Ammonia Report
...ch as nitrates, nitrites, ammonia, and ammonium compounds. This element is found in all protein molecules. Most of the nitrogen used commercially is prepared by the fractional distillation of liquid air. A ordinary pressures and at about 196° C, the nitrogen in the liquid air soon boils off, since it has a lower boiling point than oxygen. The nitrogen gas may be collected while the oxygen remains in the liquid form. Another method of preparing nitrogen from the air is to pass air over very hot copper. The oxygen of the air combines with the copper, leaving nitrogen and the noble gases (which only make up a small part of the mixture). Figure #3 – Nitrogen may be obtained from air by removing the oxygen with hot copper. Small amounts of nitrogen are prepared in the lab from nitrogen compounds. Ammonium nitrate à water + nitrogen NH4NO3 à 2H2O + N2 Ammonium nitrite is too unstable to work with conveniently in the laboratory. A mixture of sodium nitrite and ammonium chloride is used. Sodium nitrite + ammonium chloride à sodium chloride + nitrogen + water NaNO2 + NH4Cl à NaCl + N2 + 2H2O Figure #4 – Nitrogen may be prepared in the laboratory from ammonium nitrite. The Manufacture of Ammonium One of the most familiar compounds of nitrogen is ammonia. It is found in small amounts in nature, where it is formed when plant and animal materials decay. This chemical can either be prepared in the laboratory or industrially. Laboratory preparation of ammonia: In the lab, ammonia is often prepared by the reaction between ammonia and chloride and sodium hydroxide by heating the reactants with a small amount of water. Figure #5 – A laboratory preparation of ammonia. NH4Cl + NaOH à NaCl + NH4OH The ammonium hydroxide is unstable when heated and breaks down to form ammonia gas and water. NH4OH à H2O + NH3 The complete ionic reaction is: NH4+ + OH- à NH3 + H2O Sometimes it is desirable to use less expensive compounds than those shown in the above equation. Calcium hydroxide is often substituted for sodium hydroxide. (NH4)2SO4 + Ca(OH)2 à 2NH4OH + CaSO4 2NH4OHà 2NH3 + 2H2O Industrial Preparation: Large amounts of ammonia is now prepared commercially in several different ways. One of the earliest processes for the synthetic production of ammonia was the Haber process. In this process, still used today, nitrogen and hydrogen are combined directly in the presence of a catalyst, such as finely divided iron missed with potassium aluminate. N2 + 3H2 à 2 NH3 + 24, 000 calories ß The reaction usually takes place at a temperature of 500° C and a pressure of about 350 atmospheres. Under these conditions, the yield is only about 30%, but the greater speed at which ammonia is produced makes these conditions the most economical ones. Percentage of Ammonia Formed by Synthesis Under Varying Temperatures and Pressures Temperature, °C Pressures in Atmospheres 1 50 200 1000 200 15.3 74.4 85.8 98.3 300 2.2 39.4 62.8 92.6 400 0.48 15.3 36.3 79.8 500 0.13 5.6 17.6 37.5 600 0.05 2.25 8.2 31.4 700 0.022 1.05 4.1 12.9 800 0.012 0.57 2.2 900 0.007 0.33 1.3 1000 0.004 0.21 0.9 Table #1 Several catalysts have been used for the Haber process, but today the major one in use is granules of iron oxide (Fe3O4), containing small amounts of potassium oxide (K2O), and aluminium, oxide, (Al2)O3. The catalyst in the mixture is the iron oxide. The other two substances are added to prevent the catalyst from being poisoned or from losing its effectiveness. Another commercial source of ammonia is the destructive distillation of coal. As coal is heated in the absence of air, many of the nitrogen compounds it contains are converted to ammonia, which is given off together with coal has and many other valuable products. Dissolving the gas in water or sulphuric acid collects the ammonia. Some ammonia is also obtained from natural gas wells. Environmental Impact of the Manufacture and Use of Ammonia Although ammonia has many uses, it also has some destructive qualities. This chemical creates a negative environmental impact. The manufacture of ammonia creates emissions that cause air pollution and lead to smog. Ammonia found in car exhaust can also add to this problem. Some call it a smelling salts wake-up for ammonia production, which has not changed much in a half century. The energy needed for ammonia production consumes 1% of the world’s energy because synthesizing it requires enormous pressures. Fortunately, we can now save on some of this energy usage, thanks to a new ruthenium-barium catalyst that can cut pressures by 92%. The energy usage causes air pollution from the burning of fuels. The source of ammonia created from the destructive distillation of coal causes severe environmental impact from the coals’ fumes. According to the federal government's National Pollutant Release Inventory, for example, Ontario's coal plants are among the largest toxic emitters in all of Canada, accounting for 14 per cent of Ontario's total toxic releases and 19 per cent of air releases of toxins in the province. Coal plants produce more than just tonnes of smog-causing gasses like sulphur dioxide and nitrogen oxides, they are also leading sources of dangerous heavy metals and poisons such as arsenic, dioxins, lead and chromium. For years, cows have been getting a bad rap on air pollution. The problem is that waste from bovines and other livestock produce ammonia, which contributes to the smog. New research presented at the American Chemical Society meeting suggests that cars are the primary source of ammonia. Ammonia reacts readily...