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        Items

Existing Process

Proposed Process

Comments

  1

  2

Raw materials

Catalyst
i)Cost

   ii) Toxicity

Diosgenin, Acetic anhydride, Catalysts like Pyridine hydrochloride, Titanium tetrachloride and anhydride Aluminium chloride etc.

Expensive:
Pyridine hydrochloride : $200/Kg
Titanium tetrachloride:$200/10gm
Anhydrous Aluminum Chloride

 All these catalysts are environmentally hazardous, toxic  and corrosive

Diosgenin, Acetic anhydride, commercial grade Xylene

No catalyst has been used

Methods used by Glaxo and other companies are very old and based on the technology of 1952 but the present technology is developed through modern technology. In the present process acetic anhydride which is a reactant has been used not in large excess along with an aromatic hydrocarbon solvent  to give very high yield of pseudodiosgenin acetate. The reaction being homogeneous, its easy to operate.Large excess of acetic anhydride lowers the yield of the above product.

Simple but efficient
& cost effective process

In the present process the use of expensive and environmentally hazardous toxic catalysts has been completely eliminated.

Sl. No.

        Items

Existing Process

Proposed Process

Comments

3

4

5

6.
 
 7

8

iii) Recovery & cost of catalysts

Solvent used

Yield of pseudodiosgenin diacetate(2)

Oxidation process

Yield of diosone(3)

Yield of 16-DPA(over all)

Effluent generation

Catalysts used are not recoverable

High boiling solvent like n-octanoic acid
( b.p. 2370C) has been used by Glaxo

Max. 87% ( using n-octanoic acid)

Oxidant in acetic acid

55%

42-56%

Step 1: Toxic effluent

Step 2: Chromium salts

Medium boiling low cost aromatic hydrocarbon (b.p.< 1500C) has been used

92%

Oxidant in solvent

70-75%

55-62%

Step 1: nil

Step 2: Chromium salts

Doesn’t arise

In the present process, no high boiling and toxic solvent like n-octanoic acid
( corrosive nature) has been used. Besides the recovery of such solvent would be high energy intensive.

Yield under present process is better without using such high boiling solvent

The oxidation  has been done in a non toxic solvent which is recoverable

The better yield

Better process

In the present process the use of ultra-sound in the oxidation step 2 reduces the amount of chromium reagent by about 30-40% which would minimize amount of chromium salts in the effluent.