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Two-phase modelling and simula ion o he hyd o he mal ac iona ion o holm
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oak in a packed bed eac o wi h ho p essu ized wa e
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A. Cabeza, F. Sob ón, F.M. Yed o, and J. Ga cía-Se na*
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High P essu e P ocesses G oup, Depa men o Chemical Enginee ing and
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En i onmen al Tech., Uni e si y o Valladolid, 47011 Valladolid, Spain
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*Co esponding au ho : Tel.: +34 983184934
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E-mail: jgse[email p o ec ed] (J. Ga cía-Se na)
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Abs ac
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Hyd o he mal ac iona ion has been ho oughly s udied in o de o de elop a
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sus ainable p ocess o eco e he suga s o he biopolyme s con ained in biomass.
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Howe e , a physico-chemical model which conside s he main in ol ed physical
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phenomena, like po osi y a ia ions, has no been ully de eloped. Thus, he objec i e
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o his wo k was o app oach a mo e ealis ic model han o he ye published,
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inco po a ing also a no el eac ion pa hway o biomass ac iona ion. I es ablishes
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ha cellulose and hemicellulose begin hei ac iona ion in he solid, b eaking in wa e -
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soluble oligome s and suga . Besides, deace yla ion eac ions and insoluble oligome
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o ma ion om cellulose we e conside ed. Kine ics ollowed he A henius’ law and and
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i has been demons a ed ha an au oca aly ic kine ic model can be success ully used
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o simula e he biomass b eaking in soluble oligome s. The p ocess was ca ied ou in
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a ubula eac o cha ged wi h 5 g o holm oak and con inuously ed wi h ho
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p essu ized wa e . To assess he mass ans e be ween he solid and liquid, 4
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olume ic lows (5mL/min, 10mL/min, 20mL/min and 40 mL/min) and wo pa icle
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diame e s (3mm and 6mm) we e used. In he same way, empe a u e was se be ween
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175ºC and 207ºC. The la e was he main a iable due o i s e ec in biomass
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solubili y and kine ics. The model was sol ed by he Runge-Ku a’s me hod wi h 8 h
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o de o con e gence and i s disc e iza ion was pe o med by a new modi ica ion o he
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o hogonal colloca ion me hod on ini e elemen s. I was alida ed by i ing o al o ganic
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ca bon (TOC) wi h Absolu e A e age De ia ion (A.A.D. be ween 16.3% and 55.8%),
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ace ic acid concen a ion (A.A.D. be ween 44.4% and 84.4%) and pH p o iles (A.A.D.
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be ween 5.6% and 9.7%). Besides, he mass ans e be ween he solid and he liquid
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was checked and he de ia ions o he simula ion we e lowe han 8.5%.
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Keywo ds: Au oca aly ic kine ic, wo-phase simula ion, holm oak, hyd o he mal
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ac iona ion, packed bed eac o .
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2
1. In oduc ion
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Fo se e al decades pe ol has been used as he main sou ce o ene gy and aw
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ma e ial. Ne e heless, i is no a sus ainable sou ce and o he op ion will be needed in
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a nea u u e. One likely op ion would be biomass, and se e al in e na ional ins i u ions,
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such as he Eu opean Union o he O ganisa ion o Economic Co-ope a ion and
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De elopmen , ha e shown in e es abou i (King, 2009; OCDE, 2009; O ganisa ion,
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2011). The gene al idea is o de elop a hyd olysis p ocess o ob ain he suga s p esen
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in biomass, which will be con e ed in o liquid uels in a ollowing p ocess. In addi ion,
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he ex ac ion o he biomass phenolic compounds would be in e es ing due o he ac
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ha hey would be used as aw ma e ial o chemical indus y. Thus, biomass hyd olysis
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ha e been s udied ho oughly and in di e en ways, such as, enzyma ic hyd olysis,
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acid o alkaline hyd olysis (Al a ez-Vasco and Zhang, 2013; Cha les e al., 2004; Feng
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e al., 2012; Gao e al., 2013; Yoon e al., 2014). One o he mos p omising op ion
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would be he biomass ac iona ion by hyd o he mal p ocesses, as a subc i ical
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condi ions as a supe c i ical condi ions, because hey can ex ac he main ac ion o
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hese suga s only using wa e as eac i e (Can e o e al., 2013; Ga o e e al., 2002; M.
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Se ik Tunc, 2008; Moniz e al., 2013; Pa ajó e al., 2004; Rissanen e al., 2014; Zaka ia
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e al., 2015). Subc i ical condi ions e e o all empe a u e and p essu e below he
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c i ical poin and, supe c i ical condi ions, when hey a e beyond i (Figu e 1). Focusing
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in wa e , subc i ical wa e means a liquid a high p essu e and empe a u e wha
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p o ide i special p ope ies, such as lowe dielec ic cons an and densi ies (Asl and
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Khajenoo i, 2013; F anck, 1970; K use and Dinjus, 2007; Teo e al., 2010).
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Figu e 1: Phase diag am o wa e P-T (Asl and Khajenoo i, 2013). p: iple poin , bp: boiling poin , Tc, Pc and ρc:
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c i ical empe a u e, p essu e and densi y espec i ely.
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Rega ding modelling, some s udies ha e been pe o med in o de o es ablish a
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eac ion pa hway and kine ic equa ions o ep oduce he expe imen al beha iou o he
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hyd olysis eac o s. All o hem conside ha biomass is o med by h ee polyme ic
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ac ions: cellulose, hemicellulose and lignin. Cellulose and hemicellulose a e suga -
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based biopolyme s and lignin is an a oma ic biopolyme o med by phenylp opane
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uni s. Cellulose and hemicellulose a e di e en ia ed by hei s uc u e and composi ion.
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The o me is a linea polyme cons i u ed by hexoses and he la e is an amo phous
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and b anched polyme o hexoses and pen oses (Boble e , 1994; P. Ha msen, 2010).
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The mos ex ended models a e based on i s o de kine ics o cellulose and
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hemicellulose assuming ha hey decompose in o in e media e oligome p oduc s.
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These oligome s would con inue a u he bond clea age gene a ing he inal
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monome ic suga s (pen ose and hexoses). In addi ion, he deg ada ion o hese suga s
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in o se e al acids can be conside ed (Cha les e al., 2004).
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Sand a Ri as e al. (Ri as e al., 2014) s udied he acidic p ocessing o hemicellulosic
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saccha ides om pine wood and hey de eloped a monophasic globalised kine ic
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model wi h i s o de kine ics espec o he biomass. Tha model was sui able o i
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hei expe imen al da a, R2 be ween 0.975 and 0.998. Sasaki e al. (Sasaki e al., 2002)
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assessed he kine ic and mechanism o cellobiose (disaccha ide composed by wo
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glucoses) hyd olysis. This monophasic model again used i s o de kine ics and i
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could ep oduce he expe imen al beha iou . P onyk and Mazza (P onyk and Mazza,
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2010) de eloped a kine ic model wi h i s o de kine ics o he hemicellulose hyd olysis
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om T i icale S awa in a packed bed eac o , aking in o accoun he mass ans e
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be ween solid and liquid. They assumed ha wo ypes o hemicellulose can be
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p esen , one easily deg adable and o he ha dly deg adable. They conside ed ha he
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po osi y o he bed emains cons an du ing he p ocess oo. Jussi V. Rissanen e al.
