Ni-Based Catalysts for the Hydrotreatment of Fast Pyrolysis Oil

Abstract

Catalytic hydrotreatment is an attractive technology to convert fast pyrolysis oil to stabilized oil products for coprocessing in conventional crude oil refinery units. We report here the use of novel bimetallic NiCu-and NiPd-based (Picula) catalysts characterized by a high Ni content (29−58 wt %) and prepared using a sol−gel method with SiO 2 , La 2 O 3 , kaolin, ZrO 2 , and combinations thereof as the support, for the catalytic hydrotreatment of fast pyrolysis oil. The experiments were performed in a batch autoclave (1 h at 150 °C, 3 h at 350 °C, and 200 bar initial pressure at 350 °C). The catalyst with the highest nickel loading (58 wt % Ni) promoted with Pd (0.7 wt %) was the most active, yielding oil products with improved properties compared to the crude pyrolysis oil (lower oxygen content, higher solubility in hydrocarbons, and less tendency for coke formation). For all Picula catalysts, except the ZrO 2 -based catalysts, methane formation was considerably lower than for Ru/C, the benchmark catalyst in catalytic hydrotreatment of fast pyrolysis oil. To anticipate possible catalyst deactivation at very long times on stream, catalyst regeneration studies were performed using thermogravimetric analysis. Analyses of the regenerated catalysts (X-ray diffraction, high-resolution transmission electron microscopy, and Brunauer−Emmett−Teller surface area) showed the occurrence of active metal agglomeration.

Mono-, bi-, and tri-metallic Ni-based catalysts for the catalytic hydrotreatment of pyrolysis liquids

“…Thus, the fresh sample very likely contains highly dispersed NiO species responsible for a broadening of XRD reflections, while particles of larger sizes account for the sharp tops of these peaks. In the 2θ range of 30-40°, a halo is visible, which corresponds to amorphous ZrO 2 , in line with literature data [25]. In situ reduction of the catalyst at 350°C results in the formation of reflections of metallic Ni with a concomitant reduction in the relative intensity of NiO species.…”

“…The lower reduction peak starting at 250°C (Fig. 1, Ni-Cu/SiO 2 -ZrO 2 ) with a maximum at about 330°C corresponds to reduction of Cu(II) into metallic Cu(0) [25,38] and reduction of a considerable part of the oxidized Ni species [25,39]. A second broad peak extending up to 700°С is associated with hardly reducible nickel silicates.…”

“…In a later study, we reported the synthesis and application of Ni-based catalysts promoted by Cu and Pd for the catalytic hydrotreatment of PLs at 350°C in a batch autoclave [25]. Products with a high H/C ratio and low coking tendency were observed.…”

“…These conditions were selected based on earlier catalyst screening studies by our group [23,[25][26][27][28]. Both biand tri-metallic catalyst Ni-based catalysts were prepared and tested with Mo, Cu, and Pd as promoters.…”

Deactivation of solid catalysts in liquid media: the case of leaching of active sites in biomass conversion reactions

“…41,[84][85][86] In the conversion of 60 lignocellulosic biomass via pyrolysis, metal lixiviation was identified as one of the causes for catalyst deactivation when Ni nickel and Cucopper were supported over gamma -alumina. 87 De Vlieger et al reported the deactivation of Pt and Pt-Ni supported catalyst in APR of ethylene glycol. The proposed mechanism included the leaching and re-deposition of the alumina phase support, causing a loss of exposed area of the metal active sites.…”