United States Patent (19) 11) 4,420,644 Huibers et al. (45) Dec. 13, 1983

(54) LIGNIN HADROCRACKING PROCESS TO 2,998,457 8/1961 Paulsen ...... 568/806 PRODUCEPHENOL AND 4,258,221 3/1981 Knudsen et al...... 568/806 75) Inventors: Derk T. A. Huibers, Pennington; . Primary Examiner-Werren B. Lone Hugh J. Parkhurst, Jr., Plainsboro, Attorney, Agent, or Firm-V. A. Mallare; F. A. Wilson both of N.J. 57 ABSTRACT 73) Assignee: Hydrocarbon Research, Inc., A lignin-containing feed material in particulate form is Lawrenceville, N.J. mixeda with a process-derived slurrying oil and fed into (21) Appl. No.: 295,459 an ebulated catalyst bed hydrocracking reactor. Reac (22 Filed: Aug. 24, 1981 tion conditions are maintained at 650-850 F. tempera ture, 500-2500 psig hydrogen partial pressure and space 51 Int. Cl...... SS 37/00 velocity of 1.0-10 wt. lignin/hr./wt. catalyst. The eaC (52) Vir...... 5.s s2. tion products are phase separated to recover hydrogen (58) Field of Search ...... /806, 05, 99 and slurrying oil, and the resulting liquid stream is (56) References Cited passed to a thermal hydrodealkylation step. The reacted U.S. PATENT DOCUMENTS stream is fractionated to produce phenol and benzene o Taw 0 products, along with a heavy alkylated material which 2,328,749 9/1943. Sherrard et al...... 568/806 2,746,996 5/1956 Neuworth ..... 568/806 is recycled to the hydrodealkylation step to increase the 2,786,873 3/1957 Ohsol et al...... yield of phenol and benzene. 2,947,739 8/1960 Gaslini ...... 568/806 2,991,314 7/1961 Giesen ...... - 568/806 9 Claims, 3 Drawing Figures U.S. Patent Dec. 13, 1983 Sheet 1 of 2 4,420,644

A/G / ESTMATED BOND ENERGES OF GUAACYL MOETES (KCAL/MOLE)

METHYLENE LINKAGE FORMED IN 85 KRAFT PROCESS

A/G 2. CO.9 -- 3O% C - 25% C -- /

a1 77% Co.2 OH -- 15% 7% OH EST MATE OF THE PERCENTAGE BOND CLEAVAGE IN CATALYTIC HYDROCRACKING OF A KRAFT LIGNN MOETY, TO PRODUCE MIXED PHENOLS U.S. Patent Dec. 13, 1983 Sheet 2 of 2 4.420,644

