Adsorptive Separations for Environmental Applications Kartik. S Senior Research Fellow Environmental Materials Unit National Environmental Engineering Research Institute Nehru Marg, Nagpur

Soot deposited on catalyst coated ceramic foam Adsorption and Why Molecular Simulations?  Used as separation technique when constituents are in trace levels  Ease and Economy in Separation  Effective Separation  Challenging task :- Selection of Adsorbent for Separation task.  Other Separation Processes Vs Adsorption  Separation Methods :- Models are available for prediction of co- existence properties.  Adsorption :- No classic thermodynamic theory available for adsorption.(Simple models Resonable estimate of isotherms)  Development of adsorption phenomena is based on numerous experiments.

Objectives of the proposed Work Estimating the base line adsorption capacities of CO 2 on zeolites using molecular modeling. Selected adsorbents will be tested under binary mixture CO 2, N 2 at different temperatures and concentrations. Presence of moisture on activity and selectivity will be studied for functionalized adsorbents. Mass transfer coefficient, adsorption capacity and affinity can be studied for the selected adsorbents. Experimental evaluations of adsorption capacity of these functionalized adsorbents by generating adsorption isotherms for guest-host systems.

Simulation Methodology Silicalite framework (Single Unit Cell)Si 48 O 96 Al replaced Silicalite framework Al 8 Si 40 O 96 Cation Exchanged Zeolite Na 8 Al 8 Si 40 O 96 Assigned charges for atoms by forcite module and subjected to GCMC by Sorption module (2) (2)Charge balancing framework by counter ions (Na + ) by Locate option in Sorption Module

Material Studio V4.2 (Accelrys Software Inc) Average loading Fugacity of adsorbate

Grand Canonical Monte Carlo Simulations Zeolite phase Bulk phase At equilibrium temperature & chemical potential in bulk and zeolite phase are the same.

Elementary moves attempted: Sorbate molecule removal Initial State Sorbate molecule displacement Sorbate molecule addition

Case study Four adsorbents were selected –Faujasite (FAU) –Mazzite (MAZ) –ZSM-5 (MFI) –Mordenite (MOR) Adsorption Isotherms were generated by simulations along with other outputs.

Faujasite ( Na 58 [(AlO 2 ) 58 (SiO 2 ) 134 ]) 30°C 75°C Langmuir Model R 2 = R 2 = q s = 222mg/g, b= kPa -1 q s = 204 mg/g, b= kPa -1 Temp, PressReportedSimulation 30°C,100kpa130mg/g126mg/g 30°C,500kpa198mg/g194mg/g 30°C,1000kpa213mg/g206mg/g

Mazzite (Na 10 [(AlO 2 ) 10 (SiO 2 ) 26 ] 30°C 75°C q s = 99 mg/g, b= kPa -1 q s = 84 mg/g, b= kPa -1 R 2 = R 2 =0.9103

Mordenite (Na 8 [(AlO 2 ) 8 (SiO 2 ) 40 ] q s = 133 mg/g, b= kPa -1 q s = 111 mg/g, b= kPa -1 30°C 75°C R 2 = R 2 =0.9075

ZSM-5 (Na[(AlO 2 )(SiO 2 ) 95 ] q s = 122 mg/g,b= kPa -1 q s = 108 mg/g,b= kPa -1 30°C 75°C R 2 = R 2 =0.9927

Iso-steric Heat of Adsorption Temperature fluctuations can influence adsorption kinetics and equlibria Iso-steric heat governs local temperatures variations in Adsorber

100kPa 1000 kPa Faujasite

100kPa 1000kPa Mazzite

Mordenite 100 kPa 1000 kPa

ZSM Kpa 1000 Kpa

Comparison for the adsorbents AdsorbentTemepratureIsosteric Heat (kcal/mol)Adsorption Capacity (mg/g) (1000 kPa from simulation) Faujasite Mazzite Mordenite ZSM

Overall progress of the research work Zeolites SimulationsSynthesisCharacterizations Experimental Validations* FaujasiteCompleted In Progress MazziteCompleted In Progress ZSM - 5Completed In Progress MordeniteCompleted In Progress *Functionalization experiments for the enhancing adsorption capacities and selectivity are in progress

Temperatur e Controller To TCD-GC Sample Selector valve MFC CO 2 N2N2 Mixer Tubular Furnace Auto- sampler valve on GC Stream for feed Analysis Catalyst Evaluation Assembly

CO 2, N 2 He Dosing Vessel Adsorption Cell On/Off valve Volumetric Adsorption Apparatus Adsorbent

Current Activities Simulations for zeolites in Henry's law regime (0-130kPa). Selected zeolites will be subjected for methane adsorption by simulations. Synthesis of the above zeolites Evaluation are conducted in Volumetric Apparatus.

Future Activities Zeolites with different cations exchanged on framework are being designed. Synthesized zeolites will be cation exchanged and experimentally evaluated.

Thank You

Force field & MM Force field expression :Force field expression : (COMPASS, Universal, CVFF) (COMPASS, Universal, CVFF) Energy minimizationEnergy minimization Monte Carlo techniqueMonte Carlo technique

Ensembles in MM Idealization of large number of copies of system, which considered at once each one represent the possible states of the system Statistical Ensemble Imposed variables Applications Canonical Ensemble N,V,T Phase Properties (C V,P, μ) Grand Canonical Ensemble μ,V,T Adsorption Isotherm, Heat of adsorption, Siting of adsorbate, Selectiviy, Henry’s Constant Isothermal or Isobaric Ensemble N,P,T Phase Properties (C P,ρ, V)

AtomsCharge (e) Na (Zeolite)1 K (Zeolite)1.6 Si (Zeolite)0.89 Al (Zeolite)0.94 O (Zeolite)-0.45 C (CO 2 )0.8 O (CO 2 )-0.4 AtomsCharges C0.8 O-0.4