Energy & Fuels 2009, 23, 4129–4136
4129
Attenuation of Catalyst Deactivation by Cofeeding Methanol for Enhancing the Valorisation of Crude Bio-oil Ana G. Gayubo,* Beatriz Valle, Andre´s T. Aguayo, Martı´n Olazar, and Javier Bilbao Departamento de Ingenierı´a Quı´mica, UniVersidad del Paı´s Vasco, Apartado 644, 48080 Bilbao, Spain ReceiVed April 6, 2009. ReVised Manuscript ReceiVed June 10, 2009
The catalytic transformation of crude bio-oil into hydrocarbons has been studied on a catalyst prepared based on a modified HZSM-5 zeolite. Previously, the bio-oil has been subjected to stabilization treatments to minimize pyrolytic lignin deposition on the catalyst and to attenuate deactivation. Cofeeding methanol (around 70 wt %) minimizes pyrolytic lignin deposition within and outside the catalyst particles, thereby increasing the viability of crude bio-oil upgrading. Given that the origin of catalyst deactivation is coke deposition within the particles, the nature of this coke has been studied by temperature-programmed oxidation. The coke is made up of (i) thermal coke (pyrolytic lignin formed mainly by polymerization of bio-oil phenolic components) and (ii) catalytic coke (formed in the HZSM-5 zeolite from bio-oil oxygenate compounds by acid sites). These two coke fractions have been quantified, and their combustion kinetics have been determined. Cofeeding methanol contributes to decreasing the content of both types of coke, but mainly thermal coke, and so catalyst deactivation is lower. The activation energy for thermal coke combustion (E1) is more than twice that corresponding to catalytic coke combustion (E2), whereas the kinetic constant at 550 °C (k*1 ) is an order of magnitude higher than that for the catalytic coke (k*2 ). This is attributed to the latter’s location in the HZSM-5 zeolite micropores. The combustion kinetic parameters for both types of coke are dependent on methanol content in the feed.
1. Introduction Biomass and its derivatives arouse great expectations for the production of fuel, raw materials for synthesis in the petrochemical industry, and fine chemicals.1-3 In addition to the firstgeneration biofuels (bioethanol and biodiesel), bio-oil is of interest due to the prospect for production by lignocellulosic biomass flash pyrolysis and to the renewable nature of this raw material. Flash pyrolysis is characterized by the fast heating of biomass (103-104 K s-1). The products obtained are gases, volatiles, aerosols, and char. Volatiles and aerosols remain for a short residence time in the reactor (
