INVESTIGATION OF CRYSTALLINE SURFACE AREA ON DESILICATED ZEOLITE SSZ-13 USING RESPONSE SURFACE METHODOLOGY

• Main Author: Mardiana, St
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/51978
• Institution: Institut Teknologi Bandung

SSZ-13 zeolite is a type of zeolite with chabazite (CHA) framework which has good catalytic performance as a selective catalyst for NOx reduction (SCR-NH3) and MTO (methanol to olefin) reactions. However, the micropore size of SSZ-13 (3.8 x 3.8 Å) can cause limitation on diffusion and promote coke formation which can accelerate the catalyst deactivation process. This can certainly reduce the performance of zeolite SSZ-13 as a catalyst. To address this issue, porosity is added using the top-down method via controlled desilication. This method is carried out by partial detemplation before desilication so the remaining organic compounds can prevent NaOH attack, thus causing the desilication process to be controlled. For the first time, this work introduces a new indicator that can be used as characterization and categorization of the desilication process, namely the crystalline surface area (Scryst), which can be obtained from the BET surface area value and the crystallinity fraction value of the SSZ-13 zeolite. In this work, a controlled desilication process was optimized using response surface methodology (RSM). The RSM method is used because it has advantages compared to the classic method OFAT (one factor at a time), which has been frequently used so far. The advantages are the interaction between variables can be identified, and also saves time, effort, and costs. The dependent variable used is crystalline surface area, while the independent variables used are temperature and time. The stages of this research consisted of the synthesis of zeolite SSZ-13 using the hydrothermal method, followed by a partial detemplation process using calcination, and desilication. Optimization of the controlled desilication process was carried out with variations in a time range of 20- 60 minutes and a temperature range of 51-91 ? which was determined using the RSM method. The first type of data collection in the RSM method is 2k factorial to determine the interaction between variables to the response. After that, the steepest ascent method was carried out to obtain the area around the optimal point which provides a combination of independent variables with the most optimal response to be used as a new area at a later stage. Then the central composite design (CCD) to obtain optimal controlled desilication conditions with an optimal response as well which is continued by performing a stationary point analysis with mathematical matrix calculations to determine the definite optimal points. In this research, the characterization methods used were carried out by XRD, FTIR, TEM and N2 adsorption. The RSM analysis result showed the quadratic function of Y = 496.3 + 34.2A + 20.4B ? 12.6A2 – 6.7B2 – 10.5AB so that the optimal point of the controlled desilication process at temperature 92.5 ? for 53.6 minutes. The predicted crystalline surface area of 521.5 m2/g and the experimental result of 527.3 m2/g indicate a small error of 1.15 %, which shows the reliability of the RSM method in this optimization process. The contour and surface plot in the form of a simple maximum shows that temperature and time have a significant effect in the controlled desilication process. The plot shows a quadratic model that consists of an area that shows an increase in crystalline surface area, optimal area, and a decrease in crystalline surface area as the effect of an increase in temperature and time. The results also showed that the controlled desilication process could increase the crystalline surface area of the SSZ-13 zeolite to 527.3 m2/g compared to the SSZ-13 zeolite sample without controlled desilication which only had a crystalline surface area value of 395.7 m2/g. The increase in crystalline surface area value is expected to improve the performance of zeolite SSZ-13 as a catalyst.