RU2068296C1 - Method for separation of microimpurities from gas and liquid media - Google Patents

Abstract

FIELD: adsorption methods for production of pure gas and liquid media, and also for separation and concentration of microimpurities of substances of various classes in their monitoring in environment. SUBSTANCE: adsorbent for purification of media and monitoring their quality is used in form of new carbon adsorbent produced by catalytic decomposition of methane. Specific feature of structure of catalytic carbon consists in that its surface is composed not of basal faces of graphite but their end faces shifted relative to one another at distance of 0.1-10 nm that imparts its unique adsorption properties to it. EFFECT: higher efficiency. 2 dwg, 2 tbl

Description

 The invention relates to adsorption methods for purification of gas and liquid media, as well as methods for concentrating n-paraffins, cyclic and aromatic hydrocarbons, acetone, alcohols, phenols and organochlorine substances.

 The purification of gas and liquid media, including air and water, as well as various life support systems, the accumulation of microimpurities and their determination, in particular, by gas chromatography is the most important task of obtaining clean media and environmental quality control.

 The solution to this problem is largely determined by the creation and use of new adsorbents with high adsorption capacities.

 Moreover, the increase in the adsorption capacity of known materials is usually ensured by an increase in their specific surface available or for adsorption, as well as by an increase in micropore volume. The adsorption surface of known carbon adsorbents is formed by the basal faces of the graphite crystal structure or its fragments.

The most widespread solution to practical environmental problems was the use of various microporous carbon molecular sieves such as carbosive [1] organic porous polymers [2] graphite soot [3] homogeneous porous adsorbents of the mixed type XE-340 [4]
However, their insufficient adsorption dynamic capacity, which makes it possible to transmit a smaller volume of gas and liquid samples, should be noted. The closest to the invention in essence and the achieved effect are carbon materials such as carbosive and graphitized thermal soot (GTS).

 The purpose of the invention is the development of a method for the separation of n-paraffins, cyclic and aromatic hydrocarbons, acetone, alcohols, phenols and organochlorine substances from the gas volume and aqueous media for purification of the latter, as well as the accumulation of these substances (if necessary, determine them in the environment at ppm and below ) by using carbon materials with a significantly increased specific adsorption dynamic capacity (referred to the surface unit).

 To achieve this goal, it is proposed to use carbon materials whose surface is formed by non-basal faces. Such adsorbents can be obtained by known methods, in particular, by catalytic decomposition of hydrocarbons.

 Features of the structural properties of the proposed carbon material, determining its adsorption properties, are presented in FIG. 1 (a fragment of one of the threads from which its microstructure is formed is shown).

 Obtaining a catalytic fibrous carbon material is as follows.

0.1 g of a granular catalyst with a particle size of 0.25-0.5 mm, consisting of 90 wt.%, Is poured into a reactor with a diameter of 30 mm. metallic nickel and 10 wt. aluminum oxide. The catalyst is subjected to vibrational fluidization and is heated to a temperature of 550 ^o C. Then methane is fed into the reactor, which, passing through the catalyst bed, decomposes into carbon fiber and hydrogen. Methane consumption is maintained at about 12 l / h. The process is conducted for 16 hours until the catalyst is completely deactivated. Carbon is formed on nickel crystals with a size of 15 to 16 nm in the form of threads that are intertwined randomly. The granules of the deactivated catalyst increase in size by 4 5.5 times and consist of 99.3 wt. from carbon. Thus obtained carbon material is a fairly strong granules up to 5 mm in size, reproducing the shape of the initial catalyst particles. They have good flowability and are easily discharged from the reactor.

 The catalytic carbon discharged from the reactor is crushed, scattered into fractions, and a fraction of 0.25-0.5 mm is used for operation.

 A weighted amount of adsorbent (0.9300 g) is filled into the chromatographic column with an adsorption trap made of stainless steel 0.5 m long, 2 mm inner diameter (to determine the adsorption and chromatographic characteristics of phenol and chlorobenzene, the amount of sorbent was 0.1345 g, column length 35 cm )

The column is installed in a Tsvet-570 chromatograph with a flame ionization detector (DIP) and conditioned in a stream of nitrogen carrier gas at a rate of 30 ml / min at 300 ^° C for 8 hours.

где P₁ [мм рт. ст. давление на входе колонки;
P_o [мм рт. ст. давление на выходе из колонки;
m [г] масса сорбента в колонке;
S [см²/г] удельная поверхность адсорбента, которая составила для предлагаемого адсорбента 117 м²/г.The dynamic adsorption capacity, V _{A, 298} , is estimated by extrapolating to room temperature 298 K plotting the logarithm of the absolute retention volume, V _A , of the studied substances from the reciprocal temperature. The latter is determined by the formula:
V _A = (t _R -t _o • W • T _count / T _reom. • f / m • S (1),
where t _R [min] the retention time of the studied component;
t _o [min] retention time of the non-absorbable component (methane for dip);
W [ml / min] space velocity of the carrier gas;
T _count [K] column chromatography temperature;
T _reom. [K] the temperature at which the foam volumetric velocity meter of the carrier gas is located (rheometer);
f factor taking into account the pressure drop in the column and determined by the formula

where P ₁ [mm RT. Art. column inlet pressure;
P _o [mmHg Art. pressure at the outlet of the column;
m [g] sorbent mass in the column;
S [cm ² / g] specific surface of the adsorbent, which amounted to the proposed adsorbent 117 m ² / g

где N число теоретических тарелок адсорбционной колонки;
V_R=V_A•m•S удерживаемый объем адсорбата при данной температуре.The volume of the sample, which can be passed through a given amount of sorbent, ensuring complete capture of the component, is associated with the adsorption dynamic capacity of a known ratio [5 and 6]

where N is the number of theoretical plates of the adsorption column;
V _R = V _A • m • S the retained volume of the adsorbate at a given temperature.

