Platinum-rhenium Catalysts Research Articles

Bimetallic platinum rhenium catalyst for efficient low temperature dehydrogenation of perhydro benzyltoluene

H2 release from the liquid organic hydrogen carrier perhydro benzyltoluene (H12-BT) was accelerated using bimetallic Pt–Re/Al2O3 catalysts. An optimum Pt : Re ratio was identified and catalysts characterisation provided insight on Pt–Re interaction.

Hydrodeoxygenation of Isoeugenol over Carbon-Supported Pt and Pt–Re Catalysts for Production of Renewable Jet Fuel

A series of monometallic platinum and bimetallic platinum–rhenium catalysts supported on mesoporous carbon Sibunit, which is a type of mesoporous, microcrystalline carbon, were investigated for hydrodeoxygenation (HDO) of isoeugenol (IE) at 200–300 °C and 30 bar of H2, using dodecane as a solvent. Catalytic activity was tested in a batch reactor to screen the catalysts and, for comparison, also in the continuous mode. For batch experiments, complete conversion, and a high yield of the desired product, propylcyclohexane (PCH), were obtained for all bimetallic PtRe/Sibunit in 240 min, with the highest yield of PCH when Pt:Re ratio was 1:1 or 1:3. The results for Pt–Re (1:1) were reproducible, in terms of catalytic activity and reusability of catalysts, which showed no deactivation. Monometallic Pt catalysts displayed low activity. Continuous experiments were performed with PtRe(1:1)/Sibunit at 30 bar H2, 0.5 mL/min of the liquid flow, and temperatures between 75 °C and 200 °C. The distribution of products showed deoxygenation at higher temperatures, while at lower temperatures, mainly oxygenated products were formed. XPS results confirmed the presence of ReOx species, where an increase in the platinum loading resulted in a decrease in the fraction of ReOx species and subsequently lower PCH yield.

Modelling Industrial Catalytic Reforming of Lowoctane Gasoline

Naphtha reforming is one of the most important industrial processes in refineries. The products include aromatic hydrocarbons such as benzene, toluene, and xylenes, which are frillier used as high octane additives to gasoline. To increase the efficiency of the process, it is necessary to develop a new method of naphtha reforming. In this work, we have proposed a mathematical model of catalytic refining of low-octane gasoline fracdons into high-octane fractions. The model is based on kinetic equations, established for commercial gasoline reforming in the presence of the platinum-rhenium catalyst on a γ-Al2O3 carrier in the industrial-scale conditions. The equation: describe the dependence of the content of paraffinic, naphthenic, and aromatic hydrocarbon fractions on the process parameters, including volumetric rate and the reaction temperature. The mathematical model had been validated by comparing calculated results with the industrial data obtained from the commercial naphtha reforming production.

Electrolysis with Fibrous Carbon Electrodes in Recovery of Platinum Metals from Mineral and Secondary Raw Materials

Electrolytic recovery of platinum metals onto electrodes of fibrous carbon materials from solutions formed by processing of copper–nickel ores, gold- and silver-containing concentrates (gold and silver refining), platinum–rhenium catalysts, and simulated solutions from spent nuclear fuel reprocessing was studied. Combined flowsheets including electrolysis with fibrous carbon electrodes, anodic labilization of platinum metal compounds, extraction, and ion exchange were used. Platinum metals were recovered to low residual concentrations from sulfuric acid, hydrochloric acid, hydrochloric acid + thiourea, ammonia–ammonium, nitric–nitrous acid, and nitric acid solutions. The following processes were used: electrolysis at constant and varied current density, deposition–anodic dissolution, and deposition–dissolution in the short-circuited electrochemical system fibrous carbon material–metal alloy–electrolyte solution. Some processes were successfully trialed on the semicommercial and commercial scales. Trials were performed using semicommercial electrolyzers with fibrous carbon electrodes, developed in cooperation with the special designing bureau of mining and dressing equipment.

