US2377063A - Activated carbon and method of producing the same - Google Patents

Description

granulated, on the other.

Patented May 29, 1945 ACTIVATED CARBON AND METHOD OF PRODUCING THE SAME Rudolf Adler, Montreal, Quebec, Canada No Drawing. Application July 21, 1941, Serial No. 403,458. -In Czechoslovakia April 29, 1938 4 Claims.

This invention relates to the art of carbonizing organic material. More particularly, it pertains to the production of activated carbon by a novel procedure resulting in a new and improved product. In its preferred embodiments, the invention is directed to the carbonization and activation of hydrocarbons which are herein broadly referred to as of the liquid or plastic type, and is especially applicable to the treatment of such substances as crude oil, coal tar, wood tar, shale tar, as well as other tars, and Dippels oils. This application is a continuation in part of my co-pending application Serial No. 269,076.

While persistent and extensive research has been performed, the art of carbonization remains largely dependent upon empirical procedure.

istics of a carbonized product will vary with the source or properties of the starting material; and even in the case or a given source, it is difiicult, if at all possible, to accurately maintain the e1- nciency of operation or standardization of product in a given-procedure, in view ofthe usual high adsorptive power may be converted by moulding into an emcient gas adsorbing carbon.

A carbon of a low. titre in terms .of one of the above tests might be quite satisfactory for some decolorizing purposes, but hardly for conversion into gas adsorbing carbon of recognized standard.

These tests are applicable as basis of comparison diii'erences encountered in'carbonaceous material of the type utilized as well as thevariations normally attendant any empirically conducted process.

These difllculties of operation have been particularly applicable in the case of procedures directed to the obtention of activated carbon, wherein the added problem is encountered that all types of carbonaceous material do not lend themselves to effective activation, at least by available methods and that the methods required are fundamentally different for various materials. The problem has been particularly magnifled in any attempted conversion of carbonaceous material of the liquid or plastic type, such as disclosed herein.

It is the present practice in the art to classify activated carbons in terms of various standard tests, such as the methylene ,.blue. iodine and phenol tests. Moreover, a marked distinction has necessarily been made between decolorizing carbons, mostly pulverized, on the one hand, and carbons for adsorbing gases and vapors, mostly Powdered carbon of also with respect to medicinal carbons.

The usual carbonization and activation doctrine is based upon the concept that temperatures materially in excess of 700 C. will produce a carbon which is substantially incapable of activation. Subsequent to this carbonization treatment the conventional procedure has resorted to the use of steam or gases for the actual activation of the carbonized product.

Attempts to rely upon this conventional practice for the carbonization and activation of liquid or plastic type carbonaceous material which usually necessitates comparatively high temperatures for removal of volatile content, have been substantially unsuccessful both from the standpoint of efiiciency of yield and product characteristics.

It is known to treat liquid and plastic type carbonaceous materials chemically to facilitate activation. Procedures based upon such chemical treatment have been predicated on the concept of converting a tar-like hydrocarbon to a carbonized mass replete with pores and thereby adapted to a subsequent activation treatmentby steam or gas. In accordance with this manner of treatment, a tar-like substance is admixed with an inorganic chemical compound intended to function as a spacing agent. In the presence of this agent, the tar-like substance is heat treated 'at temperatures below 600 C. and preferably not in excess of 400 C. resulting in a removal of a substantial proportion of volatile content. The resultant product, characterized as a semi-coke, is then treated with a solvent adapted to extract the remaining volatile content and undesirable impurities; subsequently thereto, the residue is leached with water and then dilute acid for removing the chemical agent originally added, thereby providing a porous, carbonized product, particularly adapted for subsequent activation treatment by steam or gas. The

carbon content by burning. Moreover, the product characteristics have been of a comparatively low titre even when determined on the basis of technical types of activated carbon.

It is an object of my invention to obviate in substantial measure such dimculties and uncertainties as hereinabove described.

An additional object is to provide a method for carbonizing hydrocarbon materials by chemical treatment in a manner to effect an efficient conversion and a high degree of direct activation.

