Conversion Yield Research Articles

Dual-Stimulus-Driven Dynamically Controllable [3]Rotaxane with Tunable Organic Room-Temperature Phosphorescence.

A dual-stimulus-driven stiff-stilbene-based dynamic [3]rotaxane has been facilely developed using the threading-stoppering strategy and exhibits reversible shuttling motions and bidirectional rotations upon encountering acid-base and distinct light stimulations, respectively. Herein, the two dibenzo-24-crown-8 macrocycles can undergo reversible switching motion between two different stations along the axle suffered from acid-base stimulation, and simultaneously, the two rotaxanes can also perform cis-trans rotations upon irradiation with distinct light. In other words, the constructed rotaxanes can conduct two modes of regular motions without interference. Interestingly, reciprocating switching motion of the rings along the axle enabled the rotaxanes to exhibit controllable and reversible photoisomerization speed, conversion yield, and quantum yield. Crucially, these rotaxanes also manifest adjustable solid-state organic room-temperature phosphorescence (RTP) and photoluminescence stimulated by dual factors (acid-base and diverse light), which are further applied in information encryption and anticounterfeiting. The presented study provides an instructive way for precisely boosting photoisomerization performances and the fabrication of dual-stimuli-induced molecular machines with functions of two-mode mechanical motions and controllable pure organic RTP switches.

An effective approach for chitosan conversion to 5-hydroxymethylfurfural catalyzed by bio-based organic acid with ionic liquids additive

The primary challenges associated with converting chitin biomass into 5-hydroxymethylfurfural (5-HMF) primarily revolve around achieving high 5-HMF yields while overcoming various limitations from traditional acid-based catalysts, including complex post-treatment procedures, by-product generation, and equipment corrosion. In this view, a novel approach was developed to synthesize 5-HMF from chitosan under hydrothermal process using a mixture of DMSO and water as reaction medium. Biomass-derived organic carboxylic acids were used as catalysts due to their weaker corrosiveness compared to mineral acids. The acidity of the bio-based acid was adjusted using inexpensive ionic liquids. By combining 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) with oxalic acid (OA), an excellent 29.1 % yield of 5-HMF conversion was achieved on the optimized condition. The improved dissociation ability of OA by [BMIM]Cl played a crucial role in this outcome. Using FTIR and density functional theory (DFT) techniques allowed for the proposal of a dissociation mechanism for OA induced by [BMIM]Cl, involving hydrogen bond interactions and the weakening of the O–H bond, facilitating the easy dissociation of hydrogen in the O–H group with H+ formation. Furthermore, the untreated chitosan and the solid residues obtained during the conversion process were characterized revealing the gradual conversion and the quaternization in the NH2 group of chitosan.

Zirconium-tin phosphate as an efficient catalyst for renewable p-xylene synthesis from biobased 2,5-dimethylfuran and ethylene

Efficient production of renewable p-xylene (PX) from bio-based 2,5-dimethylfuran (DMF) and ethylene is challenging. Herein, novel nanoflake-like zirconium-tin phosphate catalysts were synthesized, and their catalytic performance was evaluated in the conversion of DMF and ethylene to PX. The DMF conversion, PX selectivity and PX yield reached up to 99%, 95.2% and 94.2%, respectively over Zr0.6Sn0.4P under relatively mild conditions. The PX productivity was 61.1 mmolPX·gcat−1·h−1, which is better than that of previously reported catalysts. By combining characterization with activity test, it was found that enhanced DMF and ethylene adsorption is beneficial to promoting the reaction between DMF and ethylene. Precise regulation of acid sites is crucial for inhibiting the occurrence of side reactions and improving the selectivity of PX. The kinetic analysis revealed that Zr0.6Sn0.4P had a relatively low apparent activation energy (39 kJ·mol−1) for this reaction than previously reported catalysts. In addition, the Zr0.6Sn0.4P catalyst exhibited an excellent reusability.

