5 research outputs found
Synthesis of Methacrylic Acid by Catalytic Decarboxylation and Dehydration of Carboxylic Acids Using a Solid Base and Subcritical Water
Methacrylic acid was synthesized
from the biobased substrates citric
acid, itaconic acid, and 2-hydroxyisobutyric acid (2-HIBA). Hydrotalcite,
a solid base catalyst, was employed to form methacrylic acid (MAA)
through decarboxylation of itaconic acid and citric acid. The effect
of temperature, catalyst mass, residence time, substrate concentration,
and fermentation media, on carboxylic acid conversion and methacrylic
acid yield was determined. Optimum MAA yields occurred at a substrate
to catalyst mass ratio of 9.6 g-substrate/g-catalyst and 21% for citric
acid and 6.4 g/g and 23% for itaconic acid (250 Ā°C, 15 min).
Catalyst reusability experiments resulted in higher methacrylic acid
yields for both citric and itaconic acid. Methacrylic acid was also
formed from 2-hydroxyisobutyric acid in a single-step dehydration
reaction. Among these three substrates, the highest yield of methacrylic
acid (71.5%) was achieved at 275 Ā°C (1 min) using 2-HIBA and
subcritical water. Finally, we tested conversion of these three acids
in a simulated residual fermentation broth (0.1 M NaOH, 0.04 M Na<sub>2</sub>SO<sub>4</sub>, 0.04 M Na<sub>2</sub>HPO<sub>4</sub>, 0.06
M glucose, 0.12 wt % albumin) and MAA yields from itaconic acid and
citric acid using hydrotalcite increased in the presence of these
fermentation āimpuritiesā and decreased slightly from
2-HIBA
Continuous Catalytic Esterification and Hydrogenation of a Levoglucosan/Acetic Acid Mixture for Production of Ethyl Levulinate/Acetate and Valeric Biofuels
A mixture of levoglucosan
(LG) and acetic acid (AA), representing
water extracted fast pyrolysis oil, was continuously converted to
ethyl levulinate (EL) and ethyl acetate (EA) using H-ZSM5 [120ā230
Ā°C, 600 psig, 80% ethanol (v/v)]. Fractional conversion of both
reactants was 65% or greater at temperatures above 120 Ā°C, and
space time yields (STY) approached 140 and 15 g/L-cat/h for EA and
EL, respectively, at 180 Ā°C (LHSV = 4.9 h<sup>ā1</sup>). Two potential pathways for EL formation from levoglucosan were
apparent, one with glucose and ethyl Ī±-d-glucopyranoside
as intermediates and the other with furfural. Adding metal functionality
(Ru/H-ZSM5) resulted in the production of valerate biofuels (esters
of carboxylic acids C3 or greater; e.g., pentanoic and hexanoic acid
ethyl esters) and EA from the mixture in the presence of hydrogen.
Conversions for LG and AA using Ru/H-ZSM5 were similar to H-ZSM5,
but ethyl levulinate space time yield declined (ā¼5 g/L-cat/h)
as valerate biofuel STY increased (ā¼10 g/L-cat/h) at an optimum
temperature of 180 Ā°C. Our results indicate that valerate biofuels
can be produced from levoglucosan (and possibly other sugars) in a
continuous single stage, integrated process. However, due to low yields
and coke formation, it is clear that ethanol/water ratios, pore size,
and acid site type and density must be optimized when coupled with
metal functionality for industrial application
Continuous Upgrading of Fast Pyrolysis Oil by Simultaneous Esterification and Hydrogenation
A mixture of fast
pyrolysis oil (FPO) and methanol (1/1 v/v) was
continuously converted to methyl levulinate (ML), methyl acetate (MA),
and C3 or greater methyl esters using metal-acid functionalized zeolites
(Ni and Ru/HZSM-5) and an iron oxide catalyst with both acid and base
sites (250 Ā°C, 600 psig). Fractional conversion of FPO components
was 60% or greater using the iron oxide catalyst, and space time yields
approached 150 and 30ā50 g/L cat/h for MA and C3 methyl esters,
respectively, at 250 Ā°C (<i>W</i>/<i>F</i> = 0.4 h, liquid hourly
space velocity = 5ā11.2 h<sup>ā1</sup>). Product yield
and concentration using the iron oxide catalyst were comparable to
those of the Ni and Ru/HZM-5 catalysts and achieved performance levels
higher than those of SiO<sub>2ā</sub>Al<sub>2</sub>O<sub>3</sub> and HZSM-5. Two potential pathways for acetic acid conversion (ketonization
and esterification) and ML formation from levoglucosan were observed.
Using the bifunctional catalysts in the presence of hydrogen resulted
in significant coke reduction (60ā80%) and the production of
esters of carboxylic acids C3 or greater (e.g., pentanoic and hexanoic
acid methyl esters) and MA from the mixture. More interestingly, contrary
to the other catalysts, an increase in phenolic levels (e.g., 2-methoxy
phenol) was observed using the iron oxide catalyst with H<sub>2</sub> and isopropanol (replacing H<sub>2</sub>), indicating the presence
of undetected lignin oligomers in the feed and their subsequent hydrogenolysis.
Simultaneous esterification and hydrogenation resulted in percent
reduction in total acid numbers ranging from 66 to 76%
Two-Stage Hydrothermal Liquefaction of Sweet Sorghum BiomassīøPart II: Production of Upgraded Biocrude Oil
The
hydrothermal liquefaction (HTL), followed by hydrodeoxygenation
(HDO) of lignin-rich biomass has a potential to improve the yield
and the quality of upgraded biocrude oil. In this study, the lignin-rich
biomass obtained from the low-temperature HTL (stage 1) of sweet sorghum
bagasse was investigated to evaluate the biocrude oil yield and its
compositions using catalytic high-temperature HTL-HDO (stage 2) and
was compared with the conventional, whole-stage HTL-HDO process. Biocrude
oil yield was achieved up to 38% during a high-temperature HTL, while
42% was obtained after catalytic (5% Ru/C) HDO process. Up to 96%
hydrocarbon content of biocrude oil was achieved, which is twice as
high as that of the conventional whole-stage HTL-HDO process. Aromatic
hydrocarbons and long-chain alkanes were also dominant in the upgraded
biocrude oil, which collectively accounted for 28% of the total hydrocarbons.
From raw sweet sorghum bagasse, the hydrocarbons yield from second-stage
HTL-HDO process (11%) was substantially increased by 78%, compared
to that of the whole-stage HTL-HDO process (7%). The upgraded biocrude
oil could be directly processed or co-processed in the existing refinery
to produce drop-in fuels
Correction to Coupling Red-Mud Ketonization of a Model Bio-Oil Mixture with Aqueous Phase Hydrogenation Using Activated Carbon Monoliths
Correction to Coupling Red-Mud Ketonization of a Model
Bio-Oil Mixture with Aqueous Phase Hydrogenation Using Activated Carbon
Monolith