Expeditious isomerization of glucose to fructose in aqueous media over sodium titanate nanotubes

Tuning of MgO's base characteristics by blending it with amphoteric ZnO facilitating the selective glucose isomerization to fructose for bioenergy development

Fructose serves as an important intermediate in the preparation of liquid fuel compounds. Herein, we report its selective production via a chemical catalysis method over ZnO/MgO nanocomposite. The blending of an amphoteric ZnO with MgO reduced the latter's unfavorable moderate/strong basic sites that can influence the side reactions in the sugar interconversion, reducing fructose productivity. Of all the ZnO/MgO combinations, a 1 : 1 ratio of ZnO and MgO showed a 20% reduction in moderate/strong basic sites in MgO with ∼2-2.5 times increase in weak basic sites (overall), which is favorable for the reaction. The analytical characterizations affirmed that MgO settles on the surface of ZnO by blocking the pores. The amphoteric ZnO undertakes the neutralization of the strong basic sites and improves the weak basic sites (cumulative) by the Zn-MgO alloy formation. Therefore, the composite afforded as high as 36% fructose yield and 90% selectivity at 90 °C; especially, the improved selectivity can be accounted for by the effect of both basic and acidic sites. The favorable action of acidic sites in controlling the unwanted side reactions was maximum when an aqueous medium contained 1/5^th methanol. However, ZnO's presence regulated the glucose's degradation rate by up to 40% compared to the kinetics of pristine MgO. From the isotopic labelling experiments, the proton transfer pathway (or LdB-AvE mechanism by the formation of 1,2-enediolate) is dominant in the glucose-to-fructose transformation. The composite exhibited a long-lasting ability based on the good recycling efficiency of up to 5 cycles. The insights into the fine-tuning of the physicochemical characteristics of widely available metal oxides would help develop a robust catalyst for sustainable fructose production for biofuel production (via a cascade approach).

Titanate Nanotubes-Based Heterogeneous Catalyst for Efficient Production of Biomass Derived Chemicals

The development of efficient heterogeneous catalytic system to convert plentiful biomass to renewable bio-chemicals is urgent need. Titanate nanotubes-based materials obtained from hydrothermal treatment have been reported as low-cost and efficient catalytic materials in chemical syntheses for bio-based chemicals production with interesting catalytic performance. This mini-review expressly revealed the significance and potential of using titanate nanotubes based material as sustainable and environmentally benign solid catalysts/supports for synthesis of various bio-based chemicals, including glycerol-derived solketal, jet fuel range alkanes precursors, biomass-derived esters, aldehydes, aromatic compounds and so on. From the current knowledge on titanate nanotubes-based material via hydrothermal method here summarized, the future lines of research in the field of catalysis/supports for bio-based chemicals production are outlined.

Improved production of titanate nanotubes by hydrothermal method for adsorption of organic dyes

Background

Increasing the yield of nanomaterials using the same reactor size and fixing most of the reactants and conditions will greatly improve the production process by saving time, energy and efforts. Titanate nanotubes are mainly prepared by hydrothermal process, in which TiO2 powder reacts with NaOH at certain conditions to form the desired nanotubes. It was reported that it is a must to use high concentrations of NaOH (10 N) to enable the tubular form formation, and the amount of NaOH from the stoichiometry point of view is much higher than that of TiO2; this means excess amounts of NaOH are not used and washed off. This work was designed to improve the production yield by making use of this excess amount of NaOH.

Results

More than 60 g of sodium titanate nanotubes was prepared using simple hydrothermal method. The prepared nanotubes were characterized by X-ray powder diffraction, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy and BET surface area analysis. The adsorption capacity of these nanotubes was tested against three commonly used dyes: methyl orange, crystal violet and thymol blue. The samples showed great affinity toward crystal violet and lower activity toward methyl orange and thymol blue, where they achieved more than 90% removal efficiency under different experimental conditions.

Conclusions

Sodium titanate nanotubes were prepared in large amounts using modified hydrothermal method. The obtained nanotubes efficiently removed crystal violet from water. This improved synthesis of titanate nanotubes will reduce the total cost of nanomaterials production, and subsequently the treatment process, since titanate nanotubes are used in adsorption and photocatalysis processes.

