RU2489207C1 - Catalyst and method of producing aliphatic hydrocarbons from carbon monoxide and hydrogen in presence thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to catalysts for producing aliphatic hydrocarbons. Described is a catalyst for producing aliphatic hydrocarbons from carbon monoxide and hydrogen, which contains iron nanoparticles and formed in situ directly in the reaction zone during heat treatment of catalyst components in a hydrogen or carbon monoxide stream in molten paraffin, characterised by that the iron nanoparticles are promoted with copper, with the following ratio of components, wt %: Cu - 5-25; Fe - the balance. Described is a method of producing aliphatic hydrocarbons from carbon monoxide and hydrogen in the presence of said catalyst.

EFFECT: low content of alkenes.

4 cl, 1 tbl, 5 ex

Description

The invention relates to the petrochemical industry, and in particular to methods for producing aliphatic hydrocarbons from carbon monoxide and hydrogen, and can be used in oil refining and petrochemicals.

Mixtures of aliphatic hydrocarbons containing 5 or more carbon atoms (C _5+), are valuable intermediates for the production of components of motor fuels and lubricating oils, are recovered from these mixtures by distillation. In addition, solid hydrocarbons (waxes) are used as constituent alloys for precision casting, components of perfumes and cosmetics.

In recent years, methods of producing hydrocarbons of various groups from alternative raw materials — coal, natural and associated petroleum gas, and biomass of various origins — have gained increasing interest. Such technologies are known from the prior art and include, as a rule, two main stages:

- obtaining a mixture of carbon monoxide and hydrogen, called synthesis gas;

- the subsequent production of hydrocarbons from synthesis gas by a method known as Fischer-Tropsch synthesis.

Of these stages, the second is the main, because it determines the yield and composition of the target products.

Catalysts that are suitable for carrying out this reaction usually contain one or more catalytically active transition metals of group VIII of the Periodic system of elements supported on oxide carriers such as Al ₂ O ₃ , SiO ₂ , TiO ₂ , etc. In particular, iron, cobalt, nickel and ruthenium are well known as active metals for such a catalyst.

On iron-containing catalysts along with saturated hydrocarbons unsaturated hydrocarbons are formed, mainly α-alkenes. Sometimes the content of alkenes can reach up to 50% wt. (Chemicals from coal. Translated from German. // Edited by I.V. Kalechitsa. - M.: Chemistry, 1980. - 616 p.). Alkenes are prone to addition reactions with the formation of explosive organic peroxides and hydroperoxides, and therefore are extremely unstable. The use of synthetic hydrocarbons obtained in the Fischer-Tropsch synthesis as components of motor fuels with a high olefin content is unacceptable. In particular, the content of alkenes in accordance with the European environmental standard EURO-4 should not exceed 18% wt.

Another promising area of using Fischer-Tropsch synthesis technology is the processing of associated petroleum gas directly at the field, followed by the supply of the resulting product to the pipeline. The high alkene content also increases the explosiveness of the transported hydrocarbon mixture.

It is possible to reduce the content of alkenes in the synthesis products by introducing promoters into the composition of the catalyst, which can enhance the hydrogenating ability of the catalyst. The most affordable and effective promoter in this case is copper (Li S., Meitzner G. D., Iglesia E. // Studies in Surface Science and Catalysis. 2001. V.136. P.387).

The most promising method for producing hydrocarbon mixtures with a high wax content is currently considered to be Fischer-Tropsch synthesis in a three-phase gas-liquid-solid system, i.e. in the presence of a catalyst suspended in a layer of high boiling liquid (Guettel R., Kuntz U., Turek T. // Chem. Eng. Technol. 2008. V.31. No. 5. P.746). Reactors of this type are called liquid phase or slurry. In a three-phase system, a finely dispersed catalyst is used, which allows one to remove internal diffusion and obtain heavier products.

The use of ultrafine catalysts with a particle size of less than 0.1 μm (the “submicron size region” or the region of “nanoparticles”) allows one to almost completely avoid intradiffusion restrictions and increase the efficiency of the catalyst.

A known method, for example, is the production of hydrocarbons from CO and H ₂ in an autoclave-type slar reactor in the presence of a nanoscale Fe-K-Mn catalyst with an average particle diameter of 7-18 nm (Bai L., Xiang HW, Li YW, Han YZ Zhong B. // Fuel. 2002. V.81. P.1577). At 22 atm and 250-300 ° C, this catalyst allows you to get a mixture of hydrocarbon products mainly gasoline fraction. However, the catalyst preparation method used in this case does not allow the efficient use of the selected promoters.