Analysis of the Engineering Process of Reforming Dead Catalysts for the Extraction of Platinum Group Metals

The analysis of the engineering process of reforming dead catalysts for the extraction of platinum group metals has been carried out. Fully-dead catalyst, having passed several cycles of regeneration and entitled to utilization, has the considerable carbonaceous deposits, both on external and internal surfaces. Their content averages 5.0% of the mass of the catalyst. The research objectively consisted in selection of the sweet roasting modes, promoting the fullest removal of the dense carbonaceous deposits from the surface of the dead platinum-rhenium catalysts. The kinetics research of carbonaceous removal deposits from the surface of the catalyst was carried out in a pipe-still heater; oxygen content, duration and temperature of sweet roasting being varied. The maximum temperature during the research reached 950°C, the maximum duration of isothermal holding didn't exceed 6 hours. The extent of carbonaceous deposits removal was calculated by changing sample weight. The kinetic curves were approximated by high-order polynomials, which made it possible to obtain a diagram, illustrating the degree of organic deposits removal, depending on temperature and firing time. It is shown that in the environment enriched to 30-35 vol. % oxygen, the engineering process of catalysts for regeneration is possible to be carried out at 650 °C, with holding for 2 hours at a specified temperature. The alternative of sweet roasting is the air blowing of dead catalysts at temperature of 800 °C within an hour. Both modes guarantee the complete removal of the dense carbonaceous deposits from the surface of the dead catalyst.

EFFECT OF DURATION OF OXYCHLORINATION ON DEGREE OF ACCESSIBILITY FOR CATALYSIS OF PLATINUM CENTERS OF PLATINUM-RHENIUM REFORMING CATALYST

The work presents the results of a chemisorption analysis of a platinum-rhenium catalyst on an alumina support after regeneration and reduction with hydrogen. Adsorption-desorption diagrams were obtained by stepwise-pulsed chemisorption of carbon monoxide on reforming catalyst samples. With an increase in the number of carbon monoxide injections from 1 to 4, the catalyst sample is poisoned, and subsequent desorption peaks indicate the termination of the interaction. With an increase in the time of oxychlorination, the CO/Pt ratio in the carrier volume increases linearly. The effect of the oxychlorination process on the chemisorption of CO and the subsequent availability of platinum nanoparticles for catalysis has been shown. The absorption on freshly prepared platinum-rhenium catalyst samples reaches a CO/Pt molar ratio of about 0.4. The results show that the duration of oxychlorination for 16–20 h allows us to achieve the value of the ratio CO/Pt, which is in the range of 0.4-0.5. This indicates that the availability of platinum centers in its composition reaches the level of a fresh catalyst, and, on the other hand, taking into account a slight excess of this ratio, we can assume that some of the Re atoms participate in the absorption of CO molecules. The presence of finely dispersed platinum particles in the composition of the regenerated catalyst was confirmed by IR spectroscopy. The analysis of catalyst samples on an IR spectrometer in the frequency range of 1900-2200 cm-1 revealed a rather wide absorption band with a pronounced extremum at 2060 cm-1. In this frequency range, there is another, slightly pronounced extremum at 2149 cm-1. However, for samples with a short duration of oxychlorination, it did not appear. An absorption band with an extremum of 2060 cm-1 can be attributed to linear vibrations of adsorbed CO molecules on the surface of particles of metallic platinum.

Experimental research on the pressure oxygen leaching rhenium of waste platinum-rhenium catalyst with low acid

Experimental material was the waste platinum-rhenium catalyst; X diffraction was used to characterize the material, and the results showed that the main phase of the waste platinum-rhenium catalyst was Al2O3. The process of rhenium pressure oxygen leaching in platinum-rhenium catalyst with low acid was put forward. The effects of leaching pressure, leaching temperature, leaching time, initial acidity of sulfuric acid and liquid-solid ratio on the leaching rate of rhenium during leaching were investigated in this paper. The results showed that the initial acidity of sulfuric acid had a significant effect on the leaching rate of platinum and rhenium. As the acidity increased, the leaching rate of platinum and rhenium also increased, and the leaching rate of carrier Al2O3 also increased. The experimental results show that the leaching of the optimal process conditions were as follows: leaching pressure 5 MPa, leaching time 3h, leaching temperature 140 °C, the initial sulfuric acid concentration 10%, liquid-solid ratio 4:1, mixing speed 350 rpm. Under these conditions, the leaching rate of rhenium and platinum was 98.11% and 83.59% respectively, and the slag rate was 75.56%. In order to prevent platinum from dispersing, ferrous sulphate was added at the end of the leaching process to reduce the platinum into the leaching residue. This process has the advantages of simple operation, high rhenium leaching rate, less impurity elements in the leaching liquid and low acidity, etc., which can provide reference for rhenium extraction from the waste platinum-rhenium catalyst.

