Reaction Of Carbon Monoxide Research Articles

Oxoferryl-Porphyrin Radical Catalytic Intermediate in Cytochrome bd Oxidases Protects Cells from Formation of Reactive Oxygen Species

The quinol-linked cytochrome bd oxidases are terminal oxidases in respiration. These oxidases harbor a low spin heme b(558) that donates electrons to a binuclear heme b(595)/heme d center. The reaction with O(2) and subsequent catalytic steps of the Escherichia coli cytochrome bd-I oxidase were investigated by means of ultra-fast freeze-quench trapping followed by EPR and UV-visible spectroscopy. After the initial binding of O(2), the O-O bond is heterolytically cleaved to yield a kinetically competent heme d oxoferryl porphyrin π-cation radical intermediate (compound I) magnetically interacting with heme b(595). Compound I accumulates to 0.75-0.85 per enzyme in agreement with its much higher rate of formation (~20,000 s(-1)) compared with its rate of decay (~1,900 s(-1)). Compound I is next converted to a short lived heme d oxoferryl intermediate (compound II) in a phase kinetically matched to the oxidation of heme b(558) before completion of the reaction. The results indicate that cytochrome bd oxidases like the heme-copper oxidases break the O-O bond in a single four-electron transfer without a peroxide intermediate. However, in cytochrome bd oxidases, the fourth electron is donated by the porphyrin moiety rather than by a nearby amino acid. The production of reactive oxygen species by the cytochrome bd oxidase was below the detection level of 1 per 1000 turnovers. We propose that the two classes of terminal oxidases have mechanistically converged to enzymes in which the O-O bond is broken in a single four-electron transfer reaction to safeguard the cell from the formation of reactive oxygen species.

Quantum Monte Carlo simulation of carbon monoxide reactivity when adsorbed at metal and oxide catalyst surfaces: Trial wave‐functions with exponential type basis and quasi‐exact three‐body correlation

AbstractReview publications show the advantages of using quantum Monte Carlo (QMC) methods when bonding interactions are modified and consequently, where the electron correlation energy varies and needs to be evaluated accurately. This article considers a model efficient metal catalyst for reactions of carbon monoxide. The ultimate aim is to help design industrially useful catalysts, since the reaction with water produces hydrogen gas selectively, that is, a clean fuel and a sustainable energy source. To narrow the gap between the industrial process and calculation, a model of platinum/oxide is studied. It is mimicked here by copper with and without adsorbed oxygen. Periodicity as well as a validated pseudo‐potential are used to limit the number of active electrons considered. A suitable code to carry out this task is CASINO. Furthermore, this code scales linearly to 100,000 processors and possesses a shared memory facility so that it is well‐suited to runs on the Blugene/P. It has been in production on such computers since early in 2011. A mixed plane‐wave/exponential type orbitals (ETO) basis is used for the systems studied. Plane waves are well‐suited to periodic solid substrates and a linear combination of ETOs for molecules. The atomic orbitals have direct physical interpretation, i.e., Coulomb Sturmians and hydrogen‐like orbitals. Their radial nodes are shown to be essential in obtaining the vitally important accurate QMC trial wave‐functions. Until 2008, ETO products on different atoms were difficult to manipulate for the evaluation of two‐electron integrals. Coulomb resolutions provide an excellent approximation that reduces these integrals to a sum of one‐electron overlap‐like integral products that each involve orbitals on at most two centers. They are thus readily evaluated. Only these integrals need to be re‐evaluated to change basis functions. In this article, QMC‐VMC variational optimisation is used with a quasi analytic two‐electron and nucleus correlation factor. The QMC diffusion Monte Carlo methodology is applied to adsorbed carbon monoxide and some of its reactions. © 2012 Wiley Periodicals, Inc.