Closest to the proposed invention is a nanosized catalyst composition, wt.%: 87-95 Fe, 2-9 K ₂ O, 1-8 Al ₂ O ₃ , which is obtained and activated directly in the reactor S. Hadzhiev, A. Lyadov. S., Krylova M.V., Krylova M.V. // Petrochemicals. T.51. No. 1. S.25. Later, the same catalyst and process was published in patent No. 2443471, IPC B01J 23/745, B82B 1/00, B01J 23/78, B01J 21/04, C07C 1/04, publ. 02/27/2012. This catalyst is prepared in situ by the decomposition of salts of its constituent components in a high molecular weight paraffin melt. The synthesis is carried out in an autoclave type slarry reactor at a temperature of 200-350 ° C and a pressure of 20-30 atm. Thus CO conversion reaches 90%, and the yield of C _{5 +} hydrocarbons of about 100 g / m ^3. The selectivity of the catalyst in relation to the formation of C ₅₊ hydrocarbons is quite high and reaches 45%.

However, the disadvantage of this catalyst is that the resulting mixture of alephatic hydrocarbons contains up to 45% alkenes, as indicated in the above article.

The objective of the invention is to create a catalyst for the production of aliphatic hydrocarbons with a low alkene content by the Fischer-Tropsch method, as well as to develop a method for producing aliphatic hydrocarbons.

The problem is solved in that the proposed catalyst for producing aliphatic hydrocarbons from carbon monoxide and hydrogen, containing nanosized iron particles promoted by copper, the catalyst is formed in situ, directly in the reaction zone during the heat treatment of the catalyst components in a stream of hydrogen or carbon monoxide and has the following composition % wt .:

Cu - 5-25; Fe is the rest.

The problem is also solved by the fact that the proposed method for producing aliphatic hydrocarbons from carbon monoxide and hydrogen in a three-phase reactor at elevated temperature and pressure in the presence of nanosized particles of an iron-containing catalyst uniformly distributed in molten paraffin activated directly in the reaction zone by carbon monoxide and hydrogen, which is carried out in the presence of this catalyst.

The activation of the catalyst is carried out at a temperature of 250-400 ° C for the time required for the formation of iron oxide (II, III), after which a mixture of carbon monoxide and hydrogen taken in a molar ratio of 1: (0.5- 2).

The components of the catalyst are introduced into molten petroleum paraffin either in the form of a mechanical mixture of salts, or in the form of their solution in a solvent which is not miscible with the liquid phase, for example, alcohol, water, ether.

In the proposed technical solution, it is possible to use catalysts that are suitable for Fischer-Tropsch synthesis containing catalytically active metals of group VIII, in particular iron, nickel, ruthenium or cobalt (preferably iron).

The technical result that can be obtained from the use of the invention is to reduce the content of alkenes in the synthesis products to 25% wt.

The catalyst is prepared from its constituent components directly in a hydrocarbon synthesis reactor (in situ), for which purpose a liquid medium representing molten petroleum paraffin, i.e. a mixture of heavy (paraffin) hydrocarbons with vigorous stirring and temperature, an effective amount of catalyst components, mainly salts, is introduced. This is the so-called catalyst precursor, which is used as a mechanical mixture or as a solution in a solvent that is not miscible with the liquid phase (alcohol, acetone, water, ether, etc.).

Then the precursor is subjected to heat treatment at a temperature of 40-450 ° C in a stream of hydrogen or carbon monoxide.

During the preparation of the catalyst, a stable colloidal solution is formed. According to small angle X-ray scattering data, the particle size of the catalyst is 20-25 nm.

The catalyst is subjected to in situ activation directly in the reactor, reducing it in a stream of hydrogen or carbon monoxide, for which, through a formed suspension containing catalyst nanoparticles at a temperature of 250-400 ° C, preferably 300-350 ° C, for 5-50 hours, more preferably 20-30 hours pass hydrogen or carbon monoxide.

Then, in the same reactor, filled with the liquid phase with the reduced catalyst, a mixture of carbon monoxide and hydrogen taken in a molar ratio of 1: (0.5-3) is fed and the synthesis of aliphatic hydrocarbons is carried out at a temperature of 200-350 ° C and a pressure of 1-50 atm with a catalyst load of 1-50 l / g cat. hours

The following examples illustrate the invention, but in no way limit its scope.

