Amorphous aluminosilicates containing about 12 wto °/0 nickel
have been synthesized bycation exchange. Approximately 40°/0 of the nickel content is present in the form of octahedral [NiH20)6]2+ ions while the bulk of NF+ is coordinated both by I-hO molecules and by oxygen atoms of the aluminosilicate framework. When the materials are heated in air at 350 -c, a change in the nickel coordination environment/geornetry and possibly also a partial oxidation take place

Nevenka Z. Rajić

Đorđe R. Stojaković

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CROATICA CHEMICA ACTACCA-1770CCACAA 60 (4) 735-739 (1987)YU ISSN 0011-1643UDe 546.74OriginaL Scientific PaperSynthesis and Characterization of Amorphous Nickel(II)AluminosilicatesNevenka Z. Rajić and Đorđe R. Stojaković*FacuLty of TechnoLogy and MetaHurgy, University of Beograd, P. O. Box 494,Yu-ll00l Beograd, YugosLaviaRecei ved December 12, 1986Amorphous aluminosilicates containing about 12 wto °/0 nickelhave been synthesized bycation exchange. Approximately 40°/0 .of the nickel content is present in the form of octahedral[Ni\H20)6]2+ ions while the bulk of NF+ is coordinated both byI-hO molecules and by oxygen atoms of the aluminosilicate frame-work. When the materials are heated in air at 350 -c, a changein the nickel coordination environment/geornetry and possibly alsoa partial oxidation take place.INTRODUCTIONSynthetic nickel-containing aluminosilicates have for some time been ofinterest since the aluminosilicate f'ramework is a very suitable support forcatalitically active nickel sites. Most attentionhas been directed to the zeolite--type aluminosilicates so that Ni-zeolites derived from the zeolite A, X, andY have been extensively investigated.v"In previous papers one of us (D. S.)studied the amorphous aluminosili-cates which are obtained if the synthesis of zeolite A is discontinued prior tothe onset of crystallization.v" Such amorphous aluminosilicates were thenused to prepare and characterize amorphous chromium(III) aluminosilicates.In this work a study has been uridertaken with the aim of synthesizing andinvestigating the corresponding nickel(II) derivatives.EXPERIMENTALReagentsThe sodium .aluminate and sodium silicate solutions were of technical grade,while sodium hydroxide, nickel(II) perchlorate,. nickeltlf) chloride, and sodiumchloride were of p. a. purity;Lristrusnenuitiorc and Chemical AnalysisThe X-ray powder diffraction analysis was performed on a Siemens Kristallo-flex 4 Diffractometer with the Ni-filtered CuK; radiation. The diffuse reflectaricespectra were obtained on a Beckman 5240 UV Spectrophotometer in the 140~350nm range, using MgO as standard; the reflection values were convertedhitbthe f (R",,) values using the Kubelka-Munk rel ationship'"!". Infrared spectra wererecorded on aModel 457 Perkin-Elmer spectrophotometer in the ·1000-350 cm?I736 N. Z. RAJlC AND Đ. R. STOJAKOVlCrange with samples in the form of KBr pellets. The elemental analysis on Al,Na and Ni was performed us ing an Unicam SP90B Series 2 Atomic AbsorptionSpectrophotometer, whereas Cl was determined by a Radiometer SelectrodeF1012Cl connected to a Radiometer M62 pH-meter; Si was determined gravi-metrically. Water content was obtained from the mass loss at 1000=c.Preparation of Amorphous Sodium Aluminosilicate (AS.4.S)This material was prepared by a previously published procedure", and hadthe following oxide formula: 1.14 Na20· 1.0A120s . 