Özben Kutlu

I was interested in composition of liquid products of torrefaction and slow pyrolysis after finishing my PhD thesis. I finally decided to go to Aston University (European Bioenergy Research Institute – EBRI) through the BRISK2 Transnational Access programme due to carry out trials and learn more details from experts. 

The propose of this visit was to investigate which valuable products could be produced by ketonization of liquid product (acetic acid, especially) obtained from low temperature slow pyrolysis; thus we were analysing the change in liquid composition by using GC-MS. This involved characterization of catalyst, slow pyrolysis process and ketonization followed by appropriate chemical and physical analysis. Small acid compounds in liquid product reduce the resulting bio-oil stability. The bio-oil stability can therefore be increased by ketonization and valuable chemicals can be produced beside valuable char via low temperature pyrolysis. Ketonization can suitably convert bio-based acids into ketones and it involves the condensation of two acid molecules to form a ketone, CO2 and H2O. Afterwards, aldol condensation and hydrogenation can be used to obtain liquid alkanes from the obtained ketones. Thus, ketonization is important for the acetic acid conversion pathway of ketonization−aldol-hydrogenation.   

In this work, beech wood was used due to suitable lignocellulosic content. The experiments, with and without ketonization, were carried out in continuous slow pyrolysis system with a feeding rate of 240 g h-1 at three different pyrolysis temperatures. The present system was modified by placing a new reactor into the pipe of volatile product for the experiments with ketonization. Zirconium oxide in pellet and powder form was used as catalyst for ketonization performed at 400°C. Besides the effects of pyrolysis temperature, ketonization and particle size of catalyst, the change in liquid composition per operating time was also investigated. Based on the initial outcomes, the colour of liquid was getting lighter than the liquid’s produced by single pyrolysis process. In addition, the amount of liquid product was significantly reduced at the end of these parallel processes. Although phenolic compounds were found as main compound in whole liquid products, similar results were observed in processes performed at 375°C and 450°C. On the other hand, it was found that more acid was produced at high temperature within the selected-range without ketonization, however the change in concentration does not significantly effect in pH values. Conclusive results can be reported after finishing analyses performing in both Institutes (EBRI and BESTMER). It has also been predicted that more trials could be carried out for extensive discussion. This experience provided by BRISK2 has been very useful for future research and collaboration, and an international publication has been predicted within this context. 

The EBRI at Aston University has exclusive education and quality research infrastructure about biomass energy technology. For this reason, my visit funded by BRISK2 provided beneficial information and supported to my occupational and educational career. For instance, I had an opportunity to be contact with other researchers and experts, discuss the experimental results with my supervisor Dr. Scott Banks, and visit to the pilot gasification plant at EBRI. As for outcomes of this visit, the established scientific contacts will be able to help me to develop bilateral projects and mobility in the near future. Finally, I would like to thank the coordinators of the BRISK2 Transnational Access project, and the friendly EBRI research team who were highly professional and helpful at all times; particularly Dr. Scott Banks and Filipe Rego. They took the time to show me the facilities and equipment at EBRI. I would highly recommend the BRISK2 project to all those who wish to share knowledge and engage in research on biomass and bioenergy technology.