12 research outputs found
Designing biomass lignins for the biorefinery
4 páginas.- 3 figuras. 17 referencias.- Comunicación oral presentada en el 16th European Workshop on Lignocellulosics and Pulp (EWLP) Gothenburg, Sweden, June 28 – July 1, 2022As ever more component monomers are discovered, lignin can no longer be regarded as deriving from just the three canonical monolignols. Pathway intermediates and additional products of truncated biosynthesis are now established lignin monomers. The array of acylated monolignols continues to expand. Game-changing findings have demonstrated that phenolics from alternative pathways, including flavonoids and hydroxystilbenes, are also involved in lignification, expanding the traditional concept. Beyond the basic science intrigue, these findings propound exciting new avenues for valorizing lignins, or for producing more readily extractable or depolymerizable lignins, in crop and bioenergy plants.We further acknowledge lots of colleagues and collaborators, and funding from the Swiss National Science Foundation (Synergia) grant # CRS115_180258, and the DOE Great Lakes Bioenergy Research Center (DOE BER Office of Science DE-SC0018409).N
A Microfluidic, Extensional Flow Device for Manipulating Soft Particles
A computer-controlled microfluidic extensional flow device is developed for trapping and manipulating micron-sized hard and soft particles. The extensional flow is generated in a diamond-shaped cross-slot that has each corner connected to a pressure-controlled liquid reservoir. By employing an imaging-based control algorithm, a particle can be made to move to an arbitrary position within the slot by adjusting the reservoir pressures and hence the fluid flow rates into/out of the slot. Thus, a soft particle can be trapped indefinitely at a point within the slot, and a known hydrodynamic force can be applied to study the dynamics of stretching and breakup of the particle. Alternatively, adhesion or coalescence dynamics of soft particles may be investigated by effecting a controlled collision between two particles. The device is validated by measuring the low interfacial tension of a compatibilized oil-water interface.MAS
Selective Hydrogenation of Unsaturated Carbon–Carbon Bonds in Aromatic-Containing Platform Molecules
The
combination of chemical and biological catalysis enables the
production from biomass of coumarin and dihydrocoumarin (DHC), opening
new routes to the formation of fine chemicals and pharmaceutical building
blocks. Each of these products requires the hydrogenation of 4-hydroxycoumarin
(4HC) to 4-hydroxydihydrocoumarin (4HDHC), which, in turn, requires
the reduction of an unsaturated C–C bond in the presence of
an aromatic ring. Using <i>in situ</i> attenuated total
reflection Fourier transform infrared (ATR-FTIR) spectroscopy, we
show that reaction at 348 K over monometallic Pd catalysts leads to
the partial reduction of the aromatic ring in 4HC, obtaining 93% selectivity
for CC bond hydrogenation at 82% 4HC conversion and with a
low turnover frequency (TOF). Decreasing the Pd dispersion from 70%
to 6% not only leads to an increase in the rate of 4HC hydrogenation,
but it also leads to an increase in the rate of overhydrogenation.
However, the formation of bimetallic PdAu nanoparticles inhibits the
overhydrogenation reaction while also doubling the TOF to a value
of 6 ks<sup>–1</sup> for 4HDHC production. A bimetallic PdAu
catalyst supported on SiO<sub>2</sub> leads to 97% selectivity for
CC bond hydrogenation at 86% 4HC conversion, while an acidic
support such as amorphous silica–alumina can be used to produce
DHC directly from 4HC
Synthesis of biomass-derived feedstocks for the polymers and fuels industries from 5-(hydroxymethyl)furfural (HMF) and acetone
Methane Conversion to Ethylene and Aromatics on PtSn Catalysts
Pt
and PtSn catalysts supported on SiO<sub>2</sub> and H-ZSM-5
were studied for methane conversion under nonoxidative conditions.
Addition of Sn to Pt/SiO<sub>2</sub> increased the turnover frequency
for production of ethylene by a factor of 3, and pretreatment of the
catalyst at 1123 K reduced the extent of coke formation. Pt and PtSn
catalysts supported on H-ZSM-5 zeolite were prepared to improve the
activity and selectivity to non-coke products. Ethylene formation
rates were 20 times faster over a PtSn(1:3)/H-ZSM-5 catalyst with
SiO<sub>2</sub>:Al<sub>2</sub>O<sub>3</sub> = 280 in comparison to
those over PtSn(3:1)/SiO<sub>2</sub>. H-ZSM-5-supported catalysts
were also active for the formation of aromatics, and the rates of
benzene and naphthalene formation were increased by using more acidic
H-ZSM-5 supports. These catalysts operate through a bifunctional mechanism,
in which ethylene is first produced on highly dispersed PtSn nanoparticles
and then is subsequently converted to benzene and naphthalene on Brønsted
acid sites within the zeolite support. The most active and stable
PtSn catalyst forms carbon products at a rate, 2.5 mmol of C/((mol
of Pt) s), which is comparable to that of state-of-the-art Mo/H-ZSM-5
catalysts with same metal loading operated under similar conditions
(1.8 mmol of C/((mol of Mo) s)). Scanning transmission electron microscopy
measurements suggest the presence of smaller Pt nanoparticles on H-ZSM-5-supported
catalysts, in comparison to SiO<sub>2</sub>-supported catalysts, as
a possible source of their high activity. A microkinetic model of
methane conversion on Pt and PtSn surfaces, built using results from
density functional theory calculations, predicts higher coupling rates
on bimetallic and stepped surfaces, supporting the experimental observations
that relate the high catalytic activity to small PtSn particles
An “ideal lignin” facilitates full biomass utilization
Lignin, a major component of lignocellulosic biomass, is crucial to plant growth and development but is a major impediment to efficient biomass utilization in various processes. Valorizing lignin is increasingly realized as being essential. However, rapid condensation of lignin during acidic extraction leads to the formation of recalcitrant condensed units that, along with similar units and structural heterogeneity in native lignin, drastically limits product yield and selectivity. Catechyl lignin (C-lignin), which is essentially a benzodioxane homopolymer without condensed units, might represent an ideal lignin for valorization, as it circumvents these issues. We discovered that C-lignin is highly acid-resistant. Hydrogenolysis of C-lignin resulted in the cleavage of all benzodioxane structures to produce catechyl-type monomers in near-quantitative yield with a selectivity of 90% to a single monomer