Single Photon Emitters in Hexagonal Boron Nitride Fabricated by Focused Helium Ion Beam

AbstractThe 2D layered hexagonal boron nitride (hBN) material is a promising platform for making single photon emitters (SPEs). Integrate SPEs with photonic cavities or waveguides, requires the deterministic positioning of these emitters as accurately as possible. Among all of the alternative techniques, He+ focused ion beam (FIB) theoretically has sub‐nanometer precision, but its practical positioning accuracy in processing SPEs is limited by the inevitable detrimental byproduct defects. So far, it remains challenging to achieve an accuracy below 100 nm for the positioning of SPEs in hBN. Here, we present a two‐step method for creating SPEs at the predetermined positions in hBN that combines the He+ FIB irradiation and thermal annealing under an oxygen atmosphere. With this method, we have realized the positioning accuracy of less than 50 nm, which, to the best of our knowledge, stands as the highest among the currently available hBN SPEs preparation methods. Moreover, the SPE conversion yield was over 35% and the emission brightness of individual SPE achieved up to 3 × 105 counts/s at room temperature. These SPEs fabricated precisely with nanoscale accuracy in hBN are expected to be good candidates for making large‐scale integrated SPEs in photonic circuits.

Synergistic effects and product yields in microwave-assisted in-situ co-pyrolysis of rice straw and paraffin wax

Microwave-assisted pyrolysis is one of the most efficient methods for solid waste management. This study employed microwave-assisted catalytic co-pyrolysis to convert Paraffin wax (PW) and rice straw (RS) into valuable char, gas, and oil products. KOH and graphite were used as the catalyst and susceptor, respectively. The RS and PW blend served as the feedstock (with a blend ratio of 0–10 g). The yields of co-pyrolysis at different blending ratios of RS: PW exhibited variations in char content (ranging from 9.8% to 22.6% by wt.), oil production (ranging from 34.1% to 76.9% by wt.), and gas formation (ranging from 13.2% to 47.5% by wt.). The effects of the RS: PW ratio on the average heating rate, feedstock conversion, and product yields were also investigated. Analyses were performed to assess the synergistic impacts on product yields, average heating rates, and conversion factors. Notably, co-pyrolysis synergy led to increased oil and char production. Furthermore, we conducted FTIR analysis on the oil and char produced through the catalytic co-pyrolysis of RS: PW. In conjunction with co-pyrolysis synergy, the catalyst facilitated the formation of amides, alkenes, aliphatic compounds, and aromatic compounds.

Enhancing photocatalytic visible-light-driven oxidation of NOx over Mott-Schottky Ag/SnO2 nanorod heterojunctions

Nitrogen oxides (NOx) is formed by primary emission from diesel engine vehicles. In this study, we synthesized and applied the photocatalytic effect over Mott-Schottky Ag/SnO2 nanorod heterojunctions toward NOx removal under visible light. In detail, the presence of Ag NPs in the Ag/SnO2 nanorod heterojunction, the number of electrons participating in the catalysis is enhanced due to the localized surface plasmon resonance (LSPR) of Ag NPs. In addition, the potential of the reducing region of SnO2 is also changed, thereby creating favourable conditions for the photocatalysis. We determined that 1.5% Ag/SnO2 nanorod heterojunction is the best sample with NO (500 ppb) photodegradation efficiency of 50.64% under visible light irradiation. Moreover, Ag/SnO2 nanorod heterojunction has an excellent stability after undergoing five times recycling and is highly applicable in practical applications with a high NO degradation and low NO2 conversion yield. The Mott-Schottky plots, Tauc plots, and trapping tests were used to build the energy scheme of the Ag/SnO2 heterojunction.