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(Rissanen e al., 2014) s udied he ex ac ion o sp uce hemicellulose and hey
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de eloped a kine ic model which could ep oduce he expe imen al beha iou in a
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cascade luidised ba ch eac o , using kine ics o n h o de o solid biomass. Mo eo e ,
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hey also conside ed he p o on concen a ion in kine ics (wi h n h eac ion o de oo)
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because ace ic acid and o he o ganics a e p oduced and sol ed du ing he ex ac ion.
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The e o e, he e a e se e al models which deal wi h biomass hyd o he mal
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ac iona ion and hey ha e ob ained good esul s. Howe e , hey a e ocused in
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hemicellulose o cellulose ac iona ion and no in bo h o hem a he same ime. In
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addi ion, hey do no conside some obse ed physical phenomena, such as, po osi y
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changes in a bed eac o o p o ons e ec in all kine ics in liquid phase.
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Thus, he aim o his a icle was o de elop a new kine ic model o biomass
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hyd o he mal ac iona ion which could ep oduce he global expe imen al beha iou in
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he mos ealis ic way as i was possible. T ying o unde s and how his hyd o he mal
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eac ion akes place and analysing he e ec o he pa icle diame e , ope a ing
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empe a u e and liquid low a e. So, i was aken in o accoun he e ec o pH, po osi y
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a ia ions and solubili y o he di e en biomass ac ions in ho wa e (K use and
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Dinjus, 2007; Mille -Chou and Koenig, 2003; Teo e al., 2010) in a no el eac ion
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pa hway. The selec ed eac o was a ubula eac o , in o de o s udy he p ocess in a
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semi-con inuous p ocess, ed wi h ho p essu ized wa e . The s udied biomass was
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holm oak because i is one o he mos common ees in he sou h o Spain and
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was es, which could be used as aw ma e ial, a e p oduced each yea du ing i s
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p uning. Rega ding kine ics, a new o mula ion was inco po a ed oo. An au oca aly ic
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model is conside ed because i was assessed, in a p e ious s udy abou biomass
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he mal deg ada ion du ing a he mog a ime ic analysis (Cabeza e al., 2015), ha i
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can ep oduce he s ong mass changes in biomass a ce ain imes o empe a u es.
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2. Expe imen al
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2.1. Ma e ial and me hods
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2.1.1. Raw ma e ials
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Holm Oak b anches we e selec ed as s udied biomass because i is one o he main
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sou ce o woody was es in he sou he n Spain. I was cha ac e ized by he Na ional
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Renewable Ene gy Labo a o y (NREL) – De e mina ion o S uc u al Ca bohyd a es
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and Lignin in Biomass- s anda ds. In o de o check he ep oducibili y, he me hod was
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applied h ee imes. The biomass was d ied and milled in he selec ed diame e s, 3
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and 6 mm. Ex ac i es we e calcula ed g a ime ically by Soxhle me hod acco ding o
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he De e mina ion o Ex ac i es in Biomass. The ini ial composi ion o he biomass
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sample is collec ed in Table 1. The alue o he lignin includes he ex ac i e lignin
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(2.36%) and he acid soluble lignin (1.05%).
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Table 1: Ini ial composi ion o he holm oak sample
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Cellulose
Hemicellulose
Lignin
g/g
g/g
g/g
0.4806
0.2060
0.3134
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All chemicals we e p o ided by Sigma. The eac i e compounds o he HPLC analysis
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we e: cellobiose (+98%), glucose (+99%), uc ose (+99%), glyce aldehyde (95%),
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py u aldehyde (40%), a abinose (+99%), 5-hyd oxyme hyl u u al (99%), lac ic acid
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(85%), o mic acid (98%), ac ylic acid (99%), mannose (+99%), xylose (+99%),
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le ulinic acid (+99%) and galac ose (+99%). Fo analysis o ca bohyd a es and lignin,
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sul u ic acid (98%) and calcium ca bona e (≥ 99.0%) we e used. Fo he de e mina ion
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o ex ac i es n-hexane (95%) was selec ed as sol en . Dis illed wa e was used in all
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assays.
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2.1.2. Expe imen al de ice
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The hyd o he mal ac iona ion p ocess was ca ied ou in a semiba ch eac o cha ged
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wi h app ox. 5 g o d y holm oak. To a oid pa icle losses wo me allic il e s we e used,
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which we e loca ed a he op and bo om o he eac o . The eac o (R-01) was a
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mic o ube model SS316 piping wi h a leng h o 38 cm and an ex e nal diame e o ½
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inch. This eac o and a p ehea e (E-02, AISI 316, leng h=200 cm, O.D.=1/8 inch)
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we e in oduced inside a ch oma og aphic o en HP568 (F-01). The sys em was ed by
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a Jasco model PU-2080 pump (P-01) and he p essu e was se using a go-
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backp essu e al e (V-01) o main ain he liquid phase. Aimed a sa ing ene gy, a
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concen ic ube hea exchange (E-01, 1/4”-3/8”) o 70 cm was ins alled be o e he
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inpu o en (hea in eg a ion). Finally, a second concen ic ube hea exchange (E-03,
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1/4”-3/8”) o 15 cm was used o cool he p oduc low down o oom empe a u e (25-
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30ºC). A p ocess low diag am o he pilo plan is shown in Figu e 2.
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F-01
T-01
P-01 E-01
V-01
E-03
T-02
P oduc s
Cooling
wa e
Cooling
wa e
Dis illed
wa e R-01
E-02
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Figu e 2: P ocess low diag am o he pilo plan . T-01: eed
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wa e ank, P-01: eed pump, E-01: hea eco e , F-01: o en.
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E-02: eed p ehea e , R-01: packed bed eac o . E-03: coole ,
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V-01: backp essu e al e and T-02: sample ank.
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Samples o he ou pu liquid we e aken om he ank T-02 measu ing pH, o al o ganic
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con en (TOC) and ace ic acid concen a ion. The solid inside o he eac o was
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collec ed and quan i ied oo. The analy ical me hods a e desc ibed nex .
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2.1.3. Solid phase cha ac e iza ion. Lignin and suga con en
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The solid phase cha ac e iza ion was done ollowing he me hod p o ided by he
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Na ional Renewable Ene gy Labo a o y (NREL) – De e mina ion o S uc u al
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Ca bohyd a es and Lignin in Biomass. The e o e, a sample o 300 mg (mi) was ea ed
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wi h 3 mL o sulphu ic acid (72%) ollowed by an incuba ion o 30 min a 30ºC. Then,
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84 mL o dis illed wa e we e in oduced and i was incuba ed o one hou a 121ºC.
