Rhenium and platinum recovery from platinum and rhenium catalysts used

A Pt-Re catalyst-based rhenium and platinum recovery solvolyticometallurgical technique has been developed by chlorinating with chlorine gas mixed with dimethylformamide and hydrochloric acid. The two-stage process conducted with burning residue after the first phase chlorination results in additional platinum transfer into the solution and makes it possible to obtain 70–94% platinum recovery and 91–96% percent rhenium recovery

     

Development of technical catalysts

Heterogeneous catalysis is the backbone of the modern chemical industry. The successful development of technical catalysts requires a highly interdisciplinary approach and a permanent close interaction between catalyst and process development. Although many modern methods are available for the characterisation of catalytic materials, still no substitute for a pilot plant test is available. Therefore the application of representative testing conditions in the laboratory or pilot plant reactor is of crucial importance. In order to identify the relationships between the often complicated solid state synthesis process during catalyst manufacture, the structural properties of the catalyst and its performance, correlation analysis are used.     

Redispersion of supported platinum catalysts

The redispersion of platinum on γ-Al₂O₃, SiO₂, and TiO₂ is experimentally studied by means of hydrogen chemisorption, X-ray diffraction, transmission electron microscopy, temperature-programmed reduction, and cyclohexene hydrogenation reaction. The increase in dispersion following treatment in oxygen below 600 °C occurs only for $\text{Pt}\text{γ-Al}{}_2\text{O}{}_3$. For $\text{Pt}\text{TiO}{}_2$, only the presence of chlorine during oxidation brings about a significant redispersion. For $\text{Pt}\text{SiO}{}_2$, redispersion does not occur under any condition. Redispersion can occur only in the presence of platinum oxide which could be stabilized by forming a complex with the support. The method for determining whether or not redispersion will occur for any systems and the conditions needed for redispersion are discussed.     

Dispersion of supported platinum catalysts in Oxygen

Further experimental evidences of redispersion on supported platinum catalysts studied by means of TPR, TPD and cyclohexene hydrogenation reaction. Pt/r-Al₂O₃ exhibits stronger interaction between the metal oxide and the support as compared with Pt/SiO₂ and Pt/TiO₂. The formation of surface complex is enhanced as oxidation temperature increases. The TPD spectrum of hydrogen on Pt/TiO₂ shifts to higher temperature upon reduction at high temperature and shifts again to its original position upon oxidation. Shift of TPD spectrum does not appear in other catalysts. The suggested mechanism for redispersion is the spreading of platinum oxide and trapping of migrating species.     

Ethanol oxidation on metal oxide-supported platinum catalysts

Ethanol is a renewable fuel that can be used as an additive to gasoline (or its substitute) with the advantage of octane enhancement and reduced carbon monoxide exhaust emissions. However, on the standard three-way catalysts, the conversion of unburned ethanol is low because both ethanol and some of its partially oxidized derivatives are highly resistant to oxidation. A combination of first-principles density-functional theory (DFT)-based calculations and in situ diffuse reflectance infrared spectroscopy (DRIFTS) analysis was applied to uncover some of the fundamental phenomena associated with ethanol oxidation on Pt-containing catalysts. In particular, the objective was to analyze the role of the oxide (i.e., γ-Al₂O₃ or SiO₂) substrate on the ethanol oxidation activity. The results suggest that Pt nanoparticles trap and accumulate oxygen at their surface and perimeter sites and play the role of sites that burn ethanol molecules and their partially oxidized derivatives to the final products. The γ-Al₂O₃ surfaces provided higher mobility of the fragments of ethanol molecules than the SiO₂ surface and hence increased the supply rate of these species to the Pt particles. This in turn produces a higher conversion rate of unburned ethanol.     

Catalytic combustion over platinum group catalysts: fuel-lean versus fuel-rich operation

Performance data are presented for methane oxidation on alumina-supported Pd, Pt, and Rh catalysts under both fuel-rich and fuel-lean conditions. Catalyst activity was measured in a micro-scale isothermal reactor at temperatures between 300 and 800 °C. Non-isothermal (near adiabatic) temperature and reaction data were obtained in a full-length (non-differential) sub-scale reactor operating at high pressure (0.9 MPa) and constant inlet temperature, simulating actual reactor operation in catalytic combustion applications.

