RU2205064C1 - Gas- and liquid-treatment adsorbent for removing halogen-containing compounds and a method of preparation thereof - Google Patents

Abstract

FIELD: sorbents. SUBSTANCE: adsorbent is composed of, wt %: zinc oxide 50.0-85.0, alkali metal compound 0.001-0.9 (on conversion to metal oxide), silicon compound 0.05-15.0 (on conversion to silicon dioxide), and aluminum - the balance. Preparation procedure: zinc oxide or zinc compound decomposing to give zinc oxide is mixed with aluminum hydroxide or oxide, alkali metal compound, naturally occurring or synthetic silicate or aluminosilicate, or silicic acid, resulting mass extruded, extrudate dried and calcined. Calcination of mass at 550 C results in 30-69% weight loss. Invention can be applied in petrochemical and chemical industries, and petroleum processing. EFFECT: increased chlorine capacity and mechanical strength. 4 cl, 1 tbl, 12 ex

Description

 The invention relates to the purification of gases and liquids from halogen-containing compounds and can be used in the oil refining, petrochemical, chemical industries, in the production of semiconductors, for solving technological problems, protecting equipment from corrosion and protecting the environment.

 Halogen-containing compounds include hydrogen chloride (HCl), hydrogen fluoride (HF), hydrogen bromide (HBr), hydrogen iodide (HI), in fact chlorine, bromine, fluorine, iodine, halogen compounds with other elements. These harmful gases are used, in particular, in the optoelectronic industry and the semiconductor industry and their release into the atmosphere is unacceptable.

 Hydrogen chloride and organic chlorides are present in petroleum fractions and refinery gases. During the catalytic reforming of gasoline fractions on polymetallic catalysts to produce high-octane gasolines, chlorides (dichloroethane, carbon tetrachloride) are added to the reforming feedstock to increase the acidity of the catalyst. As a result, excess hydrogen-containing reforming gas directed to the hydrotreating of oil fractions contains hydrogen chloride, which causes corrosion and the formation of ammonium chloride, which clogs the equipment. When hydrotreating gasoline and other fractions due to the presence of halogen-containing compounds in the feed and hydrogen-containing gas, corrosion of the equipment increases and the process technology is violated.

 For the adsorption purification of gases from halogen-containing impurities, it is known to use alkali deposited on activated carbon and soda lime, which is a mixture of NaOH and CaO, limestone impregnated with an aqueous solution of sodium hydroxide [German Patent 3708039, publ. 10/06/1988]. The disadvantages of using alkali on the carriers are due to the relatively low absorption rate, sintering of the adsorbent, causing the adsorber to become clogged, and the high solubility of the active components in water during the purification of moist gas.

 For the purification of gases and liquids from chlorine-containing impurities, an adsorbent is known containing Group VIII metals (iron, nickel), Group IB metal (copper) and / or Group IIB metal (zinc) on a carrier of aluminum oxide or hydroxide [French Patent 2776536, publ. 10/01/1999].

 The disadvantage of this adsorbent is its limited scope. Fairly good results on chlorine consumption are obtained if there are significant amounts of moisture in the gas being cleaned, in addition to hydrogen chloride, which contributes to the absorption of hydrogen chloride. However, in many cases, it is necessary to purify deeply dried gas from hydrogen chloride. So, a hydrogen-containing catalytic reforming gas contains only 10-30 ppm of moisture.

Known adsorbent for the absorption of chlorides, consisting of 2-15 (preferably 5-10) parts by weight of an inert binder (clay, silica gel, aluminum salts and hydroxides), 5-25 (preferably 10-17) parts by weight of a refractory inorganic carrier (kieselguhr, oxide silicon, alumina, ceramics) per 10 parts by weight of zinc oxide. The pore volume of the adsorbent 0.35-0.65 cm ³ / g [Japan patent 11033396].

 The disadvantage of this adsorbent is reduced chlorine consumption. Its calculation, according to examples 1 and 2 shown in the patent, showed that the amount of chlorine adsorbent absorbed by mass is only 11.3% and 11.4%, respectively.

 Closest to the technical nature of the claimed is an adsorbent containing zinc oxide, aluminum oxide and an alkali metal compound such as potassium and / or sodium carbonate or hydrogen carbonate, sodium hydroxide. The ratio of alumina to zinc oxide, expressed as the number of aluminum atoms per zinc atom, is in the range 0.05-0.60, and the ratio of sodium or potassium atoms per zinc atom is 0.05-0.50. In addition to alkali metal compounds, ammonium hydroxide can be used [US Patent 5378444, publ. 01/03/1995 - prototype].

