Selective hydroformylation–acetalization of various olefins using simple and efficient Rh-phosphinite complex catalyst

A simple and efficient Rh-phosphinite complex catalyst was studied for the selective hydroformylation of various olefins. The influence of various reaction parameters including the effect of temperature, pressure, catalyst loading, time, and solvents was studied. The protocol was also applied for the synthesis of various acetals via tandem hydroformylation–acetalization of olefins in alcohols as solvents. High activity and selectivity for acetal formation was achieved in the absence of co-catalysts with admirable substrate to catalyst mole ratio (TON 2500). The developed protocol works for a wide range of olefins to synthesize corresponding aldehydes and acetals under optimized reaction conditions.     

A hexafluorobenzene promoted ring-closing metathesis to form tetrasubstituted olefins

Highly efficient formation of tetrasubstituted olefins is described by ring-closing metathesis (RCM) using catalyst 2 in presence of hexafluorobenzene. This combination with hexafluorobenzene shows an unexpected promoting effect, which requires low catalysts loadings and allows the conversion of deficient olefins in high yields and very short reaction times.     

Development of a Ruthenium/Phosphite Catalyst System for Domino Hydroformylation–Reduction of Olefins with Carbon Dioxide

An efficient domino ruthenium‐catalyzed reverse water‐gas‐shift (RWGS)‐hydroformylation‐reduction reaction of olefins to alcohols is reported. Key to success is the use of specific bulky phosphite ligands and triruthenium dodecacarbonyl as the catalyst. Compared to the known ruthenium/chloride system, the new catalyst allows for a more efficient hydrohydroxymethylation of terminal and internal olefins with carbon dioxide at lower temperature. Unwanted hydrogenation of the substrate is prevented. Preliminary mechanism investigations uncovered the homogeneous nature of the active catalyst and the influence of the ligand and additive in individual steps of the reaction sequence.     

Carbon nanotubes-supported palladium nanoparticles for the Suzuki reaction in supercritical carbon dioxide: A facile method for the synthesis of tetrasubstituted olefins

A facile and efficient method for the synthesis of tetrasubstituted olefins in supercritical carbon dioxide was developed by using carbon nanotubes-supported palladium nanoparticles (Pd/CNTs) as the catalyst. Compared with common Pd/C, Pd/CNTs could more effectively catalyze the reaction of dibromo-substituted olefins with boronic acids, affording the corresponding tetrasubstituted olefins with moderate to good yields. This environmentally benign route with an easy-to-handle catalyst provides an appealing alternative to the currently available methods.     

Phosphine‐ and Hydrogen‐Free: Highly Regioselective Ruthenium‐Catalyzed Hydroaminomethylation of Olefins

A highly regioselective ruthenium‐catalyzed hydroaminomethylation of olefins is reported. Using easily available trirutheniumdodecacarbonyl an efficient sequence consisting of a water‐gas shift reaction, hydroformylation of olefins, with subsequent imine or enamine formation and final reduction is realized. This novel procedure is highly practical (ligand‐free, one pot) and economic (low catalyst loading and inexpensive metal). Bulk industrial as well as functionalized olefins react with various amines to give the corresponding tertiary amines generally in high yields (up to 92 %), excellent regioselectivities (n/iso>99:1), and full chemoselectivity in favor of terminal olefins.     

FCC汽油低温改质过程的烯烃转化及催化剂积炭

利用微反-色谱联合实验装置和连续式小型提升管催化裂化实验装置研究了催化裂化汽油低温改质过程中烯烃转化和催化剂积炭的过程和规律。通过对模型化合物和催化裂化汽油改质过程中催化剂活性、催化裂化汽油窄馏分、反应温度、剂油比和反应时间对烯烃转化和催化剂积炭的研究表明,大部分烯烃转化和催化剂积炭的反应发生在油剂接触极短的反应时间内,并随着催化剂活性、反应物活性、剂油比和反应温度的提高而增加。在油剂接触后很长的反应时间内,生焦量、积炭速率和烯烃的转化程度都很小,烯烃转化损失率降低,因此,催化裂化汽油在低温改质的条件下可以通过延长反应时间来提高烯烃的转化率。因此,催化裂化汽油改质的最佳工艺条件为,390℃～440℃,剂油比6,催化剂活性61～65,长反应时间,轻馏分进料。     

