Abstract:
A process for the conversion of biomass to a liquid fuel is presented. The process includes the production of diesel and naphtha boiling point range fuels by hydrocracking of pyrolysis lignin extracted from biomass.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to processes for obtaining hydrocarbons from biomass. More particularly, this invention relates to the treatment of lignin and cellulosic waste produced from pyrolysis of biomass to produce light aromatics and gasoline. 
       BACKGROUND OF THE INVENTION 
       [0002]    Renewable energy sources are of increasing importance. They are a means of reducing dependence on imported oil and provide a substitute for fossil fuels. Also, renewable resources can provide for basic chemical constituents to be used in other industries, such as chemical monomers for the making of plastics. Biomass is a renewable resource that can provide some of the needs for sources of chemicals and fuels. 
         [0003]    Biomass includes, but is not limited to, lignin, plant parts, fruits, vegetables, plant processing waste, wood chips, chaff, grain, grasses, corn, corn husks, weeds, aquatic plants, hay, paper, paper products, recycled paper and paper products, and any cellulose containing biological material or material of biological origin. The economics depend on the ability to produce large amounts of biomass on marginal land, or in a water environment where there are few or no other significantly competing economic uses of that land or water environment. The economics can also depend on the disposal of biomass that would normally be placed in a landfill. 
         [0004]    The growing, harvesting and processing of biomass in a water environment provides a space where there is plenty of sunlight and nutrients while not detracting from more productive alternate uses. Biomass is also generated in many everyday processes as a waste product, such as waste material from crops. In addition, biomass contributes to the removal of carbon dioxide from the atmosphere as the biomass grows. The use of biomass can be one process for recycling atmospheric carbon while producing fuels and chemical precursors. Biomass when heated in an environment with low or no oxygen will generate a liquid product known as pyrolysis oil. 
         [0005]    It is difficult and uneconomical to use pyrolysis oil directly, but new and improved processes can make fuels that work with engines that are currently distributed around the world without requiring upgrades to those engines. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention provides a process for producing high yields of naphtha and diesel related products from biomass. Pyrolysis oil generated from biomass is separated into an oil phase stream and a pyrolytic lignin stream. The pyrolytic lignin stream is rich in aromatic hydrocarbon rings, and is treated in a decarboxylation/hydrodeoxygenation unit generating a deoxygenated oil stream. The deoxygenated oil stream is separated to produce an aqueous phase and an organic phase. The organic phase is further treated in a hydrocracking unit under mild hydrocracking conditions to produce a hydrocarbon product stream. The product stream comprises aromatic and naphthenic compounds that are useful as gasoline and naphtha, or as additives to gasoline products. 
         [0007]    Other objects, advantages and applications of the present invention will become apparent to those skilled in the art after a detailed description of the invention. 
     
