γ-Zirconium and γ-Titanium Phosphates Platinum Intercalation Compound Preparation, characterization and thermal behaviour

Inorganic ion-exchangers with a layered structure such as γ-zirconium and γ-titanium phosphates, intercalated with organic diamines, are able to exchange Pt²⁺ ions to give new intercalation compounds that can be utilized in heterogeneous catalysis. The experiments performed at different temperatures (25 and 45°C), show different ion uptakes, greater at 45°C and for the materials derived from γ-zirconium phosphate. After platinum exchange, all the materials show an amorphization in the XRD if compared with their precursors. The thermal behaviour of the platinum materials is specific, depending on the exchanger used and the ligand inside the exchanger. Pt²⁺ ion has a catalytic effect on ligand elimination in the γ-zirconium phosphate platinum compounds, but not in those derived from γ-titanium. All the obtained yellow materials show a small step in the TG curves and simultaneously we have the Pt²⁺→Pt⁰ reduction: this is confirmed by XRD registered at the temperatures of the thermal effect, showing peaks at d_hkl=2.27 and 1.95 Å. This revised version was published online in July 2006 with corrections to the Cover Date.     

Pillared layered structures versus zeolites as sorbents and catalysts. Part 8. Catalytic destruction of some chloro- and chlorofluoro-hydrocarbons in alumina-pillared clays

Summary Pillared clays have been monitored for catalytic destruction of halocarbons. In comparison with HZSM-5 zeolites, the catalysts tested give higher chlorohydrocarbons destruction with polymers formation. Fluorochlorohydro-carbons are destroyed as well.     

Synthesis and characterization of sol-gel zirconium phosphate with template surfactants by different methods

Long chain trimethylammonium salts can be successfully used as guest molecules to produce mesoporous layered materials when intercalated in sol-gel zirconium phosphate, an inorganic ion-exchanger. The obtained materials are very similar independently of the chain length and the synthesis method batch (B) or direct intercalation (DI). They show a good thermal stability, and a very high interlayer distance if compared with their precursor. By the thermal characterization it can be observed that the surfactant is lost in two or three steps depending on its position in the host. The layered structure with the expanded interlayer distance is maintained up to 300°C. From the IR spectra the different surfactant release models for (B) and (DI) are confirmed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Incorporation of Cadmium Ions and Cadmium Sulfide Particles into Sol-gel Zirconium Phosphate. Synthesis,thermal behavior and X-ray characterization

The inorganic ion-exchanger α-zirconium phosphate was synthesized by the sol-gel method and its properties relating to the exchange of Cd²⁺ and the intercalation of CdS particles were studied. The Cd²⁺-exchange process is a fast process and the material obtained exhibits an increased interlayer distance d with respect to its precursor (9.56 vs. 7.56 Å). The resulting Cd-containing material was exposed to aH₂S gas flow to give CdS particles in the exchanger. The zirconium phosphate containing CdS particles still possesses a layered structure, with a pattern almost identical to that of the initial ion-exchanger precursor. Moreover, the material may exchange further Cd²⁺ and hence lead to a higher CdS particle content. The thermal behavior of this ion-exchangers containing Cd²⁺ or CdS particles was studied.     

Selective isomerization of α-pinene

a-Pinene isomerization was studied in gaseous and liquid phases on g-zirconium phosphate and rhodium g-zirconium phosphate. The first showed higher activity but lower reaction selectivity than the second, that led to tricyclic terpenes formation.     

Dehalogenation of 5-halo-uracil molecules induced by 100 keV proton collisions

Neutral and cationic halogen loss of singly and doubly ionised 5-X-uracil (X = F, Cl, Br, I) after collisions with 100 keV protons have been studied in the gas phase. The rates of these dissociation channels are strongly dependant on the nature of the halogen substituent. It is very weak in the case of fluorine but is a dominant channel for iodine. Dissociation mechanisms are proposed for a number of significant channels associated to dehalogenation. It is suggested that some final ion products originate from specific processes. For instance, ion products of mass 38, 39 and 40 amu are very sensitive to the nature of the primarily ejected halogen and result from pathways associated to dehydrogenation and transient formation of the dehalogenated uracil cation.     

Complexes of octadecyltrimethylammonium polyacrylate: properties in solution,gel and solid forms

A polymer-surfactant complex (OTAPA) was prepared by titration of aqueous poly(sodium acrylate) with stoichiometric amounts of octadecyltrimethylammonium chloride. The resulting product is not water-soluble and does not dissolve in most polar and nonpolar, liquids. OTAPA has peculiar thermal behaviour and interesting structural properties. It has a high melting temperature and decomposes around 350 °C. According to preliminary X-ray findings, the complex is formed by an arrangement of alkyl chains around the polymer skeleton, packed into a layered structure. The complex forms an elastic gel in ethylene glycol, and, to a much lesser extent, in glycerol or tetrahydrofuran, but is hardly water-soluble. Indeed, the occurrence of micelle-assisted dissolution and the precipitation of OTAPA from such mixtures, upon dilution with water, have been observed. Applications of OTAPA as a hydrophobic modifier of surfaces can be considered.     

Thermal behaviour of copper-dimethyl-phenanthroline species in α-and ψ-zirconium phosphates

Two methods are described in order to obtain copper-2,9-dimethyl-1, 10-phenanthroline (dmp) coordination compounds intercalated between the layers of α-Zr(HPO₄)₂·H₂O and ψ-Zr(H₂PO₄)(PO₄)·2H₂O: the direct intercalation of Cu-dmp complex species or the formation ‘insitu’ of coordination compounds. With the first exchanger both methods lead to similar products with X-ray diffraction patterns practically identical. They contain Cu(II–I)-dmp complex species that confer to the solids an initially green colour slowly turning to yellow with time or temperature when the reduction of Cu(II) to Cu(I) is complete. With λ-ZrP(H₂PO₄)(PO₄)·2H₂O, only the direct insertion is successful. TG/DTA experiments permit a better understanding of what is occurring in the materials during the copper reduction step, in correspondance of which, a strong endothermic peak and a gain in weight can be observed. They also show how the difference in the structure and chemical formula of the two exchangers affect the thermal behaviour of the two series of compounds. Deceased August 13, 1993.