comparision between modified clays & conventional catalysts used in various organic...

International Journal of Engineering Technology, Management and Applied Sciences

www.ijetmas.com November 2016, Volume 4, Issue 11, ISSN 2349-4476

13 N. Suma

Comparision between Modified Clays & Conventional

Catalysts used in Various Organic Transformations

N. Suma*

Department of Chemistry, Global Academy of Technology,

Bangarappa nagar, Near Ideal Home Township, Rajarajeshwarinagar, Bengaluru, India.

Abstract

Modified clays prove to be promising catalyst in industry compare to conventional catalysts in carrying out various

organic transformations like esterification, oxidation reactions etc. Conversion of cyclohexanol to cyclohexanone using

modified clays surfactant immobilized chromate clay [HDTMA-Cr(VI)clay] metal cation-exchanged clay impregnated

with chromate [Mn+

-mt- Cr(VI)clay]here Mn+

=Al3+

taken as an example in this article explained that although the yield

of cyclohexanone by conventional method was slightly more, than the organic transformation carried out using modified

clays, was suitable because it avoids pollution, easy to handle, possess both bronsted & Lewis acid sites, acts as green

catalyst & reusable which has shown the activity even after 3 to 4 regeneration.

Keywords: Modified clays, conventional method, oxidation of cyclohexanol, Green chemistry,

regeneration of modified clays.

Graphical Abstract

Mono distribution of Cr(VI)species immobilized by HDTMA in the clay interlayer is pictured

I. Introduction

Organic transformations like synthesis of p-cresyl phenylacetate, benzaldehyde, cyclohexanone and removal

of impurities in water carried out using conventional catalysts has disadvantage compare to use of modified

clays which acts like a Green catalysts.

Organic compounds synthesized shows wide range of applications as perfumes, antioxidant and as solvents

[1,2].They can be synthesized using variety of starting materials. The common esterification reaction or

oxidation reactions involves use of conventional Bronsted acids such as H2SO4, HF and HCl as catalyst but

these catalysts are corrosive, non-reusable, difficult to separate from the reaction mixture, cause

environmental problems, form unwanted side products, difficult to handle and tedious workup procedure. In

order to overcome these disadvantages attempts have been made to use heterogeneous catalyst systems

HDTMA-Cr(VI) K ions

4.1 nm



14 N. Suma

[3].The heterogeneous catalyst systems include zeolites [4], metal oxides like sulphated zirconia, molecular

sieves and cation exchanged montmorillonite, montmorillonite K-10.

In particular, clay catalysts have received considerable attention in different organic syntheses [5] because of

their abundance in nature, their high surface area, sorptive and ion-exchange properties which help catalytic

applications, low cost, high selective, reusable and simple operation.

Indian montmorillonite, smectite rich clay (essentially montmorillonite) is the most abundant clay and

commercial mineral form of smectites. There are reviews on the use of clays as catalysts for the synthesis of

various organic compounds [6-9].Catalytic activity of the solid acids in most of the industrially important

reactions has been investigated in liquid/vapour phase using fixed bed reactors [10,11].Montmorillonite clay,

in natural and exchanged forms, possesses both Lewis and Bronsted acidity [12] that enables it to function

efficiently in organic transformations such as dimerisation and polymerisation of unsaturated

hydrocarbons[13,14], Diels-Alder reaction benzylation of aromatics, Etherification and acetalization reactions,

disproportionation, Hydroxy acylation, Friedel-crafts reactions[15] & oxidation reactions [16].Clay-supported

reagents are prepared by the deliberate introduction of an active reagent into or onto an inert porous inorganic

clay support, where surface hydroxyl groups play a major role in these reactions [17]. Impregnation of ferric

and cupric nitrates on to montmorillonite K-10 produces a novel class of multipurpose reagents termed as

‘clayfen’ and ‘claycop’ respectively [18-20]. Clayzic is another supported reagent that is zinc chloride

impregnated montmorillonite K-10 [21]. Ammonium nitrate impregnated in montmorillonite K-10 reagent

referred to as ‘clayan’ is also one of the important supported reagent having applications in oxidative reactions

[22]. Some of the reactions does not occur when heated conventionally can be carried out in microwave using

clay supported catalysts under solvent free condition eg., reaction of carboxylic acid with benzyl halides

carried out in MW by using phase transfer catalyst. Some important organic reactions like ester synthesis,

ether synthesis [23,24], N-alkylation of benzoxazinones and benzothiazinones, hydrolysis of nitriles [25] has

explained the oxidation of primary and secondary alcohol

can be done in MW.

