Ruthenium-Zeolite Catalysts

Jacobs, in Catalysis by Zeolites , Proceedings of an International Symposium, 

Carbon-supported Catalysts. - Preparation of catalysts on carbon is very dependent on the available surface area, and supports can be divided into two broad categories  

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Aromatic Gasoline From Hydrogen/Carbon Monoxide Over Ruthenium/Zeolite Catalysts... 

SYNGAS CONVERSION OVER RUTHENIUM/ZEOLITE CATALYSTS AT 51 atm,... 

Tailoring of the product distribution is possible by a limitation of chain growth by pore size. This has been demonstrated by Ballivel Tkatchenko and Tkatchenko using zeolite catalysts. Ruthenium, iron or cobalt metal particles in Y-zcolilc supcrcagcs were prepared by thermal decomposition of the carbonyls. These metal-zeolite catalysts give selective formation of )- hydrocarbons [471. 

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. 

In this communication we wish to report a new, mild, aerobic oxidation of alcohols, catalyzed by ruthenium and cobalt(salophen)/zeolite catalysts. 

Dutta P K and Vaidyalingam A S (2003), Zeolite-supported ruthenium oxide catalysts for photochemical reduction of water to hydrogen , Micropor Mesopor Mater, 62, 107. 

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. 

The ruthenium zeolites were prepared by conventional ion exchange techniques using the Ru(NH3)e complex. The complex was decomposed at 300°C under flowing dry helium and the catalyst was reduced further under hydrogen at different temperatures. The nickel on NaY zeolite was prepared by conventional ion exchange procedures (9). The sample was dried and hydrogen reduced at 400°C. 

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. 

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... 

Carbon monoxide (C=0) and hydrogen (H2) produce methanol (CH3OH) on a ruthenium-exchanged zeolite-Y catalyst within a mbular reactor. Propose a mechanism and develop a kinetic rate law which accounts for the fact that a heterogeneous surface-catalyzed reaction occurs within the internal pores of the zeolite catalyst. Hint There are no hydrogen-hydrogen bonds in methanol. 

The value of vNN for N2 adsorbed on ruthenium-containing catalysts is very sensitive to the electronic state of the active surface. The IR spectrum of N2 adsorbed on ruthenium catalysts supported on dealuminated zeolite Y contains bands due to Ru (N2)(CO) (VN2 2218 cmvCO 2123 cm" ) and Ru (N2)2 (vN2 2207,2173... 

Co/SBA-15 catalysts with different ruthenium contents (0.05-0.5%) [104] demonstrate some advantages over other types of zeolite catalysts. The addition of Ru shifted the reduction temperature of cobalt (COjO CoO and CoO Co°) to lower temperatures and suppressed the formation of Co + species. Hydrogen spillover from ruthenium to cobalt oxide clusters was postulated. With the increase of the ruthenium content, enhancement of the catalytic activity in FT synthesis was unraveled. 

Mishra DK, Dabbawala AA, Park JJ, Jhung SH, Hwang J-S. Selective hydrogenation of D-gJueose to D-sorbitol over HY zeolite supported ruthenium nanoparticles catalysts. Catal Today 2014 232 99-107. 

Magnetic and Mdssbauer Characterization of Iron-Zeolite and Iron and/or Ruthenium on Doped-Carhon Catalysts... 

Fischer-Tropsch synthesis could be "tailored by the use of iron, cobalt and ruthenium carbonyl complexes deposited on faujasite Y-type zeolite as starting materials for the preparation of catalysts. Short chain hydrocarbons, i.e. in the C-j-Cq range are obtained. It appears that the formation and the stabilization of small metallic aggregates into the zeolite supercage are the prerequisite to induce a chain length limitation in the hydrocondensation of carbon monoxide. However, the control of this selectivity through either a definite particle size of the metal or a shape selectivity of the zeolite is still a matter of speculation. Further work is needed to solve this dilemna. 

The incorporation of a ZSM-5 class zeolite into a ruthenium Fischer-Tropsch catalyst promotes aromatics formation and reduces the molecular weight of the hydrocarbons produced. These composite catalysts can produce a high octane aromatic gasoline in good yield in a single step directly from synthesis gas. 

There are several examples of one-pot reactions with bifunctional catalysts. Thus, using a bifunctional Ru/HY catalyst, water solutions of corn starch (25 wt.%) have been hydrolyzed on acidic sites of the Y-type zeolite, and glucose formed transiently was hydrogenated on ruthenium to a mixture of sorbitol (96%), mannitol (1%), and xylitol (2%) [68]. Similarly a one-pot process for the hydrolysis and hydrogenation of inulin to sorbitol and mannitol has been achieved with Ru/C catalysts where the carbon support was preoxidized to generate acidic sites [69]. Ribeiro and Schuchardt [70] have succeeded in converting fructose into furan-2,5-dicarboxylic acid with 99% selectivity at 72% conversion in a one-pot reaction... 

Isoalkanes can also be synthesized by using two-component catalyst systems composed of a Fischer-Tropsch catalyst and an acidic catalyst. Ruthenium-exchanged alkali zeolites288 289 and a hybrid catalyst290 (a mixture of RuNaY zeolite and sulfated zirconia) allow enhanced isoalkane production. On the latter catalyst 91% isobutane in the C4 fraction and 83% isopentane in the C5 fraction were produced. The shift of selectivity toward the formation of isoalkanes is attributed to the secondary, acid-catalyzed transformations on the acidic catalyst component of primary olefinic (Fischer-Tropsch) products. 

Ruthenium is known to catalyze a number of reactions, including the Fischer-Tropsch synthesis of hydrocarbons (7) and the polymerization of ethylene (2). The higher metal dispersions and the shape selectivity that a zeolite provides has led to the study of ruthenium containing zeolites as catalytic materials (3). A number of factors affect the product distribution in Fischer-Tropsch chemistry when zeolites containing ruthenium are used as the catalyst, including the location of the metal (4) and the method of introducing ruthenium into the zeolite (3). 

The reactions are catalyzed by transition metals (cobalt, iron, and ruthenium) on high-surface-area silica, alumina, or zeolite supports. However, the exact chemical identity of the catalysts is unknown, and their characterization presents challenges as these transformations are carried out under very harsh reaction conditions. Typically, the Fischer-Tropsch process is operated in the temperature range of 150°C-300°C and in the pressure range of one to several tens of atmospheres [66], Thus, the entire process is costly and inefficient and even produces waste [67]. Hence, development of more economical and sustainable strategies for the gas-to-liquid conversion of methane is highly desirable. 

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