Industrial BasesAmmonia and Sodium Hydroxide

Ammonia: Introduction

Compound of nitrogen and hydrogen with a formula of NH3

Ammonia is found in trace quantities in the atmosphere, being produced from the putrefaction (decay process) of nitrogenous animals and vegetable matters

one of the most highly produced inorganic chemicals

Ammonia: Reactions and Equilibrium

The commercial production of ammonia by the direct combination of nitrogen and hydrogen is an example of equilibrium in the gaseous state

Low temperatures is better because more ammonia is obtained at equilibrium

While a low temperature favors a high equilibrium yield of ammonia, it also dictates that a long time will be required to obtain the yield

Ammonia: Rate and Catalysis of the Reaction

A great asset in the production of ammonia is a catalyst which speeds the reaction between nitrogen and hydrogen

Early in this century, a German academic chemist, Fritz Haber, and an industrial colleague, Carl Bosch, found that a mixture of Fe2O3 and Fe3O4 catalyzes this reaction at temperatures in the range of 400 degree Celsius to 600 degree Celsius

The Haber- Bosch process continues to be the most common method for making ammonia. The nitrogen is obtained from liquefied air, and the hydrogen is usually from natural gas decomposed by heating.

Ammonia: Manufacturing Procedures

Ammonia is produced in a process known as the Haber process, in which nitrogen and hydrogen react in the presence of an iron catalyst to form ammonia

The hydrogen is formed by reacting natural gas and steam at high temperatures and the nitrogen is supplied from the air

Other gases (such as water and carbon dioxide) are removed from the gas stream and the nitrogen and hydrogen passed over an iron catalyst at high temperature and pressure to form the ammonia.

Ammonia: Uses and Economics

Used in the production of liquid fertilizer solutions which consist of ammonia, ammonium nitrate, urea and aqua ammonia.  It is also used by the fertilizer industry to produce ammonium and nitrate salt

Dissociated ammonia is used in such metal treating operation as nitriding, carbonitriding, bright annealing, furnace brazing, sintering, sodium hydride descaling, atomic hydrogen welding and other applications where protective atmospheres are required

Ammonia: Uses and Economics

Used in manufacture of nitric acid; certain alkalies such as soda ash; dyes; pharmaceuticals such as sulfa drugs, vitamins and cosmetics; synthetic textile fibers such as nylon, rayon and acrylics; and for the manufacture of certain plastics such as phenolics and polyurethanes.

Ammonia is used as the developing agent in photochemical processes such as white printing, blue printing and in the diazo duplication process. 

Ammonia: Uses and Economics

Weak ammonia solutions are also widely used as commercial and household cleaners and detergents

Used in the rubber industry for the stabilization of natural and synthetic latex to prevent premature coagulation

The decomposition of ammonia serves as a source of hydrogen for some fuel cell and other applications

Pulp and paper industry uses ammonia for pulping wood and as a casein dispersant in the coating of paper

Sodium Hydroxide(Lye, caustic soda)

Physical Properties

•Appearance: A white crystalline substance (solid)

•Smell: Odourless

•Transparent: Only in liquid form

•Poisonous: Yes (causes burns when inhaled)

•Molecular Weight: 39.997g/mol

•Boiling point: 1390C (2534F)

•Melting point: 318C (604F)

•Density: 2.13g/cm^3

•Flammable: No

Chemical Properties

•Acidity: 13-14 pH (basic)

•Basic Type: Caustic Metallic Base

•Corrosive: High

•Reactivity: Medium

•Hygroscopic: Yes (absorbs CO2 and moisture from air)

•Solubility in Water: 1110g/L (20C)

•Soluble: in water, acids and alcohol

Neutralization

•The hydroxide ion makes sodium hydroxide a very strong base which react with any acid which will neutralise each other.

•In general, neutralisation reactions can be represented as follows in an ionic equation:OH−(aq) + H+(aq) → H2O(l)

•Sodium hydroxide reacting with an acid will generally result in a neutralisation process

•For instance, sodium hydroxide reacts with hydrochloride acid:NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Manufacture

The major method for producing sodium hydroxide is electrolysis of concentrated brine (sodium chloride solution) produces chloride gas, hydrogen gas and sodium hydroxide.