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The esul an suspension was il e ed unde acuum, washing wi h dis illed wa e , and
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d ied a 105ºC o 24 h. Then, he solid was weigh ed (m1) and calcined a 550ºC o 24
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h and weigh ed (m2) again. So, he acid insoluble lignin would ob ained
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by (𝑚1−𝑚2)𝑚𝑖
⁄. The eco e ed liquid was used o ob ain he con en o acid soluble
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lignin by spec opho ome y, measu ing he abso bance a 320 nm and using he
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ecommended abso p i i y a a wa eleng h o 30 l· g-1·cm-1. In addi ion, 30 mL we e
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neu alized wi h calcium ca bona e up o pH=6-7 ollowed by a il e ing using 0.2 µm
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il e s and inally analysed by high p essu e liquid ch oma og aphy (HPLC). The used
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HPLC column was SUGAR SH-1011 (Shodex). The mobile phase was a solu ion o
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0.01N o sul u ic acid and Milli-Q wa e . In o de o ob ain he hemicelluloses,
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celluloses and deg ada ion p oduc om suga s con en wo de ec o we e used: a
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Wa e s IR de ec o 2414 (210 nm) and Wa e s dual λ abso bance de ec o 2487 (254
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nm).
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2.1.4. Liquid phase cha ac e iza ion
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The hyd o he mal ac iona ion o biomass gene a es a complex mix u e o suga s and
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oligome s, which is di icul o analyse. So, an acid hyd olysis was pe o med o
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con e hese oligome s in o hei monome ic suga s. Samples o 10 mL we e
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hyd olyzed adding 4 mL o sulphu ic acid and hey we e incuba ed o 30 min a 30ºC.
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A e , 86 mL o dis illed wa e we e added and he sample was incuba ed o one hou
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mo e a 121ºC. Then, i was neu alized wi h calcium ca bona e un il pH=6-7 and
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il e ed using 0.2 µm il e s. Finally, i was analysed by HPLC as explained in he be o e
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sec ion.
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In addi ion, he pH and o al o ganic ca bon (TOC) we e measu ed. The pH was
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de e mined by Nahi a model 903 and he TOC was measu ed by Shimadzu equipmen
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model TOC-VCSH. The ca bon concen a ion o he s anda d solu ions co esponds o
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500 mg C/L.
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2.2. P ocedu e
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2.2.1. E ec o he olume ic low
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The e ec o he liquid low was assessed by pe o ming 4 expe imen s a di e en
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olume ic lows (5 mL/min, 10 mL/min, 20 mL/min and 40 mL/min) o wo in e als o
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empe a u e, one a ound 180 ºC and ano he a ound 190 ºC. P essu e was main ained
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a 100 ba g o ensu e he liquid phase o he wa e . The aim was o analyse how he
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mass ans e is modi ied wi h he in low.
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2.2.2. E ec o he pa icle diame e
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In o de o s udy how he pa icle diame e a ec s o he p ocess wo diame e s we e
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used, 3 mm and 6 mm. This pa ame e has impo ance because i a ec s di ec ly he
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mass ans e and he o e all p ocess due o he changes in he solid po osi y.
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2.2.3. E ec o he ope a ing empe a u e
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Expe imen s om 175ºC and 207ºC we e pe o med di ided in h ee se s. One se o
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h ee cases a ound 180ºC, o he h ee a ound 190ºC and wo a 207ºC. The idea was
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o analyse how small changes in empe a u e a ec he biomass deg ada ion in e ms
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o solubili y, as kine ics has been conside ed in o he s udies (Can e o e al., 2013;
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Rissanen e al., 2014; Sasaki e al., 2002).
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All he expe imen s and hei ope a ional condi ions a e shown in Table 2.
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Table 2: Ope a ional condi ions o he pe o med expe imen s
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Expe imen
Ope a ing
Tempe a u e
Pa icle
diame e
Real
low
Ini ial
mass
Ope a ing
ime
ºC
mm
mL/min
g
min
1
175
3
3.8
5.3124
94
2
207
3
9.6
5.3207
94
3
185
3
17.8
5.3308
94
4
180
3
32.7
5.2603
94
5
190
6
2.4
5.2637
94
6
207
6
9.5
5.4993
94
7
195
6
19.3
5.2520
94
8
180
6
34.9
5.2207
94
217
2.2.4. Model alida ion
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The aim o he model is o ep oduce he gene al beha iou o he sys em, conside ing
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empe a u e, low, pa icle diame e , pH and he main biopolyme s and oligome s
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du ing he eac ion. Fo his eason, he TOC and he pH o each expe imen we e
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measu ed and i ed. In addi ion, ace ic acid concen a ion in liquid phase was
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conside ed in he expe imen s wi h a pa icle diame e o 3 mm. The la e was aking
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in o accoun because his compound would be he main sou ce o p o ons and, o his
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eason, he basis o he au ohyd olysis. Suga concen a ion in liquid phase was only
225
simula ed in o de o check i he simula ion ag ees wi h he beha iou epo ed by
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o he au ho s.
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3. Modelling
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3.1. Hyd o he mal deg ada ion a subc i ical condi ions
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Biomass ac iona ion s a s in solid phase wi h hemicellulose and cellulose clea age
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in o oligome s o dec easing molecula weigh . In bo h cases, a a ce ain polyme
231
leng h hey became wa e -soluble, being solubilised. These solubilised oligome s su e
232
a u he hyd olysis p ocess and hey con inue deg ading in smalle oligome s down o
233
hei espec i e monome s. Finally, hese monome s (mainly educed suga s) can
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b eak in o se e al deg ada ion p oduc s, such as hyd oxyme hyl u u al, u u al, o mic
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acid, lac ic acid and o he s (Al a ez-Vasco and Zhang, 2013; Feng e al., 2012). An
236
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illus a ion o his hyd o he mal deg ada ion wi h he e olu ion o he solid and liquid
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phase wi h ime and along he eac o is schema ised in Figu e 3. Once he eac o was
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ed, wa e would s a o deg ade and o sol e biomass. Thus, i is expec ed ha ,
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because o his ex ac ion, he size o he pa icle s a s o dec ease, s a ing in he eed
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o he eac o . The eac o beha ed like a ixed bed ex ac ion column, hus, solid is
241
deple ed om bo om o op and liquid is mo e concen a ed a he ou le ( op exi in his
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case).
243
z
244
Figu e 3: Expec ed beha iou in liquid and solid phase
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inside he hyd o he mal eac o .
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3.2. Biomass solubili y
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The solubili y o polyme s in wa e mainly depends on h ee ac o s: molecula weigh ,
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c ys allini y and amoun o ac i e g oups. The highe he c ys allini y and he molecula
249
weigh a e, he lowe he solubili y is. Howe e , concen a ion o ac i e g oups
250
enhances wa e solubili y (Mille -Chou and Koenig, 2003). Cellulose is insoluble in
251
wa e due o i s c ys allini y and i s low ace yla ion deg ee, so only oligome s wi h a
252
e y low molecula weigh would be wa e soluble. Ne e heless, a high empe a u es
253
wa e dielec ic p ope ies ha e a emendous change which could enhance cellulose
254
solubili y (F anck, 1970; K use and Dinjus, 2007; Teo e al., 2010). Fo example, i s
255
ela i e alue changes, a 25 MPa, om 83 a 25 ºC o 43 a 207 ºC, and om 81 o 33
256
a he same empe a u es and 100 ba . In con as , hemicellulose has a lo o ace yl
257
g oups in i s s uc u e and i is amo phous. So, i is expec ed ha hemicellulose
258
oligome s wi h high molecula weigh could be solubilised. On he o he hand, lignin is
259
a complex s uc u e and some pa s could be soluble.
