Haber Process Research Task PDF

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The Haber Process – Research Task In 1912 Fritz Haber, a German chemist, developed the process that now bears his name for the synthesis of ammonia from nitrogen and hydrogen. So important was this process that Haber was awarded the Nobel Prize for Chemistry in 1918. The development of the Haber Process is a classic example of the influence of society upon chemistry and of the impact of chemistry on human life. The Haber Process is the process in which the gaseous elements nitrogen and hydrogen are chemically reacted together to form ammonia. The process of initiating the reaction of nitrogen with hydrogen is difficult in its natural state, leading to a need for an industrially monitored process. Nitrogen is an almost completely inert gas, meaning it does not react with other elements. By utilising the Haber process, this can be negated and nitrogen is able to react with the hydrogen. Also, at normal room temperatures and pressures, the equilibrium constant tells us that the equilibrium lies towards the reverse reaction, meaning it favours the reactants, and continues to move to the left the higher the temperature is raised. All of the above conditions hinder the synthesis of ammonia, leading to a great need for a monitored and managed process such as the Haber process. This flow diagram illustrates the industrial components of the Haber process:

Nitrogen is fractionally distilled from the air where it is abundant, whilst hydrogen is obtained by reacting petroleum fractions of natural gas with steam. This is the beginning of the industrial process, where all sulfur compounds are removed from the natural gas as they can render the catalyst ineffective. After this is when the small carbon chains are reacted with water vapours:

Another possible reaction that could occur from this includes:

Carbon monoxide is again reacted with steam to create a larger yield of hydrogen gas:

A concentrated solution such as potassium carbonate is utilised to remove the remaining carbon dioxide gas. Another way to obtain both hydrogen and nitrogen gas is to react methane in the air over a nickel catalyst to create an explosive mixture containing both essential elements;

These nitrogen and hydrogen gas volumes are ultimately adjusted to the ratio of 1:3 before entering the reaction chamber of the facility. This is where the Haber process reaction takes place and the synthesis of ammonia occurs, including the iron oxide catalyst, often mixed with small quantities of aluminium oxide and potassium oxide to increase the efficiency:

Industrially, the hydrogen and nitrogen gases initially enter the compressor. These gases are warmed by the heat from the reaction that is recycled through the heat exchanger. This is when they are added into the reaction vessel over the bed of the chosen catalysts, often iron with other compounds. The product of ammonia is cooled in the condensor to be taken away whilst leftover hydrogen and nitrogen and recycled back into the reaction vessel via the recycling pump. The synthesis of ammonia requires a careful balancing act determining the temperature and pressure at which to conduct the reaction. It is known that increasing the temperature increases the rate of reaction, but also favours the endothermic direction of the equilibrium reaction, indicated by Le Chatelier’s principle. This is not beneficial as the products side of the Haber process is an exothermic reaction. This means that the temperature must be balanced so as to increase the rate of reaction but not overly favour the reactants side of the reaction. High pressures, on the other hand, favour the side of the equilibrium reaction with the smallest number of moles of gas. In the Haber process, this would favour the products side. This means that the Haber process is best run under low temperatures and high pressure. Although factory to factory use different conditions, the most common conditions industrially are around 500 degrees Celsius and around 250 atmospheres of pressure. These conditions though come with some safety risks and costs that force the reaction to be run at less than optimal conditions, including the fact that extremely strong pipes would be required industrially and the high pressures would cost a lot to maintain, let alone the occupational safety hazard that it imparts on

the workers. The yield is further maximised by removing the products and hence keeping equilibrium pushed towards the product side. In normal room conditions, the yield is low due to low pressures and low temperatures, decreasing reaction rate. This improvement to yield is done by cooling the ammonia, first into a liquid, and removing from reaction vessel. The leftover gases are continuously recycled into the reaction chamber to minimise waste and maximise the amount of gases reacted to form ammonia. Ammonia is a covalent molecule and is most commonly known for its physical properties, including the fact that it is a colourless gas with a pungent smell that draws an instant reaction when accidentally inhaled sharply. It is also lighter than air; highly soluble; and is easily made into a liquid when a pressure of 8-10 atm is applied. This liquid form of ammonia boils at -33.5 degrees Celsius and freezes at -77.8 degrees Celsius into a white crystalline structure. Ammonia also has many chemical properties. It has a high pH, meaning it is a base, and it is a highly stable compound at normal temperatures and pressures but can be decomposed into hydrogen and nitrogen when in the presence of the iron catalyst, due to it being an equilibrium reaction:

Ammonia is also combustible in air and will easily burn in the presence of gaseous oxygen:

Ammonia has a very small number as its equilibrium constant, meaning its equilibrium reaction favours the reactants side. It also means that ammonia only ionises to a small extent in an aqueous solution.

