WO2006126913A2

WO2006126913A2 - Method for producing hydrocarbons from carbon oxides and hydrogen

Info

Publication number: WO2006126913A2
Application number: PCT/RU2006/000235
Authority: WO
Inventors: Vladislav Mikhailovich Mysov; Kazimira Gavrilovna Ione
Original assignee: Joint-Stock Company 'siberian Technological Company 'zeosit'
Priority date: 2005-05-23
Filing date: 2006-05-11
Publication date: 2006-11-30
Also published as: RU2284312C1; WO2006126913A3; WO2006126913A8

Abstract

The invention relates to organic chemistry, in particular to a method for producing C5+ hydrocarbons by a synthesis gas conversion consisting in bringing, in a first reaction area, a synthesis gas containing H2, CO and CO2 into contact with a bifunctional catalyst consisting of a metallic oxide component having the following composition: 65-70 mass % ZnO, 29-34 mass % Cr2O3, equal to 1 or less mass % W2O5 and of a oxide component consisting of a ZSM-5 or ZSM-11 zeolite, a beta-type zeolite or a SAPO-5 crystalline silicoaluminophosphate. In a second reaction area, a monofunctionaloxide catalyst containing the ZSM-5 or ZSM-11 zeolite is used. The process is carried out at a pressure of 40-100 atm and a temperature of 340-420 °C, in the first reaction area, and a temperature of 320-460 °C in the second reaction area. The thus produced liquid hydrocarbon fractions can be used in the form of low-benzol motor petrols. Said invention makes it possible to increase the C5+ hydrocarbon selectivity and the C5+ hydrocarbons yield with respect to a supplied synthesis gas.

Description

The method of producing hydrocarbons from carbon oxides and hydrogen

Technical field

The invention relates to organic chemistry, and in particular, to methods for producing hydrocarbons and, in particular, to the production of C ₅₊ hydrocarbons by catalytic conversion of a mixture of CO, H ₂ and CO ₂ (hereinafter referred to as synthesis gas). The resulting liquid hydrocarbon fractions can be used as gasoline with a low benzene content.

State of the art

A known method of producing C ₅₊ hydrocarbons from a gas containing H ₂ and CO by contacting the gas at a temperature of 220-400 ⁰ C, a pressure of 10-100 atm, a volumetric feed rate of the feed synthesis gas of 100-5000 h ^"1 and a molar ratio H ₂ / CO equal to 1-3, with a catalyst containing a mixture of an iron-containing Fischer-Tropsch synthesis catalyst in oxidized or reduced form, promoted with oxides of aluminum, silicon, alkali or alkaline earth metals, and an acid component (RU 2204546, C07C 1/04 , 2003, [I]). According to this method, the resulting liquid carbohydrate Hydrogen mixtures have a high content of iso-paraffins and olefins, as well as a moderate content of aromatic hydrocarbons of not more than 35 wt.%. There is also a method for the one-stage conversion of synthesis gas having a molar ratio of H ₂ / CO> 1.9 to hydrocarbons boiling in the range of gasoline and diesel fractions, on a mixed trifunctional catalyst, consisting of a Fischer-Tropsch synthesis catalyst (iron, promoted by oxides of aluminum, silicon, alkali and alkaline earth metals or cobalt), conversion catalyst methanol to hydrocarbons (zeolite type ZSM-5 or silicalite with SiO ₂ content> 99%) and a methanol synthesis catalyst based on copper and zinc oxides (US 5344849, C07C 1/04, 1994, [2]). The use of this catalyst at a pressure of 7-70 atm, a temperature of 200-400 ⁰ C allows for synthesis gas having a molar ratio H ₂ / CO> 1.9, get hydrocarbon mixtures boiling in the range of gasoline and diesel fractions, consisting mainly of paraffin and olefin hydrocarbons and containing aromatic hydrocarbons in the range of 9-20 wt.%. The main disadvantages of the methods [1] and [2] are the high content of olefins (up to 16 wt.% [2] and more [I]) and n-paraffins (18-24 wt.% [2] and more [I]) in C ₅₊ hydrocarbons with a relatively low content of aromatic hydrocarbons (up to 20 wt.% [2] and not more than 35 wt.% [I]). In both methods, the target products are low-octane gasoline (up to 90 wt.% In C ₅₊ ) with OCh 66-77 IM [2] and up to 80-82 IM [1] and diesel fraction of hydrocarbons (from 10 wt.% [2] and above [I]), which only after an additional hydrogenation step of olefins can be used as high-cetane diesel fuel.

