Isomerization Of Glucose Research Articles

Synergistic effects altering reaction pathways: The case of glucose hydrogenation over Fe-Ni catalysts

Carbon black (CB) supported Ni, Fe, or Fe-Ni alloy catalysts were synthesized by sol-gel to elucidate the reaction pathways over each catalyst, as well as synergistic effects in glucose to sorbitol hydrogenation. The bimetallic materials presented small and alloyed nanoparticles that were richer in reduced metallic sites at the surface than their monometallic counterparts. Glucose isomerization to fructose was favoured over Fe/CB, while glucose hydrogenation to sorbitol is the dominating pathway over Ni/CB catalyst. By contrast, sorbitol production was promoted and undesired isomerization was suppressed when Fe and Ni formed a nanoalloy. In addition, the alloy catalyst presented better stability than the corresponding monometallic catalyst. A comparison with a mechanical mixture of Fe/CB and Ni/CB monometallic catalysts demonstrated the synergy at the nanoscale in the alloy. By comparing different Fe:Ni ratios, the 1:1 formulation was identified as the best compromise to achieve a high activity while maintaining high sorbitol selectivity.

Ca(OH)2 induced a controlled-release catalytic system for the efficient conversion of high-concentration glucose to lactic acid

The catalytic conversion of carbohydrate to platform chemicals, e.g. lactic acid (LA), is the key to unlock the potential of biomass. In this study, we report that the combination of Ba(OH)2 and Ca(OH)2 can efficiently catalyse high-concentration (> 0.5 M) of glucose to relatively high yield of LA (> 40 %) under mild conditions (60 °C). Both glucose conversion and LA yield were sensitive to the pH of the catalytic system. A high loading of Ba(OH)2 led to a high initial pH of the reaction solution, resulting in serious side reactions. While, a low loading of Ba(OH)2 led to a quike decrease of OH− and Ba2+ both of which were continuously consumpted by the formed LA. The combination of Ca(OH)2 with Ba(OH)2 could significantly improve LA yield, since Ca(OH)2, with limited solubility, could act as a controlled-release catalyst for the real-time supply of OH− and Ca2+. OH− was indispensable for glucose isomerization to fructose as well as for fructose retro-aldol reaction to C3 intermediates. Ca2+ could combine with LA to form stable calcium lactate, liberating Ba2+ to catalyse the conversion of C3 intermediates to LA. Under the preliminary optimized reaction conditions, the yield of LA could be reached to 42.55 % and 38.32 % from 0.5 M and 1 M glucose, respectively. This catalytic system has advantages of mild reaction condition, short reaction time, and capable of conversion of high-concentration substrates, enabling it with a great potential for practical applications.

CaCl2 molten salt hydrate-promoted conversion of carbohydrates to 5-hydroxymethylfurfural: an experimental and theoretical study

33.6% fructose and 52.1% HMF were achieved from glucose isomerization and dehydration in CaCl2 salt hydrate. Interactions existing in β-glucopyranose-CaCl2 and β-d-fructofuranose-Ca2+ promoted the glucose isomerization and fructose dehydration.

Catalytic mechanism for the isomerization of glucose into fructose over an aluminium-MCM-41 framework

Al-Containing MCM-41 catalysts exhibit good catalytic activity toward glucose-to-fructose isomerization.

γ-Valerolactone-introduced controlled-isomerization of glucose for lactic acid production over an Sn-Beta catalyst

GVL (<20.0 wt%) invoked a controlled isomerization of glucose to fructose, thus resulting in a low fructose intermediate concentration and enabling full interaction between fructose and the Sn-Beta catalyst with a high lactic acid yield of 74.0 wt%.

Isomerization of glucose to fructose catalyzed by metal–organic frameworks

High catalytic activity is found to be due to the combination of a chromium catalyst with large pores (MIL-101(Cr)) with aprotic solvents (γ-valerolactone−10% H2O).

