Nitrogen oxides (NOx) are significant sources of air pollution. Nitrogen oxides like Nitric oxide (NO) and Nitrogen dioxide (NO2) are mainly responsible for the acid rain and smog. Nitrous oxide (N2O), also known as the laughing gas, is the major greenhouse gas that is responsible for the ozone layer's damage in the troposphere. According to the Environmental Protection Agency (EPA) report, one pound of N2O is 300 times more potent greenhouse gas than one pound of CO2. The significant emitters of Nitrogen oxides (NOx) are automobiles, agricultural sources, thermal power plants, and chemical processes like Nitric acid production plants, paint manufacturing, etc.   This study mainly focuses on the tail gas emitted from the Nitric acid production facility. The tail gas emitted during the HNO3 production consists of almost 2% of O2, 200-400 ppm of NO2, and NO, whereas 800 ppm of N2O.  As N2O is the most emitted gas from the Nitric acid production facility, it is followed by NO2 and NO, so it is essential to reduce these pollutants from the tail gas. Selective catalytic reduction (SCR) is a well-known technique currently involved in reducing NOx via the adsorption process from the Nitric acid production facility. But the costs involved in these methods are quite high. Nanoporous materials like zeolite exhibit uniform pore size and high thermal stability are said to be the promising adsorbents of NOx. The availability of a large number of zeolites makes it impossible to identify the proper zeolite for NOx adsorption experimentally. In such situations, molecular simulations are a powerful tool that can help identify the perfect zeolite. The time and cost involved in the process of molecular simulations are very low.  In this work, Monte Carlo simulations involving reaction ensemble are implemented to obtain the equilibrium composition of NOx components at desired operating conditions in the Brick molecular simulation package. This is followed by Grand Canonical Monte Carlo simulations (GCMC) and Reactive Grand Canonical Monte Carlo simulations (RXMC-GCMC) for pure and quaternary NOx gas mixture adsorption in five different zeolites (FAU, FER, MOR, MFI, and TON) using simulation package RASPA. The composition results from the reaction ensemble are validated with the composition results obtained using the Gibbs minimization technique in the MATLAB model, and the results are in good agreement. The quaternary gas mixture adsorption results in five different frameworks from RXMC-GCMC simulations are then validated in Ideal adsorbed solution theory in the Python model, and the results are in good agreement at the given operating conditions.

The energy mix of the future is likely to feature hydrogen due to its versatility. For effective use in energy storage, hydrogen has to be compressed. Conventional electrolysis of water and subsequent mechanical compression of hydrogen is an energy intensive process. A one-step conversion and compression can take place in a Electrochemical Hydrogen Compressor (EHC). This has the disadvantage that the resulting stream of high pressure hydrogen contains water. In order to assess the capability of hydrophilic zeolites as a means of selectively adsorbing this water, a in silico screening study of 6 zeolites was performed. To this end, a force field was constructed to allow for the simulation of high pressure hydrogen dehydration using Monte Carlo methods. The validity of this force field was evaluated by replicating simulation studies of adsorption of water/ hydrogen on zeolite frameworks with the presence of extra-framework cations. At the system pressure of 875 bar, prediction of the fugacity coefficient by means of the Peng-Robinson Equation of State (PR-EOS) yields inaccurate results. Therefore, these are calculated in the CFCNPT ensemble. It is demonstrated that the Ideal Adsorbed Solution Theory (IAST) is not suited to predict binary adsorption isotherms in this system. As a result of the screening study, it is found that the selectivity of water over hydrogen is almost linearly correlated to the amount of Al atoms in the zeolite framework. Furthermore, it is observed that topologies which feature a low amount of void space outperform those where significant void spaces are present. This can be attributed to the fact that the interactions of the zeolite with water are stronger than those with hydrogen in the limit of a low Si/Al ratio (Si/Al=1). It is theorized that water adsorbs preferentially at the surface of the zeolite, and competitive adsorption by hydrogen can only take place in sufficiently large void spaces.