Another object is to devise a method of carbonizing hydrocarbons of the liquid and plastic type in the presence Of a chemical compound to efficiently convert the same directly to a. novel activated carbon.

An. important object is to attain an efficient carbonization of hydrocarbons in a manner which will produce a technical activated carbon that satisfies the prevailing requirements as a decolorizer and for medicinal usage, and for being moulded into a gas adsorbing carbon.

A further object is to present a method for carbonizing hydrocarbons of the type of crude oil, coal tar, wood tar, shale tar, and other tars and Dippels oil by heat treatment in the presence of a chemical compound to attain an efficient conversion thereof to activated carbon adapted for medicinal usage as well as industrial.

Other objects, advantages, and features of my invention will become apparent from the following description which is presented by way of illustration, and is in no sense to be taken as limitative.

In accordance with the present invention, it has been found that the utilization of potassium compounds, in appropriate amount, admixed with hydrocarbons of the liquid and plastic type, such as crude oil, coal tar, wood tar, shal tar, and other tars, pitch, etc., and Dippels oils will function as a particularly expedient chemical agent in the activation of the hydrocarbon when subjected to carbonizing heat treatment under optimum temperature conditions. By calcining the mixture under the conditions of dry distillation at an optimum temperature, as within the range of 900 (L-1100 (3., an efficient conversion to activated carbon is attainable, with the resultant product of a character which will satisfy prevailing requirements from either a medicinal or technical standpoint. The product by the present invention yields an activated carbon in the range of a methylene blue titre of 24 to more than 35, whereas the corresponding titre of carbons prepared in accordance with other technical procedures is usually substantially below 15 and rarely over 20. Iodine and phenol test indications provide comparable results.

The theory upon which such improved results are obtainable is not entirely clear, nor is it apparent whether the potassium compound functions by way of a chemical reaction with the carbonaceous material or as a carbonizing catalyst. While not intending to be restricted to any theoretical concept, it is believed from extensive experiments that the result may be due to the minimization, by the presence of an appropriate potassium compound content, of any substantial coke formation during distillation. Some advantage may be attributable to the fact that the starting materials which I use are distillates of organic materials, and as such free from any inorganic constituents, so that the product consists of pure carbon. Contrary to the substances from which they have separated, these distillates are, therefore, free from solid constituents which cannot be prevented from forming coke-like substances if heated, even in the presence of the potassium compound.

In any event, the usual degree of oxidation of carbon which results from the partial burning attendant the steam or gas treatment is avoided, since resort to such expedients for activation is not necessary.

It seems clear that the function of the potassium compounds is distinctly not that of a spacing agent when the method is performed in accordance with the present invention. This is indicated by the fact that corresponding sodium, magnesium or calcium compounds have either no effect or very limited effect in attempts to utilize them in the present invention.

The irrelevancy of the spacing effect in the present invention is further confirmed by the observation that potassium hydroxide, although a desirable reagent within the scope of the invention, is not as eflicient as potassium carbonate or sulfide, although potassium hydroxide, contrary to potassium carbonat and potassium sulfide, vaporizes or develops gas during the distillation at comparably low temperatures, thereby forming pores in the carbonized mass undergoing heat treatment. The reason is obviously that the gas evolution by potassium hydroxide is detrimental to the intimate association with the carbonaceous material during the heat treatment interval. The fact that potassium hydroxide is effective in considerable measure may be attributable to its ultimate conversion, during calcination, to potassium carbonate.

By way of contradistinction, the addition of chemical reagents for the purpose of forming the void spaces within the mass of liquid or plastic carbonaceous material upon leaching after calcination, but before activation, in accordance with the prior art is deliberately intended to attain a porous carbonized product which will facilitate subsequent activation by gas or steam treatment.

Thus the prior art concept is directed to attaining maximum activation by treatment with steam or gas, under conditions of partial combustion, of the material which has been pre-treated so as to provide a maximum degree of porosity.- The product from this activation method has a Wiechowski methylene blue titre of less than 15.

