Green chemistry, catalysis and valorization of waste biomass

Accepted Manuscript Title: Green Chemistry, Catalysis and Valorization of Waste Biomass Author: Roger A. Sheldon PII: DOI: Reference:

S1381-1169(16)30012-7 http://dx.doi.org/doi:10.1016/j.molcata.2016.01.013 MOLCAA 9745

To appear in:

Journal of Molecular Catalysis A: Chemical

Received date: Revised date: Accepted date:

3-11-2015 10-1-2016 11-1-2016

Please cite this article as: Roger A.Sheldon, Green Chemistry, Catalysis and Valorization of Waste Biomass, Journal of Molecular Catalysis A: Chemical http://dx.doi.org/10.1016/j.molcata.2016.01.013 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Green Chemistry, Catalysis and Valorization of Waste Biomass

Roger A. Sheldona,b a

. University of the Witwatersrand, School of Chemistry, Private Bag 3, Wits 2050, South Africa

b

. Delft University of Technology, Department of Biotechnology, Julianalaan 136, 2628BL Delft, Netherlands

Graphical abstract

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Highlights 

Valorization of waste lignocellulosic biomass is the key to sustainable production of chemicals, liquid fuels and polymers in the long term.



Two strategies are envisaged: (i) conversion of the biomass into drop-in hydrocarbons – lower olefins, alkanes and aromatics – which form the backbone of petrochemical refineries – followed by further conversion by existing technologies or redox economic conversion directly to oxygenated products.



Whichever strategy is followed, the employment of effective catalytic methodologies, both chemo- and biocatalysis, will play a pivotal role in these developments.

Abstract This review focuses on the pivotal role of catalysis, both chemical and biological, in the development of sustainable technologies for the conversion of waste biomass to fuels, commodity chemicals and bio-based materials, such as bio-plastics, in a so-called bio-based, circular economy. Emphasis is placed on the catalytic conversion of second generation waste lignocellulosic biomass. Keywords: Lignocellulose, chemocatalysis, biocatalysis, green chemistry, sustainability

1. Introduction Green chemistry is concerned with the efficient use of (preferably renewable) resources in conjunction with the elimination of waste and avoidance of the use of toxic and/or hazardous reagents and solvents in the manufacture and application of chemical products [1,2]. Sustainable development, on the other hand, is defined as development that meets the needs of the present generation without compromising the needs of future generations to meet their own needs [3]. Sustainability consists of three components: societal, ecological and economic, otherwise referred to as the three Ps, people, planet and profit. Hence, in contrast to green chemistry, sustainability comprises an economic component. As Graedel has pointed out [4], in order for a technology to be sustainable the following conditions must be fulfilled: (i) natural resources 2

should be used at rates that do not unacceptably deplete supplies over the long term and (ii) residues should be generated at rates no higher than can be assimilated readily by the natural environment. It is abundantly clear, for example, that a society based on non-renewable fossil The author dedicates this manuscript to Prof. Ulf Schuchardt, a pioneer in the application of catalysis in biorefining, on the occasion of his 70th birthday. resources - oil, coal and natural gas - is not sustainable in the long term. In the carbon cycle, carbon dioxide in the atmosphere is converted by sunlight, in the biological process of photosynthesis, into plant biomass which eventually becomes, over a period of millions of years in geological reservoirs, fossil resources (oil, coal and natural gas). The latter are then converted in petrochemical refineries, for example, into liquid fuels which, via combustion, regenerate carbon dioxide, but in a much shorter time span. This results in a depletion of these geological reserves and, more importantly, in the shorter term increased carbon dioxide levels in the atmosphere, which are generally accepted to be a direct cause of climate change. Attention continues to be focused on waste minimization and avoiding the use of toxic and/or hazardous materials in chemicals manufacture. However, there is currently a growing emphasis on the third element of green chemistry, namely the substitution of non-renewable fossil resources – crude oil, coal and natural gas - by renewable biomass as a sustainable feedstock for the manufacture of commodity chemicals and liquid fuels [5-10]. A switch to renewable biomass as a feedstock will afford an environmentally beneficial reduction in the carbon footprint of chemicals and liquid fuels. An additional benefit could be derived from the substitution of existing products by inherently safer alternatives with reduced environmental footprints, as exemplified by biocompatible and biodegradable plastics [11]. However, it is widely accepted that the use of first generation biomass feedstocks, such as maize and edible oil seeds is not a sustainable option in the longer term because it competes, directly or indirectly, with food production. However, it has recently been argued that the rationality of biofuels is very dependent on your geographical location [12]. Nonetheless, in the European Union emphasis is firmly on the use of second generation biomass comprising lignocellulose and waste oils and fats as feedstocks in integrated biorefineries [13-15]. The ideal scenario, from the viewpoint of a truly circular economy [16] involves the valorization of waste biomass generated in agricultural production, for example, sugar cane bagasse, corn stover,

3

wheat straw, rice husks and orange peel by applying resource efficient chemo- and biocatalytic processes (Figure 1)[17]. Furthermore, driven by the need to avoid waste and find new renewable resources for fuels and chemicals, attention has recently focused on a new and promising feedstock for biorefineries: food supply chain waste (FSCW) [18-21]. Enormous amounts of organic waste, much of which goes to landfill, are generated in the harvesting, processing and use of agricultural products, including food and beverages. In developed countries, additional waste is generated when food is discarded [22]. Two decades ago the emphasis was firmly on waste prevention at source but we now recognize that in cases, such as agricultural production, where waste can’t be avoided there is a growing need for valorization of this waste, thereby creating value from unavoidable waste.

2. Primary conversion of lignocellulosic biomass The majority (60-80%) of all biomass consists of carbohydrates, which can be divided into storage carbohydrates – starch, inulin and sucrose – and structural polysaccharides, such as cellulose, hemicelluloses and chitin. In particular lignocellulose, the fibrous material that constitutes the cell walls of plants, is available in very large quantities but is much more difficult to convert than first generation biomass such as sucrose and starch. It consists of three major polymeric components: lignin (ca. 20%), cellulose (ca. 40%), and hemicellulose (ca. 25%). Irrespective of whether the final product is a liquid fuel or a platform chemical, the first hurdle to be overcome is the primary conversion of the lignocellulose feedstock. It has to be depolymerized and (partially) deoxygenated and there are basically two ways of achieving this: hydrolytic and thermochemical (see Figure 2) [23]. Thermochemical processing involves pyrolysis to a mixture of charcoal and pyrolysis oil or gasification to afford syn gas (a mixture of carbon monoxide and hydrogen), analogous to syn gas from coal gasification [24]. The syn gas can be subsequently converted to liquid fuels or platform chemicals using established technologies such as the well-known Fischer-Tropsch process or methanol synthesis, respectively. An interesting and promising twist on this theme is the use of syn gas or mixtures of carbon dioxide and hydrogen as a fermentation feedstock for the microbial production [25] of biofuels and platform chemicals, a technology being commercialized by, inter alia, Lanzatech [26] and Coskata [27]. It is interesting to note, in this context that the companies developing this 4

