Imines were synthesized from the cross-coupling of alcohols with amines catalyzed by activated carbon (AC) supported ruthenium nanoparticles under atmospheric molecular oxygen without aid of any additives. The readily prepared catalyst 5%Ru/AC showed good to excellent (yield > 90%) performances in the reaction of aromatic and heterocyclic alcohols with various amines, such as aromatic, aliphatic and heterocyclic amines. This protocol is simple, efficient, and environmentally friendly, and the catalyst can be easily recovered without major ruthenium loss.Imines were synthesized from the cross-coupling of alcohols with amines catalyzed by activated carbon (AC) supported ruthenium nanoparticles under atmospheric molecular oxygen without aid of any additives. This protocol is simple, efficient, and environment friendly, and the readily prepared catalyst 5%Ru/AC showed good to excellent performances in the reaction of aromatic and heterocyclic alcohols with various amines, such as aromatic, and aliphatic amines.

A polymer–ruthenium complex Ru(pbbp)(pydic) was synthesized from the reaction of poly-2,6-bis(benzimidazolyl)pyridine (pbbp) with RuCl3 and disodium pyridine-2,6-dicarboxylate (pydic). The Ru(pbbp)(pydic) was characterized thoroughly by spectroscopic methods. ICP analysis revealed that the percentage of complexation of 2,6-bis(benzimidazolyl)pyridine unit in pbbp was about 83%. The complex was tested as a heterogeneous catalyst for the oxidation of secondary alcohols to their corresponding carbonyl compounds in solvent-free conditions using aqueous tert-butyl hydroperoxide as oxidant. The developed catalytic system exhibited high activity and broad functional group compatibility, allowing a variety of secondary alcohols, including substituted secondary benzylic alcohols and secondary aliphatic ones, to be oxidized to the corresponding ketones in high yields. This Ru(pbbp)(pydic) could be recycled for several times, but it dissolved in part in the reaction mixture during the catalytic run leading to gradual deactivation of the catalyst with repeated runs.

A composite co-crystalline zeolite HZSM-5/11(78) was synthesized and tested in the conversion of glycerol with ammonia to pyridine bases (pyridine, 2-methylpyridine, 3-methylpyridine). The HZSM-5/11(78) showed good performance compared to other zeolites with similar Si/Al ratios such as HZSM-5(80), HZSM-11(80) and the physical mixture of HZSM-5(80) and HZSM-11(80). Characterization results from the N2 adsorption–desorption and IR of the adsorbed pyridine indicated that the good performance of HZSM-5/11(78) was related to the higher surface area and co-existence of an appropriate ratio of Lewis and Brønsted sites, which are derived from the intergrowth between zeolites HZSM-5 and HZSM-11. The parameters affecting the catalytic performance of HZSM-5/11(78) were investigated systematically. The optimal conditions for producing pyridine bases from glycerol with ammonia over this catalyst were determined, including a reaction temperature of 520 °C, 0.1 MPa pressure with a molar ratio of ammonia to glycerol of 12 : 1, and a GHSV of 300 h−1.

A ligand with both a terpyridine and a pyridine-2,6-dicarboxylate group (abbreviated as terpy–pydic) was designed and synthesized. This ligand reacted with [Ru(p-cymene)Cl2]2 to afford a novel oligomer ruthenium complex named as oligomer-Ru(terpy)(pydic) which was characterized thoroughly. Under the catalysis of this oligomer ruthenium complex, different sorts of secondary alcohols were oxidized to the corresponding kenones by the oxidant tert-butyl hydroperoxide. Besides, this catalyst can be readily recovered and recycled several times without a large loss of its efficiency.

