Article pubs.acs.org/IECR
Dechlorination of Poly(vinyl chloride) Wastes via Hydrothermal Carbonization with Lignin for Clean Solid Fuel Production Yafei Shen* Jiangsu Engineering and Technology Research Center of Environmental Cleaning Materials, Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, and School of Environmental Science and Engineering, Nanjing University of Information Science & Technology (NUIST), Nanjing 210044, China ABSTRACT: An alternative technology has been proposed for the dechlorination of poly(vinyl chloride) (PVC) wastes by hydrothermal carbonization (HTC) with lignin. The organic chloride in PVC can be converted to inorganic chloride through hydrolysis, defunctionalization, recondensation, and aromatization in the HTC process. Combined with downstream washing processes by recycling the condensed water, the inorganic chloride with high water solubility is removed from the solid products (i.e., hydrochar). The presence of lignin could significantly improve the dechlorination efficiency of PVC in the HTC process. The dechlorination performance of lignocellulosic components is given as follows: lignin > cellulose > hemicellulose. In addition, lignin can adjust the particle sizes of hydrochars by inhibiting agglomeration in the order of lignin > hemicellulose > cellulose. The hydrochar particles with a low chlorine content and a high heating value could be used as a clean coal-alternative fuel.
1. INTRODUCTION Plastic waste has become a major component of both industrial and municipal wastes because of the worldwide use of plastic products. Therefore, the disposal of plastic wastes is increasingly considered a major environmental issue. Recycling is by far the most sustainable method of plastic waste disposal. However, the variety of additives used in the manufacture of plastic goods results in separation and decontamination difficulties, which greatly limits the recycling of waste plastics. In addition, landfilling has become limited because of high population densities, high costs, and environmental concerns such as soil contamination and harmful influences on ecosystems.1 However, although waste disposal by means of incineration possesses many advantages, including a high degree of destruction, reduction of land usage, and the potential for energy recovery, thermal decomposition of the halogenated plastics can result in serious environmental problems such as toxic dioxin emission.2−4 Poly(vinyl chloride) (PVC) is a major source of chlorine for chlorinated dioxin formation during the incineration of municipal wastes. When PVC waste is burned, a lot of hydrochloric acid (HCl) can be generated; this can corrode the boiler tube and lead to the release of trace amounts of further harmful gases such as organohalogen compounds, possibly causing pollution issues.5,6 Recently, hydrothermal carbonization (HTC) as a novel thermal conversion process can be used to convert waste streams into sterilized, value-added hydrochars, especially for polymer-derived wastes including biowastes7−13 and plastic wastes.14,15 HTC as a kind of © XXXX American Chemical Society
hydrothermal processing has been mostly used on biowaste recycling, but exploration of the carbonization of plastic wastes or the utilization of HTC as a sustainable waste-to-energy technique has rarely been reported.16 On the basis of the processing conditions and target products, hydrothermal processing can be classified into different fields of applications. The main regions include HTC, liquefaction, and hydrothermal gasification. For instance, low-temperature hydrothermal processing (e.g., HTC) is often used as a sterilization step within fermentation processes to prevent bacterial cultures from reaching the environment. Starting from temperatures of about 100 °C and more likely from above 180 °C, HTC is applied to produce solid products for different purposes.17 The HTC process has proven to reach energy yields of more than 80% for woody biomass in the pilot scale.18 The energy yield of a HTC conversion process represents how much of the energy content of the starting material is converted to the solid product. Therefore, the HTC process is expected to be a future energy-efficient way of converting wet biomass to solid fuels.7,19,20 Typically, HTC of biomass is achieved in water at elevated temperatures (180−250 °C) under saturated pressures (e.g., 2−10 MPa). Chemical transformations of lignocellulosic model compounds under pressure in the HTC process, particularly Received: Revised: Accepted: Published: A
September 1, 2016 October 9, 2016 October 20, 2016 October 20, 2016 DOI: 10.1021/acs.iecr.6b03365 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
