Jesse Q. Bond

Integrated Catalytic Conversion of γ-Valerolactone to Liquid Alkenes for Transportation Fuels

Lactic Fuels In the quest to find sustainable alternatives to petrochemicals, a small cyclic ester, γ-valerolactone, derived from cellulose offers promising raw material. Bond et al. (p. 1110) show that carbon dioxide can be catalytically excised from the lactone efficiently at high pressure, leaving a mixture of butanes. In a second-stage reactor, the butanes can be strung together to form heavier hydrocarbons similar to those found in automotive and jet fuels. The method simultaneously yields fuel and a relatively pure stream of pressurized carbon dioxide amenable to sequestration or further chemical modification. A biomass-derived compound is transformed into hydrocarbon fuels and a CO2 stream amenable to sequestration. Efficient synthesis of renewable fuels remains a challenging and important line of research. We report a strategy by which aqueous solutions of γ-valerolactone (GVL), produced from biomass-derived carbohydrates, can be converted to liquid alkenes in the molecular weight range appropriate for transportation fuels by an integrated catalytic system that does not require an external source of hydrogen. The GVL feed undergoes decarboxylation at elevated pressures (e.g., 36 bar) over a silica/alumina catalyst to produce a gas stream composed of equimolar amounts of butene and carbon dioxide. This stream is fed directly to an oligomerization reactor containing an acid catalyst (e.g., H ZSM-5, Amberlyst-70), which couples butene monomers to form condensable alkenes with molecular weights that can be targeted for gasoline and/or jet fuel applications. The effluent gaseous stream of CO2 at elevated pressure can potentially be captured and then treated or sequestered to mitigate greenhouse gas emissions from the process.

Production of renewable jet fuel range alkanes and commodity chemicals from integrated catalytic processing of biomass

This article presents results from experimental studies and techno-economic analysis of a catalytic process for the conversion of whole biomass into drop-in aviation fuels with maximal carbon yields. The combined research areas highlighted include biomass pretreatment, carbohydrate hydrolysis and dehydration, and catalytic upgrading of platform chemicals. The technology centers on first producing furfural and levulinic acid from five- and six-carbon sugars present in hardwoods and subsequently upgrading these two platforms into a mixture of branched, linear, and cyclic alkanes of molecular weight ranges appropriate for use in the aviation sector. Maximum selectivities observed in laboratory studies suggest that, with efficient interstage separations and product recovery, hemicellulose sugars can be incorporated into aviation fuels at roughly 80% carbon yield, while carbon yields to aviation fuels from cellulose-based sugars are on the order of 50%. The use of lignocellulose-derived feedstocks rather than commercially sourced model compounds in process integration provided important insights into the effects of impurity carryover and additionally highlights the need for stable catalytic materials for aqueous phase processing, efficient interstage separations, and intensified processing strategies. In its current state, the proposed technology is expected to deliver jet fuel-range liquid hydrocarbons for a minimum selling price of

Production of Biofuels from Cellulose and Corn Stover Using Alkylphenol Solvents

4.75 per gallon assuming nth commercial plant that produces 38 million gallons liquid fuels per year with a net present value of the 20 year biorefinery set to zero. Future improvements in this technology, including replacing precious metal catalysts by base metal catalysts and improving the recyclability of water streams, can reduce this cost to

γ-Valerolactone Ring-Opening and Decarboxylation over SiO2/Al2O3 in the Presence of Water

2.88 per gallon.

Oxidation of levulinic acid for the production of maleic anhydride: breathing new life into biochemicals

