Production of 5-HMF from glucose using TiO2-ZrO2 catalysts: Effect of the sol-gel synthesis additive

Fabrication and characterization of a chitosan/cyclodextrin/TiO2-NPs composite for preservation of avocados

In this study, a TiO2 material with nanoparticle size of about 10-20 nm, surface area of 109 m2 g-1 was synthesized using the microwave-assisted hydrothermal method. The chitosan/TiO2 film combined with cyclodextrin (chitosan-cyclodextrin/TiO2, CS-CD/TiO2NPs) helps significantly improve the mechanical properties and enhance the antibacterial activity of the polymer film. Furthermore, the content of TiO2 nanoparticles in CS-CD/TiO2NPs also affects the tensile strength, antibacterial activity, ripening rate, ethylene production rate, and water vapor permeability during food preservation of the CS-CD film that has been studied. The CS-CD/TiO2NPs film is effective against Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aereus) reaching over 99.5% after 15 min of contact. The preservation ability of avocados coated with CS-CD/TiO2NPs was evaluated through some physiological parameters of the avocados, such as sensory evaluation, weight loss, and hardness. The results show that the use of CS-CD/TiO2NPs films extends the preservation time of avocados up to 7 days under conditions of 30 °C and 80% relative humidity.

Robust interaction of ZnO and TiO2 nanoparticles with layered graphitic carbon nitride for enhanced photocatalytic oxidative desulfurization of fuel oil: mechanism, performance and stability

Sulfur compounds in fuel such as thiophene, benzothiophene and dibenzothiophene are the primary source of SO x emissions, leading to environmental pollution and acid rain. In this study, we synthesized a layered oxygen-doped graphitic carbon nitride (OCN) structure and integrated ZnO and TiO2 nanoparticles onto the OCN surface through a microwave-assisted sol-gel method. The X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) results confirmed a robust interaction between the ZnO and TiO2 nanoparticles and the oxygen-doped g-C3N4 (OCN) surface, as indicated by the formation of C-N-Ti and C-O-Ti bonds. This interaction notably improved the optoelectronic properties of the ZnO-TiO2/OCN composite, yielding increased visible light absorption, reduced charge recombination rate, and enhanced separation and transfer of photogenerated electron-hole pairs. The oxygen doping into the CN network could alter the band structure and expand the absorption range of visible light. The ZnO-TiO2/OCN photocatalyst demonstrated remarkable desulfurization capabilities, converting 99.19% of dibenzothiophene (DBT) to dibenzothiophene sulfone (DBT-O2) at 25 °C, and eliminating 92.13% of DBT from real-world fuel oil samples. We conducted in-depth analysis of the factors impacting the redox process of DBT, including the ZnO ratio, initial DBT concentration, catalyst dosage, stability, and O/S molar ratio. Radical trapping experiments established that ˙O2 -, ˙OH and h+ radicals significantly influence the reaction rate. The obtained results indicated that the ZnO-TiO2/OCN photocatalyst represents a promising tool for future fuel oil desulfurization applications.

Ternary heterogeneous Z-scheme photocatalyst TiO2/CuInS2/OCN incorporated with carbon quantum dots (CQDs) for enhanced photocatalytic degradation efficiency of reactive yellow 145 dye in water

This study delves into the advanced integration of a ternary heterogeneous Z-scheme photocatalyst, TiO2/CuInS2/OCN (OCN: O-g-C3N4), with carbon quantum dot (CQD) to improve the degradation efficiency of reactive yellow 145 (RY145) dye in water. Through a systematic examination, we elucidated the photocatalytic mechanisms and the role of radicals, electrons, and holes in the treatment process. Our findings revealed that this novel catalyst integration significantly boosted RY145 degradation efficiency, achieving 98.2%, which is markedly higher than the efficiencies which could be achieved using TiO2/CuInS2/OCN alone. Moreover, the TiO2/CuInS2/OCN/CQD photocatalyst demonstrated superior rate performance over its components. Comprehensive evaluations, including photoelectrochemical and radical tests, further confirmed the efficiency of the integrated system, adhering to Z-scheme principles. The catalyst showcased remarkable stability, with over 94% reusability after five reaction cycles. These findings pave the way for the potential use of the TiO2/CuInS2/OCN/CQD photocatalyst as an innovative solution for water pollutant treatment via photocatalytic technology.