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treated. It can also be used as an agent to remove the soluble chlorine from the solid products by the washing process. The solid products were initially washed for 15 min by distilled or primary condensed water in a flask with a stirring speed of 600 rpm. The mass ratio of solid and water was controlled at 1:5 each time (5 cycles). After the washing process, the liquid phase was filtered by a vacuum pump, to wash out the primary HTCderived solid products. Water was recycled five times in this route. Therefore, the total mass ratio of the solid product and water was 1:1. Analytical Methods. Chlorine Analysis. The chlorine in the liquid phase was defined as soluble-Cl. For soluble-Cl analysis, the solid product in distilled water was stirred at a speed of 600 rpm for 30 min with a ratio of 1:60, and then water was separated by vacuum filtration. The total chlorine content in the liquid phase was measured by a chloride-ionselective electrode (Orion 4 star and chloride ISE Orion 9617 BNWP), and that in the solid phase was determined by Schoniger’s method.26 Therefore, the insoluble-Cl content of the solid product was calculated by the difference ([insolubleCl] = [total-Cl] − [soluble-Cl]). Each measurement was performed three times to ensure reproducibility. The average value was used. Characterization of the Solid Products. The solid products were separated by using different pore sizes of sieves (0.15−2 mm), and then the mass fraction was recorded. The proximate analysis was conducted by a thermogravimetric analyzer (Shimadzu D50, Japan). The ultimate analysis was performed by an elemental analyzer (Elementar’s Vario MICRO Cube, USA). The higher heating value (HHV) was measured by DSK200 and DCS-196 digital calorimeters. The surface characteristics of the solid products were analyzed by a scanning electron microscope (JSM-6610LA, Japan). In addition, the functional groups were analyzed by a Fourier transform infrared (FTIR) spectrometer (JIR-SPX200).
cellulose, pentoses/hexoses (glucose and xylose), starch, and phenolic compounds have been reported.21 The initial reaction occurring as biomass is heated up in water is the hydrolysis of cellulose to glucose, which is the decisive difference from thermochemical conversion.8 Generally, the hydrolysis provides a path to homogeneous reactions in an aqueous solution, which are not limited by heat and mass transfer. The same holds true for the destruction of lignin to its main product, phenol. In HTC of an organic matrix (e.g., PVC), significant decomposition processes include hydrolysis as the initial step, followed by defunctionalization such as dehydration and decarboxylation, and finally recondensation and aromatization.15 It was proven that organic chlorine in PVC could be effectively converted to inorganic chlorine via the HTC process at high temperatures (>250 °C) and high pressures, e.g., subcritical or supercritical processes.14,15 In the previous work, municipal solid wastes including PVC were pretreated by the HTC process at relatively lower temperatures (about 210 °C).22−25 The solid products could be used as coal-alternative fuels with low chlorine content. The purpose of this work is to treat the PVC wastes by HTC at a lower temperature (210 °C). The lignocellulosic components (e.g., cellulose, xylan, and lignin) will be applied and studied in terms of the dechlorination performance and the solid particlesize distribution. It is worth noting that this is the first time studying the washing process by recycling the condensed water.
2. MATERIALS AND METHODS Feedstocks. The feedstock of poly(vinyl chloride) (PVC; chlorine content, 57%) was purchased from Wako Pure Chemical Industries, Ltd. PVC was ground in a planetary ball mill to pass a 0.25 mm screen. The lignocellulosic model compounds of lignin, cellulose, and hemicellulose (e.g., xylan) purchased from Wako Pure Chemical Industries, Ltd., were blended with PVC in the HTC process. HTC Process of PVC. The laboratory-scale HTC processes was conducted in an autoclave reactor (volume, 500 mL) with an electronic heater, which was coupled with a motor stirrer, as illustrated in Figure 1. PVC (5 g) was blended with
3. RESULTS AND DISCUSSION Dechlorination Efficiency of Hydrochar. Lignocellulose, including cellulose, lignin, and hemicellulose (e.g., xylan), was blended with PVC to study the dechlorination performance in the HTC process. The chlorine in the solid phase was transformed to the liquid and gas phases (as shown in Figure 2). In this study, the dechlorination efficiency was defined as equation (E1). Generally, the addition of lignocellulosic components improved the dechlorination efficiency of the
Figure 1. Schematic of the laboratory-scale setup for HTC of PVC with lignocellulose.