 The specified adsorbent is used to purify gases from halides such as hydrogen chloride, chlorine, hydrogen fluoride, fluorine, hydrogen bromide, bromine, dichlorosilane, silicon tetrachloride, phosphorus trichloride, boron trichloride, boron trifluoride, silicon tetrafluoride.

The disadvantage of the proposed adsorbent is the relatively low capacity of the adsorbent for absorbed halide. The adsorption capacity of the adsorbent during gas purification from hydrogen chloride can be calculated according to the data given in tables 1 and 2 of the above patent, based on the amount of adsorbent (28.4 cm ³ ≈ 28.4 g), nitrogen flow rate (0.22 l / min) the concentration of hydrogen chloride in the gas (1000 ppm and 1 vol.%) and the time to breakthrough. The chlorine capacity of the adsorbent before breakthrough is at a concentration of HCl 1000 ppm and 1 vol.%, Respectively, 6.5% and 11.7% of its mass, although the mass content of zinc oxide in the adsorbent is 85%.

The adsorbent is prepared by mixing zinc oxide or a compound that decomposes to form zinc oxide, hydroxide or aluminum oxide and an alkali metal compound; if necessary, water is added to the mixture to make a cake. Then it is molded in an extruder to obtain extrudates, or the cake is dried, ground into powder and tableted with the addition of graphite. The adsorbent can be molded in the form of balls or particles of irregular shape. The adsorbent is subjected to heat treatment: drying and calcination at temperatures of 110 ^o C and 350 ^o C. The disadvantage of this method is the insufficiently high chlorine consumption and mechanical strength of the adsorbent.

In order to increase the chlorine capacity and mechanical strength of the adsorbent, an adsorbent is proposed for purification from halogen-containing compounds, including zinc and aluminum oxides, an alkali metal compound and, additionally, silicon compounds in the following ratio of components in wt.%:
Zinc oxide - 50.0-85.0
The alkali metal compound (in terms of M ₂ O) - 0.01-6.0
The silicon compound (in terms of SiO ₂ ) - 0.05-15.0
Alumina - Else
As a silicon compound, in particular, natural aluminosilicate — kaolin — is used. The composition of kaolin can be characterized by the formula Al ₂ Si ₂ O ₅ (OH) ₄ [Chemical Encyclopedia. Volume 2. - M .: Soviet Encyclopedia, 1990, p. 606]. Clays are also used, which, like kaolin (kaolinite), have a layered structure. As synthetic silicates, sodium and potassium silicates can be used.

 An essential distinguishing feature of the proposed adsorbent is the presence in its composition of silicon compounds in an amount of 0.05-15 wt.% In the calculation of silicon dioxide.

The proposed method of preparing an adsorbent containing zinc oxides, aluminum, a silicon compound and an alkali metal compound comprises mixing zinc oxide or a compound that decomposes upon heating to produce zinc oxide, hydroxide or aluminum oxide, an alkali metal compound, natural or synthetic silicate or aluminosilicate or silicon acid, extruding a mass characterized by loss on ignition at 550 ^{° C.} in the range of 30-60 wt.%, drying and calcining the extrudates.

 To prepare the adsorbent, zinc oxide or basic zinc carbonate is used, which decomposes at elevated temperatures to form zinc oxide. For a given adsorbent, the specific surface area of zinc oxide is less important than its purity from lead impurities.

 A source of alumina may be its powder or pellet of aluminum hydroxide, which during heat treatment turns into oxide. An aqueous suspension of aluminum hydroxide (pulp) may also be used.

 For this adsorbent, there is no need to use high-purity alumina. It is convenient to use aluminum oxide or hydroxide containing impurities of sodium and silicon, where the latter is bound to aluminum oxide in the form of silicate.

 For the introduction of silicon compounds, alkali metal silicates or silica sol, natural kaolin or clay silicates can be used.

 In these components, as well as in aluminum hydroxide, as a rule, alkali metal compounds are already contained in the required amounts, sufficient to obtain an adsorbent with an alkali metal content in the range of 0.01-0.10 wt.% Calculated on oxide. If you want to get an adsorbent with a higher alkali metal content (up to 6 wt.%), Sodium or potassium salts are additionally introduced into the moldable mass.

