Hydrodeoxygenation of Pinyon-Juniper Catalytic Pyrolysis Oil
Doctoral Dissertation Defense
Department of Biological Engineering
Monday, November 5 at 2:30 PM
Catalytic hydrodeoxygenation (HDO) of pyrolysis oil (bio-oil) is one of the most effective technologies to improve physico-chemical properties of bio-oil such as high acidity, poor stability, and low energy density. However, development of HDO catalysts has been a challenging task during past decades. Red mud (RM) which is an alkaline waste from alumina industry, was used to prepare a new multifunctional RM-supported nickel catalyst (Ni/RM) for the HDO of pinyon-juniper (PJ) catalytic pyrolysis oil. The Ni/RM catalyst was characterized by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), BET specific surface area, and temperature programmed reduction (TPR). The catalytic activity of Ni/RM was compared with that of commercial Ni/SiO2-Al2O3 in three major HDO processes; HDO of the organic phase pyrolysis oil, HDO of the aqueous phase pyrolysis oil, and HDO of bio-oil model compounds.
HDO of the organic fraction of PJ bio-oil using Ni/RM produced more liquid (HDO oil), less gas, and less coke as compared to the commercial catalyst. Also less hydrogen was consumed in the case of Ni/RM. HDO of the aqueous phase pyrolysis oil using Ni/RM produced liquid hydrocarbons, whereas the commercial catalyst gasified the organics compound in the aqueous phase pyrolysis oil and did not produce liquid hydrocarbon. HDO studies of bio-oil model compounds showed that the formation of hydrocarbons using Ni/RM was due to the cross-reactions of HDO intermediates (such as anisole, furans, aldehydes, and ketones) on the RM support. RM (in reduced form) catalyzed ketonization and carbonyl alkylation reactions. Furthermore, the selectivity to BTX using Ni/RM was higher than the commercial catalyst after HDO of guaiacol model compound.
Coke formation, oxidation, and formation of nickel iron oxide contributed to the deactivation of Ni/RM during HDO process. After complete deactivation, the catalytic activity of Ni/RM was entirely restored by burning off the coke and activation by reduction using a reducing gas mixture of 10% H2 and 90% N2, however, the regeneration of the commercial Ni/SiO2-Al2O3 was not possible following the same procedure and the catalyst did not show HDO activity after regeneration/reduction.