Environmental Engineering Reference
In-Depth Information
m −3 ]
c i,b
bulk concentration of component i
[mol
d p
particle diameter
[m]
[m 2
s −1 ]
D i,eff
effective diffusion coefficient of component i
mol −1 ]
E A,a
activation energy for rate constant a
[J
F
catalyst activity multiplication factor
[
-
]
n
number of carbon atoms in hydrocarbon
[
-
]
p i
partial pressure of component i
[Pa or bar]
s −1
kg cat −1 ]
r
reaction rate per unit mass of catalyst
[mol
mol −1
K −1 ]
R u
universal gas constant
[=8.314 J
T
temperature
[K]
Th
Thiele modulus
[
-
]
α
chain growth probability
[
-
]
mol −1 ]
Δ b H
adsorption enthalpy in Yates and Satterfield
expression
[J
mol −1 ]
Δ r H
reaction enthalpy
[J
η
catalyst effectiveness
[
-
]
m −3 ]
ρ cat
catalyst density
[kg
17.1
INTRODUCTION
A considerable part of the energy we consume is used to fuel vehicles in the form of
gasoline, diesel, kerosene, or other liquid fuels derived from crude oil. In the EU,
about one third of the energy consumption in 2011 was used for transportation
(tinyurl.com/388hn38). Worldwide, various steps are taken to make the transition
to more sustainable ways of fueling our cars, trucks, planes, and ships. Some radically
different solutions have been proposed, such as using hydrogen or electricity. These
have, however, two important drawbacks. First, the energy density is often low, which
decreases the range of a vehicle. Second, switching to hydrogen or electricity requires
a completely new infrastructure of supplying the fuel. Liquid transportation fuels
derived from biomass do not have these disadvantages. Their properties are much
closer to those of the currently used fuels, enabling a quick and smooth transition.
If the biomass required is grown in a sustainable way (see Chapter 1), these fuels
are much more sustainable than crude oil-derived fuels.
Much of the technology that is currently proposed or used for converting biomass
into synthetic fuels relies on earlier developments for the production of fuels from
natural gas or coal. Often, these routes rely on the production of syngas (a mixture
of mainly hydrogen and carbon monoxide) as a convenient intermediate product,
as discussed in Chapter 10. In addition to liquid fuels, we will also treat synthetic nat-
ural gas (SNG) in this chapter. Although it is not a liquid and not only used for trans-
portation, the production route is similar to that of the other synthetic fuels treated in
this chapter. Also, the gaseous compound dimethyl ether (DME) will be briefly trea-
ted, as it is strongly related to methanol production. Figure 17.1 gives an overview of
the main production routes of these fuels via syngas.
 
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