• Energy Research

The success of catalytic schemes for the large-scale valorization of CO2 does not only depend on the development of active, selective and stable catalytic materials but also on the overall process design. Here we present a multidisciplinary study (from catalyst to plant and techno-economic/lifecycle analysis) for the production of green methanol from renewable H2 and CO2. We combine an in-depth kinetic analysis of one of the most promising recently reported methanol-synthesis catalysts (InCo) with a thorough process simulation and techno-economic assessment. We then perform a life cycle assessment of the simulated process to gauge the real environmental impact of green methanol production from CO2. Our results indicate that up to 1.75 ton of CO2 can be abated per ton of produced methanol only if renewable energy is used to run the process, while the sensitivity analysis suggest that either rock-bottom H2 prices (1.5 $ kg−1) or severe CO2 taxation (300 $ per ton) are needed for a profitable methanol plant. Besides, we herein highlight and analyze some critical bottlenecks of the process. Especial attention has been paid to the contribution of H2 to the overall plant costs, CH4 trace formation, and purity and costs of raw gases. In addition to providing important information for policy makers and industrialists, directions for catalyst (and therefore process) improvements are outlined. Journal of Energy Chemistry, 68

This work investigates H2 production through aqueous phase reforming (APR) of synthetic brewery wastewater in a continuous fixed bed reactor with Pt and PtRe (3 wt %) catalysts supported on activated carbon. The influence of weight hourly space velocity (WHSV) and superficial Ar gas flow velocity (VAr) was assessed for the sake of optimisation, while reaction temperature and pressure were maintained at 225 °C and 28 bar, respectively. H2 production was found to be higher using the PtRe catalyst at the lowest WHSV (0.03 h-1) and highest VAr (0.8 cm s-1). The comparison of the maximum H2 production obtained in this work (27.9 μmol min-1) with other treatment processes shows the potential of the application of APR process for H2 production from brewery wastewater. Despite the different reaction conditions tested, the catalysts showed deactivation with time on stream, which was related to the formation of solid deposits on the surface of the catalysts. Therefore, future research should be related to the development of more stable catalysts, strategies that avoid deactivation by coking and regeneration processes.

Virtually all processes aiming for fuels and chemicals from biomass entail no less than one step for removing oxygen by hydrodeoxygenation (HDO). The bottleneck of HDO is the formation of deactivating carbonaceous species on the catalyst surface. In this work, we have studied the deactivation pathways of catalysts based on noble metal nanoparticles (Pt-Pd) supported on mildly acid supports during the HDO of raw bio-oil. At conditions of accelerated deactivation, monitoring the evolution with time on stream of hydrocarbon and oxygenated compounds in the reaction medium, the intermediates on the catalyst surface and the nature-location of deactivating species, two parallel deactivation routes have been revealed: the deposition of (i) thermal or pyrolytic lignin from alkylmethoxy phenols, on the catalyst mesopores and favored at low temperature, and; of (ii) aromatic coke from polycyclic aromatic hydrocarbons, starting on the catalyst micropores through condensation reactions and promoted by acidic sites and high temperature. Nevertheless, catalyst deactivation can be controlled within limits at harsh temperature conditions (450 degrees C) due to the preferential HDO of alkyl(methoxy) phenols into aromatics and the formation-hydrocracking steady state of the aromatic precursors of coke.

The formation, growth and transformation of carbon residue (coke) deposited on the catalyst during the raw bio-oil hydrodeoxygenation has been studied.

The performance (activity, selectivity and stability) of a Pt-Pd catalyst supported on a phosphorus-containing activated carbon (ACP) has been studied in the hydrodeoxygenation (HDO) of raw bio-oil, and compared with another bifunctional catalyst prepared with a FCC (Fluid Catalytic Cracking) catalyst as acid support. Experiments have been carried out in a fixed bed reactor under the following conditions: 400-450 °C; 65 bar; space time, 0.18 gcat h g-1bio-oil; H2:bio-oil ratio, 20 cm3H2 (STP) cm-3bio-oil; time on stream, 0-10 h. The catalyst reaches a pseudo-steady state at 450 °C after 6 h of time on stream, preserving a constant activity as a consequence of the simultaneous formation and hydrocracking of the deposited coke. In these conditions, the yield of C5+ hydrocarbons is 20 wt%. This organic liquid fraction mainly contains aromatics, and thus, it may require an additional mild hydrocracking treatment for its valorization as fuel. On the other hand, the gas fraction obtained can be used directly as fuel, and the aqueous liquid fraction (with a high concentration of methanol, 58 wt%) is interesting as co-feedstock with methanol in a methanol to olefins (MTO) unit. This work was carried out with the support of the Ministry of Economy and Competitiveness of the Spanish Government, some cofounded with ERDF funds (CTQ2009-12800, CTQ2012-36408 and CTQ2013-46172-P), the Basque Government (IT748-13), and the University of the Basque Country (UFI 11/39).