Surface-modified Improvement in Catalytic Performance of Cr(salen) Complexes Immobilized on MCM-41 in Solvent-Free Selective Oxidation of Benzyl Alcohol

Abstract

A series of typical methyl regulators were used to finely modify the Cr(salen) complex immobilized on MCM-41. Such immobilized complexes were effective catalysts for solvent-free selective oxidation of benzyl alcohol (BzOH) with 30% hydrogen peroxide (H 2 O 2 ), and they all exhibited much higher catalytic performance than their homogeneous analogue. Simultaneously, the introduction of methyl regulators was found to significantly improve the catalytic performance of immobilized complexes by modifying their surface properties. The optimal BzOH conversion reached 65.0% with 100% selectivity to benzaldehyde (BzH).

Epoxidation of Styrene with H2O2 Catalyzed by Alanine–Salicylaldehyde Schiff Base Chromium (III) Complexes Immobilized on Mesoporous Materials

“…The methyl-containing APTES-supports were prepared by following the procedures in our previous report [29]. Typically, the as-prepared APTES-support (3 g) was degassed at 50°C under 10 -2 Pa for 2 h. Then, an excess of dimethyldiethoxysilane (0.03 mol) in dry toluene (100 mL) was added, and the suspension was stirred at reflux temperature under nitrogen flow for 24 h. The resulting solid was filtered, Soxhlet-extracted with dichloromethane for 24 h and dried in air (at 60°C under 10 -2 Pa for 3 h).…”

“…In the 29 Si NMR spectrum of APTES-MCM-41 (see Fig. 1), the two resonances at about -109 and -99 ppm can be attributed to 29 Si nuclei having four Si-O-Si linkages (Q 4 ) and 29 Si nuclei having three Si-O-Si linkages and one -OH (Q 3 ), respectively. The two resonances at about -55 and -65 ppm are assigned to RSi(OSi)(OH) 2 and RSi(OSi) 3 , respectively [33].…”

“…Thus, the enhanced styrene conversion is mainly attributed to the improved H 2 O 2 efficiency, and consequently to the decreased amount of residual silanol groups in methylcontaining immobilized complexes. We have discussed the correlation between the H 2 O 2 efficiency, the conversion of reactant and the amounts of residual silanol groups in our previous report [29]. In order to obtain the best catalytic results, the effect of condition parameters on the catalytic performance of Cr(Sal-Ala)-MCM-41(CH 3 ), which is the most active catalyst in the epoxidation of styrene among all immobilized materials, was investigated.…”

Methyl Group Modified MCM-41 Supported Schiff-Base Cobalt Complex and Its Catalytic Performance in Cyclohexane Oxidation

“…In order to further improve the catalytic performance of heterogeneous catalysts, methyl groups were introduced onto the surface of carrier by some researchers. Wang et al [11] used a series of typical methyl regulators to finely modify the Cosalen complex immobilized on MCM-41 carrier, such immobilized complexes were effective catalysts for solvent-free selective oxidation of benzyl alcohol with 30 % H 2 O 2 solution as oxidant, they all exhibited much higher catalytic performance than their homogeneous analogue. Simultaneously, the introduction of methyl regulators was found to significantly improve the catalytic performance of immobilized complexes by modifying their surface properties.…”

Solvent-free oxidation of alcohols by hydrogen peroxide over chromium Schiff base complexes immobilized on MCM-41

“…Compared to homogeneous complexes, heterogeneous systems have the inherent advantages of easy separation and better handling properties, so the heterogenization of known homogeneous catalysts has attracted much attention [10][11][12][13][14][15]. A popular approach is to immobilize the homogeneous catalyst on the support through a surface-bound tether containing a functional group.…”