technology are mainly targeting waste ‘syn gas’ which is available in large quantities, e.g. from steel mills. Alternatively, lignocellulosic biomass is hydrolyzed into a mixture of cellulose, hemicellulose and lignin, together with some residual protein. Further hydrolysis of the hemicellulose and cellulose affords their constituent building blocks: C5 and C6 monosaccharides. Hydrolysis of lignocellulose is catalyzed by dilute mineral acids at elevated temperatures. Unfortunately, this can result in the formation of copious amounts of inorganic salts as waste, resulting from neutralization of the dilute mineral acid. Consequently, attention is being focused on the design of solid acid catalysts for the conversion of biomass [28,29] by analogy with the processing of crude oil fractions in the petrochemical industry. A more attractive alternative, and currently the method of choice, is the use of enzyme cocktails under milder conditions to catalyze the hydrolysis of the cellulose and hemicellulose to their substituent sugars, in a process referred to as saccharification [30]. Some form of pretreatment, such as a steam explosion, ammonia fiber expansion(AFEX) or lime treatment, is generally necessary to open up the recalcitrant lignocellulose structure and render the targeted glycoside (ether) and ester bonds accessible to the enzyme cocktails [31-33]. An interesting recent development, described by Rinaldi and Schüth and coworkers [34] is the combination of mechanical processing of lignocellulosic biomass – beechwood, pinewood, and sugar cane bagasse - with acid catalysis to afford mechanocatalytic dissolution and subsequent saccharification at 140o C for one hour The reaction medium for pretreatment of lignocelluloses is, generally speaking, water but alternative reaction media have been considered. In the Organosolv process, for example, lignocellulose is subjected to elevated temperatures (185210oC) in water/organic solvent (e.g. ethanol) mixtures [35-37]. There is no need for the addition of acid catalysts as organic acids released from the lignocellulose under these conditions are able to catalyze the cleavage of the lignin-polysaccharide complex. Alternatively, the process can be conducted at lower temperatures (e.g. 140 -160oC) by adding a mineral acid catalyst, generally giving higher selectivities. As shown in Figure 3 cellulose is removed by filtration and removal of ethanol (for recycling) by distillation results in precipitation of the lignin which is filtered off. The remaining filtrate contains hemicellulose and/or the hydrolysis products thereof. The cellulose and hemicellulose can be further hydrolyzed to mixtures of hexose (C6) and pentose (C5) sugars, respectively. The lignin is used to generate electricity but it would be much 5

more attractive to valorize the lignin coproduct by conversion to biofuels and/or commodity chemicals (see later). In a variation on the organosolv theme, ionic liquids are being considered as potential alternatives in a so-called Ionosolv process [38,39]. Some ionic liquids are able to dissolve lignocellulose [40-42] and, in combination with water, they have potential as reaction media for either chemocatalytic [43-45] or biocatalytic [46-49] hydrolysis at lower temperatures. According to a recent report [50] the ionic liquid, 1-butyl-3-imidazolium chloride, can enhance the the rate of acid-catalyzed hydrolysis in binary solvent mixtures by increasing the Hammett acidity of the catalyst dissolved in the reaction medium. Ionic liquid-based systems could become aneconomically and environmentally attractive proposition if the ionic liquid is inexpensive, non-toxic, biodegradable and recyclable [51], especially if it is itself derived from renewable raw materials [52]. Irrespective of which method is used, both the pretreatment costs and the cost of the enzyme cocktail contribute significantly to the overall cost of second generation bioethanol. Regarding the enzyme costs, they have decreased significantly over the last decade, and are still decreasing, as a result of optimization of the production and properties of the cellulytic enzyme cocktail [53,54]. Furthermore, the enzymes are currently applied on a single use, throw-away basis and further significant cost reductions can be achieved by immobilization [55,56] of the enzyme(s), for example as cross-linked enzyme aggregates (CLEAs) [57], to produce insoluble free-flowing solids which can be separated by filtration or centrifugation and recycled multiple times. However, in second generation biofuels production the immobilized enzyme generally has to be separated from other suspended solids. This can be readily achieved on a large scale and in a cost-effective manner, using magnetic CLEAs and magnetic separation equipment commonly used in the mining industry [58-60]. The C6 and C5 sugars can subsequently be used as raw materials for conversion to biofuels or platform commodity chemicals, by either fermentation or chemocatalytic processes. The enzymatic hydrolysis and the fermentation can be carried out as separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF) [61,62]. In an SHF process the fermenting organism, usually S. cerevisiae, and the enzymes can be used at their respective optimum temperature and pH but hydrolysis products can inhibit the cellulases, thus reducing their efficiency. An advantage of SSF is that the glucose is immediately consumed by the fermenting organism, thus avoiding product inhibition. In a variation on the SSF theme, 6

ethanol can be produced in a single operation from lignocellulose using cellulolytic bacteria that grow at temperatures > 70o C [63]. In this so-called consolidated bioprocessing (CBP) an organism or a mixed culture of organisms produces enzymes able to hydrolyze the cellulose and hemicelluloses in pretreated lignocellulosic biomass and conducts the fermentation of the resulting hexoses and pentoses into ethanol or other products without the need for external addition of (hemi) cellulolytic enzymes. An additional advantage of this system is that the ethanol can be evaporated during fermentation.

3. Conversion of carbohydrates to commodity chemicals There are several recent reviews on the conversion of biomass-derived sugars to commodity chemicals employing chemo- and biocatalytic technologies [64-70]. There are basically two philosophies for designing such conversions: (i) Convert the biomass to ‘drop-in’ petroleum hydrocarbons. Further processing to commodity chemicals can then be performed employing established petrochemical technologies in existing reactors in integrated manufacturing facilities for biofuels and commodity chemicals. (ii) Convert the biomass components directly to oxygenates as platform chemicals. Many commodity chemicals are ‘oxygenates” and their production in an oil refinery involves the introduction of an oxygen functionality into petroleum hydrocarbons, usually by catalytic aerobic oxidation. In contrast, the carbohydrate building blocks of cellulose and hemicellulose already contain multiple oxygen-containing functionalities. It does not seem logical, therefore, to first remove all the oxygens to generate petroleum hydrocarbons and then reintroduce oxygen functionalities by oxidation. Indeed, the concept of redox economy maintains that it is energetically more economical to avoid, as much as possible, changes in oxidation state during a multi-step process. By the same token, protein-derived amino acids should be favorable building blocks for nitrogen containing molecules (nitrogenates).

