Anisole and guaiacol hydrodeoxygenation reaction pathways over selected catalysts
Optimizing catalysts and reaction conditions for transalkylation as well as hydrodeoxygenation reactions in a hydropyrolysis process while minimizing demethylation reactions may improve carbon yield and energy recovery in the liquid product. Pyrolysis vapor model compound hydrodeoxygenation reactions were investigated in a fixed bed reactor at 350–450 °C, 1.7–15 bar (10–200 psig), with 14–60 mol % hydrogen in the feed gas mixture to determine reaction pathways under a range of reaction conditions. Anisole hydrodeoxygenation reaction pathways in the gas phase were studied over a commercially available Ni-based hydrotreating catalyst, whereas guaiacol hydrodeoxygenation reaction pathways were studied over two different commercially available Ni-based hydrotreating catalysts, a Fe-based catalyst, and a zeolite-based catalyst using online mass spectrometry analysis. Both Ni-based catalysts exhibited greater hydrodeoxygenation activity than the Fe-based and zeolite-based catalysts. Guaiacol conversion over each Ni-based catalyst reached 99.5 and 99.6%, whereas conversion over Fe-based and zeolite-based catalysts reached 27.0 and 22.7%, respectively, under the same reaction conditions. Experimental data from online mass spectrometry indicate that anisole and guaiacol undergo transalkylation and demethylation reactions followed by hydrodeoxygenation reactions over each catalyst tested.