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Nanosphere and nanotube titanates (TNT) amalgamated with different graphene oxide (GO) ratios synthesized by one pot microwave irradiation route have presented excellent potential towards hydrogen production photoelectrochemically under solar irradiation. The hybrid nanospherical array of the 50TNT-50GO photocatalyst showed a current density equal 9.2 mA cm-2 at a bias of 0.20 V vs. RHE exceeding those of the nanotubes 30TNT-70GO (4.0 mA cm-2 at 0.38 V) and 10TNT-90GO (3.7 mA cm-2 at 0.4 V). The former electrode also exhibits small Tafel slope value (40 mV dec-1), decreased particle diameter (7 nm), decreased band gap (2.6 eV) and high rate of charges transfer. The hybrid structure elucidation carried out using TEM-SAED, XRD, N2 adsorption, UV-Vis, FTIR and PL techniques approved the interfacial interaction between TNT and GO(RGO) networks that was responsible for the high quantum yield, delay of charges recombination beside the increase in the pore volume.

Zinc oxide (ZnO) nanocrystallites with different weight ratios are incorporated into carbon nanotubes (ZnO/CNTs) or graphene oxide (ZnO/GO) nanohybrids using ultrasonication/hydrothermal approach. The produced nanohybrids were tested in heterogeneous photocatalytic degradation of methylene blue dye (MB) under visible light illumination and in-situ ultrasonication. The zinc oxide incorporated carbon nanotubes nanohybrid having about 70 wt% of ZnO (ZnO(70)/CNT) showed marked visible light photocatalytic activity enhancement for MB degradation (99%, 0.5 g/L catalyst, 0.015 min−1) compared to the rest of the nanohybrids. The performance of MB degradation using ZnO(70)/CNT nanohybrid was even enhanced during employing the dual sonophotocatalysis approach achieving a rate constant of 0.019 min−1. This arises from the structural advantages at the ZnO(70)/CNT interface by which an improvement in electronic conductivity, facile electron transfer, charge carriers separation and increased oxygen vacancies were thoroughly achieved. This was highly ascertained via the catalysts characterization performed via many physiochemical techniques including XRD, TEM-SAED, FTIR, UV–Vis diffuse reflectance, and electrical conductivity, IPCE, PL and EIS. The scavenger studies of the photocatalytic and sonophotocatalytic processes of the MB degradation using ZnO(70)/CNT illustrate the importance of OH (followed by an electron) and holes (followed by OH), respectively proposing the importance of direct and indirect production of OH; as a strong oxidizing moiety.

WS2 nanoplates modified with either Ag2O (~10 nm, Ag2O/WS2) or Ag2S (around 25–35 nm; Ag2S/WS2) nano-architectures were constructed by a deposition followed by a hydrothermal approach, to form innovative p-n hetero-junction photocatalysts. The Ag2S/WS2 catalyst exhibited a marked photo-catalytic degradation (λ > 430 nm, 160 W) of diclofenac (DCF; 0.060 g/l) through H2O2 (1 × 10-4 M) under visible light illumination (K = 43.6 × 10-3 min-1) exceeding that of Ag2O/WS2 (K = 25 × 10-3 min-1). The enhanced performance of Ag2S/WS2 is attributed to anchoring Ag NPs and to the strong coupling of WS2 nano-plates with Ag2S composing higher surface area and pore volume values (26.172 m2/g, 0.073 cc/g). The detected active species during DCF degradation implicates that •O2⁻ was the major radical species. This work also studied the different influences of some dissolved inorganic ions, e.g., Cl–, PO43–, and HCO3−, on a simulated DCF degradation procedure. A remarkable photochemical activity towards H2 generation is accomplished on the heterostructure Ag2S/WS2 (1220 μmol g−1) facilitated by very low amounts of Ago and surface roughness. It was deduced that the ratio of Ag nanoparticles manipulates both the degradation and water splitting reactions since it affects the accessible number of active sites.

Well dispersed α-Fe2O3@Fe3O4 nanoparticles (7 nm) supported on mesoporous nitrogen doped titanium dioxide (N-TiO2) are synthesized by deposition self-assembly route and their performances as photocatalysts toward methylene blue (MB) degradation are evaluated. The results illustrate that the spherical yolk-shell structure of α-Fe2O3@Fe3O4@N-TiO2 at the loading of 1%; of excellent SBET (187 m2 g−1) and pore volume (0.50 cm3 g−1), achieved high photocatalytic performance for the MB degradation (20 ppm, λ > 420 nm, lamp power = 160 W) under visible light illumination (k = 0.059 min−1). The influence of the interface formation between α-Fe2O3@Fe3O4 and n-TiO2 affects severely the charges separation efficiency and enhances the electron transfer to keep on the existence of Fe3+/Fe2+ moieties; those take significant role in the reaction mechanism. The existence of the latter junction is affirmed via XRD, TEM-SAED, Raman and FTIR techniques whereas, the photogenerated charges, their separation together with their transport and recombination rates are depicted via photoluminescence, electrical conductivity, incident photon to current efficiency (IPCE), cyclic voltammetry (CV) and impedance (EIS) measurements. The catalyst loading, zero point charge, pH variation, total organic carbon (TOC%) and the effect of lamps power are thoroughly investigated. The 1%α-Fe2O3@Fe3O4@N-TiO2 photocatalyst also indicated high activity as a Fenton-like reagent accomplishing the MB degradation (100% removal) in 35 min with a rate of 0.07 min−1 at H2O2 concentration of 0.4 mM. The obtained results demonstrate that the heterojunction nanoscaled materials possess superior visible-light driven photocatalytic activity with appreciable recyclability and promising utilization as a supercapcitor (426 F g−1 at scan rate of 5 mV s−1) device.

Due to the undesirable consequences of using platinum in direct methanol fuel cells, including high cost and voltage loss due to CO poisoning, new metals, such as silver, palladium, and nickel, have been examined. These new metals have shown promising results as electrocatalysts in methanol oxidation. The mechanistic aspects of these nonplatinum metals, either in pure form or in the form of composites with oxides (either in acidic or alkaline media), have been thoroughly reviewed and discussed in this chapter. More emphasis has been directed toward correlating the morphological characteristics, chemical compositions, synthesis conditions, and structural variations of these metals with their electrochemical performances. In addition, a comparison of the electrochemical performances of these metals with platinum-based anode catalysts has also been summarized, mentioning the existing challenges that should be addressed in order to enhance their performances.

WO3 nanoplates modified with either Ag2O or Ag2S nano-architectures were synthesized by a deposition-hydrothermal route (180 °C for 5 h). They were characterized using X-ray powder diffraction, N2 sorptiometry, Transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, Photoluminescence spectroscopy, and X-ray photoelectron spectroscopy. The photo-catalytic (λ > 420 nm, 160 W) degradation of Diclofenac (DCF; 60 mg/l), was achieved using H2O2 (1 × 10−4 M) with either Ag@Ag2O/WO3 (K = 32.0 × 10-3 min-1) or Ag@Ag2S/WO3 (K = 7.3 × 10-3 min-1) catalysts. In the case of DCF degradation using radical scavengers, O2− played a key role in the degradation process whilst OH and holes acted moderately minor roles. The possible DCF degradation paths and intermediates were assessed by LC–MS. Both Ag@Ag2O/WO3 and Ag@Ag2S/WO3 catalysts were used in the photo-reduction of 4-nitrophenol (4-NP; 1.8 × 10−4 M) to 4-aminophenol (4-AP) with rate constants equal 8.3 x 10−3 min-1 and 1.6 x 10−3 min−1, respectively.

