An in situ IR spectroscopic study of methanol conversion on an SNM-1 catalyst

Kinetics and Catalysis - According to data obtained by spectrokinetic measurements under the reaction conditions of methanol conversion, formate and carbonate complexes were detected on the surface...     

CO_2加氢制甲醇用高活性和高选择性催化剂的研制

研制了一种CO2加氢制甲醇用高活性和高选择性催化剂Cu-ZnO-Al2O3(简记为RK-11),测定了其催化性能.结果表明,当原料气组成(体积分数)为68.5%H2、2.0%CO、20.5%CO2、9.0%N2,温度为240℃,气体时空速度GHSV=6 000h-1,压力为8.0MPa时,CO2转化率达35.2%,CO转化率达39.8%,甲醇的时空产率达686.1g/(L·h),而甲醇在产物中的选择性达99.3%.     

Thexyldimethylsilyl chloride,an easily accessible reagent for the protection of alcohols

The silylation of alcohols, amines, amides, mercaptans and acids with the readily available thexyldimethylsilyl chloride (TDS-Cl) is described. The stabilities of the silyl ethers are examined using different cleavage conditions and compared in part with the stabilities of the corresponding tert-butyldimethylsilyl derivatives.     

Dicatechol-diimines: easily accessible ligands for the self-assembly of dinuclear triple-stranded helicates

Dicatechol ligands 3b-g-H4 are simply prepared by imine formation of 2,3-dihydroxybenzaldehyde 2 with a series of different diamines 1b-g . An X-ray structural analysis was obtained for the butyl-bridged compound 3e-H4, showing an intramolecular proton transfer and the formation of a chinoidic "keto-amine" structure. The dicatechol derivatives 3b-g-H4 form dinuclear triple-stranded helicates M4[(3)3Ti2] with titanium(IV) ions in the presence of alkali-metal carbonate. For the phenyl- and the trans-1,4-cyclohexyl-bridged complexes, K4[(3b)3Ti2] and Na4[(3f)3Ti2], X-ray structures were obtained.     

Nature of the active component of copper-zinc-aluminium catalyst for methanol synthesis

Comparative studies of the catalytic properties and thermal stability of a copper-zinc-aluminium catalyst and its components have revealed that the catalytic activity is determined by a solid solution of copper and aluminium in zinc oxide containing OH^– and CO ₃ ^2– groups in its anion skeleton. The presence of aluminium in the solid solution ensures the increase of the catalyst thermal stability in the reaction medium.

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-- , , OH^– CO ₃ ^2– -. .

     

Carbon nanofiber supported palladium catalyst for liquid-phase reactions: An active and selective catalyst for hydrogenation of cinnamaldehyde into hydrocinnamaldehyde

Carbon nanofibers (CNFs) prepared by decomposition of ethane over a Ni/alumina catalyst, are used as support for palladium clusters. The carbon support displays a mean diameter of 40–50 nm, lengths up to several tens of micrometers, as highlighted by transmission electron microscopy (TEM) observations and a specific surface area of about 50 m²/g. The spheroidal palladium particles have a relatively homogeneous and sharp size distribution, centered at around 4 nm. This novel Pd/carbon nanofiber catalyst displays unusual catalytic properties and is successfully used in the selective hydrogenation of the C=C bond in cinnamaldehyde at a reaction temperature of around 80°C, under continuous hydrogen flowing at atmospheric pressure. The high performances of this novel catalyst in terms of efficiency and selectivity are, respectively, related to the inhibition of the mass-transfer processes over this non-porous material and to peculiar palladium–carbon interactions. It is concluded that the absence of microporosity in the carbon nanofibers favours both the high activity and selectivity which is confirmed by comparison with the commercially available high surface area charcoal supported palladium catalyst.     