Under fuel-lean conditions, Pd catalyst was the most active, although deactivation occurred above 650 °C, with reactivation upon cooling. Rh catalyst also deactivated above 750 °C, but did not reactivate. Pt catalyst was active above 600 °C. Fuel-lean reaction products were CO₂ and H₂O for all three catalysts.

The same catalysts tested under fuel-rich conditions demonstrated much higher activity. In addition, a ‘lightoff’ temperature was found (between 450 and 600 °C), where a stepwise increase in reaction rate was observed. Following ‘lightoff’ partial oxidation products (CO, H₂) appeared in the mixture, and their concentration increased with increasing temperature. All three catalysts exhibited this behavior.

High-pressure (0.9 MPa) sub-scale reactor and combustor data are shown, demonstrating the benefits of fuel-rich operation over the catalyst for ultra-low emissions combustion.     

Continuous hydrogen evolution from cyclohexanes over platinum catalysts supported on activated carbon fibers

The continuous production of hydrogen from cyclohexanes is achieved effectively using Pt/ACF (ACF = activated carbon fiber) catalysts in a fixed-bed flow reactor. The Pt catalysts are more effective than a Pd/ACF catalyst for the reaction. Besides cyclohexane, methylcyclohexane, 1,4-dimethylcyclohexane, and p-menthane can also be employed as hydrogen source in the reaction system.     

含铂催化剂中铂含量测定方法研究进展

含铂催化剂具有优良的催化性能,在石油化工、精细化工、环保材料等领域应用广泛。催化剂活性、选择性和寿命等受铂含量的影响较大,准确测定催化剂中的铂含量尤为重要。近年来,随着检测技术进步及检测设备的更新,铂的检测方法随之发展变化。综述适用于不同类型铂催化剂及铂含量范围的测定方法,包括化学法和仪器法,并对铂检测技术的发展进行展望。     

失效汽车尾气净化催化剂中铂族金属回收技术

主要对失效汽车尾气净化催化剂中的铂族金属回收技术做了综述。失效催化剂的回收技术包括催化剂预处理、铂族金属的富集、铂族金属的精炼、回收铂族金属后废渣的回收应用等多个环节。铂族金属的富集主要有火法与湿法两大工艺。火法工艺包括等离子熔炼法、金属捕集法、干式氯化法等技术;湿法工艺有载体溶解法、活性组分溶解法、全溶法及加压氰化法等技术。铂族金属的精炼主要有还原沉淀法、离子交换法、溶剂萃取法等。其中在富集工艺中火法有着处理量大、铂族金属回收率稳定、不需要处理大量废液等技术优势。     

失效汽车尾气净化催化剂中铂族金属回收技术

主要对失效汽车尾气净化催化剂中的铂族金属回收技术做了综述。失效催化剂的回收技术包括催化剂预处理、铂族金属的富集、铂族金属的精炼、回收铂族金属后废渣的回收应用等多个环节。铂族金属的富集主要有火法与湿法两大工艺。火法工艺包括等离子熔炼法、金属捕集法、干式氯化法等技术;湿法工艺有载体溶解法、活性组分溶解法、全溶法及加压氰化法等技术。铂族金属的精炼主要有还原沉淀法、离子交换法、溶剂萃取法等。其中在富集工艺中火法有着处理量大、铂族金属回收率稳定、不需要处理大量废液等技术优势。     

苯加氢制环己烷工艺及催化剂研究进展

介绍了苯加氢制环己烷工艺及催化剂研究现状,对比各工艺和催化剂的优缺点,气相法和液相法是苯加氢制环己烷的成熟工艺,在未来很长一段时间仍将是苯加氢制备环己烷的主要工艺。开发高活性、耐热性能好和抗毒能力强的贵金属催化剂是苯加氢制备环己烷催化剂的研究方向。     

Direct production of sugar alcohols from wood chips using supported platinum catalysts in water

Softwood chips have been directly converted into sugar alcohols by supported platinum catalysts in water without any acid catalysts. The cellulose and hemicellulose in the wood chips were converted with 94% conversion and 62% yield and the lignin remained as solid after the reaction.     