TiO2 Catalyzed Dihydroxyacetone (DHA) Conversion in Water: Evidence That This Model Reaction Probes Basicity in Addition to Acidity

In this paper, evidence is provided that the model reaction of aqueous dihydroxyacetone (DHA) conversion is as sensitive to the TiO₂ catalysts' basicity as to their acidity. Two parallel pathways transformed DHA: while the pathway catalyzed by Lewis acid sites gave pyruvaldehyde (PA) and lactic acid (LA), the base-catalyzed route afforded fructose. This is demonstrated on a series of six commercial TiO₂ samples and further confirmed by using two reference catalysts: niobic acid (NbOH), an acid catalyst, and a hydrotalcite (MgAlO), a basic catalyst. The original acid-base properties of the six commercial TiO₂ with variable structure and texture were investigated first by conventional methods in gas phase (FTIR or microcalorimetry of pyridine, NH₃ and CO₂ adsorption). A linear relationship between the initial rates of DHA condensation into hexoses and the total basic sites densities is highlighted accounting for the water tolerance of the TiO₂ basic sites whatever their strength. Rutile TiO₂ samples were the most basic ones. Besides, only the strongest TiO₂ Lewis acid sites were shown to be water tolerant and efficient for PA and LA formation.

Efficient One-Pot Synthesis of TiO2/ZrO2/SiO2 Ternary Nanocomposites Using Prunus × Yedoensis Leaf Extract for Enhanced Photocatalytic Dye Degradation

A simple, efficient, and ecofriendly method was employed to synthesize TiO2/ZrO2/SiO2 ternary nanocomposites using Prunus × yedoensis leaf extract (PYLE) that shows improved photocatalytic and antibacterial properties. The characterization of the obtained nanocomposites was done by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopic (EDS) analysis. The synthesized ternary nanocomposites with nanoscale pore diameters were investigated for the elimination of Reactive Red 120 (RR120) dye. The obtained results showed about 96.2% removal of RR120 dye from aqueous solution under sunlight irradiation. Furthermore, it shows promising antibacterial activity against Staphylococcus aureus and Escherichia coli. The improved photocatalytic and antibacterial activity of TiO2/ZrO2/SiO2 may bring unique insights into the production of ternary nanocomposites and their applications in the environment and biomedical field.

γ-Valerolactone Production from Levulinic Acid Hydrogenation Using Ni Supported Nanoparticles: Influence of Tungsten Loading and pH of Synthesis

γ-Valerolactone (GVL) has been considered an alternative as biofuel in the production of carbon-based chemicals; however, the use of noble metals and corrosive solvents has been a problem. In this work, Ni supported nanocatalysts were prepared to produce γ-Valerolactone from levulinic acid using methanol as solvent at a temperature of 170 °C utilizing 4 MPa of H₂. Supports were modified at pH 3 using acetic acid (CH₃COOH) and pH 9 using ammonium hydroxide (NH₄OH) with different tungsten (W) loadings (1%, 3%, and 5%) by the Sol-gel method. Ni was deposited by the suspension impregnation method. The catalysts were characterized by various techniques including XRD, N₂ physisorption, UV-Vis, SEM, TEM, XPS, H₂-TPR, and Pyridine FTIR. Based on the study of acidity and activity relation, Ni dispersion due to the Lewis acid sites contributed by W at pH 9, producing nanoparticles smaller than 10 nm of Ni, and could be responsible for the high esterification activity of levulinic acid (LA) to Methyl levulinate being more selective to catalytic hydrogenation. Products and by-products were analyzed by ¹H NMR. Optimum catalytic activity was obtained with 5% W at pH 9, with 80% yield after 24 h of reaction. The higher catalytic activity was attributed to the particle size and the amount of Lewis acid sites generated by modifying the pH of synthesis and the amount of W in the support due to the spillover effect.

Modelling and Optimisation of the Sol-Gel Conditions for Synthesis of Semi-Hexagonal Titania-Based Nano-Catalyst for Esterification Reaction

Design and fabrication of a catalyst with the highest activity can be achieved by optimising the synthesis conditions. In this study, the sol-gel synthesis conditions of citric acid concentration, gelling temperature, complex time, and calcination temperature were studied for the preparation of a novel semi-hexagonal calcium/titania-zirconia nano-catalyst used in the esterification reaction. After synthesis of around 24 samples at various conditions, their activity was tested in the esterification reaction and the results were analysed by multi-layer perceptron (MLP) and support vector machine (SVM) models. Both models predicted the actual data with high coefficients of determination, and indicated that the calcination temperature has the most influence on the activity of the prepared semi-hexagonal calcium/titania-zirconia nano-catalyst for the esterification reaction. Moreover, the genetic algorithm (GA) was utilised for optimising the preparation conditions based on the SVM model, due to its higher generalisation capability for prediction. The prepared nano-catalysts under the optimum conditions of 1.42 acid ratio, gelling temperature of 72 °C, complex time of 2.65 h, and calcination temperature of 487 °C showed good crystalline structure and metal–metal and metal–oxygen cation bonding. Finally, the fabricated catalyst had a high surface area (276.5 m2/g) with 3.5 nm pore diameter and almost uniform particle size (80–110 nm) distribution, leading to a high conversion of 97.6% in the esterification reaction, with good catalytic stability up to five times.

