Abstract:
A process for producing fatty acid methyl esters includes mixing an alcohol with a feedstock oil to prepare an alcohol/oil mixture, then reacting the alcohol/oil mixture using a first heterogeneous catalyst in an acid esterification process to produce a glycerin-containing product. The glycerin is separated from the glycerin-containing product using a coalescer to produce a biodiesel-containing feedstock and glycerin. Biodiesel is separated from the biodiesel-containing feedstock using a coalescer to produce unreacted feedstock and biodiesel. The unreacted feedstock is reacted using a second heterogeneous catalyst in a trans-esterification process to produce a glycerin-biodiesel-methanol mixture. Biodiesel and glycerin are separated in separate streams from the glycerin-biodiesel-methanol mixture, using a coalescer, to produce additional glycerin and additional biodiesel.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority pursuant to 35 U.S.C. §119(e) to U.S. provisional application Ser. No. 61/382,839, filed Sep. 14, 2010, which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field The present disclosure relates to a process for the production of fatty acid methyl esters (e.g., biodiesel), and more particularly to such a process using variable feedstock and heterogeneous catalysts. 
         [0003]    2. Description of Related Art Typical biodiesel production processes are centered on the trans-esterification of low Free Fatty Acid (FFA) lipids. FFA levels vary from 0% in highly refined and treated oils such Soybean or Canola oils to 100% in Coconut oil. When FFA&#39;s are present they are saponified (turned into soap) by the trans-esterification reaction and represent a loss in yield unless pre-treated through acid esterification. 
         [0004]    Traditional catalysts for acid esterification and base trans-esterification are homogeneous catalysts, which is to say they are in the same phase as the reactants (liquids in this case) and cannot be separated. When acid esterification is used, the acid is neutralized by a base, typically by the base catalyst which may then be used to carry out a base catalyzed trans-esterification reaction. However, the neutralization of the acid creates impurities in the form of salts which for biodiesel applications requires removal from the product stream. In the case where a producer does not use acid esterification to treat the FFA&#39;s in their feedstock, the resulting soap may also require removal from the product streams. In either case, time and energy are expended to remove excess catalyst, salts, or soap to obtain a product that may be used as biodiesel. It would be desirable to reduce or eliminate such requirements. 
       SUMMARY 
       [0005]    A process for producing fatty acid methyl esters may include mixing an alcohol (for example, methanol) with a feedstock oil to prepare an alcohol/oil mixture, then reacting the alcohol/oil mixture using a first heterogeneous catalyst in an acid esterification process to produce a glycerin-containing product. The glycerin may be separated from the glycerin-containing product using a coalescer to produce a biodiesel-containing feedstock and glycerin. Biodiesel may be separated from the biodiesel-containing feedstock using a coalescer to produce unreacted feedstock and biodiesel. The unreacted feedstock may be reacted using a second heterogeneous catalyst in a trans-esterification process to produce a glycerin-biodiesel-methanol mixture. Optionally, the process may include mixing the unreacted feedstock with additional alcohol prior to the reacting. In the alternative, or in addition, the process may include heating the unreacted feedstock prior to the reacting. Biodiesel and glycerin may be separated in separate streams from the glycerin-biodiesel-methanol mixture, using a coalescer, to produce additional glycerin and additional biodiesel. 
         [0006]    In an aspect, the process may further include producing the feedstock oil from an oily or fatty organic waste product derived from an animal or vegetable source. In another 
         [0007]    In another aspect, the process may further include recovering excess alcohol from a mixture of the biodiesel and additional biodiesel to prepare an intermediate biodiesel. Accordingly, the process may include separating a second additional glycerin stream from the intermediate biodiesel. In addition, the process may further include polishing the intermediate biodiesel to produce a refined biodiesel. This polishing may be performed using a dry polishing process. 
         [0008]    In another aspect of the process, the first heterogeneous catalyst may be, or may include, a heterogeneous strong acid cation catalyst. The second heterogeneous catalyst may be, or may include, a heterogeneous strong base anion catalyst. In a related aspect, all process steps may be free of any use of a homogeneous catalyst. 
         [0009]    Advantages of the processes as disclosed herein may include, for example, avoiding any use homogeneous catalysts, thereby avoiding the disadvantages of homogenous catalysts as summarized above. For example, the process may requires less energy to operate the processing equipment because of the use of heterogeneous catalysts. Further energy savings may be realized by the use of coalescers instead of centrifuges to recover heterogeneous catalysts. The process may be used to process variable oily feedstock with FFA ranges from 0% to 100%, and more preferably between about 1% and 100%. The process may produce a cleaner glycerin stream that requires less refining than current methods. Furthermore, the process may produce a cleaner biodiesel stream that requires less refining than current methods. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic diagram illustrating a system for processing a variable feedstock oil to obtain biodiesel and glycerin. 
