Tandem Dehydration Research Articles

Mo-based bio-derived carbon catalyst enables a tandem dehydration reaction for the direct synthesis of fuel precursors from fructose

In the pursuit of sustainable alternatives for petroleum fuels, bio-based hydrocarbons emerge as a promising choice. To explore this, a molybdenum catalyst supported on bio-derived carbon was developed, enabling the direct synthesis of fuel precursors from fructose. The catalyst was synthesized by varying the wt.% of molybdenum loading through hydrothermal treatment and carbonization. The NH3-TPD analysis revealed the presence of 1 mmol/g of acidic sites on best the catalyst. HRTEM and XPS analysis reveals that the majority of molybdenum is present as Mo6+. The synthesized catalyst effectively facilitated the dehydration of fructose to 5-hydroxymethylfurfural (5-HMF), followed by hydroxyalkylation/alkylation (DHAA) of 5-HMF with 2-methylfuran. Furthermore, compared to commercial Brønsted acid catalysts, the synthesized catalyst demonstrated remarkable performance, achieving complete fructose conversion with 36% selectivity towards the DHAA product. Moreover, an innovative approach was developed for the separation of 5,5′-((5-((5-methylfuran-2-yl)methyl)furan-2-yl)methylene)bis(2-methylfuran) and 5-HMF from dimethyl sulphoxide (DMSO) using a saturated aqueous sodium chloride (NaCl) solution in tetrahydrofuran (THF). This developed method, utilizing the bio-derived catalyst with efficient catalytic performance and effective product separation from DMSO, shows great promise for directly synthesizing fuel precursors from fructose and advancing sustainable fuel production.

A multi-functional Ru Mo bimetallic catalyst for ultra-efficient C3 alcohols production from liquid phase hydrogenolysis of glycerol

Ru and Mo bimetallic catalysts supported on active carbon modified by phosphotungstic acid (PW) were designed and applied in glycerol hydrogenolysis reaction. The physicochemical properties of the catalysts were characterized and the presence of active sites was investigated from the perspective of the glycerol hydrogenolysis performance. The MoO x is highly selective for the C—O bond cleavage of glycerol molecules, which can reasonably regulate the strong C—C bond cleavage activity of Ru nanoparticles. By using sequential deposition of Ru and Mo supported on mesoporous PW-C, the characterization results show that the combination of isolated low-valence MoO x with metal Ru particles can form “MoO x -Ru-PW”, which provides highly catalytic activity toward C—O bond cleavage, selectively producing more C3 alcohols (mainly 1,2(3)-propanediol). The glycerol conversion of 1% Mo/Ru/PW-C catalyst was 59.6%, the selectivity of C3 alcohol was 96.1%, and the selectivity of propanediol (1,2(3)-propanediol) was 94.9%. It is noteworthy that the selectivity of 1,3-propanediol reached 20.7% when the PW was 21.07% (mass). This study provides experimental evidence for the tandem dehydration and hydrogenation mechanism of the multifunctional Mo/Ru/PW-C catalyst.

AvmM catalyses macrocyclization through dehydration/Michael-type addition in alchivemycin A biosynthesis

Macrocyclization is an important process that affords morphed scaffold in biosynthesis of bioactive natural products. Nature has adapted diverse biosynthetic strategies to form macrocycles. In this work, we report the identification and characterization of a small enzyme AvmM that can catalyze the construction of a 16-membered macrocyclic ring in the biosynthesis of alchivemycin A (1). We show through in vivo gene deletion, in vitro biochemical assay and isotope labelling experiments that AvmM catalyzes tandem dehydration and Michael-type addition to generate the core scaffold of 1. Mechanistic studies by crystallography, DFT calculations and MD simulations of AvmM reveal that the reactions are achieved with assistance from the special tenuazonic acid like moiety of substrate. Our results thus uncover an uncharacterized macrocyclization strategy in natural product biosynthesis.

Methyl isobutyl ketone-enabled selective dehydration–esterification of sorbitol to isosorbide esters over the H-beta catalyst

One-step tandem dehydration–esterification of sorbitol in various fatty acids was achieved using H-beta by methyl isobutyl ketone mediation, giving selectively corresponding isosorbide esters in excellent 79–84% yields including 59–65% diesters.