An approach involving ultrasonic irradiation/hydrothermal route was employed for fabricating a series of ZnO nanospheres-carbon nanotubes (Z/CNT) and reduced graphene oxides (Z/GO) nanocomposites, at different weight % ratios of both. The synthesized catalysts were tested in heterogeneous photocatalytic degradation of 4-nitrophenol (4-NP, 10 ppm) via Fenton approach in the attendance of visible light irradiation (160 W, λ > 420), ultrasonic illumination (60 W, 20 kHz) and during coupling the latter irradiations (sonophotocatalysis). The experimental parameters for the Photo-Fenton degradation of 4-NP at the surface of the Z(70)/CNT(30) catalyst were 40 mM H2O2, pH 4, catalyst dosage of 1.75 g/L and at 25 °C. The rate constants of 4-NP degradation using the sonophotocatalytic approach (0.3 min-1); that takes 15 min to accomplish, exceeded those of sonocatalytic (0.15 min-1) and photocatalytic (0.06 min-1) systems, unveiling the synergistic performance of the former system. These values were lower when performing the reaction at the same conditions but at pH 11 to elucidate the importance of the slow releasing of ∙OH in the acid range. The sono- and photo- coupled irradiations induced a synergy percentage comprised of 30 to demonstrate the efficacy of the adopted approach and the catalyst in the degradation of 4-NP.

TiO2 synthesized using polymeric template consisting of polyethylene glycol and polyvinyl alcohol (Tev) and loaded with different wt% of Ag (2%, 6%) was exploited to create covalent bonds with carboxylate functionalized SWCNT/MWCNT moieties. The synthesized Ag free Tev–SWCNTs as well as Ag containing Tev–SWCNTs/MWCNTs have been characterized by UV–visible diffuse reflectance, powder XRD, HRTEM, and selected area electron diffraction (SAED), photoluminescence, Raman, FTIR and N2 sorptiometry. The materials containing Ag displayed high photocatalytic activity towards degradation of rhodamine B dye under visible irradiation (λmax > 450 nm). Specifically TevAg6–SWCNT has shown the best performance (0.3 g/l catalyst, 20 ppm RhB conc. and 80 min reaction time) due to the synergistic effects derived from TiO2/Ag°/SWCNT heteroarchitectures. The antibacterial activity of synthesized photocatalysts; under visible light irradiations, towards Escherichia coli and Staphylococcus aureus was tested by performing bacterial DNA and agar well diffusion method. The results revealed that TevAg6–SWCNT was able to effectively kill both gram-positive and gram-negative bacteria. Although TevAg6–SWCNT indicated higher Eg values (1.9 eV) than TevAg2–MWCNT (1.75 cV) and they both exposed not only Ag° nanoparticles but also Ag2O, the former sample confirmed more lethal action against bacterial growth as well as superior photodegradation activity. This was due to delaying the recombination of electrons and holes, increasing the SBET value as well as decreasing the spherical nanoparticles of Ag° to 3 nm diameter. The mechanisms of the dye degradation and destruction of bacterial cell membranes indicate the efficacy of OH and O2 − as reactive radical intermediates in both processes.

Bismuth oxide, tin oxide and Pd metal (Pd/SnBi3SG) hybrids, synthesized via sol–gel technique while employing polyethylene glycol template at a ratio of 3 (Bi/Sn = 3) were tested toward the photocatalytic oxidation of fluorene under ultraviolet and visible light irradiations in comparison with Pd/BiSG and Pd free SnBi3SG photocatalysts. These catalysts were characterized using X-ray diffraction (XRD), UV–vis diffuse reflectance (DRUV–vis), N2 sorptiometry, Raman spectroscopy, transmission electron microscopy (TEM) and GC–MS technique, which used for analyzing the photo-oxidation products. The actual photocatalyst exhibited the highest activity (100% conversion, TOF ≈ 9.4 × 10−6 s−1, fluorenone/fluorenol = 3/1) following oxygen flushing for 30 min (35 ml/min) before UV irradiation. This was mainly due to the close proximity between β-Bi2O3 and Bi2Sn2O7 heterojunction as well as increasing the mesoporosity margin comparatively. On the other hand, the Pd/BiSG catalyst that exhibited smaller crystallite size (20 nm vs. 44 nm) and higher surface area (21.0 vs. 12.0 m2/g) than Pd/SnBi3SG indicated lower activity (Pd/BiSG, 72% conv.). This highlights the importance of the modified electronic structure of Pd/SnBi3SG in designing efficient charge separation as well as high quantum yield value (Φ ∼ 0.1 ± 0.05) exceeding that of Pd/BiSG (3 × 10−2) and SnBi3SG (10−2) photocatalysts. The catalytic behavior and mechanism, reactivity–structure relationship and recyclable use of the hybrid photocatalysts have been thoroughly examined. An indirect chemical probe method using active species scavengers elucidated that the photo-oxidation mechanism was proceeded via holes and O2 − moieties rather than singlet oxygen moieties.

The asymmetric unit of the title compound, C10H8BrN3O2, contains two independent molecules differing primarily in the orientations of the allyl substituents [N—C—C=C torsion angles = −125.4 (16) and 116.0 (16)°]. The crystal packing involves slipped π–π stacking of indazole units, together with weak C—H...O and C—H...Br hydrogen bonds. The crystal studied was refined as a two-component twin.

In the title compound, C14H11N3O2, the indazole portion is planar to within 0.022 (2) Å and subtends a dihedral angle of 65.87 (7)° with the pendant benzene ring. In the crystal, oblique stacks of molecules extending along the a-axis direction are generated by π–π stacking interactions between the five- and six-membered rings [centroid–centroid separation = 3.6743 (19) Å] and the stacks are cross-linked by C—H...O hydrogen bonds.

Photocatalytic oxidation of neat cyclohexane (CHA) with H2O2 as an oxidant was carried out using gold modified versions of several types of materials, including titania nanotubes (Au/TNT), reduced graphene oxide (Au/RGO) as well as titania nanotubes–multiwalled carbon nanotubes composite (Au/TNT–MWCNT) under UV irradiation (125 W, λ > 296 nm). The synthesized nanoparticles were characterized using physical adsorption of nitrogen, X-ray diffraction, transmission electron microscopy and ultraviolet-visible diffuse reflectance spectroscopy, and the reaction products were analyzed by GC-MS. Both Au/RGO and Au/TNT–MWCNT catalysts promoted partial CHA oxidation with higher conversion (6–9.0%) and selectivity (60–75%) for cyclohexanone, exceeding Au/TNT, TNT–MWCNT and TNT catalysts (conv. 2.1–4%, sel. 32–55%). Au/TNT–MWCNT synthesized using hydrothermal deposition methods exhibited the highest catalytic activity. This was chiefly attributable to the high surface hydrophobicity of MWCNT that accelerated CHA adsorption, bonding of cyclohexanol and cyclohexanone to TNT as well as decomposition of H2O2 on gold nanoparticles. Increasing the surface area as well as decreasing the average particle size of Au0 to 15 nm of hexagonal shape contributed to the superior catalytic activity of Au/TNT–MWCNT, in achieving an average rate of 0.0035 mmol−1 g−1 min−1 and conversion was 9.0% after 12 h of reaction. The latter catalyst exceeded industrially synthesized Co based catalysts (3.6%) operated at high temperatures. For confirming the autoxidation process, a radical scavenger offered a proof that the oxidation follows a radical-chain mechanism. The differences in surface morphology, light absorption and surface properties of Au/TNT when incorporated with MWCNT were well investigated. The photocatalytic oxidation mechanism elucidated using active scavengers suggested that OH˙ and O2˙− play key roles in the oxidation of CHA.

