Methanol, production equilibrium

When equilibrium is reached in reaction (25), appreciable concentrations of all of the reactants may be present. If methyl acetate (the product on the right) alone is dissolved in water, it will react with water slowly to give acetic acid and methanol until equilibrium is attained ... 

The results at differential conversions with water addition can be compared with methanol production at the finite conversion in the internal recycle reactor where the water concentration as a result of water production was similar (Table 3). The two types of experiment are analogous in that at differential conditions in the microflow reactor the catalyst was uniformly exposed to the feed concentration, whereas at finite conversions in the internal recycle reactor the catalyst was uniformly exposed to the product concentration. The methanol production rate at finite conversion was similar to the methanol production rate from COj/Hj/HjO at differential conditions for both the Cu/Zn/Al-1 and Pd impregnated catalyst. Therefore, the kinetics at the particular finite conversions, well away from equilibrium, can also be described by methanol production by CO2 hydrogenation, and the inhibition of this reaction associated with the presence of the product water. Furthermore, the Pd promotion was similar under the two reaction regimes (Table 3), reinforcing the conclusion that Pd promotion of CO2 hydrogenation is active only in the presence of water. 

The present test plant for methanol synthesis is beeing easily operated. Figure 3 shows the rate of production of methanol, i.e., space time yield of methanol (STY), as a function of time on stream over the multicomponent catalyst under the reaction conditions of 523 K, 5 MPa and SV = 5,000 h 10,000 h. The production rate of methanol at SV = 5,000 h was almost the same as that at reaction equilibrium. In the case of SV = 10,000 h the methanol production rate was 600 g/l-cat-h, which is 20% lower than that at reaction equilibrium. No significant difference was observed between data obtained from the present... 

The methanol production rate was 600 g/l-cafh under the conditions of 523 K, 5 MPa and SV=10,000h which is 20% lower than that at reaction equilibrium. No significant difference was observed between data obtained from the present test and from the previous laboratory scale test.. ... 

Fig. 6 shows the results for an operatir>g pressure of 5.27 MPa., an initial operating temperature of 498 K, and three different space velocities. At the right-hand terminus of each of the three lines in Rg. 6, temperature programming can no longer maintain a constant production rate. An increase in temperature beyond the terminal point increases the rate constant, k. but this effect Is exactly counterbalanced by a decrease of the equilibrium constant, K q. At these conditions, which are representative of commercial reactor designs, temperature programming cannot be used to maintain constant methanol production because the production rate cannot be held constant for a sufficiently-long period of time. 

Since in almost all methanol production plants only some part of the raw gas is carried through a CO shift conversion unit, COS hydrolysis is more important for coal gases than COS hydrogenation which takes place parallel with the water gas reaction. The equilibrium equation for COS hydrolysis is... 

In the above section, the importance of carbon monoxide and carbon dioxide conversion and the technically attainable approach to the equilibrium has been described. However, these two parameters alone do not decide upon the optima-tion for the production of methanol from a specific synthesis gas. The methanol yield from the synthesis gas is of quite decisive importance for economically producing methanol on a commercial scale. Its this yield on which depend the quantity of synthesis gas which must be produced horn coal, cleaned, conditioned and compressed and the quantity of CO2, CO and H2 which must be removed from the methanol synthesis as purge gas and thus is lost to methanol production by the direct route. 

The typical concentrations of methanol in an HTSC application are approximately 100 to 300 ppmw. In a Low Temperature Shift Converter (LTSC) application, the methanol production is greater than that of an HTSC application. The formation of methanol is not just related to equilibrium for an LTSC but also by the catalyst characteristics and kinetics. Therefore, the catalyst vendor should be contacted in reference to calculating the expected amount of methanol from an LTSC application. 

In addition to these considerations, protection by protonation was effective because (a) the CH3OH is in equilibrium with the protected form since protons transfers between oxygen atoms are fast, (b) the use of a strong acid as the solvent leads to essentially complete conversion of the methanol product to the protected... 

Pressure affects both equilibrium position and rate of reaction in methanol synthesis. From a total loop perspective, an increase (or decrease) in operating pressure affects more than merely the reaction conditions. It also affects the condensation of product (dew point) and recycle of methanol back to the converter system. Considering any gven converter, however, calculations indicate that a 10% increase in operating pressure yields about a 10% increase in methanol production if equilibrium conditions exist. When the reaction is far from equilibrium and controlled by kinetics, the increase (or decrease) in methanol production is more than proportional to the increase (or decrease) in operating... 

