MgO/γ-Al_2O_3烷氧基化催化剂制备及结构与性能研究

在γ Al2 O3 载体上浸渍Mg (NO3 ) 2 ·6H2 O ,然后分别经 40 0、45 0和 5 0 0℃焙烧制成MgO/γ Al2 O3 固体碱催化剂。结果表明 ,MgO在γ Al2 O3 载体表面具有单层分散性质 ,当MgO的负载量低于某一数值 (阈值 )时 ,从样品的X光粉末衍射谱图上观察不到MgO的特征衍射峰 ,负载量超过阈值时开始出现MgO的晶相 ,且MgO的XRD衍射峰强度随MgO的负载量的增加而增加 ,其单分散阈值为 0 0 80 gMgO/ 10 0m2 γ Al2 O3 。应用CO2 TPD技术测定了样品的碱性 ,结果表明 ,样品在接近阈值时其碱量大幅度增加 ,碱强度提高。样品的比表面最初随着MgO负载量的增加而下降 ,但达阈值后基本保持不变。

1,7,7-三甲基双环[2.2.1]庚基环烷基(或环取代的烷基)醚的合成

近年来,我们曾报道了莰烯-三环烯在氢型丝光沸石催化下与开链醇及二醇等进行烷氧基化反应的结果。最近,Scheidll,Fran报道用浓硫酸催化莰烯与环戊醇反应,合成exo-1,7,7-三甲基双环[2.2.1]庚基环戊醚。

Preparation of nitrogen-doped carbon nanoblocks with high electrocatalytic activity for oxygen reduction reaction in alkaline solution

The oxygen reduction reaction （ORR） is traditionally performed using noble‐metals catalysts, e.g. Pt. However, these metal‐based catalysts have the drawbacks of high costs, low selectivity, poor stabili‐ties, and detrimental environmental effects. Here, we describe metal‐free nitrogen‐doped carbon nanoblocks （NCNBs） with high nitrogen contents （4.11%）, which have good electrocatalytic proper‐ties for ORRs. This material was fabricated using a scalable, one‐step process involving the pyrolysis of tris（hydroxymethyl）aminomethane （Tris） at 800℃. Rotating ring disk electrode measurements show that the NCNBs give a high electrocatalytic performance and have good stability in ORRs. The onset potential of the catalyst for the ORR is-0.05 V （vs Ag/AgCl）, the ORR reduction peak potential is-0.20 V （vs Ag/AgCl）, and the electron transfer number is 3.4. The NCNBs showed pronounced electrocatalytic activity, improved long‐term stability, and better tolerance of the methanol crosso‐ver effect compared with a commercial 20 wt%Pt/C catalyst. The composition and structure of, and nitrogen species in, the NCNBs were investigated using Fourier‐transform infrared spectroscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, and X‐ray diffraction. The pyroly‐sis of Tris at high temperature increases the number of active nitrogen sites, especially pyridinic nitrogen, which creates a net positive charge on adjacent carbon atoms, and the high positive charge promotes oxygen adsorption and reduction. The results show that NCNBs prepared by pyrolysis of Tris as nitrogen and carbon sources are a promising ORR catalyst for fuel cells.

Production of Benzoic Acid through Catalytic Transformation of Renewable Lignocellulosic Biomass

In the present work, we reported a novel route for the conversion of lignocellulosic biomass （sawdust） to a high-value chemical of benzoic acid under atmospheric pressure. The trans- formation involved the catalytic pyrolysis of sawdust into aromatics, the decomposition of heavier alkylaromatics to toluene, and the liquid-phase oxidation of toluene-rich aromatics to benzoic acid. The production of the desired benzoic acid from the sawdust-derived aro- matics, with the benzoic acid selectivity of 85.1 C-mol% and nearly complete conversion of toluene, was achieved using the MnO2/NHPI catalyst at 100 ℃ for 5 h. The in uence of adding methanol on the catalytic conversion of sawdust to the core intermediate of toluene was also investigated in detail.

Synthesis of Didodecyl Carbonate via Transesterification Catalyzed by KF/MgO

The catalytic properties of KF/MgO for the synthesis of didodecyl carbonate (DDC) by transesterification from dimethyl carbonate (DMC) and dodecanol were studied.The effects of loading amount of KF and calcining temperature were systemically investigated.The phase structure was characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR).Interaction between KF and the carrier MgO occurred in the process of calcination,and a new phase K2MgF4 formed when calcining temperature was 673 K or above.FTIR results showed that K2CO3 was observed when catalysts calcined in air.When calcining temperature was 873 K and the loading mass amount of KF was 30%,the KF/MgO catalyst exhibited the optimal catalytic properties and the yield of DDC was maximized to 80%.The excellent catalytic properties of KF/MgO was ascribed to the formation of K2MgF4+K2CO3 during the calcination in air.

