Platinum methanation catalyst

Andrussov A process for making hydrogen cyanide by reacting ammonia, methane and air at approximately 1,000°C over a platinum/rhodium catalyst ... 

Nickel-platinum bimetallic catalysts showed higher activity during ATR than nickel and platinum catalysts blended in the same bed. It was hypothesized that nickel catalyzes SR, whereas platinum catalyzes POX and, when they are added to the same support, the heat transfer between the two sites is enhanced [59, 60]. Advanced explanations were reported by Dias and Assaf [60] in a study on ATR of methane catalyzed by Ni/y-Al203 with the addition of small amounts of Pd, Pt or Ir. An increase in methane conversion was observed, ascribed to the increase in exposed Ni surface area favored by the noble metal under the reaction conditions. 

To date, the only shock tube apparatus equipped to study surface reactions is the KIST facility at ATK GASL in New York. The tests done so far have studied methane oxidation, CFI4 + 2O2 CO2 + 2H2O on the surface of an SCT ferrous-based reactor impregnated with platinum based catalyst. To isolate the effects of the screen and the catalyst on the reaction, three types of tests were run catalyzed screen with combustible gases,... 

Consequently, the direct use of hydrocarbon gases as fuel is usually considered to be impractical, although Whitesides and co-workers18 describe an aqueous fuel cell in which methane reacts with aqueous iron (III) ions over a platinum black catalyst to form CO2 and iron(II) the Fe2+ solution... 

Hydrogen cyanide (melting point -14°C, boiling point 26°C) is manufactured by the reaction of natural gas (methane), ammonia, and air over a platinum or platinum-rhodium catalyst at elevated temperature (the Andrussow process). 

In a reactor that is similar to a reformer, the reaction occurs in tubes that are heated externally to supply the endothermic heat of reaction129. Sintered corundum (a-Al203) tubes with an internal layer ( 15 microns thick) of platinum/ruthenium catalyst are used, hi some cases a platinum/aluminum catalyst may be used. To achieve adequate heat transfer, the tubes may be only % in diameter and 6V2 feet long. Selectivities of 90-91% for methane and 83-84% for ammonia are reached at 1200°C to 1300°C reaction temperatures. 

Degussa Also called BMA. The process by which this large German company is best known is its version of the Andrussov process for making hydrogen cyanide. Methane and ammonia are reacted in the absence of air, at approximately 1,400°C, over a platinum metal catalyst ... 

Alkanes and arenes can also be activated to other reactions by platinum complexes in aqueous solution (57,58). For arenes in the presence of H2PtCl5, reduction from Pt(IV) to Pt(II) occurs and the arene undergoes chlorination. The reaction is catalyzed by platinum(II) (59). Similarly, if a platinum(IV) catalyst such as HjPtClg is used, chloroalkanes are formed from alkanes. As an example, chloromethane is formed from methane (Eq. 23) (60-62). Linear alkanes preferentially substitute at the methyl... 

Feng, Kostrov and Stewart (1974) reported multicomponent diffusion data for gaseous mixtures of helium (He), nitrogen (N2) and methane (CH4) through an extruded platinum-alumina catalyst as functions of pressure (1 to 70 atm), temperature (300 to 390 K), and terminal compositions. The experiments were designed to test several models of diffusion in porous media over the range between Knudsen and continuum diffusion in a commercial catalyst (Sinclair-Engelhard RD-150) with a wide pore-size distribution. 

Poisoning of metal catalysts may provide a tool for improving selec> tivity by affecting the concentrations of ensembles required by different reaction paths. This is illustrated by steam reforming on sulfur passivated nickel catalysts and the results are compared with observations for sulfided platinum-rhenium catalysts for catalytic reforming and for a chlorine poisoned palladium catalyst for partial oxidation of methane. 

With the introduction of Pt/Re catalysts, it is possible to achieve the ensemble control with much smaller sulfur addition. The su1fur-free Pt/Re catalyst by itself has a higher relative activity for hydrogenolysis than a platinum catalyst. However, this is changed when sulfur Is present In the feed. Kughes has described the first observations in a pilot plant. The catalyst produced more methane than any other that had been tested, and the run would probably have been aborted if it had not been an ordinary catalyst screening test. However, after the first and second weeks on stream, the selectivity improved and finally became similar to that of a fresh platinum/ alumina catalyst and as the run continued, the catalyst proved to be more stable than any previous catalyst tested. These results were ascribed to the presence of sulfur in the feed and could be obtained even with very low sulfur contents, l.S ppm. ... 

