Kristalisasi asam benzoat dalam reaktor semibatch

WIJAYANTI, Ester, Ir. Supranto, MSc.,PhD

2002 | Tesis | S2 Teknik Kimia

Kristal asam benzoat ( C6H5COOH) adalah partikel padat hasil reaksi asam klorida (HCl) dan natrium benzoat (C6H5COONa) sesudah melewati konsentrasi asam benzoat saturasi. Kristalisasi asam benzoat meliputi nukleasi dan pertumbuhan knstal. Kedua proses tersebut dikendalikan oleh keadaan supersaturasi. Telah diteliti kristalisasi reaktif asam benzoat dalam reaktor semibatch untuk menganalisis model empiris kecepatan nukleasi dan kecepatan pertumbuhan kristal. Kecepatan nukleasi dan pertumbuhan kristal dievaluasi menggunakan metode momen berdasarkan data supersaturasi dan distribusi ukuran kristal pada berbagai perbandingan mol umpan (p), waktu proses (t) dan bilangan Reynolds (Re). variasi diperoleh hasil harga konstante kecepatan reaksi, k, = 1,48336 L/men.nol dan konstante kecepatan perpindahan massa volumetris, (k,.a) = 0,4509 1 L/men.mol. Semakin besar kecepatan molar umpan, konsentrasi asam benzoat saturasi dicapai lebih cepat atau waktu proses lebih pendek. Asam benzoat saturasi yaitu pada konsentrasi 0,02787 mol/L terjadi pada : t* = 19 menit jika 1: = 72 menit dan p = 0,25; 0,l dan 0,0625, t* = 15 menit jika t = 67 menit, t* = 9 menit jika t = 59,5 menit dan t* = 7 menit jika 7: = 56,52 menit. Ukuran kristal semakin besar dengan meningkatnya supersaturasi pada kisaran s : 0,0204 sampai 0,0241 dan makin kecil karena pecahnya kristal dengan meningkatnya Re pada kisaran Re : 1175,6062 sampai 4702,4246. Kecepatan nukleasi knstal asam benzoat mengikuti model exponential law : rumus

The benzoic acid ( C&ljCOOH) is the crystallization product of a reaction between hydrochloric acid ( HCI ) and sodium benzoate ( C&jCOONa ) beyond saturation concentration of benzoic acid. The crystallization process of benzoic acid includes nucleation and crystal growth wich are controlled by supersaturation condition of benzoic acid. The empirical models of nucleation rate and crystal growth of the reactive crystallization in a semibatch crystalliser were studied. The momen method was used to deduced the nucleation rate and the crystal growth base upon supersaturation and distribution of crystal size data, The efects of the reactant concentration ratio (4, processing time ( z) and Reynolds number (Re) were also examined. The results of the reactive crystallization wich was carried out for 37 minutes were chemical reaction rate constant, k, : 1.38336 L/men.mol and volumetric mass transfer rate constant, $*a) : 0.45091 L/men.mol. Increasing the feedflow rate will accelerates the saturation of benzoic acid concentration and consequently the processing time will be shorter. The saturated of benzoic acid concentration of 0.02787 mol/L occured at t * = 19 minutes for r = 72 minutes and p = 0.2, 0. 1, 0.025, t* = I5 minutes for r = 67 minutes, t* = 9 minutes for r = 59.5 minutes and t* = 7 minutes for z = 56.52 minutes. The mean size of product crystals increases by increasing supersaturation within s range of 0.0204 to 0.0241 and decreases by increasing Re number within Re range of 1175.6062 to 4702.1216. The crystals break to smaller size when Re number increases. The nucleation rate of benzoic acid satisj?es the exponential law model: formula

Kata Kunci : Asam Benzoat,Kristalisasi,Reaktor Semibatch