The polymerization of ethylene on chromium oxide catalysts II. Infrared studies

1972 ◽  
Vol 329 (1579) ◽  
pp. 375-390 ◽  
Keyword(s):  
Catalytic Activity ◽  
Adsorbed Water ◽  
Oxidation Products ◽  
Polymerization Reaction ◽  
Oxide Surface ◽  
Hydroxyl Groups ◽  
Hydrogen Atoms ◽  
Chromium Vi ◽  
Infrared Studies ◽  
Chromium Oxide Catalysts

Ethylene reduces silica supported chromium(VI) oxide catalyst at 300 °C and adsorbs as ethyl groups by a self-hydrogenation mechanism. No exchange of hydrogen atoms between ethylene and the hydroxyl groups in the oxide surface occurs. Ethyl groups are adsorbed on chromium atoms in both high (probably + 5) and low (probably + 3) oxidation states and are partially desorbed, particularly from the former, by evacuation at 300 °C. The adsorption of ethylene confers catalytic activity for the polymerization of ethylene at 50 °C on chromium(v) atoms but chromium(III) atoms on which there are adsorbed ethyl groups are inactive. The catalytic activity of the high oxidation state sites from which ethyl groups desorbed during evacuation at 300 °C depends upon the form of the adsorption isotherm of ethylene on the sites at 50 °C. The adsorption of ethylene as ethyl groups constitutes the initiation step in the polymerization reaction. The products from the oxidation of ethylene caused by contact with catalyst appear in part as adsorbed water, carboxylate, carbonate, and carbonyl species. The catalytic activity of the oxide is poisoned by the presence of the adsorbed oxidation products but is enhanced by evacuation at 300 °C which causes their desorption.

The surface chemistry of kaolinite. II. Catalysis of n-butane decomposition

1972 ◽  
Vol 25 (9) ◽  
pp. 1843 ◽  
Author(s):  
AS Buchanan ◽  
RC Oppenheim
Keyword(s):  
Catalytic Activity ◽  
Lone Pair ◽  
Acid Leaching ◽  
Hydroxyl Groups ◽  
Surface Oxygen ◽  
Hydrogen Atoms ◽  
Before And After ◽  
Hydrocarbon Reactions ◽  
Lone Pair Electrons ◽  
Oxygen Atoms

The catalytic activity of kaolinite before and after acid leaching for the decomposition of n-butane between 669 and 727 K has been compared with that of alumina natural and precipitated, and silica. The catalysis of hydrocarbon reactions on oxide surfaces appears to involve oxygen atoms which may be attached to the solid surface either physically adsorbed as the gas, as part of the lattice, or possibly as attached hydroxyl groups. Dehydrogenation of the hydrocarbon appears to be the first important step, suggesting that adsorption of the reactant involves interaction of the hydrogen atoms with lone pair electrons of surface oxygen atoms.

The polymerization of ethylene on chromium oxide catalysts I. Kinetic studies

1972 ◽  
Vol 329 (1579) ◽  
pp. 361-373 ◽  
Keyword(s):  
Rate Constant ◽  
Initial Pressure ◽  
Kinetic Studies ◽  
Order Rate Constant ◽  
Polymerization Reaction ◽  
First Order ◽  
Ethylene Pressure ◽  
Order Rate ◽  
Chromium Vi ◽  
Chromium Oxide Catalysts

The rates of polymerization of ethylene on a supported chromium (VI) oxide Phillips catalysts have been measured. Catalysts were calcined in air at 460 °C and activated by pretreatment with ethylene at 300 °C. With increasing pretreatment times the activity of the catalyst increased to a maximum, after which over-reduction occurred and the activity fell. The products of the pretreatment process were water, carbon dioxide and a trace of butenes. Rates of polymerization were first order in ethylene pressure over the temperature range studied ( – 95 to 150 °C). The first order rate constant was sensitive to the initial pressure of ethylene added to the catalyst at the temperature at which the polymerization reaction was carried out. The results are explicable in terms of the production of active centres in the catalyst surface during contact with ethylene at 300 °C. Subsequent evacuation at 300 °C produced from some of these centres sites which had to be reactivated by adsorption of ethylene at low temperatures. The extent of re-activation increased with increasing ethylene pressure. The variation of first order rate constant with temperature showed a maximum at ca . – 23 °C and an apparent activation energy of 0.8 kJ mol -1 for the range –95 to – 23 °C. At temperatures above 227 °C the rate of polymerization was extremely slow.

