J . Chem. SOC., Faraday Trans I, 1989, 85(6), 1233-1244 Fourier-Transform Infrared Studies of Copper-containing Y Zeolites Dehydration, Reduction and the Adsorption of Ammonia Joseph Howard I.C.I. p.l.c., Wilton Materials Research Centre, Wilton, Middlesbrough, Cleveland TS6 8JE Jacqueline M. Nicolt Department of Chemistry, University of Durham, South Road, Durham DHI 3LE The reduction of Cur' to Cur ions in partially Cu'*-exchanged zeolite Y by CO plus co-adsorbed NH, has been studied (298-673 K) using Fourier- transform infrared spectroscopy. While the data are complex the formation of a variety of species including [Cu(NH,)I2+, [CuCO(NH,),]+, NH: and hydrogen-bonded NH, have been identified. The data indicate that at low temperature reduction by NH, is dominant while at elevated temperature CO is a more important reducing agent.Introduction Although standard ion-exchange techniques are used to prepare partially exchanged Cur' Y zeolite [CuI'Na-Y], difficulties arise in the preparation of Cu'Na-Y due to the instability of CuI ions in aqueous solution. Direct ion-exchange of Cu' ions is only accomplished in the absence of oxygen with Cu" in liquid NH, solution. The preferred route is via the reduction of CuI'Na-Y zeolite, using C0,2 H2,, NH3,4-6 olefins6V7 etc. as reducing agents. The most frequently used reduction method is CO in the presence of NH,, described by Huang.2.8 The adsorption of NH, results in the relocation of the mobile Cu" ions in sites in or near the supercages, where they are more readily reduced by CO. By this method reduction is accomplished in 1 h at 673 K, while without NH, reduction times of ca.30 h are required. For reduction by hydrogen lower temperatures are required, but the Cu' ions so formed are found to be susceptible to further reduction to Cuo if the temperature exceeds 473 K3 Reduction by NH, or butadiene has also been shown to occur at 373 K.6 An additional mechanism by which Cu' ions are introduced into Cu"Na-Y zeolites is by autoreduction during dehydration at temperatures exceeding 623 K.', lo In this paper we report our detailed infrared studies of the dehydration of CuI'Na-Y, the adsorption of NH, on dehydrated Cu"Na-Y and of the reduction of Cu" ions in Y zeolite by CO and co-adsorbed NH, at a variety of temperatures. Copper-Ammine Complexes The formation of copper-ammine complexes in Y zeolites has been studied by a number of techniques, e.g.adsorption measurements,2. l1 X-ray diffraction,12 e . ~ . r . ~ * 13* l4 and i.r.13 spectroscopy. Adsorption of NH, by dehydrated Cu"Na-Y was shown by both e.s.r. s p e c t r ~ s c o p y ~ ~ ' ~ and X-ray diffraction12 to cause the migration of Cu" ions from sites t Current address : Reactor Radiation Division, National Bureau of Standards, Gaithersburg, MD 20899, USA.1234 + 4 4 I Cu'Na-Y reduction at 362 K for 13 h reduction at 673 K for 1 h evacuation for 3 h at 673 K F. T.I.R. Studies of Copper-containing Y Zeolites Table 1. A summary of the treatments applied to Cu'INa-Y within the small cavities, to sites in the supercages, where copper-ammine complexes were formed.From the observed e . ~ . r . ~ parameters the Cu"-ammine complex was concluded to be square planar at room temperature. On partial desorption of the NH, at 373 K, the symmetry of the complex changed to a distorted tetrahedron, the complex being formed by the coordination of Cu" to three lattice oxygens and one NH,. Upon increasing the desorption temperature (473-573 K) the original signal due to the Cu" ions in the small cavities was again observed. Adsorption isotherms of ammonia adsorbed on 13, 48 and 75% exchanged Cu"Na-Y zeolites were measured by Huang and Vasant. '' These measurements indicated complex formation to be complete at pressures of less than 20 Torrt. From the NH, uptakes, in agreement with e.s.r. result^,^ complexes of [Cu(NH,)J2+ stoichiometry were identified. For samples with a high copper content