lignocellulose (5 g) by ball-milling for 10 min. The solid mixture (10 g) and distilled water (20 g) were fed into the HTC reactor. As the temperature increased, the water steam was generated automatically. In this study, the holding time was controlled at 30 min as the reactor temperature increased to the target value (210 °C). The primary solid products were further treated by the washing process. Washing Process. In common, the condensed liquid from the HTC and dehydration processes needed to be further
Figure 2. Mass balance of chlorine in the HTC process of PVC (210 °C, 2.2 MPa). B
DOI: 10.1021/acs.iecr.6b03365 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
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Industrial & Engineering Chemistry Research solid in the HTC process. In particular, HTC of PVC with lignin showed the highest dechlorination efficiency before the washing process. It might be attributed to a synergistic effect of lignin on the enhancement of PVC dechlorination in the HTC process. DE (wt %) =
C1 − C2 × 100% C1
(E1)
where DE (wt %) represents the dechlorination efficiency, C1 (wt %) represents the chlorine content in PVC, and C2 (wt %) represents the chlorine content in hydrochar. As shown in Figure 3, the addition of lignocellulose (i.e., cellulose, lignin, and xylan) can enhance the dechlorination
Figure 4. Dechlorination efficiency of PVC by the HTC and washing process.
Figure 3. Effect of the addition of lignocellulose on the dechlorination efficiency of PVC.
efficiency of PVC in the HTC process. By HTC of PVC with lignin, the dechlorination efficiency increases from 6.33% to 15.8%. Besides, the washing process can significantly improve the dechlorination efficiency. Upon the addition of lignin, the dechlorination efficiency increases from 48.2% to 89.5% by the HTC and washing process. In general, the dechlorination performance of lignocellulosic components can be given as lignin > cellulose > hemicellulose (e.g., xylan). The mass ratio of lignocellulose and PVC is considered as an important parameter in the HTC and washing process. As shown in Figure 4, the dechlorination efficiency generally increases with an increase of its mass ratio. As for lignin, it can be found that the dechlorination efficiency increases rapidly as the lignin/PVC ration is decreased below 1.0. After that, the increase tendency is gradually weakened. From this result, it is suggested that the optimal mass ratio of lignin/PVC is 1.0. The addition of lignocellulose (e.g., lignin) has little effect on PVC dechlorination in the HTC process as the mass ratio reaches a certain value. Characterization of Hydrochars. FTIR Analysis. The functional groups of the solid products (i.e., hydrochars) can be characterized by FTIR analysis. Figure 5 shows the FTIR spectra of PVC, HTC-PVC, and HTC-PVC-lignin. It can be found that PVC contains alkane groups of CH between 2850− 3000 and 1350−1480 cm−1. The peaks between 2700 and 3000 cm−1 represent the aliphatic groups of CH, CH2, and CH3. The adsorption peaks of the alkyl halide groups of C−Cl are presented from 600 to 800 cm−1. These absorption peaks
Figure 5. FTIR spectra of PVC before and after HTC (PVC, HTCPVC, and HTC-PVC-lignin).
appear in the spectra of HTC-PVC and HTC-PVC-lignin as well. Compared with the FTIR spectra of PVC and HTC-PVC, the obvious differences take place between 1670 and 1820 cm−1, which indicates the carbonyl group of CO. Compared with the spectra of HTC-PVC-lignin and HTC-PVC, new absorption peaks appear (e.g., 1000−1100 cm−1 is the alcohol groups of C−OH, 1500−1600 cm−1 is the aromatic groups of CC, 3010−3100 cm−1 is the alkene groups of CH, and 3500−3700 cm−1 is the alcohol groups of free OH). Besides, the absorption peak from 600 to 800 cm−1 is weakened, indicating a decrease of the C−Cl group, while the absorption peak from 1670 to 1820 cm−1 is enhanced, which indicates an increase of the CO functional group. Furthermore, it is reported that thermal dechlorination of PVC mostly follows a free-radical mechanism.27 The reaction might start with the production of free radicals and chloroallylic structures characterized by low thermal stabilities. A subsequent step of HCl elimination results in polyene formation, which is a non-free-radical reaction mechanism.28 Obviously, conjugated C
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Figure 6. Possible reaction pathway of PVC decomposition in the HTC process. Reprinted with the permission from ref 15. Copyright Elsevier 2015.
