Biomass Catalytic Pyrolysis with Ni Based Catalyst to Produce Hydrogen Rich Gas

Dec. 2010Joumal of Northeast Agricultural University (English Edition)Vol.17 No.4 43-49Biomass Catalytic Pyrolysis with Ni Based Catalyst to ProduceHydrogen Rich GasWANG Mingfeng', LIU Min', XU Xiweir, LI Bosong, ZHANG Qiang', and JIAN Enchenl'20' Engineering College, Northeast Agricultural Uiversity, Harbin 150030, China' Engineering College, South China Agiculural University, Guangzhou 510642, ChinaAbstract: Hydrogen rich gas was produced using rice husk as biomass material on the continuous biomass pyrolysis apparatuswhich consisted of continuous pyrolysis reactor and secondary catalyie cracking reactor. Ni based catalysts of difent Ni/Al massratio and calcined temperature were prepared by impregnating mcthod. The catalysts were characterized by X ray diffaction (XRD),scan electron microscope (SEM) and FT-IR Spectrometer (FT-IR). Ni based catalyst showed good selectivity for H2 production frombiomass. Catalysts prepared under dfferent conditions had ltte infuence on the yields of three states products when used at the samecracking temperature. Ni/AI mass ratio played an important role in products setiviy. However, the content of NiO increased futherwhen Ni/AI mass ratio values reached 0.7: 10, and the yield ofH, slightly increased. Hydrogen yield was greatly impacted by calcinedtemperature. Catalyst calcined at 550C performed best. When the catalyst was calcined at high temperature, NiO in the catalysttransformned into NiAl20, and the acid site also changed, which caused the deactivation of the catalyst. The bydrogen yield increasedwith the cracking temperature. The highest stable yield of hydrogen was about 30% without increasing with the cracking temperature.Key words: biomass, continuous pyrolysis, catalytic cracking, hydrogenCLC number: S216 Document code: A Article ID: 1006-8104(2010)-04-0043-07pyrolysisl2 .IntroductionAmong various thermochemical conversion pro-cesses, the pyrolysis is considered to be an emergingHydrogen production plays a very important role intechnology for hydrogen production. In the pyrolysisthe development of hydrogen economy. One of theprocess, biomass is heated in the absence of oxygen,promising hydrogen production approaches is theor partially combusted in a limited oxygen supply, toconversion from biomass, which is abundant, cleanproduce a gas mixture containing mainly carbonand renewablel". Biomass as a source of renewableoxides, some methane and higher hydrocarbons inenergy has several environmental advantages overminor quantities, an oil-like liquid (named bio-oilfossil fuels. The main advantage is the lower netor tar) and a carbon rich solid residue. The influence ofemission of greenhouse gases. From a technical pointcarbon dioxide on the energy density and hydrogenof view, biomass resources (energy crops, agriculturalseparation can't be neglected. And what's more im-residues, organic, forestry, industrial or municipalportant, tar proposes a serious threaten to downstreamwastes) can be transformed into sustainable hydrogenfuel cell system, both for the electrodes and for theby thermo chemical processes like gasification and pipelines. The absence of catalyst is helpful for theReccived 11 November 2010中国煤化工Supported by Key Project of Natural Science in Guangdong Province (06Z004); ScierCNMHG_ng (0050000WANG Mingfeng (1982-). male, Ph. D, engaged in the research of biomass energy utMYH* Corresponding author. JIANG Enchen, professor, supervisor of Ph. D student, cengaged in the research of biomass energy utilization. E-mail:ecjiang@scau.edu.cnhttp: /pblish.eau.du.conJoumal of Northeast Agricultural University (English Edition)Vol.17 No.4 2010conversion of tar into an H-rich gas']. Various catalys-and cracking temperatures were concermed.ts have been introduced in pyrolysis'!. For economicreasons, the nickel catalyst is the most suitable choiceMaterials and Methodsamong metals like cobalt (Co), iron (Fe), platinum (Pt),ruthenium (Ru) and rthodium (Rh). Several nickel (Ni)Materialsbased on catalysts have been investigated