Pyrolysis of Seaweeds for Bio-oil and Bio-char Production

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1 121 A publiction of VOL. 37, 2014 CHEMICAL ENGINEERING TRANSACTIONS Guest Editors: Eliseo Rnzi, Kthrin Kohse- Höinghus Copyright 2014, AIDIC Servizi S.r.l., ISBN ; ISSN The Itlin Assocition of Chemicl Engineering DOI: /CET Pyrolysis of Seweeds for Bio-oil nd Bio-chr Production Je Hyung Choi,b, Hee Chul Woo b nd Dong Jin Suh, * Clen Energy Reserch Center, Kore Institute of Science nd Technology, 5, Hwrng-ro 14-gil, Seongbuk-gu, Seoul, , Kore b Deprtment of Chemicl Engineering, Pukyong Ntionl University, 365 Sinseon-ro, Nm-gu, Busn, , Kore *[email protected] A pyrolysis study on species of brown lge Scchrin jponic ws crried out in fixed-bed rector. The yields of bio-oil nd bio-chr obtined t 450 o C were 47 % nd 33 %, respectively. The rw S, jponic, ethnol nd cid pretreted smples nd the resulting pyrolysis products were lso chrcterized with respect to proximte nd ultimte nlysis, nd higher heting vlue. The crude bio-oil frctiontion by distilltion under reduced pressure followed by ctlytic hydrodeoxygention (HDO) over Pd/C could be employed to upgrde the bio-oil. The higher heting vlue (HHV) of HDO bio-oil product ws close to those of conventionl gsoline nd diesel. 1. Introduction Biomss-derived fuels hve received incresing ttention to give solution to the problems of fossil fuel depletion nd globl wrming. Biofuels re considered to be crbon cycle neutrl becuse CO 2 relesed into the tmosphere when burnt is fixed in the biomss by photosynthesis. In recent yers, there hs been considerble interest in producing biofuel from lge, so-clled third genertion biofuel. Mcrolge (seweeds) hve huge potentil to be used s source for the production of biofuels due to their high photosynthetic efficiency, fst growth rte, high crbohydrte content, no requirement of cultivtion lnd re nd no competition with food crops. The quculture production of mcrolge in the world hs been incresed continuously to 15 million wet-metric-ton with n nnul growth rte of 10.5 % in 2010 (FAO yerbook, 2012). Vrious types nd species of mcrolge hve trditionlly been cultivted for food in the costl regions of Est Asi. Among them, brown lge re the most suitble type for mss production in Kore becuse they grow more thn red nd green lge in the temperte regions. Mcrolge cn be converted to biofuels through biologicl nd thermochemicl routes. Pyrolysis is considered to be one of the most plusible conversion processes to produce biofuels by heting biomss in bsence of oxygen. In literture, compred to pyrolysis of lignocellulosic biomss, there re limited studies on mcrolge pyrolysis. The yields of bio-oil from brown lge pyrolysis ws not generlly high, mostly lower thn those of bio-chr since the high sh content of the lge brought low bio-oil yield by secondry tr rection. It is reported tht the mximum yield of bio-oil depends on severl prmeters such s wter nd sh contents, biomss composition, pyrolysis temperture nd vpor residence time (Fhmi et l., 2008). The pyrolysis products cn lso be ffected by the morphology of biomss primrily due to het trnsfer effects. Although fluidized-bed fst pyrolysis processes re known for the production of high yields of bio-oil, severl other pyrolysis modes hve been introduced to overcome their inherent disdvntges of high level of crrier gs flow nd the corresponding excessive energy requirements (Oyedun et l., 2012). Crude bio-oil produced by pyrolysis cnnot be used s fuel due to its high wter nd oxygen contents, nd the presence of unsturted nd phenolic moieties (Be et l., 2011). As result, bio-oils need to be upgrded or treted to improve their qulity before used for most pplictions. The im of this study ws to investigte the fesibility of bio-oil nd bio-chr production from brown lge vi fixed-bed pyrolysis, frctiontion by vcuum distilltion, nd ctlytic hydrodeoxygention. Plese cite this rticle s: Suh D.J., Choi J.H., Woo H.C., 2014, Pyrolysis of seweeds for bio-oil nd bio-chr production, Chemicl Engineering Trnsctions, 37, DOI: /CET

