SYNTHESIS AND CHARACTERIZATION OF Cu/γ-Al2O3 APPLIED AS CATALYST FOR BENZENE DECOMPOSITION

• Main Author: MAHARSI (NIM : 20215042), RETNO
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/23909
• Institution: Institut Teknologi Bandung

Gamma alumina (γ-Al2O3) has been applied as a catalyst for volatile organic compounds (VOC) decomposition due to its excellent properties, e.g. high surface area, pore structure, and good stability at a high temperature. Impregnation of active metal or metal oxide can enhance the activity of γ-Al2O3 in oxidizing the VOC. Noble metal addition, e.g. Pt, Pd, Ag, and Au, leads to superior catalytic activity of γ-Al2O3. However, the addition of noble metal is expensive for industrial purpose. Thus, the noble metal can be replaced by other metals. i.e. Cu, Ni, Co, Cr, and Mn. In this research, Cu was impregnated with into γ-Al2O3, which then was applied as a catalyst to oxidize benzene. Mesoporous gamma alumina was synthesized using urea combustion method. The concentration of urea:Al3+ was set to 0:1; 1:1; 2:1; 2,5:1; 3:1; 3,5:1; and 5:1. The role of urea was as a heat source, which help to produce pore structure of γ-Al2O3. Sample without urea has an amorphous structure with no detection of diffraction peak. The increasing of urea concentration leads to formation of γ-Al2O3 crystal. X-ray diffraction analyses reveals that the γ phase of alumina was obtained when the urea was added until composition of 2:1. More addition of urea (urea:Al3+=3,5:1) leads to transition of the γ phase completely into the α phase. The crystallite sizes of both sample, according to Scherrer’s equation are 3.53 (400) and 43.34 (113), respectively. The crystallite size of α-Al2O3 is bigger than that of γ-Al2O3. The highest specific surface area was obtained at a composition of urea:Al3+ = 2:1, followed by a composition of urea:Al3+ = 3,5:1, whish are 213 m2/g and 126 m2/g, respectively. The analyzed pore sizes are in a range of 2 to 50 nm, which indicates the formation of mesopore structure. Cu addition into alumina via a simple wet impregnation leads to formation of CuO and CuAl2O4 crystal. There is no detection of Cu or Cu2O diffraction peaks, which indicates that the oxidation was occurred while calcination. Diffraction peaks of single phase CuO were detected at sample calcined at 600 °C. As the calcination temperature is increased, the CuAl2O4 crystal become more dominant in the sample. At a higher temperature, Cu and O atoms received more energy to enter the matrix of Al2O3. The CuAl2O4 crystal also become more dominant as the Cu amount increases. After impregnation, the surface area of sample decreased drastically. This is probably due to the pores coverage by the CuO particles at the surface of γ-Al2O3, which in a good agreement with SEM analyses. Based on SEM analyses, the observed particle are CuO and Al2O3 and in accordance to the TEM analyses of sample with composition of urea:Al3+ = 2:1 (impregnated with 30 wt% of Cu and calcined at a temperature of 800 °C). Catalytic test at a fix bed reactor showed that the sample could decrease the concentration of detected benzene. Catalyst from commercial γ-Al2O3 has a benzene conversion of 19.0 %. The optimum conversion was found to be 82 % at a reaction temperature of 400 °C. the catalytic activity of synthesized sample is higher than the catalytic activity of impregnated commercial sample. Surface area is not strongly affect the catalytic activity, but the existed compound does. Low conversion of benzene could possibly due to the presence of CuAl2O4 compound. In CuAl2O4, the empty oxygen lattice of γ-Al2O3 was occupied by Cu or O atom from CuO compounds at a high calcination temperature. As a result, the electron transfer (adsorption -desorption) is blocked for benzene oxidation.