Figure 7. (A) Formation pathways of lignin hydrochar. (B) HTC conversion of lignin.
double bonds could be created by a “‘zipper’” mechanism:29 once a double bond has formed, the allylic Cl atom on the C atom adjacent to the double bond splits off from HCl, forming two double bonds during the HTC process, which, in turn, activates an adjacent chlorine to propagate the dehydrochlorination process. In aqueous suspensions, PVC degradation could be assumed by ionic chain reactions and cracking. Beyond that, nucleophilic substitution with water as the nucleophile proceeds to generate alcohols, diols, and polyols. Reactive polyenes with the diol/polyol structures are regarded as the precursors of aromatic compounds and oxygen-functionalized low-molecular-weight compounds. It is emphasized that temperatures below 450 °C and high water densities favor OH nucleophilic substitution, with water acting as a nucleophilic agent (as illustrated in Figure 6).15 In the HTC process, the lignin fragments can be decomposed to phenolics via hydrolysis and further form the phenolic hydrochar via polymerization. The phenolic hydro-
chars derived from the surface fragments of nondissolved lignin can locate on the surface of nondissolved lignin or polyaromatic char, and then the formed holes are stuffed or covered. The formation of lignin hydrochar is illustrated in Figure 7A.30,31 However, cellulose can keep the fiber skeleton with the microsphere produced after HTC.30 As a phenolic polymer, both fragmentation and condensation reactions occur in the lignin degradation under the HTC process.32,33 During the molecular transformation of lignin, the macromolecular bulk of lignin is selectively fragmented by ether bounds splitting through hydrolysis reactions (Figure 7B). Lignin conversion produces mainly an oligomeric residue by a preferential oxygen−carbon linkage splitting. Meanwhile, the oxygenated hydrocarbons with 2−6 carbon atoms and substituted phenols accumulate in the reaction medium, contributing to large amounts of hydroxyl radical generation.32 These results can also explain the increase of the dechlorination efficiency in the presence of lignin. The aromatic D
DOI: 10.1021/acs.iecr.6b03365 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
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Industrial & Engineering Chemistry Research group of CC (1500−1600 cm−1) can indicate that lignin is hydrolyzed into the phenolic substances, such as catechol and phenol, and these substances are reacted with PVC. During PVC hydrolysis and dechlorination reactions, lignin can provide a larger amount of free OH bond (600−800 cm−1). The alcohol group of C−OH (1000−1100 cm−1) can indicate that substitution of the −OH group takes place. Subsequently, the increase of CO (1670−1820 cm−1) indicates that more −OH groups are converted to the CO group via the oxidative reaction. Furthermore, the appearance of the CH (3010−3100 cm−1) group indicates the enhancement of PVC dechlorination. The mechanism can be summarized as reactions (R1)−(R3). −CH 2CHCl− → −CHCH− + HCl
(R1)
−CH 2CHCl− + [OH] → −CH 2CHOH−+[Cl]
(R2)
−CH 2CHOH− + [O] → −CH 2COOH + [H]
(R3)
hydrolysis reaction, and the solid particles are aggregated with each other to form a hard cluster. This can be attributed to PVC initially melting by thermal processing at a lower temperature. After that, the structure of the melted PVC is changed under a high pressure, thus forming a hard cluster. By HTC with cellulose, the nonhydrolyzed cellulose is stuck on the surface of hydrochar, resulting in the formation of a carinate coarse surface. This is most likely caused by the hydrophilicity of cellulose. Moreover, the outer surface of the cellulose hydrochar particles contains a high concentration of reactive oxygen groups (i.e., hydrophobic shell), whereas the oxygen in the core forms less reactive groups (i.e., hydrophilic core).34 The cellulose