Unsaturated Furan Research Articles

Biomass substrate-derived graphene-like N-doped porous carbon nanosheet-supported PtCo nanocatalyst for efficient and selective hydrogenation of unsaturated furanic aldehydes

Unsaturated furanic aldehydes are derived from lignocellulosic biomass resources and subsequently used to produce valuable chemicals. However, the highly efficient, selective hydrogenation of the biomass-derived unsaturated furan CO bond remains challenging. Here we report that graphene-like nitrogen doped porous carbon (GNPC) nanosheets are synthesized from carbon-rich, sustainable, and renewable biomass precursors (glucose, fructose and 5-hydroxymethylfurfural, HMF) with high surface areas, large pore volumes and narrow mesopores. GNPC derived from HMF is an excellent catalyst support for PtCo nanoparticles with ultrafine nanoparticles size and homogeneous distributions. This catalyst is highly efficient for hydrogenation of biomass-derived furan-based unsaturated aldehydes, with high yields, to the corresponding unsaturated alcohols under mild conditions. This design strategy should further allow the development of selective, simple, green heterogeneous catalysts for challenging chemical transformations.

Development of a reduced n-heptane/toluene/unsaturated furans-PAH reaction mechanism for dual-fuel engine applications

Furan, 2-methylfuran (MF) and 2,5-dimethylfuran (DMF) have gathered much attention in the research community. However, the reaction chemistry of the three unsaturated furans for the internal combustion engine (ICE) simulations remains scarce. Therefore, a reduced five-component reaction mechanism contains furan, MF, DMF, n-heptane and toluene was proposed for dual-fuel engine applications in present research. First, a detailed reaction mechanism for furanic fuels was reduced under a wide range of enginelike conditions by using combined reduction methods. Second, the reduced mechanism of furanic fuels was combined with an existing n-heptane/toluene mechanism containing the formation of polycyclic aromatic hydrocarbon (PAH) up to C16 to construct a combined mechanism. Third, the combined mechanism were optimized by adjusting the reaction rate constants of some significant reactions and the newly proposed reduced n-heptane/toluene/unsaturated furans-PAH mechanism comprising 98 species taking part in 253 reactions. Subsequently, the proposed mechanism was compared and evaluated with experimental measurements of ignition delay times and species mole fractions acquired from published papers. Meanwhile, new dual-fuel engine experiments were performed in a single-cylinder diesel engine, the experimental results were also used to validate the proposed mechanism. Overall, the predicted results obtained by this proposed n-heptane/toluene/unsaturated furans-PAH mechanism are in reasonable agreement with the available experimental data.

Catalyst structure-based hydroxymethylfurfural (HMF) hydrogenation mechanisms, activity and selectivity over Ni

Catalytic hydrodeoxygenation of hydroxymethylfurfural was investigated in a three-phase batch reactor over a range of reaction temperatures (170–230 °C), under 5 MPa of hydrogen, and tetrahydrofuran solvent. Nickel-based carbon-supported catalysts were also promoted by lanthanum and niobium, despite promoters alone demonstrated no activity. Based on experimentally-obtained liquid products, a reaction pathway was proposed and a microkinetic model was established, by considering adsorption, desorption and surface reaction kinetics, mass transfer and thermodynamics. An unpromoted Ni/C resulted in primarily unsaturated furan diol, a highly desirable intermediate in the polymer industry. As reaction temperatures increased > 200 °C, dehydration yielded deoxygenated products suitable for solvents and biofuel. In spite of enhancements to reducibility, La-promotion significantly decreased both hydrogenation (8-times) and deoxygenation (25-times) rate constants. Alternatively, Nb-incorporation offered additional acidity, while lower activation energies resulted in 200% higher deoxygenation rates via dehydration reactions and humin formation at lower temperatures. It exhibited the highest deoxygenation activity.

Development of a Highly Compact and Robust Chemical Reaction Mechanism for Unsaturated Furan Oxidation in Internal Combustion Engines via a Multiobjective Genetic Algorithm and Generalized Polynomial Chaos

This work focuses on the development of a highly compact and robust chemical reaction mechanism for unsaturated furan oxidation in internal combustion engines. Recently, furans have gathered much a...

