Article pubs.acs.org/jced
Thermodynamic Properties of Plant Biomass Components. Heat Capacity, Combustion Energy, and Gasification Equilibria of Lignin Olga V. Voitkevich, Gennady J. Kabo,* Andrey V. Blokhin, Yauheni U. Paulechka, and Margarita V. Shishonok Chemistry Faculty and Research Institute for Physical Chemical Problems, Belarusian State University, Leningradskaya 14, 220030 Minsk, Belarus S Supporting Information *
ABSTRACT: Heat capacities and enthalpies of formation were determined for two samples of lignin obtained from rape straw by different methods. The obtained experimental results allowed us to obtain the values of thermodynamic properties for this material. The equilibria of the processes of lignin gasification were considered. The adiabatic temperatures of the gasification and energetic characteristics of the products of lignin thermolysis were evaluated.
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INTRODUCTION Lignin as well as cellulose is the main component of plants. According to ref 1, the content of lignin may reach 0.35 of the wood mass. Coniferyl alcohol C10H12O3 is considered as a lignin prototype substance; however, the elemental composition and the structure of lignin polymeric molecules depend on the nature of plants and the method of lignin extraction. Blunk and Jenkins1 determined the enthalpies of combustion for various lignins. It was demonstrated that the carbon content of various lignin samples can differ by ± 20 %. The ash content for hardwood lignin was found to be 5.5 times higher than that for softwood lignin. The enthalpies of combustion for hardwood and softwood lignins were found to be (−21.45 and −23.50) MJ·kg−1, respectively.1 It has been established by differential scanning calorimetry (DSC) that lignin devitrifies at temperatures of about 400 K.2−4 However, the low-temperature heat capacity of lignin has not become available in literature. Thermodynamic properties of cellulose and its gasification equilibria have been studied in our laboratory before.5 Lignin thermal gasification has some important differences compared to the similar process for cellulose due to different chemical compositions of these polymers, and this is confirmed by DSC study.2 The process of lignin gasification can potentially be used for the production of fuel gas both directly from lignin and from vegetative cultures having a significant content of lignin. In this work, the results of thermodynamic study for two samples of lignin extracted from rape straw are presented. The lignin thermal gasification equilibria were analyzed with the use of the obtained data.
by cuproammonium and sulfuric methods, the main methods for lignin extraction. Cuproammonium lignin was obtained by the modified Freidenberg method.6 Grinded straw was pretreated with diethyl ether to remove resins, fats, and waxes. Then, the straw was kept in the NaOH solution (w(NaOH) = 0.05) for one day. The next day, the alkali solution was replaced with the fresh one, and the mixture was left for another day. Then, the mixture was filtered, and the residue was subsequently washed with water, dilute acetic acid, and again water. The residue was kept in boiling sulfuric acid (w(H2SO4) = 0.01) for 3 h to remove hemicellulose and shaken with cuproammonium solution for 12 h to remove cellulose. The precipitate formed after centrifugation was subsequently washed with cuproammonium solution, ammonia solution, dilute hydrochloric acid, and water. The procedures removing hemicellulose and cellulose were repeated several times. Sulfuric lignin was obtained by the Komarov modification.7 Grinded straw pretreated with diethyl ether was kept in a sulfuric acid solution (w(H2SO4) = 0.72) for 2.5 h. The resulting mixture was diluted with water and boiled for 1 h. Then, lignin was separated on a glass porous filter and washed with hot water to neutrality. Prior to the measurements, all of the samples were dried at 403 K for (40 to 60) h until the constant mass within 10−3 % was reached. The samples were then kept over P2O5 at T = 290 K for > 72 h. The ash content was determined from the mass of residue in a calorimetric bomb after combustion of a sample. The sulfur content was determined by the gravimetric method with the use of the saturated barium chloride solution.8 It was
EXPERIMENTAL SECTION Preparation and Characterization of Samples. The samples of lignin were obtained by extraction from rape straw