Reactions of carbon monoxide with free palladium oxide clusters: strongly size dependent competition between adsorption and combustion

The gas phase reactions of carbon monoxide with small mass-selected clusters of palladium, Pd(x)(+) (x = 2-7), and their oxides, Pd(x)O(+) (x = 2-7) and Pd(x)O(2)(+) (x = 4-6), have been investigated in a radio frequency ion trap operated under multi-collision conditions. The bare palladium clusters were found to readily adsorb CO yielding a highly size dependent product pattern. Most interestingly, the reactions of the pre-oxidized palladium clusters with CO lead to very similar product distributions of Pd(x)(CO)(z)(+) complexes as in the case of the corresponding pure Pd(x)(+) clusters. Consequently, it has been concluded that the investigated palladium oxide clusters efficiently oxidize CO under formation of the bare clusters, which further adsorb CO molecules yielding the previously observed Pd(x)(CO)(z)(+) product complex distributions. This CO combustion reaction has been observed even at temperatures as low as 100 K. However, for Pd(2)O(+), Pd(6)O(+), Pd(6)O(2)(+), and Pd(7)O(+) a competing reaction channel yielding palladium oxide carbonyls Pd(x)O(CO)(z)(+) could be detected. The latter adsorption reaction may even hamper the CO combustion under certain reaction conditions and indicates enhanced activation barriers involved in the CO oxidation and/or the CO(2) elimination process on these clusters.

Modified endogenous carbon monoxide production through modulation of heme oxygenase activity alters some aspects of the cold restraint stress response in male albino rats

Multiple stimulatory and inhibitory inputs regulate the hypothalamic-pituitary-adrenal axis (HPA). Although the results of the previous studies are contradictory, it has been indicated that the carbon monoxide (CO) may play a role in the HPA regulation. The aim of the present study was to investigate the effect of modified endogenous CO production on some aspects of the cold restraint stress (CRS) response in adult male albino rats. Modification of the endogenous CO was performed by altering the heme oxygenase (HO) activity; its induction was achieved by administration of the hemin (HEM) and inhibition by administration of the zinc mesoporphyrin (ZM). We found that in both the non-stressed and stressed groups the HEM significantly decreased the plasma levels of epinephrine (EPI), adrenocorticotropic hormone (ACTH), corticosterone (B), cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). On the other hand, ZM significantly increased the adrenal EPI, norepinephrine (NE), dopamine (DA), and the plasma levels of EPI, NE, DA, ACTH, B, cholesterol, triglycerides, HDL-C, and LDL-C, as compared with control and stressed rats. The role of CO reaction to the CRS response could be clarified as an anti-stress effect. This is evidenced by the inhibitory effect of HO inducer, HEM, on the HPA axis and a consequent less hazardous metabolic profile which it produced. carbon monoxide, hemin, heme oxygenase, stress.

Initiation and control of catalytic surface reactions with shaped femtosecond laser pulses

We report on femtosecond laser-induced catalytic reactions of carbon monoxide and hydrogen on single crystal surfaces under high vacuum conditions. Several product molecules are synthesized, among them also species for whose formation at least three reactants are required. By applying closed-loop optimal control, we manipulate these reactions and selectively optimize the ratio of different bond-forming reaction channels, in contrast to previous quantum control experiments aiming at bond-cleavage. Further experiments explore the nontrivial control mechanism and its sensitivity to the relative proportion of the two reactant gases.

ChemInform Abstract: A Straightforward Synthesis of Pyrazolines and Pyrazoles: Palladium‐Catalyzed Carbonylative Vinylation—Cyclocondensation Reactions of Aryl Halides.

AbstractA number of pyrazolines is synthesized by the multicomponent reaction of aryl halides, styrenes, carbon monoxide, and hydrazines.

Construction of Sensitive and Selective Zirconia-Based CO Sensors Using ZnCr2O4-Based Sensing Electrodes