it was concluded that not all the Cu" ions were formed in complex formation.In Cu'Na-Y zeolites ammonia adsorption, as with Cu"Na-Y zeolites, results in the migration of Cu' ions into sites within the supercages. Ammine complexes of [Cu(NH,),]+ stoichiometry were identified.2 Infrared measurements have previously only been p~blished'~ for NH, adsorbed onto Cu"Na-Y. By comparison with the infrared spectrum of Cu(NH,), SO,15 a band at 1275 cm-' in the spectrum of Cu"Na-Y +NH, was assigned to the [Cu(NH,),I2+ complex. Quantitative intensity measurements of the 1275 cm-' band with increasing NH, adsorption confirmed this stoichiometry. On desorption of NH, the 1275 cm-' band shifted to 1260 cm-l, which led the authors to assign this band to the tetrahedral complex described earlier from e.s.r.results. t 1 Torr z 133.322 Pa.J . Howard and J . M . Nicol 1235 n A B 1800 1700 1600 1500 1400 1300 I w avenumberkm- ' wavenumber/cm- ' Fig. 1. The dehydration of CuI'Na-Y under vacuum at various temperatures (y-axis offset, note y-scale expansion in B is twice that of A). Sample heating at: (a) 323 K; (6) 437 K; (c) 528 K; ( d ) 618 K; ( e ) 698 K for 15 h; (f) sample cooled to ambient temperature. Experimental For our studies of the adsorption of NH, and Cu" reduction we have used 'sample I ' of our previous paper." This sample of Cu,o~,Na,,.l-Y contains a number of Cu' ions introduced by autoreduction during the initial dehydration of the sample. We will refer to it hereafter as Cu"/Cu'Na-Y.The treatments applied in the present work are summarised, for clarity, in table 1. Carbon monoxide (99%, British Oxygen Company) was passed through a liquid- nitrogen trap before use. Ammonia gas (99.9%, British Oxygen Company), was dried over sodium metal and purified by the freeze-pumpthaw technique. The purity of both gases was checked by infrared spectroscopy. Infrared spectra were measured, in transmission mode, using a Nicolet 60SX Fourier-transform spectrometer. The zeolite sample consisted of a thin self-supporting disc (ca. 7 mg) 15 mm in diameter. All sample treatments (dehydration, adsorption, etc.) were carried out in situ in an all-metal cell fitted with KRS-5 windows (4 cm path length), attached to an all-metal pumping and gas-handling system.Results and Discussion The results will be presented in five stages (see table 1) : (1) the dehydration of Cu"Na-Y; (2) the adsorption of NH, on Cu"/Cu'Na-Y; (3) Cu'karbonyl complexes in the presence of NH,; (4) the reduction of Cu"/Cu'Na-Y; ( 5 ) adsorption of CO on Cu'Na-Y. The Dehydration of Cu"Na-Y Spectra of Cu"Na-Y in the region above 1200 cm-' during dehydration are depicted in fig. 1. Although the data are complex, owing to the possible presence of a range of species, a number of bands can be assigned'' using literature data (table 2). In previous studies of the dehydration of CuI'Na-Y, bands in the 365C3500 cm-l region were assigned to Cu(OH)+."~ l8 These bands disappeared on heating samples above 573 K. In the present investigation vibrations observed at 3640 and 3550 cm-' were not lost on dehydration above 573 K [fig.1 (ct(e)]. Thus it is unlikely that they are due1236 F. T.I.R. Studies of Copper-containing Y Zeolites Table 2. Summary of bands observed during the dehydration of CuI'Na-Y and their assignments wavenum ber / cm- assignment 3 740 v(0H) of Si-OHI6 3700 -+ 3000" (broad) 3640 3550 3444" 3345" (3360)"~' 1640" I 600- 1200 v(0H) of adsorbed, hydrogen-bonding, H,O 3680" v(OH) of A1-OH16 } v(0H) of framework hydroxyl groups v(0H) of copper hydroxides d(H,O) of absorbed, hydrogen-bonding H,O framework vibrations" or carbonates formed during ion exchange (3318) " Lost on dehydration. ' below 450 K the 3345cm-' band consists of two components as indicated. " Overtone or combination bands.to copper hydroxyl species, which would have decomposed at these temperatures. We assign these bands to structural hydroxyl groups, similar to those found in decationated zeolites." The remaining bands at ca. 3444 and 3345 cm-' were not previously observed during the dehydration of CU"N~-Y.'