3.1 Conversion of Carbohydrates to Hydrocarbons As shown in Figure 4, there are various chemo- and biocatalytic strategies for the conversion of hexoses and pentoses to petroleum hydrocarbons. One approach is to produce lower alcohols - ethanol, propanol and butanols - by fermentation and dehydrate them to the corresponding olefins thereby providing a direct link into existing petrochemical supply chains. 7

Indeed, it has been suggested that the optimum use of bioethanol could well be as a platform chemical rather than as a biofuel [71]. The various products and the catalytic transformations used to produce them from bio-ethanol as the feedstock have been recently reviewed [72,73]. In Brazil the bioethanol production (mainly from sucrose) substantially exceeds its consumption as a fuel and, hence, there is an incentive to find other large volume outlets. It can be readily converted to drop-in petroleum hydrocarbons such as ethylene, propylene, 1-butene and butadiene (Figure 5). For example, ethanol is readily dehydrated to ethylene over solid acid catalysts at elevated temperatures and the Brazilian company Braskem has reportedly been producing polyethylene from bio-ethylene since 2010 [72]. The ethylene can also be dimerized to 1-butene (Dimersol process) and subsequent catalytic olefin metathesis with ethylene affords two molecules of propylene, thus completing the C2, C3 and C4 triad that forms the basis of the petrochemical industry. Alternatively, ethanol can be converted to propylene in 62% yield over a scandium modified indium oxide catalyst at 550oC but improvements are needed for commercial viability [74]. Similarly, 1-butanol and isobutanol can be produced efficiently by fermentation [75-77] and various companies, including Butamax Advanced Technologies, Green Biologics, Gevo and Cobalt Technologies, are commercializing fermentative production of 1-butanol and/or isobutanol. Subsequent dehydration affords 1-butene and isobutene, respectively. Similarly, 1propanol and isopropanol can, in principle, be produced by fermentation but there is currently no commercial process forthcoming. Similarly, 2,3-butane diol [78] and 1,4-butane diol [79] can also be produced by fermentation Although they are themselves interesting commodity chemicals they can also be dehydrated to butadiene. Alternatively, hydrocarbons can be produced directly by fermentation [80], thereby circumventing the energy intensive separation of water miscible lower alcohols from the aqueous fermentation medium. Metabolic engineering is being used to re-engineer the isoprenoid pathway or fatty acid biosynthesis, in bacteria or yeast, to directly yield hydrocarbons. The envisaged products can be marketed as biofuels and/or biobased commodity chemicals. For example, isobutene can be produced by fermentation [81] and Global Bioenergies has recently reported the first production of second generation bio-isobutene by fermentation [82]. Isoprene can also be prepared by fermentation [83] and several companies, e.g. Genencor [84] and Amyris, are active in this area. Similarly, Amyris has commercialized the fermentative synthesis 8

of the sesquiterpene, β-farnesene (biofene) using a genetically modified yeast [85]. It forms the basis for a wide range of products varying from specialty products such as cosmetic ingredients, to transportation fuels such as diesel and jet fuel. A third approach to hydrocarbons from carbohydrates is to employ chemocatalytic conversion by so-called aqueous phase reforming (APR) [86]. APR was originally developed as a method for the production of renewable hydrogen [87], typically by treatment of carbohydrate feedstocks with supported Pt or Pt-Re catalysts. Subsequently this was combined with the dehydration of carbohydrates over solid acid catalysts to produce, inter alia, furfural, hydroxymethyl furfural and levulinic acid (see later), which are hydrogenated in situ to a mixture of mainly C4-C6 alkanes [88,89]. These lower alkanes can be further upgraded over heterogeneous noble metal catalysts and or solid acids to mixtures of gasoline, diesel and kerosene range alkanes or the standard mixture of aromatic hydrocarbons - benzene, toluene and xylenes (BTX) - which is produced in oil refineries. The APR technology is being commercialized by Virent Energy Systems [90]. An alternative approach, proposed for the synthesis of diesel and jet fuel range alkanes in the C9 – C12 range [91,92], involves the solidbase-catalyzed aldol condensation of furfural with 2-pentanone and 2-heptanone, followed by hydrodeoxygenation over Pd-on-solid acid catalysts. 2-Pentanone and 2-heptanone are available from base-catalyzed condensation of the acetone-n-butanol fermentation products [91] .

4. Conversion of Carbohydrates to Oxygenates Direct conversion of lignocellulose derived sugars to commodity platform chemicals can be conducted using chemical or biological catalysis, or combinations thereof [93,94].

4.1 Fermentation processes Thanks to the significant advances in metabolic engineering and synthetic biology in the last two decades [95], a wide variety of oxygenates, including lower alcohols, diols and a variety of mono- and di-carboxylic acids can be produced directly, in a redox economic and cost effective manner, by fermentation (see Figure 6). Short chain diols, such as 1,3-propane diol (1,3-PDO) and 1,4-butane diol (1,4-BDO) are produced by fermentation [96].The ground breaking development of the microbial production of 1,3-PDO in a recombinant E.coli strain by DuPont was a landmark in the application of modern biotechnology in commodity chemicals 9

production [97]. It is a starting material for the polyester, polytrimethylene terephthalate (PTT) which is used in fibers, plastics, films and coatings. Similarly, 1,4-BDO is used in the production of polybutylene terephthalate (PBT) and other polyesters. Citric acid is an example of a first generation, large volume commodity chemical which is produced by fermentation [98]. Another first generation commodity chemical produced by fermentation is lactic acid, the most important application of which is poly-lactate a bioplastic with a rapidly increasing market [99]. There are many examples of second generation carboxylic acids which can be produced cost-effectively by fermentation. Succinic acid [100] has attracted considerable attention because of potentially large volume applications in polyesters and polyamides. Microbial production is being developed by several companies: Myriant Technologies, Reverdia, Bioamber, and Purac. The Reverdia process, which has already been demonstrated at industrial scale, has a potential advantage that it uses a modified yeast that is able to conduct the fermentation at pH 3, thereby producing succinic acid directly instead of a salt which has to be neutralized, with concomitant formation of stoichiometric amounts of an inorganic chloride or sulphate as waste. Bio-acrylic acid is available via fermentative production of 3-hydroxypropionic acid (3HPA) and subsequent dehydration [101] but potential production via this route has come under pressure recently because of the availability of cheap propylene from propane dehydrogenation. Alternatively, acrylic acid can be produced by dehydration of lactic acid over, for example, calcium pyrophosphate at 375o C [102] but yields are significantly lower than from 3-HPA. Biomethacrylic acid can similarly be produced by fermentation to itaconic acid followed by decarboxylation over a Pd, Pt or Ru catalyst [103]. Several companies are actively pursuing biorenewable routes to adipic acid [93,104]. Verdezyne, for example, has employed metabolic pathway engineering to afford a feedstock agnostic process that accepts carbohydrates, vegetable oils or alkanes [105].

4.2. Chemocatalytic conversions of sugars Acid catalyzed hydrolysis of pentoses and hexoses affords furfural [106] and hydroxymethylfurfural (HMF) [107], respectively, both of which have potential as platform chemicals. Furfural has broad applications and has been produced on an industrial scale for decades. HMF, in contrast, has enormous potential [108] as a raw material for the production of 10

