(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).

Figure 1 Carbon yields (calculated out of the total carbon in the biomass feedstock) of different compound groups as a function of catalyst to biomass weight ratio. Benzene (including Benzene; Benzene, 1-ethyl, 2-methyl; Benzene, ethyl; Toluene; Xylene; Styrene), Phenol (including Phenol; Phenol, 2-methyl; Phenol, 3-methyl; Phenol, 2,3-dimethyl), Benzofuran (including Benzofuran; Benzofuran, 7-methyl; benzofuran, 2-methyl), Indene/Indane (including Indene; Indane; 1-H-indene, methyl), Naphthalene (including Naphthalene; Naphthalene, 1,2-dihydro; Naphthalene, 2-methyl; Naphthalene, 1-methyl)

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.