•Ni catalysts with varying Zn/Al atom ratios in the supports were tested.•The role of the supports on the cleavage of β-O-4 linkage was investigated.•The possible reaction pathways of β-O-4 ether linkage have been proposed.Catalytic depolymerization of lignin is still a challenge due to its low conversion and repolymerization of the reactive intermediates. Reductive depolymerization over supported nickel catalysts with probable surface acidic and basic properties is a very promising process. It is therefore very important to investigate the effect of acidity and basicity of the supports on catalytic reactivity. In this paper, we synthesized a series of nickel based catalysts supported on ZnO-Al2O3 composites with varying Zn/Al atom ratios (Zn/Al = 2, 3, 5, ∞) and tested their catalytic performances over a model compound 2-phenoxy-1-phenylethanone containing β-O-4 bond. All these catalysts showed 100% conversion by reacting at 250 °C for 2 h under 2 MPa of H2. Higher selectivity towards ethylcyclohexane could be obtained over the catalyst Ni/ZnO-Al2O3-5. The possible cleavage pathways of selective oxidized β-O-4 ether linkage have been proposed.Download high-res image (139KB)Download full-size image

A facile template-free method is developed to prepare porous Co–Mo sulfide sub-microtubes with open-ended structures via sulfurization of the Co–Mo precursor in an ethanol solution of CS2. The hollow structure significantly improves the exposure degree of active components, resulting in an ultra-high activity for HDS of dibenzothiophene.

Nitrogen oxides (mainly NO) are one of the major air pollutants that lead to a number of environmental problems such as photochemical smog, acid rain and haze. The catalytic oxidation of NO to NO2 is regarded as a key step in NOx elimination. In recent decades, a variety of NO oxidation catalysts have been developed for possible application, which can be divided into four categories, namely, supported (including noble metals and metal oxides), multi-metal oxide, perovskite type and carbon-based catalysts. In addition, the “fast SCR” catalysts which were effective for NO oxidation were also included. This paper reviewed the recent progress on catalysts and evaluated the catalytic performance in NO oxidation. As well, the mechanistic investigations and SO2/H2O tolerance were emphasized. Finally, the perspective and the future direction of NO oxidation catalysts were presented.

A series of HZSM-5 supported MnOx catalysts with different manganese contents were prepared by an incipient impregnation method and tested for the catalytic oxidation of toluene. The catalytic results indicate that 10% MnOx/HZSM-5 exhibits the optimum catalytic activity, excellent catalytic durability in dry conditions and high regeneration capability in humid conditions. The dispersion of MnOx species on the HZSM-5 surface significantly reduces coke formation and simultaneously efficiently accelerates the oxidative decomposition of coke deposition during toluene catalytic oxidation. An obvious cooperative action is present on the MnOx/HZSM-5 catalysts for the catalytic oxidation of toluene, which is originally attributed to the excellent toluene adsorption capacity and trapping ability of HZSM-5 as well as the superior redox ability of the MnOx species. The correlation between characterizations and the catalytic results reveals that the mesoporous structure and low-temperature reducibility of MnOx are key factors responsible for the catalytic performance of toluene oxidation. Moreover, the Brønsted acid sites of the HZSM-5 zeolite, as active promoters, play a significant role in the catalytic oxidation of toluene through a comparative analysis with SiO2 and Al2O3 supported MnOx catalysts. The existence of a cooperative action between the redox ability of the MnOx species and the acidic properties of the HZSM-5 zeolite in the MnOx/HZSM-5 catalysts results in a high catalytic activity for the reaction.

Spindle-like boehmites with high adsorption capacity for Congo red (CR) from water were prepared via a hydrothermal synthesis method without any surfactants. The crystallite sizes of boehmites can be subtly adjusted by hydrothermal post-treatment for various durations, and the crystalline structure, morphology and textural properties of boehmites were characterized by different techniques. The adsorption capacities and rates of CR onto boehmites were thoroughly evaluated with the help of equilibrium and kinetics experiments. The adsorption isotherms are fitted well to the Langmuir equation, and the Langmuir adsorption capacity (qmax) is as high as 427.4 mg g−1. The kinetics data show that the adsorption process can be well described by pseudo-second-order kinetics model, and besides, adsorption rate is closely related to the exposed surface area of lattice plane (020) of boehmite crystallite, because this plane has a relatively high OH density that is favourable to the adsorption of CR. The IR characterization and the relationship between the pH values of the zero point of charge (pHzpc) for different boehmites and adsorption behavior of CR suggest that the involved adsorption process is driven by the hydrogen bonding and electrostatic attraction at the same time.

