Hydrothermal-Controlled Conversion of Black Liquor Acid Sediment

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Hydrothermal-Controlled Conversion of Black Liquor Acid Sediment Directly to Phenolics Jiang yong Chu, Weikun Jiang, Shubin Wu, Lucian A. Lucia, and Ming Lei Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b02792 • Publication Date (Web): 17 Jan 2017 Downloaded from http://pubs.acs.org on January 23, 2017

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Hydrothermal-Controlled Conversion of Black Liquor Acid Sediment Directly to Phenolics Jiangyong Chua, Weikun Jianga, Shubin Wua,*, Lucian A. Luciab, Ming Leia a

State Key Lab of Pulp & Paper Engineering, South China University of Technology,

Guangzhou, Guangdong 510640, the People’s Republic of China; b

Key Laboratory of Pulp & Paper Science and Technology, Qilu University of Technology,

Jinan, Shandong 250353, the People’s Republic of China. *Tel.: +86 20 22236808. Fax: +86 20 22236808. E-mail: [email protected] (S. Wu)

Abstract

This study explored the direct conversion of black liquor acid sediment (BLAS) into phenolics by hydrothermolysis. Experiments were successfully performed in a batch-type reactor at temperature of 260 oC ~ 340 oC over 0 ~ 120 min. Depending on the reaction conditions, four products (bio-oil phase containing most of the phenolics, aqueous phase, char, and a small amount of gas) were formed and analyzed by element analysis, Fourier transform infrared spectroscopy (FT-IR), gas chromatography mass spectrometry (GC-MS), gas chromatography (GC), and pyrolysis-gas chromatography mass spectrometry (Py-GC/MS). The total bio-oil yield

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was 16 ~ 26 wt-% based on dry BLAS (D-BLAS), in which the main monomeric compounds were 2-methoxyphenol, 2, 6-dimethoxyphenol and catechol, with yields of 0.74 ~ 1.66, 0.28 ~ 4.03, 0 ~ 7.08 wt-% based on lignin in the BLAS (BLAS-L), respectively. Analysis of char suggested BLAS-L occurred by hydrothermolytic depolymerization to give aryl-ether linkages (β-O-4 and α-O-4 bonds), hydroxyl and carbonyl groups, and aromatic rings. Finally, the reactions were almost complete because the char had no functional groups of lignin at the optimal reaction condition (300 oC and 30 min).

Keywords: hydrothermal conversion; black liquor acid sediment; lignin; phenolic compounds

1. Introduction The rapid depletion of fossil resources and increasing demand for energy has propelled biomass resources to the fore as an alternative renewable feedstock for the energy and chemical industries.1 Lignin, as the third or fourth most abundant natural polymer on the earth (behind chitin, cellulose/hemicelluloses), is a leading and easily procurable biomass resource, accounting for 15-35% content and 40% energy content of all lignocellulose biomass.2 Structurally, lignin is composed of aromatic nuclei, specifically phenolic building blocks linked by ether bonds and carbon–carbon linkages. Lignin is therefore considered a sustainable candidate feedstock for aromatic chemicals3 especially for the provision of phenol, o-cresol, and catechol as intermediates. Pulping accounts as the dominant lignin procuring process in which the lignin in the woody biomass is degraded and dissolved as black liquor to provide 50 million tons per annum.4 From


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an energy perspective, black liquor lignin is an alternative renewable resource for liquid fuels and chemicals. However, when black liquor is considered to be used by a classical gasification process, it would lead to a high drying cost due to high percentage of water in black liquor. Hence, most of black liquor lignin is burned as a low value fuel, and thus to only provide heat energy during paper processing.4,5 In general, there is still lack of alternatives for its utilization, so the development of new methods for more efficient conversion of black liquor lignin to aromatics is of crucial importance. Hydrothermal conversion (HTC), a thermal-chemical conversion technique, uses liquid subcritical (or supercritical) water as the reaction medium for the conversion of wet biomass and waste streams.6-8 In past research9-12, many studies have succeeded in depolymerizing lignin into small phenolic molecules by HTC. However, these technologies have several drawbacks.13 For instance, in a typical HTC process, lignin was extracted from black liquor, precipitated, dried and purified, and was solubilized into a caustic soda solution for HTC. Apparently, the extraction and purification of lignin improves to the cost of the feedstock.13 Actually, in a sustainable biorefinery, black liquor, as a low cost lignin-rich and high moisture contents material, could be directly converted to avoid drying and purification. Therefore, HTC of black liquor is a promising technology. Depolymerizing or deconstructing black liquor lignin to value-added products is a key for the high-value usage of black liquor. Compared to hydrothermal conversion of lignin, direct hydrothermal liquefaction of black liquor not only saves energy for drying, but the inorganic salt could play a catalytic role.9 Herein, we explore a modified HTC approach to avoid extracting lignin from black liquor and directly convert BLAS into phenolics. The effects of reaction temperature (260 ~ 340 oC) and holding time (0 ~ 120 min) on the yields of four products (bio-


