Abstract

The steam reforming of bio-oil is a promising and economically feasible technology for the sustainable H2 production, yet with the main challenge of designing highly active and stable catalysts. This work aimed to study the deactivation mechanism of a NiAl2O4 spinel derived catalyst, the role of Ni and alumina sites in this mechanism and the appropriate reaction conditions to attenuate deactivation. The reaction tests were carried out in a fluidized bed reactor with prior separation of the pyrolytic lignin. The fresh or used catalysts were characterized using X-ray diffraction, temperature-programmed oxidation, X-ray photoelectron spectroscopy, scanning electron microscopy combined with energy dispersive X-ray spectroscopy, and Raman spectroscopy. For steam/carbon ratios > 3.0, space time above 0.075 h and temperature between 600−700 °C, high initial hydrogen yield is obtained (in the 85–90 % range) with CO yield near 20 %, CH4 yield below 5 % and negligible initial yield of hydrocarbons. The catalyst is more stable at 600 °C, with coke formation preferentially located on Ni sites inside the catalyst particle. Increasing the temperature favors the coke development and consequent deposition on the alumina support, leading to a rapid catalyst deactivation because the limited availability of Ni and alumina sites. These results contribute to understand the phenomenon of catalyst deactivation in the steam reforming of bio-oil and set appropriate reaction conditions to mitigate this problem with a NiAl2O4 spinel derived catalyst.

Highlights

  • The necessary energy transition towards a sustainable model implies the progressive depletion of fossil fuels and their substitution with environmentally friendly energy vectors

  • We have investigated the mechanism of deactivation by coke of a NiAl2O4 spinel derived catalyst in the SR of bio-oil (SRB)

  • We have further extended our research on deepening the insights into the catalyst deactivation by coke at different reaction conditions (600− 700 ◦C; space time, up to 0.25 (g catalyst) h (g bio-oil)− 1; and steam/carbon molar ratio (S/C), 1.5–6), with the purpose of establishing adequate reaction conditions for mitigating this problem affecting the process feasibility

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Summary

Introduction

The necessary energy transition towards a sustainable model implies the progressive depletion of fossil fuels and their substitution with environmentally friendly energy vectors. Hydrogen is a promising energy vector because it is a clean fuel and it has the maximum energy capacity [1]. The use of these raw materials makes the hydrogen production through SR unsustainable, and the challenge is to develop processes based on renewable raw materials, such as biomass. On this regards, most of the efforts focus on the SR of biomass derivatives, that of bio-oil (SRB) [4,5,6]. Bio-oil is the liquid product from the fast pyrolysis of lignocellulosic biomass [7]

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