2 Mterils nd methods 2.1 Feedstock Scchrin jponic, brown lg, s feedstock ws supplied from Wndo Islnd, Republic of Kore nd used fter drying. The feedstock ws ground with knife mill nd sieved to obtin prticles in the rnges of 3-5 mm. 2.2 Fixed-bed pyrolysis Pyrolysis ws crried out in cylindricl fixed-bed rector (33 cm in length nd 2.5 cm in dimeter) filled with screen mesh holder contining biomss prticles. Nitrogen crrier gs ws fed t flow of 0.6 L/min for 10 min to remove ir in the rector before rection. The pyrolysis vpour leving the rector ws condensed in three condensers in series (room temperture, ice wter nd liquid nitrogen cooled). The condensed liquid (bio-oil) ws collected in flsk while the solid residue (bio-chr) remined in the rector. Pyrolysis conditions were s follows: temperture, 450 C; holding time, 8 min.; Crrier gs flow rte, 0.6 L/min (2.0 cm/sec). The bio-chr yield, defined s (solid dry weight) 100 / (feed dry weight), ws obtined by weighing the biomss holder before nd fter pyrolysis while the liquid yield ws defined s (dry weight of collected liquids) 100 / (feed dry weight). The gs yield ws clculted from the blnce. 2.3 Bio-oil distilltion The produced bio-oil ws frctionted using vcuum distilltion pprtus. 1 L of the crude bio-oil ws put in round bottom flsk with two necks; one neck for distilltion temperture mesurement nd control nd the other neck for connecting the distilltion column with 10-theoreticl pltes. The temperture ws monitored t the top of the distilltion column while the system pressure ws mintined by vcuum pump (N840 Diphrgm Pump, KNF, Germny). 2.4 Hydrodeoxgention The queous nd non-queous frctions of bio-oil obtined by the vcuum distilltion were further upgrded by ctlytic hydrodeoxygention (HDO). The ctlytic rection ws performed in bench-scle trickle-bed rector with concurrent downflow of bio-oil nd hydrogen. The rector ws stinless steel tube of 475 mm in length nd n inside dimeter of 11 mm, which ws plced in n electric furnce controlled by temperture nd thermocouple locted below the ctlyst bed. The rection pressure ws mintined by Tescom bck pressure regultor. Hydrogen ws introduced into the rector vi mss flow controller (Brooks Instruments) from gs cylinder mnifold system. The bio-oil ws fed into the rector by HPLC pump (Shimdzu, Jpn). The liquid products were cooled nd collected using chiller plced t the outlet of the bck pressure regultor. In typicl experiment, 25 ml of ctlyst pellets were loded on the supporting bed consisting of glss wool nd glss beds. The rection conditions were s follows: temperture, C; pressure, 100 br; Liquid hourly spce velocity (LHSV), h -1. The upgrded product yield ws evluted on the bsis of the production of non-queous or orgnic phse oil from feed bio-oil. The upgrded bio-oil ws chrcterized by mesuring elementl compositions (C, H, O, N nd S), wter, density, ph, nd higher heting vlue (HHV). 2.5 Anlyticl methods The proximte nlysis of S. jponic determined the moisture nd sh contents ccording to the ASTM stndrd methods E 1756 nd E The content of voltile mtter ws determined using nonisotherml thermogrvimetric (TG) method by following the ASTM E method. The content of fixed crbon ws clculted by difference. The contents of voltile mtter nd therml chrcteristics of S. jponic nd bio-chr were lso obtined by the TG method. In the TG method, 20 mg of smple were heted in thermogrvimetric nlyzer (TGA 2000, TA Co., USA) t the tmosphere of 30 ml/min of N 2. The temperture ws progrmmed from room temperture to 1000 o C t rte of 20.0 o C/min. The elementl compositions (C, H, N nd S) of the S. jponic nd bio-oils were determined on n elementl nlyzer (Thermo Fisher Scientific, FlshEA 1112). The moisture content of the bio-oils ws determined through Krl-Fischer titrtion ccording to KS M The orgnic components of bio-oils were qulittively identified with GC-MS (7890A, Agilent Technologies, HP-5 cpillry column, 60 m 0.25 mm 0.25 μm). The GC oven temperture ws held t 40 C for 5 min, nd progrmmed to rmp t 5 C/min to 300 C. And then the oven ws kept t the finl temperture for 10 min. The injector temperture ws 280 C, nd n injection volume of 1 µl ws dopted with the split rtio set s 50:1. The mss spectrometer ws operted in full scn mode, nd its mss rnge ws tomic mss units. The identifiction of the chromtogrphic peks ws bsed on n utomtic librry serch (NIST librry version 2.0).