2NaCl(aq) + 2H2O(l) -----> H2(g) + Cl2(g) + 2NaOH(aq)

At the anode (positive electrode), the chloride ions (Cl-) are oxidised to chloride gas (Cl2(g)). At the cathode (negative electrode), the sodium ions (Na+) and water (H2O(l)) are reduced to hydrogen gas (H2(g)) and sodium hydroxide (NaOH(aq)).

The mercury cell process (Castner-Kellner)

At the anode, titanium is the metal and chloride ions are oxidised to chloride gas:2Cl-

(aq) -----> Cl2(g) + 2e-

At the cathode, mercury is flowing along the bottom of the cell. Sodium ions are reduced to sodium metal:Na+

(aq) + e- -----> Na(s)

An amalgam is formed when sodium metal dissolves in the liquid mercury and it is removed to the decomposer. The amalgam then reacts with water to form sodium hydroxide, hydrogen gas and mercury:2Na/Hg(l) + 2H2O(l) -----> 2NaOH(aq) + H2(g) + 2Hg(l)

Nelson diaphragm cell process

The saturated brine flows through the diaphragm and into the cathode compartment.

At the anode, carbon or titanium coated with Ru-Ti, the chlorine ions are oxidized. At the cathode, steel mesh, hydrogen gas and hydroxide are produced: 2H2O(l) + 2e -----> H2(g) + 2OH-

(aq)

The diaphragm allows the sodium ions to migrate across it and to combine with hydroxide, forming sodium hydroxide: 2H2O(l) + 2Cl-

(aq) + 2Na+(aq) ----->

2NaOH(aq) + H2(g) + Cl2(g)

Solid sodium hydroxide can be crystallised out.

Membrane cell process At the anode, titanium is the metal.

At the cathode the metal is nickel and water is reduced:2H2O(l) + 2e -----> H2(g) + 2OH-

(aq)

Sodium ions migrate across the membrane and combine with hydroxide to form sodium hydroxide in the cathode compartment:

2H2O(l) + 2Cl-(aq) + 2Na+

(aq) -----> 2NaOH(aq) + H2(g) + Cl2(g)

Soap making:

The common fats, triglyceride esters react with sodium hydroxide to form glycerol and the sodium salt of the fatty acid which is soap.

The reaction between a strong base and a fat is called ‘saponification’, can be presented by the equation

The equation can be simplified to:C18H36O2 + NaOH -> alcohol + salt of the carboxylic acid (soap)

Cleaning agent:

•Sodium hydroxide is usually added to hot water and then can be used to dissolve fat, grease, oil and protein based deposits.

•Sodium hydroxide solution is widely used in cleaning the oil which is used in making metal products.

•Compared to CFC (chlorofluorocarbon, a powerful substance to clean the oil), it does not pollute the environment.

•The industrial oil does not react easily, so it needs energy to break it up to react.

•The hot water provides the energy required to make the sodium hydroxide work efficiently.

Aluminum production:

•Aluminium ore is usually contained in the mineral bauxite that is a mixture of hydrated aluminium oxides Al2O3

and hydrated iron oxides, Fe2O3.

•In aluminum refining, sodium hydroxide will only react with aluminium oxide and form sodium aluminates (red mud), NaAl(OH)4

•After that, aluminum oxide will precipitate then be washed and heated to form pure aluminum.

The ionic equation will be: Al2O3(s) + 2 OH−

(aq) + 3 H2O(l) → 2 [Al(OH)4] (aq)

−

The equation with NaOH:Al2O3(s) + 3H2O(l) + 2NaOH(aq) -----> 2NaAl(OH)4(aq)

Paper pulp industry:

•In the process of paper making, there are two main parts: pulping and papermaking.

•There are always some excess chemicals used to pulp the paper, sodium hydroxide will help regenerate these chemicals to reduce the cost.

•Because of the corrosive property of sodium hydroxide, it will also be added to the process of bleaching to increasing the efficiency.

•It also has a function of PH control. PH stays at around 8 where the hypochlorite bleach works the most efficiently.

Environmental and health issues• Sodium hydroxide can cause

severe burns and damage to any tissues of the body, because of:

1. The reaction of sodium hydroxide with moisture generates heat and causes thermal burns (exothermic reaction).

2. The reaction of sodium hydroxide with organic molecules results in chemical burns.

•In the atmosphere, sodium hydroxide can dissolve in water vapour and form aerosols or mists which are very corrosive.

•Due to the neutralization of pH, sodium hydroxide allows specific plants to grow more efficiently by adjusting the balance of nutrients