RU2286327C1 - Method for preparing motor fuels - Google Patents

Abstract

FIELD: petroleum chemistry.

SUBSTANCE: method involves preparing synthesis gas, catalytic conversion of synthesis gas in reactor for synthesis of dimethyl ether (DME) at enhanced temperature and pressure wherein synthesis gas is contacted with catalyst followed by cooling the gaseous mixture and its separation for liquid and gaseous phases. Dimethyl ether is isolated from the liquid phase that is fed into catalytic reactor for synthesis of gasoline and the gaseous phase containing unreacted components of synthesis gas is fed to repeated catalytic conversion into additional reactor for synthesis of DME being without the parent synthesis gas. Residue of gaseous phase containing components of synthesis gas not reacted to DME after repeated catalytic conversion in additional reactor for synthesis of DME are oxidized in reactor for synthesis of carbon dioxide. Then carbon dioxide is separated and mixed its with natural gas at increased temperature and pressure that results to preparing synthesis gas that is fed to the catalytic conversion into reactor for synthesis of DME. Invention provides increasing yield of gasoline fraction and decrease of carbon dioxide waste in atmosphere.

EFFECT: improved method of synthesis.

4 cl, 1 tbl, 1 dwg, 1 ex

Description

The invention relates to the field of hydrocarbon processing, and in particular to methods for producing synthetic motor fuels and, in particular, to a method for producing dimethyl ether (DME) and synthetic gasoline by catalytic conversion of synthesis gas (SG).

A known method of producing hydrocarbons developed by Haldor Topsoe AS, when processing a synthesis gas containing hydrogen and carbon monoxide and having a molar ratio CO / H ₂ above 1 and provided that the synthesis gas entering the conversion has a molar ratio CO / CO ₂ from 5 to 20 according to US patent No. 4481305, CL. C 07 C 1/04, 1/20, 1984. According to this analogue, the process is carried out in two reactors in series at a pressure of 0.5-10.0 MPa without intermediate separation of products after the first reactor. In the first reactor, the synthesis gas is in contact with one or more catalysts that convert the synthesis gas at a temperature of 150-400 ° C to methanol and then in the same reactor in DME. Then the gas mixture is sent to the second reactor, where in the presence of a zeolite catalyst at a temperature of 150-600 ° C, DME is converted mainly into liquid hydrocarbons under normal conditions.

The main disadvantages of the method according to US patent No. 481305 are the emission into the atmosphere of unconverted components of the synthesis gas after the second reactor and the low yield of the gasoline fraction relative to the supplied carbon of the feedstock (29 wt.%).

A known process for producing gasoline from synthesis gas, in which synthesis gas is converted to gasoline through a liquid-phase process for producing dimethyl ether as an intermediate product according to US patent No. 5459166, cl. S 07 S 001 / 04,1995. Dimethyl ether is converted to gasoline on a zeolite catalyst ZSM-5 at a temperature of 340-540 ° C.

The disadvantage of this process is the release into the atmosphere of unreacted components of the synthesis gas, which reduces the yield of liquid hydrocarbons.

There is also a method of producing motor fuels from carbon-containing raw materials according to the patent of the Russian Federation No. 2143417, class. С 07 С 1/04, 41/06, 1999. The method for producing motor fuels includes, at the first stage, contacting the feedstock, which is a synthesis gas (a mixture of CO, CO ₂ and H ₂ ), with a catalyst consisting of ZSM-zeolite 5 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 is cooled and separated into a liquid fraction and a gas phase containing unconverted components of synthesis gas and DME, while DME is then isolated from the liquid fraction, and the gas phase is divided into two streams - one is for mixing with the syngas and fed into the same reactor as the first stage. The second gas stream is sent to the second stage, where in contact with a catalyst consisting of a zeolite of the ZSM-5 type and a metal oxide component containing (wt.%): ZnO 65-70, Cr ₂ O ₃ 29-34, W ₂ O ₅ 1 mixed in a mass ratio of 30-99 / 70-1, the DME and the components of the synthesis gas are converted into a gasoline fraction, gaseous hydrocarbons and an aqueous fraction.