A known method of producing hydrocarbon gasoline fractions from a gas containing H ₂ and CO ₂ or H ₂ , CO ₂ and CO by contacting the gas at a temperature of 320-440 ⁰ C, a pressure of 40-100 atm and a volume ratio of H ₂ / (CO + CO ₂ ), equal to 1-3, with a catalyst containing zeolite type ZSM-5 or ZSM-H and a metal oxide component including oxides of zinc, copper and / or chromium (RU 2089533, C07C 1/12, 1997, [3] ) According to this method, the target products of the conversion of a mixture of H ₂ , CO ₂ (and in some examples of CO) are liquid gasoline fractions of hydrocarbons with a high content (from 40 to 84 May.%) Of aromatic hydrocarbons. The main disadvantages of this method are the low yields (40-120 g / nm ^{3 of} synthesis gas) and the performance of the process for the gasoline fraction (20-125 g / l catra / h), as well as the additional consumption of expensive hydrogen for CO reduction ₂ to CO.

A known method of producing hydrocarbon gasoline fractions from synthesis gas containing H ₂ , CO and CO ₂ and having a volume ratio

H ₂ / (CO + CO ₂ ), equal to 1-3, by contacting the gas at a temperature of 320-

44O ⁰ C, pressure 40-100 atm with a catalyst containing zeolite type ZSM-5 and a metal oxide component (RU 2175960, C07C 1/04, 2001, [4]). This method uses the circulation of the gas stream after the reactor with a volume ratio of the amount of circulating gas to the original synthesis gas equal to 0.1-1000, and the process is carried out at a volumetric feed rate synthesis gas 200-5000 h ^"1 , volumetric ratios in the original synthesis gas CO / CO ₂ greater than 4 and H ₂ / CO ₂ greater than 11. According to this method, the gasoline conversion products are liquid gasoline conversion products (C ₅ -C ₁₀ hydrocarbons) and water containing methanol from 1 to 10 wt.%. In this method [4] there are disadvantages:

1) a relatively low content of aromatic hydrocarbons in C ₅₊ hydrocarbons, not exceeding 30 wt.%, Which makes it difficult to obtain marketable gasoline with an OP of more than 90 IM;

2) high residual methanol content in water - from 1 to 10 wt.%; In the present invention, in comparison with the analogue [4], an increase in the selectivity for aromatic hydrocarbons up to 45-50 wt.% And more and a decrease in methanol in water to a concentration of less than 1 wt.% Are noted.

Closest to the proposed in its technical essence is a method for producing motor fuels by catalytic conversion of the mixture Η. ₂ AND CO OR a mixture of CO, H ₂ and CO ₂ at elevated temperatures and pressures in two stages (RU 2143417, C07C 1/04, 1999, [5]). According to the selected prototype in the first stage, the feedstock is contacted with a catalyst consisting of a zeolite of the ZSM-5 type and a metal oxide component containing, wt.%: CuO - 38-64, ZnO - 24-34, Cr ₂ O ₃ - 0-22, Al ₂ O ₃ - 6-9, mixed in a mass ratio of 20-50 / 80-50, the gas stream after the first stage reactor without separation is sent to the second stage, where upon contact with a catalyst consisting of ZSM-5 type zeolite and metal oxide component containing, wt.%: ZnO - 65-70, Cr ₂ O ₃ - 29-34, W ₂ O ₅ - 1, mixed in a ratio of 30-99 / 70-1, the conversion of dimethyl ether and co components of synthesis gas into a gasoline fraction, gaseous hydrocarbons and an aqueous fraction.

The main disadvantage of the prototype is the low selectivity for C ₅₊ hydrocarbons, equal to 63-74 wt.%, And a low yield of C ₅₊ hydrocarbons to the supplied synthesis gas, equal to 114-137 g / nm ³ .

Disclosure of invention

The objective of the invention is to increase the selectivity for C ₅₊ hydrocarbons and increase the yield of C ₅₊ hydrocarbons to the supplied synthesis gas. The problem is solved in that in the method for producing hydrocarbon gasoline fractions from synthesis gas containing H ₂ , CO and CO ₂ , by sequentially contacting the gas in at least two reaction zones at elevated temperatures and pressure with a bifunctional catalyst in the first reaction zone, consisting from acid and metal oxide components, a metal oxide component is used containing metal oxides of the composition, wt.%: ZnO - 65-70, Cr ₂ O ₃ - 29-34, W ₂ O ₅ - not more than 1, and as the acid component of the bifunctional catalyst and a zeolite with a ZSM-5 or ZSM-11 structure, a beta-type zeolite or crystalline silicoaluminophosphate with a SAPO-5 structure are used, and a monofunctional acid catalyst containing a zeolite with a ZSM-5 or ZSM-11 structure is used in the second reaction zone.