The mixture is stirred, adding water, if necessary, to obtain a plastic mass and molded into extrudates. The mass used for molding should have a value of losses during calcination at 550 ^o C in the range of 30-60 wt.%. The final stage - heat treatment - consists in drying at temperatures of 50-150 ^o C and calcining at temperatures of 300-700 ^o C, preferably 350-600 ^o C. It should be noted that the composition of the adsorbent is calculated on calcined at 550 ^o C.

 An important feature of the method of preparation of the adsorbent is the use for the introduction of silicon silicates of natural or synthetic origin or silicic acid.

Another sign is the limits of losses during calcination of the moldable mass at a temperature of 550 ^o C (SPP), which are 30-60 wt.%.

 The difference between 100% and the loss on ignition characterizes the dry matter content remaining after calcination at the indicated temperature. Losses on ignition mainly determine the amount of moisture contained in the moldable mass.

 It turned out that within the indicated SPP limits, the extrudates obtained by forcing the mass through dies with a given hole diameter are characterized by the necessary mechanical strength. The mechanical strength can be characterized by the coefficient of strength for cracking the granules with a knife in kg / mm diameter. We found that the coefficient of mechanical strength of an adsorbent operating in a chemically aggressive environment of hydrogen chloride and other hydrogen halides should not be lower than 0.9 kg / mm in diameter (when splitting with a knife with a blade width of 0.1 mm according to OST 301-03-01.8-97 Industry standard. "Alumina-platinum monometallic and polymetallic catalysts, active alumina - carrier for catalysts and gas dehumidifier").

 SPP is regulated by adding water to the mixed mass and by heating the mass with evaporation of water.

 A preferred feature of the present invention is the use of a zinc compound, the content of lead impurity of which does not exceed 0.1%, based on zinc oxide. Zinc oxide and its compounds usually contain an admixture of lead. To prepare the adsorbent according to the invention, it is recommended to use purified zinc compounds or purify them of lead by any known methods [Karjakin Yu.V., Angelov II. Pure chemicals. - M.: Chemistry, 1974, p. 400].

 The advantage of the proposed adsorbent and the method of its preparation is to increase its chlorine consumption by 5-60 rel.%, And therefore, in its longer service life. The increased mechanical strength of the adsorbent also contributes to an increase in its service life.

 Analysis of the known technical solutions in the field of adsorbents for purification from halogen-containing compounds showed the absence among them of the composition and method of preparation of the adsorbent corresponding to the declared one, which allows us to conclude that the proposed technical solution meets the novelty criterion.

 The positive effect of adding predetermined amounts of these silicon compounds to the chlorine consumption of the adsorbent is unexpected.

 The industrial applicability of the proposed adsorbent and method of its preparation is confirmed by the following examples.

The purification of gases and liquids in the presence of the indicated adsorbent is carried out by passing streams contaminated with halogen-containing compounds at temperatures of 0-150 ^o C, preferably 10-90 ^o C.

 Example 1

 An adsorbent is prepared containing 70% zinc oxide, 6.7% silicon dioxide and 0.04% sodium oxide, the rest is aluminum oxide.

 Use zinc oxide with a lead impurity content of not more than 0.01%, a particle size of less than 60 micrometers, more than 99% of the particles by weight of zinc oxide passes through a sieve with openings of 56 micrometers.

Take 70 g of the specified zinc oxide, 12.2 g of kaolin, calculated on calcined at 550 ^o C, aluminum hydroxide powder with a mass content of aluminum oxide of 72% in an amount of 24.7 g. The content of sodium oxide in aluminum oxide is 0.15 wt. % Use kaolin enriched according to GOST 19607-74, grade I.

The mixture is stirred, add to it 80 cm ^{3 of} water and then 0.3 cm ³ nitric acid with a concentration of 58 wt.% To achieve the necessary plasticity of the mass. Losses after calcination at 550 ^o With the obtained mass is determined according to OST 301-03-01.9-97 "Catalysts alumina-platinum monometallic and polymetallic, active alumina - a carrier for catalysts and a gas dryer". RFPs make up 48 wt.%. After mixing the mass, the resulting cake is formed using an extruder and extrudates with a diameter of about 2.5 mm are obtained. The adsorbent is successively dried at 50 ^° C, 110 ^° C and 130 ^° C for 3 hours at each temperature and calcined in a stream of air at 500 ^° C for 3 hours. The strength factor determined by OST 301-03-01.8-97 is 1 kg / mm.

