9 research outputs found
Catalytic Conversion of Fructose to γ‑Valerolactone in γ‑Valerolactone
The one-pot conversion of fructose to γ-valerolactone
(GVL)
in GVL as solvent was confirmed by monitoring the dehydration of <sup>13</sup>C<sub>6</sub>-d-fructose to <sup>13</sup>C<sub>6</sub>-5-(hydroxymethyl)-2-furaldehyde (<sup>13</sup>C<sub>6</sub>-HMF),
the hydration of <sup>13</sup>C<sub>6</sub>-HMF to <sup>13</sup>C<sub>5</sub>-levulinic and <sup>13</sup>C-formic acids, followed by their
conversion to <sup>13</sup>C<sub>5</sub>-GVL
Table_1_Size measurement and filled/unfilled detection of rice grains using backlight image processing.docx
Measurements of rice physical traits, such as length, width, and percentage of filled/unfilled grains, are essential steps of rice breeding. A new approach for measuring the physical traits of rice grains for breeding purposes was presented in this study, utilizing image processing techniques. Backlight photography was used to capture a grayscale image of a group of rice grains, which was then analyzed using a clustering algorithm to differentiate between filled and unfilled grains based on their grayscale values. The impact of backlight intensity on the accuracy of the method was also investigated. The results show that the proposed method has excellent accuracy and high efficiency. The mean absolute percentage error of the method was 0.24% and 1.36% in calculating the total number of grain particles and distinguishing the number of filled grains, respectively. The grain size was also measured with a little margin of error. The mean absolute percentage error of grain length measurement was 1.11%, while the measurement error of grain width was 4.03%. The method was found to be highly accurate, non-destructive, and cost-effective when compared to conventional methods, making it a promising approach for characterizing physical traits for crop breeding.</p
Catalytic Conversion of Fructose, Glucose, and Sucrose to 5‑(Hydroxymethyl)furfural and Levulinic and Formic Acids in γ‑Valerolactone As a Green Solvent
The conversion of fructose, glucose,
and sucrose to 5-(hydroxymethyl)furfural
(HMF) and levulinic acid (LA)/formic acid (FA) was investigated in
detail using sulfuric acid as the catalyst and γ-valerolactone
(GVL) as a green solvent. The H<sub>2</sub>SO<sub>4</sub>/GVL/H<sub>2</sub>O system can be tuned to produce either HMF or LA/FA by changing
the acid concentration and thus allowing selective switching between
the products. Although the best yields of HMF were around 75%, the
LA/FA yields ranged from 50% to 70%, depending on the structure of
the carbohydrates and the reaction parameters, including temperature,
acid, and carbohydrate concentrations. While the conversion of fructose
is much faster than glucose, sucrose behaves like a 1:1 mixture of
fructose and glucose, indicating facile hydrolysis of the glycosidic
bond in sucrose. The mechanism of the conversion of glucose to HMF
or LA/FA in GVL involves three intermediates: 1,6-anhydro-β-d-glucofuranose, 1,6-anhydro-β-d-glucopyranose,
and levoglucosenone
Catalytic Hydrogenolysis of Polyethylene Under Reactive Separation
Deconstruction
of polyolefins by catalytic hydrogenolysis is typically
accompanied by the generation of undesired light gases. At reaction
temperatures, the desired liquid products also tend to be volatile.
Secondary cleavage of these liquid products contributes to light gas
formation. The latter process was mitigated by reactive separation,
continuously separating the liquid products from the catalyst throughout
the experiment. At equivalent conversion, the yield and selectivity
for oligomeric liquid species are increased under reactive separation,
even though the carbon–carbon bond cleavage rate is slower
than that in sealed experiments. More light gas is formed in the sealed
reactor. Under 1 atm H2 partial pressure, alkenes accompany
the typical alkane hydrogenolysis products. The alkene yield is higher,
with greater selectivity for valuable α-olefins under reactive
separation. These results provide the mechanistic insight that terminal
alkenes are primary products of carbon–carbon bond cleavage
during hydrogenolysis under experimental conditions, and secondary
deconstruction of these species produces light gases
Removing Fluoride from Double Four-Membered Rings Yielding Defect-Free Zeolites under Mild Conditions Using Ozone
We have investigated ozone treatment of as-made LTA zeolites under
mild temperature conditions (175 °C) using experiments and periodic
DFT as a method of energy savings and engineering defects such as
silanol nests in comparison with conventional calcination at 550 °C.
