507
namely, succinic, fumaric and maleic acids, 2,3-furan dicarboxylic acid, hydroxy
propionic acid, aspartic acid, glucaric acid, glutamic acid, itaconic acid, levulinic
acid, 3-hydroxy-butyrolactone, glycerol, sorbitol and xylitol/arabinitol, based on
the importance of the final products derived from them, by utilizing the existing
conversion processes [20]. With the development of novel catalysts and processes
specifically for biomass conversion, a greater number of platform chemicals were
identified, and the list was subsequently updated in 2010 to include ethanol, furfural, hydroxy methyl furfural, 2,5-furan dicarboxylic acid, lactic acid and isoprene,
besides those considered in the earlier list [21]. Development of sustainable chemistry/processes now revolves around these platform chemicals for conversion to end
products, which were otherwise being produced from fossil resources. It is pertinent
to note that as many as five biomass-derived alcohols are considered as platform
chemicals. Both sugar/starch-based and lignocellulosic feedstock-based biorefineries that follow biochemical (fermentation), thermochemical (gasification of biomass to syngas) and hybrid syngas-biochemical routes [22–25] produce a range of
alcohols, rendering them as abundantly available, low-cost and carbon- neutral platform chemicals. In this scenario, several novel catalytic processes for the conversion of alcohols into biofuels and value-added products have emerged. Salient
features of such bio-alcohols-based processes, process chemistry, development of
catalysts and future trends are described in this chapter.
2 Chemistry of Alcohols
Alcohols (R-OH) belong to an important class of oxygenates, containing highly
versatile hydroxyl (–OH) functional group(s) which are capable of undergoing a
variety of chemical transformations involving cleavage of O-H or R-O bonds [26].
Variations in the molecular structure (primary, secondary and tertiary alcohols) and
nature (mono-, di-, tri- and polyhydric alcohols) (Fig. 2) govern their reactivity and
product selectivity for various reactions like oxidation, reduction, esterification,
dehydration, dehydrogenation, nucleophilic substitution, etherification and cyclization. With the growing importance of biomass conversion processes, several other
reactions of alcohols, like aldol condensation with aldehydes and ketones, acetalization, alcohol coupling and aromatization reactions are being pursued [27]. Based on
the carbon number, alcohols can be divided broadly into different groups, C 1 –C 2
alcohols (methanol and ethanol), C 3 –C 5 alcohols (1-propanol,1-butanol, 1- pentanol)
and C 6 –C 22 long-chain alcohols (2-ethyl hexanol, 1-decanol) and sugar alcohols
(sorbitol, mannitol). Besides their applications as fuels/fuel additives, alcohols, in
general, are used as feedstocks for numerous processes related to a wide spectrum
of industrial sectors, chemical, petrochemical, polymers, pharmaceutical, fine
chemicals and agro-chemicals, detergents, personal care products, lubricants and
industrial solvents for various applications (inks, paints, coatings, etc.).
Catalytic Conversion of Alcohols into Value-Added Products
namely, succinic, fumaric and maleic acids, 2,3-furan dicarboxylic acid, hydroxy
propionic acid, aspartic acid, glucaric acid, glutamic acid, itaconic acid, levulinic
acid, 3-hydroxy-butyrolactone, glycerol, sorbitol and xylitol/arabinitol, based on
the importance of the final products derived from them, by utilizing the existing
conversion processes [20]. With the development of novel catalysts and processes
specifically for biomass conversion, a greater number of platform chemicals were
identified, and the list was subsequently updated in 2010 to include ethanol, furfural, hydroxy methyl furfural, 2,5-furan dicarboxylic acid, lactic acid and isoprene,
besides those considered in the earlier list [21]. Development of sustainable chemistry/processes now revolves around these platform chemicals for conversion to end
products, which were otherwise being produced from fossil resources. It is pertinent
to note that as many as five biomass-derived alcohols are considered as platform
chemicals. Both sugar/starch-based and lignocellulosic feedstock-based biorefineries that follow biochemical (fermentation), thermochemical (gasification of biomass to syngas) and hybrid syngas-biochemical routes [22–25] produce a range of
alcohols, rendering them as abundantly available, low-cost and carbon- neutral platform chemicals. In this scenario, several novel catalytic processes for the conversion of alcohols into biofuels and value-added products have emerged. Salient
features of such bio-alcohols-based processes, process chemistry, development of
catalysts and future trends are described in this chapter.
2 Chemistry of Alcohols
Alcohols (R-OH) belong to an important class of oxygenates, containing highly
versatile hydroxyl (–OH) functional group(s) which are capable of undergoing a
variety of chemical transformations involving cleavage of O-H or R-O bonds [26].
Variations in the molecular structure (primary, secondary and tertiary alcohols) and
nature (mono-, di-, tri- and polyhydric alcohols) (Fig. 2) govern their reactivity and
product selectivity for various reactions like oxidation, reduction, esterification,
dehydration, dehydrogenation, nucleophilic substitution, etherification and cyclization. With the growing importance of biomass conversion processes, several other
reactions of alcohols, like aldol condensation with aldehydes and ketones, acetalization, alcohol coupling and aromatization reactions are being pursued [27]. Based on
the carbon number, alcohols can be divided broadly into different groups, C 1 –C 2
alcohols (methanol and ethanol), C 3 –C 5 alcohols (1-propanol,1-butanol, 1- pentanol)
and C 6 –C 22 long-chain alcohols (2-ethyl hexanol, 1-decanol) and sugar alcohols
(sorbitol, mannitol). Besides their applications as fuels/fuel additives, alcohols, in
general, are used as feedstocks for numerous processes related to a wide spectrum
of industrial sectors, chemical, petrochemical, polymers, pharmaceutical, fine
chemicals and agro-chemicals, detergents, personal care products, lubricants and
industrial solvents for various applications (inks, paints, coatings, etc.).
Catalytic Conversion of Alcohols into Value-Added Products