Industrial chemistry Flashcards
Factors to be considered in establishing chemical industries
Capital
Labour
Technology
Supply of raw materials
Transportation and market
Site of installation
Mg as a raw material
Extraction of Mg from sea water is more profitable
Other than Na+, Mg2+ is the most abundant cation in sea water
0.13% by weight is Mg in sea water
What process is used for extraction of Mg
Dow process
Major steps of Dow process
- Thermal decomposition of limestone or Dolomite to obtain CaO (using limestone is advantageous)
- Precipitation of Mg(OH)2
- Mg(OH)2 formed is filterd and removed and reacted with concentrated HCl to get MgCl2.
- The solution is heated strongly to vaporize water.
- solid formed is fused in the steel chambers where electrolysis is done and then it is electrolized
Temperature maintained in the dow process
700-800 C
Melting point of Mg
650 C
Uses of Mg
Production of aircrafts and vehicles
Production of alloys
Percentage yield of Mg in dow’s process
99.8
Caustic soda
NaOH
Basic process of caustic soda production
A pure concentrated solution of sodium chloride is called brine. NaOH is produced by electrolyzing a brine solution. As the by-products hydrogen gas and chloride gas are released at the cathode and the anode respectively.
Types of cells used to produce caustic soda and their common name
Chlor-alkali cells
a) Mercury cells
b) Diaphragm cells
c) Membrane cells
Major steps in membrane cell method
- Removal of contaminants (SO4 2-, Mg2+, Ca2+) from brine solution
- Electrolysis in Ti anode producing Cl2 and Na+
- Electrolysis of water in Ni cathode producing H2 and OH-
- Transportation of Na+ from anode to cathode through pores of the membrane.
- Evaporation of NaOH
Uses of NaOH
- Production of soap
- Production of paper, artificial silk and dyes
- Using as a strong base
- Precipitation of heavy metal as their hydroxides in waste water treatment.
Uses of Cl2
- Bleaching textiles, woods and paper pulp
- Purifying the drinking water
- Production of HC1
- Production of chlorinated rubber, insecticides, dyes and medicine
- Production of vinyl chloride required to produce polymers like PVC
Uses of H2
- Manufacture of HCl
- Production of NH3
- Production of margarine by hydrogenation of vegetable oil
- Using as a fuel
Basic process of making soap and raw materials
Raw materials are animal fat or plant oil, NaOH or KOH
triglycerides are subject to a hydrolysis reaction with caustic soda (saponification) forming glycerol and sodium salts of long chain carboxylic acids.
Processes of soap manufacturing and their major steps
Hot process and the cold process
In the cold process, soap and glycerol are not separated
Steps of hot process
1. Saponification
2. Removal of the by-product, glycerin
3. Purification
4. Finishing
Caustic potash
KOH
Saponification
Purified vegetable oil is mixed with NaOH or KOH. Glycerin are soap (RCOONa) are produced
System is maintained at 70 C
Removal of glycerin
To decrease the solubility of soap in the aqueous phase NaCl (brine) is added. Glycerin dissolves in the salt solution.
Purification
Wet soap with salt is centrifuged
NaCl content in soap decreases to 0.5% (w/w)
Citric acid, phosphoric acid or free fatty acids associated with coconut oil are added to neutralize sodium hydroxide
Finishing
Soap heated to about 120 C is sprayed into a low pressure zone in the form of small droplets. Finally fillers, colours and perfumes are added
TFM value of soap
TFM (Total Fatty Matter) means the total fatty matter presents in soap. It is the percentage of RCOONa (soap) present in a cake of soap.
TFM value of a cake of washing soap
54-56% and the rest is fillers
Detergents
do not precipitate in hard water. The main ingredients of artificial detergents is sodium alkylbenzenesulphonate.