Reaction conditions removing products/adding reactants

Whereas in Gas Recycle the product must be removed at the same temperature and pressure at which it is formed, in Liquid Recycle the separation of product (and byproducts) from catalyst is independent of the conditions under which the products were formed. This added degree of control brings a variety of benefits. Since large gas flows are no longer required in the reactor, the liquid expansion due to gassing is reduced and more catalyst can be contained in a specific reaction vessel. Reactor temperature and reactant concentrations can be tuned for optimum catalyst performance. The conditions in the separation system can likewise be tuned for optimum performance. In particular, more severe conditions will permit better control over the concentration of heavies in the catalyst solution. 

A true steady state can be attained if, for example, the system is confined in a reaction vessel where a solution of A is continuously added to the system while some of the product is continuously removed at the same volume flow rate. Such steady states are by no means exceptional and occur often in living cells or chemical reactors. A steady state then lasts as long as the reaction conditions, including rates of inflow of reactant(s) and outflow of product(s), are kept constant. Also for other rate processes, e.g. involving mass or heat transfer, steady states are often achieved. 

D7.1 The position of equilibrium is always determined by the condition that the reaction quotient, Q must equal the equilibrium constant. K. If the mixing in of an additional amount of reactant or product destroys that equality, then the reacting system will shift in such a way as to restore the equality. That implies that some of the added reactant or product must be removed by the reacting system and the amounts of other components will also be affected. These adjustments restore the concentrations to their (new) equilibrium values. 

Le Chatelier s principle states that a change in the conditions of a chemical system at equilibrium alters the concentrations of reactants and products, and a new equilibrium results. For example, if more reactant is added to a reaction at equilibrium, the concentrations of both reactants and products change to reestablish the equilibrium, and the equilibrium constant remains unchanged. After adding reactant, the total concentration of reactant initially increases, but then it decreases to establish a new equilibrium concentration. As a result, the concentration of the product increases. In short, the change imposed on the system by adding reactant is offset when some of the added reactant is converted to product. If a product is removed from a chemical system at equilibrium, the forward reaction occurs to give more product. We saw above the equilibrium constant for the formation of ethyl ethanoate from ethanoic acid and ethanol is 4.0. What if we would like to obtain a quantitative yield of product We can achieve this in two ways ... 

Add or remove a gaseous reactant or product. The effect of these actions on the equilibrium condition is simply that caused by adding or removing a reaction component, as described previously. 

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