The asymmetric unit of the title compound, C9H6ClN3O3, contains one full molecule in a general position and a half molcule sitting on a crystallographic mirror plane. In the crystal, molecules form stacks extending along theb-axis direction through a combination of offset π–π stacking between indazole units and C—Cl...π(ring) interactions with the six-membered rings of the same units. Elaboration of the C—Cl...π(ring) interactions along thea-axis direction forms slabs of molecules parallel to [001]. The stacks are joined by a combination of C—H...O and C—H...N hydrogen bonds.

In the title compound, C9H8ClN3O2, the terminal C atom of the ethyl group deviates from the indazole ring (r.m.s. deviation = 0.008 Å) by 1.588 (3) Å. The dihedral angle between the ring system and the attached nitro group is 2.8 (3)°. In the crystal, weak C—H...O interactions link the molecules into zigzag chains propagating along [001]. In addition, weak π–π stacking interactions [centroid–centroid separations = 3.6809 (10) and 3.7393 (11) Å] help to consolidate the packing.

In the title molecule, C9H7N3O3, the indazole moiety is essentially planar and the mean plane of the acetyl substituent is twisted by 5.3 (1)° from its plane. In the crystal, weak C—H...O and C—H...N hydrogen bonds form layers parallel to (102), which are associated through π-stacking interactions to form a three-dimensional network. The structure was refined as a two-component twin.

In the title compound, C9H8ClN3O2, the orientation of the ethyl substituent is partly determined by an intramolecular C—H...Cl hydrogen bond. The indazole moiety is slightly folded with an angle of 0.70 (8)° between the five- and six-membered rings. In the crystal, molecules pack in layers parallel to [100] through C—H...π(ring) and N...;O...π(ring) interactions.

In the title compound, C10H10ClN3O3, the side chain is oriented nearly perpendicular to the mean plane of the indazole ring system. In the crystal, complementary sets of O—H...N and C—H...O hydrogen bonds form chains of molecules stacked along thea-axis direction

The asymmetric unit of the title compound, C11H11N3O4, comprises two independent molecules, both of which display positional disorder of their ethyl chains in 0.868 (4):0.132 (4) and 0.839 (4):0.161 (4) ratios. The packing is directed by a combination of C—H...O hydrogen bonds and N—O...π interactions between nitro groups and the aromatic rings.

The asymmetric unit of the title compound, C18H23ClN6O2, consists of two independent molecules differing primarily in the dihedral angles between the mean planes of the indazole and triazole moieties [78.50 (8) in one and 72.39 (7)° in the other]. One of the molecules shows positional disorder of the terminal part of its octyl chain. In the crystal, C—H...X(X= Cl, N, O) hydrogen bonds and C—H...π and π-stacking interactions are observed: together these generate a three-dimensional network.

Herein, we report the synthesis of MoO3−x nanorods via an environmentally solvothermal/annealing route, which involves refluxing of an ethanolic solution of (NH4)6Mo7O24.4H2O for 5 h at 70 °C followed by drying and calcination at 350 °C for 2 h. Graphene oxide (GO) incorporation at 1% ratio into MoO3 increases the oxygen deficient ratio (20.6%) compared to GO free MoO3 catalyst (17.3%), as emphasized by XPS results. A comprehensive characterization using XRD, TEM-SAED, UV–vis, FTIR, Raman, photoluminescence and N2 sorptiometry was illustrated. The irregular circular shape of 1%GO.MoO3−x; of Eg equal 2.7 eV, and an average diameter of 40 nm has shown higher photocatalytic action towards MB degradation (20 ppm) under visible light illumination (160 W, >420 nm) giving a rate constant of 0.016 min−1 exceeding that of MoO3−x by 18 times. Although 1%GO.MoO3−x exhibits lower surface area and pore volume than those in GO free MoO3−x, the potentiality of the former is mainly dependent on the strong linkage formed between MoO3−x and graphene sheets. Based on increasing the oxygen deficiency in 1%GO.MoO3−x, powerful oxidizing moieties are depicted to affect the MB degradation including in situ generated H2O2, O2¯ and O H species. The gas sensing property of 1%GO.MoO3−x towards 100 ppm NH3 at 200 °C was increased by 6.4 times that of GO free MoO3−x nanorods. This was mainly due to the hetero-junction formed between n-(MoO3−x) and p-type (partially reduced GO) conducting channels; affirmed via Mott-schottky plot, and the facile electron transfer from GO into MoO3−x. The mechanism of the oxygen deficit 1%GO.MoO3−x structure is also discussed, exploring that this type of sensor has a promising application to other reducing gases. The 1%GO.MoO3−x sensor exhibited long-term stability at different NH3 concentrations as well as high selectivity exceeding the corresponding pure counterparts.

Graphene oxide (1–3 wt %) interspersed on nitrogen doped mesoporous TiO2 (N-TiO2) and synthesized via deposition-precipitation technique was characterized using XRD, TEM-SAED, N2 sorptimetry, FTIR, Raman and UV–vis diffuse reflectance spectroscopy. Inspiringly, the nanoplatelets 2 wt%GO/N-TiO2 exhibited the highest photocatalytic performance than rest of nanophotocatalysts over the degradation of methylene blue dye (MB; 20 ppm, k = 0.0146 min−1), phenol (15 ppm, k = 0.0045 min−1) as well as a mixture of both (k = 0.02 min−1) under visible light irradiation. The characterization results validated that the high activity is basically depends on the intimate contact formed between N-TiO2 and GO that facilitates not only photo-generated charges transfer but also helps delaying their recombination, as confirmed from electrical conductivity, IPCE%, cyclic voltammetry and impedance results. Other parameters such as structure, morphology, surface texturing and optical properties verified the importance of decreasing the band gap (1.6 eV), crystallite size decrement (7 nm) and pore volume (0.42 cm3 g-1) enlargement than small differences in surface areas and shape similarity. Photoelectrochemical (PEC) experiments also demonstrate that the photocurrent density of 2 wt%GO/N-TiO2 is greatly boosted (3.9 mA cm−2) compared to rest of photocatalysts (1.6–2.4 mA cm-2) and pristine N-TiO2 (0.4 mA cm−2). The specific mechanistic information imposed the major role of OH and electrons together with the synergistic effects manifested from N and Ti3+ moieties. The application of the photocatalyst 2 wt%GO/N-TiO2 in treating El Manzala Lake-Egypt from humic acids (146.0 ppm); attained from different sources, has shown fascinating activity as established from COD and TOC analyses.

Silver nanoparticles were successfully assembled in self-organized polyhedral TiO 2 ; synthesized by hybrid template consisting of pluronic-85, hexadecyltrimethylammoinm bromide and triethanol amine (TPHtAg 2 ), as well as in platelets TiO 2 ; synthesized only via hexadecyltrimethylammonium bromide (THAg 2 ). X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, diffuse reflectance UV–vis spectroscopy as well as N 2 sorptiometry were used for the characterization of phase composition, surface morphology, valent states of Ag/TiO 2 , optical and surface texturing properties. These nanomaterials were tested as catalysts for 4-nitrophenol (4-NP) reduction in presence of aqueous NaBH 4 under visible-light irradiation. The results showed that the THAg 2 catalyst exhibited the best photocatalytic performance in the reduction of 4-NP into 4-aminophenol (4-AP) and revealed 98% conversion following 2 min irradiation with rate constant equal 0.025 s −1 . On the other hand, the TPHtAgS 2 catalyst, derived from using Ag 2 SO 4 as a precursor instead of AgNO 3 , indicates a conversion comprised of 80% at similar reaction conditions. The superiority of the photocatalytic reduction of THAg 2 was due to exposing Ag + ions together with Ag 0 nanoparticles (5 nm) and to the photo-induced role of carbon atoms; formed as a result of the non-complete decomposition of the template, and its synergistic effect with the anatase phase. On the contrary, TPHtAg 2 showed strong chemical interaction of Ag + ions within the hybrid templates and as a result inhibits the reduction of Ag + ion as well as the adsorption of 4-NP and eventually indicates no activity. The decreased activity and stability of TPHtAgS 2 compared with THAg 2 was due to increasing the particles size of Ag 0 (10 nm), diminishing the accessibility and reactivity of Ag + ions; which could have been worked as trapping sites with Ag o , and the limited effect of residual S 2- ions, depicted from XPS measurements.

