary, by cooling. The temperature may be varied inthe range from 50 to 5 C. below the melting pointof the wax in question.

It is obvious that during the Whole refining process the crude wax is kept well suspended in the liquid by mixing which procedure is, as a matter of fact, much easier to accomplish with wax in solid state than with wax in molten state as prescribed by prior methods. After the wax has been bleached to the degree desired, the refined product is separated from the liquid, for instance by decanting or filtering with suction, and can then be suspended again into Washing liquid and so on without losing time or resorting to the unnecessary procedures of extra heatingand cooling arising therefrom.

Should refining agents which can be regenerated electrolytically beempl'oyed 'in the present method the regeneration process can be carried out simultaneously with the refining process .itself, .or separately. Regeneration occurring simultaneously .is easier to accomplish in conjunction with the method describedin this invention than with the previously described electrolytic bleaching method because of the finely divided state of the crude waxes, the homogeneous suspension thereof in the refining liquid and the low temperatures at which refining can be accomplished and which are just suitable for electrolysis. Obviously a refining process conducted directly in an elec trolyzer is advantageous in that the bleaching agent is regenerated continuously and reacts very etfectively, so to say in statu nascendi, but not too vigorously because of the low temperature employed. To liquid drawn by suction from the electrolyzer after complete refining can immediately be re-used for a new charge of crude wax. If the refining and regeneration processes are carried out in separate reaction vessels it is naturally always possible to continually draw by suction a part of the reaction liquid from the refining vessel and have it regenerated and recycled into the refining vessel. A simultaneous refining and regenerating process of the kind described can be accomplished for instance on employing chromic acid in sulfuric acid medium or potassium permanganate in alkaline medium, the two most usual bleaching agents.

As previously mentioned the crude wax must be in a finely devided state, microcrystalline or amorphous, advantageously almost of dimensions defined in handbooks as colloidal. In the case of hard amorphous waxes a particle size of 10* to 10- mm. must be used, whereas if the fine division is obtained by crystallization in which case the mass becomes more porous, even a particle size of l to 10- mm. may be operative. In order to obtain this end it is often advantageous to cool the wax during comminution.

The present method may advantageously be employed for refining or bleaching the often dark-coloured crude waxes obtained from turf, despite the fact that oxidizing agents easily injure or damage these waxes.

The method according to the invention is illustrated by the following examples:

Example 1 100 kgs. of resin free montan wax is by mechanical means finely divided into powder with a particle size of 10 to 10- mm. and then added to the bleaching liquid consisting of a mixture of 800 kgs. 40% sulphuric acid and 200 kgs. chromic acid. By vigorously stirring the mixture the powder is homogeneously dispersed in the liquid. During the bleaching process the temperature of the liquid is raised to 50-60 C. The temperature is carefully controlled so as not to exceed the melting point of the wax powder suspended in the liquid. To prevent foam formation and too high a rise in temperature during the first step of the bleaching process the exothermic reaction is controlled by adequate cooling. When a satisfactory degree of bleaching has been attained the bleaching liquid is filtered off. The bleached wax is first washed with diluted sulphuric acid heated to 5060 C. and then with water. The yield amounts to approximately 80 kgs. bleached wax the melting point of which is 80 C.

Example 2 From a mixture obtained by extracting peat bitumen with ethyl alcohol the wax components are crystallized by cooling to a particle size of 2%r mm. The precipitation is washed with alcohol and then with water. l00 kgs. of the finely crystalline precipitation obtained in the foregoing manner are vigorously mixed while cooling with a bleaching liquid consisting of a mixture of 1000 kgs. 40% sulphuric acid and 110 kgs. chromic acid. The suspension thus obtained is introduced directly into an electrolytic cell in which the chromic sulphate formed during the whole bleaching process is continuously regenerated into chromic acid. During the bleaching process the temperature in the mixture is maintained at 40-60 C. With a view to preventing foam formation the exothermic reaction should be controlled by adequate cooling as in Example 1. The degree of bleaching is controlled by taking samples; a satisfactory degree having been attained the bleached wax is separated, for example by filtering. The bleaching liquid can be re-used directly for processing a new batch of crude wax.

The bleached wax is washed and treated as in Example 1. Approximately 86 kgs. of pale yellow wax is obtained the melting point of which varies from 81 to 82 C.

Example 3 The Wax is finely divided, bleached and treated as in Example 2 except that the bleaching process itself is carried out in a reaction vessel provided with a filtering device apart from the electrolytic cell. During the bleaching process a part of the bleaching liquid is continuously withdrawn through the filtering device and regenerated separately in the electrolytic cell and then returned to the reaction vessel.

We claim:

1. In the bleaching and refining of crude waxes the process which comprises comminuting a crude wax in solid form substantially to colloidal dimensions, dispersing the solid comminuted wax in an aqueous bleaching solution containing dissolved therein an oxidizing agent adapted to liberate oxygen and capable of bleaching the wax, heating and maintaining the mixture at temperatures producing oxidation and bleaching of the impurities in the wax but from about 5 to 50 C. below the melting point of the Wax, stirring the mixture until the solid wax is adequately bleached, and recovering the bleached wax while still in solid form.

2. The process of claim 1 wherein the crude wax is comminuted while simultaneously cooling it.

3. The process of claim 1 wherein the aqueous bleaching solution is a solution of sulfuric and chromic acids.

4.. The process of claim 1 wherein the aqueous bleaching solution is a solution of potassium permanganate and an alkali.

5. The process of claim 1 wherein the temperature is increased during the bleaching operation substantially as the concentration of the bleaching agent decreases.

6. The process of claim 1 wherein the oxidizing agent is one selected from the class consisting of chromic acid and permanganate and wherein the aqueous bleaching solution is regenerated by electrolysis during the bleaching operation.

7. The process of claim 6 wherein the oxidizing agent is chromic acid dissolved in a sulfuric acid medium.

8. The process of claim 1 wherein the oxidizing agent is one selected from the class consisting of chromic acid and permanganate and wherein the bleaching bath itself is electrolyzed to regenerate said oxididing agent during the bleaching operation.

9. The process of claim 1 wherein the oxidizing agent is one selected from the class consisting of chromic acid and permanganate and wherein a stream of aqueous bleaching solution is withdrawn from the bleaching bath, subjected to electrolysis to regenerate the oxidizing agent therein and recycled to the bleaching bath.

References Cited in the file of this patent UNITED STATES PATENTS 421,904 Bruening Feb. 25, 1890 1,777,766 Pungs et al Oct. 7, 1930 1,980,273 Hough Nov. 13, 1934

Claims (1)

1. IN THE BLEACHING AND REFINING OF CRUDE WAXES THE PROCESS WHICH COMPRISES COMMINUTING A CRUDE WAX IN SOLID FROM SUBSTANTIALLY TO COLLOIDAL DIMENSIONS, DISPERSING THE SOLID COMMINUTED WAX IN AN AQUEOUS BLEACHING SOLUTION CONTAINING DISSOLVED THEREIN AN OXIDIZING AGENT ADAPTED TO LIBERATE OXYGEN AND CAPABLE OF BLEACHING THE WAX, HEATING AND MAINTAINING THE MIXTURE AT TEMPERATURES PRODUCING OXIDATION AND BLEACHING OF THE IMPURITIES IN THE WAX BUT FROM ABOUT 5* TO 50* C. BELOW THE MELTING POINT OF THE WAX, STIRRING THE MIXTURE UNTIL THE SOLID WAX IS ADEQUATELY BLEACHED, AND RECOVERING THE BLEACHED WAX WHILE STILL IN SOLID FORM.