PRODUCTION OF LIGHT OLEFINS FROM CO2 HYDROGENATION OVER Fe/SILICALITE-2 CATALYST III. PROMOTION EFFECT OF K2O PROMOTER

K2O is a vital promoter to the Fe-MnO/silicalite-2 catalyst for light olefin formation from CO2 hydrogenation. With addition of it into the Fe-MnO/Si-2 catalyst the selectivity to light olefins increases greatly, while CH4 formation is inhibited evidently. Meanwhile, an obvious increment in CO2 conversion is also observed with the addition of K2O promoter. And it has been manifested that adding K2O to the Fe-MnO/Si-2 catalyst leads to remarkable increases in both the capacity and strength of the strong CO2 and CO adspecies. These produce much more[Cad] via their disproportionation at higher temperatures. This results in increase in the CO2 conversion and the selectivity to light olefins, and a decrease in CH4 formation.     

Visible light-induced partial oxidation of olefins on Cr-containing silica with molecular oxygen

Photocatalytic oxidation of olefins on Cr-containing silica with molecular oxygen by visible light irradiation (lambda > 400 nm) has been investigated. Cr-SiO(2) catalyst prepared by a conventional sol-gel method, containing highly dispersed chromate species, catalyzes efficient olefin oxidation with very high selectivity for partially oxidized products (>90%), whereas semiconductor TiO(2) promotes complete decomposition (CO(2) production). The Cr-SiO(2) catalyst shows much higher activity than Cr/SiO(2) prepared by an impregnation method or Cr proportional variant MCM-41 prepared by a templating method. ESR analysis reveals that photoirradiation of the chromate species with a tetrahedral coordination (T(d)(6+)) on Cr/SiO(2) and Cr proportional variant MCM-41 catalysts leads to the formation of excited state T(d)(5+) species (T(d)(5+*)), while irradiation to T(d)(6+) on Cr-SiO(2) produces T(d)(4+*) species. This can be explained by a homogeneous T(d)(6+) arrangement with Si species on the Cr-SiO(2) catalyst. On the strongly reduced T(d)(4+*), olefins are strongly attracted by an electron and/or proton donation, resulting in high oxidation activity. The Cr-SiO(2) catalyst is applicable to partial oxidation of various aliphatic and aromatic olefins with very high selectivity, and does not promote undesirable dimerization. The obtained findings suggest a potential use of Cr-SiO(2) as an efficient and recyclable heterogeneous photocatalyst for partial oxidation of olefins.     

Efficient epoxidation of electron-deficient olefins with a cationic manganese complex

The complex [MnII(R,R-mcp)(CF3SO3)2] is an efficient and practical catalyst for the epoxidation of electron-deficient olefins. This catalyst is capable of epoxidizing olefins with as little as 0.1 mol % catalyst in under 5 min using 1.2 equiv of peracetic acid as the terminal oxidant. A wide scope of substrates are epoxidized including terminal, tertiary, cis and trans internal, enones, and methacrylates with >85% isolated yields.     

Enzymatic-like mediated olefins epoxidation by molecular oxygen under mild conditions

Highly efficient epoxidation of olefins by molecular oxygen with catalytic amount of manganese meso-tetraphenylporphyrin (Mn(TPP)) at the ppm level were reported. The catalyst conferred high activity and selectivity for the olefins epoxidation under ambient temperature and atmospheric pressure. The turnover number (TON) of the catalyst could reach up to 700 million, which is comparable to enzyme catalysis.     

Efficient aziridination of olefins catalyzed by a unique disilver(I) compound

A unique disilver(I) compound is an efficient catalyst for aziridination of olefins.     