260
3.3. Au ohyd olysis
261
Ano he p ocess ha akes place in he eac o is he deace yla ion o hemicellulose
262
(Ga o e e al., 2002; Pa ajó e al., 2004) and cellulose (Gao e al., 2013), which
263
elease ace ic acid om de solid o he liquid phase. This emission o ace ic acid
264
implies a highe amoun o p o ons in he liquid phase, enhancing he hyd olysis
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eac ions in his phase.
266
3.4. Reac ion pa hway
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The eac ion mechanism is shown in Figu e 3.The idea was o de elop a pa hway
268
which would be able o ep esen he main phenomenological s eps o he p ocess, i.e.
269
he biomass solubilisa ion and he suga s o ma ion. To his end, o each cellulosic
270
ac ion wo oligome s we e used, one o ep esen he i s soluble oligome and o he
271
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o symbolize he las oligome be o e suga p oduc ion, which would co espond o he
272
dime . In addi ion, he deace yla ion o hemicellulose and cellulose we e added. The
273
o ma ion o an insoluble oligome om cellulose was in oduced aimed a aking in o
274
accoun hose cellulose ac ions ha could no decompose in o suga s a he ope a ing
275
condi ions and he cha o ma ion om cellulose polyme . Besides, a p o on
276
consump ion eac ion was in oduced because a he s a o he ope a ion pH
277
inc emen s we e obse ed. So, i is assumed ha ce ain amoun o ino ganic
278
compounds wi h basic beha iou was p esen in biomass. This alue was ini ially ixed
279
a 1% in o de o p o ide enough subs ance o he neu aliza ion bu wi hou dis u bing
280
he ini ial composi ion a lo . The solubilisa ion o cellulose and hemicellulose a high
281
empe a u es was added oo. The o ma ion o deg ada ion p oduc s was no aking
282
in o accoun because i s alue a he ope a ional condi ions was e y low and hey
283
could no be quan i ied easibly. Finally, hexoses (C6) o ma ion om cellulose and
284
hemicellulose was also conside ed.
285
CELLULOSE
CELLULOSE
OLIGOMER 1
CELLULOSE
OLIGOMER 2
CELLULOSE
OLIGOMER 3
ACETIC
ACID
WATER CELLULOSE
OLIGOMER 1
CELLULOSE
OLIGOMER 2
H+
CELLULOSE
OLIGOMER 3
WATER
ACETIC
ACID
SUGARS C6
H+
INSOLUBLE
CELLULOSE
OLIGOMER
CELLULOSE
T>195ºC
HEMICELLULOSE
HEMICELLULOSE
OLIGOMER 1
HEMICELLULOSE
OLIGOMER 1
H+
WATER
HEMICELLULOSE
T>195ºC
HEMICELLULOSE
OLIGOMER 2
HEMICELLULOSE
OLIGOMER 2
HEMICELLULOSE
OLIGOMER 3
HEMICELLULOSE
OLIGOMER 3
H+
ACETIC
ACID
WATER
SUGARS C5
1
39
15
5
2
4
11
10
76
12
814
16
HEAT
HEAT
HEAT
HEAT
WATER
WATER
WATER
HEAT
HEAT
HEAT
WATER
WATER
H+
H+
H+
WATER
BASE WATER BASE
BASE H+
13
286
Figu e 4: Reac ion pa hway o he cellulosic ac ion o
287
biomass.
288
3.5. Kine ic model
289
3.5.1. Assump ions
290
In o de o simpli y he modelling he ollowing assump ions we e done:
291
 The solid phase is homogeneous and uni o m and i beha es as a whole. Thus,
292
he e a e nei he empe a u e no concen a ion p o iles wi hin he solid along
293
he eac o .
294
 The solid po osi y only depends on he o al concen a ion o he solid phase.
295
 The e a e no signi ican di usional e ec s in he solid o liquid phase.
296
9
 Lignin beha es as an ine , aking as negligible he 2.36% o soluble lignin
297
measu ed.
298
 The eac ion o de o all he kine ics is 1 o he biomass compound. In liquid
299
phase, i is also conside ed ha he kine ics depend on p o ons concen a ion
300
wi h o de 1.
301
302
3.5.2. Solid phase balances
303
The model o he ac iona ion used a non-s a iona y mass balance o each compound
304
p esen in biomass assuming ha he concen a ion in he solid could be calcula ed as
305
he p oduc o he liquid equilib ium concen a ion and an equilib ium cons an (𝑪𝑺𝒋=𝑯𝒋·
306
𝑪𝑳𝒋
∗), see equa ion ( 1 ):
307
𝑑(1−ℰ)·𝐶𝑆𝑗
𝑑𝑡 =𝑟𝑗−𝑘𝑗·𝑎·(𝐶𝐿𝑗
∗−𝐶𝐿𝑗)
( 1 )
Taking in o accoun ha he po osi y was de ined by equa ion ( 2 ), equa ion ( 1 ) could
308
be ew i en in equa ion ( 3 ).
309
ℰ=1−𝜑·𝐶𝑡
( 2 )
310
𝑑𝐶𝑆𝑗
𝑑𝑡 =1
1−ℰ·[𝑟𝑗−𝜑·𝐶𝑆𝑗·𝑑𝐶𝑡
𝑑𝑡 −𝑘𝑗·𝑎·(𝐶𝐿𝑗
∗−𝐶𝐿𝑗)]
( 3 )
311
Fo he ine compound he mass balance is shown in equa ion ( 4 ).
312
𝑑(1−ℰ)·(𝐶𝑡−∑𝐶𝑆𝑗
𝑗=𝑁
𝑗=1 )
𝑑𝑡 =0
( 4 )
313
3.5.3. Liquid phase balances
314
In he same way ha in he solid phase, he model was ob ained by he non-s a iona y
315
mass balance o each compound p esen in his phase, see equa ion ( 5 ).
316
𝛿ℰ·𝐶𝐿𝑗
𝛿𝑡 +𝑢
𝐿·𝛿𝐶𝐿𝑗
𝛿𝑧 =𝑟𝑗+𝑘𝑗·𝑎·(𝐶𝐿𝑗
∗−𝐶𝐿𝑗)
( 5 )
And equa ion ( 5 ) could be ans o med in equa ion ( 6 ) by in oducing he de ini ion o
317
he po osi y, gi en in equa ion ( 2 ).
318
𝛿𝐶𝐿𝑗
𝛿𝑡 =1
ℰ·[𝑟𝑗−𝑢
𝐿·𝛿𝐶𝐿𝑗
𝛿𝑧 −𝜑·𝐶𝐿𝑗·𝑑𝐶𝑡
𝑑𝑡 +𝑘𝑗·𝑎·(𝐶𝐿𝑗
∗−𝐶𝐿𝑗)]
( 6 )
319
3.5.4. Kine ics
320
The kine ics o each compound in bo h phases a e gi en by he gene ic exp ession ( 7
321
).
