Furfural offers a promising, rich platform for lignocellulosic biofuels. These include methylfuran and methyltetrahydrofuran, valerate esters, ethylfurfuryl and ethyltetrahydrofurfuryl ethers as well as various C(10)-C(15) coupling products. The various production routes are critically reviewed, and the needs for improvements are identified. Their relative industrial potential is analysed by defining an investment index and CO(2) emissions as well as determining the fuel properties for the resulting products. Finally, the most promising candidate, 2-methylfuran, was subjected to a road trial of 90,000 km in a gasoline blend. Importantly, the potential of the furfural platform relies heavily on the cost-competitive production of furfural from lignocellulosic feedstock. Conventional standalone and emerging coproduct processes-for example, as a coproduct of cellulosic ethanol, levulinic acid or hydroxymethyl furfural-are expensive and energetically demanding. Challenges and areas that need improvement are highlighted. In addition to providing a critical review of the literature, this paper also presents new results and analysis in this area.

Furfural—A Promising Platform for Lignocellulosic Biofuels

In this review article, we describe the use of commercially available polymeric ion-exchange resins for a range of industrially important transformations. Recent developments both on the materials design and applications will be described. Examples of high catalytic activity will be described in areas ranging from alkylation, transalkylation, isomerization, oligomerization, acylation, esterification and nitration. The two main classes of ion-exchange resins are based upon styrene-based sulfonic acids (Amberlyst® and Dow type resins), which show very high activity in the areas of esterification and etherification, to the perfluorosulfonic acid-based catalysts including the recently developed Nafion® resin/silica nanocomposites. These show very high activity in the area of linear alkyl benzene formation, isomerization, and some select acylation type chemistries. These new types of catalysts (which have been used commercially) are adding to the ever-growing portfolio of highly active solid acid catalysts, which couple both economic and environmental drivers to improve organic transformations within the chemical industry.

Solid acid catalysis using ion-exchange resins

https://escholarship.org/content/qt8dp8p847/qt8dp8p847.pdf?t=pbx3qn

Production of Fuels and Chemicals from Biomass: Condensation Reactions and Beyond

Esterification of free fatty acids in waste cooking oils (WCO): Role of ion-exchange resins

Lignocellulosic biomass is the most abundant organic carbon source and has received a great deal of interest as renewable and sustainable feedstock for the production of potential biofuels and value-added chemicals with a wide range of designed catalytic systems. However, those natural polymeric materials are composed of short-chain monomers (typically C6 and C5 sugars) and complex lignin molecules containing plenty of oxygen, resulting in products during the downstream processing having low-grade fuel properties or limited applications in organic syntheses. Accordingly, approaches to increase the carbon-chain length or carbon atom number have been developed as crucial catalytic routes for upgrading biomass into energy-intensive fuels and chemicals. The primary focus of this review is to systematically describe the recent examples on the selective synthesis of long-chain oxygenates via different C-C coupling catalytic processes, such as Aldol condensation, hydroalkylation/alkylation, oligomerization, keto...

Carbon-Increasing Catalytic Strategies for Upgrading Biomass into Energy-Intensive Fuels and Chemicals

Alkyl levulinates are biobased chemicals with a great number of applications and great biofuel potential for blending to conventional diesel or gasoline. The present work focuses on the liquid-phase synthesis of butyl levulinate (BL) by esterification of levulinic acid (LA) with 1-butanol (BuOH) using a set of acidic ion-exchange resins. Experiments were performed at 80 °C and 2.5 MPa in a batch reactor by using an initial molar ratio AL/BuOH of 1/3 and a catalyst loading of 0.8%. It has been found that BL could be successfully obtained over ion-exchange resins with a selectivity higher than 99.5%. LA conversions ranged from 64% (Amberlyst 46, macroreticular, surface sulfonated) to 94% (Dowex 50Wx2, gel-type resin, conventionally sulfonated) at 8 h reaction time. By comparing their catalytic behavior, it was seen that resins morphology plays a very important role in the synthesis of BL making easier the access of reactants to acid sites. Accessibility of LA and BuOH to acid centers was high over highly swollen and low polymer density resins. Thus, gel-type resins with low divinylbenzene (DVB) content have been found as the most suitable to produce BL, e.g. Dowex 50Wx2, Dowex 50Wx4 and Purolite ® CT224. Among them, Dowex 50Wx2 (2% DVB) is the most efficient catalyst tested.

