Bio-oil
upgrading through its hydrodeoxygenation (HDO) using sulfided
catalysts has attracted significant attention because of its potential
to provide advanced biofuels. Although many studies have been undertaken,
a detailed understanding of the changes in the chemical composition
on the molecular level that would allow the better design of catalysts
for bio-oil upgrading is still insufficient. Therefore, we have subjected
straw bio-oil and products obtained from its hydrotreatment over a
broad range of experimental conditions to a detailed quantitative
chemical analysis. Most of the volatile compounds were quantified
by GC-MS. Among them, 115 compounds were quantified directly (i.e.,
using the appropriate standards) and more than 100 indirectly (i.e.,
based on their structural similarity with corresponding standards).
Moreover, the total concentrations of carboxylic acids, carbonyls
and phenols were quantified by the carboxylic acid number (CAN), Faix,
and Folin–Ciocalteu methods, respectively, to obtain complementary
and supporting information on the chemical composition to the GC-MS
data. The detailed quantification of most volatile compounds in the
feed and the products allowed us to create a reactivity order of the
oxygen-containing functional groups present and to understand the
origin of some of the compounds. On the basis of the results, the
upgrading of straw bio-oil from ablative fast pyrolysis at 340 °C
and 4 MPa seems to be optimal when evaluating the severity of the
reaction conditions and hydrogen consumption, on the one hand, and
the products quality, on the other hand. This provides a good starting
point for further catalyst development and optimization allowing the
long-term upgrading of the bio-oil for obtaining petroleum-refinery-compatible
feedstock.
Efficient
upgrading of fast pyrolysis bio-oils into products that
can be easily integrated into existing refinery complexes remains
to be a challenge particularly from the stability of a catalyst performance
point of view. Several NiMo catalysts, mainly alumina-supported, were
either prepared or acquired and used in hydrotreating of bio-oil from
ablative fast pyrolysis of straw. The experiments were carried out
in a fixed-bed reactor at 340 °C and 4 MPa and lasted for 80
h. Detailed monitoring of the key physicochemical properties allowed
comparing the performance of the catalysts and assessing its changes
with the time-on-stream (TOS). The quality of all products deteriorated
with the increasing TOS evidencing gradual loss of performance. Nonetheless,
the product quality over the best catalysts remained suitable for
further refinery upgrading by coprocessing during the 80-h TOS. Distillation
of a hydrotreated bio-oil into naphtha, gas oil, and atmospheric residue
allowed obtaining further insights into oxygenates present and their
distribution.
Lignin can be converted into useful precursors of fuels and fine chemicals by thermochemical conversion followed by catalytic hydrogenation using metal catalysts at severe reaction conditions. Thus, mild hydrogenation would significantly improve the sustainability of lignin valorization. Here, hydrogenation of phenols, alkylphenols, and methoxyphenols was achieved at mild reaction conditions (70 °C and atmospheric pressure) via H-transfer hydrogenation over Raney-Ni catalyst in 2-propanol and 2-butanol solvents. The transfer hydrogenation was feasible at the mild conditions, but the complexity of the reactant greatly decreased or even completely suppressed its reactivity. The position of the functional group (o-, m-, p-position) had a great effect on the reactivity of phenols. Moreover, 2-butanol enhanced the conversion of phenols in comparison with 2propanol. When comparing classic hydrogenation with H-transfer hydrogenation in presence of external H 2 , it was found that external H 2 not only regenerated H-donor solvent and ensured stable performance but also increased conversion of phenols and alkylphenols. On the other hand, the absence of external H 2 boosted the conversion of methoxy phenols. Finally, phenols extracted from a pyrolysis oil aqueous phase were hydrogenated. The conversion of phenols was greatly affected by competitive adsorption of different compounds present in the reaction mixture. External H 2 promoted hydrogenation of the complex reaction mixture and prevented condensation of the reactive species in contrast to the H-transfer hydrogenation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.