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Biochemical Engineering Journal 56 (2011) 130– 136

Contents lists available at ScienceDirect

Biochemical Engineering Journal

j o ur nal homep a ge: www.elsev ier .com/ locate /be j

ntegrated utilization of the main components of Hesperaloe funifera

. Sánchez, A. Rodríguez, E. Navarro, A. Requejo, L. Jiménez ∗

hemical Engineering Department, University of Córdoba, Córdoba, Spain

r t i c l e i n f o

rticle history:eceived 11 February 2010eceived in revised form 9 September 2010ccepted 21 April 2011vailable online 16 June 2011

eywords:esperaloe funiferaiorefineryulpaperemicelluloseigninyrolysis gasuel gas

a b s t r a c t

This work aims at the characterization and the biorefinery of Hesperaloe funifera by means of the useof its three main components: separating hemicellulose by hydrothermal treatments; cellulose pulpby various pulping processes (soda, soda–anthraquinone, ethanolamine, ethyleneglycol, diethanolamineand diethyleneglycol); and exploitation of pulping liquor, rich in lignin, by pyrolysis and gasificationprocesses.

The contents in lignin, �-cellulose, holocellulose, hemicellulose, ethanol–benzene extractives, hotwater solubles, 1% NaOH solubles and ash of H. funifera were found to be 7.3%, 40.9%, 76.5%, 35.6%, 4.0%,13.5%, 29.5% and 5.9%, respectively. The mean fibre length, 4.19 mm, exceeds those for some non-woodmaterials.

By using sulfuric acid in the hydrothermal treatment (170 ◦C, 0, 20 min after reaching operating tem-perature, 8 liquid/solid ratio, and 0.3% sulfuric acid), gives a liquid fraction containing 4.62% of glucose,10.56% of xylose, 1.28% of arabinose, and a solid fraction with a solid yield of 57.0%.

The best pulp of Hesperaloe pulp was obtained by cooking with 10% NaOH and 1% anthraquinone at155 ◦C for 30 min, exhibited good values of yield (48.3%), viscosity (737 mL/g), Kappa number (15.2), ten-

2

sile index (83.6 Nm/g), stretch (3.8%), burst index (7.34 kN/g) and tear index (3.20 mNm /g). Moreover, thesoda–anthraquinone pulps of raw material are better than the pulps from solid fraction of hydrothermaltreatments.

Finally, acidification (pH 6) of soda–anthraquinone pulping liquor was carried out to separate lignin-rich solids, by which pyrolysis gave a gas containing 1.13% H2, 31.79% CO and 1.86% CH4 by weight.Gasification of the same sample provided a gas containing 0.18% H2, 24.50% CO and 17.75% CH4.

© 2011 Elsevier B.V. All rights reserved.

. Introduction

More than 30% of the paper types used at present did (e.g. fil-er and chromatographic) not even exist only ten years ago andave emerged in response to new social needs [1]. The increas-

ng variety of paper types and uses has resulted in a substantialncrease in production, from 187 million tons in 2000 to 195 mil-ion in 2007 (i.e. an increase of 4.3%) [2]. Pulp production from woodpecies over this period has grown by 3.1%; by contrast, the use ofon-wood species for this purpose has risen much more markedly18.1%) [2], which testifies to the growing significance of the lat-er as cellulose raw materials. This phenomenon can be ascribed

o non-wood plants providing an effective alternative to wood,aper and cellulose pulp imports for developing countries withcant forest resources; also to the added value acquired by agrifood

∗ Corresponding author at: Chemical Engineering Department, Campus ofabanales, C-3, University of Córdoba, Córdoba, Spain. Tel.: +34 957 21 85 86;

ax: +34 957 21 86 25.E-mail address: iq1jiall@uco.es (L. Jiménez).

369-703X/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.bej.2011.04.012

residues used for pulping; and also to the special chemical composi-tion and morphological characteristics of non-wood raw materials(e.g. they are less compact, more porous structure, more readilyaccessible tissues and weaker fibril–fibril bonds) reduced energyconsumption and reagent consumption in cooking and bleachingprocesses.

