Indian Journal of Chemistry Vol. 45A. May 2006. pp. I 131-11:18
Alkylation of phenol with tert-butyl alcohol catalysed by some sulphated titania systems
K R Sunajadevi & S Sugunan*
Department of Applied Chemistry. Cochin University of Science and Technology. Kochi 682 022. India Email: ssg@cusat.ac.in
Recei1·ed 9 Febnwrr 2005: n:~·ised 21 Mlll'ch 20()(5
Titania sulphated titania and transition metal loaded (9'/o) sulphated titania have been prcp:1rcd by sol gel method and ch:1racteri1.ed by XRD, FriR, BET surface JreJ. EDX and UV-vis DRS. Surface acidity of these catalysts is determined by temperature programmed desorption of ::ll111110nia. Alkylation of phenol with ten-butanol in the vapour phase over the prepared systems has been studied at I atm and 160-2:W0C. The reaction provides high selectivity of alkylation at the pam position. The product selectivity has been corrc!Jtcd with the surface acidity of the systems.
IPC Code: Int. Cl.s 1301J21/00: BOIJ37/00: C071337/00
Nanocrystalline materials were first synthesized by Gleiter and co-workers in 1981 and have since become a major focus of research because of their interesting and potentially useful properties1• The nanoscalc chemistry involved in sol-gel methods is a more direct way to prepare highly divided materials2. Sol gel method is a homogeneous process, which results in a continuous transformation of a solution into a hydrated solid precursor (hydrogel). Titania sol- gel synthesis has been developed from inorganic precursors and from metal organic precursors like titanium isopropoxideJ. The advantages of sol-gel process in general are high purity, homogeneity and low temperature. For a lower temperature process, there is a reduced loss of volatile components and thus the process is more environmental friendly.
Sulphated metal oxides are strong solid acids that have recently become the focus of much interest because of the enhanced chemical properties imparted by the presence of sulphate groups4. Titania, classified as a solid acidic oxide in both the anatase and rutile crystallographic forms, has long been known to possess catalytic activity, although anatase was found to be more active than rutile5. Photocatalytic degradation of phenol using Ti02 immobilized in polyvinyl alcohol has been reported6. The chemical and catalytic properties of titania can be modified by the incorporation of metallic ions.
Friedei-Crafts alkylation is an important means of attaching alkyl chains to aromatic rings and hence is a key reaction in organtc chemistry. Alkylation of
phenol provides many industrial intermediates such as agrochemicals and polymers. Alkylation of benzene with isopropanol on mixed oxides7 and benzoylation of toluene over different sulphated zirconia and iron incorporated sulphated zirconia systems8 have been reported. The reaction of phenol alkylation with tert- butyl alcohol (TBA) have been studied extensively owing to industrial interest in the products as antioxidants, ultraviolet adsorbers and heat stabilizers of polymeric materials. The catalysts used are developed from liquid acid, metal oxide, AI salt catalyst to cation exchange resin'J. However. the reaction of tert-butlation of phenol gives numerous products depending on the nature of the catalysts as well as on the reaction temperature10• For example.
weak acid catalysts such as zeolite- Y favour tert-buty pheny ether and strond acid catalysts like zeolite, lead to meta-tert-butylphenol. On the other hand, moderate acid catalysts like SAPO-I, MCM-41, etc. produce ortlio and para tert-butyi phenol. Sakthivel et a/.10 reported the vapour phase /ert-butylation of phenol over sulphated zirconia catalyst with a high selectivity to para isomer. Incorporation of Zn and Fe in AI- MCM-41 framework is found to increase the total acidity of catalysts and the incorporated Fe(lll) is found to be in tetrahedral co-ordination. Savidha et a/. 11 explained tert butylation of phenol with /-butyl acetate over Al-MCM-41, Zn- and Fc-AI-MCM-41 and found that the phenol conversion and 4-t-butyl phenol selectivity are higher over Zn- and Fe-AI- MCM-41 than that of Al-MCM-41 catalysts.
1132 INDIAN J CHEM. SEC A. MAY 2006
Dapurkar et a/. 12 reported that mesoporous gallosilicate (GaMCM-48) molecular sieve catalyst is highly active for the tert butylation of phenol and shows a much higher substrate conversion than the analogous catalys( systems. Karthik et a/. u reported the effect of various parameters for the tert-butylation of phenol over Co-Al-MCM-41. The objective of the present study is to demonstrate the feasibility of phenol alkylation with ten-butyl alcohol over transition metal loaded sulphated titania systems.