3 3. Results nd discussion 3.1 Feedstock chrcteriztion The chrcteristics of the rw S. jponic, ethnol nd cid pretreted smples for fixed-bed pyrolysis were summrized in Tble 1. Since pyrolysis trnsforms ny type of biomss into bio-oil nd bio-chr, residul biomss fter extrction of vlue-dded compounds (ethnol pretretment) or pretretment for further biologicl conversion (cid pretretment) cn be used for pyrolysis feedstock. The sh content of S. jponic ws much higher thn tht of most lignocellulosic biomss while the crbon content ws lower ccordingly (Kim et l., 2012). The high sh content my inhibit the pyrolysis oil production, while leding to improved qulity of bio-chr s soil mendment becuse inorgnic nutrient contents remined high. A decrese of crbon nd increse of oxygen contents fter the ethnol pretretment my be involved in mild oxidtion of orgnic crbon constituents in S. jponic with hot ethnol. The sh content decresed drsticlly from 23 % to 1.46 % fter the cid pretretment. Tble 1: Proximte nd ultimte nlysis nd heting vlue of S. jponic smples Prmeter Types of biomss Rw biomss Ethnol pretreted Acid pretreted b Proximte nlysis (wt.%) Moisture c Voltile mtter d Fixed crbon e Ash f Ultimte nlysis(wt.%, dry bsis) Crbon Hydrogen Nitrogen Sulfur Oxygen e HHV g (MJ/kg) Pretreted in 98 wt.% bioethnol solution with reflux for 180 min. b Pretreted in 5 wt.% H 2 SO 4 solution t 100 o C for 500 min. c Determined ccording to the ASTM E 1756 stndrd method. d Determined by thermogrvimetric nlysis. e By difference. f Determined ccording to the ASTM E 1755 stndrd method. g The higher heting vlue (HHV) ws estimted by the correltion of Chnniwl nd Prikh (2002) Fixed-bed pyrolysis The results of fixed-bed pyrolysis of the rw nd pretreted S. Jponic were summrized in Tble 2. Compred with trditionl fst pyrolysis, fixed-bed pyrolysis produced more chr nd less oil. The product distribution ws found to be quite dependent on pretretment. Pretretment decresed bio-oil yield nd incresed tht of non-condensble gses without ny noticeble chnge in bio-chr yield. These results my be ssocited with the loss of condensble crbon sources by the pretretment, s evidenced by chnges in crbon nd oxygen content s shown in Tble 1. It ws reported tht the sh such s lkli nd lkline erth metls in biomss served s ctlysts in degrding condensed bio-oil to gs, leding to reduced bio-oil yield (Fhmi et l., 2008). Therefore, the dominnt fctor for determining the yield of bio-oil from fixed-bed pyrolysis of cid pretreted S. jponic ws the loss of condensble crbon sources rther thn sh removl. As expected, bio-chr produced from the cid pretreted S. jponic hd n incresed crbon content nd HHV with only smll sh content. This kind of bio-chr cn be used s solid fuel source. It ws observed from TGA results tht therml decomposition of S. jponic into bio-oil, bio-chr, nd gses occurred over the temperture rnge o C, mostly o C, which cn be divided into three stges (Figure 1). The first stge t tempertures up to 190 o C corresponded to dehydrtion. The second stge between 200 nd 270 o C ws ssocited with the decomposition of crbohydrtes such s lginic cid, lminrin, fucoidn nd mnnitol. The third stge up to 350 o C ws result of the decomposition of proteins. TGA curves of the feedstocks nd their corresponding bio-chrs t