A promising non-wood raw material is Hesperaloe funifera. Itis a plant of the family Agavaceae up to 80 cm tall and 1.0–1.2 mwide with long leaves up to 5 cm wide and 2–3 cm thick. Allspecies in its genus originated in Mexico and its neighbouringUSA regions, where it is used mainly for ornamental purposes.H. funifera has very modest irrigation requirements by effect ofits using the acid metabolism of Crassulaceans (CAM) for photo-synthesis. Its plants fix carbon dioxide and transpire water morestrongly at night than during the day; also, because their coef-ficient of transpiration is lower at night, they use water highlyefficiently. Based on these properties, H. funifera might be an

effective cellulose raw material to be cultivated in arid zonesin place of other species [3]; in several regions of Spain couldbe particularly interesting the cultivation of this species. High-density plantations (27,000 per hectare) can yield approximately

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R. Sánchez et al. / Biochemical En

0 tons of dry biomass per hectare [4]. These crop yields cane increased by careful control of plant flowering and the usef higher planting densities [3]. Although the fibre morphologyf H. funifera plants is especially suitable for making celluloseulp [5], little research in this direction appears to have beenonducted. In the few exceptions, the material was subjected tolkaline sulfite–anthraquinone or mechanical pulping [4,6] and theesulting paper sheets found to have very high tensile, burst andear indices—and hence to be highly suitable for making specialaper.

Interest in exploiting plant raw materials in full rather thanpecific fractions such as those used to obtain cellulose for paper-aking purposes has grown considerably in recent years. In fact,

esearchers have sought methods to additionally obtain hemicellu-ose and lignin, which are usually burnt instead. This has led to theevelopment of biorefining, which is concerned with the separationf plant components (lignin, hemicellulose and cellulose, mainly)ith a view to obtaining various products from them [7–9].

Hydrolysing polysaccharides in plant raw materials with watert a high temperature provides a solid fraction, cellulose and ligninich, and a liquid fraction containing oligomers which can be fur-her hydrolysed and fermented to obtain food additives or sugarubstrates [10,11]. The fractionation method used causes structurallterations in some compounds and detracts from quality in thenal pulp obtained from the solid fraction; the problem, however,an be overcome by using an appropriate hydrothermal treatmentor the plant material and improving the strength-related proper-ies of the pulp by beating [12,13].

Soda and soda–anthraquinone processes have been used to pulpon-wood raw materials with good results [14,15]. These processesave some advantages such as the following: a high productionesulting from the use of relatively short pulping times; good yields;pplicability to both wood and non-wood raw materials; reusabil-ty of the cooking liquors; and increased yields, more expeditiousooking and reduced Kappa numbers by effect of the joint use ofoda and anthraquinone.

Organosolv processes have been widely used at the laboratorycale and applied to various alternative raw materials [16,17]. Theost salient advantages of these processes are as follows: economy

t the small and medium scale, and efficient recovery of solventsnd by-products, reduced water, energy and reagent consumption;educed pollution and easy recovery of bleaching effluents; appli-ability to wood and non-wood raw materials; production of pulpith properties on a par with those of Kraft pulp in addition toigher yields, lower lignin contents, higher brightness, and easierleaching and refining; and the need for no additional investments

f Kraft pulping facilities are available as it suffices to use high-oiling solvents (glycols, ethanolamines) to exploit them [16,17].

One other use of biorefining is for isolating lignin from residualooking liquor. Lignin removed by organic solvents is of a muchigher value than if used as a fuel in the Kraft process. In fact, ligninan be used to obtain phenol–formaldehyde resins, polyurethanes,crylates, epoxides and composites [18]. One special use of lignin isor the production of synthesis gases by pyrolysis [19] or fuel gasesy gasification [20].

