SU747815A1 - Method of determining optimum activation temperature of carbon materials - Google Patents

Description

(54) METHOD FOR DETERMINING OPTIMALLY} ACTIVATION TEMPERATURE OF CARBON AND MA GERIALS

The invention relates to the preparation of sorbents, in particular, to methods for determining the optimal activation temperature in the preparation of carbon sorbents. A known method for determining the optimal activation temperature of carbon materials includes heating a sample of carbon material (carbon tape) with an oxygen-containing activating agent or CO in a variable temperature field, the temperature gradient of which varies linearly in length. After activation, the tape is cut in length and O1; determine the sorption activity of the segments. The segment with the maximum adsorption activity corresponds to a certain temperature, which is taken as the optimal activation temperature 1. The disadvantage of this method is the complexity, duration, and limitation of application. The complexity of the method lies in the fact that it does not exclude the determination of tape segments by the laborious methods of sorption activity, which requires a lot of time. Moreover, this method / method can only be used with regard to the angle of ftiIM fabrics. The aim of the invention is to reduce the time of determination and simplify the process. This goal is achieved by the fact that a sample of carbon material is heated at different temperatures while supplying gaseous oxygen-containing gas. the activating agent and the temperature of the corresponding & bulge burn rate of sample I-IO — g / g are taken as the optimum activation temperature. It is known that the volume of the pores (sorption capacity) of the carbon material obtained by activation with the same degree of burning is the higher, the lower the activation temperature. By studies ycTaBjfieHO that there is a temperature beyond which the above phenomenon is not observed, the pore volume remains constant and is determined only by the degree of burning. This temperature is optimal for the activation process. It has been established that the maximum temperature; the corresponding speed of the S-lOt / r-c burnout is independent of the activating gas (par.

02I air. Reducing the speed a less than 110 g / g-s does not give ysej

an increase in the volume of these pores and an excessively prolonged activation process. With an increase in the burning speed of more than 5-10 g / g s (i.e. activation at higher temperatures), the pore volume does not fully develop or does not develop, and therefore under such conditions it is impossible to obtain a sorbent.

For determination, coke from brown coal is used, which is obtained by thermal impact on brown coal of the Nazarovskoye deposit of the Kansk-Achinsk basin of Siberia without air access to a temperature of 900 ° C. Coke has the following technical analysis, wt.%: Volatile 6, ash 16, humidity 3. The size of the grains of brown coal coke is 0.10, 2 mm. The weight used in the experiments is equal to Q, 5 g.

Semi-coke from long-flame coal, which is obtained by thermal impact on Kuzbass long-flame coal without air access to temperature, Its technical analysis is as follows, wt.%: Volatile 7, ash 10, humidity 1, 5. Grain size 0.6-1 mm, weight . 1 year

Carbon fiber, which is obtained by carbonization of polyacrylonitrile fiber (PAN) when heated to 900 ° C in an inert atmosphere. Size, (diameter) of elementary fiber 57 µm, volatile 0%, moisture content O, 8%, weight, used in experiments 0.5-1 g

For experiments, a 1.5 kW detachable type electric furnace with a temperature adjustment controller (LATR-9), chromo-auleus Io or platinum-platinum-rodium thermocouple, a galvanometer with a divide value of 1 degree and thermometers (converted scales ADV-thermometer (converted scales ADV-thermometers), electroplate with 1 dividing degree and thermometers (converted scales ADV-thermometer (converted scales ADV-thermometer), with the price of 1 degree and thermo weights (converted scales ADV-thermometer (converted scales ADV-thermometer), with a galvanometer with a division value of 1 degree and thermopiles (converted scales ADV-thermometer (converted scales ADV-thermometer with a price of 1 degree and thermo weights (converted scales ADV-thermometers), galvanometer with the cost of dividing 1 degree and thermometers (converted scales ADV-thermometer (converted scales ADV-thermostat), galvanometer with the price of division 1 degree and thermometers (converted scales ADV-thermometer, converted galvanometer with a dividing price of 1 degree and thermomes (reequipped scales ADV-thermocouple-electrophoresis) .

The optimal activation temperature is determined under the following conditions: individual samples of 0.5-1 g are oxidized. A constant temperature corresponds to the oxidation of each sample, for example, for coke from brown coal the following temperatures are taken: 300, 345, 385 and final - 340 ° C, which corresponds to a loss rate in weight of 110 g / Gs, the oxidation of the sample at a given temperature is carried out in those 4eifae 15-20 minutes, a. this time, the determination of the rate of loss in weight (C) is made at least three times by dividing the loss in weight (V) by Nav (B), during which the loss occurred, t, e.

C-V

8, N

where H is a sample.

