Thermodynamic equilibrium limitations

All of the above reactions are reversible, with the exception of hydrocracking, so that thermodynamic equilibrium limitations are important considerations. To the extent possible, therefore, operating conditions are selected which will minimize equilibrium restrictions on conversion to aromatics. This conversion is favored at higher temperatures and lower operating pressures. 

Combining chromatography with a chemical reactor can be used to achieve reaction and separation within the same reactor, and this can be used to generate products beyond the normal thermodynamic equilibrium limitation. 

Finally, there may be a few opportunities for closecoupling of reaction and adsorption systems to overcome thermodynamic-equilibrium limitations or to enhance selectivity by operating with low conversions per pass. Reaction types... 

Thermodynamic equilibrium limitations exist for the first reaction, but the other reactions can be considered as irreversible, at least in the region where the conversion to styrene is attractive. Only reaction 3 is considered in the first stage calculations because there is considerable experimental evidence that the other reactions occur to only a very small extent. 

On the latter, even though oxydehydrogenation offers advantages as a means of overcoming thermodynamic equilibrium limitations, it also leads to the total or partial loss of by-product hydrogen, which in some instances can have a very significant economic impact. 

Because of these factors, typical reactions occur in a limit of strong thermodynamic disequilibrium exactly opposite to the near thermodynamic equilibrium limit of the slow variable models. Consequently, forces acting... 

The reaction is further complicated by thermodynamic equilibrium limitations, as indicated in Table I. The condensation/dehydration of acetone to MO is limited to about 20% conversion at 120 C (16). However, there is no equilibrium limitation to the overall acetone-to-MIBK reaction. This, coupled with the possibility of numerous thermodynamically favorable side reactions that are also acid/base-catalyzed (Fig. 1), suggests the need to balance the acid/base and hydrogenation properties of the selected catalyst. 

Generally, three phase fixed bed reactors are operated with concurrent downflow of gas and liquid in the trickling regime (trickle-bed reactor). Countercurrent operation is less frequent as in this case, the possible ranges of liquid and gas flow rates are very narrow. It is used when thermodynamic equilibrium limits the extent of reaction. 

The idea of breaking the thermodynamic equilibrium limitations through the use of a selective membrane in not completely new. However, it became practically feasible in the last decade due to the impressive advancement in material science and the development of a new generation of highly selective inorganic membranes (5,6,25). The reader is requested to review the advancement in this field to choose the most suitable membranes. 

The pressure of gas was 101.325 kPa. The ammonia synthesis rate was stable after passage of current for 2-6 min and this rate was at least three magnitudes higher than that of conventional catalytic reactor. The conversion of hydrogen was close to 100% which eliminated thermodynamic equilibrium limitation. The main problem of this method is that the conductivity of SCY ceramic is very poor at normal temperature. Even at 570°C, its conductivity is unsatisfied because the current density was smaller than 2 mA-cm and could not be further increased. This limited the efficiency of ammonia synthesis and theoretical research. The use of solid electrolyte with high proton conductivity at low temperature to replace the SCY ceramic may be favorable to decreasing the synthesis temperature and increasing the current density and production efficiency. 

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