Environmental Engineering Reference
In-Depth Information
HO
O
Butane
Pentane
Hexane
Pt /Al 2 O 3
HO
OH
OH
OH
502 K
Pt-Re/C catalyst
H 2 /CO x + monofunctionals:
OH
O
R
R
R
OH
R
Ketones
O
OH
Alcohols
R
R
O
R
O
R
O
R
OH
Heterocycles
Acids
FIGURE 18.13 Aqueous reforming of glucose. Treatment of aqueous streams of glucose
over catalysts at elevated temperatures leads to a plethora of either nonfunctionalized or
monofunctionalized molecules. The oxygen ends up as either CO 2 or water.
increased rates of dehydration and hydrogenation compared to hydrogenolysis and
reforming. This can be exploited to selectively produce light alkanes (see Figure 18.13).
By operating under conditions that favor C
O bond cleavage (i.e., high oxygenate feed
concentration, elevated system pressure, low temperature), a Pt
-
Re/C catalyst is able
to partially deoxygenate polyols and produce monofunctional intermediates, which
are predominantly 2-ketones, secondary alcohols, heterocycles, and carboxylic acids.
In a next step, thesemonofunctionals can be used as feedstock for a variety of upgrading
strategies: (i) C
-
Ccoupling through aldol condensation of ketones over base catalysts,
(ii) C
Ccoupling of alcohols using bifunctional metal/base catalysts in the presence of
hydrogen, and (iii) C
C coupling through ketonization of carboxylic acids in the pres-
ence of base catalysts (Corma et al., 2008). As noted previously, these upgrading
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