Inclusion of Mulberry (Morus alba) in the Rabbit Fattening Diet (Oryctolagus cuniculus)

The aim of the study was to evaluate the effects of the inclusion of mulberry foliage (Morus alba) in the diet on productive variables and carcass yield in fattening rabbits. An animal behavior test was performed by using a completely random design with 36 weaning rabbits. Four treatments were established to include mulberry in the daily diet in concentrated proportions: mulberry foliage, provided for 42 days to rabbits in the fattening phase: T1: 100:0, T2: 80:20, T3: 60:40, and T4: concentrate: mulberry ad libitum. Food consumption, weight gain, feed conversion and carcass yield were measured. Significant differences (p < 0.01) were found in mulberry consumption, final live weight and food conversion. Daily weight gain, carcass yield, digestive tract weight and cecum showed no differences between treatments (p > 0.05). In the ad libitum treatment rabbits consumed about 20% of mulberry, and their level of inclusion in the diet can be 20 and 40% without effect on the behavior of productive variables.

One-pot selective biosynthesis of Tyrian purple in Escherichia coli

Tyrian purple (6,6′-Dibromoindigo) is an ancient precious dye, which possesses remarkable properties as a biocompatible semiconductor material. Recently, biosynthesis has emerged as an alternative for the sustainable production of Tyrian purple from a natural substrate. However, the selectivity issue in enzymatic tryptophan (Trp) and bromotryptophan (6-Br-Trp) degradation was an obstacle for obtaining high-purity Tyrian purple in a single cell biosynthesis. In this study, we present a simplified one-pot process for the production of Tyrian purple from Trp in Escherichia coli (E. coli) using Trp 6-halogenase from Streptomyces toxytricini (SttH), tryptophanase from E. coli (TnaA) and a two-component indole oxygenase from Providencia Rettgeri GS-2 (GS-C and GS-D). To enhance the in vivo solubility and activity of SttH and flavin reductase (Fre) fusion enzyme (Fre-L3-SttH), a chaperone system of GroEL/GroES (pGro7) was introduced in addition to the implementation of a set of optimization strategies, including fine-tuning the expression vector, medium, concentration of bromide salt and inducer. To overcome the selectivity issue and achieve a higher conversion yield of Tyrian purple with minimal indigo formation, we applied the λpL/pR-cI857 thermoinducible system to temporally control the bifunctional fusion enzyme of TnaA and monooxygenase GS-C (TnaA-L3-GS-C). Through optimization of the fermentation process, we were able to achieve a Tyrian purple titer of 44.5 mg L−1 with minimal indigo byproduct from 500 μM Trp. To the best of our knowledge, this is the first report of the selective production of Tyrian purple in E. colivia a one-pot process.

Decoupling reaction network and designing robust VOx/Al2O3 catalyst with suitable site diversity for promoting CO2-mediated oxidative dehydrogenation of propane

Detailed thermodynamic analysis was utilized to decouple the complex reaction network of CO2-mediated oxidative dehydrogenation (CO2-ODH) of propane and unravel critical catalyst design requirements. Inspired by the unmatched ability of boron-based catalysts in limiting cracking and overoxidation reaction pathways, we exploited controlled integration of both VOx and BOx active phases onto a γ-Al2O3 support and constructed a highly efficient CO2-ODH catalyst via scalable mechanochemical synthesis route. The solvent- and template-free synthetic design strategy regulated crucial properties of the catalysts and endowed suitable site diversity as evidenced from N2-adsorption analysis, XRD, HRTEM, Raman analysis, NH3-TPD, H2-TPR, and UV–Vis diffuse reflectance spectroscopy. Consequently, excellent propane conversion and propylene yield of 61 and 34 % respectively over 12 h time on stream (TOS) at 650 °C were realized with a catalyst composed of 5 wt% vanadium and 7 wt% boron. In situ DRIFT measurement revealed insight into the dynamic changes on the catalyst surface and the corresponding evolution of reaction intermediates during the CO2-ODH process. Overall, the thermodynamic investigation re-emphasized the critical importance of effective kinetic control while the synthetic protocol illustrated a promising avenue for rational design of CO2-ODH catalysts to harness the unique advantages of boron and metal oxide-based catalysts simultaneously.

