Molecular Simulation of Reaction and Adsorption in Nanochemical Devices: Increase of Reaction Conversion by Separation of a Product from the Reaction Mixture

We present a novel simulation tool to study fluid mixtures that are simultaneously chemically reacting and adsorbing within a molecularly porous material. The method is a combination of the Reaction Ensemble Monte Carlo method and the Dual Control Volume Grand Canonical Molecular Dynamics technique. The method, termed the Dual Control Cell Reaction Ensemble Molecular Dynamics (DCC-RxMD) method, allows for the calculation of both equilibrium and non-equilibrium transport properties in porous materials, such as diffusion coefficients, permeability and mass flux. Simulation control cells, which are in direct physical contact with the porous solid, are used to maintain the desired reaction and flow conditions for the system. The simulation setup closely mimics an actual experimental system in which the thermodynamic and flow parameters are precisely controlled. We present an application of the method to the dry reforming of methane within a nanoscale reactor in the presence of a semipermeable nanomembrane modelling silicalite. We studied the effects of the nanomembrane structure and porosity on the reaction species permeability by considering three different nanomembrane models. We also studied the effects of an imposed pressure gradient across the nanomembrane on the mass flux of the reaction species. Conversion of syngas (H2/CO) increased significantly in all the nanoscale membrane reactor systems considered. The results of this work demonstrate that the DCC-RxMD method is an attractive computational tool in the design of nanoscale membrane reactors for industrial processes.

[1]  M. Lísal,et al.  THE REACTION ENSEMBLE METHOD FOR THE COMPUTER SIMULATION OF CHEMICAL AND PHASE EQUILIBRIA. II. THE BR2+CL2+BRCL SYSTEM , 1999 .

[2]  Cracknell,et al.  Direct molecular dynamics simulation of flow down a chemical potential gradient in a slit-shaped micropore. , 1995, Physical review letters.

[3]  K. Gubbins,et al.  Reactive canonical Monte Carlo : a new simulation technique for reacting or associating fluids , 1994 .

[4]  S. Murad,et al.  A new model for permeable micropores , 1992 .

[5]  F. Swol,et al.  Molecular dynamics and Monte Carlo simulations in the grand canonical ensemble: Local versus global control , 1993 .

[6]  R. Gorte,et al.  Calorimetric Study of Adsorption of Alkanes in High-Silica Zeolites , 1998 .

[7]  Henning Hopf,et al.  Beyond the Molecular Frontier. Challenges for Chemistry and Chemical Engineering. Herausgegeben vom Board on Chemical Sciences and Technologies. , 2004 .

[8]  V. Gubanov,et al.  Interaction of gases with solid surfaces , 1988 .

[9]  A. Myers,et al.  Comparison of Experimental Techniques for Measuring Isosteric Heat of Adsorption , 2000 .

[10]  K. Gubbins,et al.  Phase separation in confined systems , 1999 .

[11]  Grant S. Heffelfinger,et al.  Diffusion in Lennard-Jones Fluids Using Dual Control Volume Grand Canonical Molecular Dynamics Simulation (DCV-GCMD) , 1994 .

[12]  N. G. Almarza,et al.  A non-equilibrium molecular dynamics approach to fluid transfer through microporous membranes , 2002 .

[13]  Berend Smit,et al.  Understanding molecular simulation: from algorithms to applications , 1996 .

[14]  A. Myers,et al.  Mixed-Gas Adsorption , 2001 .

[15]  R. Gorte,et al.  A new calorimeter for simultaneous measurements of loading and heats of adsorption from gaseous mixtures , 1999 .

[16]  R. Gorte,et al.  Measurement of Excess Functions of Binary Gas Mixtures Adsorbed in Zeolites by Adsorption Calorimetry , 1999 .

[17]  C. Brooks.  Computer simulation of liquids , 1989 .

[18]  J. MacElroy.  Nonequilibrium molecular dynamics simulation of diffusion and flow in thin microporous membranes , 1994 .

[19]  D. Nicholson,et al.  Computer simulation and the statistical mechanics of adsorption , 1982 .

[20]  J. MacElroy,et al.  Simulation of a Hard-Sphere Fluid in Bicontinuous Random Media , 1989 .

[21]  A. Myers,et al.  COMPARISON OF SORPTION HEATS FROM ISOSTERIC AND CALORIMETRIC EXPERIMENTS FOR NITROGEN, OXYGEN AND CARBON DIOXIDE ON ZEOLITES OF TYPES LTA AND FAU , 2000 .

[22]  Lev D. Gelb,et al.  Pore size distributions in porous glasses : A computer simulation study , 1999 .

[23]  William R. Smith,et al.  THE REACTION ENSEMBLE METHOD FOR THE COMPUTER SIMULATION OF CHEMICAL AND PHASE EQUILIBRIA. I: THEORY AND BASIC EXAMPLES , 1994 .