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oil phase, aqueous phase, char and gas) were investigated. The chemical compositions and the detail yields of the bio-oil were analyzed by Ultrahigh Pressure Liquid Chromatography-High Resolution Mass Spectrometry (UHPLC-ESI-HR MS) and GC/MS system. In addition, for further understanding the conversion mechanism of BLAS, the chemical characteristics of char was examined by elemental analysis, FT-IR, and Py-GC/MS.

2. Methods 2.1. Materials BLAS was prepared by the conventional kraft pulping process14: sodium hydroxide and sodium sulphide were the cooking liquor for eucalyptus wood chips and the liquor-to-wood mass ratio was 4:1. Effective alkali was 25%, and sulfidity was 25%. Temperature was slowly heated to 180 oC over 90 min and holding time was set at constant 120 min. Then, temperature was dropped to ambient temperature after 50 min. After cooking, black liquor was collected. Under the stirring conditions, the addition of diethylene triamine pentacetic acid (DTPA) to black liquor facilitated metal-ion removing. Later, 2 M sulfuric acid was slowly added until pH = 2, causing lignin precipitation. The solution was kept overnight at room temperature. The supernatant was removed by siphon. Later, 2 mol/L sodium hydroxide was slowly added to solution until pH = 7. Finally, the black liquor acid sediment (BLAS) was collected, and then as a raw feedstock was directed involved into the reaction. The BLAS were dried in a vacuum drying oven at 105 oC to constant weight, after which a DBLAS of 26.7 g/L (based on the BLAS) was obtained. It was calculated10 that 48.0 wt-% of D-


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BLAS was lignin. Five milliliters of BLAS was used to determine the carbohydrate content (about 1.5 g/L based on the BLAS) by spectrophotometric analysis at 500 nm, and 10-1000 g/mL glucose (Sigma, 99.9%) was used as the standard.15 The ash content of dry BLAS (26.5 wt-%) was measured by weight difference when the D-BLAS was burned in muffle at a temperature of 575 oC in air. 2.2. Reaction and separation processes The experiments were performed in a 300 mL stainless reactor with a stirrer and temperature controller. Typically, 150 mL of BLAS were loaded in the reactor. Nitrogen gas was used to purge the reactor before sealed. For each experiment, the temperature of reactor was raised from ambient to specified temperatures of 260, 280, 300, 320 or 340 oC, then the experiment was maintained for 0 ~ 120 min. The error of the temperature controller was within ±2 oC. During the reaction, the mixture was stirred continuously at 200 rpm. After cooling to room temperature with water, gas was collected from the reactor before the autoclave was opened. Thereafter, the mixture was taken and the inside of reactor was thoroughly washed with deionized water and ethyl acetate. The mixture was adjusted to pH =2 by the addition of 1.7 M hydrochloric acid, filtered using a G3 funnel and washed with deionized water of 100 mL. The char was collected after filtering, washing, and then was dried at 105 oC and weighted. The liquid phase was extracted using 200 mL ethyl acetate to obtain ethyl acetate phase. The ethyl acetate phase was dried with anhydrous sodium sulfate, filtered and finally the bio-oil was obtained by vacuum rotary evaporation at 60 oC. The aqueous phase was frozen at −10 oC overnight (∼12 h), and then freeze-dried to obtain water soluble solids, which was vacuum-dried overnight at room temperature before weigh. Each run was repeated for at least 2