Received: December 6, 2011 Accepted: April 23, 2012 Published: May 18, 2012
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© 2012 American Chemical Society
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assumed that sulfur in the samples was contained in the form of sulfate salts. Since this is the most oxidized form of sulfur, there was no need to introduce the appropriate correction to the combustion energy. At least three experiments were made for each determination. X-diffractograms were obtained with a HZG-4a diffractometer (Cu Kα radiation source, Ni filter). The measurements were performed in a step mode. The lignin samples were prepared in the form of a flat disk of equal mass using the pressout technique. The C, H, N, and S contents were determined with an Elementar Vario El analyer. The O content was calculated from the difference of the above values and 100 %. The heat capacity of lignin in the temperature range of (5 to 370) K was measured in a TAU-10 adiabatic calorimeter (Termis, Moscow).9 The detailed description of the calorimeter construction and the experimental procedures was published earlier.10 The temperature was measured with an Fe/Rh resistance thermometer (R0 = 50 Ω) calibrated on ITS-90 by VNIIFTRI (Moscow). The relative uncertainty of the heat capacity measurements was ± 4·10−3 over the main temperature range of (20 to 370) K and did not exceed ± 2·10−2 at T < 10 K. The experimental heat capacities were smoothed with the polynomial equations. For all of the polynomials, the rms deviations of experimental points from the smoothing curves did not exceed half of the uncertainty in the corresponding temperature range. The combustion energy of the lignin samples was determined in a combustion calorimeter equipped with a stainless-steel bomb of 326 cm3 volume.11 The energy equivalent of the calorimeter εcalor = 14595.5 ± 4.2 J·K−1 was determined from 10 experiments on the combustion of benzoic acid (K-2 grade, mass fraction purity of 0.99993). A Pt crucible was used in the combustion experiments. The initial oxygen pressure in the bomb was 3.09 MPa. For the reduction of the data to standard conditions, conventional procedures12 were used. The compressed pellets for calorimetric experiments were kept over P2O5. When a pellet was loaded into the calorimetric bomb, its exposure to air did not exceed 10 min. The maximum error in the specific enthalpies of combustion caused by the adsorption of water during this time did not exceed 0.02 kJ·g−1 which is much less than the uncertainty of these quantities. DSC and thermogravimetric (TG) analysis was performed with a Netzsch STA 449 Jupiter instrument. The sample of sulfuric lignin of about 5 mg mass was placed in an alumina crucible. The curves in the temperature range (300 to 873) K were recorded at a 10 K·min−1 scanning rate under nitrogen gas.
Table 1. Elemental Composition of Studied Samples w·100
a
component
cuproammonium
sulfuric
C H S N O ash
50.2 ± 0.2 4.99 ± 0.05 0.04 ± 0.01; 0.31a ± 0.02 0.87 ± 0.03 43.2 ± 0.2 0.70a ± 0.03
58.2 ± 0.6 5.62 ± 0.21 1.35 ± 0.03; 1.54a ± 0.11 3.29 ± 0.02 29.9 ± 0.7 1.62a ± 0.31
Sulfur content determined after combustion in a calorimetric bomb.
Figure 1. X-ray patterns for sulfuric (1) and cuproammonium (2) lignins.
Figure 2. Experimental (○) and calculated using the data from ref 4 (−) heat capacities cp for sulfuric lignin.
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RESULTS AND DISCUSSION Characterization of Samples. The results of elemental analysis are presented in Table 1. The following procedure was used for the definition of a conditional structural unit for lignin. The number of carbon atoms was assumed to be equal to 10. The numbers of hydrogen and oxygen atoms were determined from the results of the elemental analysis and the ash content in the samples. Thus obtained conditional structural units were C10H11.9O6.5 (M = 236.1 g·mol−1) for cuproammonium lignin and C10H11.5O3.9 (M = 193.4 g·mol−1) for sulfuric lignin. These molar masses were close to M = 223.5 g·mol−1 and M = 191.6 g·mol−1 calculated for hardwood and softwood lignin.1 A conditional structural unit of sulfuric lignin C10H11.5O3.9 is similar to the structural units of softwood lignin from ref 1. This
Figure 3. Experimental heat capacities cp for cuproammonium lignin.