ENEZNB8 _22 TONEHdL.82

82 G2

4,420,644 1. 2 TABLE 1-continued LIGNIN HYDROCRACKING PROCESS TO PRODUCE PHENOL AND BENZENE ANALYSIS OF KRAFT LIGNIN CHARGE STOCK (W '%) Oxygen (Na2CO3 + Na2SO4) 0.64 Oxygen (organic sulfur) 0.60 This invention pertains to the catalytic hydrocrack Oxygen (organic) 25.23 ing of lignin-containing feedstocks to produce mono Sodium (Na2CO3 + Na2SO4) 0.52 aromatic phenol-containing products. It pertains partic 100.00 ularly to such lignin hydrocracking process followed by Organic, W % hydrodealkylation of the mono-aromatic liquid to pro Carbon 64.89 10 Hydrogen 5.67 duce phenol and benzene products. Oxygen 25.23 BACKGROUND OF INVENTION 95.79 Lignin is an aromatic polymer found in all vascular plants. It is currently produced as a co-product of paper U.S. Pat. No. 2,328,749 to Sherrard discloses an early pulp and burned for its fuel value. When petroleum 15 batch-type process for catalytic hydrogenation of wood feedstock was cheap, lignin was not worth recovering material to remove lignin and make cellulose. Also, U.S. as a chemical feedstock. However, as petroleum feed Pat. No. 2,947,739 to Gaslini discloses a process for stocks become scarcer and more expensive, and an ever hydrogenation of ligno-cellulosic materials using solu increasing percentage comes from foreign sources, ble metal carbonyl catalyst at relatively low tempera more consideration is being given to using lignin, which 20 ture and pressure conditions. U.S. Pat. No. 2,991,314 to is a domestic renewable feedstock, as a source of mono Giesen discloses a continuous non-catalytic process for aromatics products, particularly phenol. cleavage of lignin to produce phenols at temperatures Lignin comprises roughly 25% of lignocellulosic above 300° C. and pressure above 350 atm. to yield biomass, which includes all vascular plants. Lignin distillable lignin products. Also, hydrogenation of lignin. gives plants rigidity and protection and helps regulate 25 using the Noguchi batch-type process developed in the permeation of water. It is formed within the plant Japan is disclosed by Goheen in Adv. in Chem. Ser. No. primarily by the dehydrogenative polymerization of 59,226 (1966). However, further process improvements three precursors: trans-coniferyl, trans-sinapyl and are needed to develop a continuous process for hydro trans-p-coumaryl alcohol. The relative amounts of each cracking lignin-containing feedstocks and produce high component and their linkages vary with wood types. 30 yields of useful phenol and benzene products along with Trans-coniferyl alcohol is always the major component, some distillable oils. and hardwood lignins contain more trans-sinapyl struc SUMMARY OF INVENTION tures. In wood pulping via the kraft process, cellulose, hem This invention discloses a catalytic hydrocracking icellulose and lignin are separated by dissolving hemi 35 process for converting lignin-containing feedstocks to cellulose and lignin in an alkaline sodium sulfate/ mono-aromatic phenol-containing products. The lignin solution at elevated temperature and pressure, yielding containing feed is first slurried with a process-derived the so-called black liquor. Wood lignin is considerably oil and depolymerized by a hydrocracking reaction changed by kraft cooking. Condensations involving step. The resulting stream is then treated to recover a formaldehyde or active beta-carbonyl derivatives leads hydrogen-containing gas and aromatic fuel oil, a por to methylene linked aromatic rings and an increase in tion of which is recycled as slurrying oil. The remaining molecular weight. At the same time, alkaline cleavage mono-aromatics are usually then hydrodealkylated to of phenolic occurs. As a result of the alkaline produce phenol and benzene products. The invention cleavage, phenolic hydroxyls increase from 0.3 per also discloses the chemistry of lignin hydrocracking and monomer in the protollignin to almost 1.0 in the dis 45 hydrodealkylation of the resulting intermediate materi solved lignin. als to produce aromatic fuel oil and high yields of phe When sufficiently depolymerized, the lignin pheno nol and benzene products. A heavy alkylated material late form dissolves in the black liquor. The phenolic stream is recycled to the hydrodealkylation step for groups can be liberated by acidification with carbon further reaction to increase the yield of phenol and dioxide obtained from stack gases. This causes the lignin 50 benzene products. to precipitate, aided by the salting-out effect of the The catalytic hydrocracking step, which is regarded sodium salts of the black liquor. Lignin is filtered at as the best method for lignin depolymerization, is oper 60-80' C. Further purification by solution in dilute ated at sufficient temperatures so that the initiating step alkali and reprecipitation with sulfuric acid gives a kraft is thermal bond rupture to form free radical lignin frag lignin, such as that used as feedstock in our invention 55 ments. This is followed by