DE893644C - Production of activated carbons with the same properties from different carbonaceous starting materials, especially for the adsorption of small-molecule gases and low-concentration vapors - Google Patents

Description

Production of activated carbons with the same properties from different ones carbonaceous starting materials, especially for the adsorption of small molecules Gases and low-concentration vapors In the literature there are numerous processes for Production of activated carbons from a wide variety of carbon-containing raw materials described with various activating agents. Depending on the nature of the too processing starting material is here a certain activating agent in applied certain amount; according to the known method is also depending on the type of activated carbon to be produced, a certain starting material with a certain amount of an activating agent implemented.

It has now surprisingly been found that activated carbons with the same properties are obtained from various carbon-containing starting materials with the aid of chemicals containing potassium and sulfur by using 25 to 56 parts by weight, preferably 35 to 46 parts by weight, of potassium for every zoo parts by weight of carbon of the starting material.

This fundamentally new knowledge is of great importance for the Production of activated carbons, since now with changing starting materials there is always one the same coal can be produced; the procedure is still significant for the production of such coals, for which a special starting material so far, such as Coconut shells, almond shells, etc., were considered to be absolutely usable on their own. Furthermore, the new process brings great savings in activation chemicals, because it was found that in most cases an unnecessarily high consumption of chemicals took place. The new, highly active carbon is ideally suited for the adsorption of small molecules Gases and low concentration vapors. _ Example 1 25o parts by weight of peat (water content = 30%, carbon content, based on dry matter, = 54 0/0) are 38.5 Parts by weight of potassium (as potassium hydroxide solution or potassium sulfide or polysulfide from the recovered Lye) and 19.25 parts by weight of sulfur (either as elemental sulfur or mashed as polysulphide or sulphide sulfur from the recovered liquor). Then it is shaped by means of a hydraulic press and the moldings at 400 to 6oo ° carbonized. The material is annealed at 700 to 10000 ° in the absence of atmospheric oxygen, cooled in the absence of air, leached and washed with water or acid and water. Then, if possible with the exclusion of air, the material with steam at 500 to 550 ° Treated for 1 to 2 hours. Example 2 187.5 parts by weight pretreated with sulfuric acid Sawdust (water content = 2o 0/0, carbon content, based on dry matter, = 63 0/0) are, as described in Example 1, with the same amounts of activating agents treated in the manner described. Example 3 156 parts by weight of ashed lignite (Water content = 110/0, carbon content, based on dry matter, = 68 0/0) are, as described in example x, with the same amounts of activating agents treated in the manner described. Example 4 118 parts by weight of charcoal (water content = 6 0/0, carbon content, based on dry matter, = 85 0/0), as in Example 1 described; with "the same amounts of activating agent in the described Treated wisely. -The above examples give coals that are within the experimental error limits have matching properties and further to be referred to as new coal.

Below are comparisons of some of the key properties given the new coals with known coals, which have the superiority of the new Clearly show coal.

Small molecular gases and low concentration vapors are predominant retained in the coal by pure surface adsorption. For this purpose a coal with the largest possible inner surface is desired, i.e. one if possible fine-pored coal.

So far it has been possible to use the various known methods by changing the working conditions, the pore size of the activated carbon produced in to some extent, but those possibilities were very limited, man was partly due to very specific, difficult to access raw material (coconut shells, Almond shells, etc.) and could fine-pore coals with a very high level of effectiveness not manufacture.

To test the activated carbons, which are used for the adsorption of gases and vapors and for the recovery of solvents, the adsorption capacity of the carbon for benzene vapor mixtures of 289 g, 32 g, 3.2 g and 0.32 g per cubic meter at 2o ° is determined, corresponding to 9/10, 1/10, 1/100 and 1 / 100o saturation of the benzene vapor.

The course of the isotherm gives the proportion and the pore distribution in the investigated activated carbon again. The loads at high degrees of saturation are a measure of the proportion of relatively coarse pores that are responsible for capillary condensation are decisive, and the loadings at low degrees of saturation are a measure of the proportion of micropores and the entire inner'active surface, which for the pure surface adsorption is decisive.

In the drawing, the 1 / 1o00 benzene load is dependent on the Mash ratio, based on the carbon content of the starting material, shown.

In Table I, the benzohsotherms of two common industrial activated carbons are compared with the new carbon. Table I. Coal A Coal B New money g C, H "/ xoo ccm coal Weight per liter ......... 300 400 420 Benzene saturation centration 9/10 ....... 2o, o 20.0 24.0 the same. 1 / 1o. . . . . . 13.5 16, o 20.0 also 1 / 1o0 ...... 6.5 10.0 16, o also 1 / 10a0 ...... 3.5 4.5 12.0 Coal A is a commercially available, coarse-pored coal for the adsorption of large-molecular substances at relatively high concentrations. Coal B is a commercially available fine-pored coal for the adsorption of small molecular substances and low-concentration vapors. From the benzene load at 1 / "" steam saturation one sees the great superiority (almost three times) of the new coal over the commercially available coal B.

In industrial use, those previously produced allowed Activated carbons the economical extraction or recovery of hydrocarbons with up to 4, at most 3 carbon atoms and up to a relatively high minimum concentration. The fine-pored activated carbons produced by the new process allow one economical production of hydrocarbons with 2 and -1 carbon atoms and also up to far lower minimum concentrations. Also for extraction The new coals are eminently suitable for noble gases.

Table II clearly shows the superiority of the new coal in the recovery of C.H4 (as an example of a small-molecule gas) from gas mixtures of different concentrations. Table II Volume conc. Coal BI New Coal I factor C.H4 g CH "/ 100 ccm coal I o / o. . . . . 0.240 o.6o9 2.5 20/0 ...... 0352 o, 861 2.5 5% ...... 0.52 0 1.765 2.6 100 / ....... 0.800 2, 0 79 2.6 150/0 ....... 1.020 2.625 2.6 For this small molecular gas, the new coal is about 2.6 times superior to the commercially available coal B.

A good gas mask charcoal must have a fine-pored structure and a As large an inner surface as possible is required, since the war gas concentrations in question are very low, a number of warfare agents are small molecular and also that Retention is due to the fine pores of the activated carbon.

In Table III, the benzene isotherms of a known, good gas masked carbon C are compared with the gas masked carbon produced by the new process. Table III Coal CI New Coal Loading in g CeH./ioo ccm coal Weight per liter ............ 420 425 Benzene saturation concentration tration 9 / l0 ........... 22.5 22.5 the same. 1 / 1a ........... 19.5 19.5 also 1 / l00 ............ 13.5 16.5 the same. 1/1000 ........... 7.5 13.0 This also clearly shows the superiority of the new coal at low degrees of saturation.

Table IV shows this superiority when tested with low concentration chloropicrin. Both coals were tested under the same conditions. Table IV Coal CI New Coal Resistance time. . . . . . . . . . 25 minutes 58 minutes Chloropicrin retention ability .......... 12 minutes 25 minutes These examples clearly show the importance of the proportion of micropores or the inner active surface, which is characterized by the loading at 1/100 benzene saturation.

Claims (1)

PATENT CLAIM: Production of activated carbons with the same properties from various carbon-containing raw materials with the help of potassium and sulfur in the proportion of potassium sulphide or chemicals containing potassium polysulphides, especially for the adsorption of small molecular gases and low concentrations Vapors, characterized in that there are 100 parts by weight of carbon of the starting material 25 to 56 parts by weight, preferably 35 to 46 parts by weight of potassium are used will.