Ruthenium-zeolite activation

Fig. 11. Dependence of the catalytic activity (turnover number) of ruthenium A, X, Y, L, and mordenite zeolites for the hydrogenation of benzene on the surface area S of the ruthenium zeolite O, mordenite-4 , A-2 A, X-l A, X-2 0, Y-I . Y-4 , L-2 3, L-4. (Reproduced from Ref. 115 with permission from the authors.)...

The same workers (234) also studied the methanation behavior of bimetallic clusters of Ru/Ni and Ru/Cu in zeolite Y. Such clusters can be formed by metals, such as ruthenium and copper which are immiscible as bulk metals (235, 236). The turnover numbers versus bimetallic cluster composition are shown in Fig. 22. Dilution of ruthenium with copper clearly causes a marked decrease in specific activity. This decrease in activity is also accompanied by a decrease in methanation selectivity. This was attributed to an inhibiting effect of copper on the ruthenium hydrogenolysis activity. 

Carbon monoxide is hydrogenated over ruthenium zeolites in both methanation and Fischer-Tropsch conditions. is exchanged in the zeolite as the amine complex. The zeolites used are Linde A, X, Y, and L, natural chabazitey and synthetic mordenite from Norton. The zeolites as a support for ruthenium were compared with alumina. The influence of the nature of the zeolite, the ruthenium metal dispersion and the reaction conditions upon activity and product distribution were investigated. These zeolites are stable methanation catalysts and under the conditions used show a narrow product distribution. The zeolites are less active than other supports. Sintering of ruthenium metal in the zeolite supercages shows only minor effects on methanation activity, although under our Fischer-Tropsch conditions more C2 and C3 are formed. 

Fischei>-Tropsch (F.T.) Activity. Carbon monoxide also was hydrogenated over ruthenium zeolites under F. T. conditions low reaction temperature (>260°C), low CO/H2 ratios (=1), and longer contact times. The catalysts used were 6.6 and 8.6 wt % Ru on Y and X zeolite, respectively. 

Influence of the Zeolite on the Product Distribution. When a less acidic support was used for ruthenium, better activity was found under methanation conditions. Using the same argument, under F. T. conditions a higher selectivity for formation of higher hydrocarbons is expected when a less acidic support is used. In this respect, pertinent data are given over RuX and Y zeolites in Table V. The X zeolite is known to be less acidic than the Y zeolite. There is indeed a definite influence of the zeolite matrix in the indicated direction higher products are formed over zeolite X. 

Ruthenium zeolites are active and stable methanation catalysts. Under the Fischer-Tropsch conditions used here they show a narrow product distribution. When the size of the ruthenium particles enclosed in the zeolite cages is increased, there is hardly any eflFect found on the methanation activity. Under F. T. conditions a higher amount of C2 and C3 products are formed. Zeolites are generally less active than other supports. In the class of zeolite supports, the less acidic zeolites act as promoters of the CO hydrogenation under methanation conditions the... 

We report here results related to the catalytic behaviour of dodecacarbonyl-tri-iron and tri-ruthenium, bis(cyclopentadienyl-dicarbonyliron) and octacarbonyl-di-cobalt deposited on Y-zeolites under F-T conditions. The influence of the nature of the zeolite and of the metal, the dispersion of the metal and the reaction conditions upon activity and products distribution were investigated. 

Comparison of Initial Methanation Activities for Zeolite and Alumina Supported Ruthenium Catalysts... 

Mossbauer studies of the impregnation of silica with ruthenium chloride solution and subsequently dried at 383 K have reported (59) the presence of a ruthenium surface complex resembling RuC13 xH20. Recent work (128) has shown that Mossbauer spectra of "Ru supported on alumina, silica, activated charcoal, and X- and Y-zeolite are sensitive to the nature of the preparation and treatment of the samples. 

Low Temperature Water Gas Shift Activity of Ruthenium in Zeolites in Relation to Its Chemistry... 

The shapc-selective catalysis by metal carbonyls deposited in Y zeolites has also been studied by Ballivet-Tkalchenko and Tkaichenko [47. 1351-Iron, cobalt and ruthenium carbonyls in the supercages of acidic and neutral Y zeolites were examined. The product distributirm i limited to the range Ci C9. Fc3(CO)i3 on Na Y zeolite is an active catalyst, whereas Fe3(CO)i2- HY is inactive. However, the addition of the acidic HY zeolite to the Fc3(CO)ii-Y... 

The production of hydrogen from methane over zeolite supported metal catalysts can be examined as an alternative to steam reforming because the concomitant aromatization reactions can increase the economic potential of the process. For methane aromatization, Mo/ZSM5 catalysts have been intensively studied since their first report in 1993 (/, 2). In 1997 (3), the promotional effect of ruthenium over Mo/ZSM5 catalysts was reported. Other second metals have also been studied to improve catalyst activity and stability and a review on this topic is available 4). 

Zeolites are also able to decompose N2O. Li and Armor (11] prepared 25 zeohte samples by exchanging the cation Na+. These catalysts were tested for the catalytic decomposition of N2O. The Co- and Cu-exchanged zeolites are active at temperatures ranging from 623 K to 673 K. Rhodium and ruthenium supported on ZSM-5 are active catalysts between 523 and 573 K. 

A Co(salophen)/zeolite catalyst was prepared by the template synthesis method. This catalyst proved to be active in the ruthenium catalyzed oxidation of benzyl alcohol. The heteroge-nized Co(salophen), having the same amount of complex produced a higher rate in the oxidation reactions than the free complex. It can be explained by the sites isolation theory. In the case of the heterogenized catalyst it was not necessary to use an extra axial ligand such as triphenylphosphine. It was also found that in the case of Co(salophen)/zeolite catalyst the choice of the solvent was not so critical, as in the case of the free complex. 

Iron-phthalocyanine (Fe-Pc) encapsulated in Y and VPI-5 zeolites were used for the oxidation of alkanes or olefins in presence of t-butylhydroperoxide or H2O2 (Fig. 9). Fe-Pc-Y also catalyzed the oxidation of cyclohexane to cyclohexanol and cyclohexanone with t-butylhydroperoxide ( TBHP ). Ruthenium perfluorophthalocyanine complexes encapsulated in NaX ( Ru-Fi6 Pc-X ) were active for the oxidation of cyclohexane with TBHP at room temperature.Manganese(II) bipyridyl complexes in faujasite ( Y ) zeolite are active for the oxidation of cyclohexene to adipic acid in the presence of H2O2 at room temperature. Similarly oxidation reactions have been reported using copper complexes encapsulated in X,Y, and VPI-5 molecular sieves. 

Fig.2. Activity in MeOH oxidation of Y zeolite-included ruthenium (SI), rutheniun-iron (S2) and iron (S3) oxides per unit mass of metal as the function of Ru (1-4), RuFe (5,6) and Fe (7-9) loading...

Methanation Activity. AcnviTY and Selectivity. In Figure 1 are compared the methanation activity of 0.5 wt % Ru on NaY zeolite and on alumina, and 1% Ni on NaY zeolite. It is seen that the initial activity of the two ruthenium catalysts is comparable, while the nickel catalyst is... 

Influence of the Reduction Temperatube. RuNaY zeolite, containing 5.6 % Ru by weight, is taken as a representative catalyst to illustrate the influence of the reduction temperature on the methanation activity. The dispersion of the ruthenium metal phase measured by desorption of chemisorbed hydrogen and by CO chemisorption is given in Table I. 

---