RESEARCH ON REUSE OF PAPERMAKING LIGNIN-CONVERSION OF LIGNIN TO BTX BY CATALYTIC PYROLYSIS IN A POWD

JOURNAL OF .2004 AprilTIANJIN UNIVERSITY OF SCIENCE AND TECHNOLOGYVol.19 SuppRESEARCH ON REUSE OFstraw and wheat straw are used for papermaking,PAPERMA KING LIGNINwhich occupy 70-80% of the raw material. However,-CONVERSION OF LIGNIN TO BTXit is the difficulty in papermaking waste liquidtreatment as well as the lack of capital，technologyBY CATALYTIC PYROLYSIS IN Aand environmental protecting consciousness. etc. thatPOWDER PARTICLE FLUIDIZED BEDmakes the sulphonate in papermaking lignininsufficiently utilized but a pollution source.Chang Wang, Chongwo Li, Qingzhu JiaTherefore, in order to effectively utilize the resourcesor to solve environment pollution problem, it isCollege of Material Science & Chemicalextremely important to efficiently utilize lignin.Engineering，Tianjin University of Science &There are many researches and discoveries on theTechnologyutilization of lignin domestic and abroad1-4)，the1038 Dagunan Road, Tianjin City, 300222, P.R.regions of which are very wide. As yet, most of theChinaresearches are still on the laboratory stage. BecauseE-mail:wangc88@163.comof the competition from petroleum products andeconomic effect on utilization of lignin as well as theABSTRACTheterogeneity of its physico-chemical property, eventhough it can be converted to variant chemicalsExperiments on the catalytic pyrolysis of thethrough adition, condensation, polymerization, andpapermaking lignin were conduced by using a newmodification means etc.， its quality and costs cantype of powder-particle fluidized bed to improve thehardly achieve the better economic effect, whichyield of the light aromatic hydrocarbon, ie. benzene,increases the difficulty of practical usage. Accordingtoluene, xylene and naphthalene (BTXN), in whichto its structure, pyrolysis conversion can decomposethe primary decomposition and secondary catalyticthe lignin polyaromatic hydrocarbon into lightreaction occur simultaneously at ambient pressure.aromatic hydrocarbon as fundamental chemical stockThe effect of catalyst species, fuidizing gases andfeed. With the economic development of china inpyrolysis temperature on the yield of the BTXN wererecent years, the demands of these chemical stockinvestigated. The content of sulfur is high in thefeed have increased gradually, the growth rate ofpapermaking lignin,and the volatile matter iswhich reaches 21.9% However, 95% of the existingeffected by the temperature. In the case of the inertstock feed comes from petroleum chemicals. ifmedia silica sand, the yield and the distribution of thelignin, byproducts of paper making,can be utilized,pyrolysis products were almost unchanged under thedevelopment of pyrolysis conversion can not onlydifferent kind of atmosphere. In the case of thereduce the dependence to petroleum,but alsocatalyst CoMo-B with hydrogen atmosphere, thereplace or make up the shortage of petroleum, andintermediate BTXN yield reached 2.52wt%, dry, 3.3promote sustainable economic developmenttimes as much as that in the case of silica sand.efficiently.Gasification and pyrolysis are two main means ofTherefore， in order to obtain valuable BTXN as anintermediate in the pyrolysis as much as possible, it isutilizing clean biomass. papermaking lignin and plantextremely important to select high sulfur resistancebiomass have similar properties: low pyrolysistemperature and large yield of volatile matter.and hydrogenization activity catalyst.Generally, the volatile matter is polyaromaticKEYWORDS: Lignin, Biomass, Catalytichydrocarbon, the secondary decomposition of whichcan be controlled through different reaction conditionPyrolysis, BTX, Fluidized Bedin order to obtain the different desired pyrolysisproducts. Therefore, authors are aiming at trying forArticle ID:1672- -6510 (2004) supp- -0369- -05the development of a process, in which the valuablechemicals, ie. the light aromatic hydrocarbonsINTRODUCTIONBTXN are first obtained from biomass as much asPlant consists essentially of three main polymers:possible through the catalytic pyrolysis by using alignin, cellulose, and hemicellulose, which are thenew type of powder-particle fluidized bed proposedmost abundant and renewable hydrocarbon resourcesby our group5. Then