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times until the yield has good reproducibility, and then the average yield was used to calculate the product yield. 2.3. Calculations The monomer selectivity and yield of different products were calculated using the following equation: Bio-oil yield wt-%=mbio-oil/mD-BLAS×100%; Gas yield wt-% = mgas/mD-BLAS×100%; Char yield wt-% = mchar/mD-BLAS×100%; Other yield wt-% = mother/mD-BLAS×100%; Monmer yield wt-% = mmonomer/mBLAS-L×100%; Monomer Selectivity (MS) % = mmonomer/mbio-oil×100%; Total MS % = the summation of Monomer Selectivity (MS) %. Where mbio-oil = mass of bio-oil, mD-BLAS = mass of D-BLAS, mgas = mass of gas, mchar = mass of char, mother = mass of solid in aqueous phase, mmonomer = monomer phenolic mass in bio-oil, mBLAS-L= mass in BLAS-L. 2.4. Analysis and characterization A Vario EL cube element analyzer (Elementar, Germany) was used to determine the main elements of D-BLAS and char.


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FT-IR spectral measurements were done with a Nicolet iS50 Fourier transform infrared spectrometer (Thermo Fisher Nicolet, American) in the 4000-400 cm-1 wavenumber range at a resolution of 2 cm-1 wavelength. Gas chromatograph (GC) with a PerkinElmer Clarus 600 GC-Model Arnel 1115PPC Refinery Gas Analyzer (PerkinElmer CT, USA) was used to determine and quantify the yields of H2, CH4, CO and CO2 compounds. The chemical composition and the detail yields of bio-oil obtained from hydrothermal conversion of BLAS was quantitatively analyzed by gas chromatograph (Agilent HP6890) equipped with a mass selective detector (Agilent 5973) with a quartz capillary column (30 mm× 0.25 mm × 0.25 mm). Temperature program was set at 40 oC and maintained for 10 min; followed by a rate of 10 oC/min to 280 oC, maintained for 2 min. Compounds were identified using the NIST library of mass spectra. And the external standard curves of main monophenolics were shown in Fig. S1. The mass detection of oil was used by UHPLC-ESI-HR MS (Agilent1290 / maXis impact, Germany) with electrospray ionization in positive mode (ESI+). The nitrogen gas (99.99%) was as carrier gas, and flowed at a speed of 4.0 L/min. Atomization pressure was 0.3 Bar. A 0.6 ml/min flow of ultra-high purity methanol was used as mobile phase. The acceleration voltage and capillary voltage was 2000 V and 3500 V, respectively. Scan ions were detected in 50-1500 m/z. Analytical Py-GCMS experiments were conducted using a pyrolysis (Tandem u-Reactor Rx3050TR) connected to a GCMS (Agilent 7890B). The target pyrolysis temperatures and injector temperatures were maintained at 600 oC and 320 oC, respectively. Helium gas (99.99%) was


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used as sweep gas at flow rate of 1 mL/min. The pyrolytic vapors were directly analyzed by the GCMS with a ZB-5HT capillary column (30 m × 0.25 mm × 0.25 um) in a split mode of 80:1. The temperature of GC column was initially set at 40 oC for 2 min, and then the temperature increased to 200 oC at 6 oC/min, maintained for 2 min, and subsequently increased to 380 oC at 20 oC/min. The mass spectrometer was operated in EI mode at 70 eV. All pyrolytic products were identified through the NIST library of mass spectra.

3. Results and discussion 3.1. Yield The reactive conditions and product yields of various phases are shown in Table 1 where it is observed that the product yields were significantly changed by the reaction temperature and holding time. When the holding time was fixed at 30 min, the yield of bio-oil increased with reaction temperature. A maximum yield of 22.38 wt-% was obtained at 300 oC, and then slightly decreased to19.96 wt-% at 340 oC. Meanwhile, the gas yield increased from 6.17 wt-% to 9.35 wt-% which showed that the secondary decomposition of bio-oil to gas had taken place;16 moreover, the char yield slightly increased from 6.73 wt-% to 7.53 wt-% in this stage, indicating that the polymerization of bio-oil to char also occured.17 The effect of holding time on the product yields was examined over the range of 0 ~120 min for 300 oC. It was clearly that the biooil yield increased in the first 30 min and then maintained a steady state (~ 19 wt-%). The highest yield of bio-oil (22.38 wt-%) was obtained at 300 oC in 30 min. Comparing the data of lignin depolymerization in literature (in table S1), it can be found that the yields of bio-oil were quite acceptable.