Nowadays, ammonia has a vast amount of industrial uses: • manufacture of rayon and urea - cellulose is reacted with a mixture of copper and ammonia to make it soluble and able to be made into rayon. Ammonia is also a main constituent of urea which is often used industrially in agriculture. • cleansing agent for furniture and glass surfaces in the furniture industry - as ammonia is a base, it reacts with fats and oils to disintegrate them, making it a good cleaning agent. • in ice plants as a refrigerant - ammonia is a cheap and effective way to cool refrigerants. It also has a very low impact on the environment, but can become poisonous if the quantity is too high. • manufacture of fertilisers - utilised as a source of nitrogen which is essential to plant growth. This can increase the growth rate of plants and is often used industrially on crops. • manufacture of nitric acid - the ammonia is oxidized with the aid of a catalyst and platinum, which is then made to react with water to form nitric acid used in industry. This nitric acid is often again treated with ammonia to create fertilisers and explosives. • manufacture of sodium carbonate - the Solvay process of ammonia-soda process creates sodium bicarbonate (soda ash). The ammonia acts as a buffer in the reaction, keeping it from becoming too acidic from a build-up of hydrochloric acid.

One of the processes in which hydrogen gas is extracted for the Haber process includes a combustion reaction:

A combustion reaction can be very dangerous and the possibility of a build up of carbon monoxide would render the iron catalysts completely ineffective. This can be costly as all of the catalyst would need to be replaced. This is one of the main reasons that the Haber process must be continually monitored and managed. The temperature and pressure of the reaction vessel must also be continuously monitored as the temperature and pressure must consistently be balanced, as mentioned above. Workers will consistently check the catalytic converter, heat exchanger and recycling pump. If the balance were to be disrupted then the energy input into the reaction vessel would have to be much higher and must more costly. Monitoring of the vessel minimises energy lost from the industry and a balance of the rate of reaction in the synthesis of ammonia, maximising the yield. Too high temperature and pressure also poses a hazard to the workers around the reaction vessel, but overly high temperatures can also damage catalysts and overly high pressures can rupture the reaction vessel. The ration of nitrogen:hydrogen entering the reaction vessel must also be monitored and kept at a 1:3 ratio so as not to allow a build up of any of the reactants. Minor gases leaking in from the atmosphere must also be monitored and managed, and once past a 5% concentration must be removed. Samples of the ammonia may also be taked at regular intervals to check for any possible contamination. The reaction vessel is also continually checked for structural integrity and seals staying viable.

Much was happening across the world during the time that Fritz Haber was designing the process to synthesise ammonia. He began this process on a very small scale using his own apparatus shortly before the beginning of World War I. It was during this time that Britain had a naval blockade preventing Germany’s resources of ammonia and nitrates coming from South America. With this happening, Germany would not be able to keep up with the demand for these resources in creating explosives and fertilisers for farming. Fritz Haber was able to offset this problem by creating a way to synthesise ammonia without the need for bird manure supplies from outside of the country. By utilising the gases in the way that they were it didn’t require resources that could be blocked by the naval blockades, and they hence could continue creating explosives and fertilisers to contribute to their war efforts. Without this synthesis of ammonia, Germany’s war efforts would not have lasted and the war could have been ended much earlier. This would have happened as Germany would have been unable to sustain their food supplies for long enough and they would be unable to create the amount of explosives that they did. This could have been positive for the Allied Forces and would have led to less deaths during the war time. Fritz Haber was very patriotic to Germany though, and other than the synthesis of ammonia he continued to utilise his chemistry to create other weapons, including the use of chlorine gas in the trenches. He introduced a new form of chemical warfare which changed the ways of war. Overall, the Haber process has led to many negative, but also positive, consequences. He prolonged the war due to his ability to synthesise ammonia for explosives and fertilisers for farming. This was very negative for the Allied Forces. On the other hand, the synthesis of ammonia allowed for the world to offset the decline in food and averted the possibility of widespread starvation. This is a positive implication for the entire world. Ammonia is also industrially synthesised to be used in many worldwide applications. I believe the Haber process has led to an overall positive improvement to the world....