Hybrid TiO 2 nanostructures with engineered morphologies (flakes, spheres and buds) supporting Ag nanocrystals were produced by a simple synthetic approach based on cooperative sol–gel chemistry of either titanium iso-propoxide or n-butoxide and self-assembly of polyvinyl alcohol with polyethylene glycol. The as-synthesized catalysts were characterized using XRD, TEM, DRUV–Vis, N 2 sorptiometry and FTIR spectroscopy and their performances toward 4-nitrophenol (4-NP) reduction were also investigated. Among the structures investigated, the catalyst derived from n-butoxide (Ttev) exhibited the best catalytic performance in the reduction of 4-NP to 4-aminophenol (4-AP) in 2 min with 100% conversion when loaded with 2% Ag ions (TtevAg 2 ). In concordance, the TevAg 6 catalyst; derived from isopropoxide, of bud shape and particle sizes of 20 nm showed a comparable activity to that of TtevAg 2 and exhibited a rate constant of 6.9 × 10 −3 s −1 resembling that of 7.2 × 10 −3 s −1 for TtevAg 2 exceeding that of TevAg 2. Enhancing the activity of TevAg 6 and TtevAg 2 compared to TevAg 2 was rationalized in terms of the surface content of Ag o nanoparticles of medium sizes (15–20 nm) inside mesoporous network of TiO 2 of tailored morphology (proportional amounts of buds and spheres structures) as well as pore volume values. No deactivation for the former catalysts was observed after repeated recycling.

Copper phthalocyanine (CuPc) complexes either deposited on alumina (CuPc/Al); synthesized by sol–gel, or encapsulated inside zeolite-X (CuPc/ZX) while in situ synthesis were characterized by X-ray diffraction (XRD), DSC, FT-IR, diffuse reflectance UV–vis, dynamic light scattering and N2 adsorption techniques. These materials were tested for photocatalytic oxidation of cyanide in comparison with ZX and CuPc free complex. Unlike the case on Al, CuPc was accommodated inside ZX, as confirmed from lattice parameter increment (from 25.101 of ZX to 25.250 A of CuPc/ZX) and decreasing both SBET and pore volume (705 m2/g, 0.550 cm3/g) as compared to the neat zeolite (837 m2/g, 0.684 cm3/g). Bending modes vibrations of δC–H showed bands at 1041 and 970 cm−1 for CuPc/Al where CuPc/ZX did not, suggesting that these bonds are formed while CuPc vibrating on the former. Contrarily, they are restricted in the latter proposing accommodation of the complex inside zeolite cages as emphasized from ΔS values that showed marked decrease in disorderness (−29 J/mol K) compared with CuPc (−13 J/mol K). In accordance, Q band revealed a red shift from 614 to 632 nm. A very strong photo-oxidation capability of oxidizing CN− was exhibited for the encapsulated complex (CuPc/ZX; 100% removal in 1 h; rate constant = 0.1 min−1) comprehending the importance of electron transfer reactions within ZX to external surfaces, and the zeolite framework that seems participating efficiently in the electron transfer process.

Manganese (10 wt.%) supported on titania synthesized by sol–gel (Mn/TiO 2SG ) and impregnation (Mn/TiO 2D-imp ) methods in addition to their precursors TiO 2SG and TiO 2D (Degussa) materials were characterized by measuring the surface texturing, Fourier transform infrared spectroscopy, X-ray diffraction, particle size (analyzer) and electrophoretic mobility (zeta potential). These materials were tested for adsorption and mineralization (in the presence of UV irradiation) of indigo carmine (IC) dye. Through comparison of the results, the photocatalytic degradation of Mn/TiO 2D-imp indicated the highest activity (98%) comparatively. This was due to 34% of the support titania is covered by Mn species in Mn/TiO 2D-imp mainly as Mn 2 O 3 moieties, as validated from IR results (605, 714 cm −1 ). On the other hand, Mn in Mn/TiO 2SG was incorporated in titania lattice mainly in tetrahedral coordination sites as β-MnO 2 (655, 693 cm −1 ) and only exposes surface coverage comprises of 10%. The adsorption of IC dye onto TiO 2D was considerably higher (88%) than rest of materials due to increasing OH groups, large surface to volume ratio and moderate pore radius (33 Ǻ) that was accessible to facile IC diffusion. TiO 2SG and Mn/TiO 2SG presented lower activity either in adsorption and photocatalysis compared with Mn/TiO 2D-imp . There is no apparent size effect on IC degradation over former catalysts since they have comparable values (48–43 nm). The influence of time on the decolorization rate of IC on Mn/TiO 2-Dimp was thoroughly investigated and well pH regulated and correlated with ZPC of MnO x species and surface properties.

Titanium-mordenites catalysts prepared by impregnation (TiMimp), solid-solid interaction (TiMss) and in situ incorporation during synthesis (TiMin); using ortho-phenylenediamine as a new templating agent under hydrothermal conditions (TiCl4, 160 °C, 6 days), were thoroughly characterized by TG/DTA, N2 adsorption, XRD, FTIR, UV–vis and pyridine-FTIR. They were tested; in comparison with TiO2 Degussa, for degradation of meta-chlorophenol (MCP) in the presence of UV-light irradiation. It was possible to correlate the results obtained for MCP degradation over various catalysts with their structural and acidic properties. The photocatalytic degradation of MCP has been modeled to Langmuir-Hinshelwood rate law. TiMss showed the highest degradation rate (0.060 min−1) followed by those of TiMimp (0.050 min−1), TiMin (0.025 min−1) and TiO2-Degussa (0.018 min−1), respectively. The marked higher rate observed for the former catalyst was due to the larger pore radius (29 A), acidity and the extra-framework TiO2 anatase species (of absorption at 340 nm). Very strong emphasize to the state of titania within the three samples (TiM) was demonstrated and most importantly Si O Ti linkages (950–940 cm−1) were observed and correlated with photoactivities of all samples. Degradation products of MCP, including both aromatic and aliphatic intermediates, were monitored by HPLC. Chloride ions, on the other hand, were followed up during the degradation processes. Formic acid (formate) was identified as a final intermediate in the solution before it further mineralized to CO2. Reasonable degradation pathway for MCP molecule is proposed on the basis of structural identification of several by-products.

