Effect of Oxygen Capacity and Oxygen Mobility of Pure Bismuth Molybdate and Multicomponent Bismuth Molybdate on their Catalytic Performance in the Oxidative Dehydrogenation of n-Butene to 1,3-Butadiene

Pure bismuth molybdate (γ-Bi₂MoO₆) and multicomponent bismuth molybdate (Co₉Fe₃Bi₁Mo₁₂O₅₁) catalysts were prepared by a co-precipitation method, and were applied to the oxidative dehydrogenation of n-butene to 1,3-butadiene. The Co₉Fe₃Bi₁Mo₁₂O₅₁ catalyst showed a better catalytic performance than the γ-Bi₂MoO₆ catalyst in terms of conversion of n-butene and yield for 1,3-butadiene, indicating that the multicomponent bismuth molybdate was more efficient than the pure bismuth molybdate in the oxidative dehydrogenation of n-butene. It was revealed that the crucial factor determining the catalytic performance of Bi–Mo-based catalyst in the oxidative dehydrogenation of n-butene is not the amount of oxygen in the catalyst involved in the reaction (oxygen capacity) but the intrinsic mobility of oxygen in the catalyst involved in the reaction (oxygen mobility). The enhanced catalytic performance of Co₉Fe₃Bi₁Mo₁₂O₅₁ was due to its facile oxygen mobility.     

丁烯氧化脱氢钼铋系催化剂:晶相之间的协同效应

钼铋系催化剂以其优良的性能一直以来都是丁烯氧化脱氢研究和应用的热点。本文简述了已有研究中对钼铋系催化剂及改性后的多组分催化剂的晶相结构及其与反应性能间关系的研究进展。指出在钼铋催化剂中,有较多晶格缺陷的α-Bi₂(MoO₄)₃提供吸附位,氧流动性较强的γ-Bi₂MoO₆提供晶格氧,二者的协同作用提高了催化剂的活性。而在改性后的多组分钼铋系催化剂中,添加的组分与钼铋元素结合生成新的晶相,产生了更多的晶格缺陷及氧供体,从而提升了催化性能。对于钼铋系催化剂进一步改进的方向,本文认为在添加组分的方法基础上,还可以从催化剂表面结构方面入手,进行进一步的深入探究。     

Microwave assisted solvent-free synthesis of dihydropyrimidinones by Biginelli reaction over Si-MCM-41 supported FeCl3 catalyst

Among the Si-MCM-41 or montmorillonite K 10 clay supported ZnCl₂, AlCl₃, GaCl₃, InCl₃ and FeCl₃ catalysts, FeCl₃/Si-MCM-41 shows best performance for the microwave-assisted synthesis of dihydropyrimidinones by the Biginelli reaction involving multicomponent condensation of aromatic aldehyde, ethyl acetoacetate and urea in the absence of any solvent. It is a promising catalyst for the microwave-assisted reaction providing high product yield in a short period (3.0–5.0 min).     

Novel stereo controlled glycosylation of 1,2,3,4,6-penta-o-acetyl-β-d-glucopyranoside using MgO–ZrO2 as an environmentally benign catalyst

Glycosylation reactions are most commonly encountered in nature. Synthetically, glycosylations are carried out with Lewis acid catalysts or mineral acids. However an environmental threat associated with catalysts has encouraged process modification by alternative development of solid catalysts based glycosylation reactions, which are commercially viable as well. In this contribution comparative study of glycosidic bond formation of 1,2,3,4,6-penta-o-acetyl-β-d-glucopyranoside with various alcohols over variety of reaction promoters/catalyst like p-toluene sulphonic acid, HCl, H₂SO₄ and MgO–ZrO₂ were taken up to evaluate the performance of this potential promoter/catalysts systems. The best catalyst for the selective synthesis of alkyl-β-d-glucopyranosides was MgO–ZrO₂ which remains active upto three runs. This replacement of homogeneous acid catalysts by heterogeneous base catalyst shows alkyl-β-d-glucopyranoside as major product at comparatively low temperature range. The effects of variety of parameters were studied in a batch reactor. The mechanism of the reaction over basic mixed metal oxide at 363 K is put forth.     