~~ l8 B y comparing the v(0H) adsorption frequencies of copper hydroxide corn pound^'^-^' with these bands, they appear to be due to copper hydroxyl complexes that were probably formed during ion exchange. At elevated temperatures these species are observed to disappear, with the probable formation of non-linear coupled copper pairs (CU-O-CU)~+, which have previously been detected by e.s.r. spectroscopy.22 A summary of all band assignments in the 4000-1200 cm-' region is given in table 2.The Region Below 1200 cm-' Additional evidence for the presence of copper hydroxides should be found in the 1000-670 cm-' region, where the d(0H) vibration of these species has been reported.ls3 21 In fact in fig. 2(a) all the bands, except that at 900 cm-', may be assigned to vibrations of the internal and external tetrahedral linkages of the zeolite framework as described by F l a ~ ~ i g e n . ~ ~ The intensity of the 900 cm-' band gradually decreased with increasing dehydration temperature and is lost above 523 K. This behaviour correlates well with that of the features at 3444 and 3360 cm-' and we therefore assign the band to 6(OH) of a copper hydroxide species. From the available evidence, however, we are unable to determine whether these species are bridging or linear.During dehydration the external linkage band at 970 cm-' is observed to shift to 950 cm-' and more structure appears in the 700-600cm-' region. These changes reflect the migration of the mobile copper cations into the sodalite cage sites, as well as the formation of non-linear coupled copper pairs. 22 During dehydration of CuI'Na-Y we have shown previously'' that a number of Cu' centres are introduced into our samples by the autoreduction mechanism.' In the following section the sample is described as Cu"/Cu'Na-Y to reflect the Cu"/Cu' content.J. Howard and J. M. Nicol 1237 wavenumber/cm- ' Fig. 2. Transmission infrared spectra in the 120WOO cm-' region of CuI'Na-Y during dehydration under vacuum (y-axis offset). Sample heating as in fig.1. wavenumber/cm- ' wavenumber/cm- ' Fig. 3. The adsorption of ammonia on Cu"/CurNa-Y. (y-axis offset). ( a ) Zeolite background; (6) adsorption of 1.2 Torr of NH,; (c) spectrum (b) after 30 min; ( d ) evacuation of (c) for 15 minutes. The Adsorption of NH, on Cu'*/Cu'Na-Y As part of our studies of the reduction of Cu"Na-Y zeolite by NH, plus CO, separate studies of the adsorption of CO and NH, were performed. Details of the CO adsorption experiments are given elsewhere. lo Here we summarise our findings of ammonia adsorption and compare them to the previous i.r. study of Flentge et a1.131238 F. T.I.R. Studies of Copper-containing Y Zeolites Table 3. Assignment of bands in the 3800-1200cm-1 region due to NH3 adsorbed on Cu"/Cu'Na-Y ~~~ ~ band/cm-l assignment 3700-3500 (broad) 3400 (broad sh) 3374 (sh) 3319 3269 3216 3181 1627 (sh) 1610 (sh) 1580 1475 1420 1273 1 hydrogen-bonding hydroxyl groups hydrogen- bonding y(NH) v(NH) of NH,f or hydrogen bonded NH, v(NH) of [CU(NH,),]~+ [ref.(15), (25)] coordinately bound NH, zeolite framework deformations of NH; dd(NH3) of [CU(NH 3)4)4I " d,(NH,) of [Cu(NH,),I2+ [ref. (1 3)] The spectrum of ammonia adsorbed (1.2 Torr) on dehydrated Cu"/Cu'Na-Y is shown in fig. 3. Intense bands are observed in the 3800-3000cm-' [v(NH)] and 1700-1200 cm-' [G(HNH)] regions due to the formation of [Cu(NH,),I2+ complexes within the zeolite cages. After 30 min contact time the features due to adsorbed NH, were observed to increase in intensity. These intense features remain even after evacuation for 15 min.The spectral features can be assigned by comparison with published data on gaseous NH3,24 Cu(NH,) S0,15725 and the previous study of NH, adsorbed on Cur1Na-Y.13 A summary of these assignments is given in table 3. The 1700-1200 cm-' Region A band at 1273 cm-l in the spectrum of CuI'Na-Y has been assigned to the symmetric deformation of [Cu(NH,),I2+ com~lexes.