Greener and Efficient Epoxidation of 1,5-Hexadiene with tert-Butyl Hydroperoxide (TBHP) as an Oxidising Reagent in the Presence of Polybenzimidazole Supported Mo(VI) Catalyst

Alkene epoxidation with TBHP as an oxidising reagent using heterogeneous Mo(VI) catalyst is an environmentally friendly process since it eliminates acid waste and chlorinated by-products often associated with the conventional industrial method that uses stoichiometric peracid such as peracetic acid and m-chloroperbenzoic acid. Polybenzimidazole supported Mo(VI) complex, i.e., PBI.Mo has been successfully prepared, characterised and assessed for the epoxidation of 1,5-hexadiene in the presence of tert-butyl hydroperoxide (TBHP) as an oxidising reagent. A quadratic polynomial model has been developed, demonstrating the yield of 1,2-epoxy-5-hexene in four independent variables. The effects of different parameters such as reaction temperature, feed mole ratio of 1,5-hexadiene to TBHP, catalyst loading, and reaction time were studied. Response surface methodology (RSM) using Box-Behnken Design (BBD) was employed to study the interaction effect of different variables on the reaction response. This study presents the optimization of 1,5-hexadiene epoxidation in a batch reactor using TBHP as an oxidant and a polymer-supported Mo(VI) catalyst.

Recent Advances in Greener and Energy Efficient Alkene Epoxidation Processes

The chemical industry is considered to be one of the largest consumers of energy in the manufacturing sector. As the cost of energy is rising rapidly, coupled with the increasingly stringent standards for the release of harmful chemicals and gases into the environment, more attention is now focused on developing energy efficient chemical processes that could significantly reduce both operational costs and greenhouse gas emissions. Alkene epoxidation is an important chemical process as the resultant epoxides are highly reactive compounds that are used as platform chemicals for the production of commercially important products for flavours, fragrances, paints and pharmaceuticals. A number of epoxidation methods have been developed over the past decade with the ultimate aim of minimising waste generation and energy consumption. In this review paper, some of the recent advances in epoxides synthesis using energy efficient processes are discussed. The epoxidation methods may provide sustainability in terms of environmental impact and energy consumption.

Efficient Noble-Metal-Free Catalysts Supported by Three-Dimensional Ordered Hierarchical Porous Carbon

Development of heterogeneous catalysts has attracted increasing attention, owing to their remarkable catalytic performance and recyclability. Herein, we report well-developed heterogeneous catalysts with a three-dimensional ordered hierarchical structure, constructed from nickel or cobalt nanoparticles embedded in porous carbon. The obtained catalysts were fully characterized by several techniques. On account of the uniform distribution of metal nanoparticles in the porous carbon matrix and large diffusion channels that allow for effective mass transport, the catalysts exhibited superior catalytic performance for styrene epoxidation reaction. In particular, the catalysts showed good catalytic activity, high selectivity and excellent recyclability toward the styrene epoxidation. Thus, this facile approach developed allows for fabricating advanced heterogeneous catalysts with high catalytic activities for useful practical applications.

Cobalt hollow nanospheres: controlled synthesis, modification and highly catalytic performance for hydrolysis of ammonia borane

Size tunable cobalt hollow nanospheres with high catalytic activity for the ammonia borane (AB) hydrolysis have been synthesized by using the solvothermal method. The complexation between Co²⁺ and ethylenediamine is observed to be critical for the formation of the cobalt hollow nanospherical structure. The morphology of the cobalt hollow nanospheres can be regulated by adjusting the original ethylenediamine/ethanol volume ratio, reaction time and temperature. Impressively, the magnetic property study reveals that the coercivity of the as-synthesized cobalt hollow nanospheres is much enhanced compared with that of bulk cobalt materials. Meanwhile, Co/Pt bimetal hollow nanospheres (CoPtHS) and graphene-cobalt hollow composite nanospheres (CoHS-rGO) have also been explored. In comparison with the cobalt hollow nanospheres, both the CoPtHS and CoHS-rGO show higher catalytic activities and better repeatability for the catalytic hydrogen generation from AB hydrolysis. Moreover, it is noted that these catalysts could be recycled by using the magnetic separation method.

Mesoporous NiCo2O4 Nanoplates on Three-Dimensional Graphene Foam as an Efficient Electrocatalyst for the Oxygen Reduction Reaction

Catalysts for the oxygen reduction reaction (ORR) are highly important in fuel cells and metal-air batteries. Cheap ORR catalysts with ultrahigh electrochemical activity, selectivity, and stability are extremely desirable but still remain challenging. Herein, mesoporous NiCo₂O₄ nanoplate (NP) arrays on three-dimensional (3D) graphene foam are shown to be a highly economical ORR catalyst. This mesoporous mixed-valence oxide can provide more electrocatalytic active sites with increased accessible surface area. In addition, graphene-foam-supported NiCo₂O₄ NP arrays have a 3D hierarchical porous structure, which is of great benefit to ion diffusion and electron transfer. As a result, the mesoporous NiCo₂O₄ NP arrays/graphene foam catalyst exhibits outstanding ORR performance with the four-electron reduction of O₂ to H₂O in alkaline media. Furthermore, the mesoporous catalyst shows enhanced electrocatalytic activity with a half-wave potential of 0.86 V vs RHE and better stability compared with a commercial Pt/C catalyst.

Preparation of hollow CuO@SiO2 spheres and its catalytic performances for the NO + CO and CO oxidation

The hollow CuO@SiO₂ spheres with a mean diameter of 240 nm and a thin shell layer of about 30 nm in thickness was synthesized using an inorganic SiO₂ shell coating on the surface of Cu@C composite that was prepared by a two-step hydrothermal method. The obtained hollow CuO@SiO₂ spheres were characterized by ICP-AES, nitrogen adsorption-desorption, SEM, TEM, XRD, H₂-TPR, CO-TPR, CO-TPD and NO-TPD. The results revealed that the hollow CuO@SiO₂ spheres consist of CuO uniformly inserted into SiO₂ layer. The CuO@SiO₂ sample exhibits particular catalytic activities for CO oxidation and NO + CO reactions compared with CuO supported on SiO₂ (CuO/SiO₂). The higher catalytic activity is attributed to the special hollow shell structure that possesses much more highly dispersed CuO nanocluster that can be easy toward the CO and NO adsorption and the oxidation of CO on its surface.

Hierarchical three-dimensional NiCo2O4 nanoneedle arrays supported on Ni foam for high-performance supercapacitors

A novel NiCo₂O₄ nanoneedle arrays with bottom crosslinked nanosheets grew on Ni foam as advanced binder-free electrodes via a facile one-step hydrothermal method followed by annealing in air, which exhibited high electrochemical performance.

Preparation of 4A-zeolite-based Ag nanoparticle composite catalyst and research of the catalytic properties

4A-zeolite base silver nanoparticles (Ag NPs) composite catalyst was prepared and the catalytic properties were researched.

A “rolling ball method” to make glass fiber reinforced hollow epoxy macrospheres used for a three phase epoxy syntactic foam

Glass fiber reinforced hollow epoxy macrospheres (GFR-HEMS) were prepared by a “rolling ball method” and embedded into a mixture of epoxy–hardener and 33.3 wt% HGMS to make a three phase epoxy syntactic foam.

Facile synthesis of highly ordered mesoporous cobalt–alumina catalysts and their application in liquid phase selective oxidation of styrene

We illustrate the preparation of highly ordered mesoporous cobalt–alumina catalysts with highly homogeneously dispersed Co(ii) species via an evaporation-induced triconstituent cooperative co-assembly method.