           [0011]      FIG. 2  is a flow diagram illustrating an example of a process flow by which a variable feedstock oil may be converted into biodiesel and glycerin. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    A system  100  and process  200  for the production of fatty acid methyl esters from variable feedstock is shown in  FIGS. 1 and 2 , respectively. The system  100  and process  200  may that use heterogeneous catalysts to perform the acid catalyzed and base catalyzed reactions is disclosed herein. The novel system and process may include a combination of acid esterification  210  using a suitable heterogeneous catalyst together with base esterification  220  using a suitable heterogeneous catalyst, in an integrated process  100 . Accordingly, the use of homogeneous catalysts with their accompanying disadvantages in the production of fatty acid methyl esters from variable feedstock may be avoided altogether. 
         [0013]    Additionally, this process may utilize coalescers to perform the task of separating various materials normally reserved for centrifuges or gravity separation, for example, the coalescers  114 ,  116 ,  128 ,  132  and  144  shown in system  100  of  FIG. 1 . These coalescers may be mechanical liquid-liquid coalescers as used in the refining art to separate hydrocarbons from aqueous liquids. Corresponding coalescing operations  212 ,  214 ,  224 ,  226 , and  236  are depicted in the process  100  of  FIG. 2 . Coalescers offer the advantages of speed and compact size over gravity separation and energy efficiency and low maintenance over centrifuges. 
         [0014]    Using the multiple coalescers, the system  200  and process  100  may perform several more product separations than conventional processes. Reactions in the process  100 , as with any chemical reaction, proceed in a manner until equilibrium is established. By frequently removing products, the reaction dynamics may be shifted towards the production of more products at an increased rate. 
         [0015]    The benefits of the disclosed system  100  and process  200  may include lower equipment costs resulting from the use of non-corrosion resistant materials because the use non-corrosive catalysts do not necessitate it. A further benefit may include the production of product streams requiring significantly less refinement to meet ASTM or EIN specifications, because there are no excess catalysts that need to be treated or impurities (salts) present from the neutralization of catalysts. Use of the process may enable reduction of operating costs related to the use of non-hazardous catalysts which do not require special handling or storage procedures as compared to soluble acids and bases, and the use of low maintenance coalescers which have no moving parts and do not require frequent maintenance schedules. 
         [0016]    The catalyst for the acid esterification step  210  may be a heterogeneous strong acid cation catalyst, for example, an insoluble polymeric strong acid catalyst. The acid esterification operation  210  may be performed using a series of fixed bed heterogeneous esterification catalyst beds  108 ,  110 ,  112  receiving a pretreated feedstock from a crude feedstock reservoir  102  passed through a pretreatment processor  104  and mixed with an alcohol (e.g., methanol) provided  206  from an alcohol reservoir  106  via a mixing valve. The catalyst for the base trans-esterification step may be a heterogeneous strong base anion catalyst, for example, an insoluble polymeric strong base catalyst. The base trans-esterification operation  210  may be performed using a series of fixed bed heterogeneous trans-esterification catalyst beds  122 ,  124  and  126  receiving unreacted (recovered) feedstock oil from the coalescer  114  and alcohol from the reservoir  106  mixed via an intervening mixing valve. The method of containment for the heterogenous catalyst may follow manufacturer&#39;s recommendation. 
         [0017]    The feedstock  102  may be provided  202  to a pre-treatment unit  104 , which may perform a pretreatment process  204  including filtering, drying and heating until MIU is less than a desired threshold (e.g., less than 2%), the moisture content is less than a separate defined threshold (e.g., below 1%), and there are no impurities above a third threshold (e.g. greater than 50 microns). More extensive filtration, for example to exclude impurities greater than 5 microns may be preferred or required, depending on the intended application. In addition, the feedstock may be heated  204  in the unit  104  to a temperature required in order to achieve a flow rate as recommended by the catalyst manufacturer for the catalyst used in the reaction vessels  108 ,  110 ,  112 . In general, the feedstock viscosity decreases, and flow rate therefore increases, in proportion to temperature depending on the average molecular weight and other properties of the feedstock. One of ordinary skill may determine an optimal temperature and quantity of heating required for a particular feedstock and heterogeneous catalyst in use. 
         [0018]    After pretreatment including filtration, drying and heating  204 , methanol or other alcohol may be mixed  208  with the feedstock oil, for example, using a mixing valve as shown in system  100 . This mixture may be sent to the acid esterification reaction vessels  108 ,  110 ,  112 . Again the flow rate may be as specified by the catalyst manufacturer. The acid esterification process  210  using the heterogenous catalyst may produce crude fatty acid methyl esters (FAME) and crude glycerin. Multiple reaction vessels  108 ,  110 ,  112  may be used in order to achieve the production volumes required. 