4 124 tempertures higher thn 350 o C were quite similr, indictive of further decomposition of bio-chr into solid residues. Tble 2: Results of fixed-bed pyrolysis of S. jponic smples Prmeter Types of biomss Rw biomss Ethnol pretreted Acid pretreted Product Yields (wt.%) Bio-oil Biochr Gs Proximte nlysis of bio-chr (wt.%) Moisture Voltile mtter b Fixed crbon c Ash d Ultimte nlysis of bio-chr (wt.%, dry bsis) Crbon Hydrogen Nitrogen Sulfur Oxygen c HHV e (MJ/kg) Determined ccording to the ASTM E 1756 stndrd method. b Determined by thermogrvimetric nlysis. c By difference. d Determined ccording to the ASTM E 1755 stndrd method. e The higher heting vlue (HHV) of bio-chr ws estimted by the correltion of Chnniwl nd Prikh (2002). Conversion (%) Rw biomss Ethnol pretreted biomss Acid pretreted biomss Biochr from rw biomss Biochr from ethnol pretreted biomss Biochr from cid pretreted biomss Temperture ( o C) Figure 1. TGA profiles of S. jponic smples nd their corresponding bio-chrs 3.3 Bio-oil distilltion Bio-oil is thermlly unstble mixture of hundreds of oxygented orgnic compounds. Atmospheric distilltion t high tempertures is thus not considered to be suitble technique for the crude bio-oil seprtion (Brown, 2011). Distilltion under reduced pressure llows thermlly unstble compounds to be distilled t lower tempertures. As shown in Tble 3, the three distilled frctions of the crude bio-oil were obtined t temperture o C with reduced pressure of 40 mmhg: the frction I (first distillte, boiling point (bp) < 40 o C), the frction II (second distillte, 40 o C < bp < 160 o C), nd the residue (third

5 distillte, bp > 160 o C). The lightest frction (frction I) contining mostly wter ws more thn 50 % of the crude bio-oil, but not used for further ctlytic upgrding. The frction II could be seprted into two liquid phses: the upper non-queous portion nd the lower queous portion. The H/C rtio of frction II ws in the rnge of , which is closer to the vlue for romtics rther thn for lknes. Bio-oil is composed of heterocyclic romtic compounds such s 1-(2-furnyl)-ethnone, dinhydromnnitol, isosorbide nd cyclopentene etc (Kim et l., 2012). Bio-oil is known to be complex mixture of oxygented orgnic compounds. The queous phse oil (O/C = 0.40) contined more quntities of oxygented compounds thn the non-queous phse oil (O/C = 0.12). The distilled bio-oil ws upgrded by ctlytic hydrogention to remove oxygen nd sturte double bonds, leding to n incresed H/C nd decresed O/C. The lower H/C rtio of solid coke implies high degree of unsturted structures like romtic compounds. Tble 3: Results of reduced pressure distilltion of S. jponic bio-oil Distilltion Yield Wter Ultimte nlysis Appernce Temp. (wt.%, wet content (wt.%) ( o C) bsis) (wt.%) C H O H/C O/C Frction Ⅰ < Bright yellow Frction Ⅱ Phse seprtion Non-queous phse Drk brown Aqueous phse Ornge Residue (solid coke) > Blck Loss Hydrodeoxygention Most studies on ctlytic upgrding to dte hve been done using model compounds of bio-oil rther thn rel bio-oil. In this work the distillte frction II ws used s feedstock for ctlytic upgrding by hydrodeoxygention. A commercil crbon supported plldium (1 wt/% Pd/C, Aldrich) ws chosen s ctlyst. The mximum yield of HDO product oil ws 0.37 g/g feed under the rection conditions of 400 o C, 0.48 h -1 LHSV nd 100 br H 2 pressure. The fuel properties of HDO bio-oil product were compred with those of gsoline nd diesel (Tble 4 nd Figure 2). The HHV of HDO bio-oil product with decrese of its oxygen content from 21.9 % to 8.7 % ws incresed to 37.5 MJ/kg compred with 18.9 MJ/kg of mcrolge