The current emphasis on green chemistry reflects a shift from conventional method of synthesis of fine

chemicals using strong acids the historic approach with environmental friendly modified clays, which enable

them to function as efficient catalysts in organic transformations and eco acceptability. Green chemistry seeks

new technologies that are cleaner and economically competitive.

The term " GREEN CHEMISTRY" was coined by Professor Paul Anastas, who is known as the father of

green chemistry, at US Environmental Protection Agency Green Chemistry is the effort of reducing or

eliminating the use of or generation of hazardous substances in the design, manufacture and application of

chemical products [26].

Catalysis has wide ranging applications in chemical industry and has a major impact on the quality of human

life as well as economic progress. The development in catalysis has made a significant impact on the rapid

growth of chemical industry in all sectors.

In recent years catalysis is also looked upon as a solution to eliminate or replace polluting processes with

catalytic processes, which are clean technologies. Catalysis provides the chemist and the technologist with a

valuable tool for developing existing industries on a more economic and sound footing, besides developing

new industrial processes. Catalysts not only reduce the cost of production but also, as a general rule, make

possible a significant improvement in the quality of the products [27].

The advantage of using modified clays surfactant immobilized manganate & chromate clays[HDTMA-

Mn(VII)clay & HDTMA-Cr(VI)clay] metal cation-exchanged clays impregnated with manganate and

chromate [Mn+

-mt-Mn(VII)/Cr(VI)clays] instead of conventional catalysts used for organic synthesis is that

HDTMA-Br causes swelling and at the same time displaces the exchangeable ions in the interlayer [28].

Oxyanions of transition metals such as chromates, manganates, molybdates and tungstates are good oxidising

agents and are used in organic reactions[29,30] These when treated with clays modified with HDTMA get

immobilized in the interlayer and are quite stable and remain intact even at very low pH. Such novel

surfactant immobilized interlayer oxidants can be advantageously used as supported oxidizing catalysts.



15 N. Suma

The main objective of this paper is to show that modified clays such as HDTMA-immobilized interlayer-

Cr(VI) (surfactant immobilized chromate clay) and Mn+

-mt-Cr(VI) (metal cations like A1 impregnated on

chromate clay) has been successful in bringing about organic transformations like conversion of cyclohexanol

to cyclohexanone compare to conventional procedures that make use of hazardous homogeneous catalysts.

Modified clays surfactant immobilized chromate clays & metal cation-exchanged clays impregnated with

chromate presented in the study are obtained by simple modification of naturally available clays, which are

eco-friendly, can be regenerated and are reusable [31].

2. Material & experimental method

2.1 Material used

The clay mineral used in this study was montmorillonite (mt), smectite rich clay from Bhuj area in Gujarat,

India, containing essentially montmorillonite with a CEC in the range from 0.98 to 1.01 meqg-1

of clay. The

cation exchange capacity (CEC) of the clay was determined by repeated treatment of clay sample (about 0.5

g) with 1N BaCl2 at pH 7 followed by displacement of the exchanged barium with 0.1 N HCl. The barium

was determined by gravimetric method as barium sulphate [32].The CEC values of Indian montmorillonite

were found to be 0.98 meq g-1

. The composition of Indian montmorillonite samples was found by XRF. The

composition of Indian montmorillonite was found to be 44.8% SiO2, 0.89% TiO2, 13.6% Al2O3, 11.5% Fe2O3,

0.07% FeO, 1.97% MgO, 1.69% CaO, 3.16% Na2O, 0.13% K2O, 0.24% P2O5 and 22.0% LOI.T. Chemicals

used cyclohexanol, ethylacetate (solvent) procured by Sigma Aldrich. Cyclohexanol was purified by

distillation and recrystallization methods before use. The solvent was dried and distilled over calcium chloride

before use.

2.2 Experimental method

2.2.1 Preparation of modified clay

2.2.1.a Preparation of surfactant immobilized chromate clay [HDTMA-Cr(VI)clay]

A 5.0 g of HDTMA-Br (hexadecyl trimethylammoniumbromide) was dissolved in 200ml of distilled water.

Then around 10g of clay was added and stirred on magnetic stirrer for half an hour. The mixture was

subjected to centrifugation and the modified clay from the centrifuge tube was transferred to a beaker to which

around 2g of K2Cr2O7 dissolved in minimum water was added. It was mixed by stirring on a magnetic stirrer

and then centrifuged.

