Deoxygenation of m-Cresol: Deactivation and Regeneration of Pt/γ-Al₂O₃ Catalysts

Abstract

Pt/Al2O3 catalysts were used to deoxygenate m-cresol, which was used as a bio-oil model compound. The catalysts were characterized by XRD, TEM, XPS, hydrogen chemisorption, and BET surface analyses. The coke deposits on spent catalysts were analyzed by TPO. In this work, the catalysts deactivation and regeneration were addressed. Deactivation was caused by carbonaceous deposits formed mainly by cresol condensation products, in a parallel-type coke formation mechanism. The amount of carbon formed on the catalyst strongly depends on the metal/acid functions ratio. The gas phase reaction was carried out in a fixed bed reactor in the presence of H2 at 300 °C and atmospheric pressure. The regeneration by coke removal using hydrogen or air was addressed. It was found that treatments in air at mild temperature led to the recovery of the catalytic activity, while the effectiveness of the treatment with H2 strongly depends on the temperature, not being possible to recover the activity at 400 and 500 °C, while at 450 °C the catalyst was regenerated. This is because at the higher temperature, the coke left on the support had higher toxicity. The influence of platinum loading on activity and selectivity was also studied, and it was concluded that the selectivity to the desired deoxygenated product can be regulated by changing the metal content on the catalyst. The metal/acid sites ratio plays a key role in the coke deposition rate.

Catalytic Pyrolysis of Chilean Oak: Influence of Brønsted Acid Sites of Chilean Natural Zeolite

“…Thus, stronger Brønsted acid sites will cause bond breakage, transforming oxygenated compounds into other species. Stronger sites are needed here, considering that oxygenated compound removal is limited by the C-O bond breakage possibility and also the C-O bond strength varies from one family to other (e.g., the strength of C-O bonds attached to an aromatic ring in phenols or to aryl ethers is greater than that of bonds attached to an aliphatic C in alcohols or aliphatic ethers [28]). Brønsted acid sites are claimed as responsible for acid catalyzed reactions such as cracking, dimerization, cyclization, and dehydrocyclization [29].…”

“…These types of reactions increase the average molecular weight, viscosity, and water content. Moreover, phase separation can eventually occur in the long-term storage of bio-oils [28]. …”

A Novel High-Activity Zn-Co Catalyst for Acetylene Acetoxylation

“…In the equations, Φ A1 is the mass fraction of C 2 H 2 in the raw gas, Φ A2 is the mass fraction of remaining C 2 H 2 and Φ VAc is the mass fraction of VAc. Table 2 shows the calculation of carbon balances after the catalytic tests [28]. The mass of C fed into the reactor was calculated as the total amount of reactant fed during the reaction time.…”

Advances in Upgrading Lignin Pyrolysis Vapors by Ex Situ Catalytic Fast Pyrolysis

“…The reaction proceeds through two major reaction pathways (Scheme ): one, direct deoxygenation to toluene (DDO route); two, hydrogenation of m ‐cresol to methylcyclohexanone and methylcyclohexanol on Pt, followed by fast dehydration on Brønsted acid sites to methylcyclohexene, which is either hydrogenated to methylcyclohexane on Pt or ring contracted to dimethylcyclopentanes and ethylcyclopentane on the Brønsted acid sites (HYD route) . In the vapor‐phase HDO of m ‐cresol on Pt/γ‐Al 2 O 3 , Zanuttini and co‐workers note that the yields of toluene, benzene, and methylcyclohexane depend on the metal loading, the H 2 / m ‐cresol ratio, and the reaction temperature . Toluene hydrogenation to methylcylohexane is favored at low reaction temperatures.…”

“…[73] In the vapor-phase HDO of m-cresol on Pt/ g-Al 2 O 3 ,Z anuttini and co-workers note that the yields of toluene,b enzene,a nd methylcyclohexane depend on the metal loading, the H 2 /m-cresol ratio, and the reaction temperature. [74] Toluene hydrogenationt om ethylcylohexane is favored at low reaction temperatures.T he yield of toluene reaches amaximum at approximately 300 8C, and higher temperaturesl ead to the demethylation of toluene to benzene. Deactivation and regenerationo ft he Pt/g-Al 2 O 3 catalyst in the vapor-phase HDO of m-cresol has also been investigated.…”