ARTICLE pubs.acs.org/IECR
Temperature Effect on Hydrothermal Decomposition of Glucose in Sub- And Supercritical Water Chutinan Promdej† and Yukihiko Matsumura‡,* †
Department of Mechanical Systems Engineering, ‡Division of Energy and Environmental Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527 Japan ABSTRACT: Hydrothermal decomposition of glucose was conducted at 573733 K. The glucose solution (1.5 wt %) was gasified in a tubular reactor at 25 MPa. Gas products, char particles, and liquid products were observed, and the product yields were determined as a function of temperature. Char was only produced under the subcritical water condition (573 and 623 K) and was drastically suppressed under the supercritical condition. Intermediate compounds were produced and further decomposed to other products. This change can be attributed to the change in water properties from the subcritical to the supercritical region. The kinetic parameters of glucose decomposition pathways were also determined by assuming the first-order reaction. The rate constant of overall glucose decomposition showed Arrhenius behavior, but some reactions deviated from Arrhenius behavior in the supercritical region. Since it was expected that radical reactions would obey the Arrhenius equation and not be affected by water properties, but that ionic reactions would be influenced by the dielectric constant or ion product, and deviate from Arrhenius behavior in supercritical water, the temperature effect was considered a good method for distinguishing between ionic and radical reactions. On the basis of this concept, reactions in the reaction network of the supercritical water gasification of glucose were successfully classified into ionic and radical reactions.
1. INTRODUCTION Biomass is an abundant carbon-neutral and renewable resource that has the potential to produce energy. Among the various technologies applicable for biomass conversion, supercritical water gasification (SCWG) is a promising process for gasifying biomass with high moisture content into desirable products such as H2 and CH4. Another technology employing hot compressed water is direct liquefaction, in which the biomass can be directly converted into liquid fuel. These treatments of biomass are called hydrothermal treatment, and hot compressed water, or sub- and supercritical water, is used as a reaction medium in gasification1,2 and liquefaction.3,4 At hydrothermal conditions, water is a high potential solvent for organic components and gases, and also plays the role of an acid/base catalyst because of its high ionic product (Kw = 1011),5,6 especially in the subcritical region. In the SCWG process, biomass is easily decomposed but, concurrently, polymerizations of the biomass can occur. Polymerization reactions that produce char and tar materials can cause serious problems in the SCWG process because they not only reduce the gasification efficiency, but also can plug the reactor. Conditions for polymerization and char formation become more favorable in the heating up section at lower temperatures in the SCWG process,79 which makes it difficult to completely gasify biomass material. Therefore, the mechanism of hydrothermal gasification of biomass has drawn the attention of many researchers. Investigation of this decomposition mechanism using model compounds gives us some insight on this behavior. The dominant compound in most biomass is glucose, obtained from the rapid hydrolysis of cellulose. Thus, glucose can be used to effectively reproduce the reaction characteristics of SCWG. r 2011 American Chemical Society
Many researchers have employed glucose as a model compound, and pointed out its interesting decomposition behavior in hot compressed water.911 Some recent studies show a thermodynamic analysis of glucose in supercritical water gasification from the theoretical point of view12,13 and catalytic hydrothermal gasification to produce hydrogen rich gas from glucose.14,15 Reactions of glucose in SCWG have been investigated using both flow reactors9,16 and batch reactors. A lot of side products are found during the hydrothermal gasification. Glucose decomposition is not a simple pyrolysis to produce gaseous products. For example, polymerization of hydroxymethylfurfuraldehyde (5-HMF) and furfural takes place in glucose decomposition and leads to char formation. Reactions taking place in the SCWG process normally include both ionic and radical reactions. The ionic reactions should proceed more in the subcritical region where the dielectric constant and the ion product are high. In contrast, the radical reactions should be favored in steam and less dense supercritical water. Both reactions proceed competitively around the critical point of water.6,17 Few studies, nevertheless, cope with the reaction characteristics of model biomass in supercritical water gasification in terms of reaction kinetics. Kabyemela et al.18 investigated glucose decomposition with a short residence time at 573673 K under 2540 MPa. Their experiments identified the key compounds in the liquid effluent and provided data with which to construct a reaction pathway. This has been potentially fruitful, as the kinetics of glucose may be useful in understanding the reaction Received: February 11, 2011 Accepted: May 18, 2011 Revised: May 11, 2011 Published: May 18, 2011 8492