The sample was washed 3-4 times with distilled water, centrifuged and air dried. The air dried sample was

ground to a fine powder and weighed. The sample was activated at 373K for 30 min prior to the activity test.

2.2.2.b Preparation of metal cation-exchanged clays impregnated with chromate [Mn+

-mt- Cr(VI)clay]

taking example of [Al3+

-mt- Cr(VI)clay]

In order to know the effect of surface acidity on the oxidizing ability of chromate ions, metal-ion exchanged

clay known to show varying acidities was prepared by standard procedure [33]. The method involves stirring

of 5 g montmorillonite clay sample with 200 ml of 0.5 M salt solution (AlCl3) containing the respective cation

for 24 hrs. The clay was then centrifuged and washed with distilled water repeatedly until the washings

showed negative test for anions. Subsequently the clay sample was dried at 100oC for 4hrs and ground to a

fine powder. The Mn+

-exchanged montmorillonite clay catalyst was labeled as Mn+

-mt, where

Mn+

= Al3+

. Catalyst sample was activated at 100oC for 30 minutes prior to their activity evaluation.

About 1g of metal ion-exchanged clay thus prepared was treated with varying amounts ranging from 0.1 to 0.9

g of K2Cr2O7 dissolved in 5 ml of distilled water in order to impregnate the oxyanion on the surface of the

exchanged clay.The mixture was stirred and the impregnated clays thus obtained (Al3+

-mt- Cr2O72-

) was air

dried and subsequently ground to a fine powder. They were activated at 373K for 30 min prior to the activity

test for the oxidation of cyclohexanol to cyclohexanone [34].

2.3 Characterisation of modified clays prepared

The modified clays prepared were characterized by XRD, TGA & SEM



16 N. Suma

2.3.1 X-ray powder diffraction

XRD is the widely used technique for qualitative and quantitative analysis of crystalline compounds. The

XRD patterns of the clay samples were recorded on Siemens D5005 diffractometer using Cu-K radiation

source between 2 values 3 and 40o, model Bruker AXS GmbH for 20-layer LB films deposited onto silicon

substrates using Ni/C-Goebel mirror for: - monochromization and suppression of fluorescence radiation. The

spectra were taken with 0.05 step, exposure time of 3 s, voltage of 45 kV and current of 30 mA. The basal

spacing of clay samples was calculated utilizing d001values. The basal distances were calculated from the peak

position using the Bragg equation. Fig. 1(a), Fig. 1 (b) & Fig. 1(c), shows the powder XRD patterns of Indian

montmorillonite clay (IB) (raw clay), HDTMA immobilized Cr(VI) clays & Al3+

-mt- Cr(VI)clays.

It was observed that basal spacing of Raw montmorillonite is 14.7 Å. Whereas for HDTMA immobilized

Cr(VI) clay basal spacings are 28.88 Å & 40.57 Å respectively and for Al3+

-bent- Cr(VI)clay was 14.98 Å.

There was enhancement of basal spacing of HDTMA immobilized Cr(VI) clay(surfactant immobilized clays)

compare to raw montmorillonite clay. The reason for this enhancement may be due to swelling of the

interlayers by intercalation of quaternary ammonium cation such as HDTMA. It corresponds to the shifting of

d001 peak of most of the modified samples to lower diffraction angles or lower 2θ values, than that of the

montmorillonite clay.

Fig 1a XRD pattern of montmorillonite clay sample (raw clay)

Fig 1 b XRD pattern of HDTMA immobilized Cr(VI) dispersed clay

0 2 4 6 8 10 12 14 16 0

1000

2000

3000

4000

5000

d=20.55Å

2

In

ten

sit

y

(arb

.un

its)

d=40.57Å

2

10 20 30 40 0

100

200

300

400

500

600

700

d=14.7 Å

Intensity

(arb.units)



17 N. Suma

XRD patterns of metal cation exchanged clay [Al3+

-mt- Cr(VI)clay] and raw-mt, was

observed it was found almost at same 2θ value, however the intensity of the peak for [Al3+

-bent- Cr(VI)clay]

was more compared to that of the raw-mt clay catalyst. The reason for this observation may be the increased

crystallinity due to regular arrangement of exchanged species in the modified forms as compared to that in the

parent sample.

Fig 1 c XRD pattern of Al

3+-mt- Cr(VI)clay

23.2 Surface area analysis Surface areas are one of the important factors in determining the catalyst performance and a method of

assessing the efficiency of the catalyst supports and promoters.

