Effect of different alkali catalysts on hydrothermal liquefaction of biopulp with the recirculation of the concentrated aqueous phase

In response to the over-generation of municipal solid waste (MSW) which is stem from the unprecedented growth of the human population and urbanization in recent decades, many disposal approaches have been established. However, approaches such as incineration or landfilling can intensify the risk of environmental contamination. Therefore, the need for a technology that not only is able to mitigate the hazardous substances, but also take advantage of that to produce value-added material like bio-fuel has been highly demanded. Among different thermochemical pathways, hydrothermal liquefaction (HTL) is the only technology capable of exploiting wet material to produce liquid bio-crude. Since the mid-decads of the 20th century, numerous researchers tried to improve the technology from different angles aiming to the elevated bio-crude production yield and subsequently higher energy recovery (ER). In order to promote the bio-crude, in terms of quantity and/or quality, many studies aimed at the utilization of the homogeneous catalysts. As a sub-branch of the homogeneous catalysts, alkaline salts (known as alkaline catalysts) including K2CO3, KOH, Na2CO3, etc. have been proved to be competent while associated with subcritical water medium during HTL process. Prohibition of coke formation in the further upgrading steps, as well as increment of the bio-crude production, are amongst the most eye-catching impacts of alkaline catalysts that have been studied so far. Although it has been reported that these substances can potentially change the reaction pathways occurring in the medium, the fundamental chemistry behind the variations has been ignored to a high extent. Digging into the chemical mechanisms taking place during the HTL process, this study will focus on comparing different alkaline catalysts in a lab-scale 12ml microbatch reactor at 350°C for 15 minutes.