Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Thermodynamic Equilibrium of the Reaction

Enzymes, as catalysts, accelerate the reaction rates (a kinetic factor). The forward reaction and the back reaction are accelerated to the same degree. The position of equilibrium (a thermodynamic measure), which is not influenced by the enzyme, yields information about the maximum conversion and therefore is of basic importance for process development. Two examples will serve to demonstrate this principle. [Pg.193]

Aminoacylase stereospecifically cleaves N-acetyl-L-aminoacids to acetate and l-aminoacid, a reaction well known for the production of optically pure L-aminoacids (Eq. (2)). [Pg.194]

N-acetyl-L-amino acid ----------, 1 L-amino acid + acetate (2) [Pg.194]

The equilibrium conversion for hydrolysis of the acetyl-L-aminoacid depends on the initial oncentration. Only at zero concentration may one hundred percent conversion be attained (Fig. 7-6). [Pg.194]

In the industrial acylase process, an increase of both substrate concentration and conversion is desired to reduce costs, but, as a thermodynamic principle, in cases of increasing mole number during the reaction, the equilibrium conversion decreases with rising substrate concentration. [Pg.194]


In 2010, Ramstrom and coworkers showed that hemithioacetal (HTA) formation from reaction between a thiol derivative and a given aldehyde (or ketone) was a fast and reversible process in water, and therefore suitable for DCC-based systems (Fig. 8b) [65]. Because the thermodynamic equilibrium of the reaction of HTA formation is significantly displaced toward the two reactants, a virtual library of ten possible HTA was generated by mixing in water five aliphatic thiols and two aldehydes (one aromatic and one aliphatic). When carried out in the presence of an enzyme (i.e., (3-galactosidase) free of any cystein residues in its active site to avoid HTA formation between the library components and the enzyme itself, the formation of a specific HTA was highly favored as determined by saturation... [Pg.306]

A decrease in the stationary chemical potential (concentration) of most reactive catalyst species (including intermediate reactant—reaction center complexes) and an increase in chemical potentials (concentrations) of less reactive species against their chemical potentials (concentrations) under conditions of thermodynamic equilibrium of the reaction medium Existence of reversible nonequiUbrium reconstruction of the active component surface or bulk... [Pg.251]

The high molar conversion obtainable in esterifications catalyzed by dry mycelia encouraged us to investigate the partition of water in these heterogeneous systems further. The objechve was to verify whether mycelia were able to affect the thermodynamic equilibrium of the reactions by modifying the parhtioning of the water formed during the esterificahon. The synthesis of two esters by lyophilized mycelia of R. oryzae CBS 112.07 was studied and the results were compared with those obtained with a commercial immobilized CALB (Novozym 435). [Pg.88]

Many researchers have studied the thermodynamic equilibrium of the reactions occurring in the gasification process. The reaction enthalpies and equilibrium constants of some reactions at different gasification temperature are listed in Table 4.5. [Pg.170]

Corresponding to the above discussion about enzyme kinetics, the numerator is nearly identical for all different bi-bi-mechanisms (for bi-uni mechanisms, respectively), as the numerator characterizes the thermodynamic equilibrium of the reaction (which is independent of a kinetic mechanism). [Pg.222]

FDH catalyzes the oxidation of formate to carbon dioxide, concomitant with the reduction of NAD+ to NADH (Fig. 16.6-4). Because of the favorable thermodynamic equilibrium of the reaction and the volatility of the reaction product, the enzyme is commonly applied for in situ regeneration of NADH during asymmetric synthesis of chiral compounds1131. [Pg.1247]

Thermodynamic equilibrium of the reaction mixture for reversible reactions. [Pg.14]

Like catalysts in general, enzymes can only accelerate reactions but have no impact on the position of the thermodynamic equilibrium of the reaction. Thus, in principle, enzyme-catalyzed reactions can be run in both directions. [Pg.4]

The catalytic dehydrogenation (DHYD) of ethylbenzene (EB) to styrene (ST) is the major industrial process for the styrene production [1]. The industrial process is usually realized in the temperature regime between 550-620°C with an excess of overheated water vapor mainly over a potassium promoted iron oxide catalyst [1]. Because this process is limited by the thermodynamic equilibrium of the reaction and because it is very energy... [Pg.383]

PSA Reactor. The idea of a PSA reactor was first suggested by Vaporciyan aud Kadlec (1987 1989). The basic idea is to combine sorption and catalytic reaction in order to shift the thermodynamic equilibrium of the reaction. The sorbent selectively adsorbs one of the products and is regenerated during the low pressure half-cycle. By doing so, the conversion is increased and simultaneous separation is also accomphshed. Vaporciyan and Kadlec (1989) demonstrated the idea for CO oxidation reaction by mixing a 5A zeolite sorbent and a Pt/alumina catalyst in the adsorber. This idea was pursued by Sircar and co-workers (Carvill... [Pg.37]

