Conversion of Guaiacol on Noble Metal Catalysts: Reaction Performance and Deactivation Studies

Abstract

Guaiacol, a phenol derived compound produced by the thermal degradation of lignin, was selected as a model compound to study the catalytic hydrodeoxygenation (HDO) process for upgrading pyrolysis bio-oils. Guaiacol is among the major components of bio-oils; however, it is thermally unstable which leads to catalyst deactivation. In the present study, four noble metal catalysts (Pt, Pd, Rh, and Ru) supported on activated carbon were tested in a fixed-bed reactor at atmospheric pressure and their performance for the guaiacol HDO process was measured. Our results showed that, among the tested catalysts, Pt has higher deoxygenation activity and shows little deactivation for 5 h. Additionally, the operating temperature for the Pt catalyst was optimized and found to be 300 °C. Finally, results from catalyst characterization demonstrated that polyaromatic deposits, especially the condensed ring compounds, are the most likely cause for catalyst deactivation.

Application, Deactivation, and Regeneration of Heterogeneous Catalysts in Bio-Oil Upgrading

“…This was accompanied by the formation of large aromatic ring structures [96]. Deactivation mechanisms of Ru/C and Pt/C catalysts during the HDO conversion of guaiacol confirmed that coking due to the polyaromatic deposits, particularly condensed ring series compounds, were the main cause of catalyst deactivation [147].…”

Hydrodeoxygenation of Lignin-Derived Phenols: From Fundamental Studies towards Industrial Applications

“…It was concluded in [34] that demethoxylation was catalyzed by metal sites using Co-and Ni-catalysts supported with Al-MCM-41 at 400 • C under atmospheric pressure [34]. Cyclopentanone formation occurred during HDO of guaiacol over Pt/C catalyst at 300 • C under atmospheric pressure [31]. The proposed reaction network for guaiacol HDO proposed over Pt/C is shown in Figure 13a.…”

“…Catalysts 2017, 7, x FOR PEER REVIEW 18 of 42 atmospheric pressure [31]. The proposed reaction network for guaiacol HDO proposed over Pt/C is shown in Figure 13a.…”

“…Catalyst deactivation and continuous HDO have been intensively investigated for phenolic compounds [31,33,42,49,50,57]. Catalyst stability, activity as a function of time-onstream [31,33,36,39,42,43,47,48,58,59,61], reuse [30,54,[56][57][58]63], regeneration [34,36], origin of the catalyst deactivation [30], chemical composition of coke [31], thermogravimetrical analysis of the spent catalysts [62], modelling of deactivation [33] are also very important from the industrial point of view.…”

“…Catalyst stability, activity as a function of time-onstream [31,33,36,39,42,43,47,48,58,59,61], reuse [30,54,[56][57][58]63], regeneration [34,36], origin of the catalyst deactivation [30], chemical composition of coke [31], thermogravimetrical analysis of the spent catalysts [62], modelling of deactivation [33] are also very important from the industrial point of view. Since the real bio-oils contain in addition to lignin derived compounds also water [59], acetic acid or furfural [56] as well several catalyst poisons, such as chlorine, potassium and sulphur containing compounds [47], it is very important not only to investigate HDO of model compounds but also the real feed [30] using different approaches, such as a single component feed, co-feed studies, real bio-oil [30], simulated bio-oil [40], adsorption studies [48,79] as well as continuous operation [33,36,39,42,43,48].…”