 Example 2

An adsorbent is prepared containing 70% zinc oxide, 3.3% silicon dioxide, 0.04% sodium oxide, and the rest is aluminum oxide. The preparation method is similar to that shown in Example 1, except that 6.1 g of kaolin and 85.4 g of aluminum hydroxide cake containing 28% alumina are taken. The content of sodium oxide per calcined alumina is 0.15%. The amount of added water and nitric acid is similar to Example 1, but the mixture is heated to 60-80 ^o C. while stirring.

PPP moldable mass at 550 ^o With - 52 wt.%.

 The strength coefficient of the adsorbent is 1.1 kg / mm.

 Example 3

 An adsorbent is prepared containing 70% zinc oxide, 11.7% silicon dioxide and 0.03% sodium oxide, the rest is aluminum oxide. The preparation method is similar to that in Example 1, with the change that take 21 g of Glukhov clay containing 55% of the kaolinite phase and 12.5 g of aluminum hydroxide powder.

PPP moldable mass at 550 ^o With - 44 wt.%.

 The coefficient of strength of the adsorbent is 1.2 kg / mm.

 Example 4

An adsorbent is prepared containing 55% zinc oxide, about 6.0% potassium oxide, 0.1% silicon dioxide, and alumina - the rest. To this end, 55 g of zinc oxide, 8.8 g of potassium carbonate, 1.5 cm ^{3 of} silicic acid sol containing 0.1 g of silicon dioxide and 51.4 g of aluminum hydroxide powder are mixed. 60 cm ^{3 of} water and then 0.5 cm ^{3 of} nitric acid with a concentration of 58 wt.% Are added to the mixture. After stirring, the mixture is molded.

PPP moldable mass at 550 ^o With - 48 wt.%.

 The coefficient of strength of the adsorbent is 1.0 kg / mm.

 Example 5

An adsorbent is prepared containing 55% zinc oxide, 0.05% silicon dioxide, 0.01% sodium oxide, aluminum oxide - the rest. The preparation method is similar to that in Example 1, with the difference that they take 55 g of zinc oxide, use aluminum hydroxide containing 0.1% silicon dioxide in the form of aluminosilicate and 0.02% sodium oxide based on their oxides, moreover, aluminum hydroxide powder take in the amount of 63 g. With stirring, the mass is introduced into it 70 cm ^{3 of} water and then 0.8 cm ^{3 of} nitric acid with a concentration of 58 wt.%.

PPP moldable mass at 550 ^o With - 45.5 wt.%.

 The coefficient of strength of the adsorbent is 1.2 kg / mm.

 Example 6

An adsorbent is prepared containing 85% zinc oxide, 0.1% silicon dioxide and 0.1% sodium oxide, the rest is aluminum oxide. The preparation method is similar to that described in Example 1, with the difference that the amount of aluminum hydroxide is 20.8 g, and silicon dioxide and sodium oxide are introduced in the form of sodium nine-silicate in an amount of 0.45 g. 35 cm ^{3 of} water are introduced into the mixture.

PPP moldable mass at 550 ^o With - 30 wt.%.

 The adsorbent strength coefficient is 0.9 kg / mm.

 Example 7

An adsorbent is prepared containing 50% zinc oxide, 0.04% sodium oxide, 15% silicon dioxide, and the rest is aluminum oxide. To this end, 50 g of zinc oxide is mixed with 27.3 g of kaolin and 31.5 g of aluminum hydroxide containing 72% alumina. The content of sodium oxide in alumina is 0.15%. The adsorbent is prepared in accordance with Example 1, but 160 cm ^{3 of} water are introduced into the mixture. With stirring, the mixture is heated to 60 ^o C.

PPP moldable mass at 550 ^o With - 60 wt.%.

 The adsorbent strength coefficient is 0.9 kg / mm.

 Example 8 (comparative).

 An adsorbent is prepared containing 55% zinc oxide, 0.05% silicon dioxide, 0.01% sodium oxide, and the rest is aluminum oxide. The composition of the adsorbent and the method for its preparation are similar to those described in Example 5, but use zinc oxide, which contains 0.15% lead.

