Keywords: Algae; Hydrothermal; Liquefaction; Solvent; Bio-oil; Bio fuels
they also have lower dielectric constant compared to water.All these advantages make methanol and ethanol promising
. Introduction
epletion of carbon fossil resources (oil, gas and coal) andncreased efforts to mitigate CO2 emissions have led to theeed for development of new generation of transportation
uels. This may involve a partial or complete replacement ofossil resources by carbon-neutral renewable ones. Biomass is
promising feedstock since it is abundant and cheap and cane transformed into fuels and chemical products (Huber et al.,006; Huber and Corma, 2007).
The use of macro algae for energy production has receivedess attention so far though macro algae are being cultivatedince long for several purposes (food production, chemicalsxtraction) in China, Korea, Philippines, and Japan. Theirroductivity is in the range of 1–15 kg m−2 y−1 dry weight
10–150 tdw ha−1 y−1) for a 7–8 month culture. Brown algaeLaminaria, Sargassum) or red algae have been used so far foruch purposes (Aresta et al., 2003).
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∗ Corresponding author.E-mail addresses: [email protected], [email protected] (T. BhaReceived 28 August 2012; Received in revised form 4 March 2014; Acce
Hydrothermal studies for liquefaction of lignocellulosicbiomass have garnered interest over the last two decades.Hydrothermal liquefaction technology produces liquid oilswhich are immiscible in water, with much higher calorificvalues and a range of chemicals including vanillin, phenols,aldehydes, and organic acids, etc. (Appell et al., 1971; Boococket al., 1979; Goudriaan et al., 2001; Yokoyama et al., 1984).
However, the biomass liquefaction using water as sol-vent usually produces a relatively lower yield of water-insoluble oily products than other organic solvents such asmethanol, ethanol, 1-propanol, and acetone (Chumpoo andPrasassarakich, 2010; Cemek and Kucuk, 2001; Liu and Zhang,2008; Miller et al., 1999; Yamazaki et al., 2006; Yang et al.,2009). Among all these solvents, methanol (239.45 ◦C, 8.09 MPa)and ethanol (240.75 ◦C, 6.14 MPa) have low boiling points,much lower critical points than water (373.95, 22.06 MPa) and
ydrothermal liquefaction of macro algae Ulva fasciata. Process Safety.03.002
2 Process Safety and Environmental Protection x x x ( 2 0 1 4 ) xxx–xxx
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solvents for the liquefaction of biomass to produce valuablehydrocarbons (Zhou et al., 2012).
Zou et al. (2009) studied the thermo catalytic liquefactionof microalgae Dunaliella tertiolecta in ethylene glycol acidi-fied with H2SO4 as catalyst at 120–200 ◦C and bio-oil obtainedin their study was composed of benzofuranone, fatty acidmethyl ester and fatty acid hydroxyethyl ester. Huang et al.(2011) studied liquefaction of microalgae Spirulina in sub-/supercritical ethanol at 280–380 ◦C to obtain a bio-oil yield of45.3%. Yang et al. (2011) studied hydro-liquefaction of microal-gae Dunaliella salina in ethanol under moderate conditions(200 ◦C, 2 MPa and 60 min) with Ni/REHY as catalyst. Highestbio-oil yield of 72% was observed. Zhou et al. (2012) investi-gated the liquefaction of macro algae Enteromorpha prolifera insub-/supercritical alcohols for the production of ester com-pounds.
The present study aimed to enhance the yields of liquidproducts with increased functionality and utilize the liquidhydrocarbons as chemical feedstock. In this direction, we havestudied the effect of different solvents (methanol, ethanol andwater) on the bio-oil yield, product distribution and nature ofthe liquid and solid products obtained from the liquefaction ofmacro algae. Liquid products were characterized with the helpof FTIR, 1H NMR and 13C NMR. The solid products obtainedwere characterized using FTIR and SEM.
2. Methods
2.1. Materials
The macro algae sample (MAUF) and its compositional anal-ysis (Table 1) was provided by CSIR-Central Salt & MarineChemicals Research Institute (CSMCRI). As seen from thetable, the macro algae have high carbohydrate content andlow lipid content. The protein content was considerable in allthe macro algae samples. The macro algae samples show highmoisture and ash content (Kumar et al., 2011).