322
16
12
1.7045
571
0.9821
13
3.3634
1170
0.9843
14
7.0680
1053
0.9803
15
10.1160
3392
0.9129
16
2.3708
1516
0.9800
476
Table 5 and Figu e 12 show he alues o he accele a ion ac o s which we e di e en
477
o m ce o. β1,Co1 and β2,Co2 inc eased hei alues wi h empe a u e and low. Which was
478
expec ed because hey we e used o simula e he biomass b eaking in o oligome s o
479
dec easing molecula weigh . And, i empe a u e o low a e inc eased, his b eaking
480
would be mo e ab up . So, highe accele a ion ac o would be needed. On he o he
481
hand, β11,Co1, β11,Co2, β15,Co1 and β15,Co2 showed he opposi e beha iou . This could be caused by
482
he ac ha hey we e used o simula e he e ec o he biomass deg ada ion in ace ic
483
acid p oduc ion. So, wi h highe empe a u es and lows, he eleasing would be as e .
484
I is ema kable ha β11,Co1, β11,Co2, β15,Co1 and β15,Co2 ha e he same alues. This was caused
485
by he ac ha all o hem ep esen he ace ic acid o ma ion.
486
Table 5: Accele a ion ac o s.
487
Expe imen
β1,Co1
β2,Co2
β11,Co1
β11,Co2
β15,Co1
β15,Co2
1
2.2
9.0
11.0
11.0
11.0
11.0
2
3.0
10.5
7.0
7.0
7.0
7.0
3
4.0
12.0
4.5
4.5
4.5
4.5
4
3.5
11.0
4.0
4.0
4.0
4.0
5
2.5
10.0
10.0
10.0
10.0
10.0
6
3.0
10.5
7.0
7.0
7.0
7.0
7
4.1
12.5
4.0
4.0
4.0
4.0
8
3.5
11.0
3.8
3.8
3.8
3.8
Co1: cellulose; Co2: hemicellulose.
488
489
490
Figu e 12: Accele a ion ac o s e olu ion. β11,Co1 was only
491
ep esen ed because i had he same alues ha β11,Co2,
492
β15,Co1 and β15,Co2.
493
494

17
4.2.2. Mass ans e pa ame e s
495
Table 6 collec s he calcula ed alues o he equilib ium cons an s o he soluble
496
componen s a he s udied empe a u es. The ela ion wi h empe a u e was con i med
497
as linea by a eg ession analysis whose coe icien R2 was e e g ea e han 0.9507
498
(Figu e 13). I is ema kable ha compound 1 and 2 (cellulose and hemicellulose
499
espec i ely) would s a o sol e a empe a u es g ea e han 195ºC. This could be
500
explained by changes in he pola i y o he wa e wi h empe a u e.
501
Table 6: Equilib ium cons an s (dimensionless) be ween solid and liquid phases.
502
T
Co1
Co2
Co3
Co4
Co5
Co6
Co10
Co12 1
Co13
ºC
190
0.00
0.00
0.34
0.40
0.34
0.52
3.50
0.15
0.08
175
0.00
0.00
0.10
0.15
0.10
0.30
2.00
0.03
0.05
195
0.15
0.10
0.40
0.48
0.40
0.58
4.00
0.20
0.09
185
0.00
0.00
0.24
0.27
0.24
0.36
3.00
0.09
0.07
180
0.00
0.00
0.13
0.16
0.13
0.30
2.50
0.06
0.06
207
0.50
0.45
0.52
0.63
0.52
0.72
4.80
0.28
0.12
R2
-
-
0.9724
0.9715
0.9724
0.9507
0.9902
0.9886
0.9963
Co1: cellulose; Co2: hemicellulose; Co3: cellulose oligome 1 ( i s oligome soluble om
503
cellulose); Co4: hemicellulose oligome 1 ( i s oligome soluble om hemicellulose); Co5:
504
cellulose oligome 2 (las oligome om cellulose be o e suga p oduc ion); Co6:
505
hemicellulose oligome 2 (las oligome om hemicellulose be o e suga p oduc ion); Co10:
506
ace ic acid; Co12: hemicellulose oligome 3 (deace yla ed oligome om hemicellulose);
507
Co15: cellulose oligome 3 (deace yla ed oligome om cellulose); Co13: base (ino ganic
508
compound). 1Compound 12 and 15 had he same equilib ium cons an .
509
510
511
Figu e 13: Equilib ium cons an e olu ion wi h empe a u e.
512
Compound 5 and 15 we e no showed because hey had he
513
same equilib ium cons an ha compound 3 and 12
514
espec i ely.
515
516
Table 7 and Table 8 shows he calcula ed mass ans e coe icien s (mul iplied by he
517
speci ic exchange a ea) ob ained om he adjus men s. Table 7 ha e he pa ame e s
518
wi h a pa icle diame e o 3 mm and Table 8 wi h a pa icle diame e o 6 mm. The
519
necessi y o use wo se s o pa ame e s would be explained by he ac ha he
520
18
exchange a ea depends on he pa icle diame e . In addi ion, i was checked he
521
ela ion be ween hem and he liquid low. And i esul ed as linea wi h R2 highe han
522
0.9434. The changes o hese mas ans e coe icien s a e ep esen ed in Figu e 14
523
and Figu e 15 o 3 mm and 6 mm espec i ely.
524
Table 7: Mass ans e coe icien s (min-1 ·102) wi h a pa icle diame e o 3mm.
525
Q
Co1
Co2
Co3
Co4
Co5
Co6
Co10
Co121
Co13
mL/min
3.8
0.0
0.0
2.6
15
2.6
22
200
1.5
0.9
9.6
1.1
1.1
3.0
18
3.0
25
220
1.6
1.2
17.8
0.0
0.0
4.0
20
4.0
27
340
1.8
1.5
32.7
0.0
0.0
8.0
26
8.0
37
500
2.1
2.0
R2
-
-
0.9434
0.9905
0.9434
0.9795
0.9825
0.9980
0.9923
Co1: cellulose; Co2: hemicellulose; Co3: cellulose oligome 1 ( i s oligome soluble om
526
cellulose); Co4: hemicellulose oligome 1 ( i s oligome soluble om hemicellulose); Co5:
527
cellulose oligome 2 (las oligome om cellulose be o e suga p oduc ion); Co6: hemicellulose
528
oligome 2 (las oligome om hemicellulose be o e suga p oduc ion); Co10: ace ic acid; Co12:
529
hemicellulose oligome 3 (deace yla ed oligome om hemicellulose); Co15: cellulose oligome
530
3 (deace yla ed oligome om cellulose); Co13: base (ino ganic compound). 1Compound 12 and
531
15 had he same mass ans e coe icien .
532
533
Table 8: Mass ans e coe icien s (min-1 ·102) wi h a pa icle diame e o 6 mm.
