RU2443471C2 - Catalyst and method of producing aliphatic hydrocarbons from carbon oxide and hydrogen in its presence - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to petrochemical industry, particularly, to catalyst and method of producing aliphatic hydrocarbons from carbon oxide and hydrogen. Catalyst comprises nanosized particles of iron, potassium and aluminium oxides is and produced in-situ in reaction zone during heat treatment of catalyst components in current of carbon oxide or hydrogen, that features the following composition, in wt %: Fe - 87-95, K₂O - 2-9, Al₂O₃ - 1-8. Invention covers the method of producing aliphatic hydrocarbons from carbon oxide and hydrogen in three-phase reactor at 200-350°C and 20-30 atm in the presence of catalyst described above.

EFFECT: simplified process, higher C₅₊ selectivity and efficiency.

5 cl, 1 tbl, 9 ex, 1 dwg

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, including the production of synthetic motor fuels and lubricants, gas chemistry, coal chemistry.

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

The traditional method of producing hydrocarbons, including aliphatic ones, is oil refining - the main natural raw material for the production of these products.

However, 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 become increasingly interesting. 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.

Fischer-Tropsch synthesis is a catalytic process. 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.

In industry, the most widely used are iron catalysts, which are prepared in various ways: by co-precipitation of the components on a support, as described by H. Kolbel and M. Ralek. Catalysis Reviews - Science and Engineering. 1980. V.21, p. 225, by melting known from A. Huff and C.N.Satterfield. Journal of Catalysis. 1984. V. 85, p. 370, by laser pyrolysis described in US Pat. No. 4,687,753, B01J 27/22, 1987, etc.

The synthesis of hydrocarbons from carbon monoxide and hydrogen proceeds with a large release of heat, which can lead to local overheating of the catalyst and, as a consequence, to the loss of its catalytic activity. In the practical implementation of the process, much attention is paid to the development of reactors capable of efficiently removing heat generated during the reaction.

For this purpose, reactors with a fixed, fluidized or suspended catalyst bed are used (R. Guettel, U. Kunz, T. Turek. Reactors for Fischer-Tropsch Synthesis // Chemical Engineering & Technology. 2008. V.31. No. 5. PP. 746-754).

The most promising method 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 (R. Guettel, U. Kuntz, T. Turek // Chemical Engineering and Technology. 2008, V.31, No. 5, 746-754). Reactors of this type are called liquid phase or slurry. Slarry reactors have several advantages: they can efficiently remove heat of reaction, minimize the transverse temperature gradient, and prevent the formation of local overheating; the solid catalyst can be removed from the reactor or introduced into it without stopping overload; the use of a finely divided catalyst allows to remove the internal diffusion; carbon monoxide-rich synthesis gas obtained from coal gasification can be used; the cost of a slarry reactor is 20–40% lower than the cost of an apparatus with a fixed catalyst bed of the same power.

Fine synthesis catalysts of 25-100 microns in size prepared by precipitation, melting or spray drying are usually used to carry out synthesis in slarry reactors. This allows not only to facilitate heat removal, but also to reduce the effect of internal diffusion on the activity and selectivity of the catalytic system. A slurry reactor typically uses a suspension of a reduced (activated) catalyst, which is a metal supported on a fine oxide support with a particle size of 30-100 μm, as described in US patent No. 6835756, C07C 27/00, 2004.

Another example is the composition catalyst, wt.%: Fe - 83.2, Cu - 4.2, K - 3.4, SiO ₂ - 9.2, prepared by co-precipitation (D. Bukur "Improved iron catalysts for slurry phase Fischer -Tropsch synthesis ”, website address on the Internet http://www.netl.doe.gov/publications/proceedings/04/UCR-HBCU/abstracts/Bukur.pdf). At 260 ° С and 21 atm, the conversion of carbon monoxide on it reached 90%. The selectivity of the catalyst to produce hydrocarbon products reaches about 50% (the rest is accounted for by the number of CO _2). In the obtained hydrocarbon products, the share of liquid hydrocarbons (C ₅₊ ) is about 85%.

However, the catalyst does not show stability and quickly deactivates, as a result of which the conversion of carbon monoxide decreases.

In addition, a catalyst with particle sizes greater than 0.1 μm, in the described case 25-100 μm, can be obtained by similar precipitation.