~~ On evacuation of gaseous NH, for 15 min at room temperature [fig. 3(d)] we observe the intensity of this band to increase slightly. This infers that the number of [Cu(NH,),I2+ complexes initially increased on evacuation. In contrast, it was observed previously that the presence of excess NH, had no effect on the intensity of the 1273 cm-l band.l3 However, it was noted that in highly exchanged samples not all the CU" ions were participating in complex formation, and that sample pretreatment affected the availability of cations 'for complex formation. 11, l3 A possible explanation for the behaviour of the 1273 cm-l band in the present work is that, on removal of excess NH, from the cages, additional CU" ions enter the supercages to form ammine complexes from sites that are probably located just inside the sodalite cages at sites SII.The 3800-3100 cm-' Region In this region bands due to v(NH) and structural hydroxyl groups are observed (fig. 3; table 3). A difference spectrum of the data before and after NH, adsorption [fig. 3(b) minus fig. 3(a) show that on adsorption of NH, the hydroxyl bands observed at ca. 3740, 3640 and 3550 cm-l in the background spectrum are considerably reduced in intensity.This reduction is commensurate with their (a) hydrogen bonding to an NH, molecule (as indicated by the broad band at ca. 3700-3500 cm-l), and (b) having formed NH,+ species. Evidence for NH; is provided by the existence of the deformation modes of these species, which are observed at ca. 1475 and 1420 cm-l. On evacuation, furtherJ. Howard and J. M . Nicol 1239 2200 2000 w avenumber /cm- ' Fig. 4. The adsorption of CO onto autoreduced Cu"/Cu'Na-Y with preadsorbed NH,. (a) Zeolite background : evacuation of NH, for 15 min [spectrum 3 (d)]. (b) sample (a) + 0.5 Torr of CO; (c) sample (a)+8.0 Torr of CO; ( d ) evacuation. difference spectra show that hydroxyl bands reappear as the coordinating NH, molecules are removed from the zeolite cavities.Bands observed below 3400 cm-l are due to v(NH). These may arise from several possible species, e.g. copper-ammine complexes, NH, hydrogen-bonding to framework hydroxyl groups and NH;. No unique assignment may be made from the data available but the most probable assignments are summarized in table 3. The bands at 3269, 3216 and 3181 cm-l are best assigned to [Cu(NH,)J2+ ions by comparison with similar ammine complexes,15, 25 whereas the assignment of the 33 19 cm-l band remains unclear. This latter feature could be associated with any of the species listed earlier. The shoulder at ca. 3374 cm-' and the general broad band beneath the sharper features in the 3400-3000 cm-l region are, from their width, assigned by hydrogen-bonding NH, and to NH; species. Cu'-Carbonyl Complexes in the Presence of NH, After the removal of gaseous NH, from the sample, by evacuation for 15 min, CO was adsorbed (fig.4) onto the zeolite. Although no direct evidence for Cu'(NH,), complexes was obtained from the i.r. data, published adsorption measurements2 have shown NH, to initiate the migration of the CuI ions towards the supercages, where cuprous-ammine complexes are formed. Previously, Huang8 observed the v(C0) vibration of Cu'CO(NH,). complexes in the presence of NH, (10 Torr) at 2080 cm-l. The u(C0) band was observed to almost disappear on evacuating the sample for 5 min. After partial1240 F. T.I.R. Studies of Copper-containing Y Zeolites I 1 3800 3500 3200 2900 2600 2300 2000 1700 1400 wavenumber/cm- ' Fig.5. Adsorption of NH, and CO onto Cu"/Cu1Na-Y (y-axis offset). (a) Background [spectrum 4(d)]; (b) sample (a)+ 10.7 Torr of NH,; (c) sample (b) + 146 Torr of CO. desorption of the NH, (evacuation for 2 h at 298 K) a band was observed at 2125 cm-l &th CI P h n l l l A e r at %IQh rm-1 nn