Decarbonylation of furfural over oxide catalysts

Gas chromatography has been used to investigate the products accompanying tetrahydrofuran prepared by hydrogenation of furan, without isolating the latter pure from the gas mixture obtained by decarbonylating furfural over oxide catalysts. A number of unknown impurities accompanying tetrahydrofuran and furan, are identified. It is found that tetrahydrofuran contains isopropanol, along with furan,-methylfuran, and-methyltetrahydrofuran. Furan itself contains-methylfuran, and a number of unknown impurities, among them acetone. Ethane is found among the gaseous products of decarbonylation. Thus over Zn and Mn oxide catalysts there is joint hydrogenolysis of the furan ring, and ring opening at positions 1–5 and 3–4.     

Antiknock properties of furfural derivatives

Preparative amounts of furfuryl alcohol ethers and furfural acetals were prepared from renewable vegetable raw materials. The blending reseach octane numbers of mixing of furan derivatives in straight-run gasoline were estimated: butyl furfuryl ether, 97.8 ± 7; propyl furfuryl ether, 112 ± 6; furfural diethyl acetal, 105 ± 6, furfural ethylene glycol acetal, 108 ± 7; furfurylamine, 194 ± 4. These results demonstrate prospects for using furan derivatives as available biofuels.     

Transformations of heterocyclic compounds on membrane catalysts

The transformations of furan, -methylfuran, furfural, and 2,3-dihydrofuran on a palladium — nickel membrane catalyst at 50–300°C under conditions of diffusion of hydrogen through the catalyst were investigated. Under these conditions furan is hydrogenated to tetrahydrofuran in quantitative yield. Considerable amounts of furan, the hydrogenation of which in the presence of the above-named derivatives is inhibited, are detected in the catalyzate along with hydrogenation products in the transformations of -methylfuran, furfural, and 2,3-dihydrofuran.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 599–601, May, 1975.     

Self-aggregation of liquids from biomass in aqueous solution

Aggregation of several chemicals from biomass: furfural derived compounds (furfural, 5-methylfurfural, furfuryl alcohol and tetrahydrofurfuryl alcohol), lactate derived compounds (methyl lactate, ethyl lactate and butyl lactate), acrylate derived compound (methyl acrylate) and levulinate compounds (methyl levulinate, ethyl levulinate and butyl levulinate) in aqueous solution has been characterised at T = 298.15 K through density, ρ, speed of sound, u, and isentropic compressibilities, κ_S, measurements. In addition the standard Gibbs free energies of aggregation have been also calculated. Furthermore, in order to deepen insight the behaviour of these chemicals in aqueous solution, the solubility of these compounds has been measured at T = 298.15 K.     

Methylthiofurane: Herstellung und Reaktionen

Preparation and Reactions of Methylthiofurans By lithiation of 3,4-dimethoxyfuran, 2-methylfuran and furan, followed by reaction with dimethyldisulfide, the methylthiofurans 2, 8 , and 10 have been prepared. Reaction of 8 with maleic anhydride has yielded 6-methyl-3-(methylthio)phthalic anhydride ( 9 ), a yellow substance with a strong greenish fluorescence, obviously formed by elimination of H₂O from an unstable cycloadduct. An analgous reaction of 2 resulted in an unexpected mixture from which the following yellow compounds were isolated: 3-hydroxy-4,5-dimethoxy-6-(methylthio)phthalic anhydride ( 3 ), 4-hydroxy-5-methoxy-3,6-bis(methylthio)phthalic anhydride ( 4 ), and bis(S-methyl) (2Z,4E,6Z)-2,3,6,7-tetramethoxy-4,5-bis(methylthio)-2,4,6-octatrienethioate ( 5 ). Compound 5 is also formed on standing of 2 at RT. Mild acid hydrolysis of 2 results in ring-opening accompanied by an intramolecular oxido-reduction to yield S-methyl(3Z)-3-methoxy-4-(methylthio)-2-oxo-3-butenethioate ( 6a ). The structures of compounds 5 and 6a have been determined by X-ray analysis.     

Reaction of furan compounds with hydrogen peroxide in the presence of vanadium catalysts

The reactions of furan and a number of its derivatives (furfural, furan-2-carboxylic acid, 2-furfuryl alcohol, and others), in systems containing H₂O₂ and vanadium compounds, proceed through a mechanism of radical hydoxylation of the furan ring with the formation of 5-hydroxy-2(5H)-furanone and maleic acid. The total yield and ratio of the synthesized compounds depend on the reaction conditions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1462–1467, November, 1991.     

A mass spectrometric study of substituted furfuryl compounds

The mass spectra of six furfuryl compounds — namely, furfuryl alcohol, 5-furfuryl-furfuryl alcohol, difurfuryl ether, difurylmethane, 2,5-difurfurylfuran, and 4-furfuryl-2-pentenoic acid-γ-lactone — have been studied. Their fragmentation mechanisms are discussed in detail with particular emphasis on the modes that lead to the formation of aromatic fragments. The majority of the fragment ions are formed by elimination of CO and C₂H₂ from even-electron precursor ions and HCO from odd-electron precursor ions. Molecules containing two furan rings linked by a methylene group give mass spectra that exhibit large abundances of aromatic fragment ions.     

