Steam reforming of raw bio-oil over Ni/La2O3-αAl2O3: Influence of temperature on product yields and catalyst deactivation

Oxidative Steam Reforming of Raw Bio-Oil over Supported and Bulk Ni Catalysts for Hydrogen Production

“…Although it can be attenuated with operating conditions suitable for minimizing its possible causes (such as high space-time values and S/C ratios for minimizing coke deposition [27]), the industrial development of the process will require using regeneration strategies that allow the complete recovery of the activity corresponding to the fresh catalyst. Consequently, together with a high activity, H 2 selectivity, and stability in the reaction, the regenerability of the catalyst (that is, the ability for recovering the activity of the fresh catalysts subsequent to a suitable regeneration strategy), is a key factor for the selection of the catalyst.…”

“…The performance of the catalysts in the OSR of raw bio-oil has been compared under the operating conditions indicated in Section 4.3, which were selected according to the previous results on the SR and OSR of bio-oil [15,21,26,27]. These conditions (700 • C, S/C = 6, O/C = 0.34, with low space-time values) provide high bio-oil conversion and H 2 yield, but with quite a rapid deactivation of the catalysts (due to the low space-time), in order to allow a rapid comparison of the catalysts stability.…”

“…For all the catalysts, two different combustion domains are observed: the main peak burns at low temperature, in the 300-450 • C range, and the position of its maximum differs depending on the nature of the support, in the order Ni/Ce < NiAl 2 O 4 < Ni/LaAl; the minority peak burns at high temperature, with a maximum near 600 • C. In the literature, the first peak is attributed to the combustion of encapsulating coke of amorphous nature and deposited on the metal sites (that catalyse the combustion reaction at a lower temperature), thus having a high impact on deactivation. The coke burning at high temperature is attributed to a more structured coke (with a high content of condensed polyaromatics) deposited on the support and, consequently, with a lower impact on deactivation [26,27,61]. The low content of coke deposited on the support for Ni/Ce catalyst could be explained by the redox properties of the CeO 2 support and its capacity for O 2 storage, which enhances the lattice oxygen exchange with O 2 in the gas phase and favours coke gasification during the reaction [62].…”

“…Thus, Politano and Chiarello [23] have proven the relevance of the co-adsorption of other compounds in the reaction medium on the adsorption of CO on Ni sites, with the formation of intermediate COH with the adsorbed H. This complex behaviour of Ni sites makes the interpretation of the results difficult. The experimental runs were carried out in an experimental device with two units in series (thermal step and catalytic step, the latter in fluidized bed reactor), whose adequacy for SR and OSR of aqueous and raw bio-oil has been previously proven, as it minimizes operating problems (such as plugging of reactor piping) as well as catalyst deactivation in the reforming step [15,21,22,[24][25][26][27]. The properties of the catalysts have been determined with different techniques (N 2 adsorption-desorption, Temperature Programmed Reduction (TPR), X-ray Diffraction (XRD)), in order to explain the differences in the kinetic behaviour of the catalysts.…”

Temperature Programmed Oxidation Coupled with In Situ Techniques Reveal the Nature and Location of Coke Deposited on a Ni/La2O3‐αAl2O3 Catalyst in the Steam Reforming of Bio‐oil

“…The reaction equipment for the reforming of bio‐oil consists of two units or steps in‐series: (i) a raw bio‐oil thermal treatment step, intended to retain the carbonaceous solid (thermal pyrolytic lignin) formed by re‐polymerization of phenolic compounds in raw bio‐oil; and (ii) a catalytic fluidized bed reactor, where steam reforming of the volatile stream leaving the thermal step takes place, over a Ni/La 2 O 3 ‐αAl 2 O 3 catalyst. A detailed description of the equipment has been previously reported elsewhere . The runs were performed at the following operating conditions: thermal step, 500 °C; catalytic step, at two temperatures (550 and 700 °C) with two different values of steam‐to‐carbon molar ratio ( S/C =1.5 and 6.0); space time, 0.19 g catalyst h g bio‐oil −1 ; time on stream, 4–7 h; atmospheric pressure.…”