RU2116960C1 - Nitrogen fixation method - Google Patents

Abstract

FIELD: nitrogen compound production. SUBSTANCE: nitrogen-containing gases are brought into contact with catalyst at atmosphere pressure and low temperatures, where catalyst consists of carbonyl complexes of transition metals, in particular, platinum group metals, in the form of solids, solutions or suspensions with neutral, acidic or alkaline medium. Nitrogen- containing gases may include reducing and/or oxidizing agents. Final products are ammonia or nitrogen oxides. EFFECT: enhanced process efficiency.

Description

 The method relates to the field of inorganic chemistry.

 As is known, molecular nitrogen under normal conditions exhibits chemical inertness. Therefore, its translation into a bound state requires mild conditions - elevated temperatures and high pressure, as is the case when ammonia is produced from nitrogen and hydrogen. Such a process is energy intensive and requires the use of special expensive equipment. Therefore, the development of molecular nitrogen binding methods under mild conditions is an important task that they are trying to solve with the help of various transition metal complexes [1].

 Closest to the proposed is a method of producing ammonia from hydrogen and nitrogen at low temperatures and pressure in the presence of molybdenum compounds containing metal-hydrogen bonds [2].

 The disadvantage of this method is the low yield of the final product (0.4%) and a productivity of 0.1% per hour.

 The proposed method is based on the high activity of CO molecules included in the composition of carbonyl complexes of transition metals, in particular metals of the platinum group.

имеется высокая термодинамическая возможность протекания. Однако реакции (1, 2, 3) в мягких условиях (комнатные температуры и атмосферное давление) не протекают из-за высоких значений энергий активации.So, for reactions (1, 2, 3)

there is a high thermodynamic flow capability. However, reactions (1, 2, 3) under mild conditions (room temperature and atmospheric pressure) do not occur due to high activation energies.

 At the same time, the CO molecules that make up the carbonyl complexes are significantly activated and are able to enter into reduction reactions that do not proceed with free CO molecules.

So, the reaction in solution
2Cu ^II + CO + H ₂ O = 2Cu ^I + CO ₂ + 2H ⁺ (4)
not leaking. But in the presence of palladium (II) salts, which form carbonyl complexes with CO, reaction (4) easily proceeds under mild conditions [3].

The essence of the proposed method lies in the fact that the gas mixture containing nitrogen is in contact with the catalyst - carbonyl complexes of transition metals. In this case, nitrogen is bound into compounds where it can be both in reduced (NH ₃ ) and in oxidized form (NO, N ₂ O), which is primarily determined by the composition of the gas mixture in contact with the catalyst.

The process proceeds under mild conditions - at atmospheric pressure and temperatures from room temperature to 200 - 300 ^o C.

 The catalyst may be in dry form, in the form of an aqueous or aqueous-organic pulp, as well as in the form of a solution. In this case, the initial liquid phase may be acidic, alkaline or neutral.

Example 1. 700 mg of a carbonyl plate [Pt (CO ₂ ] _{n was} pulped in 150 ml of a 0.1 N hydrochloric acid solution. A mixture of CO + air in a volume ratio of 1 was passed through this pulp at t = 60 ^° C and atmospheric pressure with stirring) : 2 at a rate of 10 ml / min for 30 minutes

8.5 mg of N ₂ O were detected in the exhaust gases.

Per reaction
CO + N ₂ + O ₂ = N ₂ O + CO ₂
the yield of bound nitrogen is ≈ 20%.

Example 2. 35 mg of platinum carbonyl [Pt (CO) ₂ ] _{n was} dissolved in 50 ml of a NaOH solution. A mixture of CO + air was passed through this solution at t = 20 ^° C, atmospheric pressure, and stirring in a volume ratio of 1: 2 at a rate of 10 ml / min for 30 minutes.

5.1 mg of bound oxidized nitrogen was found in the solution based on NO ₂ .

For the reaction
4CO + N ₂ + 4O ₂ = 4CO ₂ + 2NO ₂
the yield of bound nitrogen is 12.3%
Example 3. 60 mg of rhodium, 40 mg of ruthenium and 12 mg of iridium in the form of its carbonyl chlorides —Rh ₂ (CO) ₂ Cl ₂ , Ir ₂ (CO) ₂ Cl ₂ , Ru (CO) ₂ Cl _{2 were} dissolved in 35 ml a liquid consisting of 5 ml of H ₂ O and 30 ml of methanol and having a pH of 9. A mixture of CO + H ₂ in a volume ratio of 1: 1 for 1.3 hours was passed through this solution at 30 ^° C, atmospheric pressure and stirring for 1.3 hours at a speed 10 ml / min. The exhaust gases were absorbed in a solution of hydrochloric acid. Bound nitrogen was calculated based on ammonium chloride 9 mg
For the reaction
3CO + N ₂ + 3H ₂ O = 2NH ₃ + 3CO ₂
the yield of bound nitrogen is 1.4%.

Example 4. 500 mg of carbonyl composition Pt ₇ Pd ₂ (CO) ₁₅ in the form of crystals were placed in a boat in a tube furnace. At t = 200 ^° C and atmospheric pressure, a gas mixture of CO, N ₂ and water vapor was passed over the catalyst in a volume ratio of 3: 1: 2 at a rate of 10 ml / min for 2 hours.

 12 mg of ammonia were found in the exhaust gases.

Per reaction
3CO + N ₂ + 3H ₂ O = 2NH ₃ + 3CO ₂
the yield of bound nitrogen was 4.75%.

 As can be seen from the above examples, carbonyl complexes of transition metals, in particular platinum metals, allow the catalytic bonding of molecular nitrogen under mild conditions.

 Literature.

1. Shilov A.E. Advances in Chemistry, 1974, v. 43, p. 863
2. The patent of Germany N 956674, 1957.

 3. Spitsyn V.I., Fedoseev I.V., Ponomarev A.L., Elesin A.I. J. Inorg. Chemistry, 1978, v. 26, no. 2, p. 454.

Claims (4)

 1. The method of binding of nitrogen by contacting gases containing nitrogen with a catalyst, characterized in that carbonyl complexes of transition metals are used as a catalyst.  2. The method according to claim 1, characterized in that nitrogen is part of the gases containing reducing agents and / or oxidizing agents.  3. The method according to claim 1, characterized in that the catalyst may be dry, mixed with a liquid phase or in the form of a solution.  4. The method according to claim 3, characterized in that the use of aqueous or aqueous organic solutions with acidic, alkaline or neutral environments.