One-Pot Tandem Dehydration–Hydrogenation of Xylose with Formic Acid over Co Catalysts

The transformation of sugars is a sustainable method of production of high value-added chemicals and fuels. Traditional procedures used H2SO4 for sugar dehydration, followed by hydrogenation with f...

Quantitative synthesis of 2,5-bis(hydroxymethyl)furan from biomass-derived 5-hydroxymethylfurfural and sugars over reusable solid catalysts at low temperatures

Quantitative production of 2,5-bis(hydroxymethyl)furan (BHMF) was achieved at room temperature (25 °C) via highly selective hydrogenation of biomass-derived 5-hydroxymethylfurfural (HMF) employing alkali salt KF as catalyst and polymethylhydrosiloxane (PMHS) as hydrogen source. A moderate turnover frequency (TOF: 4.2 h−1) was observed for this mild and sustainable reaction process. Moreover, a combination of Amberlyst-15 with KF could successfully catalyze the direct synthesis of BHMF from hexose sugars such as fructose and inulin via tandem dehydration and hydrogenation in a single pot. This catalytic system is more selective compared with H2-participated counterpart, giving a high BHMF yield and selectivity of up to 98% and >99% from HMF, respectively. Moreover, the catalytic performance of KF could remain for at least five consecutive cycles in the conversion of HMF to BHMF.

Direct syngas conversion to liquefied petroleum gas: Importance of a multifunctional metal-zeolite interface

It is challenging to fabricate a multifunctional catalyst for consecutively catalyzing multiple reactions. Herein, we report a well-defined metal-zeolite interface derived from a CuZnAl@H-Beta core@shell catalyst to realize one-step syngas conversion to liquefied petroleum gas (LPG). The multifunctional interface between CuZnAl core and H-Beta zeolite shell is composed of Cu and acid zeolite with a content gradient, through which synthesized methanol via syngas on the core will pass. The interface is able to catalyze the tandem dehydration of methanol to olefins on acid sites and olefin hydrogenation to C3–4 saturated hydrocarbons (LPG fraction) over exposed Cu sites on the interface instead of noble metals in conventional catalysts. The selectivity of LPG in hydrocarbons over the prepared capsule catalyst reaches as high as 77% accompanied by a record low methane and C2 selectivity (<2.0%).

Tandem dehydration–transfer hydrogenation reactions of xylose to furfuryl alcohol over zeolite catalysts

Dehydration and transfer hydrogenation tandem reactions of xylose to furfuryl alcohol in water/isopropanol were performed on MFI, FAU and BEA zeolites.

One‐Pot Deoxygenation of Fructose to Furfuryl Alcohol by Sequential Dehydration and Decarbonylation

AbstractFructose was deoxygenated to furfuryl alcohol (FFA) by tandem dehydration and decarbonylation in one pot over the AlCl3⋅6 H2O/Pd(OAc)2 catalyst combination to give a high FFA yield of 40.6 %. AlCl3⋅6 H2O behaves as an effective Lewis acid to catalyze the dehydration of fructose to 5‐hydroxymethylfurfural (HMF), and subsequently, Pd(OAc)2 catalyzes the removal of a CO moiety from HMF to produce FFA selectively. The hydroxyl group on the HMF intermediate was stabilized by poly(1‐vinyl‐2‐pyrrolidinone) through an intermolecular hydrogen bond, which accelerated the dehydration of fructose and inhibited the hydrogenation of HMF by formic acid. The decarbonylation of HMF was promoted and the unwanted decomposition of fructose was inhibited through the use of 4 Å molecular sieves. This research highlights a “one‐pot” catalytic system to transform renewable carbohydrates into fine chemicals by tandem dehydration and decarbonylation reactions without the separation or purification of HMF.

Evidence for the Bifunctional Nature of Pt–Re Catalysts for Selective Glycerol Hydrogenolysis

Rhenium substantially promotes the rate of Pt-catalyzed glycerol hydrogenolysis to propanediols and shifts the product selectivity from 1,2-propanediol to a mixture of 1,2 and 1,3-propanediols. This work presents experimental evidence for a tandem dehydration–hydrogenation mechanism that occurs over a bifunctional Pt–Re catalyst. Infrared spectroscopy of adsorbed pyridine and the rate of aqueous-phase hydrolysis of propyl acetate were used to identify and quantify Bronsted acid sites associated with the Re component. Near-ambient-pressure XPS revealed a range of Re oxidation states on the Pt–Re catalysts after reduction in H2 at 393 and 493 K, which accounts for the presence of Bronsted acidity. A mechanism involving acid-catalyzed dehydration followed by Pt-catalyzed hydrogenation was consistent with the negative influence of added base, a primary kinetic isotope effect with deuterated glycerol, an inverse isotope effect with dideuterium gas, and the observed orders of reaction.

