Aromatic Chemicals by Iron‐Catalyzed Hydrotreatment of Lignin Pyrolysis Vapor

Abstract

Lignin is a potential renewable material for the production of bio-sourced aromatic chemicals. We present the first hydrotreatment of lignin pyrolysis vapors, before any condensation, using inexpensive and sustainable iron-silica (Fe/SiO2 ) and iron-activated carbon (Fe/AC) catalysts. Lignin pyrolysis was conducted in a tubular reactor and vapors were injected in a fixed bed of catalysts (673 K, 1 bar) with stacks to investigate the profile of coke deposit. More than 170 GC-analyzable compounds were identified by GCxGC (heart cutting)/flame ionization detector mass spectrometry. Lignin oligomers were analyzed by very high resolution mass spectrometry, called the "petroleomic" method. They are trapped by the catalytic fixed bed and, in particular, by the AC. The catalysts showed a good selectivity for the hydrodeoxygenation of real lignin vapors to benzene, toluene, xylenes, phenol, cresols, and alkyl phenols. The spent catalysts were characterized by temperature-programmed oxidation, transmission electron microscopy (TEM), and N2 sorption. Micropores in the Fe/AC catalyst are completely plugged by coke deposits, whereas the mesoporous structure of Fe/SiO2 is unaffected. TEM images reveal two different types of coke deposit: 1) catalytic coke deposited in the vicinity of iron particles and 2) thermal coke (carbonaceous particles ≈1 μm in diameter) formed from the gas-phase growth of lignin oligomers.

Solvent free depolymerization of Kraft lignin to alkyl-phenolics using supported NiMo and CoMo catalysts

“…2,3 Several approaches have been reported for the valorization of lignin. These include enzymatic methods, 4,5 thermal treatment in the absence of air (pyrolysis), 6,7 base catalysed depolymerizations [8][9][10][11] and various chemo-catalytic methods like catalytic hydrotreatment in which lignin is reacted with gaseous hydrogen or a hydrogen donor solvent. 2,[12][13][14] Oxidative approaches are also known and have also recently been established.…”

Advances in Upgrading Lignin Pyrolysis Vapors by Ex Situ Catalytic Fast Pyrolysis

“…Olcese and co-workers have used Fe/SiO 2 and Fe/AC(activated carbon) to hydrotreat lignin pyrolysis vapor at 400 8C under atmosphere H 2 pressure. [94] Both catalysts show good selectivity for the HDO of real lignin vapors to benzene,t oluene,x ylenes,p henol, cresols,a nd alkyl phenols.T he catalytic stability of Fe/SiO 2 is much better than that of Fe/AC, because the mesoporouss tructure of the former is not affected by coke deposits.R ezaei and co-workers have also synthesized an iron-based catalyst (Fe/Hb)f or the ex situ CFP of lignin and palm kernel shell waste with ah igh lignin content of approximately 50 wt %. TheF e/Hb catalyst is efficient in producing aromatic hydrocarbons.L ignin-derived phenolics can also be effectively deoxygenated to aromatics through ah ydrogenolysis reaction promoted by Fe active sites.…”

“…Olcese and co‐workers have used Fe/SiO 2 and Fe/AC (activated carbon) to hydrotreat lignin pyrolysis vapor at 400 °C under atmosphere H 2 pressure . Both catalysts show good selectivity for the HDO of real lignin vapors to benzene, toluene, xylenes, phenol, cresols, and alkyl phenols.…”

Catalytic upgrading of gaseous tars over zeolite catalysts during coal pyrolysis

“…The coking deposition on the catalyst corresponds to coke species made up of components with different H/C ratios [23]. In general, the coking deposition on the catalyst can be divided into two kinds: one is referred to as thermal coke and the other is called catalytic coke [24][25][26]. The fraction that can be burned at low temperature (peak in the 400-480°C range) is considered as thermal coke, mainly consisting of adsorbed high boiling products (heavy compounds).…”