Alkylation occurs selectively at the pom position. The observed activities could be correlated with the acidity of the catalyst.
Materials and Methods
Catalyst preparation
Cr, M n, Fe, Co, N i, Cu and Zn load eel (9%) sulphated titania nano powders were prepared by sol- gel process using titanium isopropoxide (Aldrich 98%) as the starting material. Titanium isopropoxicle was added to water-nitric acid mixture in the ratio 5:60:0.5 with constant stirring. Precipitation occurred immediately and the precipitates were stirred continuously at room temperature to form a highly dispersed sol. To this, Cr, Mn, Fe, Co, Ni, Cu and Zn nitrate solutions (9 wt%) were aclclecl separately and stirred again for about 4 h. After keeping the sol for aging. it was concentrated and dried at 60°C.
Sulphation was clone using 0.5 M sulphuric acid solution (2 mL g·1 of the hydroxide). The precipitate was dried at l I
o o c
for 12 h in an air oven and powdered below 100 microns mesh size and calcined at 500°C for 5 h in a muffle furnace. The general sample notation STX(9) stands for sulphated titania with 9 wt% of X metal oxide whereas T and ST denote pure and sulphated titania respectively.Physico-chemical characterization
The catalyst samples were characterized by different physico-chemical techniques such as XRD analysis, infrared spectra. BET surface area, energy dispersive X-ray (EDX) analysis, diffuse reflectance liV-vis spectral analysis and acidity cletennination by temperature programmed desorption of ammonia.
X-ray powder diffraction (XRD) patterns have been recorded on a Rigaku D-max C X-ray diffractometer using Ni filtered Cu Ka radiation source ()c = 1.5406
A).
~The XRD phase present in the samples was identified with the help of JCPDS data files.Simultaneous determination of surface area and pore
volumes of the catalyst samples was clone on a Micromeritics Gemini-2360 surface area analyzer under liquid N2 temperature using N2 gas as the adsorbent. Previously activated samples at 500°C were degassed at 350°C under nitrogen atmosphere for 4 h prior to each measurement. The pore volumes of the samples were measured by the uptake of nitrogen at a relative pressure of 0.9. FTIR spectra of the samples were recorded using a agna 550 icolet instrument by the KBr elise method in the range 400- 4000 cm·1• Quantitative elemental analysis of the samples was clone by EDX measurements using EDX- JEM-35 instrument (JEOL Co. link system AN-1000 Si-Li detector). Samples were prepared by dusting the titania powder onto double sided carbon tape.
mounted on a metal stub. Diffuse reflectance UV-Vis spectra 200 and 800 nm of the samples were recorded at room temperature between using MgO as standard in the Ocean Optics AD 2000 instrument with CCD detector. Temperature programmed desorption of ammonia was clone in the range or I 00-600°C in a conventional flow-type apparatus at a heating rate or 20°C min-1
Catalytic activity
The alkylation of phenol (Merck) with tert-butyl alcohol (Qualigens) was carried out at atmospheric pressure in a fixed bed, tubular clown flow reactor using 0.5 g of the catalyst placed on a glass wool bed packed between silica beads. The catalyst was activated at 500°C for 2 h prior to catalytic runs. The reactor was heated to the requisite temperature using a tubular furnace controlled by a digital temperature controller cum indicator and the temperature is monitored using a thermocouple. A reaction mixture of phenol and tert-butyl alcohol with a molar ratio or I :2 was feel into the reactor by means of a syringe pump, at a flow rate of 4 mL h-1• The products vverc collected with a condenser and the liquid products were analyzed by gas chromatography (Chemito GC 1000) using a BPI capillary column (12 m x 0.32 mm) with FID detector, nitrogen a:; carrier gas (injection and detection port temperatures-i SO"C.
temperature programme-60°C-l-l OOC-1 50°C).