stabilization of these free (Table 1). Kraft lignin has a typical average molecular radicals with hydrogen dissolved in the reaction slurry weight of about 3500, which indicates that the average feedstream. In a parallel simultaneous reaction, a softwood kraft lignin is comprised of about 20 starting methyl radical is removed from the methoxy side units. group. In order to obtain good phenol yields, repolyn 60 erization to produce heavy oil and hydrogenation of the TABLE 1 aromatic ring and more than one of the hydroxyl groups ANALYSIS OF KRAFT LIGNIN CHARGE STOCK (W%) must be avoided. Ash by Combustion 1.40 FIG. 1 shows the estimated bond energies of the Water 1.02 quaiacyl moieties as they occur in kraft lignin mole Carbon (organic) 64.89 65 Carbon (Na2CO3) 0.08 cules. These bond energies are approximate and do not Hydrogen (ex. H2O) 5.67 take into account interactions with other substituents. Sulfur (Na2SO4) 0.16 As discussed above, in lignin these quaiacyl moieties are Sulfur (organic) 1.19 linked, mostly with alkylaryl linkages; i.e., be 4,420,644 3 4. tween a phenolic and the carbon atom - of a side chain. In kraft lignin, part of these -aryl TABLE 2-continued linkages are hydrolyzed, while new methylene linkages PRODUCT(Run YELDSUMMARY 144-57-4 are formed. FIG. 1 shows the most likely places of W 2 of thermal bond rupture, which are: 5 origin (a) alkyl-aryl linkages between quaiacyl-type moi- C5H12 1.0 eties; . ." ... -- . . Subtotal 25.2 (b) methyl-oxygen linkages of the methoxy groups H2O 17.9 attached to the aromatic ring; and C6-300' F. Neutrals 8.3 (c) methylene linkages between quaiacyl moieties. 10 :: SE s: Only after thermal bond rupture, which reduces lig- ... renols 8.7 nin to at most a quaiacyl-type tetramer, can the hydro- 500 F.-- 2.4 cracking catalyst play a useful role, as whole kraft lignin Subtotal 80.5 Uponmolecules entering are thetoo catalyst, large to further enter depolymerizationthe catalyst pores. of Sgical- H2 ConsumptionTotal 105.75.73 the lignih tetramer and removal of substituents will O occur. In our process, the hydrocracking reaction condi- TABLE 3 tions are maintained within the broad range of 300 F-465. F. PHENOLS COMPOSITION 650-850 F. temperature and 500-2500 psig hydrogen 2 (Analysis in W. 26) partial pressure. The feed rate or space velocity is main- Run Number 144-57-4 tained within the range of 1.0-10 pound lignin/hr.- phenol s /pound catalyst and preferably 0.3-6 pound lignin/hr.- o-Cresol 3.62 /pound catalyst (WHSV), The lignin-containing feed 25 m-Cresol 11.88 will have particle size smaller than about 40 mesh (0.016 p-Cresol 9.72 inch). Useful particulate catalysts comprise oxides of Eol 3. iron, cobalt, molybdenum or nickel, or combination o-n-Propylphenol . . 794 thereof, on a support comprising alumina, silica, or p-n-Propylphenol 2007 combination thereof. Catalyst particle size should be 30 100.00 within the range of 0.020-0.130 inch effective diameter, ...... and... A preferably product yield 0.040-0.080 summary inch resulting diameter. from hydrocrack. . . . doneHydrodealkylation in a separate reactor of the withoutmixed phenols a catalyst. can better Studies be ing lignin in an ebulated bed catalytic reaction step is indicate that the molar selectivity for the thermal hy ganicshow lignin"in Table was 2. convertedIt shows thatto phenols. 37.5 W2% The ofte 465-500 35 drodealkylation96. About 37 mole of cresols% of the to cresolsphenols is is dehydroxylated about 60 moie F. fraction contains some catechol (b.pt,474 F.). Table, and the remainder cracked to gas. To obtain this high 3 shows a detailed analysis of the phenols fraction, lead-, selectivity, the reaction is run at a lower temperature ing to FIG.2, which presents an estimate of the percent and longer residence time than for conventional age of bond cleavage in catalytic hydrocracking of kraft 40 hydrodealkylation. Conversion per pass is about 30%. lignin moieties to produce the observed mixture of phe nols. FIG. 2 shows that the hydroxy groups in the 3 DESCRIPTION OF DRAWINGS position are removed about five times as fast as the FIG. 1 is a diagram showing estimated bond energies hydroxy groups in the 4-position. Of the total number of for kraft process lignin molecules. potentially available hydroxy groups, including those 45 FIG. 2 is a diagram showing percentage bond cleav occurring in the proto-lignin as methyl ether, only 28% age in hydrocracking kraft lignin. are retained, FIG. 3 is a schematic diagram showing the essential Since only one hydroxy group per aromatic ring is process steps of the invention. desired, the selectivity of producing alkyl phenols in this particular experimental run was 56%. Of the re- so DESCRIPTION OF PREFERREDEMBODIMENT maining 44%, 11% can probably be found in fractions As shown in FIG. 3, kraft lignin feed material in boiling above 465 F., which contain two hydroxy particulate form at 10, such as kraft lignin having analy groups, while 33% of the aromatic rings lost both hy- sis shown in Table 1, is mixed at 12 with a process droxy groups. As shown in Table 2, 14.0 W% of the derived oil 11. The resulting slurry feed, containing organic lignin was converted to aromatic hydrocarbons 55 pulverized lignin and lignin-derived oil, is pressurized at boiling below 465 F. 14 and passed with hydrogen gas at 15 into the bottom TABLE 2 slurryE. it. and gas16 feedgoing are passed ity upwardly throughE.g. flow Propus, ESEMMary distributor grid plate 17. The reactor liquid is recircu W% of 60 lated through the catalyst bed, passing downward Organic Lignin through conduit 18 and recycle pump 19 to grid 17. The CO 3.9 liquid feed rate and liquid recycle upward flow velocity CO2 1.8 maintained in the reactor are sufficient to keep the cata CH4. 