scholarly journals Exploring Basic Components Effect on the Catalytic Efficiency of Chevron-Phillips Catalyst in Ethylene Trimerization

2018 ◽  
Author(s):  
Ebtehal Naji-Rad ◽  
Martí Gimferrer ◽  
Naeimeh Bahri-Laleh ◽  
Mehdi Nekoomanesh-Haghighi ◽  
Roghieh Jamjah ◽  
...  
Keyword(s):  
Density Functional ◽  
Catalytic Efficiency ◽  
Catalyst System ◽  
Ethylene Oligomerization ◽  
Side Reactions ◽  
Phillips Catalyst ◽  
Ethylene Trimerization ◽  
Main Components ◽  
Catalytic Cycles ◽  
Work Effect

In the present work, effect of basic components on the energy pathway of ethylene oligomerization by landmark Chevron-Phillips catalyst has been explored in detail using density functional theory (DFT). Studied factors were chosen considering the main components of Chevron-Phillips catalyst, i.e. ligand, cocatalyst and halocarbon compounds, comprising i) the type of alkyl substituents in pyrrole ligand as methyl, iso-propyl, tert-butyl, and phenyl, as well as the simple hydrogen, and the electronwithdrawing fluoro and trifluoromethyl; ii) the number of Cl atoms in Al-compound (as AlMe2Cl, AlMeCl2 and AlCl3) which indicates halocarbon amount and iii) cocatalyst type as alkylboron, alkylaluminium, or alkylgallium. Besides main ingredients, solvent effect, from toluene or methylcyclohexane, on oligomerization pathway was explored as well. In this regard, the full catalytic cycles for the main product (1-hexene) formation as well as side reactions, i.e. 1-butene release and chromacyclononane formation, were calculated on the basis of the metallacycle based mechanism. Based on results, a modification on the Chevron-Phillips catalyst system, to reach higher 1-hexene selectivity and activity, is suggested.

Ionic binuclear ferrocenyl compounds containing 1,1,3,3-tetracyanopropenide anions – synthesis, structural characterization and catalytic effects on thermal decomposition of main components of solid propellants

2015 ◽  
Vol 70 (5) ◽  
pp. 317-326 ◽  
Author(s):  
Dongmei Zhao ◽  
Jizhen Li ◽  
Fuqiang Bi ◽  
Yahui Yang ◽  
Xiaoni Gao ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Density Functional ◽  
Catalytic Efficiency ◽  
Density Functional Theory Calculations ◽  
Redox System ◽  
Molecular Structures ◽  
Solid Propellants ◽  
Composite Solid Propellants ◽  
Main Components ◽  
Catalytic Effects

AbstractAlkyl-substituted ferrocenes are typical burning-rate catalysts in composite solid propellants, but their high migration tendency and volatility has impeded their extensive applications. By introducing the concept of ionic energetic compounds, eight new ionic binuclear ferrocenyl compounds, [FcCH2N(CH3)2(CH2)nN(CH3)2CH2Fc]2+ (X–2) (Fc = ferrocenyl; X– = 1,1,3,3-tetracyano propenide; n = 3–10; the compounds being numbered consecutively 1–8), were prepared and characterized. The molecular structures of 1, 2, and 4 were determined by single-crystal X-ray diffraction, and their cations were studied by density functional theory calculations (DFT). Compounds 1–5 show high thermal stability but 6–8 are slightly volatile. The results of cyclic voltammetry studies suggest that each salt exhibits a quasireversible redox system. Catalytic effects of the new salts on thermal degradation of ammonium perchlorate (AP), 1,3,5-trinitro-1,3,5-triaza-cyclo-hexane (RDX), and 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), have been investigated by DSC and/or TG methods. The results show that the new compounds can bring the peak temperatures of both AP and RDX down significantly and enhance their heat release dramatically, indicating that the ferrocenyl salts possess high catalytic efficiency for the thermal decomposition of AP and RDX. Their catalytic activities are nearly equal to or higher than that of the corresponding nitrates and picrates, as well as their mononuclear counterparts. Compound 6 also efficiently catalyzes the thermal decomposition of hydroxyl-terminated polybutadiene (HTPB) and 1:1 mixtures of HTPB and AP.

scholarly journals Exploring Basic Components Effect on the Catalytic Efficiency of Chevron-Phillips Catalyst in Ethylene Trimerization

Catalysts ◽  
2018 ◽  
Vol 8 (6) ◽  
pp. 224 ◽  
Author(s):  
Ebtehal Naji-Rad ◽  
Martí Gimferrer ◽  
Naeimeh Bahri-Laleh ◽  
Mehdi Nekoomanesh-Haghighi ◽  
Roghieh Jamjah ◽  
...  
Keyword(s):  
Catalytic Efficiency ◽  
Phillips Catalyst ◽  
Ethylene Trimerization

