Ricardo Rebelo

Currently I am the head of the Department of Chemistry and the coordinator of the research group SINETEC – Synthesis and Technology, at Regional University of Blumenau, in the state of Santa Catarina, Southern Brazil. This group was founded in 2002 and it has the organic synthesis as a key tool to achieve its objectives. One of the main concern of our group rely on the valorisation of the local biodiversity, specially associated to the Atlantic Rainforest, through the identification of abundant secondary metabolites and their use in process of technological importance, such as the biomass valorisation within the biorefinary concept.  

Along the last years, the SINETEC group has identified two aromatic species as potential sources of the arylpropanoid safrole, which more recently has been the starting material for the synthesis of a new Bronsted-Lowry acidic ionic liquid based imidazole (IL HSO4). It is known the use of acidic IL in the treatment of lignocellulosic biomass, to produce according to specific targets, furfural, a versatile chemical for industrial applications.            

BRISK2 gave the opportunity to visit Rig 1 of National Laboratory of Energy and Geology (LNEG) in Lisbon, where was possible to evaluate the performance of the IL HSO4 in the treatment of Brazilian sugar-cane bagasse for the production of furfural via hemicellulose hydrolysis. All the required facilities were available for a small scale biomass processing and characterization. During the course of my visit, it was possible to carry out experiments with and without solvent under standard conditions aiming the selective conversion of hemicellulose to furfural. 

The IL HSO4 containing the piperonyl unit derived from safrole, was previously purified by using charcoal in ethanol followed by its characterisation. The biomass used was also submitted to previous characterisation by quantitative acid hydrolysis for the determination of its macromolecular composition: cellulose, hemicellulose, xylan, arabinan, acetyl groups, Klason lignin and ash.The biomass treatments without solvent were carried out in a 15 mL vial hermetically sealed under continuous magnetic stirring in an oil bath. When the reaction was performed in the presence of THF (tetrahydrofuran), a more robust flask (Ace vessel-pressurized glassware) was employed. The thermal stability of the IL HSO4 was also investigated under the same experimental conditions for biomass treatment. The following steps were performed in each treatment: (i) thermal-IL HSO4 biomass treatment; (ii) water addition for fractioning and further filtration; (ii) HPLC analysis of aqueous phase; (iv) quantitative acid hydrolysis of the solid; (v) filtration for lignin and other compounds separation; (vi) HPLC analysis of the aqueous phase and (vii) calcination of the lignin fraction for ash determination. In the HPLC analysis standards of glucose, xylose, arabinose, hydroxymethylfurfural (HMF), furfural and acetic acid were used. When the reaction was conducted with THF, an additional step was necessary. The THF from the reaction flask was transferred to another flask and the biomass washed 3 times with THF to provide a final volume of 10 mL. This was also analysed by HPLC under the same analytical conditions to the other fractions.  

The preliminary results were promising, especially when THF was used, opening an opportunity for further research with this new IL HSO4 to furfural production and obtaining highly enriched cellulose material.    

 Finally, I would like to thanks to BRISK2 not only to the opportunity to have access to a research facility and expertise on biomass valorisation based on biorefinary concept, gaining an important knowledge on the field, but also to create an unique opportunity for further international collaboration with the hosting institution.     

Acknowledgments 

I would like to thank all the personnel at LNEG, particularly Dr. Rafal Lukasik, research supervisor, Dr. Francisco Gírio, Head of the Unit of Bioenergy – LNEG, Dra. Cristina Oliveira for the CG-FID and Karl-Fischer analysis, Dra. Joana Bernardo, laboratory collaborator, Belina Ribeiro for the HPLC analysis and Maria do Céu Penedo for general assistance. Thanks also to all my colleagues in the laboratory.