 Example 9

An adsorbent is prepared whose composition and preparation method are similar to those described in Example 1, but basic zinc carbonate in an amount of 96.8 g is used as the starting zinc compound. In addition, the mass is heated with stirring at a temperature of 70-80 ^o C.

PPP moldable mass at 550 ^o With - 50 wt.%.

 The adsorbent strength coefficient is 0.9 kg / mm.

 Example 10

The chlorine capacity of the obtained adsorbents is determined before the breakthrough of hydrogen chloride. For this purpose, 10 cm ^{3 of} crushed adsorbent, a fraction of 0.25-1.00 mm, are loaded into the adsorber. Drained air containing 4 g / m ³ hydrogen chloride is passed through an adsorber at a temperature of 25 ^{° C.} and atmospheric pressure. The breakthrough time is recorded and the chlorine capacity of the adsorbent is determined as a percentage of absorbed chlorine based on the weight of the initial adsorbent. The results of determining the chlorine capacity of adsorbents prepared according to Examples 1-9 are shown in the table.

 Examples 1-3 show that when the content of zinc oxide in the adsorbent 70%, the maximum chlorine consumption is achieved when the content of silicon dioxide is 6.7%, which is introduced using kaolin.

 When reducing the content of zinc oxide to 55% (Example 5), the chlorine consumption is lower than at 70%.

 When increasing the content of zinc oxide from 70 to 85% (Example 6), the amount of chlorine takes up relatively little, while the mechanical strength of the adsorbent deteriorates. Therefore, according to the invention, the content of zinc oxide 85% is the maximum permissible value.

 Examples 4, 5 and 7 show the boundary content of the components of the adsorbent.

 Chlorine consumption is low when zinc oxide contains an admixture of lead (0.15 wt.%) (Example 8).

 When using basic zinc carbonate, instead of zinc oxide, approximately the same chlorine capacity is obtained as for the adsorbent prepared on the basis of zinc oxide (see Examples 1 and 9).

The coefficient of mechanical strength of the adsorbents is 0.9 kg / mm and above, when the losses after calcination at 550 ^o With the moldable mass are in the range of 30-60 wt.% (See examples 1-7 and 9).

 Example 11

Purification of chlorides is subjected to straight run gasoline fraction N.K.-70. Raw material contains 44.9 million ^-1 chlorine (as organochlorines) ^-1 and 140 million sulfur.

100 cm ^{3 of the} adsorbent prepared according to Example 5 are loaded into the reactor of the plant. Purification is carried out at 50 ^° C, a pressure of 35 kg / cm ² and a feed of 200 cm ³ / h.

 Determine the chlorine content in the samples after 60, 80 and 100 hours of operation, it is 23.7 ppm, 21.5 ppm and 22.4 ppm, respectively. The chlorine content remains at approximately the same level, it is possible to remove approximately half of the chlorine from the hydrocarbon feedstock.

 Example 12

The adsorbent capacity is determined during gas purification from hydrogen bromide. The test conditions are similar to those described in Example 11, but helium, which contains hydrogen bromide at a concentration of 4 g / m ^3, is used as the gas. On the adsorbent prepared according to Example 5, the bromine capacity is 33%.

 The example illustrates the suitability of using the inventive adsorbent for the absorption of other halogen-containing compounds, in addition to hydrogen chloride.

Claims (3)

1. The adsorbent for the purification of gases and liquids from halogen-containing compounds, including zinc and aluminum oxides, an alkali metal compound, characterized in that it further comprises a silicon compound in the following ratio of components, wt. %:
Zinc oxide - 50.0-85.0
The alkali metal compound (in terms of M ₂ O) - 0.01-6.0
The silicon compound (in terms of SiO ₂ ) - 0.05-15.0
Alumina - Else
2. The adsorbent under item 1, characterized in that the zinc oxide contains not more than 0.1 wt. % lead impurities. 3. A method of preparing an adsorbent for the purification of gases and liquids from halogen-containing compounds, described in paragraphs. 1 and 2 of the formula, comprising mixing zinc oxide or a zinc compound, decomposing with the formation of zinc oxide, hydroxide or aluminum oxide, a compound of an alkali metal, natural or synthetic silicate, or aluminosilicate, or silicic acid, extruding a mass characterized by loss on ignition at 550 ^o With in the range of 30-60 wt. %, drying and calcining the extrudates. 4. The method according to p. 3, characterized in that the drying is carried out at 50-150 ^o C, calcination at 350-600 ^o C.

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