Hydrogen–Deuterium Exchange Reactions of Aromatic Compounds and Heterocycles by NaBD4‐Activated Rhodium,Platinum and Palladium Catalysts

Conventional thermal and microwave conditions were compared for hydrogen–deuterium (H/D) exchange reactions of aminobenzoic acids catalysed by NaBD₄‐activated Pd/C or RhCl₃ with D₂O as the deuterium source. We also investigated different NaBD₄‐activated metal catalysts (including Pd/C, RhCl₃ and Pt/C) under microwave conditions for an efficient H/D exchange of aromatic and heterocyclic compounds. Even higher deuterium incorporations were obtained for Pd/C and Pt/C catalyst mixtures due to the previously observed synergistic effect. Finally, we have applied these optimised conditions for one‐step syntheses of the MS standards of several pharmaceutically active compounds.     

Aromatic reduction of residue oil of naphtha cracking over bimetallic Pt−Pd catalysts supported on mesoporous molecular sieve

An Al-containing mesoporous molecular sieve (Al-MMS) was prepared by hydrolysis of H₂SiF₆ and Al(NO₃)₃·9H₂O. NH₃-TPD results suggest that the acidity of Al-MMS was less than that of dealuminated zeolite. Y. The potential use of mesoporous molecular sieve as a new support material for dearomatization of residue oil of naphtha cracking was described. In case of C₉ ⁺ and PGO feed, Pt?Pd/Al-MMS showed a higher activity than Pt?Pd/dealuminated zeolite Y catalyst. This is ascribed to its better accessibility of bulky molecules, and much less cracking activity due to mild acidity, indicating high yield of liquid. Thus, Pt?Pd/Al-MMS catalyst can be applied effectively to the hydrogenation of aromatic compounds in the residue oil of a commercial naphtha cracker.     

SYNTHESIS AND CHARACTERIZATION OF A SILICA-SUPPORTED CARBOXYMETHYLCELLULOSE PLATINUM COMPLEX AND ITS CATALYTIC BEHAVIORS FOR HYDROGENATI0N OF AR0MATICS

A silica-supported carboxymethylcellulose platinum complex (abbreviated as SiO_2-CMC-Pt) has been prepared and characterized by XPS. Its catalytic properties for hydro-genation of aromatic compounds were studied. The results showed that this catalystcould catalyze the hydrogenation of phenol, anisol, p-cresol, benzene and toluene to cyclo-hexanol, cyclohexyl methyl ether, p-methyl cyclohexanol, cyclohexane and methylcyclo-hexane, respectively in 100% yield at 30℃ and 1 atm. In the hydrogenation of phenol,COO/Pt ratio in SiO_2-CMC-Pt has much influence on the initial hydrogenation rate andthe selectivity for the intermediate product, cyclohexanone. The highest initial rate andthe highest yield of cyclohexanone both occur at COO/Pt ratio of 6. The complex is stableduring the reaction and can be used repeatedly.     

Pt/ZrO2:An Efficient Catalyst for Aerobic Oxidation of Toluene in Aqueous Solution

The heterogeneous oxidation of toluene in aqueous medium has been investigated. Artificially contaminated water with aromatic compound (toluene) was exposed to a simple platinized zirconia (1% Pt/ZrO₂) catalyst in the presence of molecular oxygen. This selective oxidation of toluene to benzyl alcohol, benzaldehyde and benzoic acid provides a step for removing toluene from wastewater or converting it into less harmful substances. Different parameters, e.g. the reaction time, temperature, pressure, the amount of catalyst and agitation, etc influenced the toluene conversion and selectivity. Typical batch reactor kinetic data were obtained and fitted to the classical Langmuir‐Hinshelwood model, Mars‐van Krevelen model as well as to the Eley‐Rideal model of heterogeneously catalyzed reactions. The Eley‐Rideal model was found to give a better fit. 1% Pt/ZrO₂ was observed to be the most active for oxidation of toluene at 333 K in oxygenated atmosphere [p(O₂) ca. 101 kPa] with a nominal stirring speed ≧900 r/min. It was found that catalytic oxidation may be an effective method for the removal of volatile organic compounds from aqueous solutions and comparable to other advanced oxidation processes.     

