Density functional theory studies on hydroxylamine mechanism of cyclohexanone ammoximation on titanium silicalite-1 catalyst

Selective Oxidation Using In Situ-Generated Hydrogen Peroxide

ConspectusHydrogen peroxide (H2O2) for industrial applications is manufactured through an indirect process that relies on the sequential reduction and reoxidation of quinone carriers. While highly effective, production is typically centralized and entails numerous energy-intensive concentration steps. Furthermore, the overhydrogenation of the quinone necessitates periodic replacement, leading to incomplete atom efficiency. These factors, in addition to the presence of propriety stabilizing agents and concerns associated with their separation from product streams, have driven interest in alternative technologies for chemical upgrading. The decoupling of oxidative transformations from commercially synthesized H2O2 may offer significant economic savings and a reduction in greenhouse gas emissions for several industrially relevant processes. Indeed, the production and utilization of the oxidant in situ, from the elements, would represent a positive step toward a more sustainable chemical synthesis sector, offering the potential for total atom efficiency, while avoiding the drawbacks associated with current industrial routes, which are inherently linked to commercial H2O2 production. Such interest is perhaps now more pertinent than ever given the rapidly improving viability of green hydrogen production.The application of in situ-generated H2O2 has been a long-standing goal in feedstock valorization, with perhaps the most significant interest placed on propylene epoxidation. Until very recently a viable in situ alternative to current industrial oxidative processes has been lacking, with prior approaches typically hindered by low rates of conversion or poor selectivity toward desired products, often resulting from competitive hydrogenation reactions. Based on over 20 years of research, which has led to the development of catalysts for the direct synthesis of H2O2 that offer high synthesis rates and >99% H2 utilization, we have recently turned our attention to a range of oxidative transformations where H2O2 is generated and utilized in situ. Indeed, we have recently demonstrated that it is possible to rival state-of-the-art industrial processes through in situ H2O2 synthesis, establishing the potential for significant process intensification and considerable decarbonization of the chemical synthesis sector.We have further established the potential of an in situ route to both bulk and fine chemical synthesis through a chemo-catalytic/enzymatic one-pot approach, where H2O2 is synthesized over heterogeneous surfaces and subsequently utilized by a class of unspecific peroxygenase enzymes for C-H bond functionalization. Strikingly, through careful control of the chemo-catalyst, it is possible to ensure that competitive, nonenzymatic pathways are inhibited while also avoiding the regiospecific and selectivity concerns associated with current energy-intensive industrial processes, with further cost savings associated with the operation of the chemo-enzymatic approach at near-ambient temperatures and pressures. Beyond traditional applications of chemo-catalysis, the efficacy of in situ-generated H2O2 (and associated oxygen-based radical species) for the remediation of environmental pollutants has also been a major interest of our laboratory, with such technology offering considerable improvements over conventional disinfection processes.We hope that this Account, which highlights the key contributions of our laboratory to the field over recent years, demonstrates the chemistries that may be unlocked and improved upon via in situ H2O2 synthesis and it inspires broader interest from the scientific community.

Mesoporous acidic polymeric ionic liquids as novel solid acids for catalytic hydrolysis of ketoxime reactions

In this study, a series of mesoporous acidic polymeric ionic liquids were successfully synthesized and characterized to explore their structures and properties. Examination of catalytic performance using cyclohexanone oxime's maximum conversion were investigated, and the Box–Behnken design was used to achieve the highest hydrolysis conversion. Excellent catalytic activity, structural stability, and an easy recovery feature were all displayed by the Poly(VBS-DVB)HSO₄ catalyst. Additionally, a possible reaction pathway involving hydrogen protons was proposed for the present hydrolysis. Moreover, a series of ketoximes were also examined including acetone oxime, butanone oxime, cyclopentanone oxime and acetophenone oxime over Poly(VBS-DVB)HSO₄ catalyst. The conversion of ketoxime was not less than 80.44%, and the results also demonstrated excellent catalytic performance. Synthesis of mesoporous acidic polymeric ionic catalysts with good properties would be very important for their applications.

In this study, a series of mesoporous acidic polymeric ionic liquids were successfully synthesized and characterized to explore their structures and properties.

A novel hydroxylamine ionic liquid salt resulting from the stabilization of NH2OH by a SO3H-functionalized ionic liquid

Hydroxylamine was stabilized by ionic liquid, producing a novel hydroxylamine salt that exhibits improved reactivity in one-step synthesis of caprolactam.

Lewis acidic strength controlled highly selective synthesis of oxime via liquid-phase ammoximation over titanosilicates

The Lewis acidity of titanosilicates determines oxime selectivity in ammoximation by influencing the reaction activation energy of Ti–OOH for the highly efficient formation of NH₂OH.