Liquid Phase Chemical Reactors Essay Example

Liquid Phase Chemical Reactors Essay Example Liquid Phase Chemical Reactors Paper Liquid Phase Chemical Reactors Paper It is also used in the laboratories in obtaining design, interpretation of rate of reaction and numerical treatment of kinetics experimental data for different types of reacting systems. The use of a batch reactor for the most part eliminates the effects due to fluid flow on the resulting reaction rates. Consequently, the data reflect the intrinsic kinetics for the reaction being investigated. The objectives of this experiments To find the reaction rate constant in a batch stirred tank reactor for the specification of ethyl acetate with dilute sodium hydroxide. To determine the effect of temperature on reaction rate constant. To find the values of rate constant and Awareness parameters. Equipment used Arm field batch stirred tank reactor A stop clock A conductivity meter Water bath (tank) with a thermostat Funnel A heat controller Two flasks of one liter each and Stock solutions (0. 1 M sodium hydroxide and 0. MM ethyl acetate). The key results obtained include Table showing rate constant, , , in a batch stirred tank reactor. T( Rate constant/ 25 30 To conclude All the objectives where met as the results below shows and from those results there is a clear indication that conductivity is inversely proportional to he temperature also the reaction rate constant is directly proportional to the temperature . From the experiment it shows that in a batch reactor, since there is no inflow or outflow, the reactants concentration reduces with time. For an overall second order reaction (first order in both components) like the one that was done in the lab, the reaction rate is also dependent on the concentration of the reactants unlike a zero order reaction that is independent of the concentrations of the reactants. Conductivity of a solution decreases with time as the solution loses it ions, it will become less conductive. The things that I learnt doing this experiment are What I have learnt from this experiment was that conductivity is used instead of concentration may be since they both directly proportional to each other and affected with the same parameters. Also I have learnt how the rate Of a reaction could be increased or decreased by factors such as temperature. Introduction A batch reactor is used in chemical processes for small scale operation, for testing new processes that have not been fully developed, for the manufacturer of expensive products and for processes that are difficult to convert to continuous operations. The advantage of batch reactor is high conversion which be obtained by leaving the reactant in the reactor for long periods of time but it also has the disadvantages of high labor costs per batch and the difficulty of large scale production. In a batch reactor, all the reactants are loaded at once, the concentration then varies with time, but at any one time it is uniform throughout. Agitation serves to mix separate feeds initially and to enhance heat transfer. Batch reactors are popular in practice because of their flexibility with respect to reaction time and to the kinds and quantities of reactions that can process. The characteristic of batch reactor such as the total mass of each batch is mixed, each batch is a closed system and the reaction (residence) time for all elements of fluid is the same. A chemical reactor is an equipment unit in a chemical process where chemical reactions take place to generate a desirable product at a specified production rate, using a given chemistry. The reactor configuration and its operating conditions are selected to achieve certain objectives such as maximizing the profit of the process, and minimizing the generation of pollutants, while satisfying several design and operating constraints (safety, controllability, availability of raw materials, etc. ). Usually, the performance of the chemical reactor plays a pivotal role in the operation and economics of the entire process since its operation affects most other units in the process (separation units, utilities, etc. ). Chemical reactors usually fulfill three main requirements: 1 . Provide appropriate contacting of the reactants. 2. Provide the necessary reaction time for the formation of the desirable product. 3. Provide the heat-transfer capability required to maintain the specified temperature range. In many instances these three requirements are to complimentary, and achieving one of them comes at the expense of another. A batch experimental reactor is used for slow reactions since species compositions can be readily measured with time. Batch reactors are used widely in industry at all scales. Batch reactors are tanks , commonly provided with agitation and a method of heat transfer ( usually by coils or external jacket) . This type of reactor is primarily employed for relatively slow reactions of several hours duration, since the downtime for filling and emptying large equipment can be significant. Agitation is used to maintain homogeneity and to improve heat transfer. In a batch reactor it consists of a tank, integral heating and cooling system; one or more fluid reagents are introduced into a tank reactor equipped with an impeller which helps to stirs the reagents to ensure proper perfect mixing. Batch chemical reactors are used for a variety of process operations such as solids dissolution, product mixing, chemical reactions, batch distillation, crystallization, liquid/liquid extraction and popularization. Chemical reactors vary widely in size, shape and method of operation; the simple types of reactor are: batch reactor (BRB); based on omelet mixing, plug flow reactor (PR); based on plug flow, continues stirred tank reactors (CAST); based on back-mix flow and laminar flow reactor (ELF); based on laminar flow. Batch reactors are used both in laboratories and industrial process for prod icing chemicals. In the laboratories, it is used in Of kinetics experimental data for different types Of reacting systems. In industries, it is used for small scale production; especially for situations whereby switching from one process or product to another are required; such as in manufacture of pharmaceuticals. It is also used in the production f polyvinyl chloride (involving suspension of popularization) and emotion popularization latex Generally several factors could influence the rate of a chemical reaction. Some of these factors include: Temperature Concentration State of reactants (that is if they are solid, liquid or gas) Order of reaction Theory The overall mass balance for the stirred reactor can be written as: Rate of change within the reactor = Input -?output-Loss by reaction For batch operation, the