Methods for producing biodiesel

Abstract

Transesterification, esterification, and esterification-transesterification (both one-step and two-step) for producing biofuels. The process may be enhanced by one or more of the following: 1) applying microwave or RF energy; 2) passing reactants over a heterogeneous catalyst at sufficiently high velocity to achieve high shear conditions; 3) emulsifying reactants with a homogeneous catalyst; or 4) maintaining the reaction at a pressure at or above autogeneous pressure. Enhanced processes using one or more of these steps can result in higher process rates, higher conversion levels, or both.

1 . A method of converting feedstock having carboxylic acid and triglyceride into a biodiesel using an esterification process and a transesterification process, the method comprising: 
 performing an esterification process including mixing the feedstock with an alcohol to produce a reactant mixture;    contacting the reactant mixture with an acid catalyst; and    applying RF or microwave energy to at least one of the carboxylic acid, the alcohol, the catalyst, the mixture and a combination thereof to convert the carboxylic acid to a biodiesel; and    performing a transesterification process to convert the triglyceride to a biodiesel.    
   
   
       2 . The method of  claim 1 , wherein the carboxylic acid comprises a free fatty acid derived from at least one of tall oil, rendered oils, animal fats, and soap stock.  
   
   
       3 . The method of  claim 1 , wherein the alcohol comprises a C1-C6 alcohol.  
   
   
       4 . The method of  claim 3 , wherein the alcohol comprises at least one of methanol and ethanol.  
   
   
       5 . The method of  claim 1 , wherein the acid catalyst comprises at least one of a zeolite in the acid form, a strong cation exchange resin in the hydrogen form, a Lewis acid, and mixtures thereof.  
   
   
       6 . The method of  claim 1 , further comprising maintaining a pressure at or greater than autogeneous pressure.  
   
   
       7 . The method of  claim 6 , further comprising maintaining a pressure between about 10 and about 100 psig above autogeneous pressure.  
   
   
       8 . The method of  claim 1 , wherein an average power density of the RF or microwave energy is maintained between about 0.01 watts/cc and about 100 watts/cc.  
   
   
       9 . The method of  claim 1 , wherein applying RF or microwave energy includes modulating the energy.  
   
   
       10 . The method of  claim 9 , wherein modulating includes at least one of amplitude modulation, frequency modulation, pulse width modulation, and combinations thereof.  
   
   
       11 . The method of  claim 1 , wherein the RF or microwave energy comprises a frequency from about 400 MHz to about 5 GHz.  
   
   
       12 . The method of  claim 1 , wherein the triglyceride and carboxylic acid are present in at least one of plant oil, animal oil and a combination thereof.  
   
   
       13 . The method of  claim 12 , wherein the triglyceride and carboxylic acid are present in an oil derived from at least one of soybeans, corn, sunflower, palm, nut, safflower, olives, cotton, linseed, mustard seed, rapeseed, canola, peanuts, coconut, castor beans, tall oil, soapstock, raw or rendered animal fats, brown grease, white grease, yellow grease, lard or tallow from pork, chicken, mutton, beef, horse and combinations thereof, as well as wastes, effluents and residues from the processing of such materials, and combinations thereof.  
   
   
       14 . The method of  claim 1 , wherein performing the transesterification process includes combining the reactant mixture with a second catalyst comprising at least one of an alkaline catalyst and an acid catalyst.  
   
   
       15 . The method of  claim 14 , wherein the second catalyst comprises at least one of a hydroxide of Group 1 or 2 metals, a silicate of Group 1 or 2 metals, a carbonate of Group 1 or 2 metals, a strong anion exchange resin in the hydroxide form, an oxide of aluminum and magnesium, zeolite in the acid form, a strong cation exchange resin in the hydrogen form, a Lewis acid, and mixtures thereof.  
   
   
       16 . The method of  claim 1 , wherein the second catalyst is a heterogeneous catalyst and wherein a relative velocity between the reactant mixture and the catalyst is at least about 0.005 m/s.  
   