Specific surface area of clay samples were determined by BET methods using a Quantachrome NOVA 1000

surface area analyzer at liquid nitrogen temperature [35]. Nitrogen was used for adsorption and desorption

studies.

Prior to the analysis, the clay samples were degassed for 2 hrs at 100oC. The modified clay sample was found

to have a specific surface area in the range of 5-8 m2g

-1 whereas the specific surface area of montmorillonite

clay (raw clay) is 18 m2g

-1 [36].

The low specific surface area of modified clay compare to montmorillonite clay indicates most of the

exchange sites of the organo-clays were satisfied by HDTMA species with large molecular size. This was

attributed to the inaccessibility of the internal surface to nitrogen gas, caused due to the nearly total blocking

of the micro pores in the surfactant loaded material.

2.3.3 Thermo gravimetric analysis Thermal analysis was used to determine the changes in chemical or physical properties of a material as a

function of temperature in a controlled atmosphere.

Thermo gravimetric analysis of clay samples was carried out using Perkin Elmer 7 Series Thermal Analysis

System in dry air atmosphere at the heating rate of 10 oC min

-1 in the temperature range 30

oC and 800

oC. It

ws carried out to analyse the temperature at which loss of hydration and hydroxyl groups takes place.

Clay minerals are usually associated with three types of water, which include physisorbed water, water

coordinated to exchangeable cations and structural water. On thermal treatment, physisorbed water comes out

at lower temperature and structural water comes out at high temperature and coordinated water comes out at

relatively moderate temperature and depends on the extent of coordination. In order to study extent of

coordination of water in modified clay catalysts, thermo gravimetric analysis was carried out. TGA curves of

Indian montmorillonite clay, HDTMA immobilized Cr(VI) clay & metal cation exchanged clay [Al3+

-mt-

Cr(VI)clay] are shown in Fig. 2(a), Fig.2(b) & Fig.2(c).



18 N. Suma

Fig 2(a) TGA Pattern of Indian montmorillonite clay

Fig 2(b) TGA Pattern of HDTMA immobilized Cr(VI)

Fig 2( c) TGA Pattern of Al

3+-mt- Cr(VI)

0 100 200 300 400 500 600 700 800

80

85

90

95

100

W

eigh

t %

Temperature (oC)



19 N. Suma

TGA curve of Indian montmorillonite clay exhibits an initial sharp decrease due to the loss of hydration water

and a second one beyond about 120ºC due to the gradual loss of the hydroxyl groups. The loss at 300-450ºC

was due to hydroxyl water associated with Indian montmorillonite's structure. Between 450 and 650ºC, an

additional amount of water was lost. There was negligible weight loss above 700ºC.

TGA curve of HDTMA immobilized Cr(VI) clay exhibit a weight loss upto 2% below 130 ºC due to

Physisorbed water, around 30% weight loss between 200-400 ºC due to co ordinated water and beyond 400 ºC

<3% weight loss due to structural water. Comparison of TGA patterns of Indian montmorillonite, with

HDTMA immobilized Cr(VI) clay indicate that the loss of hydrated water occurs slightly at a lower

temperature in case of Indian montmorillonite compared to HDTMA immobilized Cr(VI) clay. This indicates

that hydrated water apparently are less strongly held to Na+-ions in Indian montmorillonite clay and more

strongly held to high polar cations present in HDTMA immobilized Cr(VI) clay.

The TGA plot of Al3+

-mt catalyst was observed, the weight loss due to hydrated water was about 12%, which

occurred below 120 oC. The weight loss between 120 and 650

oC was only about 6% and there was no

significant weight loss beyond 650 oC. The loss of hydrated water occurs slightly at a lower temperature in

case of raw-mont compared to Al3+

-mt catalyst. The hydrated water apparently are less strongly held to Na+-

ions in raw-mont and more strongly held to high polar cation present in Al3+

-mt- Cr(VI)clay.

2.3.4 Scanning electron microscope

This was another method for characterization of clay. JEOL JSM-840A scanning electron microscope was

used in the present characterization. The method adopted was, all samples stubs were coated with a thin layer

of colloidal graphite prior to deposition of the clay sample, which in turn was coated with a thin film of gold

to prevent charging [37].

Fig. 3(a), Fig. 3(b) indicates the SEM of Indian montmorillonite HDTMA immobilized Cr(VI) clay. SEM

picture indicated that surface area of Indian montmorillonite clay was more than the modified clay.