In this work, H. funifera is characterized in terms of major com-onents (cellulose, hemicellulose, lignin and extractives), and alsof hot water solubles, 1% NaOH solubles and ash, by using con-entional chemical methods. Following characterization, H. funiferaamples were subjected to hydrothermal treatments, to removes much hemicellulose, and different pulping processes to pro-uce pulp paper (using soda, soda–anthraquinone, ethyleneglycol,iethyleneglycol, ethanolamine or diethanolamine). Finally, theooking liquors were acidified to separate solid fractions that were

ubjected to pyrolysis and gasification in order to obtain synthesisases and fuel gases.

ring Journal 56 (2011) 130– 136 131

2. Experimental

2.1. Raw material characterization

Following drying at air temperature (on site collection) froman initial humidity of 90% to a final of 9%, the leaves of H. funiferawere cold ground in a Retsch SM 2000 mill to avoid alterations in itscomponents. The ground product was sieved and the 0.25–0.40 mmfraction (sieves No. 60 and 40 in the Tyler series) saved for analysis.The contents in lignin, �-cellulose, ethanol–benzene extractives,hot water solubles, 1% NaOH solubles and ash of the raw materialwere determined in accordance with the following TAPPI stan-dards: T-222, T-203 0S-61, T-204, T-257, T-212 and T-211. Thecontent in holocellulose was obtained by the method of Wise [21].

The fibre length distribution of H. funifera was determined byusing a Visopan projection microscope.

2.2. Hydrothermal treatment

The raw material was subjected to hydrothermal treatment pro-cess in a 15 L batch reactor that was heated by means of an outerjacket and stirred by rotating the vessel via a motor connectedthrough a rotary axle to a control unit including the required instru-ments for measurement and control of pressure and temperature.

Experiments were conducted at 150–190 ◦C, for 10–20 min afterreaching the operating temperature, with sulfuric acid concentra-tions of 0–0.5%, maintaining the liquid/solid ratio at 8:1.

After hydrothermal treatment, the material is separated into 2fractions (solid and liquid) by filtration.

2.3. Pulping

For pulping processes the same reactor described in the previoussection was used.

Soda, soda–anthraquinone, ethyleneglycol, diethyleneglycol,ethanolamine and diethanolamine were used, with following oper-ating condition; temperature of 155–185 ◦C, time 30–90 min, and10–80% concentration of the different reagents and organic solvent.The liquid/solid ratio was always 8:1. After each process was com-pleted, cooked material was unloaded from the reactor, washedto remove residual cooking liquor and fiberized in a disintegra-tor at 1200 rpm for 30 min, which was followed by beating in aSprout–Bauer refiner. Finally, the fiberized material was passedthrough a filter of 0.16 mm pore size to remove uncooked particles.

2.4. Analysis of liquid and solid fractions of hydrothermaltreatment

To determine the glucose, xylose and arabinose contentsweighed 10–20 g of the liquid fraction to be analyzed and taken toan ISO bottle of 100 mL. Sulfuric acid is added until the concentra-tion of 4% by weight and the ISO bottle is introduced in an autoclavefor 20 min at 2 atmospheres (121 ◦C). Then the ISO bottle is cooledwith water to room temperature and analyzed by HPLC [12].

The yield of the solid fraction is determined by gravimetry.

2.5. Characterization of pulp and paper sheets

The pulp samples obtained were characterized in terms of yield(gravimetrically), and also for Kappa number, viscosity and beating

Paper sheets were obtained with an Enjo-F39-71 former andanalyzed for tensile index, stretch, burst index, tear index and

132 R. Sánchez et al. / Biochemical Engineering Journal 56 (2011) 130– 136

Table 1Chemical composition of Hesperaloe funifera and other raw materials.

Raw material Holocellulose, % �-Cellulose, % Lignin, %

Hesperaloe funifera 76.5 40.9 7.3Kenaf [23] 78.9 49.5 15.6Bagasse [24] 73.9 45.3 21.7Cotton stalks [25] 72.9 58.5 21.5Wheat straw [26] 72.2 44.1 18.3Paulownia fortunei [27] 75.8 43.6 20.5Sunflower stalks [23] 66.9 37.6 10.8

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Empty fruit bunches [28] 84.7 60.6 16.9Rice straw [29] 60.7 41.2 21.9

rightness in accordance with the following TAPPI standards T-494,-404, T-403, T-414 and T-525, respectively.