2.6Si02 • 7.1H20. Infraredspectrum (cm-i): 3380(vs, b), 3240(sh), 2890(w), 2800(w), 2300(vw), 1620(w,b), 1100(sh),1000(vs,b), 840(w, b), 700(s,b), 570(s,b) 420(s,b) (vs-very strong, s-strong, b-broad,m-medium, w-weak, vw-very weak, sh-shoulder).Preparation of Amorphous Nickel-Substituted Aluminosilicate1. Using nickel(II)perchlorate. - ASAS (50 g, 0.110 mol) was suspended into1.0 dm" .of aqueous Ni(Cl04h (c = 0.4 mol/drn"), and the suspension was kept in aclosed flask for five days at room temperature with occasional stirring. Thesuspension was then filtered through a filter of B-3 porosity, the solid thoroughlywashed with water and dried in air at room temperature to a constant mass.This gave 58 g of a light-green powder. Anal. found (%): Al 10.06; Na 0.64;Ni 11.46; Si 13.60; 'mass loss at 1000=c, 36.370/0.This composition corresponds tothe following oxide formula: 1.0NiO· 0.1Na20 . 1.0AhOs . 2.6Si02 . 10.9H20 (prod-uct I). The X-ray powder diffraction pattern of I shows it to be an amorphousmaterial (no diffraction maxima are present in the 2 g range of 7-65 aC). Diffusereflectance spectrum (nm): 1140, 692, 650, 380. Infrared spectrum (cm"): 3380(vs, b),3180(sh), 2880(m), 2780(m), 2300(w), 1620(m,b), 1430(w,b), 1370(w), 1070(sl1), 1000(vs,b), 850 (s, b), 610(s,vb), 420(s,b) (vb-very broad).II. Using nickel(II)-chloride. - The procedure was the same as that underI except that NiCl-, instead of Ni(CI04h was employed. The work-up yielded 58g of a light-green powder. Anal. found (0/0): Al 10.11; Na 0.51; Ni 12.51; Si 13.77;Cl - not found; mass loss at 1000<c, 34.38010.This corresponds to the followingoxide formula: 1.1NiO· 0.05Na20 . 1.0Ah03 . 2.6Si02 . 10.4H20 (product II). TheX-ray powder diffraction pattern as well as the diffuse reflectance and IR spectraof II were the same as those of 1.Treatment of I with Aqueous NaerA sample of I (10 g, 0.002 mol) was suspended into 1.0 dm" of aqueous NaCl(c = 2 mol/dmš) and the suspension was kept in a closed flask for five days atroom temperature with occasional stirring, The suspension was then filtered(yielding a light-green filtrate), the solid thoroughly washed with water anddried in air at room temperature to a constant mass. This gave 8.4 g of alight-green product. Anal, found(Ofo): Al 11.48; Na 2.93; Ni 7.99; Si 15.48; massloss at 1000=c, 31.01010.The corresponding oxide formula is: 0.64.NiO· 0.3Na20 . 1.0A120s . 2.6 Si02 . 8.1H20.RESULTS AND DlSCUSSlONAmorphous nickel-substituted aluminosilicates have been obtained hytreatmg an amorphous sodium aluminosilicate of the composition 1.14 Na20 .. 1.0 Alz03 . 2.6 Si02 . 7.1 H20 (ASAS) with aqueous Ni(Cl04)2 or NrCl, whilehaving in the reaction system the Ni : Na mol ar ratio of 3 : 2. The products are:with Ni(Cl04)2:1.0 NiO, 0.1 Na20 . 1.0 A1203 • 2.6 Si02 . 10.9 H20with NiClz:1.1 NiO, 0.05 Na20 . 1.0 Alz03 • 2.6 Si02 . 10.4 H20(1)(II)AMORPHOUS NICKEL(II)-AL UMINOSILICA TES 737It is seen that the Nat by Ni2+ ionic exchange is not accompanied by anychange in the SiOi A1203 molar ratio, which indicates that no degradation ofthe aluminosilicate framework occurs in the process. This is contrasted withthe analogous preparation of the amorphous chromium(III)-substituted alumi-nosilicate" where dealumination of the framework takes place to a conside-rable degree. The difference in behavior can be attributed to a significantlylower acidity of aqueous nickel(II), as compared to aqueous chromiumflflj.v-'?An increase in the water content relative to that found in ASAS is observedfor both I and II. A similar increase has been reported for the analogousconversion of crystalline sodium aluminosilicates (zeolites) into crystallinenickel-substituted aluminosilicates (nickel zeolites).'" This increase can beexplained by the fact that the trend in the size of hydrated ionic radii isgenerally opposite to that found for crystal ionic radii-" (Ni2+ having a smallercrystal radius than Na+ 15).