534
Q
Co1
Co2
Co3
Co4
Co5
Co6
Co10
Co121
Co13
mL/min
2.4
0.0
0.0
2.4
14
2.4
20
180
1.4
0.8
9.5
1.0
1.0
2.5
15
2.5
24
215
1.5
1.1
19.3
1.5
1.5
4.5
16
4.5
30
350
2.0
1.5
34.9
0.0
0.0
8.2
18
8.2
38
520
2.3
2.0
R2
-
-
0.9522
0.9978
0.9522
0.9984
0.9868
0.9583
0.9956
Co1: cellulose; Co2: hemicellulose; Co3: cellulose oligome 1 ( i s oligome soluble om
535
cellulose); Co4: hemicellulose oligome 1 ( i s oligome soluble om hemicellulose); Co5:
536
cellulose oligome 2 (las oligome om cellulose be o e suga p oduc ion); Co6: hemicellulose
537
oligome 2 (las oligome om hemicellulose be o e suga p oduc ion); Co10: ace ic acid; Co12:
538
hemicellulose oligome 3 (deace yla ed oligome om hemicellulose); Co15: cellulose oligome
539
3 (deace yla ed oligome om cellulose); Co13: base (ino ganic compound). 1Compound 12 and
540
15 had he same mass ans e coe icien .
541
542
Figu e 14: Mass ans e coe icien s e olu ion wi h liquid
543
low o a pa icle diame e o 3 mm. Compound 5 and 15
544
19
we e no showed because hey had he same mass ans e
545
coe icien ha compound 3 and 12 espec i ely.
546
547
Figu e 15: Mass ans e coe icien s e olu ion wi h liquid
548
low o a pa icle diame e o 6 mm. Compound 5 and 15
549
we e no showed because hey had he same mass ans e
550
coe icien ha compound 3 and 12 espec i ely.
551
4.3. Simula ed beha iou
552
As i was men ioned in pa 3.7, a simula ion o he solid and liquid phase was
553
pe o med in o de o compa e i wi h he expe imen al beha iou showed by o he s
554
au ho s. In Figu e 16 i is shown he b eaking o cellulose in solid phase o he i s
555
expe imen . I can be obse ed ha he cellulose would decompose i s in o he i s
556
soluble oligome which would b eak in o he las oligome be o e he suga o ma ion.
557
In addi ion, his las oligome would b eak in o ace ic acid and a deace yla ed oligome .
558
In pa allel, he o ma ion o insoluble oligome would ake place oo. A he end o he
559
ope a ion, cellulose would be p esen only as oligome s and he a ia ion o he
560
cellulose mas would be o 29%. Hemicellulose b eaking was simula ed oo. The
561
beha iou was simila o he cellulose bu he a ia ion o he concen a ion was highe
562
(86%). The 14% o hemicellulose ha emained in solid would be as deace yla ed
563
oligome due o hei lowe solubili y.
564
565
Figu e 16: Cellulose b eaking in solid phase. Co1: cellulose;
566
Co3: cellulose oligome 1 ( i s oligome soluble om
567
cellulose); Co5: cellulose oligome 2 (las oligome om
568
cellulose be o e suga p oduc ion); Co15: cellulose oligome
569
3 (deace yla ed oligome om cellulose); Co17: insoluble
570
cellulose oligome .
571
20
572
Figu e 17 shows he simula ion o he hemicellulose oligome s decomposi ion in liquid
573
phase o he expe imen 1. I is ema kable ha he main pa o biomass is ex ac ed
574
as oligome and ha a he end o he p ocess, only suga s would be ob ained.
575
576
Figu e 17: Hemicellulose oligome s b eaking in liquid phase.
577
Co4: hemicellulose oligome 1 ( i s oligome soluble om
578
hemicellulose); Co6: hemicellulose oligome 2 (las oligome
579
om hemicellulose be o e suga p oduc ion); Co7: Suga s
580
C6; Co8: Suga s C5; Co12: hemicellulose oligome 3
581
(deace yla ed oligome om hemicellulose).
582
The simula ions o he es o he expe imen s we e pe o med oo. The maximum
583
con e sion o hemicellulose and cellulose was achie ed in he expe imen 2, 94% and
584
61% espec i ely. These esul s would be expec ed because i was done a he highes
585
empe a u e (207ºC) and wi h he lowes pa icle diame e (3mm). In addi ion, i
586
con i ms he idea o empe a u e is he main p ocess a iable, which was also exposed
587
in he sec ion 4.1.
588
Hemicellulose esul s ag ee wi h he beha iou epo ed by o he au ho s. M. Se ik
589
Tunc e al. (M. Se ik Tunc, 2008) s udied he hyd o he mal ac iona ion o ha dwood
590
biomass a 150ºC o 500 min. They ound ha cellulose was no ex ac ed a any ime
591
and ha a ound 67 % hemicellulose was eco e ed a 500 min (23% a 100 min). In
592
addi ion, hey epo ed ha he main o he ex ac ed biomass was as oligome and ha
593
a he end o he p ocess only monome s we e ob ained. Ca l P onyk e al. (P onyk and
594
Mazza, 2010) assessed he hyd o he mal ac iona ion o i icale s aw also a 150ºC
595
and hey ob ained simila esul s o M. Se ik Tunc e al. Jussi V. Rissanen e
596
al.(Rissanen e al., 2014) analysed he hemicellulose ex ac ion om sp uce om
597
120ºC o 170ºC, eco e ing 80% o hemicellulose a 170ºC wi h an ope a ing ime o 50
598
min. Rega ding cellulose, he calcula ed yields we e highe han he epo ed by o he
599
au ho s. Mohd Ra ein Zaka ia e al.(Zaka ia e al., 2015) ob ained yield a ound 15% a
600
180ºC and 23% a 210ºC (bo h a e 10 min o ope a ion in ba ch eac o ). Pa ícia
601
Moniz e al.(Moniz e al., 2013) pe o med expe imen s also in a ba ch eac o and he
602
ex ac ion o cellulose a 170ºC was 6.2% and a 200ºC 9.8%. These disc epancies
603
could be explained by he ac ha ou sys em was a semi-con inuous p ocess, which
604
could enhance mass ans e and cellulose b eaking, wi h ope a ing ime longe han
605
10 min (94 min). Besides, he pH su e ed a ia ions du ing he p ocess in ou eac o
606
which could enhance he cellulose ac iona ion. The pH dec eased down o 3.65 in he
607
expe imen 1 and un il 3.78 in he expe imen 2. In addi ion, i was less han 4 om 34
608
min o 94 min o he o me and lowe han 4.5 om 24 min o 94 min o he la e .
609
21
Mo eo e , he o al amoun o hemicellulose in he sample was a ound 1g and he
610
measu ed ex ac ed mass was be ween 1.6 g and 2.8 g (Figu e 5). So, a conside able
611
amoun o cellulose should be ex ac ed.
612
Finally, he mass balance be ween he solid and liquid phase was checked. Table 9
613
a ays he alues o he inal mass in he solid a e he ex ac ion calcula ed by
614
simula ion and he expe imen al da a. The disc epancies a e lowe han 8.5%. Besides,
615
he a e age di e ence be ween he simula ed and expe imen al inal mass was 0.1189
616
g and he a e age soluble lignin was 0.1253 g. The e o e, he main pa o hese
617
di e ences (and o he TOC de ia ions) would be caused by his soluble lignin
618
conside ed as ine .
619
Table 9: Compa ison be ween he simula ed and expe imen al inal mass in he solid.
