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Bio-Based Chemicals from Renewable Biomass for Integrated Biorefineries

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energies Review Bio-Based Chemicals from Renewable Biomass for Integrated Biorefineries Kirtika Kohli 1 , Ravindra Prajapati 2 and Brajendra K. Sharma 1,* 1 Prairie Research Institute—Illinois Sustainable Technology Center, University of Illinois, Urbana Champaign, IL 61820, USA; [email protected] 2 Conversions & Catalysis Division, CSIR-Indian Institute of Petroleum, Dehradun, Uttarakhand 248005, India; [email protected] * Correspondence: [email protected] Received: 10 December 2018; Accepted: 4 January 2019; Published: 13 January 2019 Abstract: The production of chemicals from biomass, a renewable feedstock, is highly desirable in replacing petrochemicals to make biorefineries more economical. The best approach to compete with fossil-based refineries is the upgradation of biomass in integrated biorefineries. The integrated biorefineries employed various biomass feedstocks and conversion technologies to produce biofuels and bio-based chemicals. Bio-based chemicals can help to replace a large fraction of industrial chemicals and materials from fossil resources. Biomass-derived chemicals, such as 5-hydroxymethylfurfural (5-HMF), levulinic acid, furfurals, sugar alcohols, lactic acid, succinic acid, and phenols, are considered platform chemicals. These platform chemicals can be further used for the production of a variety of important chemicals on an industrial scale. However, current industrial production relies on relatively old and inefficient strategies and low production yields, which have decreased their competitiveness with fossil-based alternatives. The aim of the presented review is to provide a survey of past and current strategies used to achieve a sustainable conversion of biomass to platform chemicals. This review provides an overview of the chemicals obtained, based on the major components of lignocellulosic biomass, sugars, and lignin. First, important platform chemicals derived from the catalytic conversion of biomass were outlined. Later, the targeted chemicals that can be potentially manufactured from the starting or platform materials were discussed in detail. Despite significant advances, however, low yields, complex multistep synthesis processes, difficulties in purification, high costs, and the deactivation of catalysts are still hurdles for large-scale competitive biorefineries. These challenges could be overcome by single-step catalytic conversions using highly efficient and selective catalysts and exploring purification and separation technologies. Keywords: renewable biomass; hydrodeoxygenation (HDO); dehydration; hydrogenation; biomass-derived chemicals; biorefinery; catalytic conversion 1. Introduction A dependence on fossil-based energy sources, decreasing accessibility to crude oil, motivation to protect the environment from disastrous carbon emissions, and an increasing world population have led to increased interest in becoming less energy dependent than in the past. These concerns have motivated researchers to develop technologies for renewable resources to substitute petroleum derivatives. The best approach to compete with fossil-based refineries is the processing of biomass in integrated biorefineries. The integrated biorefineries employed various biomass feedstocks and conversion technologies to produce biofuels and bio-based chemicals. From an industrial point of view, a biorefinery should require the most efficient conversion processes for the production of high valued chemicals and biofuels [1–3]. Biomass feedstocks, such as agricultural residues and wood chips, Energies 2019, 12, 233; doi:10.3390/en12020233 www.mdpi.com/journal/energies EnergiesEnergies 20192019, ,1212, ,x 233 FOR PEER REVIEW 22 of of 39 40 valued chemicals and biofuels [1–3]. Biomass feedstocks, such as agricultural residues and wood chips,constitute constitute an inexpensive an inexpensive renewable renewable resource resource for commercial for commercial large-scale large-scale biorefineries, biorefineries, as these as these waste wasteproducts products are widely are widely available available and and can can sequester sequester carbon. carbon. The The target target chemicals chemicals includeinclude alcohols [4], [4], organicorganic acids acids such such as as formic formic acid acid and and levulinic levulinic acid acid [5], [5], and and furanics furanics such such as as 5-hydroxymethylfurfural 5-hydroxymethylfurfural (5-HMF)(5-HMF) and and furfurals furfurals [6]. [6]. These These chemicals chemicals can can furt furtherher be be converted converted to to a a range range of of derivatives derivatives that that havehave potential potential applications applications in in biofuels, biofuels, polymers, polymers, and and solvent solvent industries. industries. The The possible possible scheme scheme for for a a chemo-catalyticchemo-catalytic biorefinery biorefinery is is shown shown in in Figure Figure 11.. Catalytic hydrolysis & depolymerization Catalytic Cellulose and Biofuels Lignin HDO hemi-cellulose Chemical conversion Fermentation Dehydration Alcohols Furfurals Phenols (Biofuel & chemicals) (Biofuel & chemicals) Aromatics Aqueous phase Dibasic acids reforming Olefins Hydrocarbon & bio-hydrogen (Biofuel & chemicals) FigureFigure 1. 