Controlling the selectivity to chemicals from lignin via catalytic fast pyrolysis Original Research Article

The catalytic fast pyrolysis of alkaline lignin to useful chemicals was investigated using zeolite catalysts with different acidity and pore size. The catalyst played dual roles in this process. In its acid form, it catalytically converted the depolymerized intermediates into desirable and more stable products. This and their surface prevented repolymerization and coke formation. The yield of liquid and the selectivity to desired products can be controlled by tuning of the acidity and pore size of the catalyst. Using no catalyst yielded 40 wt.% of liquid, which mainly consisted of 6 wt.% (carbon yield) of phenols and 19 wt.% (carbon yield) of phenol alkoxy species. The highest yield of phenol alkoxy species was obtained over H-ZSM5 of extremely low number of acid sites; liquid yield of 51 wt.% and carbon yield of 24 wt.%. The highest yield of liquid (75 wt.%) was obtained over H-USY, which had the largest pore size and lowest Si/Al ratio, thus the largest number of acid sites among all the catalyst tested; the carbon yield of aromatic hydrocarbons was around 40 wt.% at 650 °C. Depolymerized lignin products undergo consecutive reaction to form phenol alkoxy, phenols, and eventually aromatic hydrocarbons.