dx.doi.org/10.1021/ie200298c | Ind. Eng. Chem. Res. 2011, 50, 8492–8497
Industrial & Engineering Chemistry Research pathways of cellulose. Matsumura et al.19 and Yoshida et al.20 evaluated the kinetics of glucose decomposition in water under supercritical pressure. Previously, our research group9 systematically studied the mechanism of char formation in the biomass model compound: 5-HMF and glucose. The 5-HMF concentration has no effect on the gasification pathway, but the increasing 5-HMF concentration strongly promotes the polymerization pathway. The rate of char formation in the glucose experiment was found to be 2 orders of magnitude higher than that for the 5-HMF experiment. The behavior of the reaction rates, however, have not been thoroughly elucidated in terms of the temperature effect. However, the temperature range only extended to 673 K because the research target was set on char production, and the reaction under 673 K was conducted mainly for a reference purpose. By conducting gasification at 723 K, the authors observed reaction rate constants decreasing with temperature for some reactions.21 This decrease in the reaction rate constants is attributed to the property changes that take place in water from the subcritical region to the supercritical region. Both ionic and radical reactions take place under hydrothermal conditions. If a reaction is a radical one, than it will not be affected by the change in dielectric constant or ion product, and Arrhenius behavior is expected. However, if a reaction is ionic, then change in the dielectric constant and the ion product will affect the stability of the ions participating in the reaction, and deviation from Arrhenius behavior will result. Thus, by detailed analysis of the temperature effect on the reaction rate of each reaction, it should be possible to determine which reactions are ionic and which reactions are radical. This knowledge will be helpful to elucidate the reactions that take place during the heating up period of the supercritical water gasification, and for designing an effective reactor for this purpose. However, a detailed analysis has not yet been reported. Thus, the purpose of this work is to determine the temperature effect on each reaction in the reaction network of glucose decomposition under the hydrothermal condition, and also to find which reactions are ionic and which reactions are radical.
ARTICLE
used in this work was D-glucose (purity >99.5%) obtained from Sigma Aldrich and deionized water. 2.2. Analytical Method. The reaction products were analyzed in similar ways to those from the experiments of previous works.9 The liquid product was analyzed by a total organic carbon (TOC) analyzer to quantify the amounts of carbon in the liquid product (nonpurgeable organic carbon or NPOC) and in the dissolved gas product (inorganic carbon or IC). Furfural and 5-hydroxymethylfurfural (5-HMF) were analyzed by HPLC (high-performance liquid chromatography) with an RSpak DE413 L column (Shodex). The analytical conditions were as follows: flow rate 0.5 cm3/min; eluent 0.005 M HClO4 aqueous solution/CH3CN = 90/10; oven temperature 313 K. Glucose and fructose were analyzed by HPLC using a sugar KS-802 column (Shodex). The analytical conditions were as follows: flow rate 0.8 cm3/min; eluent water; oven temperature 333 K. The gas product was analyzed using a gas chromatograph (GC) equipped with both TCD (thermal conductivity detector) and FID (flame ionization detector). CO2 and CO were detected by TCD with He as the carrier gas. CH4, C2H4, and C2H6 were detected by FID with He as the carrier gas. H2 was detected by TCD with N2 as the carrier gas. The solid product included particles suspended in the liquid effluent and particles entrapped in the inline filter. The particles in the liquid effluent were obtained by filtering the effluent through a mixed cellulose ester membrane (0.1 μm pore size; Millipore) using vacuum suction. The particles entrapped in the inline filter were taken out with an ultrasonic cleaning device. 2.3. Definition of Product Yield. Product yields of glucose decomposition from the experimental results were calculated on the basis of the carbon content in the glucose feedstock: ðproduct yieldÞ ¼
ðcarbon content in productÞ½mol C=dm3 0:083½mol=dm3 6½mol C=mol ð1Þ
The total carbon balance of this work was higher than 90% in most cases.
