Formation Mechanism Of Co Research Articles

New insight into the CO formation mechanism during formic acid oxidation on Pt(111)

Density functional theory (DFT) calculations show a new concerted mechanism of formic acid (HCOOH) oxidation on Pt (111), which involves the simultaneous formation of CO 2 and CO via the HCOOH dimer in an elementary step. The newly proposed mechanism rationalizes the easy CO poisoning of Pt-based catalysts and improves our understanding for the mechanism of catalytic HCOOH oxidation. ► A new dimer model of formic acid oxidation (HCOOH) on Pt (111) surface is presented. ► The mechanism of simultaneous formation of CO 2 and CO is obtained. ► The easy CO poisoning of Pt-based catalysts is rationalized.

Thermogravimetric-Fourier transform infrared spectrometric analysis of CO2 gasification of reed (Phragmites australis) kraft black liquor

CO2 gasification of the reed (Phragmites australis) kraft black liquor (KBL) and its water-soluble lignin (WSL) was analyzed by thermogravimetry coupled with Fourier transform infrared spectrometry (TG–FTIR). In KBL gasification, major mass loss of KBL occurred between 150 and 1000°C, followed by a further slow mass loss until the heating was stopped and the TG curve leveled off. The TG profiles of the WSL and the KBL were similar during gasification; however, the differential thermogravimetry (DTG) curves and mass decrease from 300°C of the TG curves of the WSL and the KBL were different because of their dissimilar ingredients. The CO formation mechanism was the same and independent of structural types of lignins between reed and wood in their KBL CO2 gasification.

Cosmic ion bombardment of the icy moons of Jupiter

A large number of experiments have been performed in many laboratories in the world with the aim to investigate the physico-chemical effects induced by fast ions irradiating astrophysical relevant materials. The laboratory in Catania (Italy) has given a contribution to some experimental works. In this paper I review the results of two class of experiments performed by the Catania group, namely implantation of reactive (H +, C +, N +, O + and S +) ions in ices and the ion irradiation induced synthesis of molecules at the interface between water ice and carbonaceous or sulfurous solid materials. The results, discussed in the light of some questions concerning the surfaces of the Galilean moons, contribute to understand whether minor molecular species (CO 2, SO 2, H 2SO 4, etc.) observed on those objects are endogenic i.e. native from the satellite or are produced by exogenic processes, such as ion implantation. The results indicate that: – C-ion implantation is not the dominant formation mechanism of CO 2 on Europa, Ganimede and Callisto. – Implantation of sulfur ions into water ice produces hydrated sulfuric acid with high efficiency such to give a very important contribution to the sulfur cycle on the surface of Europa and other satellites. – Implantation of protons into carbon dioxide produces some species containing the projectile (H 2CO 3, and O–H in poly-water). – Implantation of protons into sulfur dioxide produces SO 3, polymers, and O 3 but not H–S bonds. – Water ice has been deposited on refractory carbonaceous materials: a general finding is the formation of a noteworthy quantity of CO 2. We suggest that this is the primary mechanism to explain the presence of carbon dioxide on the surfaces of the Galilean satellites. – Water ice has been deposited on refractory sulfurous materials originating from SO 2 or H 2S irradiation. No evidence for an efficient synthesis of SO 2 has been found.

On studies of formation, diffusion mechanisms and prevention measures of CO during HEGF in low permeability oil reservoirs

High energy gas fracture(HEGF)has been one of central measures used to increase production and effusion in low permeability reservoirs. But there are some problems of this technology. One of them is that large number of toxic and harmful gases caused by it will trigger severe CO poisoning events. In this paper, the formation-gathering rule and countermeasures of CO for HFGF were studied across-the-board in low permeability reservoirs. The study showed that the primary reasons to produce CO are HEGF itself and that high temperature gases for HEGF reacted with associated gas and oil. At the same time, the formation mechanism of CO was illuminated. The study was of great theoretical value to prevent CO in effect for low permeability reservoirs, and was of great guiding significance for the rational development of similar oilfields.

Effects of annealing treatment on the formation of CO 2 in ZnO thin films grown by metal-organic chemical vapor deposition

Post-growth annealing was carried out on ZnO thin films grown by metal-organic chemical vapor deposition (MOCVD). The grain size of ZnO thin film increases monotonically with annealing temperature. The ZnO thin films were preferential to c-axis oriented after annealing as confirmed by X-ray diffraction (XRD) measurements. Fourier transformation infrared transmission measurements showed that ZnO films grown at low temperature contains CO 2 molecules after post-growth annealing. A two-step reaction process has been proposed to explain the formation mechanism of CO 2, which indicates the possible chemical reaction processes during the metal-organic chemical vapor deposition of ZnO films.