Understanding of gas-phase methane pyrolysis towards hydrogen and solid carbon with detailed kinetic simulations and experiments

Methane (CH4) pyrolysis is studied in a tubular flow reactor for the production of hydrogen and solid carbon by combining kinetic modelling, numerical simulation and experiments in a high-temperature flow reactor. Operating conditions are varied such as temperature in the range of 1273–1873 K, hydrogen addition to the feed with a molar H2:CH4 ratio between 0 and 4, and residence time in the range of 3–7 s. Elementary-step reaction mechanisms consisting of pyrolysis and carbon coupling reactions among C1, C2, aromatic and polycyclic aromatic hydrocarbon species are used in the numerical simulations of the species profiles in flow direction. A thermodynamic analysis is performed to acquire the boundary conditions for operation as well to estimate probable by-products (C2H2, C2H4, C2H6, C6H6, C16H10 etc.) over the temperature range. Gas-phase kinetic modelling is performed revealing that CH4 conversion starts at temperatures above 1273 K. Higher temperatures increase CH4 conversion and H2 yield peaking at 1573 K. The cooling temperature gradient downstream of the hot zone in the reactor causes reverse reactions in gas-phase suppressing CH4 conversion. H2 addition to the feed is found to be a crucial parameter for controlling the by-product formation. In the experimental study, a solid carbon yield of 84 % is achieved while gaseous by-products remain less than 1 mol-% at 1673 K, H2:CH4 ratio of 2, and residence time of 5 s. Gas-phase reactions are found to be coupled to surface reactions at higher temperatures.

A robust mesoporous sulfated zirconium‐doped KIT‐6 solid acid catalyst for the hydrolysis of microcrystalline cellulose

AbstractBACKGROUNDThe exploration of a robust solid acid catalyst for the efficient hydrolysis of cellulose is a research hotspot due to the need for clean production and sustainable development. KIT‐6 silica offers abundant three‐dimensionally interconnected mesopores, which are expected to be superior to mesoporous structures with one‐ or two‐dimensional channels due to faster diffusion of reactants and products during reaction. The catalytic conversion of microcrystalline cellulose is examined in detail over a functionalized KIT‐6 catalyst prepared by the method of Zr addition and subsequent sulfation.RESULTSIn terms of cellulose conversion and product yield, the activity of the catalysts followed the order of sulfated Zr‐KIT‐6 > Zr‐KIT‐6 > SO42−‐KIT‐6 > KIT‐6. Over the sulfated Zr‐KIT‐6 catalyst with a Si/Zr molar ratio of 7:1, a maximum cellulose conversion of 95.0% was achieved with glucose yield of 23.4%, 5‐hydroxymethylfufural yield of 4.9% and levulinic acid yield of 11.7% under the optimized reaction conditions: reaction temperature of 200 °C, reaction time of 2 h, catalyst amount of 0.3 g, cellulose‐to‐water mass ratio of 1:1.CONCLUSIONThe sulfated Zr‐KIT‐6 catalyst possessed the strongest and richest Brønsted acid sites, which readily provided protons for the cleavage of β‐1,4 glycosidic bonds in cellulose, thus conferring superior catalytic activity in cellulose hydrolysis. A plausible pathway at the initial stage of cellulose hydrolysis over the catalyst was proposed. © 2023 Society of Chemical Industry (SCI).