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differences of the specific heat capacity for sulfuric lignin and microcrystalline cellulose are more essential (Figure S1, SI). Combustion Calorimetry. The energies of combustion for the lignin samples determined in an isoperibol calorimeter are presented in Table 3 and S4 of the SI. The obtained values correspond to the reactions:
formula was used in the subsequent calculations of lignin gasification equilibria. The X-ray patterns of lignin samples (Figure 1) represented the diffuse diffraction patterns with a maximum of an amorphous halo in the range of (19 to 23)°. Heat Capacity. The experimental specific heat capacities cp of lignin samples in the condensed state in the temperature range of (5 to 370) K are presented in Figures 2 and 3 and Tables S1 and S2 of the Supporting Information (SI). No phase transitions or anomalies in the heat capacity curves for all of the samples were found. The heat capacity of the sample of sulfuric lignin was extrapolated below T = 80 K according to Kelley et al.13 with the use of the equation:
(C10H11.9O6.5)n (amorph) + 9.725nO2 (g) = 10nCO2 (g) + 5.95nH 2O(l) (C10H11.5O3.9)n (amorph) + 10.925nO2 (g)
cSL(T ) = a + b(T /K) cCL(T )
= 10nCO2 (g) + 5.75nH 2O(l)
The energy of combustion for cuproammonium lignin is about 0.1Δcuo more positive than that for sulfuric lignin. It can be caused by the increase of the hydrogen mass fraction in sulfuric lignin. The differences between the energies of combustion for the samples calculated on the ash-free basis (Table 3) become even more pronounced. The obtained values of the specific energies of combustion are in satisfactory agreement, taking into account different compositions of the samples. The values of the specific energies of combustion for the lignins obtained in this work agree within ± 0.05 Δcuo with the energies of combustion for lignin reported earlier.1 The specific energy of combustion for sulfuric lignin is more negative than the corresponding value for cellulose5 by about 0.3Δcuo. The enthalpies of formation for the lignin samples (Table 3) were calculated using ΔfHom(CO2(g)) = −(393.52 ± 0.13) kJ·mol−1 and ΔfHom(H2O(l)) = −(285.83 ± 0.04) kJ·mol−1.14 Thermal Gasification of Lignin. The main products of wood and cellulose pyrolysis are normally gaseous CO, CO2, H2, CH4, H2O, and solid carbon.15 In the subsequent thermodynamic calculations it was assumed that thermodynamic functions of solid carbon formed during thermolysis are equal to those of graphite. As follows from the thermodynamic analysis presented below, at T = 298.15 K, thermodynamically favorable products would be graphite, water, methane, and CO. The thermodynamic stability of lignin was estimated in the following hypothetical reactions:
where cSL(T) and cCL(T) are the specific heat capacities of sulfuric and cuproammonium lignin at temperature T, respectively. The a = 0.9006 and b = −3.232·10−4 coefficients were found by the method of least-squares from the smoothed heat capacities in the temperature range of (80 to 230) K. The root-mean-square (rms) deviation of the experimental values from the calculated ones was 6·10−3. The specific heat capacities of samples 1 and 2 are compared in Figure 4.
Figure 4. Comparison of heat capacity of lignins: ●, cuproammonium; ⧫, sulfuric [cp(SL)]; ∗, ref 4.