Molybdenum Oxide-Modified Iridium Catalysts for Selective Production of Renewable Oils for Jet and Diesel Fuels and Lubricants

Supported inverse metal–metal oxide catalysts have received significant research interest owing to their effective hydrodeoxygenation (HDO) activity toward biomass substrates, but the high cost of the reported catalysts poses a challenge for commercialization. We present the synthesis of a series of metal–metal oxide catalysts, Ir–MOx/SiO2 (M = Re, Mo, W, V, or Nb) and M′–MoOx/SiO2 (M = Rh, Ru, Pt, or Pd) and their HDO performance on multifuran (high carbon) substrates to produce renewable jet and diesel fuels and lubricant base oils. A MoOx-modified Ir/SiO2 catalyst with a Mo/Ir ratio of 0.13 (Ir–MoOx/SiO2) exhibits the highest product yield (78–96%) under mild reaction conditions. Controlled experiments using probe substrates reveal that furan ring hydrogenation and C–O hydrogenolysis of saturated and unsaturated furan rings occur in a sequential manner. The carbon atom adjacent to the furan or saturated furan ring of substrates or intermediate compounds undergoes slow C–C bond scission, resulting in a ...

Production of deoxygenated high carbon number hydrocarbons from furan condensates: Hydrodeoxygenation of biomass-based oxygenates

Two-step hydrodeoxygenation of furan trimers using supported Ni catalysts was successfully performed by substituting expensive noble metal catalysts for hydrodeoxygenation, which can contribute to the development of feasible hydrodeoxygenation processes with which to prepare high-carbon-number hydrocarbon fuels. Although more cracking of hydrocarbon products was observed for the Ni catalysts, the substitution of noble metal catalysts with Ni catalysts was successful, leading to good HDO activity. The combination of the first step of Ni/CeO2 (hydrogenation) and the second step of Ni/tungstated zirconia (hydrodeoxygenation) led to complete deoxygenation, achieving 87.8% of the theoretical maximum yield of the oil phase product, which is slightly lower than the value of 91.1% for the combination of the first step of Pd/C (hydrogenation) and Ru/tungstated zirconia (hydrodeoxygenation). The roles of first-step hydrogenation were revealed as the hydrogenation of unsaturated furan rings and the hydrolysis of saturated furan rings.

Two-step continuous upgrading of sawdust pyrolysis oil to deoxygenated hydrocarbons using hydrotreating and hydrodeoxygenating catalysts

The two-step hydrodeoxygenation of pine sawdust pyrolysis oil, or bio-oil, is performed using pairs of first-step hydrotreating and second-step hydrodeoxygenating catalysts. The reaction results demonstrate that the combination of hydrotreating carbon-supported 5wt% Pd (5wt% Pd/C) and hydrodeoxygenating tungstate-zirconia-supported 3wt% Ru (3wt% Ru/WZr) catalysts produced the highest yield of oil products and the lowest yield of cokes and tars. The hydrodeoxygenated liquid products are further analyzed using FT-IR, which indicates the removal of carbonyls and hydroxyls along with an increase of methyls. The roles of hydrotreating Pd/C are further studied using GC/MS results of the hydrotreated liquid products; these results indicate that the hydrogenation of carbonyls to alcohols and the saturation of furans occur during the first step of the hydrotreating process. The removal of carbonyls and unsaturated furans can suppress their strong adsorption to noble metal surfaces and then their carbonization to cokes.

Ignition characteristics of saturated and unsaturated furans

Ignition characteristics of saturated and unsaturated furans

Ignition characteristics of a bio-derived class of saturated and unsaturated furans for engine applications