chemicals, polymers and biofuels but its production has not yet been reduced to commercial practice. HMF can be oxidized to give 2,5-diformylfuran (DFF) and further to furan-2,5dicarboxylic acid (FDCA), a potential building blocks for polymers (Figure 7). However, acid catalyzed dehydration of hexoses to hydroxymethyl furfural (HMF) in a cost-effective manner is a significant challenge, mainly owing to the unstable nature of HMF towards further reaction under the acidic reaction conditions to, inter alia, levulinic acid (see below) [109]. Dumesic and colleagues reported [110] that relatively high fructose conversions (90%) and HMF selectivities (80%) could be obtained with acid catalyzed dehydration in a biphasic aqueous DMSO system. These dehydrations can also be performed more selectively with metal chloride catalysts in ionic liquids as reaction media [111] but downstream processing is an issue to be resolved. One way to circumvent unwanted byproduct formation in HMF production under acidic conditions is to convert it in situ to a more stable derivative. Avantium, for example, developed a process for the conversion of hexoses to more stable HMF ethers by conducting the acid catalyzed dehydration in the presence of an alcohol, such as methanol or ethanol [112]. HMF, and, presumably, HMF methyl ether, can be converted in high yield to the dimethyl ester of furan-2,5-dicarboxylic acid (FDCA) by catalytic aerobic oxidation over a nanogold-on-titania catalyst in methanol [113]. In another variation on this theme, glucose, fructose, cellulose or even corn stover were directly converted to chloromethyl furfural (CMF) in 70-90% yield by reaction with aqueous HCl at 100oC [114]. Subsequent reaction with water afforded, depending on the temperature, high yields of HMF or levulinic acid (LA), with concomitant regeneration of the HCl (Figure 7). The reaction was conducted in 1,2-dichloroethane but presumably this could be replaced by a more environmentally acceptable solvent. Aerobic oxidation of HMF to FDCA can be performed with chemo- or biocatalysts. For example, catalytic oxidation over Pd nanoparticles immobilized on core shell C@Fe3O4 magnetic particles in 87% selectivity to FDCA at 98% HMF conversion, was recently reported [115]. Fraaije and coworkers reported the aerobic oxidation of aqueous HMF to FDCA in which all three individual oxidation steps were catalyzed by the same flavin-dependent HMF oxidase [116] Reaction of HMF with water, under acidic conditions, affords levulinic acid (LA) with elimination of formic acid (Figure 8). LA and its esters are viewed as platform chemicals in their own rights and are precursors of various bioplastics and other polymers and the bio-based solvent, methyl tetrahydrofuran,. Hydrogenation of aqueous LA over a ruthenium catalyst in 11

supercritical carbon dioxide, afforded γ-valerolactone (GVL) in 100% selectivity [117] (Figure 8). The LA partitions into the aqueous phase and the GVL into the carbon dioxide phase. Similarly, Dumesic and coworkers reported [118] the highly selective hydrogenation of LA to GVL over a Ru/Sn-on-C catalyst. Alternatively, the hydrogen could be replaced by the formic acid generated as the coproduct in the formation of LA from HMF [119]. GVL has been proposed as a sustainable liquid fuel and a platform chemical [120,121]. For example, ring opening with methanol, followed by dehydration, affords methyl pentenoate, a potential precursor of dimethyl adipate and, hence, a nylon-6,6 intermediate [122]. Lange and coworkers [123] described the production of so-called valeric fuels by acid catalyzed hydrolysis of hexoses to LA followed by hydrogenation to a mixture of GVL and valeric acid and subsequent esterification with ethanol. GVL has even been used, on a laboratory scale at least, as a solvent for the direct mineral acid-catalyzed conversion of lignocellulosic biomass, e.g. corn stover or wood, into pentoses and hexoses [124,125]. GVL promotes saccharification through complete dissolution of the biomass, including the lignin. Another potentially interesting sugar-derived platform chemical is isosorbide which is of interest as an industrial monomer [126]. It is produced by hydrogenation of sucrose to sorbitol, followed by acid-catalyzed dehydration to sorbitan and subsequently isosorbide. Interestingly, it has recently been reported [127] that cellulose can be directly converted into isosorbide using a hydrogenation catalyst, in combination with ZnCl2 as both a Lewis acid catalyst and a molten salt reaction medium, as depicted in Figure 9. Isosorbide is of interest a a raw material for bio-based polyesters. It can also be converted to the corresponding diketone by aerobic oxidation in the presence of acetylamino-TEMPO/HNO3 [128] or Laccase/TEMPO [129] as a chemo- or biocatalyst, respectively. The diketone can be subsequently converted to the diamine which can be used to produce bio-based polyamides.

5. Bio-based aromatics and lignin valorization: the new frontier. In the preceding discussion the conversion of lignocellulosic biomass to hydrocarbons largely results in the formation, directly or indirectly, of aliphatic hydrocarbons as alkane liquid fuels or lower olefins, including the big three base chemicals of the petrochemical industry: ethylene propylene and butadiene. However, many commodity chemicals are derived from the big three aromatic fractions – benzene, toluene and xylenes (BTX) - produced in oil refineries: 12

by catalytic reforming of naphtha. Hence, there is a need for routes from waste lignocellulosic biomass to aromatic platform chemicals. An obvious source of aromatics is the lignin produced as the inevitable coproduct of lignocellulose hydrolysis conversion to carbohydrates. Lignin is the dominant aromatic polymer in nature and comprises 20-30% by weight of plant biomass but accounts for 37% of the carbon content. It is an amorphous, three dimensional polymer derived from three primary monolignols - p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol which generate the hydroxyphenyl (H), guaiacyl (G) and syringyl (S) lignin subunits (Figure10). Traditionally, in the large scale processing of lignocellulose the coproduced lignin is burnt to generate the power needed to drive the process. However, biorefineries that convert cellulosic biomass to liquid transportation fuels will generate 60% more lignin than is needed to power the operation. One cellulosic ethanol plant, for example, will produce 100-200000 tonnes of lignin per annum and it was estimated that ca. 60 x 106 tonnes of lignin per annum could be generated by 2022 in the US alone [130]. Hence, it is clear that there is a pressing need for methods for the valorization of this lignin. Selective valorization of lignin is one of the major challenges in the development of biobased refineries. In addition to being a complex, heterogeneous polymeric substrate, which would lead to complex mixtures of oligomers and low molecular weight products, an extra challenge is provided by the fact that its exact structure is dependent on its source and the method of pretreatment. However, recent advances in metabolic pathway engineering of the biosynthesis of the three primary lignols -, in planta genetic engineering - are making it possible to produce plants with pre-designed ratios of the H, G and S subunits, affording lignin structures that are less recalcitrant, easier to process and form more attractive mixtures of low molecular weight products [130]. For example, genetically modified poplar containing high S type lignin has been reported [131] Both chemical [132] and biological [133] catalysis can be used for the selective conversion of lignin. One can envisage various strategies: catalytic (hydro)cracking [132], hydrolysis, hydrogenation [132] and oxidation [132,134,135]. Interestingly, it was recently reported [136] that the lignin contained in the lignocellulose from wild type poplar, which consists of G and S subunits, is converted directly to a mixture of 2-methoxy-4-propylphenol (dihydroeugenol) and 2,6-dimethoxy-4-propylphenol, respectively, by hydrogenation over a ZnCl2 / Pd-on-C catalyst in aqueous methanol at 225oC and 35 bar. Similarly, the high-S lignin 13

from genetically modified poplar afforded mainly 2,6-dimethoxy-4-propylphenol. The carbohydrate fraction in these reactions, left behind as a solid residue, was further converted to mainly glucose by enzymatic hydrolysis and the methoxyphenols could be converted, by hydrodeoxygenation,

to

propylcyclohexane

and,

by

subsequent

dehydrogenation,

to

propylbenzene (Figure 11). Similarly, dihydroxylation of phenols to aromatic hydrocarbons, via hydrogen transfer, dehydration and dehydrogenation, over a Raney Ni/zeolite beta catalyst combination and isopropanol as hydrogen donor [137]. Alternatively, aromatics can be produced from the carbohydrate fraction of lignocellulose by fermentation to precursors of aromatics or by acid catalyzed hydrolysis to furan derivatives and further conversion to aromatics. These approaches are discussed in the following section using the important industrial monomer, terephthalic acid, as the example.

