(278e) Value Added Products From Lignocellulose Based Biochar

The European fuel market is facing two major challenges. One challenge is the rising need of motor fuels which is at present satisfied with rising imports. The second challenge is to meet the directives of the European Commission to increase the amount of biofuels within the field of motor fuels to 10% until 2020 [1].

This target cannot be achieved with industrially established technologies such as production of biofuels (biodiesel, bioethanol). New complementary technologies are required to aim this goal. One of the main suggestions is the usage of whole plant energy which is not in competition with the food industry. Possible feedstock with respect to the total usage of the plant is lignocellulose biomass like wood or straw.

Gasification of the feedstock and liquefaction by Fischer-Tropsch-Synthesis is an established pathway utilized for example by Coren Company (GER). Although gasification and liquefaction by Fischer-Tropsch Synthesis are very complex processes with an overall efficiency of 50% [2], it is favoured at present.

Another promising route of producing liquid energy carriers from biomass is Liquid-Phase-Pyrolysis. Preliminary research work in this field was accomplished with promising results [3]. Beside condensibles biochar is a major product of Liquid-Phase-Pyrolysis with a broad field of applications.

The specific surface area of biochar gives access to chemical modification even including intermediates for fuel synthesis. In comparison with Fischer-Tropsch synthesis direct liquefaction of biochar needs less upgrade of the feed. The direct liquefaction is a heterogeneous catalytic high temperature/high pressure process. Several catalysts and coal based feed was investigated in the past [4].

Focus of the present project is the validation of liquefaction processes with biochar and with selected catalysts. Liquefaction by catalytic hydrogenation is carried out in a batch reactor of 1100 ml volume. The reactor can be operated at a maximum pressure of 20 MPa and a maximum temperature of 400 °C. Batch size is 25g to 50g of biochar dissolved in n-alkane carrier. Prior to liquefaction biochar was carefully mixed/impregnated with the catalyst (5 wt% at maximum) and dried to minimize physically dissolved water. Overall kinetics of liquefaction is deduced from hydrogen consumption records.

With molybdenum oxide based catalysts and hydrogenation at T=370 °C and P = 18 MPa the formation of a wide range of alkanes <C30 as well as cycloalkanes is observed. Latter substances are assumed to be derivatives of the lignin structure. Asphaltenes could not yet be identified but are still subject of investigations, because adsorption on the solid residues can not yet be excluded.

Beside oxide based catalysts sulphide based catalysts are subject of catalyst screening. In both cases the recycling of catalysts as well as product poisoning is governing direction of investigations.

[1]        2009/28/EC, EU Directive. Directive on the promotion of the use of energy from renewable sources. Strasbourg : European Union, 2009.

[2]        Coren, Company. Information & Press. [Online] 24. 01 2011. http://www.choren.com/informationen/faq/.

[3]        Verena, Mertlitz. Dissertation: Flüssigphasen-Pyrolyse biogener Edukte. Graz : TU Graz, 2010.

[4]        Sol, Weller et.al. Coal Hydrogenation Catalysts Batch Autoclave Tests. Industrial & Engineering Chemistry. 42, 1950, 330-334.