Design and implementation of a cost-effective, safe, and precise lean-rich generating system for the evaluation of NOX storage reduction catalysts: performance analysis, statistical modeling, and multiple response optimization – A guideline for future research and application

Abstract

Mixing is a critical factor in chemical reaction engineering, particularly in the development of new catalysts for pollutant removal, such as NOx storage reduction catalysts. Comprehensive performance evaluation in laboratory experiments requires high-quality test gases. Several techniques have been developed for generating these gases, each with specific advantages and limitations. This research presents a simple, safe, and cost-effective gas generation system for laboratory applications, including evaluating adsorbents and catalysts, particularly NOx storage reduction catalysts, and for toxicological studies using precise dynamic methods like gas stream mixing and evaporation. Components of the dynamic system—including gas cylinders, connections, mixing chambers, rotameters, the quartz reactor with preheating chamber, bubbler systems, and tubular heaters—are comprehensively described. Statistical modeling and optimization were employed to determine the optimal operating conditions. The optimal conditions were identified as NO (924 ppm), O₂ (15 %), CO (9999 ppm), and a space velocity of 105,921 h⁻¹. Additionally, the system's ability to generate various mixtures of gases (NO, O₂, and CO) and vapors (toluene and water) was assessed. The system was further evaluated under fan-on and fan-off modes to assess its performance under varying turbulent conditions. A detailed analysis was performed to determine the relative errors, time to reach steady-state conditions, and actual concentrations produced under different expected concentrations (NO: 100–200 ppm, O₂: 3–15 %, CO: 500–10,000 ppm, toluene: 64–8999 ppm, relative humidity: 0.14–22.69 %), space velocity (70,000–140,000 h⁻¹), bubbler flow rates (10–600 mL/min), and saturator temperatures (5–20 °C). Fundamental equations for calculating conversion, selectivity, and yield of a component of interest, carbon-messing, and carbon balance in the mixture are also provided.

Keywords

• Dynamic gas generator
• NOX storage reduction catalyst
• Statistical modeling
• Optimization