Search

In this paper, CuOx@Ag/CeO2 catalysts were synthesized by simple wet-chemical method and equal volume impregnation method. The obtained catalysts were subjected to soot temperature programmed oxidation (soot-TPO) activity tests and were further characterized by various techniques such as X-ray diffraction (XRD), transmission electron microscopy/high-resolution transmission electron microscopy (TEM/HR-TEM), N2 physisorption, X-ray photoelectron spectroscopy (XPS) and H2- temperature programmed reduction (H2-TPR). The results show that CuOx@Ag/CeO2 synthesized presents well controlled core-shell structures, with nano-cube like Cu2O as the core and Ag decorated polycrystalline CeO2 grafting layers as the shell. Such core-shell structured CuOx@Ag/CeO2 can successfully construct a secondary oxygen delivery channel (CuOx → CeO2 → Ag) to effectively transfer bulk oxygen of the catalyst to the soot, resulting in its excellent soot oxidation activity compared to CuOx@CeO2. The potential benefiting effect by Ag introduction over Cu@Ag/Ce can be concluded as: (i) pumping lattice oxygen and accelerating gaseous O2 dissociation to generate significantly increased active surface oxygen content; (ii) modulating a moderate surface oxygen vacancies concentration to maintain more highly active O2– species.

CeO2–ZrO2 mixed oxides with controlled morphologies (i.e., nanorod, nano-polyhedral and disordered shape) were synthesized through either hydrothermal or coprecipitation method, and the corresponding supported Pd/CeO2–ZrO2 catalysts were also prepared by conventional impregnation. The obtained catalysts were subjected to systematic structural/physio-chemical characterizations as well as three-way catalytic performance evaluations. The results showed that CeO2–ZrO2 mixed oxides presented different exposed crystal planes: namely disordered CZ-di mainly exposed (111) crystal planes, nanorod CZ-ro mainly exposed (111) crystal planes and few (100) crystal planes, while nano-polyhedral CZ-po exposed both (111) and (100) crystal planes. Clear structure-activity relationship could be demonstrated between the TWC (Three-way catalysts) performance of Pd/CeO2–ZrO2 and such different microstructures, as (100) and (111) crystal planes exposed by CZ-ro and CZ-po were beneficial for the surface oxygen vacancies formation, thus increasing the Pd-support interaction and effectively decreasing the light-off temperature of HC and NO elimination. On the other hand, the disordered CZ-di retained more lattice oxygen content, leading to better catalytic activity of CO elimination for the corresponding Pd/CZ-di catalyst.

In order to disposal the herb residue of Chinese medicine which is easy to decay and harmful to the environment. The residue of lemon grass after extraction (distilled lemon grass, DLG), as an herb...

Series of Cu-USY zeolite catalyst with different Cu loading content were synthesized through simple impregnation method. The obtained catalysts were subjected to selective catalytic reduction of NO

Vinyl sulfides and vinyl sulfones are ubiquitous structures in organic chemistry because of their presence in natural and biologically active compounds and are very frequently encountered structural motifs in organic synthesis. Herein we report an efficient synthesis of vinyl sulfides and vinyl sulfones via transition metal-free sodium iodide-mediated sulfenylation of alcohols and sulfinic acids with solvent-controlled selectivity.

1,4-Dioxenes and 4,7-dihydrooxepines present interesting potential as motifs for the incorporation of biologically relevant molecules, agrochemicals and materials. In this study, two efficient intermolecular (3 + 2 + 1) and (5 + 2) cycloadditions for the synthesis of 1,4-dioxenes and 4,7-dihydrooxepines are achieved with gold catalysis.

UV chemical degradation is a low-cost and sustainable wastewater treatment technology that protects the environment. In this study, computational fluid dynamics (CFD), mass transfer, and photochemical kinetic models combined with the continuous flow mode of UV/H2O2 were applied for the photochemical reaction of internal airlift circulation photocatalytic reactor to improve the efficiency of the reaction. Results show that with the increase in gas flow rate, the turbulence intensity and internal circulation effect of liquid in the reactor can be enhanced under the condition of constant baffle spacing. The CFD simulation prediction results of the chemical components in the liquid flow show that H2O2 has a high correlation with the OH radical formation, which depends on the intensity of UV. Thus, the degradation rate of methylene blue (MB) has a high correlation with UV intensity. The degradation efficiency of MB is improved with the increase in gas velocity by comparing the experimental data with the numerical simulation data. The experimental data are generally lower than the numerical prediction data, and although a certain difference range is observed, the overall prediction results are better.