Oxidative dehydrogenation of n-butene to 1,3-butadiene over multicomponent bismuth molybdate (M9Fe3Bi1Mo12O51) catalysts: Effect of divalent metal (M)

Multicomponent bismuth molybdate (M^II₉Fe₃Bi₁Mo₁₂O₅₁) catalysts with different divalent metal (M^II = Mg, Mn, Co, Ni, and Zn) were prepared by a co-precipitation method, and were applied to the oxidative dehydrogenation of n-butene to 1,3-butadiene. Effect of divalent metal (M^II) on the catalytic performance of M^II₉Fe₃Bi₁Mo₁₂O₅₁ catalysts was investigated. X-ray photoelectron spectroscopy (XPS) measurements were conducted to determine the oxygen mobility of M^II₉Fe₃Bi₁Mo₁₂O₅₁ catalysts. It was found that the catalytic performance of M^II₉Fe₃Bi₁Mo₁₂O₅₁ catalysts was closely related to the oxygen mobility of the catalysts. The yield for 1,3-butadiene was monotonically increased with increasing oxygen mobility of the catalysts. Among the catalysts tested, the Co₉Fe₃Bi₁Mo₁₂O₅₁ catalyst with the highest oxygen mobility showed the best catalytic performance in the oxidative dehydrogenation of n-butene.     

Transesterification of Pistacia chinensis oil for biodiesel catalyzed by CaO-CeO2 mixed oxides

This study investigates the use of CaO-CeO₂ mixed oxides as solid base catalysts for the transesterification of Pistacia chinensis oil with methanol to produce biodiesel. These CaO-CeO₂ mixed-oxide catalysts were prepared by an incipient wetness impregnation method and characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. The cerium improved the heterogeneous catalytic stability remarkably due to the defects induced by the substitution of Ca ions for Ce ions on the surface. The best catalyst was determined to be C0.15-973 (with a Ce/Ca molar ratio of 0.15 and having been calcined at 973 K), considering its catalytic and anti-leaching abilities. The effects of reaction parameters such as the methanol/oil molar ratio, the amount of catalyst amount and the reaction temperature were also investigated. For the C0.15-973 regenerated after five reuses, the biodiesel yield was 91%, which is slightly less than that of the fresh sample. The test results revealed that the CaO-CeO₂ mixed oxides have good potential for use in the large-scale biodiesel production.     

Preparation of Cu/ZnO catalyst using a polyol method for alcohol-assisted low temperature methanol synthesis from syngas

A polyol method was used to prepare Cu/ZnO catalysts for alcohol-assisted low temperature methanol synthesis from syngas. Unlike conventional low temperature methanol synthesis, ethanol was employed both as a solvent and a reaction intermediate. Catalyst characterization revealed that Cu/ZnO catalysts were successfully and efficiently prepared using the polyol method. Various preparation conditions such as PVP concentration and identity of ZnO precursor strongly influenced the catalytic activity of Cu/ZnO catalysts. Copper dispersion and catalyst morphology played key roles in determining the catalytic performance of the Cu/ZnO catalyst in alcohol-assisted low temperature methanol synthesis. A high copper dispersion and platelike Cu/ZnO structure led to high catalytic activity. Among the catalysts tested, 5_Cu/ZnO_Zn(Ac)₂ had the best catalytic performance due to its high copper dispersion.     