 A large adsorption dynamic capacity, as follows from (3), allows, on the one hand, to pass large volumes of polluted air and water during their purification, and, on the other hand, to accumulate large quantities of the above substances in the atmosphere in small quantities, and thereby lower the limit of their detection.

при адсорбции веществ разных классов, исходя из температурной зависимости абсолютных удерживаемых объемов адсорбатов

откуда

2,3R tg α, где R 8,314 дж/град. моль;
a угол наклона прямой логарифмической зависимости абсолютного удерживаемого объема сорбата от обратной температуры.In addition, the adsorption capacity of the new adsorbent was evaluated by the values of the differential molar change in internal energy

during the adsorption of substances of different classes, based on the temperature dependence of the absolute retained volumes of adsorbates

where from

2.3R tg α, where R 8.314 J / deg. mole;
a the angle of inclination of the direct logarithmic dependence of the absolute retained volume of the sorbate from the reciprocal temperature.

 The essence of the invention is illustrated by the following examples.

 Example 1. In a chromatographic column (adsorption trap), a catalytic carbon sorbent obtained by catalytic decomposition of methane on a nickel catalyst is loaded according to the procedure described above, the surface of which is formed by parallel oriented ends of the basal faces of the graphite crystal structure, offset to a distance of 0.1-10 nm. This column is placed in a chromatograph and at successively set temperatures: 473K, 523K, 538K, 548K, 558K, 568K, the absolute retention volumes of n-pentane are determined by the formula (1).

 The sample is started using a Hamilton syringe, taking 2 μl of a steam-air mixture of n-pentane from a penicillin jar containing liquid n-pentane and a closed self-sealing silicone rubber cap.

 In the table. Figure 1 shows the absolute retention volumes of n-pentane at different temperatures.

 Examples 2 5. Similar to example 1, but differ in the adsorbents taken.

Example 6. The absolute retained volume of benzene (at room temperature) on the surface of catalytic carbon formed by parallel oriented ends of the basal faces of the graphite crystal structure was determined by extrapolating to room temperature a graph of the dependence of ln V _A on inverse temperature.

In the table. 2 shows the value of V _{A, 298} for benzene.

 Example 7 18. Similar to example 6, but differ in the adsorbates taken.

 Examples 19 to 31. Given for comparison and similar to examples 6-18, but characterized in that the graphite thermal carbon black [3] is used as the sorbent, the surface of which is composed of the base faces of the graphite crystal structure. In these examples, the adsorption dynamic capacity of aromatic hydrocarbons, n-paraffins, cyclohexane, methanol, ethanol, propanol, acetone, phenol, chlorobenzene and water is compared with the adsorption dynamic capacity for these adsorbates for a catalytic carbon material whose surface is formed by parallel oriented ends of the basal faces graphite crystal structures (table. 2).

 Examples 32 44. Similar to examples 6 to 18 and are given for comparison, in which Ambersorb XE-340 is used as a sorbent [4] and in which the adsorption dynamic capacity shown in the table. 2 sorbates is compared with the adsorption dynamic capacity with respect to the indicated adsorbates for catalytic carbon, the surface of which is formed by parallel oriented ends of the basal faces of the graphite crystal structure, offset to a distance of 0.1 to 10 nm (Table 2).

From the data table. 2 shows that for a catalytic carbon adsorbent, the adsorption dynamic capacity in relation to aromatic hydrocarbons, n-paraffins, cyclohexane, methanol, ethanol, propanol, acetone, phenol and chlorobenzene is several orders of magnitude higher than that for known carbon sorbents. This makes it possible to recommend this adsorbent for both air and water purification, including various life support systems (V _{A, 298} for water is only 1.3 ml / m ² ).

и ее зависимость от числа углеродных атомов в н-парафине.Example 45. Similar to examples 6 to 18, but characterized in that for the characterization of adsorbents is used the value

and its dependence on the number of carbon atoms in n-paraffin.

 In FIG. Figure 2 shows this dependence for catalytic carbon, the surface of which is formed by the ends of the basal faces of the graphite crystal structure (curve 1).

от числа атомов С в парафине получена для графитированной термической сажи (кривая 3) и карбосива (кривая 2).Examples 46 47. Similar to example 45 and are given for comparison, in which the dependence

of the number of C atoms in paraffin was obtained for graphitized thermal soot (curve 3) and carbosive (curve 2).

от числа атомов углерода в молекуле н-парафина для всех трех адсорбентов показывает существенные различия в адсорбционном взаимодействии взятых адсорбатов и свидетельствуют о высокой адсорбционной способности каталитического углеродного адсорбента. Так, величина

для н-гексана в 3 раза выше для каталитического углерода, поверхность которого составлена торцовыми гранями структуры кристалла графита, чем для ГТС, поверхность которой состоит из базисных граней, и примерно в 1,5 раза выше, чем для карбосива.Dependency Comparison

of the number of carbon atoms in the n-paraffin molecule for all three adsorbents shows significant differences in the adsorption interaction of the adsorbates taken and indicate a high adsorption capacity of the catalytic carbon adsorbent. So, the value

for n-hexane is 3 times higher for catalytic carbon, the surface of which is composed of the end faces of the graphite crystal structure, than for GTS, the surface of which consists of basic faces, and is about 1.5 times higher than for carbosive.

Claims (1)

 The method of separation of microimpurities from gas and liquid media by chromatography on a carbon-containing sorbent, characterized in that the separation is carried out on an adsorbent, the surface of which is formed by parallel oriented ends of the basal faces of graphite, offset to a distance of 0.1 to 10.0 nm, obtained by the decomposition of hydrocarbons on the catalyst.

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