Selective fructose dehydration to 5-hydroxymethylfurfural from a fructose-glucose mixture over a sulfuric acid catalyst in a biphasic system: Experimental study and kinetic modelling

A two-step process combining the (equilibrium) glucose isomerization to fructose with selective dehydration of fructose in the obtained sugar mixture to 5-hydroxymethylfurfural (HMF), where glucose is largely unconverted and recycled, represents an attractive concept to increase the overall efficiency for HMF synthesis. This work presents experimental and modelling studies on the conversion of such fructose-glucose mixture to HMF using the sulfuric acid catalyst in a water-methyl isobutyl ketone biphasic system under a wide range of conditions (e.g., temperature, catalyst and sugar concentrations). Through detailed product analyses and ESI-MS spectroscopy, the excess formation of formic acid (together with humins) by the direct sugar/HMF degradation was confirmed and included in the reaction network (neglected in most literatures). The kinetic modelling based on batch experiments in monophasic water well describes the measurements thereof, whereas distinct deviations were found in the prediction of typical literature kinetic models. The incorporation of HMF equilibrium extraction into the developed kinetic model, with consideration of phase volume change as a function of temperature and partial phase miscibility, enables to predict reaction results in the biphasic system in batch. This kinetic model allows to optimize conditions for HMF synthesis that are favored in continuous reactors with minimized back mixing. Based on the model implications, the biphasic system was optimized with slug flow microreactors to better address process intensification and scale-up aspects. Using a simulated fructose-glucose mixture feedstock to represent commercially available high fructose corn syrups, a maximum HMF yield of 81% was obtained at 155 °C over 0.05 M H2SO4 at a residence time of 16 min in the microreactor, with 96% fructose conversion and over 95% of glucose remaining unconverted.

Enhanced conversion of glucose to fructose over naturalattapulgite catalyst promoted by CeO2 in water

AbstractFructose is an important platform compound for the production of chemicals and renewable fuels. Here, the CeO2/ATP catalysts were developed for glucose isomerization in water. The effects of CeO2 loading, glucose concentration and the catalyst dosage to glucose ratio on the activity for the reaction were investigated. Glucose was easily transformed over ATP in the presence of CeO2, and the 10 % CeO2/ATP catalyst exhibited a good fructose yield of 36.4 %. Meanwhile, the reaction activity of glucose was affected by glucose concentration and the catalyst dosage to glucose ratio, and more fructose would be generated at lower glucose concentration, wherein the highest yield of fructose was obtained 39.2 % at 5 % of glucose solution with the catalyst dosage to glucose ratio of 0.1. In addition, the characterization resultsrevealed that CeO2 had a positive interaction with ATP on the adjustment of its structural properties and the amount and distribution of basic sites, and therefore facilitated glucose isomerization.

The "blue bottle" experiment in the colloidal dispersions of smectites

The Blue Bottle Experiment involves a reversible redox process of decolorizing methylene blue (MB) by reaction with glucose (Glc) at basic pH. The direction of the reaction is affected by the concentration of dissolved O2. In this work, the reactions that took place in the presence and absence of nanoparticles of smectites (a group of layered silicates) were compared. The method of absorption spectroscopy with a diode-array detector was chosen for studying the reaction. It was possible to measure the full spectrum in a fraction of a second, and thus several hundred spectra were obtained for each experiment. Spectral matrices were analyzed using the chemometric method of multivariate curve resolution (MCR). Analysis of the results revealed not only the formation of known reaction products (a leuco-form of MB, the oxidation products of Glc) but also some other processes related to the changes of the reactants in a basic environment, slow dye decomposition, glucose isomerization, and the formation of MB molecular aggregates. The injection of colloidal smectite particles into the reaction system effectively stopped the redox reaction of MB with Glc, which may be important for dye stabilization in hybrid materials with smectites. This property was not related to the type of smectite, which instead affected the molecular aggregation occurring in the heterogeneous systems.

Effective isomerization of glucose to fructose by Sn-MFI/MCM-41 composites as Lewis acid catalysts

Zeolites as heterogenous catalysts have continuously attracted researchers’ interest due to the potentials for industrial biomass conversion. However, combining hierarchical structure and uniformly dispersed active sites in crystalline zeolites catalysts remains challenging. In this study, in-situ hydrothermal synthesis of Sn-MFI/MCM-41 composites were investigated with hexadecyl trimethylammonium bromide (CTAB) as the structure-directing agent by a stepwise heating. The resulting catalyst was characterized with hexagonal mesochannels, high BET area and crystalline MFI domains. Compared with previously reported tin-containing zeolites, enhanced glucose conversion and fructose selectivity was observed on the resulting Sn-MFI/MCM-41 materials, giving a fructose selectivity of 84%.

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.