A catalyst of 4.6% Cu supported on HZSM-5 with Si/Al of 38 [4.6% Cu/HZSM-5(38)] was prepared in this work. Pyridine bases including pyridine and 2- and 3-picoline, were obtained over this catalyst from glycerol and ammonia. The parameters influencing the catalyst performance were studied thoroughly. An optimized process for the reaction of glycerol with ammonia to form the pyridine bases was also obtained. Under the optimized conditions, which include a reaction temperature of 520 °C, atmospheric pressure with an ammonia/glycerol molar ratio of 7:1, and a GHSV of 300 h−1, the total carbon yield of the pyridine bases was nearly 42.8%. Characterization results from the IR of the adsorbed pyridine indicated that the doping of copper into HZSM-5(38) led to significant changes in the Lewis/Brønsted ratio. An appropriate proportion of the two types of acid sites is important to determine the total selectivity of pyridine bases. XRD analysis showed that copper was initially present in the CuO state and then converted into elemental Cu reduced by H2 generated in situ in the catalytic run. TEM and nitrogen adsorption–desorption characterization revealed that the catalyst deactivation was mainly caused by carbonaceous deposits on the catalyst. The catalyst can be regenerated online by blowing air into the reactor at 550 °C for 6 h. The slight decrease of the activity of the regenerated 4.6% Cu/HZSM-5(38) compared with that of the fresh one could be ascribed to the partial sintering of copper particles and dealumination of the catalyst in the catalytic run.

A novel N,N,N-tridentate ligand known as 2-(2-pyridylmethylamino)ethylbenzimidazole (pymaeb) was designed and synthesized. This ligand in combination with disodium pyridine-2,6-dicarboxylate (pydic) reacted with RuCl3 to afford a novel complex Ru[2-(2-pyridymethylimino)ethylbenzimidazole]pyridinedicarboxylate [Ru(pymieb)(pydic)] which was characterized by NMR, IR, HR-MS and single crystal X-ray diffraction. Crystal structure analysis revealed that the complex has a distorted octahedral geometry. The complex showed excellent activity for the oxidation of various alcohols with TBHP as oxidation under mild and solvent-free conditions.A novel Ru(II) complex Ru(pymieb)(pydic) was synthesized and characterized by NMR, FT-IR, HR-MS and single crystal X-ray diffraction. The complex showed excellent activity for the oxidation of various alcohols with TBHP as oxidant under mild and solvent-free conditions.

A novel deep eutectic solvent supported TEMPO (DES–TEMPO) composed of N,N-dimethyl-(4-(2,2,6,6-tetramethyl-1-oxyl-4-piperidoxyl)butyl)dodecyl ammonium salt ([Quaternium-TEMPO]+Br−) and urea was prepared. An efficient catalytic system for the oxidation of alcohols with molecular oxygen as terminal oxidant has been developed from DES–TEMPO and Fe(NO3)3·9H2O. The DES–TEMPO/Fe(NO3)3 system showed good performances on the selective oxidation of various alcohols to the corresponding aldehydes and ketones under mild and solvent-free conditions. The DES could be recovered easily and recycled up to five times in the oxidation of benzyl alcohol without significant loss of catalytic activity.

The oxidative kinetic resolution of racemic secondary alcohols was efficiently catalyzed by a chiral Mn(III)–salen complex using sodium hypochlorite (NaClO) as an oxidant in the presence of 8 mol% N-bromosuccinimide (NBS) in a dichloromethylene-water mixture solvent at room temperature. Excellent ee’s (up to 99 %) of chiral secondary alcohols were achieved in most cases.

Four ionic liquids (ILs) with both a pyridine N-oxide moiety and an imidazolium moiety combined by an amide spacer were synthesized through a series of reactions including amidation, peroxidation, quaterization and anion exchange reaction. Their structures were fully characterized by 1H NMR, FT-IR, UV–vis and HR–MS. The ionic liquids were used respectively as additives in the methyltrioxorhenium (MTO) catalyzed epoxidation of olefins with 30% H2O2 as an oxidant. The catalytic results displayed that the ILs had excellent performances in suppressing epoxide ring-opening reaction, which led to the significant improvement of the selectivity of the MTO-catalyzed epoxidation with low loadings compared to other substances as additives. The coexistence of the pyridine N-oxide and imidazolium moieties in the structures of ILs is necessary in improving the MTO-catalyzed epoxidation reaction. It was also displayed that the improvement degree on the selectivity of epoxidation depended on the type of anion of the ILs, but not the position of the substituent with imidazolium moiety in the ring of pyridine N-oxide. Meanwhile, the results also showed that the introduction of the ILs caused the decrease of the epoxidation rate, but this side effect was small compared to those of other substances used as additives.Graphical abstractMethyltrioxorhenium-catalyzed epoxidation of olefins with pyridine N-oxide ionic liquids as additives and 30% hydrogen peroxide as an oxidant.Highlights► Four novel ionic liquids (ILs) with pyridine N-oxide moiety were synthesized. ► The ILs as additives significantly increased the selectivity of MTO-catalyzed epoxidation. ► The ILs as additives improved the lifetime of MTO in the epoxidation. ► The anion type of the ILs is important in improving the selectivity of epoxidation.