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0008]    The FIGURE is a process flow scheme for one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0009]    In the U.S. and worldwide, there are huge amounts of cellulosic waste, or biomass, which is not utilized, but is left to decay, often in a landfill, or just in an open field. The material includes large amounts of wood waste products, and leaves and stalks of crops or other plant material that is regularly discarded and left to decay in fields. This material can be pyrolyzed to make a pyrolysis oil, but due to the high water content of the pyrolysis oil, often greater than 25%, high total acid number of approximately 70, and phase incompatibility with petroleum based materials, pyrolysis oil has found little use. 
         [0010]    The current invention is a process for substantially converting pyrolytic lignin material into naphtha and diesel boiling range components, having low acidity and ultra-low sulfur content. The pyrolytic lignin is separated from pyrolysis oil and contains potentially high value products in the form of aromatic and naphthenic compounds. Pyrolytic lignin is a complex structure that comprises aromatic rings that are linked by oxygen atoms or carbon atoms, and can be broken into smaller segments when decarboxylated or hydrodeoxygenated and further reduced under mild hydrocracking conditions, while maintaining the aromatic ring structures. 
         [0011]    In one embodiment, as shown in the FIGURE, pyrolysis oil is separated in a separation unit  10 , generating a pyrolytic lignin stream and a water rich phase stream comprising organic compounds. The pyrolytic lignin stream is passed to a hydrotreating unit  20 , generating a deoxygenated light oil stream. The hydrotreating unit  20  performs decarboxylation and hydrodeoxygenation of the pyrolytic lignin breaking the bonds holding the aromatic rings together by breaking the oxygen linkages and forming water and CO 2  from the oxygen and leaving smaller molecules comprising an aromatic ring, such as alkylbenzenes and polyalkylbenzenes. The deoxygenated light oil stream is passed to a separation unit  30  where the deoxygenated light oil is separated into an aqueous stream and an organic stream. The organic stream is passed to a hydrocracking unit  40  where mild hydrocracking is performed, thereby generating a product stream. The product stream comprises aromatic and naphthenic compounds for use in gasoline or naphtha boiling range products. A small amount of diesel is produced which can be put into diesel boiling range products 
         [0012]    The product stream can be further processed by passing the product stream to a reforming unit. The reforming unit reduces the naphthenic content and generates an aromatic rich product stream for use in gasoline. 
         [0013]    The separation of the pyrolysis oil in the separation unit  10  can be performed by adding water to the pyrolysis oil creating a mixture comprising a lighter water rich phase stream and a heavier lignin rich phase. The two phases are separated using known technology into the water rich phase for subsequent reforming, and the pyrolytic lignin stream comprising lignin. Since the pyrolytic lignin is denser than the water rich phase of the pyrolysis oil, examples of separation processes include gravity separation, or centrifuging. 
         [0014]    In another embodiment, the process comprises passing the water rich phase stream to a reforming unit  50 . The reforming unit  50  acts on the water rich phase to generate a hydrogen stream. The reforming of the water rich stream can be performed with either steam reforming or through partial oxidation. The hydrogen stream generated from the reforming can be passed to the hydrotreating unit  20  for the decarboxylation and hydrodeoxygenation of the lignin. 
         [0015]    The pyrolytic lignin stream is hydrotreated to decarboxylate and hydrodeoxygenate the lignin by partial cracking of the pyrolytic lignin molecules into smaller molecules comprising an aromatic ring. Decarboxylation minimizes the hydrogen consumption during the breaking of the bonds holding the aromatic units in the lignin molecules together. This also limits the amount of hydrogenation of the aromatic rings. The hydrotreating is operated at a pressure from about 3.4 MPa (500 psia) to about 14 MPa (2000 psia), and preferably is operated at a pressure from about 3.4 MPa (500 psia) to about 12 MPa (1800 psia). This is lower than the normal operation pressures for hydrotreating pyrolysis oils which is in the range from 14 MPa (2000 psia) to 21 MPa (3000 psia). 
         [0016]    In an alternate embodiment, pyrolysis oil is separated in a separation unit  10 , generating a pyrolytic lignin stream and a water rich phase stream. The pyrolytic lignin stream is passed to a hydrotreating unit  20 , generating a deoxygenated light oil stream. The hydrotreating unit  20  decarboxylates and hydrodeoxygenates the pyrolytic lignin to generate a deoxygenated light oil stream. The deoxygenated light oil stream is passed to a hydrocracking unit  40  where a product stream is generated comprising aromatic compounds for use in naphtha boiling range products, or gasoline. 
         [0017]    In an alternative to the above embodiments, the deoxygenated light oil stream is drawn off as a vapor before passing the deoxygenated light oil stream to the hydrocracking unit  40 , or to the separation unit  30 . This promotes a longer residence time for the liquid pyrolytic lignin phase. 
         [0018]    The organic phase stream is separated from the deoxygenated lignin stream and further processed through a cracking process. The hydrocracking unit is operated at a pressure from about 3.4 MPa (500 psia) to about 14 MPa (2000 psia), and preferably is operated at a pressure from about 3.4 MPa (500 psia) to about 12 MPa (1800 psia). Operating conditions for the hydrocracking unit further include operating at a temperature between about 260° C. (500° F.) and 455° C. (850° F.), and preferably at a temperature between about 340° C. (650° F.) and 435° C. (810° F.). 
         [0019]    The hydrocracking unit includes a catalyst having a cracking function. The catalyst is a combined zeolitic and amorphous silica-alumina catalyst with a metal deposited on the catalyst. The catalyst includes at least one metal selected from nickel (Ni), chromium (Cr), molybdenum (Mo), tungsten (W), cobalt (Co), rhodium (Rh), iridium (Ir), ruthenium (Ru), and rhenium (Re). In one embodiment, the catalyst includes a mixture of the metals Ni and Mo on the catalyst. The catalyst is preferably a large pore catalyst that provides sufficient pore size for allowing larger molecules into the pores for cracking to smaller molecular constituents. The metal content deposited on the catalysts used are deposited in amounts ranging from 0.1 wt. % to 20 wt. %, with preferred values for the metals including, but not limited to, nickel in a range from 0.5 wt. % to 10 wt. %, tungsten in a range from 5 wt. % to 20 wt. %, and molybdenum in a range from 5 wt. % to 20 wt. %. The metals can also be deposited in combinations on the catalysts with preferred combinations being Ni with W, and Ni with Mo. 
         [0020]    Zeolites used for the catalysts include, but are not limited to, beta zeolite, Y-zeolite, MFI type zeolites, mordenite, silicalite, SM 3 , and faujasite. 
       EXAMPLE 
       [0021]    The pyrolysis oil was separated into two streams before hydrotreating the pyrolytic lignin, a pyrolytic lignin stream and a water soluble pyrolysis oil phase stream. The separation was performed using two methods, a water precipitation method and a density method. The pyrolytic lignin has an enriched carbon content and a reduced oxygen content relative to the pyrolysis oil before separation, as shown in Table 1. The amount of pyrolytic lignin that is recoverable from the pyrolysis oil before hydrotreating is about 30% by weight of the pyrolysis oil. Different separation methods can yield slightly different results. The elemental analyses in Table 1 are shown on a moisture free basis as indicated by “mf”. 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Pyrolysis 
                 Pyrolytic 
                 Water Soluble 
                 Pyrolytic 
                 Water Soluble 
               
