Javier Fermoso

Multifunctional Pd/Ni–Co Catalyst for Hydrogen Production by Chemical Looping Coupled With Steam Reforming of Acetic Acid

High yield of high-purity H2 from acetic acid, a model compound of bio-oil obtained from the fast pyrolysis of biomass, was produced by sorption-enhanced steam reforming (SESR). An oxygen carrier was introduced into a chemical loop (CL) coupled to the cyclical SESR process to supply heat in situ for the endothermic sorbent regeneration to increase the energy efficiency of the process. A new multifunctional 1 %Pd/20 %Ni-20 %Co catalyst was developed for use both as oxygen carrier in the CL and as reforming catalyst in the SESR whereas a CaO-based material was used as CO2 sorbent. In the sorbent-air regeneration step, the Ni-Co atoms in the catalyst undergo strong exothermic oxidation reactions that provide heat for the CaO decarbonation. The addition of Pd to the Ni-Co catalyst makes the catalyst active throughout the whole SESR-CL cycle. Pd significantly promotes the reduction of Ni-Co oxides to metallic Ni-Co during the reforming stage, which avoids the need for a reduction step after regeneration. H2 yield above 90 % and H2 purity above 99.2 vol % were obtained.

Assessing biomass catalytic pyrolysis in terms of deoxygenation pathways and energy yields for the efficient production of advanced biofuels

The present work focuses on the pathways through which catalytic pyrolysis of biomass into bio-oil proceeds and the effect of the operation conditions on parameters like bio-oil oxygen composition and mass yield, and also additional indicators, such as the distribution of both the oxygen and the chemical energy contained in the initial biomass among the different products. Acid washed wheat straw was used as biomass feedstock. The pyrolysis tests were performed in a lab-scale downdraft fixed-bed reactor working at atmospheric pressure, employing a nanocrystalline H-ZSM-5 zeolite as catalyst. A systematic study was carried out by decoupling both the thermal and catalytic reactions in order to evaluate the influence of three key variables: temperature of the thermal zone; temperature of the subsequent catalytic step and catalyst/biomass ratio. Increasing the pyrolysis temperature in the thermal zone resulted in more bio-oil* (bio-oil in water-free basis) production to the detriment of char and water fractions. In contrast, a significant reduction in bio-oil* fraction, due to decarbonylation and decarboxylation, occurred when increasing the catalytic bed temperature from 400 up to 500 °C. A similar effect was observed by varying the catalyst/biomass ratio since it increased the production of CO, CO2, light olefins and coke at the expense of a decline in the bio-oil* yield. Nevertheless, this bio-oil contains oxygen amounting to as low as 10 wt%, while retaining about 38% of the energy yield. Char, coke and gaseous hydrocarbons contain a great part of the biomass chemical energy, hence their formation should be suppressed or minimized to further improve the bio-oil* energy yield. At high catalyst/biomass ratios, the bio-oil becomes rich in aromatic compounds, both oxygenated and hydrocarbons, while the amount of sugars, furans, carboxylic acids, and other oxygenated products is strongly reduced.

Pyrolysis of microalgae for fuel production

This chapter provides a review of the state of the art relative to microalgae pyrolysis as a route to produce advanced biofuels. The review is focused on the liquid fraction directly obtained from pyrolysis, called bio-oil, the target product of the process. This bio-oil can be directly used as fuel in simple boilers and turbines for the production of heat and electricity or converted to advanced biofuels by further upgrading routes like catalytic pyrolysis. Accordingly, the technology of pyrolysis is first explained and classified into different operation modes. Thereafter, the key roles that the reaction conditions and the pyrolysis mode play on the yield and quality of bio-oils are described. Finally, a brief overview of the current maturity level of the technology, highlighting the main technological challenges as well as a comparison in terms of environmental and energy balances with other microalgae conversion processes is presented.

Engineering the acidity and accessibility of the zeolite ZSM-5 for efficient bio-oil upgrading in catalytic pyrolysis of lignocellulose

The properties of the zeolite ZSM-5 have been optimised for the production and deoxygenation of the bio-oil* (bio-oil on water-free basis) fraction by lignocellulose catalytic pyrolysis. Two ZSM-5 supports possessing high mesopore/external surface area, and therefore enhanced accessibility, have been employed to promote the conversion of the bulky compounds formed in the primary cracking of lignocellulose. These supports are a nanocrystalline material (n-ZSM-5) and a hierarchical sample (h-ZSM-5) of different Si/Al ratios and acid site concentrations. Acidic features of both zeolites have been modified and adjusted by incorporation of ZrO2, which has a significant effect on the concentration and distribution of both Bronsted and Lewis acid sites. These materials have been tested in the catalytic pyrolysis of acid-washed wheat straw (WS-ac) using a two-step (thermal/catalytic) reaction system at different catalyst/biomass ratios. The results obtained have been assessed in terms of oxygen content, energy yield and composition of the produced bio-oil*, taking also into account the selectivity towards the different deoxygenation pathways. The ZrO2/n-ZSM-5 sample showed remarkable performance in the biomass catalytic pyrolysis, as a result of the appropriate combination of accessibility and acidic properties. In particular, modification of the zeolitic support acidity by incorporation of highly dispersed ZrO2 effectively decreased the extent of secondary reactions, such as severe cracking and coke formation, as well as promoted the conversion of the oligomers formed initially by lignocellulose pyrolysis, thus sharply decreasing the proportion of the components not detected by GC-MS in the upgraded bio-oil*.