INTEGRATED PROCESSES FOR ANAEROBIC CONVERSION OF HYDROGEN AND CARBON OXIDES TO ALCOHOL

• US 20140228598A1
• Filed: 07/15/2013
• Published: 08/14/2014
• Est. Priority Date: 02/08/2013
• Status: Active Grant

• Current Assignee: Synata Bio, Inc.
• Original Assignee: Coskata, Inc.
• Inventors: Datta, Rathin, Calderone, Steve, Merkel, Loula Sassaris
• Granted Patent: US 9,365,870 B2
• Time in Patent Office: Days
• US Class Current: 568/840
• CPC Class Codes: C12P 7/04 acyclic
• CPC Class Codes: C12P 7/065 with microorganisms other than yeasts
• CPC Class Codes: C12P 7/08 produced as by-product or from waste or cellulosic material substrate
• CPC Class Codes: C12P 7/16 Butanols
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel
• CPC Class Codes: Y02P 20/10 Process efficiency

Abstract

Integrated processes are disclosed for reducing the carbon foot print related to the use of non-renewable hydrocarbon gas streams for producing alcohols by anaerobic bioconversion of reformed gas. These processes combine renewable and non-renewable gas sources of hydrogen, carbon monoxide and carbon dioxide to produce alcohol. Thus the invention found a highly a practical way to make use of non-renewable carbon oxide sources while still lowering the carbon footprint of such alcohols produced thereby, especially when combined with corn ethanol production. In the case of motor fuel use, the renewable portion of the alcohol produced in this manner provides a reduction in greenhouse gases by 50% or more when compared to gasoline.

Claims

1. A continuous process for reducing the greenhouse gas release associated with the production of alcohol from natural gas by the anaerobic bioconversion of a combined gas substrate comprising carbon monoxide, hydrogen and carbon dioxide in an aqueous menstruum containing microorganisms suitable for converting said substrate to alcohol wherein the combined gas substrate is formed from at least two different gases comprising a first gas provided at least in part by a gas stream derived from the reforming of a hydrocarbonaceous gas and a second gas stream comprising carbon dioxide provided at least in part from a gas stream derived from a renewable resource, said process, comprising:

a) continuously contacting said combined gas substrate with said aqueous menstruum to bioconvert the combined gas substrate to alcohol and provide an alcohol-containing menstruum and a depleted gas phase;

b) continuously withdrawing at least a portion of the depleted gas phase from said aqueous menstruum; and

,

c) continuously or intermittently withdrawing a portion of said aqueous menstruum for recovery of said alcohol which contains carbon from a renewable resource, said withdrawal being sufficient to maintain the alcohol in said aqueous menstruum below a concentration that unduly adversely affects the microorganisms; and

, wherein the composition of the at least two different gases provide a gas substrate having a ratio of electrons to carbon atoms in the range of about 5.2;

1 to 6.8;

1,

wherein the depleted gas phase has a mass quantity of CO2 that is lower than the mass quantity of CO2 in the combined gas stream.

2. The process of claim 1 wherein the first gas stream is derived from the steam reforming of a natural gas stream comprising methane and at least 90% of the electrons available in the methane are conserved in the reformed gas produced by the steam reforming.

3. The process of claim 1 wherein the second gas stream comprises at least about 40 mole percent carbon dioxide and the combined gas substrate has a ratio of electrons to carbon in the range of 5.5:

1 and 6.5;

1.

4. The process of claim 1 wherein the second gas stream comprises renewable carbon and at least a portion of the carbon in the alcohol is from a renewable resource.

5. The process of claim 1 wherein the second gas stream comprises a carbon dioxide containing effluent from a carbohydrate to alcohol plant that converts carbohydrates to an ethanol product.

6. The process of claim 5 wherein a water stream, recovered from the step of conversion of the combined gas substrate to alcohol, passes to an evaporation unit associated with the carbohydrate to alcohol plant associated therewith for sterilization of the water stream and removal of sodium therefrom to produce a treated water stream that supplies water to the carbohydrate to alcohol plant.

7. The process of claim 5 wherein a water stream recovered from an evaporation unit associated with from the carbohydrate to alcohol plant supplies make-up water to the step of conversion of the combined gas substrate to alcohol.

8. The process of claim 1 wherein said alcohol is at least one alcohol selected from the group consisting of ethanol, propanol, i-butanol, or n-butanol.

9. The process of claim 1 wherein said alcohol is ethanol.

10. The process of claim 1 wherein said continuously contacting said combined gas substrate with said aqueous menstruum takes place in a bioreactor assembly that continuously passes at least a portion the combined gas substrate and the menstruum through one or more membrane modules while maintaining at least one of the modules at a ratio of electrons to carbon atoms in the range of about 5.2:

1 to 6.8;

1;

adding at least one of carbon monoxide, carbon dioxide and hydrogen to a substrate gas inflow of each module to obtain a desired range of electrons to carbon atoms therein;

maintaining a desired alcohol concentration in each of the modules;

withdrawing menstruum from one or modules and adding menstruum to one or more modules; and

, continuously withdrawing a substrate depleted gas phase from at least one of the modules.

