Indian Journal of ChemistryVol. 25A, January 1986, pp. 104-106

Preparation & Properties of a New ZeolitePrepared by the Interaction of

Tetramethylammonium Ion withHydrophilite

(Miss) SANGEETA BHATTACHARYA & SAT! PRASADBANERJEP

Department of Chemistry, Dr H S Gour Vishwavidyalaya, Sagar470003

Received 21 May 1985; revised and accepted 29 July 1985

Commercial Hydrophilite, a desiccant and having similar proper-ties as 4A type zeolites. has been interacted with tetramethylam-monium cation to prepare a zeolite with organic base. The TMA-interacted Hydrophilite has been tried as a support for H ,S, CO,and NH J adsorption. Results of TG, IR spectroscopic and XRDstudies of the TMA-interacted and adsorbed samples have beendiscussed.

Commercial Hydrophilite, a desiccant used in paintand allied industries, is reported to be similar tosynthetic 4A type zeolites in properties. In this study anattempt has been made to synthesise a new organic-based zeolite by interaction of Hydrophilite withtetramethylammonium (TMA) cation; the new ma-terial has been used as an adsorbent for hydrogensulphide, carbon dioxide and ammonia with a view totesting its potential for pollution control. Effect ofheating upto 800°C has been followed by TG analysisand IR spectroscopy. X-ray diffraction studies of theTMA(I)-Hydrophilite and its adsorbed derivativesprovide useful information on their structures ascompared with those of 4A zeolites I.

The Hydrophilite sample was supplied by the RasEnterprises, Bombay, as a white, odourless powder.The solid material was at first kept immersed in asaturated aqueous tetramethylammonium(l) iodidesolution for several days and later eluted with fresh lotsof the same solution. Filtering and air-drying resultedin the formation of a grey, exchanged sample ofHydrophilite. Separate portions of this sample werekept in closed conical flasks provided with inletsthrough which constant streams of hydrogen sulphideand carbon dioxide were passed. The TMA(I)-Hydro-philite samples were thus exposed to a continuousstream of these gases for about four hours to ensuremaximum adsorption. Another portion of TMA(I)-Hydrophilite was kept immersed in liquor ammonia ofspecific gravity 0.88 for several days. It was laterfiltered and air-dried. The TMA(l)-Hydrophilite andits three adsorbed samples. which were all grey incolour. were subjected to TG analysis upto 800"C at a

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heating rate of IDoe min -I, using a thermobalancesupplied by FCIl, Sindri. The residues left afterthermal treatment were all white except that of theCO 2-adsorbed sample which was light brown. IRspectra of the samples and their residues were re-corded? in KBr in the range 4000-650cm -Ion aSpektromom 2000 IR spectrophotometer. The mid-IRregion of the spectra was of particular interest for astudy of the effect of adsorption and interaction andthe changes in the framework structure brought aboutby heating. The X-ray diffractograms were obtainedbetween 28 angles of 5° and 70' using CuK radiationof 1.5418A and a Philips X-ray unit PWI i40.

IR spectra of the TMA(I)-Hydrophilite and all theadsorbed derivatives show major absorption bands forhydroxyl groups (vOH, 3300 cm -I), water molecules(bHOH, 1640cm -I) and framework vibrations ofHydrophilite (below 1300cm -I). Presence ofTMA(l)cation is indicated by a small band at 1500cm-1

(bHNH) and a shoulder around 1400cm -1 (8HNH).The intensities of these vary from one adsorbedderivative to another characterising the nature of theadsorbate. The intensity of the NHiI) band around1400 em -I is increased in the case of the N H 3 adsorbedTMA(I)-Hydrophilite. The H 2S and CO 2 adsorbedsamples, on the other hand. show increased intensity ofthe band around 1500cm -1. Heating upto 800cCremoves TMA(I) and the adsorbates as the I R spectraof the residues after heating exhibit no bands at 1500and 1400 em -1. However, the bands due to IOH,water molecules and framework vibrations remainunchanged. This confirms the ability of these Hydro-philite samples to remain hydrated even after heatingupto 800'C. They also remain crystalline. Absence ofIR bands at 2348 and 2353 cm -1 in the case of CO 2-

adsorbed TMA(i l-Hydrophilite eliminates the possi-bility of physical adsorption of this gas at roomtemperature. The bands around 1500 and 1430cm . 1

can be assigned to monodentate carbonate species':".An earlier study> has shown that factors like the highheats of adsorption and the significant resistance tointernal diffusion complicate the adsorption of CO 2"

Studies relating to H lS adsorption on zeolite haveshown that adsorption results in simultaneous for-mation of water and only negligible quantities areoxidised to SO 2 ". Moreover. the pore-size of theadsorbent also affects the adsorption".

The TG data (Fig. I. Table 1) of the Hydrophilitederivatives under investigation can be interpreted onthe basis of the reported behaviour of TMA(l)-zeoliteslike Omega and Offretite. Pyrolytic decomposition of

NOTES

Sample

I. Hydrophilite2. TMA(I)-Hydrophilite3. NH ,adsorbed-sample4. H 2S-adsorbed-sample5. CO 2-adsorbed-sample

Table I-Summary of Thermal DataTotal mass loss (%) Max. rate of loss eC) Temps. showing variations in II mass/z, Temp.

