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 ¹³C₆-d-fructose to ¹³C₆-5-(hydroxymethyl)-2-furaldehyde (¹³C₆-HMF), the hydration of ¹³C₆-HMF to ¹³C₅-levulinic and ¹³C-formic acids, followed by their conversion to ¹³C₅-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 H₂SO₄/GVL/H₂O 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> ¹H and ¹³C spectra during the hydrogenolysis of benzyl phenyl ether, catalyzed by Ni/γ-Al₂O₃ at ca. 250 °C, both with and without H₂ (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 H₂. 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 Cu₂WS₄ 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 catalystsan important strategy for obtaining renewable chemicals from biomassmany 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