CZ200781A3 - Activated charcoal from renewable resources, particularly grains - Google Patents

Abstract

The activated carbon sorbent produced by roasting cereal grains at temperatures of 200 to 600 degC, optionally in the presence of an activating gas, for sorption of in particular hydrogen sulfide, carbon disulfide, SO2, mercaptan and polychlorinated dibenzodioxin, dibenzofuran and biphenyl has a grain size up to 1000 .mu.m, specific surface area 375 to 1200 m.sup.2.sup.-1.n., pore volume 0.20 to 0.60 cm.sup.3.ngsup.-1.n. and a carbon content of 65 to 89 wt.

Description

Technical field:

Sorbent - activated carbon produced from renewable sources - grain of cereal origin

The invention relates to an activated carbon sorbent made of natural renewable material under suitable operating conditions. The sorbent is suitable for the purification of gases in the chemical industry, in particular for the purification of gases from sulfur compounds, ammonium compounds, but especially for the capture of polychlorinated dibenzodioxins PCDD, polychlorinated dibenzofurans PCDF and polychlorinated biphenyls PCB.

State of the art:

Materials of this type are highly active carbon-containing substances and preserve the structure of the original natural material. They are commonly produced by heat treatment of various natural substances, such as coconut shells, banana hulls, wood and other suitable natural materials. In addition to these materials, various types of polymers, coal and blast furnace pitches can be used for the production of sorbents. These substances can be defined as high carbon materials in the original structure. Their production is based on the heat treatment of the original material, so that the thermal decomposition (thermal fission) of the building blocks of terpenes, sugars, starches and others into carbon occurs. Subsequent activation with a suitable activation medium (water vapor, carbon dioxide, oxygen, methane, nitrogen or other inert gases or mixtures thereof) creates surface active centers in the form of micropores, mesopores and macropores.

Description of the invention, a novel process for producing activated carbon

Activated carbon sorbent produced from renewable sources - grain of cereal origin is first roasted at a temperature of 200 ° C to 600 ° C and subsequently activated at temperatures from 600 ° C to 1000 ° C with a suitable activation medium. Activation removes undesirable residual content of volatile organic compounds and at the same time reacts carbon and activation medium to form active centers - pores. The material so produced contains 65 to 89 wt. of carbon with a specific surface area of 375 to 1200 m ² g ^-1 . The pore volume ranges from 0.20 to 0.60 crrrg ^-1 .

The grain size of the activated carbon is chosen from 0.090 mm to 3.0 mm and has a specific surface area of 375 to 1200 m ² g ^1, depending on the application.

The properties of activated carbon according to the invention are dependent on the operating conditions of the activation and the activation medium used.

The preparation of activated carbon from renewable sources consists in that the carbonaceous material formed after roasting in the temperature range of 200 ° C to 600 ° C from cereal grain is activated by a suitable activation medium at temperatures of 600 ° C to 1000 ° C and subsequently granulated for further use. The temperature gradient corresponds to the type of equipment used, which can be stationary or rotary, either batch or continuous. The principle of activated carbon production is given by heating the input material in the absence of air, reducing the content of volatile decomposable organic substances, increasing the carbon, ash content and enormous increase of the specific surface due to the flow of a suitable activation medium. The specific surface area of the activated carbon produced in this way is many times larger than the original cereal grain up to 1200 m ² g ^-1 , measured by the BET method.

The specific surface area achieved depends primarily on the temperature conditions of activation, the activation medium used and the activation time.

The activated carbon thus produced has a high sorption capability for common emissions of sulfur compounds, but above all for the above-mentioned PCDDs, PCDFs and PCBs as laboratory tested.

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Technical solutions:

The specific surface area obtained is not dependent on the size of the input grain or the roasting temperature gradient, but above all on the activation temperature, the activation time and the activation gas.

The table shows the specific surface area, carbon content and pore volume of the six samples of cereal grain activated carbon produced as a function of the steam activation time.

Sample identification Parameter specific surface carbon content pore volume 1 -1 nrg ¹ % wt. -, 3--1 cm g vz. 1 activated carbon 390 82 0.22 vz. 2 activated carbon 510 86 0.25 vz. 3 activated carbon 440 88 0.24 vz. 4 activated carbon 375 89 0.20 vz. Activated carbon 730 86 0.40 vz. Activated carbon 1180 65 0.54