and found toRice husk samples have been taken from the Ricebe very effective in terms of tar removal-91.Processing Plant in Zengcheng, Guangzhou City.In this paper, Ni based on catalysts were preparedBefore experiments, the samples were dried, milled,and the activity was evaluated on the continuous bio-sieved and then separated in fractions. Particles ofmass pyrolysis apparatus. XRD, SEM and FT-IR tech-biomass with a size smaller than 0.35 mm were used.nologies were used to characterize the catalyst. Diffe-The proximate analysis and ultimate analysis resultsrent Ni/Al mass ratios, catalyst calcined temperaturesare shown in Table 1.Table 1 Proximate analysis and ultimate analysis of rice husk (wt%)Industry analystElemental compositionMoistureVolatile material Carben fixationAshC0N2.4767.5717.312.6742.738.390.580.16can make active component more effective.In thisCatalyst preparation and characterizationpaper, XRD (x-ray diffraction), SEM (scanning elec-The reagents for catalyst preparation were as follows:tron microscope) and FT-IR (fourier transform infraredNi(NO3)2* 9H2O (≥98.50%) was purchased fromspectroscopy) were used to characterize the catalyst.Chemical Fu Chen Reagent Co, Ltd. in Tianjin;X-ray powder diffractograms were recorded followingy-Al2O3 (≥93%) was purchased from Xinyu Chemicalthe step-scanning procedure (step size=0.028, twoPacking Plant in Jiangxi, water used in experimenttheter degree scanning from 5 to 80) by using a com-was deionized. Ni based catalysts were prepared byputerised D/max-Ra diffractometer (Cu Ka radiation,impregnating method. The diameter of Al2O3 ball is1=0.15418 nm). SEM was performed with FEI-XL303-5 mm, the alumina purity is 93%, and specific surfaceenvironmental scanning electron microscope with acce-area is about 200 m'.g'. Steep the Al2O3 in deionizedlerating voltage 20 kV. FT-IR was tested on Brukerwater for 2 h at room temperature to make sure theVERTEX70 Spektrometer: samples were desorbed atpore canal is flled with water molecule. Then soak the300C and 0.01 Pa atmosphere for 2 h, then were cool-Al2O3 with aqueous solutions of Ni(NO3)2●9H2O fored to room temperature to adsorb of pyridine for 0.5 h.4 h. Dry AlO, after soakage at 70C overnight. MakeAfter the systerm reached equilibrium, samples weresure Ni(NO3)2 has almost been adsorbed on the surfaceheated to 200C desorption 1 h. Then placed samplesof Al2O3. The material was then calcined in air forin diffuse reflectance annex. Spectrum acquisition range4 h each at temperature from 500C to 700C. Thewas 600-4 000 cmi ', with resolution of 4 cm' , and KBramount of NiO loading on the catalyst was controlledwas as the background. 1 450 cm' was characteristicby changing the concentration of Ni(NO3)2●9H2Owave of L acid, and 1 540 cm' belonged to B acid.solution. As the resistance of volatiles spreading into中国煤化工the catalyst particles is very big, the reaction priorlyCataCNMH G_takes place at the outer surface, so this type of catalystThe cumnsuvus caiaiyil pjivij on apparatus for bio-E-mail: xuebaoenglish@neau.edu.cnWANG Mingfeng et al. Biomass Catalytic Pyrolysis with Ni Based Catalyst to Produce Hydrogen Rich Gas.45.mass catalytic pyrolysis is shown in Fig. 1. It consistedcracking reactor for deep decomposition, then enter-of drive motor, electric fumace, pyrolysis reactor, car-ed into the condenser, wood vinegar and tar were col-bon box, cracking furmace, cracking reactor and gaslected here. Non-condensing gas exhausted from thecondenser. Biomass powder was fed from the spiraloutlet. Continuous pyrolysis temperature was 500C.feeder on pyrolysis reactor and pyrolyzed during con-Cracking temperatures were 600"C, 700C, and 800C.veying. Char from the process of pyrolysis was collet-200 g catalyst was used for each test. Pyrolysis gased by the charcoal box. The pyrolysis gas went through thecomposition was measured by the Agilent GC6820.TO GCFig. 