The main disadvantage of the known method of producing motor fuels from carbon-containing raw materials according to the patent of the Russian Federation No. 2143417 is the withdrawal of a part of the gas stream from the circulation circuit, which reduces the yield of DME, and hence the gasoline fraction, based on the supplied carbon oxides.

There is also a method of producing motor fuels from natural gas according to the patent of the Russian Federation No. 2226524, class. C 07 C 1/04, 41/06, 43/04, C 10 G 3/00, 2004, adopted as the closest analogue (prototype) of the proposed method. A method of producing motor fuels includes the production of synthesis gas by non-catalytic gas-phase oxidative conversion of natural gas with oxygen at a temperature of 800-1500 ° C and a pressure of 1-10 MPa. Then, a catalytic conversion of synthesis gas is carried out in a dimethyl ether synthesis reactor, followed by cooling of the resulting gas mixture and its separation into a liquid and gas phase. In this case, DME is isolated from the gas phase, which is sent to the gasoline synthesis catalytic reactor, and the gas phase, which contains the unconverted components of the synthesis gas, is sent to re-catalytic conversion to the additional DME synthesis reactor without mixing with the initial synthesis gas. The gas stream after an additional DME synthesis catalytic reactor is cooled and the gas stream is separated into a liquid and gas phase, while liquid products - water and DME are condensed from the gas stream, and the gas phase, which is the remainder of the unreacted components of the synthesis gas, is removed from the technological process. To obtain a gasoline fraction, DME is sent to a gasoline synthesis catalytic reactor in which DME is contacted with a catalyst consisting of high-silicon zeolite and metal oxide components such as ZnO, Na ₂ O, rare earth oxides, and DME is converted into a gasoline fraction, gaseous hydrocarbons and an aqueous fraction, followed by separation of the gasoline fraction.

The main disadvantage of the known method for producing motor fuels from natural gas is the removal of unconverted components of the synthesis gas from the process, which reduces the yield of DME, and hence the gasoline fraction, calculated on the supplied carbon oxides. Another disadvantage of this method is the release into the atmosphere of environmentally harmful carbon dioxide contained in the remainder of the synthesis gas.

The objective of the proposed method for producing motor fuels is to increase the yield of DME and, accordingly, the gasoline fraction calculated on the processed carbon oxides due to the disposal of unconverted components of the synthesis gas, as well as reducing the emission of carbon dioxide into the atmosphere.

The problem in the invention is solved due to the fact that the method of producing motor fuels from natural gas includes the production of synthesis gas, catalytic conversion of synthesis gas in a dimethyl ether synthesis reactor (DME) at elevated temperature and pressure, in which the synthesis gas is introduced into contact with the catalyst, followed by cooling the gas mixture and separating it into a liquid and gas phase, while dimethyl ether is isolated from the liquid phase, which is sent to a gasoline synthesis catalytic reactor, and the gas phase, with containing unconverted components of the synthesis gas, is sent to re-catalytic conversion to an additional DME synthesis reactor without adding the initial synthesis gas, while the remainder of the gas phase containing unconverted components of the synthesis gas after re-catalytic conversion in an additional DME synthesis reactor is oxidized to a carbon dioxide synthesis reactor, then carbon dioxide is separated and mixed with natural gas at elevated temperature and pressure, whereby a synthesis gas is obtained which apravlyayut the catalytic conversion in the DME synthesis reactor.

The oxidation of the remainder of the gas phase, including the unconverted components of the synthesis gas, namely carbon monoxide, carbon dioxide, hydrogen and nitrogen, can be carried out with atmospheric oxygen at a temperature of 400-700 ° C to obtain a hot gas mixture containing carbon dioxide, nitrogen and water vapor .