chars collected from the systemon the earth. The annual yield of rice straw, wheatare further used as gasification or combustion sourcestraw, bagasse, reed, and bamboo in our country hastocon-y. In this work, a中国煤化工ed bed reata,exceeded 1 billion tons. 30% of the yield of riceY片C NM H G: easy control of-369-Journal of Tianjin University of Science and TechnologyVol.19 Supppyrolysis temperature, high speed of temperatureTable 2 Analyses of the medium particlesraising, convenient collection of the char， andcontinuous operation, was used to catalyticallyMedupyrolyze papermaking lignin, for investigating theCMeB 2545 1140.021NOi4 ,effects of catalyst species, atmosphere gases andpyrolysis temperature on the yield and distribution of301278-53 260.2691.57S02:100the decomposition products in the secondary gas●Atmospbert g#: Alr, Tmperoure: 863 Kphase reaction process.2. Experimental SetupThe experimental setup shown in Fig.l consisted offive components,that iscontinuous flow,powder-particle fluidized bed reactor installed in anelectric furmnace, a micro-feeder for continuouslyatsupplying fine lignin powder，being wrapped by aribbon heater, for separating the char from gases and]collecting the char, a gas-bag and a cold-trap fordetermining the yields of compositions produced bypyrolysis. The reactor with a gas distributor preparedby a sintered quartz filter, being quartz tube of 25mm i.d.and 300 mm of the distance from thedistributor to the gas exit, was heated electrically inFg.1 Schematke diegrom of the experinent apparstusthe furnace. Sample feed was entrained and fed intothe reactor by the micro-feed. Then the particles inEXPERIMENTALthe reactor were fluidized at the desired flow，andsimultaneously the reactor was heated rapidly to the1. Samples and Catalystdesired level. In order not to make the productsCalcium lignosulphonate in a paper mill was used indeposit and adhere on the top of the reactor, a bit ofreaction gas flowed in it. Furthermore, the lid on thehe pyrolysis experiments.The ultimate andtop of the reactor can be opened in order to clean theproximate analyses of these chips were shown iTable 1. To compare the results of their pyrolysis, areactor and pack and take off the fluidized mediumkind of cellulose in a paper mill was used and theparticles before and after pyrolysis.analysis value was also listed in the table. According3. Procedureto the table, the contents of sulfur and ash in ligninThe experimental procedure was as fllows. A givenare high, which reach respectively 5.5wt%, dry, andweight of the lignin powder and the medium particle14.6wt%. Each chip was broken into fine particles of(catalyst particle) were packed in the micro-feederless than 125 mesh in diameter, by a grinder. Inertand the reactor respectively and the extent of themedia silica sand and catalyst CoMo-B were used ascloseness of the system were checked in vacuothe medium particles in the PPFB，which were against gas leak, and a smal amount of nitrogencommercial products. The properties of the particlesstream flows into the system slowly until ambientwere showed in Table 2. These particles were groundpressure, and simultaneously the reactor was heatedand sieved to 250-540pum. In this study, three kindsto the desired level. Then the nitrogen was exchangedof nitrogen, helium, methane and hydrogen wereby the gas required for studying of pyrolysis. Minutesused as fluidizing gas for pyrolysis of thelater, sample feed was fed into the reactor by themicro feeder, typically for 40 minutes. The gases,papernaking lignin, respectively.liquid and solid of reaction products were collectedTable 1 Analyses of the samplesto be analyzed quantitatively. The gases collected inthe gasbag were analyzed by a gas chromatography (Sample.Utmst nmalyb |时%,dt} Roximak aahls|% ]Shimadzu-12A with TCD and FID) equipped with anCHNS0MohV.MAsbhRCactivated carbon column of 2 m to determine thecompositions of Hydrocarbon gases (HCG: C-C])1lgnin4.20 5绅诽s拣10 6都0.10 1的臻45and inorganic gases (IOG: CO2、CO). Compositionsof Benzene, Toluene， Xylene and NaphthaleneCelludose 429《的0.90●51.38$10以弹0.25 27.5were(BT)| 中国煤化二-on liquid (HCD)_chromatography* Undeterminedbut uYHC N M H Grith particles of.370-VoL.19 Supp .Journal of Tianjin University of Science and TechnologvPorapark-P. In addition, the relationship betweenweight losses and pyrolysis temperature were2. Effects of the kinds of the ambient gas ondetermined through TG-7000 thermobalancethe yield of the pyrolysis product(sinku-riko LTD.)