The first examples of skeletal rearrangements on metals were reported by the Soviet school of catalysis. A major step in hydrocarbon chemistry was the finding that platinum, unlike palladium and nickel, selectively catalyzes the hydrogenolysis of cyclopentane hydrocarbons. At about 300°C, on the classical Zelinskii platinum-charcoal catalyst, cyclopentane yields -pentane as sole reaction product (3, 4), while palladized charcoal is completely inactive (J) and nickel-alumina produces all the possible acyclic hydrocarbons, from methane to pentane (5-7). 

On the basis of activity and activity maintenance, the use of an iridium-alumina catalyst in reforming appears very reasonable (35,36). However, in our experience, the yields of low molecular weight alkanes (methane and ethane) are higher with an iridium-alumina catalyst than with a platinum-alumina catalyst, resulting in lower yields of C5+ reformate. Because of the higher value of C5+ reformate relative to products such as methane and ethane, the iridium-alumina catalyst is not used, despite its higher activity and better activity maintenance. 

As a result of the higher yields of methane and ethane in the run on the platinum-iridium catalyst, the hydrogen concentration in the recycle gas stream was lower than in the run on the platinum-rhenium catalyst. Consequently, the hydrogen partial pressure at the reactor inlet was also lower. The average hydrogen partial pressures were 15.1 and 16.5 atm, respectively, for the runs on the platinum-iridium and platinum-rhenium catalysts. The difference in hydrogen partial pressure at a fixed total pressure is a consequence of the different compositions of the gaseous products, which, in turn, reflect... 

Figure 5.10 shows that C5+ yields are equivalent for the platinum-rhenium catalyst and the combined catalyst system and about 1.0 to 1.5 vol% higher than for the platinum-iridium catalyst. Methane and ethane yields for the combined catalyst system are higher than those for the platinum-rhenium catalyst but lower than those for the platinum-iridium catalyst. Yields of H2 are about equivalent for the combined catalyst system and the platinum-iridium catalyst and are lower than those for the platinum-rhenium catalyst. Similarly, the yields of C3 and C4 hydrocarbons are about equivalent for the platinum-iridium catalyst and the combined catalyst system but are lower than the yields for the platinum-rhenium catalyst. 

Figure 2 Ignition curve for methane/air mixtures on a platinum foil catalyst. Shown is the catalytic ignition temperature vs equivalence ratio. Sot all experimental data points are shown.)...

Hydrogen cyanide is produced industrially by thermolysis of formamide, or from methane and ammonia on platinum-rhodium catalysts (following a process developed by Leonid Andrussow (1896-1988) in 1927 at BASF in Ludwigs-hafen) (Fig. 5.196). 

Lenz et al. [73] described the development of a 3 kW monolithic steam-supported partial oxidation reactor for jet fuel, which was developed to supply a solid oxide fuel cell (SOFC). The prototype reactor was composed of a ceramic honeycomb monolith (400 cpsi) operated between 950 C at the reactor inlet and 700°C at the reactor outlet [74]. The radial temperature gradient amoimted to 50 K which was attributed to inhomogeneous mixing at the reactor inlet. The feed composition corresponded to S/C ratio of 1.75 and O/C ratio of 1.0 at 50 000 h GHSV. Under these conditions, about 12 vol.% of each carbon monoxide and carbon dioxide were detected in the reformate, while methane was below the detection limit. Later, Lenz et al. [74] described a combination of three monolithic reactors coated with platinum/rhodium catalyst switched in series for jet fuel autothermal reforming. An optimum S/C ratio of 1.5 and an optimum O/C ratio of 0.83 were determined. Under these conditions 78.5% efficiency at 50 000 h GHSV was achieved. The conversion did not exceed 92.5%. In the product of these... 

It will be recalled that methane (CH4) can be converted to nitromethane (H3CNO2) by the action of nitric acid on methane at high temperature (Chapter 6, Equation 6.10). The nitration of other alkanes by the same process can also be effected, but separation of the multitude of isomers that can be formed (from all but the simplest alkanes) can be difficult. Nitroalkanes, R-NO2 (sometimes accompanied by their corresponding nitrite isomers, R-ONO), can also be prepared (as shown in Chapter 7, Table 7.5e) by treatment of alkyl halides with nitrite anion (ONO ). Reduction of nitroalkanes (R-NO2) with hydrogen (H2) in the presence of a platinum (Pt) catalyst or lithium aluminum hydride (LiAIlT,) in ether produces the corresponding amine (Equation 10.18). 

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