Copper supported on phenanthroline-functionalized porous polymer as an active catalyst for the oxidative carbonylation of methanol

Porous organic polymer has recently attracted tremendous interest because of its potential to combine the best features of homogeneous and heterogeneous catalysts. In this study, copper supported on phenanthroline-functionalized porous polymer (Cu@PCP-Phen) was prepared by a co-polymerization method and used as a heterogeneous catalyst for dimethyl carbonate synthesis via the oxidative carbonylation of methanol. The catalyst was characterized by N₂ adsorption, scanning electron microscopy, transmission electron microscopy, ¹³C solid-state nuclear magnetic resonance, and X-ray photoelectron spectroscopy, which suggested that it possessed a big surface area, hierarchical porous structure, and strong electron-donating effect toward copper species. The Cu@PCP-Phen catalyst showed high catalytic activity, which was significantly higher than those achieved with Cu-based catalysts under similar reaction conditions. In addition, the catalyst can be easily separated and reused at least six times with only a slight decrease in activity. The salient features of this protocol are the simplicity in handling of the catalyst, high catalytic activity, excellent selectivity, low copper leaching, and good catalyst recyclability.     

Cu-SSZ-39, an active and hydrothermally stable catalyst for the selective catalytic reduction of NOx

A Cu-exchanged SSZ-39 zeolite has been synthesized and tested for the selective catalytic reduction (SCR) of NOx. This material shows an excellent catalytic activity, and most importantly, an extraordinary hydrothermal stability.     

Observation of an unprecedented Cu Bis-His site: crystal structure of the H129V mutant of nitrite reductase

Copper nitrite reductases contain both an electron-transfer type 1 Cu site and a catalytic type 2 Cu site. We have mutated one of the type 2 copper ligating histidines to observe the effect on catalytic turnover. This mutation has created a unique site where Cu is ligated by 2 His Nepsilon2 atoms alone.     

Water-soluble palladium nanoparticles as an active catalyst for highly selective hydrogenation of nitrobenzene to aniline

Palladium (Pd) nanoparticles (NPs) stabilized by tri-block copolymer polyoxyethylene–polyoxypropylene–polyoxyethylene (P123) micelles were synthesized in water using a hydrogenation reduction method. Well-dispersed P123 micelles in the aqueous phase favored the stabilization of Pd NPs. The P123–Pd micellar catalyst was first applied in the liquid phase hydrogenation of nitrobenzene (NB), showing excellent catalytic activity, and the only reaction product detected was aniline (AN). Using water as the reaction medium and under mild conditions, both the preparation of catalysts and NB hydrogenation were convenient and environmentally friendly. Under the optimal conditions, the isolated catalyst phase could be recycled at least five times, and the catalytic activity and selectivity remained unchanged. A reaction scheme was suggested. First-order kinetics was determined at 3.0 MPa hydrogen pressure and temperature 30–75 °C, and the activation energy was 40.18 kJ mol^?1. This work provides an environmentally benign and effective method for the hydrogenation of NB to AN.     

Synthesis of beta-lactones: a highly active and selective catalyst for epoxide carbonylation

A new highly active and selective catalyst for the synthesis of beta-lactones from CO and epoxides is reported. The catalyst, [(N,N'-bis(3,5-di-tert-butylsalicylidene) phenylenediamino)Al(THF)2][Co(CO)4] ([(salph)Al(THF)2][Co(CO)4]) is easily prepared from the corresponding (salph)AlCl and NaCo(CO)4. At 50 degrees C and 880 psi of CO, the catalyst (1 mol %) carbonylates epoxides such as propylene oxide, 1-butene oxide, epichlorohydrin, and isobutylene oxide to the lactones beta-butyrolactone, beta-valerolactone, gamma-chloro-beta-butyrolactone, and beta-methyl-beta-butyrolactone in high yield. (R)-Propylene oxide was carbonylated to (R)-beta-butyrolactone with retention of stereochemistry.     

Nickel supported carbon nanofibers as an active and selective catalyst for the gas-phase hydrogenation of 2-tert-butylphenol

Nickel supported fishbone carbon nanofibers (CNFs) have been prepared by vacuum impregnation (VI) and homogeneous deposition-precipitation (HDP) methods with different nickel loadings (ca. 5%, 9% and 12%) with the aim to study the influence of the metal incorporation method and the nickel loading in the catalytic activity of gas-phase hydrogenation of 2-tert-butylphenol (2-TBP). Moreover, the influence of the nature of the support was also studied by preparing nickel catalysts supported on other carbon (active carbon (AC) and graphite (G)) and non-carbonaceous materials (alumina (AL) and yttria-stabilized zirconia (YSZ)). Different techniques were employed to characterize both the supports and the final Ni catalysts: atomic absorption spectrometry, N(2) adsorption-desorption analysis, temperature-programed reduction (TPR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Catalytic results revealed that the nickel particle size and support properties affected directly to both the catalytic activity of hydrogenation of 2-TBP, and the rate of secondary reactions such as cis to trans isomerization and 2-tert-butylcyclohexanone (2-TBCN) hydrogenation.     