cannot prohibit aggregation of the hydrochar particles. As mentioned above, cellulose can prevent the fiber skeleton from forming a microsphere after the HTC process.30 The produced hydrochar can condense around the fiber skeleton. Compared with HTC-PVC, the hydrochar of HTCPVC-cellulose is still a cluster but is easier to grind. It is noted that the solid particles remain uniform without aggregation after HTC with hemicellulose or lignin. The presence of lignin significantly inhibits the solid particle agglomeration. In general, lignin has a high potential for PVC dechlorination followed by reduction of the hydrochar particle size. Hydrochar with fine particle sizes favors of the downstream thermal process. The effect on the hydrochar particle adjustment is given as follows: lignin > hemicellulose (e.g., xylan) > cellulose. Properties of PVC-Derived Hydrochars. The properties of the hydrochars derived from HTC of PVC with different lignocellulosic components were analyzed, and the results are presented in Table 1. From proximate analysis, it was found
Scanning Electron Microscopy (SEM) Analysis. Figure 8 shows the SEM micrographs of PVC before and after HTC. It can be observed that the uniform hydrochar particles are agglomerated after HTC. Additionally, PVC presents a porous structure that is caused by a swelling reaction during the
Table 1. Properties of PVC-Derived Hydrochars PVC
PVC + cellulose
Proximate Analysis (wt %, dry basis) moisture 0.00 0.08 volatile matter 91.62 92.65 fixed carbona 8.38 6.02 ash 0.00 1.25 Ultimate Analysis (wt %, dry basis) C 45.36 53.28 H 3.82 5.26 Oa 21.29 27.21 Cl 29.53 14.25 H/C 1.01 1.18 O/C 0.35 0.38 HHV (MJ/kg) a
26.15
30.43
PVC + lignin
PVC + xylan
0.02 83.77 11.85 4.36
0.13 87.86 9.16 2.85
59.50 6.33 28.19 5.98 1.28 0.35
51.80 4.93 25.03 18.24 1.14 0.36
31.80
29.08
Calculated by the difference.
that the hydrochars of PVC + cellulose and PVC + xylan could adsorb water in the atmosphere compared with that of PVC + lignin. Meanwhile, an increase of the ash content in the hydrochar of PVC + lignin may be contributed to the higher ash content of lignin. From ultimate analysis, the atomic ratios of H/C and O/C could be obtained. Consequently, the corresponding Van Krevelen diagrams of the hydrochars were similar to that of lignite.35 In addition, the HHVs of the hydrochars increased from 26.15 to 32.80 MJ/kg by HTC with lignocellulosic components. In particular, the highest HHV was achieved with the addition of lignin. Therefore, HTC of the PVC wastes with lignin has a high potential for the production of coal-alternative solid fuels.
Figure 8. SEM micrographs of PVC-derived solid fuels before and after HTC (210 °C, 30 min). E
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(10) Makela, M.; Benavente, V.; Fullana, A. Hydrothermal carbonization of lignocellulosic biomass: effect of process conditions on hydrochar properties. Appl. Energy 2015, 155, 576. (11) Kambo, H. S.; Dutta, A. Strength, storage, and combustion characteristics of densified lignocellulosic biomass produced via torrefaction and hydrothermal carbonization. Appl. Energy 2014, 135, 182. (12) Heilmann, S. M.; Molde, J. S.; Timler, J. G.; Wood, B. M.; Mikula, A. L.; Vozhdayev, G. V.; Colosky, E. C.; Spokas, K. A.; Valentas, K. J. Phosphorus reclamation through hydrothermal carbonization of animal manures. Environ. Sci. Technol. 2014, 48, 10323. (13) Kang, S.; Li, X.; Fan, J.; Chang, J. Characterization of hydrochars produced by hydrothermal carbonization of lignin, cellulose, D-xylose, and wood meal. Ind. Eng. Chem. Res. 2012, 51, 9023. (14) Kubatova, A.; Lagadec, A. J. M.; Hawthorne, S. B. Dechlorination of lindane, dieldrin, tetrachloroethane, trichloroethene, and PVC in subcritical water. Environ. Sci. Technol. 