B - the duration of the determination of the optimum activation temperature by the proposed method varies from within 2-3 hours,

Air, water vapor and carbon dioxide rai5 with a flow rate of 0.180, 36 are used as oxidizing media.

Example 1. In order to determine the optimal activation temperature for coke from the brown coal of the Nazarovskoye deposit, obtained by coking to a temperature of 900 ° C, the coke is crushed to a grain size of 0.1-0.2 mm, take four weights of

5 0.5 g and oxidized alternately at the following temperatures, C 300, 345 and. 385. To carry out the experiment, a thermobalance, a 1.5 kW electric detachable furnace equipped with a temperature rise regulator - latr and xpoMe ib-alumel thermocouple with a galvanometer - are taken. In a furnace heated to a predetermined temperature, for example, a container with a hinge is placed before (further up to,) and

5 air is activated for 20 minutes. During the activation, the loss in weight is recorded three times after 5 and 10 minutes, and the rate of loss in weight (speed

D obgara). The table shows the results at different temperatures, C: 300, 345, 385 and the magnitude of the rate of loss in weight, g / g-s: 3 ,, 3.65х10 5, 4.2x10-5, 1.2 10, 1, 2x10

5 1, -4x10-2.5x1ol 2.55 / 10 2.35 / 10-.

FIG. 1 shows a graph of the 4-speed of the burned speed in the loss-. All the temperature.

As can be seen from the graph, the temperature of 340 ° C corresponds to the rate of loss in

0 weight 1y g / g. with. Experienced checking this temperature at a rate of oxidized. nor confirms the accuracy of the optimal activation temperature.

Example. 2. It is graphically -determined that the burning speed of 510 V / rc corresponds to a temperature of 39 ° C in Example 1, but activation (oxidation) is carried out at 250–450 ° C.

Example 3. 0.5 g of carbon

0 fiber derived from polyacrylonitrile fiber (PAI) at 900 ° C. According to the method described in example 1, the burning speeds were determined in air at. 350 400

5 and. Graphically, it was found that the burning speed of 510 g / g. Corresponds to temperature. Experimental determination confirms this amount of obgar at 460 ° C.

Example 4. According to the method described in Example 3, the optimum temperature was determined: carbon fiber activation tours in an atmosphere of carbon dioxide, and the flow rate. 5 carbon dioxide was 0.36 m / g.

The measurement of the velocities was carried out at 700, 800, 850® and 1050 ° C. 4Pa The optimal activation temperature was found that corresponds to a speed of 5 10 g / HS. Experimental verification confirms the correctness of determining the optimal activation temperature.

Example 5. Carbon fiber, as in Example 3 and by the same method, is activated with water vapor, the steam consumption being 0.36. The burning speed (weight loss) was measured at 700 s, 850 ° C and 1050 ° C. At first it was graphically and then experimentally established that the burning speed of 5 lOr / Gs corresponds to the temperature.

Detachment

Reheating the oven to the set temperature

Activation (oxidation

Processing .activated tape

Calculation of the rate of loss in weight and the construction of a graph of the dependence of speed on temperature

Determination of sorption activity

Total:

As can be seen from the table, according to the preparatory operations and activation time, the known method has an advantage in terms of duration, but the need for further determinations of sorption activity (in order to (Determine the optimal activation temperature) makes it very long (at least 2 days), for example, by determining the content in samples of hygroscopic moisture according to GOST 8719-58 or by the adsorption method.

Example b. The optimum activation temperature of the semi-coke obtained from the long-flame brand coal (e) is determined by heating it without air access to 670 s. The grain size of the semi-coke of the weighed portion is 0.6-1 mm. A weighed amount of 1 g was taken. The burned speed was determined at 340 ° C, 37 ° C and DOZS. The optimum activation temperature of 400 ° C (which corresponds to a rate of 1lOr / g-s) is determined graphically. An experimental check confirms this temperature.

The table shows the time spent on the determination of the optimal activation temperature for the proposed and known methods.

one

53 "5 15

5 5

130x1 30

em

Not

During the heating of the furnace

Not

No and activation

10 From 2

No days until 2 weeks

From 2

165 days to 2 weeks

The accuracy of determining the optimum temperature consists of the accuracy of weighing, which is 0.5 mg, of the accuracy of temperature measurement and the accuracy of time measurement, 1 second and the standard error of the determination is 2 to 5 degrees depending on temperature (275-1000 ° C) .

Thus, the proposed method greatly simplifies the determination of the optimal activation temperature, since it is based on only one step.

Claims (1)

The claims of the materials, including heating samples of the carbon material while supplying a gaseous oxygen-containing activating agent, characterized in that, in order to reduce the time of determination and simplification of the process, the samples are heated at different temperatures and the temperature corresponding to a burn speed of 1-10 ^h - 5 “10 ' ⁴ g / g · s, taken as the optimal activation temperature.