Metathetical Degradation and Depolymerization of Unsaturated Polymers

1997 ◽  
Vol 70 (3) ◽  
pp. 519-529 ◽  
Author(s):  
J. C. Marmo ◽  
K. B. Wagener
Keyword(s):  
Molecular Weight ◽  
Transition Metal ◽  
Catalytic System ◽  
Lewis Acid ◽  
Catalyst System ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Side Reactions

Abstract The employment of transition metal catalysts has been a viable route in the degradation and depolymerization of unsaturated polymers. Initially, unsaturated polymers were degraded with a catalytic system containing a transition metal and a Lewis acid cocatalyst (WCl6/SnBu4). Degradation chemistry was effective in reducing the molecular weight of the polymer, however, the classical catalyst system induces side reactions which generates ill-defined products. These side reactions were obviated by using a preformed alkylidene without a Lewis acid cocatalyst, and perfectly difunctional telechelics were synthesized.

scholarly journals Porphyrin-based homogeneous catalysts for the CO2 cycloaddition to epoxides and aziridines

2019 ◽  
Vol 23 (04n05) ◽  
pp. 305-328 ◽  
Author(s):  
Daniela Intrieri ◽  
Caterina Damiano ◽  
Paolo Sonzini ◽  
Emma Gallo
Keyword(s):  
Catalytic Efficiency ◽  
Bifunctional Catalysts ◽  
Fine Chemicals ◽  
Cyclic Carbonates ◽  
Metal Porphyrin ◽  
Co Catalysts ◽  
Component Systems ◽  
Two Component ◽  
Two Component Systems ◽  
Catalytic Cycles

The direct insertion of carbon dioxide (CO2) into three-membered rings, such as epoxides and aziridines, represents a relevant strategy to obtain cyclic carbonates and oxazolidinones, which are two useful classes of fine chemicals. The synthesis of these compounds can be efficiently catalyzed by a combination of metal porphyrin complexes and various co-catalysts in homogeneous systems. The catalytic efficiency of these systems is discussed herein by taking into account both the characteristics of the metals and the nature of the co-catalysts, either when used as two-component systems or when combined in bifunctional catalysts. Moreover, mechanistic proposals of the CO2 cycloaddition processes are reported to provide a rationale of catalytic cycles in order to pave the way for designing more active and efficient catalytic procedures.

scholarly journals Density functional theory (DFT) investigation on the structure and photocatalysis properties of double-perovskite Gd1−xCaxBaCo2O5+δ (0 ≤ x ≤ 0.4)

RSC Advances ◽  
2019 ◽  
Vol 9 (35) ◽  
pp. 20161-20168
Author(s):  
Rong Zhang ◽  
Bo Xiang ◽  
Lei Xu ◽  
Liru Xia ◽  
Chunhua Lu
Keyword(s):  
Density Functional Theory ◽  
Charge Transfer ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Catalytic Efficiency ◽  
Double Perovskite ◽  
Functional Theory ◽  
Ca Doping ◽  
Valence States

Ca-doping affects the overall catalytic efficiency by adjusting the distribution of Co valence states and oxygen vacancies due to the strengthening of the charge transfer between O-2p and Co-3d orbitals upon substitution of Gd by Ca.

scholarly journals Second-Generation Manganese(III) Porphyrins Bearing 3,5-Dichloropyridyl Units: Innovative Homogeneous and Heterogeneous Catalysts for the Epoxidation of Alkenes

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 967 ◽  
Author(s):  
Neves ◽  
Rebelo ◽  
Faustino ◽  
Neves ◽  
Simões
Keyword(s):  
Heterogeneous Catalysts ◽  
Second Generation ◽  
Supported Catalyst ◽  
Catalytic Efficiency ◽  
Major Product ◽  
Aqueous Hydrogen Peroxide ◽  
Tert Butyl Hydroperoxide ◽  
Merrifield Resin ◽  
Catalytic Cycles ◽  
First Time

The synthesis, characterisation and homogeneous catalytic oxidation results of two manganese(III) porphyrins of the so-called second-generation of metalloporphyrin catalysts, containing one or four 3,5-dichloropyridyl substituents at the meso positions are reported for the first time. The catalytic efficiency of these novel manganese(III) porphyrins was evaluated in the oxidation of cyclooctene and styrene using aqueous hydrogen peroxide as the oxidant, under homogeneous conditions. High conversions were obtained in the presence of both catalysts, obtaining the corresponding epoxide as the major product. The asymmetric metalloporphyrin, chloro[5,10,15-tris(2,6-dichlorophenyl)-20-(3,5-dichloropyridin-4-yl)porphyrinate]manganese(III), CAT-4, evidences a similar activity to that obtained with the well-known and highly efficient second-generation metalloporphyrin catalyst, chloro[5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrinate]manganese(III), CAT-2. CAT-4 was covalently attached onto Merrifield resin and 3-bromopropylsilica supports. The solid materials obtained were characterized by several techniques including diffuse reflectance, UV—VIS spectrophotometry, SEM and XPS. The catalytic results for the oxidation of cyclooctene and styrene using the immobilized catalysts are also presented. The Merrifield-supported catalyst showed to be very efficient, leading to five catalytic cycles in the oxidation of cyclooctene, using tert-butyl hydroperoxide as the oxidant.