CuNiAl hydrotalcites supported BiOCl were prepared by one-step synthesis for the selective oxidation of glycerol to glyceraldehyde with H2O2 as oxidant. The prepared catalysts were found to be efficient due to the synergetic catalysis of surface oxygen vacancies, active Cu2+ ions in the HT-lattice and abundant surface –OH groups of catalysts. The optimal glycerol conversion could reach 75.4% with 82.4% of the selectivity to glyceraldehyde. Moreover, the catalyst could be reused at least 6 times, and a possible reaction mechanism was also proposed. Inexpensive and environmentally friendly BiOCl/CuNiAl-HTs were synthesized by one-step for the highly selective oxidation of glycerol to glyceraldehyde. The glycerol conversion could reach 75.4% with 82.4% selectivity to GLAD. Such a highly efficient catalytic performance could be attributed to the synergistic effect of oxygen vacancies and the coordination of glycerol on Bi3+ in the supported BiOCl catalyst.

Series of nano rod shaped CeO2-MnOx catalysts with different Ce/Mn molar ratios were synthesized through facile hydro-thermal method and subjected to chlorobenzene (CB) complete catalytic oxidation tests. Detailed structural/chemical characterizations such as TEM/HRTEM, Rietveld XRD, N2 adsorption/desorption, UV-Raman and H2-TPR were conducted. Results show that the designed nano rod shaped CeO2-MnOx binary oxides can be promising with highly efficient catalytic performance towards the complete oxidation of CB. The Ce/Mn-1/8 catalyst (Ce/Mn molar ratio 1:8) is verified as the most outstanding candidate among all the CeO2-MnOx catalysts obtained, which not only presents best catalytic activity but also gives less production of hazardous polychlorinated byproducts, along with excellent durability. Further characterizations reveal that such catalytic advantages can be attributed to both the unique morphology effect and the Ce-Mn strong interaction in the nano rod shaped CeO2-MnOx catalysts. The designed nano rod shaped CeO2-MnOx catalyst mainly exposes the more defective {100} facet, generating lattice micro-strain and favorable for forming more oxygen vacancies. While the formation of todorokite/vernadite phase with special tunnel-like structure which promoting the migration of lattice oxygen to catalyst surface. Moreover, the strong interaction between CeO2 and MnOx can promote the (Ce4+/Ce3+ ↔ Mn4+/Mn3+) redox cycles and is beneficial for CB deep oxidation. Increasing Mn content leads to higher content of todorokite/vernadite phases, surface Mn4+ enrichment and shorter nano rods with more exposes lattice defects, thus rendering enhanced Ce-Mn strong interaction and morphology effect in Ce/Mn-1/8 catalyst.

A series of mesoporous nano-MgO-ZrO2 with various Mg:Zr atomic ratios were prepared via simple co-precipitation process without addition of a template. It was demonstrated by XRD, N2 adsorption-desorption and TEM that these samples still kept well mesoporous structure even after calcination at 600 °C. During the preparation process, divalent Mg2+ ions could be incorporated into tetragonal ZrO2 lattice to form a solid solution. More important, the surface basic density of these catalysts closely depended on their Mg content. Then, the resulting MgO-ZrO2 catalysts were used as basic catalysts for the dipropyl carbonate (DPC) synthesis via transesterification of n-propanol and dimethyl carbonate. The relationship between the basic property of solid base and their catalytic performance was clarified in detail. Among all the materials, the catalyst with Mg:Zr atomic ratio = 0.5 showed the best catalytic performance. Under the suitable reaction conditions, the yield of DPC could reach 98.5% with 100% selectivity. In addition, based on the reusability test and catalyst characterization, this catalyst exhibited extraordinary structure stability and it could be reused at least four times without obvious loss of reactivity.

The Mn-containing mixed-oxide-supported bismuth oxychloride (BiOCl) catalysts were prepared by calcining their corresponding parent hydrotalcite supported BiOCl. The crystal structure of BiOCl was found to be intact during calcination, while significant differences appeared in the chemical state of Mn and the redox capacities of the catalysts before and after calcination. Compared to the hydrotalcite-supported catalysts, the mixed-oxide-supported BiOCl showed much higher catalytic performance in the oxidation removal of formaldehyde due to the synergetic catalysis of more surface oxygen vacancies and higher surface basicity. The complete removal of formaldehyde could be achieved at 70 °C, and the removal efficiency was maintained more than 90% for 21 h. A possible reaction mechanism was also proposed.

