Deactivation of Ni-MoS2 by bio-oil impurities during hydrodeoxygenation of phenol and octanol

Abstract

Deactivation of Ni-MoS2 by bio-oil impurities during hydrodeoxygenation of phenol and octanol, Applied Catalysis A, General http://dx.doi.org/10. 1016/j.apcata.2016.06.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Graphical abstractHighlights  Impurities as Cl, S, and K found in bio-oil will deactivate or inhibit MoS2-type catalyst by competing for the active sites  MoS2-based catalysts will produce sulfur containing hydrocarbons during HDO, but these can be removed again if a sufficiently high residence time is used enabling desulfurization of the product  Chlorine binds more strongly to the active sites of MoS2 based catalysts compared to H2O and H2S, while K irreversibly deactivates the catalyst 3 AbstractThe stability of Ni-MoS2/ZrO2 toward water, potassium, and chlorine containing compounds during hydrodeoxygenation (HDO) of a mixture of phenol and 1-octanol was investigated in a high pressure gas and liquid continuous flow fixed bed setup at 280°C and 100 bar. To maintain the stability of the catalyst, sufficient co-feeding of a sulfur source was necessary to avoid oxidation of the sulfide phase by oxygen replacement of the edge sulfur atoms in the MoS2 structure. However, the addition of sulfur to the feed gas resulted in the formation of sulfur containing compounds, mainly thiols, in the oil product if the residence time was too low. At a weight hourly space velocity (WHSV) of 4.9 h -1 the sulfur content in the liquid product was 980 ppm by weight, but this could be decreased to 5 ppm at a WHSV of 1.4 h -1 . A high co-feed of sulfur was needed when water was present in the feed and the H2O/H2S molar ratio should be below ca. 10 to maintain a decent stability of the catalyst. Chlorine containing compounds caused a reversible deactivation of the catalyst when co-fed to the reactor, where the catalytic activity could be completely regained when removing it from the feed. Commonly, chlorine, H2O, and H2S all inhibited the activity of the catalyst by competing for the active sites, with chlorine being by far the strongest inhibitor and H2S and H2O of roughly the same strength. Dissimilar, potassium was a severe poison and irreversibly deactivated the catalyst to <5% degree of deoxygenation when impregnated on the catalyst in a stoichiometric ratio relative to the active metal. This deactivation was a result of adsorption of potassium on the edge vacancy sites of the MoS2 slabs.

Influence of Bio-Oil Phospholipid on the Hydrodeoxygenation Activity of NiMoS/Al2O3 Catalyst

“…However, to understand the active phase dispersion and morphology, TEM analysis was performed on the catalyst (NiMo_1.3 PC) collected from the experiment with the highest amount of PC (Figure 8a). Bright Field (BF) micrographs (Figure 8a) showed the characteristic lamellar pattern of the Ni promoted active MoS 2 phase [16]. Comparing this pattern to the catalyst (NiMo_0 PC) without PC ( Figure S1) indicates an increase in the stacking degree of MoS 2 to 4.4 ± 1.7 with PC exposure compared to 2.3 ± 1 without.…”

“…Bio-oil impurities include sulfur, nitrogen, phosphorus bearing compounds, alkali, and alkaline earth materials, such as Na, Ca, Fe, Mg, etc. [12,16,17].…”

“…There are excellent reviews/articles on the deactivation of hydroprocessing catalysts [32,33]. Several deactivation studies of HDO catalysts have been carried out considering possible bio-oil impurities, like trap grease phospholipid, chlorine (Cl), potassium (K), and iron (Fe) [12,16,17]. Mortensen et al [16] concluded that irreversible K deactivation of NiMoS 2 /ZrO 2 catalyst was due to the occupancy of vacant sites near the MoS 2 slab edges.…”

“…Several deactivation studies of HDO catalysts have been carried out considering possible bio-oil impurities, like trap grease phospholipid, chlorine (Cl), potassium (K), and iron (Fe) [12,16,17]. Mortensen et al [16] concluded that irreversible K deactivation of NiMoS 2 /ZrO 2 catalyst was due to the occupancy of vacant sites near the MoS 2 slab edges. Recently, Arora et al [12] showed that Fe preferentially blocks the Ni sites to shift the activity and selectivity of NiMoS/Al 2 O 3 .…”

The Influence of Water on the Performance of Molybdenum Carbide Catalysts in Hydrodeoxygenation Reactions: A Combined Theoretical and Experimental Study

“…CoMo catalysts showed great performance forb oth processes, HYD and DDO, but typicallyr equire constant co-feeding of sulfur to prevent deactivation, leading to undesired contaminations in the product. [15][16][17][18] Recently,t ransition-metal carbides have gained attention because of their excellent performance in HDO reactions and their cheap price. [4] In contrast to noble-metal catalysts, molybdenum and tungsten carbides were reported to efficiently remove oxygen with hydrogen-efficient behavior,a st he hydrogenationo fu nsaturated CÀCb onds could be reduced.…”