We have studied ozone treatment on LTA samples synthesized with 1,2-dimethyl-3-(4-methylbenzyl)
imidazolium (denoted as “BULKY”) as the primary organic
structure-directing agent (OSDA) and with various amounts of tetramethylammonium
(TMA) as a secondary OSDA. Ozone treatment of LTA-BULKY at 175 °C
was found to give defect-free, pristine LTA materials as determined
by 29Si NMR, 13C NMR, Raman spectra, and DFT
to assign the spectra. This represents a significant and unexpected
finding: that fluoride ions can be completely removed from double
four-membered rings (D4Rs) under such mild conditions. Ozone treatment
of LTA-BULKY-TMA samples removed BULKY but left behind TMA/F, giving
a new and more diverse structural landscape of Si environments in
LTA. Ab initio MetaDynamics calculations provide
pathways with relatively low barriers, explaining how fluoride ions
can be removed from D4Rs, leaving behind defect-free LTA materials
under mild conditions
<i>Operando</i> MAS NMR Reaction Studies at High Temperatures and Pressures
<i>Operando</i> MAS NMR
studies provide unique insights
into the details of chemical reactions; comprehensive information
about temperature- and time-dependent changes in chemical species
is accompanied by similarly rich information about changes in phase
and chemical environment. Here we describe a new MAS NMR rotor (the <i>WHiMS</i> rotor) capable of achieving internal pressures up
to 400 bar at 20 °C or 225 bar at 250 °C, a range that includes
many reactions of interest. The MAS NMR spectroscopy enabled by these
rotors is ideal for studying the behavior of mixed-phase systems,
such as reactions involving solid catalysts and volatile liquids,
with the potential to add gases at high pressure. The versatile operation
of the new rotors is demonstrated by collecting <i>operando</i> <sup>1</sup>H and <sup>13</sup>C spectra during the hydrogenolysis
of benzyl phenyl ether, catalyzed by Ni/γ-Al<sub>2</sub>O<sub>3</sub> at ca. 250 °C, both with and without H<sub>2</sub> (g)
supplied to the rotor. The 2-propanol solvent, which exists in the
supercritical phase under these reaction conditions, serves as an
internal source of H<sub>2</sub>. The NMR spectra provide detailed
kinetic profiles for the formation of the primary products toluene
and phenol as well as secondary hydrogenation and etherification products
Interspersed Reticulate Cu<sub>2</sub>WS<sub>4</sub> Nanocrystal–PVDF/Ni Triboelectric Nanogenerators for Rhodamine B Degradation
Decahedral
Cu2WS4 nanocrystal grains with
a three-layer body-centered tetragonal crystal phase were successfully
prepared by a simple hydrothermal method. Then, the interspersed reticulate
Cu2WS4 nanocrystal–poly(vinylidene difluoride)
(PVDF)/Ni composites were prepared by filling the mixed sol of organic
ferroelectric polyvinylidene difluoride (PVDF) and Cu2WS4 nanocrystal grains into the void of Ni foam. Subsequently,
polytetrafluoroethylene (PTFE)/Cu was used as a negative triboelectric
layer, the prepared interspersed reticulate Cu2WS4 nanocrystal–PVDF/Ni composites were used as the positive
triboelectric layer, and then the interspersed reticulate triboelectric
nanogenerators (TENGs) were assembled. The use of the interspersed
reticulate Ni electrode in the TENGs effectively reduces the effective
thickness of the triboelectric layer, and the incorporation of Cu2WS4 nanocrystal grains into ferroelectric PVDF
increases the dielectric constant of the triboelectric layer by enhancing
the space charge polarization. Obviously, a reduction of the effective
thickness and an increase of the dielectric constant further enhance
the output VOC by nearly 20 times and
the JSC of the Cu2WS4 nanocrystal–PVDF/Ni TENG by nearly 10 times, and TENG has