Phosgene-Free Synthesis of Phenyl Isocyanate by Catalytic Decomposition of Methyl N-Phenyl Carbamate over Bi2O3 Catalyst

A phosgene-free approach for the synthesis of phenyl isocyanate (PI) was developed, using the heterogeneous catalytic decomposition of methyl N-phenyl carbamate (MPC). Twenty oxide-catalysts were investigated and compared; the Bi₂O₃ catalyst gave the better catalytic performance. From bismuth (III) nitrate pentahydrate, Bi₂O₃ was prepared by different methods, which included the direct decomposition, mechano-chemical method, direct precipitation and indirect precipitation. The catalysts were characterized by N₂ adsorption/desorption, XRD, FTIR and TEM analyses. After optimization, the Bi₂O₃ catalyst prepared by direct calcination of bismuth (III) nitrate pentahydrate at 723 K in air for 4 h gives the best activity. When the reaction was carried out at the boiling temperature of o-dichlorobenzene (ODCB) at normal pressure, the optimal reaction conditions over Bi₂O₃ catalyst are as follows: the mass ratio of catalyst/MPC is 0.05, mass ratio of ODCB/MPC is 15:1, reaction time of 60 min. The optimized conversion of MPC and the yield of PI are 86.2% and 78.5%, respectively. There was a good durability for the Bi₂O₃ catalyst, and the species of Bi (III) ions of catalyst were partially oxidized to Bi (IV) ions during the reaction, supported by the results of XRD and XPS techniques.     

The effects of catalysts in biodiesel production: A review

Biodiesel fuel has shown great promise as an alternative to petro-diesel fuel. Biodiesel production is widely conducted through transesterification reaction, catalyzed by homogeneous catalysts or heterogeneous catalysts. The most notable catalyst used in producing biodiesel is the homogeneous alkaline catalyst such as NaOH, KOH, CH₃ONa and CH₃OK. The choice of these catalysts is due to their higher kinetic reaction rates. However because of high cost of refined feedstocks and difficulties associated with use of homogeneous alkaline catalysts to transesterify low quality feedstocks for biodiesel production, development of various heterogeneous catalysts are now on the increase. Development of heterogeneous catalyst such as solid and enzymes catalysts could overcome most of the problems associated with homogeneous catalysts. Therefore this study critically analyzes the effects of different catalysts used for producing biodiesel using findings available in the open literature. Also, this critical review could allow identification of research areas to explore and improve the catalysts performance commonly employed in producing biodiesel fuel.     

EPOXIDATION OF FUNCTIONALIZED OLEFINS OVER SOLID CATALYSTS

Heterogeneous catalytic epoxidation of functionalized olefins in the liquid phase has been reviewed, focusing on catalyst performance and its interrelation with the crucial parameters of the catalytic systems. Efficient catalysts include supported and mixed oxides, framework-substituted (“redox”) molecular sieves, layered-type materials, heterogenized homogeneous catalysts, and some others. Among the various substrates, allylic and homoallylic alcohols, and unsaturated carbonyl compounds have received most attention so far. The great variety of available catalysts enables selective epoxidation of most substituted olefins. The mechanistic understanding of heterogeneous catalytic epoxidation is still underdeveloped, rendering catalyst design rather empirical. A considerable potential for future development lies in the area of “heterogenization” of successful homogeneous catalysts especially for asymmetric epoxidation. Crucial requirements in the development of heterogeneous catalytic epoxidation catalysts are, besides good catalytic performance and cheap oxidant, recyclability and resistance to leaching of the active component. Some of the examples shown in the literature do not fulfill the latter requirement.     

Hydroformylation of mixed octenes catalyzed by supported rhodium-based catalyst

In order to solve the difficult separation between catalyst and products in homogeneous system, the activated carbon (AC)-supported rhodium-based catalyst (Rh/AC) was prepared. Hydroformylation of mixed octenes catalyzed by Rh/AC was studied, and compared to that catalyzed by RhCl(CO)(TPPTS)₂ [TPPTS: trisodium salt of tris(m-sulphonylphenyl) phosphine], and [Rh(CH₃COO)₂]₂-Ph₃PO (Ph₃PO: triphenyl phosphine oxide). The performance test of the catalysts showed the Rh/AC presented higher catalytic activity, selectivity and air-stability. During the recycle experiments Rh/AC could be used 4 times without significant loss of rhodium. The effects of the supports, rhodium loading and reaction conditions on the catalytic performance of Rh/AC were investigated. The results showed petroleum coke-based activated carbon with higher surface area and more basic groups was advantageous to the formation of aldehydes. The heterogeneous Rh/AC catalyst displayed higher catalytic activity and reusability.     

