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1.
We report the relationships between the degradation behaviors (i.e. the degradation kinetics, degradation activation energy, weight loss conversion, and char formation) and the structure features in three modified novolac resins bearing different curable functional groups and aromatic units i.e. Carbonyl phenyl azo novolac resin (CPAN), 4-(4-hydroxyphenyl azo) benzyl ester novolac resin (HPDEN) and Carbonyl phenyl 4-(4-hydroxyphenyl azo) benzyl ester novolac resin (CHABN). These modifications enhanced the thermal stability of the cured novolac resins by delaying the decomposition temperature up to 30-100 °C and produced prominent residue char yield up to 68% (CPAN), 56% (HPDEN) and 64% (CHABN), respectively. The two heavily cross-linked samples, CPAN and CHABN displayed even higher Ea than HPDEN. All modified novolacs displayed much higher decomposition activation energy (over 237 KJ/mol*K) compared with the generic phenolic (PN).  相似文献   

2.
Gasification uses steam increases H2 content in the syngas. Kinetics of gasification process can be improved by using K2CO3 catalyst. Controlled heating rate in pyrolysis step determines the pore size of charcoal that affects yield gas and H2 and CO content in the syngas. In previous research, pyrolisis step was performed without considering heating rate in pyrolysis step. This experiment was performed by catalytic steam gasification using lignite char from pyrolysis with controlled heating rate intended to produce maximum yield of syngas with mole ratio of H2/CO ≈ 2. Slow heating rate (3 °C/min) until 850 °C in the pyrolysis step has resulted in largest surface area of char. This study was performed by feeding Indonesian lignite char particles and K2CO3 catalyst into a fixed bed reactor with variation of steam/char mole ratio (2.2; 2.9; 4.0) and gasification temperature (750 °C, 825 °C, and 900 °C). Highest ratio of H2/CO (1.682) was obtained at 750 °C and steam/char ratio 2.2. Largest gas yield obtained from this study was 0.504 mol/g of char at 900 °C and steam/char ratio 2.9. Optimum condition for syngas production was at 750 °C and steam/char mole ratio 2.2 with gas yield 0.353 mol/g of char and H2/CO ratio 1.682.  相似文献   

3.
A polymeric blend has been prepared using urea formaldehyde (UF) and epoxy (DGEBA) resin in 1:1 mass ratio. The thermal degradation of UF/epoxy resin blend (UFE) was investigated by using thermogravimetric analyses (TGA), coupled with FTIR and MS. The results of TGA revealed that the pyrolysis process can be divided into three stages: drying process, fast thermal decomposition and cracking of the sample. There were no solid products except ash content for UFE during combustion at high temperature. The total mass loss during pyrolysis at 775 °C is found to be 97.32%, while 54.14% of the original mass was lost in the second stage between 225 °C and 400 °C. It is observed that the activation energy of the second stage degradation during combustion (6.23 × 10−4 J mol−1) is more than that of pyrolysis (5.89 × 10−4 J mol−1). The emissions of CO2, CO, H2O, HCN, HNCO, and NH3 are identified during thermal degradation of UFE.  相似文献   

4.
Solubilities of l -glutamic acid, 3-nitrobenzoic acid, p -toluic acid, calcium-l -lactate, calcium gluconate, magnesium- dl -aspartate, and magnesium- l -lactate in water were determined in the temperature range 278 K to 343 K. The apparent molar enthalpies of solution at T =  298.15 K as derived from these solubilities areΔsolHm (l -glutamic acid,msat =  0.0565 mol · kg  1)  =  30.2 kJ · mol  1,ΔsolHm (3-nitrobenzoic acid, m =  0.0188 mol · kg  1)  =  28.1 kJ · mol  1, ΔsolHm( p - toluic acid, m =  0.00267 mol · kg  1)  =  23.9 kJ · mol  1,ΔsolHm (calcium- l -lactate tetrahydrate,m =  0.2902 mol · kg  1)  =  25.8 kJ · mol  1,ΔsolHm (calcium gluconate, m =  0.0806 mol · kg  1)  =  22.1 kJ · mol  1, ΔsolHm(magnesium-dl -aspartate tetrahydrate, m =  0.1469 mol · kg  1)  =  11.5 kJ · mol  1, andΔsolHm (magnesium- l -lactate trihydrate,m =  0.3462 mol · kg  1)  =  3.81 kJ · mol  1.  相似文献   