，in order to obtain amounts ofFig. 3 shows the effcts of the kinds of the ambientvolatile in the lignin at different pyrolysisgas on the yield and distribution of the product. Thetemperature.operating conditions were as follows: pyrolysistemperature: 873K, superficial gas velocity: 0.32m/s,static bed height: 0.08m， continuous feed reactionRESULTS AND DISCUSSIONtime 40min. Fig.3 ilustrates that in the atmosphere ofHe, silica sand is a kind of inert medium. the yield ofIOG, HCG and HCL in the decomposition produet1. Effects of pyrolysis temperature on thecompared with 50wt% volatile matter at the samevolatile matter of the lignintemperature is very low, up to 8.72wt% ,dry,The variations of weight loss of the lignin and1.02wt% ,dry and 0.35wt% ,dry , and HCL is almostcellulose with pyrolysis temperature measured by thebenzene. It is indicated that the tar from primarythermobalance at heating rate of 60K/min underpyrolysis can hardly be decomposed in secondarynitrogen atmosphere are shown in Fig.2, in which thepyrolysis. The yield of HCG and HCL in thevariation of the weight loss of the cellulose was alsopyrolysis product increases apparently, respectivelypresented for comparison to them. The curve for theup to 1.92wt%, dry, and 0.76%, dry, up to 2 times ofcellulose with the pyrolysis temperature, as comparedas much as that in the atmosphere of He，in contrast,with that of the lignin is sharper at about 573K,the yield of IOG increases lttle. The increase of thealmost constant over the temperature. The losses ofdecomposition yield illustrates that even in the casethe weight in the figure can be considered as gas andof silica sand, H2 can promote. the secondaryliquid volatile products from the pyrolysis of thepyrolysis. The free radical from primary pyrolysissample. The curve of variation of the volatile mattermay activate partial hydrogen, and these activefor the cellulose with the pyrolysis temperature ishydrogen free radical can make not only thesharp at about 600K, up to 67wt%，almost constantdecomposed small molecule stable but also theover the temperature, because the cellulose ismacromolecular decomposed further.Theapproximate to a linear polymer based on glucose asdistribution of the decomposition product is differentthe monomer. Release of volatile matter out of thein the case of He and H2，but the yield of it is stillpaper making ligniris affected heavily by thelow, because silica sand does not have catalyticpyrolysis temperature, and starts at 370K, the yeildofactivity.which is first slower and then during the pyrolysisincrease of the pyrolysis temperature fom 550K to750K becomes faster, and then lower gradually, up to60wt%，dry at 1173K. It is indicated that thepapermaking lignin has a complex structure and is ahigh molecular compound. Compared to cellulose, it%Hoonas different decomposition property, differentH;pyrolysis temperature, and different yield of theH。:volatile matter.00 r。CllulohyuognHelumPig. 8 Dintribution of pyrolysis producds of bigainsof3. Effects of catalyst CoMo-B on the yield ofAtmosphero: NHeating rato: 1Khthe pyrolysis productFig.4 shows the effects of catalyst CoMo-B on theyield of the product. The operating conditions werePyrolyuis tempereture [K I873K, superficialPig.2 Vsriation of woight los of clulloo and ligningas中国煤化工higt 0.08m.YHC N M H G40min. Catalyst371-Journal of Tianjin University of Science and TechnologyVol.19 SuppCoM-B is a kind of popular industrial catalyst,which has hydrogenization activity in the atmosphereof hydrogen. It is indicated that the yield of HCG andHCL in the pyrolysis product increases apparently,respectively up to 8.55wt%，dry， and2.52%， dry.HCG. The HCG is mainly saturated hydrocarbon, thedistribution of which decreases with the increase ofcarbon atom. The yield of the light aromaticcompound increases 3 times as much as that in theAtmosphere: N:case of silica sand,and the yield of xylene andHeting rato: 1Khnaphthalene also increases to some extent. It is800indicated that .he tar from primary decomposition ispyrolys temperature [K Ipolymuclear aromatic