Recent Advances in the Brønsted/Lewis Acid Catalyzed Conversion of Glucose to HMF and Lactic Acid: Pathways toward Bio-Based Plastics

One of the most trending topics in catalysis recently is the use of renewable sources and/or non-waste technologies to generate products with high added value. That is why, the present review resumes the advances in catalyst design for biomass chemical valorization. The variety of involved reactions and functionality of obtained molecules requires the use of multifunctional catalyst able to increase the efficiency and selectivity of the selected process. The use of glucose as platform molecule is proposed here and its use as starting point for biobased plastics production is revised with special attention paid to the proposed tandem Bronsted/Lewis acid catalysts.

Magnesium Impregnated on NaX Zeolite Synthesized from Cogon Grass Silica for Fast Production of Fructose via Microwave-Assisted Catalytic Glucose Isomerization

Fructose is a crucial intermediate in the production of several chemical platforms. Fructose is mainly produced from glucose isomerization either through immobilized enzymes or heterogeneous catalysts using a conventional heating source, and this is time-consuming. Thus, this work discloses a fast production of fructose via microwave-assisted catalytic glucose isomerization using Mg catalysts supported on NaX zeolite from cogon grass silica. The catalysts were prepared by the impregnation of magnesium nitrate solution and subsequently transformed into MgO on NaX by calcination. The effect of 3, 6 and 9 wt.% Mg content on NaX on the performance of glucose isomerized to fructose was tested at 90 °C for 15 min. The best catalyst was selected for studying the effect of reaction times of 5, 15, 30 and 60 min. Results from X-ray diffraction (XRD), N2 sorption and CO2 temperature-programmed desorption (CO2-TPD) suggested that crystallinity, surface area and micropore volume decrease but basicity increases with Mg content. The X-ray photoelectron spectroscopy (XPS) result confirmed the presence of mixed phases of MgO and Mg2CO3 in all catalysts. The glucose conversion enhanced with the Mg loading but the fructose yield gave the highest value with Mg of 6 wt.%, probably due to the tuning of high active sites and surface area. The greatest fructose selectivity and yield (71.9% and 25.8%) were obtained within 15 min by microwave-assisted catalytic reaction, shorter than the reported value in the literature, indicating a suitable reaction time. Mg (6 wt.%)/NaX catalyst preserves the original catalytic performance up to three cycles, indicating that it is a promising catalyst for fructose production.

Effect of the Solvent on the Basic Properties of Mg–Al Hydrotalcite Catalysts for Glucose Isomerization

We suggested the existence of a relationship between the base properties of Mg–Al hydrotalcite catalysts and the solvents employed in the industrially important isomerization of glucose produce fructose. We prepared Mg–Al hydrotalcite catalysts with different Mg/Al atomic ratios to tune the basic properties of the catalyst. The prepared catalysts were used in the glucose isomerization conducted in various solvents. Experimental results confirmed that the catalysts exhibited different activities in the different solvents. We also implemented the Hammett indicator method, which allows to analyze the basic properties of the catalysts in various solvents. According to evidence, the basic properties of the catalysts varied substantially in different solvents. Notably, increases in the catalysts’ base properties matched the observed increases in fructose yield of the glucose isomerization. Consequently, we suggested that, in order to prepare efficient Mg–Al hydrotalcite catalysts for glucose isomerization, the interaction between the solvent used to conduct the reaction and the basic properties of the catalyst, which are in turn influenced by the solvent, should be considered.

Optimized preparation and regeneration of MFI type base catalysts ford-glucose isomerization in water

Eco-friendly solid bases possessing hierarchical MFI structure ford-glucose isomerization tod-fructose. Optimizing catalyst synthesis and composition for enhanced stability.

Sodium titanate nanotubes for efficient transesterification of oils into biodiesel

In this work, sodium titanate nanotubes were prepared by a hydrothermal method for 23 h at 160 °C and characterized by high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) methods, and Fourier transform infrared (FT-IR) spectroscopy. The obtained nanotubes were used as catalysts in the transesterification of pure and cooked oils under different experimental conditions (molar ratio, temperature, catalyst weight, and time). The catalyst showed high efficiency depending on the chosen conditions. The biodiesel yield was found to be 95.9% at 80 °C for 2 h. The catalyst also showed high activity for cooked oil conversion, with yields of 96.0, 96.0, and 93.58% for the first, second, and third uses of oil, respectively. The methanol was recycled and used in another transesterification experiment, and the biodiesel yield reached 91%. Density functional theory, Monte Carlo simulation, and molecular dynamics simulation were employed to clearly understand the transesterification mechanism. The transesterification reaction is represented by a pseudo-first-order kinetics model. Graphical Abstract .