No abstract

It has long been established that a suspension of nanosized solid particles in liquids provide useful advantages in industrial heat transfer fluid systems. Numerous investigations on nanofluids show a significant enhancement in thermal conductivity over the base fluid in which these nanoparticles are dispersed. However, the stability of the suspension is critical in the development and application of these new kind of heat transfer fluids. Rather, high discrepancy in the published data for the same nanoparticles on the physical and thermal characteristics of nanofluids is primarily due to different methods adopted by different researchers to obtain stable nanofluids. Sedimentation and agglomeration of nanoparticles in nanofluids and their dispersion stability has not been well addressed in the literature. Hence, there is a need to establish a standard method of preparation of these nanofluids so as to obtain a unified data which can eventually be utilized for the application of nanofluids. This chapter focuses on the stability of nanofluids prepared via two step process. Different parameters that affect the stability of nanofluids have been discussed. Different techniques that have been used for the evaluation of the stability characteristics of nanofluids have been elucidated.

Methyl nonanoate was synthesized in a batch reactor by esterification of nonanoic acid with methanol catalyzed by the cation exchange resins, Dowex 50Wx2, Amberlyst 35, and Amberlyst 15. The effect of various parameters such as speed of agitation, catalyst loading, molar ratio, and reaction temperature on degree of conversion has been reported. The conversion of nonanoic acid to methyl nonanoate was found to increase with an increase in temperature in the range of 303.15−333.15 K and the increase was appreciable with an excess use of methanol in the reaction mixture. Nonideality of the liquid phase was taken into account by using activities instead of concentration. The activity coefficients were calculated using the UNIFAC group contribution method. The possible mechanism of reaction was mathematically treated using theories of the Eley−Rideal model based on inhibition by water and methanol on the Amberlyst 15. The reaction rate constants and the adsorption coefficients for methanol and water were determined from the experimental data established at three different temperatures for the effect of initial concentration of acid and alcohol. The kinetics reported in this study was obtained under conditions free of both external and internal mass transfer resistance. Activation energy and pre-exponential factor of the reaction were found to be 47.6 kJ mol −1 and 3.2 × 10 4 L 2 g −1 mol −1 h −1 , respectively.

A comprehensive kinetic investigation of the esterification of nonanoic acid with 1-propanol in the liquid phase was carried out using Amberlyst 15. Kinetic experiments were conducted using a batch reactor system at a stirrer speed of 500 rpm over the temperature range 323.15 −363.15 K. The catalyst loading was varied from 4% (w/v) to 8% (w/v), and acid to alcohol molar ratios of 1:1, 1:5, 1:10, and 1:15 were used. It was found that both external and internal diffusion limitations did not affect the overall reaction rate. The conversion of nonanoic acid increased with increasing temperature and catalyst loading. The Eley−Rideal (E−R) model was tested to correlate the kinetic data, and the activity coefficients were estimated using the UNIFAC model to account for the nonideal thermodynamic behavior of reactants and products. The model predicted the kinetic behavior of the studied system reasonably well. Water was found to be more strongly adsorbed than other species present in the system. The activation energy, preexponential factor, and standard enthalpy for the esterification was estimated to be 55.4 kJ/ mol, 2.3 × 10 5 L 2 g −1 mol −1 h −1 , and −218.08 J•mol −1 , respectively, by this model. The influence of alcohol carbon chain length was studied, and their effects on reaction kinetics were compared. It was observed that activation energy increases with increases in chain lengths of alcohols.

No abstract

The kinetic behavior of esterification of lactic acid with isopropanol over an acidic cation exchange resin, Amberlyst 15, was studied under isothermal condition. Isopropyl lactate synthesized in this reaction is an important pharmaceutical intermediate. The experiments were carried out in a stirred batch reactor in the temperature range of 323.15 to 353.15 K. The effect of various parameters such as temperature, molar ratio and catalyst loading was studied. Variation in parameters on rate of reaction demonstrated that the reaction was intrinsically controlled. Kinetic modeling was performed using Eley-Rideal model which acceptably fits the experimental data. The activation energy was found to be 22.007 kJ/mol and frequency factor was 0.036809 l2 g-1 mol-1 min-1 for forward reaction. The value of entropy for the forward reaction was found to be 182.317 J K-1 mol-1 . © 2011 BCREC UNDIP. All rights reserved

(Received: 19th January 2011, Revised: 16th March 2011; Accepted: 16th March 2011)

[How to Cite: A.P. Toor, M. Sharma, S. Thakur, and R. K. Wanchoo. (2011). Ion-exchange Resin Catalyzed Esterification of Lactic Acid with Isopropanol: a Kinetic Study. Bulletin of Chemical Reaction Engineering and Catalysis, 6(1): 39-45. doi:10.9767/bcrec.6.1.791.39-45]

[How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.791.39-45 ]

View in

No abstract

Esters are an important pharmaceutical intermediates and very useful perfumery agents. In this study the esterification of acetic acid with n-butanol and iso-butanol over an acidic cation exchange resin, Amberlyst 15 were carried out. The effects of certain parameters such as temperature, catalyst loading, initial molar ratio between reactants on the rate of reaction were studied. The experiments were conducted in a stirred batch reactor in the temperature range of 351.15 K to 366.15K.Variation of parameters on rate of reaction demonstrated that the reaction was intrinsically controlled.The activation energy for the esterification of acetic acid with n-butanol and iso butanol is found to be 28.45 k J/mol and 23.29 kJ/mol respectively. ©2011 BCREC UNDIP. All rights reserved.

(Received: 16th December 2010, Revised: 19th March 2011; Accepted: 7th April 2011)

[How to Cite: A.P. Toor, M. Sharma, G. Kumar, and R. K. Wanchoo. (2011). Kinetic Study of Esterification of Acetic Acid with n-butanol and isobutanol Catalyzed by Ion Exchange Resin. Bulletin of Chemical Reaction Engineering and Catalysis, 6(1): 23-30. doi:10.9767/bcrec.6.1.665.23-30]

[How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.665.23-30 ]

| View in