The separation of carbon dioxide from nitrogen and water vapor can be carried out by cooling the hot gas mixture in a heat exchanger-utilizer, then the cooled gas mixture can be directed to the lower part of the carbon dioxide absorber, in which it is brought into contact with the countercurrent cold cold solution of the absorbent, a solution of absorbent carbon dioxide, then a solution of absorbent saturated with carbon dioxide is heated in a heat exchanger-heat exchanger and fed to the desorber-regenerator, in which the solution of absorbent add to the stream of hot lean absorbent solution and the stream of carbon dioxide.

The resulting carbon dioxide can be mixed with natural gas at a temperature of 700-1300 ° C and a pressure of 0.5-5.0 MPa, and synthesis gas is obtained, which is fed to the catalytic conversion in a dimethyl ether synthesis reactor.

Thanks to the claimed method, a technical result is obtained, namely, the yield of DME and, accordingly, of the gasoline fraction is increased by increasing the degree of conversion of carbon oxides to DME by utilizing unconverted carbon oxides of the synthesis gas. In addition, the emission of carbon dioxide into the atmosphere has been reduced, which is consistent with the requirements of the Kyoto Protocol.

The drawing shows a diagram of the technological process for producing motor fuels.

According to the inventive method for producing motor fuels, high-temperature reactor (VTR) 1 is fed with natural gas and air, where at an elevated temperature of 800-1500 ° C and a pressure of 1-10 MPa, synthesis gas is obtained by direct non-catalytic gas-phase oxidative conversion (mixture of CO, H ₂ , CO ₂ and N ₂ ), which are sent to a heat exchanger, and then to a DME synthesis catalytic reactor 2, where the synthesis gas is brought into contact with a catalyst consisting of metal oxide components, such as CuO, ZnO, at a temperature of 220-240 ° С, Cr ₂ About ₃ and Al ₂ About ₃ .

The gas stream after the DME synthesis catalytic reactor 2 is cooled and absorbed by countercurrent flow with liquid methanol in a scrubber 3, separating the gas stream into a liquid and gas phase, while water and DME are separated from the gas stream. The gas phase, which is the non-converted components of the synthesis gas, is fed into an additional DME synthesis catalytic reactor 4 without mixing with the original synthesis gas at a temperature of 220-240 ° C, where these non-converted components of the synthesis gas are brought into contact with a catalyst consisting of metal oxide components.

The gas stream after an additional catalytic reactor 4 for the synthesis of DME is cooled and absorbed by countercurrent flow with liquid methanol in a scrubber 5, separating the gas stream into a liquid and gas phase, while liquid products — water and DME — are condensed from the gas stream, and the gas phase representing the remains of unreacted components of the synthesis gas, are not removed from the process, and sent to the reactor 6 synthesis of carbon dioxide.

The high solubility of DME in methanol and water contributes to its extraction from the gas stream. Next, the liquid phase, which is methanol enriched in dimethyl ether, is sent from scrubbers 3 and 5 to a distillation column 7, where DME is separated from methanol and water at a pressure of 1.2 MPa, which allows, if necessary, to obtain DME as the target product. In this case, after distillation column 7, DME is fed to storage 8, and methanol is returned to the process.

