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US-20260125336-A1 - ONE-STEP PROCESS FOR PRODUCING DIMETHYL ETHER

US20260125336A1US 20260125336 A1US20260125336 A1US 20260125336A1US-20260125336-A1

Abstract

The invention concerns a process for the conversion of ammonia (NH 3 ) and CO x , wherein x=1-2, to dimethyl ether (DME) wherein a feed comprising NH 3 and CO x , wherein x=1-2, is provided to a reactor to obtain a reaction product comprising DME, wherein the reactor comprises a catalyst for converting NH 3 to nitrogen (N 2 ) and hydrogen (H 2 ), a catalyst for converting H 2 and CO x , wherein x=1-2, to DME, and a sorbent material capable of adsorbing water. The invention furthermore concerns a composition a catalyst for converting NH 3 to nitrogen (N 2 ) and hydrogen (H 2 ), a catalyst for converting H 2 and CO x , wherein x=1-2, to DME, and a sorbent material capable of adsorbing water and the use of that composition in the conversion of ammonia (NH 3 ) and CO x , wherein x=1-2, to dimethyl ether (DME).

Inventors

  • Jurriaan Boon
  • Earl Lawrence Vincent Goetheer

Assignees

  • NEDERLANDSE ORGANISATIE VOOR TOEGEPAST-NATUURWETENSCHAPPELIJK ONDERZOEK TNO

Dates

Publication Date
20260507
Application Date
20230718
Priority Date
20220719

Claims (15)

  1. 1 . A process for the conversion of ammonia (NH 3 ) and CO x , wherein x=1-2, to dimethyl ether (DME) wherein in a reaction step a) a feed comprising NH 3 and CO x , wherein x=1-2, is provided to a reactor to obtain a reaction product comprising DME, wherein the reactor comprises a catalyst for converting NH 3 to nitrogen (N 2 ) and hydrogen (H 2 ), a catalyst for converting H 2 and CO x , wherein x=1-2, to DME, and a sorbent material capable of adsorbing water.
  2. 2 . The process according to claim 1 wherein the reaction temperature is in the range of 150° C.-400° C., preferably in the range of 200° C.-300° C.
  3. 3 . The process according to claim 1 , wherein the reaction pressure is in the range of 1-100 bara, preferably in the range of 20-80 bara, even more preferably in the range of 30-70 bara.
  4. 4 . The process according to claim 1 , wherein the feed comprises H 2 , preferably wherein the feed comprises in the range of 1-20 mol % of H 2 on total of the feed.
  5. 5 . The process according to claim 1 , wherein carbon selectivity towards DME is at least 50%, preferably at least 70%, more preferably at least 90%.
  6. 6 . The process according to claim 1 , wherein the catalyst for converting NH 3 to N 2 and H 2 is a metal based catalyst, preferably a metal/support catalyst, a metal alloy catalyst, a metal composite catalyst and/or a metal oxide catalyst.
  7. 7 . The process according to claim 1 , wherein the catalyst for converting H 2 and CO x , wherein x=1-2, to DME is selected from a bifunctional catalyst for converting H 2 and CO x , wherein x=1-2, to DME or a combination of a methanol synthesis catalyst and a methanol dehydration catalyst, preferably the catalyst for converting H 2 and CO x , wherein x=1-2, to DME is an alumina containing copper/zinc oxide based catalyst.
  8. 8 . The process according to claim 1 , wherein the reactor comprises in the range of 20-90 wt. % of the sorbent material capable of adsorbing water based on total of the catalyst for converting NH 3 to N 2 and H 2 , the catalyst for converting H 2 and CO x , wherein x=1-2, to DME, and the sorbent material capable of adsorbing water.
  9. 9 . The process according to claim 1 , wherein the sorbent material capable of adsorbing water is a molecular sieve having a pore diameter in the range of 2-50 Å, preferably in the range of 2-10 Å, even more preferably in the range of 2-5 Å, preferably the sorbent material capable of adsorbing water is a zeolite, more preferably an LTA zeolite.
  10. 10 . The process according to claim 1 , further comprising a second step b) after step a) which is a sorbent regeneration step wherein the sorbent material is contacted with a purge gas.
  11. 11 . The process according to claim 10 , wherein the temperature in step b) is at least 100° C. higher than the temperature of step a) and/or wherein the pressure of step b) is at least 10 bar lower than the pressure of step a), preferably wherein the temperature in step b) is at least 150° C. higher than the temperature of step a) and/or wherein the pressure of step b) is at least 20 bar lower than the pressure of step a).
  12. 12 . The process according to claim 10 , having two or more reactors comprising the catalyst for converting NH 3 to N 2 and H 2 , the catalyst for converting H 2 and CO x , wherein x=1-2, to DME, and the sorbent material capable of adsorbing water, preferably wherein at least one reactor of the two or more reactors is performing step a).
  13. 13 . A composition comprising a catalyst for converting NH 3 to N 2 and H 2 , a catalyst for converting H 2 and CO x , wherein x=1-2, to DME and a sorbent material capable of adsorbing water.
  14. 14 . (canceled)
  15. 15 . A reactor comprising the composition of claim 13 , preferably the reactor is a fixed bed reactor or a fluidized bed reactor, more preferably the reactor is a fluidized bed reactor.