(C10H11.5O3.9)n (amorph)
In ref 4, the heat capacity of lignin was determined by DSC in the range (350 to 450) K and reported as a graphical image. The original plot was digitized, and the obtained values are compared with those from this work in Figure 4. The difference between the results did not exceed 0.02cp in the temperature range of (350 to 370) K. The heat capacities4 were used for the calculation of thermodynamic properties of sulfuric lignin to 450 K. It was found that the heat capacity of sulfuric lignin in the temperature range of (350 to 370) K is on the average 0.016cp higher than that from ref 4. So, the heat capacity of sulfuric lignin (Figure 3) above T = 370 K was assumed to be equal to the capacity of lignin from ref 4 scaled by 1.016. The parameters of glass transition for the sulfuric lignin based on the scaled results4 were found to be Tg = 408.5 K and Δ1g1cp = 0.329 J·K−1·g−1. The smoothed values of heat capacity and standard thermodynamic functions for the studied lignin samples are presented in Tables 2 and S3 of the SI. The specific heat capacities for sulfuric lignin and amorphous cellulose differ by ≤0.05cp in the temperature range of (180 to 370) K and ≤0.15cp below T = 180 K (Figure S1, SI). However, the
= 9.075nC(graphite) + 3.90nH 2O(l) + 0.925nCH4(g) (1)
(C10H11.9O6.5)n (amorph) = 9.45nC(graphite) + 5.95nH 2O(l) + 0.55nCO(g) (2)
The thermodynamic parameters of the reactions were calculated using the data of ash free lignin from Tables 2 and 3, Table S3 of Supporting Information, and ref 14 were (per mole of lignin monomeric units) Δr Hm,l = −(466 ± 13) kJ ·mol−1 Δr Hm,2 = −(1526 ± 34) kJ ·mol−1
Δr Sm,1 = 257.4 ± 1.2 J ·K−1·mol−1 Δr Sm,2 = 297.7 ± 1.4 J ·K−1·mol−1 1905
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Table 2. Thermodynamic Properties for Sulfuric Lignin (C10H11.5O3.9)na Δ0THom/T
Cp,m −1
−1
−1
−1
J·K ·mol
J·K ·mol
0 20 40 60 80 100 120 140 160 180 200 220 240 260 273.15 280 298.15 300 320 340 360 380b
0.0 11.87 32.90 53.68 72.74 89.55 105.4 120.5 135.5 150.5 165.6 180.8 196.5 212.3 222.5 227.7 242.0 243.5 260.0 274.1 288.8 307.3
0.0 4.081 13.16 23.25 33.29 42.88 51.99 60.70 69.11 77.32 85.39 93.36 101.3 109.2 114.4 117.1 124.3 125.0 133.0 140.9 148.6 156.5
420b 440b
413.3 428.0
174.5 185.8
T/K
Δ0TSom −1
−(Gom(T)−Hom(0))/T −1
−1
J·K ·mol
J·K ·mol
Amorphous 0.0 5.831 20.41 37.73 55.84 73.90 91.64 109.0 126.1 142.9 159.6 176.0 192.4 208.8 219.5 225.1 239.8 241.3 257.6 273.8 289.8 305.9 Liquid 340.4 360.1
−1
−ΔfHom kJ·mol
−1
−ΔfGom kJ·mol−1
0.0 1.749 7.248 14.48 22.55 31.02 39.65 48.32 56.98 65.60 74.16 82.67 91.14 99.56 105.1 107.9 115.5 116.3 124.6 132.9 141.2 149.4
673.9 675.6 680.3 685.7 689.4 693.1 695.9 698.3 700.6 702.8 704.7 706.7 708.5 710.2 711.1 711.6 712.9 713.0 714.2 715.3 716.2 716.9
673.9 669.7 657.2 641.1 625.7 608.1 591.4 573.5 555.3 537.1 518.2 499.9 481.1 461.9 448.9 442.4 424.8 423.0 404.1 384.9 365.4 345.6
165.9 174.3
709.9 708.4
306.2 287.0
a
Per mole of monomeric units. bThermodynamic functions were extrapolated using the correlation between heat capacities for sulfuric lignin and lignin from ref 4
Table 3. Standard Energies and Enthalpies of Combustion and Formation for Lignin Samples (M(1) = 236.1 g·mol−1 and M(2) = 193.4 g·mol−1)
a
−Δcu°(298.15 K)
−Δcu°(298.15 K)a
−Δch°(298.15 K)
−ΔfHom(298.15 K)a,b
sample
kJ·g−1
kJ·g−1
kJ·g−1
kJ·mol−1
(C10H11.9O6.5)n (1) (C10H11.5O3.9)n (2)
22.74 ± 0.19 24.70 ± 0.02
22.88 ± 0.14 25.12 ± 0.09
22.87 ± 0.14 25.13 ± 0.09
236 ± 34 718 ± 18
Ash-free samples. bPer mole of monomeric units.