620
Expe imen
m eal
msim
Disc epancy
g
g
%
1
3.5656
3.6333
1.90
2
2.5278
2.7324
8.09
3
2.9585
3.0238
2.21
4
2.8148
2.8345
0.70
5
2.8736
3.1070
8.12
6
2.6857
2.8498
6.11
7
2.6739
2.7401
2.48
8
2.7061
2.8366
4.82
621
5. Conclusions
622
A kine ic model o he wo-phase simula ion o he hyd o he mal ac iona ion o holm
623
oak has been de eloped. The kine ic cons an s ollow he A henius’ law and he mas
624
ans e coe icien s and equilib ium cons an ha e a linea dependency wi h low and
625
empe a u e espec i ely. This model can ep oduce he TOC, pH and ace ic acid
626
concen a ion wi h ela i e low di e ences. The de ia ions a e be ween 16.3% and
627
55.8% o he TOC, be ween 5.6% and 9.7% o he pH and be ween 44.4% and 84.4%
628
o he ace ic acid. Besides i is able o simula e he beha iou in solid and liquid phase
629
in ag eemen wi h he expe imen al da a epo ed by o he au ho s. The mass balance
630
be ween he solid and he liquid was calcula ed wi h de ia ions lowe han 8.5%, which
631
a e mainly caused by he ac ha soluble lignin is no conside ed. I is ema kable ha
632
cellulose ex ac ion is much highe han expec ed. Howe e , his esul can be
633
explained by he ac ha he sys em is a semi-con inuous p ocess wi h high ope a ing
634
imes and a s ong d op o he pH. Mo eo e , he main pa ame e s ha could a ec
635
mass ans e , e. g. pa icle diame e , olume ic low and empe a u e, a e s udied.
636
Being empe a u e he mos impo an o hem. I would be in e es ing in a u u e wo k
637
o in oduce he deg ada ion p oduc o ma ion in he model and he eleased suga s.
638
Un o una ely, ha would equi e o inc ease he numbe o i ings pa ame e e en
639
mo e. The e o e, ano he app oach should be conside ed o pe o m a mo e de ailed
640
s udy. The bes op ion would be a pobla ional model in which ac i a ion ene gies and
641
solubili y o he oligome s we e unc ion o hei molecula weigh .
642
Acknowledgemen s
643
644

22
The au ho s acknowledge he Spanish Economy and Compe i i eness Minis y,
645
P ojec Re e ence: ENE2012-33613 and he egional go e nmen (Jun a de
646
Cas illa y León), P ojec Re e ence: VA330U13 o unding. Ál a o Cabeza
647
would like o hank o he Spanish Minis y o Educa ion Cul u e and Spo s,
648
aining p og am o uni e si y p o esso s ( e e ence FPU2013/01516) o he
649
esea ch aining con ac .
650
Nomencla u e
651
652
Ac onyms
653
654
Co1: Cellulose.
655
Co2: Hemicellulose.
656
Co3: Cellulose oligome 1 ( i s oligome soluble om cellulose).
657
Co4: Hemicellulose oligome 1 ( i s oligome soluble om hemicellulose).
658
Co5: Cellulose oligome 2 (las oligome om cellulose be o e suga p oduc ion).
659
Co6: Hemicellulose oligome 2 (las oligome om hemicellulose be o e suga
660
p oduc ion).
661
Co7: Suga s C6.
662
Co8: Suga s C5.
663
Co10: Ace ic acid.
664
Co12: Hemicellulose oligome 3 (deace yla ed oligome om hemicellulose).
665
Co13: Base (ino ganic compound).
666
Co15: Cellulose oligome 3 (deace yla ed oligome om cellulose).
667
Co17: Insoluble cellulose oligome .
668
TOC: To al O ganic Con en .
669
A.A.D.: A e age absolu e De ia ion.
670
671
Subindex and supe index
672
673
pH-SIM: Simula ed pH.
674
pH: Expe imen al pH.
675
TOC-SIM: Simula ed TOC.
676
TOC: Expe imen al TOC.
677
[Ace ic acid]-SIM: Simula ed ace ic acid concen a ion.
678
[Ace ic acid]: Expe imen al ace ic acid concen a ion.
679
G eek le e s and symbols
680
23
681
ℰ: Po osi y o he bed, dimensioless.
682
𝐶𝑆𝑗: Cocne a ion o he compound “j” in he solid phase, mg/L.
683
𝑟𝑗: Reac ion a e o he compound “j”, mg/min·L.
684
𝑘𝑗·𝑎: Mass ans e coe icien mul iplied by he speci ic exchange a ea, min-1.
685
𝐶𝐿𝑗
∗: Equilib ium concen a ion o he compound “j” in liquid phase, mg/L.
686
𝐶𝐿𝑗: A e age concen a ion o he compound “j” along he eac o in liquid phase, mg/L.
687
𝐻𝑗: Equilib ium cons an be ween he solid and he liquid, dimensionless.
688
𝐶𝑡: To al concen a ion in he solid, mg/L.
689
𝜑: Rela ion ac o be ween po osi y and he o al concen a ion in solid phase,
690
dimensionless.
691
𝐶𝐿𝑗: Concen a ion o he compound “j” in he liquid phase, mg/L.
692
Ф𝑖,𝑗: S oichiome ic coe icien o he compound “j” o he eac ion “i”, mg.
693
𝑟𝑖: Reac ion eloci y “i”, mg/min·L.
694
𝛼𝑖,𝑗: Ini ial eloci y ac o o he compound “j” in he eac ion “i”, dimensionless.
695
𝛼𝑖,𝐶𝑒𝑙: Ini ial eloci y ac o o cellulose in he eac ion “i”, dimensionless.
696
𝛼𝑖,𝐻𝑐𝑒𝑙: Ini ial eloci y ac o o hemicellulose in he eac ion “i”, dimensionless.
697
𝛽𝑖,𝑗: Accele a ion ac o o he compound “j” in he eac ion “i”, dimensionless.
698
𝛽𝑖,𝐶𝑒𝑙: Accele a ion ac o o cellulose in he eac ion “i”, dimensionless.
699
𝛽𝑖,𝐻𝑐𝑒𝑙: Accele a ion ac o o hemicellulose in he eac ion “i”, dimensionless.
700
𝑘𝑖: Kine ic cons an , mg-1·min-1.
701
𝐶𝑓𝑗: Concen a ion o he compound “j” in he phase “ ”, mg/L.
702
𝐶𝐶𝑒𝑙: Concen a ion o cellulose in he solid phase, mg/L.
703
𝐶𝐻𝑐𝑒𝑙: Concen a ion o hemicellulose in he solid phase, mg/L.
704
𝐶𝑆𝐿𝑂: Concen a ion o he las oligome be o e suga p oduc ion ( om hemicellulose o
705
cellulose) in he solid phase, mg/L.
706
𝑢: Liquid eloci y in he eac o , m/min.
707
𝑁: Numbe o compounds, dimensionless.
708
𝑛𝑟𝑒𝑐: Numbe o eac ions, dimensionless.
709
𝐿: Leng h o he eac o , m.
710
𝑧: Coo dina e along he leng h o he eac o , dimensionless.
711
𝑡: Ope a ing ime, min.
712
24
𝑥𝑖𝐸𝑋𝑃: Expe imen al alue o he i ed a iable.