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The yields of water-soluble products (others in Table 1) were 43.9-57.3 wt-% which may represent a high content of inorganic salts in BLAS.9 In addition, the products from the decomposition of carbohydrates17 and the oligomers from the depolymerization of lignin could also be another reason for the high yields of water-soluble products. The monomer selectivity was always below 20% in the obtained oil, so it was further proved the oligomer was existent. In order to characterize the oligomer, the UHPLC-ESI-HR MS was used, and Fig. S1 showed the typical ESI+ mass spectrogram of oil from the hydrothermal conversion of BLAS at 300 oC and 30 min. The m/z value measured for an ion corresponds generally to its molecular weight. The results showed a relatively narrow distribution of m/z between 250 and 400, so the most of oil was focused on dimmers and trimmers. Because monomer phenolics of bio-oil were the main target products, there was no detail analysis to the water-soluble products and the oligomers. 3.2. Bio-oil analysis 3.2.1. Qualitative analysis of bio-oil compounds The representative monomeric products of bio-oil were analyzed by GC/MS. There were various types of chemicals (Table S2) including acids, alcohols, aromatics, derivatives of furan and other compounds containing N and S. The peak area percentages of monomeric products are shown in Fig. S3. Aromatics (95.10%) were the dominant compounds in the bio-oil, and it can be naturally expected because the phenylpropane monomers were the basic unit of the lignin structure. Among the aromatic compounds, 2-methoxyphenol (27.65%) and 2, 6dimethoxyphenol (36.67%) were the major products, whereas other aromatics (including methyl, hydroxyl, methoxy, and ethyl groups on the aromatic ring) were also obtained. It implied that demethylation and alkylation reaction of aromatic ring occurred during the hydrothermal


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conversion of BLAS. In addition to the aromatics, a small amount of furan compounds were also obtained, and it could be because carbohydrates content were not completely removed from the BLAS. As previously reported18, the conversion of cellulose and xylose can result in the formation of furan compounds. 3.2.2. Quantitative analysis of main monomers aromatics The compounds obtained from HTC of BLAS were mainly monomeric aromatic products linked to phenolic hydroxyl and aromatic methoxyl groups. The main monomers phenols (included 2-methoxyphenol, 4-methy-2-methoxyphenol, phenol, 2, 6-dimethoxyphenol, 4hydroxyl-3-methoxyacetophenone and catechol) were quantitatively analyzed with external standards using GC/MS; the influence of reaction temperature on the main monomeric phenols products yield was presented in Fig. 1. It was observed that the yield of the 2-methoxyphenol increased and then decreased after 320 oC. In contrast, the yield of the phenol decreased and then increased with temperature. Similarly to the result of 2-methoxyphenol, 2, 6-dimethoxyphenol increased from 2.88 wt-% to 4.03 wt-% when the temperature increased from 260 oC to 280 oC, and then a markedly decrease to 0.28 wt-% at 340 oC. Catechol was not observed under low reaction temperature. However, what was surprising was the amount of the catechol increased to 7.08 wt-% when temperature increased to 340 oC, and its MS% reached 15.46 wt-%. These results suggested that the degradation of lignin in BLAS was not sufficient at the lower temperature. As the temperature increasing, the more linkage bonds were cleaved, and it directly resulted the increasing of 2-methoxyphenol, 4-hydroxyl-3-methoxyacetophenone and 2, 6dimethoxyphenol. Then, as the temperature continuing to increase, more and more methyl or methoxyl fell off from the 2-methoxyphenol and 2, 6-dimethoxyphenol, and transferred into phenol or catechol. These results were in agreement with past work: higher reaction temperature