rearlm;ccinn nf C'n Fiirthpr pvariiatinn ('7 h a t 191 K \ followed by CO adsorption at room temperature resulted in a band at 2150 cm-l with a shoulder at 2135 cm-l; this band was, however, not now removed on evacuation. In the present work, the adsorption of CO (0.1 Torr) onto Cu'I/CuINa-Y with preadsorbed NH, resulted in the observation of one weak band at 2111 cm-l. Raising the CO pressure to 8 Torr caused the intensity of the 2111 cm-l band to increase significantly and a second band to appear at 2069 cm-l.Both hands were removed by evacuation for 5 min at beam temperature. Since it has previously been shown that only CU' ions adsorb CO," these two bands must reflect CuI ions in either different sites or complexed to different numbers of NH, molecules. We have previously correlated the different v(C0) vibrational frequencies found for CO adsorbed on Cu'-containing Y zeolites with CuI-carbonyl complexes located in S, or S;, S;, and S,, sites.1° The lower frequency band was only observed with a significant overpressure of CO. The large wavenumber shift in this band, compared with those previously observed in Cul- containing Y zeolites, reflects an increased amount of n-bonding between the CO ligand and the CuI ion.Such a complex is expected to be located in the supercages, where CO n-bonding has been predicted to be most effective.g Coordination of NH, ligands to the Cul ion, will, by donating electron density, increase the amount of n back-bonding possible between CU' and the coordinating CO molecule. This will result in a greater shift in the CO vibration frequency compared with the gas phase. The observation of this band only at high CO pressures, may indicate that a significant pressure of CO is needed to allow coordination to a Cu' ion surrounded by the NH, ligands. In the case of the higher-frequency band at 2111 cm-', less n-bonding is envisaged in the species responsible for this complex. It is possibly associated with Cu' ions that are coordinating to both framework oxygens and NH, ligands in or near the six-rings between the supercages and sodalite cages.In this location n-bonding will be less effective owing to the influence of the framework oxygens and the reduced number of coordinating NH, ligands. Of the bands due to adsorbed NH,, only the band at 1273 cm-' is observed to be significantly perturbed by the adsorption of CO as, on adsorption, its intensity decreases. This suggests that displacement of the [Cu(NH,),I2+ complexes occurs onJ . Howard and J . M . Nicol 1241 2400 2200 2000 1800 1600 1400 1200 w avenumber/cm- ' Fig. 6. The reduction of Cu"Na-Y by CO in the presence of NH,. (y-axis offset) (a) Zeolite+ 10.7 Torr NH,+ 146 Torr of CO. Sample heated at: (b) 358 K; (c) 358 K for 13 h ; (d) 473 K; (e) 673 K.Cul-carbonyl formation. This observation was also made when adsorbing NH, and CO prior to the reduction of CU" discussed in the next section. The Reduction of Cu"Na-Y The reduction of Cu" ions in Y-zeolite with CO in the presence of NH, has been shown to occur within 1 h at 673 K2,' The reduction of our sample by this method is discussed here. For reduction, NH, at 10.7 Torr and CO at 146 Torr were introduced at room temperature. The infrared spectra of the zeolite after addition of NH, and CO are shown in fig. 5. Bands assignable to Cu-ammine and Cu'CO(NH,), complexes discussed in the previous sections are clearly visible. The position of the intense v(C0) band of the carbonyl complex at 2060 cm-l is shifted slightly with respect to that noted earlier. This is presumably due to a slight increase in n-bonding within the Cu'CO(NH,),complexes. Bands displaying fine structure within ca.2220-2100 cm-l are due to gaseous CO present in the sample cell. During reduction, spectra were measured at various stages as depicted in fig. 6 and 7. After heating at 673 K for 1 h, a noticeable drop in the transmission of the sample was observed, although