composition. The deviation of gases from ideality was not considered. The equilibrium compositions of the products of thermolysis for sulfuric and cuproammonium lignin at various temperatures, pressures, and various lignin/H2O/O2 initial ratios are presented in Figures 5 to 8 and Tables S5 to S11 of the SI. At T > 1200 K, the main components of the equilibrium mixture are hydrogen, carbon monoxide, and solid carbon (Figures 5 and 6 and Tables S5, S6, and S9, SI). However, when water and oxygen are added to the system, hydrogen and carbon monoxide become the main products (Figures 7 and 8 and Tables S7, S8, S10, and S11 of the SI). The maximum equilibrium yield (mole per kilogram of mixture) of the (CO + H2) fuel gas is reached when a significant amount of water is introduced into the reaction system (Figure 7 and Tables S7 and S10 of the SI). The thermogravimetric curve of the sulfuric lignin (Figure 9) demonstrated that the decomposition occurred above T = 470 K and the maximal decomposition rate was observed at T = 620 K. The residual sample mass at T = 870 K was about 0.45 of the initial mass that is close to the value estimated from the
Δr Gm,1 = −(543 ± 13) kJ ·mol−1 Δr Gm,2 = −(1614 ± 34) kJ ·mol−1
which means that these equilibria are almost completely shifted to the right side of the equations. If one assumes that the residual enthropy of lignin is about 20 J·K−1·mol−1, which is typical for similar polymers,16 then the Gibbs energy changes in the reactions will not significantly change: ΔrGm,1 = −(537 ± 13) kJ·mol−1, ΔrGm,2 = −(1608 ± 34) kJ·mol−1. We calculated the equilibrium compositions for the products of lignin thermolysis over the temperature range of (298 to 1700) K by the method of minimization of isobaric potential17 limiting the list of allowed products to the following components: CO(g), CO2(g), H2(g), CH4(g), H2O(g), O2(g), Cgraphite. The hydrogen and oxygen contents in the lignin monomeric units were rounded to integers. We suppose that such an assumption is acceptable in the considered analysis because of the uncertainty in the lignin structure and 1906
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Figure 5. Equilibrium compositions of pyrolysis for sulfuric lignin at P = 1 bar: ●, H2O; ◊, CO2; ▲, CH4; ×, C; ■, CO; △, H2.
Figure 8. Equilibrium composition of reaction mixture for the initial composition (sulfuric lignin/H2O/O2 = 1:1:2): ●, H2O; ◊, CO2; ▲, CH4; ×, C; ■, CO; △, H2. P = 1 bar, initial T = 300 K.
Figure 6. Equilibrium compositions of pyrolysis for sulfuric lignin at P = 30 bar: ●, H2O; ◊, CO2; ▲, CH4; ×, C; ■, CO; △, H2.
Figure 9. DSC (solid line, endo, down), TG (dashed line), and DTG (dash−dotted line) curves for sulfuric lignin.
Since the adiabatic pyrolysis temperature for the 1:6 mixture of lignin and water is 701 K, additional energy is required to heat the products to 1200 K, and their equilibrium conversion can be evaluated using the cycle: Figure 7. Equilibrium composition of reaction mixture for the initial composition sulfuric lignin/H2O = 1:6 at P = 1 bar: ●, H2O; ◊, CO2; ▲, CH4; ×, C; ■, CO; △, H2.
equilibrium composition of the mixture formed during thermolysis of sulfuric lignin equal to 0.40 of the initial mass (Figures 5 and 9 and Table S5 of the SI). The total energy required for heating of lignin from (470 to 870) K was estimated from the DSC curve to be 0.20 MJ·mol−1. The equilibrium compositions of the products of thermolysis for sulfuric lignin were calculated at the various lignin/H2O initial ratios. The maximal theoretical yield of fuel gas (CO + H2) can be reached at T > 1200 K and ratio C10H12O4/H2O = 1:6 (Figure 7 and Table S7 of the Supporting Information).