The acid component of the bifunctional catalyst has a molar ratio of SiO ₂ / Al ₂ O _{3 of} not more than 200. The zeolite of the monofunctional acid catalyst has a molar ratio of SiO ₂ / Al ₂ O _{3 of} not more than 200.

Gas contacting in the first reaction zone is carried out at a pressure of 40-100 atm and a temperature of 340-420 ⁰ C.

Gas contacting in the second reaction zone is carried out at a pressure of 40-100 atm and a temperature of 320-460 ⁰ C.

The process is carried out at a volumetric feed rate of the feed synthesis gas of 200-5000 h ^"1 and volumetric ratios in the feed synthesis gas H ₂ / (CO + CO ₂ ) = 1-3, CO / CO ₂ > 2 and H ₂ / CO ₂ > 6.

The process is carried out during circulation of a gas stream with a volume ratio of the amount of circulating gas to the initial synthesis gas equal to 1-1000.

Distinctive features of the invention are:

1) in the first reaction zone, the metal oxide component of the bifunctional catalyst is used, containing, wt.%: ZnO - 65-70, Cr ₂ O ₃ - 29-34, W ₂ O ₅ - not more than 1;

2) a zeolite with a structure of ZSM-5 or ZSM-I l, a zeolite of the beta type, is used as the acid component of a bifunctional catalyst or crystalline silicoaluminophosphate with a SAPO-5 structure, having a molar ratio of SiO ₂ / Al ₂ O _{3 of} not more than 200;

3) in the second reaction zone, a monofunctional acid catalyst is used containing a zeolite with a structure of ZSM-5 or ZSM-11, having a molar ratio of SiO ₂ / Al ₂ O _{3 of} not more than 200;

4) gas contacting in the first reaction zone is carried out at a pressure of 40-100 atm and a temperature of 340-420 ⁰ C;

5) gas contacting in the second reaction zone is carried out at a pressure of 40-100 atm and a temperature of 320-460 ⁰ C; b) the process is carried out at a volumetric feed rate of the feed synthesis gas of 200-5000 h ^"1 , having a volumetric ratio of H ₂ / (CO + CO ₂ ) equal to 1-3, CO / CO ₂ > 2 and H ₂ / CO ₂ >b;

7) the process is carried out during circulation of a gas stream with a volume ratio of the amount of circulating gas to the original synthesis gas equal to 1-1000.

The choice of a catalyst for the conversion of synthesis gas to hydrocarbon products is based on the fact that in the temperature range 340-420 ⁰ C the combination of a metal oxide catalyst for the synthesis of methanol and an acid component allows you to remove the thermodynamic limitation of the reaction of methanol synthesis due to the formation of aromatic hydrocarbons and iso-paraffins . Therefore, in the present invention, bifunctional catalysts are used to obtain the gasoline fraction of hydrocarbons, which include oxides Zn, Cr, and W, which convert synthesis gas to methanol at temperatures of 340-42O ⁰ C, and high-silica zeolites with the structure are used as the acid component of bifunctional catalysts ZSM-5 or ZSM-11, beta-type zeolite or crystalline silicoaluminophosphate with a SAPO-5 structure.

