Tracking Lattice Distortion Induced by Defects and Framework Tin in Beta Zeotypes.

The use of powder X-ray diffraction (PXRD) coupled with lattice parameter refinement is used to investigate the crystal structure of Sn-Beta materials. A newly developed semiempirical PXRD model with a reduced tetragonal unit cell is applied to obtain the characteristic crystallographic features. There is a robust correlation between lattice parameters and the concentration of tin and defects for materials prepared via hydrothermal (HT) and postsynthetic (PT) methods.

Toward Replacing Ethylene Oxide in a Sustainable World: Glycolaldehyde as a Bio-Based C Platform Molecule.

Fossil-based platform molecules such as ethylene and ethylene oxide currently serve as the primary feedstock for the C -based chemical industry. However, in the search for a more sustainable chemical industry, fossil-based resources may preferentially be replaced by renewable alternatives, provided there is realistic economic feasibility. This Review compares and critically discusses several production routes toward bio-based structural analogues of ethylene oxide and the required adaptations for their implementation in state-of-the-art C -based chemical processes.

Sensitive NMR method for detecting carbohydrate influx into competing chemocatalytic pathways.

Reaction pathways are often tracked with stable isotopes in order to determine the provenance of products in the pathway and to deduce mechanistic information. NMR spectroscopy can provide direct insight into the specific labelling position of the stable isotope. We suggest a simple assay that allows rapid quantitative measurements of isotope distributions in biomass-derived products using commercially available carbohydrate substrates and routine instrumentation.

Thermal Cracking of Sugars for the Production of Glycolaldehyde and Other Small Oxygenates.

Thermal cracking of sugars for production of glycolaldehyde, a potential renewable platform molecule, in yields up to 74 % with up to 95 % carbon recovered in the condensed product is demonstrated using glucose as the feed. The process involves spraying an aqueous sugar solution into a fluidized bed of glass beads. Continuous operation is carried out for more than 90 h with complete conversion and stable product selectivity.

Discovery and Exploration of the Efficient Acyclic Dehydration of Hexoses in Dimethyl Sulfoxide/Water.

Current gaps in the development of sustainable processes include a lack of strategies to systematically identify and optimize the formation of new products. The dehydration of hexoses to 5-hydroxymethylfurfural (HMF) is a particularly widely studied process. In an attempt to identify a new high-selectivity conversion of glucose, quantitative NMR spectroscopy is used to screen conditions that have been reported to yield high conversions of glucose but low formation of HMF.

Ex Situ Formation of Methanethiol: Application in the Gold(I)-Promoted Anti-Markovnikov Hydrothiolation of Olefins.

A protocol for the Au-promoted anti-Markovnikov hydrothiolation of olefins using ex situ generated methanethiol is reported. The use of S-methylisothiourea hemisulfate salt as a solid precursor for methanethiol generation ensures a safe and reliable deliverance of a stoichiometric amount of this thiol. The procedure was shown to work for a broad range of olefins providing the corresponding hydrothiolated adduct in good to excellent yields.

generation of stoichiometric HCN and its application in the Pd-catalysed cyanation of aryl bromides: evidence for a transmetallation step between two oxidative addition Pd-complexes.

A protocol for the Pd-catalysed cyanation of aryl bromides using near stoichiometric and gaseous hydrogen cyanide is reported for the first time. A two-chamber reactor was adopted for the safe liberation of generated HCN in a closed environment, which proved highly efficient in the Ni-catalysed hydrocyanation as the test reaction. Subsequently, this setup was exploited for converting a range of aryl and heteroaryl bromides (28 examples) directly into the corresponding benzonitriles in high yields, without the need for cyanide salts.

Effects of Alkali-Metal Ions and Counter Ions in Sn-Beta-Catalyzed Carbohydrate Conversion.

Alkali-metal ions have recently been shown to strongly influence the catalytic behavior of stannosilicates in the conversion of carbohydrates. An effect of having alkali-metal ions present is a pronounced increase in selectivity towards methyl lactate. Mechanistic details of this effect have remained obscure and are herein addressed experimentally through kinetic experiments and isotope tracking.

Quantitative NMR Approach to Optimize the Formation of Chemical Building Blocks from Abundant Carbohydrates.

