Utilization of electromagnetic and acoustic irradiation in enhancing heterogeneous catalytic reactions

Effect of Microwave Irradiation on the Catalytic Activity of Palladium Supported Catalysts in the One-Step Isomerisation of Cinchona Alkaloids to Δ3,10-Isobases

“…1. The alkene protons of =HC-Me from (Z)-and (E)-Δ 3,10 -isomers give two separate signals according to the literature data [12,13,25]. Determination of unconverted substrates can be possible from integration of peaks: =CH 2 protons (two doublets at ~4.90-5.10 ppm) or -CH= (multiplet at ~6.00 ppm).…”

“…This procedure was tested to find the optimal Literature data [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] Oxidative cleavage [12][13][14][15] time for conversion of 1a or 2a to the isomers (Z/E)-3a or (Z/E)-4a. We monitored the ongoing conversion progress of substrates by taking micro-samples of the reaction mixture regularly, at 10-min intervals, which after extraction with diethyl ether in the presence of aqueous ammonia were analyzed by TLC (silica gel plates, methoxyethanol).…”

“…Microwave enhancement of many catalytic syntheses has been described [24][25][26]. Recently are described transformations of polar organic molecules in water with enhancing energy efficiency by microwaves with core/shell catalysts [27].…”

Effects of Ultrasound and Microwaves on Selective Reduction: Catalyst Preparation and Reactions

“…This innovation was devised to create more compact, safer, energy efficient and environmentally friendly processes. [15][16][17][18] Essentially, US has no direct action on chemical bonds, however, the significant enhancement in selectivity, rates and yields under mild reaction conditions in both homogeneous and heterogeneous systems has been achieved by means of sonication (the act of applying US energy), [17][18][19] which can even increase reactivity almost a million-fold. [20] The chemical and physical effects of US arise from cavitation phenomenon which produces localized extreme conditions (shortlived hot spots).…”

“…[25] When a cavitation bubble violently collapses near a solid surface, the high-speed jets of liquid are driven into the surface of a particle. [17] These jets and shock waves can cause surface coating removal as well as producing localized high temperatures and pressures. [26] Catalyst activity is therefore increased by catalyst surface deformation that exposes fresh, highly active surface and reduces the diffusion length in the catalyst pores.…”