Process for producing ethanol

• US 20060019360A1
• Filed: 06/29/2005
• Published: 01/26/2006
• Est. Priority Date: 03/11/1999
• Status: Active Grant

• Current Assignee: ZeaChem, Inc.
• Original Assignee: ZeaChem, Inc.
• Inventors: Verser, Dan, Eggeman, Tim
• Granted Patent: US 7,351,559 B2
• Time in Patent Office: Days
• US Class Current: 435/161
• CPC Class Codes: C07C 29/149 with hydrogen or hydrogen-containing gases
• CPC Class Codes: C07C 31/08 Ethanol
• CPC Class Codes: C07C 67/08 by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
• CPC Class Codes: C07C 69/14 of monohydroxylic compounds
• CPC Class Codes: C12P 7/06 Ethanol, i.e. non-beverage
• CPC Class Codes: C12P 7/14 Multiple stages of fermentation; Multiple types of microorganisms or re-use of microorganisms
• CPC Class Codes: C12P 7/54 Acetic acid vinegar C12J
• CPC Class Codes: C12P 7/56 Lactic acid
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y02P 20/10 Process efficiency

Abstract

A process for producing ethanol including a combination of biochemical and synthetic conversions results in high yield ethanol production with concurrent production of high value coproducts. An acetic acid intermediate is produced from carbohydrates, such as corn, using enzymatic milling and fermentation steps, followed by conversion of the acetic acid into ethanol using esterification and hydrogenation reactions. Coproducts can include corn oil, and high protein animal feed containing the biomass produced in the fermentation.

Claims

1-56. -56. (canceled)

57. A method for effectively recovering an ester from a dilute solution of a carboxylic acid salt, comprising the steps of:

(a) acidifying said carboxylic acid salt with carbon dioxide to produce the corresponding carboxylic acid and calcium carbonate, and simultaneously esterifying the carboxylic acid with an alcohol to form an ester; and

(b) recovering said ester.

58. The method of claim 57, wherein said acidifying and esterifying take place at low or nearly atmospheric pressure.

59. The method of claim 57, wherein said calcium carbonate is recycled to a fermentation broth in order to help maintain a desired pH.

60. The method of claim 57, wherein said ester is a volatile ester.

61. The method of claim 57, wherein said alcohol is selected from the group consisting of methanol, ethanol, or mixtures thereof.

62. The method of claim 57, wherein said ester is recovered by distillation.

63. The method of claim 62, wherein said distillation is a reactive distillation is capable of pushing the acidification and esterification equilibria to high conversion to the desired ester product.

64. The method of claim 57, wherein said ester is converted to ethanol.

65. The method of claim 57, wherein said acidifying, esterifying and recovery take place in an reaction column, using the steps comprising:

(a) feeding a dilute solution of a carboxylic acid salt in water mixed with alcohol to the top of a reaction section of said column;

(b) feeding carbon dioxide gas to the bottom of the reaction section of said column;

(c) reacting carbon dioxide with said carboxylic acid salt and an alcohol in a reaction zone in a center section of said column, resulting in the formation of calcium carbonate and an ester of the carboxylic acid salt, wherein said ester is more volatile than water;

(d) concentrating said ester by vaporizing a mixture containing excess alcohol and water and an azeotrope comprising said ester, water and alcohol, and separating the azeotrope from the excess alcohol and water;

(e) returning the excess alcohol and water to the reaction zone.

66. The method of claim 65, wherein the step of concentrating said ester further comprises concentrating the ester present in said azeotrope.

67. The method of claim 66, wherein said azeotrope of ester, water and alcohol is broken by the addition of water, thereby causing a phase separation between an ester-rich portion on one hand and a water and alcohol-rich portion on the other.

68. A method for converting a carbohydrate source and a natural gas source to an easily transportable liquid product comprising the steps of:

(a) converting said carbohydrate source to acetic acid, acetate, or mixtures thereof by fermentation;

(b) converting said acetic acid, acetate, or mixtures thereof to ethyl acetate;

(c) converting at least part of said ethyl acetate to ethanol using hydrogen obtained from said natural gas source; and

(d) transporting said ethanol or ethyl acetate to a location different than the location where it is produced.

69. The method of claim 68, wherein said carbohydrate source and said natural gas source are located within an economically feasible distance of each other and wherein said remote location to which said ethanol or ethyl acetate is transported is located at a distance at which it is uneconomical to transport the natural gas and carbohydrate.

70. The method of claim 69, wherein said economically feasible distance is less than about 500 miles and wherein said uneconomical distance is greater than about 1,000 miles.

71. The method of claim 69, wherein said carbohydrate source and said natural gas source are located on one or more Caribbean Islands and said remote location is located on the Gulf Coast.

72. The method of claim 69, wherein said carbohydrate source and said natural gas source are located in Australia, New Zealand or both and said remote location is Japan, Taiwan, Korea or China.

73. The method of claim 68, wherein said fermentation comprises the production of lactic acid, lactate or mixtures thereof in a first fermentation and the production of acetate, acetic acid or mixtures thereof in a second fermentation.

74. The method of claim 68, wherein hydrogen is obtained from said natural gas by steam reforming.

75. A method to produce ethanol from a carbohydrate source wherein at least about 80% of carbon in said carbohydrate source is converted into said ethanol, said method comprising:

(a) enzymatically hydrolyzing said carbohydrate source to sugars and amino acids;

(b) converting carbohydrates, sugars and amino acids into lactic acid, lactate, or mixtures thereof by homolactic fermentation;

(c) converting said lactic acid, lactate, or mixtures thereof into acetic acid, acetate, or mixtures thereof by homoacetic fermentation;

(d) maintaining the pH of the fermentation broths at about pH 6 to about pH 8, using a base;

(e) obtaining a biomass byproduct which is useful as an animal feed from the fermentation;

(f) acidifying said acetate with carbon dioxide to produce acetic acid and calcium carbonate and simultaneously esterifying acetic acid with an alcohol to form acetate ester;

(g) recovering said acetate ester using reactive distillation;

(h) producing hydrogen by subjecting natural gas to steam reforming; and

(i) hydrogenating acetate ester to said ethanol.