~--~aI I1200 1400Figure 1. Electronic spectra of I(or II): a) prior to heat treatment; b) after heattreatment at 350 "C; c) after heat treatment at 800 =c.Diffuse reflectance spectra of I and II (Figure la) exhibit in the 350-1400nm spectral range four absorption maxima: at 380 nm, 650 nm, 692 nm, and1140 nm. The position of the maxima is in accord with octahedrally coordi-nated Ni2+, i. e. with the following band assignments.t"3A2g (F) ~ 3T2g (F)3A2g (F) -~ 3Tlg(F)/lEg3A2g (F) ~ 3T19 (P)1140 nm650 nm, 692 nm (doublet)380 nmThe splitting of the middle band is due to spin-orbit coupling which mixesthe 3Tlg(F) and IEg states.F and it has also been found in some other octa-hedral Ni2+ comlexes with oxygen ligands, e. g. in nickle zeolites.!" Thespectra of I and II differ somewhat from the spectrum of the free[Ni(H20)6J2+ion, the latter having maxima at 1110 nm, 715 nm, 660 nm, and400 nm.l'' This suggests that the Ni2+ species in I and II is not coordinated738 N. Z. RAJIĆ AND Đ. R. STOJAKOVIĆexclusively by H20 molecules as it is usually assumed for nickel zeolites,12,20-~~but that at least some of the nickel(II) is also coordinated by the oxygenatoms of the aluminosilicate framework. Such mixed coordination providesan explanation for the fact that only about 40010 of Ni2+ can be replacedby Na+ when I is treated with a concentrated NaCl solution. Namely, asthe aluminosilicate framework can coordinate transition metal ions in biden-tate fashion," it is the chelate effect that prevents the complete replacementof Ni2+ by Na". It, therefore, follows that ~ 600/0 of the total nickel contentis coordinated simultaneously by H20 and the framework O-atoms, whereasthe rest (i. e. the exchangeable part) is coordinated only by H20 molecules.Infrared spectra of I and II also indicate that coordinative bonds existbetween Ni2+ and the framework O-atoms. The 800-500 cm'" region in theIR spectra of aluminosilicates is con'~idered to be particularly sensitive tochang es in the mode of linking of Si04 and Al04 tetrahedra.23,24 If the IRspectra of ASAS and of I (or II) are compared, it is in this region thatnotable differences can be found (Figure 2): whereas two bands are cha-racteristic of ASAS (at 700 crn? and 570 cm+), only one broad band is seenfor I (or II) (at 610 cm"). Such differences could be expected to arise asa consequence of the Ni2+ -framework interaction, since the interaction isbound to affect, to some extent, the adjacent Si-O and Al-O bonds andthereby affect the mode of linking of the corresponding Si04 and Al04tetrahedra.600 400WavMumber /cm"Figure 2. Infrared spectra of ASAS (a) and of material I (or II) (b) in the800-350 cm? region.ac:o'-.