Highly enantioselective cyclopropanation of trisubstituted olefins

A highly efficient asymmetric cyclopropanation of trisubstituted olefins with methyl diazoacetate has been developed in terms of an elaborate modified chiral bisoxazoline/copper complex as a catalyst. A broad scope of substrates is compatible with this catalyst system, including various trisubstituted olefins bearing different aryl-, fused aryl- and alkyl-substituents, providing an easy access to optically active 1,1-dimethyl cyclopropanes in good yields with excellent diastereo- and enantio-selectivity.     

An improved synthesis of a ketone catalyst for asymmetric epoxidation of olefins

An efficient synthesis of a ketone catalyst for asymmetric epoxidation of olefins from D-glucose in six steps is described.     

Hydrogenation of unsaturated compounds in the presence of palladium-containing modified carbon nanofibers

Palladium-containing carboxylated carbon nanofibers were studied as catalysts for hydrogenation of double bond >C=C< in olefins, unsaturated alcohols, and acids, as well as for hydrogenation of nitroarenes. The developed catalyst is 7 times more efficient than the industrial analog (Pd/C).     

Suppression of methane formation during Fisher-Tropsch synthesis using manganese-cobalt oxide supported on H-5A zeolite as a catalyst

In Fischer-Tropsch synthesis reaction, methane formation is one of the side reactions which must be suppressed in order to get better catalytic selectivity for light olefins. In the present study, we have modified cobalt based Fischer-Tropsch catalyst and developed a process to minimize methane production, consequently to produce maximum yield of light olefins. Manganese-cobalt oxide supported on H-5A zeolite catalyst was synthesized using modified H-5A zeolite, to increase its surface acid sites. Increased acidity of zeolite plays a major part in the suppression of methane formation during the Fischer-Tropsch reaction. The modified zeolite results in the electronic modification of catalyst surface by creating new active catalytic sites. The results are compared with other supported catalysts along with unmodified zeolite. Appreciable reduction in methane formation is achieved on modified zeolite supported catalyst in comparison with unsupported catalyst.     

Silica-alumina supported transition metal oxide catalyst for alkylation of aromatic compounds

Titanium oxide on silica-alumina support is described to be an efficient regenerable catalyst for alkylation of aromatic compounds with alkyl halides, alcohols and olefins, and the reaction is proposed to be initiated by the protonated metal active species present in the catalyst.     

Novel palladium(II) complex containing a chelating anionic N-O ligand: efficient carbonylation catalyst

[reaction: see text] A novel palladium(II) complex containing chelating anionic pyridine-2-carboxylato and labile tosylato ligands is a highly efficient catalyst for the carbonylation of organic alcohols and olefins to carboxylic acids/esters. Carbonylation of primary, secondary, and tertiary alcohols as well as linear and functionalized terminal olefins was studied. In all cases remarkable activity and selectivity were observed. The catalyst is stable under reaction conditions even in the absence of excess phosphine ligands.     

Design of a highly efficient catalyst for the oxaziridinium-mediated epoxidation of olefins by Oxone

2,3,3-Trimethyl-7-nitro-3,4-dihydroisoquinolinium tetrafluoroborate is a highly efficient catalyst for the oxaziridinium-mediated epoxidation of a variety of olefins, including monosubstituted ones.     