Example 1

43.29 g of iron nitrate Fe (NO ₃ ) ₃ · 9H ₂ O and 1.30 g of copper nitrate Cu (NO ₃ ) ₂ · 5H ₂ O are dissolved in 25 ml of distilled water.

The catalyst obtained from such a mixture has a composition, wt.%:

Cu - 4.8; Fe is the rest.

The average particle size of the obtained catalyst is 250-270 nm.

The catalyst is activated in an autoclave (in situ) in a stream of carbon monoxide at 300 ° C for 24 hours.

Then, the synthesis of hydrocarbons is carried out on the catalyst, passing through an activated synthesis gas catalyst with a molar ratio of CO: H ₂ equal to 1: 1, in the temperature range from 220 ° C to 320 ° C and a pressure of 30 atm.

The experimental results are shown in the table.

Example 2

43.29 g of iron nitrate Fe (NO ₃ ) ₃ · 9H ₂ O and 2.61 g of copper nitrate Cu (NO ₃ ) ₂ · 5H ₂ O are dissolved in 25 ml of distilled water.

The catalyst obtained from such a mixture has a composition, wt.%:

Cu - 9.1; Fe is the rest.

The average particle size of the obtained catalyst is 250-270 nm.

The preparation of the catalyst, its activation and the synthesis of hydrocarbons from CO and H _{2 are} carried out similarly as described in example 1.

The experimental results are shown in the table.

Example 3

43.29 g of iron nitrate Fe (NO _{3) 3} · 9H ₂ O and 3.89 g of copper nitrate Cu (NO _{3) 2} · 5H ₂ O was dissolved in 25 ml of distilled water.

The catalyst obtained from such a mixture has a composition, wt.%:

Cu - 13.0; Fe is the rest.

The average particle size of the obtained catalyst is 250-270 nm.

The preparation of the catalyst, its activation and the synthesis of hydrocarbons from CO and H _{2 are} carried out similarly as described in example 1.

The experimental results are shown in the table.

Example 4

43.29 g of iron nitrate Fe (NO ₃ ) ₃ · 9H ₂ O and 7.90 g of copper nitrate Cu (NO ₃ ) ₂ · 5H ₂ O are dissolved in 25 ml of distilled water.

The catalyst obtained from such a mixture has a composition, wt.%:

Cu 23.3; Fe is the rest.

The average particle size of the obtained catalyst is 250-270 nm.

The preparation of the catalyst, its activation and the synthesis of hydrocarbons from CO and H _{2 are} carried out similarly as described in example 1.

The experimental results are shown in the table.

Example 5 (prototype)

A catalyst containing 87.7 Fe, 8.8 K ₂ O, 3.5 Al ₂ O ₃ (average particle size 650-750 nm), obtained as described in the prototype, is tested in the reaction of producing aliphatic hydrocarbons by the Fischer-Tropsch method under conditions proposed technical solutions.

The experimental results are shown in the table.

Thus, the proposed catalyst allows to obtain aliphatic hydrocarbons by the Fischer-Tropsch method with high selectivity with respect to C ₅₊ hydrocarbons (at the prototype level), but with a significantly lower alkene content (up to 25% compared to 45% of the prototype).

Claims (4)

1. A catalyst for producing aliphatic hydrocarbons from carbon monoxide and hydrogen, containing nanosized iron particles and formed in situ directly in the reaction zone during heat treatment of the catalyst components in a stream of hydrogen or carbon monoxide in molten paraffin, characterized in that the nanosized iron particles are promoted with copper at the following ratio of components, wt.%: Cu - 5-25; Fe is the rest. 2. A method of producing aliphatic hydrocarbons from carbon monoxide and hydrogen in a three-phase reactor at elevated temperature and pressure in the presence of nanosized particles of an iron-containing catalyst uniformly distributed in molten paraffin activated directly in the reaction zone by carbon monoxide and hydrogen, characterized in that the process is carried out in the presence of the catalyst according to claim 1. 3. The method according to claim 2, characterized in that the activation of the catalyst is carried out at a temperature of 250-400 ° C for 24 hours, after which a mixture of carbon monoxide and hydrogen taken in a molar ratio of 1: (0.5 -2). 4. The method according to claim 2, characterized in that the components of the catalyst are introduced into the molten paraffin in the form of their mechanical mixture or their solution in a solvent not miscible with the liquid phase, for example alcohol, water, ether.