This work is a continuous of our previous work in M.Sc study. Our previous work was concerned with the use of locally produced V2O5 (technical grade) in the preparation of catalyst successfully employed in the oxidation of n-butane to Malice Anhydride. The catalyst was evaluated using geomechanic system (France) specially built for catalytic test and modified to our proposes. The results had indicated to a functional catalyst. The catalytic properties were attributed to several factors (highly disordered, P/V around 1.1, adequate specific surface area, preparation method and other factors) (1). Since the catalytic activity of Vanadyl Acid Phosphate towards the reaction of n-butane oxidation to maleic anhydride (MA) was achieved in our previous work. It is useful to study the effect of addition (TiO2) anatase as a support on structural properties and surface chemistry of the catalyst. This precursor is prepared in an alternative method never mentioned in the literature. Route (A) depends on the reaction of the technical grade (V2O5) with (o- H3PO4 ) in order to prepare the intermediate phase (VOPO4.2H2O) which is then reduced by a mixture of (benzyl alcohol and isobutanol) to reach the assigned phase VO (H2PO4)2 . While the traditional route (B) depends on the reduction of vanadium pentoxide by alcohol mixture and then adding phosphoric acid to the reduced phase.The structural properties and surface chemistry of vanadyl acid phosphate and the intermediate phase prepared by route (A) and vanadyl hydrogen phosphate hemihydrate prepared by route (B) are studied after carrying out physical and chemical analysis in international known laboratories in U.S.A, Germany, Republic of Ukraine and U.A.E. by using special techniques devoted in catalytic structural and surfaces studies.The identification of the prepared phases was carried out by using X- ray diffraction (XRD). The results of phases identification show the co- existence of traces of other phases like VO (H2PO3)2 with the dominated main phase prepared by rout (A). These results also indicate that a very pure phase was never reached phase which is known phenomenon in the field of preparation of (VPO) system. It was found through these identification examination that the addition of TiO2 (anatase) could affect the resultant phases prepared in rout (B), since a monohydrate composition (VOHPO4.H2O) is obtained instead of Vanadyl Hydrogen Phosphate Hemihydrate (VOHPO4.0.5H2O) normally prepared without the use of support . No effect of support is observed on the main phase prepared by route (A).The differential thermogravimetric behaviors for the precursors were studied. This study highlights only the supported and unsupported precursors in order to assign the effect of TiO2 (anatase) on the thermal behavior, two effects were observed; the first one is increase the percentage of total loss of weight for supported Vanadyl Acid Phosphate (13.86 %), the second effect is the types of stage which in the precursor started it dehydration; the unsupported phase started the dehydration in (2 endothermic peak between 50-27º C) while the supported phase started its dehydration in one endothermic peak between ( 110-180 º C ). The total loss in weight of supported VO (H2PO4)2 is reported here for the first time.The comparison of FTIR spectrum of prepared supported and unsupported phases with laboratory grade and technical grade of vanadium pentoxide are achieved. The obtained results emphasis on the presence of wide shifts in the band positions. These shifts reflect the deformation of the angles and lengths of bonds in these phases. Laser Raman spectroscopy could be helpful in this aspect. Structural properties were further confirmed by studying the effect of presence of TiO2 (anatase) is accorded in the structure, and layers of mono vanadate layer are identified in all prepared phases. However the poly vanadate layers are identified only in the prepared Vanadyl acid phosphate. This phenomenon is very useful to support the employment of this phase, as a catalyst in the conversion of n-butane to maleic anhydride and it is very good sign of expected catalytic activity.The oxidation state of Vanadium ion and the percentage distribution for V (5+), V (4+) and V (3+) in the bulk of precursors are studied for supported and unsupported phases by using redox titration technique. The results indicated that in the presence of the support the vanadium ion oxidation states change towards (4+) oxidation state.Desorption at Argon temperature technique was used for specific surface area determination. The results state that there are significant increases in the specific surface area when adding support to the intermediate phase VOPO4.2H2O (16 m2.g -1) and the result show an increase in this value for supported VO (H2PO4)2 (11 m2. g -1). A specific surface area value for supported phase is reported here for the first time.The X- ray photoelectron spectroscopy (XPS) technique was used in order to study the surface chemistry of the two precursors (VOHPO4.0.5H2O), and VO (H2PO4)2 and the intermediate phase VOPO4.2H2O. The results pointed out the presence of structural elements (V, P ,O), and detectable percentage of inorganic impurities on the surface and also imply the presence of Nitrogen (N 1s) which is attributed to ammonium metavanadate, This compound was used as intermediate in technical grade vanadium pentoxide preparation. The results also suggest the presence of several oxygen species on the prepared phases. The results also indicate that the average oxidation state for prepared precursors on the surface is (5 +). By using this technique which can offer the (P/ V) atomic ratio, the prediction of catalytic activity of supported phase can be assumed.The Lewis and Bronsted acidity centers on the surface of the samples were effectuated by adsorption of Pyridine and 2, 6- Dimethyl pyridine adsorption. The results indicated the doubled value of Lewis acidity centers in the presence of the support in VO (H2PO4)2 phase (2.050 X107 mol. m2) for unsupported sample and (4.420050 X107mol.m2) for supported sample). This is another signal to predict the activity as mentioned in the literature.The investigation of the surface of the prepared phase's samples has indicated the formation of lamellar crystalline character which is identical to those proposed by literature. Finally, the combination between energy dispersive X-ray (EDX) techniques with Scanning Electron Microscope (SEM) technique was carried out on samples in order to reach the elementally atomic percentage down to depth of 1 µm from the surface. The results indicated the presence of TiO2 in selected spots. In general this work emphasize on the intercalation phenomenon between structure layers and solid solution formation through out several analysis which are made. This work can predict enhancement of Vanadyl Acid Phosphate VO (H2PO4)2 prepared phase by the presence of TiO2 as a support in the n-butane oxidation to Maleic Anhydride.
