M.SHEHZAD course work project base PPT.pptx

Physics

1. Plasma-Enhanced Catalytic Synthesis of Ammonia over a Ni/Al2O3 Catalyst at Near-Room Temperature MUHAMMAD SHEHZAD Submitted To Dr. SHAFIQ UR REHMAN Department of Physics Agriculture University Faisalabad

2. Plasma--4th State of Matter “Plasma” named by Irving Langmuir in 1920’s! The standard definition of a plasma is as the 4th state of matter (solid, liquid, gas, plasma), where the material has become so hot that (at least some) electrons are no longer bound to individual nuclei. Thus a plasma is electrically conducting, and can exhibit collective dynamics.!   I.e., a plasma is an ionized gas, or a partially-ionized gas."

3. INTRODUCTION: Ammonia is one of the most important chemicals used in modern society. It is a vital precursor in the synthesis of many useful products, including fertilizers, plastics, resins, explosives , and synthetic fabrics. It is produced on an industrial scale from N2 and H2 using the Haber-Bosch process, which is typically carried out at 450−600 °C and 150−300 bar in the presence of a highly active catalyst. This process emits over 300 million metric tons of CO2 each year and is highly energy-intensive, consuming 1−2% of the world’s primary energy supply: the largest in the chemical industry. The key to reducing the energy consumption of ammonia synthesis processes is, therefore, in activating the N2 bond at lower temperatures to avoid the requirement of high pressures. Biochemical processes, electrochemical processes, and plasma processes with mild operating conditions are considered promising alternatives to thermal catalytic production of ammonia

4. Catalyst Preparation and Characterization Five wt % M/Al2O3 (M = Fe, Ni, and Cu) catalysts were prepared by incipient wetness impregnation using nitrate salts (Alfa Aesar , 99.5%) as the metal precursor. Al2O3 catalyst support (3g) was added to the solution of nitrate salts. The slurry was continuously stirred at 60 °C for 2 h, after which it was aged overnight at room temperature. The samples were then dried at 110 °C for 5 h and calcined at 500 °C for 5 h. The catalysts were then sieved to 40−60 mesh and reduced by Ar /H2 mixed gas (100 mL min−1; Ar /H2 = 7:3) at 500 °C for 5 h before the plasma reaction. These catalysts, after reduction, will hence forth be referred to as “fresh catalysts”.

5. CONTINEOUS… X-ray diffraction (XRD) patterns of the fresh and spent catalysts were recorded by a Rigaku D/max-2200 diffractometer using a Cu Kα radiation source in the 2θ range from 20° to 80°. High-resolution transmission electron microscopy (HRTEM) analysis of the fresh catalysts was carried out using a Tecnai G2 F20 microscope operating at an acceleration. The particle size distribution of each catalyst was determined through the analysis of more than 300 particles from the TEM images. X-ray photoelectron spectroscopy (XPS) analysis was performed on a Thermo ESCALAB 250Xi instrument using an Al Kα X-ray source calibrated with C1s (284.8 eV ). A low-resolution survey and high-resolution region scans were measured at the binding energy of interest for each of the spent catalysts.

6. Experimental Setup

7. RESULTS The plasmas produced in N2−H2 gas using different reactor configurations (plasma only,Al2O3 and Ni/Al2O3) were characterized using ICCD and BOLSIG+ calculations. There were no obvious changes to the discharge properties when packing the discharge area with different M/Al2O3 catalysts; therefore, only the results for the catalyst that gave the best performance in plasma-catalytic synthesis of ammonia, Ni/Al2O3, will be discussed here. Images of the discharge areas of unpacked, Al2O3-packed and Ni/Al2O3-packed reactor configurations, are shown with the plasma off in Figure (a−c), respectively y. The time-averaged ICCD images presented in Figure (d−f) show the emission in the discharge area. Figure d shows typical filaments were produced in the discharge area in the absence of packing material. Filling the entire discharge gap with Al2O3 or Ni/Al2O3 (Figure e and f, respectively) significantly reduced the gas void in the plasma-catalyst zone.

8. In short Plasma-enhanced synthesis of ammonia using transition metal catalysts (M/Al2O3, M= Fe, Ni, Cu) has been achieved at ambient pressure and near room temperature with a water electrode DBD reactor. Compared to plasma synthesis of NH3 Without a catalyst, plasma-catalysis significantly enhanced the NH3 synthesis rate and energy efficiency, which increased with Different catalysts in the order: Ni/Al2O3 > Cu/Al2O3 > Fe/ Al2O3 > Al2O3. All of the catalysts provided stable performances for at least 6 h, and Ni/Al2O3 maintained an efficient performance when recycled five times. The highest NH3 Synthesis rate of 471 μmol g−1 h−1 was achieved with Ni/ Al2O3, which was 100% higher than that of plasma only. The performance was moderate compared to the state of the art. As there were no notable differences in the discharge characteristics for the three different metal catalysts, These results suggest that the catalytic effects provided by the chemistry of the catalyst surface are dominant over the physical effects of The catalysts in the plasma-catalytic synthesis of ammonia.