Chemorheological analysis and model-free kinetics of acid catalysed furfuryl alcohol polymerization

The complete curing of furfuryl alcohol (FA), was studied by chemorheological analysis and model-free kinetics under isothermal and non-isothermal modes. Polymerization of FA under acidic catalysis involves complex reactions, with several steps (such as condensations and Diels-Alder cycloadditions). To account for the polymerization complexity, kinetic analysis of DSC data was performed with a model-free isoconversional method. The obtained E(alpha)-dependencies were closely-correlated with the variation of complex viscosity during curing. Linear condensations are predominant during the early curing stage and are followed by two distinct stages of branching cycloadditions. Gelation and vitrification, identified by rheometric measurements, were associated with a decrease of the overall reaction rate that becomes controlled by diffusion of small oligomers. Before vitrification, the rate of crosslinking is limited by the mobility of longer polymer chains and diffusion encounters a large energy barrier due to the cooperative nature of the motions, leading to higher E(alpha) values.     

Kinetics of homopolycondensation of furfuryl alcohol

The kinetic features of the homopolycondensation of furfuryl alcohol in an aqueous medium in the presence of acids of different strengths have been studied. The second order of the reaction with respect to the monomer has been established. A kinetic scheme of the polycondensation reaction has been proposed, and the activation parameters of the process have been calculated.     

The acid-catalyzed polycondensation of furfuryl alcohol: Old puzzles unravelled

This paper describes mechanistic studies aimed at understanding the origin of two important side events accompanying the linear polycondensation of furfuryl alcohol in acidic media. The first process concerns the formation of conjugated sequences along the polymeric chains. The use of model monomers and compounds simulating the structure of the linear polymer provided for the first time a full understanding of the reactions leading to multiple unsaturations. The main culprits for this process are the labile hydrogen atoms on the methylene moiteties bridging the furan rings. The second anomaly in these systems concerns the formation of networks following a complex branching mechanism. Again, model structures helped to pinpoint the origin of this process and to propose plausible reactions to describe it.     

Polycondensation kinetics of orthosilicic acid in a hydrothermal solution

The polycondensation kinetics of orthosilicic acid in hydrothermal solutions was studied experimentally at different temperatures, pH, and ionic strengths. As a result of the mathematical processing of experimental data, equations approximating the time dependence of the polycondensation process and the dependence of the polycondensation rate constant on the solution ionic strength were obtained. Experimental data on the kinetics of the reverse process of dissolving colloidal silica were obtained at different temperatures and pH.     

Kinetics of furfuryl alcohol polymerisation by iodine in methylene dichloride

The kinetic studies of furfuryl alcohol polymerisation by iodine in methylene dichloride showed a pseudo-first-order behaviour in monomer. The pseudo-first-order constant obtained varies linearly with the concentration of iodine. Our previous work on the system concluded for a pseudo-cationic polymerisation mechanism based on the admission of non-ionic propagating species. The good fitting among the experimental monomer concentration data and the one obtained from computer simulation justifies the mechanism proposed for the system. The set of estimated values of the rate parameters is also reported.     

Conformers, infrared spectrum and UV-induced photochemistry of matrix-isolated furfuryl alcohol

The infrared spectra of furfuryl alcohol (2-furanmethanol, FFA) were investigated for FFA monomers isolated in low-temperature argon matrices. The structural interpretation of the obtained experimental spectra was assisted by analysis of the molecule's conformational landscape. According to the DFT(B3LYP)/6-311++G(d,p) calculations, five different minimum energy structures were found on the potential energy surface of the molecule. They can be defined by the orientation of the OCCO and CCOH dihedral angles: GG', GG, TG, TT, GT (G = +gauche, G' = -gauche, T = trans) and have a symmetry equivalent configuration: GG' = G'G, GG = G'G', TG = TG', GT = G'T. When zero-point energies are taken into account, only three (GG', GG, and TT) out of the five unique minima correspond to stable structures. The most stable conformer GG' (OCCO, 72.7°; CCOH, -59.3°), which in gas phase at room temperature accounts for ～65% of the total population, was the only form isolated in the argon matrices at 14 K. The other two relevant forms convert into conformer GG' during matrix deposition. The low temperature glassy and crystalline states of FFA were also obtained and their infrared spectra assigned, suggesting the sole existence of the GG' conformer also in these phases. The photochemical behavior of FFA induced in situ, by tunable UV-laser, was also studied. The longest wavelength resulting in photochemical changes in the structure of the irradiated sample was found to be λ = 229 nm. Such UV irradiation of the matrix-isolated FFA led to production of formaldehyde and different isomeric C(4)H(4)O species. Cycloprop-2-ene-1-carbaldehyde and buta-2,3-dienal (two conformers) are the main initial C(4)H(4)O photoproducts formed upon short-time excitation at λ = 229 nm. But-3-ynal (two conformers) was the principal photoproduct resulting from prolonged excitation at λ= 229 nm, being consumed upon irradiation at shorter wavelengths (λ < 227.5 nm). Vinyl ketene is produced from FFA in the trans conformation and undergoes isomerization to the cis form upon irradiation at λ < 227.5 nm. Cyclopropene, propyne, allene, and CO were also identified in the irradiated matrices (in particular at the later stages of irradiation), suggesting that the photoproduced aldehydes partially decarbonylate during the performed photochemical experiments.     