6.6 lyst bed expanded by 10-150% over its settled height C2H6 1.9 65 and in an ebullated condition. SE f The ebulated bed catalytic reactor, which resembles C4H10 io a bed of boiling solids, is ideal for hydrocracking lignin. C5H10 0.7 The random ebullated motion of the catalyst particles 4,420,644 5 6 promotes good contact and uniform reactor tempera tures and helps prevent plugging. The light products TABLE 5-continued PHENOLYIELDS FROM LIGNIN HYDROCRACKING formed, such as monoaromatics, vaporize and rise rap COMPARING THE HR AND NOGUCHI PROCESSES idly to the top of the reactor, where they exit as stream HRI Noguchi 21 before they have time to react further. For effective %, Phenol % Phenol hydrogenation, the reaction conditions in reactor 16 are % Phenois calcu- % Pheno calcu usually maintained within the range of 650-850 F. Compound produced lated produced" lated temperature and 500-2500 psig hydrogen partial pres TOTAL 37.5 29.9 2.0 17.7 sure. Preferred reaction conditions are 700-825 F. "Wt 7%, based on organic content of lignin. temperature and 600-2000 psig hydrogen partial pres O "Based on 100% dealkylation to phenol. sure. Space velocity used is 0.1-10 weight feed/hr./wt. catalyst, and preferably 0.3-6 weight feed/hr./wt. cata Liquid stream 26 containing the resulting monoaro lyst. Fresh catalyst is added at connection 20a as needed matics is usually passed to a thermal hydrodealkylation to maintain desired catalyst activity, and used catalyst is step 30. Hydrogen is added at 32. Dealkylation reaction removed at connection 20b, 15 conditions are maintained within the ranges of The effluent 21 from lignin hydrocracking reactor 16 900-1350 F. temperature and 300-1250 psig hydrogen is passed to phase separation-fractionation step 22, from partial pressure. Following reaction, liquid stream 34 is which the gas portion 23 is passed to hydrogen purifica withdrawn and passed to fractionation unit 36. A phe tion unit 24 for removal of sulfur and other impurities at nol product'stream is removed at 37 and benzene prod 31. The recovered hydrogen at 25 is recycled to reactor 20 uct at 38: Unreacted alkyl phenols and alkylbenzenes 39 16 for reuse, while make-up hydrogen is added at 25a as are recycled to hydrodealkylation reactor 30 for further needed. A heavy oil stream having normal boiling range reaction to increase the yields of phenol and benzene. of 500-900 F. is withdrawn at 27, a portion 28 can be Based on our present experimental results, it is esti used as aromatic fuel oil, and the remainder is recycled mated that lignin can be processed to yield 20.2 W% to the slurry mixing tank 12 to provide the required 25 phenol, 14.4 W% benzene, 13.1 W% fuel oil and 29.1 slurrying oil. W% fuel gas. If the hydrogen and fuel requirements of The advantage of hydrocracking lignin in an ebul a Lignol process plant are not provided from outside lated bed catalytic reactor can be seen by comparing its sources, the net fuel oil yield is reduced to 109 W%. In products yield with that of the Noguchi process, which this case, hydrogen is generated from the hydrocarbon is a catalytic batch hydrocracking process developed by 30 gas produced in the lignin hydrocracker vent gas stream the Noguchi Institute in Japan. As shown in Table 4, the 23. n ebullated bed reactor produced less gas and water, a The price advantage of phenol over benzene makes it comparable amount of light distillate, a significantly worthwhile to try to obtain higher phenol yields with higher amount of phenols and a lower amount of heavy improved hydrocracking catalysts and with reaction oils. The phenols distribution of both processes is given 35 conditions further optimized to improve alkyl phenol in Table 5. If one assumes that the entire phenols yield selectivities from the present 56% to possibly 80%. If could be hydrodealylated to produce phenol, the pres- : advanced dealkylation techniques could also boost the ent process would yield 29.9 W% lignin as phenol and phenol yield from 60 to 80%, the phenol yield of this the Noguchi process only 17.7 W%. Lignol process could be increased from 20 to 38 W%. TABLE 4 LGNIN HYDROCRACKING PRODUCT DISTRIBUTION (W% of Organic Lignin) Process HR Noguchi Reactor Type Continuous Ebullated Bed Batch Gas 25.2 (H2S, CO, 7.5 CO2, C-C5) Water 17.9 27.5 Light Distillate 14.0 (BP < 465 F) 14.0 (BP < 464 F.) Phenols 37.5 (300 F. ( BP (465 F). 