Rudy F. Parton

Iron-phthallocyanines Encaged in Zeolite Y and VPI-5 Molecular Sieve as Catalysts for the Oxyfunctionalization of n-Alkanes

Abstract The preparation of iron-phthallocyanines encaged in molecular sieves was made from ferrocene impregnated in zeolite Y and VPI-5 molecular sieve. Both catalysts exhibit shape selectivity in the oxyfunctionalization of alkanes with tertiary butyl hydroperoxide as oxygen donor at 298 K and 0.1 MPa. As shown by turnover numbers resistance of the zeolite encaged complexes against oxidative destruction and activity in the oxidation of n-alkanes exceed by far those of free iron-phthallocyanines. Molecular graphics analysis shows the complex in both molecular sieves and presents a qualitative interpretation of the higher shape selectivity in the regioselective oxidation of n-octane on iron-phthallocyanine encaged in zeolite Y than in VPI-5.

A dimeric form of Jacobsen's catalyst for improved retention in a polydimethylsiloxane membrane

Abstract A dimeric form 1 of Jacobsens catalyst was synthesized for better steric occlusion in a polydimethylsiloxane membrane. In homogeneous conditions, the dimer is about as active and enantioselective as Jacobsens catalyst itself. The relationship between leaching of the complex out of the membrane on one hand and the solubility of the complex and the swelling of the membrane in the solvent used on the other, showed that leaching could be avoided only if low solubility was combined with low swelling or in the case of complete insolubility. As the dimer is less soluble and larger than the monomeric form, this form leaches less. The yields and enantioselectivities of the heterogenised system are comparable to those of the homogeneous monomer.

Membrane occluded catalysts: a higher order mimic with improved performance

Abstract A general method to immobilise homogeneous catalysts and to improve the performance of heterogeneous catalysts is discussed. The method consists in embedding the catalysts in hydrophobic PDMS (polydimethylsiloxane)-membranes. Inspired on a complete structural mimic of cytochrome P-450 up to the level of the membrane, this technique gives superior properties to the membrane resident catalyst. The scope and limitations of this method are discussed by two examples of heterogeneous catalysts, i.e., FePc-Y (iron phthalocyanine zeolite Y) and [Mn(bpy) 2 ] 2+ -Y (manganese bis(bipyridyl) zeolite Y), and three examples of homogeneous complexes, i.e., FePc, Ru-binap ([2,2′-bis(diphenylphosphino-1,1′-binaphtyl]chloro( p -cymene)-ruthenium chloride) and the Jacobsen catalyst ( N,N′ -bis(3,5-di- tert -butylsalicylidene)-1,2-cyclohexane-diamine manganese chloride). Due to changed sorption in the zeolites, catalyst activity is enhanced and deactivation is suppressed. Furthermore, the membrane incorporation makes the use of a solvent redundant. For homogenous complexes, this procedure represents a general method for heterogenisation. Moreover, the technique opens new ways in the field of oxidation chemistry, where solvents are necessary to homogenise reagents which usually differ in polarity.

Shape-Selective Catalysis in Zeolites with Organic Substrates Containing Oxygen

Publisher Summary With the advent of acid 10-membered ring (10-MR) zeolites as heterogeneous catalystsin hydrocarbon transformations, several new concepts on selectivity such as transition state and product shape s electivity, to name t h e most important ones, were developed. In the meantime it was established that these concepts were suitable for data rationalization and property prediction not only on acid catalysts but on metal, bifunctional and even basic catalysts o f zeolitic origin as well. The aim o f this chapter is to examine whether these concepts are valid when other than hydrocarbon substrates are converted on the mentioned shapes elective zeolites and related materials.

Synergism of ZSM-22 and Y zeolites in the bifunctional conversion of n-alkanes

Abstract Intimate mixtures of bifunctional catalysts based on ZSM-22 and Y zeolites do not show merely the intermediate catalytic properties between those found for the individual zeolites. Such mixtures produce enhanced yields of multibranched isodecanes from n-decane. A mechanistic explanation for this synergetic effect is given. New experimental evidence is provided for the occurrence of free gas-phase olefinic intermediates in bifunctional catalysis with zeolites.

Shape-selective zeolite catalysed synthesis of monoglycerides by esterification of fatty acids with glycerol

The monoglyceride selectivity obtained in the direct esterification of free fatty acids, such as dodecanoic acid or lauric acid, with glycerol is compared when catalysed either homogeneously or heterogeneously. Firstly, a relationship between the fatty acid chain length and temperature is established which quantifies auto-esterification. Subsequently, reaction conditions are chosen so as to avoid this homogenous reaction and to determine both the catalytic and selective effect of the zeolite. These conditions are valid until the critical micel concentration (CMC) of monoglycerides is reached. Due to the relatively low reaction temperature (385 K), side reactions other than esterification can be prevented. The use of solid catalysts limits the consecutive esterification into higher glycerides, thanks to a preferential adsorption of the polyol. Before emulsification of the reaction mixture, exclusively monoglycerides are formed on twelve-membered ring zeolites by shape selective esterification inside the pores. Variation of the crystal size shows that on ten-membered ring zeolites the reaction occurs on the external surface, consequently the monoglyceride selectivity is much lower and comparable to non-shape selective catalysts.