Catalytic steam gasification of bituminous coal for syngas production with catalyst derived from calcium-rich construction demolition waste

A disposable Ca-containing catalyst was generated from a sort of calcium-rich construction demolition waste and utilized in the steam gasification of a bituminous coal in a fixed bed reactor. The effects of catalyst loading amount, gasifying temperature and catalyst loading method on steam gasification with respect to the production of syngas with high H2/CO mole ratio and CH4 content were investigated. The H2 and CO molar yields as well as carbon conversion increased noticeably with the increase of catalyst loading amount despite there was a saturation quantity. After loading 6.0 wt% catalyst into coal by kneading method, the carbon conversion and total gas molar yield increased from 52.56% and 136.06 mmol/g-C to 62.77% and 160.23 mmol/g-C, respectively. At low temperature, kneading method displayed superiority over mechanical mixing method in steam gasification performance of bituminous coal while they had approximately the same catalytic effect on coal steam gasification at high temperature. Characterization of SEM images and Raman spectroscopy of coal chars derived from catalytic pyrolysis confirmed that addition of catalyst changed the micro-crystal structure and formed more defects and amorphous structures. Overall, the catalyst showed satisfactory catalytic effect in steam gasification of bituminous coal and could be used as a suitable alternative of CaO for syngas production.

Facile synthesis of functionalized polysiloxanes with nonconventional fluorescence by oxa-Michael addition reaction

ABSTRACTDeveloping a novel methodology for the synthesis of functionalized polysiloxanes is highly desirable because of their extensive applications in engineering, textile, construction, electronics, and medical systems. Herein we introduce the oxa-Michael addition reaction as an efficient methodology to prepare a series of functionalized polysiloxanes from hydroxyalkyl-containing polysiloxanes and vinyl monomers using phosphazene base as the catalyst. The effects of various factors, including reaction time, feed ratio and solvent, were explored in this reaction. It was found that the reaction can be carried out under mild reaction (room temperature in 6 h to 24 h) with moderate to high conversion yields (60% to 99%). In particular, vinyl monomers with strong electron-withdrawing groups (e.g., cyano and sulfone groups) have higher reactivity, and the functionalized polysiloxanes can be obtained quantitatively or near-quantitatively. Interestingly, their molecular weights determined by gel permeation chromatography (GPC) reveal that the Si-O-Si skeletons were attacked by phosphazene base and re-arranged during the reaction, thus leading to improved molecular weights and more uniform molecular weight distributions in the final products than the original polysiloxanes. Moreover, these polysiloxanes exhibited intriguing nonconventional fluorescence due to the presence of unique chromophores, and those containing cyano and sulfone groups particularly exhibit the best fluorescence performance. More organosilicon materials could be developed under this simple strategy.

Ratiometric Fluorescence Biosensing of Tandem Biemissive Ag Clusters Boosted by Confined Catalytic DNA Assembly.

The reaction kinetics and yield of traditional DNA assembly with a low local concentration in homogeneous solution remain challenging. Exploring confined catalytic DNA assembly (CCDA) is intriguing to boost the reaction rate and efficacy for creating rapid and sensitive biosensing platforms. A rolling circle amplification (RCA) product containing multiple tandem repeats is a natural scaffold capable of guiding the periodic assembly of customized functional probes at precise sites. Here, we present a RCA-confined CCDA strategy to speed up amplifiable conversion for ratiometric fluorescent sensing of a sequence-specific inducer (I*) by using string green-/red-Ag clusters (sgAgCs and srAgCs) as two counterbalance emitters. Upon recognition of I*, CCDA events are operated by two toehold-mediated strand displacements and localized in repetitive units, thereby releasing I* for recycled signal amplification in the as-grown RCA concatemer. The local concentration of reactive species is increased to facilitate rapider dsDNA complex assembly and more efficient input-output conversion, on which the clustering template sequences of sgAgCs and srAgCs are blocked and opened, enabling srAgCs synthesis but opposite to sgAgCs. Thus, the fluorescence emission of srAgCs goes up, while sgAgCs go down. With the resultant ratio featuring inherent built-in correction, rapid, sensitive, and accurate quantification of I* at the picomolar level is achieved. Benefiting from efficient RCA confinement to enhance reaction kinetics and conversion yield, this CCDA-based strategy provides a new paradigm for developing simple and diverse biosensing methodologies.