The future role of biomass-derived chemicals relies on the formation of diverse functional monomers in high yields from carbohydrates. Recently, it has become clear that a series of α-hydroxy acids, esters, and lactones can be formed from carbohydrates in alcohol and water solvents using tin-containing catalysts such as Sn-Beta. These compounds are potential building blocks for polyesters bearing additional olefin and alcohol functionalities.

Mechanism and stereoselectivity of zeolite-catalysed sugar isomerisation in alcohols.

Glucose isomerisation to fructose can occur by different pathways and the mechanism of zeolite-catalysed glucose isomerisation in methanol has remained incompletely understood. Herein, the mechanism is studied using an H-C HSQC NMR assay resolving different fructose isotopomers. We find that zeolite-catalysed glucose isomerisation proceeds predominantly via a hydride shift into the pro-R position of fructose, thus resembling the stereoselectivity of the enzymatic isomerisation process.

Shape-selective Valorization of Biomass-derived Glycolaldehyde using Tin-containing Zeolites.

A highly selective self-condensation of glycolaldehyde to different C molecules has been achieved using Lewis acidic stannosilicate catalysts in water at moderate temperatures (40-100 °C). The medium-sized zeolite pores (10-membered ring framework) in Sn-MFI facilitate the formation of tetrose sugars while hindering consecutive aldol reactions leading to hexose sugars. High yields of tetrose sugars (74 %) with minor amounts of vinyl glycolic acid (VGA), an α-hydroxyacid, are obtained using Sn-MFI with selectivities towards C products reaching 97 %.

Tin-containing silicates: alkali salts improve methyl lactate yield from sugars.

This study focuses on increasing the selectivity to methyl lactate from sugars using stannosilicates as heterogeneous catalyst. All group I ions are found to have a promoting effect on the resulting methyl lactate yield. Besides, the alkali ions can be added both during the preparation of the catalyst or directly to the solvent mixture to achieve the highest reported yield of methyl lactate (ca.

Design of a metal-promoted oxide catalyst for the selective synthesis of butadiene from ethanol.

The synthesis of buta-1,3-diene from ethanol has been studied over metal-containing (M=Ag, Cu, Ni) oxide catalysts (MO(x)=MgO, ZrO2, Nb2O5, TiO2, Al2O3) supported on silica. Kinetic study of a wide range of ethanol conversions (2-90%) allowed the main reaction pathways leading to butadiene and byproducts to be determined. The key reaction steps of butadiene synthesis were found to involve ethanol dehydrogenation, acetaldehyde condensation, and the reduction of crotonaldehyde with ethanol into crotyl alcohol.

Conversion of sugars to lactic acid derivatives using heterogeneous zeotype catalysts.

Presently, very few compounds of commercial interest are directly accessible from carbohydrates by using nonfermentive approaches. We describe here a catalytic process for the direct formation of methyl lactate from common sugars. Lewis acidic zeotypes, such as Sn-Beta, catalyze the conversion of mono- and disaccharides that are dissolved in methanol to methyl lactate at 160 degrees C.

C factors pinpoint resource utilization in chemical industrial processes.

This Full Paper illustrates the use of the C factor (CO(2)/product mass ratio) as a parameter to evaluate the CO(2)-burden of a product. The C factor contains information of the total amount of CO(2) emitted in order to produce a product, and thus enables a direct comparison of different processes from a CO(2) aspect. We illustrate how this simple concept can be used to evaluate different resource types and processes.

The renewable chemicals industry.

The possibilities for establishing a renewable chemicals industry featuring renewable resources as the dominant feedstock rather than fossil resources are discussed in this Concept. Such use of biomass can potentially be interesting from both an economical and ecological perspective. Simple and educational tools are introduced to allow initial estimates of which chemical processes could be viable.

Unsaturated aldehydes as alkene equivalents in the Diels-Alder reaction.

A one-pot procedure is described for using alpha,beta-unsaturated aldehydes as olefin equivalents in the Diels-Alder reaction. The method combines the normal electron demand cycloaddition with aldehyde dienophiles and the rhodium-catalyzed decarbonylation of aldehydes to afford cyclohexenes with no electron-withdrawing substituents. In this way, the aldehyde group serves as a traceless control element to direct the cycloaddition reaction.