Fe/SiO_2纳米复合物上合成气制低碳烯烃催化性能研究

分别采用一步合成法和常规共沉淀法制备了Fe/SiO2催化剂,通过N2物理吸附、X射线衍射、透射电镜、傅里叶变换红外光谱和程序升温还原等方法对催化剂进行了表征,并在固定床反应器中对其费托合成制低碳烯烃的催化性能进行了评价。结果表明,与共沉淀铁基催化剂不同,采用一步合成法制备的纳米复合物主要由Fe3O4相构成,形貌呈规则球形,平均粒径为30 nm,尺寸分布窄,更容易还原。一步合成法制得的Fe/SiO2催化剂对费托合成反应具有较高的活性和低碳烯烃选择性、较低的甲烷选择性和良好的稳定性。     

The selective dealkylations: the formylations of the three easily accessible calix[4]arene conformers immobilized by propyl and isopropyl groups

Formyl groups were introduced to the para positions of the three easily accessible calix[4]arene conformers immobilized by four propyl or isopropyl groups by Duff reaction. Propyl group led to exhaustively formylated products due to the weak steric hinderance effect. While as for the isopropoxy calix[4]arenes, with the increase of steric hinderance, 1,3-alternate conformer gave exhaustively formylated product with no alkyl group dealkylating; partial cone conformer gave the tetraformylated proximal A,B-diether in 1,3-alternate conformation; and cone conformer led to triformylated derivatives accompanied by the selective dealkylations of three or two diametrical alkyl groups. The results indicated that the structures of the products were greatly influenced by the steric hinderance effect of the starting compounds.     

An ultrastable and easily regenerated HOF for the selective storage and separation of light hydrocarbons

正Recently,crystalline porous materials such as metal-organic frameworks(MOFs)and covalent organic frameworks(COFs)have attracted much interest not only in chemistry but also in materials science due to their tunable structures and functional channels.They have some inherent disadvantages of being difficult to solution process and recovery,which might limit their wide usage.As a new kind of porous crystals,hydrogen-bonded organic frameworks(HOFs)have     

Mesoporous iron phosphate as an active, selective and recyclable catalyst for the synthesis of nopol by Prins condensation

Mesoporous iron phosphate is found to be a highly active and recyclable heterogeneous catalyst for the selective synthesis of nopol by Prins condensation of beta-pinene and paraformaldehyde in acetonitrile at 80 degrees C.     

TiO2-anatase-supported oxorhenate catalysts prepared by oxidative redispersion of metal Re0 for methanol conversion to methylal: A multi-technique in situ/operando study

TiO₂-anatase-supported rhenium catalysts were prepared by oxidative redispersion of metallic rhenium. The structure and the activity of the as-prepared catalysts were found to be similar to those prepared by the incipient wetness impregnation technique. Interestingly, our results suggest that the active phase of those catalysts retain oxorhenate species in which the rhenium could be involved as Re⁶⁺ in small clusters, as suggested by UV–visible absorption and XPS experiments. Such catalysts were found to be highly active in methanol conversion to methylal. However, we have evidenced that the low rhenium surface coverage catalyst is prone to surface poisoning because of the formation of rhenium carbonyl species and coke in the absence of oxygen. A comprehensive multi-techniques in situ and operando study made it possible to show that the redox couple(s) implied in the target reaction involve Re⁷⁺, Re⁶⁺and Re⁴⁺ species and to make a rational link between the pieces of the puzzle.     

Alumina as an versatile catalyst for the selective acetalization of aldehydes

Alumina was found to be an effective and convenient catalyst for acetalization of aldehydes to the corresponding 1,3-dioxoranes and 1,3-dioxanes. It can be used for selective protection of only formyl group of ketoaldehydes.