The oxidation of alcohols to carbonyl compounds is one of the most fundamental reactions in synthetic organic chemistry. In order to achieve the realization of dehydrogenation reactions with high atomic efficiency, suitable catalysts and oxidants are considered as the key factors to obtain the optimum activity and aldehydes/ketones selectivity. This review aims to make an overview on the reasonable reaction mechanism and promising catalytic system of alcohols dehydrogenation.

The carbon-covered aluminas were prepared by using different monocarboxylic acids as carbon sources to modify active alumina, and then were used as supports to prepare supported CoMo catalysts for hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). These monocarboxylic acid molecules can be readily converted to carbon species by thermal decomposition in a nitrogen atmosphere and deposited on an alumina surface. The carbon species can then effectively weaken the interaction between active metals and alumina, which improves the migration and growth of surface Mo species. This result further affected the morphology and orientation of surface sulfur species, that is, the slab length and stacking number of the MoS2 slabs, which closely relates to HDS activity. Since the surface Mo species supported on the alumina modified with acetic acid consisted of the MoS2 slabs with the shortest lengths, leading to the presence of more easily reducible sulfur species during the reaction, the corresponding catalyst exhibited the highest HDS activity for 4,6-DMDBT. In addition, the stacking numbers for all of the catalysts were relatively low, which hindered the adsorption of 4,6-DMDBT on the brim sites of the MoS2 stacks, and thus the HDS reaction mainly occurred through the direct desulfurization route.

One series of isostructural lanthanide phosphonates, namely [Ln2(H2L)3][(H2O)5] (H4L = (5-methyl-1,3-phenylene)bis(phosphonic acid); Ln = Eu (1), Gd (2), Tb (3), and Dy (4)), have been successfully synthesized from a V-shaped rigid ligand. Systematic characterizations using single-crystal and powder X-ray diffraction (XRD), thermogravimetric analyses (TGA), and photoluminescence spectroscopy were accomplished. It was found that these compounds all crystallize in the cubic I213 space group, showing three-dimensional framework structures. The frameworks are stable up to 350 °C and show their respective characteristic metal-centered emissions. The photoluminescence properties were also theoretically investigated by using a newly developed software program – LUMPAC. The energy transfer and back energy transfer rates were estimated, and the T1 → 5D1 and T1 → 5D0 channels were revealed to be the dominant pathways. The combination of experimental and theoretical studies on the photoluminescence properties substantially supports the understanding and design of highly luminescent inorganic–organic hybrid materials.

For the first time, methyltrioxorhenium (MTO) is used as a catalyst for the extractive and catalytic oxidative desulfurization (ECODS) of model oil and fluid catalytic cracking (FCC) gasoline, with 30% H2O2 as the oxidant and ionic liquids as the solvent and extractant for the removal of organic sulfur at moderate temperatures (below 60 °C). The ECODS is highly efficient with low catalyst loading (1–5 mol %). The mono- and bisperoxorhenium compounds formed via the reactions of MTO and H2O2 are proven to be catalytic active species for the oxidation of organic sulfides, such as thioethers, thiophene, and alkyl thiophenes contained in the FCC gasoline. After the oxidation, the oxidized products were easily extracted into the ionic liquid phase from the oil phase. The sulfur removal can reach up to 99% for the model oil (with an initial sulfur content of 200 μg/mL) and 91% of the Fushun FCC gasoline (with an initial sulfur content of ca. 142 μg/mL) within 2 h under the optimized conditions. The octane number of the gasoline is reduced by only about 0.7, without significant changes in hydrocarbon group composition after desulfurization.

The Cu-doped Ce0.8Zr0.2O2 (CZ) catalyst was investigated in terms of its NO oxidation activity, structure and surface characteristics. The Cu/CZ catalyst with 6 wt% Cu loading and 550 °C calcination temperature of CZ support showed the best catalytic performance, and over 50% NO conversion was obtained in a wide temperature range (250–370 °C). Moreover, this catalyst showed good resistance to H2O and SO2. The dispersion of CuO species on the smaller crystallite size CZ support was favorable for NO adsorption. The Cu–Ce–Zr solid solution provided the sites of oxygen vacancies, prompted the formation of active oxygen, which in sum improved the oxidation activity of NO.