While the use of smaller catalysts with a particle size of less than 0.1 μm (the “submicron size region” or the region of “nanoparticles”) allows almost completely to avoid intra-diffusion restrictions and increase the efficiency of the catalyst.

Closest to the proposed invention is a nanoscale Fe-K-Mn catalyst and a method for producing hydrocarbons from CO and H ₂ in an autoclave-type slar reactor in its presence (L.Bai, H.-W.Xiang, Y.-W. Li, YZHan, B.Zhong // Fuel. 2002. V.81. P.1577).

The catalyst is prepared by co-precipitation of an oxalic acid aqueous solution from a solution of Fe and Mn acetates. The mixture of oxalates is decomposed in air at 500 ° C, and then impregnated with potassium nitrate (1% K ₂ O) and dried at 120 ° C.

The resulting catalysts have an average particle diameter of 7-18 nm. The synthesis is carried out in a flowing autoclave with stirring, placing 20 g of a catalyst suspended in 320 g of liquid paraffin with a boiling point of more than 340 ° C. The catalyst is activated in situ with synthesis gas under the conditions: 3.5 atm, 275 ° C, 2H ₂ + CO, 1 l / gKat. · H. Hydrocarbon synthesis conditions: 22 atm, 250-300 ° C, 2H ₂ + CO, 2 l / gKat. · H.

Under these conditions, the conversion of CO reaches 90% and proceeds with the formation of the following hydrocarbon products, wt.%: CH ₄ - 21; C ₂ -C ₄ hydrocarbons - 40; C ₅₊ hydrocarbons - 39. The catalyst productivity for the target products - C ₅₊ hydrocarbons is 170-200 g / kg Cat. · H, which corresponds to a C ₅₊ content in products equal to 31%.

The disadvantage of the described method is the complexity of the technology for preparing a fine-grained catalyst, which includes the deposition of the active component and promoters, drying and calcination.

In addition, in the case of ultrafine particles, the introduction of the promoter by the impregnation method, as is carried out in the described technical solution, is ineffective. The catalyst thus obtained has a low selectivity for the target synthesis products — liquid hydrocarbons (C ₅₊ ) _{—and a} relatively low productivity.

Simplifying the preparation of the catalyst and improving its efficiency would significantly improve the overall economy of the process.

The objective of the invention is to obtain an active and selective catalyst for producing hydrocarbon products from synthesis gas (CO and H ₂ ) by the Fischer-Tropsch method, carried out in a three-phase reactor, that is, in a slarry process in which the stage of preparation of the catalyst would be simplified, as well as in the development of a method for producing aliphatic hydrocarbons, mainly C ₅₊ hydrocarbons, as the most valuable intermediates for the production of components of motor fuels and lubricating oils.

The problem is solved in that the proposed catalyst for producing aliphatic hydrocarbons from carbon monoxide and hydrogen, containing nanoscale particles of iron and potassium, which additionally contains potassium oxide and alumina, while the catalyst is formed in situ directly in the reaction zone during the heat treatment of the catalyst components in the flow of hydrogen or carbon monoxide and has the following composition, wt.%:

Fe - 87-95,

K ₂ O - 2-9,

Al ₂ O ₃ - 1-8.

The problem is also solved by the fact that the proposed 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 suspended in the liquid hydrocarbon phase, activated directly in the reaction zone by carbon monoxide and hydrogen, which is carried out in the presence of this catalyst at a temperature of 200-350 ° C and a pressure of 20-30 atm.

The activation of the catalyst is carried out at a temperature of 250-400 ° C for the time necessary 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 the reactor 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, etc.

The catalyst may in addition include promoters known to those skilled in the art, such as potassium, aluminum, zirconium, titanium, manganese, and others.

The technical result that can be obtained from the use of the present invention is to simplify the process by the fact that the hydrocarbon production method allows combining in one reactor the stages of preparation of the catalyst, its activation with hydrogen or carbon monoxide and the synthesis of hydrocarbons from CO and H ₂ .

Another technical result is to increase the selectivity of the catalyst in relation to the formation of target hydrocarbons With ₅₊ (up to 90%) and the productivity of the catalyst for these products (up to 300-360 g / kgKat. · H).

The catalyst is prepared from its constituent components directly in a hydrocarbon synthesis reactor (in situ), for which an effective amount of catalyst components is introduced into the liquid medium, which is a molten mixture of hydrocarbons - also paraffins or ceresins, or individual paraffin, with intensive stirring and temperature, mainly salts. 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 electron microscopy and scattering of monochromatic radiation, such a solution contains particles of a solid phase with a size of 10-30 nm, associated in aggregates with a size of 500-700 nm.