Ignition characteristics in the form of derived cetane numbers (DCN) of (hydro) furanic species are investigated experimentally in an Ignition Quality Tester. Further, quantum chemistry calculations at CBS-QB3 level of theory are applied to determine bond dissociation energies (BDEs) and thereby suggest the initial reactions of the ignition process for all of these fuels. Using the calculated BDEs, it is found that the ignition characteristics are similar among furans and among tetrahydrofurans, but strongly differ between these molecular classes. It is shown that the ignition behavior of aromatic furans is determined by the ring structure, which correlates with a negligible side chain influence. Hence, furan fuel structures can be chosen with respect to feasibility of the production pathways and engine compatibility. On the contrary, the side chain length for tetrahydrofurans defines the potential application paradigm. Tetrahydrofurans with short side chains are candidates for SI application, whereas 2-butyltetrahydrofuran may be a candidate for diesel application. The influence of the number and location of double bonds in the ring is illustrated with the additional study of dihydrofurans, and the influence of other functional groups is evaluated for (tetrahydro) furfuryl alcohols.To investigate possible fuel application scenarios, a second part of this study investigates DCNs of furanic fuel blends in n-heptane and diesel fuel. A DCN mixing rule is found to be approximately linear and for blends with up to 20mol% furans, the side chain structure (alkyl, alcohol) has no distinct influence on the blend DCN.

Comparison of Catalytic Characteristics of Biomass Derivates with Different Structures Over ZSM-5

The conversion of three major biomass derivates was conducted in a quartz tubular fixed bed reactor over a ZSM-5 catalyst. As the model compounds of polyols, saturated furans and unsaturated furans, ethylene glycol (EG), tetrahydrofuran (THF) and furan were pyrolyzed to find out the influence of chemical structure on the catalytic characteristics. The effect of pyrolysis temperature (400 ∼ 650 °C), weight hourly space velocity (2.9 ∼ 15.5 h−1) and partial pressure (2.12 ∼ 20.49 Torr) on the feed conversion, product yield and selectivity were investigated. The hydrogen to carbon effective ratio (H/Ceff) was referred to, to analyze the capacity of biomass derivates being converted to chemicals (olefins and aromatics). The results showed that the existence of rings and C=C had great effect on the catalytic characteristics. The conversion of furan was much lower (mainly less than 60 %) than that of EG and TH,F which were close to 100 %. It was also found that the chemical yield of THF was slightly more than that of EG, which can be attributed to its relative higher H/Ceff of 1.5. Furan produced the highest coke yield, which was more than 15 %, whereas that of EG and THF was only around 5 %. The serious coking of furan led to the lowest chemical yield, which was less than 35 %. This study paves a way for the mechanism study on catalytic characteristics of biomass-derived feedstocks over zeolite catalysts.

Does Tetrahydrofuran Ring Open upon Ionization and Dissociation? A TPES and TPEPICO Investigation

The threshold photoelectron spectrum (TPES) of tetrahydrofuran (THF) is compared to that of the unsaturated furan molecule. In general, there is a similarity in the orbital ionization profile for the two species, though unlike furan, THF exhibits (modest) vibrational detail only in the (9b)(-1) X (2)B band. An adiabatic ionization energy of 9.445 +/- 0.010 eV has been derived from the onset of the TPES spectrum. Threshold photoelectron photoion coincidence spectroscopy was used to explore the loss of a hydrogen atom from ionized THF over the photon energy range of 9.9-10.4 eV. RRKM fitting of the resulting breakdown curves yields an E(0) of 0.85 +/- 0.03 eV (82 +/- 3 kJ mol(-1)) (AE = 10.30 +/- 0.04 eV). If the G3 IE of 9.48 eV is used to convert the experimental data from photon energy to THF ion internal energy, E(0) = 0.81 +/- 0.01 eV (78 +/- 1 kJ mol(-1)). The latter value is closer to the G3 E(0) of 72 kJ mol(-1) for the formation of the cyclic ion 1. A variety of ring-opening reactions were also probed at the B3-LYP/6-31+G(d) and G3 levels of theory. The distonic isomer (*)CH(2)CH(2)CH(2)OCH(2)(+) lies 70 kJ mol(-1) higher than ionized THF, which places it within 1 kJ mol(-1) of the threshold for the dissociation to 1. All of the probed H-loss products from the distonic isomer (which includes singlet and triplet species) lie significantly higher in energy than ion 1, eliminating the possibility that ionized THF dissociates to m/z 71 via a ring-opening reaction in the present experiment. The derived Delta(double dagger)S value for the dissociation, 8 +/- 5 J K(-1) mol(-1), is also consistent with the formation of 1. The experimentally derived E(0) values can be used to derive the Delta(f)H(o)(0) for ion 1. Together with the Delta(f)H(o)(0) values for the THF ion (752.0 +/- 2 kJ mol(-1), derived from the neutral Delta(f)H(o)(0) of -154.9 +/- 0.7 kJ mol(-1) and experimental IE of 9.445 +/- 0.010 eV) and H atom (218.5 kJ mol(-1)) our E(0) of 82 +/- 3 kJ mol(-1) yields a Delta(f)H(o)(0) for ion 1 of 620 +/- 4 kJ mol(-1) (Delta(f)H(o)(298) = 594 +/- 4 kJ mol(-1)), in good agreement with the G3 Delta(f)H(o)(0) of 621 kJ mol(-1). Appearance energies for all fragment ions up to photon energies of 34 eV are also reported and discussed in comparison with the available literature.