A novel method for the synthesis of phenylacetonitrile by amination of styrene oxide catalyzed by a bimetallic catalyst Zn30.1Cr4.3/γ-Al2O3 was established. A yield as high as 87.9% was received when the reaction was conducted on a fixed-bed reactor dosed with 30 ml (21 g) catalyst at 693 K under ammonia at atmospheric pressure by keeping the liquid velocity of styrene epoxide diluted with toluene (styrene oxide:toluene = 20:80 (m:m)) at 0.2 ml min−1 and the gas velocity of ammonia at 300 ml min−1. The lifetime of the catalyst was evaluated and the activity of the catalyst could be recovered by continuously blowing air into the fixed-bed at 723 K for 3.5 h online. The catalyst was characterized by XRD, XPS, TEM and IR of adsorbed pyridine. The characterization results indicated that the dehydration reaction in the tandem reaction mainly took place on the Lewis acid sites and revealed that ZnAl2O4 is the active species for the dehydrogenation of imine to nitrile. The doping of chromium on to the γ-Al2O3 supported zinc catalyst Zn29.9/γ-Al2O3 could diminish the size of ZnAl2O4 crystallites, which is in favor of the dehydrogenation reaction. The deactivation of the catalyst is due to the carbonaceous deposits generated from the chemical adsorption of some alkaline substances in the catalytic run.

Two novel Cu(II) complexes were synthesized through the reaction of 2-aminomethyl pyridine (AMP) with CuCl2·2H2O by changing the metal/ligand ratio. Their structures were thoroughly characterized by FT-IR, elemental analysis and X-ray diffraction method. The results revealed that complex 1 [Cu(AMP)Cl2] consists of isolated binuclear molecules unit and displays distorted tetragonal pyramid. Complex 2 [Cu(AMP)2(H2O)2]Cl2 exhibits a octahedral geometry. The complexes were both evaluated as catalysts in the tetralin oxidation with TBHP as oxidant. Complex 1 showed high catalytic activity and selectivity towards α-tetralone under mild conditions. Thus, under the optimized conditions (acetonitrile 10 ml, catalyst 0.045 mmol, tetralin 4.5 mmol, 65% TBHP 22.5 mmol, T = 50 °C), the conversion of tetralin reached 89% with a selectivity of 71% towards α-tetralone. Compared with complex 1, complex 2 displayed low catalytic activity mainly due to the strong steric hindrance from the two coordinated 2-aminomethyl pyridine molecules.Graphical abstractTwo novel Cu(II) complexes were synthesized and evaluated as catalysts in the tetralin oxidation with TBHP as oxidant. Complex 1 showed good performances in the catalytic reaction.Research highlights▶ Two novel Cu(II) complexes were synthesized and characterized thoroughly. ▶ Complex 1 showed high activity and selectivity in the tetralin oxidation by TBHP. ▶ Their catalysis in tetralin oxidation are related to the structure of the complexes.

Several chiral Schiff-base ligands with sugar moieties at C-3 (3′) or C-5 (5′) of salicylaldehyde were synthesized from reaction of salicylaldehyde derivatives with diamine. These ligands coordinated with Mn(III) to afford the corresponding chiral salen–Mn(III) complexes characterized by FT-IR, MS, and elementary analysis. These complexes were used as catalysts for the asymmetric epoxidation of unfunctionalized alkenes. Only weak enantioselectivity is induced by the chiral sugar moieties at C-3 (3′) or C-5 (5′) in the case of absence of chirality in the diimine bridge moiety. It was also shown that the sugars at C-5 (5′) having the same rotation direction of polarized light as the diimine bridge in the catalyst could enhance the chiral induction in the asymmetric epoxidation, but the sugars with the opposite rotation direction would reduce the chiral induction.

