CHEMICAL TECHNOLOGY

1. Soda-Ash process

Solvay process is used in the manufacture of soda ash

CO2 is passed through a concentrated aqueous solution sodium chloride and ammonia. NaCl + CO2 + NH3 + H2O –> NaHCO3 + NH4Cl; ammonium bicarbonate is a precipitate. In a basic solution, NaHCO3 is less soluble than NaCl. The NH3 buffers the solution at a basic pH. Without NH3, a hydrochloric acid byproduct would render the solution acidic and arrest the precipitation. The carbon dioxide required is produced by (calcination) heating limestone at 950°C – 1100°C.

NaHCO3 the precipitate in the reaction is filtered out from hot NH4Cl solution and solution are heated with quicklime.

Ammonia produced is recycled back. NaHCO3 is calcined (160°C – 230°C) to give Na2CO3, CO2, and H2O.

Calcium chloride sodium chloride liquor is used in soda ash industry

1.Leblanc process for Na2CO3 (soda ash)

Raw material: salt, H2SO4, limestone, and coal

2.Single superphosphate from phosphate rock

Single superphosphate contains P (7 – 9.5%), P2O5 (16 – 20%), Ca (18- 21%), S (11 – 12%), pH < 2. Where soil is markedly acidic, i.e. rich in iron

Because iron and aluminum phosphates are insoluble, phosphate becomes unavailable in plants. That is why Single SuperPhosphate is not used in acidic soils until its limited.

3.Triple superphosphate from phosphate rock

Triple superphosphate contains P2O5 (44 – 55%), Ca (15%), pH (1 – 3), water solubility of P > 90%

4.Vinyl acetate from ethylene

Ethylene and acetic acid with O2 in presence of Palladium catalyst

5.Acrylonitrile (CH2CHCN vinyl nitrile) from propylene

Catalytic ammoxidation of propylene – SOHIO process

The reactants pass through reactor only once before being quenched in aqueous H2SO4. Excess propylene, CO, CO2, and N2 that do not dissolve are vented directly into the atmosphere or incinerated. The aqueous solution consists of acrylonitrile, acetonitrile, hydrocyanic acid, and (NH4)2SO4 (excess NH3). Acetonitrile or acrylonitrile are separated by distillation

6. Urea (Bosch –Meiser process)

The composition to fresh feed to the high-temperature high-pressure urea autoclave is excess liquid ammonia and compressed CO2. Consists of two equilibrium reactions

  • Carbamate formation

First is carbamate formation, fast exothermic reaction at high
temperature and pressure

The overall conversion of NH3 and CO2 to urea is exothermic. The reaction heat from first drives the second. It follows Le Chatelier’s principle. The condition that favors carbamate formation has an unfavorable effect on urea conversion equilibrium. The first reaction of high temperature (around 190oC) needed for second is compensated by conducting the process under high pressure (140 – 175 bar) which
favors the first reaction.

7.Chlorobenzene – caustic process: For phenol

Raw material: – C6H6, NaOH, HCl. This process is competitive when low-cost chlorine is available. This means that the process must be coupled to chlor-alkali plant. Steps involved:

  • Chlorination

  • Causticization
  • Hydrolysis

8. Cumene process for phenol

Raw material: – Cumene, Air, H2SO4, NaOH

9.H2 from natural gas

Following are the steps to produce hydrogen from natural gas

  • Steam methane reforming

High temperature (HT) followed by low temperature (LT)

  • PSA for H2 purification

This method produces a large number of greenhouse gases.

10. Fisher-Trope synthesis

Converts CO+H2 to liquid HC High temperature (150°C – 300°C), high pressure favors reaction; higher pressure favors longer chain.

  • High-temperature fisher trope (HTFT)

330°C – 350°C, Fe as a catalyst, used for coal to liquid

  • Low-temperature fisher trophy (LTFT)

Used for gas to liquid, Fe to Co catalyst.
Reaction steps:

The reaction involves
a. Associative adsorption of CO
b. Splitting of CO bond
c. Dissociative adsorption of 2H2
d. Transfer of 2H to oxygen to yield H2O
e. Desorption of H2O
f. Transfer of 2H to form CH2

11.Formaldehyde form methanol

Two methods

  • Dehydrogenation or oxidative dehydrogenation in presence of Ag or Cu catalyst
  • Oxidation in presence of Fe containing MoO catalyst

12. Dehydrogenation of ethylbenzene

13. Synthesis gas to methanol

14Formation of Nylon 6,6

Nylon 6,6 (so-called due to 6 C-atom between N atoms) is formed from the condensation polymerization of hexamethylene diamine and adipic acid

15. Dehydration of Ethanol

Dehydration of ethanol is an exothermic reversible reaction conducted at high pressure in the industry.