The unconverted components of the synthesis gas (CO, H ₂ , CO ₂ , etc.) in the reactor 6 for the synthesis of carbon dioxide are mixed with air and oxidized at a temperature of 400-700 ° C to obtain a stream of hot gas containing mainly nitrogen, water vapor and dioxide carbon. The hot gas stream is sent to a heat exchanger-utilizer 9, where heat is removed from it and a cold gas stream is obtained, which is sent to the lower part of the carbon dioxide absorber 10. In the carbon dioxide absorber 10, the cold gas stream is brought into contact with the cold lean absorbent solution stream supplied to the top of the carbon dioxide absorber 10 countercurrent to the cold gas stream, and carbon dioxide is absorbed from the cold gas by absorption to produce waste gas streams that are discharged from the top parts of the carbon dioxide absorber 10, and the carbon dioxide-saturated absorbent stream, which is sent to the heat exchanger-utilizer 9. In the heat exchanger-utilizer 9, the saturated absorbent flow to the heat is removed from the hot gas stream and the resulting hot saturated absorbent stream is fed into the middle part of the stripper-regenerator 11. In the stripper-regenerator 11, the hot saturated absorbent stream is separated by heating the absorbent in the lower part of the stripper-regenerator 11 to the hot, poor absorbent stream removed from the bottom of the stripper-regenerator 11, and a stream of carbon dioxide, which is removed from the top of the stripper-regenerator 11 and sent for recycling in a high temperature reactor 1, where carbon dioxide the ode is mixed with methane at a temperature of 700-1300 ° C and a pressure of 0.5-5.0 MPa and receive synthesis gas, which is cooled and sent to a catalytic conversion in a DME synthesis reactor 2. The flow of hot lean absorbent is sent to the refrigerator 12, where heat is removed from it to produce a cold, poor absorbent stream, which is fed to the upper part of the absorber 10.

To obtain the gasoline fraction, dimethyl ether (DME) from the distillation column 7 is sent to a gasoline synthesis catalytic reactor 13, in which DME at a temperature of 380-420 ° C is brought into contact with a catalyst consisting of high-silicon zeolite and metal oxide components such as ZnO, Na ₂ O, rare earth metal oxides, and turn DME into a gasoline fraction, gaseous hydrocarbons and an aqueous fraction, followed by separation of the gasoline fraction.

The following is an example illustrating the applicability of the proposed method.

Example

Characteristics of raw materials:

The composition of the air, vol.%: Nitrogen 78,09; oxygen 20.95; argon 0.93; undefined gases rest.

The composition of natural gas, vol.%: Methane 97%; ethane 2%; undefined gases rest.

The composition of the stream of carbon dioxide sent for recycling, vol.%: Carbon dioxide 99%; undefined gases rest.

Natural gas and air are supplied to the head of the high-temperature reactor (VTR) 1, and at a temperature of 1600 ° C and a pressure of 5.00 MPa and direct non-catalytic gas-phase oxidative conversion, synthesis gas of the composition (in terms of dry gas) is obtained

Hydrogen 3.2 Carbon monoxide 14.5 Carbon dioxide 2.1 Methane 0.56 Nitrogen Rest

The conversion of carbon from the starting hydrocarbons to carbon monoxide is 89%.

Recycled carbon dioxide is mixed with additional natural gas and fed into the middle part of the high-temperature reactor 1, where, by mixing with the previously obtained synthesis gas, additional synthesis gas is synthesized by means of a natalytic carbon dioxide conversion of natural gas at a temperature of 1100 ° C and a pressure of 5.00 MPa with a final composition (in terms of dry gas)

Hydrogen 34.2 Carbon monoxide 20.5 Carbon dioxide 3.6 Methane 0.8 Nitrogen Rest

The conversion of carbon recycled carbon dioxide and additional natural gas to carbon monoxide 80%.

Due to this, the emission of carbon dioxide into the atmosphere is prevented, which improves the environmental characteristics of the production method.

The resulting synthesis gas is sent to a dimethyl ether synthesis catalytic reactor 2, where the synthesis gas is contacted with a catalyst consisting of metal oxide components, such as

CuO 21-50 wt.%, ZnO 20-30 wt.%, Cr ₂ O ₃ 15-25 wt.% And Al ₂ O ₃ 5-40 wt.%, At an initial temperature of 220 ° C, a final 260 ° C and receive gas composition (vol.%):

Component Start of synthesis End of synthesis After extracting DME Hydrogen 34.2 26.1 27.5 Carbon monoxide 20.5 10.0 10.5 Carbon dioxide 3.6 9.1 9.6 Methane 0.8 0.96 1.00 Nitrogen 40.9 48.9 51,4 DME 0 4.8 Less than 0.1 Methanol 0 0.25 Less than 0.1

The conversion of the initial carbon monoxide CO to DME is 58.3%.