Chemical and Structural Changes by Gold Addition Using Recharge Method in NiW/Al2O3-CeO2-TiO2 Nanomaterials

NiWAu trimetallic nanoparticles (NPs) on the surface of support Al2O3-CeO2-TiO2 were synthesized by a three-step synthetic method in which Au NPs were incorporated into presynthesized NiW/Al2O3-CeO2-TiO2. The recharge method, also known as the redox method, was used to add 2.5 wt% gold. The Al2O3-CeO2-TiO2 support was made by a sol-gel method with two different compositions, and then two metals were simultaneously loaded (5 wt% nickel and 2.5 wt% tungsten) by two different methods, incipient wet impregnation and ultrasound impregnation method. In this paper, we study the effect of Au addition using the recharge method on NiW nanomaterials supported on mixed oxides on the physicochemical properties of synthesized nanomaterials. The prepared nanomaterials were characterized by scanning electron microscopy, BET specific surface area, X-ray diffraction, diffuse reflectance spectroscopy in the UV-visible range and temperature-programmed desorption of hydrogen. The experimental results showed that after loading of gold, the dispersion was higher (46% and 50%) with the trimetallic nanomaterials synthesized by incipient wet impregnation plus recharge method than with impregnation plus ultrasound recharge method, indicating a greater number of active trimetallic (NiWAu) sites in these materials. Small-sized Au from NiWAu/ACTU1 trimetallic nanostructures was enlarged for NiWAu/ACT1. The strong metal NPs-support interaction shown for the formation of NiAl2O4, Ni-W-O and Ni-Au-O species simultaneously present in the surface of trimetallic nanomaterial probably plays an important role in the degree of dispersion of the gold active phase.

Tuning Brønsted and Lewis acidity on phosphated titanium dioxides for efficient conversion of glucose to 5-hydroxymethylfurfural

5-Hydroxymethylfurfural (HMF) derived from cellulosic sugars has become increasingly important as a platform chemical for the biorefinery industry because of its versatility in the conversion to other chemicals. Although HMF can be produced in high yield from fructose dehydration, fructose is rather expensive because it requires multiple processing steps. On the other hand, HMF can be produced directly from highly abundant glucose, which could reduce time and cost. However, an effective and multifunctional catalyst is needed to selectively promote the glucose-to-HMF reaction. In this work, we report a bifunctional phosphated titanium dioxide as an efficient catalyst for such a reaction. The best catalyst exhibits excellent catalytic performance for the glucose conversion to HMF with 72% yield and 83% selectivity in the biphasic system. We achieve this by tuning the solvent system, controlling the amount of Brønsted and Lewis acid sites on the catalyst, and modification of the reaction setup. From the analysis of acid sites, we found that the addition of phosphate group (Brønsted acid site) onto the surface of TiO2 (Lewis acid site) significantly enhanced the HMF yield and selectivity when the optimum ratio of Brønsted and Lewis acid sites is reached. The high catalytic activity, good reusability, and simple preparation method of the catalyst show a promise for the potential use of this catalytic system on an industrial scale.

Cellulose and TiO2–ZrO2 Nanocomposite as a Catalyst for Glucose Conversion to 5-EMF