compound.Throughhydropenolysis, more and high value added aromaticPg.5 Weight lous of the lignin chor obtainedin the pyrolywiscompounds can be obtained. The yield of I0Gdoesn't increase; the distribution of it changes greatly,the char. In addition, the color of deep condensationmainly the yield of CO. In the case of catalystmethanol solution becoming sable illustrates thatCoMo-B, I0G CO2 and CO react as fllows:partial tar is not decomposed by catalytic pyolysis.CO2+H2→CO+H2O(1)4. Effects of pyrolysis temperature on theCO+H2→CH+H2O(2)yield of the catalytic hydrogenization productPartial CO2 is converted to CO，and partial CO isFig.6 shows the effects of pyrolysis temperature onconverted to methane. Therefore, catalyst CoMo-Bthe yield of the catalytic hydrogenization product.can not only promote the secondary decomposition ofThe operating conditions were as follows:tar but also promote the reaction of IOG CO, CO2atmosphere gas: H2, superficial gas velocity: 0.32m/s,with hydrogen to obtain more CO and methane.static bed height: 0.08m, continuous feed reactionHowever; as far as the yield of the entiretime: 40min. It can be seen that the yield of I0Gdecomposition products is concerned, there is stillincreased with increasing pyrolysis temperature, anquite a lttle tar not decomposed. The reason for itthe increase is mainly due to Co, in contrast the yieldmay be that the sulfide produced in the pyrolysisof CO2 almost independent of temperature. Inmakes catalyst CoMo-B partially poisoned and loseaddition to the secondary discomposition improvedactivity，and then affects the secondary reaction ofby the development of the catalyst activity， COgas phase.Fig.5 ilustrates the decompositioncomes from the reaction of the activated char andproperty of the char collected in the cyclone. Thewater vapor discomposed from the lignin. the yield ofvolatile matter consists of the volatile matter fromHCG doesn 't increase; the distribution of it changesitself and partial tar which is not decomposed butgreatly. The yield of methane in HCG increased withabsorbed by the char during the separation procedureincreasing pyrolysis temperature, and the yield ofin the cyclone. According to the curve of weight lossethane and propane decreased gradually. It isof the char, the content of volatile matter is high inindicated that methane has a more stable structure inhydrocarbon, and the raise of pyrolisis temperatureimproves the hydrogenization cativity of the catalystand promotes the generation of methane. With theEL 87SK0.2mraise of pyrolysis temperature, the yield of the light%aromatic hydrocarbon first increases and thendecreases. The reason of increase is that pyrolisistemperature improves the hydrogenization activity ofthe catalyst and promotes the secondarydecomposition of tar. The reason of decrease is thatthe raise of pyrolysis temperature gives rise to thecarbon deposition on the surface of catalyst andreduces active state of catalyst surface. Therefore, Inorder to obtain valuable BTXN as an intermnediate inCMorBthe pyrolysis as much as possible, it is extremelyPig.4 Ditribution ad the probysis produete dligminimpresistance andfor tbe catalyeta o SiO2 and CoMoBbhydre中国煤化工YHCNMHG372 -Vol.19 SuppJournal of Tianjin University of Science and Technology1) Release of volatile matter out of the paper10吕∞making lignin is affected heavily by the pyrolysistemperature，and starts at 370K，the yeildofwhich is first slower and then during thepyrolysis increase of the pyrolysis temperaturefrom 550K to 750K becomes faster， and thenlower gradually, up to 60wt%, dry at 1173K.2) In the case of the inert media silica sand, theyield and the distribution of the pyrolysisC唱products are almost unchanged under the0 CHdifferent kind of atmosphere.o3) In the case of the” catalyst CoMo-B withhydrogen atmosphere，the intermediate BTXN业LLi.且yield is apparently improved and reached2.52wt%，dry， 3.3 times as much as that in thecase of silica sand.与思Nophtheboo CoMoB. h.082mh4) In order to obtain valuable BTXN as an0.08m.40minintermediate in the pyrolysis as much as possible,Paloeoeo,it is extremely important to select high sulfurresistance and hydrogenization activity catalyst.5.REFERENCES8486566873 883Reactio temperature [K][4] Gupta,P. 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