Conversion of the starting carbon monoxide CO to methanol 1%.

The resulting mixture was cooled to 50 ° C and separated into a liquid and gas phase when fed countercurrently with liquid methanol in a scrubber 3 at a pressure of 5.1 MPa, methanol enriched with dimethyl ether was sent to DME separation in a distillation column 7 at a helmet pressure of 1.2 MPa and a temperature of 60 ° C, after which DME is fed to the storage device, and methanol is returned to the process.

The synthesis gas containing unconverted components is heated to 220 ° C, sent for re-catalytic conversion to reactor 4 in contact with a catalyst of the same composition at a pressure of 5 MPa and a final temperature of 250 ° C.

The resulting composition has, vol.%:

Component Start of synthesis End of synthesis After extraction DME Hydrogen 27.5 23.9 24.4 Carbon monoxide 10.5 6.2 6.4 Carbon dioxide 9.6 11.7 12.0 Methane 1.00 1,1 1,1 Nitrogen 51,4 55.0 56.1 DME Less than 0.1 1,5 Less than 0.1 Methanol Less than 0.1 0.5 Less than 0.1

Additional conversion in DME: 50.6%

Additional conversion to methanol: 5.1%

Complete conversion to the target products from carbon source of natural gas: 96.3%

The resulting mixture is cooled to 50 ° C and separated into liquid and gas phases when fed countercurrently with liquid methanol in a scrubber 5 at a pressure of 4.9 MPa, methanol enriched with dimethyl ether is sent to the DME separation in the same distillation column 7 at a pressure in helmet 1, 2 MPa and a temperature of 60 ° C, after which DME is fed to the storage tank, and methanol is returned to the process.

The synthesis gas containing carbon dioxide, carbon monoxide, hydrogen, methane and nitrogen remaining after DME extraction is sent to the carbon dioxide synthesis reactor 6, in which the residual syngas is oxidized with air at a temperature of 550 ° C, which ensures the production of hot gas containing nitrogen, argon, water vapor, carbon dioxide.

The composition of the gas obtained in the reactor 6, vol.%:

Nitrogen 74.6 Argon 0.6 Carbon dioxide 10.1 Water vapor 14.7

The content of environmentally harmful carbon monoxide, nitrogen oxides and ammonia does not exceed the MPC.

To separate carbon dioxide from nitrogen and water vapor, the hot gas obtained in reactor 6 is sent to a heat exchanger-utilizer 9, where it is cooled to 50 ° C and the obtained cold gas is sent to the lower part of the carbon dioxide absorber 10, in which it is brought into contact with the countercurrent with cold poor absorbent (aqueous solution of monoethanolamine) and get a stream of carbon dioxide-saturated absorbent and waste gas containing nitrogen 98 vol.%, argon 1.3 vol.%, carbon dioxide the rest.

The absorbent saturated with carbon dioxide is fed to the heat exchanger-utilizer 9, heated by removing heat from the hot gas from the reactor 6, and the desorber-regenerator 11 is sent, in which it is separated by desorption to recirculated carbon dioxide and hot lean absorbent. The hot lean absorbent is cooled in the refrigerator 12 and the resulting cold lean absorbent is sent to absorb carbon dioxide in the absorber 10. The recirculated carbon dioxide is sent to natural gas for mixing and fed to the VTP 1 reactor to produce synthesis gas.