2.2. Apparatus and experimental procedure
Hydrothermal liquefaction experiments were conducted ina 500 ml autoclave at 300 ◦C using distilled water and alco-holic solvents (CH3OH and C2H5OH) for 15 min. In a typicalhydrothermal liquefaction experiment, the reactor was loadedwith 10 g of macro algae (wet basis) and 60 ml of distilledwater/alcoholic solvent. Then the reactor was purged fivetimes with nitrogen to remove the inside air. Reactants wereagitated vertically at ∼50 cycles min−1 using stirrer. The tem-perature was then raised up to 300 ◦C at heating rate of5 ◦C min−1 and kept for 15 min. The pressure during the pro-cess was autogenous and maximum pressure was in the rangeof 1000 to 1300 psi. After reaction, the reactor was left tocool down to room temperature. The gaseous products werevented. Solid and liquid products were separated by filtrationunder vacuum. The detailed separation and analysis proce-dure has been described elsewhere (Karagöz et al., 2005). Themass balance equations are provided in Appendix A.
2.3. Analysis of feed and reaction products
Macro algae and solid products obtained after hydrothermalupgrading (HTU) were analyzed using SEM and FTIR. The bio-
Please cite this article in press as: Singh, R., et al., Effect of solvent on the hydrothermal liquefaction of macro algae Ulva fasciata. Process Safetyand Environmental Protection (2014), http://dx.doi.org/10.1016/j.psep.2014.03.002
oil samples were analyzed using FTIR and NMR. SEM imageshave been collected on FEI Quanta 200 F, using tungsten
a See appendix Eq. (1).b See appendix Eq. (2) for water case and Eq. (3) for methanol/ethanol case.c See appendix Eq. (4).d See appendix Eq. (5).e See appendix Eq. (6).
fisppc1
o51
(N
3
TmTasyceEcoowslowlcoaowE2tswuiwfb
ta
mal aliphatic ester whereas the peaks at 1707 and 1709 cm−1
1000 1500 2000 2500 3000 3500 4000
0
20
40
60
80
100
120
140
% T
ran
sm
itta
nce
Waven umber, cm-1
H2O
CH3OH
C2H
5OH
lament doped with lanthanum hexaboride (LaB6) as an X-rayource, fitted with an ETD (Everhart Thornley Detector), whichreferentially work as a secondary electron detector. The sam-le for SEM has been subjected to disperse on a carbon paperoated adhesive followed by gold coating. The 13C NMR andH NMR spectra of the bio-oil samples have been collectedn Bruker Avance III 500 MHz NMR spectrometer operating at00.13 MHz and 125.77 MHz resonance frequency for 1H and3C, respectively using 5 mm broad band probe and CDCl3Merck 99.5%) as solvent. The FTIR spectra were recorded onicolet 8700 FTIR spectrometer.
. Results and discussion
he product distributions from hydrothermal liquefaction ofacro algae using different solvents are presented in Table 2.
he total bio-oil yield was 11% during liquefaction with waternd this increased to 44% and 40% with the use of alcoholicolvents CH3OH and C2H5OH respectively. The total bio-oilield was composed of bio-oil1 yield and bio-oil2 yields. Inase of liquefaction with water, the bio-oil1 was obtained afterxtracting the water soluble fraction with diethyl ether andq. (2) was used to calculate the bio-oil1 yield whereas inase of liquefaction with alcoholic solvents, the bio-oil1 wasbtained by directly evaporating the alcoholic solvent and bio-il1 yield in this case was calculated using Eq. (3). The bio-oil2as obtained by extraction of solid residue with acetone by
oxhlet extraction in all cases and Eq. (4) was used to calcu-ate bio-oil2 yield. The bio-oil1 yield was much higher in casef liquefaction with alcoholic solvents than liquefaction withater. The bio-oil1 yield observed was 42% and 39% in case of
iquefaction with CH3OH and C2H5OH respectively whereas inase of liquefaction with water, the bio-oil1 yield was 3%. Thebserved yield of bio-oil2 was almost same in case of CH3OHnd C2H5OH with values of 2% and 1% respectively whereasbserved bio-oil2 yield was 8% in case of liquefaction withater. The observed yield of solid bio residue calculated using
q. (6), was minimum in case of liquefaction with water at4%. The solid bio residue yield was higher in case of liquefac-ion with alcoholic solvents than liquefaction with water. Theolid bio residue yield was maximum in case of liquefactionith C2H5OH at 41%. The yield of gaseous products calculatedsing Eq. (5) was almost constant in all the three cases. Max-
mum conversion of 76% was observed in case of liquefactionith water. As clearly seen from Table 2, the solvent used
or hydrothermal liquefaction study significantly affected theiomass conversion process.