The catalyst is subjected to in situ activation directly in the reactor, restoring 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, a mixture of carbon monoxide and hydrogen taken in a molar ratio of 1: (0.5-2) is fed into the same reactor, filled with a liquid phase with an activated catalyst, and aliphatic hydrocarbons are synthesized at a temperature of 200-350 ° C and a pressure of 1- 50 atm with a catalyst load of 5-6 l / gKat. · H.

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

Example 1

43.3 g of iron nitrate Fe (NO ₃ ) ₃ · 9H ₂ O, 1.9 g of aluminum nitrate Al (NO ₃ ) ₃ · 9H ₂ O and 0.12 g of KOH are dissolved in 25 ml of methanol. The resulting solution is poured in a stream of hydrogen with vigorous stirring to 100 ml of individual nonadecane (n-paraffin C ₁₉ H ₄₀ ), placed directly in an autoclave and preheated to a temperature of 300 ° C.

The catalyst obtained from such a mixture has a composition, wt.%: 93.5 Fe, 2.8 K ₂ O, 3.7 Al ₂ O ₃ .

The average particle size of the resulting catalyst is 650-750 nm.

The catalyst is activated in an autoclave (in situ) in a stream of hydrogen at 300 ° C for 48 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: 1.8, at a temperature of 300 ° C. and a pressure of 30 atm.

The experimental results are shown in the table.

Figure 1 shows the particle size distribution obtained by the method of dynamic dispersion of monochromatic radiation for the catalyst described in example 1, the distribution for other catalysts look similar.

Example 2

43.3 g of iron nitrate Fe (NO ₃ ) ₃ · 9H ₂ O, 1.9 g of aluminum nitrate Al (NO ₃ ) ₃ · 9H ₂ O and 0.4 g of KOH are dissolved in 25 ml of methanol.

The catalyst obtained from such a mixture has a composition, wt.%: 87.7 Fe, 8.8 K ₂ O, 3.5 Al ₂ O ₃ .

The average particle size of the catalyst is 650-750 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

43.3 g of iron nitrate Fe (NO ₃ ) ₃ · 9H ₂ O, 1.9 g of aluminum nitrate Al (NO ₃ ) ₃ · 9H ₂ O and 0.4 g of KOH are dissolved in 25 ml of distilled water.

The catalyst obtained from such a mixture has a composition, wt.%: 87.7 Fe, 8.8 K ₂ O, 3.5 Al ₂ O ₃ .

The average particle size of the catalyst is 500-600 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

43.3 g of iron nitrate Fe (NO ₃ ) ₃ · 9H ₂ O, 1.9 g of aluminum nitrate Al (NO ₃ ) ₃ · 9H ₂ O and 0.4 g of KNO _{3 are} ground in a porcelain mortar. The resulting mechanical mixture is added in a stream of hydrogen with vigorous stirring to 100 ml of individual nonadecane placed in an autoclave and preheated to a temperature of 300 ° C.

The catalyst obtained from such a mixture has a composition, wt.%: 87.7 Fe, 8.8 K ₂ O, 3.5 Al ₂ O ₃ .

The average particle size of the catalyst is 660 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

43.3 g of iron nitrate Fe (NO ₃ ) ₃ · 9H ₂ O, 1.0 g of aluminum nitrate Al (NO ₃ ) ₃ · 9H ₂ O and 0.12 g of KOH are dissolved in 25 ml of methanol.

The catalyst obtained from such a mixture has a composition, wt.%: 95.2 Fe, 2.9 K ₂ O, 1.9 Al ₂ O ₃ .

The average particle size of the catalyst is 500-600 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 6

The preparation of the catalyst and the synthesis of hydrocarbons from CO and H _{2 is} carried out similarly to those described in example 2. Activation of the catalyst composition, wt.%: 93.5 Fe, 2.8 K ₂ O, 3.7 Al ₂ O ₃ - is carried out at a temperature of 325 ° C for 48 hours

The experimental results are shown in the table.