The gasoline fraction is obtained by directing DME into a gasoline synthesis catalytic reactor 13 at 2 MPa, in which DME is brought into contact with a catalyst consisting of a high-silicon CVN zeolite developed according to TU 38.401528-85 and a ratio of SiO ₂ / Al ₂ O ₃ = 42 (70 %) and metal oxide components, such as ZnO (2%), Na ₂ O (0.05-0.1%), rare earth metal oxides (1%), and turn DME into a gasoline fraction at a temperature of 320-360 ° С, gaseous hydrocarbons and an aqueous fraction followed by evolution of a gasoline fraction. The yield of the gasoline fraction is 90% for DME carbon. The composition of the gasoline fraction is shown in the table:

Name of components The content of components in the gasoline fraction, in% Paraffins C ₄ 0,07 Paraffins C ₅ 0.67 Paraffins C ₆ 3.57 Paraffins C ₇ 7.26 Paraffins C ₈ 6.84 Paraffins C ₉ 4.69 Naphthenes C ₆ 0.25 Naphthenes C ₇ 0.27 Naphthenes C ₈ 3.86 Naphthenes C ₉ 2.98 Naphthenes C ₁₀ 12.80 Naphthenes C ₁₀ -C ₁₁ 25.83 Aromatic hydrocarbons C ₈ 13.03 Aromatic hydrocarbons C ₉ 17.88 Total one hundred

The resulting composition of the hydrocarbon components of the gasoline fraction corresponds to AI-92 engine fuels.

The obtained technical result

- Due to the recycling of carbon dioxide, the emission of carbon dioxide is reduced by more than 100 times.

- Due to the recirculation of carbon dioxide, the degree of conversion of the source of natural gas to gasoline fractions is increased to 95%.

- Due to the oxidation of residual synthesis gas by air at a temperature of 550 ° C, the content of carbon monoxide, nitrogen oxides and ammonia in gas emissions is lower than the MPC.

The inventive method for producing motor fuels from natural gas increased the yield of DME and, accordingly, the gasoline fraction by increasing the degree of conversion of carbon oxides by utilizing unconverted carbon oxides of synthesis gas in DME, and also reduced the emission of environmentally harmful carbon dioxide into the atmosphere.

Claims (4)

1. A method of producing motor fuels from natural gas, including the production of synthesis gas, catalytic conversion of synthesis gas in a dimethyl ether synthesis reactor (DME) at elevated temperature and pressure, in which the synthesis gas is brought into contact with the catalyst, followed by cooling of the gas mixture and dividing it into a liquid and gas phase, while dimethyl ether is isolated from the liquid phase, which is sent to a catalytic synthesis gasoline reactor, and the gas phase containing the unconverted components of the synthesis gas is sent to replay catalytic conversion to an additional DME synthesis reactor without adding the initial synthesis gas, characterized in that the gas phase residue containing the components of the synthesis gas not converted to DME after repeated catalytic conversion in an additional DME synthesis reactor is oxidized in a carbon dioxide synthesis reactor, then carbon dioxide is separated and mixed with natural gas at elevated temperature and pressure, resulting in the production of synthesis gas, which is sent for catalytic conversion to a synth reactor for DME. 2. The method according to claim 1, characterized in that the oxidation of the remainder of the gas phase, including the unconverted components of the synthesis gas, namely carbon monoxide, carbon dioxide, hydrogen and nitrogen, is produced with air at a temperature of 400-700 ° C to obtain a hot gas mixture containing carbon dioxide, nitrogen and water vapor. 3. The method according to claim 1, characterized in that the separation of carbon dioxide from nitrogen and water vapor is carried out by cooling the hot gas mixture in a heat exchanger-utilizer, then the cooled gas mixture is sent to the lower part of the carbon dioxide absorber, in which it is brought into contact with the countercurrent with cold, poor absorbent solution, while saturating the absorbent solution with carbon dioxide, then the absorbent solution saturated with carbon dioxide is heated in a heat exchanger-heat exchanger and fed to the desorber-regenerator, in which the solution the sorbent is separated into a stream of hot lean absorbent solution and a stream of carbon dioxide. 4. The method according to claim 1, characterized in that the carbon dioxide is mixed with natural gas at a temperature of 700-1300 ° C and a pressure of 0.5-5.0 MPa, and synthesis gas is obtained.