Bifunctional Polyoxometalates for the Combined Hydrodeoxygenation and Alkylation Reactions to Upgrade Pyrolysis Oil

Bifunctional Polyoxometalates for the Combined Hydrodeoxygenation and Alkylation Reactions to Upgrade Pyrolysis Oil

E. Anderson, A. Crisci, K. Murugappan and Y. Román-Leshkov

Department of Chemical Engineering Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, MA 02139 (USA)

E-mail: yroman@mit.edu

Pyrolysis oil contains a variety of phenols, phenolic methyl ethers and small oxygenates that must be selectively deoxygenated before use as a high-value fuel additive. Traditional hydrodeoxgyenation catalysts, such as transition metal oxides and platinum group metals, convert phenolic methyl ethers and other small oxygenates into light gases, coke, or fully saturate the aromatic compounds. Here, we will show that bifunctional polyoxometalate catalyst selectively deoxygenate and alkylate anisole into alkylated benzenes.  A 56 % selectivity for alkylated aromatics at a 75 % anisole conversion was observed over 16 hours on stream with minimal deactivation. Furthermore, it was demonstrated that small oxygenates such as acetic acid can also be deoxygenated and coupled to form alkylated aromatics. The active acid sites were probed thorough detailed kinetic studies coupled with materials characterization leading to the identification of a potential reaction mechanism. These catalysts offer a strategy to simultaneously deoxygenate and upgrade bio-oil components.

Figure 1. Product distribution (C-mol %) for the reaction of anisole (200 μL/hr) over a bifunctional polyoxometallate catalyst on TiO₂ (10 %; 300 mg) at 320 °C with 1 Atm of hydrogen (70 mL/min). Inset (a) and (b) display the percent distribution of alkylated oxygenates and alkylated aromatics, respectively. Products described as “Other” are cyclohexene and dimethylether.