.6. Processing of residual liquor

The liquors from the different pulping processes were treatedith sulfuric acid at pH 6, 4 and 2 to obtain various solid fractionshich were then dried at room temperature (in air) and subjected

o pyrolysis in a helium atmosphere and gasification with a 9:1ixture of helium and oxygen.The experimental system consists in a quartz tube, 10 mm wide,

here the sample is introduced uniformly occupying an apprecia-le length of the tube (approx. 350–400 mm) [22]. A horizontalctuator (servomechanism that supplies and transmits a mea-ured amount of energy for the operation of another mechanismr system) introduces with a constant linear velocity the tubeith the lignocellulosic material inside a furnace maintained at

he desired temperature (850 ◦C). The operating conditions usedor pyrolysis and gasification have been selected among commonlysed for similar lignocellulosic material experiments. The raw gasbtained from lignocellulosic material was analyzed by GC-TCDShimadzu GC-14A Gas Chromatograph) and GC-FID (ShimadzuC-17A) [22].

. Results and discussion

.1. Characterization of H. funifera

The contents in lignin, �-cellulose, holocellulose, hemicellulose,thanol–benzene extractives, hot water solubles, 1% NaOH sol-bles and ash of H. funifera were found to be 7.3%, 40.9%, 76.5%,5.6%, 4.0%, 13.5%, 29.5% and 5.9%, respectively. Table 1 compareshe holocellulose, �-cellulose and lignin contents of this speciesith those of other non-wood materials [23–29]. As can be seen,. funifera has the lowest proportion of lignin and an �-celluloseontent similar to those of the other raw materials except EFB andotton stalks, which surpass it in this respect. A low hemicelluloseontent can raise the necessary energy to obtain a given tensiletrength level with respect to conifer pulp [30].

Fig. 1 shows the fibre length distribution curve for H. funifera and photograph of a sample of fibres. The mean fibre length, 4.19 mm,xceeds those for some non-wood pulping raw materials such asenaf (1.3 mm), reed (1.2 mm), switchgrass (1.1 mm), miscanthus

able 2haracterization of liquid and solid fractions resulting from hydrothermal treatment of H

Experiment Operation conditions (◦C;min; % H2SO4)

Glucose, %

1 150; 20; 0 0.64

2 190; 20; 0 1.24

3 150; 20; 0.1 3.36

4 150; 20; 0.5 3.57

5 170; 10; 0.3 4.62

Fig. 1. H. funifera fibre size distribution graph and fibre photograph.

(1.0 mm), cotton stalks (0.8 mm) and wheat straw (0.7 mm) [31].Fibre length and thickness are correlated with a number of mechan-ical properties of paper. Thus, long fibres have a favourable effecton tensile index and tear index; also, thin-walled fibres of a smalldiameter result in increased paper strength, bonding and ease ofsheet formation [30]. The long fibres of H. funifera are extremelystrong and possess a small linear mass, which ensures the obtain-ment of paper with good surface properties.

3.2. Characterization of products of the hydrothermal treatments

Table 2 shows the values of operating variables, and the resultsof characterization of the liquid fractions (glucose, xylose and ara-binose contents) and the solid fractions (yield) obtained during thehydrothermal treatments tested. The liquid/solid ratio was alwayskept at 8:1. The choice of the values of operating variables wasdone considering the values used for similar materials: bagassefrom sugar cane [10], Arundo donax [12] and sunflower stalks [13].

Comparing the results of experiments 1 and 2 (Table 1), it canbe seen that when temperature increases (from 150 to 190 ◦C) thevalues of the sugar content of the liquid fraction increase and the

values of solid yield of the solid fraction decrease. The same effectsoccur when there is an increase in the concentration of sulfuricacid, which acts as a catalyst (experiments 1, 3 and 4 of Table 2).Some interesting operating conditions are those of experiment 5

esperaloe funifera.

