13
Introduction
New microorganisms and enzymes will have to be developed to make these processes
more efficient and economical. The fermentation process can generate specific types
of products and will require basic understanding of the applications of genomics and
proteomics to different types of lignocellulosic materials.
1.2.9 ChAPTer 10: ProduCTion oF SynTheTiC FuelS By SuPerCriTiCAl WATer
Water under supercritical conditions behaves very differently than at room temperature. Water has high solubility for many organic and cellulosic compounds
under these conditions. The density, viscosity, and other properties facilitate the
conversion of a variety of feedstock to fuels such as hydrogen, methane, and syngas. Since the pioneering work of Modell at Massachusetts Institute of Technology
(MIT), this technology has made enormous progress and now many pilot-scale
operations for the application of this technology to generate synfuels have become
a reality.
In recent years, the interest in the use of supercritical water for the production
of fuels and chemicals has been rapidly expanding. As mentioned earlier, the main
reason is that the unique properties of supercritical water allow a variety of organic
reactions to be carried out in the supercritical phase. In these reactions, water not
only plays a benign role of solvent but also plays a role as an active reactant or a catalyst. Properties of water under supercritical conditions ensure that important organic
reactions can be carried out in a homogeneous medium.
Supercritical water can play five different functions: (1) a medium in which
numerous types of organic chemical synthesis occur, (2) a medium for partial or
complete oxidation of numerous hazardous or nonhazardous materials, (3) a medium
in which complex materials decompose and produce liquids and gases, (4) a medium
for thermal or catalytic gasification of simple and complex materials to produce fuels
such as methane and hydrogen, and (5) a medium to generate hydrogen by catalytic
gasification and reforming of various carbonaceous materials. Chapter 10 outlines
the role of supercritical water in each of these functions with a special emphasis on
the functions that generate synthetic fuels.
Collectively, Chapters 4–10 illustrate various thermochemical, catalytic, and biotechnological options to convert coal, biomass, waste, and their mixtures to a variety
of synthetic gaseous, liquid, and solid fuels. In all of these cases, water provides an
important role of a reaction medium, a reactant, or a catalyst.
1.2.10 ChAPTer 11: ProduCTion oF hydrogen By WATer diSSoCiATion
Water can also be a direct source of fuel. Hydrogen can be generated from water by
its dissociation. Hydrogen is the cleanest form of energy and may be the only longterm solution to our energy needs.
Chapter 11 examines three basic methods to dissociate water to produce hydrogen: electrolysis, photocatalytic or photobiological dissociation, and thermal or thermochemical dissociation. Various ramifications of each of these methods are also
briefly examined. The chapter also briefly assesses other novel methods for the production of hydrogen from water.
Introduction
New microorganisms and enzymes will have to be developed to make these processes
more efficient and economical. The fermentation process can generate specific types
of products and will require basic understanding of the applications of genomics and
proteomics to different types of lignocellulosic materials.
1.2.9 ChAPTer 10: ProduCTion oF SynTheTiC FuelS By SuPerCriTiCAl WATer
Water under supercritical conditions behaves very differently than at room temperature. Water has high solubility for many organic and cellulosic compounds
under these conditions. The density, viscosity, and other properties facilitate the
conversion of a variety of feedstock to fuels such as hydrogen, methane, and syngas. Since the pioneering work of Modell at Massachusetts Institute of Technology
(MIT), this technology has made enormous progress and now many pilot-scale
operations for the application of this technology to generate synfuels have become
a reality.
In recent years, the interest in the use of supercritical water for the production
of fuels and chemicals has been rapidly expanding. As mentioned earlier, the main
reason is that the unique properties of supercritical water allow a variety of organic
reactions to be carried out in the supercritical phase. In these reactions, water not
only plays a benign role of solvent but also plays a role as an active reactant or a catalyst. Properties of water under supercritical conditions ensure that important organic
reactions can be carried out in a homogeneous medium.
Supercritical water can play five different functions: (1) a medium in which
numerous types of organic chemical synthesis occur, (2) a medium for partial or
complete oxidation of numerous hazardous or nonhazardous materials, (3) a medium
in which complex materials decompose and produce liquids and gases, (4) a medium
for thermal or catalytic gasification of simple and complex materials to produce fuels
such as methane and hydrogen, and (5) a medium to generate hydrogen by catalytic
gasification and reforming of various carbonaceous materials. Chapter 10 outlines
the role of supercritical water in each of these functions with a special emphasis on
the functions that generate synthetic fuels.
Collectively, Chapters 4–10 illustrate various thermochemical, catalytic, and biotechnological options to convert coal, biomass, waste, and their mixtures to a variety
of synthetic gaseous, liquid, and solid fuels. In all of these cases, water provides an
important role of a reaction medium, a reactant, or a catalyst.
1.2.10 ChAPTer 11: ProduCTion oF hydrogen By WATer diSSoCiATion
Water can also be a direct source of fuel. Hydrogen can be generated from water by
its dissociation. Hydrogen is the cleanest form of energy and may be the only longterm solution to our energy needs.
Chapter 11 examines three basic methods to dissociate water to produce hydrogen: electrolysis, photocatalytic or photobiological dissociation, and thermal or thermochemical dissociation. Various ramifications of each of these methods are also
briefly examined. The chapter also briefly assesses other novel methods for the production of hydrogen from water.