Nano-structured titanium dioxide materials were synthesized hydrothermally (TiCl4, 353 K, 5 days) via assembling through cationic surfactants in particular cetyltrimethylammonium bromide (CTAB) and cetylpyridinum bromide (CPB). The bulk chemical and phase compositions, crystalline structure, particle morphology, thermal stability and surface texturing were determined by means of X-ray powder diffractometry (XRD), Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermal analyses (DTA/TGA) and N2 sorptiometry. The acidity of synthesized materials was studied by FTIR spectroscopy of adsorbed pyridine as a probe molecule. The results revealed that the crystallites size of all materials lie in the range of 10.1–18.2 nm and organized in a morphological structure that change from nano-sized spheres to cotton fibrils shape. Surfaces thereon exposed were found to assume high specific areas (240–418 m2 g−1) and micro–mesoporous surfaces with pore size in the range 23.2–43.7 A. Rutile phase was only produced for all TiO2 materials assembled by cationic surfactants following heating up to 623 K. The transformation of rutile to anatase TiO2 was coincided with the developed interaction between vanadia and titania assembled by CPB template. The V in the resulting vanado-titanate was entirely incorporated in TiO2 structure. The as-synthesized phases of either rutile or anatase were maintained after calcining at 973 K exhibiting a significant thermal stability. Pyridine adsorption at RT indicated the involvement of acid–base site pair on all TiO2 assembled by cationic templates where that prepared by conventional method only exposed Lewis and Bronsted acid sites with a higher tendency to the latter comparatively.

Hydrothermally synthesized ZSM-5 zeolites using tetrapropyl-ammonium bromide (TPA-Br), Xylitol (Xy) and tetrapropyl-ammonium bromide + Xylitol templates; those compared with that of the parent having the same Si/Al molar ratio (64) and purchased from Mobil, were characterized with several physicochemical techniques including N2 adsorption, XRD, TG/DSC, FTIR and pyridine-FTIR. The effect of various templates on the crystallinity, crystallites size, surface properties and thermal stabilities of the produced ZSM-5 were investigated. ZSM-5 synthesized using TPA-Br + Xy; of S BET = 393 m2 g−1, exhibited a crystallinity percentage comprises of 142% when compared with that of the parent (taken at 100% crystallinity) and measured as well a crystallites size of 61 nm exceeding that derived from Xy (41 nm) that measured the lowest crystallinity percentages (71%), lowest S BET (303 m2 g−1) and highest yield (65%) between all samples. The former sample showed high thermal stability (till 1,000 °C) when compared with that derived from TPA-Br, as illustrated from TG/DSC thermograms that provided a criteria on decreasing the pore radius as a result of enclosing appreciable amounts of TPA+ and Xy inside narrow pores of ZSM-5. This sample also indicated a hydrophobic tendency when compared with that devoted from TPA-Br. Pyridine adsorption measurements showed that addition of Xy to TPA-Br stimulate the existence of basic sites in addition to acidic ones (mainly Bronsted ones) that was in the middle between that derived from Xy and TPA-Br templates. More infomations on the textural properties, morphologies, vibrational tetrahedral co-ordination T(Si or Al)–O modes and acidity were evaluated and discussed.

Alkylnaphthalene succinimides are synthesised and evaluated as flow improvers, pour point depressants and ashless dispersant additives for fuels and crankcase lubricating oils. The synthesis is based on reacting alkylated naphthalene with maleic anhydride in the presence of the following amines: ethylene diamine, diethylene triamine and tetraethylene pentamine. Chlorinated paraffin wax is used as an alkylating agent for naphthalene. Results showed that magnitude in pour point depression as well as cold filter plugging point depression for the tested fuels are highly related to the molecular weight of alkylnaphthalene succimides

Nanostructured titanium dioxide and vanadium oxide supported over titanium dioxide was synthesized using a template synthesis route method under hydrothermal conditions (at 353 K for 5 days) via sodium dodecyl sulfate surfactant. The influence of pH (2.0–9.0) and thermal treatment (623 and 773 K) on the structural, surface acidity and textural properties of TiO2 and V2O5/TiO2 materials was investigated using XRD, thermal analyses, SEM, FTIR, N2 adsorption and pyridine-FTIR measurements. The synthesized TiO2 and V2O5/TiO2 showed high mesoporosities with different pore sizes ranging from 24.6 to 40.6 A and exhibited nano-sized crystals varying from 7.5 to 15.1 nm. All templated samples exhibited very high surface areas; commencing from 263 to 465 m2/g, as well as pore volume up to 0.73 cm3/g. The synthesized samples exhibited a pure anatase crystalline phase for TiO2 in the pH range 4.8–9, in which substantial amounts of mesopores were developed where that prepared at pH = 2.0 showed the formation of only rutile phase with higher affinity to micropores. Surface acid strength was greater for highly dispersed V containing TiO2 due to a strong interaction of the VOx species with support centers that act as electron attractor centers creating Lewis acid sites. It was found that pH has a paramount effect influencing both the nature of pores and the type of TiO2 formed. The photocatalytic reduction of Hg2+ in water by UV irradiation was chosen to evaluate the activities of the synthesized materials.

Sulfated (5 wt.%) TiO2 and non-sulfated TiO2 (rutile) modified by NH4VO3 using incipient wetness impregnation technique to achieve a loading of 2 wt.% V2O5 were thoroughly characterized by means of X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV–vis absorption spectroscopy, N2 sorptiometry, particle size analyzer and pyridine-FT-IR that was used to investigate the acidity of the samples. Degradation of methylene blue (MB) dye was tested for the effectiveness of the samples. The results revealed that MB degradation was highly improved with V supported on TiO2–SO4 and showed a conversion comprises of 98% after UV irradiation (emitting at 400 nm) for 70 min exceeding that of SO4 free TiO2 sample (78%) obtained at the same period of illumination. This was due to the large surface area (345 m2 g−1), small crystallites size, reduced band-gap energy and presence of basic sites namely O2− and OH− moieties those take part in the reaction as additional oxidizing agents. The photocatalytic degradation of MB was found to follow first order rate kinetics. More information on the activity, surface texturing, kinetics and TOC removal were well evaluated, compared and discussed for all samples.

Aqueous solutions of cerium nitrate of increasing concentrations (2.5, 5 and 7.5 wt.% Ce) have been contacted with the components forming Mordenite zeolite; during forming the gel under hydrothermal conditions, for allowing the accessibility of Ce ions to proceed into compensating positions in Mordenite structure. These materials were characterized by the methods of FTIR, XRD, N 2 adsorption and UV–vis diffuse reflectance spectroscopy. The interaction of NO and CO adsorptions; at room temperature, on thermally pre-treated (300 °C, 10 −5 Torr, 3 h) as well as pre-reduced (50 Torr, 500 °C, 1 h) samples were studied by in situ Fourier transform infrared spectroscopy. XRD and FTIR results indicate that the Ce atoms are mostly present in internal surfaces in Mordenites for 2.5 and 5CeMOR samples whereas for 7.5CeMOR, a decrease in diffusion of Ce to be in compensating positions is perceived; as conceived from lowering the lattice volume, pointing to the presence of discrete amounts of CeO 2 (582 cm −1 ) and cerium silicate (Si–O–Ce; 797 cm −1 ) species. All the samples indicate intra-crystalline mesopores as depicted from V l – t plots particularly the 7.5CeMOR sample that showed the highest wide-pore volume (0.073 cm 3 /g), lowest pore radius (21 A) and thus, revealed the highest S BET between all samples (363 m 2 /g). UV–vis characterization of 7.5CeMOR sample shows octahedral Ce species (345, 360 and 390 nm) in small clusters inside zeolite channels and most probably originated from cerium silicates having different coordination with NaMOR along with discrete amounts of CeO 2 (420 nm) species. CO readily adsorbs on the Ce 3+ sites of the pre-reduced 7.5CeMOR catalyst, rather than those on Ce 4+ , to display minor amounts of carboxylate and dominant amounts of monodentate carbonate that were amenable to decompose to produce CO 2 gas (2335 cm −1 ). On the other hand, the in situ interaction of nitric oxide (NO) gas on the 7.5CeMOR catalyst led to the formation of a series of nitrosyl species: N 2 O (2240 cm −1 ), NO (1908 cm −1 ), N 2 O 3 (1880 cm −1 ) and (NO) 2s,as (1844, 1734–1720 cm −1 ). Such nitrosyl complexes were favorably formed on Ce 3+ in 7.5CeMOR those exchanged Na ones.

