Thermodynamics methanol formation

The first reaction produces methanol with a low hydrogen consumption, but evolves significantly greater amounts of heat. The second reaction evolves less heat, but consumes more hydrogen and produces the byproduct steam. Thermodynamically, low temperatures and high pressures favor methanol formation. The reactions are carried out with copper-containing catalysts with typical reactor conditions of 260°C and 5 MPa (Probstein and Hicks, 1982). 

Methanol formation is exothermic, requiring removal of the enthalpy of reaction. Thermodynamically, the conversion to methanol increases by reacting at low temperatures. Also, there is a reduction in the number of moles during reaction, according to Equation 3.5.2, indicating that the converter should operate at a high pressiure to increase conversion. 

Thermodynamically, a decrease in reaction temperature or an increase in reaction pressure can favor the synthesis of methanol. A reaction temperature higher than 513 K facilitates CO2 activation and, consequently, methanol formation [4,5,197]. 

Based on the thermodynamic evaluation by Bonura et al. [217], the conversion of methanol to DME on the acidic zeolite sites rapidly approaches the equilibrium level at all the investigated temperatures because it is a fast reaction. Moreover, they also observed a promoting effect of the reaction temperature on the relative rate of methanol synthesis from CO2 rather than CO, on the basis of thermodynamics. Hence, based on their findings, the authors have proposed the reaction in Scheme 7.32. It turns out that, apart from the methanol dehydration reaction, 3 which takes place very fast at any temperature, reactions 1-2-4 affect the methanol formation depending on their relative reaction rates. The thermodynamic analysis of the main reaction paths involved in the synthesis of DME by CO2 hydrogenation reveals that, under kinetic conditions, the CO concentration dramatically increases with temperature therefore, low reaction temperamre and recycling unreacted COx/H2 mixtures could be a solution to improving the methanol/DME productivity. 

Propylene oxide is a colorless, low hoiling (34.2°C) liquid. Table 1 lists general physical properties Table 2 provides equations for temperature variation on some thermodynamic functions. Vapor—liquid equilibrium data for binary mixtures of propylene oxide and other chemicals of commercial importance ate available. References for binary mixtures include 1,2-propanediol (14), water (7,8,15), 1,2-dichloropropane [78-87-5] (16), 2-propanol [67-63-0] (17), 2-methyl-2-pentene [625-27-4] (18), methyl formate [107-31-3] (19), acetaldehyde [75-07-0] (17), methanol [67-56-1] (20), ptopanal [123-38-6] (16), 1-phenylethanol [60-12-8] (21), and / /f-butanol [75-65-0] (22,23). 

In theory two carbanions, (189) and (190), can be formed by deprotonation of 3,5-dimethylisoxazole with a strong base. On the basis of MINDO/2 calculations for these two carbanions, the heat of formation of (189) is calculated to be about 33 kJ moF smaller than that of (190), and the carbanion (189) is thermodynamically more stable than the carbanion (190). The calculation is supported by the deuterium exchange reaction of 3,5-dimethylisoxazole with sodium methoxide in deuterated methanol. The rate of deuterium exchange of the 5-methyl protons is about 280 times faster than that of the 3-methyl protons (AAF = 13.0 kJ moF at room temperature) and its activation energy is about 121 kJ moF These results indicate that the methyl groups of 3,5-dimethylisoxazole are much less reactive than the methyl group of 2-methylpyridine and 2-methylquinoline, whose activation energies under the same reaction conditions were reported to be 105 and 88 kJ moF respectively (79H(12)1343). 

Huffman found that treatment of cholan-12-one (65b) with lithium and ammonia for 2 hours followed by addition of propanol gives 40 % of a pinacol together with 48.5 % of 12-ols in which the ratio of 12j5 12a is 19 1. This predominance of the 12 -ol was interpreted in terms of slow formation of a dianion of type (62) followed by its equilibration to the thermodynamically most stable configuration, i.e. one which affords the 12j5-ol upon protonation. An alternative explanation is that reduction in the presence of methanol involves protonation of a ketyl such as (61) by methanol, whereas in the absence of methanol reduction proceeds via the dianion (62) which is protonated on... 

As for the salt formation and single-electron transfer, thermodynamics for simple redox processes may be applied to predict their selectivity. As a first approximation, a cation with red lower and higher than 0.2 V would give a salt and a radical pair, respectively, when combined with [2 ]. In practice, the cations which were found to give salts with [2 ] have red values more negative than —0.8 V. On the other hand, quantitative single-electron transfer has been observed from [2 ] to the heptaphenyltropylium ion which is relatively unstable p/fR+ —0.54 in methanol (Battiste and Barton, 1968) and E ed —0.30 V vs. Ag/Ag in acetonitrile (Kitagawa et al., 1992). 