21.0 (338. F. ( BP (.464°F) Heavy Oil 11.0 (BP < 465 F) 20.0 (BP < 464 F.) Total 105.7 1000 Noguchi may not have taken hydrogen consumption into account. 55 Lignin is a renewable resource material which can help reduce use of petroleum feedstocks. The conver TABLE 5 sion of lignin to phenol and benzene is technically and PHENOLYIELDS FROM LGNN HYDROCRACKING economically feasible with this Lignol process. More COMPARING THE HR AND NOGUCHI PROCESSES over, there is room for further improvement in process HRI Noguchi 60 economics. A process, such as Lignol, can be used in % Phenol % Phenol tandem with the production of fuel ethanol from cellu % Phenols calcu- % Phenol calcu lose. For every gallon of ethanol produced from news Compound produced" lated produced lated print, for example, one pound of phenol and 0.7 pound Phenol 2.5 2.5 3.0 3.0 of benzene could be produced. Even more attractive Cresol 9.5 8.3 0.0 8.7 65 Ethylphenol 12.5 9.6 4.3 3.3 economics could be achieved if the alkyl phenols, such Propylphenol 10.5 7.5 2.0 1.4 as cresols, ethylphenol, and propylphenols, resulting Xylenol 2.6 2.0 .2 .9 from lignin hydrocracking were sold as products for Unidentified m .5 .5 specialized applications. 4,420,644 7 Although we have disclosed certain preferred em 5. The process of claim 4, wherein the hydrodealkyla bodiments of our invention, it is understood that certain tion conditions used are temperature within the range of adaptations and modifications can be made thereto all 900-1350 F. and hydrogen partial pressure within the within the spirit and scope of the invention, which is range of 300-1250 psig. defined by the following claims. 5 6. A process for hydrocracking of lignin-containing We claim: feed materials to produce mono-aromatic phenolic 1. A process for hydrocracking lignin-containing feed products, comprising: materials to produce mono-aromatic phenolic products, (a) mixing the lignin-containing feed with sufficient comprising: process-derived slurrying oil to provide a pump (a) mixing the lignin-containing feed with sufficient O able slurry mixture; & process-derived slurrying oil to provide a pump (b) feeding the lignin and oil slurry with hydrogen able slurry mixture; ' into a hydrocracking reaction zone containing an (b) feeding the lignin and oil slurry with hydrogen ebullated bed at a particulate catalyst comprising into a hydrocracking reaction zone containing an molybdenum oxides on alumina support; ebullated bed of particulate catalyst; 15 (c) maintaining said catalytic reaction Zone at temper ... (c) maintaining said catalytic reaction zone attemper ature. within range of 700-825' F., hydrogen par ... ature within range of 650-850 F., hydrogen par-, tial pressure of 600-2000 psig, and space velocity ...tial pressure of 500-2500 psig, and space velocity within the range of 0.3-6 wit: feed/hr./wt, catalyst; is within the range of 0.1-10 wit/hr./wt. catalyst; " (d) phase separating the reaction zone effluent stream (d) phase separating the eaction zone effluent stream 20 ... . to recover a hydrogen-containing gas stream and ... to recover a hydrogen-containing: gas stream and 'aromatic ieils having, normal boiling range of ... aromatic oils having normal boiling, trange of 500-900 F. as said slurrying oil; 500-900. F. as said slurrying oil; and ...... (e) withdrawing: a mono-aromatic liquid product (e) withdrawing a mono-aromatic liquid product stream boiling below about 500'. F. and containing stream, boiling below about 500 F. and containing 25 at least about 25W % phenolics and passing it with at least about 25 W% phenolic product...... hydrogen to a hydrodealkylation step; and 2. The process of claim 1, wherein the catalyst com (f) fractionating the hydrodealkylated stream to prod prises 12-18 W % molybdenum oxides on alumina sup uct phenol and benzene products. 7. The process of claim 6, wherein the hydrotreating 3. The process of claim 1, wherein the hydrocracking 30 step (e) is performed at conditions of 1000-1250 F. reaction conditions are maintained within the range of temperature and 300-1100 psig hydrogen partial pres 700-825' F. temperature and 600-2000 psig hydrogen St. partial pressure. , . . . . . 8. The process of claim 6, wherein a heavy hy 4. The process of claim 1, wherein the liquid product drodealkylated material stream from step (f) is recycled from step (e) is passed with hydrogen to a hydrodeal 35 to the hydrodealkylation step (e) to increase the yield of kylation step, and the resulting mono-aromatic stream phenol and benzene products. . . boiling below about 500 F. is fractionated to produce 9. The process of claim 6, wherein a portion of the phenol and benzene product while recycling the heavy 500-900 F. aromatic oil is removed as fuel oil product. alkylated phenols and for further reaction. it

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