The carbon monoxide (CO) sensitivity of a mixed-potential-type yttria-stabilized zirconia (YSZ)-based tubular-type sensor utilizing a ZnCr(2)O(4) sensing electrode (SE) was tuned by the addition of different precious metal nanoparticles (Ag, Au, Ir, Pd, Pt, Ru and Rh; 1 wt % each) into the sensing layer. After measuring the electromotive force (emf) response of the fabricated SEs to 100 ppm of CO against a Pt/air-reference electrode (RE), the ZnCr(2)O(4)-Au nanoparticle composite electrode (ZnCr(2)O(4)(+Au)-SE) was found to give the highest response to CO. A linear dependence on the logarithm of CO concentration in the range of 20-800 ppm at an operational temperature of 550 °C under humid conditions (5 vol % water vapor) was observed. From the characterization of the ZnCr(2)O(4)(+Au)-SE, we can conclude that the engineered high response toward CO originated from the specific properties of submicrometer sized Au particles, formed via the coalescence of nanosized Au particles located on ZnCr(2)O(4) grains, during the calcining process at 1100 °C for 2 h. These particles augmented the catalytic activities of the gas-phase CO oxidation reaction in the SE layer, as well as to the anodic reaction of CO at the interface; while suppressing the cathodic reaction of O(2) at the interface. In addition, the response of the ZnCr(2)O(4)(+Au)-SE sensor toward 100 ppm of CO gradually increased throughout the 10 days of operation, and plateaued for the remainder of the month that the sensor was examined. Correlations between SEM observations and the CO sensing characteristics of the present sensor were suggestive that the sensitivity was mostly affected by the morphology of the Au particles and their catalytic activities, which were in close proximity to the ZnCr(2)O(4) grains. Furthermore, by measuring the potential difference (emf) between the ZnCr(2)O(4)(+Au) and a ZnCr(2)O(4) electrode, sensitivities to typical exhaust component gases other than CO were found to be negligible at 550 °C.

Modeling for the catalytic coupling reaction of carbon monoxide to diethyl oxalate in fixed-bed reactors: Reactor model and its applications

A two-dimensional (2D) pseudo-homogeneous reactor model was developed to simulate the performance of fixed-bed reactors for catalytic coupling reaction of carbon monoxide to diethyl oxalate. Reactor modeling was performed using a comprehensive numerical model consisting of two-dimensional coupled material and energy balance equations. A power law kinetic model was applied for simulating the catalytic coupling reaction with considering one main-reaction and two side-reactions. The validity of the reactor model was tested against the measured data from different-scale demonstration processes and satisfactory agreements between the model prediction and measured results were obtained. Furthermore, detailed numerical simulations were performed to investigate the effect of major operation parameters on the reactor behavior of fixed bed for catalytic coupling reaction of carbon monoxide to diethyl oxalate, and the result shows that the coolant temperature is the most sensitive parameter.

Laser induced and controlled chemical reaction of carbon monoxide and hydrogen

Bimolecular chemical reaction control of gaseous CO and H(2) at room temperature and atmospheric pressure, without any catalyst, using shaped femtosecond laser pulses is presented. High intensity laser radiation applied to a reaction cell facilitates non-resonant bond breakage and the formation of a range of ions, which can then react to form new products. Stable reaction products are measured after irradiation of a reaction cell, using time of flight mass spectroscopy. Bond formation of C-O, C-C, and C-H bonds is demonstrated as CO(2)(+), C(2)H(2)(+), CH(+), and CH(3)(+) were observed in the time of flight mass spectrum of the product gas, analyzed after irradiation. The formation of CO(2) is shown to be dependent on laser intensity, irradiation time, and on the presence of H(2) in the reaction cell. Using negatively chirped laser pulses more C-O bond formation takes place as compared to more C-C bond formation for unchirped pulses.

Gas Chromatography Study of Reactions of Carbon Monoxide at Different Operating Temperatures within a PEMFC

This work used gas chromatography to study the reaction of carbon monoxide at a trace concentration of 1 part per million with oxygen and water in a proton exchange membrane fuel cell operated at temperatures of 10 and 80 ºC and an anode catalyst loading of 0.1 mg Pt cm-2. CO was found to enhance a carbon corrosion reaction that showed a strong thermal dependence over the temperatures tested. CO readily reacted with oxygen at 80 ºC while virtually no conversion to CO2 was observed at 10 ºC. The water gas shift reaction appeared to have been enhanced via electrochemical promotion since nearly 100 % conversion of CO was observed at both temperatures despite being kinetically limited at the temperatures used in this work. Potential oscillations were also observed for the first time for a cell with a Pt/C catalyst

CFD modeling of gas flow in porous medium and catalytic coupling reaction from carbon monoxide to diethyl oxalate in fixed-bed reactors