Surface coupling of methyl radicals for efficient low‐temperature oxidative coupling of methane

Selective coupling of methyl radicals to produce C_(2) species(C2H4 and C2H6)is a key challenge for oxidative coupling of methane(OCM).In traditional OCM reaction systems,homogeneous transformation of methyl radicals in O_(2)‐containing gases are uncontrollable,resulting in limited C_(2) selectivity and yield.Herein,we demonstrate that methyl radicals generated by La_(2)O_(3)at low reaction temperature can selectively couple on the surface of 5 wt%Na2WO4/SiO_(2).The controllable surface coupling against overoxidation barely changes the activity of La_(2)O_(3)but boosts the C_(2)selectivity by three times and achieves a C_(2)yield as high as 10.9%at bed temperature of only 570℃.Structure‐property studies suggest that Na_(2)WO_(4) nanoclusters are the active sites for methyl radical coupling.The strong CH_(3)·affinity of these sites can even endow some methane combustion catalysts with OCM activity.The findings of the surface coupling of methyl radicals open a new direction to develop OCM catalyst.The bifunctional OCM catalyst system,which composes of a methane activation center and a CH_(3)·coupling center,may deliver promising OCM performance at reaction temperatures below the ignition temperature of C2H6 and C2H4(~600℃)and is therefore more controllable,safer,and certainly more attractive as an actual process.

Dyestuff wastewater treatment by combined SDS-CuO/TiO_2 photocatalysis and sequencing batch reactor

Combined technology of SDS-CuO/TiO2 photocatalysis and sequencing batch reactor （SBR） were applied to treating dyestuff wastewater. Photocatalysis was carried out in a spiral up-flow type reactor as pre-treatment. SDS-CuO/TiO2 photocatalyst was prepared by modification of nano-TiO2 using CuO and sodium dodecyl sulfate （SDS）. Results show that the SDS-CuO/TiO2 photocatalyst contains two kinds of crystals, including TiO2 and CuO. The band gap of this photocatalyst is 1.56 eV, indicating that it can be excited by visible light （2〈794.87 nm）. And characterization also shows that there are alkyl groups on its surface. It takes 40 rain to improve the biodegradability of dyestuff wastewater. Five-day biochemical oxygen demand （BODs） and dehydrogenase activity （DHA） of wastewater reach the maximum value when dissolved oxygen is higher than 2.97 mg/L. SBR reactor was used to treat this biodegradability improved wastewater. Chemical oxygen demand （COD） and colority decline to 72 mg/L and 20 times, respectively, when the sludge loading is 0.179 kg（COD）/[kg（MLSS）＇d], dissolved oxygen is 4.09 mg/L and aeration time is 10 h.

Redox-triggered hydroarylation of o-(hydroxyalkyl)arylalkynes with arylsulfonyl chlorides using visible light catalysis

A new radical-mediated method for the synthesis of 1-(2-(1,2-diarylvinyl)phenyl)ethan-1-ones by the redox hydroarylation of o-(hydroxyalkyl)arylalkynes with arylsulfonyl chlorides is described. This visible light catalysis method proceeds via a sequence of the radical addition of aryl group across the C?C triple bond, protonation and redox reaction, and represents a new redox transformation reaction directed by a neighboring hydroxyl group.

CsOH catalyzed aerobic oxidative synthesis of p-quinols from multi-alkyl phenols under mild conditions

p-Quinols are ubiquitous structural motifs of various natural products and pharmaceutical compounds,and versatile building blocks in synthetic chemistry.The reported methods for the synthesis of p-quinol require stoichiometric amounts of oxidants.Molecular oxygen is considered as an ideal oxidant due to its natural,inexpensive,and environmentally friendly characteristics.During the ongoing research of C–H bond hydroxylation,we found that multi-alkyl phenols could react with molecular oxygen under mild conditions.Herein,we describe an efficient oxidative de-aromatization of multi-alkyl phenols to p-quinols.1 atm of molecular oxygen was used as the oxidant.Many multi-alkyl phenols could react smoothly at room temperature.Isotopic labeling experiment was also performed,and the result proved that the oxygen atom in the produced hydroxyl group is from molecular oxygen.