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was favorable to the yields of phenol and catechol.19 In addition, this result was also confirmed in the following sections (see in 3.3). The effects of reaction time on main monomers phenols products yield were presented in Fig. 2. The yield of phenolic compounds was strongly correlated to the conversion temperature; however residence time had a relatively weak influence on yields. As it shown in Fig. 2, the yields of 2-methoxyphenol and 4-methy-2-methoxyphenol ranged from 0.76-1.66 wt-% and 0.09-0.14 wt-%, respectively. The phenol yield was close to 0.05 wt-% that remained nearly constant. 4-Hydroxyl-3-methoxyacetophenone increased slightly from 0.12 wt-% to 0.29 wt-% after 120 min. Catechol yield increased significantly from 1.33 wt-% to 4.80 wt-% after 30 min and then stabilize in 3.56 ~ 4.00 wt-%. In addition, the yield of 2, 6-dimethoxyphenol significantly increased from 0.12 to 2.62 wt-% as the reaction time ranged from 0 min to 30 min, followed by a decrease to 0.28 wt-% after further increasing reaction time to 120 min. The results also suggested that short holding time (0 ~ 60 min) was not sufficient for lignin conversion, but long holding time (>60 min) favored further polymerization of already degraded lignin intermediates. The maximum yield of 2-methoxyphenol (1.66 wt-%) and 2, 6-dimethoxyphenol (4.03 wt-%) in bio-oil was obtained (Fig. 2) at a reaction temperature of 300 oC when the reactive time was 30 min, and the maximum yield of catechol was 7.08 wt-% at 340 oC (30 min). Compared with the bio-oil obtained by the HTC of kraft lignin,13 the amount of catechol in bio-oil that derived from the HTC of BLAS significantly increased. Previous research20 established that 2methoxyphenol decomposition was carried out at temperatures of 380 oC, and the yield of catechol was only 5.09%. In this study, the bio-oil distribution from direct degradation of BLAS


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was significantly different to the degradation of lignin. It suggested some components of the BLAS played a catalytic role in the degradation of lignin, especially for demethylation. 3.3. Gas products analysis. The effect of reaction temperature and time on gas composition was shown in Fig. 3 and 4, respectively. Results indicated that the main gas product from the BLAS conversion was CO2, and trace amounts of fuel gases including CO, CH4 and H2. Higher temperatures and longer reaction times benefitted yields of H2 and CH4. The formation of H2 was mainly considered from the hydrolysis of water. Self-ionization of water was usually endothermic and slow,21 so both high reaction temperature and long reaction time promoted the increasing of hydrogen yields. The CH4 fraction increased with the increase of temperature and time. It was produced from cracking of the methyl group.21,22 The methyl group cleavage from 2-methoxyphenol and 2, 6dimethoxyphenol resulted in the formation of catechol and CH4. The changing trend of CH4 was in accordance with the quantitative analysis of 2-methoxyphenol, 2, 6-dimethoxyphenol, and catechol. During hydrothermal conditions, the conversion of the substituted groups and aliphatic structures in lignin led to CO2 and CO release from the carboxyl group. The decline of CO yield (at 280 oC in Fig. 3 or 30 min in Fig. 4) and along with increase of CO2 and H2 yield, was an indication that the water-gas shift reaction (i.e., CO + H2O → H2 + CO2) may have occurred under the conditions.21

3.4 Char analysis


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Under hydrothermal conversion conditions, most of the value-added products were bio-oil compounds, but the char was useful for understanding the conversion mechanism. Therefore, the char was characterized by elemental analysis, FT-IR, and Py-GCMS. The elemental analyses of samples are listed in Table 2. Compared with the D-BLAS, the carbonization of char caused a significantly increase in carbon contents. Moreover, the high heat value (HHV) from the char of BLAS was higher, and it could be because the behaviors of deoxygenation occurred for the hydrothermal conversion of BLAS was stronger than those of lignin, a finding consistent with the results of GCMS. The FT-IR spectra of char under various reaction temperatures and holding times are presented in Fig. 5 and 6, respectively. As temperature and time increased, the intensity of functional groups showed a stepwise drop. Clearly, the char after 60 min displayed nearly no aromatic O-H bands (3390 cm-1). Under the very mild condition of 260 oC and short time (< 30min), the weakened absorbance at 1715 cm-1 implied that decarbonylation occurred, while it caused high yields of CO and CO2 (see Fig. 3 and 4). In addition, the absorbance from the aryl-ether linkages (mainly including β-O-4 and α-O-4 ether bonds) at 1120 and 1034 cm-1 weakened in intensity for the char with both reaction temperature and time increasing. This was expected due to the breakage of aryl-ether linkages to form alkyl groups and hydroxyl groups.23,24 The lower intensity of absorbance at 1605, 1515, 1425, 834 cm-1 that was attributed to the vibrations of aromatic rings, indicated that aromatic rings of lignin a stepwise decomposed during the hydrothermal conversion.25,26 The ion chromatograms of char that decomposed by Py-GCMS at different reaction conditions are shown in Fig. S4 and S5, respectively. It was clear that the peaks diminished with


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temperature and time. Detailed pyrolytic products (mainly phenolics) are given in Table S3 and S4. When the reaction temperature was 260 oC, a complex distribution of products was observed. The products mainly consisted of different single-benzene ring structure aromatics. These results suggested that the degradation of lignin in BLAS was not sufficient at the lower temperature, and there were unconverted lignin in the char. When the temperature rose to 320 oC, only two products were found in the chromatogram, i.e., benzene and toluene. The results suggested the coke almost had no functional groups of lignin, and as such, it is composed of benzene or biphenyl type structures. Meanwhile, it also suggested that the conversion of BLAS at 320 oC was nearly complete. Similarly, with prolonged time, these products showed a stepwise drop in types and relative amounts consistent with the FT-IR of char.