713
𝑥𝑖𝑆𝐼𝑀: Simula ed alue o he i ed a iable.
714
𝑜: To al numbe o expe imen s, dimensionless.
715
𝑘: P e-exponen ial ac o o he kine ic cons an , mg-1·min-1.
716
𝐸𝑎/𝑅: Ac i a ion ene gy, K.
717
𝑅2: Coe icien R2, dimensionless.
718
𝑇: Ope a ing empe a u e, ºC.
719
𝑚𝑟𝑒𝑎𝑙: Final solid mass, g.
720
𝑚𝑠𝑖𝑚: Simula ed inal solid mass, g.
721
722
Lis o igu es
723
Figu e 1: Phase diag am o wa e P-T (Asl and Khajenoo i, 2013). p: iple poin , bp:
724
boiling poin , Tc, Pc and ρc: c i ical empe a u e, p essu e and densi y espec i ely.
725
Figu e 2: P ocess low diag am o he pilo plan . T-01: eed wa e ank, P-01: eed
726
pump, E-01: hea eco e , F-01: o en. E-02: eed p ehea e , R-01: packed bed eac o .
727
E-03: coole , V-01: backp essu e al e and T-02: sample ank.
728
Figu e 3: Expec ed beha iou in liquid and solid phase inside he hyd o he mal eac o .
729
Figu e 4: Reac ion pa hway o he cellulosic ac ion o biomass.
730
Figu e 5: Ex ac ed biomass depending on he liquid low and pa icle diame e .
731
Figu e 6: Maximum Toc in liquid phase depending on he liquid low and pa icle
732
diame e .
733
Figu e 7: Fi ing o he TOC o he i s expe ience. TOC: expe imen al TOC;. TOC-
734
SIM: simula ed TOC.
735
Figu e 8: Fi ing o he ace ic acid concen a ion in liquid phase o he i s expe ience.
736
[Ace ic-Acid]: expe imen al ace ic acid concen a ion; [Ace ic-Acid]-SIM: simula ed
737
ace ic acid concen a ion.
738
Figu e 9: Fi ing o he pH o he i s expe ience. pH: expe imen al pH; pH-SIM:
739
simula ed pH.
740
Figu e 10: Linea eg ession o he kine ics om eac ion 1 o 8.
741
Figu e 11: Linea eg ession o he kine ics om eac ion 9 o 16.
742
Figu e 12: Accele a ion ac o s e olu ion. β11,Co1 was only ep esen ed because i had
743
he same alues ha β11,Co2, β15,Co1 and β15,Co2.
744
Figu e 13: Equilib ium cons an e olu ion wi h empe a u e. Compound 5 and 15 we e
745
no showed because hey had he same equilib ium cons an ha compound 3 and 12
746
espec i ely.
747
Figu e 14: Mass ans e coe icien s e olu ion wi h liquid low o a pa icle diame e o
748
3 mm. Compound 5 and 15 we e no showed because hey had he same mass
749
ans e coe icien ha compound 3 and 12 espec i ely.
750
Figu e 15: Mass ans e coe icien s e olu ion wi h liquid low o a pa icle diame e o
751
6 mm. Compound 5 and 15 we e no showed because hey had he same mass
752
ans e coe icien ha compound 3 and 12 espec i ely.
753
Figu e 16: Cellulose b eaking in solid phase. Co1: cellulose; Co3: cellulose oligome 1
754
( i s oligome soluble om cellulose); Co5: cellulose oligome 2 (las oligome om
755
25
cellulose be o e suga p oduc ion); Co15: cellulose oligome 3 (deace yla ed oligome
756
om cellulose); Co17: insoluble cellulose oligome .
757
Figu e 17: Hemicellulose oligome s b eaking in liquid phase. Co4: hemicellulose
758
oligome 1 ( i s oligome soluble om hemicellulose); Co6: hemicellulose oligome 2
759
(las oligome om hemicellulose be o e suga p oduc ion); Co7: Suga s C6; Co8:
760
Suga s C5; Co12: hemicellulose oligome 3 (deace yla ed oligome om
761
hemicellulose).
762
763
Lis o ables
764
Table 1: Ini ial composi ion o he holm oak sample
765
Table 2: Ope a ional condi ions o he pe o med expe imen s
766
Table 3: Fi ings A.A.D.
767
Table 4: Kine ic cons an pa ame e s.
768
Table 5: Accele a ion ac o s.
769
Table 6: Equilib ium cons an s (dimensionless) be ween solid and liquid phases.
770
Table 7: Mass ans e coe icien s (min-1 ·102) wi h a pa icle diame e o 3mm.
771
Table 8: Mass ans e coe icien s (min-1 ·102) wi h a pa icle diame e o 6 mm.
772
Table 9: Compa ison be ween he simula ed and expe imen al inal mass in he solid.
773
774
Re e ences
775
Al a ez-Vasco, C., Zhang, X., 2013. Alkaline hyd ogen pe oxide p e ea men o
776
so wood: Hemicellulose deg ada ion pa hways. Bio esou ce Technology 150, 321-327.
777
Asl, A.H., Khajenoo i, M., 2013. Subc i ical Wa e Ex ac ion, Mass T ans e -
778
Ad ances in Sus ainable Ene gy and En i onmen O ien ed Nume ical Modeling.
779
InTech.
780
Boble e , O., 1994. Hyd o he mal deg ada ion o polyme s de i ed om plan s.
781
P og ess in Polyme Science (Ox o d) 19, 797-841.
782
Cabeza, A., Sob ón, F., Yed o, F.M., Ga cía-Se na, J., 2015. Au oca aly ic kine ic
783
model o he mog a ime ic analysis and composi ion es ima ion o biomass and
784
polyme ic ac ions. Fuel 148, 212-225.
785
Can e o, D.A., Be mejo, M.D., Coce o, M.J., 2013. Kine ic analysis o cellulose
786
depolyme iza ion eac ions in nea c i ical wa e . The Jou nal o Supe c i ical Fluids 75,
787
48-57.
788
Capa , R., Khezami, L., Bu nham, A.K., 2004. Assessmen o a ious kine ic models
789
o he py olysis o a mic og anula cellulose. The mochimica Ac a 417, 79-89.
790
Ca ey, G.F., Finlayson, B.A., 1975. O hogonal colloca ion on ini e elemen s. Chemical
791
Enginee ing Science 30, 587-596.
792
Cha les, E.W., S ephen, R.D., Michael, E.H., John, W.B., Ca he ine, E.S., Liisa, V.,
793
2004. Hyd olysis o Cellulose and Hemicellulose, Polysaccha ides. CRC P ess.
794
Feng, Y., Qi, X., Jian, H.L., Sun, R.C., Jiang, J.X., 2012. E ec o inhibi o s on
795
enzyma ic hyd olysis and simul aneous saccha i ica ion e men a ion o lac ic acid
796
p oduc ion om s eam explosion p e ea ed lespedeza s alks. BioResou ces 7, 3755-
797
3766.
798
F anck, E.U., 1970. Wa e and aqueous solu ions a high p essu es and empe a u es.
799
Pu e Appl. Chem 24, 13-30.
800