Hydrothermally synthesized ZSM-5 zeolite modified by manganese (Mn/ZSM-5) or lanthanum (La/ZSM-5) or mixture of both (Mn–La/ZSM-5) using impregnation technique was characterized by powder XRD, FTIR and N 2 adsorption measurements. These materials were tested for discoloration (adsorption) and mineralization (in the presence of UV irradiation) of indigo carmine (IC) dye. The results indicate that MnO x incorporated ZSM-5 that showed the highest lattice volume and pore radius between all samples presented the highest photocatalytic activity, comparatively. However, the Mn-La/ZSM-5 catalyst exhibited the lowest activity even when compared with the parent ZSM-5 sample. This was in part due to evoking of Mn 3 O 4 species at the expense of Mn 2 O 3 ones, which were proposed to be the active sites of the reaction. This reaction was found to be acidity dependent since Mn/ZSM-5 showed significant bands at 3650 and 3619 cm −1 those in contrast appeared shapely in La/ZSM-5, whereas for Mn–La/ZSM-5 only a band at 3619 cm −1 was obtained. On the other hand, the decolorization activity showed comparable high rates for Mn/ZSM-5 and Mn–La/ZSM-5 samples (100% removal) implying that the adsorption process is more referred to acid-base site pairs where the photocatalytic activity seems to be more restricted to acidic sites. The influence of pH, catalyst amount and time on the decolorization rate of IC on Mn/ZSM-5 was thoroughly investigated and correlated with ZPC of MnO x species, various exposed species of MnO x and surface properties.

The 8 wt.% MoO3-modified CeO2 materials were prepared by three different methods namely, impregnation, wet mechanical mixing and co-precipitation and characterized by thermal analyses (TG and DTA), X-ray diffractometry, infrared spectroscopy, UV–vis diffuse reflectance spectroscopy as well as nitrogen sorptometry. Their catalytic activities in the oxidation of CO to CO2 were also examined. The results showed that the material prepared by co-precipitation provided the highest activity, comparatively. This was due to the concomitant strong metal oxide-support interaction revealed for this material that validated by XRD and FTIR results those showed diminishing in particles size of the two ions and formation of Mo O Ce linkages (760 cm−1), respectively. The UV–vis spectrum of this material showed the predominant presence of tetrahedral Mo6+ reflecting the highest dispersion among all samples. This material exhibited as well the highest specific surface area (96 m2/g) and rather presented mesopores of regular distribution. Important correlations between the latter material and those prepared by impregnation and wet mechanical mixing in view of proposed interaction between ions, morphology, surface texturing and their effects on the activity of CO oxidation were evaluated and discussed. It is inferred that surface molybdate that permit the formation of Mo6+ in highly dispersed state beside the Ce3+/Ce4+ redox couples were responsible for the revealed catalytic activity.

Cetyltrimethylammonium bromide (CTAB)-modified mesoporous molecular sieve FSM-16, prepared by a hydrothermal process (373 K, 3 days), was tested as an adsorbent for acid dye (acid yellow, AY, and acid blue, AB) removal in comparison with as-prepared FSM-16 and activated carbon (AC) derived from rice husk (50 vol% H 3 PO 4 , 773 K, 2.5 h). The adsorption isotherms, sorption kinetics, and pH effects upon acid dyes sorption on the adsorbents were thoroughly investigated. The structures of different adsorbents were characterized by XRD, FTIR spectroscopy, N 2 adsorption measurements, and thermogravimetric (TG) analysis. It was found that the ultimate capacity of the adsorbents varied in the order FSM-16 > modified FSM-16 > AC and followed first-order rate kinetics. The adsorption isotherm of acid dyes on FSM-16 is of type IV, according to the IUPAC classification, drastically different from that of CTAB/FSM-16, which showed a type I isotherm. The latter sample had better adsorption performance at low concentration of acid dyes than the former. As compared to activated carbon of microporous character, the CTAB/FSM-16 sample achieved higher performance at low concentrations. This was due to the successful narrowing of the pore opening of FSM-16 using CTAB with maintenance of a considerable portion of the pore volume. Powder XRD and N 2 adsorption studies of the CTAB/FSM-16 material indicated that the textural properties of the support were preserved during the hydrothermal synthesis and that the channels remained accessible, despite a significant reduction in surface area (ca. 26%). TG studies, on the other hand, confirmed that the modified material presented a higher hydrophobicity than that of the CTAB-free FSM-16 sample.

The H-mordenite zeolite catalyzes the polymerization of N , N -diethanol acrylamide (DEAA) with phthalic anhydride (PA) yielding polyesteramide (PEA) resin. The Fe modified mordenites showed lower activity than that of H-mordenite that presented high stability on multiple recycling. The formation of DEAA; the principal step in forming PEA, was occurred through the condensation reaction of diethanol amine (DEA) and acrylic acid (AA) with 91% selectivity in addition to 9% devoted for the corresponding ester (diethanol amine monoacrylate; DEMA). The IR spectroscopic study of DEAA formation in the presence of mordenite zeolite reveals the greater affinity of the reactants specifically AA to protons that are likely to be the initiators of the DEAA formation. The formation of ester was confirmed through the appearance of a band at 1735 cm −1 attributed to the stretching vibration of CO of ester groups. A possible reaction mechanism is proposed based on data reported in the literature and the results of the present investigation. The activation energy of the DEAA formation was found to be 35.5 kJ mol −1 , for non-catalyzed and 11.46 kJ mol −1 , for the H-mordenite catalyzed one. The acidic and textural properties of the catalytic samples have been measured using NH 3 adsorption (at 150 °C) and N 2 adsorption (at −196 °C), respectively. The results obtained indicate the importance of the zeolite acid selectivity towards amide and ester formation.

Iron-modified mesoporous and microporous zeolite materials, namely FSM-16 and NaY as well as dealuminated NaY (del-NaY), were prepared using cyclopentadienyl iron dicarbonyl diamer [(C 5 H 5 )Fe(CO) 2 ] 2 via a chemical vapor deposition (CVD) technique. XRD, FTIR, TG/DSC, N 2 adsorption and Mossbauer measurements were used to characterize the various materials. An isomorphous substitution of Fe 3+ into the framework of NaY zeolite was accomplished as determined from the Mossbauer results (IS≤0.3) as well as from the increase in the unit cell volume. As a further confirmation, some framework IR bands (780 and 574 cm −1 ) showed a shift towards lower frequencies upon iron incorporation along with the existence of a band at 686 cm −1 ascribed to SiOFe linkages. The latter band was emphasized on the basis of comparison of NaY before and after the CVD treatment with the precursor of the Fe complex. Two types of octahedral Fe 3+ components were revealed in FSM-16 and del-NaY samples specified as intrazeolitic iron oxide clusters and α-Fe 2 O 3 species, which were localized on the external surfaces of zeolites and occupied small percentages (18–22%) compared with the former species. The surface area of the support NaY was preserved after the CVD treatment rather than FSM-16 that showed a reduction (24%). The catalytic activities of various samples for the liquid phase hydroxylation of phenol using H 2 O 2 were found to be in the order: Fe/NaY>Fe/FSM-16>Fe/del-NaY. The higher activity of the Fe/NaY sample was attributed to the high dispersity of Fe ions that are located in framework positions and to the high crystallinity.

