Reaction equilibrium liquid phase

For the liquid phase, the equilibrium ratios have only been estimated. For the range 233-263 K, its value was estimated in the range 4.5-5. corresponding to ca. 48 % dissociation. The heat of reaction in liquid phase was calculated to be in the range 0.624-0.756 kcal/mole (ref. 2). 

Graaf et al (27,2reaction rate for methanol syn esis in gas-catalyst phases and extended it to three phase methanol synthesis using gas-liquid solubilities in thermodynamical equilibrium described by Henry s law. The rates for the three reactions (ZY= 3) in liquid phase are given by equations T12 and T13. Where, a. represents the stoichiometric coefficient of yxth species in the rth reaction of liquid phase and M- represents the molecular weight of yxth species. rix (mol/Kgcat sec) is the rate of reaction on catalyst surface for three reactions. 

Derivation of chemical equilibrium relationships for simple reactions Reactions in gas phase Reactions in liquid phase Explore yourself References Bibliography... 

Before the modern theory of an elementary act was formulated, the disturbance of the equilibrium distribution of the energy among the degrees of freedom was proposed in [130] as one of the possible causes for the decreased value of the preexponential factor. This proposition, however, seems to be improbable for a slow reaction in liquid phase. 

The equilibrium conversion can be increased by employing one reactant in excess (or removing the water formed, or both). b. Inerts concentration. Sometimes, an inert material is present in the reactor. This might be a solvent in a liquid-phase reaction or an inert gas in a gas-phase reaction. Consider the reaction system... 

Product removal during reaction. Sometimes the equilibrium conversion can be increased by removing the product (or one of the products) continuously from the reactor as the reaction progresses, e.g., by allowing it to vaporize from a liquid-phase reactor. Another way is to carry out the reaction in stages with intermediate separation of the products. As an example of intermediate separation, consider the production of sulfuric acid as illustrated in Fig. 2.4. Sulfur dioxide is oxidized to sulfur trioxide ... 

In a liquid-liquid extraction, the analyte (or interferent) is extracted from one liquid phase into a second, immiscible liquid phase. When the analyte is involved in secondary equilibrium reactions, it is often possible to improve selectivity by carefully adjusting the composition of one or both phases. 

The liquid-phase rate coefficient is strongly affected by fast chemical reactions and generally increases with increasing reac tion rate. Indeed, the condition for zero hquid-phase resistance m/k-d) imphes that either the equilibrium back pressure is negligible, or that... 

The definition of Kp obviously applies to tlie reaction of Eq. (4.6.1). Assuming that a K value is available or calculable, this equation may be used to detennine the partial pressures of the participating components at equilibrium. For liquid phase reactions, K is given approximately by... 

The metathetic reaction occurs in the gas phase at relatively high temperatures (150°-350°C) with molybdenum or tungsten supported catalysts or at low temperature (=50°C) with rhenium-based catalyst in either liquid or gas-phase. The liquid-phase process gives a better conversion. Equilibrium conversion in the range of 55-65% could be realized, depending on the reaction temperature. ... 

Similar to the alkylation and the chlorination of benzene, the nitration reaction is an electrophilic substitution of a benzene hydrogen (a proton) with a nitronium ion (NO ). The liquid-phase reaction occurs in presence of both concentrated nitric and sulfuric acids at approximately 50°C. Concentrated sulfuric acid has two functions it reacts with nitric acid to form the nitronium ion, and it absorbs the water formed during the reaction, which shifts the equilibrium to the formation of nitrobenzene ... 

The mass transfer coefficient is calculated for a given diffusivity coefficient and reaction rate constant at the equilibrium concentration of oxygen. When oxygen is continuously transported and removed from the liquid phase we may write ... 

Units in SI system Si Stanton number h/Cf,pu Dimensions depend ort order of reaction. Suffixes 0 Value in bulk of phase 1 Phase 1 2 Phase 2 A Component A B Component B AB Of A in B b Bottom of column equilibrium with bulk of other phase G Gas phase / Interface value. L Liquid phase u Overall value (for height and number of transfer units) value in bulk of phase i Top of column Dimensions in in M. N, 1. T. 

In this reaction, there is a gas phase and a liquid phase. Likewise, the equilibrium between a solid and its saturated solution is heterogeneous ... 

The production process chosen in this work involved at least bromine in the liquid phase. In order to implement a production process, it is important to have knowledge of the reaction s kinetics, i.e. how soon is the equilibrium attained. In cases where the BrCI should be used immediately following its production, it is important to avoid high levels of unreacted chlorine, since it might result in undesired chlorinations etc. 

Little has been reported on the kinetics of this reaction in the liquid phase in one experiment at - 50°C, it has been reported that equilibrium was established within 30 seconds. It has been reported that the formation of BrCl in polat solvents is much faster than in non-polar solvents (ref. 1) hence, for the next reaction, one might expect some auto-catylitical behaviour. It was also reported in a review... 

The ozonolysis of ethylene in the liquid phase (without a solvent) was shown to take place by the Criegee mechanism.This reaction has been used to study the structure of the intermediate 16 or 17. The compound dioxirane (21) was identified in the reaetion mixture at low temperatures and is probably in equilibrium with the biradical 17 (R = H). Dioxirane has been produced in solution but it oxidatively cleaves dialky] ethers (such as Et—O—Et) via a chain radical process, so the choice of solvent is important. 