Iterative Synthesis of Fused Oligofurans

The authors present an elegant three-step sequence to append fused furan rings onto the olefin of unsaturated furan systems. The sequence can then be repeated, eventually arriving at highly symmetric oligomeric polyfurans. The sequence of reactions, which is performed on both sides of the symmetric molecule concurrently, consists of a copper-catalyzed cyclopropanation using ethyl diazoacetate, followed by reduction of the resultant ester to the primary alcohol which is then oxidized using IBX. The oxidation presumably results in the formation of an aldehyde which then undergoes an immediate rearrangement to the furan system. The authors describe the intermediate as having a ”push-pull" substitution pattern on the cyclopropane, with the electrons of the furan forcing to open the cyclopropane followed by back-attack via the oxygen atom of the enolate providing the furan product.

Design, synthesis and evaluation of furanocoumarin monomers as inhibitors of CYP3A4

A number of furanocoumarins isolated from grapefruit juice have been found to inhibit CYP3A4 activity in vitro. In this study, we have designed and synthesised a range of analogues based on bergamottin to investigate the relationship between chemical structure and inhibition of CYP3A4 activity. Studies were performed using human liver microsomes and human intestinal S9 fraction, with testosterone as the marker substrate. With the exception of the coumarin and phenolic furanocoumarin derivatives, which were inactive, the alkyloxy-furanocoumarin analogues were found to inhibit CYP3A4 activity in a dose dependent manner, with observed IC50 values ranging from 0.13 +/- 0.03 to 49.3 +/- 1.9 microM. The unsaturated furan derivatives were found to exhibit time-dependent inhibition, showing a 2-, 4- and 14-fold increase in potency for 6',7'-epoxybergamottin, 6',7'-dihydroxybergamottin and bergamottin, respectively after a preincubation period of ten minutes. Reduction of the furan moiety resulted in an 11-fold decrease in inhibitory potency, suggesting that this functional group is key to the interaction between these compounds and CYP3A4.

Modular Mo-based catalysts for efficient asymmetric olefin metathesis. Catalytic enantioselective synthesis of cyclic ethers and acetals

Chiral Mo-based complexes 1– 3 promote the catalytic enantioselective ring-closing metathesis of various polyenes to afford unsaturated furans, pyrans and siloxanes efficiently and in high ee (70–98% ee). The structural modularity of this class of chiral catalysts plays a critical role in these studies. Modification of the diolate or imido moities of these chiral catalysts gives rise to a range of complexes that can be screened for higher reactivity and/or enantioselectivity.

Hydrosilylation of unsaturated (hetero)aromatic aldehydes and related compounds catalyzed by transition metal complexes

[Rh(COD)CI] 2 has been found to be a more active catalyst than Ir, Ru, Pt and Pd complexes for the hydrosilylation of unsaturated furan and aromatic aldehydes with HSiEt 3. 1,4- and 1,2-addition reactions giving unsaturated silyl ethers in cis- and trans-configurations occurred as well as the hydrogenation reactions which produce the corresponding saturated silyl ethers. The migration of the ethyl group was observed in the hydrosilylation of 3-ethyl-3-(5-nitrofuryl)acrolein. The dehydrogenative silylation occurred in the reactions of cinnamyl alcohol and furan-2-acrylic acid.

Fatty acids : XVIII. Gas-liquid chromatographic behaviour of unsaturated furan esters

Fatty acids : XVIII. Gas-liquid chromatographic behaviour of unsaturated furan esters