         [0019]    The resulting FAME/glycerin product stream from the reaction vessels may be sent to a coalescer  116  for performing a first coalescing process  212  to separate the crude glycerin product from the rest of the product stream. It is anticipated that the input to the first coalescer  116  will include some substantial proportion of unreacted feedstock. The first coalescer may separate the product stream into a crude glycerin stream and a mixed FAME/unreacted feedstock stream. The crude glycerin stream may be sent to the crude glycerin storage unit  142  to be held  222  until further processing. 
         [0020]    The other product stream from the first coalescer  116 , comprising mixed FAME and unreacted feedstock which has had the glycerin removed from it, may now be provided to a second coalescer  114  to separate the crude biodiesel from unreacted feedstock using a second coalescing process  214 . The second coalescing process  214  may produce a crude biodiesel output stream and a separate unreacted feedstock steam. The crude biodiesel stream may be sent to the crude biodiesel storage unit  118  to be held  232  for further processing. 
         [0021]    The second product stream from the second coalescer  114  should now contain only (or primarily) the unreacted feedstock oil, possible including residual methanol. As shown at  216 , the unreacted feedstock may be mixed with the desired amount of methanol to obtain a feedstock oil mixture, using a mixing valve. After mixing it may be necessary to heat  218  the feedstock oil mixture in order to achieve the desired flow rate required by the trans-esterification catalyst, using a pre-treatment unit  120 . The heated feedstock mixture may be provided to the trans-esterification reaction vessels  122 ,  124 .  126  for performing a base trans-esterification process  220 . Multiple reaction vessels may be employed in order to achieve the production volumes required. 
         [0022]    The resultant product stream from the trans-esterification process  220  may now include crude biodiesel, crude glycerin and excess methanol. This resultant product stream may be sent to a third coalescer  128  performing a coalescing process  224  to separate the crude glycerin from the biodiesel and methanol product stream. The crude glycerin stream may be sent to the crude glycerin storage unit  142  to be accumulated and held  222  for further processing. The crude biodiesel stream may be sent to the crude biodiesel storage  118  to be held  232  for further processing  234  for recovery of residual methanol. 
         [0023]    From the crude biodiesel storage  118 , biodiesel may be sent to the methanol recovery unit  130 . Any suitable method and equipment may be utilized in process  234  for methanol recovery, as known to one of ordinary skill in the art. The resultant methanol stream may be returned to methanol storage  106 ,  206  to be recycled for treating more feedstock. 
         [0024]    The resultant biodiesel product stream from the methanol recovery unit  130  performing the recovery process  234  may be sent to a fourth coalescer  132  performing a coalescing process  236  to separate any remaining crude glycerin from the crude biodiesel. The crude glycerin stream from the coalescer  132  may be sent to the crude glycerin storage  142  to be held  222  for further processing. 
         [0025]    The crude biodiesel stream from the fourth coalescer  132  performing a coalescing process  236  may be provided to the biodiesel polishing units  134 ,  136 ,  138  performing any suitable drying and polishing process  238  as known in the art. One of ordinary skill in the art may use any suitable methods and equipment for drying and polishing  238  the crude FAME to produce refined FAME/biodiesel output at  240 . A dry polishing method, as opposed to water washing, may be preferable. The resulting refined biodiesel may be sent to a storage unit  140 . 
         [0026]    From the crude glycerin storage unit  142 , glycerin may be provided to a fifth coalescer  144  performing a coalescing process  226  to separate refined glycerin from waste MONG (Matter Organic Non-Glycerol). In the alternative, the crude glycerin may be refined by any suitable alternate method as known in the art. The resulting refined glycerin may be provided to a storage unit  146 . The resulting waste MONG may be accumulated and held  228  in a storage unit  148  until disposal as a first byproduct. The refined glycerin may be provided to the glycerin storage unit  146 , where it may be accumulated and held  230  until disposal as a second byproduct. Thus, the system  100  and process  200  may be used to convert an input of variable feedstock oils and methanol into refined biodiesel, refined glycerin, and MONG outputs for any suitable application. Residual methanol may be recovered and reused, while the heterogeneous catalysts are not consumed. However, the catalysts may lose effectiveness over time and need to be replaced. 
         [0027]    Having thus described an embodiment of a process for the production of fatty acid methyl esters (e.g., biodiesel) using variable feedstock and heterogeneous catalysts, it should be apparent to those skilled in the art that certain advantages of the within system have been achieved. It should also be appreciated that various modifications, adaptations, and alternative embodiments thereof may be made without departing from the scope and spirit of the present technology. The scope of what is claimed should be determined by the appended claims interpreted in accordance with the foregoing specification, and is not limited by the examples hereinabove.