Microwave Irradiation Coupled with Physically Mixed MeOx(Me=Mn, Ni) and Cu-ZSM-5 Catalysts for the Direct Decomposition of Nitric Oxide under Excess Oxygen

A critical review on the technique and mechanism of microwave-based denitrification in flue gas

Microwave radiation has received extensive attention due to its significant thermal and non-thermal effects, and the development of MW-based denitrification in flue gas has become one of the most promising methods to avoid the defects of ammonia escape, high temperature and cost in traditional SCR. This review introduces the thermal and non-thermal effects of microwaves and divides MW-based denitrification methods into MW reduction and oxidation denitrification, systematically summarizes these denitrification methods, including MW discharge reduction, MW-induced catalytic reduction using active carbon, molecular sieves, metal oxides (transition metals, perovskites, etc.), MW-induced oxidation denitrification with and without additional oxidant, and discusses their removal pathway and mechanism. Finally, several research prospects and directions regarding the development of microwave-based denitrification methods are provided.

NO direct decomposition: progress, challenges and opportunities

The progress in catalyst R&D, challenges, and opportunities for NO direct decomposition are summarized.

Development of MgCo2O4–BaCO3 composites as microwave catalysts for the highly effective direct decomposition of NO under excess O2 at a low temperature

The catalytic NO decomposition reaction is a hot research topic.

Microwaves in the Catalytic Valorisation of Biomass Derivatives

The application of microwave irradiation in the transformation of biomass has been receiving particular interest in recent years due to the use of polar media in such processes and it is now well-known that for biomass conversion, and particularly for lignocellulose hydrolysis, microwave irradiation can dramatically increase reaction rates with no negative consequences on product selectivity. However, it is only in the last ten years that the utilisation of microwaves has been coupled with catalysis aiming towards valorising biomass components or their derivatives via a range of reactions where high selectivity is required in addition to enhanced conversions. The reduced reaction times and superior yields are particularly attractive as they might facilitate the transition towards flow reactors and intensified production. As a consequence, several reports now describe the catalytic transformation of biomass derivatives via hydrogenation, oxidation, dehydration, esterification and transesterification using microwaves. Clearly, this technology has a huge potential for biomass conversion towards chemicals and fuels and will be an important tool within the biorefinery toolkit. The aim of this chapter is to give the reader an overview of the exciting scientific work carried out to date where microwave reactors and catalysis are combined in the transformation of biomass and its derivatives to higher value molecules and products.

A new type of power energy for accelerating chemical reactions: the nature of a microwave-driving force for accelerating chemical reactions

The use of microwave (MW) irradiation to increase the rate of chemical reactions has attracted much attention recently in nearly all fields of chemistry due to substantial enhancements in reaction rates. However, the intrinsic nature of the effects of MW irradiation on chemical reactions remains unclear. Herein, the highly effective conversion of NO and decomposition of H₂S via MW catalysis were investigated. The temperature was decreased by several hundred degrees centigrade. Moreover, the apparent activation energy (Ea’) decreased substantially under MW irradiation. Importantly, for the first time, a model of the interactions between microwave electromagnetic waves and molecules is proposed to elucidate the intrinsic reason for the reduction in the Ea’ under MW irradiation, and a formula for the quantitative estimation of the decrease in the Ea’ was determined. MW irradiation energy was partially transformed to reduce the Ea’, and MW irradiation is a new type of power energy for speeding up chemical reactions. The effect of MW irradiation on chemical reactions was determined. Our findings challenge both the classical view of MW irradiation as only a heating method and the controversial MW non-thermal effect and open a promising avenue for the development of novel MW catalytic reaction technology.

Microwave catalytic effect: a new exact reason for microwave-driven heterogeneous gas-phase catalytic reactions

The microwave catalytic effect (lowering of activation energy) under microwave irradiation results in NO conversion exceeding that realized through conventional heating.

Microwave selective effect: a new approach towards oxygen inhibition removal for highly-effective NO decomposition by microwave catalysis over BaMn(x)Mg(1-x)O3 mixed oxides at low temperature under excess oxygen

A significant microwave selective effect on oxygen inhibition removal was found for NO decomposition through microwave catalysis over BaMn(x)Mg(1-x)O3 catalysts. Especially, the NO conversion and N2 selectivity were up to 99.8% and 99.9%, respectively for the BaMn(0.9)Mg(0.1)O3 catalyst even with the coexistence of 10% oxygen and low temperature of 250 °C.