Исследование процесса подготовки дезактивированных катализаторов риформинга к извлечению металлов платиновой группы

The analysis of the engineering process of reforming dead catalysts for the extraction of platinum group metals has been carried out. Fully-dead catalyst, having passed several cycles of regeneration and entitled to utilization, has the considerable carbonaceous deposits both on external and internal surface. Their content averages 5.0% of the mass of the catalyst. The research objective consisted in selection of the sweet roasting modes promoting the fullest removal of the dense carbonaceous deposits from the surface of the dead platinum-rhenium catalysts. The kinetics research of carbonaceous removal deposits from the surface of the catalyst was carried out in a pipe-still heater; oxygen content, duration and temperature of sweet roasting being varied. The maximum temperature during the research reached 950°C, the maximum duration of isothermical holding didn't exceed 6 hours. The extent of carbonaceous deposits removal was calculated by changing sample weight. The kinetic curves were approximated by high-order polynomials, which made it possible to obtain a diagram illustrating the degree of organic deposits removal depending on the temperature and firing time. It is shown that in the environment enriched to 30-35 vol. % oxygen, the engineering process of catalysts for regeneration is possible to be carried out at 650 °C, with holding for 2 hours at the specified temperature. The alternative of sweet roasting is the air blowing of dead catalysts at temperature of 800 °C within one hour. Both modes guarantee the complete removal of the dense carbonaceous deposits from the surface of the dead catalyst.

Kinetics research on rhenium of the waste platinum-rhenium catalyst under pressure oxygen leaching

Experimental material was the waste platinum-rhenium catalyst; the kinetics of rhenium in PT rhenium catalyst failed by pressure oxygen leaching was studied. The effects of leaching pressure, temperature, sulfuric acid acidity, stirring speed and particle size on the kinetics of rhenium leaching were investigated in this paper. The results showed that sulfuric acid, leaching temperature, leaching pressure and particle size had a significant effect on the leaching rate of rhenium; the chemical reaction control model can well describe the rhenium gas liquid-solid reaction process in the waste platinum-rhenium catalyst for pressure oxygen leaching. In the experimental range, the apparent activation energy is determined to be 42.96kJ/mol, which is in agreement with the chemical reaction control model.

Hydrodeoxygenation of Isoeugenol over Alumina-Supported Ir, Pt, and Re Catalysts.

Hydrodeoxygenation (HDO) of isoeugenol (IE) was investigated using bimetallic iridium–rhenium and platinum–rhenium catalysts supported on alumina in the temperature and pressure ranges of 200–250 °C and 17–40 bar in nonpolar dodecane as a solvent. The main parameters were catalyst type, hydrogen pressure, and initial concentration. Nearly quantitative yield of the desired product, propylcyclohexane (PCH), at complete conversion in 240 min was obtained with Ir–Re/Al2O3 prepared by the deposition–precipitation method using 0.1 mol/L IE initial concentration. High iridium dispersion together with a modification effect of rhenium provided in situ formation of the IrRe active component with reproducible catalytic activity for selective HDO of IE to PCH. The reaction rate was shown to increase with the increasing initial IE concentration promoting also HDO and giving a higher liquid phase mass balance. Increasing hydrogen pressure benefits the PCH yield.

Application of Silica Chemically Modified by Sulfur-Containing Groups to the Separation and Determination of Platinum and Rhenium in Catalysts Based on Aluminum Oxide

Adsorbents based on silica chemically modified by sulfur-containing groups (dithiocarbamate, thiodiazolethiol, mercaptophenyl, and aminobenzothiazole) quantitatively extract (recovery ≥99%) platinum( IV) from solutions ranging from 4 M HCl to pH 6. Under the conditions of the adsorption separation of platinum(IV), rhenium(VII) is not extracted and remains in the solution. The subsequent quantitative (98–99%) adsorption of rhenium(VII) is achieved in the presence of a 1000-fold excess of tin(II) chloride. Adsorption on the surface of adsorbents leads to the formation of platinum(II) complexes with sulfur-containing groups, luminescent at 77 K on irradiation with UV light. The luminescence spectra of surface platinum( II) complexes are located in the region of 550–700 nm. In the adsorption of rhenium(III) in the presence of tin(II) chloride, intensely colored brown complexes of rhenium formed on the surface of adsorbents. Electron paramagnetic resonance showed that, in the surface complexes, rhenium is in the oxidation state 2+. Silicas chemically modified by sulfur-containing groups were used in the development of procedures for the sequential isolation and determination of platinum and rhenium in solutions after the decomposition of aluminum–platinum–rhenium catalysts.

