Etherification of dimethylbutene with methanol over clay-based acid catalysts

Etherification of a typical C₆ olefin, 2,3-dimethyl-1-butene, with methanol was investigated over commercial ion-exchange resins and several clay-based acid solids prepared by sulfuric acid treatment or impregnation of sulfated zirconia and Nafion. The commercial resin catalyst Amberlyst 15 is effective but nonselective to ether production, while Nafion is less active. For two clay systems, montmorillonite-based catalysts generally exhibit higher activities than bentonite and MT-H₂SO₄will be a highly active and selective catalyst than the supported sulfated zirconia and Nafion.     

Chemical catalysed recycling of waste polymers: Catalytic conversion of polypropylene into fuels and chemicals over spent FCC catalyst in a fluidised-bed reactor

Polypropylene (PP) was pyrolysed over spent FCC commercial catalyst (FCC-s1) using a laboratory fluidised-bed reactor operating isothermally at ambient pressure. The influence of reaction conditions including catalyst, temperature, and ratio of polymer to catalyst feed and flow rates of fluidising gas was examined. The yield of gaseous and liquid hydrocarbon products at 390 °C for spent FCC commercial catalyst (87.8 wt%) gave much higher yield than silicate (only 17.1 wt%). Greater product selectivity was observed with FCC-s1 as a post-use catalyst with about 61 wt% olefins products in the C₃-C₇ range. The selectivity could be further influenced by changes in reaction conditions. Valuable hydrocarbons of olefins and iso-olefins were produced by low temperatures and short contact times used in this study. It is also demonstrated that a post-use catalyst system under appropriate conditions the resource potential of polymer waste can be economically recovered and also can address the recycling desire to see an alternative to solve a major environment problem.     

Heterogenized peroxopolyoxotungstate catalyst on the surface of clicked magnetite‐graphene oxide nanocomposite: Magnetically recoverable epoxidation catalyst

A new heterogeneous catalyst for the epoxidation of olefins was prepared by immobilization of peroxophosphotungstate anions on the surface of clicked magnetite‐graphene oxide as magnetically recoverable support. To prepare the heterogeneous catalyst, the clicked magnetite‐graphene oxide support was prepared by thiolene click reaction of thiol functionalized graphene oxide with vinyl modified magnetite nanoparticles. The tailored support was then modified with aminopropyl groups followed by electrostatic interaction with peroxophosphotungstate anions to achieve the desired heterogeneous catalyst. Characterization of the catalyst was performed by various physicochemical methods which confirmed the successful immobilization of peroxopolyoxotungstate species on the surface of clicked magnetite‐graphene oxide. Catalytic activity of the catalyst revealed its high catalytic activity and selectivity in the epoxidation of various olefins in the presence of H₂O₂ as green oxidant. This heterogeneous catalyst can be magnetically reused several times without significant loss of activity and selectivity.     

Catalytic asymmetric dihydroxylation of olefins with recyclable osmate-exchanged chloroapatite catalyst

An osmate-exchanged chloroapatite (CAP-OsO₄) catalyst was prepared by an ion-exchange technique. CAP-OsO₄ efficiently catalyses asymmetric dihydroxylation of olefins including α,β-unsaturated esters and amides to afford the corresponding diols in high yields and enantioselectivities. The catalyst was reused for several cycles with consistent activity.     

Catalytic cracking of C<Subscript>5</Subscript> raffinate to light olefins over NaOH-treated ZSM-5

A series of ZSM-5 catalysts (ZSM-5 (X)) treated with different NaOH concentration (X = 0, 0.05, 0.1, and 0.2 M) were prepared for use in the production of light olefins (ethylene and propylene) through catalytic cracking of C₅ raffinate. The effect of NaOH concentration on their physicochemical properties and catalytic activity was investigated. It was found that textural and physicochemical properties of ZSM-5 (X) catalysts were strongly influenced by the NaOH concentration. Mesopore volume of ZSM-5 (X) catalysts increased with increasing NaOH concentration, while acidity of the catalysts decreased with increasing NaOH concentration. Conversion of C₅ raffinate and yield for light olefins (ethylene and propylene) showed the volcano-shaped curves with respect to NaOH concentration (X). This implies that NaOH treatment of ZSM-5 was an efficient method to produce light olefins through catalytic cracking C₅ raffinate, and that optimal NaOH concentration was required for maximum production of light olefins. Among the catalysts tested, ZSM-5 (0.05) catalyst showed the best catalytic performance due to its favorable porosity and acidity.     