Two series of dealuminated Na-mordenite zeolites (DML and DMH) were impregnated, in comparison with the parent nondealuminated NaMSP, in aqueous nitrate solutions of Cu and Ni to achieve varying loadings for both of the cations. These samples were characterized by N(2) adsorption, XRD, DSC of ammonia desorption, ammonia volumetric sorption, IR of ammonia adsorption, and FTIR-photoacoustic (FTIR-PAS) techniques. The FTIR-PAS spectrum of CuNi-loaded NaMSP shows a band at 935 cm(-1) ascribed to O(3)Siz.sbnd;Oz.sbnd;SiO(3) linkages produced as a result of dealumination caused by the synergistic effect of Cu and Ni cations under the preparation conditions. As a confirmation, this band was intensified upon acid dealumination (DML) where, at the extent of dealumination (DMH), collapsing of the zeolite structure was obtained subsequent to cation modification. In addition, the dealumination effect was markedly enhanced upon increasing the load of Cu in proportion to Ni. A total erosion of OH group characteristics of Siz.sbnd;(OH)z.sbnd;Al at 3610 cm(-1) was depicted when the Ni content exceed that of Cu where it did not show any change when the Cu content surpasses that of Ni. The amount of adsorbed ammonia measured volumetrically was enlarged after dealumination as well as after increasing the contents of the modificating cations. The IR study of ammonia adsorption revealed a band at 1428 cm(-1), in either nondealuminated or dealuminated-modified samples, assigned to stronger Bronsted acid sites than those at 1455 cm(-1). The band at 1428 cm(-1) was markedly enhanced in the latter samples than in the former. This was due in part to the replacement of the protons by cations, producing sufficiently mobile protons. In conformity, DeltaH values obtained for DSC effects via ammonia desorption were enhanced after dealumination. Other correlations with XRD and surface texturing on one hand and the structural variations following cations incorporation on the other hand are evaluated and discussed.

The transformation of ethanol on Fe ion-exchanged mordenite was compared in the temperature range of 200–400 °C for samples prepared in the solution and solid states. Ethane and methane were found as rather major products, compared to acetaldehyde and acetone. Diethyl ether was also detected as a dehydration product. The conversion was found to increase monotonically (to 96%) with increasing the Fe content (to 100%) and reaction temperature to 400 °C. The selectivity towards acetaldehyde and acetone was found maximum at the temperature 300 °C. Decrease in the catalyst Bronsted acidity due to ion-exchange in solution caused a marked increase in the selectivity toward acetaldehyde at 300 °C. At variance, Fe ion-exchanged in the solid state resulted in a higher Bronsted acidity catalyst of higher selectivity to acetone. The solid state exchanged catalyst formed more coke at 400 °C. The higher zeolite acidity catalyzes the ethane propagation into the coke precursors. The extraordinary formation of ethane as a dominant transformation product (in the absence of H 2 gas supply) is explained mainly to the O-abstracting affinity of the Fe 3+ ion. Methane may be formed as a result of decomposition reaction at high temperatures. Mossbauer and XRD were applied for characterizing different Fe species involved as active sites in the reaction. Coke deposited on the catalysts was measured by TGA. Other helpful information was obtained from BET of N 2 -adsorption and FT–IR of NH 3 -adsorption. Fair correlation between the active sites responsible for formation of the various products and the zeolite acidity is discussed along with a possible role for the surface area and pore structure in the reaction activity and selectivity.

The CeO2-modified ZrO2 support was impregnated in an aqueous solution of ammonium heptamolybdate to achieve a loading of 8 wt.% Mo. This material (Mo/Zr(Ce)) was characterized, in comparison with Mo/Zr, by X-ray diffraction, FT-IR and UV–VIS diffuse reflectance spectroscopy as well as low temperature N2 adsorption and electrical conductivity measurements. The X-ray results showed that the particles size of MoO3 on Zr(Ce) (24.7 nm) was lower than those on ceria free Zr (36.7 nm). The IR results indicated that a strong interaction between Mo species and zirconia was recognized in the Mo/Zr(Ce) sample by the appearance of a new band at 858 cm−1 attributed to a Mo–O–Zr linkage, which was not detected in the Mo/Zr sample. The UV–VIS spectra showed that both octahedral (291 nm) and tetrahedral (249 nm) Mo6+ were detected in the Mo/Zr sample where tetrahedral arrangement (246 nm) was only adopted for Mo6+ in the Mo/Zr(Ce) sample. The addition of either Ce or Mo to zirconia causes a marked increase in the specific surface area of the samples. The conductivity measurements showed that all samples exhibit a semiconducting behavior.

The surface species formed from the reaction of CO+H(2)O and CO+O(2) and decomposition of HCOOH on Au incorporated into H-mordenite zeolite have been studied by means of in situ FTIR spectroscopy. On H-mordenite, a bidentate formate species (2912, 1536, and 1390 cm(-1)) is produced upon exposure to the CO+H(2)O gas mixture at 323 K, as well as different carbonate-like species (1956, 1852, 1705, and 1360 cm(-1)). The latter species was extensively formed in a short time and was responsible for hindering the CO(2) adsorbed species. However, Au/H-mordenite presented different vibration modes of formate species with a high emphasis on the monodentate ones (2950, 2916, 2896, 1690, and 1340 cm(-1)). The HCOOH adsorption on Au/H-mordenite showed two bands at 1622 and 1590 cm(-1) of the nu(as)(OCO) species, suggesting the formation of two types of formate species. The decomposition rate of the formate species formed on Au moieties was faster than that formed on H-mordenite. This was consistent with the calculated activation energies of CO(2) formation that showed a lower value (40.1 kJ/mol) on the former sample than on the latter one (63.3 kJ/mol). A dehydrogenation mechanism is proposed (HCOOH--H(2)+CO(2)) for the decomposition of HCOOH on the Au/H-mordenite catalyst. On the other hand, the Au/H-mordenite catalyst activated the CO oxidation reaction. This reaction proceeded mainly through the formation of carboxylate species at first, which tended to obviate with time, preferring the formate species. The latter species resulted from the interaction of CO with OH stretching of the zeolite assisted by the presence of gas phase O(2). The formate species is further decomposed with time to carbonate species. Copyright 2000 Academic Press.

Sulfated Fe2O3 catalysts impregnated with different molybdenum contents varied from 2 to 42 wt.%, were examined by temperature-programmed pyridine desorption via differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The acidity of these catalysts were investigated and compared with those corresponding to SO42−/free Fe2O3 ones. ΔH values (obtained from DSC) and amounts of pyridine irreversibly adsorbed (obtained from TG) showed that the concentration of Lewis acid sites decreased with increasing Mo loading. On the other hand, the sulfated Fe2O3 supported Mo catalysts showed an increase in the concentration of acid sites to almost 10 times that of the corresponding SO42−/free Fe2O3 catalysts. In addition, the enthalpies of pyridine desorption from SO42−/Fe2O3 supported Mo catalysts were higher than those for the SO42−/free Fe2O3 catalysts. This indicated the strength of acid sites on the former samples compared with those on the later ones. Comparative FT-IR spectroscopic analyses of pyridine adsorption have been investigated to study the nature of the acid sites and to assess the effect of SO42− species on the surface acidity. It was found that the presence of SO42− species enhanced the surface acidity and helped the formation of Bronsted sites earlier at the 2 wt.% Mo loading. These were manifested by the presence of vibrational bands at 1635 and 1540 cm−1. These bands were only detected at a loading of 5 wt.% Mo when the support was SO42−/free Fe2O3. Important correlations and shifts in the IR absorption bands were evaluated and discussed.

