Chitosan as biosupport for the MW-assisted synthesis of palladium catalysts and their use in the hydrogenation of ethyl cinnamate

Metal Catalysts for the Efficient Transformation of Biomass‐derived HMF and Furfural to Value Added Chemicals

“…explored microwave assisted hydrogenation of furfural over Cu/TiO 2 and achieved complete conversion with 99 % selectivity to furfuryl alcohol in cyclopentyl‐methyl ether, however, the conventional heating process resulted in a very lower conversion . Studies suggested the formation of hot spots in heterogeneous catalysts during microwave irradiation, where these hot spots resulted in the higher dielectric constants with increment in temperature of catalyst active sites, and hence to higher reaction rate . As TiO 2 has high dielectric constant, the absorption of microwave could be very high which resulted to the superheating of material .…”

“…[52] Studies suggested the formation of hot spots in heterogeneous catalysts during microwavei rradiation, where these hot spots resulted in the higherd ielectric constantsw ith increment in temperature of catalysta ctive sites, and hence to higher reaction rate. [54][55][56][57][58] As TiO 2 has high dielectric constant, the absorption of microwavec ould be very high which resulted to the superheating of material. [56] However,R omano et al did not explain the observed high selectivity of furfuryl alcohol, as the formationo ft he hot spot under microwavei rradiation could also lead to loss the selectivity for furfuryla lcohol.…”

Microwave‐Assisted Selective Hydrogenation of Furfural to Furfuryl Alcohol Employing a Green and Noble Metal‐Free Copper Catalyst

“…Recently,m icrowave-assisted reactions have become more popularamong the scientific community.Microwaveirradiation enablesafast,u niform, and efficient dielectric heating of the reactionm edia, generating an increasei nr eaction rates as well as reducing the energy consumption. [29][30][31][32][33][34] The use of this technique represents ab reakthrough in terms of sustainability, efficiency,d evelopment of new materials, and cost reduction. [31,[35][36][37] To the besto fo ur knowledge,t he use of micro-wave irradiation has not been reported in FALh ydrogenation aiming at producing FOL.…”

“…[30,32,49] Severala uthors observedt he formation of hot spots in heterogeneous catalysts during microwave irradiation as ar esult of the materials' high dielectric constants and loss tangent. [31,32,51,52] This could increaset he temperature of the active sites of the catalysts locally above the temperature of the bulk, which could explain higher reactionr ates. [31,47,51] Following this hypothesis,T iO 2 has ah igh dielectric constant of approximately5 0, which suggests that it absorbs microwavei rradiation very well, getting superheated above the solvent bulk temperature.…”

“…[31,32,51,52] This could increaset he temperature of the active sites of the catalysts locally above the temperature of the bulk, which could explain higher reactionr ates. [31,47,51] Following this hypothesis,T iO 2 has ah igh dielectric constant of approximately5 0, which suggests that it absorbs microwavei rradiation very well, getting superheated above the solvent bulk temperature. [47] However, we have not come to ac onclusion as to how this effectc ould explain the enhancement in selectivity we observei nF igure 5a s hot spots would typicallyr esult in al oss of selectivity.I ndeed, the reaction in the microwavei sn ot only faster but also hinders the consecutive conversion of methyl furfural to methyl furan resulting in almost 100 %s electivity.W ea lso know that higher reaction temperatures result in loss of selectivity at isoconversion ( Figures S3 and S4);t his would suggest that hot spots should have anegative effect on selectivity as well.…”