Co-feed Effects

The co-fed gas and solvent have a dramatic effect on the selectivity and service life of the catalysts. With Ni-X, a striking extension of catalyst life was associated with the use of H2 as carrier gas [32]. The use of H2 for Pd-containing H-Y improved the Beckmann rearrangement [33]. It was proposed that the prime function of the Pd is to promote formation of Brpnsted acid sites. 

Sato et al found that over highly siliceous ZSM-5 the selectivity for s-caprolac-tam was increased by use of CO2 as carrier gas [18,20]. Catalytic performance also improved greatly when methanol was co-fed with oxime [56]. Up to a methanol/ oxime ratio of unity lactam selectivity increased and then leveled off. Oxime conversion was little changed up to the ratio of unity and decreased beyond this value. It has been claimed [65] that addition of methanol and a small amount of H2O to cyclohexanone oxime resulted in long catalyst life. 

The deactivation rate over In-MFl decreased when a mixture of carbon dioxide and methanol was used as diluent gas [23]. This effect was prominent when the catalysts were modified with noble metals and it was speculated that carbon dioxide or methanol, with the aid of platinum, reduced the carbonaceous deposits. 

As described above, favorable effects of higher alcohols were widely observed with large-pore zeolites [40], although the use of 1-hexanol was not so beneficial to 10- or 8-MR zeolites as to 12-MR zeolites [41]. An IR study revealed that the adsorption/interaction of methanol on the H-BEA (Si/Al = 12.8) catalyst was stronger than that of 1-hexanol. The relatively strong Brpnsted acid sites, probably 

The solvent effect is not limited to zeolitic catalysts. For W03/S102 solvents such as methanol and acetonitrile increased e-caprolactam selectivity compared with that for benzene [12]. 

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