A METHOD FOR GENERATING SYNGAS FOR USE IN HYDROFORMYLATION PLANTS

Abstract

A method for the generation of syngas for use in hydroformylation plants comprises the steps of evaporating water to steam, mixing the steam with carbon dioxide in any desired molar ratio and feeding the resulting gas to a solid oxide electrolysis cell (SOEC) or an SOEC stack at around 700 C. while supplying an electrical current to the cell or cell stack to convert the feed gas to syngas. An advantage is that the syngas can be generated on the site where it is intended to be used.

Claims

1. A method for the generation of syngas for use in hydroformylation plants, comprising the steps of: evaporating water to steam, mixing the steam with carbon dioxide in the desired molar ratio, and feeding the resulting gas to a solid oxide electrolysis cell (SOEC) or an SOEC stack at a sufficient temperature for the cell or cell stack to operate while supplying an electrical current to the cell or cell stack to effect the conversion of the feed gas to syngas, either fully or in part.

2. The method according to claim 1, wherein steam is electrochemically converted to hydrogen in an SOEC or an SOEC stack, and part of the hydrogen formed is allowed to react with carbon dioxide to form carbon monoxide and steam via the reverse water gas shift (RWGS) reaction, thus resulting in a mixture of hydrogen, steam, carbon monoxide and carbon dioxide.

3. The method according to claim 1, wherein the operating temperature is in the range from 650 to 800 C.

4. The method according to claim 3, wherein the operating temperature is around 700 C.

5. The method according to claim 1, wherein the electrolysis current is in the range from 1 to 100 A.

6. The method according to claim 1, wherein the ratio between carbon monoxide and hydrogen in the gas mixture is in the range from 0.85:1.15 to 1.15:0.85.

7. The method according to claim 1, wherein the product stream from the SOEC stack is subjected to a separation process in a separation unit to remove unconverted carbon dioxide from the syngas product.

8. The method according to claim 7, wherein the separation unit is a pressure swing adsorption (PSA) unit comprising an adsorption step consisting of two or more adsorption columns, each containing adsorbents with selective adsorption properties towards carbon dioxide.

Description

EXAMPLE 1

CO.SUB.2 .Electrolysis

[0039] An SOEC stack consisting of 75 cells is operated at an average temperature of 700 C. with pure CO.sub.2 fed to the cathode at a flow rate of 100 Nl/min, while applying an electrolysis current of 50 A. Based on the above equation (5), the conversion of CO.sub.2 under such conditions is 26%, i.e. the gas exiting the cathode side of the stack consists of 26% CO and 74% CO.sub.2.

EXAMPLE 2

H.SUB.2.O Electrolysis

[0040] An SOEC stack consisting of 75 cells is operated at an average temperature of 700 C. with pure steam fed to the cathode at a flow rate of 100 Nl/min (corresponding to a liquid water flow rate of approximately 80 g/min), while applying an electrolysis current of 50 A. Based on the above equation (4), the conversion of H.sub.2O under such conditions is 26%, i.e. the gas exiting the cathode side of the stack consists of 26% H.sub.2 and 74% H.sub.2O.

EXAMPLE 3

Co-Electrolysis

[0041] An SOEC stack consisting of 75 cells is operated at an average temperature of 700 C. with a mixture of steam and CO.sub.2 in a molar ratio of 1:1 being fed to the cathode with a total flow rate of 100 Nl/min, while applying an electrolysis current of 50 A. In the stack, steam is electrochemically converted into H.sub.2 according to reaction (2). Assuming that any electrochemical conversion of CO.sub.2 via reaction (1) is negligible, 52% of the fed steam is electrochemically converted into hydrogen. Were the RWGS reaction not present, the gas exiting the stack would have the following composition: 0% CO, 50% CO.sub.2, 26% H.sub.2 and 24% H.sub.2O. However, due to the RWGS reaction, some of the produced hydrogen will be used to generate CO. Therefore, the gas exiting the stack will actually have the following composition: 10.7% CO, 39.3% CO.sub.2, 15.3% H.sub.2, and 34.7% H.sub.2O. The ratio of CO:H.sub.2 in the product gas is thus 1:1.43.

EXAMPLE 4

Co-Electrolysis

[0042] An SOEC stack consisting of 75 cells is operated at an average temperature of 700 C. with a mixture of steam and CO.sub.2 being fed to the cathode in a molar ratio of 41:59 with a total flow rate of 100 Nl/min, while applying an electrolysis current of 50 A. In the stack, steam is electrochemically converted into H.sub.2 according to reaction (2). Assuming that any electrochemical conversion of CO.sub.2 via reaction (1) is negligible, 64% of the fed steam is electrochemically converted into hydrogen. Were the RWGS reaction not present, the gas exiting the stack would have the following composition: 0% CO, 59% CO.sub.2, 26% H.sub.2 and 15% H.sub.2O. However, due to the RWGS reaction, some of the produced hydrogen will be used to generate CO. Therefore, the gas exiting the stack will actually have the following composition: 13.2% CO, 45.8% CO.sub.2, 13.0% H.sub.2, and 28.0% H.sub.2O. The ratio of CO:H.sub.2 in the product gas is thus 1:1.01.