Catalytic asymmetric dihydroxylation of olefins using polysulfone-based novel microencapsulated osmium tetroxide

A polysulfone based novel polymer-supported osmium catalyst has been developed. The catalyst was prepared from commercially available polysulfone, based on a microencapsulation technique and was employed in the asymmetric dihydroxylation of various olefins using (DHQD)₂PHAL as the chiral ligand and NMO as the co-oxidant in H₂O-acetone-CH₃CN (1:1:1). The catalyst was recovered by simple filtration and was reused to obtain excellent yields with good enantioselectivity up to five times.     

MoO<Subscript>2</Subscript>(acac)<Subscript>2</Subscript> supported on MCM-41: An efficient and reusable catalyst for alkene epoxidation with <Emphasis Type="Italic">tert</Emphasis>-BuOOH

A new heterogeneous catalyst prepared by immobilization of MO₂(acac)₂ on Mobil Catalytic Material, MCM-41, is reported. This catalyst, MoO₂(acac)₂-MCM-41, was successfully applied for efficient epoxidation of olefins with tert-BuOOH in 1,2-dichloroethane as solvent. The catalyst was characterized by elemental analysis, FT-IR, UV-Vis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). This catalyst can be reused several times without significant loss of its catalytic activity.     

Synthesis,characterization, and catalytic activity of supported molybdenum Schiff base complex as a magnetically recoverable nanocatalyst in epoxidation reaction

A heterogeneous nanocatalyst was prepared via covalent anchoring of dioxomolybdenum(VI) Schiff base complex on core–shell structured Fe₃O₄@SiO₂. The properties and the nature of the surface-fixed complex have been identified by a series of characterization techniques such as SEM, EDX, XRD, TGA, FT-IR, and VSM. The synthesized hybrid material was an efficient nanocatalyst for selective oxidation of olefins to corresponding epoxides with t-BuOOH in high yields and selectivity. The catalyst could be conveniently recovered by applying an external magnetic field and reused several times without significant loss of efficiency.     

Preparation of modified Ce-SAPO-34 catalysts and their catalytic performances of methanol to olefins

The modified Ce-SAPO-34 catalysts were prepared with three methods, i.e., the liquid ion exchange with air calcination, impregnation with air calcination and impregnation with steam calcination methods. The catalytic performances of the catalysts for methanol to olefins were investigated. The properties of the catalysts were characterized using XRD, BET, XRF, FT-IR and NH₃-TPD. The results indicated that compared to the SAPO-34 catalyst the catalyst prepared with the impregnation and air calcination prolonged the lifetime by 40 min and improved the selectivity to ethylene by 5% (mol) and the catalyst prepared with the impregnation and steam calcination showed the best modification effect, prolonging the lifetime by 70 min and improving the ethylene selectivity by 10% (mol). The catalyst prepared with the liquid ion exchange showed similar behaviour as the SAPO-34 catalyst. It was verified that the porous structure and surface acidity of these catalysts determined their catalytic behaviors.     

Catalytic Transformation of Bio-oil to Olefins with Molecular Sieve Catalysts

Catalytic conversion of bio-oil into light olefins was performed by a series of molecular sieve catalysts, including HZSM_-5, MCM_-41, SAPO_-34 and Y_-zeolite. Based on the light olefins yield and its carbon selectivity, the production of light olefins decreased in the following order:HZSM_-5>SAPO_-34>MCM_-41>Y_-zeolite. The highest olefins yield from bio-oil using HZSM_-5 catalyst reached 0.22 kg/kg_bio-oil with carbon selectivity of 50.7% and a nearly complete bio-oil conversion. The reaction conditions and catalyst characterization were investigated in detail to reveal the relationship between the catalyst structure and the production of olefins. The comparison between the pyrolysis and catalytic pyrolysis of bio-oil was also performed.     