An Expedition Through the Last Decade of Heterocycle Construction by Using Palladium, Iron, Copper, or Iodine/tert-Butyl Hydroperoxide

Over the past decade, our group has developed a series of synthetic methods for the preparation of heterocycles by using two different approaches: transition-metal-catalyzed cyclization and ­iodine/oxidant-catalyzed oxidative cyclization. Transition-metal salts of palladium or iron and nanoparticulate copper(II) oxide have been used as catalysts for the synthesis of heterocyclic compounds. Palladium-catalyzed Wacker-type oxidative heterocyclic cyclization, iron-catalyzed benzylation and tandem dehydration annulation, and nanoparticulate copper(II) oxide-catalyzed heterogeneous oxidative cyclizations have been developed in our laboratory. For iodine-catalyzed reactions, we have developed an oxidative tandem cyclization, an oxidative decarboxylative coupling cyclization, a direct Mannich-like reaction, and an oxidative amination catalyzed by diiodine and tert-butyl hydroperoxide under mild condition. These methods have enriched the range of synthetic strategies available for the construction of heterocyclic skeletons and they have potential applications in the fields of medicinal chemistry and materials science. 1 Introduction 2 Transition Metal-Catalyzed Heterocyclic Cyclization 2.1 Palladium-Catalyzed Wacker-Type Oxidative Heterocyclic Cyclization 2.1.1 Synthesis of 2-Methyl-2H-chromen-3(4H)-ones 2.1.2 Synthesis of 2-Methylquinolines 2.1.3 Synthesis of Pyrroles from Amino Acids 2.2 Lewis acid Iron(III) Chloride Catalyzed Intermolecular Cyclization Through Benzylation 2.2.1 Preparation of Functionalized 4H-Chromenes 2.2.2 Preparation of 3-Quinolinecarboxylic Acid Esters 2.2.3 Preparation of Highly Functionalized 2,3-Dihydro-1H-pyrroles 2.3 Syntheses of Quinazolines and 2-Aryldihydrobenzofurans Catalyzed by Nanoparticulate Copper(II) Oxide or Copper(I) Chloride 2.3.1 Synthesis of Quinazolines in the Presence of Copper(II) Oxide Nanoparticles 2.3.2 One-Pot Synthesis of 2-Aryl-2,3-dihydro-1-benzofurans Catalyzed by Copper(I) Chloride 3 Diiodine/tert-Butyl Hydroperoxide-Catalyzed Heterocyclic Cyclization 3.2 Synthesis of Highly Functionalized Oxazoles 3.3 Synthesis of 2-Phenylquinazoline by sp3 C–H Functionalization with Diiodine/tert-Butyl Hydroperoxide 3.4 Synthesis of Quinazolines Through Amination of Primary a-Amino Acids or sp3 C–H Bonds Adjacent to Nitrogen or Oxygen Atoms 3.5 Synthesis of Benzofurans and Naphthofurans 4 Conclusion

The effect of hydrochloric acid on the conversion of glucose to 5-hydroxymethylfurfural in AlCl3–H2O/THF biphasic medium

The effect of hydrochloric acid (HCl) on the conversion of glucose to 5-hydroxymethylfurfural (HMF) in AlCl3–H2O/THF biphasic system was investigated. The route via isomerization to fructose followed by tandem dehydration to HMF is the dominant pathway. Lewis acid sites of Al3+ aqua/hydroxo complexes play the leading role for the dehydration step. The introduction of a suitable amount to HCl increases the amount of Brønsted acid sites and improves the selectivity for HMF. The maximum HMF yield from glucose is enhanced from 51% to 62% in the presence of 0.1M HCl. The introduction of HCl lowers the reaction rate of glucose-to-fructose isomerization but enhances the reaction rate of fructose dehydration. Higher loading of HCl (1.0M) leads to increased direct dehydration of glucose to humins and results in lower selectivity to HMF.