Cooperative Acid‐Base Sites of Solid Ba‐Zr Mixed Oxide Catalyst for Efficient Isomerization of Glucose to Fructose in Aqueous Medium

AbstractEfficient and highly selective isomerization of glucose to fructose was achieved by using the inexpensive Ba−Zr mixed metal oxide catalyst. Catalyst was prepared by varying Ba−Zr ratios using co‐precipitation method. Various phases formed, planes exposed, morphology, elemental composition and particle size, basic site density and strength, oxidation state of elements were well studied by using various characterization techniques. The XRD analysis clearly indicates the presence of Ba+2 and Zr+4 in the form of BaO, ZrO2 and BaZrO3 phases. The SEM and HR‐TEM images indicate that, Ba−Zr (2 : 1) catalyst prepared showed uniform morphology with spherical and rod‐shaped particles ranging from 300 to 600 nm. Under the optimized reaction conditions Ba−Zr (2 : 1) catalyst exhibited excellent results in terms of 57 % of glucose conversion with 89 % selective formation of glucose. The presence of both acidic as well as basic sites play vital roles in activating the substrate molecules to selectively yield fructose. Ba−Zr (2 : 1) catalyst showed excellent recyclability performance up to four recycles.

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.

Supercritical CO2–subcritical H2O system: A green reactive separation medium for selective conversion of glucose to 5-hydroxymethylfurfural

The supercritical CO2 (scCO2)-subcritical H2O (subH2O) system offers a metal- and additive-free reaction solvent that can be used for organic synthesis. The enhanced formation of carbonic acid and ionization of water under elevated pressures and temperatures promote the production of hydronium and hydroxyl ions that can catalyze the conversion of a number of organic compounds. Furthermore, the biphasic nature of the system allows for the simultaneous extraction of less polar products from the aqueous solution by a flowing scCO2 stream. In this study, we investigated the use of scCO2-subH2O as a reactive separation medium for the conversion of glucose to 5-hydroxymethylfurfural (HMF). The highest HMF yield achieved was 32.6 % with a selectivity of 52.7 %. These values corresponded to a 20.25 % and 41.9 % increase in the yield and selectivity that were achieved in the experiments performed under batch operations. The improvement was primarily attributed to the extraction of some of the HMF from the solution. The highest separation efficiency so far was 12.7 %. We also performed semi-empirical quantum calculations to determine a possible mechanism of the production of HMF from glucose. The two-step process, which involved the isomerization of glucose to fructose and the dehydration of fructose to HMF, was shown to proceed with only the OH– and H3O+ that are inherent in the solvent system as catalysts. Insights from both kinetic data and quantum calculations revealed that the reaction is highly favored in the acidic environment of the scCO2-subH2O system.

Catalytic conversion of glucose in fructose utilizing high-silica zeolite Sn-ZSM-12

Abstract Tin incorporation in high-silica ZSM-12 zeolite was evaluated using different concentrations of tin and different structure-directing agents (SDA), in order to be used in the glucose isomerization reaction in fructose. The tetraethylammonium hydroxide SDA successfully formed the structure of the high silica zeolite ZSM-12; however, in this system, the addition of Sn prevented the formation of the ZSM-12 zeolite. Therefore, tetraethylammonium bromide was used as SDA, but the syntheses of high-silica ZSM-12 zeolite without and with tin incorporation were not effective. Then methyltriethylammonium chloride was used as SDA, and the high-silica ZSM-12 structure was formed only with the incorporation of tin. The samples with ZSM-12 structure and different concentrations of tin were evaluated in reaction of glucose conversion to fructose. It was found that the sample with the lowest tin content ( Sn / Si = 0 . 005 ) achieved the highest glucose conversion and the highest fructose yield.

Solvent‐Activated Hafnium‐Containing Zeolites Enable Selective and Continuous Glucose–Fructose Isomerisation

AbstractThe isomerisation of glucose to fructose is a critical step towards manufacturing petroleum‐free chemicals from lignocellulosic biomass. Herein we show that Hf‐containing zeolites are unique catalysts for this reaction, enabling true thermodynamic equilibrium to be achieved in a single step during intensified continuous operation, which no chemical or biological catalyst has yet been able to achieve. Unprecedented single‐pass yields of 58 % are observed at a fructose selectivity of 94 %, and continuous operation for over 100 hours is demonstrated. The unexpected performance of the catalyst is realised following a period of activation within the reactor, during which time interaction with the solvent generates a state of activity that is absent in the synthesised catalyst. Mechanistic studies by X‐ray absorption spectroscopy, chemisorption FTIR, operando UV/Vis and 1H–13C HSQC NMR spectroscopy indicate that activity arises from isolated HfIV atoms with monofunctional acidic properties.