4. Conclusions Considering the additional costs of treating lignin, directly hydrothermal conversion of BLAS was a more competitive and promising method. Its high selectivity of phenolic compounds was established, especially for catechol (7.08 wt-% under optimized conditions). Other main chemical compound in bio-oil were 2-methoxyphenol (0.74-1.66 wt-%), 2, 6-dimethoxyphenol (0.28-4.03 wt-%) based on BLAS-L. During hydrothermal treatment of BLAS, the decreased amount of aryl-ether linkages, hydroxyl and carbonyl groups, and aromatic rings in BLAS occurred at 280-320 oC and 0-60 min. As the temperature and time increased, these functional groups in char samples showed a stepwise drop whereas the pyrolysis products of char remarkably reduced. In addition, the coke


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almost had no functional groups of lignin, but was composed of benzene or biphenyl type structures.

ACKNOWLEDGMENT The authors acknowledge the support of the Natural Sciences Foundation of China (No.31270635 and No.31670582) and the National Basic Research Program of China (973 program, No. 2013CB228101).

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(14) Jiang, W.; Lyu, G.; Liu, Y.; Wang, C.; Chen, J.; Lucia, L. A. Quantitative analyses of lignin hydrothermolysates from subcritical water and water-ethanol systems. Ind. Eng. Chem. Res. 2014, 53 (25), 10328-10334. (15) Crawford, R.L.; Pometto, A.L. Methods in Enzymology. Academic Press Inc. San Diego. 1988. (16) Ye, Y.; Fan, J.; Chang, J. Effect of reaction conditions on hydrothermal degradation of cornstalk lignin. J. Anal. Appl. Pyrolysis. 2012, 94, 190-195. (17) Sakaki, T.; Shibata, M.; Miki, T.; Hirosue, H.; Hayashi, N. Decomposition of cellulose in near-critical water and fermentability of the product. Energ. Fuel. 1996, 10, 684-688. (18) Karagoz, S.; Bhaskar, T.; Muto, A.; Sakata, Y.; Oshiki, T.; Kishimoto, T. Low-temperature catalytic hydrothermal treatment of wood biomass: analysis of liquid products. Chem. Eng. J. 2005, 108 (1), 127-137. (19) Asmadi, M.; Kawamoto, H.; Saka, S. Thermal reactions of guaiacol and syringol as lignin model aromatic nuclei. J. Anal. Appl. Pyroly. 2011, 92(1), 88-98. (20) Wahyudiono, Sasaki, M.; Goto, M. Thermal decomposition of guaiacol in sub- and supercritical water and its kinetic analysis. J. Mat. Cycles. Waste Manag. 2011, 13 (1), 68-79. (21) Yong, T. L.-K.; Matsumura, Y. Reaction kinetics of the lignin conversion in supercritical water. Ind. Eng. Chem. Res. 2012, 51 (37), 11975-11988. (22) Ragauskas, A. J.; Beckham, G. T.; Biddy, M. J. Lignin valorization: improving lignin processing in the biorefinery. Science. 2014, 344(6185), 1246843-1246843.


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(23) Nunn, T. R.; Howard, J. B.; Longwell, J. P.; Peters, W. A. Product compositions and kinetics in the rapid pyrolysis of milled wood lignin. Ind. Eng. Chem. Des. Dev. 1985, 24, 844852. (24) Kawamoto, H.; Ryoritani, M.; Saka, S. Different pyrolytic cleavage mechanisms of β-ether bond depending on the side-chain structure of lignin dimers. J. Anal. Appl. Pyrol. 2008, 81, 8894. (25) Faix, O. Classification of Lignins from Different Botanical Origins by FT-IR Spectroscopy. Holzforschung. 1991, 45(s1), 21-28. (26) Lin, Stephen Y.; Dence C. W. Methods in lignin chemistry. Springer Science & Business Media. 2012.