A description of the Wiechowski test can be found in the following original publications: Wiechovski, Prager med. Wochenschr. (1909) Pharmakologische Studie uber Tierkohle.

Derselbe, ibid. (1909) Pharmakolog. Grundlagen einer therapeutischen Verw. der Tierkohle. Derselbe, Verh. d. deutsch. Kongr. f. innere Med. Wiesba'den (19.14). In accordance with the previously expressed concept that the efficiency of the invention may depend upon the most intimate association of chemical reagent with the carbonaceous material, i. e., under conditions of minimum porosity during calcination, is the indication that the procedure herein disclosed is applicable to liquid'and plastic type carbonaceous materials, and not to solids illustrated by wood, coal or the like. It will be apparent that these latter are not physically constituted for the appropriate intimate contact between the potassium compound and the carbonaceous starting material.

Setting forth in more detail, features of the invention by way of illustrative example, the process in accordance with the invention may involve mixing organic substances of the class consisting of crude oil, coal tar, wood tar, shale tar and other tars and Dippels oil with a large amount of a potassium compound embracing of such substances as potassium salts and potassium hydroxide. Illustrative of potassium compounds which may be utilized are the carbonate sulphate, sulphide, sulphite, cyanide, and hydroxide. While optimum results are obtainable by utilizing equal parts of the potassium compound and carbonaceous material, a material degree of activation may be attained by resort to substantially less quantities of potassium compound; for efficient general operation, approximately 30% by weight of the potassium compound has been found desirable as a lower limit for attaining suitable activation in accordance with the invention.

If the organic material utilized is not normally liquid at atmospheric temperature, as the case with some tars, pitches and the like, these substances may be pre-heated to the liquid state, and then admixed with the potassium compound. The admixture of potassium compound and organic material, whether or not pre-heating of the latter is required, is prepared in the form of a stiff paste and then subjected to distillation at gradually increasing temperatures up to an approximate range of 900 C.-1100 C. which repre- I sents the approximate activation temperature range. An optimum temperature for activation has in some instan es proven to be approximately 1050 C. This heat treatment results in the obtention of distillates of the same or improved value, as compared with ordinary distillation treatment, and a solid residue. The. residual mass is then leached with water or other solvents to remove the chemical agent which may be recovered by ultimate evaporation of the solution. The substance remaining after the leaching treatment consists of practically pure, deep black, highly active carbon manifesting a very high adsorptive power, as evidenced by a titre of between 24 and in excess of 35. After drying the activated carbon, it may be utilized as granr During the first stage of heating or calcination.

reduced pressure or vacuum conditions may be maintained; alternatively steam may be resorted to for accelerating the evolution of distillates.

The top temperature employed should be Following is an exemplary procedure involving the features of the invention.

Example No. 1

tion of steam in accordance with the usual practice. The distillate is collected in accordance with usual practice, while escaping gases may be effectively introduced into fire to provide an auxiliary supply of fuel. ground to 60-100 mesh, is transferred to a muflie furnace and further degasified by heating to approximately 900-1100 0., preferably under the usual conditions of dry distillation which avoid any substantial oxidation, maintaining said top temperature for 1-2 hours. The residual carbon from the muille is cooled, freed from its potassium contents by leaching with water, and then dried. The potassium compound may then be recovered in its solid form by evaporation of the leaching solution. The pure carbon obtained from coal tar or brown tar is usually between 33-45% by weight of the starting material.

The invention may also be carried through with good results, if, instead of potash, potassium hydrate or the potassium salts of weak acids, in particular the sulphide, sulphite cyanide, etc. of potassium are admixed with the liquid carbon containing material to form a paste. Also the salts of such strong acids which, when being heated to high temperatures in the presence of carbon, are converted (reduced) into salts of weak. acids, as for example potassium sulphate which can be converted into potassium sulphide, may be used with advantage.

Example No. 2

kg. of pit coal tar are mixed with 100 kg. of potash and heated in a still to 400 C., the distillate being collected in the usual manner. The residue remaining in the still is further treated at approximately 900-1100 C., as in the previous example.

