RU2081820C1 - BINARY PHOSPHATES Ca10,5-1,5xFex(PO4)7 (0<x<1) AS MATERIALS FOR PURIFICATION OF GASEOUS MIXTURE AGAINST HYDROGEN - Google Patents

Abstract

FIELD: production of phosphates. SUBSTANCE: desired binary phosphates having formula given in specification are prepared by solid phase synthesis. Said compounds have high efficiency at purification of gaseous mixtures against hydrogen at 600-1500 C. EFFECT: improved quality of desired compound. 2 tbl

Description

The present invention relates to inorganic chemistry, namely, to a new derivative of vitlocite-like phosphates, which can be used as materials for the purification of gas mixtures from hydrogen, of the general formula:
Ca _10.5-1.5x Fe _x (PO ₄ ) ₇ • (O <x≅1) I.

The objective of the invention is the creation of a new material used for the purification of gas mixtures from hydrogen at a wider temperature range, without changing its structure with repeated use, i.e. with its possible regeneration. The proposed material is double phosphate Ca _10.5-1.5x Fe _x (PO ₄ ) ₇ , where (0 <x≅1) I. Patent search showed that double phosphate I was synthesized for the first time.

Compound I was obtained by solid phase synthesis according to the known method [1]. The synthesis of compound 1 proceeds according to the following reaction, for example, for x = 1
3Ca ₃ (PO ₄ ) ₂ + FePO ₄ = Ca ₉ Fe (PO ₄ ) ₇ .

, c= 37•10(2)

федоровская группа R3c. Выход продукта 96% Элементарный состав, вес.Example 1. A mixture of 9.3 g (0.03 mol) of Ca ₃ (PO ₄ ) ₂ and 1.5 (0.01 mol) of FePO _{4 was} placed in an alundum crucible. The reaction mixture was annealed in a muffle furnace at 900-950 ^o C for 48 hours. The composition of the resulting material was controlled using x-ray phase analysis. At the same time, lines characterizing the vitlokit-like structure were found in the X-ray diffraction pattern. Indication of x-ray lines was carried out under the assumption of trigonal syngony. Unit cell parameters refined by least squares

, c = 37 • 10 (2)

Fedorov group R3c. Yield 96%. Elemental composition, weight.

Found
CaO 46.68
Fe ₂ O ₃ 7.37
P ₂ O ₅ 45.95.

Known double phosphate Cu _0.5 Zr ₂ (PO ₄ ) ₃ II, which can absorb hydrogen from gas mixtures [2] The disadvantage of this compound is its ability to absorb hydrogen in a narrow temperature range (400-800 ^o C).

The efficiency of hydrogen absorption by compound I was determined by Mössbauer spectroscopy and by the amount of hydrogen absorbed in a specially created installation at a temperature of 600-1500 ^o C and different concentrations of hydrogen in the gas mixture (c ₁ = 3.33 vol. H ₂ , c ₂ = 6.67 vol. H ₂ , c ₃ = 10,0 vol. H ₂ ). The activated gas mixture consisted of two components: argon (nitrogen) and hydrogen, as well as CO (CO ₂ ) and hydrogen.

Example 2. Preparation of samples. Compound 1, thoroughly rubbed in an agate mortar, was placed in a quartz boat in the form of a powder or tablets that were pre-compressed and deposited at 900 ^° C for 3 hours (ρ = 90-95% of theoretical).

 Example 3. The study of the conditions for the absorption of hydrogen by compound I was carried out on a specially designed installation, the main part of which is a quartz reactor; a sample of known mass and a monometer were placed in it. The sample was heated in a stream of argon (nitrogen) at a certain temperature for 30 minutes. Then, the calculated amount of hydrogen in the pressurized system was introduced into the reactor, and the change in volume depending on the temperature was monitored using a manometer. The results of kinetic studies are presented in table 1.

As can be seen from table 1, in the transition from the initial concentration of hydrogen (c ₁ = 3.33 vol.) To the initial concentration (c ₃ = 10.0 vol. H ₂ ), the amount of hydrogen absorbed in 15 minutes increased by 2.8 times . In addition, hydrogen uptake, regardless of the initial concentration, was stopped after 12 minutes at this temperature. Table 2 presents the experimental data on the change in the volume of absorbed hydrogen at 800 ^o C.

As can be seen from table 2 for 12 min at an initial concentration of hydrogen c ₂ = 6.67 vol. H ₂ absorbed 1.6 times more than with c ₁ = 3.33 vol. H ₂ . It should be noted that at 800 ^o C the absorbed air is 1.3-1.8 times more than at 600 ^o C for the corresponding initial hydrogen concentrations. Moreover, regardless of the initial hydrogen concentration and temperature, the equilibrium between the hydrogen absorbed by the sample and remaining in the gas mixture is established within 12 minutes of the experiment. A similar pattern is observed in the temperature range 900-1500 ^o C.

≅100% в образце обнаружено 10%Fe³⁺ и 90%Fe²⁺. Таким образом, экспериментальные результаты, полученные при изменении объема поглощенного водорода, полностью совпадают с данными, рассчитанными при помощи мессбауэровской спектроскопии.Example 4. The study of the reaction of reduction of Fe (III +) to Fe (II +) in the test sample by Mössbauer spectroscopy. The recovered sample of compound I was studied by Mössbauer spectroscopy. Since, as a result of the reduction of compound I, Ca ₉ Fe is formed $\genfrac{}{}{0ex}{}{\text{3+}}{\text{1-x}}$ Fe $\genfrac{}{}{0ex}{}{\text{2+}}{\text{x}}$ H _x (PO ₄ ) ₇ , then the hydrogen content in the reduced sample was monitored using Mössbauer spectroscopy by the content of ferrous iron in the sample. It was found that at a concentration of hydrogen in the gas mixture equal to

≅100% in the sample was found to be 10% Fe ³⁺ and 90% Fe ²⁺ . Thus, the experimental results obtained by changing the volume of absorbed hydrogen completely coincide with the data calculated using Mössbauer spectroscopy.

A new compound is obtained that exhibits high efficiency in the purification of gas mixtures from hydrogen at temperatures of 600-1500 ^o C without changing the structure. At the same time, in a gas mixture containing 100% hydrogen, 5-10% hydrogen remains, depending on the temperature: with increasing temperature, the gas mixture cleans up more fully.

Claims (1)

Calcium double phosphate of the general formula Ca <Mv> 10.5-1.5x <D> Fe _x (PO ₄ ) ₇ , where 0 <x <$ E => 1 as a material for cleaning gas mixtures from hydrogen.

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