Physisorption and chemisorption of C2–C8 linear alkenes in H–FAU, H–BEA, H–MOR, and H–ZSM-5 have been quantified up to 800 K by combining QM-Pot(MP2//B3LYP:GULP) with statistical thermodynamics calculations. The influence of the zeolite topology and the alkene CC double bond position on the alkene sorption thermodynamics is addressed on the basis of linear variations of sorption enthalpies and entropies as a function of the carbon number. The physisorption strength and entropy losses increase in the order H–FAU < H–BEA < H–MOR < H–ZSM-5. Higher physisorption strength is computed for 2-alkenes (H–MOR) and 2-, 3-, and 4-alkenes (H–ZSM-5) as compared with 1-alkenes. Protonation of physisorbed alkenes leads to significantly more stable alkoxides. In contrast to the physisorption, higher chemisorption strength does not lead to larger chemisorption entropy losses. Also, the intrinsic stability of the alkoxides, i.e., relative to gas phase H2 and graphite, only depends on the carbon number and not on the detailed alkoxide structure in H–FAU, H–BEA, and H–MOR. In the narrower pores of H–ZSM-5, the 3- and 4-alkoxides are however more stable than the 2-alkoxides.

Kinetics and thermodynamics of isobutene protonation in H-FAU, H-MOR., H-ZSM-5, and H-ZSM-22 have been studied in a temperature range of 300-800 K, combining PW91-D//PW91 periodic density functional :theory calculations with statistical thermodynamics. At temperatures relevant for industrial zeolite-catalyzed processes (500-800 K), the tert-butyl carbenium ions more stable than the tert-butoxy in H-MOR, H-ZSM-5, and H-ZSM-22. Entropy contributions govern the standard Gibbs free energy stability of the chemisorbed intermediates. Due to the absence of a C-O covalent bond, formation of the tert-butyl carbenium ion is accompanied by a lower entropy :Loss and, consequently, has a higher stability than the tert-butoxy in H-MOB., H-ZSM-5, and H-ZSM-22. At 800 K, the protonation toward tert-butoxy in H-FAU, H-MOB, and H-ZSM-5 and to the tert-butyl carbenium ion in H-ZSM-22 is 5 to 7 orders of magnitude faster than the protonation toward isobutoxy. Among the four zeolites, the lowest activation energy is found in H-ZSM-22

The adsorption of C1-C4 primary alcohols at the Al12-O24(H)-Si12 intersection site in H-ZSM-5 is investigated using periodic density functional theory (DFT) calculations and adding a damped interatomic potential to the DFT results to account for dispersive van der Waals interactions (DFT-D). A good agreement between predicted and experimentally available adsorption enthalpies for C1-C3 alcohols is obtained. The effect of the H-ZSM-5 framework is sampled for adsorption of the C1-C4 alcohols in the straight and the zigzag channel. A variety of possible geometries, including hydrogen-bonded (physisorbed) and protonated (chemisorbed) complexes, are located as stable minima indicating that the potential energy surface connecting them is broad and very shallow. Experimental infrared (IR) spectra of the C1-C4 alcohols are interpreted based on harmonic frequency calculations for the most stable physisorbed and chemisorbed complexes. The stability of the adsorbed alcohols is governed by an interplay between their intrinsic basicity, van der Waals dispersive interactions and steric constraints exerted by the zeolite framework. In essence, steric constraints destabilize local hydrogen bonding and/or Coulomb alcohol-Brønsted acid site interactions while dispersive van der Waals interactions enhance the stability of physisorbed and chemisorbed complexes. Due to the prevalence of van der Waals interactions over steric constraints, C1-C4 alcohols adsorb preferentially in the more compact zigzag channel than in the straight channel. Both the physisorption and chemisorption energies increase linearly with 13 to 15 kJ mol(-1) per carbon atom in the straight and the zigzag channel, respectively.

A stable single vial lipoplex formulation has been of a T-connector. Homogenous cationic liposome prepdeveloped that can be stored frozen without losing either arations were prepared by extrusion in two different size biological activity or physical stability. This formulation was ranges of either 400 or 100 nm. Extruded liposomes proidentified by systematically controlling several formulation duced more monodisperse and physically stable lipoplex variables and without introducing either stabilizers or surformulations than unextruded liposomes, but the formufactants. Analytical assays were used to unambiguously lations prepared with 100 nm liposomes were less active characterize the formulations. The critical formulation parain in vitro transfection assays than either the 400 nm or meters were: (1) the size of the cationic liposomes; (2) the unextruded liposomes. Low ionic strength and 5% sorbitol rate and method of DNA and cationic liposome mixing; and were required for the lipoplex formulations to survive freez-(3) the ionic strength of the suspending vehicle. The mixing ing and thawing. A frozen lipoplex formulation stored for conditions were precisely controlled by using a novel, spemore than a year maintained its biological activity. These cially designed continuous flow pumping system in which results have broad implications for the pharmaceutical the DNA and liposome solutions were mixed at the junction development of lipoplex formulations for gene delivery.

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