Methanol kinetic mechanism

Jr., A Comprehensive Kinetic Mechanism for CO, CH20, and CH3OH Combustion, Int.J. Chem. Kinet. 39, 109-136 (2007) Held, T., The Oxidation of Methanol, Isobutene, and Methyl tertiary-Butyl Ether, No. 1978-T, PJi.D. Dissertation, Princeton University, Princeton, NJ, 1993 Burgess, D. R. F., Jr, Zachariah, M. R., Tsang,... 

Combined with methanol crossover, slow anode kinetics lead to a power density of a DMFC that is three to four times lower than that of a hydrogen fuel cell. Much work has been focused on the anodic oxidation of methanol. The mechanism of the... 

Jiang CJ, et al. Kinetic mechanism for the reaction between methanol and water over a Cu-Zn0-Al203 catalyst. Appl Catal A Gen. 1993 97(2) 145—58. 

Since 1979, numerous reviews have appeared on the kinetics, mechanisms, and process chemistry of the metal-catalyzed methanol carbonylation reaction [11, 14-20], especially the Monsanto rhodium-catalyzed process. In this section, the traditional process chemistry as patented by Monsanto is discussed, with emphasis on some of the significant improvements that Monsanto s licensee, Celanese Chemicals (CC) has contributed to the technology. The iridium-based methanol carbonylation process recently commercialized by BP Chemicals Ltd. (BP) will be discussed also. 

Muller CM, Seshadri K, Chen JY. Reduced kinetic mechanism for counterflow methanol diffusion flames. In Reduced kinetic mechanisms for applications in combustion systems, Lecture notes in physics. Berlin/Heidelberg Springer-Verlag 1993. 

De Bortoli AL, Andreis GSL. Asymptotic analysis for coupled hydrogen, carbon monoxide, methanol and ethanol reduced kinetic mechanism. Lat Am Appl Res 2012 42 299-304. 

Example 6.11.5 Kinetic mechanism of the methanol synthesis reaction catalyzed with Cu/Zn0/Al20j/Zr02 (developed by Lim et al., 2009)... 

Methanol synthesis served as the model for the true mechanism. Stoichiometry, thermodynamics, physical properties, and industrial production rates were all taken from the methanol literature. Only the reaction mechanism and the kinetics of methanol synthesis were discarded. For the mechanism a four step scheme was assumed and from this the... 

Here a four-step mechanism is described on the framework of methanol synthesis without any claim to represent the real methanol mechanism. The aim here was to create a mechanism, and the kinetics derived from it, that has an exact mathematical solution. This was needed to perform kinetic studies with the true, or exact solution and compare the results with various kinetic model predictions developed by statistical or other mehods. The final aim was to find out how good or approximate our modeling skill was. 

Remarks The aim here was not the description of the mechanism of the real methanol synthesis, where CO2 may have a significant role. Here we created the simplest mechanistic scheme requiring only that it should represent the known laws of thermodynamics, kinetics in general, and mathematics in exact form without approximations. This was done for the purpose of testing our own skills in kinetic modeling and reactor design on an exact mathematical description of a reaction rate that does not even invoke the rate-limiting step assumption. 

To facilitate the use of methanol synthesis in examples, the UCKRON and VEKRON test problems (Berty et al 1989, Arva and Szeifert 1989) will be applied. In the development of the test problem, methanol synthesis served as an example. The physical properties, thermodynamic conditions, technology and average rate of reaction were taken from the literature of methanol synthesis. For the kinetics, however, an artificial mechanism was created that had a known and rigorous mathematical solution. It was fundamentally important to create a fixed basis of comparison with various approximate mathematical models for kinetics. These were derived by simulated experiments from the test problems with added random error. See Appendix A and B, Berty et al, 1989. 

The UCKRON AND VEKRON kinetics are not models for methanol synthesis. These test problems represent assumed four and six elementary step mechanisms, which are thermodynamically consistent and for which the rate expression could be expressed by rigorous analytical solution and without the assumption of rate limiting steps. The exact solution was more important for the test problems in engineering, than it was to match the presently preferred theory on mechanism. 

Asano and co-workers have reported die kinetic effects of pressure, solvent, and substituent on geometric isomerization about die carbon-nitrogen double bond for pyrazol-3-one azomethines 406 (R = H), 406 (R = NO2) and 407, (Scheme 93). The results demonstrate the versatility of die inversion mechanism. The rotation mechanism has been invalidated. First-wder rate constants and activating volumes for diermal E-Z isomerization for 406 (R = H) and 406 (R = NO2) are given at 25°C in benzene and methanol (89JOC379). 