63.235.064.830.732.9

720380380400360

200, 340, 440, 72080, 120, 260, 320, 380,420, 520120, 220, 260, 300, 380, 460200, 260, 300, 400, 460, 540180, 260, 320, 360, 440, 560

5

3

TMA(J) takes place at two different temperaturesindicating two different cation environments'". Rapiddecomposition of the quaternary cation has beenreported to occur above 300°C, generating three typesof hydroxyl groups through unstable methoxy in-termediates. The present study is in agreement withthis reported thermal behaviour. All the four sampleshave a maximum rate of mass loss between 360 and400°C. Mass loss to the extent of 85% to 95% takesplace upto 500°C. While TMA(I)-Hydrophilite and itsH 2S and <CO 2 adsorbed samples show 85% loss upto500°C, the NH 3 adsorbed sample shows 95% loss uptothis temperature. Losses of water, adsorbed speciesand the TMA(I) occur upto 500cC and further massloss above this temperature is the result of dehy-droxylation. NH 3 adsorbed sample shows the presenceof two volatile cations 1 0 and a high degree of adsor-ption. A very rapid mass-loss step, corresponding toabout 60% of the total loss. is observed between 360°and 380°C due to deammoniation and loss ofTMA(I).The H 2S adsorbed sample shows dehydration upto280°C, followed by desorption of adsorbate andTMA(I) decomposition around 400°C. The CO 2 ad-

20 400 760TEMP,oC

Fig.l- TG plots of Hydrophilite (curve l ), its TMA(I)-exchanged(curve2) and NH, (curve3), H 2S (curve4) and CO2 (curve5)

adsorbed TMA(I)-Derivatives

o0'----37 25 15-26

Fig.2 - X-ray Diffractograms of TMA(I)-Hydrophilite (I), its H ,S adsorbed (2), CO 2 adsorbed (3). N H,adsorbed (4). derivatives and Hydrophilite (5), between 28 angles 5' (17.67A) and 37" (2.43A)

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INDIAN J. CHEM .. VOL. 25A, JANUARY 1986

Tablez=-Xcray Data of Different Samples

d(A) Intensity d(A) IntensityHydrophilite TMA(l)-Hydrophilite

12.28 14.26 m8.67 m 9.83 m7.03 m 7.76 m5.47 m 5.91 m4.35 vw 4.80 w4.10 m 4.31 m3.71 4.083.40 w 3.88 m3.28 3.56 w2.96 v s 3.43 s2.90 w 3.30 w2.75 w 3.10 s2.62 3.04 m2.05 vw 2.85 w

2.712.54 w2.10 w

d(A) Intensity d(A) IntensityH 2S-adsorbed sample CO 2-adsorbed sample

13.60 m 13.00 m9.41 m 9.21 m7.30 m 7.50 m5.75 m 5.68 m4.62 m 4.62 m4.21 m 4.19 m3.99 v s 3.97 v s3.80 s 3.803.48 m 3.48 m3.35 3.35 s3.04 s 3.23 w2.99 s 3.04 s2.80 m 2.98 s2.67 s 2.80 m2.48 m 2.67 s2.29 w 2.64 m2.19 w 2.48 m2.10 w 2.27 w

2.18 w2.08 w

d(A) Intensity d(A) Intensity

:-'Hradsorbed sample

13.39 m 3.04 v s9.21 m 2.96 w7.44 m 2.80 w5.68 m 2.73 w4.23 m 2.67 m3.80 s 2.20 w3.49 m 2.08 w3.3:;

vs = very strong, s = strong, m = medium, w = weak, vw = very weak

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sorbed sample also shows similar sequence of steps.The TG behaviour is slightly different for this de-rivative because of the coking phenomenon. Duringhydrocarbon transformations over zeolites. carbo-naceous residues and eventually. 'coke' are formed.The brownish residue after TG analysis indicates thepresence of carbon deposited as a result of interactionof the gas with the organic species of the tetramethyl-ammonium ion.

The X-ray diffractograms are shown in Fig.2. Fromthe relative intensities and the d spacings (Table2) ofthe parent Hydrophilite and the four new derivatives itbecomes clear that Hydrophilite is similar to synthetic4A zeolite in its X-ray characteristics. In cage struc-tures such as that of zeolite A the channel networkpermits three-dimensional diffusion of all guest mo-lecules small enough to enter the channel system. TheXRD data of the TMA(l)-exchanged Hydrophiliteand its adsorbed derivatives show that the crystallinestructure is unaltered even after cation exchange andadsorption. Changes in reflections of the new de-rivatives as compared to Hydrophilite indicate thatstructure of NH 3 adsorbed TMA(I)-Hydrophilite ismore akin to 4A zeolite structure and the variationsdepend on the nature of the interacted species. Themaximum peak intensity for the adsorbed derivativesis found around d values 3.99A, 3.97A and 3.04A forH 2S, CO 2 and NH 3 respectively. One reason for theappearance of more intense peaks in the diffracto-grams of the adsorbed derivatives of TMA(l)-Hydro-philite is the heaviness of the samples due to thepresence of adsorbed gases as compared to the lessdense TMA(I)-Hydrophilite.

The authors thank Mjs Ras Enterprises, Bombay,for the free samples of Hydrophilite.

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