The use of alcoholic solvents significantly increased the
Please cite this article in press as: Singh, R., et al., Effect of solvent on the hand Environmental Protection (2014), http://dx.doi.org/10.1016/j.psep.2014
otal bio-oil yield but the solid bio residue yield also increasednd conversion decreased. The role of methanol and ethanol
in the liquefaction was not only that of solvent, but also ashydrogen-donors that could promote the formation of bio-oil. The major functions of solvent during the liquefaction ofbiomass are decomposition of the raw biomass material andproviding active hydrogen. The presence of active hydrogencould stabilize liquefaction intermediates and prevent themfrom forming compounds that are more difficult to decomposeresulting in increase of bio-oil yield.
4. Analysis of bio-oil1
FTIR spectrum of the bio-oil1 obtained from liquefaction ofMAUF with water and alcoholic solvents is shown in Fig. 1. Thebands from 2854 to 2965 cm−1 in the bio-oil1 obtained by theliquefaction of macro algae with H2O, CH3OH and C2H5OH aredue to the C H stretching vibrations, indicating the presenceof alkyl C H groups. The absorbance of these peaks in bio-oilwas stronger in case of liquefaction with water and methanolthan the bio-oil obtained by liquefaction with ethanol. Thebroad band at around 3300 cm−1 is attributed to the O H orN H stretching vibration caused by water or O H groups orN H groups present in bio-oil. The C O stretching vibrationat 1707, 1709, 1723 and 1740 cm−1 respectively in the bio-oil1 samples obtained using different solvents indicate thepresence of ketones, aldehydes, esters, or acids. In case of liq-uefaction of macro algae with water strong absorbance peak at1723 cm−1 was obtained, in case of C2H5OH the C O peak wasobserved at around 1707 cm−1 where as in case of liquefac-tion of macro algae with methanol two peaks were observedat 1741 and 1710 cm−1. The peak at 1740 cm−1 is due to nor-
ydrothermal liquefaction of macro algae Ulva fasciata. Process Safety.03.002
4 Process Safety and Environmental Protection x x x ( 2 0 1 4 ) xxx–xxx
H2O
CH3OHC2H5OH
H2O
CH3OHC2H5OH
Fig. 2 – (a): 1H NMR spectral distribution of functionalgroups present in bio-oil1 based on integrated peak areasassigned to characteristic spectral regions. (b): 13C NMRspectral distribution of functional groups present in bio-oil1based on integrated peak areas assigned to characteristic
may be due to the carboxylic acid or C O group of ester inconjugation with the C C or with phenyl group. The bandsin the region from 1050 to 1250 cm−1 were attributed to C Ovibrations, showing the possible existence of acids or alcoholsin the bio-oil and were present in bio-oil1 derived from threefeeds (Shuping et al., 2010).
The C H bending vibrations at 1364 and 1459 cm−1,together with the C O bending vibration at 1215 cm−1, sug-gest the presence of fats and esters (Zou et al., 2009). This isin accordance with the nature of bio-oil obtained from Zhouet al. (2012) in their study, which was composed of mainlyester components. In addition, some other absorbance peaksappearing at the band of 650–900 cm−1 are ascribed to the C-Hbending vibrations from aromatics (Zhou et al., 2010). Carbo-hydrate content of macro algae produced bio-oil1 with strongC O stretch (1730–1700 cm−1), C O stretch (1320–1210 cm−1),and C O alcohol stretch peaks (1260–1000 cm−1) and thesepeaks were present in the bio-oil1 derived from liquefactionof macro algae using different solvents (Vardon et al., 2011).
The FTIR spectra of various bio-oil1 samples from macroalgae samples using different solvents as reaction mediumshows the same peaks, indicating the presence of same func-tional groups in the bio-oil samples from the three macro algaesamples. The spectra differ only in the relative intensity ofsome peaks. The FTIR spectra were in accordance with thevarious peaks obtained in the NMR spectra of the bio-oils.