The reaction enthalpy ΔrH1 was determined from the cycle:
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Table 4. Adiabatic Temperatures of Conversion and Equilibrium Compositions for (C10H12O4)n−H2O−O2 Mixtures at the Initial T = 300 K and P = 1 bar lignin
H2O
1 1 1 1 1 1 1 1
1 6 1 1
−ΔcHomb
content in equilibrium mixturea
initial amount/moles O2
H2O
CO2
CH4
C
CO
H2
∑(CO+H2)
O2
Ta/K
1 2 2 5 11
1.777 2.339 5.351 1.400 0.8018 0.4493 2.811 4.808
0.934 1.191 2.282 1.492 1.134 0.6274 1.186 3.373
0.878 1.125 2.391 0.420 0.2025 0.1215 0 0
7.833 7.405 5.243 5.473 2.734 2.955 0 0
0.355 0.280 0.085 2.615 5.930 6.296 8.814 6.627
2.467 2.411 1.867 4.761 5.793 5.308 3.189 1.192
2.822 2.690 1.952 7.376 11.72 11.60 12.00 7.820
0 0 0 0 0 0 1.616·10−3 3.910
823 796 701 935 1011 1053 2640 3290
−ΔcHom(gas)c
−1
kJ·mol
−4484 −4479 −4457 −4382 −4317 −4326 −3266 −2164
kJ·mol−1 −1402 −1565 −2394 −2228 −3242 −3163 −3266 −2164
a Mole per mole of lignin monomeric units. bLower heating value for the equilibrium mixture per mole of lignin monomeric units. cLower heating value for the gaseous components of the equilibrium mixture per mole of lignin monomeric units.
ΔrH1 = ΔrH4 + ΔrH5 = 1024.7 + 603.9 = 1628.6 kJ per mole of lignin monomeric units. Therefore, the additional energy expenditure for obtaining the equilibrium mixture at T = 1200 K is ΔrH3 = ΔrH1 = 1628.6 kJ per mole of lignin monomeric units. So, the thermodynamically controlled conversion of lignin resulting in formation of the equilibrium mixture at T = 1200 K leads to the loss of 0.13 of the lower energy value compared to the lignin combustion. In technical realization of this process the energy consumed for heating of the initial mixture and the products can be partly recycled using the high-grade heat flow (0.13nH2O(g) + 0.08nCO2(g) + 0.10nCH4(g) + 9.70nCO(g) + 11.67nH2(g)). For example, the enthalpy change when the gas mixture is cooled from (1200 to 500) K is −475.1 kJ per mole of lignin monomeric units, and only 0.03 of the lower energy value is lost. The adiabatic temperature of lignin combustion in oxygen Ta = 3290 K is very high, and at this temperature water substantially dissociates into hydrogen and oxygen. It leads to the high content of oxygen in the equilibrium mixture (Table 4) and to decrease the total yield of combustible gases CO + H2. Among the studied initial compositions, the highest equilibrium yield of gases CO + H2 of (11.6 to 12.0) mole per mole of lignin monomeric units is reached when the oxygen content is (2 to 5) mole per 1 mole of lignin monomeric units (compositions 5 to 7 in Table 4). The processes with compositions 5 and 6 (Table 4) where the adiabatic temperatures are not too high (Ta < 1000 K) are technically preferable. The use of an excess of air as an oxidizer makes the lower energy value of the resulting mixture more positive.
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Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors acknowledge Ekaterina Abramovich from Research Institute for Physical Chemical Problems of Belarusian State University for help in TGA/DSC measurements.
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ASSOCIATED CONTENT
S Supporting Information *
Experimental heat capacity and thermodynamic functions for lignin samples (Tables S1 to S4); equilibrium compositions of mixtures of lignin pyrolysis and conversion with water (Tables S5 to S11). This material is available free of charge via the Internet at http://pubs.acs.org.
