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Publication costs assisted by Institut de Catalyse, CNRSThe epr spectra of Cu(II) complexes with ammonia and pyridine formed in the cages of NaY zeolite have been investigated as a function of temperature. The parallel component of the Cu2+ hyperfine splitting decreases with temperature increasing from 4.2 to 400°K. This temperature dependence results from a vibration with sharp frequency coupling to the hyperfine splitting and it is shown to obey a law of the type C, ( ) = C,|(0) -LM[coth (huijTkT) -1], where is the molecular Cu-N stretching vibration frequency. Far-ir data are found to be in excellent agreement with the epr determined values and support the present interpretation of the temperature effect. The Cu-N molecular vibration frequency is found to depend greatly on the interaction of the complex with its surroundings, hence giving a way of determining its location in the zeolitic structure.

The importance of molecular sieves catalysts in industrial catalysis has increased significantly over the past two decades. To date, all commercial applications of zeolite catalysts have involved acidic zeolites, particularly the ultra stable rare earth Y-type zeolite used in the catalytic cracking processes. Recent investigations of zeolite chemistry have revealed some particular features of both basic and acidic zeolites and have opened the new field of improved fuel processing. The new chemical evidence has raised the possibility that physico-chemical features play a role in catalysis. A large effort has therefore been devoted to the shape-selectivity properties of such materials. Moreover, increasing interest has been focussed recently on the understanding of crystallization of zeolites during synthesis, in the synthesis of new zeolites and in the chemical modifications of zeolites with the objective of expanding the applications of such materials.The word zeolite stems from the Greek "zeo" (boiling) and "litos" (stone) meaning a material able to eliminate large amounts of water when heated. More than forty different structures of zeolites have been identified while grea progress has been gained in synthetic zeolites, particularly by Linde and Mobil .Zeolites are usually alumino silicates with a general formula M D (Al Si, 0 N 0 o ), mH o 0 χ y x+2y n-(x+2y) 2n ' 2 where M and D cj^esignajje respectively a mono-(H + , Na + , K + , cjt. .) or a divalent (Ba , Mg , Ca ,...) cation. They are formed of A10.

Synthesis and Characterization of New VPO Catalysts for Partial n-Butane Oxidation to Maleic Anhydride.-Phosphorus-vanadium mixed oxide (VPO) catalysts are prepared using V3+ (VCl3) and V5+ (V2O5) which comproportionate to V4+ to a great extent, and H3PO4 as precursors. The preparation of VPO catalysts is performed in aqueous and organic media using varying V3+/V5+ ratios in the precursor to control the V4+/V5+ ratio in the catalyst. The best catalyst in both media are obtained with a V3+/V5+ ratio of 1. The results of XRD, IR, Raman, and UV diffuse reflectance spectroscopy, 31P MAS NMR, and XPS show that these catalysts consist of an oxidized surface (γ-VOPO4; V5+) in interaction with a reduced matrix ((VO) 2P2O7; V4+). -(BATIS, N. H.; BATIS, H.; GHORBEL, A.; VEDRINE, J. C.; VOLTA, J. C.; J. Catal. 128 (1991) 1, 248-263; Inst. Rech. Catal., CNRS, 69626 Villeurbanne, Fr.; EN) 1