5.
Chiral copper(II) complexes of secondary bisamines derived from 1,2-diaminocyclohexane were successfully used in the diastereoselective nitroaldol reaction. The reactions were carried out in the presence of 10 mol % of the Cu(II) complex and 7.7 mol % of i-Pr2NEt in 2-propanol at ?30 °C. Good to excellent yields, enantioselectivities of up to 99%, and moderate to excellent diastereoselectivities were obtained for both aromatic or aliphatic aldehydes and various prochiral nitrocompounds forming the corresponding β-nitroalcohols with two contiguous stereocenters.  相似文献   

6.
The coupling of propiolic acid with aryl iodides afforded the aryl alkynyl carboxylic acids and aryl alkynes in generally good yields. Aryl alkynyl carboxylic acids were obtained when the reaction was performed in the presence of Pd(PPh3)2Cl2 (2.5 mol %), dppb (5.0 mol %) and DBU (5 equiv) at 50 °C. For the synthesis of the terminal aryl alkynes, the reaction was conducted in the presence of Pd(PPh3)2Cl2 (2.5 mol %), dppb (5.0 mol %), DBU (5.0 equiv), and Cu(acac)2 (10 mol %) at 25 °C for 5 h, and further reacted at 60 °C for 6 h.  相似文献   

7.
A heat-flow Calvet microcalorimeter was adapted for the measurement of sublimation enthalpies by the vacuum-drop method, with samples of masses in the range 1 mg to 5 mg. The electrically calibrated apparatus was tested by determining the enthalpies of sublimation of benzoic acid and ferrocene, at T =  298.15 K. The obtained results, ΔcrgHmo(C7H6O2)  =  (88.3  ±  0.5)kJ · mol  1and ΔcrgHmo(C10H10Fe) =  (73.3  ±  0.1)kJ · mol  1, are in excellent agreement with the corresponding values recommended in the literature. Subsequent application of the apparatus to the determination of the enthalpy of sublimation of η5-bis-pentamethylcyclopentadyenyl iron, at T =  298.15 K, led to ΔcrgHmo(C20H30Fe)  =  (96.8  ±  0.6)kJ · mol  1.  相似文献   

8.
Heat capacity of platinic acid, hydrogen hexahydroxyplatinate(IV)H2Pt(OH)6 , was measured from T =  7 K toT =  310 K by means of adiabatic calorimetry. The standard entropy and the standard Gibbs energy of formation of platinic acid in the crystalline state were determined to be 176.5  ±  3.6 J · K  1· mol  1and   988.8  ±  3.8 kJ · mol  1, respectively.  相似文献   

9.
The gas release properties and char structural evolution during the pyrolysis of cotton stalk were investigated. The evolution characteristics of volatile products were examined by pyrolysis–Fourier transform infrared spectroscopy (FTIR)/thermal conductivity detection (TCD) analysis (Py–FTIR/TCD). The char chemical structure and physical characteristics were investigated by means of FTIR and N2 physisorption techniques. Evolution characteristics of the main volatile products were given. The evolution of CO2 was approximately 26 °C earlier than that of CO. CH4 evolution covered over a wider temperature range of 300–600 °C, with a maximum at 394 °C. The amount of hydroxyl, aliphatic CH and olefinic CC bonds in the char decreased significantly above 250 °C. The aromatization process started at ≈350 °C and continued to higher temperatures, leaving the char enriched with condensed aromatic ring systems. The BET surface area increased continually with increasing temperature to reach a maximum value of 4.68 m2/g at 500 °C and decreased at higher temperatures. The micropore volume showed a similar behavior to the surface area, while the mesopore volume and total pore volume always increased.  相似文献   

10.
Electrochemical lithium intercalation within graphite from 1 mol dm 3 solution of LiClO4 in propylene carbonate (PC) was investigated at 25 and − 15 °C. Lithium ions were intercalated into and de-intercalated from graphite reversibly at − 15 °C despite the use of pure PC as the solvent. However, ceaseless solvent decomposition and intense exfoliation of graphene layers occurred at 25 °C. The results of the Raman spectroscopic analysis indicated that the interaction between PC molecules and lithium ions became weaker at − 15 °C by chemical exchange effects, which suggested that the thermodynamic stability of the solvated lithium ions was an important factor that determined the formation of a solid electrolyte interface (SEI) in PC-based solutions. Charge–discharge analysis revealed that the nature of the SEI formed at − 15 °C in 1 mol dm 3 of LiClO4 in PC was significantly different from that formed at 25 °C in 1 mol dm 3 of LiClO4 in PC containing vinylene carbonate, 3.27 mol kg 1 of LiClO4 in PC, and 1 mol dm 3 of LiClO4 in ethylene carbonate.  相似文献   