The main compounds identified by Zhou et al. (2010) and(Anastasakis and Ross, 2011) in hydrothermal liquefaction ofmacro algae includes ketones, phenols, nitrogen heterocycles,saturated fatty acids, and unsaturated fatty acids. The ketonesand phenols are believed to be derived from the decompo-sition of carbohydrates and nitrogen-containing compoundsfrom the decomposition of proteins. Fatty acids are the mostabundant group in the bio-crudes although the levels of lipidin seaweeds are known to be low (Anastasakis and Ross, 2011).Analysis of hydrocarbons from U. fasciata indicates similartype of functional groups in FTIR in case of liquefaction withwater in our study. The formation of esters may be explainedon the basis that with the use of alcoholic solvents, acids getconverted to their corresponding methyl and ethyl esters.
Similar to FTIR, 1H NMR spectra showed a high percentageof aliphatic functional groups for all bio-oil1 and a summaryof integrated peak area regions assigned to different func-tional group classes is provided in Fig. 2a and b. All bio-oil1samples displayed a low percentage of methoxy/carbohydratefunctionality (4.5–6.0 ppm). No proton resonated in this regionusing water as reaction medium for liquefaction. When alco-holic solvents were used as the reaction medium, the protonpercentage was 3.5% and 0.3% respectively with CH3OH andC2H5OH.
The region of the spectrum between 6.0 and 8.5 ppmcorresponds to the aromatic region of spectrum. The down-field spectrum regions (9.5–10 ppm) of bio-oils arise from thealdehydes. Aromatic/hetero-aromatic functionality was alsoobserved in all bio-oil1 samples (6.0–8.5 ppm) in agreementwith findings from FTIR. Aldehyde functionality (9.5–10.0 ppm)was absent from all samples despite the observed C O func-tional groups (1730–1700 cm−1) by FTIR. The appearance ofsuch FTIR bands can also be due to other carbonyl-bearinggroups like protonated carboxylic acids, carboxylic acid esters,amides, and ketones.
The most up field region of the spectra from 0.5 to 1.5 ppm
Please cite this article in press as: Singh, R., et al., Effect of solvent on the hand Environmental Protection (2014), http://dx.doi.org/10.1016/j.psep.2014
represents aliphatic protons attached to carbon atoms atleast two bonds away from a C C or heteroatom (O or N) i.e.
spectral regions.
alkane group protons [Mullen et al., 2009]. The next integralregion from 1.5 to 3.0 ppm represents aliphatic protons � toheteroatom or unsaturation. The bio-oil1 derived from macroalgae samples using different solvents has higher percentageof the protons in the region from 0.5 to 3.0 ppm. In case ofliquefaction with H2O and CH3OH more than 80% of theprotons resonate in this region whereas in case of liquefac-tion with C2H5OH the proton percentage in this region wasaround 70%. The region is further divided into two regions0.5–1.5 ppm and 1.5–3.0 ppm. In case of liquefaction of macroalgae with H2O as reaction medium, the proton percentage ishigher in the region from 1.5 to 3.0 (50%) ppm than the protonpercentage in the region from 0.5 to 1.5 (37%) ppm. With theuse of alcoholic solvents (CH3OH and C2H5OH) as the reactionmedium for macro algae liquefaction, the proton percentagein the region from 0.5 to 1.5 ppm is higher than the protonpercentage in the region from 1.5 to 3.0 ppm. More than 50%of the protons resonate in the region from 0.5 to 1.5 ppm incase of liquefaction of macro algae with alcoholic solvents,which shows that the use of alcoholic solvents increased
ydrothermal liquefaction of macro algae Ulva fasciata. Process Safety.03.002
the aliphatic content of the bio-oil1 in comparison to thebio-oil1 obtained from the liquefaction of macro algae with
Process Safety and Environmental Protection x x x ( 2 0 1 4 ) xxx–xxx 5
HliT3(m
ctHracctH6iti(fs5orseaoelma9utrtampctfCTaovlc
4
FabtaptC
1000 1500 200 0 250 0 3000 350 0 400 0
0
20
40
60
80
100
120
% T
ran
sm
itta
nce
Waven umber, cm-1
MAUF
H2O
CH3OH
C2H
5OH
Fig. 3 – FTIR of macro algae (MAUF) and Bio-residueobtained using different solvent.