When the reactor system in methanol synthesis operates under kineticalfy controlled conditions, an increase in the circulating rate causes methanol production to decrease. If equilibrium is being achieved, however, one can expect that a 2.53% increase in production will be realized for a 5% increase in circulation and that a 56% increase in production will result from a 10% increase in circulation, and so forth. 

As mentioned in the Preface, a small number of industrial applications of reactive distillation have been around for many decades. One of the earhest was a DuPont process in which dimethyl terephthalate was reacted with ethylene glycol in a distillation column to produce methanol and ethylene terephthalate. The reactants were fed into the middle of the column where the reversible reaction occurred. The more volatile, low-boiling methanol product was removed from the top of the column, and the high-boiling ethylene terephthalate product was removed from the bottom. The removal of the products from the reaction zone drove the reversible reaction toward the product side. This is one of the fundamental advantages of reactive distillation. Low chemical equilibrium constants can be overcome and high conversions achieved by the removal of products from the location where the reaction is occurring. 

You have a saturated vapor feed containing 5% water and 95% methanol. You want to feed this to the bottom of a column to make 99.99% product methanol and a waste of 90% methanol. The equilibrium line in this case is... 

Based on an average tray efficiency of 90 percent for the hydrocarbons, the eqiiilibniim-based model calculations were made with 36 equilibrium stages. The results for the distillate and bottoms compositions, which were very close to those computed by the rate-based method, were a distillate with 0.018 mol % ethylbenzene and less than 0.0006 mol % styrene, and a bottoms product with only a trace of methanol and 0.006 mol % toluene. 

In the case of 1,3-diphenylisoindole (29), Diels-Alder addition with maleic anhydride is readily reversible, and the position of equilibrium is found to be markedly dependent on the solvent. In ether, for example, the expected adduet (117) is formed in 72% yield, whereas in aeetonitrile solution the adduet is almost completely dissociated to its components. Similarly, the addition product (118) of maleic anhydride and l,3-diphenyl-2-methjdi.soindole is found to be completely dissociated on warming in methanol. The Diels-Alder products (119 and 120) formed by the addition of dimethyl acetylene-dicarboxylate and benzyne respectively to 1,3-diphcnylisoindole, show no tendency to revert to starting materials. An attempt to extrude carbethoxynitrene by thermal and photochemical methods from (121), prepared from the adduct (120) by treatment with butyl-lithium followed by ethyl chloroform ate, was unsuccessful. 

A low-pressure process has been developed by ICl operating at about 50 atm (700 psi) using a new active copper-based catalyst at 240°C. The synthesis reaction occurs over a bed of heterogeneous catalyst arranged in either sequential adiabatic beds or placed within heat transfer tubes. The reaction is limited by equilibrium, and methanol concentration at the converter s exit rarely exceeds 7%. The converter effluent is cooled to 40°C to condense product methanol, and the unreacted gases are recycled. Crude methanol from the separator contains water and low levels of by-products, which are removed using a two-column distillation system. Figure 5-5 shows the ICl methanol synthesis process. 

In its present form, intermediate 12 is not a viable substrate for the crucial Dieckmann condensation it must undergo prior epimerization at C-16. When intermediate 12 is treated with sodium methoxide in hot methanol, enolization at C-16 occurs and an equilibrium is established between 12 and a diastereomeric substance, intermediate 11. Once formed, 11 can either revert back to 12 through the planar enolate form, or it can participate in a productive cyclization reaction to give a new six-membered ring. Under these conditions, the desired transformations take place with exceptional facility to give, after acidification of the reaction medium, enol ester 10. 

The lack of a substrate isotope effect suggests very extensive internal return and is readily explained in terms of the fact that conversion of the hydrocarbon to the anion would require very little structural reorganisation. Since koba = k 1k 2/(kLl+k 2) and k 2 is deduced as > k2, then kobs = Kk 2, the product of the equilibrium constant and the rate of diffusion away of a solvent molecule, neither of the steps having an appreciable isotope effect. If the diffusion rates are the same for reactions of each compound then the derived logarithms of partial rate factors (above) become pAT differences between benzene and fluorobenzene hydrogens in methanol. However, since the logarithms of the partial rate factors were similar to those obtained with lithium cyclohexylamide, a Bronsted cor-... 

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