Visible-light-driven quantitative photooxidation of anthracene to anthraquinone under mild conditions

This paper discloses a mild and atom-economic photo-oxidation protocol for visible-light-driven quantitative oxidation of anthracene (AN) to anthraquinone (AQ), which can obtain excellent AN conversion (∼100%) and AQ yield (99.2%) without any catalysts and additives under 10 h of visible light illumination. In addition, the protocol also works well with other chemical molecules that have a similar structure. In this protocol, AN is directly oxidized from AN to AQ without the observation of the intermediate anthrone (AO). Based on a series of control tests, as well as free radical quenching and electron paramagnetic resonance (EPR) spin trapping studies, it can be inferred that the process of photo-oxygenation in AN is most likely initiated by its photo-excited state, denoted as AN*. This photo-excited state has the ability to activate molecular oxygen (O2) by an electron transfer mechanism, resulting in the formation of a superoxide free radical (O2•-). Following this, the process of photo-oxidation is progressively controlled by the oxygenated product AQ, which acts as an active photo-catalyst. AQ is derived from the oxidation of AN by O2•- and its presence accelerates the process of photo-oxidation due to its rapid accumulation. Furthermore, the yield of AQ can be improved by enhancing the light intensity of the light source, timely separating the yellow solid oxidation product AQ formed during the reaction, and pre-adding the oxidation product AQ to the protocol as an active photocatalyst.

Efficient and accurate fractionation of eucalyptus using glycolic acid-catalyzed hydrothermal treatment and alkali treatment comprehensive technology

The effective utilization of lignocellulosic biomass is the key to evaluating the profitability of the process, and precise fractionation is a prerequisite for effective utilization. In this study, a high yield of fermentable sugars and lignin rich in phenolic hydroxyl groups were successfully obtained from eucalyptus using glycolic acid-catalyzed hydrothermal and alkaline treatment. The results showed that 88.20% of xylan and 85.07% of lignin were separated, and 62.68% of lignin was extracted from the hydrolysate. The extracted lignin has a complete structure and is rich in guaiacyl and syringyl units, which is conducive to the subsequent high-value utilization of lignin. 85% of glucan was recovered, and the glucose conversion yield was 84.24% after enzymatic hydrolysis. The hydrolysate can be concentrated, impurity removed, and purified to produce biofuels or chemicals after the precipitation of lignin. In summary, the two-step process based on glycolic acid has great potential in converting eucalyptus into biomass energy and chemicals, and this process is a promising precision fractionation strategy.

Fabricating Pt0-acid synergy in Pt/Beta phenol hydrodeoxygenation catalysts via a surface modification strategy of Beta molecular sieves

As for metal/zeolite supported phenol hydrodeoxygenation catalysts, it is important to improve the dispersion of metallic sites and build synergistic relationship between metallic and acid sites. The current research proposes a surface modification strategy by introducing CTAB in the NaOH etching of Beta. CTAB interacts with crystal defects to inhibit excessive crystal destruction. Aluminum atoms are protected from being removed and acid sites are reserved. Generated silicon hydroxyl groups anchor Pt0 particles. Pt0 particles are spatial resisted on the internal surface of catalysts to activate C–O bonds of phenol. Preserved acid sites provide reactive sites for dehydration reaction of cyclohexanol on the external surface of Pt/Beta-H. The high phenol conversion (i.e., 92.26 %) and cyclohexane yield (i.e., 7.18 %) were obtained at 80 °C due to the functional synergistic effect between acid and Pt0 sites. Proposed surface modification strategy proposes references for the structure design and development of efficient phenolics hydrodeoxygenation catalysts.

