Coke formation of model compounds relevant to pyrolysis bio-oil over ZSM-5

Abstract

Formation of coke during biomass catalytic pyrolysis deteriorates the selectivity to valuable liquid products and deactivates the catalyst, due to pore blocking and active site poisoning. In this work we investigate reaction mechanisms of coke formation and the structure of coke, formed from model compounds of relevance to biomass catalytic pyrolysis. Specifically, toluene, propylene, tolualdehyde and furan are catalytically pyrolyzed over ZSM-5, focusing on their yields to catalytic coke. Pyrolysis over inert silica is also performed, in order to understand the extent of thermal reactions. The pyrolysis product distribution of each model compound is presented and discussed in comparison with coke formation mechanisms proposed in the literature. It is shown that coke is mainly formed via oligomerization and polymerization of aromatic hydrocarbons and olefins. Catalytic reactions enhance the production of coke with higher crystallinity, less condensed structure and higher H/C ratio. Catalytic pyrolysis of toluene and tolualdehyde produces coke of similar structure, containing significant amounts of aliphatic carbons. Among the model compounds studied, furan produces the most condensed form of coke with no aliphatic carbons.

Bifunctional Ni‐ZSM‐5 Catalysts for the Pyrolysis and Hydropyrolysis of Biomass

“…MAHs and olefins in the hydrocarbonp ool undergo alkylation, cyclization, and rearrangement reactions (R D )t of orm higher-molecular-weight aromatics,s uch as naphthalenes and PA Hs. [52] They ields of naphthalenes and PA Hs decreased drastically as the pressure increased. Additionally,t he presence of Ni resulted in the formationo ff ewer naphthalenes and PA Hs.H owever, the yield to these compounds was unaffected by an increase in pressured uring hydropyrolysis.…”

“…In addition, Zhang and Moutsoglou have demonstrated that lignin‐derived phenols also contribute to the hydrocarbon pool after they undergo dehydration, cracking, oligomerization, and isomerization (R C ). Du et al . have proposed that in a hydrogen‐deficient environment, monoaromatic compounds alkylate and oligomerize over catalyst acid sites to form naphthalenes and PAHs (R D ), which further polymerize to form coke (R E ).…”

“…MAHs and olefins in the hydrocarbon pool undergo alkylation, cyclization, and rearrangement reactions (R D ) to form higher‐molecular‐weight aromatics, such as naphthalenes and PAHs . The yields of naphthalenes and PAHs decreased drastically as the pressure increased.…”

“…In addition, Zhang and Moutsoglou [51] have demonstrated that lignin-derived phenols also contribute to the hydrocarbon pool after they undergo dehydration, cracking,o ligomerization, and isomerization( R C ). Du et al [52] have proposed that in ah ydrogen-deficient environment,m onoaromatic compounds alkylate and oligomerize over catalyst acid sites to form naphthalenes and PA Hs (R D ), which further polymerizet of orm coke (R E ). In addition, French and Czernik [6] have found that the thermal decomposition of lignin in particular produces high yields of char (R F )c ompared to that of cellulose or hemicellulose.F urthermore,s econdary char may also originate from the reactionso fi ntermediate vapors( R E )a sp roposed by Mettler et al [53] In this work, we expanded the pyrolysis reactionn etwork of Wang et al [48] by the addition of reactions of the hydrocarbon pool with H 2 .T he reactionss hown in Scheme1 that re- quire the presence of H 2 ared epicted in blue.T he methanation of hydrocarbons and carbon oxides (R G )i naH 2 -rich atmosphere is well known for industriala pplications,s uch as coal utilization.…”

Synthesis, characterization and activity performance of nickel-loaded spent FCC catalyst for pine gum hydrogenation

“…soluble and insoluble. 25,26 The former includes aromatics with 2-3 rings adsorbed on the external surface and PAHs with 2-7 rings adsorbed inside the pore, while the latter is conrmed as an amorphous structure, and may consist of a disordered arrangement of polyaromatic molecules. Bibby et al 27 and Behera et al 28 presented the formation, nature and properties of coke, and studied the techniques for analyzing and characterizing coke.…”