Activation energy methanol synthesis

BHET formation is conducted at temperatures of 200 to 250 °C to achieve reasonable reaction rates. The activation energies of the two reactions are of the order of 25 000-30 000 cal/mol [4, 5], The BHET formation is usually conducted under pressure to keep the ethylene glycol in the liquid state. Terephthalic acid is slurried with ethylene glycol for the esterification reaction. Dimethyl terephthalate is dissolved in ethylene glycol and BHET for a liquid-phase transesterification reaction. The synthesis of BHET is driven to this material by the removal of water or methanol. The reactions are reversible at reasonable rates if the concentrations of water or methanol reactants are held high. 

Zn/AljOj catalysts, 31 249 -Zn/Cr Oj catalysts, 31 250 -ZnO/AljO, 31 276, 292-295 -ZnO binary catalyst, 31 257-287 activity patterns, 31 271-274 BET argon surface areas, 31 259 calcination, 31 261-262 catalytic testing, 31 272 chemisorption, 31 268-271 CO2 effects, selectivity, 31 284-285 color spectra, 31 259-261 component comparison, 31 258-259 methanol synthesis, 31 246-247 modifiers, weakening of adsorption energy, 31 283... 

The apparent activation energy for the synthesis reaction of methyl tert-butyl ether or MTBE, was found to be 64 KJ/mole. The best activity and selectivity for MTBE were observed at temperatures of 85 - 90 °C, and contact times of circa 2.5 h when the methanol / isobutene molar ratio was kept within the 1.2 - 1.5 range. There was a fierce competition between the ethyl tert-butyl ether formation and that of diethylether at reaction temperatures higher than 85 °C. 

Recently, experimental and theoretical evidence for a model of the active site of industrial methanol synthesis that combines the role of ZnO and defects in Cu has been presented [58]. Planar defects have been shown to lead to changes in surface faceting of the Cu nanoparticles (Figure 5.3.8C) associated with formation of steps and kinks that were assumed to represent high-energy surface sites of special catalytic activity. For a series of Cu/ZnO-based catalysts, a linear correlation of the defect concentration with the intrinsic activity of the exposed Cu surface was observed. In addition, (partial) surface decoration of Cu with ZnOx by SMSI has been... 

Values of Activation Energies of Methanol Synthesis from Carbon Monoxide, Efk), and from Carbon Dioxide, E,(k ), and Adsorption Enthalpies AH and Entropies AS Derived from the Kinetic Model Utilizing Constants in Table IX ... 

Shustorovich and Bell [83] employed the BOC-MP method to examine the energetics of the elementary steps in mthanol synthesis by hydrogenation of CO on copper and palladium. Sellers and coworkers [84] examined the elementary steps in methanol synthesis from CHt on platinum. These studies have identified some of the same intermediate Segments discussed in the present study. For the reaction, CHsOHads CHiOHads + Hads on Pt(l 11), the activation energy computed with the BOC-MP method is 14.4 kcal/mol (0.63 eV), 0.2 eV higher than our X calculated value. 

Today methanol has become a very important feedstock for the production of many chemicals. Use as a clean fuel has increased and methanol is used in the production of the popular oxygenated fuel additive, MTBE. It has also been postulated that methanol could be a carrier of energy for safe transportation between remote countries. Furthermore, to prevent a greenhouse effect caused by COj generated from the tremendous oxidation reactions on the earth, methanol synthesis from CO2 is regarded as one of the potential solutions to decrease CO2 by the reaction with hydrogen which is produced by electrolysis of water, for example. Due to the increasing demand for methanol, many researchers are involved in the development of more active methanol synthesis catalysts. 

Fuel cells with improved catalysts would allow the most efficient use of fossil fuels for the direct generation of electricity. There is major interest in the electrochemical reaction of synthesis gas or, better still, methane. It would be desirable to simultaeously generate energy and to produce valuable oxidation products in a fuel cell. Another interesting fuel is methanol, but technical reahzation has so far been unsuccessful because of the associated high activation energies. 

Bond Order Conservation-Morse Potential (BOC-MP) formalism is used to study the change in activation energy for different elementary steps involving all possible chemical species on any metallic smrface in order to identify optimum catalysts for the production of methane, methanol or ethylene from synthesis gas. All possible steps are analyzed for the methanation reaction. It is assumed that the reaction occurs on pure metallic surfaces, thus, the influence of the support or promoters is not taken into account. The method suggests that Ni is a more selective for methanation reaction, in agreement with the fact that Ni/SiOz is the real catalyst used industrially. On the other hand on the surface of Fe or W the reaction may residt in the formation of adsorbed C, also in agreement with experiment. 

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