Fig 3(a) SEM pictures of Indian montmorillonite at a magnification of 1700X



20 N. Suma

Fig 3(b) SEM pictures of HDTMA immobilized Cr(VI) clay at a magnification of 2000X

2.4 Experimental Procedure

2.4.1 Experimental method under conventional method

The preparation of cyclohexanone from cyclohexanol

Scheme 1: Schematic representation of oxidation of cyclohexanol by conventional method

This preparation showed that a ketone can be prepared by the oxidation of a secondary alcohol. In a similar

way, an aldehyde can be prepared from a primary alcohol, but since aldehydes are easily oxidised further to

carboxylic acids, they must be distilled off from the reaction mixture as formed.

RCH2OH -> RCHO -> RCO2H

(primary alcohol) (aldehyde) (acid)

Procedure:

8.82 gram of K2Cr2O7 was dissolved in 40 mL of aquades in Erlenmeyer 100 mL and it was added by 7 mL of

concentrated sulfuric acid carefully. This orange-red solution was cooled down at room temperature. As much

as 0.065 mole of cyclohexanol was mixed with 25 mL of aquades in Erlenmeyer 250 mL. Then, dichromate

solution was added into mixture of cyclohexanol and it was shaken. The temperature was kept at 350 C by

cooling in the ice water. When the temperature was constant, the flask was moved from the ice water and it

was added by 0.2 gram of oxalic acid to reduce the excess of dichromate. After that, this mixture was moved

into round flask 150 mL and it was added by 35 mL of aquades, and then it was extracted 3 times by using

ether (3x 25 mL). The ether layer was collect, it washed by aquades and Na-bicarbonate, then it was separated

and the ether layer was dried by anhydrous substance. Then, it was filtered and entered into 50 mL of flask

and it was distilled.

2.4.2 Experimental method using modified clays

The liquid phase oxidation reaction was carried out in a 100 ml round-bottomed flask fitted with a reflux

condenser, 14mmol of cyclohexanol was taken in the flask.15ml of ethyl acetate solvent and a known weight



21 N. Suma

of modified clay samples were added to the alcohol. The reaction mixture was refluxed for 12 hrs. The flask

was cooled and the clay was separated by filtration. From the filtrate, the solvent was distilled off under

reduced pressure. The product left behind in the distillation flask was separated. The product was identified by

infrared spectroscopy (Nicolet AVATAR 320 FTIR) and further characterized by gas chromatography (GC).

Scheme 2: Schematic representation of oxidation of cyclohexanol over modified clay

2.4.2. 1 Characterization of Product

The products obtained by the reaction using HDTMA-immobilized-interlayer Cr(VI)clay was identified by

comparing the TLC with authentic sample.

The product obtained was further confirmed by infrared spectroscopy (Nicolet AVATAR 320 FTIR).The IR

spectra of products are as shown in Fig.4.

The product formed was further confirmed by Gas chromatography spectra. The GC of products are as shown

in Fig.4, Fig.4(a),Fig.4(b) & Fig.4(c).

IR spectral analysis of the product

The IR spectrum of the sample was recorded using Nicolet AVATAR 320 FT-IR spectrophotometer by KBr

pellet technique.

The procedure adopted was :i) preparation of very thin self-supporting wafers of the catalyst material under

high pressure.ii) Mix of catalyst powder with KBR and spectrum was taken.

Fig 4 IR spectra of obtained by oxidation of cyclohexanol using HDTMA-immobilized-interlayer

Cr(VI)clay

OH

Cyclohexanone

Modified Clay O

Cyclohexanol

solvent



22 N. Suma

Gas chromatography analysis of produc

Gas chromatography is a method for both qualitative and quantitative analysis of different compounds within

a test sample. The mobile phase is a carrier gas, usually an inert gas such as helium or an unreactive gas such

as nitrogen, and stationary phase is a microscopic layer of liquid or polymer on an inert solid support inside

glass or metal tubing called a column. The different compounds elute at different times called retention time.

By comparing with the retention time for an authentic sample, it was possible to identify the products

obtained in a reaction.

By comparing the area of the peak for known amount of authentic sample and the area of the peak for the

product in the GC plot it was possible to calculate % yield of the products in a reaction.

Fig. 4(a) & Fig.4(b) are gas chromatograms for authentic samples of cyclohexanol and cyclohexanone

respectively. Fig.4(c) is gas chromatograms of the product obtained on oxidation of cyclohexanol using

HDTMA-immobilized-interlayer-Cr(VI) clay.