11.
The present investigation describes the preparation of nano-SiO2-phenolic novolac resin nanocomposite through in situ polymerisation. CP MAS 13C NMR and FTIR analyses indicate the formation of chemical linkage between the inorganic and organic components. The decomposition temperature of the nanocomposite is ∼70 °C higher than the neat phenolic resin. The char content of the nanocomposite at any intermediate temperature is higher than that of neat resin. The limiting oxygen index value of the neat resin is 38 whereas it is 43 for the nanocomposite. So, the nanocomposite possesses excellent flame retardant property. Both the nanocomposite and the neat resin were isothermally pyrolysed and the products were separated and identified using GC–MS. The decomposition product analysis shows a difference in the decomposition product distribution. This variation is discussed in the light of the proposed structure for the SiO2-phenolic nanocomposite.  相似文献   

12.
The solubility of anthracene was measured in pure water and in sodium chloride aqueous solution (salt concentration, m/mol · kg?1 = 0.1006, 0.5056, and 0.6082) at temperatures between (278 and 333) K. Solubility of anthracene in pure water agrees fairly well with values reported in earlier similar studies. Solubility of anthracene in sodium chloride aqueous solutions ranged from (6 · 10?8 to 143 · 10?8) mol · kg?1. Sodium chloride had a salting-out effect on the solubility of anthracene. The salting-out coefficients did not vary significantly with temperature over the range studied. The average salting-out coefficient for anthracene was 0.256 kg · mol?1.The standard molar Gibbs free energies, ΔtrG°, enthalpies, ΔtrH°, and entropies, ΔtrS°, for the transfer of anthracene from pure water to sodium chloride aqueous solutions were also estimated. Most of the estimated ΔtrG° values were positive [(20 to 1230) J · mol?1]. The analysis of the thermodynamic parameters shows that the transfer of anthracene from pure water to sodium chloride aqueous solution is thermodynamically unfavorable, and that this unfavorable condition is caused by a decrease in entropy.  相似文献   

13.
This paper is part of a project which studies pyrolysis as an alternative for recycling printed circuit board (PCB); the sample (2.0 cm × 2.0 cm) was pyrolyzed under nitrogen atmosphere, at 300, 400, 500, 600 and 700 °C in a tubular type oven, maintaining 30 min, and during the pyrolysis process the organic part is decomposed to pyro-oils and pyro-gases, which can be used as fuels or chemical material resources: the solid residues of about 75–80 wt.%, liquid yields of ∼9.0 wt.% and gas yields of 12–14 wt.%. No significant influence of temperature was observed over 500 °C, however, there was certainly influence under 500 °C in both volatile substance. The pyro-oils have fairly high gross calorific values (∼30 kJ/kg), mainly with aromatic and with oxygenated compounds. The pyro-gas is very rich in CO, CO2, H2, CH4 and in small part of O2; after being purged it can be combusted for the pyrolysis self-sustain. The tensile strength decreases about 35% at 773 K, while the impact and tear strength increases above 773 K, and then decreases along with the temperature increase. The strength changes can offer guidance for used as a replacement for virgin fibres in SMC manufacture. The residues are better laminated can be easily liberated for metals recovery.  相似文献   