A series of anion intercalated transition metal hydroxides and their calcined mixed metal oxides were prepared for the solvent-free selective oxidation of toluene with O 2 . The results revealed that the anion modified mixed metal oxides showed much better catalytic performance than their parent hydroxides. Moreover, the anions were also found to play important role in the catalytic performance and thermal stabilities of modified catalysts. Unexpectedly, iodide ion exhibited high thermal stability in the mesoporous structures of mixed metal oxides even at high temperatures of 1073 K. Under the optimal reaction conditions, the highest toluene conversion reached 15.5% with 100% of the selectivity to benzaldehyde.

A series of Mg–Al layered-double hydroxides (LDHs) intercalated by sulphonato-Schiff base complexes were prepared for the selective oxidation of glycerol (GLY) with O2 as oxidant. The results revealed the LDH hosted complexes were effective catalysts, and their catalytic performance were closely related to the structures and composition of catalysts, the base environments of reaction mixtures as well as the reaction conditions. Among them, LDH hosted copper complex displayed the highest catalytic performance, and the GLY conversion could reach 82.5 with 86.1 % of the selectivity to glyceric acid (GLYAC). Moreover, the catalytic performance remained after being recycled seven times. LDH hosted transition metal complex catalysts were promising catalysts for the selective oxidation of GLY to glyceric acid with O2. The catalytic performance of catalysts and the product distribution were found to be closely related to the structures and composition of catalysts, the base environments of reaction mixtures as well as the reaction conditions. The best GLY conversion reached 82.5 with 86.1 % of the selectivity to GLYAC.

The side reactor concept (SRC), comprising a non-reactive column coupled with side reactors, is proposed for the synthesis of ethylene glycol (EG) by ethylene oxide (EO) hydration. Parallel isothermal continuous stirred tank reactors are employed and the combinations of the reactors and the column are cautiously examined. A preliminary analysis of the operating conditions for the reaction and separation and the detailed SRC configurations (such as the side stream rate, side stream location) are performed to generate the suggested values or ranges for their further optimization. The decisive variables are subsequently optimized by a sequential design procedure. The significant effects of the key decision variables on the trade-off between the reaction cost and the separation cost are well investigated. The reactor–separation unit, configured with a total liquid withdrawn and recycled back to the column stage below, demonstrates better system performance. Furthermore, the reaction at elevated temperature (150 °C) conductive for reaction and the separation occurring at the distillation temperature range of 106∼204 °C (124 kPa) gives out improved economic performance. Flexibility in the operating conditions in SRC makes it a competitive alternative to the RD process for EG production.

An efficient synthesis of ketones (III) and thiazoles (VI) is achieved by trapping in-situ generated α-oxo gold carbenes with MesOH or thioamides (V), respectively.

Three amphiphilic sulphonato-salen–chromium(III) complexes immobilized on MCM-41 were prepared for the solvent-free selective oxidation of benzyl alcohol with 30 % hydrogen peroxide. The immobilized complexes were effective catalysts and exhibited much higher catalytic performance than their corresponding homogeneous analogues and immobilized lipophilic complexes. Under the optimum reaction conditions, benzyl alcohol conversion could reach 60.3 % with 100 % of the selectivity to benzaldehyde. In addition, the catalysts could be recycled at least five times. The immobilized amphiphilic sulphonato-salen–chromium(III) complexes were effective in the selective oxidation of benzyl alcohol due to the increased accessibility of oxidant to catalyst and reactant. The best benzyl alcohol conversion reached 60.3% with 100% of the selectivity to benzaldehyde.

A series of CuNiAl hydrotalcites (HTs) were prepared and used to the selective oxidation of glycerol with O 2 . The results revealed that elemental composition, structures and the surface properties of the obtained catalysts significantly influenced their catalytic performance. Among them, amino-functionalized CuNiAl-HTs showed excellent catalytic performance due to their enhanced surface Lewis basicity. Under the optimal reaction conditions, the highest conversion of glycerol reached 68.1% with 76% of the selectivity to glyceric acid; moreover, the catalytic performance remained after being recycled 6 times.