This work demonstrated the use of green material catalysts, produced from Sengon sawdust waste, to obtain nanocellulose biopolymers. The green material catalysts were utilized as catalysts support of TiO2−ZrO2 binary oxide in the form of nanocomposite materials with superior synergistic properties. The isolation of nanocellulose was achieved using a hydrolysis method with a yield of 63.40%. The TiO2 and ZrO2 nanoparticles have average particle sizes of around 25 and 15 nm, respectively, and the binary oxides of TiO2–ZrO2 pretained an average particle size of 30 nm were used. Furthermore, the nanocellulose combined with the TiO2−ZrO2 binary oxide had formed a cellulose/TiO2−ZrO2 nanocomposite with an average particle size of 30 nm. This indicates that the supporting nanocellulose can stabilize the nanoparticles and avoid aggregation. Moreover, the nanocomposites can be used as a catalyst for the conversion of glucose to 5-ethoxymethylfurfural (5-EMF). The catalytic activity increased with the nanoparticle effect obtained ZrO2, TiO2, TiO2-ZrO2, and cellulose and TiO2-ZrO2 nanocomposite, in 15.50%, 20.20%, 35.20%, and 45.50% yields, respectively. The best yield of 5-EMF was 45.50%, with reaction conditions of 1:1 TiO2–ZrO2 ratio, 4 h reaction time, and 160 °C reaction temperature. The use of nanocellulose biopolymer generated from Sengon sawdust waste in Indonesia provides a promising catalyst support material as an alternative green catalyst. In addition, the glucose carbohydrates can be converted to biofuel feedstocks in the development of a renewable alternative energy. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

High-throughput monitoring of biomass conversion reaction with automatic time-resolved analysis

Reactions of biomass conversions are of great importance in fine chemistry for substantial development. While numerous studies have been performed to search for functional materials to catalyze biomass conversions, a robust and high-throughput analytical method is rather limited, which may hamper further integration and automation of the reactions. Here we propose an automatic and sequential method for the investigation of glucose conversion. By combining sequential sample injection and high-speed capillary electrophoresis (HSCE) techniques, we can monitor the glucose conversion from the beginning toward the end with a good temporal resolution. The HSCE assays are performed using short capillaries (effective length of 10 cm, i.d./o.d. of 50 μm/365 μm), and the analytes are separated at an electric field of 467 V/cm and are detected by UV-absorption at 200 nm with mixed 0.2 mM CTAB, 10 mM borate, 20 mM sorbic acid (pH 12.2) as the background electrolyte. All compounds involved in the reaction, including all products (fructose, 5-hydroxymethylfurfural, formic acid and levulinic acid) and the remaining substrate glucose, are efficiently separated and simultaneously detected from just one analysis with a temporal resolution of one minute. The method exhibits high-resolution separation, a wide linear range with limit-of-detection down to μg/mL-level, as well as excellent repeatability in sequential analysis. It is indicated that the proposed method is of great value in the analysis of complicated biomass conversion and could be potentially applied in various catalytic chemical reactions.

In Situ Synthesis of Sn-Beta Zeolite Nanocrystals for Glucose to Hydroxymethylfurfural (HMF)

The Sn substituted Beta nanocrystals have been successfully synthesized by in-situ hydrothermal process with the aid of cyclic diquaternary ammonium (CDM) as the structure-directing agent (SDA). This catalyst exhibits a bifunctional catalytic capability for the conversion of glucose to hydroxymethylfurfural (HMF). The incorporated Sn acting as Lewis acid sites can catalyze the isomerization of glucose to fructose. Subsequently, the Brønsted acid function can convert fructose to HMF via dehydration. The effects of Sn amount, zeolite type, reaction time, reaction temperature, and solvent on the catalytic performances of glucose to HMF, were also investigated in the detail. Interestingly, the conversion of glucose and the HMF yield over 0.4 wt% Sn-Beta zeolite nanocrystals using dioxane/water as a solvent at 120 °C for 24 h are 98.4% and 42.0%, respectively. This example illustrates the benefit of the in-situ synthesized Sn-Beta zeolite nanocrystals in the potential application in the field of biomass conversion.

Sn-Based Porous Coordination Polymer Synthesized with Two Ligands for Tandem Catalysis Producing 5-Hydroxymethylfurfural

5-Hydroxymethylfurfural (HMF) is a biomass-derived important platform compound. Developing an efficient catalyst for producing HMF from a biomass source is important. Herein, using the ligands 5-sulfoisophthalic acid (SPA) and imidazole (Imd), a tin-based porous coordination polymer was synthesized, namely SPA-Imd-TinPCP. This novel material possesses a multifunctional catalysis capability. The coordinated tin (IV) can catalyze the isomerization of glucose to fructose. The ligand imidazole, as an additional base site, can catalyze glucose isomerization. The sulfonic group of the ligand SPA can catalyze the dehydration of fructose to HMF. SPA-Imd-TinPCP was used as a catalyst for the conversion of glucose to HMF. HMF yields of 59.5% in dimethyl sulfoxide (DMSO) and 49.8% in the biphasic solvent of water/tetrahydrofuran were obtained. Consecutive use of SPA-Imd-TinPCP demonstrated that, after reusing it five times, there was no significant activity loss in terms of the glucose conversion and HMF yield.