SU609086A1 - Method of investigating material sorbtion properties - Google Patents

Description

one

The invention relates to methods for studying the structure of highly-dispersing and porous solids, in particular adsorbents and catalysts, as well as methods for studying the solubility of gases in liquids.

The adsorption isotherm of gas or vapor on the surface of a solid and the absorption (dissolution) isotherm of liquid are the most important physicochemical characteristics. The adsorption isotherms allow us to determine the specific surface area of a highly dispersed or porous solid, pore volume, and pore distribution over effective radii. From the dissolution isotherm, it is possible to obtain the data necessary for calculating the processes of distillation and rectification.

A known method for studying the sorption characteristics of materials is to place the samples in a confined space, to evacuate, admit the sorbate and measure the adsorbed amount of sorbate on the sample.

The disadvantage of this method is the length of the process of determining and the complexity of the equipment used.

The prototype of the invention is a method for studying the sorption properties of materials, which consists in absorbing sorbate from a gas stream by a sorbent in a vessel, displacing the sorbate with a non-sorbing gas, and recording

extruded sorbate and determination of the obtained data sorption properties.

The disadvantage of this method is the need to stabilize the flow rate of the gas at the inlet g

vessel.

The purpose of the invention is to simplify the method. The goal is achieved by the fact that during the process of sorption and desorption, the difference in the volume of the gas entering the vessel with the sorbent and the volume of gas released from it is continuously recorded. During sorption, this difference is equal to the amount of sorbate absorbed by the sorbent from the stream, and during desorption it is equal to the amount of sorbate released from the sorbent into the stream by a given time. The concentration of sorbate in the stream of its mixture with a non-absorbed carrier gas is fixed by a detector installed on the outlet from the vessel with the sorbent. FIG. 1 is a schematic diagram of an apparatus for carrying out the proposed method; in fig. 2 shows a scheme for measuring the adsorption and desorption isotherms of n-butane; in fig. 3 - isotherm of adsorption and desorption of n-butane on silica gel; in fig. 4 - isotherm of n-hexane dissolution in hexadecane.

Through a serially connected counter 1, state 2 sorbent, detector 3 and counter 4 pass a mixture of non-sorbing gas and sorbate or pure sorbate. Concentration

sorbate in the mixture can be constant or

variable. After reaching the desired level of saturation of the sorbent under equilibrium conditions, through the system 1-4, a pure non-absorbed gas or a mixture of sorbate and non-absorbed gas, in which the concentration of sorbate is less than the equilibrium, is passed through. The signals from counters 1 and 4 are stored in subtraction unit 5. The concentration dependence of the amount of sorbate recorded by the recorder is the isotherm of sorption and desorption.

Example 1. Measurement of the total isotherm of adsorption and desorption of n-butane on silica gel KSK-2.

Non-sorbing gas (hydrogen) is continuously passed at a volume rate of 10 ml / min through valve 6 (Fig. 2), mixer 7, counter 1, U-shaped tube (vessel) 2 with silica gel, detector 3 but thermal conductivity and counter 4. Mixer volume equals 100 ml; the length of the U-shaped tube is 15 cm; its diameter is 0.5 cm; the mass of silica gel - 0.93 g; particle size in the range of 0.2-0.5 mm. Tube 2 is thermostated at 0 ° C with melting ice. Then the valve 6 is closed and, opening the valve 8, is passed through the mixer 7 and the system 1-4 n-butane.

After the end of the adsorption process, the valve 8 is closed and, by opening the valve 6, the carrier gas is passed through until the end of the desorption process. Block 5 subtracts the amount of gas absorbed by the sorbent or released from it in the form of the difference between the readings of counters 1 and 4. Detector 3 records the concentration of n-butane, which is then converted into relative pressure P / Rd, where P is the vapor pressure of n-butane in space above the surface of the adsorbent; PS is the saturated vapor pressure of liquid n-butane. From these data, the points of a adsorption isotherm and the points b of the desorption isotherm shown in FIG. 3. The solid line is shown to compare the isotherm obtained by the static method.

Example 2. Measurement of the solubility isotherm of n-hexane to hexadecium.

Non-sorbing gas (nitrogen) is continuously passed at a rate of about 4 ml / min through counter 1 (Fig. 1), a bubbler (vessel) 2 with a volume of 15 ml containing 0.447 g of hexadecane, detector 3 and counter 4. Then 0.084 pulsed into the bubbler g n-hexane. The bubbler thermostatic at 30 ° C liquid

thermostat. The subtraction unit records the amount of n-hexane released from the solution, in the form of the difference between the readings of counters 1 and 4. From these data, the amount of n-hexane remaining in the solution and the concentration are calculated. The detector records the concentration of n-hexane in the gas, which is then converted into vapor pressure. FIG. 4 shows the solubility isotherm points constructed using this data. Solid line built by

data static method.

The invention clears the field of sorption properties, as it allows to measure both the adsorption and desorption branches of the isotherm. The proposed method is different.

simplicity, since it is not necessary to stabilize and measure the flow rate. In addition, the use of a differential measurement circuit (counter at the entrance to the vessel — the counter at the exit of the vessel) compensates for errors

from changes in environmental parameters.

Claims (1)

Invention Formula The method of studying the sorption properties of materials by absorbing sorbate from a gas stream by a sorbent in a vessel, displacing the sorbate with a non-sorbing gas, registering the displaced sorbate, and determining the sorption properties from the data obtained, in order to simplify In the process of sorption and desorption, the difference in the volume of gas entering the vessel with the sorbent and the volume of gas released from it, by which the sorption properties of the material are judged, is continuously recorded. L - i to the registrar // figure 1 "2-JLff ff%., Ji to the registrar Figure 2  "I-o R, mm N 100