3. RESULTS AND DISCUSSIONS 2. EXPERIMENTAL SECTION 2.1. Experimental Procedure. Details on the continuous flow
reactor and the procedures used in this work have been described previously.9 In brief, an initial concentration of glucose solution (7.5 wt %) was mixed with the preheated water at a 1:4 ratio by volume just before entry into the reactor zone, a point from which sudden heating of the glucose solution to the reaction temperature would be assured. The tubular reactor was made of SS316 steel and measured 20 m in length, with inner and outer diameters of 1 and 1.59 mm, respectively. The product effluent discharged from the exit of the reactor was mixed with cold deionized water for rapid cooling. Large solid particles were entrapped inside the inline filters. The liquid effluent (with dispersed char particles) was collected at the liquid sampling point. The gas production rate was measured by the pressure change inside the vacuumed gas sampling port. The system was controlled by a backpressure regulator. The reaction pressure was set at 25 MPa, the temperature was set in the range from 573 to 723 K, and the residence time was set up to 60 s by adjusting the feedstock flow rate. The reacted concentration of glucose was 1.5 wt % (0.083 mol/dm3 at room temperature). The feedstock
3.1. Product Distribution. Product yield of the hydrothermal decomposition of glucose is shown in Figure 1. The liquid phase samples contain a huge number of different compounds. It was not useful to determine all of them. Fructose, 5-HMF, furfural, other water-soluble products (TOC), char and gas were employed to construct the reaction network in this work as in the previous study.9,21 The glucose decomposition illustrated in Figure 1 is rapid, and it is accelerated with the temperature rise. Glucose is almost completely decomposed in 60 s even at the lowest subcritical temperature of 573 K, and in only 0.5 s at the highest supercritical temperature of 733 K. The change of overall glucose decomposition rate with the reaction temperature is known to follow the Arrhenius behavior,9 and the change in Figure1 appears to agree with this finding. Glucose undergoes isomerization to fructose which further produces 5-HMF and furfural. Fructose was both rapidly formed and rapidly decomposed, its rate increasing with temperature up to the maximum temperature under supercritical conditions (733 K). The maximum fructose yield tends to decrease when the temperature increases. This suggests that the isomerization of 8493
dx.doi.org/10.1021/ie200298c |Ind. Eng. Chem. Res. 2011, 50, 8492–8497
Industrial & Engineering Chemistry Research
ARTICLE
Figure 1. The product distribution of the hydrothermal decomposition of glucose in the different temperature and residence time.
glucose to fructose is not promoted in the supercritical region. One of the possible reasons is the low ionic product (Kw) property of water in supercritical water leading to the prohibition of the ionic reactions. Buhler et al.17 clarified that the ionic reaction is preferred at high pressures and/or lower temperatures. Kruse and Gawlick22 have suggested that the supercritical condition favors free-radical reactions indispensable to the production of the gaseous product. This isomerization of glucose to fructose is known to be an ionic reaction, and thus agrees with
these previous observations, and this fact supports our strategy of classifying ion reactions and radical reactions by the effect of temperature on each reaction rate. 5-HMF and furfural products, which are the ring intermediate compounds of glucose hydrothermal gasification, can be polymerized to char product and/or gasified to a desirable gas. The yields of 5-HMF and furfural increase and then stay constant in the subcritical region, but those in the supercritical region slowly further decrease. This behavior confirms that 5-HMF and 8494
dx.doi.org/10.1021/ie200298c |Ind. Eng. Chem. Res. 2011, 50, 8492–8497
Industrial & Engineering Chemistry Research
ARTICLE
furfural, which are the intermediate compounds of the glucose decomposition are further decomposed to other products. The subcritical condition shows their constant yield because the formation rate and decomposition rate are the same. The supercritical condition, however, shows the higher decomposition rates of 5-HMF and furfural due to the water property explained above. TOC yield rapidly increases at the higher temperature and then declines over the long residence time. This indicates that the TOC product is produced and then is decomposed to other products as in the case for 5-HMF and furfural. Gas product monotonously increases with temperature up to the supercritical temperature (733 K). The char production is confined to the subcritical region, and the yield of char increases with temperature in this subcritical region. This implies that char production is based on the same mechanism within the subcritical region, and that it is strongly prohibited in the supercritical region. In view of the drastic change in the pattern of char production from the subcritical to supercritical conditions, it may be reasonable to assume that the low dielectric constant under supercritical temperatures inhibited char production, which is ionic. Namely, the ionic reactions necessary to form the aromatic compounds that facilitate the char production are inhibited.