Conversion of bio-oxygenates into hydrocarbons in the presence of a commercial Pt–Re/Al2O3 catalyst

It was found that the preliminarily reduced commercial platinum–rhenium catalyst PR-71 exhibited high activity in the conversion of ethanol into C4–C12 olefins and in the cross-condensation reactions of ethanol with glycerol, acetone, n-propanol, and isopropanol. Acetone and glycerol exhibited the highest reactivity in the cross-condensation reactions; this manifested itself in an increase in the total yield of the target fraction of C4–C12 hydrocarbons and in a more than 10-fold increase in the yield of products containing the odd numbers of carbon atoms, as compared with the conversion of individual ethanol. The structural studies performed by extended X-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy showed that the high selectivity of PR-71 can be caused by the formation of bimetallic Pt–Re and Pt–Al clusters in the course of the prolonged preliminary reduction of the catalyst.

Aqueous‐Phase Hydrogenation of Saturated and Unsaturated Ketones and Aldehydes over Supported Platinum–Rhenium Catalysts

AbstractThe hydrogenation rates of C=C and C=O bonds in methyl vinyl ketone and crotonaldehyde were measured over a series of silica‐supported Pt‐Re catalysts (1:1 atomic ratio of Pt/Re) in liquid water with H2 (15 psig) at 333 K. The hydrogenation of methyl vinyl ketone did not produce any unsaturated alcohol because of the rapid hydrogenation of C=C relative to that of C=O. The addition of Re to Pt impacted the rate of C=C hydrogenation negatively in methyl vinyl ketone and crotonaldehyde, but promoted the selectivity of C=O hydrogenation in crotonaldehyde in which the unsaturated alcohol increased from 5 % on Pt to 21 % on Pt‐Re. The addition of Re to Pt also promoted the rate of C=O hydrogenation in 2‐butanone, whereas little effect was observed during the hydrogenation of butanal. The results of electron microscopy and H2 chemisorption on the Pt‐Re catalysts showed the increasing interaction between Pt and Re with the increasing metal weight loading, and results from rate measurements suggest that oxophilic Re can be used to promote the Pt‐catalyzed hydrogenation of carbonyl groups in multifunctional molecules.

Physicochemical properties of spent Achinsk refinery reforming platinum-rhenium catalyst

The physicochemical and technical properties of the R-98 reforming catalyst partially spent on a LK-6Us unit in the Achinsk refinery and changes in these characteristics during operation after four regeneration cycles have been studied. It has been found that during the time on stream of the catalyst, a reduction in the specific surface area, partial phase transformation of the oxide support, and buildup of carbon deposits and metal impurities serving as catalyst poisons take place. The regeneration did not afford complete recovery of the properties. In total, the above irreversible changes in the catalyst characteristics led to gradual degradation of the efficiency upon reforming.

Processing of deactivated platinum-rhenium catalysts

The literature review of processing methods for deactivated platinum-rhenium catalysts is presented, including a description of technologies used in practice. All known methods are divided into 2 main groups: 1) with complete dissolution of the catalyst base and 2) based on selective recovery of platinum and rhenium. Advantages and disadvantages of technological processes are discussed. It is noted that with regard to sharply rising prices of rhenium and the finiteness of its reserves, it is essential to practically implement the methods that provide high recovery of not only platinum, but also rhenium.

