Ruthenium product distribution over

Table V. Product Distribution over Ruthenium Zeolites ...

In a recent communication (250), deviations from Schulz-Flory kinetics were observed for a RuNaY synthesis gas conversion catalyst (see Fig. 24). A comparative catalyst, prepared by impregnating silica with ruthenium, i.e., Ru/SiOz, and tested under the same conditions, yielded a product distribution which gave a good fit to Schulz-Flory kinetics. The sharp decrease in chain growth probability for Cf0 products over RuNaY is perhaps surprising for such a relatively large-pore zeolite. Further studies (251-253) on this system indicated that there was a correlation between the ruthenium particle size in the zeolite and the product distribution. 

Investigations into these topics are presented in this volume. Iron, nickel, copper, cobalt, and rhodium are among the metals studied as Fischer-Tropsch catalysts results are reported over several alloys as well as single-crystal and doped metals. Ruthenium zeolites and even meteo-ritic iron have been used to catalyze carbon monoxide hydrogenation, and these findings are also included. One chapter discusses the prediction of product distribution using a computer to simulate Fischer-Tropsch chain growth. 

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. 

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. 

Tandem GM-RGM (see Scheme 20) can be employed for the synthesis of complex ring systems from simple starting materials. A very noteworthy example of this reaction serves as the cornerstone for the total synthethis of the natural product cyclindrocyclophane. The GM-RGM reaction of diene 182 was completely selective for formation of the head-to-tail isomer 183. The selectivity was attributed to thermodynamic control the head-to-head dimer 184 is considerably less stable. In an effort to synthesize pyrenophorin derivatives, the formation of cyclic dimers (e.g., 186) and trimers (e.g., 187) from treatment of acrylate ester-alkene derivatives (e.g., 185) with various ruthenium metathesis catalysts was examined.The product distribution was very time and concentration dependent higher concentrations favor the trimer over the dimer. 

Figure 6.6 Large-scale production and characterisation of SILP and SCILL catalyst materials. Left a schematic drawing of the toroidal movement of the support particles in an air coater during impregnation with the solvent-diluted ionic liquid catalyst solution. Right an SF.M-EDX picture for material characterisation, exemplified for a spherical y-alumina coated with (RurCOloClolol in rCjdmimirOTfl to check the elemental distribution ruthenium Tdark grey area at the external surface of the catalyst pelleti sulfur Hight grey spots distributed over the catalyst pellet ilOOl.

The hydrogenation of C02 in the presence of amines to give dialkylformamides has been carried out directly in an IL/scC02 system. In this case, the ionic liquid was shown to play a dual role [74]. It is an effective solvent for the ruthenium phosphine catalyst and at the same time allows a distinct phase distribution of the polar carbamate intermediates and the less polar products formed during the conversion of C02. As a result, the selectivity of the reaction can be increased over conditions where scC02 is used as the sole reaction medium. 

Tanaka has recently reviewed the hydrogenation of ketones with an emphasis on the mechanistic aspects of the reaction.233 Numerous references related to this subject can be found in his article. Deuteration of cyclohexanones and an application of NMR spectroscopy to the analysis of deuterated products have revealed that on ruthenium, osmium, iridium, and platinum, deuterium is simply added to adsorbed ketones to give the corresponding alcohols deuterated on the Cl carbon, without any deuterium atom at the C2 and C6 positions, while over palladium and rhodium the C2 and C6 positions are also deuterated.234 A distinct difference between rhodium and palladium is that on rhodium deuterium is incorporated beyond the C2 and C6 positions whereas on palladium the distribution of deuterium is limited to the C2 and C6 carbons.234,235 From these results, together with those on the deuteration of adamantanone,236 it has been concluded that a Tt-oxaallyl species is formed on palladium while deuterium may be propagated by an a, 3 process237 on rhodium via a staggered a, 3-diadsorbed species. 

The reaction of ethylene with deuterium was studied (61) between 0 and 80° used alumina-supported catalysts. A selection of the results and some of the calculated distributions are shown in Table XXI. The addition reactions are first-order in deuterium and zero in ethylene. At < 50° some 50% of the initial products are exchanged ethylenes over ruthenium and some 25% over osmium. These figures are unaffected by alteration in the ethylene pressure but are suppressed by increasing deuterium pressure. The relative rates of both exchange processes increase with rising temperature, and the following activation energy differences have been derived ... 

Production of Higher-Molecular-Weight Hydrocarbons. Kinetics, Surface Science, and Mechanisms The hydrogenation of carbon monoxide over iron, cobalt, and ruthenium surfaces produces a mixture of hydrocarbons with a wide range of molecular-weight distribution. Most of the hydrocarbons produced are normal paraffins however, olefins and alcohols in smaller concentrations are also obtained. 

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