The novel approach finally taken was to conduct the reaction and purification steps in a reactor-distillation column in which methyl acetate could be made with no additional purification steps and with no unconverted reactant streams. Since the reaction is reversible and equilibrium-limited, high conversion of one reactant can be achieved only with a large excess of the other. However, if the reacting mixture is allowed to flash, the conversion is increased by removal of the methyl acetate from the liquid phase. With the reactants flowing countercurrently in a sequence of... 

Solution Example 11.5 treats a system that could operate indefinitely since the liquid phase serves only as a catalyst. The present example is more realistic since the liquid phase is depleted and the reaction eventually ends. The assumption that the gas-side resistance is negligible is equivalent to assuming that a = ag throughout the course of the reaction. Equilibrium at the interface then fixes a = ag/Ku at all times. Dropping the flow and accumulation terms in the balance for the liquid phase, i.e.. Equation (11.11), gives 0 = kiAiV(ag/KH - ai) - Vikafi... 

B bulk property d deactivation e effective property G gas phase i component index i reaction index L liquid phase p catalyst particle property equilibrium conditions... 

One of the most important characteristics of IL is its wide temperature range for the liquid phase with no vapor pressure, so next we tested the lipase-catalyzed reaction under reduced pressure. It is known that usual methyl esters are not suitable for lipase-catalyzed transesterification as acyl donors because reverse reaction with produced methanol takes place. However, we can avoid such difficulty when the reaction is carried out under reduced pressure even if methyl esters are used as the acyl donor, because the produced methanol is removed immediately from the reaction mixture and thus the reaction equilibrium goes through to produce the desired product. To realize this idea, proper choice of the acyl donor ester was very important. The desired reaction was accomplished using methyl phenylth-ioacetate as acyl donor. Various methyl esters can also be used as acyl donor for these reactions methyl nonanoate was also recommended and efficient optical resolution was accomplished. Using our system, we demonstrated the completely recyclable use of lipase. The transesterification took place smoothly under reduced pressure at 10 Torr at 40°C when 0.5 equivalent of methyl phenylthioacetate was used as acyl donor, and we were able to obtain this compound in optically pure form. Five repetitions of this process showed no drop in the reaction rate (Fig. 4). Recently Kato reported nice additional examples of lipase-catalyzed reaction based on the same idea that CAL-B-catalyzed esterification or amidation of carboxylic acid was accomplished under reduced pressure conditions. ... 

Intelligent engineering can drastically improve process selectivity (see Sharma, 1988, 1990) as illustrated in Chapter 4 of this book. A combination of reaction with an appropriate separation operation is the first option if the reaction is limited by chemical equilibrium. In such combinations one product is removed from the reaction zone continuously, allowing for a higher conversion of raw materials. Extractive reactions involve the addition of a second liquid phase, in which the product is better soluble than the reactants, to the reaction zone. Thus, the product is withdrawn from the reactive phase shifting the reaction mixture to product(s). The same principle can be realized if an additive is introduced into the reaction zone that causes precipitation of the desired product. A combination of reaction with distillation in a single column allows the removal of volatile products from the reaction zone that is then realized in the (fractional) distillation zone. Finally, reaction can be combined with filtration. A typical example of the latter system is the application of catalytic membranes. In all these cases, withdrawal of the product shifts the equilibrium mixture to the product. 

Equilibrium for a single reaction in the liquid-phase. A significant proportion of fine chemistry processes occur in the liquid phase. The equilibrium constant is expressed by Eqn. (5.4-8), which can be rewritten as ... 

Equilibrium in multiphase and/or multireaction systems. If more than one phase is present in the system, a criterion of phase equilibria has to be satisfied together with the chemical equilibrium criterion. For instance, in a gas-liquid system components are in chemical equilibrium in the phase where the reaction occurs, but vapour-liquid equilibria between the gas and the liquid phases must also be taken into account. To determine the equilibrium composition of a reacting mixture in both phases, chemical equilibrium constants as well as data concerning vapour-liquid equilibria for all components of the reaction mixture should be known. In the equilibrium state ... 

Several experiments using different organic solvents in different biphasic media are necessary to find the adequate distribution of the reaction components. A series of experiments are essential for the choice of a process and for scaling-up. Experiments using Lewis cells [44] may yield useful results for understanding equilibrium, kinetics, and interactions between organic solvent-substrate and/or organic solvent-biocatalyst. A study of two-liquid phase biotransformation systems is detailed below in Sections II-IX. 

The volumetric ratio of the two liquid phases (j6 = Forg/ Faq) can affect the efficiency of substrate conversion in biphasic media. The biocatalyst stability and the reaction equilibrium shift are dependent on the volume ratio of the two phases [29]. In our previous work [37], we studied the importance of the nonpolar phase in a biphasic system (octane-buffer pH 9) by varying the volume of solvent. The ratio /I = 2/10 has been the most appropriate for an improvement of the yield of the two-enzyme (lipase-lipoxygenase) system. We found that a larger volume of organic phase decreases the total yield of conversion. Nevertheless, Antonini et al. [61] affirmed that changes in the ratios of phases in water-organic two-phase system have little effect upon biotransformation rate. 

The equilibrium conversion can be calculated from knowledge of the free energy, together with physical properties to account for vapor and liquid-phase nonidealities. The equilibrium conversion can be changed by appropriate changes to the reactor temperature, pressure and concentration. The general trends for reaction equilibrium are summarized in Figure 6.8. 

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