Hydrogen-Rich Syngas Production via Dry and Steam Reforming of Methane in Simulated Producer Gas over ZSM-5-Supported Trimetallic Catalysts

This study investigated the production of hydrogen-rich syngas from renewable sources using durable and efficient catalysts. Specifically, the research focused on steam methane reforming (SRM) and dry methane reforming (DRM) of simulated producer gas from biomass steam gasification in a fluidized bed reactor. The catalysts tested are ZSM-5-supported nickel-iron-cobalt-based trimetallic catalysts in different ratios, which were prepared via the wet impregnation method. Synthesized catalysts were characterized using XRD, BET, H2-TPR, and SEM techniques. The results of the SRM with the simulated producer gas showed that the 20%Ni-20%Fe-10%Co/ZSM-5 trimetallic catalyst, at a gas hourly space velocity (GHSV) of 12 L·h−1·g−1 and reaction temperature of 800 °C, achieved the highest CH4 conversion (74.8%) and highest H2 yield (65.59%) with CO2 conversion (36.05%). Comparing the performance of the SRM and DRM of the simulated producer gas with the 20%Ni-20%Fe-10%Co/ZSM5 at a GHSV of 36 L·h−1·g−1 and 800 °C, they achieved a CH4 conversion of 67.18% and 64.43%, a CO2 conversion of 43.01% and 52.1%, and a H2 yield of 55.49% and 42.02%, respectively. This trimetallic catalyst demonstrated effective inhibition of carbon formation and sintering, with only 2.6 wt.% carbon deposition observed from the thermo-gravimetric analysis of the used catalyst from the SRM of the simulated producer gas, thus promoting the potential of the ZSM-5-supported trimetallic catalysts in methane reforming.

Expression and characterization of an organic solvent tolerant recombinant lipase from Staphylococcus capitis SH6 for food wastewater treatment

The study illustrated here aims on an organic solvent tolerant lipase from Staphylococcus capitis (SCL). The gene part, encoding the mature lipase, was cloned and sequenced. The concluded polypeptide sequence, equivalent to the protein, consist of 388 amino acid residues with a molecular mass of about 45 kDa. A structure-based alignment of the SCL amino acid sequence shows high identities with those many staphylococcal lipases. From this alignment of sequences, the catalytic triad (Ser 117, Asp 308 and His 347) of SCL could be identified. The mature part of the SCL was expressed in Escherichia coli and the recombinant lipase (r-SCL) was purified to homogeneity. The purified r-SCL presented a quite interesting stability at low temperatures (< 30 °C) and the enzyme was found to be highly stable in polar organic solvent and at a pH ranging from 3 to 12. After that, we have demonstrated that the recombinant enzyme may be implicated in the biodegradability of oily wastewater from effluents of fast-food restaurants; the maximum conversion yield into fatty acids obtained at 30 °C, was 65%.

Synergistic effect of silanols in mesopores leading to unexpected catalysis of dendritic mesoporous silica particles in the aqueous-phase synthesis of 5-hydroxymethylfurfural from fructose

Synthesis of 5-hydroxymethylfurfural (5-HMF) from fructose in water over acids catalysts usually produces unsatisfactorily low yield and selectivity due to inevitable side reactions, i.e., rehydration and condensation. Unprecedentedly, these complications in the aqueous phase synthesis of 5-HMF could be overcome by dendritic mesoporous silica particles (DMSNs). In the hydrothermal reactions of fructose, it was discovered that the synergy of silanols and mesopores transformed seemingly inert DMSNs into active catalysts, leading to a fructose conversion and 5-HMF yield of over 90%. The silanols on DMSNs offered weak Brønsted acid sites for catalyzing the dehydration of fructose to 5-HMF, while undesired reactions were substantially prohibited. The presence of glucose in the reaction suggests that fructose converts to 5-HMF via the acyclic route, and the competing reaction is indeed the isomerization. As revealed experimentally, mesopores full of silanols promoted the conversion of fructose to 5-HMF, but mesopores with a few silanols were relatively hydrophobic, offering a preferential partitioning of 5-HMF in mesopores of DMSNs. DFT analysis theoretically supported that in the presence of silanols, transforming fructose to 5-HMF is thermodynamically more favorable than the isomerization of fructose to glucose.