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REFERENCES
(1) Blunk, S. L.; Jenkins, B. M. Combustion properties of lignin residue from lignocellulose fermentation; University of California: Davis, CA, 2000. (2) Hatakeyama, H.; Kubota, K.; Nakano, J. Thermal analysis of lignin by differential scanning calorimetry. Cellulose Chem. Technol. 1972, 6, 521−529. (3) Hatakeyama, T.; Nakamura, K.; Hatakeyama, H. Studies on heat capacity of cellulose and lignin by differential scanning calorimetry. Polymer 1982, 23, 1801−1804. (4) Thermal properties of green polymers and biocomposites; Hatakeyama, T., Hatakeyama, H., Eds.; Kluwer Academic Publishers: New York, 2004. (5) Blokhin, A. V.; Voitkevich, O. V.; Kabo, G. J.; Paulechka, Y. U.; Shishonok, M. V.; Kabo, A. G.; Simirsky, V. V. Thermodynamic properties of plant biomass component. Heat capacity, combustion energy, and gasification equilibria of cellulose. J. Chem. Eng. Data 2011, 56, 3523−3531. (6) Khimiya tselulozy i yeyo sputnikov; Rogovin, Z. A., Shorygina, N. N., Eds.; Goskhimizdat: Moscow-Leningrad, USSR, 1953. (7) Komarov, F. P. Acetylation of lignin. Bum. Promst. 1934, 12, 30− 36. (8) USSR Standard GOST 3877-88. Petrochemicals. A Method of Sulfur Determination by Combustion in a Calorimetric Bomb; Standards Publishing House: Moscow, 1989; pp 5−8. (9) Pavese, F.; Malyshev, V. M. Routine measurements of specific heat capacity and thermal conductivity of high-Tc superconducting materials in the range 4−300 K using modular equipment. Adv. Cryog. Eng. 1994, 40, 119−124. (10) Blokhin, A. V.; Kabo, G. J.; Paulechka, Y. U. Thermodynamic properties of [C6mim][NTf2] in the condensed state. J. Chem. Eng. Data 2006, 51, 1377−1388. (11) Kabo, G. J.; Blokhin, A. V.; Kabo, A. G. Investigation of thermodynamic properties of organic substances. Chemical Problems of Creation of New Materials and Technologies; Ivashkevich, O. A., Ed.; Belarusian State University: Minsk, 2003; Vol. 1, pp 176−193. (12) Hubbard, W. N.; Scott, D. W.; Waddington, G. Experimental Thermochemistry; Interscience Publishers: New York, 1956. (13) Kelley, K. K.; Parks, G. S.; Huffman, H. M. A new method for extrapolating specific heat curves of organic compounds below the temperature of liquid air. J. Phys. Chem. 1929, 33, 1802−1805.
AUTHOR INFORMATION
Corresponding Author
*Tel.: +375-17-2003916. E-mail:
[email protected]. Funding
This work was financially supported by the Ministry of Education of the Republic of Belarus. 1908
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(14) Chase, M. W. NIST-JANAF Thermochemical Tables, 4th ed.; National Institute of Standards and Technology: Gaithersburg, MD, 1998. (15) Kislov, V. M.; Glazov, S. V.; Chervonnaya, N. A.; Patronova, L. I.; Salganskaya, M. V.; Manelis, G. B. Gasification of biomass in a hyperadiabatic heating mode of combustion. Khim. Tver. Topl. 2008, 3, 9−14. (16) Lebedev, B. V. Khimicheskaya Termodinamika Alifaticheskikh Polial’degidov I Al’degidov; Nizhny Novgorod State University: Nizhny Novgorod, Russia, 2001. (17) Thermochemistry and Equilibria of Organic Compounds; Frenkel, M., Ed.; VCH Publications: New York, 1993.
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dx.doi.org/10.1021/je2012814 | J. Chem. Eng. Data 2012, 57, 1903−1909