During a long run, the acid component of the bifunctional catalyst is gradually coked, accompanied by a decrease in the selectivity for aromatic hydrocarbons and an increase in the methanol content in the reaction products. A decrease in the level of aromatic hydrocarbons in the gasoline fraction of hydrocarbons below a certain minimum limit may lead to a deterioration in antiknock properties commercial gasoline. An increase in the methanol content in the reaction products creates additional problems for its removal from the water formed during the synthesis, and also leads to an increase in the consumption of the initial synthesis gas. In order to stabilize the process indicators, the present invention uses a monofunctional acid catalyst for gas contacting in the second reaction zone, which prevents the “leak” of methanol and maintains the selectivity for aromatic hydrocarbons at a level sufficient to maintain a high octane number of the obtained gasoline. The choice of conditions for the process of synthesis of a gasoline fraction from a gas containing H ₂ , CO and CO ₂ is due to the following factors. Increased pressure is necessary for deeper conversion of synthesis gas. The lower limit of the temperature range of the bifunctional catalyst (340 ° C) is determined by the minimum activity of the catalyst; exceeding the upper temperature limit (420 ° C) reduces the life of the metal oxide component of the bifunctional catalyst. The gas is contacted with a monofunctional acid catalyst in the second reaction zone, depending on the value of the "methanol" duration and the duration of the acid catalyst, at a temperature of 320 to 46O ⁰ C. The volumetric feed rate of the synthesis gas is determined by the activity of the bifunctional catalyst used at a fixed pressure and temperature . The ratio between H ₂ and CO, as well as between CO and CO ₂ , is determined by the stoichiometry of chemical reactions of hydrocarbon synthesis. Based on theoretical assumptions, the experiments were carried out under conditions sufficiently close to the stoichiometric relationship between “C”, “O” and “H” and, therefore, favorable for the synthesis of methanol and its conversion into C ₅ -C _{1O hydrocarbons} . We previously showed [3] that at high concentrations of CO ₂ in the synthesis gas (above 10 vol.%), The yield of the gasoline fraction of hydrocarbons and the productivity of the bifunctional catalyst decrease. Therefore, in the proposed method, the lower limits of the content of CO ₂ in the synthesis gas were introduced in the form of volumetric ratios CO / CO ₂ > 2 and H ₂ / CO ₂ > 6. An important role in achieving high selectivity and productivity of the process for C ₅₊ hydrocarbons gas flow circulation after separation of liquid products. Firstly, the constant removal of water and liquid hydrocarbons from the contacting gas significantly suppresses the reaction of formation of inactive carbon dioxide and reduces the rate of occurrence of cracking reactions of C ₅₊ hydrocarbons. Secondly, the high linear velocities of the circulating gas flow in combination with the constant ablation of excess heat from the catalysis zone have a positive effect on the temperature distribution in the reactor, and improve the processes of heat transfer and mass transfer. Circulation of a gas stream with a volume ratio of the amount of circulating gas to the initial synthesis gas (circulation ratio) can be from 1 to 1000, but it is better to have a circulation ratio in the range of 5-400.

Embodiments of the invention Example 1 (prototype). The synthesis gas of the composition, vol.%: H ₂ - 68, CO - 29 and CO ₂ - 3 are fed to the installation with a space velocity of 2300 h ^"1 (calculated on the total volume of the catalysts of the 1st and 2nd stage), mixed with circulating gas before entering the dimethyl ether synthesis reactor (DME) and the resulting gas mixture is contacted with a catalyst consisting of ZSM-5 type zeolite and a metal oxide component containing, wt.%: CuO - 62, ZnO - 30, Al ₂ O ₃ - 8, mixed in a mass ratio of 35/65, at a temperature of 300 ⁰ C and a pressure of 80 atm. In the reactor, carbon oxides and hydrogen are converted into DME with selectivity exceeding gas flow after the DME synthesis reactor without isolating the products is sent to the second stage, where upon contact with a catalyst consisting of ZSM-5 type zeolite and a metal oxide component containing, wt.%: ZnO - 67, Cr ₂ O ₃ - 32, W ₂ O ₅ - 1, mixed in a mass ratio of 30/70, at a temperature of 400 ⁰ C and a pressure of 80 atm, DME, carbon oxides and hydrogen are converted into a gasoline fraction, gaseous hydrocarbons and an aqueous fraction (more than 98 wt. % H ₂ O). DME conversion of more than 99%; the total conversion of the components of the synthesis gas ("input - output" from the installation) is at least 90%. The gas stream after the second stage reactor is cooled and liquid products — condensed hydrocarbons, water and methanol — are separated from the gas phase in a separator. Liquid products are sequentially separated into a gasoline fraction, methanol water and carbon Hydrocarbons C ₃ -C ₄ . To prevent the accumulation of light hydrocarbons, part of the gas stream after the separator is constantly removed from the circulation circuit, and the main gas stream is mixed with synthesis gas and fed to the DME synthesis reactor. Example 2

