Abstract:
The present disclosure relates generally to processes and systems for the hydrodeoxygenation of an oxygenate feedstock that increases the conversion of oxygenates to hydrocarbons while avoiding detrimental effects resulting from increasing the severity of the hydrodeoxygenation reaction.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a non-provisional application which claims the benefit of and priority to U.S. Provisional Application Ser. No. 62/299,521 filed Feb. 23, 2016, titled “Systems for Hydrodeoxygenation of Oxygenates,” which is hereby incorporated by reference in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    None. 
       FIELD OF THE INVENTION 
       [0003]    The present invention relates to improvements in the hydrodeoxygenation of oxygenates. 
       BACKGROUND 
       [0004]    In typical applications for hydrocarbon production from oxygenated hydrocarbons, also known as oxygenates, the raw oxygenate feedstock is subjected to hydrodeoxygenation (HDO). Chemically, hydrodeoxygenation removes oxygen from the feedstock molecules in the presence of gaseous hydrogen and a HDO catalyst, and rejects it in the form of water. Oxygenates can have different relativities during HDO. Certain oxygenates, such as those with either low molecular weights or phenolic compounds, have a lower HDO reactivity than other oxygenates. Increasing the severity of the HDO process (e.g., increasing reaction temperature, increasing residence time, increasing hydrogen partial pressure) can be employed to insure these refractory oxygenates are converted. However, undesired side reactions such as cracking to lights and coking of the catalyst are also promoted at higher HDO severities. The final oxygenate conversion during HDO is typically a compromise between the product value lost in the form of unreacted oxygenates, and the cost savings in the form of higher overall HDO product yield and longer catalyst run times. 
         [0005]    Following HDO, unreacted oxygenates in the initial HDO product will typically partition between the hydrocarbon and the aqueous portions of the initial HDO product stream. Because oxygenates are typically highly polar, the unreacted oxygenates tend to partition preferentially into the water phase of the initial HDO product. Although the hydrocarbon portion of the initial HDO product can be subjected to additional HDO polishing or separation, the aqueous portion containing large amounts of unreacted oxygenates typically is either discarded or subjected to an energy intensive separation of water from the oxygenates. 
         [0006]    Subjecting the aqueous HDO product to additional HDO is extremely difficult due to the elevated water content which increases the heating and cooling requirements, damages the HDO catalyst, lowers the hydrogen partial pressure during subsequent HDO, and increases the required size and cost of the second HDO reactor. 
         [0007]    Accordingly, a need exists for systems that allow more efficient HDO of oxygenates without increasing the severity of the process. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0008]    Certain embodiments of the present inventive system comprise a system for the hydrodeoxygenation of oxygenates, comprising: a) a reactor containing a hydrodeoxygenation catalyst and configured to contact the hydrodeoxygenation catalyst with an feedstock comprising oxygenates to produce an at least partially-deoxygenated product; b) a first separator operable to receive the partially-deoxygenated product and phase-separate the partially-deoxygenated product into an aqueous phase comprising unreacted oxygenates, a non-aqueous phase comprising hydrocarbons, and light gases comprising hydrogen; c) a mixer configured to receive the aqueous phase and to mix the aqueous phase with a solvent that is immiscible with water to produce an emulsion, wherein the solvent is capable of dissolving unreacted oxygenates; d) a second separator configured to receive the emulsion and phase separation of the aqueous phase from the solvent, thereby allowing extraction of unreacted oxygenates from the aqueous phase into the solvent and producing a solvent comprising unreacted oxygenates; d) a distillation apparatus configured to receive the solvent comprising unreacted oxygenates and to produce a separated solvent and separated unreacted oxygenates. e) a conduit configured to receive the separated unreacted oxygenates and return them to the reactor. 
         [0009]    Certain embodiments of the system further comprise a light gas purifier operable to receive the light gases from the first separator and to produce separated hydrogen gas, wherein said light gas purifier is further configured to redirect the separated hydrogen gas to the reactor. 
         [0010]    Certain embodiments of the system further comprise a conduit configured to receive the separated solvent and return it to the mixer. 