3.2. Reaction Rates. The kinetics of glucose decomposition at these conditions (573733 K) can be useful in understanding the char formation in the heating section of the supercritical water gasification process. Here, the reaction kinetics are evaluated from the reaction pathway observed, as shown in Figure 2, again as in the previous study.9 We assume that for all of the reactions, the reaction order is unity. The change in yield for each compound in this reaction network is calculated using the differential equations below:
d½glucose ¼ ðkgf þ kgf u þ kgt þ kg5 Þ½glucose dt
ð2Þ
d½f ructose ¼ kgf ½glucose ðkf 5 þ kff u þ kf t Þ½fructose ð3Þ dt d½5 HMF ¼ kg5 ½glucose þ kf 5 ½f ructose k5t ½5 HMF dt
k5c ½5HMF
ð4Þ
d½f urf ural ¼ kgf u ½glucose þ kf f u ½f ructose ðkf ut þ kf uc Þ½f urf ural dt
ð5Þ d½TOC ¼ kgt ½glucose þ kf t ½f ructose þ k5t ½5 HMF dt þ kf ut ½f urf ural ktc ½TOC ktg ½TOC ð6Þ d½char ¼ kf uc ½f urf ural þ k5c ½5 HMF þ ktc ½TOC dt d½gas ¼ ktg ½TOC dt
ð7Þ ð8Þ
where [glucose] = glucose yield [] [fructose] = fructose yield []
Figure 2. Proposed formation pathways of glucose char particles.
Table 1. Kinetic Parameters Obtained from the First Order Model for Glucose Decomposition k [s1] kinetic parameters
reaction
573 K9
623 K9
673 K9
698 K
723 K
733 K
gf
isomerization
2.09 102
2.21 101
2.86 101
1.62 101
1.30 101
1.42 101
gfu gt
dehydration decomposition
0 5.13 102
0 9.30 101
1.60 101 3.60
2.20 101 6.26
7.18 102 5.74
9.35 102 6.49
g5
dehydration
6.00 103
3.27 102
2.15 101
2.76 101
5.23 102
7.51 102
f5
dehydration
1.62 101
3.30 101
3.82 101
3.00 101
1.32 101
1.50 101
ffu
dehydration
5.94 102
2.74 101
1.91 101
1.18 101
9.32 102
8.70 102
ft
decomposition
0
0
0
0
0
0
5t
decomposition
0
2.45 105
0
3.03 102
4.07 102
3.98 102
5c
polymerization
1.59 103
1.28 102
0
0
0
0
fut fuc
decomposition polymerization
0 0
9.94 103 0
0 0
1.44 102 0
1.23 102 0
5.80 102 0
tc
polymerization
9.35 104
1.29 103
1.60 103
1.16 103
9.30 104
6.44 104
2.69 10
3
3
3
3
2
2.27 102
7.81 10
2
tg g
gasification total reaction
2.35 10 1.18
6.64 10 4.26
8495
9.27 10 6.92
1.46 10 6.00
6.80
dx.doi.org/10.1021/ie200298c |Ind. Eng. Chem. Res. 2011, 50, 8492–8497
Industrial & Engineering Chemistry Research
ARTICLE
Figure 3. Arrhenius plot of the rate constant of the overall glucose decomposition (kg) for literature comparison.
[5-HMF] = 5-HMF yield [] [furfural] = furfural yield [] [TOC] = liquid product yield [] [char] = char yield [] [gas] = gas yield [] ki = rate constant [s1] t = residence time [s] The rate constants determined by the least-squares method are shown in Table 1. Note that the ratio of the rate constants for the reactions of the same reactants denotes the ratio of the amount of the reactant which is converted into each product. The overall decomposition rate of glucose (kg) is shown in Figure 3. This Arrhenius plot for the present work gives a pre-exponential factor of 6.9 107 s1 and an activation energy of 95.54 kJ/mol for the temperature range up to 733 K. These parameters are consistent with those of the previous studies, which are also shown in Figure 3. The activation energies of 121 and 96 kJ/mol have been determined from the work by Matsumura et al.19 and Kabyemela et al.,18 respectively. The Arrhenius plots for each reaction in the reaction network are shown in Figure 4. Although the rate constant for glucose decomposition systematically changes with the reaction temperature up to the supercritical temperature, following the Arrhenius characteristics, the results shown in Figure 4 indicate that the individual reaction rates do not necessarily follow the Arrhenius behavior. For example, the rate constants for 5-HMF and furfural formation from glucose, decrease in the supercritical region. As for decomposition of 5-HMF, Luijkx et al.23 have shown that the 5-HMF degradation shows a non-Arrhenius behavior, or change in reaction mechanism: in subcritical water, production to 1,2,4-benzenetriol is favored, meanwhile, in supercritical water, pyrolytic degradation to other furfurals is enhanced. In this work, although not starting from 5-HMF, it was observed that decomposition of 5-HMF to form char suddenly reduced in the supercritical region, meanwhile decomposition to form TOC followed the Arrhenius behavior even in the supercritical region. The former corresponds to production of 1,2,4benzenetriol, which further reacts to produce char, and the latter corresponds to pyrolytic degradation. The kinetic analysis results of this study agree with the well-known classical observations. The decrease of kgf, kffu kf5, and kft in the supercritical region is presumably caused by the reduction of ion product in the supercritical condition. Watanabe et al.6 proposed that water in the hydrothermal condition played the role of an acid or base
Figure 4. Arrhenius plot of the rate constant of the hydrothermal decomposition of glucose.