Technically viable and economic conversion of lignocellulosic biomass into chemicals and fuels is an important challenge. One effective strategy is to first partially remove oxygen to produce reactive intermediates, denoted as platform molecules, followed by conversion of these molecules into desired products. These platform molecules have fewer functional groups than carbohydrates in biomass (e.g. , xylose, glucose), offering the potential for selective catalytic upgrading processes. One such platform molecule, which is receiving considerable attention in the literature, is levulinic acid (LA). From LA a variety of fuels and chemicals can be made, such as valeric acid esters, methyltetrahydrofuran (MTHF), and LA esters and ketals. Another valuable product is g-valerolactone (GVL), obtained from the reduction of LA. GVL can be used directly as a fuel additive, or as a precursor for fuels and chemicals. It is possible to achieve LA yields greater than 50 % by using aqueous solutions of sulfuric acid for cellulose deconstruction; 12] however, the commercial production of LA and its derivatives presents serious challenges. First, LA must be separated from the mineral acid to recycle the acid catalyst and avoid negative effects in downstream processes. Second, LA is produced in a low concentration, and its purification/recovery is expensive. Finally, the solvents normally used (e.g. , water) have lower boiling points than LA, which means that to recover the product by distillation the solvent needs to be evaporated. In this Communication, we show that alkylphenol solvents (i.e. , substituted benzene compounds containing a hydroxyl group and alkyl groups, R ; see Figure 1) can be used to selectively extract LA from aqueous solutions of sulfuric acid, thereby eliminating the previously mentioned drawbacks. In addition, alkylphenol solvents extract GVL from water with a higher partition coefficient compared to LA. Accordingly, the GVL concentration in the alkylphenol solvent can be increased by the conversion of LA to GVL combined with the recycle of this stream for successive extractions, thus facilitating recovery of GVL from the solvent by distillation. Importantly, we show that a carbon-supported Ru–Sn catalyst can be used for the selective reduction of LA to GVL by H2 in the presence of alkylphenols, without hydrogenation of the solvent. Finally, the aqueous phase containing sulfuric acid after extraction of LA by the alkylphenol solvent can be recycled for subsequent cycles of cellulose deconstruction, providing an effective strategy for sulfuric acid management in the process. An advantage of using alkylphenol solvents is that the alkyl groups strongly modify the physical properties of the solvent. For example, while phenol is relatively soluble in water, the presence of a longer alkyl chain increases the hydrophobicity of the molecule, decreasing the solubility of the alkylphenol in polar media (e.g. , water) and increasing the boiling point, which facilitates purification of the product at the top of a distillation column without need to evaporate the solvent. The alkyl chain length can be chosen to be sufficiently long to have a high boiling point, while keeping a good balance between hydrophilic and hydrophobic groups to extract LA and not sulfuric acid. Table 1 shows that with 2-sec-butylphenol, the partition coefficient for LA extraction remains at a value of approximately 2 (entries 1–3), while the partition coefficient for extraction of formic acid (FA) increases when the concentration of the products is increased. When the length of the alkyl chain of the alkylphenol increases, the polarity of the alkylphenol is reduced and the partition coefficient for LA decreased to 1.2 when using 4-n-pentylphenol (entry 4) and to 0.8 when using 4-n-hexylphenol (entry 5). The FA partition coefficient does not change significantly. GVL is more hydrophobic than LA and thus the partition coefficients are higher (entries 6–8), which allows the GVL concentration to be increased by successive recycling steps after hydrogenation of LA (Figure 1). However, as the amount of GVL in the 2-sec-butylphenol organic phase increases (entries 9–12), the LA partition coefficient decreases. Thus, the extent of solvent recycling prior to distillation represents a compromise between achieving high concentrations of GVL while also maintaining a high partition coefficient for LA extraction. Another advantage of the alkylphenol solvents is that the extraction can be carried out at elevated temperatures (entry 13), suggesting that the process could be carried out at the temperatures employed for cellulose deconstruction, thereby minimizing the need for heat exchangers, leading to energy and equipment savings. In addition, sulfuric acid was not detected in the organic phase for any of the entries in Table 1. Thus, it is possible to use the aqueous phase for multiple steps of cellulose deconstruction. After extraction of LA, the next step in the process is hydrogenation of LA to GVL. Previous literature reports that ruthenium on carbon (Ru/C) could be an effective catalyst. However, Ru/C hydrogenated the C=C bonds in 2-sec-butylphenol, forming butylcyclohexanol and butylcyclohexanone (corresponding to 0.3 % conversion of 2-sec-butylphenol at conditions listed in Table 2, entry 1). In addition, the Ru/C catalyst undergoes deactivation with time-on-stream in the presence of FA, even at [a] Dr. D. M. Alonso, Dr. S. G. Wettstein, Dr. J. Q. Bond, Prof. T. W. Root, Prof. J. A. Dumesic Chemical and Biological Engineering Department University of Wisconsin Madison, WI 53706 (USA) Fax: (+ 1) 608-262-5434 E-mail : dumesic@engr.wisc.edu Supporting Information for this article is available on the WWW under http://dx.doi.org/10.1002/cssc.201100256.