2002, 36, 1337. (15) Poerschmann, J.; Weiner, B.; Woszidlo, S.; Koehler, R.; Kopinke, F. D. Hydrothermal carbonization of poly(vinyl chloride). Chemosphere 2015, 119, 682. (16) Berge, N. D.; Ro, K. S.; Mao, J.; Flora, J. R. V.; Chappell, M. A.; Bae, S. Hydrothermal Carbonization of Municipal Waste Streams. Environ. Sci. Technol. 2011, 45, 5696. (17) Kieseler, S.; Neubauer, Y.; Zobel, N. Ultimate and proximate correlations for estimating the higher heating value of hydrothermal solids. Energy Fuels 2013, 27, 908. (18) Tremel, A.; Stemann, J.; Herrmann, M.; Erlach, B.; Spliethoff, H. Entrained flow gasification of biocoal from hydrothermal carbonization. Fuel 2012, 102, 396. (19) Gao, P.; Zhou, Y.; Meng, F.; Zhang, Y.; Liu, Z.; Zhang, W.; Xue, G. Preparation and characterization of hydrochar from waste eucalyptus bark by hydrothermal carbonization. Energy 2016, 97, 238. (20) Á lvarez-Murillo, A.; Sabio, E.; Ledesma, B.; Román, S.; González-García, C. M. Generation of biofuel from hydrothermal carbonization of cellulose. Kinetics modelling. Energy 2016, 94, 600. (21) Kruse, A.; Funke, A.; Titirici, M. M. Hydrothermal conversion of biomass to fuels and energetic materials. Curr. Opin. Chem. Biol. 2013, 17, 515. (22) Prawisudha, P.; Namioka, T.; Yoshikawa, K. Coal alternative fuel production from municipal solid wastes employing hydrothermal treatment. Appl. Energy 2012, 90, 298. (23) Muthuraman, M.; Namioka, T.; Yoshikawa, K. Characteristics of co-combustion and kinetic study on hydrothermally treated municipal solid waste with different rank coals: a thermogravimetric analysis. Appl. Energy 2010, 87, 141. (24) Lu, L.; Namioka, T.; Yoshikawa, K. Effects of hydrothermal treatment on characteristics and combustion behaviors of municipal solid wastes. Appl. Energy 2011, 88, 3659. (25) Jin, Y.; Lu, L.; Ma, X.; Liu, H.; Chi, Y.; Yoshikawa, K. Effects of blending hydrothermally treated municipal solid waste with coal on cocombustion characteristics in a lab-scale fluidized bed reactor. Appl. Energy 2013, 102, 563. (26) Haslam, J.; Hamilton, J. B.; Squirrell, D. C. M. The determination of chlorine by the oxygen flask combustion method: a single unit for electrical ignition by remote control and potentiometric titration. Analyst 1960, 85, 556. (27) Starnes, W. H. How and to what extent are free radicals involved in the nonoxidative thermal dehydrochlorination of poly(vinyl chloride)? J. Vinyl Addit. Technol. 2012, 18, 71. (28) Starnes, W. H.; Ge, X. Mechanism of autocatalysis in the thermal dehydrochlorination of poly(vinyl chloride). Macromolecules 2004, 37, 352. (29) Nagai, N.; Smith, R. L.; Inomata, H.; Arai, K. Direct observation of polyvinylchloride degradation in water at temperatures up to 500 °C and at pressures up to 700 MPa. J. Appl. Polym. Sci. 2007, 106, 1075.
4. CONCLUSIONS Organic chloride in PVC can be transformed into inorganic chloride via hydrolysis in the HTC process. The washing process by the condensed water further removed soluble-Cl from the solid products. The addition of lignocellulose, especially for lignin, can significantly improve the dechlorination efficiency, which increases from 6.33% to 15.8% by HTC of PVC with lignin. Followed by the washing process, the dechlorination efficiency increases from 48.2% to 89.5%. The dechlorination performance of lignocellulosic components can be given in the following order: lignin > cellulose > hemicellulose (e.g., xylan). In addition, the HHVs of the hydrochars increased from 26.15 to 31.80 MJ/kg by HTC with lignocellulosic components. In particular, the highest HHV was achieved by the addition of lignin. Therefore, HTC with lignocellulosic biomasses will be an efficient way for PVC waste treatment along with the production of solid fuels. Several future works will be performed, including analyses of gas and liquid products, pilot-scale experiments on HTC of PVC and lignocellulosic biomass, and thermal processing of the solid product.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The author declares no competing financial interest.