1. TheThe possible possible scheme scheme for for aa chemo-catalytic chemo-catalytic biorefinery. biorefinery. LignocellulosicLignocellulosic biomass is mainlymainly composedcomposed of of cellulose cellulose (34–54 (34–54 wt wt %), %), hemicellulose hemicellulose (19–34 (19–34 wt wt %), %),and and lignin lignin (11–30 (11–30 wt %) wt [ 7%)]. Cellulose,[7]. Cellulose, the major the major component component of biomass, of biomass, is present is present as half as of half the organic of the organiccarbon incarbon the biosphere in the biosphere [7–9]. The [7–9]. development The develo of processespment of and processes technologies and technologies to convert lignocellulosic to convert lignocellulosicbiomass to fuels biomass and value-added to fuels and chemicals value-added (given chemicals in Figure (given2) remains in Figure a significant 2) remains challenge. a significant In this challenge.context, the In majorthis context, difficulty the major in producing difficulty a highin producing yield of targeta high chemicalsyield of target and fuelschemicals is the and complex fuels ischemical the complex composition chemical of lignocellulosiccomposition of biomass lignocellu feedstocks.losic biomass Structurally, feedstocks. cellulose Structurally, contains anhydrous cellulose containsglucose unitsanhydrous and hemicellulose glucose units consists and hemicellulose of different C5 consists sugar of monomers. different C5 On sugar the other monomers. hand, lignin On the is a othercomplex, hand, three-dimensional, lignin is a complex, and three-dimensional, cross-linked biopolymer and cross-linked havingphenylpropane biopolymer having units phenylpropane with relatively unitshydrophobic with relatively and aromatic hydrophobic properties and [aromatic10,11]. Due prop toerties these differences[10,11]. Due in to their these chemical differences composition in their chemicaland structure, composition cellulose, and hemicellulose, structure, cellulose, and lignin he havemicellulose, different and chemical lignin reactivities.have different In addition chemical to reactivities.the complex In nature addition of bio-resources, to the complex the nature inert chemical of bio-resources, structure andthe compositionalinert chemical ratiostructure of carbon, and compositionalhydrogen, and ratio oxygen of carbon, in molecules hydrogen, in biomass and oxygen present in difficultiesmolecules in thebiomass chemo-catalytic present difficulties conversion in theof biomasschemo-catalytic to fuels andconversion chemicals. of biomass Therefore, to besidesfuels and using chemicals. the natural Therefore, lignocellulosic besides biomassusing the as naturala reactant, lignocellulosic researchers biomass often use as a model reactant, compounds researchers for often conversion use model process compounds studies. for Inconversion addition, processthe development studies. In of addition, highly active the development and selective of catalysts highly foractive the chemo-selectiveand selective catalysts catalytic for conversion the chemo- of selectivelignocellulosic catalytic biomass conversion to desired of lignocellulosic products remainsbiomass to a dauntingdesired produc challenge.ts remains a daunting challenge. Energies 2019, 12, 233 3 of 40 Energies 2019, 12, x FOR PEER REVIEW 3 of 39 Cellulose Hydrolysis Glucose C1 C2 C3 C4 C5 C6 Methane Ethanol Lactic acid Maleic acid Furfural Sorbitol Formic acid Acetic acid Glyceraldehyde Erythrose Levulinic acid Fructose CO2 Glycol aldehyde Pyruvaldehyde Mannitol CO + H2 Hydroxyacetone 5-HMF ϒ-valerolactone Hydrolysis Hydrogenation/ Hemi-cellulose Xylose Tetrahydrofurfural Deoxygenation Pentanoic acid 1-pentanol C-O Cleavage Guaiacols Hydrogenation/ Alcohols Lignin + Phenol Deoxygenation Hydrocarbons monomers Figure 2. Potential chemicals and fuels obtained from lignocellulosic biomass. Many review articles on chemicals obtained from bio-resources have been published, such as those focused on a large varietyvariety ofof biomassbiomass feedstocks/substratesfeedstocks/substrates and and reaction reaction types, as well as those dealing with specific specific feedstocks such as carbohydrates, triglycerides, cellulose, hemicellulose, lignin, lignin, 5-hydroxymethylfurfural [12], [12], furfural [13], [13], and lignocellulosic biomass [[14].14]. Some reviews were dedicated to
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