Hydrogenolysis of Furfuryl Alcohol to 1,2-Pentanediol Over Supported Ruthenium Catalysts

Hydrogenolysis of the furan rings of furfural and furfuryl alcohol, which can be obtained from biomass, has attracted attention as a method for obtaining valuable chemicals such as 1,2-pentanediol. In this study, we examined the hydrogenolysis of furfuryl alcohol to 1,2-pentanediol over Pd/C, Pt/C, Rh/C, and various supported Ru catalysts in several solvents. In particular, we investigated the effects of combinations of solvents and supports on the reaction outcome. Of all the tested combinations, Ru/MgO in water gave the best selectivity for 1,2-pentanediol: with this catalyst, 42 % selectivity for 1,2-pentanediol was achieved upon hydrogenolysis of furfuryl alcohol for 1 h at 463 K. In contrast, reaction in water in the presence of Ru/Al₂O₃ afforded cyclopentanone and cyclopentanol by means of hydrogenation and rearrangement reactions.     

Donor-Acceptor Complexes in Copolymerization. XXXVI. Alternating Diene-Dienophile Copolymers. 4. Copolymerization of Furan and 2-Methylfuran with Maleic Anhydride

Abstract

The copolymerization of furan and 2-methylfuran with maleic anhydride in the presence of a radical catalyst yields equimolar, alternating copolymers in which the furan units have a 2,5-linkage (NMR and IR). The copolymerization appears to have a floor temperature of about 40°C. The furan-maleic anhydride Diels-Alder adduct polymerizes in solution in the presence of a radical catalyst at temperatures above 60°C to yield the identical copolymer as is obtained from the monomers. The adduct undergoes a retrograde reaction above 60°C to regenerate the monomers which then copolymerize through excitation of the ground state comonomer charge transfer complex.     

Furan compounds

By reductive amination, starting from furfural, 5-methylfurfural, β-(2-furyl)acrolein, and monoethanolamine, we have obtained N-furfurylaminoethanol, N-(5-methyl-2-furfuryl)aminoethanol, and N-[1-(α-furyl)-3-propyl]aminoethanol. By reductive amination combined with the subsequent hydrogenation of the furan ring we have obtained N-tetrahydrofurfurylaminoethanol and N-(5-methyltetrahydro-2-furfuryl)aminoethanol.     

Selective conversion of furfuryl alcohol to 2-methylfuran over nanosilica supported Au:Pd bimetallic catalysts at room temperature

Using gold and palladium supported catalysts, the selective hydrogenation of furfuryl alcohol into 2-methylfuran at 25 °C was examined. The use of 2-methylfuran has become applicable in the perfumery and personalised care product industry, and it has been shown that there are two conditions under which Au:Pd/SiO₂ catalysts are successful for selectivity to 2-methylfuran at 25 °C and (1 bar, H₂). Moreover, this study has shed light on the effectiveness of several reaction conditions (supports and catalyst amount).     

PHOTOCOPOLYMERIZATION OF MALEIC ANHYDRIDE AND VINYL ACETATE IN TETRAHYDROFURAN~*

The copolymerization of maleic anhydride and vinyl acetate in tetrahydrofuran was studied. Results show that the maximum copolymerization rate is in 0.6 mole fraction of maleic anhydride, indicating the involvement of maleic anhydride-tetrahydrofuran charge transfer complex in the chain initiation process. ESR study provides collateral evidence for the formation of maleic anhydride radical and tetrahydrofuran radical.     

Syntheses based on 5-methylfurfural

Conclusions A series of derivatives of furan and tetrahydrofuran were synthesized on the basis of 5-methylfurfural: alkyl(5-methylfuryl)carbinols, alkyl(5-methyltetrahydrofuryl)carbinols, 2-methyl-5-alkenylfurans, 2-methyl-5-alkylfurans, and 2-methyl-5-alkyltetrahydrofurans.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 1829–1831, October 1966.     

Characterization of Extra-framework Cations in Zeolites. A temperature-programmed desorption (TPD) study

We have investigated the interaction of a few 5-ring organic compounds (cyclopentane, cyclopentene, furan, 2-methylfuran, 2,5-dihydrofuran and tetrahydrofuran) with alkali-metal cation-exchanged faujasites (LSX, X and Y types) by means of temperature-programmed desorption (TPD). The desorption behavior at higher temperatures of all probe molecules on the sodium ion containing faujasites with different Si/Al ratios reflects the higher cation content of zeolites with greater aluminum content. Only the desorption profiles of tetrahydrofuran and 2,5-dihydrofuran show, depending on the kind of cation, additional desorption features at higher temperatures. Using a regularization method, desorption energy distribution functions for furan and tetrahydrofuran were calculated. The calculated desorption energy distributions clearly illustrate the very different adsorption behavior of furan and tetrahydrofuran which leads to large differences in the binding energies between the corresponding adsorption complexes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reaction of 4-R-2-phenyltetrahydrobenzo[b]pyrylium and 9-R-sym-octahydroxanthylium salts with furfural and related compounds