   
       17 . The method of  claim 1 , wherein the second catalyst is a homogeneous catalyst, and wherein the method further comprises emulsifying the reactant mixture with the second catalyst.  
   
   
       18 . A method of converting a triglyceride to an alkyl ester and glycerol using a transesterification process, the method comprising: 
 mixing the triglyceride with an alcohol to produce a reactant mixture;    flowing the reactant mixture over a heterogeneous catalyst with a relative velocity of at least 0.005 m/s to obtain high reactant shear at a reactant-catalyst interface; and    producing alkyl ester and glycerol.    
   
   
       19 . The method of  claim 18 , wherein mixing occurs before flowing.  
   
   
       20 . The method of  claim 18 , wherein mixing occurs at the same time as flowing.  
   
   
       21 . The method of  claim 18 , wherein the triglyceride are present in at least one of plant oil, animal oil and a combination thereof.  
   
   
       22 . The method of  claim 21 , wherein the triglyceride is present in an oil derived from at least one of soybeans, corn, sunflower, palm, nut, safflower, olives, cotton, linseed, mustard seed, rapeseed, canola, peanuts, coconut, castor beans, tall oil, soapstock, raw or rendered animal fats, brown grease, white grease, yellow grease, lard or tallow from pork, chicken, mutton, beef, horse and combinations thereof, as well as wastes, effluents and residues from the processing of such materials, and combinations thereof.  
   
   
       23 . The method of  claim 18 , wherein the alcohol comprises a C1-C6 alcohol.  
   
   
       24 . The method of  claim 23 , wherein the alcohol comprises at least one of methanol and ethanol.  
   
   
       25 . The method of  claim 18 , wherein mixing includes combining the triglyceride and the alcohol in a ratio of at least about 10% alcohol by weight.  
   
   
       26 . The method of  claim 18 , wherein the catalyst comprises at least one of an alkaline catalyst and an acid catalyst.  
   
   
       27 . The method of  claim 26 , wherein the catalyst comprises at least one of a hydroxide of Group 1 or 2 metals, a silicate of Group 1 or 2 metals, a carbonate of Group 1 or 2 metals, a strong anion exchange resin in the hydroxide form, an oxide of aluminum and magnesium and mixtures thereof.  
   
   
       28 . The method of  claim 26 , wherein the catalyst comprises at least one of a zeolite in the acid form, a strong cation exchange resin in the hydrogen form, a Lewis acid, and mixtures thereof.  
   
   
       29 . The method of  claim 18 , wherein the relative velocity between the reactant mixture and the catalyst is at least about 0.01 m/s.  
   
   
       30 . The method of  claim 29 , wherein the relative velocity between the reactant mixture and the catalyst is at least about 0.05 m/s.  
   
   
       31 . The method of  claim 18 , further comprising maintaining a pressure at or greater than autogeneous pressure.  
   
   
       32 . The method of  claim 31 , wherein the method takes place at a pressure between about 10 psig and about 100 psig above the autogeneous pressure.  
   
   
       33 . The method of  claim 18 , further comprising applying RF or microwave energy to at least one of the triglyceride, the alcohol, the catalyst, and a combination thereof.  
   
   
       34 . The method of  claim 33 , wherein applying RF or microwave energy includes controlling at least one of a frequency, power density, field strength, and a combination thereof.  
   
   
       35 . The method of  claim 34 , wherein an average power density is maintained between about 0.01 watts/cc and about 100 watts/cc.  
   
   
       36 . The method of  claim 35 , wherein an average power density is maintained between about 0.05 watts/cc and about 10 watts/cc.  
   
   
       37 . The method of  claim 36 , wherein an average power density is maintained between about 0.1 watts/cc and about 3 watts/cc.  
   
   
       38 . The method of  claim 33 , wherein applying RF or microwave energy includes modulating the energy.  
   
   
       39 . The method of  claim 38 , wherein modulating includes at least one of amplitude modulation, frequency modulation, pulse width modulation, and combinations thereof.  
   
