(24f) Fast Catalytic Pyrolysis of Biomass and Relevant Model Compounds Studied in a Spouted Bed Reactor: Effect of Catalyst Type and Loading

Fast
Catalytic Pyrolysis of Biomass and Relevant Model Compounds Studied in a Spouted
Bed Reactor: Effect of Catalyst Type and Loading

Shoucheng Du, Nicholas Fleming, Julia
Valla, George M. Bollas

Department of Chemical and
Biomolecular Engineering, University of Connecticut, Storrs, CT

Thermal decomposition of
lignocellulosic biomass produces low-quality biooils and high char yields. Introduction
of catalyst in biomass fast pyrolysis can enable in-situ catalytic upgrading,
thus providing an effective way to directly convert biomass into relatively
high-quality product. As is shown in Figure 1, increasing catalyst amount can improve
the bio-oil quality by increasing the carbon yields of non-oxygenated compounds
via deoxygenation reactions. On the other hand, besides the catalyst loading, different
types of the catalyst have also been studied in order to improve the bio-oil
quality (aromatic yield).

Carlson et
al. [1,2] studied glucose fast catalytic pyrolysis in a
micro-pyroprobe reactor and they showed that the coke oxygenates yield (mostly
furan compounds) increase and the aromatic yield decreases as the
catalyst-to-glucose ratio decreases (from 19 to 1.5). However, the aromatic
selectivity is not a strong function of catalyst-to-glucose ratio. They also
studied the effects of different catalyst types (ZSM-5, Silicalite,
Beta-zeolite, Silica-alumina, and Y-zeolite) on the coke, oxygenate,
aromatic yields and concluded that ZSM-5 was the best catalyst with respect to
the aromatic yield due to its Brønsted acidity , pore size and structure. For
the aromatic selectivity, they showed that Y-zeolite, beta-zeolite and SiO₂-Al₂O₃
selectively produce smaller aromatics, such as benzene and toluene, while ZSM-5
and silicalite, which have the same pore structure, are selective to larger
aromatics, including naphthalene and indane. These observations show that the
aromatic yield is affected by both the catalyst type and loading, while the
aromatic selectivity is mostly affected by the catalyst type (pore structure
and active sites). Moreover, Jae et al. [4] studied the effects of different structures (different
pore size but all in the range of micropores) of zeolite catalysts on the
aromatic yield in fast catalytic pyrolysis of glucose with a pyroprobe reactor.
They concluded that ZSM-5 has optimal zeolite structure (pore size) for biomass
conversion to aromatics. Furthermore, Foster et al. [5] performed fast catalytic pyrolysis of wood and
glucose with modified ZSM-5 catalysts (with different silica to alumina ratios
23, 30, 50, 80 and mesopore structures) in a pyroprobe reactor. They found
that the aromatic yield from glucose pyrolysis reached a maximum with zeolites
of silica to alumina ratio of 30. They also showed that mesoporous ZSM-5 favored
the production of larger alkylaromatics in both glucose and wood pyrolysis due
to the relaxation of shape-selectivity, but did not affect the total aromatic
yield significantly.

Figure 2 Schematic of the existing spouted bed reactor setup for biomass (catalytic) pyrolysis

However, most
of the studies performed to study the catalyst effect on the quality of the
resulting pyrolysis bio-oil are in micro-pyroprobe reactors. This arouses an
interest for a similar investigation performed in a real fluidized bed reactor.
Thus, in this study, investigations on the effect of catalyst types and loading
on the bio-oil quality are performed in a spouted bed reactor, shown in Figure
2. Different biomass and relevant model compounds, such as pine sawdust,
glucose and cellulose are used as the feedstocks. Comparison of the results
regarding aromatic yield, aromatic selectivity between different feedstocks,
catalyst types and catalyst loadings will be presented.

References:

[1]      T.R.
Carlson, G. A. Tompsett, W.C. Conner, G.W. Huber, Topics in Catalysis 52 (2009)
241.

[2]      T.R. Carlson, J. Jae,
Y.-C. Lin, G. A. Tompsett, G.W. Huber, Journal of Catalysis 270 (2010) 110.

[3]      H. Zhang, R. Xiao, B.
Jin, D. Shen, R. Chen, G. Xiao, Bioresource Technology 137C (2013) 82.

[4]      J. Jae, G. A.
Tompsett, A.J. Foster, K.D. Hammond, S.M. Auerbach, R.F. Lobo, G.W. Huber,
Journal of Catalysis 279 (2011) 257.

[5]      A.J. Foster, J. Jae,
Y.-T. Cheng, G.W. Huber, R.F. Lobo, Applied Catalysis A: General 423-424 (2012)
154.