钯配合物催化烯烃氧化合成酮类物质的研究进展

本文系统地评述了钯配合物催化烯烃氧化合成酮类物质的研究进展。综述了改进Wacker 类催化剂催化活性的几种方法。总结了烯烃氧化合成酮类物质反应的几种典型催化体系及其作用机理。着重介绍了Pd (Ⅱ) HPA (杂多酸)、Pd (Ⅱ) FePc (酞菁铁)、Pd (Ⅱ) HQ (氢醌) FePc、Pd (Ⅱ) HQHPA、Pd (Ⅱ) CuSO₄ HPA 等Wacker 类催化体系在烯烃氧化合成酮类物质中的应用; 对Pd (Ⅱ) LCoNO₂、PdCl₂(MeCN)₂ CuCl、Pd (OAc)₂ 吡啶、氟两相等非Wacker 类催化体系在烯烃氧化合成酮类物质中的应用也作了讨论。     

Rod-shaped porous alumina-supported Cr2O3 catalyst with low acidity for propane dehydrogenation

Direct catalytic propane dehydrogenation (PDH) to obtain propylene is a more economical and environmentally friendly route for propylene production. In particular, alumina-supported Cr₂O₃ catalysts can have better potential applications if the acidic properties could be tuned. Herein, a series of rod-shaped porous alumina were prepared through a hydrothermal route, followed by calcination. It was found that the acidity of the synthesized alumina was generally lower than that of the commercial alumina and could be adjusted well by varying the calcination temperature. Such alumina materials were used as supports for active Cr₂O₃, and the obtained catalysts could enhance the resistance to coke formation associated with similar activity in PDH reaction compared to the commercial alumina. The amount of coke deposited on a self-made catalyst (Cr-Al-800) was 3.6%, which was much lower than that deposited on the reference catalyst (15.7%). The lower acidity of the catalyst inhibited the side reactions and coke formation during the PDH process, which was beneficial for its high activity and superior anti-coking properties.     

The Synthesis of Some t- Alkylnaphthalenes

Alkylation of aromatics with olefins using boron trifluoride-phosphoric acid has been reported to give high yields of monoalkylates with a minimum of side reactions.¹ However, much of this previous work was carried out without the use of modern techniques to separate and identify various fractions. Relatively little, in general, is known about the products resulting from the reaction of naphthalene with olefins using acidic catalysts.^1,2,3 This is probably because of the difficulty involved in separating the various isomers. The relatively mild and non-destructive properties reported for boron trifluoride-phosphoric acid catalyst suggested that it might be suitable for the preparation of 2-t-alkyl naphthalene derivatives in high yield and with little isomerization. This proved to be true and below are reported t- alkylnaphthalenes prepared from olefins using this catalyst.     

Mild hydrotreating over NiMo/sepiolite catalyst

Summary In order to introduce an alternative catalyst for hydrotreating (HDT) reaction a study of NiMo supported on natural sepiolite catalysts is presented. The sepiolite catalyst has been prepared in this laboratory and a NiMo/Al₂O₃ commercial catalyst is used as a reference. The textural properties of the materials and their catalytic activity in hydrotreating (HDT) and hydrodesulfuration (HDS) using a FCC feed at 400-475°C and 50 MPa total pressure, have been evaluated. The support of the commercial catalyst is alumina containing mesopores. The sepiolite support is a hydrated magnesium phylosilicate containing micropores but with an open structure that confers the possibility to use it as a catalyst. The hydrotreating conversion (wt.% HDT) is defined here as the net hydrotreating conversion into products boiling below 380°C. For the commercial catalyst the wt.% HDT was only 5% higher than for the catalyst supported on sepiolite and the product selectivity was very similar. HDS conversion was 20% lower for the sepiolite supported catalyst. Taking into account these results the sepiolite is a suitable support of HDS catalysts.     

[Cu(H2btec)(bipy)]∞: Reusable Metal Organic Polymer Catalyst for Epoxidation Reactions

Summary: The search of new inorganic materials with better catalytic properties is an important field of research. Reusability, efficiency and atom economy correspond to the main parameters to characterize a catalyst. In this work, we inform the effectiveness of [Cu(H₂btec)(bipy)]_∞ (H₄btec = 1,2,4,5-benzenetetracarboxylic acid) as an heterogeneous coordination polymer catalyst for the oxidation of olefins. The catalyst exhibits good atom economy, high turnover numbers and good selectivity for a ratio of 4000/1 substrate/catalyst for cyclohexene and styrene oxidation. Furthermore, the catalyst was recycled and reused for seven consecutive cycles, retaining the structural integrity and effectiveness as catalyst in all the performed experiments.     