2O. The proton percentage is higher in this region in case ofiquefaction with C2H5OH (57%) than the proton percentagen case of liquefaction of CH3OH (52%) as reaction medium.he proton percentage was very less in the region from 1.5 to.0 ppm in case of liquefaction of macro algae with ethanol13%) as reaction medium compared to the liquefaction of
acro algae with H2O (50%) as well as methanol (31%).13C NMR spectra provided greater detail due to their large
hemical shift regions and pointed to a high aliphatic con-ent (0–55 ppm) of bio-oil1 obtained from liquefaction with
2O as well as alcoholic solvents as reaction medium. Theegion from 0 to 28 ppm in 13C NMR is composed of the shortliphatics. The next integrated region is 28–55 ppm which isomposed of long and branched aliphatics. The carbon per-entage in the region from 0 to 55 ppm in 13C NMR spectra ofhe bio-oil1 obtained from liquefaction of macro algae with
2O (64%) as well as alcoholic solvents (78% with CH3OH and3% with C2H5OH) is very high. The highest carbon percentagen the region from 0 to 28 ppm is obtained in case of liquefac-ion with C2H5OH (47%). The carbon percentage in the bio-oil1n this region was almost same in case of liquefaction with H2O32%) as well as CH3OH (31%). The bio-oil1 obtained from lique-action of macro algae with CH3OH (47%) as reaction mediumhowed very high carbon percentage in the region from 28 to5 ppm compared to the bio-oil1 obtained from liquefactionf macro algae with H2O (32%) as well as C2H5OH (16%). Theegion between 55 and 95 ppm in the 13C NMR spectra repre-ents carbon atoms adjacent to an O atom in carbohydrates,thers, or alcohols. Also, carbon atoms adjacent to nitrogentoms would resonate in this region. Around 23% carbons res-nate in this region in case of liquefaction of macro algae withthanol as reaction medium. The carbon percentage was veryow in this region in the bio-oil1 obtained from liquefaction of
acro algae with methanol as well as with water. Aromaticsnd olefinic compounds resonate in downfield region between5 and 165 ppm. All the bio-oils obtained from macro algaesing different solvents showed the aromatic and olefinic con-ent. The bio-oil obtained from macro algae using water aseaction medium showed higher aromatic and olefinic con-ent compared to the bio-oil1 obtained from macro algae usinglcoholic solvents, methanol as well as ethanol as reactionedium. The bio-oil1 obtained from the macro algae sam-
les using water as reaction medium have around 2% carbonontent in the region from 165 to 180 ppm, corresponding tohe esters and carboxylic acid carbons. The bio-oil1 obtainedrom macro algae using alcoholic solvents CH3OH (0.52%) and
2H5OH (2.1%) have very less carbon content in this region.he region from 180 to 215 ppm corresponds to the aldehydesnd ketones. 13C NMR showed no carbon content in bio-oil1btained from liquefaction of macro algae using alcoholic sol-ents as reaction medium in this region. Whereas in case ofiquefaction with water as reaction medium, very less carbonontent of around 2% was obtained in this region.
