Biomass pyrolysis: Thermal decomposition mechanisms of furfural and benzaldehyde

Abstract

The thermal decompositions of furfural and benzaldehyde have been studied in a heated microtubular flow reactor. The pyrolysis experiments were carried out by passing a dilute mixture of the aromatic aldehydes (roughly 0.1%-1%) entrained in a stream of buffer gas (either He or Ar) through a pulsed, heated SiC reactor that is 2-3 cm long and 1 mm in diameter. Typical pressures in the reactor are 75-150 Torr with the SiC tube wall temperature in the range of 1200-1800 K. Characteristic residence times in the reactor are 100-200 μsec after which the gas mixture emerges as a skimmed molecular beam at a pressure of approximately 10 μTorr. Products were detected using matrix infrared absorption spectroscopy, 118.2 nm (10.487 eV) photoionization mass spectroscopy and resonance enhanced multiphoton ionization. The initial steps in the thermal decomposition of furfural and benzaldehyde have been identified. Furfural undergoes unimolecular decomposition to furan + CO: C4H3O-CHO (+ M) → CO + C4H4O. Sequential decomposition of furan leads to the production of HC≡CH, CH2CO, CH3C≡CH, CO, HCCCH2, and H atoms. In contrast, benzaldehyde resists decomposition until higher temperatures when it fragments to phenyl radical plus H atoms and CO: C6H5CHO (+ M) → C6H5CO + H → C6H5 + CO + H. The H atoms trigger a chain reaction by attacking C6H5CHO: H + C6H5CHO → [C6H6CHO]* → C6H6 + CO + H. The net result is the decomposition of benzaldehyde to produce benzene and CO.

Understanding the mechanism of catalytic fast pyrolysis by unveiling reactive intermediates in heterogeneous catalysis

“…Because of the small reactivity of pure phenol over H-USY and the missing labelled products ( 13 CO) from labelled anisole, deoxygenation of phenol and anisole could also be excluded over H-USY3940.…”

Measuring biomass fast pyrolysis kinetics: State of the art

“…These theoretical calculations suggest that glycol, formic acid, and hydroxyacetaldehyde are formed via ring opening of xylose. Vasiliou et al () performed similar experiments to derive the unimolecular pyrolysis kinetics of furfural, a decomposition product of cellulose and hemicellulose.…”

“…Besides, these studies can also help in designing a suitable catalyst to improve the selectivity towards desired products (Butler et al, ; Li et al, ). Numerous studies have been performed over the years to decode the kinetic mechanisms of biomass fast pyrolysis (Agarwal, Dauenhauer, Huber, & Auerbach, ; Bai et al, ; Bai & Brown, ; Banyasz, Li, Lyons‐Hart, & Shafer, ; Bradbury, Sakai, & Shafizadeh, ; Branca, Di Blasi, Mango, & Hrablay, ; Broido & Nelson, ; Choi et al, ; Chu, Subrahmanyam, & Huber, ; Custodis, Hemberger, Ma, & van Bokhoven, ; Debiagi et al, ; Faravelli, Frassoldati, Migliavacca, & Ranzi, ; Gai et al, ; Huang, Liu, Tong, Li, & Wu, ; Huang, Liu, Wei, Huang, & Li, ; Kawamoto, Murayama, & Saka, ; Kawamoto & Saka, ; Khachatryan, Xu, Wu, Pechagin, & Asatryan, ; Kim, Bai, & Brown, ; Lou, Wu, & Lyu, ; Mayes & Broadbelt, ; Mayes, Nolte, Beckham, Shanks, & Broadbelt, ; Mettler, Mushrif, et al, 2012; Miller & Bellan, ; Norinaga, Shoji, Kudo, & Hayashi, ; Nowakowska, Herbinet, Dufour, & Glaude, ; Patwardhan, Dalluge, Shanks, & Brown, ; Patwardhan, Satrio, Brown, & Shanks, ; Piskorz, Majerski, Radlein, Vladars‐Usas, & Scott, ; Piskorz, Radlein, & Scott, ; Ranzi et al, , ; Ranzi, Debiagi, & Frassoldati, , ; Ronsse, Dalluge, Prins, & Brown, ; Scheer et al, ; Scheer, Mukarakate, Robichaud, Nimlos, & Ellison, ; Shafizadeh & Fu, ; Shen & Gu, ; Shen, Gu, & Bridgwater, ; Shen, Xiao, Gu, & Luo, ; Varhegyi, Jakab, & Antal, ; Vasiliou et al, ; Vinu & Broadbelt, ; Wang, Ru, Lin, & Luo, ; Werner, Pommer, & Broström, ; Zhang, Li, Yang, & Blasiak, ; Zhang, Nolte, & Shanks, ; Zhou, Li, Mabon, & Broadbelt, ; Zhou, Nolte, Mayes, Shanks, & Broadbelt,…”

“…Alternatively, model compounds of the three biomass constituents have been used to derive the details of intermediate species generated during their thermal decomposition. Pyrolysis of model compounds also provides insights on the influence of the substituent functional groups or bond linkages on the product distribution (Asatryan et al, ; Asmadi, Kawamoto, & Saka, ; Buckingham et al, ; Choi et al, ; Custodis et al, ; Jarvis et al, ; Kawamoto & Saka, ; Khachatryan et al, ; Lou et al, ; Nowakowska et al, ; Patwardhan et al, ; Robichaud, Nimlos, & Ellison, ; Scheer et al, ; Scheer et al, ; Scheer, Mukarakate, Robichaud, Ellison, & Nimlos, ; Vasiliou et al, ; Wang, McDonald, et al, ; Xu et al, ; Zhou, Nolte, et al, ).…”

UV-tunable laser induced photolysis of matrix isolated anisole

“…Thus, anisole serves as an important model compound and understanding its decomposition pathways is closely related to the biomass combustion. Because of these reasons the pyrolysis of anisole and related compounds has recently attracted attention and was found to produce a number of interesting radicals [2,[3][4][5][6][7][8][9][10]. It was shown for anisole [2,3] using a hyperthermal tubular reactor and time-of-flight mass spectrometer that the first step in the thermal decomposition of this compound was the C O bond breakage and formation of the methyl and phenoxy radicals, followed by carbon monoxide liberation to form cyclopentadienyl radical.…”