bio-oil (Trinh et l., 2013), pproched to 45 MJ/kg of conventionl gsoline nd diesel. As expected, the H/C rtio of the HDO product incresed with decresing the O/C rtio. The double bonds of unsturted compounds were sturted by hydrodeoxygetion. Prticulrly in the queous phse of the distillte frction II, heterocyclic romtic compounds such s dinhydromnnitol nd isosorbide could lso be deoxygented. According to totl ion chromtogrms, the HDO product comprising 16.2% liphtics, 18.2% romtics, 29.4% cyclopentnes, 5.1% cyclohexnes, 20.7% heterocyclics, nd 10.4% furnes showed somewht similr pttern to gsoline (Figure 2). 125 Tble 4: Fuel properties of HDO bio-oil produced from S. jponic compred with typicl properties of gsoline nd diesel Properties This work Gsoline Diesel Moisture content (wt.%) Density (@ 15 o C, kg/m 3 ) ph Ultimte nlysis (wt.%) Crbon Hydrogen Nitrogen Sulfur Oxygen HHV (MJ/kg) Summer gsoline nd diesel in Republic of Kore

6 126 Diesel Abundnce Gsoline HDO product Time (min) Figure 2. Totl ion chromtogrms of the HDO product, gsoline nd diesel 4. Conclusion Bio-oil nd bio-chr were produced by pyrolysis of species of brown lge Scchrin jponic in fixed-bed rector t 450 o C. The yields of bio-oil, bio-chr nd non-condensble gses were 47 %, 33 % nd 20%, respectively. Pretretment of S jponic with ethnol or cid decresed bio-oil yield due to loss of condensble crbon sources. The crude bio-oil ws frctionted into three frctions by distilltion with reduced pressure 40 mm Hg. The second frction under boiling point rnge of o C ws upgrded by ctlytic hydrodeoxygention (HDO). The mximum yield of HDO product over 1 wt.% Pd/C ws 0.37 g/g feed under the rection conditions of 400 o C, 0.48 h -1 LHSV nd 100 br H 2 pressure. The H/C rtio of the HDO product incresed with decresing the O/C rtio. The higher heting vlue (HHV) of HDO bio-oil product ws incresed to 37.5 MJ/kg from 18.9 MJ/kg for mcrolge bio-oil, close to those of conventionl gsoline nd diesel (45 MJ/kg). Acknowledgement This work ws finncilly supported by the Ministry of Ocens nd Fisheries of Kore (contrct no ). References Americn Society for Testing Mteril, ASTM E , 2006, Stndrd test method for voltile mtter in the nlysis of prticulte wood fuels, West Conshohocken, (Pennsylvni): ASTM Interntionl. Be Y.J., Ryu C., Jeon J.-K., Prk J., Suh D.J., Suh Y.-W., Chng D., Prk Y.-K., 2011, The chrcteristics of bio-oil produced from the pyrolysis of three mrine mcrolge, Bioresour. Technol., 102, Brown R.C., 2011, Thermochemicl Processing of Biomss: Conversion into Fuels, Chemicls nd Power. Wiley, Hoboken, United Sttes. Chnniwl S.A., Prikh P.P., 2002, A unified correltion for estimting HHV of solid, liquid nd gseous fuels, Fuel, 81, Fhmi R., Bridgwter A.V., Donnison I., Ytes N. 2008, The effect of lignin nd inorgnic species in biomss on pyrolysis oil yield, qulity nd stbility. Fuel, 87, FAO yerbook, 2012, Fishery nd quculture sttistics, Food nd Agriculture Orgniztion of the United Ntions. Kim S.S., Ly H.V., Choi G.-H., Kim J., Woo H.C., 2012, Pyrolysis chrcteristics nd kinetics of the lg Scchrin jponic, Bioresour. Technol. 123, Oyedun A.O., Lm K.-L., Gebreegzibher T., Lee H.K.M., Hui C.-W., 2012, Optimistion of Operting Prmeters in Multi-Stge Pyrolysis, Chemicl Engineering Trnsctions, 29, Trinh N.T., Jensen A.P., Dm-Johnsen K., Knudsen N.O., Sørensen H.R., Hvilsted S.A., 2013, Comprison of lignin, mcrolge, wood, nd strw fst pyrolysis, Energy Fuels 27,