overall mass balance can be rearranged to: Rate of change within the reactor Loss by reaction I. E. For a material A: Where: CACAO is input concentration of A in the input stream CA = exit concentration of A in the exit stream RA rate of reaction of A. In homogeneous reaction systems, reaction rates depend on the concentration of the reactants. Collision theory indicates a rate increase if the concentration of one or both of the reactants is increased. Conversely, lowering the concentration should have the opposite effect. However, the specific effect of concentration changes in a reaction system has to be determined by experimental methods. Increasing the concentration Of substance A in reaction with substance B old increase the reaction rate, decrease it or have no effect on it depending on the particular reaction. It is important to recognize that the balanced equation for the net reaction does not indicate how the reaction rate is affected by a change in concentration of reactants. The general form of the rate law for a bimolecular reaction is: The reaction to be studied in this experiment for the batch reactor was for the specification Of ethyl acetate with dilute sodium hydroxide. The equation is as shown below: Specification is the name given to the chemical reaction that occurs when a getable oil or animal fat is mixed with a strong alkali. The products of the reaction are two: soap and glycerin. Water is also present, but it does not enter into the chemical reaction. The water is only a vehicle for the alkali, which is otherwise a dry powder. It is commonly refers to the reaction of a metallic alkali such as Lye (A. K. A. Sodium Hydroxide or Noah) with an animal or vegetable fat, or oil to produce soap. In this reaction, two products result: Soap and Glycerin. The equation is as shown below: The structural formula is shown below: Sodium Hydroxide (Noah) is a caustic base or metallic alkali Noah is used in his experiment which means it will result in a hard soap will result. In specification, the metallic alkali, in this case sodium hydroxide (Noah) breaks down the fat with which it is mixed. In soap making, fats used can either be vegetable oils like olive Oil, or animal fats. When the oil Or fat is mixed with the base the process takes place it can be endothermic reaction meaning it absorbs surrounding heat or exothermic reaction releasing heat. In the reaction the rate is expected to depend on the concentration of A and B. The order of the reaction in both components is first; therefore the action has an overall order of two, since the overall order is the sum of the power order of each of the components. Thus, from Equating equation (1) and (2) it gives: However, if the two concentration are made equal from the start, then; Integrating gives the equation 5 below: From equation (5), a graph of against can be plotted which will give a slope that is equal to rates constant Concentration of hydroxide, is the concentration of reactant A in the exit stream at time t is the initial concentration of Noah is the conductivity of the solution at time t is the conductivity Of the solution at the end Of reaction s the initial conductivity at time t = O The relationship between reaction rate and temperature is explained by Awareness equation which is given as: is the reaction rate constant is the universal gas constant (8. 314] mol-K-1) is temperature is the activation energy (k mol-l) is Awareness constant or pre-exponential factor (5-1) for a first order reaction By applying natural logarithm to both sides, equation 7 above can be re- written as shown below: A plot of against would yield a strai ght line graph from which A can be obtained as the intercept of the line at. The activation energy (EAI) can then be obtained from the slope of the graph which is given as. Thus if the slope, S z, then the activation energy can be estimated as: Reactions with low activation energy are relatively temperature-insensitive while those with high activation energies are very temperature sensitive. Therefore, any given reaction is much more temperature-sensitive at a low temperature than at a high temperature. Thus the batch stirred tank reactor allows to measure rates of reaction by observing the change of reactant concentration within the reactor with time. It can also easily change and control the temperature of the system. Experimental equipment 1 Figure 1: Layout of the experimental equipment Description As seen in figure 2, the experimental diagram shows the equipment used in the laboratory practical and the layout. These include: 1. Arm field batch reactor, which was the main equipment that was used for the experiment to take place where the reactants were mixed in; 2. A stop clock for measuring time (in seconds) after start up as the run proceed; 3. A portable conductivity meter, which measures the time dependent conductivity of the solution in the tank. The unit on the meter is Siemens m-l; 4. Water bath with a thermostat, here ethyl acetate and sodium hydroxide were place in other to maintain their temperature; 5. Funnel used to pour ethyl acetate and diluted sodium hydroxide into the batch reactor; 6. Heat controller used to control the temperature for the experiment at the different temperature; 7. Flasks used to measure out 1 liter Of each reactant(ethyl acetate and sodium hydroxide); 8. Water solution used to put the conductivity probe inside while the reactants were poured into the reactor; 9. A thermometer for measuring the water temperature. Experimental Procedure 1 . The reaction temperature was initially set to 25 co on the thermostatic tat. 2. Two 1 liter flasks were filled to the mark with sodium hydroxide solution and ethyl acetate solution respectively. They were then placed in the bath. 3. The reaction temperature was set on the reactor control panel. 4. The conductivity meter was set up and its probe end was placed in the bath to come reaction temperature. 5. The flasks were allowed to reach reaction temperature. 6. The solution of sodium hydroxide (1 liter) was added to the reactor, as well as the solution of ethyl acetate (1 liter) was added to the reactor and the clock was started when ca. 50% was added. 7. After 30 seconds, the ca. 200 ml ample was withdrawn from the reactor and straight after that, its conductivity was measured, noting time. The sample was then returned to the reactor and the probe to the bath. 8. This was repeated every 30 seconds for 10 minutes. 9. The experiment was allowed to run for another 20 minutes, this time taking readings every 3 minutes. 10. The experiment was then repeated at different temperatures of ICC and ICC Observations It was observed that the conductivity readings obtained at ICC, ICC and ICC decreases with time.