Shriniwas D. Samant

Kinetics of wet air oxidation of phenol and substituted phenols

Abstract Wet air oxidation (WAO) of aqueous solutions of phenol and substituted phenols namely, o -, m - and p -chlorophenols, o -, m -cresols, o - and p -methoxyphenols, o -ethylphenol and 2,6-dimethylphenol, were carried out. The process was studied in a 1 litre stainless steel autoclave at temperatures in the range of 150–180°C. The oxygen partial pressure was varied from 0.3 to 1.5 MPa and the initial phenol concentration was 200 mg/l. The oxidation of phenols in water involves a free-radical mechanism and proceeds in two steps. The oxidation reaction was found to be first order in oxygen and also first order with respect to phenolic substrates in both steps. The values of activation energy were found to be in the range of 12.4 x 10 3 -201 x 10 3 kJ/kmol. The conditions have been found under which the overall oxidation reaction becomes reaction controlled or mass transfer controlled. The values of mass transfer coefficient have been obtained. The data based on bench scale shows wet air oxidation of phenols can achieve destruction efficiencies exceeding 99.9%. The reduction of COD during oxidation of all phenols was also measured. Greater than 90% COD reduction was achieved. Some aspects of the process design of the oxidation reactor have been discussed.

The enhanced activity of Sb after supporting on K10 in the benzylation of benzene using benzyl chloride and benzyl alcohol

Abstract K10 was modified under aqueous and non-aqueous conditions using SbCl 3 and the resultant catalysts were used for the Friedel–Crafts benzylation of benzene with benzyl chloride (BzCl) and benzyl alcohol (BzOH). Effect of activation temperature on the activity of the catalysts was also studied. The catalysts activated at 120°C in both the cases were found to be more active. The outstanding observation of this investigation was the significant catalytic activity associated with Sb(III), particularly in view of the fact that SbCl 3 is known to be the least active Lewis acid under homogeneous conditions.

Friedel-Crafts Benzylation of Arenes Using FeCl3 Impregnated Montmorillonite K10.

Abstract FeCl3 impregnated Montmorillonite K10 was found to catalyze the Friedel-Craftsbenzylation of arenes. Monobenzylation, with the para isomer predominating, was achieved with trace amounts of dibenzylated product.

Benzylation of arenes in the presence of Montmorillonite K10 modified using aqueous and acetonitrile solutions of FeCl3

Abstract Montmorillonite K10 was modified by treating it with FeCl3 dissolved in acetonitrile and water. The catalysts thus prepared were activated at different temperatures and were used for the reaction of benzyl chloride with various arenes. The reactions were carried out at different temperatures and it was found that the difference in the activity was marked when the reaction was carried out at 40°C. The maximum activity was associated with Montmorillonite K10 modified by FeCl3 in acetonitrile solution and activated at 120°C.

One‐Pot Synthesis of Benzimidazoles from o‐Nitroanilines under Microwaves via a Reductive Cyclization

Abstract An efficient microwave irradiation synthesis of 2‐substituted benzimidazoles in one step via the Na2S2O4 reduction of o‐nitroanilines in the presence of aldehydes is described. The method is simple and a good option to obtain the title compounds in a very short time.

tert-Butylation of phenols using tert-butyl alcohol in the presence of FeCl3-modified montmorillonite K10

Abstract tert -Butylation of phenol and cresols using tert -butyl alcohol as an alkylating agent was studied in the presence of Fe-modified montmorillonite K10 catalysts in liquid phase. The catalysts were prepared by treating montmorillonite K10 with aqueous and acetonitrile (organic) solution of FeCl 3 . The present study demonstrates the potential of K10 catalysts in the production of tert -butylphenol with high activity and selectivity. One hundred percent tert -butylation was observed in all the catalysts. Regioselectivity in the reaction is also studied.

Sonochemical bromination of acetophenones using p-toluenesulfonic acid–N-bromosuccinimide

Substituted acetophenones react with N-bromosuccinimide (NBS) and p-toluenesulfonic acid (p-TsOH) in the presence of ultrasound in methanol at 35 +/- 2 degrees C to give alpha-bromoacetophenones in high yield. In the absence of ultrasound the reaction takes place at the boiling point of methanol (65 degrees C) and takes longer time. The reaction does not take place in the absence of p-TsOH thermally or sonically. However the reaction is possible under photochemical conditions in the absence of p-TsOH. The best solvent for the reaction was found to be methanol.

Ultrasound‐Assisted Pechmann Condensation of Phenols With β‐Ketoesters to Form Coumarins, in the Presence of Bismuth(III) Chloride Catalyst

Abstract Ultrasound was found to synergistically accelerate the condensation of phenol with β‐ketoesters in the presence of BiCl3. In the absence of ultrasound, under the same conditions, the reaction was found to be slow. Thus, the reaction can be carried out in the presence of ultrasound at room temperature (28–30°C), with a considerable reduction of reaction time, with high yield and high purity of coumarins.

Sonochemical chloro-oxidation of phenols using HCl-H2O2.

The reaction of phenol, 2-nitrophenol, thymol, 1-naphthol and 1-hydroxy-2-naphthoic acid with HCl-H2O2 was carried out in the presence and in the absence of ultrasound. In the presence of ultrasound phenol, 2-nitrophenol and thymol gave only the chlorinated products, while 1-naphthol and 1-hydroxy-2-naphthoic acid gave chlorinated quinones as the major products. The reactions with ultrasound were compared with those without ultrasound.

Semiquantitative characterization of ultrasonic cleaner using a novel piezoelectric pressure intensity measurement probe

Abstract A piezoelectric pressure intensity measurement probe (PPIMP) consisting of a stainless-steel horn with a piezoelectric crystal fitted at the top is de developed to visualize the pressure and hence the ultrasound intensity profile inside an ultrasonic cleaner. The probe is connected to an oscilloscope. The three-dimensional pressure and hence ultrasound intensity distribution is presented.