Xylose, % Arabinose, % Solid yield, %

1.40 0.45 87.32.53 0.61 77.67.79 0.99 73.28.28 1.14 64.8

10.56 1.28 57.0

gineering Journal 56 (2011) 130– 136 133

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R. Sánchez et al. / Biochemical En

Table 2), that is intermediate values for temperature (170 ◦C), time10 min) and acid concentration (0.3%), which provide good valuesor concentrations of sugar liquid fraction, although the solid yieldf the solid fraction was considerably reduced; this mode of oper-tion is more economical because it operates at temperature, timend acid concentration lower than the highest used in this work.

.3. Characterization of products of the pulping processes

.3.1. Pulps and paper sheets of original raw materialTable 3 shows the results of the characterization of H. funifera

oda, soda–anthraquinone and organosolv (ethanolamine,iethanolamine, ethyleneglycol and diethyleneglycol) pulpbtained under the conditions summarized in Table 3, in terms ofield, Kappa number, viscosity and beating grade.

The pulping action of anthraquinone is well-known and involvesedox catalysis of some reactions occurring during cooking of theaw material; electrons in the aldehyde groups of carbohydratesresent in its fibres are transferred to the anthraquinone moleculend the aldehyde groups transformed into carboxyl groups as aesult; this stabilizes carbohydrates and increases pulp yield [32].ur soda–anthraquinone pulp samples (P1–P3) exhibited betterield, Kappa number and viscosity than those obtained in thebsence of catalyst. Thus, the Hesperaloe pulp obtained by cook-ng with 10% NaOH and 1% anthraquinone at 155 ◦C for 30 minP1) exhibited the highest yield (48.3%) and viscosity (737 mL/g)n addition to a fairly small Kappa number (15.2).

The pulp samples obtained with the amine solvents (P7–P12)xhibited better yield, Kappa number, viscosity and beating gradehan those provided by the glycols. The highest yield (59.6%) washat for the pulp obtained by using a 60% ethyleneglycol concen-ration at 160 ◦C for 30 min (P13); diethanolamine provided pulpith a similar yield but significantly better values for the otherroperties. Thus, the best Kappa number (20.1) was obtained byulping with 70% diethanolamine at 170 ◦C for 60 min (P11) or an0% concentration of the amine at 180 ◦C for 90 min. The reactiononditions seemingly have little influence on Kappa number; thishould allow Hesperaloe pulp with a comparable Kappa numbero be obtained by using a lower temperature, time and solventoncentration—and hence with reduced production costs. This islso the case with viscosity, which peaked in the pulp samplesbtained with diethanolamine (P10–P12); such samples differedy only 26 mL/g between the level obtained under the most and

east drastic conditions: 814 mL/g for P11 vs 788 mL/g for P10.Also Table 3 shows the results of the characterization of paper

heets made from the previous Hesperaloe pulp samples. As can beeen, the sheets obtained from soda pulp possess better physicalroperties than those obtained from soda–anthraquinone pulp. Theest tensile index, stretch, burst index and tear index were obtainednder the mildest conditions used (P4), i.e. with the least reagentnd heating energy consumption.

The physical properties of the paper obtained from the amineulp samples were better than those for paper from the glycolulp samples. The best tensile index was achieved by using 60%thanolamine at 160 ◦C for 30 min. Also, the best brightness, stretch,urst index and tear index were obtained with ethanolamine, bothnder mild and under drastic operating conditions.

Table 4 shows the results of the characterization of pulp andaper sheets from other raw materials [15,29,32–34]. As can beeen, abaca surpasses Hesperaloe in yield, viscosity, stretch and tear

ndex. Oil palm surpasses Hesperaloe in tear index and viscosity, andhe opposite is true of the other pulp and paper properties. Sugar-ane bagasse provides a better yield and tear index than Hesperaloe.inally, rice straw and kenaf are similar to H. funifera in yield, but Ta

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134 R. Sánchez et al. / Biochemical Engineering Journal 56 (2011) 130– 136

Table 4Properties of pulps and paper sheets obtained using different reagents of various raw materials.

