Catalytic pyrolysis of MDF wastes over beta zeolite-supported platinum

Abstract

The increasing demand for clean energy and for the environmental protection has driven the search for new technologies that minimize the impacts of the excessive consumption of fossil fuel. Catalytic pyrolysis emerges as a promising alternative route for producing energy and chemicals from biomass, because of its flexibility, low cost and simplicity. However, the process still requires active catalysts that can be tailored for each application. With this goal in mind, catalysts based on platinum (1 %) supported on beta zeolite with different SAR (30, 60 and 90) were evaluated in the fast pyrolysis of pre-treated medium density fiber (MDF) residues in this work. Beta zeolite was prepared using silica extracted from coal ash came from a thermoelectric plant. Non-oxygenated compounds, such as BTEX (benzene, toluene, ethylbenzene and xylenes), other monoaromatics (21.2–26.5 %), naphthalene derivatives (5–29.2 %), polyaromatics (0–6.1 %) and linear hydrocarbon (0.4–11.9 %), as well as oxygenates (1.0–11.8 %), were produced over the catalysts in contrast with oxygenates (80.2 %) and linear hydrocarbons (6.6 %) formed without any catalyst. The catalysts changed the products distribution, the amount varying according to SAR and platinum. The platinum-containing catalysts with SAR 30 and 60 produced the highest amount of BTEX (41.1 and 42.0 %, respectively), the most valuable compounds among the products and formed negligible amounts of polyaromatics (0.3 %), the main coke precursor. They also produced low amounts of oxygenates (5.3: SAR 30 and 1.4 %: SAR 60). Among the BTEX compounds, the catalyst with SAR 30 produced more benzene, toluene and xylenes than that with SAR 60 which in turn formed more ethylbenzene. The catalyst with SAR 90 was the least selective to BTEX. This work showed that platinum supported on beta zeolites (SAR 30 and 60) are promising options to produce BTEX from MDF fast pyrolysis, with the advantage of tailoring the catalysts to obtain high yields of benzene, toluene, xylenes and ethylbenzene. Moreover, the process used two kinds of residues (MDF and coal ash), contributing to environmental protection.