A comprehensive two-dimensional heterogeneous reactor model was developed to simulate the flow behavior and catalytic coupling reaction of carbon monoxide (CO)–diethyl oxalate (DEO) in a fixed-bed reactor. The two-temperature porous medium model, which was revised from a one-temperature porous medium model, as well as one equation turbulent model, and exponent-function kinetic model was constructed for the turbulent velocity scale comparing with laminar flow and simulation of the catalytic coupling reaction. The simulation results were in good agreement with the actual data collected from certain pilot-plant fixed bed reactors in China. Based on the validated approach and models, the distributions of reaction parameters such as temperature and component concentrations in the reactor were analyzed. The simulations were then carried out to understand the effects of operating conditions on the reactor performance which showed that the conduction oil temperature in the reactor jacket and the CO concentration are the key impact factors for the reactor performance.

Synthesis and study of novel catalysts based on hollandite K2Ga2Ti6O16

The results of experimental studies of synthesis of the hollandite phase K2Ga2Ti6O16 using initial mixtures of different dispersion compositions obtained by two methods, i.e., mechanical dispersion (MD) (followed by solid-phase sintering) and sol-gel method (Pechini method, MP), are reported. The catalytic properties of the obtained materials in the reactions of carbon monoxide (CO) and hydrogen (H2) oxidation have been determined. It has been demonstrated that an increase in the catalytic activity in the CO oxidation reaction is observed on the samples obtained using the sol-gel method, in which the hollandite phase content is higher and crystallization is more complete. The samples obtained using the MD method are characterized by a low porosity and activity in comparison with those produced by the Pechini method.

CO Emission Characteristics in a Designed Premixed Burner

Carbon monoxide (CO) formed in gas instantaneous water heater combustion systems is a significant pollutant source in the domestic environment. With the advance of reaction science and computer performance, mathematical modeling is working for comprehensive simulation of CO formation to provide a valuable tool to study the insight and understanding of the CO reaction of combustion systems. In this approach, the chemical reactions of combustion are described by nine species and six steps. Numerical results show that the predicted CO level is less than 0.1% when diameter of round fire hole is 0.6 or 0.7mm and the excess air ratio is 1.3. The vortex appearing between two bunch of round fire holes results in a thermal agglomeration and O2 decrease. At this place, CO2 is decomposed into CO and O and CO and the reaction is mainly controlled by CO2 pyrolysis. At this time, the increase of excess air is helpful to reduce CO production. Our results indicate the excess air ratio should be kept above 1.3 to meet with the fifth class of NO emission in gas instantaneous water heater standard GB 6932－2001.

Interaction of a porous carbon particle with steam and carbon dioxide

As part of a diffusion-kinetic model of gasification of a porous carbon particle in steam and carbon dioxide, this paper presents a study of heat- and mass-transfer processes both inside the porous particle and in the gas phase above its surface. The radiation heat transfer between the particle and the walls of the furnace is taken into account. Heterogeneous reactions of carbon with steam and carbon dioxide and the homogeneous reaction of carbon monoxide with steam. are considered. In addition, allowance is made for pressure variation in the porous particle due to an increase in gas mass during heterogeneous reactions. Dependences of the gasification rate on the composition of the reaction mixture, pressure, furnace temperature, and particle size, and the inner surface area of the porous carbon particle.

ChemInform Abstract: Vicinal C‐Functionalization of Alkenes. Pd/Light‐Induced Multicomponent Coupling Reactions Leading to Functionalized Esters and Lactones.

AbstractThe four‐component reaction of alkenes, iodoalkanes, carbon monoxide and alcohols is induced by Xe light and leads to functionalized esters.

Hydrogenation of carbon monoxide over cobalt nanoparticles supported on carbon nanotubes

This paper describes a catalytic reaction of hydrogen and carbon monoxide (Fischer–Tropsch synthesis (FTS)) over carbon nanotubes (CNTs) supported cobalt nanoparticles. We have investigated the effect of calcination of the catalysts on FTS performance using X-ray diffraction (XRD), H 2 chemisorption, temperature programmed reduction (TPR), temperature programmed oxidation (TPO), and transmission electron microscopy (TEM) techniques. With the increase of outer diameter of CNTs, specific surface area of the catalyst decreases while Co particle size increased accompanying with a decrease in CO conversion. The FTS performance is similar for samples calcined in N 2 or air at temperature below 550 °C. Over 550 °C, the results are much different in that the Co/CNTs can keep its activity due to the unchanged CNTs structure in N 2 while the Co/CNTs almost lose activity owing to the loss of CNTs structure and sintering of cobalt oxide clusters in air.