scholarly journals The Synthesis of Poly(Vinyl Alcohol) Grafted with Fluorinated Protic Ionic Liquids Containing Sulfo Functional Groups

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4158
Author(s):  
Patrycja Glińska ◽  
Andrzej Wolan ◽  
Wojciech Kujawski ◽  
Edyta Rynkowska ◽  
Joanna Kujawa
Keyword(s):  
Ionic Liquids ◽  
Vinyl Alcohol ◽  
Proton Exchange ◽  
Polymer Materials ◽  
Polymerization Reaction ◽  
Poly Vinyl Alcohol ◽  
Hydroxyl Groups ◽  
Protic Ionic Liquids ◽  
Synthesis Route ◽  
Sulfo Groups

There has been an ongoing need to develop polymer materials with increased performance as proton exchange membranes (PEMs) for middle- and high-temperature fuel cells. Poly(vinyl alcohol) (PVA) is a highly hydrophilic and chemically stable polymer bearing hydroxyl groups, which can be further altered. Protic ionic liquids (proticILs) have been found to be an effective modifying polymer agent used as a proton carrier providing PEMs’ desirable proton conductivity at high temperatures and under anhydrous conditions. In this study, the novel synthesis route of PVA grafted with fluorinated protic ionic liquids bearing sulfo groups (–SO3H) was elaborated. The polymer functionalization with fluorinated proticILs was achieved by the following approaches: (i) the PVA acylation and subsequent reaction with fluorinated sultones and (ii) free-radical polymerization reaction of vinyl acetate derivatives modified with 1-methylimidazole and sultones. These modifications resulted in the PVA being chemically modified with ionic liquids of protic character. The successfully grafted PVA has been characterized using 1H, 19F, and 13C-NMR and FTIR-ATR. The presented synthesis route is a novel approach to PVA functionalization with imidazole-based fluorinated ionic liquids with sulfo groups.

scholarly journals Catalytic activity of metals in heterogeneous Fenton-like oxidation of wastewater contaminants: a review

2021 ◽  
Author(s):  
Sajid Hussain ◽  
Eleonora Aneggi ◽  
Daniele Goi
Keyword(s):  
Catalytic Activity ◽  
Emerging Contaminants ◽  
Influencing Factor ◽  
Oxidation Products ◽  
Metal Oxidation ◽  
Heterogeneous Fenton ◽  
Solution Ph ◽  
Copper Manganese ◽  
Different Types ◽  
Metallic Catalyst

AbstractInnovations in water technology are needed to solve challenges of climate change, resource shortages, emerging contaminants, urbanization, sustainable development and demographic changes. In particular, conventional techniques of wastewater treatment are limited by the presence of poorly biodegradable organic matter. Alternatively, recent Fenton, Fenton-like and hybrid processes appear successful for cleaning of different types of liquid wastewaters. Here, we review the application of metallic catalyst-H2O2 systems in the heterogeneous Fenton process. Each metallic catalyst-H2O2 system has unique redox properties due to metal oxidation state. Solution pH is a major influencing factor. Catalysts made of iron and cerium form stable complexes with oxidation products and H2O2, thus resulting in reduced activities. Copper forms transitory complexes with oxidation products, but copper catalytic activity is restored during the reaction. Silver and manganese do not form complexes. The catalyst performance for degradation and mineralization decreases in the order: manganese, copper, iron, silver, cerium, yet the easiness of practical application decreases in the order: copper, manganese, iron, silver, cerium.

scholarly journals High catalytic activity for formaldehyde oxidation of an interconnected network structure composed of δ-MnO2 nanosheets and γ-MnOOH nanowires

2020 ◽  
Vol 8 (4) ◽  
pp. 429-439
Author(s):  
Ying Tao ◽  
Rong Li ◽  
Ai-Bin Huang ◽  
Yi-Ning Ma ◽  
Shi-Dong Ji ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Network Structure ◽  
Manganese Oxides ◽  
Active Oxygen Species ◽  
Low Cost ◽  
High Dispersion ◽  
Hydroxyl Groups ◽  
High Catalytic Activity ◽  
Interconnected Network ◽  
Surface Hydroxyl