Parameter Abaca [15] Phoenix dactiliferasoda [32]

Phoenix dactiliferasoda–AQ [32]

Bagasse [33] Rice straw Organosolv [29] Kenaf [34]

Yield, % 90.7 42.1 44.2 82.7 35.6–53 58.1Kappa number 10.6 28.9 25.5 92.9 17.0–75.3 25.5Viscosity, mL/g 1428 814 937 – 673–956 –Tensile index, Nm/g 55.9 37.3 43.1 62.9 21.1–23.7 11.4

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A comparison of Fig. 2 (sample I) with that for the sample II, andthe data in Table 7 (obtained from the mentioned figures), revealsthat pyrolysis of the solid fraction extracted by acidifying the sodacooking liquor at pH 6 produced less H2 but more CO than that

Stretch, % 5.12 – –

Burst index, kN/g – 1.9 2.2

Tear index, mNm2/g 19.03 10.7 10.0

rovide a worse tear index and better values of the other studiedroperties.

.3.2. Comparison of pulp and paper sheets obtained from solidraction of the hydrothermal treatment and from original raw

aterialTable 5 shows the results of the characterization of cellulose

ulp obtained from H. funifera and solid fractions consid-red hydrothermal treatment, using soda–anthraquinone andiethanolamine; in this table also specifies the conditions of oper-tion hydrothermal treatment and operation pulping.

The yields obtained after pulping processes of the solid frac-ion hydrothermal treatments are lower than those obtained inhe pulping of the original raw material, no significant differenceetween them (soda–anthraquinone and diethanolamine pulps).

The Kappa number is lower in pulp obtained from solid fractionydrothermal treatment.

In the case of the viscosity of the pulps, it is possible to see signif-cant differences when performing a hydrothermal treatment priorulping, on the original raw material: the viscosity of the former isbout half of those obtained in the case of the raw material.

The considered mechanical properties of the paper sheets of theellulosics pulps obtained after a previous hydrothermal treatmentre lower than the values found for sheets of cellulose pulp obtainedrom the original raw material.

Finally, the maximum brightness of the paper sheets cor-esponds to the soda–anthraquinone pulp of the solid fractionydrothermal treatment of raw material, and the minimum to sodaulp of the raw material and the diethanolamine pulps of the solidraction hydrothermal treatment.

.4. Exploitation of residual liquors of pulping processes

The residual liquors from the soda–anthraquinone (P1) andiethanolamine (P10) processes, which proved the most efficientethods for pulping H. funifera plant material (of those considered

n Table 3), were acidified in order to isolate lignin-rich fractions.able 6 shows the results obtained at different pH values.

Soda cooking an amount of 500 g of H. funifera plant materialrovided pulp in a 48.3% yield. Based on the lignin contents of theaw material (7.3%) and pulp (3.07%), the cooking liquor shouldave contained 29.09 g of lignin. This amount, however, was muchreater than the combination of the three individual fractions:5.27 g. Since the solid fractions contain additional componentsuch as hemicellulose and ash, only part of the lignin in the liquorsas recovered by acidification. The diethanolamine pulping pro-

ess provided similar results: the amount of lignin obtained fromhe cooking liquor was 18.15 g (pulp yield was 55.1% and the pulpontained 6.66% lignin), but the solid fractions in combination onlyontained 12.66 g.

As can be seen from Table 6, acidification of the soda liquor atH 6 (sample I) extracted the highest proportion of solid fraction91.0%). Therefore, using lower pH values to obtain other solid frac-ions (sample 2) may be counterproductive as they will add little

– 1.95–1.99 0.682.8 1.0–1.2 2.46.0 0.3–0.4 11.8

to the previous one and unnecessarily raise the cost of neutral-izing the effluent. The main solid fraction in the liquor from thediethanolamine process, which accounted for 63.3% by weight, wasobtained at pH 4 (sample IV); by contrast, only 14.3% was extractedat pH 2 (sample V). Using a pH below 4 may be counterproductivefor the same reasons as with the soda liquor.

Samples of the different solid fractions (samples I and V in col-umn 2 of Table 6) were pyrolysed and gasified in a horizontaltubular reactor. The total amount of gases obtained from each sam-ple, using pyrolysis and gasification, is shown in Table 6 (columns 4and 5), observing that the amounts are higher for gasification. Theseresulting gases are analyzed by GC/FID and GC/TCD; the results areshown in Table 7. In the case of sample I, the concentration profilesfor the synthesis gases and fuel gases are shown in Fig. 2. There aresimilar figures for the remaining samples considered (II–V), whichare not presented in this paper.