席夫碱Mo(VI)功能化介孔SiO2的制备及其催化烯烃环氧化研究

采用共缩聚法制备有机-无机杂化材料,以介孔SiO_2材料为载体,分别嫁接席夫碱配体和配位乙酰丙酮钼,得到Mo(VI)席夫碱修饰的介孔SiO_2(Mo-SB-Cl-SiO_2-0.5-1).所制备的材料采用XRD,SEM,N2吸附-脱附和TEM技术对其结构进行了表征.考察了Mo-SB-Cl-SiO_2-0.5-1催化液相烯烃环氧化性能,结果表明:Mo-SB-Cl-SiO_2-0.5-1催化剂对烯烃环氧化具有高的转化率和优良的催化活性.与后嫁接法制备的催化剂相比,Mo-SB-Cl-SiO_2-0.5-1催化剂催化活性得到明显提高,催化环己烯环氧化的转化率和选择性分别为85%和99%.在不同烯烃的研究中,环辛烯具有最高的转化率和选择性,分别为87%和99%.催化剂重复使用4次后,环己烯的转化率没有明显下降,选择性仍然高达98%,表明Mo-SB-Cl-SiO_2-0.5-1具有较好的催化稳定性.     

Silica‐coated nano‐Fe3O4‐supported iminopyridine palladium complex as an active,phosphine‐free and magnetically separable catalyst for Heck reactions

A novel magnetic nanoparticle‐supported iminopyridine palladium complex was successfully prepared by attaching palladium acetate to iminopyridine ligand‐functionalized silica‐coated nano‐Fe₃O₄. The as‐prepared catalyst was well characterized and was evaluated in Heck reactions in terms of activity and recyclability. It was found to be highly efficient for the reactions of various aryl iodides and aryl bromides having electron‐withdrawing groups with olefins under phosphine‐free and inert atmosphere‐free conditions. Moreover, the catalyst could be conveniently recovered using an external magnet, and the recyclability was influenced by the base in the Heck reaction. The catalyst could be reused at least six times with no significant loss in activity when triethylamine acted as the base.     

Alternating copolymer of butadiene and propylene. III

Alternating copolymerizations of butadiene with propylene and other olefins were investigated by using VO(acac)₂–Et₃Al–Et₂AlCl system as catalyst. Butadiene–propylene copolymer with high degree of alternation was prepared with a monomer feed ratio (propylene/butadiene) of 4. Alternating copolymers of butadiene and other terminal olefins such as butene-1, pentene-1, dodecene-1, and octadiene-1,7 were also obtained. However, the butadiene–butene-2 copolymerization did not yield an alternating copolymer but a trans-1,4-polybutadiene.     

Synthesis of poly(2‐ethylhexyl acrylate)/clay nanocomposite by in situ living radical polymerization

This investigation reports the preparation of tailor‐made poly(2‐ethylhexyl acrylate) (PEHA) prepared via in situ living radical polymerization in the presence of layered silicates and characterization of this polymer/clay nanocomposite. Being a low T_g (?65 °C) material, PEHA has very good film formation property for which it is used in paints, adhesives, and coating applications. 2‐Ethylhexyl acrylate was polymerized at 90 °C using CuBr and Cu(0) as catalyst in combination with N,N,N′,N″,N″‐pentamethyl diethylenetriamine (PMDETA) as ligand. A tremendous enhancement in reaction rate and polymerization data was achieved when acetone was added as additive to increase the efficiency of the catalyst system. PEHA/clay nanocomposite was prepared at 90 °C using CuBr as catalyst in combination with PMDETA as ligand. Different types of clay with same loading were also used to study the effect on reaction rate. The molecular weight (M_n) and polydispersity index of the prepared nanocomposites were characterized by size exclusion chromatography. The active end group of the polymer chain was analyzed by ¹H NMR analysis and by chain extension experiment. Polymer/clay interaction was studied by Fourier Transform Infrared spectrometry and wide‐angle X‐ray diffraction analyses. Distribution of clay in the polymer matrix was studied by the transmission electron microscopy. Thermogravimetric analysis showed that thermal stability of PEHA/clay nanocomposite increases on addition of nanoclay. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Phosphine-free rhodium-catalyzed hydroarylation of diaryl acetylenes with boronic acids

Rh(CO)₂(acac) was found to be an efficient and simple catalyst in hydroarylation of diaryl acetylenes with boronic acids in the absence of phosphine ligand. Thus, triaryl-substituted olefins were prepared in good to excellent yields. No 1,4-rhodium shift was observed in the catalytic cycle.