The role of rhenium in the conversion of glycerol to synthesis gas over carbon supported platinum–rhenium catalysts

Reaction kinetics measurements were carried out to study the conversion of aqueous solutions of glycerol (30 and 80 wt%) over carbon-supported Pt and Pt–Re catalysts at temperatures from 483 to 523 K. The results of these studies show that the turnover frequencies for production of H2, CO, CO2, and light alkanes (primarily methane) all increase upon the addition of Re to Pt/C catalysts. The molar ratio of H2/CO increases, while the CO/CO2 ratio decreases with Re addition, indicating increased rate of water–gas shift. For glycerol conversion over a Pt–Re/C catalyst with an atomic Pt:Re ratio of 1:1, increasing pressure or decreasing temperature leads to an increase in the production of alkanes and light oxygenated hydrocarbons (ethanol, methanol, propanediols, and acetone) at the expense of CO and CO2. Temperature-programmed desorption studies and microcalorimetric measurements indicate that addition of Re to Pt modifies the interaction of CO with surface sites. X-ray absorption spectroscopy and transmission electron microscopy studies provide evidence indicating that Pt–Re/C catalysts consist primarily of bimetallic nanoparticles with sizes below 2 nm, and Re inhibits the sintering of these nanoparticles during reaction conditions for glycerol conversion. The results of these reaction kinetic studies and characterization studies indicate that the performance of Pt–Re/C catalysts for glycerol conversion is related to the formation of Pt–Re nanoparticles, for which Re promotes the overall rate of glycerol reforming by reducing the binding energy of CO to Pt, thereby leading to less extensive blocking of surface sites by reaction intermediates and/or products. In addition, the presence of Re facilitates water–gas shift and CO bond cleavage reactions.

Modern domestic reforming catalysts for gasoline fractions

A variety of extruded RB-type reforming catalysts were developed on the basis of the AI-01 support; the technology is based on the application of special extra-pure specimens of pseudoboehmite monohydrate. The use of the AI-01 supportmade it possible to considerably increase the quality of platinum-rhenium catalysts, as well as their resistance, activity, selectivity, and stability. The industrial practice of the application of RB-type catalysts on the AI-01 support demonstrated their high efficiency comparable with the characteristics of the best foreign contact catalysts. The industrial manufacture of active alumina as a support for reforming catalysts in the spherical form was launched on the basis of alcoholate extra-pure pseudoboehmite as in the case of AI-01. Reforming RB-44Sh catalyst on a spherical support has a number of advantages over extruded catalyst; this catalyst is planned for application on the industrial scale on semiregenerative units in 2007.

Gas-phase conversion of glycerol to synthesis gas over carbon-supported platinum and platinum–rhenium catalysts

The rate of glycerol conversion to H 2/CO gas mixtures was measured under kinetically controlled reaction conditions over carbon-supported platinum and platinum–rhenium catalysts. The reaction is fractional order with respect to glycerol and zero order with respect to hydrogen, with activation barriers of 60–90 kJ mol −1. The addition of an equimolar amount of Re to Pt/C increases the production rate of CO by a factor of 5 at low conversion ( < 20 % ) and while co-feeding H 2, both of these factors leading to low pressures of CO in the reactor. At higher conversion conditions (20% conversion to gas-phase products) and without co-feeding H 2, the Pt–Re/C catalyst is an order of magnitude more active than Pt/C. Accordingly, Re has a greater promotional effect on the rate of glycerol conversion at conditions leading to higher CO pressures, suggesting that the primary promotional effect of Re is to weaken the interaction of CO with the surface, thereby decreasing the CO coverage and allowing the catalyst to operate at high rates in the presence of gaseous CO. Temperature-programmed reduction (TPR) studies of carbon-supported Pt and Re catalysts showed a peak near 460 K for Pt/C and near 650 K for Re/C. The position of the TPR peak for Re shifted to lower temperature on addition of Pt to Re, suggesting interaction between Pt and Re species, leading to alloy formation.

Thermocatalytic removal of carbonaceous materials

Decomposition and removal of carbonizate was performed over platinum catalysts supported on two types of alumina differing in the surface area: low surface area one (LSA) and high surface one (HSA). For the sake of comparison, the performance of platinum catalyst supported on silica and bimetallic platinum-rhenium catalysts was analyzed. It has been shown that all platinum catalysts examined caused an increase in the removal of carbonizate. The activity of these catalysts was independent of the kind of support applied or addition of rhenium as a second component.

Thermocatalytic removal of carbonaceous materials

Decomposition and removal of carbonizate was performed over platinum catalysts supported on two types of alumina differing in the surface area: low surface area one (LSA) and high surface one (HSA). For the sake of comparison, the performance of platinum catalyst supported on silica and bimetallic platinum-rhenium catalysts was analyzed. It has been shown that all platinum catalysts examined caused an increase in the removal of carbonizate. The activity of these catalysts was independent of the kind of support applied or addition of rhenium as a second component.