Example No. 3

100 kg. pit coal tar intimately mixed with 100 kg. dry, finely ground potassium hydroxide are gradually heated to 400 0., the mixture being agitated by any suitable means during the earlier stages of the distillation. The solid residue obtained is thereafter heated in a separate container, at approximately 1000 C. for 1 to 2 hours, and, after having cooled down, leached out wit water or other solvent and dried.

It will thus be seen that the invention herein, as illustrated by the above considered exemplary embodiments, provides a novel and effective method for efllciently producing technical carbon of high titre and improved decolorizing and adsorbing characteristics.

While I have described my invention in accordance with desirable embodiments, it is obvious that many variations and modifications may be resorted to without departing from the spirit or substance of the invention as defined in the following claims.

I claim:

1. A process of distillation and activation which comprises preparing a non-compressed, non-agglomerated mixtures consisting of a. carbonaceous The still residue, desirably substance oi the class consisting of crude oil, coal tar, wood tar, shale tar and Dippels oil, and a substantial quantity of a potassium compound suflicient in amount to render the carbonaceous material active when subjected to appropriate heat treatment, distilling said mixture to a temperature of between 350-400 C. until said mixture assumes a solid state as such or on cooling, grinding said solid residue of the distilling treatment, transferring the said ground residual material to a high temperature zone and heating said residual material to a temperature between 900-1100 C., leaching the potassium compound from the resultant carbon, and recovering directly, without resort to conventional steam or gas activation steps, an activated carbon product of a methylene blue titre of at least 20, said potassium compound having at no stage of the process entered into chemical reaction with the activated product or with the substance from which the product is obtained.

2. A process for distillation and activation which comprises preparing a non-compressed, non-agglomerated mixture consisting of a corbonaceous, tarry substance oi liquid or semi-liquid consistency and a potassium compound in an amount which is at least 30 per cent by weight of the carbonaceous substance, distilling and heating said mixture to a temperature of approximately 900-1100" C. until the hydrocarbon content of said carbonaceous material, because of its non-compressed and non-agglomerated state, has been readily and substantially eliminated and the carbon content substantially completely activated,

leaching said potassium compound from said substantially completely activated carbon, and recovering directly, without resort to conventional steam or gas activation steps, an activated carbon product of a methylene blue titre of at least 20, said potassium compound having at no stage of the process entered into chemical reaction with the activated product or with the substance from which the product is obtained.

3. A process for distillation and activation which comprises preparing a non-compressed, non-agglomerated mixture consisting of a carbonaceous substance selected from the class consisting of crude oil, coal tar, wood tar, shale tar, and Dippels oil, and a, potassium compound in an amount which is at least 30 per cent by weight of the carbonaceous substance, distilling and heating said mixture to a temperature of approximately SiOO-IIOO C. until the hydrocarbon content of said carbonaceous material, because of its non-compressed and non-agglomerated state, has been readily and substantially eliminated and the carbon content substantially completely activated, leaching said potassium compound from said substantially completely activated carbon, and recovering directly, without resort to conventional steam or gas activation steps, an activated carbon product of a methylene blue titre of at least 20, said potassium compound having at no stage of the process entered into chemical reaction with the activated product or with the substance from which the product is obtained.

4. A process for distillation and activation which comprises preparing a non-compressed, non-agglomerated mixture consisting of a carbonaceous substance selected from the class consisting of crude oil, coal tar, wood tar, shale tar, and Dippels oil, and a? potassium salt selected from the group consisting of potassium carbonate, potassium sulfate, potassium sulfide, potassium sulfite and potassium cyanide, the potassium salt being used in an amount which is at least 30 per cent by weight of the carbonaceous substance, distilling and heating said mixture to a temperature of approximately 900-1100 C. until the hydrocarbon content of said carbonaceous material, because of its non-compressed and non-agglomerated state, has been readily and substantially eliminated and the carbon content substantially completely activated, leaching said potassium salt from said substantially completely activated car-