               
                   
                 Oil 
                 Lignin 
                 Pyrolysis Oil 
                 Lignin 
                 Pyrolysis Oil 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Weight % 
                 100 
                 27 
                 73 
                 32 
                 68 
               
               
                 Separation 
                   
                 Water 
                 Water 
                 Density 
                 Density 
               
               
                 method 
                   
                 precipitation 
                 precipitation 
               
               
                 % C mf 
                 44.7 
                 69 
                 35.8 
                 62.3 
                 36.5 
               
               
                 % H mf 
                 7.2 
                 6.9 
                 7.3 
                 6.9 
                 7.3 
               
               
                 % N mf 
                 0.2 
                 0.3 
                 0.2 
                 0.3 
                 0.2 
               
               
                 % O mf 
                 47.9 
                 23.8 
                 56.7 
                 30.5 
                 56.0 
               
               
                 Heating value 
                 6560 
                 11800 
                 4653 
                 10330 
                 4810 
               
               
                 LHV Btu/lb 
               
               
                   
               
             
          
         
       
     
         [0022]    Based on the autoclave tests for production of naphtha boiling range and diesel boiling range products, the yields from pyrolytic lignin are shown in Table 2. The CO 2  yield is based on an atomic O balance based on the feed oxygen content and the amount of water collected in the products. The hydrogen consumption is estimated from an atomic H balance based on the feed and products hydrogen contents. The production of 2250 bpd of lignin is estimated from the yield of lignin from pyrolysis oil, and using an estimate of 7500 bpd of pyrolysis oil. About 30% of the pyrolytic lignin can be converted to gasoline type products. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Yield from Hydrocracking Pyrolytic Lignin 
               
             
          
           
               
                   
                 Wt % 
                 Bpd 
               
               
                   
                   
               
             
          
           
               
                   
                 Feed 
                   
                   
               
               
                   
                 Pyrolytic lignin 
                 100 
                 2250 
               
               
                   
                 H2 
                 4–5 
               
               
                   
                 Products 
               
               
                   
                 Lt. ends 
                 15 
               
               
                   