Solvent-Activated Hafnium-Containing Zeolites Enable Selective and Continuous Glucose-Fructose Isomerisation.

The isomerisation of glucose to fructose is a critical step towards manufacturing petroleum‐free chemicals from lignocellulosic biomass. Herein we show that Hf‐containing zeolites are unique catalysts for this reaction, enabling true thermodynamic equilibrium to be achieved in a single step during intensified continuous operation, which no chemical or biological catalyst has yet been able to achieve. Unprecedented single‐pass yields of 58 % are observed at a fructose selectivity of 94 %, and continuous operation for over 100 hours is demonstrated. The unexpected performance of the catalyst is realised following a period of activation within the reactor, during which time interaction with the solvent generates a state of activity that is absent in the synthesised catalyst. Mechanistic studies by X‐ray absorption spectroscopy, chemisorption FTIR, operando UV/Vis and 1H–13C HSQC NMR spectroscopy indicate that activity arises from isolated HfIV atoms with monofunctional acidic properties.

Tighter Confinement Increases Selectivity of d‐Glucose Isomerization Toward l‐Sorbose in Titanium Zeolites

AbstractAqueous‐phase isomerization of d‐glucose to d‐fructose and l‐sorbose is catalyzed in parallel by Lewis acidic Ti sites in siliceous frameworks. Glucose isomerization rates (per Ti, 373 K) are undetectable when Ti sites are confined within mesoporous voids (Ti‐MCM‐41, TiO2‐SiO2) and increase to detectable values when Ti sites are confined within the smaller 12‐membered ring (12‐MR) micropores of Ti‐Beta. Isomerization rates decrease to lower values (by ≈20×) with further decreases in micropore size as Ti sites are confined within 10‐MR pores (Ti‐MFI, Ti‐CON), likely because of intrapore reactant diffusion restrictions, and reach undetectable values within the 8‐MR pores of Ti‐CHA as size exclusion prevents glucose from accessing active sites. Remarkably, the selectivity toward l‐sorbose over d‐fructose increases systematically as spatial constraints around Ti sites become tighter, and is >10 on Ti‐MFI. These findings demonstrate the marked influence of confinement around Ti active sites on the selectivity between parallel stereoselective sugar isomerization pathways.

Tighter Confinement Increases Selectivity of d-Glucose Isomerization Toward l-Sorbose in Titanium Zeolites.

Aqueous-phase isomerization of d-glucose to d-fructose and l-sorbose is catalyzed in parallel by Lewis acidic Ti sites in siliceous frameworks. Glucose isomerization rates (per Ti, 373 K) are undetectable when Ti sites are confined within mesoporous voids (Ti-MCM-41, TiO2 -SiO2 ) and increase to detectable values when Ti sites are confined within the smaller 12-membered ring (12-MR) micropores of Ti-Beta. Isomerization rates decrease to lower values (by ≈20×) with further decreases in micropore size as Ti sites are confined within 10-MR pores (Ti-MFI, Ti-CON), likely because of intrapore reactant diffusion restrictions, and reach undetectable values within the 8-MR pores of Ti-CHA as size exclusion prevents glucose from accessing active sites. Remarkably, the selectivity toward l-sorbose over d-fructose increases systematically as spatial constraints around Ti sites become tighter, and is >10 on Ti-MFI. These findings demonstrate the marked influence of confinement around Ti active sites on the selectivity between parallel stereoselective sugar isomerization pathways.

Gallium and tin exchanged Y zeolites for glucose isomerisation and 5-hydroxymethyl furfural production

This study demonstrates the use of gallium and tin modified Y zeolites as catalysts for the conversion of glucose into fructose, mannose and 5-Hydroxymethyl furfural. These catalysts can be synthesised via a simple and scalable procedure that uses commercially available Y zeolite. The catalysts were characterised by various techniques including elemental analysis, electron microscopy, nitrogen physisorption, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, solid state nuclear magnetic resonance spectroscopy and X-ray absorption near edge spectroscopy. It is found that tin containing Y zeolite generate a glucose conversion of 36 % and total product yield of 17 % in water. Meanwhile, gallium containing Y zeolite shows an HMF yield of 33 % when reactions were conducted in DMSO. The recyclability of tin and gallium containing Y zeolites were studied in DMSO and the activities of both materials were shown to remain stable. Furthermore, the spent catalysts can be regenerated via calcination in air.