6. Biobased Polymers: Renewable PET From a sheer volume point of view an attractive outlet for renewable biomass is in polymers and there is increasing pressure to substitute oil-based polymers with more sustainable renewable alternatives. However, this will only possible if the latter can compete on price and have equivalent or better properties in the envisaged applications. The ease of recyclability and/or biodegradability is also important from the viewpoint of sustainability. Various scenarios can be envisaged. First, conversion of renewable biomass to industrial monomers which are subsequently converted, using existing technology, to existing polymers, e.g. bio-ethylene to biopolyethylene. Second, conversion of biomass to new monomers which are subsequently polymerized. In this case a new product has to be introduced into the market. Third, the biomass is converted directly into a polymer which also has to be introduced into the market, generally to replace an existing oil-based polymer, e.g. carbon fibers from lignin. One of the largest volume industrial polymers is undoubtedly, the ubiquitous polyethylene terephthalate (PET) with an annual global production of >50 million tonnes and applications in fibers and plastic bottles for soft drinks and water. In the current drive towards a bio-economy, PET is an obvious target for manufacture from renewable biomass and considerable effort is focused on the development of a renewable PET bottle. The two key raw materials are ethylene glycol and p-terephthalic acid, which are produced from the two petroleum hydrocarbons, ethylene and p-xylene, respectively. Hence, the 14

simplest way to

produce a bio-based PET is to start from bioethanol-derived bio-ethylene, thereby generating a ca. 30% bio-based PET. In order to produce 100% bio-based PET it is necessary to use bio-pxylene as the raw material for the p-terephthalic acid. This would constitute the largest single application of a bio-based aromatic hydrocarbon. As discussed above, this can be achieved by aqueous phase reforming (APR) of C6 sugars and further upgrading to a mixture of benzene, toluene and xylenes (BTX) from which the required bio-p-xylene can be separated. This approach is being developed by Virent. The second route, being developed by Gevo [138], starts from bio-isobutanol which is converted, using existing technology based on the Prins reaction, to p-xylene (Figure 12). A third route involves catalytic hydrogenation of HMF to 2,5dimethylfuran followed by Diels-Alder reaction of the latter with ethylene in n-heptane, at 250oC and 62 bar, followed by in situ dehydration over zeolite H-beta , producing p-xylene in 90% yield [139]. Other zeolites can also be used, e.g. zeolite HY [140] Another approach to producing a renewable ‘plant bottle’ is to design an alternative biobased plastic which can replace the PET. The Dutch company, Avantium, followed this strategy to produce polyethylene furandicarboxylate (PEF) by replacing terephthalic acid with FDCA as shown in Figure 13. In a recent cradle-to-grave comparison [141] of the energy and greenhouse gas balance of biobased PEF, derived from corn-based fructose, with that of fossil-based PET it was concluded that PEF production would reduce the non-renewable energy use (NREU) by 40 -50% and the greenhouse gas (GHG) emissions by 45-55%. A further reduction of GHG emissions could be obtained by switching from corn-based to waste lignocellulose based PEF. In addition to the more favorable energy and GHG emissions balance, PEF bottles reportedly have superior properties to PET bottles [142]. For example, they have better so-called barrier properties with regard to gas permeability of oxygen, carbon dioxide and water, providing for longer-lasting carbonated drinks. They also have a more attractive glass transition temperature and melting point which translates to a better ability to withstand heat and be processed at lower temperatures. We note, however, that both PET and PEF have the disadvantage of poor biodegradability.

7. Conclusions and Future Prospects The waste-based bio-economy is an important component of the transition from a linear take. make, dispose - economy to a sustainable circular economy and the employment of 15

effective chemo- and bio-catalytic processes forms an integral part of this development. Advances in chemo- and biocatalytic methodologies are and will continue to be the cornerstone of of biomass conversion to biofuels, commodity chemicals and biomaterials.

References [1] R.A. Sheldon, I.W.C.E. Arends, U. Hanefeld, Green Chemistry and Catalysis, Wiley-VCH, Weinheim, 2007. [2] P.T. Anastas, J.C. Warner (Eds.), Green Chemistry: Theory and Practice, Oxford University Press, Oxford, 1998. [3] C. G. Brundtland, Our Common Future, The World Commission on Environmental Development, Oxford University Press, Oxford, 1987. [4] T. E. Graedel, in J. Clark, D. J. Macquarrie, eds., Handbook of Green Chemistry and Technology, Wiley, New York, 2002, pp 56-61. [5] P. Imhof and J. C. van der Waal (Eds), Catalytic Process Development for Renewable Materials,Wiley-VCH, Weinheim, 2013. [6] S.-T. Yang, H. A. El-Enshasy, N. Thongchul, Bioprocessing Technologies Biorefinery for Sustainable Production of Fuels, Chemicals and Polymers, Wiley, Hoboken, 2013. [7] R. A. Sheldon, Green Chem. 16 (2014) 950-963 [8] S. G. Wettstein, D. M. Alonso, E. I. Gürbüz, J. A. Dumesic, Curr. Opin. Chem. Eng. 1 (2012) 218–224 [9] P. Gallezot, Chem. Soc. Rev. 41 (2012)1538- 1558. [10] A. Corma, S. Iborra, A. Velty, Chem. Rev. 107 (2007) 2411- 2502. [11] E. De Jong, A. Higson, P. Walsh and M. Wellisch, Biofuels Bioprod. Bioref. 6 (2012) 606624. [12] L. A. Horta Nogueira, J. R. Moreira, U. Schuchardt, J. Goldemberg, Energy Policy 61 (2013) 595–598 [13] J.H. Clark, J. Chem. Technol. Biotechnol., 82 (2007) 603-609. [14] C.H. Christensen, J. Rass-Hansen, C.C. Marsden, E. Taarning, K. Egeblad, ChemSusChem, 1 (2008) 283-289. [15] G. W. Huber, A. Corma, Angew. Chem. Int. Ed. 46 (2007) 7184-7201. 16

