chapter covers important aspects in the adsorption mechanism of alcohols and water
in (mainly) hydrophobic zeolite pores, such as cluster formation and hydrogen
bonding. These effects inevitably also play a role when looking at the diffusion of
alcohols inside the zeolite pores. Finally, this chapter will cover some examples of
studies where hydrophobic zeolites have been used to recover bio-alcohols, such as
biobutanol and bioethanol, from model solutions or fermentation broths via fixedbed separations.
Keywords Adsorption · Biobutanol · Chabazite · LTA · Silicalite
1 The Production of Renewable Alcohols in a Biorefinery
Important environmental challenges, such as global warming and pollution, lead to
an increasing pressure on chemical industry to move away from fossil-based feedstocks. An alternative source of energy (fuels) and materials (platform chemicals) is
waste biomass from the agricultural or food industry. The conversion of biomass to
fuels and chemicals can be performed either via more traditional, catalytic processes
[1–3] or via bioconversion or fermentation processes, based on the use of enzymes
and microorganisms [1, 4–8].
In fermentation processes, a biomass-based substrate is very selectively converted
into a chemical product via a microorganism. The desired chemical product can be
either a side-product or a main product of the natural metabolism of the microbe.
Microorganisms can be genetically engineered to increase the yield of the desired
product [9–11]. Furthermore, during a fermentation, the usually high selectivity of
the microbe metabolism can be exploited under mild process conditions. For
instance, fermentation processes usually take place at relatively low temperatures
(20–40
C) and mild pH [6, 11, 12]. These mild process conditions and high
selectivity of microorganisms are significant advantages of fermentation processes
compared to catalytic conversions [1–3].
Many different promising platform molecules can be produced via fermentation:
organic acids (succinic acid, lactic acid, acetic acid, . . .) [13–16], hydrocarbons
(isoprene, isobutene, . . .) [17, 18], diols (butanediol, propanediol) [19, 20], and
short-chain alcohols [6, 9, 12, 21, 22]. Large-scale productions of alcohols via
fermentation are performed worldwide, for example, in Brazil using sugarcane as
feedstock [23, 24]. Besides being a biofuel replacement for gasoline, bioethanol can
be dehydrated into ethylene, which is a key component in the material industry
[25, 26]. 1-butanol or n-butanol is another example, which can serve as a feedstock
for the production of butene [27]. The production of n-butanol via the acetonebutanol-ethanol (ABE) fermentation processes was carried out worldwide on a very
large scale before World War II [22] but phased out with the discovery of cheap
fossil-based resources. While it has remained important in Russia and China [28], it
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B. Claessens et al.
in (mainly) hydrophobic zeolite pores, such as cluster formation and hydrogen
bonding. These effects inevitably also play a role when looking at the diffusion of
alcohols inside the zeolite pores. Finally, this chapter will cover some examples of
studies where hydrophobic zeolites have been used to recover bio-alcohols, such as
biobutanol and bioethanol, from model solutions or fermentation broths via fixedbed separations.
Keywords Adsorption · Biobutanol · Chabazite · LTA · Silicalite
1 The Production of Renewable Alcohols in a Biorefinery
Important environmental challenges, such as global warming and pollution, lead to
an increasing pressure on chemical industry to move away from fossil-based feedstocks. An alternative source of energy (fuels) and materials (platform chemicals) is
waste biomass from the agricultural or food industry. The conversion of biomass to
fuels and chemicals can be performed either via more traditional, catalytic processes
[1–3] or via bioconversion or fermentation processes, based on the use of enzymes
and microorganisms [1, 4–8].
In fermentation processes, a biomass-based substrate is very selectively converted
into a chemical product via a microorganism. The desired chemical product can be
either a side-product or a main product of the natural metabolism of the microbe.
Microorganisms can be genetically engineered to increase the yield of the desired
product [9–11]. Furthermore, during a fermentation, the usually high selectivity of
the microbe metabolism can be exploited under mild process conditions. For
instance, fermentation processes usually take place at relatively low temperatures
(20–40
C) and mild pH [6, 11, 12]. These mild process conditions and high
selectivity of microorganisms are significant advantages of fermentation processes
compared to catalytic conversions [1–3].
Many different promising platform molecules can be produced via fermentation:
organic acids (succinic acid, lactic acid, acetic acid, . . .) [13–16], hydrocarbons
(isoprene, isobutene, . . .) [17, 18], diols (butanediol, propanediol) [19, 20], and
short-chain alcohols [6, 9, 12, 21, 22]. Large-scale productions of alcohols via
fermentation are performed worldwide, for example, in Brazil using sugarcane as
feedstock [23, 24]. Besides being a biofuel replacement for gasoline, bioethanol can
be dehydrated into ethylene, which is a key component in the material industry
[25, 26]. 1-butanol or n-butanol is another example, which can serve as a feedstock
for the production of butene [27]. The production of n-butanol via the acetonebutanol-ethanol (ABE) fermentation processes was carried out worldwide on a very
large scale before World War II [22] but phased out with the discovery of cheap
fossil-based resources. While it has remained important in Russia and China [28], it
86
B. Claessens et al.