AbstractAmong the transition metal oxide catalysts, manganese oxides have great potential for formaldehyde (HCHO) oxidation at ambient temperature because of their high activity, nontoxicity, low cost, and polybasic morphologies. In this work, a MnO2-based catalyst (M-MnO2) with an interconnected network structure was successfully synthesized by a one-step hydrothermal method. The M-MnO2 catalyst was composed of the main catalytic agent, δ-MnO2 nanosheets, dispersed in a nonactive framework material of γ-MnOOH nanowires. The catalytic activity of M-MnO2 for HCHO oxidation at room temperature was much higher than that of the pure δ-MnO2 nanosheets. This is attributed to the special interconnected network structure. The special interconnected network structure has high dispersion and specific surface area, which can provide more surface active oxygen species and higher surface hydroxyl groups to realize rapid decomposition of HCHO.

scholarly journals Molecular-Level Insight into How Hydroxyl Groups Boost Catalytic Activity in CO2 Hydrogenation into Methanol

Chem ◽  
2018 ◽  
Vol 4 (3) ◽  
pp. 613-625 ◽  
Author(s):  
Yuhan Peng ◽  
Liangbing Wang ◽  
Qiquan Luo ◽  
Yun Cao ◽  
Yizhou Dai ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Molecular Level ◽  
Co2 Hydrogenation ◽  
Hydroxyl Groups ◽  
Insight Into

Hollow structured CoSn(OH)6-supported Pt for effective room-temperature oxidation of gaseous formaldehyde

2016 ◽  
Vol 09 (06) ◽  
pp. 1642009 ◽  
Author(s):  
Jing Zhou ◽  
Yong Zhao ◽  
Lifan Qin ◽  
Chen Zeng ◽  
Wei Xiao
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
Room Temperature ◽  
Synergetic Effect ◽  
Hollow Structure ◽  
Pt Nanoparticles ◽  
Hydroxyl Groups ◽  
High Catalytic Activity ◽  
Temperature Oxidation ◽  
X Ray

Uniform CoSn(OH)6 hollow nanoboxes and the derivative with Pt loading (Pt/CoSn(OH)6) were herein synthesized and characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). SEM and TEM analyses showed that CoSn(OH)6 possessed mesoporous hollow structure and Pt nanoparticles with size of 2–8[Formula: see text]nm were uniformly dispersed on the surface of CoSn(OH)6 nanoboxes. The performances of the catalysts for the formaldehyde (HCHO) removal at room temperature were evaluated. These Pt/CoSn(OH)6 catalysts exhibited a remarkable catalytic activity as well as stability for room-temperature oxidative decomposition of gaseous HCHO, while the corresponding CoSn(OH)6 only showed adsorption. The synergetic effect between the highly dispersed Pt nanoparticles and the CoSn(OH)6 nanoboxes with mesoporous hollow structure, a large surface area and abundant surface hydroxyl groups is considered to be the main reason for the observed high catalytic activity of Pt/CoSn(OH)6.

Crystal structure of atropine sulfate monohydrate, (C17H24NO3)2(SO4)·(H2O)

2019 ◽  
Vol 34 (4) ◽  
pp. 389-395 ◽  
Author(s):  
James A. Kaduk ◽  
Amy M. Gindhart ◽  
Thomas N. Blanton
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Water Molecule ◽  
Powder Diffraction ◽  
Density Functional ◽  
Atropine Sulfate ◽  
Strong Hydrogen Bond ◽  
Hydroxyl Groups ◽  
Hydrogen Atoms ◽  
Sulfate Anion

The crystal structure of atropine sulfate monohydrate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Atropine sulfate monohydrate crystallizes in space group P21/n (#14) with a = 19.2948(5), b = 6.9749(2), c = 26.9036(5) Å, β = 94.215(2)°, V = 3610.86(9) Å3, and Z = 4. Each of the two independent protonated nitrogen atoms participates in a strong hydrogen bond to the sulfate anion. Each of the two independent hydroxyl groups acts as a donor in a hydrogen bond to the sulfate anion, but only one of the water molecule hydrogen atoms acts as a hydrogen bond donor to the sulfate anion. The hydrogen bonds are all discrete but link the cations, anion, and water molecule along [101]. Although atropine and hyoscyamine (atropine is racemic hyoscyamine) crystal structures share some features, such as hydrogen bonding and phenyl–phenyl packing, the powder patterns show that the structures are very different. The powder pattern for atropine sulfate monohydrate has been submitted to ICDD for inclusion in the Powder Diffraction File™.

Sign in / Sign up

Export Citation Format

Share Document