[16] http://www.ellenmacarthurfoundation.org/publications. [17] C. O. Tuck, E. Perez, I. T. Horvath, R. A. Sheldon and M. Poliakoff, Science, 337 (2012) 695-699. [18] L. A. Pfaltzgraff, M. De Bruyn, E. C. Cooper, V. Budarin and J. H. Clark, Green Chem., 15 (2013) 307-314. [19] C. S. K. Lin, L. A. Pfaltzgraff, L. Herrero-Davila, E. B. Mubofu, S. Abderrahim, J. H. Clark, A. A. Koutinas, N. Kopsahelis, K. Stamatelatou, F. Dickson, S. Thankappan, Z. Mohamed, R. Brocklesby, R. Luque, Energy Environ. Sci., 6 (2013) 426-464. [20] R. Luque, J. H. Clark Sust. Chem. Process. 1:10 (2013). [21] J.H. Clark, L. A. Pfaltzgraff, V. L. Budarin, A. J. Hunt, M. Gronnow, A. S. Matharu, D. J. Macquarrie, J. R. Sherwood, Pure Appl. Chem., 85 (2013), 1625–1631. [22] T. Stuart, Waste: Uncovering the Global Food Scandal, Penguin, 2009. [23] J.P. Lange, Biofuels Bioprod. Bioref. 1 (2007) 39-48. [24] R.A. Sheldon, Chemicals from Synthesis Gas, Reidel, Dordrecht, 1983. [25] P. C. Munasinghe and S. K. Khanal, Bioresource Technol. 101 (2010) 5013–5022; A. M. Henstra, J. Sipma, A. Rinzema and A. J. M. Stams, Curr. Opin. Biotechnol., 18 (2007) 200-206. [26] J. Daniell, M. Köpke and S. D. Simpson, Energies 5 (2012) 5372-5417; www.lanzatech.com [27] www.coskata.com [28] R. Rinaldi, F. Schüth, Energy Environ. Sci., 2 (2009) 610-626; see also J.M. Thomas, J.C. Hernandez-Garrido, R. Bell, Top Catal., 52 (2009) 1630-1639. [29] P.L. Dhepe, A. Fukuoka, ChemSusChem, 1 (2008) 969-975. [30] U. Bornscheuer, K. Buchholz, J. Seibel, Angew. Chem. Int. Ed. 53 (2014) 10876-10893. [31] P. Kumar, D.M. Barrett, M.J. Delwiche, P. Stroeve, Ind. Eng. Chem. Res., 48 (2009) 37133729. [32] V. Menon, M. Rao, Prog. Energ. Combust. Sci. 38 (2012) 522-550. [33] P. Alvira, E. Tomas-Pejo, M. Ballesteros, M. J. Negro, 101 (2010) 4851-4861. [34] M. Käldstrӧm, N. Meine, C. Farès, R. Rinaldi, F. Schüth, Green Chem. 16 (2014) 24542462. [35] X. Zhao, K. Cheng, D. Liu, Appl. Microbiol. Biotechnol. 82 (2009) 815–827 [36] J. Wildschut, A. T. Smit, J. H. Reith, W. J.J. Huijgen, Biores. Technol. 135 (2013) 58–66. [37] J. Viell, A. Harwardt, J. Seiler, W. Marquardt, Biores. Technol. 150 (2013) 89–97. 17

[38] A. Brandt, J. Gräsvik, J. P. Hallett, T. Welton, Green Chem., 15 (2013) 550-583.. [39] A. Brandt, M. J. Ray, T. Q. To, D. J. Leak, R. J. Murphy, T. Welton, Green Chem. 13 (2011) 2489-2499. [40] M. Zavrel, D. Bross, M. Funke, J. Büchs, and A. C. Spiess, Biores. Technol. 100 (2009) 2580–2587. [41] J. Long, X. Li, B. Guo, F. Wang, Y. Yu, L. Wang, Green Chem., 14 (2012) 1935-1941. [42] T. Vancov, A.-S. Alston, T. Brown, S. McIntosh, Renewable Energy, 45 (2012) 1-6. [43] R. Rinaldi, R. Palkovits, F. Schüth, Angew. Chem. Int. Ed., 47 (2008) 8047-8050. [44] C. Li, Q. Wang, Z.K. Zhao, Green Chem., 10 (2008) 177-182. [45] R. Rinaldi, Angew. Chem. Int. Ed. 53 (2014) 8559-8560. [46] Z. Qiu, G. M. Aita and M. S. Walker, Biores. Technol. 117 (2012) 251–256. [47] K. Nakashima, K. Yamaguchi, N. Taniguchi, S. Arai, R. Yamada, S. Katahira, N. Ishida, H. Takahashi, C. Ogino and A. Kondo, Green Chem., 13 (2011) 2948–2953 [48] K. Ninomiya, H. Soda, C. Ogino, K. Takahashi and N. Shimizu, Biores. Technol. 128 (2012) 188−192. [49] S. K. Khare, A. Pandey, C. Larroche, Biochem. Eng. J. xxx (2015) xxx [50] H. F. Nunes de Oliveira, C. Farès, R. Rinaldi, Chem. Sci. 6 (2015) 5215-5224. [51] A. George, A. Brandt, K. Tran, S. M. S. Nizan, S. Zahari, D. Klein-Marcuschamer, N. Sun, N. Sathitsuksanoh, J. Shi, V. Stavila, R. Parthasarathi, S. Singh, B. M. Holmes, T. Welton, B. A. Simmons, J. P. Hallett, Green Chem., 17 (2015) 1728-1734. [52] X.-D. Hou, N. Li and M.-H. Zong, ACS Sustainable Chem. Eng. 2 (2014) 1063–1071. [53] A. Margeot, B. Hahn-Hagerdal, M. Edlund, R. Slade, F. Monot, Curr. Opin. Biotechnol. 20 (2009) 372-380. [54] C. Ayrinhac, A. Margeot, N. Lopes Ferreira, F. B. Chaabane, F. Monot, G. Ravot, J.-M. Sonet, L. Fourage, Org. Proc. Res. Dev. 15 (2011) 275-278. [55] R. A. Sheldon, S. Van Pelt, Chem. Soc. Rev. 42 (2013) 6223-6235. [56] M. C. R. Franssen, P. Steunenberg, E. L. Scott, H. Zuilhof, J. P. M. Sanders, Chem. Soc. Rev. 42 (2013) 6491-6533. [57] R.A. Sheldon, Appl. Microbiol. Biotechnol. 92 (2011) 467-477. [58] R. A. Sheldon, M. J. Sorgedrager, B. Kondor, Non-leachable magnetic cross-linked enzyme aggregate, PCT Int. Appl. (2012) WO 2012/023847 A2 to CLEA Technologies B.V. 18