The condensation of furfural, 5-methylfurfural, and 2-thiophenecarbaldehyde with 4-R-2-phenyltetrahydrobenzo[b]pyrylium and 9-R-sym-octahydroxanthylium salts was studied. Condensation conditions under which acidophobic aldehydes of the furan series do not undergo resinification were found. 8-Furfurylidene and 8-thenylidene derivatives of 4-R-2-phenyltetrahydrobenzo[b]pyrylium and bisfurfurylidene and bisthenylidene derivatives of 9-R-sym-octahydroxanthylium salts were obtained for the first time. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1160–1165, August, 2008.     

Cu(111)面上糠醇加氢生成2-甲基呋喃的反应机理

采用广义梯度近似的密度泛函理论并结合平板模型的方法,详细研究了糠醇在Cu(111)面上反应生成2-甲基呋喃的反应历程,优化了糠醇在Cu(111)面的吸附模型,并采用完全线性同步和二次同步变换的方法,对三种可能的反应机理中的各反应步骤进行了过渡态搜索.结果表明,糠醇主要通过支链上OH与Cu(111)面相互作用,易形成ψCH2和ψCH2O中间体(ψ代表呋喃环).糠醇进一步加氢机理很可能为:引入的氢物种明显降低了糠醇分解形成的中间体ψCH2的活化能,并促进了它的形成;中间体ψCH2更易从糠醇中获得H而生成2-甲基呋喃.该过程的控速步骤为ψCH2O*→ψCHO*+H*,活化能为199.0kJ/mol,总反应是2ψCH2OH=ψCH3+ψCHO+H2O.     

Coffee aroma—Statistical analysis of compositional data

Solid-phase microextraction in headspace mode coupled with gas chromatography-mass spectrometry was applied to the determination of volatile compounds in 30 commercially available coffee samples. In order to differentiate and characterize Arabica and Robusta coffee, six major volatile compounds (acetic acid, 2-methylpyrazine, furfural, 2-furfuryl alcohol, 2,6-dimethylpyrazine, 5-methylfurfural) were chosen as the most relevant markers. Cluster analysis and principal component analysis (PCA) were applied to the raw chromatographic data and data processed by centred logratio transformation.     

沉淀剂对CuZnAl催化剂糠醛气相加氢制糠醇选择性的影响

采用共沉淀法制得分别以NaOH、Na_2CO_3和Na_2CO_3/NaOH为沉淀剂的CuZnAl-1、CuZnAl-2和CuZnAl-3催化剂,采用X射线衍射(XRD)、N2吸附-脱附、H_2-程序升温还原(H_2-TPR)、热重和NH_3-程序升温脱附(NH3-TPD)等方法对催化剂进行了表征,并在固定床反应器上研究了沉淀剂对CuZnAl催化剂糠醛气相加氢制糠醇选择性的影响。结果表明,糠醛加氢在三种催化剂上均有较高转化率,而CuZnAl-3催化剂对糠醇有较高选择性。沉淀剂对CuZnAl催化剂的物相结构、比表面积、酸性和氧化还原性均有较大影响。以Na_2CO_3/NaOH为沉淀剂得到的CuZnAl-3催化剂具有适宜的比表面积、CuO晶相、较弱的酸性位,且表面CuO易于还原,这些因素有利于催化反应生成糠醇。CuZnAl-3催化剂上糠醛气相加氢制糠醇优化工艺参数为:常压、反应温度180℃、氢醛物质的量比为5∶1、糠醛体积空速0.3h~(-1);糠醛转化率为99.4%,糠醇选择性为98.3%。     

Furan compounds

By reductive amination, starting from furfural, 5-methylfurfural, -(2-furyl)acrolein, and monoethanolamine, we have obtained N-furfurylaminoethanol, N-(5-methyl-2-furfuryl)aminoethanol, and N-[1-(-furyl)-3-propyl]aminoethanol. By reductive amination combined with the subsequent hydrogenation of the furan ring we have obtained N-tetrahydrofurfurylaminoethanol and N-(5-methyltetrahydro-2-furfuryl)aminoethanol.For part XXXIII, see [1].     

Reactions of furan derivatives with aliphatic carbonyl compounds in acid medium

Sixteen new derivatives of the furan and of the 1,1-difurylmethane series were synthesized by the reactions of furan, 2-methylfuran, 2-(3′-acetoxypropyl)furan, 2-(3′-butyl)furan, 1-cyclopropyl-2-αfurylcyclopropane, and 1,1-difurylethane with saturated and α, β-unsaturated aliphatic carbonyl compounds in acid medium.