An examination of the intrinsic activity and stability of various solid acids during the catalytic decarboxylation of γ-valerolactone

γ-Valerolactone (GVL) has been identified as a promising, sustainable platform molecule that can be produced from lignocellulosic biomass. The chemical flexibility of GVL has allowed the development of a variety of processes to prepare renewable fuels and chemicals. In the present work involving a combination of computational and experimental studies, we explore the factors governing the ring-opening of GVL to produce pentenoic acid isomers, as well as their subsequent decarboxylation over acid catalysts or hydrogenation over metal catalysts. The ring-opening of GVL has shown to be a reversible reaction, while both the decarboxylation and hydrogenation reactions are irreversible and kinetically controlled under the conditions studied (temperatures from about 500 to 650 K). The most significant contributor to lactone reactivity toward ring-opening is the size of the ring, with γ- lactones being more stable and less readily opened than δ- and ε-analogues. We have observed that the presence of either a C═C double bond or a lactone (which opens to form a C═C double bond) is necessary for appreciable rates of decarboxylation to occur. Olefinic acids exhibit higher rates of decarboxylation than the corresponding lactones, suggesting that the decarboxylation of alkene acids provides a lower energy pathway to olefin production than the direct decarboxylation of lactones. We observe lower rates of decarboxylation as the chain length of alkene acids increases; however, acrylic acid (3-carbon atoms) does not undergo decarboxylation at the conditions tested. These observations suggest that particular double bond configurations yield the highest rates of decarboxylation. Specifically, we suggest that the formation of a secondary carbenium ion in the β position leads to high reactivity for decarboxylation. Such an intermediate can be formed from 2- or 3-alkene acids which have at least four carbon atoms.

Role of Acid Catalysis in the Conversion of Lignocellulosic Biomass to Fuels and Chemicals

Levulinic acid (LA) is a biomass-derived platform chemical that could play a central role in emerging industries as an intermediate that facilitates production of bio-based commodities. In this context, we present a novel, catalytic pathway for the synthesis of maleic anhydride (MA) via oxidative cleavage of the methyl carbon in LA over supported vanadates. The approach is demonstrated in a continuous flow, packed bed reactor, and we have observed that VOx supported on SiO2 achieves single-pass MA yields as high as 71%. Preliminary analysis suggests that LA might compete with butane as an industrial MA feedstock. Finally, bifunctional LA and monofunctional 2-pentanone display contrasting oxidative cleavage selectivities, indicating that methyl carbon cleavage during vapor phase oxidation over supported vanadates is unique to LA.

Catalysis: The Technology Enabler for New, Low Carbon Energy Technologies

Rates of γ-valerolactone (GVL) decarboxylation were measured in the gas phase under anhydrous conditions from 523–723 K over a series of solid acids including amorphous silica alumina, MFI zeolites, supported phosphotungstic acid, and γ-Al2O3. Through consideration of decarboxylation rates obtained under differential conditions, we examine the roles of Bronsted and Lewis acidity, deprotonation energy, and catalyst morphology in defining the intrinsic activity and stability of each material. In aluminosilicates, Bronsted sites associated with framework aluminum appear to contribute the majority of decarboxylation activity. Of the aluminosilicates tested, Bronsted sites in MFI are more intrinsically active than analogous sites in ASA; however, zeolite micropores hinder GVL diffusion and lead to mass transfer limitations at high temperatures. Relative to bridging hydroxyls, coordinatively unsaturated aluminum sites are substantially less active and do not contribute significantly to decarboxylation rates in materials having both framework and extraframework aluminum. Decarboxylation barriers scale with the deprotonation energy of Bronsted acid sites; however, lower deprotonation energies do not necessarily imply higher intrinsic activity in GVL decarboxylation. At 623 K, catalyst stability is highest in materials having large pore dimensions, Lewis sites as primary catalytic centers, and Bronsted sites with relatively high deprotonation energies.

Catalytic conversion of biomass to biofuels

Acid catalysts are ubiquitous in biomass conversion because of their ability to deoxygenate molecules by way of multiple chemical pathways. In this chapter, the importance and current state of acid catalysis for the conversion of lignocellulose into chemicals and fuels is outlined in the context of aqueous-phase processing. Selected examples are used to highlight the use of catalytic materials featuring Bronsted or Lewis acid sites in lignocellulosic biomass conversion processes, and to showcase the role of acidity in catalytic coupling and process intensification. The chapter presents some of the outstanding challenges to acid catalysis and includes a perspective on its future outlook in an integrated biorefining strategy.

RuSn bimetallic catalysts for selective hydrogenation of levulinic acid to γ-valerolactone

Driven largely by growth in non-OECD countries, global energy demand is projected to increase by at least fifty percent over the next twenty years. As things stand, the majority of that energy is likely to be generated by conventional technologies, 76 % of which rely on combustion of fossil resources and, therefore, have a substantial carbon footprint. With widespread concern over resource sustainability and anthropogenic climate change, our intuitive response to such projections is generally negative: How can we possibly sustain increased energy production for a growing populace and simultaneously avoid the environmental consequences of largescale energy production?