Fig 4(a) GC plot for authentic sample of cyclohexanol

Fig 4(b) GC plot for authentic sample of cyclohexanone



23 N. Suma

Fig 4(c) GC plot obtained by oxidation of cyclohexanol using HDTMA-immobilized-interlayer-Cr(VI)

clay

Inference from GC plot,

Peak at retention time 7.01 indicates presence of cyclohexanone

Peak at retention time 8.15 indicates presence of cyclohexanol

Peak at retention time 14.85 for standard used DMSO

Thus, from the retention time for an authentic sample, the product was identified as cyclohexanone. By

comparing the area of the peak for known amount of authentic sample and the area of the peak for the product

in the GC plot the percentage yield of the product was determined. The area of the product obtained

from GC plot was 3064035.24 & area of authentic sample was 6007.9 from this yield of the product obtained

was 51% for the oxidation of cyclohexanol using HDTMA-immobilized-interlayer-Cr(VI) clay.

3. Results & discussion

3.1 Results from the oxidation carried out by convention method

A conventional method reaction was carried out keeping 14hrs as reaction time, in order to know the effect on

yield of cyclohexanone.

The reaction was carried out by refluxing 14mmol of cyclohexanol, dichromate solution & 7ml of conc

sulphuric acid.

3.2 Results from the oxidation carried out using modified clays

A reactions with modified clays were carried out at reaction time 14hrs, in order to know the effect on yield

of cyclohexanone.

The reaction was carried out by refluxing 14mmol of cyclohexanol, 0.5g of HDTMA-immobilized-interlayer

Cr(VI)clay (surfactant immobilized-interlayered- chromate clay) & Al3+

-mt- Cr(VI) clays (metal(Al) cation-

exchanged clay impregnated with chromate) using the solvent (Ethyl acetate=15ml).

The results are shown in Graph 1.

The results obtained from conventional method and by using modified clays are compared it was found that

the yield of cyclohexanone by conventional method was slightly higher than the results obtained with the use

of modified clays. Although the % of cyclohexanone was more by conventional method, the oxidation of



24 N. Suma

cyclohexanol using modified clays (both surfactant immobilized and impregnated) have advantage over

conventional method.

Conventional method of oxidation of cyclohexanol using potassium dichromate involves use of acid

which was corrosive. Modified clays (surfactant immobilized and impregnated with dichromate) are non

corrosive and safe to handle.

Conventional method of oxidation of cyclohexanol uses alkaline potassium permanganate or Conc

HNO3. However, here ring cleavage takes place and adipic acid was obtained as the product. The reaction

cannot be stopped at the intermediate stage of cyclohexanone formation. Whereas, using modified clay,

HDTMA-immobilized-interlayer & Al3+

-mt-Mn (VII)/ cyclohexanone was obtained as the sole product and

ring cleavage does not take place.

The major advantage of using these modified clays for organic transformations was that they can be

recovered after the reaction and reused [38].

Graph 1: Yield of cyclohexanone by conventional method & using modified clays

Mechanism of oxidation of cyclohexanol to adipic acid by conventional method and to cyclohexanone

using modified clays

OH O

CrO3

COOH

COOH CrO3

Adipic acid Cyclohexanol Cyclohexanone



25 N. Suma

Scheme 3: Schematic representation of oxidation of cyclohexanol over chromium oxide, alkaline

KMnO4 & Con HNO3

3.3 Results from regeneration of modified clays

The modified clays separated from the reaction mixture were washed several times with distilled water. It was

dried at 100 ْC for 1hr and ground to a fine powder. The modified clays recovered from the reaction mixture

were reused for the oxidation reaction. The yield of cyclohexanone was almost same even after three

regenerations.

4. Conclusions

The major aim of this article is to compare between modified clays & conventional catalysts used in various

organic transformations taking one of the example of synthesis of cyclohexanone from cyclohexanol by

oxidation.

Attempts had been made in is paper to discuss the suitability of modified clays in industry because of their

ecofriendly, less cost & reusable and better than use of solvents & acids which are volatile organic compounds

and inevitably lead to environmental damage, through pollution, risks to human health. So, all traditional and

old synthetic routes giving adverse effects to the mankind and all living beings have to be replaced by

modified clays’ non-hazardous & environmental-friendly chemicals.

A major thrust in chemical industries today is to produce chemicals without any damage to the surrounding

environment and to solve the burning environmental problems. In recent years, there is a significant shift in

the attitude of chemists to develop environmental friendly processes also called green processes.

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comparision between modified clays & conventional catalysts used in various organic...

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