14.
A calorimetric and thermodynamic investigation of two alkali-metal uranyl molybdates with general composition A2[(UO2)2(MoO4)O2], where A = K and Rb, was performed. Both phases were synthesized by solid-state sintering of a mixture of potassium or rubidium nitrate, molybdenum (VI) oxide and gamma-uranium (VI) oxide at high temperatures. The synthetic products were characterised by X-ray powder diffraction and X-ray fluorescence methods. The enthalpy of formation of K2[(UO2)2(MoO4)O2] was determined using HF-solution calorimetry giving ΔfH° (T = 298 K, K2[(UO2)2(MoO4)O2], cr) = −(4018 ± 8) kJ · mol−1. The low-temperature heat capacity, Ср°, was measured using adiabatic calorimetry from T = (7 to 335) K for K2[(UO2)2(MoO4)O2] and from T = (7 to 326) K for Rb2[(UO2)2(MoO4)O2]. Using these Ср° values, the third law entropy at T = 298.15 K, S°, is calculated as (374 ± 1) J · K−1 · mol−1 for K2[(UO2)2(MoO4)O2] and (390 ± 1) J · K−1 · mol−1 for Rb2[(UO2)2(MoO4)O2]. These new experimental results, together with literature data, are used to calculate the Gibbs energy of formation, ΔfG°, for both phases giving: ΔfG° (T = 298 K, K2[(UO2)2(MoO4)O2], cr) = (−3747 ± 8) kJ · mol−1 and ΔfG° (T = 298 K, Rb2[(UO2)2(MoO4)], cr) = −3736 ± 5 kJ · mol−1. Smoothed Ср°(Т) values between 0 K and 320 K are presented, along with values for S° and the functions [H°(T)  H°(0)] and [G°(T)  H°(0)], for both phases. The stability behaviour of various solid phases and solution complexes in the (K2MoO4 + UO3 + H2O) system with and without CO2 at T = 298 K was investigated by thermodynamic model calculations using the Gibbs energy minimisation approach.  相似文献   

15.
Preliminary tests of the chlorination of two iron oxides (wüstite and hematite) in various chlorinating gas mixtures were performed by thermogravimetric analysis (TGA) under non-isothermal conditions. Wüstite started to react with chlorine from about 200 °C generating ferric chloride and hematite as the final reaction products. The presence of a reducing and oxidizing agent in the chlorinating gas mixtures influenced the chlorination reactions of both iron oxides, during non-isothermal treatment, only at temperatures higher than 500 °C.The chlorination kinetics of hematite with Cl2 have been studied in details between 600 and 1025 °C under isothermal chlorination. The values of the apparent activation energy (Ea) were about 180 and 75 kJ/mol in the temperature ranges of 600–875 and 875–1025 °C, respectively. The apparent reaction order with respect to Cl2 was found to be 0.67 at 750 °C. Mathematical model fitting of the kinetics data was carried out to determine the most probable reaction mechanisms.  相似文献   

16.
In this paper, we explore the copper/palladium-cocatalyzed cross-coupling reactions of 1-aryl-2-trimethylsilylethynes with aryl iodides, bromides, and chlorides as coupling partners, to furnish unsymmetrically disubstituted ethynes in moderate to excellent yields. Various aryl iodides were subjected to reaction under the optimized conditions with 5 mol % of Pd(PPh3)2 and 50 mol % of CuCl. The steric properties of the aryl iodide proved more influential to the outcome of the cross-coupling reaction than electronic factors. In addition, we succeeded in synthesizing unsymmetrical diarylethynes using two different aryl iodides in one-pot. Furthermore, under the same reaction conditions with 10 mol % of PdCl2, 40 mol % of P(4-FC6H4)3, and 50 mol % of CuCl as catalyst, we succeeded in synthesizing unsymmetrical diarylethynes from various aryl bromides. Finally, we explored reactions with aryl chlorides and duly discovered that unsymmetrical diarylethynes were obtainable in moderate to good yields when 10 mol % of Pd(OAc)2, 10 mol % of (?)-DIOP, and 10 mol % of CuCl were used. These reactions proceed through a direct activation of a carbon–silicon bond in alkynylsilanes by CuCl to generate the corresponding alkynylcopper species via transmetalation from silicon to copper. Mechanistic investigations on the reaction of alkynylsilanes with aryl bromides confirmed that the trimethylsilyl bromide generated in situ retarded both transmetalation steps between CuCl and alkynylsilane, and between palladium(II) species formed by oxidative addition and alkynylcopper species.  相似文献   

17.
Heat capacities of 2,2-dimethyl-1,3-propanediol(CH3)2C(CH2OH)2 were measured in the temperature range between T =  13 K and T =  350 K using an adiabatic calorimeter. The compound underwent a first-order phase transition at T =  (314.5  ±  0.1) K. The enthalpy and the entropy of transition were (12.52  ±  0.02)kJ · mol  1and (39.81  ±  0.08)J · K  1· mol  1, respectively. Measurement of the fusion peak by d.s.c. showed that the purity of the sample was 0.9999 mass fraction and the entropy of fusion was 9.9 J · K  1· mol  1. Another first-order phase transition was observed at T =  (60.4  ±  0.1) K with the associated entropy change of (2.93  ±  0.05)J · K  1· mol  1. Heat capacities of two deuterated samples,(CH3)2C(CH2OD)2 and(CD3)2C(CD2OD)2 , were also measured and the results were compared with those on the natural compound. Possible mechanisms of the transition have been discussed from the isotope effects on the thermodynamic quantities associated with the transition. Standard thermodynamic functions of the compounds are tabulated.  相似文献   

