Basic Principles Chemical processes, Unit Processes And Unit Operations In Organic Chemical Industries
Chemical processes usually have three interrelated elementary processes
Processes may involve homogeneous system or heterogeneous systems. In homogeneous system, reactants are in same phase-liquid, gases or solids while heterogeneous system include two or more phases; gas liquid, gas–solid, gas-gas, liquid–liquid, liquid solid etc. Various type reactions involve maybe reversible or irreversible, endothermic or exothermic, catalytic or non-catalytic. Various variables affecting chemical reactions are temperature pressure, composition, catalyst activity, catalyst selectivity, catalyst stability, catalyst life, the rate of heat and mass transfer. The reaction may be carried out in batch, semi batch or continuous. Reactors may be batch, plug flow, CSTR. It may be isothermal or adiabatic. Catalytic reactors may be packed bed, moving bed or fluidised bed Along with knowledge of various unit processes and unit operation following information are very important for the development of a process and its commercialization [Austin,1984] Basic Chemical data: Yield conversion, kinetics
Unit Processes and Unit Operations in Chemical
Chemical process is combination of unit processes and Unit operation. Unit process involves principle chemical conversions leading to synthesis of various useful product and provide basic information regarding the reaction temperature and pressure, extent of chemical conversions and yield of product of reaction nature of reaction whether endothermic or exothermic, type of catalyst used. Unit operations involve the physical separation of the products obtained during various unit processes. Various unit processes in chemical industries are given in Table M-I 3.1. Various chemical reactions and its application in process industries are given in Table M-I 3.2.
Nitration involves the introduction of one or more nitro groups into reacting molecules using various nitrating agents like fuming, concentrated, aqueous nitric acid mixture of nitric acid and sulphuric acid in batch or continuous process. Nitration products find wide application in chemical industry as solvent, dyestuff, pharmaceuticals, explosive, chemical intermediates. Typical products: TNT, Nitrobenzene, m-dinitrobenzene, nitroacetanilide, alpha nitronaphthalene, nitroparaffins
Table M-I 3.1: Unit Processes in Chemical Process Industries
Alkylation and Hydro delkylation
Amination by reduction
Hydroformyl ati on
Amination by ammonalysis
Chlorination and Oxy chlorination
B i omethhanati on
Oxidation and partial oxidation
Cracking; Thermal, steam cracking, catalytic
Polymeristion: Addition and condensation
Chain growth and step growth,Bulk, Emulsion, suspension, solution, Radical and coordination polymeristion
Ditozitation and coupling
Reforming: Steam reforming
Gasification of coal and biomass
Desulphurisation and hydro desulphurisation
Estertification and Trans Estrerificartion
Fisher-Tropsch (FT) Process
The Fisher-Tropsch process produce a variety of hydrocarbons (alkanes: CnH(2n+2)) by involves a series of chemical reaction.
(2n+1) H2 + nCO→ CnH(2n+2)+ nH2O
FT process is used for synthesis of alkanes.
In this reaction attach substituent’s to an aromatic ring. Two main types of Friedel-Crafts reaction are acylations reaction and alkylation reactions, both proceeding by electrophilic aromatic substitution.
Friedel-Crafts process used in alkelation reactions.
In this process Isomeric mixture of normal- and iso-aldehydes get produces by utilizing syngas (CO and H2) and olefinic hydrocarbons as reactants. It is exothermic process, this process thermodynamically favorable at ambient pressure and temperatures. This reaction also called as hydroformylation reaction.
RCH=CH2+CO+H2→RCH2CH2CHO + R(CH3)CHCHO
Oxosynthesis used for production of alcohols.
In this process, organic reaction of primary amide converts into a primary amine with one fewer carbon atom.
Hofman process typical examples are conversion of aliphatic amides to aliphatic amines and aromatic amides to aromatic amines.
Any chemical reaction involving free radicals, generally radical generated
from radical initiators such as peroxide or azo bis compounds. Radical reactions are chain reactions with chain initiation, propagation and termination steps. Free radical reactions are used many organic synthesis and polymerization reactions
Beckmann rearrangement is acid catalyzed rearrangement of an oxime to an amide, which developed by German chemist Ernst Otto. A typical example of Beckmann rearrangement is synthesis of caprolactam from cyclohexanone. Caprolactam is monomer for nylon 6.
Wacker process is similar to hydroformylation and used for aldehyde compounds. A typical example of wacker process is oxidation of ethylene to acetaldehyde in the presence of Pd catalyst.
2CuCl+ 0.5 O2+2HCl→2CuCl2+H2O
TNT is produce in a three-step process: First, toluene is nitrated with a mixture of sulfuric acid and nitric acid to produce mono-nitrotoluene or MNT. The MNT is separated and then renitrated to dinitrotoluene or DNT. In the final step, the DNT is nitrated to trinitrotoluene or TNT using an anhydrous mixture of nitric acid and oleum.