Acetamide/SO2Cl2 as an efficient reagent for Friedel–Craft’s acylation of aromatic compounds under ultrasonic and microwave conditions

Acetamide/SO₂Cl₂ reagent has been developed for effective Friedel–Craft’s acylation of aromatic compounds. Acylation of aromatic compounds with acetamide/SO₂Cl₂ was much more effective and faster than analogous (acetamide/SOCl₂) and (acetamide/POCl₃) reagents even under conventional conditions. However, microwave and ultrasonic assisted reactions afforded high yields of products in very short reaction times (30–40 min under sonication and 3–4 min under microwave assisted conditions).     

Catalytic behaviour of Pt loaded on AlPO4-5 and AlPO4-11 in the aromatization of C6?C8 alkanes

Pt/AlPO₄-5 and Pt/AlPO₄-11 showed some characteristics of monofunctional aromatization catalysts and higher aromatic selectivity inn-heptane aromatization than inn-hexane aromatization. Especially they exhibited resistance for thiophene poisoning.     

Pt Nanoparticles Supported on Nitrogen‐Doped‐Carbon‐Decorated CeO2 for Base‐Free Aerobic Oxidation of 5‐Hydroxymethylfurfural

Currently, the base‐free aerobic oxidation of biomass‐derived 5‐hydroxymethylfurfural (HMF) to produce 2,5‐furandicarboxylic acid (FDCA) is attracting intense interest due to its prospects for the green, sustainable, and promising production of biomass‐based aromatic polymers. Herein, we have developed a new Pt catalyst supported on nitrogen‐doped‐carbon‐decorated CeO₂ (NC‐CeO₂) for the aerobic oxidation of HMF in water without the addition of any homogeneous base. It was demonstrated that the small‐sized Pt particles could be well dispersed on the surface of the hybrid NC‐CeO₂ support, and the activity of the supported Pt catalyst depended strongly on the surface structure and properties of the catalysts. The as‐fabricated Pt/NC‐CeO₂ catalyst, with abundant surface defects, enhanced basicity, and favorable electron‐deficient metallic Pt species, enabled an almost 100 % yield of FDCA in water with molecular oxygen (0.4 MPa) at 110 °C for 8 h without the addition of any homogeneous base, which is indicative of exceptional catalytic performance. Furthermore, this Pt/NC‐CeO₂ catalyst also showed good stability and reusability owing to strong metal–support interactions. An understanding of the role of surface structural defects and basicity of the hybrid NC‐CeO₂ support provides a basis for the rational design of high‐performance and stable supported metal catalysts with practical applications in various transformations of biomass‐derived compounds.     

Rapid reduction of heteroaromatic nitro groups using catalytic transfer hydrogenation with microwave heating

A method for the rapid, safe reduction of heteroaromatic and aromatic nitro groups to amines is described using catalytic transfer hydrogenation under microwave heating conditions. Commonly available Pd/C or Pt/C catalyst is extremely effective with 1,4-cyclohexadiene as the hydrogen transfer source. In the case of substrates containing potentially labile aromatic halogens, Pt/C is effective and results in little or no dehalogenation. In general, the reactions are complete within 5 min at 120 °C.     

Isomerization of <Emphasis Type="Italic">n</Emphasis>-Heptane on Platinum-Zeolite Catalysts in the Presence of Cyclohexane and Benzene

Effect of cyclohexane and benzene on the isomerization of n-heptane on Pt/BEA-Al₂O₃ and Pt/MORAl₂O₃ catalysts was studied. In the presence of catalysts with platinum deposited from a [Pt(NH₃)₄]Cl₂ solution, cyclohexane and benzene inhibit the conversion of n-heptane. At the same time, the presence of cycloalkanes and aromatic hydrocarbons leads to an increase in the isomerization selectivity due to the suppression of side reactions of hydrocracking. Samples based on the BEA zeolite were found to be more active as compared with similar samples based on mordenite.     

Sustainable Heterogeneous Platinum Catalyst for Direct Methylation of Secondary Amines by Carbon Dioxide and Hydrogen

Pt and MoO_x co‐loaded TiO₂ is found to be highly effective for direct methylation of aliphatic and aromatic secondary amines by CO₂ and H₂ under solvent‐free conditions. This is the first additive‐free and reusable heterogeneous catalytic system with acceptable turnover number.     