Approaches to bi- and trimetallic platinum and palladium complexes using the DPPEPM ligand

Bis{(diphenylphosphinoethyl)phenylphosphino}methane (DPPEPM) reacts with [PtR₂(cod)] in 1:1 ratio to give [PtR₂(DPPEPM-PP)] (2a, R=Me; 2b, R=Ph), whereas with [PtCl₂(cod)] or [PdCl₂(cod)] it yields the ionic species [M(DPPEPM-PP)₂]²⁺ (3 and 4). With [MClMe(cod)], the product is [MMe(DPPEPM-PPP)]⁺ (5, M=Pt; 6, M=Pd), in which one of the internal P atoms of the ligand is uncoordinated. These complexes undergo oxidation of the free P atom to give 7 and 8 on standing in solution. Complexes 2–4 may be used to construct bimetallic and trimetallic mixed metal complexes. The molecular structures of 7 and [PtMe₂(μ-DPPEPM)PdCl₂] (11) are reported.     

Sonovoltammetry at platinum electrodes: surface phenomena and mass transport processes

Application of simultaneous ultrasound to representative solution-phase reversible voltammetric couples produce a step-shaped voltammogram at platinum electrodes of both macro and micro dimensions. The limiting current increases with ultrasonic power, but is not markedly affected by ultrasonic frequency in the 20–800kHz region. In contrast the complex voltammetry of a platinized platinum electrode surface within the hydrogen adsorption regime in aqueous acid medium is very little affected by sonication. Factors affecting the reproducibility of sonoelectrochemical experiments when employing ultrasonic sources are discussed.Author to whom correspondence should be addressed     

State of platinum in zirconia and sulfated zirconia catalysts

Platinum is present in a metallic state following activation in air at 725C of both 5 wt% Pt/ZrO₂ and 5 wt% Pt/SO ₄ ^2– /ZrO₂. Reduction of either catalyst at 725C produces a Pt-Zr alloy, and these reduced catalysts, upon recalcination in air at 725C, form metallic Pt crystallites. Likewise, reduction of these uncalcined catalysts at 725C in H₂ leads to a Pt-Zr alloy formation. However, treatment of these uncalcined catalysts in H₂ at 450C does not produce Pt crystallites large enough to detect by XRD.     

Electrooxidation of methanol at platinum–ruthenium catalysts prepared from colloidal precursors: Atomic composition and temperature effects

The electrocatalytic oxidation of methanol was investigated on PtRu electrodes of different atomic compositions at several temperatures (from 25 to 110 °C). Very active catalyst nanoparticles supported on active carbon (Vulcan XC 72) were obtained using the colloidal synthesis developed by Bönnemann et al. [11], allowing easy variation of the atomic composition. These electrocatalysts were characterized by TEM, EDX and XRD; results indicate that they consist of platinum nanoparticles decorated by ruthenium. Methanol oxidation was studied as a function of composition, temperature and methanol concentration. Two effects were investigated: the effect of the working temperature and the effect of the atomic composition. It appeared that for lower methanol electrooxidation overvoltages, the best catalysts are ruthenium-rich, whereas at higher overvoltages the best one is the Pt + Ru (80:20)/C composition, irrespective of the working temperature, either in half-cell or in a single DMFC.     

Hydrogenation of natural oils with platinum metal group catalysts

Studies in the hydrogenation of natural oils with catalysts of the platinum metals group have been limited mainly to platinum and palladium with only scant attention to rhodium, ruthenium, iridium and osmium. This preference was dictated largely by economics, palladium being the only noble metal catalyst truly competitive on a usecoat basis with nickel in the hydrogenation of low-priced oils. This paper discusses the noble metal catalysts as a group, points out similarities and differences among the metals relevant to the hydrogenation of natural oils, and describes some of the practical applications of catalysis by palladium. One of 10 papers to be published from the Symposium “Hydrogenation”, presented at the AOCS Meeting, New Orleans, April 1970.