Figure 2 shows copper-to-aluminum molar ratio and surface area
data as a function of VPIE temperature. At lower temperatures,
the amount of copper(I) chloride evaporated was not sufficient for
complete exchange, and this was evident from the CuCl material
left in the corresponding reactor section. Increasing the VPIE
temperature to 550 or 600 °C resulted in zeolites with Cu/Al ratios
greater than unity. This was due to a temperature not high enough
to evaporate the CuCl excess from within the voids/cages of
Y-zeolite. Clear evidence of this is the noticeable decrease in surface
area between 550 and 600 °C (see Figure 2). However, a
temperature of about 700 °C results in almost 95% ion exchange
(Cu54H3[Al57Si135O384]) and a higher surface area. At 700 °C, CuCl
excess is completely evaporated, and this was corroborated by the
absence of the salt from its original reactor location at the end of
the VPIE process and by a white crystalline ring formed at the
reactor outlet. Spoto et al.13 also made these observations during a
VPIE process to produce Cu(I)-ZSM-5. The Cu(I)-Y (VPIE@700
°C) surface area is not as high as the original H-Y one, but this is
due to the high copper loading. Trigueiro et al.14 studied the effect
of metal ion exchange high loading on the surface area of faujasite
zeolites, and their results agree well with ours.