the relative intensities of the bands remained unchanged. On removal of the zeolite disc from the cell its pink-brown colour indicated that some1242 F.T.I.R. Studies of Copper-containing Y Zeolites r Fig. 7. The reduction of Cu"Na-Y at 673 K (y-axis offset). (a) Sample heated at 673 K for 1 h; (b) evacuation of gas phase at 673 K; (c) evacuation for 3 h ; ( d ) sample cooled to ambient temperature.Cuo clusters had been formed, reducing the transmittance of the sample. This is observed to have no effect on the CO-Cu' complexes formed (section 5). The spectra in fig. 6 and 7 show a number of aspects of interest: (1) The bands at ca. 1444 cm-l and 1484 cm-l are due to NH,+ ions formed as a result of H+ production during reduction by NH,. These species reach their maximum intensity at 473 K [fig. 6(d)]. Above this temperature the decomposition of NH; occurs leaving H+ in the zeolite framework. This observation indicates that at low temperatures NH, is the preferred reducing agent. (2) Bands observed in the 2160-2060 cm-l region (2060,2120 and 2160 cm-l) are due to Cu'-Co complexes. The shift to higher wavenumber with increasing temperature indicates a migration of the Cu' ions into the sodalite cavity sites where z-bonding is less effective.The intensities of the bands are much reduced above 358 K, showing a reduction in the stability of the complexes. This temperature corresponds well with that observed previously for the desorption of CO from Cu'karbonyls in Y zeolites.1° (3) On heating at 358 K for 13 h [fig. 6(c)] a new band is observed at ca. 2230 cm-l. At the same time a band reappears in the region of 1275 cm-l. On heating to higher temperatures both of these bands disappear. The agreement in the wavenumber of these new bands with the v(NN), and v(NO), vibrations of gaseous N,O, which are observed at 2224 and 1285 cm-', re~pectively,~~ leads us to tentatively assign them to N,O.The N,O is a product of the reduction of Cu" by NH,. This is in agreement with the formation of NH; ions and indicates that at low temperatures NH, and not CO is the preferred reducing agent. (4) Bands which appear above 473 K in the 2400-2300 cm-l region are due to gaseous CO,, a product of the reduction of the Cu" ions by CO. The observation of CO, indicates that above 358 K reduction is occurring via the CO reduction mechanism. ( 5 ) On heating above 573 K a shoulder develops at 1320 cm-l, which is not lost on subsequent evacuation and cooling of the sample. This band may possibly be due to the symmetric deformation of the Cu'-(NH,), complexes. (6) After evacuation and cooling the residual structure in the spectrum is due to ammine carbonyl complexes, NH; and OH- species.These points show that a variety of species are formed during the reduction of Cu"J. Howard and J. M . Nicol 1243 2200 2170 2140 2110 2080 2200 2170 2140 2110 2080 wavenumber/cm-' Fig. 8. The adsorption and desorption of CO on Cu'Na-Y: (a) zeolite background after reduction ; (6) sample (a) + 0.2 Torr CO ; (c) sample (a) + 2.1 Torr CO; ( d ) sample (a) + 9.4 Torr CO; (e) evacuation of gas phase; (f) evacuation for 10 min. by CO in the presence of NH,. The data are complicated by the fact that NH, on its own may reduce Cu" ions. At low temperatures the appearance of NH; species as well as the identification of N,O, indicates that this is indeed the preferred mechanism. Only at temperatures above 473 K is CO, observed, indicating that reduction by CO is the preferred route.The Adsorption of CO on Cu'Na-Y The spectra obtained where CO is adsorbed onto CuINa-Y are shown in figure 8. Bands due to Cul-carbonyl complexes are observed at ca. 2156 and 2143 cm-l. The intensity pattern of these bands is similar to those obtained previously for CO adsorbed on autoreduced Cu"Na-Y zeolite.1° This indicates that the majority of the Cu' ions are located in SII, sites (2143 cm-l) within the zeolite framework, while a smaller number