1 Sketch of biomass continuous pyrolysis reactor system1, Motor; 2, Pyrolysis reactor; 3, Eletric furnace; 4, Char cllection container; s, Cracking reactor; 6, Electric furmace; 7, Condensing system.in decrease of liquid yield. Cracking at the same tem-Results and Discussionperature, the catalyst prepared under different con-ditions have lttle influence on the yields of three stateCoke, liquid and gas yieldsproducts.Coke, liquid and gas yields of rice husk catalyticWith the secondary cracking temperature increased,cracking by Ni based on catalysts are shown in Table 2.the liquid yield sharply decline by using Ni0.7-550The results showed that Ni based catalyst promotedcatalyst (Ni/AI=0.7: 10, calcined temperature To wasvoltile decomposition into small molecules resulting550"C, the same as below).Table2 Coke, liquid and gas yields of rice husk catalytic cracking under Ni-ALO,Test conditionTar(wt%) Liquid(wt%) Gas(wt%购) Loss (wt %)Ni/Al6(min)T。(C)T,(C)T(C)0.2: 1055050060034.1025.1034.895.910.5:105034.8225.0834.675.430.7:103.5425.7435.135.591.0:10 .s5025.9433.68.710033.7524.6133.91.730.7: 1034.5525.8933.55.0134.8324.6733.67700”o4钱82.16800中国煤化工6.15DYHCNMHG14-Retention time; T-Calcined temperature; T-Pyrolysis temperature; Tx-Cracking tempouaushttp: /plblih.eau.edu.con.46.Joumnal of Northeast Agricultural University (English Edition)Vol.17 No.4 2010mass ratio, the selectivity to hydrogen increasedEffects of Ni content on the hydrogen yieldsignificantly. Above all, the higher content of activeHydrogen yields of rice husk catalytic pyrolysis atsubstance, the higher catalytic activity, which proved600"C under Ni based catalyst calcined at 550C withNiO/Al2O, catalytic had a strong selectivity to hydro-different proportional of Ni/AI are shown in Fig. 2.gen. However, the content of NiO increased furtherNi/Al mass ratio played an important role in productswhen Ni/Al mass ratio values reached 0.7: 10, theselectivity. It was indicated that by increasing Ni/Alyield of H2 slightly increasd.16.0014.000 Ni/A1=0.2:1010.00 |目Ni/Al=0.5:108.00图Ni/Al=0.7: 10■Ni/Al=1.0: 104.002.00810131517192125273538404550556Time (min)Fig.2 Hydrogen yields of rice husk catalytic cracking at 600 under Ni based catalystCatalyst calcined at 550"C had the highest hydrogenEffects of calcined temperature on the hydro-yield which was about 10% when the hydrogen yieldgen yieldbecame stable. The variation trend of H2 was similarThe hydrogen yield of rice husk catalytic pyrolysiswhen calcined temperature was 500"C. However, theat 600C by using catalyst calcined at different tem-proportion of H2 decreased when the calcined tem-peratures is shown in Fig. 3. Ni/Al of catalyst usedperature increased. It could be concluded that thewas 0.7: 10. It was distinctly that the hydrogen yieldcatalyst calcined at high temperature had low activity.was great impacted by the calcined temperature.The best calcined temperature was 550C.8r6F2-四500C calcined0一■Ss0C calcined图600C calcined■700C calcined5 8101315171921232527293235384045505560中国煤化工Fig. 3 Hydrogen yield of catalyst calcined at dffrente temperaturesMYHCNMHGE-mail: xuebaoenglish@ neau.edu.cnWANG Mingfeng e1 al. Biomass Catalytic Pyrolysis with Ni Based Catalyst to Produce Hydrogen Rich Gas.47.the stronger fluctuation of hydrogen yield got. ForEffects of secondary catalytic cracking tem-instance, when the secondary cracking temperatureperature on the hydrogen yieldwas 800C, the highest bydrogen yield reached 40%Under the condition of Ni/Al mass ratio 0.7: 10 andfor a short time then decreased to 30%.catalyst calcined temperature is 550'C, the hydrogenThe data showed that the highest stable yield ofyields at different secondary catalytic crackinghydrogen was about 30% without increasing thetemperatures SY (600C, 700"C and 800"C) are showncracking termperature. It meant that the yield of hydro-in Fig. 4. It showed that the hydrogen yield increasedgen has reached the maximum. This was related withwith the cracking temperature. Before it reached alow water content of rice husk powder, which wasstable state, the yield of H2 had firstly increased thenabout 2%-3%, therefore, the provided amount of Hde-creased. The higher the cracking temperature was,was very low.0-更35-2600C cracked25-8 700C cracked图800C cracked20-15一自05.8101315171921232527293235384045505560Time (min)Fig. 4 Hydrogen yield of rice husk catalytic cracking at dfferent temperaturesCharacterization of Ni-based catalystSEM characterizationXRD characterizationNi0.7-550 catalyst was characterized by SEM, shownNi0.7-550(Ni/Al=0.7: 10, calcination temperature T。