Table 2. Classification of Reactions in SCWG of Glucose ionic reaction
radical reaction
non-Arrhenius
Arrhenius
gf
isomerization
gt
decomposition
gfu
dehydration
5t
decomposition
g5
dehydration
fut
decomposition
f5
dehydration
tg
gasification
ffu
dehydration
ft
decomposition
5c fuc
polymerization polymerization
tc
polymerization
catalyst because of its Hþ and OH ions. Reduction of the ion product reduces the concentration of Hþ and OH ions, and thus acid- or base-catalyzed reactions in water at high pressures and high temperatures should show a non-Arrhenius kinetic behavior. Thus, this behavior of reaction rate with temperature is a good method for distinguishing between ion reactions and free radical reactions: the former showing non-Arrhenius behavior, 8496
dx.doi.org/10.1021/ie200298c |Ind. Eng. Chem. Res. 2011, 50, 8492–8497
Industrial & Engineering Chemistry Research and the latter showing Arrhenius behavior. The resulting classification is shown in Table 2 for reference purposes.
4. CONCLUSIONS The hydrothermal gasification of glucose was conducted under subcritical (573623 K) and supercritical water (673733 K) conditions. Product yields of fructose, 5-HMF, furfural, TOC, gas, and char were observed. The char formation only occurs under the subcritical condition. Under the supercritical condition it is drastically suppressed. Aromatic compounds are produced and further decomposed to gas or char products. Change in product yields are thought to be due to the change in water properties in the supercritical region. The kinetics of glucose decomposition at these conditions have been determined under sub- and supercritical conditions. The overall glucose decomposition rate is well expressed by the Arrhenius equation, but the reaction rate of some individual reactions in the reaction network decreases in the supercritical region. The different water properties under the sub- and supercritical conditions have affected the reaction mechanism, which has ionic and radical reactions. This behavior of reaction rate with temperature is a good indicator for distinguishing between ion reactions and free radical reactions: the former showing non-Arrhenius behavior, and the latter showing the Arrhenius behavior. The reactions in the reaction network for the supercritical water gasification of glucose can be well classified, using these criteria, into ionic and radical reactions. ’ AUTHOR INFORMATION Corresponding Author
*Fax: þ81-82-422-7193. E-mail:
[email protected].
’ REFERENCES (1) Yanik, J.; Ebale, S.; Kruse, A.; Saglam, M.; Y€uksel, M. Biomass gasification in supercritical water: II. Effect of catalyst. Int. J. Hydrogen Energy 2008, 33, 4520. (2) Chakinala, A. G.; Brilman, D. W. F.; van Swaaij, W.P.N.; Kersten, A. R. S. Catalytic and non-catalytic supercritical water gasification of microalgae and glycerol. Ind. Eng. Chem. Res. 2010, 49, 1112. (3) Akhtar, J.; Kuang, S. K.; Amin, N. S. Liquefaction of empty palm fruit bunch (EPFB) in alkaline hot compressed water. Renewable Energy 2010, 35, 1220. (4) Tymchyshyn, M.; Xu, C.(C.). Liquefaction of bio-mass in hotcompressed water for the production of phenolic compounds. Bioresour. Technol. 2010, 101, 2483. (5) Akiya, N.; Savage, P. E. Roles of water for chemical reactions in high-temperature water. Chem. Rev. 2002, 102, 2725. (6) Watanabe, M.; Sato, T; Inomata, H.; Smith, R. L., Jr.; Arai, K.; Kruse, A.; Dinjus, E. Chemical reactions of C1 Compounds in nearcritical and supercritical water. Chem. Rev. 2004, 104, 5803. (7) Matsumura, Y.; Harada, M.; Nagata, K.; Kikuchi, Y. Effect of heating rate of biomass feedstock on carbon gasification efficiency in supercritical water gasification. Chem. Eng. Commun. 2006, 193, 649. (8) Karayildirim, T.; Sinag, A.; Kruse, A. Char and coke formation as unwanted side reaction of the hydrothermal biomass gasification. Chem. Eng. Technol. 2008, 11, 1561. (9) Chuntanapum, A.; Matsumura, Y. Char formation mechanism in supercritical water gasification process: A study of model compounds. Ind. Eng. Chem. Res. 2010, 49, 4055. (10) Klingler, D.; Vogel, H. Influence of process parameters on the hydrothermal decomposition and oxidation of glucose in sub- and supercritical water. J. Supercrit. Fluids 2010, 55, 259.