[59] A. Bhattacharya, B. I. Pleschke, Enz. Microb. Technol. 61-62 (2014) 17-27. [60] K. J. Khorshidi, H. Lenjannezhadian, M. Jamalan, M. Zeinali, J. Chem. Biotechnol. 2015, Ahead of print. [61] K. Olofsson, M. Bertilsson, G. Liden, Biotechnol. Biofuels 3:17 (2010) [62] M. M. Ishola, A. Jahandideh, B. Haidarian, T. Brandberg, M. J. Taherzadeh, Biores. Technol. 133 (2013) 68-73. [63] V. A. Svetlitchnyi, O. Kensch, D. A. Falkenhan, S. G. Koreska, N. Lippert, M. Prinz, J. Sassi, A. Schickor and S. Curvers, Biotechnol. Biofuels, 6:31 (2013) 1-15. [64] C. Chatterjee, F. Pong, A. Sen, Green Chem., 17 (2015) 40-71. [65] J. S. Luterbacher, D. M. Alonso, J. A. Dumesic, Green Chem. 16 (2014) 4816-4838. [66] X. Tong, Y. Ma, Y. Li, Appll. Catal. A: General, 385 (2010) 1-13. [67] P. Y. Dapsens, C. Mondelli, and J. Perez-Ramírez, ACS Catal. 2 (2012) 1487−1499 [68] J. J. Bozell, G. R. Petersen, Green Chem 12 ( 2010) 539-. [69] T. M. Carole, J. Pellegrino, M. D. Paster, Appl. Biochem. Biotechnol. 113 (2004) 871-885. [70] E. de Jong, A. Higson, P. Walsh, M. Wellisch, Biofuels, Bioprod. Bioref. 6 (2012) 606–624. [71] J. Rass-Hansen, H. Falsig, B. Jørgensen, C.H. Christensen, J. Chem. Technol. Biotechnol. 82 (2007) 329-333. [72] J. M. R. Gallo, J. M. C. Bueno, U. Schuchardt, J. Braz. Chem. Soc., 25 (2014) 2229-2243. [73] J. A. Posada, A. D. Patel, A. Roes, K. Blok, A. P. C. Faaij, M. K. Patel, Biores. Technol. 135 (2013) 490-499. [74] S. Mizuno, M. Kurosawa, M. Tanaka, M. Iwamoto, Chem. Lett. 41 (2012) 892- . [75] P. Dürre, J. Biotechnol. 2 (2007) 1525-1534. [76] P. Dürre, Curr. Opin. Biotechnol. 22 (2011) 331-336. [77] W. Higashida, Y. Li, Y. Yang, J. C. Liao, Appl. Environ. Micrbiol. 77 (2011) 2727-2733. [78] E. Celinska, W. Grajek, Biotechnol. Adv. 27 (2009) 715-725; X.-J. Ji, H. Huang, P. K. Ouyang, Biotechnol. Adv. 29 (2011) 351-364. [79] H. Yim, R. Haselbeck, W. Niu, C. Pujol-Baxley, A. Burgard, J. Boldt, J. Khandurina, J. D. Trawick, R. E. Oosterhout, R. Stephen, J. Estadilla, S. Teisan, H. B. Schreyer, S. Andraer, T. H. Yang, A. Y. Lee, M. J. Burk, S. Van Dien, Nature Chem. Biol. 7 (2011) 445-452. [80] N. Ladygina, E.G. Dedyukhina, M.B. Vainshtein, Proc. Biochem. 41 (2006) 1001–1014.

19

[81] B. N. van Leeuwen, A. M. van der Wulp, I. Duijnstee, A. J. van Maris, A. J. Straathof, Appl. Microbiol. Biotechnol. 93 (2012) 1377-1387. [82] http://www.biofuelsdigest.com/bdigest/2015/08/23/global-bioenergies-makes-isobutenefrom-wood-sugars-in-rd-breakthrough/ [83] J. Yang, G. Zhao, Y. Sun, Y. Zheng, X. Jiang, W. Liu, M. Xian, Biores. Technol. 104 (2012) 642–647. [84] G. M. Whited, F. J. Feher, D. A. Benko, M. A. Cervin, G. K. Chotani, J. C. McAuliffe, R. J. LaDuca, E. A. Ben-Shoshan, K. J. Sanford, Ind. Biotechnol. 6 (2010) 152-163. [85] https://farnesene.net/ ; https://amyris.com/innovation/biofene/ [86] J. N. Chheda, J. A. Dumesic, Catalysis Today 123 (2007) 59–70 [87] R.D. Cortright, R. R. Davda, J. A. Dumesic, Nature, 418 (2002) 964–967. [88] G. W. Huber, R. D. Cortright, J. A. Dumesic, Angew. Chem. Int. Ed. 43 (2004) 1549-1541. [89] J. N. Chheda, G. W. Huber, J. A. Dumesic, Angew. Chem. Int. Ed. 46 (2007) 7164-7183. [90] www.virent.com [91] J. Yang, N. Li, S. Li, W. Wang, L. Li, A. Wang, X. Wang, Y. Cong, T. Zhang, Green Chem. 16 (2014) 4879-4884. [92] See also G. W. Huber, J. N. Chheda, C. J. Barrett, J. A. Dumesic, Science, 308 (2005) 1446-1450); H. Olcay, A. V. Subramanian, R. Xing, J. Lajoie, J. A. Dumesic, G. W. Huber, Energy Environ. 6 (2013) 205-216; R. M. West, Z. Y. Liu, M. Peter, J. A. Dumesic, ChemSusChem, 1 (2008) 417-424. [93] R. Beerhuis, G. Rothenburg, N. R. Shiju, Green Chem. 17 (2015) 1341-1361. [94] T. J. Schwartz, B. J. O’Neill, B. H. Shanks, J. A. Dumesic, ACS Catalysis, 4 (2014) 20602069. [95] J. M. Clomburg, R. Gonzalez, Appl Microbiol Biotechnol. 86 (2010) 419–434; V. G.Yadav, M. DeMey, C. G. Lim, P. K. Ajikumar, G. Stephanopoulos, Metabol. Eng. 14 (2012) 233–241; J. D. Keasling, Metabol. Eng. 14 (2012) 189–195. [96] A.-P. Zeng, W. Sabra, Curr. Opin. Biotechnol. 22 (2011) 749-757. [97] G. Kaur, A. K. Srivasta, S. Chand, Biochem. Eng. J. 64 (2012) 106-118; R.K. Saxena, P. Anand, S. Saran, J. Isar, Biotechnol. Advan. 27 (2009) 895–913 [98] K. Zhang, B. Zhang, S.-T. Yang, in ref. 6, pp. 375-398. [99] N. Thongchul, in ref. 6. pp. 293-316. 20

