365
synthesis of n-butyl levulinate. Further text of the chapter provides insight of our
related research efforts, starting with a brief introduction to zeolites.
7 Synthesis of Levulinic Esters Using Zeolites as Solid
Acid Catalysts
Zeolites are inorganic crystalline materials of aluminum and silicates having an
intricate and delicate porous structure. These materials are distinguished in terms of
the framework “corner atoms” and have cavities and channels in their design.
Different constituent atoms and their subsequent arrangements lead to a plethora of
structures which are formally attributed with a nomenclature by the Structure
Commission of the International Zeolite Association (IZA-SC) [150] . The famously
known sieves, viz., zeolites, MOFs, aluminophosphates, as well as a few other silicates, fall under this category. Although each of these materials is equally important
and finds relevant applications in various fields [151, 152], the likes of zeolites and
silicates are many in the recent times [153].
Zeolites are naturally occurring three-dimensional microporous aluminosilicates
interlinked by oxygen atoms and possessing specific sized molecular pores, cavities, and channels.
Henceforth, they are widely used as ion-exchange materials, adsorbents, and
solid acid catalysts in various industrial sectors, like oil refining plants, petroleum
industry, water purification, wastewater treatment plants, and perfumery industry,
and in effluent treatment. Due to the presence of uniform molecular cavities, pores,
and channel system, they allow entry of selective molecules which in turn depends
on the size of channels, pores, and cavities [69, 154–159]. The constituent atoms
can be replaced by a variable number of other elements imparting interesting properties and the same applicability. The channels and cavities possess a diameter in the
range of 0.3–1.3 nm, depending upon the structure. Generally, the values of internal
surface area and pore volume are 800 m
2
g
−1
and 0.35 cm
3
g
−1
, respectively
[160, 161].
A comprehensive insight into the formation, mechanistic growth, as well as
structures of the zeolitic materials has been elaborately presented by Barrer and
Richard [162]. They present the growth and crystallization mechanism as a bottomup phenomenon wherein small preformed framework building blocks known as the
secondary building units (SBUs) condense into the three-dimensional microporous
structures [150]. The synthesis strategy of microporous zeolites involves the precursors, viz., alumina and silica polycondensed using the sol-gel process. The method
often involves the use of structure-directing materials commonly termed as templates. The templates bring about a horizon of crystalline structures that can be
synthesized and put forward into applications. The templates used are mostly organics of amines, quaternary ammonium cations, cyclic ethers, and coordination compounds (or the organometallics) [163]. A perfect highly ordered porous structure
Solid Acid-Catalyzed Esterification of Levulinic Acid for Production of Value-Added…
synthesis of n-butyl levulinate. Further text of the chapter provides insight of our
related research efforts, starting with a brief introduction to zeolites.
7 Synthesis of Levulinic Esters Using Zeolites as Solid
Acid Catalysts
Zeolites are inorganic crystalline materials of aluminum and silicates having an
intricate and delicate porous structure. These materials are distinguished in terms of
the framework “corner atoms” and have cavities and channels in their design.
Different constituent atoms and their subsequent arrangements lead to a plethora of
structures which are formally attributed with a nomenclature by the Structure
Commission of the International Zeolite Association (IZA-SC) [150] . The famously
known sieves, viz., zeolites, MOFs, aluminophosphates, as well as a few other silicates, fall under this category. Although each of these materials is equally important
and finds relevant applications in various fields [151, 152], the likes of zeolites and
silicates are many in the recent times [153].
Zeolites are naturally occurring three-dimensional microporous aluminosilicates
interlinked by oxygen atoms and possessing specific sized molecular pores, cavities, and channels.
Henceforth, they are widely used as ion-exchange materials, adsorbents, and
solid acid catalysts in various industrial sectors, like oil refining plants, petroleum
industry, water purification, wastewater treatment plants, and perfumery industry,
and in effluent treatment. Due to the presence of uniform molecular cavities, pores,
and channel system, they allow entry of selective molecules which in turn depends
on the size of channels, pores, and cavities [69, 154–159]. The constituent atoms
can be replaced by a variable number of other elements imparting interesting properties and the same applicability. The channels and cavities possess a diameter in the
range of 0.3–1.3 nm, depending upon the structure. Generally, the values of internal
surface area and pore volume are 800 m
2
g
−1
and 0.35 cm
3
g
−1
, respectively
[160, 161].
A comprehensive insight into the formation, mechanistic growth, as well as
structures of the zeolitic materials has been elaborately presented by Barrer and
Richard [162]. They present the growth and crystallization mechanism as a bottomup phenomenon wherein small preformed framework building blocks known as the
secondary building units (SBUs) condense into the three-dimensional microporous
structures [150]. The synthesis strategy of microporous zeolites involves the precursors, viz., alumina and silica polycondensed using the sol-gel process. The method
often involves the use of structure-directing materials commonly termed as templates. The templates bring about a horizon of crystalline structures that can be
synthesized and put forward into applications. The templates used are mostly organics of amines, quaternary ammonium cations, cyclic ethers, and coordination compounds (or the organometallics) [163]. A perfect highly ordered porous structure
Solid Acid-Catalyzed Esterification of Levulinic Acid for Production of Value-Added…