Functionalized nanocarbon materials as catalysts for the ethanolysis of furfuryl alcohol

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New insights on the thermal degradation pathways of neat poly(furfuryl alcohol) and poly(furfuryl alcohol)/SiO2 hybrid materials

Poly(furfuryl alcohol)/SiO₂ hybrid material was prepared and properties characterized in comparison with those of neat poly(furfuryl alcohol) (PFA) thermoset. A morphological study conducted by transmission electron microscopy (TEM) on the hybrid material reveals well-dispersed silica nanoclusters. Combination of micro- and submicro-structural organizations between the organic and inorganic networks generates new thermo-mechanical performances. A study of relaxation process by dynamic mechanical analysis (DMA) gives some evidence of the nanoconfinement effect on the hybrid network. These restrictions on the molecular mobility lead to an increase of thermal stability of the PFA/SiO₂ material compared to the unfilled matrix. Thermogravimetric analyses (TGAs) coupled with GC-MS have permitted us to highlight a multi-step degradation pathway and chain scission reactions are proposed based on identified VOCs.     

Properties of solutions formed by water, furfuryl alcohol, and poly(ethylene glycol) (10) isooctyl phenol ether

Original measuring cell was used to study the electrical conductivity, viscosity, and light transmission of the ternary system constituted by water, furfuryl alcohol, and OP-10 foaming agent at 20°C. The optical characteristics of the solutions and formation of emulsions and liquid-crystalline phases were examined.     

NiB/SiO2非晶态合金催化剂用于糠醇加氢制四氢糠醇的研究

用化学镀方法制备了负载型NiB/SiO2非晶态合金催化剂,并采用ICP、BET、TEM、XRD等手段研究了NiB在SiO2表面的存在状态及非晶性质。研究了糠醇在该催化剂上加氢制备四氢糠醇的反应行为,考察了反应温度、压力、搅拌速度等因素对催化剂性能的影响。结果表明,在2.0MPa、120℃、550r/min时,糠醇的转化率在99％以上,四氢糠醇的选择性可达100％。在此条件下和骨架Ni的催化性能相当。     

Study of the γ-alumina polymerization of furfuryl alcohol

The γ-alumina polymerization of furfuryl alcohol produces a polymer differing in structure from that obtained by polymerization with acid catalysts. In order to gain a better understanding of the basic chemistry of this method of polymerization furfuryl alcohol, studies were done, both with γ-alumina-polymerized and acid-polymerized furfuryl alcohol resins, concerning both the chemical nature of the resin constituents, and the manner in which these constituents affect resin molecular size distribution as measured by gel permeation chromatography. Because of numerous side reactions, the γ-alumina polymerization of furfuryl alcohol was found to result in the early elimination of many of the molecules containing functional groups necessary to the sustenance of polymerization. As a consequence even at advanced degrees of polymerization there remain relatively large amounts of low molecular weight components that have not further polymerized. At the higher degrees of polymerization, the high molecular weight end of the resin molecular size distribution was observed to be significantly enhanced over that of the acid-polymerized resins. The latter behavior is attributed to the occurrence of crosslinking reactions made possible by the higher temperature required for polymerization with γ-alumina. It is further concluded that the curing processes of γ-alumina-polymerized furfuryl alcohol resins proceed by a mechanism unlike that of the acid-polymerized resins.     

Molar excess volumes of furfuryl alcohol and aromatic hydrocarbons at 25°C

Molar excess volumes of mixing V^E for binary mixtures of furfuryl alcohol with the aromatic hydrocarbons benzene, toluene, ethylbenzene, and o-, m-, and p-xylene were determined for the entire composition range at 25°C. V^E was negative for the mixtures containing benzene, toluene and pxylene but positive for mixtures containing ethylbenzene and o- and m-xylene. The results are discussed in terms of specific interaction present in the binary mixture and are compared with those previously reported for tetrahydrofuran, fur an or furfural binary mixtures with aromatic hydrocarbons.     

Efficient valorization of biomass-derived furfuryl alcohol to butyl levulinate using a facile lignin-based carbonaceous acid

Research on Chemical Intermediates - The preparation and application of biorenewable carbon-based catalyst are attracting increasingly attention in the field of green and sustainable chemistry....     

反相高效液相色谱法测定糠酸、糠醇和糠醛

提出了反相高效液相色谱法（HPLC）同时测定糠酸、糠醇和糠醛的新方法,采用C18色谱柱,流动相为V（乙腈）：V（水）=50：50,流速为1.0 mL/min;检测波长为220 nm;柱温为25℃.在4 min内可以将3种组分完全分离.糠酸、糠醇、糠醛检出限（S/N=3）分别为：0.101、0.042、0.406 mg/L.平均回收率分别为101.4%、98.5%、95.3%.相对标准偏差（RSD）分别为0.87%、0.66%、0.43%.     

Polycondensation Stoichiometry

Some examples demonstrate the feasibility of interpreting the results of polycondensation from stoichiometry. Utilizing only the consequences of stoichiometric principles, it is possible to draw conclusions of the basic principles of forming polymers in the polycondensation process and to substantiate the physical meaning of a number of averaged values used during calculations. The results confirm the relationships found earlier by means of other methods and make it possible to draw significant conclusions with respect to the character of the process and the peculiarities of the products obtained.     

Polycondensation equilibrium and the kinetics of the catalyzed transesterfication in the formation of polyethylene terephthalate

The polycondensation equilibrium constant for bis(β-hydroxyethyl) terephthalate was found to be 0.50. By means of this value for determining the relative reactivity of two kinds of hydroxyl groups, the kinetic data were found to fit a third-order reaction for the transesterification: one order each with respect to hydroxyl group, methoxy group, and catalyst. An order with respect to hydroxyl group, which had previously been in doubt, was proved in a series of experiments in which the concentration of ethylene glycol was varied. Third-order rate constants were determined for the reactions catalyzed by lead, zinc, and calcium salts, and the activation energies were found to be 12.5, 15.0, and 14.5 kcal./mole, respectively. The results are consistent with the author's theory of aromatic transition states and are difficult to explain on the basis of ionic theories of reaction mechanism.