Reduction of aromatic compounds with Al powder using noble metal catalysts in water under mild reaction conditions

In water, Al powder becomes a powerful reducing agent, transforming in cyclohexyl either one or both benzene rings of aromatic compounds such as biphenyl, fluorene and 9,10-dihydroanthracene under mild reaction conditions in the presence of noble metal catalysts, such as Pd/C, Rh/C, Pt/C, or Ru/C. The reaction is carried out in a sealed tube, without the use of any organic solvent, at low temperature. Partial aromatic ring reduction was observed when using Pd/C, the reaction conditions being 24 h and 60 °C. The complete reduction process of both aromatic rings required 12 h and 80 °C with Al powder in the presence of Pt/C.     

Titanium isopropoxide/pyridine mediated Knoevenagel reactions

We report a Ti(OiPr)₄/pyridine-mediated Knoevenagel reaction between aromatic ketones and cyanoacetamides to provide Knoevenagel olefin products in good to excellent yields. Almost in all cases studied, a single geometrical isomer was formed and isolated under the Ti(OiPr)₄/pyridine condensation conditions. This methodology was also demonstrated to be highly effective between some other Knoevenagel active methylene compounds and aromatic ketones.     

Transmetalation Reactions of Aromatic Dilithionickelole: Synthesis of Heterobimetallic Complexes Featuring Metalloles as Diene Ligands

The aromatic metallole dianions are important metallaaromatic compounds because of their various reactivities and extensive synthetic applications. Herein we report the reactions of dilithionickelole with MgCl₂, EtAlCl₂, Cp*ScCl₂, Cp*LuCl₂ and Pt(COD)Cl₂ (COD=1,5-cyclooctadiene) affording a series of Ni/M heterobimetallic complexes of the general formula (η⁴−C₄R₄M)Ni(COD), in which the metalloles act as diene ligands, as suggested by single-crystal X-ray, NMR and theoretical analyses. In these reactions, two electrons of the nickelole dianion transferred to Ni, representing different reactivity compared with main-group metallole dianions.     

Indirect electrochemical destructive oxidation of aromatic compounds with reactive oxygen species

The indirect destructive electrooxidation of benzene, phenol, and N-methyl-p-aminophenol with active oxygen species generated in situ from O₂, H₂O₂, and H₂O in aqueous solutions with various pH values has been carried out using different cell designs with Pt, Pb/PbO₂, and Ru-Ti oxide anodes. The indirect oxidation of the aromatic compounds mineralizes them into CO₂ and H₂O or converts them into simple monocarboxylic or dicarboxylic acids, which can be utilized by microorganisms in subsequent biotreatment.     

Nonoxidative conversion of methane and <Emphasis Type="Italic">n</Emphasis>-pentane over a platinum/alumina catalyst

Methane adsorption on the Pt–H/Al₂O₃ and Pt/Al₂O₃ catalysts begins at Т = 475°C and is accompanied by the appearance of hydrogen in the reaction medium. At a higher temperature is raised to 550°C, the amount of adsorbed hydrogen increases to 1.1 and 0.8 mol/(mol Pt), respectively. According to the calculated degree of methane dehydrogenation on platinum sites at Т = 550°C, the Н/C ratio is 1.3 (at/at) for the Pt–H/Al₂O₃ catalyst and 1.5 (at/at) for the Pt/Al₂O₃ catalyst. The introduction of n-pentane into the reaction medium increases the yield of aromatic hydrocarbons (benzene and toluene) by a factor of 8.8 over the arene yield observed in individual n-pentane conversion. A mass spectrometric analysis of the arenes obtained with the Pt/Al₂O₃ catalyst has demonstrated that 37.5% of the adsorbed methane is involved in the methane–n-pentane coaromatization yielding benzene and toluene.     

Study of Pt/TiO2 nanocomposite for cancer-cell treatment

The increasing incidence of cancer all over the world demands new, effective and secure materials for treatment. In this paper, we propose Pt/TiO₂ nanocomposite for cancer-cell treatment because noble metal nanoparticles are supposed to enhance the photocatalytic activity of TiO₂ nanoparticles. To evaluate the cancer-cell killing effect of our Pt/TiO₂ nanocomposite, TiO₂ and Au/TiO₂ nanoparticles are also introduced. The prepared Pt/TiO₂ nanocomposite are characterized with transmission electron microscopy (TEM) and UV–vis adsorption spectra. Results of cell treatment indicate that Pt/TiO₂ nanocomposite, as extremely stable metal–semiconductor nanomaterial, can exhibit a very high photodynamic efficiency under a mild ultraviolet radiation. And our Pt/TiO₂ nanocomposite shows to be more effective in cancer-cell treatment than TiO₂ and Au/TiO₂ nanoparticles. As a result, Pt/TiO₂ nanocomposite may be supposed to have a promising application for cancer-cell treatment.     