Results and Discussion
Catalyst characterization
All peaks measured by XRD analysis could be assigned to those of Ti02 crystal. The average crystallite size is calculated (Table I) using Scherrer
SUNAJADEVI & SUGUNAN: ALKYLATION OF PHENOL CATALYSED 13Y SULPHATED TITANIA SYSTEMS 1133
Table I - Su;·face parameters of the prepared systems
System Crystallite size Elemental com[>OSition from EDX (%) Pore diameter BET surface area Pore volume
(nm) Ti01 so-~ Metal
T 12.71 100
ST 9.62 95.34 4.66
STCr(9) 6.38 81.60 10.58
STMn(9) 19.39 83.52 9.64
STFe(9) 13.56 82.92 10.21
STCo(9) 15.07 80.18 11.30
STNi(9) 18.14 79.09 12.85
STCu(9) 16.57 79.42 11.97
STZn(9) 14.86 82.77 10.18
equation from the I 0 I reflection of anatase 14• The average crystallite size L, as given by Scherrer equation is L = 0.9N'~ Cos 0, where A.= wavelength of the X-ray used, 0 = glancing angle and ~ = FWHM (half the width of the peak with maximum intensity).
It has been reported that the degree of crystallization of the sulphated oxides is much lower than that of the oxides without sulphate treatment15. From the XRD patterns (Figs J and 2), it is clear that the rutile phase is completely eliminated in the case of sulphated samples. Sulphation retards the transformation from anatase to rutile in comparison with the sample without sulphation. Dispersion of SO/ species hinders agglomerization of the titania particles indicating delayed crystallization. In addition to stabilizing anatase Ti02 crystallites, sulphate surface species inhibit Ti02 crystallite sintering leading to lower crystallite than in pure Ti02. Since no titanium sulphate is detected by XRD for the catalysts examined in the present study, the sulphur may exist in a form of sulphate on the surface of Ti02. Choo et a/.16 reported that there was no formation of titanium sulphate for the ST calcined even at 900°C. In order to identify the state of sulphur species on the surface of Ti02, they examined the sulphated supports by XPS and found that the sulphur compound exists in a form of sulphate (S04
2.) on the catalyst surface. The bulk structure of titania remains virtually unchanged by the incorporation of metal ions, except for a lowering in crystallinity. The absence of any characteristic peaks of the metal oxides, suggests that these oxides are present in the form of dispersed oxide species, since the total content of them is rather small.
7.82 n.84 6.81 8.52 8.06 8.61 7.05
::J
~
.£
(/)c: Q)
c
10
10
(nm) (m" g·l) (cc g·1)
102.8 35 0.09
92.3 91 0.21
53.1 128 0.17
57.1 98 0.14
49.3 138 0.17
44.9 98 0.11
46.3 95 0.11
55.0 80 0.11
44.9 98 0.11
20 30 40 50 60 70
28 in degrees
Fig. I - XRD profiles of (a) T and (b) ST.
20 30 40 50 60 70
28 in degrees
Fig. 2 -XRD profiles of STCr(9) STMn(9) STFe(9) STCo(9) STNi(9) STCu(9) STZn(9).
1134 INDIAN J CI-IEM. SEC A. MAY 2006
Energy dispersive X-ray analysis
Energy dispersive X-ray analysis yields the chemical composition of the prepared samples. The elemental compositions of individual systems are presented in Table 1. The sulphate content of the metal incorporated sample is considerably higher, when compared with simple sulphated system, which indicates that metal doping brings about a considerable reduction in the extent of sulphate loss from the catalyst surface. It may be assumed that the dispersion of iron particles restricts the sulphate species more or less to the surface. minimizing their migration into the bulk.
FTIR spectroscopy
IR spectrum of pure titania (Fig. 3) contains two major absorption bands at 3383 and 1630 cm·1• These bands may be attributed to the hydroxyl groups; the former corresponds to the stretching and the latter to the bending modes of OH group. In comparison with pure titania, the infrared spectra of sulphated metal oxides exhibit a strong absorption band at 1375-1390 cm·1 and a broad peak with shoulders at around I I 00-1200 cm-1 (Fig. 4 ). The peaks at I 029, I 076 and 1222 cm-1 are typical of the S=O mode of vibration of a chelating bidentate sulphate ion coordinated to a metal cation 17. When SO.t is bound to the titania surface, the symmetry can be lowered to either C," or C2v. The sulphate species modified the electronic environment around the Ti-1+ ion by anchoring SO.t in either bridging biclentate or chelating biclentatc complexes18·19. The bands obtained in the 1200-1100 cm-1 regions are typical of sulphato complexes in a biclentate configuration with C2,. symmetr/ 0. Thus, the IR spectral bands of the samples closely agree to the biclentate sulphate complex structure having bands around 1119 and 1129 cm-1• The bands observed in the range of 400-900 em ·I are the vibration modes of
0 . 0 "I,,
anatase skeletal -Tt- bonds- ·--. In the low energy region of the spectrum the bands at 595 and 467 cm-1 are assigned to ben eli ng vibrations of Ti-0 boncls2'.