Fig. 2. Concentration profiles for the synthesis and fuel gases obtained from the solidfraction extracted from the soda–anthraquinone cooking liquor at pH 6 (sample I).

R. Sánchez et al. / Biochemical Engineering Journal 56 (2011) 130– 136 135

Table 5Characteristics of pulp and paper sheets of H. funifera and solid fractions from hydrothermal treatments.

Types of pulping Pulping yield Kappa number Viscosity, % Brightness, % Tensile index, Nm/g Burst index, kN/g

Hydrothermal treatment (170 ◦C, 10 min,0.3% H2SO4) + pulping (155 ◦C, 20 min, 5%soda, 1% anthraquinone)

52.3 22.3 373 64.9 44.7 3.61

Soda pulping (155 ◦C, 20 min, 5% soda, 1%anthraquinone)

57.8 24.9 711 54.8 73.6 6.13

Hydrothermal treatment (170 ◦C, 10 min,0.3% H2SO4) + pulping (155 ◦C, 30 min, 50%diethanolamine)

54.0 28.6 397 54.1 52.1 4.23

Diethanolamine pulping (155 ◦C, 30 min,50% diethanolamine)

57.7 23.7 765 60.5 87.1 7.59

Table 6Solid fractions extracted by acidification of the cooking liquor and overall proportions of gases obtained by their pyrolysis and gasification.

Liquor pH for extraction of solidfraction

Amounts of solids extracted (g)and proportion with respect to thebody of fractions

Total amount of gases obtained (%with respect to the extractedfraction)

Pyrolysis Gasification

Soda pulping pH = 6 (Sample I) 13.90 (91.0%) 91.0 96.1pH = 4 (sample II) 1.14 (7.5%) 82.6 98.0pH = 2 0.23 (1.5%) – –

ef

et

aopCCI

da

acm

sr

TC

Diethanolamine pulping pH = 6 (sample III)

pH = 4 (sample IV)

pH = 2 (sample V)

xtracted at pH 4. Also, gasification of the solids extracted at pH 6rom the same liquor produced slightly more H2 but less CO.

The amounts of H2 and CO obtained by gasifying the fractionxtracted from the soda cooking liquor at pH 6 were smaller thanhose obtained by pyrolysis. The opposite was true of CH4 and CO2.

For samples III, IV and V, a comparison of figures similar to 2,nd the data in Table 7, reveals that pyrolysis of the solid fractionbtained by acidification of the diethanolamine cooking liquor atH 6 (sample III) produced decreased amounts of H2, CH4, CO andO2 relative to pH 2 (sample V); and decreased amounts of H2 andH4 and increased amounts of CO and CO2 relative to pH 4 (sample

V).On the other hand, gasification of fraction extracted at pH 6 pro-

uced increased amounts of H2, but decreased amounts of CH4, COnd CO2, relative to pH 4 and 2.

A comparison of the amounts of gases obtained by gasificationnd pyrolysis of the solid faction extracted from the diethanolamineooking liquor at pH 4 reveals that gasification produced less H2 butore CO, CO and CH than pyrolysis.

2 4As can be seen from Table 7, pyrolysis of the solids from the

oda cooking liquor provided increased amounts of H2, CO and CO2elative to the diethanolamine liquor. However, pyrolysis of the

able 7omposition of evolved gases generated by pyrolysis and gasification of the solid fraction

Process Samples Composition, g

H2

Pyrolysis Sample I 1.13

Sample II 1.54

Sample III 0.64

Sample IV 0.74

Sample V 0.97

Sample (III + IV) 0.71

Gasification Sample I 0.18

Sample II 0.17

Sample III 4.92

Sample IV 0.26

Sample V 0.15

Sample (III + IV) 1.48

2.84 (22.4%) 77.9 87.58.01 (63.3%) 75.1 97.31.81 (14.3%) 74.1 99.6

soda liquor fractions extracted at pH 4 and 2 provided decreasedamounts of CH4 relative to diethanolamine.