Thermodynamic inhibitors Antinucleants Growth modifiers Slurry additives Anti-agglomerates Methanol or glycol modify stability range of hydrates. Prevent nucleation of hydrate crystals. Control the growth of hydrate crystals. Limit the droplet size available for hydrate formation. Dispersants that remove hydrates. 

Papisov et al. (1974) performed calorimetric and potentiometric experiments to determine the thermodynamic parameters of the complex formation of PMAA and PAA with PEG. They investigated how temperature and the nature of the solvent affected the complex stability. They found that in aqueous media the enthalpy and entropy associated with the formation of the PMAA/PEG complex are positive while in an aqueous mixture of methanol both of the thermodynamic quantities become negative. The exact values are shown in Table II. The viscosities of aqueous solutions containing complexes of PMAA and PEG increase with decreasing temperature as a result of a breakdown of the complexes. 

Ethanol can be derived from biomass by means of acidic/enzymatic hydrolysis or also by thermochemical conversion and subsequent enzymatic ethanol formation. Likewise for methanol, hydrogen can be produced from ethanol with the ease of storage/transportation and an additional advantage of its nontoxicity. Apart from thermodynamic studies on hydrogen from ethanol steam reforming,117-119 catalytic reaction studies were also performed on this reaction using Ni-Cu-Cr catalysts,120 Ni-Cu-K alumina-supported catalysts,121 Cu-Zn alumina-supported catalysts,122,123 Ca-Zn alumina-supported catalysts,122 and Ni-Cu silica-supported catalysts.123... 

The kinetics and thermodynamics of complex formation in methanol for the interaction of cryptands 2.1.1,2.2.1 and 2.2.2 with the alkali metal... 

Methanol still proceeds through an initial C H bond scission, but reacts with water before the OH bond breaks. Alternatively, formaldehyde formation likely occurs along the same pathway as CO formation. This is true if HCO is an intermediate in the decomposition pathway. Furthermore, the lack of a kinetic isotope effect for CH3OD indicates that formaldehyde is not the product of an initial O-H scission.94 Because formaldehyde and formic acid are not the thermodynamically favored products of methanol oxidation, they must be the result of kinetic limitations preventing the full oxidation to C02, analogous to the production of H202 for the reduction of oxygen (see next section). 

Thorough thermodynamic and kinetic investigation of solvolysis of 4,6-dinitrotetrazolo[l,5- ]pyridine 11 in water and methanol has been carried out <2003OBC2764>. It has been shown that in water the anionic rr-complex 12 is formed exclusively, whereas addition of methanol results in partial formation of the neutral carbinolamine-type adduct 13 at low pH (Scheme 4). All these results indicate that 11 is an even more powerful electrophile than dinitrobenzofuroxane. 

High-pressure experiments promise to provide insight into chemical reactivity under extreme conditions. For instance, chemical equilibrium analysis of shocked hydrocarbons predicts the formation of condensed carbon and molecular hydrogen.17 Similar mechanisms are at play when detonating energetic materials form condensed carbon.10 Diamond anvil cell experiments have been used to determine the equation of state of methanol under high pressures.18 We can then use a thermodynamic model to estimate the amount of methanol formed under detonation conditions.19... 

A particularly interesting Michael acceptor is dimethyl 2-hexen-4-ynedioate since it can react at either position of the double or triple bond to form 1,4- or 1,6-addition products. Winterfeldt and Preuss183 treated this substrate with several secondary amines and observed exclusive attack at C-5 with formation of the 1,6-addition products (equation 78). In contrast to this, sodium methanolate added at CM to give the 1,4-adduct as a mixture of E/Z isomers (equation 79) with increasing reaction time, the product distribution was shifted towards the thermodynamically more stable , -product184. Acheson and... 

A catalytic example of C-S bond breakage in benzothiophene has been reported by Bianchini [47], A catalytic desulfurisation was not yet achieved at the time as this is thermodynamically not feasible at such mild temperatures because of the relative stability of metal sulfides formed. Bianchini used a water-soluble catalyst in a two-phase system of heptane-methanol/water mixtures in which the product 2-ethylthiophenol is extracted into the basic aqueous layer containing NaOH. Figure 2.43 gives the reaction scheme and the catalyst. The 16-electron species Na(sulfos)RhH is suggested to be the catalyst. Note that a hydrodesulfurisation has not yet been achieved in this reaction because a thiol is the product. Under more forcing conditions the formation of H2S has been observed for various systems. 

This interconversion can also be performed in solvents, and the rate of the isomerization is dependent on the solvent used. In the dipolar aprotic solvent DMSO the rate of the reaction is fast, but in methanol, acetone, or dioxane the rate is low. However, the value of the equilibrium constant is scarcely influenced by the solvent ( 134/133 = 6-10) (75JHC985).This is not too surprising, since the equilibrium position is controlled by the relative thermodynamic stability of the isomers, which is a function of their heats of formation and of solvation. Undoubtedly, the heat of formation is the more important factor to the thermodynamic stability (75JHC985). 

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