The synthesis gas is fed to the plant at a space velocity of 820 h ^"1, based on the total amount of catalysts is mixed with the circulating gas prior to entering into the hydrocarbon synthesis reactor, and the resulting gas mixture is contacted in the 1st reaction zone with a bifunctional catalyst, of a zeolite co worthwhile type ZSM-5 and a metal oxide component, at a temperature of 400 ⁰ C and a pressure of 80 atm. The gas stream after contacting with a bifunctional catalyst without isolating the products is sent to the 2nd reaction zone, where upon contact with a monofunctional catalyst containing zeolite type ZSM-5, at a temperature of 400 ⁰ C and a pressure of 80 atm, additional conversion of hydrocarbons, methanol and DME occurs the formation of high-octane gasoline (C ₅₊ ), C ₁ -C ₄ hydrocarbons and water. After contacting, the gas stream is cooled and liquid products are separated from the gas phase in a separator. Liquid products are sequentially separated into a gasoline fraction, methanol water and CO ₂ and C ₃ -C ₄ hydrocarbons dissolved in them. To prevent the accumulation of methane and light hydrocarbons, part of the gas stream after the separator is constantly removed from the circulation loop, and the main gas stream is mixed with the initial synthesis gas and fed to the hydrocarbon synthesis reactor.

Examples 3-10. The catalysts used are similar to example 2. They differ in the conditions for the implementation of the method. Example 11

Similar to example 2. It is characterized in that a composition consisting of a zeolite of the ZSM-11 type and a metal oxide component is used as a bifunctional catalyst. Example 12

Similar to example 2. It is characterized in that a zeolite of the ZSM-11 type is used as a monofunctional catalyst. Example 13

Similar to example 2. It is characterized in that as a bifunctional catalyst, a composition consisting of a beta type zeolite and a metal oxide component is used. Examples 14-15.

Similar to example 2. Differ in that as a bifunctional catalyst using a composition consisting of crystalline silicoaluminophosphate with the structure of SAPO-5 and a metal oxide component. The volumetric ratios of the components in the feed synthesis gas, the conditions and the main process indicators are shown in table 1.

The molar ratios of SiO ₂ / Al ₂ O ₃ in the acid component of the bifunctional catalyst and in the zeolite of the monofunctional catalyst are presented in table 2.

Industrial applicability.

As can be seen from the results presented in table 1, the proposed method allows to obtain C ₅₊ hydrocarbons with a content of 20-60 wt.% Aromatic hydrocarbons and has the following advantages compared to the prototype:

1) the selectivity for the formation of C ₅₊ hydrocarbons is higher on average by 10-11%;

2) the yield of C ₅₊ hydrocarbons calculated on the basis of the initial synthesis gas is 1.1-1.2 times higher.

Table 1.

Comparison of parameters and indicators of the processes of conversion of synthesis gas according to the prototype and the claimed method

Continuation of table 1.

Continuation of table 1.

Table 2.

Molar ratios of SiO ₂ / Al ₂ O ₃ used zeolites and crystalline silicoaluminophosphate

Claims

CLAIM

1. A method of producing hydrocarbon gasoline fractions from synthesis gas containing H ₂ , CO and CO ₂ by sequentially contacting the gas in at least two reaction zones at elevated temperatures and pressure with a bifunctional catalyst in the first reaction zone consisting of an acid and the metal components, characterized in that the metal oxide component of the bifunctional catalyst comprises a metal oxide composition, wt%:. ZnO - 65-70, Cr ₂ O ₃ - 29-34, W ₂ O ₅ - no more than 1, and as the acid component bifunktsionalnog catalyst is structured zeolite ZSM-5 or ZSM- 11, zeolite beta or a crystalline silicoaluminophosphate with the structure SAPO-5, and the second reaction zone using an acidic monofunctional catalyst comprising a zeolite with structure ZSM-5 or ZSM-Il.

2. The method according to p. 1, characterized in that the acid component of the bifunctional catalyst has a molar ratio of SiO ₂ / Al ₂ O ₃ not more than 200.

3. The method according to p. 1, characterized in that the zeolite monofunctional acid catalyst has a molar ratio of SiO ₂ ZAl ₂ O ₃ no more

200.

4. The method according to p. 1, characterized in that the contacting of the gas in the first reaction zone is carried out at a pressure of 40-100 atm and a temperature of 340-420 ⁰ C.

5. The method according to p. 1, characterized in that the contacting of the gas in the second reaction zone is carried out at a pressure of 40-100 atm and a temperature of 320-46O ⁰ C.

6. The method according to p. 1, characterized in that the process is carried out at a volumetric feed rate of the feed synthesis gas of 200-5000 h ^"1 and volumetric ratios in the feed synthesis gas H ₂ / (CO + CO ₂ ) = 1 - 3, CO / CO ₂ > 2 and H ₂ / CO ₂ > 6.

7. The method according to p. 1, characterized in that the process is carried out during circulation of a gas stream with a volume ratio of the amount of circulating gas to the original synthesis gas equal to 1-1000.