Ammonia is a leading chemical industry in the world. Because ammonia is used to prepare other chemicals and has its uses. In this tutorial we are going to cover followings.
Ammonia is compound which has molecular formula of NH3. It is a gas in room temperature. In laboratories, ammonia is as aqueous ammonium hydroxide (NH4OH) solution. Ammonia is a very toxic compound and have to use it very carefully.
Ammonia is a very toxic, sharp suffocating odor, colourless gas. Ammonia is basic gas and it is found as aqueous ammonium hydroxide solution in the laboratory. Ammonia dissolve very well in water.
In this section, we discuss how raw materials are converted to ammonia and what conditions (optimum conditions) should be maintained to get desired product. Reactions involving in ammonia production is explained with each step.
Pressure and temperature of air is increased. Then air can be converted to liquid phase. That liquid air is done fractional distillation. From this method N2 is separated.
CH4(g) + H2O(g) → CO(g) + 3H2(g)
CO + H2O(g) → H2(g) + CO2(g)
Hydrogen and nitrogen react and give ammonia. But this reaction is a reversible one. After starting the reaction, it will start the backward reaction to give hydrogen and nitrogen. Forward reaction is a exothermic.
Standard enthalpy of the reaction is -46 kJ mol-1. This value is important in designinga new plant.
Forward reaction is a exothermic one. Therefore using low temperature will increase the forward reaction and give higher percentage of ammonia. But having low temperature will reduce the reaction rate. So, have to wait much time to take the product. By considering both product amount and production rate, temperature is decided.
4000C - 4500C temperature is applied.
In forward reaction, two molecules are given by reacting four molecules. ( one N2 molecule + three H2 molecules). Therefore pressure is decreased, volume is decreased due to decrease of number of molecules. So increasing the pressure will bring the reaction more forward (producing more NH3). But Equipments which are affordable to high pressure are expensive. Also to generate high pressure, cost is high.
Therefore Around 200 atm pressure should be given.
1:3 N2 : H2 volume ratio
Reaction does not come to completeness. Hence there are remaining N2(g) & H2(g) with NH3(g) in the product. Product is cooled here. When product is being cooled ammonia becomes to liquid state from gaseous state. But N2(g) & H2(g) are in gaseous state.
As the final product liquid ammonia is separated.
Unreacted nitrogen and ammonia is resent to the react.
Ammonia has so many uses in industrial scale and domestic scale.
Ammonia industry may cause several environmental pollution due to its products and physical conditions.
Boiling point of ammonia is higher than both hydrogen and nitrogen. So we can easily liquidize ammonia by pressurizing while hydrogen and nitrogen remain as gaseous state. So liquid nitrogen can be separated from unreacted hydrogen and nitrogen.
Haber process is performed at 530-560 0C temperature. Therefore, products coming out of the reactor have a large heat. This heat can be used pre-heat the reactants, nitrogen and hydrogen. This will reduce energy requirement of the plant and economical.
In petroleum refining plant, H2 gas and NH3 are produced in petroleum refining. But ammonia is in aqueous state and with HCl. So NH3 exists as ammonium chloride ( NH4Cl ). If we want to recover ammonia from ammonium chloride, we can add aqueous NaOH to the aqueous NH4Cl solution with heating.
Hydrogen gas is produced mainly in the petroleum industry to the world. This hydrogen gas is stored and used for many industrial applicaations.
In use of catalyst or catalyst developer, we have to increase surface area to increase the efficiency of catalyst pprocess. Then When iron powder is used because they have a larger surface area than a iron piece.
Hydrogen gas can be obtained by Steam-Methane Reforming. Following reactions occur in this process.
Reaction of nitrogen and hydrogen is an exothermic reaction (at standard state, it's value is -46 kJ mol-1 ). So we can say, haber process reaction is an exothermic reaction.