Effect of Metallic Oxides Containing Composite Electrodes on Crystallization and Ferroelectric Properties of Pb(Zr0.52,Ti0.48)O3 Thin Films Deposited by the Sol-Gel Method

In order to suppress polarization fatigue and decrease the leakage current of the PZT capacitor, composite electrodes consisting of MO₂ (RuO_x or IrO_x) as an effective diffusion barrier and considerably large amounts of Pt were deposited by magnetron co-sputtering to yield heterostructured PZT capacitors, Pt/(Pt+MO₂)//PZT(52/48)//(Pt+MO₂)/(Pt+M)/M/Pt/Ti(Ta)/SiO₂/Si(1 0 0), and the crystallinity and the orientation, the morphology of the surface and the cross section, and the composition depth profile of the PZT capacitor were examined by XRD analysis, SEM and AES, respectively, and the ferroelectric properties were measured. The results indicated that by adjusting the distribution and composition of the RuO₂ phase, the polarization loss of the PZT capacitor can be suppressed to as small as 5% after polarization reversals of 10⁹ while maintaining the effective polarization dP_r = P_r* – P_r ^{^} at 15 C/cm². The suppression of the polarization fatigue was found more effective with (Pt+IrO₂) electroding than (Pt+RuO₂) electroding. The leakage current of the PZT capacitor electroded with (Pt+MO₂) was a little larger than that of the PZT capacitor with Pt electrode. The possible reason was suggested.     

Properties of Bulk In-Pt Intermetallic Compounds in Methanol Steam Reforming

Heterogeneous catalysts are often complex materials containing different compounds. While this can lead to highly beneficial interfaces, it is difficult to identify the role of single components. In methanol steam reforming (MSR), the interplay between intermetallic compounds, supporting oxides and redox reactions leads to highly active and CO₂-selective materials. Herein, the intrinsic catalytic properties of unsupported In₃Pt₂, In₂Pt, and In₇Pt₃ as model systems for Pt/In₂O₃-based catalytic materials in MSR are addressed. In₂Pt was identified as the essential compound responsible for the reported excellent CO₂-selectivity of 99.5 % at 300 °C in supported systems, showing a CO₂-selectivity above 99 % even at 400 °C. Additionally, the partial oxidation of In₇Pt₃ revealed that too much In₂O₃ is detrimental for the catalytic properties. The study highlights the crucial role of intermetallic In−Pt compounds in Pt/In₂O₃ materials with excellent CO₂-selectivity.     

Transient Currents of Carbon Monoxide and Methanol Adsorption on Platinum Electrodes and Determination of Composition of Chemisorption Layers

Transients of currents during the adsorption of CO on polycrystalline (pc) Pt in solutions of H₂SO₄ and H₂SO₄ + HCl are measured at a constant potential. The obtained values are compared with relevant reference data for Pt electrodes. Possible reasons for the established differences are discussed. Transient currents for the methanol adsorption on pcPt and Pt/Pt are compared. A method for correct determination of the composition of a chemisorption layer, which forms during dissociative adsorption of simple organic compounds of the type of RH _m , is considered. Experimental data on the methanol adsorption suggest that adsorption products on pcPt are chiefly species of CO. On Pt/Pt, at low potentials, in addition to CO one should assume the adsorption of species of HCO in perceptible amounts.     

Reactivity and Structure of Difluorophosphine Compounds and Their Platinum Complexes

Abstract

Various novel organodifluorophosphines involving aromatic and aliphatic substituents were prepared and used as ligands in reactions with (COD)PtCl₂ or K₂PtCl₄; complexes of the type cis-dichlorobis(organodifluorophos-phine)platinum(II) or tetrakis (organodifluorophosphine)platinum(O) were formed. The ³¹P-n.m.r. data of these compounds were correlated with Pt-P bond lengths found from X-ray diffraction studies. The hydrolysis of RPF₂ and Pt(RPF₂)₄ with water leads to the formation of RP(F)(O)(H) or [RP(F)(OH)]₂[RP((F)]₂Pt. Both products were characterized by n.m.r. spectra and by X-ray structure determinations.