碳纳米管封装铁纳米粒子催化剂上CO加氢制低碳烯烃

由于石油资源的逐步枯竭,近年来费托(F-T)反应因其可以高效将煤、天然气和生物质等转化成液体燃料和高值化学品而越来越受到人们的关注。相比于Co, Ni和Ru等F-T催化剂, Fe基催化剂因其价格低廉,产物分布广而被广泛研究。以合成气直接制备低碳烯烃的F-T过程为例,铁基催化剂通常会因积碳和烧结的问题,而导致失活。因此,人们通常使用一些氧化物载体,比如氧化硅,氧化铝或者分子筛来分散并稳定铁粒子。但是这类氧化物载体通常与铁有非常强的相互作用,特别是在铁粒子较小的情况下,容易生成一些难于还原的硅酸铁和铝酸铁。而活性炭、碳纤维等惰性载体与铁的相互作用较弱,不足以稳定小的铁粒子在而反应过程中聚集。近来,我们组提出了利用石墨烯碳层封装过渡金属粒子作为催化剂,利用“穿透”的金属电子来催化反应,从而可以使活性中心和反应介质隔离,有效地增强了非贵金属催化剂的活性和稳定性。在此基础上,我们组和其他课题组的研究表明,一系列石墨烯碳层封装的非贵金属催化剂在燃料电池阴极氧还原反应,电催化析氢反应,染料敏化太阳能电池中的I3–还原反应以及催化氧化还原反应中都有着广泛的应用前景。这种材料中碳层不仅能在氧化气氛、酸性介质中保护包覆的金属,防止其被氧化或者腐蚀,还与包覆的金属有着较强的相互作用,可以促进非贵金属的电子向碳层表面的转移,有望在一些苛刻的反应条件下实现对贵金属催化剂的替代。本文进一步拓展了其在高温反应中的应用,发现豆荚状碳纳米管封装的金属铁纳米粒子在合成气制备低碳烯烃中可以有效防止金属铁纳米粒子的烧结和聚集,因此表现出优异的低碳烯烃选择性和催化稳定性。我们利用一步化学反应法合成了豆荚状碳纳米管封装的铁纳米粒子催化剂(Pod-Fe),并通过酸洗除去碳管外面裸露的铁粒子。透射电镜(TEM)和X射线衍射(XRD)表明酸洗后铁粒子被包覆在碳管内,并且呈金属态,而酸洗前,则还有大量的氧化铁粒子分布于碳管外部(FeOx/Pod-Fe)。将酸洗前后的两个催化剂用于固定床气相F-T反应中。通过调节空速和温度考察了它们的催化反应性能,结果表明两个催化剂在不同的反应条件下都有着良好的低碳烯烃选择性。不同反应温度下,它们表现出不同的变化趋势：Pod-Fe活性随着温度的升高而缓慢增长,至380 oC都没有明显的失活现象;而对于FeOx/Pod-Fe催化剂,随着温度的升高, CO的转化率先升高,在300 oC时达最高,但随着温度进一步升高,活性迅速降低,呈现一个火山型曲线。 TEM结果发现,反应后FeOx/Pod-Fe催化剂粒子上产生了很多杂乱的碳丝,并且铁粒子有着明显的聚集长大。而Pod–Fe催化剂即使在380 oC反应后,其形貌仍然保持完好,没有积碳产生,粒子也没有发生聚集和长大。进一步在320 oC下120 h的寿命试验发现, Pod-Fe催化剂的初始活性较低,但经20 h的活化阶段,活性会先增加后略有下降,20 h后趋于稳定。而FeOx/Pod-Fe催化剂在反应初始虽然表现出较高的活性,但是随着时间进行,活性迅速下降一半以上,最后趋于稳定。同时结合反应后TEM和XRD的结果发现碳管外部裸露的铁粒子会在反应过程中形成碳化铁物种,并随着反应进行产生聚集,并伴有大量积碳,导致活性迅速下降;而碳层的包覆对于铁粒子有着很好的稳定作用,使得铁粒子能够在高温反应中保持稳定,并且没有积碳的产生。由此可见石墨烯碳层可以有效保护其包覆的金属粒子,并且能够提高其在高温反应下的低碳烯烃选择性和稳定性。此类催化剂有望在一些苛刻条件下的多相催化反应中得到广泛应用。     

新型四氮锰配合物催化烯烃环氧化反应的研究

合成了一种新型四氮配体(1,3-bis(pyridin-2-ylmethyl)imidazolidine)及其相应的锰(MnⅡ)配合物,并将其应用于催化过氧乙酸氧化烯烃的环氧化反应中,考察了催化剂当量及氧化剂当量等一系列条件对反应结果的影响,并在优化条件下研究了各种底物的适用范围,最终取得了很好的化学选择性及85％～9...