A series of transition metal complexes of 3-[N,N′-bis-3-(salicylidenamino)ethyltriamine] (salten) immobilized on MCM-41 were prepared for the solvent and additive-free selective oxidation of cyclohexanol with 30 % hydrogen peroxide (H2O2). The immobilized complexes were effective catalysts and exhibited much higher catalytic performance than their homogeneous analogues. Moreover, the metal centers were found to play important roles in the catalytic performance of immobilized complexes. When the immobilized chromium complex was used as catalyst, the optimal cyclohexanol conversion could reach 90.5 % with 100 % of the selectivity to cyclohexanone. In addition, the catalytic performance remained after being recycled five times. Owing to the different 3d electronic numbers of metal centers, eight kinds of immobilized Schiff base complexes exhibited significantly different catalytic performance in the selective oxidation of cyclohexanol with 30 % H2O2. The optimal cyclohexanol conversion could reach 90.5 % with 100 % of the selectivity to cyclohexanone over immobilized chromium complex.

A Mg Al layered-double hydroxides (LDH) intercalated by sulphonato-salen-chromium(III) complex was used to the selective oxidation of glycerol (GLY) using 3% H2O2 as oxidant. The results revealed that the LDH hosted chromium complex was effective heterogeneous catalyst. And the main product was the C3 oxygenated products of secondary alcohol‐dihydroxyacetone (DHA). Under the optimal reaction conditions, the highest conversion of GLY reached 73.1% with 43.5% of the selectivity to DHA. Moreover, the catalytic performance remained after being recycled 6 times. In addition, the reaction probably involved an enzyme mimetic mechanism.

The fluorine-modified Mg–Al mixed oxides were synthesized by thermal decomposition of the fluorine-containing Mg–Al hydrotalcites, and their physicochemical properties were characterized by ICP, TGA, XRD, FTIR, CO2-TPD and N2 adsorption/desorption techniques. It was found that weak basic sites were gradually transformed into moderate and strong basic sites during thermal decomposition, and thus weak basic sites (OH− groups), moderate basic sites (Mg–O, Mg–F and Al–O pairs) and strong basic sites (coordinatively unsaturated F− and O2− ions) were all produced in the as-prepared samples. Furthermore, the basicity of moderate basic sites could be controlled by the change of fluorine content, which caused the change in the amounts of Mg–F pairs. In the synthesis of propylene glycol methyl ether from methanol and propylene oxide, the base-catalytic performance of the obtained samples was shown to be closely associated with their moderate basic sites.

Alanine–salicylaldehyde Schiff base chromium (III) complex was immobilized on mesoporous silica gel (SiO2), MCM-41 and SBA-15. The resulting immobilized complexes were promising catalysts for the epoxidation of styrene with 30% hydrogen peroxide, and they all showed much higher catalytic performance than their homogeneous analogue. Simultaneously, the catalytic performance of immobilized complexes was found to be closely related to the textual and surface properties of the supports used. The complex immobilized on methyl-containing MCM-41 exhibited the highest catalytic performance. Under optimal reaction conditions, the highest conversion of styrene reached 80.2% with 77.0% selectivity to epoxide. In addition, the catalytic performance remained stable after six times of recycling. A series of immobilized alanine–salicylaldehyde Schiff base chromium (III) complexes were promising catalysts for the epoxidation of styrene with 30% hydrogen peroxide. Moreover, the different textural and surface properties of supports significantly influenced their catalytic performance.

A series of chromium(III) Schiff base complexes immobilized on MCM-41 were prepared and characterized by various physicochemical and spectroscopic methods. The complexes were used for the selective oxidation of alcohols by 30% hydrogen peroxide without any organic solvent, phase transfer catalyst or additive. The immobilized complexes proved to be effective catalysts and generally exhibited much higher catalytic performance than their corresponding homogeneous analogs. The catalytic performance of the immobilized complexes was also found to be closely related to the Schiff base ligands used. Under the optimal reaction conditions, secondary alcohols, cyclic alcohols and benzyl alcohol were prevailingly oxidized to their corresponding ketones or aldehydes.

