Process Integration

The ultimate "greening" of fine chemical synthesis is the replacement of multistep syntheses by the integration of several atom-efficient catalytic steps. For example, Figure 9.9 shows the new Rhodia, salt-free caprolactam process involving three catalytic steps. The last step involves cyclization in the vapor phase over an alumina catalyst in more than 99% conversion and more than 99.5% selectivity.

Another example of the substitution of classic routes for chemical synthesis by multistep catalytic processes is the Rhodia vanillin process (Figure 9.10),8 which involves four steps, all employing a heterogeneous catalyst.

Finally, the Lonza nicotinamide process (Figure 9.11),15 involves the integration of both heterogeneous catalysis with a final step employing enzymatic catalysis.

Ni Catalyst + 2 HCN NC

Nl-U

AUO.

i2w3

Overall: ^^

^^ + 2 HCN + H20 + H2

-Caprolactam + NH3

Figure 9.9 Salt-free caprolactam process.

Caprolactam

Figure 9.9 Salt-free caprolactam process.

h2o2

Solid catalyst

Aq.H2CO H-MOR

CH3OH

OCH,

CH2OH

OCH,

CH2OH

CH3OH

La phosphate gas phase 250°C

Noble metal catalyst

OCH,

OCH,

OCH,

OCH,

Overall: C^O + H202 + CH3OH + H2CO + 1/2 02-> 0^03 + 3 H20

Figure 9.10 Rhodia vanillin process.

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