Grignard reagent reduced nanocarbon material in oxidative dehydrogenation of n-butane

Single atom manganese catalyst boosting selective oxidation of alcohols with activated peroxymonosulfate

Selective oxidations are important reactions in organic synthesis for fine chemical industry and conventional methods are expensive and produce a lot of toxic wastes. Herein, we demonstrate a facile and environmentally benign technique for liquid phase selective oxidation based on graphene-supported Mn single-atom-catalyst (SAMn-G) for efficient peroxymonosulfate (PMS) activation. The active Mn component in the developed SAMn-G catalyst reached single-atomic dispersion on graphene substrate via the coordination of individual Mn atoms with the doped N from the graphene framework. SAMn-G activated PMS via a nonradical-dominated pathway, which could convert aromatic alcohols into aldehydes or ketones at a mild temperature. The SAMn-G catalyst exhibited superior conversion and aldehyde selectivity in alcohol oxidation in comparison with their counterpart catalysts possessing either homogeneous Mn ions or oxide particles. The high activation efficiency of SAMn-G is due to the synergistic effect between Mn atoms and graphene substrate, as well as the dominated reaction pathway from nonradical oxidation, which is more selective than these free radicals to oxidize the alcohols. Concerted experimental evidence indicates that the non-radical oxidation process was highly possible to follow the electron transfer mechanism by PMS/organic adsorption on the surface of the catalyst. This study provides a fundamental understanding of PMS activation mediated by single atom catalyst for organic synthesis and the achieved insights can also help the catalyst design for other liquid phase selective oxidation processes.

Selective oxidation of alcohols by graphene-like carbon with electrophilic oxygen and integrated pyridinic nitrogen active sites

The selective oxidations of alcohols into corresponding aldehydes or ketones are essential reactions for organic synthesis. The development of facile, green and cost-effective protocols to accomplish selective oxidation is highly attractive. Here, we present the selective oxidation of alcohols using peroxymonosulfate (PMS) oxidants with N-doped graphene-like carbon (NG) synthesized via a metal-free approach without producing a large amount of hazardous wastes. In the tested selective oxidation reaction, over 96% of benzyl alcohol (BzOH) was converted into benzaldehyde (BzH) with high selectivity under mild conditions. The synthesized NG catalyst contains abundant electrophilic oxygen species, serving as the major active sites for the generation of reactive radicals from PMS to enable the selective oxidation of BzOH in the radical pathway. Besides, non-radical oxidation of BzOH occurs via the electron transfer through the surface coordinated complex, dominantly upon the N species. Particularly, the configuration of integrated pyridinic N is possible to create active domains for BzOH oxidation with activated PMS. This work opens a new avenue to convert metal-free raw materials into effectively functionalized carbon materials, coupled with their potential applications in the selective oxidation of alcohols.

Oxidative dehydrogenation of light alkanes to olefins on metal-free catalysts

Metal-free boron- and carbon-based catalysts have shown both great fundamental and practical value in oxidative dehydrogenation (ODH) of light alkanes. In particular, boron-based catalysts show a superior selectivity toward olefins, excellent stability and atom-economy to valuable carbon-based products by minimizing CO2 emission, which are highly promising in future industrialization. The carbonaceous catalysts also exhibited impressive behavior in the ODH of light alkanes helped along by surface oxygen-containing functional groups. This review surveyed and compared the preparation methods of the boron- and carbon-based catalysts and their characterization, their performance in the ODH of light alkanes, and the mechanistic issues of the ODH including the identification of the possible active sites and the exploration of the underlying mechanisms. We discussed different boron-based materials and established versatile methodologies for the investigation of active sites and reaction mechanisms. We also elaborated on the similarities and differences in catalytic and kinetic behaviors, and reaction mechanisms between boron- and carbon-based metal-free materials. A perspective of the potential issues of metal-free ODH catalytic systems in terms of their rational design and their synergy with reactor engineering was sketched.