Hydrodeoxygenation (HDO) of Aliphatic Oxygenates and Phenol over NiMo/MgAl2O4: Reactivity, Inhibition, and Catalyst Reactivation

Abstract

This study provides new insights into sustainable fuel production by upgrading bio-derived oxygenates by catalytic hydrodeoxygenation (HDO). HDO of ethylene glycol (EG), cyclohexanol (Cyc), acetic acid (AcOH), and phenol (Phe) was investigated using a Ni-MoS2/MgAl2O4 catalyst. In addition, HDO of a mixture of Phe/EG and Cyc/EG was studied as a first step towards the complex mixture in biomass pyrolysis vapor and bio-oil. Activity tests were performed in a fixed bed reactor at 380–450 °C, 27 bar H2, 550 vol ppm H2S, and up to 220 h on stream. Acetic acid plugged the reactor inlet by carbon deposition within 2 h on stream, underlining the challenges of upgrading highly reactive oxygenates. For ethylene glycol and cyclohexanol, steady state conversion was obtained in the temperature range of 380–415 °C. The HDO macro-kinetics were assessed in terms of consecutive dehydration and hydrogenation reactions. The results indicate that HDO of ethylene glycol and cyclohexanol involve different active sites. There was no significant influence from phenol or cyclohexanol on the rate of ethylene glycol HDO. However, a pronounced inhibiting effect from ethylene glycol on the HDO of cyclohexanol was observed. Catalyst deactivation by carbon deposition could be mitigated by oxidation and re-sulfidation. The results presented here demonstrate the need to address differences in oxygenate reactivity when upgrading vapors or oils derived from pyrolysis of biomass.

Biomass hydrodeoxygenation catalysts innovation from atomistic activity predictors

“…As shown by many previous reports, transition metals such as Fe [12,13], Co [14,15], Ni [16][17][18], Cu [16,19], Mo [20][21][22], Ru [23,24], Rh [14,25], Pd [26][27][28][29], W [30], Pt [28,[31][32][33], or bimetallic combinations such as, AuPd [34], NiFe [7,[35][36][37], NiCu [38,39], NiMo [14,40,41], and PtNi [31,42] are highly active catalysts in the HDO reaction.…”

The Hydrodeoxygenation of Glycerol over NiMoSx: Catalyst Stability and Activity at Hydropyrolysis Conditions

“…After multiple glycerol HDO reactions followed by three total regenerations through calcination and sulfiding, the surface area of the NiMoS x /Al 2 O 3 was 128.1 m 2 /g. This loss of surface area could be due to sintering of the active NiMoS x planar structure manifested in a loss of surface area and active Ni−Mo−S edge sites [23,43–44] . High temperature calcination may also cause a change in the NiMoO x structure resulting in a less active NiMoS x catalyst upon sulfiding [45] …”

“…Glycerol HDO over NiMoS x catalyst with and without sulfur co-feeds (2100 ppm H 2 S equivalent), showing conversion and product yields with varying contact times. Reaction conditions: 400°C, 270 psig, 72.5-80 wt % glycerol and 0-7.5 % DMSO in water [23,[43][44] High temperature calcination may also cause a change in the NiMoO x structure resulting in a less active NiMoS x catalyst upon sulfiding. [45]…”

Carbon Deposition Behavior of Ni Catalyst Prepared by Combustion Method in Slurry Methanation Reaction

“…The primary reason for the stability and the deactivation of Ni catalyst is the carbon deposition of Ni [24]. At present, there are a large number of studies on the mechanism of carbon deposition [25], the structure of carbon deposition [26], the influence of carbon deposition on the activity of catalyst [27][28][29][30]. In the methanation reaction, the carbon deposition is mainly derived from the disproportionation of CO and decomposition of CH 4 .…”