An interesting kinetic study has been made of the cleavage of aryltrimethyl-stannanes by aqueous methanolic alkali at 50°C695. This reaction is base-catalysed as shown by the following rates (105Arx) for cleavage of the 3-trifluoro-methylphenyl compound in methanol (3 vol.) at the concentrations (in parentheses) of sodium hydroxide (2 vol.) 148 (3.805 M), 173.5 (5.33 M), 207 (7.71 M). The mechanism approximates to that given in equilibria (270) and (271)... 

The preparation and chemistry of nickel trithiocarbonate complexes have been studied in detail, and both [NKCSs) ] and [Ni(CS4)2 have been isolated (379). Shul man and co-workers (379) reprepared the known [Ni(NH3)3(CS3)]and [Ni(en)3]CS3, and the kinetics of the reaction of Ni(II) with the trithiocarbonate ion in methanol was studied the results confirmed the previously proposed ion-pair mechanism (380). 

Table 5 shows the rate ratios between ethylenes differing by an increase by two in number of alkyl substituents. It can be observed that in solvents as different as methanol, ethanol, and acetic acid, the rate ratio is always around 10, that is of the same order of magnitude of the increase in Kf. This indicates that substituent effects are not much more influential on the kinetic constants that on Kf. A possible rationalization of the lower accelerating effects by alkyl substituents on the bromination rate, relative to what could be expected for an AdgCl mechanism on... 

The methanolic cupric bromide oxidation of propargyl alcohol to trans-BrCH-CBrCH20H (30%) and Br2C=CBrCH20H (18%) and, under other reaction conditions, Br2C-CBr-CH20H (93 %) follows simple second-order kinetics with a rate coefficient of 1.5 x 10 l.mole . sec at 64 °C. A mechanism of ligand-transfer in a 7t-complex is proposed. ... 

The electrocatalytic oxidation of methanol has been thoroughly investigated during the past three decades (see reviews in Refs. 21-27), particularly in regard to the possible development of DMFCs. The oxidation of methanol, the electrocatalytic reaction, consists of several steps, which also include adsorbed species. The determination of the mechanism of this reaction needs two kinds of information (1) the electrode kinetics of the formation of partially oxidized and completely oxidized products (main and side products) and (2) the nature and the distribution of intermediates adsorbed at the electrode surface. 

The crucial aspect is thus to determine the fate of the ( CHO), species. Possible mechanisms for its oxidative removal are schematically shown in Fig. 9. From this scheme, it appears that the desorption of the formyl species can follow different pathways through competitive reactions. This schematic illustrates the main problems and challenges in improving the kinetics of the electrooxidation of methanol. On a pure platinum surface, step (21) is spontaneously favored, since the formation of adsorbed CO is a fast process, even at low potentials. Thus, the coverage... 

The Holy Grail of catalysis has been to identify what Taylor described as the active site that is, that ensemble of atoms which is responsible for the surface reactions involved in catalytic turnover. With the advent of atomically resolving techniques such as scanning tunnelling microscopy it is now possible to identify reaction centres on planar surfaces. This gives a greater insight also into reaction kinetics and mechanisms in catalysis. In this paper two examples of such work are described, namely CO oxidation on a Rh(llO) crystal and methanol selective oxidation to formaldehyde on Cu(llO). 

The electrophilic bromination of ethylenic compounds, a reaction familiar to all chemists, is part of the basic knowledge of organic chemistry and is therefore included in every chemical textbook. It is still nowadays presented as a simple two-step, trans-addition involving the famous bromonium ion as the key intermediate. T]nis mechanism was postulated as early as the 1930s by Bartlett and Tarbell (1936) from the kinetics of bromination of trans-stilbene in methanol and by Roberts and Kimball (1937) from stereochemical results on cis- and trans-2-butene bromination. According to their scheme (Scheme 1), bromo-derivatives useful as intermediates in organic synthesis... 

Kinetic solvent isotope effect as a measure of electrophilic assistance to bromide ion departure limiting values rate data in ethanol, methanol and their aqueous mixtures using Bentley s TBr scale its decrease corresponds to the involvement of nucleophilic assistance. R = (/caqhtOII//cAcoH)r as a measure of nucleophilic solvent assistance. Model for a limiting bromination mechanism. Ruasse et al. (1991). /Ruasse and Zhang (1984). 9Argile and Ruasse (to be published). Modro et al. (1979). 

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