Conference Dates

March 8-13, 2009


The concept of biomass refinery or biorefinery, has attracted great attention during the last decade. The idea is to process lignocelullosic residues converting the resulting products or fractions of them into a variety of fine chemicals or high added value products and raw materials serving as a feedstock for other valuable chemicals and commodities.

One of the most interesting paths for the thermochemical conversion of biomass is fast pyrolysis of biomass followed by catalytic steam reforming of the liquid pyrolysis products (bio-oil) or its fractions. The product gas from this process is a H2 rich with moderate CO content which, conveniently conditioned, may serve as a valuable feedstock in the production of various chemicals, offering numerous possibilities.

The bio-oil is a complex mixture of oxygenated organic compounds and water in a 85/15 mass ratio. The main constituents include alcohols, carboxylic acids, sugars, aldehydes and ketones, as well as more complex carbohydrates and lignin derived materials. It can be split into two main fractions by water addition: a highly valued organic fraction that can be used as a feedstock to produce fine chemicals, and water insoluble and an aqueous fraction, less valuable, that can be catalytically steam reformed.

The catalysts for the steam reforming process are usually nickel based, similar to those commercial employed in the catalytic steam reforming of natural gas and naphthas. Their main advantages are their high activity and selectivity to hydrogen, as well as their relative low cost compared to other catalysts based on noble metals. However, there still remains the challenge of developing nickel based catalysts with an adequate resistance to deactivation by coke deposition. Therefore, the aim of the present work is to develop a suitable nickel coprecipitated catalyst for the catalytic steam reforming of the aqueous fraction of biomass pyrolysis liquids. The catalyst must be not only active and selective to hydrogen, but resistant to deactivation by coke deposition and to attrition, in order to be fed in a future in a fluidized bed setup.

In the present work, the catalytic steam reforming of model compounds of the aqueous fraction of bio-oil has been studied with Ni/Al coprecipitated catalysts in a microscale fixed bed setup. Several catalysts with different nickel contents have been tested at 650 ºC. The effect of promoters (Cu and Mg) on product gas yields has also constituted a matter of study. Further work will be accomplished with the aqueous fraction of bio-oil.

The experimental setup consists of a fixed bed inside a tubular quartz reactor operating at atmospheric pressure. The bed is constituted by a mixture of sand (used as inert filler) and a Ni-based catalyst. The experimental procedure implies in-situ reduction of the catalyst with hydrogen and further reforming of the organic. The exiting flow is forced into a condenser and finally the remaining product gases are analysed on-line with a Micro GC before venting. Typically, 20-30 mg of catalyst were used and the organic was fed by means of a HPLC metering pump.