occupy S, sites (21 56 cm-l). The band at 21 78 cm-l is associated with the Lewis-acid sites in the zeolite framework, and has been discussed elsewhere.'O The similarity in CO adsorption spectra in Cu'Na-Y zeolites prepared by either CO/NH, reduction or autoreduction shows that the distribution of Cu' ions in the framework must be similar.Conclusions Infrared spectra of CuI'Na-Y during dehydration revealed the presence of copper hydroxyl species formed during ion exchange of the zeolite. These species were found to dissociate on heating the sample above 530 K, possibly to (cu-0-C~)~' and H,O. In the presence of ammonia the formation of copper-ammine complexes has been observed, as well as the interaction of ammonia with the structural hydroxyl groups. The latter interactions were only revealed in difference spectra. The formation of NH,+ species was shown by the presence of bands at ca. 1450 cm-l. In addition, a band at 1273 cm-l, characteristic of the d(NH,), vibration of the [Cu(NH,)J2+ complex, was shown to increase in intensity on the evacuation of NH,, and to decrease in intensity in the presence of CO.This behaviour has not been reported by other authors who have studied the same systems. We have associated the behaviour of the 1273 cm-l bands with (a) the removal of excess NH, from the cages on evacuation which allows additional1244 F. T.I.R. Studies of Copper-containing Y Zeolites [Cu(NH3),l2+ complexes to form and (b) the formation of Cu'CO(NH,), complexes in the presence of CO which either disassociate some of the [Cu(NH3),l2+ and/or perturb the d(NH,), mode to move to a lower wavenumber. Spectra of the reduction of Cu'INa-Y with CO and co-adsorbed NH, indicate that at low temperatures reduction by NH, was preferred, whereas at higher temperatures reduction by CO dominates the reduction mechanism.The adsorption of CO by Cu'Na-Y showed the CU' cations to be located in the same sites as those observed previously in autoreduced CuI'Na-Y. We would like to thank the S.E.R.C. for the provision of a quota studentship to one of us (J.M.N.) and Durham University for the provision of research facilities. References 1 U. K. Kruerke, US. Patent No. 3476 462, February 24, 1970. 2 Y. Y. Huang, J. Catal., 1973, 30, 187. 3 R. G, Herman, J. H. Lunsford, H. Bayer, P. A. Jacobs and J. B. Uytterhoeven, J. Phys. Chem., 1975, 4 W. B. Williamson, D. R. Flentge and J. H. Lunsford, J. Catal., 1975, 37, 258. 5 E. F. Vansant and J. H. Lunsford, J. Phys. Chem., 1972, 76, 2860. 6 I. E. Maxwell and E. Drent, J. Catal., 1976, 41, 412. 7 I. E. Maxwell, R. S. Downing and S. A. J. Van Langen, Acta Phys. Chem., 1978, 24, 215. 8 Y. Y. Huang, J. Am. Chem. SOC., 1973,95, 6036. 9 P. A. Jacobs, W. de Wilde, R. A. Schoonheydt and J. B. Uytterhoeven, J. Chem. SOC., Faraday Trans. 79, 2388 1, 1976, 72, 1221. 10 J. Howard and J. M. Nicol, Zeolites, 1988, 8, 142 11 Y. Y. Huang and E. F. Vansant, J. Phys. Chem., 1973, 77, 663. 12 P. Gallezot, Y. Ben Taarit and B. Imelik, J. Catal., 1972, 26, 295. 13 D. R. Flentge, J. H. Lunsford, P. A. Jacobs and J. B. Uytterhoeven, J. Phys. Chem., 1975, 79, 354. 14 C. Naccache and Y. Ben Taarit, Chem. Phys. Lett., 1971, 11, 11. 15 I. Nakagawa and T. Shimanouch, Spectrochim. Acta, 1966, 22, 759. 16 J. Ward, A.C.S. Monograph 171, 1976, p. 1 18. 17 J. Ward, Trans. Faraday SOC., 1971, 67, 1489. 18 Y. Ben Taarit, J. Primet and C. Naccache, Compt. Rend., 1970, 67, 1434. 19 P. Tarte, Spectrochim. Acta, 1958, 13, 107. 20 W. B. McWhinnie, J. Znorg. Nucl. Chem., 1965, 27, 1063. 21 J. R. Ferraro and W. R. Walker, Znorg. Chem., 1965, 4, 1362. 22 C. Chao and J. H. Lunsford, J. Chem. Phys., 1977, 57, 2890. 23 E. M. Flanigen, A.C.S. Monograph 171, 1976, p. 80. 24 T. Shimanouchi, Tables of Molecular Vibrational Frequencies, Consolidated Volume I (NSRDS-NBS 39, 25 K. H. Schmidt and A. Muller, J . Mol. Struct. 1974, 22, 343. 1972). Paper 7/00084G ; Received 2 1st December, 1987