good output stability. Lastly, the TENG was successfully used as the
power supply to perform the electrocatalytic degradation of RhB, which
exhibits high efficiency and excellent duration stability. The works
provide good ideas and methods for the treatment of marine pollutants
Operando Solid-State NMR Observation of Solvent-Mediated Adsorption-Reaction of Carbohydrates in Zeolites
In
the liquid-phase catalytic processing of molecules using heterogeneous
catalystsan important strategy for obtaining renewable chemicals
from biomassmany of the key reactions occur at solid–liquid
interfaces. In particular, glucose isomerization occurs when glucose
is adsorbed in the micropores of a zeolite catalyst. Since solvent
molecules are coadsorbed, the catalytic activity depends strongly
and often nonmonotonically on the solvent composition. For glucose
isomerization catalyzed by NaX and NaY zeolites, there is an initial
steep decline when water is mixed with a small amount of the organic
cosolvent γ-valerolactone (GVL), followed by a recovery as the
GVL content in the mixed solvent increases. Here we elucidate the
origin of this complex solvent effect using operando solid-state NMR
spectroscopy. The glucopyranose tautomers immobilized in the zeolite
pores were observed and their transformations into fructose and mannose
followed in real time. The microheterogeneity of the solvent system,
manifested by a nonmonotonic trend in the mixing enthalpy, influences
the mobility and adsorption behavior of the carbohydrates, water,
and GVL, which were studied using pulsed-field gradient (PFG) NMR
diffusivity measurements. At low GVL concentrations, glucose is depleted
in the zeolite pores relative to the solution phase, and changes in
the local structure of coadsorbed water serve to further suppress
the isomerization rate. At higher GVL concentrations, this lower intrinsic
reactivity is largely compensated by strong glucose partitioning into
the pores, resulting in dramatic (up to 32×) enhancements in
the local sugar concentration at the solid–liquid interface
Supported Platinum Nanoparticles Catalyzed Carbon–Carbon Bond Cleavage of Polyolefins: Role of the Oxide Support Acidity
Supported platinum nanoparticle catalysts
are known to
convert
polyolefins to high-quality liquid hydrocarbons using hydrogen under
relatively mild conditions. To date, few studies using platinum grafted
onto various metal oxide (MxOy) supports have been undertaken to understand the
role of the acidity of the oxide support in the carbon–carbon
bond cleavage of polyethylene under consistent catalytic conditions.
Specifically, two Pt/MxOy catalysts (MxOy = SrTiO3 and SiO2–Al2O3; Al = 3.0 wt %, target Pt loading 2 wt % Pt ∼1.5
nm), under identical catalytic polyethylene hydrogenolysis conditions
(T = 300 °C, P(H2) = 170 psi, t = 24 h; Mw = ∼3,800
g/mol, Mn = ∼1,100 g/mol, Đ = 3.45, Nbranch/100C = 1.0), yielded a narrow distribution of hydrocarbons with molecular
weights in the range of lubricants (Mw = Mn Đ = 1.5). While Pt/SrTiO3 formed saturated
hydrocarbons with negligible branching, Pt/SiO2–Al2O3 formed partially unsaturated hydrocarbons (<1
mol % alkenes and ∼4 mol % alkyl aromatics) with increased
branch density (Nbranch/100C = 5.5). Further
investigations suggest evidence for a competitive hydrocracking mechanism
occurring alongside hydrogenolysis, stemming from the increased acidity
of Pt/SiO2–Al2O3 compared
to Pt/SrTiO3. Additionally, the products of these polymer
deconstruction reactions were found to be independent of the polyethylene
feedstock, allowing the potential to upcycle polyethylenes with various
properties into a value-added product