Layered double hydroxide-like Mg_3Al_(1–x)Fe_x materials as supports for Ir catalysts: Promotional effects of Fe doping in selective hydrogenation of cinnamaldehyde

Supported Ir catalysts were prepared using layered double hydrotalcite‐like materials,such as Mg3Al1-xFex,containing Fe and Al species in varying amounts as supports.These Ir catalysts were applied for the selective hydrogenation of cinnamaldehyde(CAL).When x was changed from 0(Ir/Mg3Al)to 1(Ir/Mg3Fe),the rate of CAL hydrogenation reached a maximum at approximately x=0.25,while the selectivity to unsaturated alcohol,i.e.,cinnamyl alcohol,monotonously increased from 44.9%to 80.3%.Meanwhile,the size of the supported Ir particles did not change significantly with x,remaining at 1.7-0.2 nm,as determined by transmission electron microscopy.The chemical state of Ir and Fe species in the Ir/Mg3Al1-xFex catalysts was examined by temperature programmed reduction by H2 and X‐ray photoelectron spectroscopy.The surface of the supported Ir particles was also examined through the in‐situ diffuse reflectance infrared Fourier‐transform of a probe molecule of CO.On the basis of these characterization results,the effects of Fe doping to Mg3Al on the structural and catalytic properties of Ir particles in selective CAL hydrogenation were discussed.The significant factors are the electron transfer from Fe2+in the Mg3Al1–xFex support to the dispersed Ir particles and the surface geometry.

Cyclic oligourea synthesized from CO_(2):Purification,characterization and properties

Carbon dioxide(CO_(2)) as a sustainable resource instead of toxic reagents has attracted considerable attention in synthesis of chemicals and polymeric materials.Herein,a kind of cyclic oligourea was synthesized via polycondensation of CO_(2) with 4,7,10-trioxa-1,13-tridecanediamine(TTD)followed by effective separation and purification processes.We developed an efficient separation strategy in which the linear oligourea molecules were selectively transformed to macromolecular polyurea molecules by a reaction of the–NH_(2) end group with 4,4’-diphenylmethane diisocyanate(MDI),followed by separation from cyclic oligourea using selected solvents.The structure and physicochemical properties were confirmed by MALDI-TOF mass spectra,NMR,Cryo-EM,thermal analysis and solubility measurement.The well-defined cyclic oligourea was produced with a high purity(99.4%)and the average-number molecular weight(Mn)of 1040 Da.It is semi-crystalline in structure with a melting point of 106℃and glass transition point of-10℃.The cyclic oligourea presented characteristically difference to its linear analogue.This work provides a new member to cyclic polymer family.

One-Pot Room-Temperature Synthesis of Mg Containing MCM-41 Mesoporous Silica for Aldol Reactions

One-pot synthesis of Mg containing MCM-41(Mg-MCM-41) materials was respectively carried out by a room temperature(RT) method and a hydrothermal(HT) method for aldol condensation of 4-nitrobenzaldehyde and acetone and self-condensation of acetone. The RT method can prepare MCM-41 materials containing large amounts of Mg while maintaining the structural characteristics of MCM-41 even at very low Si/Mg ratios(large Mg loadings), but the HT method cannot. The RT method can also give more active catalysts than the HT method, because the catalysts prepared by the RT method are more basic than those prepared by the HT one. The characterization indicates that Mg atoms in the Mg-MCM-41 prepared by the RT method exist as MgO disperses well on the wall surface of pores, while those in Mg-MCM-41 prepared by the HT method are included in the bulk with a smectite-like structure.

Synthesis of powdered silver nanoparticles using hydrogen in aqueous medium

Environmentally benign one-pot protocol is used in the synthesis of silver nanoparticles （AgNPs） in powder form, involving the reduction of silver nitrate in the presence of fully hydrolyzed polyvinyl alcohol （PVA） as stabilizer by hydrogen （H2） as reducing agent in aqueous medium. Fully hydrolyzed biodegradable PVA has extremely low cytotoxicity, making it a favorable stabilizer from green perspective. In the present methodology, essentially naked silver nanoparticles are obtained in good yield. The prepared sil- ver nanoparticles were characterized by TEM, XRD, EDAX, UV-Vis spectroscopy and DLS histogram, and studied for its activity as a recyclable catalyst for synthesis of different enaminones.