Sw:face area and pore volume measurements
Table I shows the surface parameters of the prepared systems. As evident from the data, sulphated titania showed a higher surface area compared to pure titania. Jt is already reported that the retention of surface area by the sulphated samples occurs even after high temperature calcination, and is explained on the basis of the higher resistance to sintering acquired by eloping with sulphate ions2.J. Addition of transition
4000 3500 3000 2>00 2000 1.'00 .000 ,00
Wave Numbers (cnY') Fig. 3- FTIR spectra ofT and ST.
4000 2000 1000
Wave Numbers (cm~l)
Fig. 4- FTIR spectra of STCr(9) STMn(9) STFe(9) STCo(9J STNi(9) STCu(9) STZn(9l.
SUNAJADEVI & SUGUNA :ALKYLATION OF PHENOL CATALYSED BY SULPHATED TITANIA SYSTEMS 1135
metal species causes a further setback to the crystallization and sintering process, which is evident from the higher surface area of the samples in comparison with the simple sulphated system. The metal oxide species along with the sulphate ions prevent the agglomeration of titania particles resulting in a higher surface area. Only exception is STCu(9) samples for which there was a slight lowering of surface area compared to ST. Among the different metal incorporated systems, there was no significant variation in the surface area value.
Assuming the pores are cylindrical, the average pore diameter is calculated using the formula: d
=
4Vp!S,, where d is the average pore diameter, V, is the pore volume, and SP is the surface area15• Decrease in the pore diameter is observed after sulphation. Metal incorporated samples also show a decrease in pore diameter.UV-vis dijjitSe reflectance spectroscopy
UV -vis DRS is used to probe the band structure, or molecular energy levels, in the materials since UV- Vis light excitation creates photo generated electrons and holes. Zhang eta/. 25 reported the UV- Vis spectra of titania samples calcined at different temperatures. In all the samples, characteristic band for tetrahedrally coordinated titanium appears at about 300-380 nm. The absorption IS associated to
the 02.-1Ti4+ charge transfer corresponding to
electronic excitation from the valence band to the conduction band. A111, , and band gap energy calculated for the present catalysts are given in Table 2. The band gap energy is found to increase after sulphate modification and metal incorporation. The presence of the doping ions caused significant absorption shifts into the lower wavelength region compared to pure titania.
Temperature programmed desorption of ammonia
It is generally recognised that ammonia is an excellent probe molecule for testing acidic properties of solid catalysts as its strong basicity and small molecular size allow detection of acidic sites located in very narrow pores also20. Acid site distribution in Table 2 shows the presence of weak (I 00-200°C).
medium (200-400°C) and strong (400-600°C) acid sites. Pure titania shows only low acidity and sulphation increase its acidity. It is well established that for sulphated metal oxides, the electron withdrawing inductive effect of the sulphate groups through the bridged oxygen atoms generates high surface acidity. The sulphating agent being acidic, preferentially attacks the basic sites, and converts them to acidic sites leading to increase in the total acidity. Incorporation of metal ions also changes the acidity considerably. The nature of the acid sites is greatly altered by the nature of the ions incorporated into the lattice. The distribution change may be a coupled effect of the crystalline and structural changes.
The change in the acid strength distribution for the different systems may be related to the interaction of the added metal cations with the Ti02. All metal incorporated systems show lower acidity compared to sulphated titania. The increased loading of sulphate on Ti02, as evident from EDX, can form the polynuclear type of sulphate complex and increase the coverage of the Ti metal ion by the sulphate ion. The polynuclear sulphate cannot extract as many electrons as isolated sulphate, to generate a strong acidity. Samantaray et a/.15 reported a decrease in surface acidity at high sulphate concentrations. It is reported in literature that the generation of total and strong acidity is not affected by the type of sulphate species. such as isolated and polynuclear, but by the coverage Table 2- Band gap energy from UV-Yis DRS and acidity from ammonia-TPD
Catalyst Allla'\ Band gap Amount of ammonia desorbed (mmol !:!.1)
(nm) energy (eY) Weak Medium Strung Total
T ]72 3.25 CUI 0.20 O.Ol 0.52
ST 322 ].76 0 50 0.32 0. 09 0.91
STCr(9) ]10 ].90 0.-+2 0.47 0.02 0.91
STMn(9) ]14 J.X5 0.]7 0.46 0.01 0.84
STFe(9) ]20 3.78 0.]6 (l.\4 0.03 0.73
STCo(9) .\21 ]77 0 . .\7 0.35 0.0 I 0.73
STNi(9) 32: ] 76 0.37 0.35 0.00 072
STCu(9) ~')~'"~ ,.