EPOXIDATION OF FUNCTIONALIZED OLEFINS OVER SOLID CATALYSTS

Heterogeneous catalytic epoxidation of functionalized olefins in the liquid phase has been reviewed, focusing on catalyst performance and its interrelation with the crucial parameters of the catalytic systems. Efficient catalysts include supported and mixed oxides, framework-substituted (“redox”) molecular sieves, layered-type materials, heterogenized homogeneous catalysts, and some others. Among the various substrates, allylic and homoallylic alcohols, and unsaturated carbonyl compounds have received most attention so far. The great variety of available catalysts enables selective epoxidation of most substituted olefins. The mechanistic understanding of heterogeneous catalytic epoxidation is still underdeveloped, rendering catalyst design rather empirical. A considerable potential for future development lies in the area of “heterogenization” of successful homogeneous catalysts especially for asymmetric epoxidation. Crucial requirements in the development of heterogeneous catalytic epoxidation catalysts are, besides good catalytic performance and cheap oxidant, recyclability and resistance to leaching of the active component. Some of the examples shown in the literature do not fulfill the latter requirement.     

Organofunctionalized catalyst surfaces highly active and selective for carbon–carbon bond-forming reactions

This article illustrates two types of organofunctionalized heterogeneous catalysts for variety of organic carbon–carbon bond-forming reactions, summarizing our previous reports and also presenting new data. Organic amines with an alkoxysilane moiety were immobilized on inorganic silica-alumina surfaces (SA-NR₂) by simple silane-coupling reactions between the silica-alumina surface (SA) and the alkoxysilane. This SA-NR₂ acted as acid–base bifunctional heterogeneous catalysts for carbon–carbon bond-forming reactions, such as cyano-ethoxycarbonylation, Michael reaction of nitriles, and nitro-aldol reaction. These reactions did not occur with either SA or homogeneous amine compounds. In addition, the mixture of SA and homogeneous amine showed low catalytic activity due to undesirable acid–base neutralization reaction. Achiral organic silane-coupling reagents with a variety of functional groups were also immobilized on a SiO₂ surface that had been immobilized with chiral bis(oxazoline) (BOX), to which Cu ions were coordinated to make chiral Cu–BOX complexes on the SiO₂ surface. The SiO₂-supported Cu–BOX complex catalyst functionalized with achiral 3-methacryloxypropyltrimethoxysilane dramatically increased enantioselectivity in the asymmetric Diels–Alder reaction of cyclopentadiene and 3-acryloyl-2-oxazolidinone. The organofunctionalized catalysts showed much better performances for the C–C bond-forming reactions compared to the corresponding homogeneous systems. The heterogeneous catalysts thus obtained were characterized by solid-state ¹³C and ²⁹Si MAS NMR, FT-IR, UV/vis, XAFS, ESR, XRF, and elemental analysis.     

Die großtechnische Oxosynthese mit immobilisiertem Katalysator

Industrial Oxo Synthesis with Immobilised Catalyst. The use of water-soluble catalysts represents a significant advance in homogeneous catalysis; “immobilisation” of the catalyst in a second immiscible liquid phase has the effect of “heterogenisation” and allows the advantages of heterogeneous processing (long lifetimes, straightforward technology) to the combined with those of the homogeneous mode (gentle reaction conditions, high activity and selectivity). In particular, the decisive advantage of homogeneous catalysts, viz. the wide range of variation of their steric and electronic properties which can be adapted to the specific reaction at hand, can be exploited for tailoring highly effective catalysts. Moreover, the mode of action of these homogeneous catalysts remains understandable as a model and under the reaction conditions chosen – in complete contrast to the case of many heterogeneous catalytic systems. The first successful industrial application of water-soluble catalysts was in the oxo process of Ruhrchemie/Rhǒne Poulenc. The following article reports on ten years' experience with this process and the HRh(CO)[P(msulphophenyl-Na)₃]₃ catalyst.     