         [0011]    Certain inventive embodiments comprise a process for hydrodeoxygenation of oxygenates, comprising: a) contacting a feedstock comprising oxygenates with a hydrodeoxygenation catalyst in the presence of hydrogen gas at a temperature and pressure suitable for hydrodeoxygenation of at least a portion of the oxygenates to produce a partially-deoxygenated product; b) phase-separating the partially-deoxygenated product into an aqueous phase comprising unreacted oxygenates, a non-aqueous phase comprising hydrocarbons, and light gases comprising hydrogen; c) mixing the aqueous phase with a water-insoluble solvent and extracting unreacted oxygenates from the aqueous phase into the water insoluble solvent, followed by separating the phases to produce a solvent comprising unreacted oxygenates; d) distilling the solvent to produce a separated solvent and separated unreacted oxygenates, where the separated unreacted oxygenates are utilized as at least a portion of the oxygenate feedstock. 
         [0012]    In certain embodiments of the process, the light gases are separated to recover hydrogen that is recycled for use in the HDO reaction. 
         [0013]    In certain embodiments of the process, the separated solvent is utilized as at least a portion of the water insoluble solvent. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    A more complete understanding of the present invention and benefits thereof may be acquired by referring to the follow description taken in conjunction with the accompanying drawings in which: 
           [0015]    The FIGURE is a simplified schematic in accordance with an embodiment of the present disclosure. 
       
    
    
       [0016]    The invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale. It should be understood that the drawings and their accompanying detailed descriptions are not intended to limit the scope of the invention to the particular embodiment disclosed, but rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0017]    The inventive process comprises a hydrodeoxygenation (HDO) process improvement that increases oxygenate conversion to liquid hydrocarbon fuels (or a component thereof) without the need to increase HDO severity, which would sacrifice the overall yield via: 1) increased production of light hydrocarbons from cracking, and 2) decreased catalyst lifespan due to an increased coking rate. 
         [0018]    An embodiment of the inventive process and system  100  is generally illustrated in the FIGURE. The HDO reaction is conducted in HDO reactor  115  that contains an HDO catalyst (not depicted) and contains inlets for receiving an input of oxygenate feedstock  105 , hydrogen gas  107 , and recycled oxygenates  110 . Following the HDO reaction in the HDO reactor  115 , a first HDO product  120  is directed to a first separator  125  that is configured to phase-separate the first HDO product  120  into an aqueous phase  130  comprising unreacted oxygenates, a non-aqueous phase  135  comprising hydrocarbons, and light gases  140  comprising hydrogen. The light gases  140  are directed to a light gas fractionator  145  that produces a hydrogen fraction  150  that is recycled to the HDO reactor  115 , while other light gases  155  are directed for use in other processes or combusted (not depicted). 
         [0019]    The aqueous phase  130  is directed to a mixer  160  that also receives a fresh water-insoluble solvent  165  capable of dissolving unreacted oxygenates. The mixer  160  also receives recycled water-insoluble solvent  170 . The mixer  160  is configured to combine the aqueous phase  130  with the water-insoluble solvent  170  and output the resulting emulsion  175  to a second separator  180  that is configured to allow simultaneous phase-separation of the aqueous phase  130  from the water-insoluble solvent  170  while simultaneously facilitating extraction of unreacted oxygenates from the aqueous phase into the water-insoluble solvent. A non-exclusive example of such a water-insoluble solvent is a hydrocarbon fraction rich in aromatics (e.g, FCC light cycle oil or FCC heavy cycle oil). 
         [0020]    Further referring to the FIGURE, water-insoluble solvent containing extracted, unreacted oxygenates are directed from the second separator  180  to distillation column  185  to produce separated unreacted oxygenates  190  and water-insoluble solvent  170 , which is returned to mixer  160 . The separated unreacted oxygenates  190  are optionally directed trough a purge splitter  195  that either directs the unreacted oxygenates to be purged  200 , or returned to HDO reactor  115  as recycled oxygenates  110 . 
         [0021]    Although the systems and processes described herein have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims. Those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein. Thus, the invention disclosed herein is specifically intended to be as broad as the claims below and those variations and equivalents that are encompassed by the scope of the claims.