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Esterification of levulinic acid with butanol over ion exchange resins

The liquid-phase addition of ethanol to isobutene to give ethyl tert-butyl ether (ETBE) on the ion exchange resin Lewatit K2631 has been studied. Rate data were obtained free of mass transfer influence in a continuous differential reactor operated at 1.6 MPa and 40--90 C, measuring steady-state conversions <10% for ethanol-isobutene and ethanol-isobutene-ETBE feeds. The reaction is highly temperature-sensitive. Isobutene has an enhancing effect on the rate whereas ethanol has an inhibitor one. Besides, low ETBE concentrations enhance the reaction but as chemical equilibrium is approached the ether shows an inhibitor effect, as expected. As alcohol-olefin-ether mixtures behave nonideally, kinetic analysis has been performed by using the UNIFAC liquid-phase activities of isobutene, ethanol, and ETBE. The best kinetic model stems from an Eley-Rideal mechanism in which the ethanol, adsorbed on one center, reacts with the isobutene from solution to give the ether adsorbed on one center. Surface reaction is the rate-limiting step. Two additional centers take part in this step.

Kinetics of the Liquid-Phase Synthesis of Ethyl tert-Butyl Ether (ETBE)

Thermally stable ion-exchange resins as catalysts for the liquid-phase dehydration of 1-pentanol to di-n-pentyl ether (DNPE)

Dimerization of 2-methyl-1-butene and 2-methyl-2-butene mixture using Amberlyst 35, Amberlyst 15, Amberjet 1500H, Purolite CT-175 and Purolite CT-275 as catalysts was carried out in a discontinuous stirred tank reactor at 353 K in methanol and ethanol presence in a molar ratio isoamylenes/alcohol = 9. Amberlyst 35 was found to be the most active resin. Alcohol presence appeared to improve the selectivity for diisoamylenes: no significant amounts of trimers, tetramers or cracking products were obtained in the studied conditions. Almost all the alcohol react in the first reaction stages to form ether. Both alcohols gave the same correlation between isoamylenes conversion and diisoamylenes selectivity: as conversion increases, selectivity increases, diisoamylenes yield and isoamylenes conversion being lower in ethanol than in methanol presence. 2,3,4,4-tetramethyl-1-hexene, 3,4,4,5-tetramethyl-2-hexene and 3,4,5,5-tetramethyl-2-hexene were the main dimers obtained.

Acid ion-exchange resins catalysts for the liquid-phase dimerization/etherification of isoamylenes in methanol or ethanol presence

The dehydration reaction of 1-pentanol to di-n-pentyl ether (DNPE) and water in the liquid phase was studied at 110–180 ◦ C and 1 MPa on sulfonic styrene–divinylbenzene (S/DVB) copolymers and the perfluoroalkanesulfonic resin NR50. S/DVB-based catalysts were macroreticular and gel-type resins both sulfonated conventionally and oversulfonated. Macroreticular resins tested include resins whose working phase in catalysis is gel phase (i.e. Amberlyst-15 and Amberlyst-35) and XN1010 whose working phase in catalysis is macropores surface. By comparing 1-pentanol conversion, selectivity to DNPE and initial reaction rates at 150 ◦ C it is concluded that gel-type S/DVB resins that swell moderately in the reaction medium, as CT-224, are the more suitable catalysts for the reaction. NR50, which is thermally stable up to 200 ◦ C, is the most selective catalyst tested but it is too much expensive for industrial use. Selectivity to DNPE decreases as temperature increases showing that side reaction of dehydration to 1-pentene is more sensitive to temperature. Apparent activation energies for the dehydration reaction of 1-pentanol to DNPE were found to be about 100 kJ/mol. © 2002 Elsevier Science B.V. All rights reserved.

Carles Fité

Papers

Esterification of levulinic acid with butanol over ion exchange resins

Kinetics of the Liquid-Phase Synthesis of Ethyl tert-Butyl Ether (ETBE)

Thermally stable ion-exchange resins as catalysts for the liquid-phase dehydration of 1-pentanol to di-n-pentyl ether (DNPE)

Acid ion-exchange resins catalysts for the liquid-phase dimerization/etherification of isoamylenes in methanol or ethanol presence

Dehydration of 1-pentanol to di-n-pentyl ether over ion-exchange resin catalysts