[100] A. Cukalovic, C.V. Stevens, Biofuels Bioprod. Bioref. 2008, 2, 505-529. [101] K. N. G. Valdehuesa, H. Liu, G. M. Nisola, W.-Jin. Chung, S. H. Lee and S. J. Park, Appl. Microbiol. Biotechnol. 97 (2013) 309–332. [102] V. C. Ghantani, M. K. Dongare, S. B. Umbarkar, RSC Adv. 4 (2014) 33319-33326; V. C. Ghantani, S. T. Lomate, M. K. Dongare, S. B. Umbarkar, Green Chem. 15 (2013) 1211-1217. [103] J. Le Nôtre, S. C. Witte-van Dijk, J. van Haveren, E. L. Scott, J. P. Sanders, ChemSusChem. 7 (2014) 2712-2720. [104] T. Polen, M. Spelberg, M. Bott, J. Biotechnol.167 (2013) 75-84 [105] S. Picataggio, T. Beardslee,U.S. Patent No. 8,241,879 (2012) to Verdezyne; see also T. Beardslee, S. Picataggio, Lipid Technol. 24(10) (2012) 223-225. [106] J.-P. Lange, E. van der Heide, J. van Buijtenen, and R. Price, ChemSusChem.5 (2012) 150 -166. [107] R.-J. Van Putten, A Sousa Dias, E. de Jong, in ref. 5, pp. 81-117. [108] R.-J. van Putten, J. C. van der Waal, E. de Jong, C. B. Rasrendra, H. J. Heeres and J. G. de Vries, Chem. Rev. 2013, 113, 1499−1597. [109] S. P. Simeonov, J. A. S. Coelho, and Carlos A. M. Afonso, ChemSusChem 2012, 00, 1 – 4 [110] Y. Romain-Leshkov, J. N. Chheda and J. A. Dumesic, Science, 312 (2006) 1933-1937. [111] T. Stahlberg, W. Fu, J. M Woodley, and A. Riisager, ChemSusChem 4 (2011) 451–458. [112] G. J. M. Gruter and F. Dautzenberg, Eur. Pat. 1834950A1, 2007 and Eur. Pat. 1834951A1, 2007 to Avantium. [113] E. Taarning, I.S. Nielsen, K. Egeblad, R. Madsen, C. Christensen, ChemSusChem, 1 (2008) 75-78; E. Taarning, C.H. Christensen, Chemistry Today, 25 (6) (2007) 70-73; see also O. Casanova, S. Iborra, A. Corma, ChemSusChem, 2 (2009) 1138-1144. [114] M. Mascal, E.B. Nikitin, Green Chem., 10 (2010) 370-373. [115] B. Liu, Y. Ren, Z. Zhang, Green Chem. 17 (2015)1610-1617. [116] W. P. Dijkman, C. Binda, M. W. Fraaije, A. Mattevi, ACS Catalysis, 5 (2015) 1833-1839 [117] R.A. Bourne, J.G. Stevens, J. Kie, M. Poliakoff, Chem. Commun., (2007) 4632-4634 [118] S. G. Wettstein, J. Q. Bond, D.M. Alonso, H. M. Pham, A. K. Datye, J. A. Dumesic, Appl. Catal. B, 117-118 (2012) 321-329. [119] I.T. Horvath, H. Mehdi, V. Fabos, L. Boda, L.T. Mika, Green Chem., 10 (2008) 238-242. [120] I. T. Horvath, Green Chem. 10 (2008) 1024-1028. 21

[121] D. M. Alonso, S. G. Wettstein, J. A. Dumesic, Green Chem., 15 (2013) 584–595 [122] J.-P. Lange, J.Z. Vestering, R.J. Hahn, Chem. Commun., 2007, 3488-3490. [123] J.-P. Lange, R. Price, P. M. Ayoub, J. Louis, L. Petrus†, L. Clarke, and H. Gosselink, Angew. Chem. Int. Ed. 49 (2010) 4479 –4483 [124] J. S. Luterbacher, J. M. Rand, D. M. Alonso, J. Han, J. T. Youngquist, C. T. Maravelias, B. F. Pfleger, J. A. Dumesic, Science, 343 (2014) 277-280. [125] J. S. Luterbacher, A. Azarpira, A. H. Motagamwala, F. Lu, J. Ralph, J. A. Dumesic, Energy Environ. Sci.,8 (2015) 2657-2663. [126] M. Rose and R. Palkovits, ChemSusChem, 5 (2012)167-176 [127] R. Menegassi de Almeida, J. Li, C. Nederlof, P. O’Connor, M. Makkee, J.A. Moulijn, ChemSusChem, 3 (2010) 325-328. [128] U. Dingerdissen, J. Pfeffer, T. Tacke, T. Haas, H. Schmidt, F. Klasovsky, R. Sheldon, M. Janssen, M. Volland, M. Rimbach, S. Rinker, US 2011/0251399 A1 (2011) to Evonik Degussa GMBH. [129] J. Gross, K. Tauber, M. Fuchs, N. G. Schmidt, A. Rajagopalan, K. Faber, W. M. F. Fabian, J. Pfeffer, T. Haas, W. Kroutil, Green Chem., 16 (2014) 2117–2121. [130] A. J. Rasgaauskas, G. T. Beckham, M. J. Biddy, R, Chandra, F. Chen, M. F. Davis, B. H. Davison, R. A. Dixon, P. Gilna, M. Keller, P. Langan, A. K. Naskar, J. N. Saddler, T. J. Tschaplinski, G. A. Tuskan, C. E. Wyman, Science, 344 (2014) 709[131] S. D. Mansfield, K. -Y. Yang, C. Chapple, New Phytol. 194 (2012) 91-101. [132] J. Zakzeski, P. C. A. Bruijnincx, A. L. Jongerius, B. M. Weckhuysen, Chem. Rev. 110 (2010) 3552-3599. H. Leisch, S. Grosse, K. Morley, K. Abokitse, F. Perrin, J. Denault and P. C.K. Lau, Green Proc. Synth 2 (2013) 7–17. [133] T. D. H. Bugg, R. Rahmanpour, Curr. Opin. Chem. Biol. 29 (2015) 10-17. [134] R. Ma, Y. Xu, X. Zhang, ChemSusChem 8 (2015) 24-51. [135] C. Crestini, M. Crucianelli, M. Orlandi, R. Saladino, Catal. Today, 156 (2010) 8-22. [136] T. Parsell, S. Yohe, J. Degenstein, T. Jarrell, I. Klein, E. Gencer, B. Heweteson, M. Hurt, J. I. Kim, H. Choudhari, B. Saha, R. Meilan, N. Mosier, F. Ribeiro, W. N. Delgass, C. Chapple, H. I. Kenttämaa, R. Agrawal, M. M. Abu-Omar, Green Chem. 17 (2015) 1492-1499. [137] X. Wang, R. Rinaldi, Angew. Chem. Int. Ed. 52 (2013) 11499-11503.

22

[138] M. W. Peters, D. E. Henton, J. D. Taylor, T. J. Talylor, L. E. Manzer, WO 2012/061372 A1 (2012) to Gevo [139] C.-C. Chang, S. K. Green, C. L. Williams, P. J. Dauenhauer, W. Fan, Green Chem. 15 (2013) 1869-1879. [140] P. T. M. Do, J. R. McAtee, D. A. Watson, R. F. Lobo, ACS Catal. 3 (2013) 41-46.; see also C. L. Williams, C.-C. Chang, P. Do, N. Nikbin, S. Caratzoulas, D. G. Vlachos, R. F. Lobo, W. Fan, P. J. Dauenhauer, ACS Catal. 2 (2012) 935-939. [141] A. J. J. E. Eerhart, A. P. C. Faaij, M. K. Patel, Energy. Environ. Sci. 5 (2012) 6407-6422. [142] See http://avantium.com/yxy/products-applications/PEF-bottles.html

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Figure 1. The bio-based economy Figure 2. Methods for lignocellulose conversion Figure 3. Organosolv pretreatment of lignocellulose with ethanol. Figure 4. Carbohydrates to hydrocarbons Figure 5. Commodity chemicals from (bio)ethanol. Figure 6. Commodity chemicals by fermentation of biomass derived sugars. Figure 7. Acid catalyzed conversion of pentoses and hexoses to furan derivatives. Figure 8. Conversion of HMF to levulinic acid (LA) and γ-valerolactone (GVL). Figure 9. Isosorbide by hydrogenation of glucose and dehydration Figure 10. Partial lignin structure and the three monolignol building blocks. Figure 11. Hydrogenolysis of lignin catalyzed by ZnCl2 / Pd-on-C. Figure 12. Bio-polyethylene terephthalate (PET) Figure 13. Avantium process: bio-polyethylene furandicarboxylate (PEF)

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