One Pot Synthesis of Methyl N-Phenyl Carbamate from Aniline, Urea and Methanol

Methyl N-phenyl carbamate (MPC) was synthesized from aniline, urea and methanol. The effects of catalysts, loading amounts, preparation condition of catalyst and reaction condition on the synthesis of MPC were investigated. It was shown that KNO₃ modified zeolite HY gave the best performance to MPC formation among the evaluated catalysts, over which 93.1% aniline conversion and 82.6% MPC selectivity were obtained under the optimum reaction condition. Additionally, a possible catalytic mechanism to the formation of MPC in this reaction was proposed.     

Catalytic performance of multicomponent bismuth molybdates (NiXFe3Bi1Mo12O42+X) in the oxidative dehydrogenation of C4 raffinate-3 to 1,3-butadiene: Effect of nickel content and acid property

Multicomponent bismuth molybdate (Ni_XFe₃Bi₁Mo₁₂O_42+X) catalysts were prepared by a co-precipitation method with a variation of nickel content, and were applied to the oxidative dehydrogenation of C₄ raffinate-3 to 1,3-butadiene. Conversion of n-butene and selectivity for 1,3-butadiene over Ni_XFe₃Bi₁Mo₁₂O_42+X catalysts showed volcano-shaped curves with respect to nickel content. As a consequence, yield for 1,3-butadiene also showed a volcano-shaped curve with respect to nickel content. Among the catalysts tested, Ni₉Fe₃Bi₁Mo₁₂O₅₁ showed the best catalytic performance. Acid properties of Ni_XFe₃Bi₁Mo₁₂O_42+X catalysts were measured by NH₃-TPD experiments, with the aim of correlating the catalytic performance with the acid property of the catalysts. It was observed that either total acidity or acid strength was not directly correlated with the catalytic performance of Ni_XFe₃Bi₁Mo₁₂O_42+X catalysts. However, the conversion of n-butene was increased with increasing surface acidity of the catalyst. The largest surface acidity of the Ni₉Fe₃Bi₁Mo₁₂O₅₁ catalyst was responsible for its enhanced catalytic performance in the oxidative dehydrogenation of C₄ raffinate-3. The facile oxygen mobility of the γ-Bi₂MoO₆ phase in the Ni₉Fe₃Bi₁Mo₁₂O₅₁ catalyst also played an important role in enhancing the catalytic performance of the Ni₉Fe₃Bi₁Mo₁₂O₅₁ catalyst.     

Effect of Divalent Metal Component (MeII) on the Catalytic Performance of MeIIFe2O4 Catalysts in the Oxidative Dehydrogenation of n-Butene to 1,3-Butadiene

A series of metal ferrite (Me^IIFe₂O₄) catalysts were prepared by a co-precipitation method with a variation of divalent metal component (Me^II = Zn, Mg, Mn, Ni, Co, and Cu) for use in the oxidative dehydrogenation of n-butene to 1,3-butadiene. Successful formation of metal ferrite catalysts with a random spinel structure was confirmed by XRD, ICP-AES, and XPS analyses. The catalytic performance of metal ferrite catalysts in the oxidative dehydrogenation of n-butene strongly depended on the identity of divalent metal component. Acid properties of metal ferrite catalysts were measured by NH₃-TPD experiments, with an aim of correlating the catalytic performance with the acid property of the catalysts. It was revealed that the yield for 1,3-butadiene increased with increasing surface acidity of the catalyst. Among the catalysts tested, ZnFe₂O₄ catalyst with the largest surface acidity showed the best catalytic performance in the oxidative dehydrogenation of n-butene.     