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ACKNOWLEDGMENTS This work is financially supported by the Startup Fund for Introducing Talent at NUIST (Grant 2243141501046). The authors also gratefully acknowledge financial support by the National Natural Science Foundation of China (Grant 21607079).
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REFERENCES
(1) Saquing, J. M.; Saquing, C. D.; Knappe, D. R. U.; Barlaz, M. A. Impact of plastics on fate and transport of organic contaminants in landfills. Environ. Sci. Technol. 2010, 44, 6396. (2) Katami, T.; Yasuhara, A.; Okuda, T.; Shibamoto, T. Formation of PCDDs, PCDFs, and coplanar PCBs from polyvinyl chlorine during combustion in an incinerator. Environ. Sci. Technol. 2002, 36, 1320. (3) Hatanaka, T.; Kitajima, A.; Takeuchi, M. Role of chlorine in combustion field in formation of polychlorinated dibenzo-p-dioxins and dibenzofurans during waste incineration. Environ. Sci. Technol. 2005, 39, 9452. (4) Choi, J.; Kim, O.; Kwak, S. Y. Suppression of dioxin emission in co-incineration of poly(vinyl chloride) with TiO2-encapsulating polystyrene. Environ. Sci. Technol. 2007, 41, 5833. (5) Yu, J.; Sun, L.; Ma, C.; Qiao, Y.; Yao, H. Thermal degradation of PVC: A review. Waste Manage. 2016, 48, 300. (6) Shen, Y.; Zhao, R.; Wang, J.; Chen, X.; Ge, X.; Chen, M. Wasteto-energy: Dehalogenation of plastic-containing wastes. Waste Manage. 2016, 49, 287. (7) Funke, A.; Ziegler, F. Hydrothermal carbonization of biomass: a summary and discussion of chemical mechanisms for process engineering. Biofuels, Bioprod. Biorefin. 2010, 4, 160. (8) Libra, J. A.; Ro, K. S.; Kammann, C.; Funke, A.; Berge, N. C.; Neubauer, Y.; Titirici, M. M.; Fühner, C.; Bens, O.; Kern, J.; Emmerich, K. H. Hydrothermal carbonization of biomass residuals: a comparative review of the chemistry, processes and applications of wet and dry pyrolysis. Biofuels 2011, 2, 71. (9) Xiao, L.; Shi, Z.; Xu, F.; Sun, R. Hydrothermal carbonization of lignocellulosic biomass. Bioresour. Technol. 2012, 118, 619. F
DOI: 10.1021/acs.iecr.6b03365 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
Article
Industrial & Engineering Chemistry Research (30) Kang, S.; Li, X.; Fan, J.; Chang, J. Characterization of hydrochars produced by hydrothermal carbonization of lignin, cellulose, D -Xylose, and wood meal. Ind. Eng. Chem. Res. 2012, 51, 9023. (31) Kang, S.; Li, X.; Fan, J.; Chang, J. Hydrothermal conversion of lignin: A review. Renewable Sustainable Energy Rev. 2013, 27, 546. (32) Barbier, J.; Charon, N.; Dupassieux, N.; Loppinet-Serani, A.; Mahe, L.; Ponthus, J.; Courtiade, M.; Ducrozet, A.; Quoineaud, A. A.; Cansell, F. Hydrothermal conversion of lignin compounds. A detailed study of fragmentation and condensation reaction pathways. Biomass Bioenergy 2012, 46, 479. (33) Ragauskas, A. J.; Beckham, G. T.; Biddy, M. J.; Chandra, R.; Chen, F.; Davis, M. F.; Davison, B. H.; Dixon, R. A.; Gilna, P.; Keller, M.; Langan, P.; Naskar, A. K.; Saddler, J. N.; Tschaplinski, T. J.; Tuskan, G. A.; Wyman, C. E. Lignin valorization improving lignin processing in the biorefinery. Science 2014, 344, 1246843. (34) Sevilla, M.; Fuertes, A. B. The production of carbon materials by hydrothermal carbonization of cellulose. Carbon 2009, 47, 2281. (35) Kambo, H. S.; Dutta, A. A comparative review of biochar and hydrochar in terms of production, physico-chemical properties and applications. Renewable Sustainable Energy Rev. 2015, 45, 359.
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