•Hierarchically porous structures and varying acidity of ZSM-5 were obtained by facile desilication and/or dealumination.•Amount of weak acid sites of acidic ZSM-5 was correlated with ethylene selectivity over various ZSM-5 catalysts.•Weak acid sites facilitated ethylene production, probably because decreased catalytic Brønsted acidity led to decreased diethyl ether formation.•Stable ethanol conversion and ethylene selectivity over post-treated ZSM-5 within time-on-stream of around 12 h.•Reaction pathways for diethyl ether and ethylene formations from ethanol were investigated by theoretical calculation.Microporous ZSM-5 zeolite was post-treated by desilication with sodium hydroxide, dealumination with oxalic acid, or both of them in a sequential way to finely tune the zeolite catalysts with hierarchically porous structure and varying acidity. In the catalytic dehydration of ethanol, diethyl ether and ethylene were two main products competitively formed at 200 °C and atmospheric pressure. The post-treated ZSM-5 catalysts could display stable ethanol conversion and ethylene selectivity within time-on-stream of around 12 h. The correlation between the steady-state ethylene selectivity and the amount of weak acid sites from ammonia temperature-programmed desorption (NH3-TPD) indicated that the weak acid sites facilitated the ethylene production during ethanol transformation under present reaction conditions. The reaction pathways for diethyl ether and ethylene formations from ethanol were investigated by theoretical calculation. Both the activation energies and natural charges of the transition states strongly supported that the selectivity for the diethyl ether tended to deteriorate with decreasing catalytic Brønsted acidity.Graphical abstractDownload high-res image (103KB)Download full-size image

The carbon-covered aluminas were prepared by using different monocarboxylic acids as carbon sources to modify active alumina, and then were used as supports to prepare supported CoMo catalysts for hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). These monocarboxylic acid molecules can be readily converted to carbon species by thermal decomposition in a nitrogen atmosphere and deposited on an alumina surface. The carbon species can then effectively weaken the interaction between active metals and alumina, which improves the migration and growth of surface Mo species. This result further affected the morphology and orientation of surface sulfur species, that is, the slab length and stacking number of the MoS2 slabs, which closely relates to HDS activity. Since the surface Mo species supported on the alumina modified with acetic acid consisted of the MoS2 slabs with the shortest lengths, leading to the presence of more easily reducible sulfur species during the reaction, the corresponding catalyst exhibited the highest HDS activity for 4,6-DMDBT. In addition, the stacking numbers for all of the catalysts were relatively low, which hindered the adsorption of 4,6-DMDBT on the brim sites of the MoS2 stacks, and thus the HDS reaction mainly occurred through the direct desulfurization route.

A series of HZSM-5 supported MnOx catalysts with different manganese contents were prepared by an incipient impregnation method and tested for the catalytic oxidation of toluene. The catalytic results indicate that 10% MnOx/HZSM-5 exhibits the optimum catalytic activity, excellent catalytic durability in dry conditions and high regeneration capability in humid conditions. The dispersion of MnOx species on the HZSM-5 surface significantly reduces coke formation and simultaneously efficiently accelerates the oxidative decomposition of coke deposition during toluene catalytic oxidation. An obvious cooperative action is present on the MnOx/HZSM-5 catalysts for the catalytic oxidation of toluene, which is originally attributed to the excellent toluene adsorption capacity and trapping ability of HZSM-5 as well as the superior redox ability of the MnOx species. The correlation between characterizations and the catalytic results reveals that the mesoporous structure and low-temperature reducibility of MnOx are key factors responsible for the catalytic performance of toluene oxidation. Moreover, the Brønsted acid sites of the HZSM-5 zeolite, as active promoters, play a significant role in the catalytic oxidation of toluene through a comparative analysis with SiO2 and Al2O3 supported MnOx catalysts. The existence of a cooperative action between the redox ability of the MnOx species and the acidic properties of the HZSM-5 zeolite in the MnOx/HZSM-5 catalysts results in a high catalytic activity for the reaction.