Lattice oxide ion-transfer effect demonstrated in the selective oxidation of propene over silica-supported bismuth molybdate catalysts

Silica-supported bismuth molybdate catalysts were prepared by impregnation in a highly dispersed state and by coprecipitation in a largely crystallized state. Their catalytic behavior was investigated in the oxidation of propene to acrolein. The highly dispersed bismuth molybdate catalysts on silica were found to be intrinsically active but poorly selective to acrolein. When we increased the loading amount the oxidation activity drastically increased. The poor acrolein selectivity of this catalyst was improved by continuous use in the catalytic oxidation for making the particle size of the dispersed bismuth molybdate larger. The catalytic activity and selectivity were little influenced by the loading amount in the cases of the coprecipitated catalysts. The results demonstrate that, for the activity and selectivity, bismuth molybdate catalysts need to be of a certain particle size which can provide sufficient lattice oxide ions during the catalytic redox cycle.     

Hybrid organic-inorganic Cu(II) iminoisonicotine@TiO2@Fe3O4 heterostructure as efficient catalyst for cross-couplings

Two novel mononuclear copper (II) complex catalysts were synthesized from a new tridentate iminoisonicotine ligand (HL) by coordination with Cu(II) ion, with (CuL@TiO₂@Fe₃O₄) and without (CuL) immobilization on TiO₂-coated nanoparticles of Fe₃O₄. The ester moiety on the back of the ligand was utilized for immobilization on nanoparticles of Fe₃O₄. Both ligand and CuL complex were fully characterized by using alternative spectral techniques (nuclear magnetic resonance, infrared, ultraviolet-visible and mass spectroscopy, and elemental analyses). Different analytical techniques were used to identify the structural feature and morphology of the immobilized copper catalyst (CuL@TiO₂@Fe₃O₄) shell-shell-core system. The structural analysis revealed that the catalyst system is composed of both agglomerated nanospheres and deformed nanorods. Both copper catalysts, immobilized CuL@TiO₂@Fe₃O₄ and un-immobilized CuL were studied in heterogeneous and homogeneous catalysis, respectively, for Suzuki-Miyaura (C–C) and Buchwald-Hartwig (C–N) cross-coupling reactions of various heteroaryl halides. Both catalysts showed good catalytic potential under the controlled optimal reaction conditions. In contrast to the homogeneous catalyst (CuL), the heterogeneous catalyst (CuL@TiO₂@Fe₃O₄) showed slightly better catalytic performance. The characteristic obtains supported the catalytic potential of the current samples. Reusability/recycling of both catalysts was also investigated in C–C cross-coupling reactions. It was found that the homogeneous catalyst (CuL) could be only recycled up to three times, whereas the heterogeneous one (CuL@TiO₂@Fe₃O₄) could be reused up to seven times with good efficiency.     

钼铋复合金属氧化物催化低碳烯烃选择氧化制备醛类研究进展

低碳烯烃选择氧化制备醛类等含氧化合物是生产有机化工中间体及产品的关键步骤,钼铋复合金属氧化物因其优异的催化性能在相关工业界和学术界受到广泛关注,然而目前关于该催化剂上选择氧化反应机制和催化反应本质等科学问题的认识尚未形成统一理论。本文系统综述了钼铋复合金属氧化物在催化低碳烯烃选择氧化制备醛类反应中的研究进展,包括催化剂微观结构的三种调控手段,即主组分钼酸铋物相结构、助剂及载体等对反应性能的影响,并对反应机理进行了深入讨论与总结。最后展望了钼铋复合金属氧化物在该选择氧化反应中的发展前景,为钼铋复合金属氧化物修饰改性及开发高效低碳烯烃选择氧化制含氧化合物催化剂提供思路。