Copper aluminum mixed oxide (CuAl MO) catalyst: A green approach for the one-pot synthesis of imines under solvent-free conditions

Abstract

Activated carbon templated Copper Aluminum mixed oxide (CuAl MO) catalysts have been synthesized and studied for direct imine formation by oxidative coupling of alcohols and amines under solvent free conditions. Among the catalysts, CuAl MO 20%C (catalyst synthesized by adding 20% activated carbon) shows the best activity and selectivity for this reaction. Here, air is used as the oxidant which is considered as the most economical and green oxidant among different oxidizing agents. Pyridine adsorption results confirmed that the presence of higher number of Lewis acidic sites enhances the catalytic activity of the material. Various alcohol and amine substrates were readily converted into the corresponding imines in good to excellent yields. According to catalytic activity studies and TG-MS data, surface oxygen availability and facile reversibility of oxygen readsorption on the surface account for the superior activity and high durability of the CuAl MO 20%C catalyst. The regenerated catalyst showed 92% conversion with 100% selectivity even after the 4 th reuse.

Hollow MnFe2O4@C@APBA Nanospheres with Size Exclusion and pH Response for Efficient Enrichment of Endogenous Glycopeptides

“…Even so, the as-synthesized HMCAs are magnetically responsive enough to be conveniently extracted from the liquid through an external magnetic field, facilitating 28,29 The broad bands at 3400 cm −1 were caused by the stretching of OH groups, mainly from the adsorbed H 2 O molecules. 30,31 The peak of the spectrum at 1380 cm −1 was due to B−O bond stretching, and the absorption bands at 1650 cm −1 were related to the benzene ring of the APBA, indicating the introduction of the APBA. 32,33 The peak at 1662 cm −1 was corresponded to amide CO stretching vibration, which indicated the combination of the carboxyl group of HMC and the amino group of APBA.…”

“…The prepared MnFe 2 O 4 , HMC, APBA, and functionalized nanomaterial HMCAs were characterized by Fourier-transform infrared spectroscopy, as shown in Figure a. The two peaks at 452 and 575 cm –1 were attributed to the Mn­(II)–O and Fe­(III)–O bonds of spinel-type oxide caused by existence of the manganese ferrite matrix in the composites. , The broad bands at 3400 cm –1 were caused by the stretching of OH groups, mainly from the adsorbed H 2 O molecules. , The peak of the spectrum at 1380 cm –1 was due to B–O bond stretching, and the absorption bands at 1650 cm –1 were related to the benzene ring of the APBA, indicating the introduction of the APBA. , The peak at 1662 cm –1 was corresponded to amide CO stretching vibration, which indicated the combination of the carboxyl group of HMC and the amino group of APBA. , All these results confirmed the successful grafting of APBA onto the HMC nanocomposites. X-ray photoelectron spectroscopy (XPS) was used to gain insights into the chemical compositions and valency of HMCAs.…”

Hollow @CuMgAl double layered hydrotalcites and mixed oxides with tunable textural and structural properties, and thus enhanced NH3-NOx-SCR activity

“…This goal can be achieved through alkaline etching that utilizes the amphoteric features of the Al 3+ ion in the LDHs crystal 19,20 or by the introduction of a foreign substance during the synthesis of the LDH materials. The synthesis can be performed in the presence of carbon-containing precursors, such as activated carbon, 21 date palm ash, 22 and all types of ionic and non-ionic surfactant molecules, 23–26 which can then be removed by thermal treatment, helping to fine-tune the surface properties of the resulting mixed oxides.…”

Nickel Doped Aluminophosphate‐5 as an Efficient Heterogeneous Catalyst for Imine Synthesis by Direct Condensation of Alcohols and Amines at Room Temperature

“…However, large‐scale applications of homogeneous catalysts are restricted by their inability to be recycled and the pure oxygen oxidant that may result from the high separation and equipment input. To circumvent such problems, many solid catalysts including manganese octahedral molecular sieve (OMS‐2), CeO 2 , MnCo 2 O 4 and CeO 2 /mesoporous carbon (MC) have been developed and examined for the heterogeneous catalysis of the condensation reaction . Promisingly, most of these heterogeneous catalysts allows for the use of oxygen diluted in air as an efficient oxidant during the syntheses of imines.…”