Synthesis of novel ionic liquid ([C4CNmim]+PF6 −) and application to preparation of polyketone

N-valeronitrile-N′-methylimidazolium hexafluorophosphate ([C4CNmim]+PF6−), as a novel ionic liquid with polar nitrile functional group, was prepared. The structure of the ionic liquid was characterized by using IR and 1H NMR. As a medium, the ionic liquid plays an important role in copolymerization of carbon monoxide (CO) with styrene (St). Some synthetic conditions were determined, including the usage of ionic liquid, palladium composite catalyst and methanol, CO pressure, reaction time and reaction temperature. The influence of these factors on catalytic activity was analyzed. The results show that the catalytic activity has reached 1 724.1 gStCO/(gPd·h) and the catalyst could be reused 5 times under the optimal condition: composite catalyst 0.015 mmol, ionic liquid 3 mL, methanol 0.75 mL, CO pressure 2 MPa, reaction time 2 h and reaction temperature 70 °C. This CO/St copolymerization within [C4CNmim]+PF6− system could facilitate ionic liquids with efficient and economical applications to polymeric materials.

Gas Chromatography Study of Carbon Monoxide Reactions at Different Temperatures and a Trace Concentration Level within a PEMFC

not Available.

Theoretical Study of the Reaction of Carbon Monoxide with Oxygen Molecules in the Ground Triplet and Singlet Delta States

Quantum chemical calculations were carried out to study the reaction of carbon monoxide with molecular oxygen in the ground triplet and singlet delta states. Transition states and intermediates that connect the reactants with products of the reaction on the triplet and singlet potential energy surfaces were identified on the base of coupled-cluster method. The values of energy barriers were refined by using compound techniques such as CBS-Q, CBS-QB3, and G3. The calculations showed that there exists an intersection of triplet and singlet potential energy surfaces. This fact leads to the appearance of two channels for the triplet CO+O(2)(X(3)Σ(g)(-)) reaction, which produces atomic oxygen in the ground O((3)P) and excited O((1)D) states. The appropriate rate constants of all reaction paths were estimated on the base of nonvariational transition-state theory. It was found that the singlet reaction rate constant is much greater than the triplet one and that the reaction channel CO+O(2)(a(1)Δ(g)) should be taken into consideration to interpret the experimental data on the oxidation of CO by molecular oxygen.

Synthesis of ( E)-2-(1-ferrocenylmethylidene)malonic acid derivatives by a cobalt-catalyzed domino reaction of ethyl diazoacetate, carbon monoxide and ferrocenylimines

The domino reaction of ethyl diazoacetate, carbon monoxide and ferrocenylimines was investigated in the presence of Co 2(CO) 8 as catalyst. In most cases the main products are 2-(1-ferrocenylmethylidene) malonates formed by an N(1)–C(4) cleavage of the primarily derived β–lactams. The latter compounds could only be isolated when the reaction was carried out at relatively low CO pressure, using an excess of ethyl diazoacetate. trans- N-( tert-Butyl)-3-ethoxycarbonyl-4-ferrocenyl-β-lactam proved to be the most stable one among these compounds and could be isolated in 55% yield. N-alkyl β-lactams were shown to undergo acidic cleavage leading to the E isomers of 2-(1-ferrocenylmethylidene) malonates as the main products. The structures of the two new compounds, ( E)-2-ethoxycarbonyl-3-ferrocenyl- N-(( R)-1-phenylethyl)-2-propenamide and trans- N-( tert-butyl)-3-ethoxycarbonyl-4-ferrocenyl-β-lactam were confirmed by X-ray crystallography. The relative thermodynamical stability of the products as well as the energetics of the acid-mediated cleavage of the β-lactam ring was elucidated with DFT calculations.