A secondary amino group modified MCM-41 (mobile crystalline material number 41) was synthesized and used as a support for the immobilization of a salen oxovanadium complex via a multi-grafting method. The immobilized complex was characterized by UV–Vis spectroscopy, X-ray diffraction (XRD), N2 adsorption and ICP analysis techniques. The immobilized complex was found to be an effective catalyst for oxidation of cyclohexane using H2O2 as an oxidant under mild conditions. A conversion of 45.5% of cyclohexane was obtained with a selectivity of 100% of the cyclohexanone/cyclohexanol mixture when the reaction was run at 60 °C for 12 h in acetonitrile. Decomposition of the complex, which leads to the deactivation of the catalyst, is observed and a decomposition mechanism is discussed.

A chiral Manganese (III) salen complex was immobilized on the walls of MCM-41 (mobile crystalline material) through the multi-grafting method. The immobilized complex was characterized by XRD, FTIR, UV-Vis, ICP and Nitrogen sorption, and was applied to the asymmetric epoxidation of unfuctionalized alkenes including 1,2-dihydronaphthalene, α-methylstyrene, cis-β-methylstyrene, styrene using NaClO and m-chloroperbenzoic acid (m-CPBA) as oxidants respectively. The immobilized complex showed good activity and enantioselectivity in the epoxidation of 1,2-dihydronaphthalene by using NaClO as oxidant. It could also be run for 4 times in the epoxidation of α-methylstyrene without obvious loss of activity or enantiomeric excess.

A secondary amino-modified mesoporous molecular sieve MCM-41 was obtained by reaction of bis(3-(triethoxysilyl)propyl)amine with MCM-41. The chiral Salen-Mn (III) complex was anchored onto the modified MCM-41 by a multi-step grafting method and two heterogenized catalysts with different Mn contents were obtained. The catalysts were characterized by XRD, N2 adsorption, ICP, FT-IR and DR UV-Vis. Their catalysis on asymmetric epoxidation of several olefins was studied with NaClO and m-CPBA as oxidants respectively. It was found that both the activity and enantioselectivity of the catalysts decreased after the homogeneous catalyst was heterogenized. The reasons resulting in the decrease of catalytic performance were discussed.

•Acetonitrile and propionitrile were obtained from the amination of glycerol.•The parameters influencing the catalytic performance were studied thoroughly.•The possible pathways for the generation of the products are given.•The doping of potassium increases the BET surface of iron oxide based catalyst.•The reasons for the deactivation of catalyst Fe20K0.2/γ-Al2O3 were revealed.An Fe19.2K0.2/γ-Al2O3 catalyst for the catalytic amination of glycerol to propionitrile was prepared. Acetonitrile as a major product was obtained over this catalyst from the amination of glycerol. Additionally, propionitrile, ethylene and propylene were also obtained. The parameters influencing the catalyst performance were studied thoroughly, and an optimised process for the amination of glycerol to acetonitrile and propionitrile over the catalyst was obtained. Under the optimised conditions, which were a reaction temperature of 525 °C, an atmospheric pressure with an ammonia/glycerol molar ratio of 8:1 and GHSV of 1338 h−1, the total yield of acetonitrile and propionitrile was 58.4%, and the converted amount of glycerol over one gram of catalyst reached 0.42 g h−1. The catalyst was characterised by XRD, XPS, TEM and IR of the adsorbed pyridine. The characterisation results indicated that the dehydration reaction in the tandem reaction mainly occurred on the Lewis acid sites and revealed that both Fe2O3 and Fe3O4 are active species for the dehydrogenation of imines to nitriles, but the former is more active than the latter. It also revealed that the catalyst deactivation was due to carbon deposits, the transformation of Fe2O3 to the Fe3O4 phase, as well as agglomeration of the Fe2O3 or Fe3O4 phase during the catalytic run and regeneration process.Graphical abstractDownload high-res image (59KB)Download full-size image