Search

Epoxidation of alkenes is a valuable transformation in the synthesis of fine chemicals. Described herein are the design and development of a continuous flow process for carrying out the epoxidation of alkenes with a homogeneous manganese catalyst at metal loadings as low as 0.05 mol%. In this process, peracetic acid is generated in situand telescoped directly into the epoxidation reaction, thus reducing the risks associated with its handling and storage, which often limit its use at scale. This flow process lessens the safety hazards associated with both the exothermicity of this epoxidation reaction and the use of the highly reactive peracetic acid. Controlling the speciation of manganese/2-picolinic acid mixtures by varying the ligand:manganese ratio was key to the success of the reaction. This continuous flow process offers an inexpensive, sustainable, and scalable route to epoxides.

Bimetallic catalysts consisting of Pd and Pt on TiO2-zeolite (mordenite, beta, ZSM-5) supports were prepared and tested for the combustion of methane. The activity of the catalysts was found to be dependent on the zeolite topology and SiO2 : Al2O3ratio and was linearly dependent on the proportion of Pd and Pt present in a bimetallic phase observed in XRD diffractograms of the catalysts. This linear dependence was valid for a range of zeolites used. STEM-EDS and electron tomography showed the Pd and Pt to be largely co-located and XAS and XPS indicated that the metals are mostly present in the form of oxide nanoparticles with a minor contribution from the metals at high SiO2 : Al2O3ratios. Catalyst characterization showed there to be little difference overall in the metal loading and physical characteristics of the samples and NH3-TPD suggested that the activation of methane over acid sites is not important. Adding water to the feed, slightly reduced the conversion but did not affect the deactivation profile of the catalysts tested.

Sulfoxidation reactions of 4,6-dimethyl-2-methylthiopyrimidine have been performed using titanosilicate catalysts in ionic liquids, dioxane and ethanol. The ionic liquid reactions showed superior reactivity compared with molecular solvents. Moreover, on examination of the recycling of the catalyst, a significant increase in the stability of catalyst was found both in terms of recycling activity and leaching of the titanium from the catalyst. The mechanism by which the ionic liquid reduces the solubilisation of the catalysts is explored.

Heterogeneous catalytic oxidation of a series of thioethers (2‐thiomethylpyrimidine, 2‐thiomethyl‐4,6‐dimethyl‐pyrimidine, 2‐thiobenzylpyrimidine, 2‐thiobenzyl‐4,6‐dimethylpyrimidine, thioanisole, and n‐heptyl methyl sulfide) was performed in ionic liquids by using MCM‐41 and UVM‐type mesoporous catalysts containing Ti, or Ti and Ge. A range of triflate, tetrafluoroborate, trifluoroacetate, lactate and bis(trifluoromethanesulfonyl)imide‐based ionic liquids were used. The oxidations were carried out by using anhydrous hydrogen peroxide or the urea–hydrogen peroxide adduct and showed that ionic liquids are very effective solvents, achieving greater reactivity and selectivity than reactions performed in dioxane. The effects of halide and acid impurities on the reactions were also investigated. Recycling experiments on catalysts were carried out in order to evaluate Ti leaching and its effect on activity and selectivity.

Chloroindateiii ionic liquids are versatile reaction media for Friedel–Crafts acylation reactions; the system is catalytic and totally recyclable, using an aqueous workup, with no leaching of the indium into the product phase.

For Abstract see ChemInform Abstract in Full Text.