The Mg–Al layered-double hydroxides (LDHs) intercalated by three kinds of sulphonato-salen-chromium(III) complexes were prepared and characterized by FTIR, UV–vis, XRD and elemental analysis. It was found that the homogeneous complexes were successfully intercalated into the LDH interlayer via the method of anion exchange followed by coordination with chromium(III) chloride. And the resulting LDH hosted chromium complexes were shown to be effective heterogeneous catalysts for the solvent-free oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using 30% H2O2 as oxidant. Furthermore, owing to the different local environment of the central metal ion chromium(III), the catalyst with the backbone of o-C6H4 displayed the highest catalytic performance followed by the NH(CH2CH2)2 with the (CH2)2 showing the lowest BzH yield. In addition, a tentative mechanism was also discussed.

A series of fluorine-modified Mg–Al mixed oxides were synthesized by thermal decomposition of the fluorine-containing Mg–Al hydrotalcites and then were characterized by ICP, TGA, XRD, FTIR, CO2-TPD and N2 adsorption/desorption technique. The results revealed that the mesoporous structure was formed during calcination and that fluorine was successfully introduced into the Mg–Al mixed oxides via the phase of MgF2. Simultaneously, such fluorine-modified Mg–Al mixed oxides were effective catalysts for the O-methylation of phenol with dimethyl carbonate (DMC), and their catalytic performance was found to be closely correlated with their basicity. With the optimal catalyst composition, the highest yield of anisole reached 99.3%, with a DMC/phenol molar ratio of 2 at 473 K.

A series of Cr(salen) complexes immobilized on MCM-41 via four typical linkers was prepared for the selective oxidation of benzyl alcohol (BzCH2OH) to benzaldehyde (BzCOH). The results revealed that the complex-immobilized materials were effective catalysts and all exhibited much higher catalytic performance than their homogeneous analogue. Simultaneously, the catalytic performance of complex-immobilized materials was found to be closely related to the degree of flexibility of the linkers and the coordination abilities of terminal functional groups in linkers. The complex-immobilized via flexible aminopropyl linker displayed the highest catalytic performance, and the optimal BzCH2OH conversion could reach 52.5% with 100% of the selectivity to BzCOH.

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 (H2O2), 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).

An efficient synthesis of ketones (III) and thiazoles (VI) is achieved by trapping in-situ generated α-oxo gold carbenes with MesOH or thioamides (V), respectively.

Most homogenous gold catalyses demand ≥ 0.5 mol% catalyst loading. Owing to the high cost of gold, these reactions are unlikely to be applicable in medium- or large-scale applications. Here we disclose a novel ligand design based on the privileged (1,1'-biphenyl)-2-ylphosphine framework that offers a potentially general approach to dramatically lowering catalyst loading. In this design, an amide group at the 3'-position of the ligand framework directs and promotes nucleophilic attack at the ligand gold complex-activated alkyne, which is unprecedented in homogenous gold catalysis considering the spatial challenge of using ligand to reach anti-approaching nucleophile in a linear P-Au-alkyne centroid structure. With such a ligand, the gold(I) complex becomes highly efficient in catalysing acid addition to alkynes, with a turnover number up to 99,000. Density functional theory calculations support the role of the amide moiety in directing the attack of carboxylic acid via hydrogen bonding.

A series of chromium (III) Schiff base complexes immobilized on amorphous silica gel (SiO2), MCM-41 and SBA-15 were prepared and use for the selective oxidation of benzyl alcohol (BzOH). The results revealed that the complex immobilized on ordered mesoporous MCM-41 exhibited the highest catalytic performance. Such a significant difference in the catalytic performance of the immobilized complexes could be due to their different inner coordination structures as well as the different local concentration of reactant and objective product around their active sites, which all originated form their different support structures.

The Mg-Al hydrotalcites (HTs) precursors containing different anions (CO 3 2- , F - , Cl - , Br - ) were prepared by hydrothermal method and characterized by XRD patterns. The results showed that the precursors had the different anions structure. The mesoporous Mg-Al mixed oxides modified by different anions were calcined from the resulting HTs and theirs catalytic performances were tested in the reaction of propylene oxides (PO) with methanol. Among them, the fluorine-modified mixed oxides exhibited much high catalytic performance, which was ascribed to the fluorine nucleophilicity and the high basicity.

A series of Au–silica (nanosphere) catalysts were prepared by in situ synthesis; highly dispersed gold nanoparticles (GNPs, 6.4 nm) were obtained, and catalytic tests showed good catalytic activity and epoxidation selectivity. To investigate the origin of the GNPs, the solids were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and other instruments. Some reaction parameters, such as solvent, oxidant concentration, catalyst concentration and reaction time, have been investigated and reaction conditions are optimized.