Cyclohexane oxidation with tertiary-butylhydroperoxide catalyzed by iron-phthalocyanines homogeneously and occluded in Y zeolite

Oxidation of cyclohexane to cyclohexanol and cyclohexanone at room temperature is achieved on iron phthalocyanine complexes encapsulated in Y zeolites with tertiary butyl hydroperoxide as oxygen atom donor. Sorption measurements show a high preference of the catalyst for polar reagents and products like acetone, cyclohexanol, cyclohexanone and tertiary butyl hydroperoxide. Therefore, the mode of addition of peroxide and the use of solvent have a strong influence on the reaction rate. A fed-batch type set-up with slow addition of the peroxide to the reaction mixture is proven to be the best system, minimizing the decomposition reaction of the peroxide and maximizing its selective oxidation reaction. Conversion of cyclohexane with iron-phthalocyanines encapsulated in Y zeolites is relatively high (up to 25%) with efficiencies between 40 and 10% and high selectivities for cyclohexanone (95%). Cyclohexanol is converted up to 70% with efficiencies around 70%, because the alcohol function is more sensitive to oxidation and sorption effects favor cyclohexanol compared to cyclohexane. The iron-phthalocyanine Y zeolites are regenerable for both reactions. Activities obtained by the zeolite encapsulated iron-phthalocyanines are higher than the homogeneous complexes which are oxidatively destroyed under reaction conditions and therefore not regenerable.

Surface modification of carbon black by oxidation and its influence on the activity of immobilized catalase and iron-phthalocyanines

A non-porous carbon black is oxidized using different reagents (H2O2 3 M, HNO3 0.3 M at 95 degrees C, O-2 at 400 and 600 degrees C) and used as support for the enzyme catalase as well as for iron-phthalocyanines, enzyme mimics, Characterization of the oxidized carbons is done by X-ray photoelectron spectroscopy, gas-adsorption and electrophoretic mobility measurements, The treatments do not change the texture of the carbon black. Hydrogen peroxide and nitric acid increase the surface oxygen concentration, and make the charge of the carbon surface more negative, whereas oxidation with molecular oxygen has the opposite effect, The surfaces with a higher oxygen content and negative charge preserve a higher activity of adsorbed catalase, presumably because less deformation of the enzyme occurs as a result of higher repulsive electrostatic interactions and lower hydrophobic interactions. The same order is found for the dismutase-like activity of the iron-phthalocyanines supported on the carbon; the selective oxidation of hydrocarbons, i.e. the oxygenase activity follows the reverse order. Thus, sorption effects determine the selectivity of iron-phthalocyanine. Zeolite Y, which has a higher electrical charge and surface oxygen concentration compared to the oxidized carbons, is responsible for a higher ratio of dismutase-like activity with respect to oxygenase-like activity.

Zeolites as Partial Oxygenation Catalysts

The use of zeolite catalysts for partial oxygenations of organic substrates with dioxygen or with peroxidic oxygen sources is reviewed. Oxidative properties were introduced in zeolites by incorporation of transition metals, either as charge neutralizing or lattice cations, supported oxides, or encaged organometallic complexes. Catalyzed reactions include the oxyfunctionalization of alkanes, the epoxidation or Wacker oxidation of alkenes, the oxidation of butadiene to furan or maleic anhydride and the hydroxylation of aromatics.

Synthesis, Characterization and Catalytic Performance of Nitro-substituted Fe-phthalocyanines on Zeolite Y

Abstract Nitro substituted iron-phthalocyanines on Y zeolite are synthesized via a ligand exchange reaction starting from a mixture of solids containing ferrocene, 4-nitro-1,2-dicyanobenzene and dry Y zeolite. The nature and loading of the catalyst is verified by Vis-NIR and solid state 13 C-NMR. Purification by soxhlet extraction demonstrates that the nitro-substituted phthalocyanines are not located in the supercages but are adsorbed at the outer surface of Y zeolite crystals. On the contrary, unsubstituted phthalocyanines are encapsulated in the supercages. Nitro-substitution improves considerably the activity of the complexes, as shown by the catalytic oxidation of cyclohexane to cyclohexanol and cyclohexanone at 298 K and 0.1 MPa with tertiary butyl hydroperoxide as oxygen donor.