ARTICLE
(11) Weiss-Hortala, E.; Kruse, A.; Ceccarelli, C.; Barna, R. Influence of phenol on glucose degradation during supercritical water gasification. J. Supercrit. Fluids 2010, 53, 42. (12) Letellier, S.; Marias, F.; Cezac, P.; Serin, J. P. Gasification of aqueous biomass in supercritical water: A thermodynamic equilibrium analysis. J. Supercrit. Fluids 2010, 51, 353. (13) Voll, F. A. P.; Rossi, C. C. R. S.; Silva, C.; Guiradello, R.; Souza, R. O. M. A.; Cabral, V. F.; Cardozo-Filho, L. Thermodynamic analysis of supercritical water gasification of methanol,ethanol, glycerol, glucose, and cellulose. Int. J. Hydrogen Energ. 2009, 34, 9737. (14) Youssef, E. A.; Chowdhury, M. B. I.; Nakhla, G.; Charpentier, P. Effect of nickel loading on hydrogen production and chemical oxygen demand (COD) destruction from glucose oxidation and gasification in supercritical water. Int. J. Hydrogen Energy 2010, 35, 5034. (15) Fang, Z.; Minowa, T.; Fang, C; Smith, R. L., Jr.; Inomata, H.; Kozinski, J. A. Catalytic hydrothermal gasification of cellulose and glucose. Int. J. Hydrogen Energy 2008, 33, 981. (16) Goodwin, A. K.; Rorrer, G. L. Conversion of glucose to hydrogen-rich gas by supercritical water in a microchannel reactor. Ind. Eng. Chem. Res. 2008, 47, 4106. (17) B€uhler, W.; Dinjus, E.; Ederer, H. J.; Kruse, A.; Mas, C. Ionic reactions and plrolysis of glycerol as competing reaction pathways in near- and supercritical water. J. Supercrit. Fluids 2002, 22, 37. (18) Kabayemela, B. M.; Adshiri, T.; Malaluan, R. M.; Arai, K. Kinetics of glucose epimerization and decomposition in subcritical and supercritical water. Ind. Eng. Chem. Res. 1997, 36, 1552. (19) Matsumura, Y.; Yanachi, S.; Yoshida, T. Glucose decomposition kinetics in water at 25 MPa in the temperature range of 448673 K. Ind. Eng. Chem. Res. 2006, 45, 1875. (20) Yoshida, T; Yanachi, S; Matsumura, Y. Glucose decomposition in water under supercritical pressure at 448498 K. J. Jpn. Inst. Energy 2007, 86, 700. (21) Promdej, C.; Chuntanapum, A.; Matsumura, Y. Effect of temperature on tarry material production of glucose in supercritical water gasification. J. Jpn. Inst. Energy 2010, 89, 1179. (22) Kruse, A.; Gawlik, A. Biomass Conversion in Water at 330410°C and 3050 MPa. Identification of Key Compounds for Indicating Different Chemical Reaction Pathways. Ind. Eng. Chem. Res. 2003, 42, 267. (23) Luijkx, G. C. A.; van Rantwijk, F.; van Bekkum, H. Hydrothermal formation of 1,2,4-benzenetriol from 5-hydroxymethyl-2-furaldehyde and D-fructose. Carbohydr. Res. 1993, 242, 131.
8497
dx.doi.org/10.1021/ie200298c |Ind. Eng. Chem. Res. 2011, 50, 8492–8497