   
       40 . The method of  claim 33 , wherein the RF or microwave energy comprises a frequency from about 1 MHz to about 100 GHz.  
   
   
       41 . The method of  claim 40 , wherein the RF or microwave energy comprises a frequency from about 100 MHz to about 10 GHz.  
   
   
       42 . The method of  claim 41 , wherein the RF or microwave energy comprises a frequency from about 400 MHz to about 5 GHz.  
   
   
       43 . A method of converting a triglyceride to an alkyl ester and glycerol using a transesterification process, the method comprising: 
 mixing the triglyceride with an alcohol to produce a reactant mixture;    emulsifying the reactant mixture with a homogeneous catalyst;    applying RF or microwave energy to at least one of the triglyceride, the alcohol, the catalyst, and a combination thereof, and producing alkyl ester and glycerol.    
   
   
       44 . The method of  claim 43 , wherein the triglyceride is present in at least one of plant oil and animal oil.  
   
   
       45 . The method of  claim 44 , wherein the triglyceride is present in an oil derived from at least one of soybeans, corn, sunflower, palm, nut, safflower, olives, cotton, linseed, mustard seed, rapeseed, canola, peanuts, coconut, castor beans, tall oil, soapstock, raw or rendered animal fats, brown grease, white grease, yellow grease, lard or tallow from pork, chicken, mutton, beef, horse and combinations thereof, as well as wastes, effluents and residues from the processing of such materials, and combinations thereof.  
   
   
       46 . The method of  claim 43 , wherein the alcohol comprises a C1-C6 alcohol.  
   
   
       47 . The method of  claim 46 , wherein the alcohol comprises at least one of methanol and ethanol.  
   
   
       48 . The method of  claim 43 , wherein mixing includes combining the triglyceride and the alcohol in a ratio of at least about 10% alcohol by weight.  
   
   
       49 . The method of  claim 43 , wherein the catalyst comprises at least one of an alkaline catalyst and an acid catalyst.  
   
   
       50 . The method of  claim 43 , further comprising maintaining a pressure at or greater than autogeneous pressure.  
   
   
       51 . The method of  claim 50 , wherein the method takes place at a pressure between about 10 and about 100 psig above the autogeneous pressure.  
   
   
       52 . The method of  claim 43 , further comprising applying RF or microwave energy to at least one of the triglyceride, the alcohol, the catalyst, and a combination thereof.  
   
   
       53 . The method of  claim 52 , applying RF or microwave energy includes controlling at least one of a frequency, power density, field strength, and a combination thereof of the RF or microwave energy to control the reaction between the catalyst and the reactants.  
   
   
       54 . The method of  claim 53 , wherein an average power density is maintained between about 0.01 watts/cc and about 100 watts/cc.  
   
   
       55 . The method of  claim 54 , wherein an average power density is maintained between about 0.05 watts/cc and about 10 watts/cc.  
   
   
       56 . The method of  claim 55 , wherein an average power density is maintained between about 0.1 watts/cc and about 3 watts/cc.  
   
   
       57 . The method of  claim 52 , wherein applying RF or microwave energy includes modulating the energy.  
   
   
       58 . The method of  claim 57 , wherein modulating includes at least one of amplitude modulation, frequency modulation, pulse width modulation, and combinations thereof.  
   
   
       59 . The method of  claim 52 , wherein the RF or microwave energy comprises a frequency from about 1 MHz to about 100 GHz.  
   
   
       60 . The method of  claim 59 , wherein the RF or microwave energy comprises a frequency from about 100 MHz to about 10 GHz.  
   
   
       61 . The method of  claim 60 , wherein the RF or microwave energy comprises a frequency from about 400 MHz to about 5 GHz.  
   
   
       62 . A method of converting a carboxylic acid to an alkyl ester using an esterification process, the method comprising: 
 mixing the carboxylic acid with an alcohol to produce a reactant mixture;    contacting the reactant mixture with an acid catalyst; and    applying RF or microwave energy to at least one of the carboxylic acid, the alcohol the catalyst and a combination thereof to produce an alkyl ester.    
   