: uo
0 . .\X () 35 000 0.73STZn{9) 31~ 3.XX 0.](> 0.35
o.o:'
0.741136 INDIAN J CHEM. SEC A. MAY 2006
of the surface of the Ti by sulphate ions27.
Accordingly, it is concluded that the free Ti 1on surrounding the sulphate is responsible for the generation of strong acid sites.
Tert-butylation of phenol
All the prepared systems were tested for act1v1ty over a reaction time of 2 h under the reaction conditions, temperature of 200°C. flow rate of 4 mL h-1 and a reactant ratio of I :2. An attempt to correlate the surface acidity with the product selectivity has been carried out. The major products obtained during the studies are 2-tert butyl phenol (2-TBP), 4-tert butyl phenol (4-TBP) and 2,4-di-tert-butyl phenol (2,4-DTBP). 2-tert butyl phenol easily isomerizes to 4-tert butyl phenol whereas the reverse reaction is not significant. There is no formation of 3-TBP, which may be formed in the presence of Bronsted acid sites.
ln the case of our samples, the Bronsted sites are weaker, and hence no 3-TBP formation is expected.
Trace amount of tert-butyl phenyl ether (TBPE) was detected.
Pure titania exhibited poor activity towards tert- butylation of phenol under the specified reaction conditions. The reaction proceeds very efficiently over different sulphated titania systems. An attempt to investigate the influence of the metal loading on catalytic activity is quite reasonable. As expected, variation in metal loading had a significant impact on the catalytic activity. In comparison with simple sulphated system, metal incorporated samples are more efficient for the buty lation reaction (Table 3 ).
Chromium loaded samples show the highest activity when compared with the other systems. In all cases, ort/10 and para isomers were obtained with a high selectivity for the para isomer. Usha et a/.28 reported the same observation for mesoporous aluminophosphate and heteropolyacid supported aluminophosphate molecular sieves towards the tert butylaiton of phenol. The p/o ratio was maximum for chromium and minimum for iron. The acid base properties of the catalysts affect the final selectivity of
"Q 28 h
heterogeneous catalysts- . It was reported that. as t e Brcinsted acid sites over the catalyst increases, the selectivity for para isomer increases. Figure 5 gives the correlation between the product selectivity and the acidity assessed by ammonia TPD. lt was observed that the p/o ratio was very low in the case of pure titania and sulphated titania. Metal incorporation increased the selectivity to para isomer.
Table 3 - Catalytic activity and product selectivities over the prepared systems (amount of catalyst: 0.5 g. !low rate: -+ mL h·1•
phcnoi:TBA: I :2. reaction time: 2 h. reaction temperature: 200°C)
Systems Conversion Selectivit~ ('Yo) plo of phenol 2-TBP 4- TBP 2.4-DTBP Ratio
(wt%)
T 14.90 2:1.53 50.64 2.54 2.15
ST 28.45 19.81 65.64 5.44 3.] I STCr(9) 34.12 14.47 70.95 4.98 4.83
STMn(9) 33.85 14.94 70.02 3.47 4.68
STFe(9) 29.47 20.04 67.32 4.62 3.]6 STCo(9) 32.94 19.79 69.05 4.25 3.4l)
STNi(9) 32.54 16.72 68.89 2.45 4.12
STCu(9) 31.25 17.17 68.01 2.92 3.96
STZn(9) 31.09 17.63 67.98 4.09 3.85
:=- - - 8 0
OJ
0
E
~-fr----6
.s
"0 Q) ~€ ~ I >-
0 5
L
60 :~"0 ti
I a; Q)
z (f)
0 c
=>
0 0
E 40
< f- f-(f) §: Ci) Ci) Ci) §: Ci) Ci)
0 f- c :::;; Q) u_ u 0 z f- '5 u c N
f- f- f- f- f-
(f) (f) (f) (f) (f)
(f) (f)
--...-Medium acidity -tr-4-TBP selectivity(%)
-~ 0.2 8
0
.s
E 6l
"0 Q)
€ c
Sl 0.1 4 ·:;
Q) ·u
"0 Q)
I a;
z 2 (f)
0
/'
c 0 => 0 0
E f- f-
~ Ci) Ci) Ci) §: Ci) Ci)
< (f) u c Q) 0 '5 c
:::;; u_ u z u N
f- f- f- f- f- f- f-
(f) ({) (f) ({) (f)
(f) (f)
--...-Strong acidity -tr-2,4-DTBP selectivity(%)
Fig. 5- Correlation between acidity and product selectivity.