•..b800When products I or II are heated in air at 3500C for 2 h their colorchanges from light-green to brown; the same behavior had been reportedfor nickel zeolites.s" The brown material exhibits only one absorptionmaximum (at 400 nm) in its electronic spectrum (Figure lb). The color changeprimarily reflects the change in the nickel coordination geometry andAMORPHOUiS NIOK'ELJ(lI) -A'LUMINOSILfCATĐS 739environment eaused by the departure of water from the system during thethermal treatment.P." However, in view of the basieity of the aluminosilieatemedium, a partial oxidation of niekel(II) to Ni (III) or Ni (IV) could be yetanother cause of the color change." Further heating of the brown materialat 8000e results in a deeomposition of the aluminosilicate frameworkš"yielding a light-yellow produet. The electronic speetrum of the latter (Figurele), again shows four absorption maxima (at 1130 nm, 700 nm, 620 nm, and400 nm) eharaeteristic of oetahedral Ni2+ eoordination by oxygen ligands. Thespectrum differs somewhat from the speetrum of NiO (NiO having maximaat 1163 nm, 741 nm, 671 nm, and 406 nm'"), so that the produet of the 8000etreatment can not be described as a simple mixture of oxides (NiO, Ab03,and Si02) but rather as a mixed oxide.Acknowledgement. - This work was finaneially supported by the ResearehFund of Serbia, Belgrade.REFERENCES1. J. Mi c h a l i k, M. N ara y ana, and L. K eva n, J. Phys. Chem. 88 (1984) 5236.2. N. Da vid ova, P. P e s h e v, and D. S h o p o v, J. Catal, 58 (1979) '198.3. P. H. Ka s a i, R. J. B i s h o p, and D. Me Leo d, J. Phys. Chem. 82 (1978) 279.4. E. Gall e i, D. E i s e n b a e h, and A. Ah med, J. Catal. 33 (1974) 62.5. M. SeI e ni n a and K. W ene k e, Z. anorg. allg. Chem. 387 (1972) 190.6. Đ. S toj ako v i ć and D. Vas o v i ć, Monatsh. Chem. 116 (1985) 581.7. D. Vas o v i ć and Đ. S toj ako v i ć, J. Serb. Chem. Soc. 50 (1985) 523.8. D. Vas o v i ć and Đ. S toj ako v i ć, J. Serb. Chem. Soc. 50 (1985) 113.9. T. S u r l e s, J. O. Eri e k s o n, and D. P rie s ner, International LaboratoryMay/June 1975, p. 29.10. G. Kor t lim, W. Bra u n, and G. He r zog, Angew. Chem. 75 (1963) 653.11. D. W. Bre c k, Zeolite Molecular Sieves, New York, J. Wiley and Sons, 1974,pp. 441-507.12. P. E. R ile y and K. S e f f, J. Phys. Chem. 79 (1975) 1594.13. 1. Gal and P. Rad ova n o v, J. C. S. F ara day I 71 (1975) 1671.14. F. A. Co t to n and G. W i 1k i n s o n, Advanced Inorganic Chemistry, 4thEd., New York, J. Wiley and Sons, 1980, p. 255.15. Ibid., p. 14.16. A. B. P. Lever, Inorganic Electronic Spectroscopy, Amsterdam, Elsevier, 1984,p. 507.17. C. J. B all h a u s e n, Introduction to Ligand Field Theory, New York, MeGrowHill, 1962, p. 264.18. E. Ga r b o v s k i, Y. Kod rat off, M. Mat h i e n, and B. Ime li k, J.Chim. Phys. 69 (1972) 1386.19. RefY, p. 787.20. T. A. E g e r t o n and J. C. Vie k e r man, J. C. S. Faraday I 69 (1973) 39.21. K. K 1i e r and M. R il1e k, J. Phys. Chem. Soluls 29 (1968) 95l.22. H. H o ser, S. Kr z y z a n o w s k i, and F. Tri f i r o, J. C. S. F'araday I70 (1974) 665.23. Ref.9, p. 415.24. F. W o 1f and H. F u e r t i g, Tonind. Ztg. Keram. Rundschau 90 (1966) 310;C. A. 66 (1967) 22586k.25. K. S e f f, Acc. Chem. Research 9 (1976) 121.26. Ref.", p. 485.27. Ref.1G,p. 505.740 N. Z. RAJlC AND Đ. R. STOJAKOVICSAZETAKNevenka Z. Rajić i f)orđe R. StojakovićAmorfni aluminosilikati sa oko 12 mas. % nikla dobijeni su jonskom izme-nom. Oko 40% nikla nalazi se u obliku oktaedarski koordiniranih jona [Ni(H20)6F+,a preostali nikal koordiniran je sa molekulima vode i kiseonikovim atomima izaluminosilikatne rešetke. Zagrevanjem na vazduhu, na oko 3500C dolazi do pro-mena u koordinaciji, odnosno geometriji nikla, a moguće je da dolazi i do deli-mične oksidacije nikla.

Synthesis and Characterization of Amorphous Nickel(II) Aluminosilicate

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