Example 7

The preparation of the catalyst and the synthesis of hydrocarbons from CO and H _{2 is} carried out similarly as described in example 2. Activation of the catalyst composition, wt.%: 93.5 Fe, 2.8 K ₂ O, 3.7 Al ₂ O ₃ - is carried out at a temperature of 300 ° C for 68 hours

The experimental results are shown in the table.

Example 8

43.3 g of iron nitrate Fe (NO ₃ ) ₃ · 9H ₂ O, 1.9 g of aluminum nitrate Al (NO ₃ ) ₃ · 9H ₂ O and 0.4 g of KOH are dissolved in 25 ml of methanol.

The catalyst obtained from such a mixture has a composition, wt.%: 87.7 Fe, 8.8 K ₂ O, 3.5 Al ₂ O ₃ .

The average particle size of the catalyst is 500-600 nm.

The preparation of the catalyst, its activation and the synthesis of hydrocarbons from CO and H _{2 are} carried out similarly to those described in example 1, except that the activation is carried out in carbon monoxide.

The experimental results are shown in the table.

Example 9

43.3 g of iron nitrate Fe (NO ₃ ) ₃ · 9H ₂ O, 1.9 g of aluminum nitrate Al (NO ₃ ) ₃ · 9H ₂ O and 0.4 g of KOH are dissolved in 25 ml of water.

The catalyst obtained from such a mixture has a composition, wt.%: 87.7 Fe, 8.8 K ₂ O, 3.5 Al ₂ O ₃ .

The average particle size of the catalyst is 500-600 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 8.

The experimental results are shown in the table.

The results presented in the table show that the proposed method allows efficient synthesis of hydrocarbons from carbon monoxide and hydrogen in a three-phase catalytic reactor in the presence of a catalyst prepared in situ and activated in situ. The proposed method makes it possible to carry out the synthesis of hydrocarbons from CO and H ₂ at a CO conversion of up to 80%, and selectivity for liquid products up to 86%. At the same time, the productivity of the catalyst for the target synthesis products is 200-390 g / kgKat. · H.

The results of the production of aliphatic hydrocarbons Example The composition of the mixture for the preparation of the catalyst, g Solvent Catalyst Activation Conditions CO conversion,% Productivity, g / kgKat. · H The composition of the hydrocarbon
dov, wt.% Fe Nitrate Koh Al nitrate Gas T, ° C τ, h C ₁ -C ₄ C ₅₊ one 43.3 0.12 1.9 Methanol H ₂ 300 48 60.0 225 45.6 54,4 2 43.3 0.40 1.9 Methanol H ₂ 300 48 51.8 199 50,2 49.8 3 43.3 0.40 1.9 Water H ₂ 300 48 60.3 240 61.2 38.8 four 43.3 0.40 1.9 No H ₂ 300 48 40.8 260 14.1 85.9 5 43.3 0.12 1,0 Methanol H ₂ 300 48 82.3 327 29.7 70.3 6 43.3 0.12 1.9 Methanol H ₂ 325 48 43.9 235 47.4 52.6 7 43.3 0.12 1.9 Methanol H ₂ 300 68 78.5 389 41.3 58.7 8 43.3 0.12 1.9 Methanol With 300 24 68.3 319 14.3 85.7 9 43.3 0.12 1.9 Water With 300 24 78.3 326 24.4 75.6

Claims (5)

1. A catalyst for producing aliphatic hydrocarbons from carbon monoxide and hydrogen, containing nanosized iron particles, characterized in that it further comprises potassium oxide and alumina, the catalyst is formed in situ directly in the reaction zone during the heat treatment of the catalyst components in a stream of carbon monoxide or hydrogen and has the following composition, wt.%:
Fe 87-95 K ₂ O 2-9 Al ₂ O ₃ 1-8 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 suspended in the liquid hydrocarbon phase activated directly in the reaction zone by carbon monoxide or hydrogen, characterized in that the catalyst according to claim .1, the temperature for producing aliphatic hydrocarbons is 200-350 ° C, and the pressure is 20-30 atm. 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 the time required for the formation of iron oxide (II, III), and to obtain aliphatic hydrocarbons using a mixture of carbon monoxide and hydrogen, taken in molar ratio 1: (0.5-2). 4. The method according to claim 2, characterized in that the catalyst components are introduced into the reactor in the form of a mechanical mixture of salts or in the form of their solution in a solvent not miscible with the liquid phase. 5. The method according to claim 4, characterized in that the solvent is not miscible with the liquid phase, use alcohol or water, or ether.

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