Aromatic extract residues occur as by-products in petroleum refineries, through the process of refining lubricant oil. These residues are considered as having low economic value, and their disposal may even cause problems for the refineries. The present work looks at upgrading these residues by using them to synthesise different petroleum additives, e.g., antioxidants, ashless dispersants, pour-point depressants, and flow improvers for lubricating crankcase oils and for fuels. The antioxidants were synthesised by reacting mono-aromatics with phosphorus pentasulphide (P2S5) in the presence of zinc oxide (ZnO). Ashless dispersant additives were synthesised by reacting alkylated mono-aromatics (using chlorinated paraffin wax as an alkylating agent) with formaldehyde solution (37%) in the presence of polyisobutylene succinimide. Fuel pour-point depressants and flow improvers can be synthesised by acylating di-aromatics via a Friedel-Crafts reaction. Comparative evaluation of the synthesised products with commercial additives showed them to have good comparative performance properties.

The adsorption of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS) surfactants on silica gel has been measured as a function of added molybdenum and NaCl by volumetric isotherms (from solution) as well as Fourier-transform IR spectroscopy (FTIR-PA), in the solid state. The adsorption of both surfactants onto molybdenum-modified silica surfaces shows two phase transitions, whereas only one phase is obtained upon the adsorption of these surfactants onto the parent silica. CTAB shows a significant increase upon adsorption onto molybdenum-modified silica compares with SDS especially following the addition of NaCl (0.5M), due to the evolution of MoO 3 species following calcination, the high degree of CTAB structure change with the addition of NaCl, and the lower degree of interference of Cl − and CTA + ions than that of SD − ions. The volumetric isotherms were shown to be a good tool for elucidating the adsorption mechanism. The IR spectra of CTAB adsorbed onto the molybdenum-silica system in the hydroxyl group region, at the extent of the electrolyte concentration, showed that adsorption occurs mainly via H-bonded silanols owing to steric crowding might be obtained at increasing electrolyte concentrations, which prevent the terminal hydroxyl groups from reacting properly, and the relatively long alkyl chain of CTAB compared with that of SDS.

Adsorption of pyridine on copper-silica catalysts is studied by differential scanning calorimetry (DSC) and Fourier transform-infrared/photoacoustic spectroscopy (FT-IR/PA), in the region of mid-frequency vibrations as well as in the region of hydroxyl groups. The adsorption of pyridine on copper-silica catalysts shows three modes of sorption in the 1650-1400 cm −1 region: physisorption or hydrogen-bonded (HPY), and two sites of Lewis acid sorption (LPY(I) and LPY(II)). The Lewis band at 1609 cm −1 was very strong compared with the 1450 cm −1 band since the former band showed a shift to higher wavenumbers whereas the latter showed a shift to lower wavenumbers. A relationship was found between the DSC scans, in the low temperature range (240-140°C), and the 1450-1443 cm −1 band. On the other hand, the high temperature DSC scans (400-360°C) were correlated with the behaviour of the 1609–1612 cm −1 band. The volumetric results of pyridine adsorption on 9 and 15 wt.% Cu catalysts show a constant behaviour; however, this constancy was also reflected by carbon monoxide adsorption, demonstrated by a similar behaviour of both 2128 and 2259 cm −1 bands. This was attributed to the blocking of the small pores of silica earlier at the 9 wt.% Cu loading. A new broad band at 2248–2259 cm −1 , not identified in the ion-exchange catalysts, was obtained and attributed to CO adsorbed on agglomerated copper clusters.

Pyridine adsorption is used to study the acidic sites of silica-supported CuOMoO 3 catalysts, with reference to CuO/SiO 2 and MoO 3 /SiO 2 catalysts. At low wt% of copper, both Lewis and Bronsted acid sites are present on the CuOMoO 3 /SiO 2 surface. A substantial decrease and then vanishing of the Bronsted acidity is obtained as a result of increasing the copper loading. An approach confining the prevalence of Lewis acidity over the Bronsted ones is described and discussed. A new band of Lewis acidity is observed at 1574 cm −1 and attributed to the presence of CuMoO 4 species. This band is not observed in the individual oxide form of both CuO/SiO 2 and MoO 3 /SiO 2 catalysts. Carbon monoxide adsorption on CuOMoO 3 /SiO 2 catalysts reflects a major dispersion if it is compared with CuO/SiO 2 and MoO 3 /SiO 2 catalysts and also gives a picture about the expected structures of these supported oxide catalysts. Copper is found also to exert a major control on the mode of interaction of molybdenum species with the silica surface. Moreover, important correlations and shifts in the IR bands are evaluated and discussed.

Styrene alkylmethacrylate succinimide phosphoric acid additives are synthesised and evaluated for use in multigrade crankcase lubricating oils as multifunctional viscosity index improvers having both antioxidant and dispersant properties. The synthesis is based on reacting styrene alkylmethacrylate (prepared by the reaction of styrene and 2-ethylhexylmethacrylate at different styrene/methacrylate mole ratios under various reaction conditions) with maleic anhydride and tetraethylenepentamine in the presence of phosphoric acid. Comparative evaluation of the properties of the synthesised products (e.g., viscosity properties, shear stability, oxidation stability and dispersive power) with commercial additives showed they were suitable for use as viscosity index improvers.

The adsorption of the cationic surfactant cetyltrimethylammonium bromide (CTAB) on silica gel and on molybdenum-modified silica gel substrate, in the solid state, was studied by differential scanning calorimetry and Fourier transform IR photoacoustic spectroscopy (FTIR-PA) techniques. Examination of the solid state IR spectra of CTAB absorbed onto molybdenum—silica substrate, as a function of temperature, shows a new band at 938 cm −1 shifted to 961 cm −1 (during the temperature flow), representing a chemisorption via the interaction of the head group of the surfactant (CH 3 ) 3 N + and MoO stretching vibration species. In the presence of NaCl, shifting of the high temperature exothermic peak at 411°C to 451°C was obtained, providing an enhancement of cetyltrimethylammonium chloride adsorption onto molybdenum—silica substrate and a considerable reduction in the Δ H value is observed. This decrease in the Δ H value was obtained as a result of the interference of the less reactive site Na + ions in the adsorption, because of substitution of Na + for Mo 6+ ions.

Preparation of Pt-Cr/Al 2 O 3 catalysts is achieved by treatment of a monometallic alumina-supported platinum sample (0.16 wt.-% platinum) with CrO 2 Cl 2 vapour or by impregnation of this sample with aqueous solutions of various chromium-containing compounds such as (CrO 3 ) x , K 2 Cr 2 O 7 and (NH 4 ) 2 Cr 2 O 7 or their mixtures. The change in acidity of the support is estimated by measuring thermal desorption of ammonia. The activity of the obtained samples in isomerization and dehydrocyclization is studied in model reactions with n-pentane, methylcyclopentane and n-hexane. It is established that modification of Pt/Al 2 O 3 catalysts by chromium ions directly influences the support acidity, depending on the nature of the compounds used, and exercises an indirect effect on the state of the metallic platinum centers. The electronic state of the active sites changes simultaneously due to the presence of electron-exchange effects between platinum and chromium. As a result of these combined effects, the rate of the reaction and selectivity of the catalysts change.