18.
Low-temperature calorimetric measurements have been performed on DyBr3(s) in the temperature range (5.5 to 420 K ) and on DyI3(s) from T=4 K to T=420 K. The data reveal enhanced heat capacities below T=10 K, consisting of a magnetic and an electronic contribution. From the experimental data on DyBr3(s) a C0p,m (298.15 K) of (102.2±0.2) J·K−1·mol−1 and a value for {S0m (298.15 K)  S0m (5.5 K)} of (205.5±0.5) J·K−1·mol−1, have been obtained. For DyI3(s), {S0m (298.15 K)  S0m (4 K)} and C0p,m (298.15 K) have been determined as (226.9±0.5) J·K−1·mol−1 and (103.4±0.2) J·K−1·mol−1, respectively. The values for {S0m (5.5 K)  S0m (0)} for DyBr3(s) and {S0m (4 K)  S0m (0)} for DyI3(s) have been calculated, giving S0m (298.15 K)=(212.3±0.9) J·K−1·mol−1 in case of DyBr3(s) and S0m (298.15 K) =(233.1±0.7) J·K−1·mol−1 for DyI3(s). The high-temperature enthalpy increment has been measured for DyBr3(s) in the temperature range (525 to 799 K) and for DyI3(s) in the temperature range (525 to 627 K). From the results obtained and enthalpies of formation from the literature, thermodynamic functions for DyBr3(s) and DyI3(s) have been calculated from T→0 to their melting temperatures at 1151.0 K and 1251.5 K, respectively.  相似文献   

19.
Vapour pressures of water over saturated solutions of cesium chloride, cesium bromide, cesium nitrate, cesium sulfate, cesium formate, and cesium oxalate were determined as a function of temperature. These vapour pressures were used to evaluate the water activities, osmotic coefficients and molar enthalpies of vapourization. Molar enthalpies of solution of cesium chloride, ΔsolHm(T = 295.73 K; m = 0.0622 mol · kg−1) = (17.83 ± 0.50) kJ · mol−1; cesium bromide, ΔsolHm(T = 293.99 K; m = 0.0238 mol · kg−1) = (26.91 ± 0.59) kJ · mol−1; cesium nitrate, ΔsolHm(T = 294.68 K; m = 0.0258 mol · kg−1) = (37.1 ± 2.3) kJ · mol−1; cesium sulfate, ΔsolHm(T = 296.43 K; m = 0.0284 mol · kg−1) = (16.94 ± 0.43) kJ · mol−1; cesium formate, ΔsolHm(T = 295.64 K; m = 0.0283 mol · kg−1) = (11.10 ± 0.26) kJ · mol−1 and ΔsolHm(T = 292.64 K; m = 0.0577 mol · kg−1) = (11.56 ± 0.56) kJ · mol−1; and cesium oxalate, ΔsolHm(T = 291.34 K; m = 0.0143 mol · kg−1) = (22.07 ± 0.16) kJ · mol−1 were determined calorimetrically. The purity of the chemicals was generally greater than 0.99 mass fraction, except for HCOOCs and (COOCs)2 where purities were approximately 0.95 and 0.97 mass fraction, respectively. The uncertainties are one standard deviations.  相似文献   

20.
The complex cis-Pt(Ph3Ge)2(PMe2Ph)2 underwent smooth isomerization to give the trans-isomer at room temperature via an associative five-coordinated intermediate. Thermodynamic parameters and activation energy for the cis to trans isomerization were obtained, ΔH# = 105 kJ mol−1, ΔS# = 12.5 J mol−1 K−1, and Ea = 107 kJ mol−1, respectively. Heating of trans-Pt(Ph3Ge)2(PMe2Ph)2 at 50 °C for 36 days produced trans-PtPh(Ph3Ge)(PMe2Ph)2 followed by the formation of trans-PtPh2(PMe2Ph)2, Pt(PMe2Ph)4, and Ph4Ge finally via elimination of the phenyl group from Ph3Ge ligand with liberation of the Ph2Ge unit and subsequent reductive elimination of the remaining Ph3Ge ligand at 80 °C for 1 month.  相似文献   

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