HETEROGENEOUS CATALYTIC ESTERIFICATION OF ACETIC ACID USING MODIFIED ALUMINOSILICATE

AUTHOR: EZEUDU CATHERINE OBAINUJU

DEPARTMENT: CHEMICAL ENGINEERING

AFFILIATION: NNAMDI AZIKIWE UNIVERSITY, AWKA

The esterification of propanol with acetic acid using locally produced clay catalysts was studied in a batch reactor. Two clays obtained from Nteje, Anambra state and Udi, Enugu state, were activated with 1MH2SO4 and Fe-pillared before being used for esterification reaction. Instrumental Analysis, Fourier Transform Infra-red (FTIR) and Scanning Electron Microscope (SEM) carried out on all samples showed that the Fe-PNC is a very good catalyst for the esterification reaction. The effect of process parameters (mole ratio, reaction temperature and catalyst mass), using the unactivated, activated and Fe-pillared clays as catalyst was studied. The highest conversion of 86.34% was obtained for mole ratio (acid:alcohol) of 1:1 for Fe-pillared Nteje clay while a conversion of 85.66% was obtained for Fe-pillared Udi clay. Conversions of 83.70%, 82.71%, 82.52%, 81.95% were also obtained for activated Nteje clay, activated Udi clay, unactivated Nteje clay and unactivated Udi clay respectively. The study showed that conversion increases with increasing temperature and catalyst mass but reduces with increasing mole ratio. The optimization of the process parameters was done using the central composite design of the response surface methodology. The study showed that the Fepillared Nteje Clay gave optimization parameters of 1:1 mole ratio, catalyst mass of 1g, reaction temperature of 325.74K, and for these conditions a conversion of 86.573% was obtained which is in good agreement with the experimental of 86.48%. The activated Nteje clay gave a mole ratio of 1:1, catalyst mass of 1.06g, temperature of 332.93K and conversion of 84.177%. Unactivated Nteje clay also gave a mole ratio of 1:1, catalyst mass of 1g, reaction temperature of 327.95K and conversion of 82.616%. The Fe-pillared Udi gave optimization parameters of 1:1 mole ratio, catalyst mass of 1g, temperature of 327.25K and a conversion of 85.748% under these conditions. Activated Udi clay gave a mole ratio of 1:1, catalyst mass of 1g, reaction temperature of 333.19K and conversion was 83.102%. The unactivated Udi clay gave the lowest conversion of 82.284% for optimization parameters of 1:1 mole ratio, catalyst mass of 1g and reaction temperature of 335.02K. Mechanistic modelling was performed using five models, Pseudo-Homogeneous, Eley Ridael, Langmuir Hinshlewood-Hougen Watson (LHHW), Acid-Complex, and Alcohol-Complex models. The Graphical User Interface (GUI) of the non-linear regression tool of MATLAB software was used in modelling the experimental data. From the graphical presentations and Root Mean Square Error (RMSE) of the models, the Acid-Complex model gave the best fit. There were indications that the reactions also proceeded with Alcohol-Complex mechanism as a parallel reaction. Elucidating the mechanism of the clay catalysed reaction is essential in the design of the appropriate reactor for the reaction. The use of clay in esterification reactions is encouraged because it is one of the environmental friendly catalysts.

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