Shape-controlled Synthesis and Formation Mechanism of Co<SUB>3</SUB>O<SUB>4</SUB> by Solvothermal Method

Shape-controlled Synthesis and Formation Mechanism of Co<SUB>3</SUB>O<SUB>4</SUB> by Solvothermal Method

A “User‐Friendly” Chemical Approach Towards Paramagnetic Cobalt Phosphide Hollow Structures: Preparation, Characterization, and Formation Mechanism of Co2P Hollow Spheres and Tubes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Low temperature catalytic partial oxidation of methane for gas-to-liquids applications

The catalytic partial oxidation (CPO) of methane in the presence of steam (low temperature catalytic partial oxidation, LTCPO) over noble metal catalysts was investigated. The “dry” CPO over ruthenium and rhodium catalysts was studied by thermogravimetric analyses coupled with IR spectroscopy. For CPO conditions, high CO selectivities at comparably low temperatures were observed for a rhodium/γ-alumina catalyst (5% rhodium) and a 1% ruthenium/TiO 2 catalyst giving evidence that a direct reaction mechanism is involved at low temperatures. It was found that under CPO conditions at low temperatures (<450 °C) the catalysts are in an oxidised state, which is probably responsible for the formation of carbon dioxide. At higher temperatures, the catalysts are in a reduced state. The CO selectivity increases with the reduction of the catalyst. Our results indicate that a direct CO formation mechanism is also possible for ruthenium/alumina catalysts. The platinum catalysts studied in the LTCPO of methane were less active than rhodium and ruthenium catalysts and revealed a lower hydrogen yield. It was found that the steam reforming activity of the ruthenium/alumina catalyst was reduced inhibited by ceria. The long term stability (80 h) of a ruthenium catalyst for LTCPO of methane was demonstrated.

A “User‐Friendly” Chemical Approach Towards Paramagnetic Cobalt Phosphide Hollow Structures: Preparation, Characterization, and Formation Mechanism of Co2P Hollow Spheres and Tubes

AbstractUser‐friendly chemistry principles have been implemented for the synthesis of hollow Co2P structures. In comparison with the original organometallic approach, the resulting alternative route is safe, simple, and inexpensive. The X‐ray diffraction (XRD) pattern, X‐ray photoelectron spectra (XPS), field emission scanning electron microscope (FESEM) images, and transmission electronic microscope (TEM) images were used to characterize the products, which exhibit paramagnetic behavior down to 2 K, as determined with a commercial superconducting quantum interference device (SQUID) magnetometer. The experimental investigations suggest that the formation of Co2P hollow structures, hollow spheres, and tubes can be explained by an aggregation mechanism and a thermodynamically governed regime. Initially formed Co2P nanoparticles are driven to aggregate into Co2P hollow spheres by the gas bubbles produced. The formation of Co2P tubes then occurs from the hollow spheres via hollow vessels in a thermodynamically governed process. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)

分子線赤外発光法によるPd単結晶表面上における定常的CO＋NO反応

The infrared chemiluminescence technique was applied to the steady-state CO oxidation by NO on Pd(111) and Pd(110) to measure the internal energy of CO2 desorbed from surfaces. In this paper, on the basis of the results of CO oxidation by O2, we elucidate the CO2 formation mechanism of CO + NO reaction. From the comparison of IR emission spectra of CO2 between CO + NO and CO + O2 reactions, it is found that the vibrational energy states of CO2 in CO + NO reaction are similar to those in CO + O2 reaction. This indicates that the reaction path of CO2 formation in CO + NO is the same as that in CO + O2. The vibrational states are much dependent on the surface structure: the CO2 molecules produced on flat Pd(111) were highly excited (especially bending mode) than those on Pd(110) which has atomically rough surface.

Study on the Mechanism of CO Formation in Reverse Water Gas Shift Reaction Over Cu/SiO2 Catalyst by Pulse Reaction, TPD and TPR

The mechanism of reverse water gas shift reaction over Cu catalyst was studied by pulse reaction with QMS monitoring, temperature programmed desorption (TPD) and temperature programmed reduction (TPR) of Cu/SiO2 catalyst. The reduced and/or oxidized copper offered low catalytic activity for the dissociation of CO2 to CO in the pulse reaction study with 1 ml volume of He/CO2, but the rate of CO formation was significantly enhanced with H2 participating in the reaction. The TPD spectra of CO2 obtained by feeding H2/CO2 over copper at 773 K provided strong evidence of the formation of formate at high temperature. The formate derived from the association of H2 and CO2 is proposed to be the key intermediate for CO production. The formate dissociation mechanism is the major reaction route for CO production.

CO2 clathrate-hydrate formation and its mechanism by molecular dynamics simulation

Abstract Molecular dynamics simulation has been conducted in order to obtain the fundamental understanding for the formation mechanism of CO 2 clathrate-hydrate that suppresses the dissolution of liquid CO 2 isolated at deep ocean floor. It was demonstrated that the H 2 O molecules formed a characteristic cage structure of type I clathrate around the CO 2 guest molecules after 260 ps from the initial condition of H 2 O molecules at pressurized water state. CO 2 clathrate-hydrate formation kinetics has elucidated that the interactions between the CO 2 guest molecules would form a low potential region, which has an effect to suppress the H 2 O molecules motions in a two-dimensional plane and assist to form cage structures consisted of 5 and 6 membered rings.

Carbon isotope effect studies in the mechanism of reactions of alkynes with formic acid

Carbon-13 fractionation observed in the course of carbon monoxide formation in the reaction of phenylacetylene with the large excess of liquid formic acid in the temperature interval 20–100°C has been investigated and compared with the13C fractionation in the dehydration of pure liquid formic acid. The anomalous temperature dependence of the13C fractionation has been interpreted as caused by the change of the kinetics and of the mechanism of CO formation from the one involving13C−H bond rupture rate determining step (operating in the presence of phenylacetylene) to the mechanism according to which HCOOH decarbonylates in liquid state. No large increase of the13C fractionation with rising of the reaction temperature from 70 to 134°C has been found in the case of decarbonylation of F.A. in the presence of large excess of phenylacetylene. The13C KIE was of 1.020 in the temperature interval 90–133.7°C in this case.