                 Gasoline 
                 30 
                 1010 
               
               
                   
                 Diesel 
                 8 
                 250 
               
               
                   
                 Water, CO2 
                 51–52 
               
               
                   
                   
               
             
          
         
       
     
         [0023]    Experiments were run to reduce the oxygen content and stabilize the product through hydrotreating and decarboxylation of the pyrolytic lignin. The hydrotreated lignin was subject to hydrocracking to produce naphtha and distillate range components. The experiments performed were batch experiments and were run in an autoclave. The hydrotreating of the lignin was compared with a commercial process from the Pacific Northwest National Labs (PNNL). Although there was a reduction in the liquid yield, there was an increase in the quality of the liquids. The tests showed a significant increase in oxygen removal, and a significant increase in the amount of naphtha overall yield, i.e. an increase of over 40% in the production of naphtha over the PNNL process. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Comparison of hydrotreating methods for Pyrolytic Lignin 
               
             
          
           
               
                   
                   
                 PNNL HT 
                 UOP HT 
               
               
                   
                   
               
             
          
           
               
                   
                 WHSV 
                 0.52 
                 1.0 
               
               
                   
                 LHSV 
                 0.22 
                 0.68 
               
               
                   
                 Catalyst 
                 Pt/C 
                 Ni/Mo 
               
               
                   
                 Pressure (psia) 
                 1900–2000 
                 1500 
               
               
                   
                 Liquid yield % 
                 55.6 
                 40.8 
               
               
                   
                 % oxygen removal 
                 60 
                 93 
               
               
                   
                 % oxygen in product 
                 19.5 
                 5.9 
               
               
                   
                 Acid number of product 
                 34 
                 15 
               
               
                   
                 % naphtha in liquid 
                 30 
                 60 
               
               
                   
                   
               
             
          
         
       
     
         [0024]    Additional results can be seen in Table 4 from a series of autoclave experiments. The experiments were run at temperatures from 350C to 370C and at a pressure of 10.4 MPa (1500 psig). The feed to catalyst ratios were from 3:1 to 6:1, the WHSV varied from 1 to 1.5 and the LHSV varied from 0.67 to 1.01. The results indicated high oxygen removal and good liquid yields of naphtha liquids and diesel liquids. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Product Yield from Additional Pyrolytic Lignin Hydrotreating 
               
               
                 Experiments 
               
             
          
           
               
                   
                 Product ranges 
               
               
                   
                   
               
             
          
           
               
                   
                 Water, % of feed 
                 7.5–33  
               
               
                   
                 Naphtha, % 
                 19–30 
               
               
                   
                 Diesel, % 
                 12–30 
               
               
                   
                 Total liq., % 
                 38–60 
               
               
                   
                 % oxygen removed 
                 90–96 
               
               
                   
                 % O in naphtha 
                 1.3–8.6 
               
               
                   
                 % O in diesel 
                 2.3–7.3 
               
               
                   
                   
               
             
          
         
       
     
         [0025]    In addition, the gasoline content produced from autoclave experiments on pyrolytic lignin yielded a naphtha product with significant aromatic and naphthene content as shown in Table 5. 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 properties of starting pyrolytic lignin vs. naphtha produced from 
               
               
                 pyrolytic lignin 
               
             
          
           
               
                   
                 Pyrolytic lignin 
                 gasoline 
               
               
                   
                   
               
             
          
           
               
                   
                 BP (10–90% pt) ° C. 
                 Too heavy 
                 71–226 
               
               
                   
                 Density 
                 1.2 
                 0.81 
               
               
                   
                 Acid number (mg KOH/g) 
                 168 
               
               
                   
                 Oxygen, % (by dif) 
                 29.7 
                 1.3 
               
               
                   
                 % aromatics 
                   
                 34.4 
               
               
                   
                 % naphthenes 
                   
                 39.1 
               
               
                   
                 % olefins 
                   
                 2.7 
               
               
                   
                 % paraffins 
                   
                 23.8 
               
               
                   
                   
               
             
          
         
       
     
         [0026]    While the invention has been described with what are presently considered the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.