Liquid-Phase Hydrodeoxygenation of Guaiacol over Mo2C Supported on Commercial CNF. Effects of Operating Conditions on Conversion and Product Selectivity

Rui Moreira,José Pinilla,Isabel Suelves,Elba Ochoa,António Portugal

doi:10.3390/catal8040127

Rui Moreira, José Pinilla + Show 3 more

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https://doi.org/10.3390/catal8040127

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Abstract

In this work, a Mo2C catalyst that was supported on commercial carbon nanofibers (CNF) was synthetized and tested in the hydrodeoxygenation (HDO) of guaiacol. The effects of operating conditions (temperature and pressure) and reaction time (2 and 4 h) on the conversion of guaiacol and products selectivity were studied. The major reaction products were cresol and phenol, followed by xylenols and toluene. The use of more severe operating conditions during the HDO of guaiacol caused a diversification in the reaction pathways, and consequently in the selectivity to products. The formation of phenol may have occurred by demethylation of guaiacol, followed by dehydroxylation of catechol, together with other reaction pathways, including direct guaiacol demethoxylation, and demethylation of cresols. X-ray diffraction (XRD) analysis of spent catalysts did not reveal any significant changes as compared to the fresh catalyst.

Highlights

Lignocellulosic bio-oils cannot be fractionally distilled for the separation of petrochemical cuts in the current oil industry infrastructure, because they repolymerize upon heating due to the chemical and thermal instability related with their high oxygen content [1,2]
When comparing the CNFo with the carbon nanofibers (CNF), it can be seen from Table 1 that the HNO3 pretreatment did not have any impact on the pore volume or surface area of the as received material, since the differences observed lies within the equipment experimental error
In the literature [24,25,26], the evolution of CO2 during TPD (Temperature Programmed Desorption) has been assigned to the existence of acid groups over carbonaceous supports caused by the decomposition of carboxylic acids, carboxylic anhydrides, and lactones upon heating, while the evolution of CO has been assigned to the presence of basic and neutral groups over such support materials that is caused by the decomposition of phenols, ethers, quinones, and carbonyls

Summary

Introduction

Lignocellulosic bio-oils cannot be fractionally distilled for the separation of petrochemical cuts in the current oil industry infrastructure, because they repolymerize upon heating due to the chemical and thermal instability related with their high oxygen content [1,2]. Bio-oils must be further processed (upgraded) before they can be used as liquid fuel or as a source of industrial chemicals. Liquid-phase hydrodeoxygenation (HDO) is a catalytic upgrading process that is undertaken in a wide range of pressures (2–30 MPa) and temperatures (423–723 K), where hydrogen is used to exclude excess oxygen from lignocellulosic bio-oil, with the purpose of getting a product that is chemically similar to crude [2,3]. High pressures are used to ensure adequate solubility of hydrogen in the reaction media, this way increasing its availability in the vicinity of the catalyst particles and accelerating the reaction rate [2]. All of the catalysts suffer from irreversible deactivation that is caused mainly by coking, active phase loss, and water poisoning [2,3,4,5]

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