scholarly journals Treponema denticola cystalysin exhibits significant alanine racemase activity accompanied by transamination: mechanistic implications1

2003 ◽  
Vol 371 (2) ◽  
pp. 473-483 ◽  
Author(s):  
Mariarita BERTOLDI ◽  
Barbara CELLINI ◽  
Alessandro PAIARDINI ◽  
Martino Di SALVO ◽  
Carla BORRIVOLTATTORNI
Keyword(s):  
Kinetic Parameters ◽  
Binding Sites ◽  
Ph Dependence ◽  
Catalytic Efficiency ◽  
Partition Ratio ◽  
Side Reactions ◽  
Treponema Denticola ◽  
Steady State Kinetic ◽  
Reaction Specificity ◽  
State Kinetic

To obtain information on the reaction specificity of cystalysin from the spirochaete bacterium Treponema denticola, the interaction with l- and d-alanine has been investigated. Binding of both alanine enantiomers leads to the appearance of an external aldimine absorbing at 429nm and of a band absorbing at 498nm, indicative of a quinonoid species. Racemization and transamination reactions were observed to occur with both alanine isomers as substrates. The steady-state kinetic parameters for racemization, kcat and Km, for l-alanine are 1.05±0.03s−1 and 10±1mM respectively, whereas those for d-alanine are 1.4±0.1s−1 and 10±1mM. During the reaction of cystalysin with l- or d-alanine, a time-dependent loss of β-elimination activity occurs concomitantly with the conversion of the pyridoxal 5′-phosphate (PLP) coenzyme into pyridoxamine 5′-phosphate (PMP). The catalytic efficiency of the half-transamination of l-alanine is found to be 5.3×10−5 mM−1·s−1, 5-fold higher when compared with that of d-alanine. The partition ratio between racemization and half-transamination reactions is 2.3×103 for l-alanine and 1.4×104 for d-alanine. The pH dependence of the kinetic parameters for both the reactions shows that the enzyme possesses a single ionizing residue with pK values of 6.5–6.6, which must be unprotonated for catalysis. Addition of pyruvate converts the PMP form of the enzyme back into the PLP form and causes the concomitant recovery of β-elimination activity. In contrast with other PLP enzymes studied so far, but similar to alanine racemases, the apoform of the enzyme abstracted tritium from C4′ of both (4′S)- and (4′R)-[4′-3H]PMP in the presence of pyruvate. Together with molecular modelling of the putative binding sites of l- and d-alanine at the active site of the enzyme, the implications of these studies for the mechanisms of the side reactions catalysed by cystalysin are discussed.

Theoretical insights into the reactivity of Fe-based catalysts for water oxidation: the role of electron-withdrawing groups

2018 ◽  
Vol 20 (21) ◽  
pp. 14919-14926 ◽  
Author(s):  
Penglin Xu ◽  
Shaojin Hu ◽  
Hou-Dao Zhang ◽  
Xiao Zheng
Keyword(s):  
Density Functional Theory ◽  
Water Oxidation ◽  
Density Functional ◽  
Catalytic Efficiency ◽  
Oxidation Catalysts ◽  
Functional Theory

The relative catalytic efficiency of a series of Fe-based water oxidation catalysts is elucidated by comprehensive calculations using density functional theory methods.

Chromium-Based Catalyst for Ethylene Tetramerization to 1-Octene

2011 ◽  
Vol 347-353 ◽  
pp. 3392-3395
Author(s):  
Bao Jun Zhang ◽  
Bu Wei Yu ◽  
Gang Wang ◽  
Jian Zhong Li ◽  
Si Han Wang ◽  
...  
Keyword(s):  
Catalyst System ◽  
Ethylene Oligomerization ◽  
Steric Effects ◽  
Molar Ratio ◽  
Ethylene Tetramerization ◽  
Electric Effects

Novel diphoshinoamine(PNRNP) ligands have been used in ethylene oligomerization with Cr(III) compounds and cocatalyst. The results indicate that the catalyst system can yield 1-octene in selectivities up to 80%. Another novel diphoshinoamine ligands (((Ar2P)2N)2R)(R=cyclopropylamine) also were synthesized and characterized. Factors which affect the result of ethylene tetramerisation, such as cocatalyst, temperature, pressure and the molar ratio of Al/Cr were examined. Steric effects and electric effects were also considered in this report.

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