11. An alcohol derived from the anaerobic bioconversion of a gas substrate by a process comprising:

a) steam reforming a carbonaceous gas from a non-renewable source to produce a reformed gas having an electron carbon ratio of greater than 7;

1 and at least 90% of the available electrons from the methane in the carbonaceous gas;

b) combining the reformed gas a with renewable gas derived from a renewable carbon source to provide a gas substrate comprising hydrogen, carbon monoxide, and carbon dioxide in which between about 20 and 70 percent of the carbon in the gas substrate is from renewable carbon in the renewable gas, the balance of the gas substrate stream is made from non-renewable carbon in the reformed gas, and the electron to carbon (e/C) ratio of the gas substrate is in a range from 5.5;

1 to 6.7;

1;

c) continuously contacting said substrate gas with an aqueous menstruum containing anaerobic microorganisms to bioconvert the substrate gas to alcohol and provide an alcohol-containing menstruum and a substrate depleted gas phase, wherein said contacting is in a bioreactor assembly containing said menstruum;

d) continuously withdrawing a substrate depleted gas phase from said aqueous menstruum, said depleted gas phase having a lower mass quantity of CO2 than the mass quantity of CO2 in the combined gas stream; and

,

e) continuously or intermittently withdrawing a portion of said menstruum for recovery of said alcohol, said withdrawal being sufficient to maintain the alcohol in said menstruum below a concentration that unduly adversely affects the microorganisms.

12. The process of claim 11 wherein the bioconversion of the gas substrate to alcohol converts at least about 85 mole percent of hydrogen and carbon oxides in the gas substrate.

13. The process of claim 11 in which between about 30 and 50 percent of the carbon in the gas substrate is from renewable carbon.

14. The process of claim 11 wherein said steam reforming is performed in a steam reformer having at least one gas reforming section and at least one hotbox section and at least a portion of the depleted gas phase is passed to the hotbox section of the steam reformer.

15. The process of claim 11 wherein said reformed gas and said renewable gas comprise at least about 25 mole percent carbon dioxide, said renewable gas having an electron to carbon ratio not greater than about 0.1:

1 to provide an overall gas substrate having an electron to carbon ratio in the range of about 5.5;

1 to 6.5;

1.

16. The process of claim 11 wherein the mole ratio of carbon dioxide to methane in the depleted gas phase is less than about 0.2:

1.

17. An integrated process for reducing the greenhouse gas release associated with making alcohol from natural gas that uses a combined gas substrate of 1) a CO2 rich gas from an anaerobic fermentation of carbohydrates and 2) a reformed natural gas that provides a substrate comprising carbon monoxide, hydrogen and carbon dioxide, the process comprising:

a. a carbohydrate substrate to alcohol process comprising;

i. bioconverting the carbohydrate substrate under fermentation conditions—

including the presence of a first biocatalyst and an aqueous broth containing the carbohydrate substrate—

to provide an alcohol-containing broth containing the biocatalyst and a carbon dioxide gas;

ii. removing the carbon dioxide gas from the alcohol-containing broth and recovering at least a portion of the carbon dioxide as a carbon dioxide stream;

iii. separating alcohol by distillation from said alcohol-containing broth and providing a whole stillage containing water, unconverted carbohydrates and at least a portion of the biocatalyst;

iv. separating the whole stillage by centrifugation to provide a thin stillage and distillers grains;

v. evaporating water from the thin stillage to provide a concentrate containing unconverted carbohydrates; and

,

b. a reformed gas to alcohol process comprising;

i. continuously introducing said combined gas substrate into a bioreactor assembly containing an aqueous menstruum and a second biocatalyst to bioconvert the combined gas substrate to alcohol and providing an alcohol-containing menstruum and a depleted gas phase;

ii. continuously withdrawing the depleted gas phase from said aqueous menstruum;

iii. continuously or intermittently withdrawing a portion of said menstruum for recovery of said alcohol,

iv. separating the withdrawn portion of said menstruum by distillation to provide alcohol and an aqueous stillage,

wherein at least a portion of the carbon dioxide stream from step (a)(ii) is used as a portion of the gas substrate in step (b)(i) to provide a gas substrate having an electron to carbon atom ratio of between about 5.2;

1 and 6.8;

1.

18. The process of claim 17 wherein at least a portion of the combined gas substrate of step (b)(i) comprises reformed gas derived from steam reforming.

19. The process of claim 17 where the carbohydrate substrate comprises sugar.

20. The process of claim 17 wherein 20 to 70 percent of the carbon oxides in the combined gas substrate comes from renewable carbon, the balance of the carbon oxides in the combined gas substrate comes from non-renewable carbon, and the e/C ratio is in a range from 5.5:

1 to 6.5;

1 and more preferably in the range of 5.7;

1 to 6.4;

1.

21. The process of claim 20 wherein 30 to 50% of the carbon oxides are from the processing of corn to make alcohol.

22. The process of claim 17 wherein the reformed gas substrate is produced by the non-oxidative reforming of a methane containing gas that conserves at least 90 and preferably at least 95% of the electrons available from the methane.