Higher pressure is unfavourable for the thermodynamic equilibrium of the reaction, however, an elevated system pressure up to 10 bar is beneficial for the kinetics of the reaction [12]. At 1 bar and 400 °C only negligible amounts of ammonia still remain in the reaction mixture according to thermodynamics. [Pg.46]

Membrane reactors offer an inherent ability to combine reaction, product concentration, and separation in a single unit operation and are especially suited for reactions such as water gas shift reaction with conversions limited by the thermodynamic equilibrium of the reaction. The use of a membrane reactor for the continuous separation of hydrogen from the reformate allows the reformer to be mn at lower temperatures and, at the same time, provides process intensification by eliminating the shift reactors, PreOx (preferential oxidation) reactor and hydrogen separator. [Pg.671]

The composition of the gas produced is determined by the thermodynamic equilibrium of these reactions at the exit temperature, which is given by the adiabatic heat balance based on the composition and flow of the feed, steam and oxygen added to the reactor. [Pg.189]

Detonation, Chapman-Jouguet Parameters or Chapman-Jouguet Variables. Parameters are properties, or thermodynamic coordinates of the reaction products at equilibrium or completion of the reaction. These parameters are denoted by subscript CJ, like in P -j... [Pg.230]

The Eyring approach has the advantage that the pseudothermodynamic activation parameters can be readily related to the true thermodynamic quantities that govern the equilibrium of the reaction. The Arrhenius equation, on the other hand, is easier to use for simple interpolations or extrapolations of rate data. [Pg.27]

Reactions (2) and (3) are reversible tile concentrations of the five components CH, H20, C02, CO and H2 which result are governed by thermodynamic equilibrium. Raising the reaction temperature shifts the equilibrium for both reactions to the right. Thus at low temperatures the exothermic reaction (]) predominates, while at high temperatures the overall reaction is endothermic, At approximately 500-550°C the reacdon is thermally neutral,... [Pg.1558]

Chemical reactivity is influenced by solvation in different ways. As noted before, the solvent modulates the intrinsic characteristics of the reactants, which are related to polarization of its charge distribution. In addition, the interaction between solute and solvent molecules gives rise to a differential stabilization of reactants, products and transition states. The interaction of solvent molecules can affect both the equilibrium and kinetics of a chemical reaction, especially when there are large differences in the polarities of the reactants, transition state, or products. Classical examples that illustrate this solvent effect are the SN2 reaction, in which water molecules induce large changes in the kinetic and thermodynamic characteristics of the reaction, and the nucleophilic attack of an R-CT group on a carbonyl centre, which is very exothermic and occurs without an activation barrier in the gas phase but is clearly endothermic with a notable activation barrier in aqueous solution [76-79]. [Pg.329]

A relevant characteristic of the technology should be the ability to remove the water selectively and continuously in order to shift the chemical equilibrium to full conversion. Because the presence of a liquid water phase will lead to rapid deactivation of the solid catalyst, operating conditions for water-free organic liquid should be found. In addition, the thermodynamic behavior of the reaction mixture is nonideal, particularly with respect to the couple alcohol-water. [Pg.232]

Frequently the kinetic description of catalyst deactivation and coke formation is complicated by instationary reaction conditions prevailing during the respective experiments. In this paper two experimental methods are presented.which enable the determination of such kinetics avoiding this problem 4 Use of a concentration controled continuously operated recycle reactor 4 Experimentation at the thermodynamic equilibrium of the main reaction to determine the coke formation kinetics at well defined operating conditions... [Pg.257]

Chronologically, the effon was im tially dirreted towards a better petrochemical upgrading of toluene and m-xylene, which continue to be used as solvents and in the gasoline pool. Toluene is thus converted to benzene by hydrodealkylation. Through i omerizatioo,. m-.xyiene yields the onho and para isomers in proportions corresponding to thermodynamic equilibrium in the reaction conditions, namely a mixture of Cg from which the... [Pg.235]


See other pages where Thermodynamic Equilibrium of the Reaction is mentioned: [Pg.171]    [Pg.27]    [Pg.389]    [Pg.1192]    [Pg.209]    [Pg.193]    [Pg.276]    [Pg.84]    [Pg.41]    [Pg.349]    [Pg.171]    [Pg.27]    [Pg.389]    [Pg.1192]    [Pg.209]    [Pg.193]    [Pg.276]    [Pg.84]    [Pg.41]    [Pg.349]    [Pg.106]    [Pg.228]    [Pg.92]    [Pg.217]    [Pg.191]    [Pg.173]    [Pg.548]    [Pg.10]    [Pg.106]    [Pg.160]    [Pg.280]    [Pg.162]    [Pg.116]    [Pg.256]    [Pg.341]    [Pg.20]    [Pg.574]    [Pg.110]    [Pg.112]    [Pg.73]   


SEARCH



Equilibrium of reactions

Equilibrium thermodynamics

Reactions thermodynamics

Thermodynamic reactions

Thermodynamics Equilibrium/equilibria

Thermodynamics of equilibria

Thermodynamics of reactions

© 2024 chempedia.info