   
       63 . The method of  claim 62 , wherein mixing occurs before flowing.  
   
   
       64 . The method of  claim 62 , wherein mixing occurs at the same time as flowing.  
   
   
       65 . The method of  claim 62 , wherein the carboxylic acid comprises a free fatty acid derived from at least one of tall oil, rendered oils, animal fats, and soap stock.  
   
   
       66 . The method of  claim 62 , wherein the alcohol comprises a C1-C6 alcohol.  
   
   
       67 . The method of  claim 66 , wherein the alcohol comprises at least one of methanol and ethanol.  
   
   
       68 . The method of  claim 62 , wherein mixing includes combining the carboxylic acid and the alcohol in a ratio of at least about 11% alcohol by weight.  
   
   
       69 . The method of  claim 62 , wherein the catalyst comprises an acid catalyst.  
   
   
       70 . The method of  claim 69 , wherein the acid catalyst comprises at least one of a zeolite in the acid form, a strong cation exchange resin in the hydrogen form, a Lewis acid, and mixtures thereof.  
   
   
       71 . The method of  claim 62 , further comprising maintaining a pressure at or greater than autogeneous pressure.  
   
   
       72 . The method of  claim 71 , wherein the method takes place at a pressure between about 10 and about 100 psig above the autogeneous pressure.  
   
   
       73 . The method of  claim 62 , wherein applying RF or microwave energy includes controlling at least one of a frequency, power density, field strength, and a combination thereof.  
   
   
       74 . The method of  claim 62 , wherein an average power density is maintained between about 0.01 watts/cc and about 100 watts/cc.  
   
   
       75 . The method of  claim 62 , wherein applying RF or microwave energy includes modulating the energy.  
   
   
       76 . The method of  claim 75 , wherein modulating includes at least one of amplitude modulation, frequency modulation, pulse width modulation, and combinations thereof.  
   
   
       77 . The method of  claim 62 , wherein the RF or microwave energy comprises a frequency from about 1 MHz to about 100 GHz.  
   
   
       78 . A method of converting a carboxylic acid to an alkyl ester using an esterification process, the method comprising: 
 mixing the carboxylic acid with an alcohol to produce a reactant mixture; 
 flowing the reactant mixture over a heterogeneous acid catalyst with a relative velocity of at least 0.005 m/s to obtain high reactant shear at a reactant-catalyst interface; and  
   producing alkyl ester.    
   
   
       79 . The method of  claim 78 , wherein mixing occurs before flowing.  
   
   
       80 . The method of  claim 78 , wherein mixing occurs at the same time as flowing.  
   
   
       81 . The method of  claim 78 , wherein the carboxylic acid comprises a free fatty acid derived from at least one of tall oil, rendered oils, animal fats, and soap stock.  
   
   
       82 . The method of  claim 78 , wherein the alcohol comprises a C1-C6 alcohol.  
   
   
       83 . The method of  claim 82 , wherein the alcohol comprises at least one of methanol and ethanol.  
   
   
       84 . The method of  claim 78 , wherein mixing includes combining the carboxylic acid and the alcohol in a ratio of at least about 11% alcohol by weight.  
   
   
       85 . The method of  claim 84 , wherein the catalyst comprises at least one of a zeolite in the acid form, a strong cation exchange resin in the hydrogen form, a Lewis acid, and mixtures thereof.  
   
   
       86 . The method of  claim 78 , wherein the relative velocity between the reactant mixture and the catalyst is at least about 0.01 m/s.  
   
   
       87 . The method of  claim 86 , wherein the relative velocity between the reactant mixture and the catalyst is at least about 0.05 m/s.  
   
   
       88 . The method of  claim 78 , further comprising maintaining a pressure at or greater than autogeneous pressure.  
   
   
       89 . The method of  claim 88 , wherein the method takes place at a pressure between about 10 and about 100 psig above the autogeneous pressure.  
   
