Kinetics of Esterification of Palmitic acid with Ethanol- Optimization Using Statistical Design of Experiments

Abstract

Abstract-The aim of this study was to apply statistical design of experiments for optimization of esterification reaction and to obtain the kinetics of the reaction. The present system of study was palmitic acid with ethanol using homogeneous catalyst sulphuric acid. The reactions were performed in a batch reactor and the progress of the reaction was monitored using Karl Fischer Titrator. To reduce the number of experiments and in order to achieve optimum conditions of the reaction, statistical design of experiments was carried out. Using Box-Behnken response surface analysis with three factors, three central points and one block, a table was designed with 15 experiments. The variable influencing the rate of reaction are temperature, mole ratio of reactants and catalyst concentration. The conversion is complete at a temperature of 73 o C, initial molar ratio of reactants of 9.39 and at a catalyst concentration of 6.4 wt%. Integral method of analysis was used to analyze the batch reactor data and the order of the reaction was obtained. The reaction rate constants, frequency factor and activation energy of the reaction were determined. I. INTRODUCTIONThe synthesis of carboxylic acid esters is an industrially important operation because of its application in vast areas ranging from domestic use to food industry [1]- [7]. Organic esters can be synthesized by different methods. The most important method is the direct reaction of organic acid with alcohol in the presence of acid catalyst [1]. As esterification reactions are very slow and reversible, it requires several days to reach equilibrium in the absence of catalyst. The acid catalysts include H 2 SO 4 , HCl, HI and some strong organic acids [2]. Generally esterification is carried out in the presence of sulphuric acid as catalyst because of its high acid strength. This acid strength is responsible for the release of H + ions and thereby protonate the caboxilic acid [3].The present work is concentrated on the production of ethyl palmitate, which is an important organic ester produced by the esterification of palmitic acid with ethanol in the presence of sulphuric acid as catalyst. Palmitic acid (A) + ethanol (B) ↔ ethyl palmitate (C)+ water (D)This ethyl palmitate ester has a soft and waxy odour and is used to give fragrance to saffron, cream, vanilla and flavors of milk, fish etc. For the large scale production of ethyl palmitate reaction kinetics should be well determined [2]. Usually rate of reaction is influenced by many factors such temperature of reaction, initial mole ratio of reactants, type of catalyst, catalyst concentration and mechanical agitation rate etc. Among these variables temperature of the reaction mixture, initial mole ratio of reactants and catalyst concentration were chosen and the other two parameters were kept constant for the entire study. Here an attempt is made to correlate the variables with the yield through a statistical design tool and trying to develop kinetics model of palmitic acid esterification reaction. II. MATERIAL AND METHO...

Unravelling mass transport in hierarchically porous catalysts

“…Apparent activation energies for palmitic acid esterication over the 210 and 430 nm macropore hierarchical catalysts also indicate a switchover from diffusion limited to reaction-rate limited esterication with increasing macropore size, rising from 34 AE 3 kJ mol À1 (210 nm) to 45 AE 3 kJ mol À1 (430 nm). The latter barrier is in fair agreement with the homogeneous acid catalysed value of 56 kJ mol À1 , 42 suggesting that esterication over the 430 nm macropore catalyst is largely free from mass transport limitations.…”

“…For propanoic acid, esterication was independent of macropore size, as may be anticipated from its small kinetic diameter ($0.48 nm) and hence minimal diffusive restriction by the pore network. A recent PFG NMR study on organic acid diffusion through mesoporous SBA-15 and KIT-6 silicas 47 reported that the effective tortuosity increased with acid chain length, and that pore walls enhanced diffusion possibly by disrupting the dynamic hydrogen bonding network present throughout the liquid mixture (as has previously observed for polyols and polyol/ methanol mixtures [41][42][43][44] ). It follows that propanoic acid selfdiffusion may be dominated by hydrogen-bonding dynamics, rather than by pore network tortuosity, consistent with the present ndings that propanoic acid TOF and D 0 /D iso (equated here to macropore size) are uncorrelated.…”

Production and Isolation of n‐Butyl Acrylate Using Pervaporation‐Aided Esterification Reaction: Kinetics and Optimization

“…4 b and 5 b show the influence of both the catalyst concentration (P 2 ) and A/V 0 (P 4 ) on the conversion and water flux. With an increase in the amount of catalyst, the conversion of acrylic acid rises due to the availability of more H + ions which enhances the reaction producing more conversion [31,32]. The plot in Fig.…”

“…4 a-f and 5 a-f, respectively. According to Beula and Sai [31], closer contour lines require the less amount of variables and a wide gap between contour lines indicates the demand of a high quantity of variables for enhancement in response. Figs.…”

“…For the design of an integrated reactor it is essential to compute the kinetic parameters such as equilibrium constant, rate constants, and activation energy for the reaction. The reaction temperature helps to determine the rate constants and equilibrium constants [31]. For this purpose, experiments were performed at three different temperatures, i.e., 50, 60, and 70°C.…”