Gasification provided very small amounts of H2 with all frac-tions except that extracted from diethanolamine liquor at pH 6.The fractions extracted at the lower pH values (samples II and V)gave greater amounts of CO and CO2. Finally, the largest amountsof CH4 were obtained from the diethanolamine liquor extracted atthe intermediate pH.

Based on the foregoing, the solid fraction extracted fromsoda liquor at pH 6 is the best source for producing synthe-sis gases (H2 + CO) by pyrolysis, and so is the fraction extractedfrom diethanolamine liquor (sample V) for obtaining fuel gases(H2 + CO + CH4) by gasification.

Table 7 shows the composition of the synthesis gases and fuelgases obtained from the combination of the two fractions extractedat pH 4 (samples III and IV: sample (III + IV)). As can be seen, pyrol-ysis of sample I produced greater amounts of synthesis gases andfuel gases than did the combination of samples III + IV; the actualdifference was even more marked than suggested by the results

if one considers that the amounts of sample I and sample III + IVobtained from 500 g of pulp were 13.90 and 10.85 g, respectively.On the other hand, gasification of samples I and III + IV produced

s.

/100 g sample

CO CO2 CH4

31.70 22.40 1.8616.30 19.00 1.8113.00 14.80 1.5510.50 12.80 2.3713.60 16.80 3.7011.16 13.33 2.16

24.50 52.90 17.7632.40 67.20 17.6620.40 38.40 14.0123.00 48.60 23.2653.40 51.60 16.0122.32 45.94 20.84

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36 R. Sánchez et al. / Biochemical En

imilar amounts of synthesis and fuel gases; however, since themount of sample I extracted exceeded that of sample III + IV, theormer fraction is to be preferred as it provides greater amounts ofases and requires less acid for extraction.

. Conclusions

A comparison of the chemical properties of H. funifera with thosef non-wood raw materials including kenaf, bagasse, cotton stalks,heat straw, paulownia, sunflower stalks, empty fruit bunches

EFBs) and rice straw confirms that H. funifera provides an effectivelternative raw material for obtaining cellulose pulp and paper. Inddition, the fibre length is much higher than that of alternativeaw materials considered.

A hydrothermal treatment of H. funifera (170 ◦C, 10 min aftereaching the operating temperature, a liquid/solid ratio of 8, and aulfuric acid concentration of 0.3%) provides a liquid fraction thatontains an acceptable value for the contents of glucose, xylose andrabinose, although the yield of the solid fraction is low. Then theres the fact that the characteristics of the pulp and paper obtainedrom the solid fraction of the hydrothermal treatment, are worsehan those obtained directly from the original H. funifera. It is there-ore concluded that hydrothermal treatment is not appropriate ifhe cellulose of the solid fraction is used for paper pulp production.

Based on the results of the characterization of pulpnd paper obtained by cooking H. funifera with soda,oda–anthraquinone, ethyleneglycol, diethyleneglycol,thanolamine and diethanolamine, the best pulp from thislternative raw material was that obtained by using 10% soda con-aining 1% anthraquinone at 155 ◦C for 30 min. These conditionsesulted in a good yield, Kappa number, viscosity, drainage index,ensile index, stretch, burst index and tear index.

A comparison of the amounts of synthesis gases (H2 + CO) anduel gases (H2 + CO + CH4) generated by pyrolysis and gasificationf the solid fractions obtained by acidifying the liquors from theoda–anthraquinone and diethanolamine processes revealed thathe best results were those for the soda–anthraquinone liquorxtracted at pH 6. These conditions allow an alternative exploita-ion of lignin-rich fractions in the residual cooking liquor.

cknowledgements

The authors are grateful to Ecopapel, S.L. (Écija, Seville, Spain) forheir support, to Spain’s DGICyT for funding this research within theramework of Projects PPQ2007-65074-C02-01 and TRACE2009-064, and to the Ramón y Cajal programme (Spain’s Ministry ofducation and Science) for additional funding.

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