Tables Table 1 Yield of various products for hydrothermal treatment of BLAS at different reaction conditions. Bio-oil

Gas

Char

Others

(wt-%)

(wt-%)

(wt-%)

16.46

4.43

6.92

57.29

13.99

18.71

4.41

7.20

49.89

300/30

17.00

22.38

6.17

6.73

49.08

320 /30

14.22

22.37

8.01

7.12

43.86

Temperature No. (°C) /time (min)

Total MS %

Yield %)

1

260/30

8.27

2

280/30

3 4

(wt-


18

Page 19 of 23

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

5

340/30

12.61

19.96

9.35

7.53

46.56

6

300/0

11.03

17.17

3.18

4.68

53.13

7

300/60

13.99

19.52

7.74

7.77

49.17

8

300/90

14.32

19.15

9.61

9.61

52.22

9

300/120

18.86

19.05

9.06

9.06

56.54

Table 2 Element analysis of D-BLAS, Char from hydrothermal conversion of lignin or BLAS. Element analysis (wt-%)

HHV

Sample C D-BLAS

H

O

N

S

(MJ/kg)

52.64 4.84 35.66 0.16 6.71 20.91

Char of Lignin (300 °C/30 min) 59.65 5.76 28.29 0.13 6.17 25.20 Char of BLAS (260 °C/30 min)

68.36 5.50 24.08 0.18 1.88 27.99

Char of BLAS (300 °C/30 min)

69.82 4.40 24.03 0.17 1.58 27.20

Char of BLAS (300 °C/60 min)

68.97 4.14 25.44 0.14 1.31 26.41

(HHV=35.2C+116.2H+6.3N+10.5S-11.1O).

Figures


19

Energy & Fuels

8

2-Methoxyphenol 4-Methy-2-methoxyphenol Phenol 2,6-Dimethoxyphenol 4-Hydroxyl-3-methoxyacetophenone Catechol

7

Monomer yield (wt-%)

6 5 4 3 2 1 0

260

280

300

320

340

o

Temperature ( C)

Fig. 1 Effects of reaction temperature on main monomer phenols yield. Reaction conditions: BLAL 150 mL, time=30 min.

8

2-Methoxyphenol 4-Methy-2-methoxyphenol Phenol 2,6-Dimethoxyphenol 4-Hydroxyl-3-methoxyacetophenone Catechol

7 6 Monomer yield (wt-%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 23

5 4 3 2 1 0

0

30

60

90

120

Time (min)


20

Page 21 of 23

Fig. 2 Effects of reaction time on main monomer phenols yield. Reaction conditions: BLAL 150 mL, temperature=300 oC.

10

0.35

CO2 H2

0.30

CH4

8

Gas yield (wt-%)

CO

0.25

6

0.20 0.15

4

0.10

Gas yield (wt-%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

2 0.05 0

260

280

300

320

340

0.00

o

Temperature ( C)

Fig. 3 Effects of reaction temperature on gas composition. Reaction conditions: BLAL 150 mL, time=30 min.


21

Energy & Fuels

10

0.35

CO2 H2

8

0.30

CH4

Gas yield (wt-%)

CO

0.25

6

0.20 0.15

4

0.10

Gas yield (wt-%)

2 0.05 0

0

30

60

90

120

0.00

Time (min)

Fig. 4 Effects of reaction time on gas composition. Reaction conditions: BLAL 150 mL, temperature=300 oC.

1454 1515 1605 1425

1120 1215 1034

3390 2934 1715

834

o

Char/340 C Transmittance (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 23

o

Char/320 C o

Char/280 C o

Char/260 C BLAS-L D-BLAS

4000

3500

3000

1500

1000 -1

Wavenumbers (cm )

Fig. 5 FT-IR spectra of D-BLAS, BLAS-L and char in different reaction temperature.


22

Page 23 of 23

3390

2934

1715

1454 1515 1605 1425

1120 1215 1034

834

Char/120min Transmittance (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Energy & Fuels

Char/90min Char/60min Char/0min BLAS-L D-BLAS

4000

3500

3000

1500

1000 -1

Wavenumbers (cm )

Fig. 6 FT-IR spectra of D-BLAS, BLAS-L and char in different reaction time.


23

Hydrothermal-Controlled Conversion of Black Liquor Acid Sediment

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