.1. Analysis of solid products
ig. 3 shows the FTIR spectra of the macro algae feed MAUFnd the bio residues obtained under various conditions. Theroad band around 3406 cm−1 in the macro algae is assignedo the stretching vibrations of hydrogen bonded O H groupsnd N H groups, and these bands indicate the presence ofolysaccharides carbohydrates and the proteins present in
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he macro algae. The peak at 1647 cm−1 is assigned to the O group of amides which arises due to the presence of
proteins in the feed. The peak around 1451 cm−1 is due to theCH3 bending vibration. The peak at 1103 cm−1 is assigned tothe C O stretching vibration of secondary alcohol and peakat 1056 cm−1 is due to the C O stretching vibration of theprimary alcohol which confirms the presence of polysaccha-rides carbohydrates. Initial MAUF feed have strong stretchingvibration peaks corresponding to the O H and N H groups,but those transmittance decreases in the bio residue at 300 ◦Cin case of liquefaction with water as well as alcoholic sol-vents. The peaks at 1542 and 1254 cm−1 disappeared in the bioresidue. The peak at 1542 cm−1 was due to the N-H bendingvibration due to the protein content of macro algae MAUF. Thepeak at 1254 cm−1 was due to the C O stretching vibrationdue to presence of alcohols. The peak around 1647 cm−1
corresponding to the C O group of amides due to the pres-ence of proteins in the feed is not detected at 300 ◦C. Theabsence of above mentioned peaks in the bio residue samplesconfirms the decomposition of the carbohydrates and pro-teins present in the macro algae MAUF under hydrothermalliquefaction with water as well as alcoholic solvents. Usingwater as solvent, the peak at 1451 cm−1 disappeared in bioresidue and a peak at 1466 cm−1 appeared whereas in case ofliquefaction with alcoholic solvents, the peak in bio residueshifted to 1440 cm−1 for CH3OH and 1432 cm−1 for C2H5OH.The absorbance corresponding to these peaks increased inbio residue using water as solvent relative to the alcoholicsolvents as well as MAUF. During liquefaction with alcoholicsolvents, the strong absorbance peak at 1158 cm−1 for CH3OHand 1161 cm−1 for C2H5OH were observed in bio residue sam-ples. In case of liquefaction with water, the peak at 1156 cm−1
was obtained with weak absorbance. These observationssuggest that the bio residue obtained from liquefaction withalcoholic solvents was different from the bio residue obtainedfrom liquefaction with water.
SEM images (Fig. 4) of the bio residue showed that that thebio residue obtained in case of liquefaction with water wasdifferent from liquefaction with alcoholic solvents (C2H5OHand CH3OH). The bio residue obtained with alcoholic solvents(C2H5OH and CH3OH) was composed of spherical moieties.The SEM images of the bio residue obtained with CH3OH andC2H5OH were almost similar. In case of liquefaction with waterno spherical moieties were observed in SEM images and the
ydrothermal liquefaction of macro algae Ulva fasciata. Process Safety.03.002
Hydrothermal liquefaction of U. fasciata was carried out at300 ◦C using various solvents (H2O, CH3OH and C2H5OH). Theuse of alcoholic solvents significantly increased the bio-oilyield. The bio-oil yield was 44% and 40% in case of lique-faction with CH3OH and C2H5OH respectively whereas thebio-oil yield was 11% with H2O. Use of alcoholic solventsincreased the aliphatics percentage in bio-oil1 and aliphaticester compounds were present in bio-oil1. Nature of bioresidue obtained using alcoholic solvents was different frombio residue obtained using H2O. SEM images show presenceof spherical moieties in bio residue obtained using alcoholicsolvents. The results clearly show that supercritical ethanolliquefaction was an effective way to remove oxygen and utilizecarbon and hydrogen in macro algae to produce value addedhydrocarbons.
Acknowledgements
The authors thank the Director, CSIR-Indian Institute ofPetroleum (IIP) for his support and encouragement. RS thanksCouncil of Scientific and Industrial Research (CSIR) for pro-
Please cite this article in press as: Singh, R., et al., Effect of solvent on the hand Environmental Protection (2014), http://dx.doi.org/10.1016/j.psep.2014
viding fellowship in the form of Senior Research Fellowship(SRF). The authors thank NMR, FTIR and SEM analysis groups
ples obtained using different solvents.
and other analytical staff for the characterization. The authorsthank CSIR, Government of India for providing financial sup-port in the form of XII Five Year Plan project (CSC0116/BioEn).
Appendix A.
Eqs. (1)–(6) refer to Table 2
Conversion (wt.%) = WMA − Wresidue
WMA× 100 (1)
Bio-oil1 yield (wt.%) = Wether soluble
WMA× 100 (2)
Bio-oil1 yield (wt.%) = W(C2H5OH/CH3OH)soluble
WMA× 100 (3)
Bio-oil2 yield (wt.%) = Wacetone soluble
WMA× 100 (4)
Gas yield (wt.%)
ydrothermal liquefaction of macro algae Ulva fasciata. Process Safety.03.002
Amount of biomass taken (g) + Amount of solvent added (g)(5)
Process Safety and Environmental Protection x x x ( 2 0 1 4 ) xxx–xxx 7
R
R
A
A
A
B
C
C
G
H
H
H
K
K
esidue yield (wt.%) = Wresidue
WMA× 100 (6)
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