In the present study, the reaction was promoted by medium and strong acid sites. Strong acid sites are necessary to get higher selectivity of 2.4-DTBP while medium acid sites are helpful in enhancing the selectivity of 4-TBP. Corma et a/.30 reported the same observation in zeolites Y. Medium acid sites may promote the isomerization or transalkylation reaction of o-TBP to p-TBP, while strong acid sites are helpful in forming 2,4-DTBP. The catalytic alkylation of
SUNAJADEVI & SUGUNAN: ALKYLATION OF PI-IE OL CATALYSED BY SULPHATED TITANIA SYSTEMS 1137
OH C(CH,)
~ 3
.,&
@] C(CH3)3
[A) TBPE, [B]2·TBP, [C) 4-TBP, [D)2,4·DTBP
Fig. 6- General scheme for ten-butylation of phenol.
phenol with alcohols gives rise to two distinct classes of products depending on the site where the alkyl group alkylates phenol. The formation of 0-alkylated products depends both on the intrinsic properties of the alcohol and on the structural and acid-base properties of the catalysts. Corma et a/30 found that the alkylation of phenol by TBA over the solid acid HNa-Y zeolites at 303 K occurs both at 0-atoms and C-atoms, but the 0-alkylation had a higher selectivity, whereas ring alkylation alone occurred at higher temperatures.
Zhang el a!.~ already reported that the strong acidity was required for the formation 2.4-DTBP and acid sites of medium strength were responsible for the formation of 4-TBP. Figure 5 indicates thar the selectivity to 4- TBP and 2.4-DTBP lies nicely with the medium and strong acid sites from the TPD of ammonia of the prepared systems. Presence of high concentration of moderate-to-strong acid sites over mesoporous H-GaMCM-48 also shows high selectivity towards 4-TBP31•
Mechanism of the reaction
The interesting aspect of this reaction is the selectivity of alkylation at the para position. General scheme of the reaction is given in Fig. 6. The generally accepted mechanism for aromatic alkylation is that the tertiary carbenium ion interacts with adsorbed phenol forming a n-complex. which then rearranges to 0-complcx by the electrophile attacking a ring carbon atom. The complex on proton elimination gives tert-butyl phenol. 1t has been suggested that Bronsted acid sites interact with the n-
cloud of aromatic ring bringing the molecule parallel to the surface3c.:n_ This will allow alkylation at the para position easier as compared to the orrlio positions. The para selectivity of the catalysts can be attributed to the nature of adsorption of phenol over the catalyst surface. According to Tanabe3~. the phenolate ion is adsorbed such that the orrho position is very near to the catalyst surface in the case of basic catalysts such as MgO, hence the ortho position can be alkylated. However, the interaction of acidic catalysts are different which influence the electron current around the benzene ring such that the aromatic ring lies parallel to the catalyst surface favouring para alkylation. Also, it has been reported35 that the steric hindrance in the transition state due to the substitution of bulkier terr-butyl group at the ortho positions.
enhances the para selectivity.
Conclusions
Transition metal loaded sulphated titania has excellent catalytic activity for lert-butylation of phenol with butyl alcohol. Selectivity towards para product is shown to be high compared to other products. The acidity plays an important role in this reaction. Medium acid sites are helpful to produce 4-TBP while strong acid sites govern the formation of 2.4-DTBP.
Acknowledgement
The authors are thankful to Regional Sophisticated Instrument Facility (RSIC), llT Bombay. India for FT-IR analysis. Financial assistance from CSIR. ew Delhi to KRS is gratefully acknowledged.
References
I Zhang Y H, Chan C K. Porter J F & Guo W. J Mater Res. 13 (9) ( 1998).