Description of samples: vz. 1 - was activated for one hour at a temperature of 840 ° C and a grain size of 2 to 3 mm vz. 2 - was activated for two hours at a temperature of 840 ° C and a grain size of 2 to 3 mm vz. 3 - was activated for one hour at a temperature of 840 ° C, grain size 2 to 3 mm and subsequently treated by grinding to a grain size less than 90 μιη vz. 4 - not activated only was degassed to a temperature of 850 ° C, grain size of 2 to 3 mm and subsequently treated by grinding to a grain size less than 90 pm vz. 5 - was activated for three hours at a temperature of 855 ° C, a grain size of 2 to 3 mm and subsequently treated by grinding to a grain size of less than 90 µm vz. 6 - has been activated for six hours at a temperature of 860 ° C, a grain size of 2 to 3 mm and subsequently treated by grinding to a grain size of less than 90 pm • 44

Example of use of activated carbon produced from renewable sources

The example was carried out on a sorbent - activated carbon produced according to the present invention having specific surface area of 440 m ² g 'and ^f grain size less than 90 pm, which was activated with steam for one hour at 840 ° C.

Example: Sorption properties of cereal grain activated carbon sorbent for PCDD / F and PCB

Sorption properties of sorbent were tested by liquid chromatography method using different strength elution liquids. The experiment procedure follows the procedure used to selectively separate dioxins and coplanar PCBs based on their high affinity for graphitized carbon sorbents. The sorbent was prepared by mixing 5.2 g of sorbent and 100 g of Celite, which serves as an inert carrier. 200 mg of sorbent was packed into a column 8 mm in diameter between two glass wool plugs (the bed contained 10.4 g of sorbent). The column was conditioned and purified by eluting with 50 ml toluene and 10 ml dichloromethane. 200 to 10,000 pg of PCDD / F congeners and coplanar PCBs were loaded onto the column as shown in the table.

The column was then countercurrently eluted with solvents having different elution strengths:

fraction 5 ml dichloromethane fraction 1.5 ml 10% toluene in dichloromethane fraction 50 ml toluene fraction 50 ml toluene

Internal PCDD / F and PCB standards were added to the individual fractions, and gas-chromatographic analysis with GC-MS mass detection was performed after concentration. The results are shown in the table.

The sorbent is able to trap dioxins and bind them very tightly. Release is only possible by displacement with a large volume of solvent with a strong electron bond with the sorbent surface. AX-21 coal (Anderson Company USA) used for dioxin separation has similar behavior, or Carbopack C (Supelco USA) recommended in the latest EPA-US methods.

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Table: Test of sorbents - activated carbon produced from renewable sources

PCDD / F PCB amount PCDD / F PCB elution liquid dichloromethane 10% toluene 0-50 ml toluene 50-100 ml toluene yield yield yield Yield pg % % % % 2,3,7,8 TeCDD 200 ND 0.2 91 2 1,2,3,7,8 PeCDD 1000 ND 0.1 103 1 1,2,3,4,7,8 HxCDD 1000 ND 0.1 86 2 1,2,3,6,7,8 HxCDD 1000 ND 0.1 94 2 1,2,3,7,8,9 HxCDD 1000 ND 0.0 92 2 1,2,3,4,6,7,8 HpCDD 1000 ND 0.1 91 2 OCDD 2000 ND 0.0 102 2 2,3,7,8 TeCDF 200 ND 0.4 93 2 1,2,3,7,8 PeCDF 1000 ND 0.0 88 1 2,3,4,7,8 PeCDF 1000 ND 0.0 84 2 1,2,3,4,7,8 HxCDF 1000 ND 0.1 83 2 1,2,3,6,7,8, HxCDF 1000 ND 0.0 98 2 2,3,4,6,7,8 HxCDF 1000 ND 0.0 83 2 1,2,3,7,8,9 HxCDF 1000 ND 0.0 85 1 1,2,3,4,6,7,8 HpCDF 1000 ND 0.0 87 2 1,2,3,4,7,8,9 HpCDF 1000 ND 0.1 81 2 ODDF 2000 ND 0.1 121 2 PCB 81 1000 ND 11.4 88 1 PCB 77 10000 ND 1.5 90 1 PCB 126 1000 ND 0.6 95 1 PCB 160 1000 ND 0.2 105 1

ND analyte not detected

Claims (1)

RIGHT TO PROTECT 1. Activated carbon sorbent produced by roasting cereal grain at temperatures of 200 ° C to 600 ° C and subsequently activated at temperatures of 600 ° C to 1000 ° C, optionally in the presence of an activating gas, is intended primarily for sorption of hydrogen sulfide, carbon disulphide, sulfur dioxide, mercaptans, and in particular polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs). Cereal grain activated carbon is characterized by having a grain size of up to 1000 gm, a specific surface area of 375 to 1200 m ² g ^-1 and a pore volume of from 0.20 to 0.60 cm ³ g ^-1 , with a carbon content of the sorbent-active the coal is 65 to 89% by weight.