Description

INTRODUCTION Dimethyl ether (DME) is a valuable compound useful in the chemical industry, e.g. as precursor of dimethyl sulphate, acetic acid or for olefin production. It is an important research chemical and is used as refrigerant and propellant. Moreover, DME may find more widespread use in the future, as it is being developed as novel fuel, e.g. as replacement for or additive to propane in LPG and as diesel fuel additive. DME can be produced by catalytic hydrogenation of CO, e.g. using synthesis gas (a fuel gas mixture consisting primarily of hydrogen and carbon monoxide). This can be done directly or by first converting syngas into methanol. The direct method of producing of DME from syngas involves contacting the synthesis gas with a bifunctional catalyst comprising a methanol synthesis catalyst and a methanol dehydration catalyst, such that isolation and purification of the methanol is not required. A reaction scheme for the synthesis of dimethyl ether from syngas has been developed: Methanol synthesis:CO2 + 3 H2↔CH3OH + H2OWater gas shift:CO + H2O↔H2 + CO2Methanol dehydration:2 CH3OH↔CH3OCH3 + H2OOverall:3 CO + 3 H2↔CH3OCH3 (DME) + CO2 As syngas typically comes from non-renewable sources, alternatives raw material are considered to produce DME. One of the options is to make use of CO2, such as obtained from CO2 capture (Mota et al., Catalysts 11, 411, 2021). CO2 can be combined with H2 and converted into DME, the overall reaction equation is: For DME synthesis typically a combination of CO and CO2 is used for feedstock. Both the conversion of CO and CO2 together with H2 are equilibrium reactions. The reaction efficiency can be improved by capturing the water by a sorbent capable of adsorbing water as is described in WO 2017/121817 and by Van Kampen et al. (Reaction Chemistry & Engineering, 6(2), 244-257 (2021)). The process of WO 2017/121817 and Van Kampen et al. is named the SEDMES, sorption enhanced dimethyl ether synthesis. The reaction preferably is carried out at elevated pressure up to 200 bara and relative low temperatures, around 250° C. The H2 for the SEDMES process can origin for example from electrolysis of water, using green electricity. A disadvantage of H2 is that storage and transport is not straightforward as the volumetric energy density is low. Therefore other options to store and transport H2 are considered. One of these options is ammonia NH3 (Lucentini et al., Ind. Eng. Chem. Res., 60, 18560-18611, 2021). Ammonia can be cracked to deliver H2 and N2. The H2 can subsequently be used in the SEDMES process. The use of NH3 to deliver H2 for the SEDMES process has not been described in the art. One of the reasons may be that cracking of NH3 is inefficient as after cracking a gaseous mixture of H2 and N2 needs to be separated. Without separation the reactant density during SME synthesis is low as in the above reaction equation next to 6 molecules H2 also 2 molecules of N2 are present. Moreover a larger volume of gas needs to be pressurized, which is energy inefficient. NH3 cracking is typically carried out at temperatures above 500° C., preferably around 800-900° C. and at ambient pressure. Therefore there is need for a process for producing DME that makes use of renewable sources and that provides for an efficient conversion of the renewable sources. SUMMARY OF THE INVENTION The inventors now found that NH3 cracking and DME synthesis can be carried out in a one-step process. In this one step process a catalyst for converting NH3 to nitrogen (N2) and hydrogen (H2), a catalyst for converting H2 and COx, wherein x=1-2, to DME and a sorbent material capable of adsorbing water is present. This process has several benefits. First of all, due to the integration of NH3 cracking and DME synthesis only one reactor is needed instead of a separate cracking reactor and a separate DME synthesis reactor. The capital expenditure and operations costs therefore will be lower. In addition due to the process integration the heat generated during DME synthesis can be in situ transferred to the endothermic cracking reaction, instead that the heat needs to be transferred through a less efficient heat exchanger circuit. No heat will be lost. Also the risk for a run-away of the highly exothermic DME synthesis reaction needs less effort to mediate as the in-situ heat transfer tempers the heat development in the reactor. As is demonstrated by the inventors conventional NH3 cracking requires a very high temperature and a low pressure to reach a sufficiently high conversion. The endothermic nature of the cracking reaction in combination with a positive entropy is debit for this. Surprisingly in the process of the invention the temperature can be lowered considerably whilst still reaching full conversion for the NH3 cracking. The inventors believe that by in situ coupling of H2 generation (NH3 cracking) with H2 consumption (DME synthesis) the cracking reaction is pulled towards full conversion, even at lower temper