   
       90 . The method of  claim 78 , further comprising applying RF or microwave energy to at least one of the carboxylic acid, the alcohol, the catalyst, and a combination thereof.  
   
   
       91 . The method of  claim 90 , wherein applying RF or microwave energy includes controlling at least one of a frequency, power density, field strength, and a combination thereof.  
   
   
       92 . The method of  claim 91 , wherein an average power density is maintained between about 0.01 watts/cc and about 100 watts/cc.  
   
   
       93 . The method of  claim 92 , wherein an average power density is maintained between about 0.05 watts/cc and about 10 watts/cc.  
   
   
       94 . The method of  claim 93 , wherein an average power density is maintained between about 0.1 watts/cc and about 3 watts/cc.  
   
   
       95 . The method of  claim 90 , wherein applying RF or microwave energy includes modulating the energy.  
   
   
       96 . The method of  claim 95 , wherein modulating includes at least one of amplitude modulation, frequency modulation, pulse width modulation, and combinations thereof.  
   
   
       97 . The method of  claim 95 , wherein the RF or microwave energy comprises a frequency from about 1 MHz to about 100 GHz.  
   
   
       98 . The method of  claim 97 , wherein the RF or microwave energy comprises a frequency from about 100 MHz to about 10 GHz.  
   
   
       99 . The method of  claim 98 , wherein the RF or microwave energy comprises a frequency from about 400 MHz to about 5 GHz.  
   
   
       100 . A method of converting a carboxylic acid to an alkyl ester using an esterification process, the method comprising: 
 mixing the carboxylic acid with an alcohol to produce a reactant mixture;    emulsifying the reactant mixture with a homogeneous acid catalyst;    applying RF or microwave energy to at least one of the carboxylic acid, the alcohol, the catalyst, and a combination thereof; and    producing alkyl ester.    
   
   
       101 . The method of  claim 100 , wherein the carboxylic acid comprises a free fatty acid derived from at least one of tall oil, rendered oils, animal fats, and soap stock.  
   
   
       102 . The method of  claim 100 , wherein the alcohol comprises a C1-C6 alcohol.  
   
   
       103 . The method of  claim 102 , wherein the alcohol comprises at least one of methanol and ethanol.  
   
   
       104 . The method of  claim 100 , wherein mixing includes combining the carboxylic acid and the alcohol in a ratio of at least about 11% alcohol by weight.  
   
   
       105 . The method of  claim 100 , further comprising maintaining a pressure at or greater than autogeneous pressure.  
   
   
       106 . The method of  claim 105 , wherein the method takes place at a pressure between about 10 and about 100 psig above the autogeneous pressure.  
   
   
       107 . The method of  claim 100 , further comprising applying RF or microwave energy to at least one of the carboxylic acid, the alcohol, the catalyst, and a combination thereof.  
   
   
       108 . The method of  claim 107 , applying RF or microwave energy includes controlling at least one of a frequency, power density, field strength, and a combination thereof.  
   
   
       109 . The method of  claim 107 , wherein an average power density is maintained between about 0.01 watts/cc and about 100 watts/cc.  
   
   
       110 . The method of  claim 109 , wherein an average power density is maintained between about 0.05 watts/cc and about 10 watts/cc.  
   
   
       111 . The method of  claim 110 , wherein an average power density is maintained between about 0.1 watts/cc and about 3 watts/cc.  
   
   
       112 . The method of  claim 107 , wherein applying RF or microwave energy includes modulating the energy.  
   
   
       113 . The method of  claim 112 , wherein modulating includes at least one of amplitude modulation, frequency modulation, pulse width modulation, and combinations thereof.  
   
   
       114 . The method of  claim 107 , wherein the RF or microwave energy comprises a frequency from about 1 MHz to about 100 GHz.  
   
   
       115 . The method of  claim 114 , wherein the RF or microwave energy comprises a frequency from about 100 MHz to about 10 GHz.  
   
   
       116 . The method of  claim 115 , wherein the RF or microwave energy comprises a frequency from about 400 MHz to about 5 GHz.