2 Pecchi G. Reyes P. Orellana F. Lopez T, Gomez R & Fierro J L G, J Tech Biotech. 74 ( 1999) I.
:; Lopez T. Gomez R, Pecci reyes G. Bokhmi X & Novara 0 P.
Muter Le/1, 40 (1999) 59.
4 Kumar Krishnankutty Nair P, Appl Cared A. 119 (1994) 163.
5 Signorctto M. Pinna F & Strukul G. Cmal Len, 36 ( 1996) 129.
6 Sanjay R T & Rhave N S, lnd J Chem. 44A (2005) 2262.
7 Sujit R J. Nivedita S C & Manohar R S. Ind J Chem. 43A (2004) 1428.
8 Sujcl Haridas, Deepa C S, Srcejarani K & Sugunan S. lnd J Chon. 44A (2005) 2208.
9 Zhang K. Zhang H. Hung C. Xiang S. Liu S. Xu D & Li H.
Appl Caw/ A, 166 (1988) 89.
I 0 Sakthivcl A, Saritha N & Selvam P. Cared Le/1, 72 (200 I) 225 and the references therein.
1138 INDIAN J CHEM. SEC A, MAY 2006
II Saviclha R. Pandurangan A, Palanichamy M & M11rugesan V.
J Mol Caw/ A Che111. 21 I (2004) 165.
12 Dapurkar S E & Selvam P . ./ColO!. 224 (2004) 178.
13 Karthik M. Tripathi A K, Gupta N M. Yinu A, Hartmann M.
Palanichamy M & Murugesan V, Appl Caw/ A: General, 268 (2004) 139.
14 Lipson H & Steeple H, fllloprer(l/ion oj' X-my powder Diffracrion Pal/ems (Macmillan. London). 1970.
15 Samantaray S K. Mishra T & Parida K M. J Mol Carat A Che111. 156 (2000) 267.
16 Choo ST. Lee Y G. Nam I S. Ham S W & Lee J B. Appl Caw/ A Gen. 200 (2000) 177.
17 Yadav G D & Nair J J. Micmpor Mesopor M(l/er. 33 (1999) I.
18 Chen J P & Yang R T . .I Ca10/. 139 (1993) 277.
19 Arata A. Adv Carat. 37 ( 1990) 165.
20 Nakamoto K. lnfi·ared and Ra111an Specrra oj' Inorganic a111/
Coordin(l/ion Conrpowrds. 4'11 ecln (Wiley. New York). 1986.
21 Cristallo G, Roncari E. Rinaldo A & Trifiro F. Appl Carat A Gen. 209 (200 I) 249.
22 Gallarclo-Amores J M. Armaroli T. Ramis G. Finocchino E
& Busca G, Appl Car a/ B Environ. 22 ( 1999) 249.
23 Lopez T. Moreno J A. Gomez R. Bokhimi X. Wang J A.
Madeira H Y. Pecchi G & Reyes P. J Mater Che111, 12 (2002) 714.
24 Babu J. Sunajadevi K R & Sugunan S. lnd J Che111. 43 (2004) 473.
25 Zhang Q. Gao L & Guo J. Appl Ca10/ B Em•iron. 26 (2000) 207.
26 Auroux A & Gcrvasini A, J Phys Che1n. 94 ( 1990) 6371.
27 Jung S M & Grange P. Cowl Today. 59 (2000) 305.
28 Usha Nandhini K. Banumathi Arabindoo. Palanichamy M &
Murugesan Y. J Mol Caw! A Chen1223 (2004) 201.
29 Tanabe. Solid Acids and Bases and Their Catalwic Properties (Academic Press, New York). 1970.
30 Corma A. Garcia H & Primo J, J Che111 Res. t 1988) 40.
31 Selvam P & Dapurkar S E, Ca10/ Today. 96 (2004) 135.
32 Parton R F. Jacobs J M. Van Ootehem H. Jacobs P A, Srud S1uf Sci Car a/. 46 ( 1989) 21 I.
33 Tanabe K. Srud Sruf Sci Catal. 20 ( 1985).
34 Tanabe K, Caralysis bv Acids and Bases (Elsevier.
Amsterdam), 1985.
35 Parton R F, Jacobs J M, Huybrechts D R & Jacobs P A. Srud Surf Sci Carat, 46 ( 1989) 163.
