Sorption thermodynamics, siting, and conformation of long n-alkanes in silicalite as predicted by configurational-bias Monte Carlo integration

Journal Article · Thu Feb 16 00:00:00 EST 1995 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100007a042· OSTI ID:6767847

Maginn, E J; Bell, A T; Theodorou, D N ^[1]

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1. Lawrence Berkeley Lab., CA (United States) Univ. of California, Berkeley, CA (United States)

The low-occupancy adsorption thermodynamics of n-alkanes ranging in length from C[sub 4] to C[sub 25] in the zeolite silicalite is predicted from molecular simulations. A bias Monte Carlo (MC) technique is described which permits these calculations to be carried out with modest computational expense. In addition, a general, systematic coarse-graining methodology is developed which enables the location and shape of chains of arbitrary length to be accurately described using a small number of degrees of freedom. By coupling this methodology with the bias Monte Carlo technique, the free energy of sorbed chains is calculated as a function of the coarse-grained configuration of chains. The results indicate that, at high temperature, n-alkanes probe all the accessible regions of the zeolite pore network, favoring high-entropy conformations that access more than one type of channel environment. As temperature decreases to room temperature, short chains continue to populate all regions of the zeolite, while chains longer than n-octane align along the straight channels in highly localized low-energy configurations. Macroscopic thermodynamic results, such as Henry's law constants and isosteric heats of adsorption, are calculated and compared to experimentally obtained values. 51 refs., 19 figs., 8 tabs.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6767847
• Journal Information: Journal of Physical Chemistry; (United States), Vol. 99:7; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ALKANES
ADSORPTION
SILICATE MINERALS
SORPTIVE PROPERTIES
ADSORPTION HEAT
MATHEMATICAL MODELS
MONTE CARLO METHOD
NUMERICAL DATA
SIMULATION
SORPTION
TEMPERATURE DEPENDENCE
THERMODYNAMICS
ZEOLITES
CALCULATION METHODS
DATA
ENTHALPY
HYDROCARBONS
INFORMATION
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
MINERALS
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
SURFACE PROPERTIES
THERMODYNAMIC PROPERTIES
360600* - Other Materials
360606 - Other Materials- Physical Properties- (1992-)
400201 - Chemical & Physicochemical Properties
661300 - Other Aspects of Physical Science- (1992-)
990200 - Mathematics & Computers