Environmental Engineering Reference
In-Depth Information
10
1st condenser
2nd condenser
8
6
4
2
0
0 0 0 0 0 0
Temperature of 1st condenser (°C)
60
70
80
90
FIGURE 11.11
Staged condensation; acetic acid distribution over the first and second
condenser. The reactor temperature is 480
C. The second condenser operates at 20
C.
Spray columns are used. (Source: Reproduced with permission from Westerhof et al.
(2011). © American Chemical Society.)
11.8 CATALYTIC PYROLYSIS
Catalytic pyrolysis has been considered to overcome the problematic characteristics
of pyrolysis oil, as mentioned in the introduction, and to more selectively produce
target compounds. Impregnating specific compounds such as H
2
SO
4
and ZnCl
2
into
the biomass particles in order control the primary reactions and the use of heteroge-
neous catalysts in the reactor to steer the secondary reactions have received signif-
icant attention in the last years. This section is not intended to give a detailed account
of catalytic pyrolysis, but merely to mention its scope. Dickerson and Soria (2013)
listed and reviewed the developments. Selective oxygen removal from the pyrolysis
vapors, preferably by decarboxylation, aiming at increasing the heating value and
decreasing the acidity of bio-oil, has been studied most. Deoxygenation reactions
are catalyzed by acids, and the most studied ones are solid acids such as zeolites
and clays. Aiming at the production of chemicals, yields of aromatics of ca. 20% (car-
bon basis) when using modified ZSM-5 zeolites have been reported (Cheng et al.,
2012). All reported results on catalysis to steer the heterogeneous reactions show that
low product yields and excessive coke and water formation are still items that need
considerable attention.
The company KiOR (United States; see Internet References) developed a fluid cat-
alytic cracking (FCC)-like catalytic pyrolysis process. Not much detailed information
is available about this process. However, patent information available indicates the
use of alkali and alkaline earth catalysts on mildly acidic support oxides such as
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