in Fig. 6. The surface of Ni0.7-550 catalyst waswas 550"C, the same as below) and Ni0.7-700 werecovered by flaky particles of different size, most of theused in XRD characterization.particles are smaller than 5 μm, and there were also theThe result of XRD is shown in Fig. 5. As thesame pore.calcined temperature increased, NiO diffraction peakFT-IR characterizationwas weaker. By contrast, NiAl2O, diffraction peakNi0.7-550 and Ni0.7-700 were used in FT-IR charac-was stronger. It showed that reaction between NiOterization. The result is shown in Fig. 7. The peaksand Al2O3 was occurred and NiAl2O4 which had spinelof the two samples were slightly similar. There wasstructure, bright blue color, more chemical stabilitya, certain amount of hydroxyl which closely relatedand lower activity was generated when Ni-basedwith catalyst action such as dehydration reacted bycatalyst was calcined at high temperature. XRD resulthydroxyl and hydrogen. Research showed that theshowed that reaction between active component andSiO2* AlO, surface was covered with two hydroxylcarrier should happen to product the substance withgroup中国煤化工:re3460cm'andspinel structure after calcined at high temperature,3 520|Y片C N M H Gappeared betweenwhich caused the deactivation of the catalyst.3400 and 3 600 cm* must come from the interactionhttp: /publish.neau.edu.cn.48.Joumal of Northeast Agricultural University (English Edition)Vol. 17 No.4 2010of activated metal oxide and carrier.origin software was used to calculate the peak area ofL acid, B acid peak area could be corresponding toL acid and B acid to measure the amount of acid sitesthe numbers of acid sites of catalysts. In this paper, theof catalysts. The results are shown in Table 3.00 M75N077000 t1 000400 t甚00200 t1020304050607010.20.3040506070Position [2Theta] (Copper(C))a Ni0.7-SS0b Ni0.7-700Fig.5 Results of XRD characterization of catalystsSoWoNE足SCAm9mFig.6 Results of SEM characterization of catalysts一550C calcined--. 700'C calcined...700C calcined500100015002000250030000350040001400 1450 1500 1550 1600 1650Wave number (cm)Wave poumber (cm')Fig. 7 Test results ofL acid and B acid of catalystsTable 3 Results of peak area ofL acid, B acid and total acid content of catalystsItemL acidB acidTotal acid contentNi0.7-5505.46中国煤化工1891Ni0.7-7007.10MHCNMHG20.86E- -mail: xuebaoenglish@ neau. edu.cnWANG Mingfeng et al. Biomass Catalytic Pyrolysis with Ni Based Catalyst to Produce Hydrogen Rich Gas.49.With calcined temperature increasing, the volumeacid content increased. The large density of acid siteof L acid increased, while the volume of B acidon the surface of catalyst made carbon deposition ondecreased, but the total acid content increased. Thethe acid site easily and resulted in deactivation of thechange of the amount of L acid, B acid and the totalcatalyst.acid content would cause the different activities andmechanisms of the catalyst.ReferencesResearches showed that the active site of catalystINiM,LeungDYC,LeungMKH,etal.Anoveriewofhydrogenwas the acid site. The more the acid site per unit areaproduction from biomass []. Fuel Processing Technology, 2006,was, the higher activity the catalyst had. However, the87: 461-472.large densities of acid site on the surface of catalysts2 Kazi K M F, Jllez P, Chornet E. Preimpregnation: an importantmade carbon deposition on the acid site easily andstep for biomass refining processes [] Biomass Bioenergy, 1998,resulted in deactivation of the catalyst.15(2): 125-141.3 Rapagna s, Jand N, Foscolo P U. 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Ind Eng Chem Res, 1998, 37(12):was stable and deactivated, which caused the deactiva-4617- 4624.tion of the catalyst.0 Huang Z T. Industry catalyst manual [M]. Beijing: ChemicalWith calcined temperature increasing, the totalIndusty Press, 2004: 237.中国煤化工MYHCNMHGhttp: /publish.neau .edu.cn