Iron/zeolite catalysts, catalytic

Catalytic Evaluation In order to investigate support effects in these iron/zeolite catalysts prepared from Fe3(C0)12 by the extraction technique, three catalysts of similar weight percent iron loading were evaluated for their ability to catalyze synthesis gas conversion these catalysts were 15.0% Fe/ZSM-5, 16.4% Fe/Mordenite andl5.0% Fe/13X. All catalysts were evaluated under similar conditions as described in the experimental section. Catalytic data is presented in the accompanying figures in each figure the first three points for each catalyst are data obtained at 280°C, the second three points are data at 300°C. 

Catalytic oxidative dehydrogenation of propane by N20 (ODHP) over Fe-zeolite catalysts represents a potential process for simultaneous functionalization of propane and utilization of N20 waste as an environmentally harmful gas. The assumed structure of highly active Fe-species is presented by iron ions balanced by negative framework charge, mostly populated at low Fe loadings. These isolated Fe sites are able to stabilize the atomic oxygen and prevent its recombination to a molecular form, and facilitate its transfer to a paraffin molecule [1], A major drawback of iron zeolites in ODHP with N20 is their deactivation by accumulated coke, leading to a rapid decrease of the propylene yield. 

In the direct ammoxidation of propane over Fe-zeolite catalysts the product mixture consisted of propene, acrylonitrile (AN), acetonitrile (AcN), and carbon oxides. Traces of methane, ethane, ethene and HCN were also detected with selectivity not exceeding 3%. The catalytic performances of the investigated catalysts are summarized in the Table 1. It must be noted that catalytic activity of MTW and silicalite matrix without iron (Fe concentration is lower than 50 ppm) was negligible. The propane conversion was below 1.5 % and no nitriles were detected. It is clearly seen from the Table 1 that the activity and selectivity of catalysts are influenced not only by the content of iron, but also by the zeolite framework structure. Typically, the Fe-MTW zeolites exhibit higher selectivity to propene (even at higher propane conversion than in the case of Fe-silicalite) and substantially lower selectivity to nitriles (both acrylonitrile and acetonitrile). The Fe-silicalite catalyst exhibits acrylonitrile selectivity 31.5 %, whereas the Fe-MTW catalysts with Fe concentration 1400 and 18900 ppm exhibit, at similar propane conversion, the AN selectivity 19.2 and 15.2 %, respectively. On the other hand, Fe-MTW zeolites exhibit higher AN/AcN ratio in comparison with Fe-silicalite catalyst (see Table 1). Fe-MTW-11500 catalyst reveals rather rare behavior. The concentration of Fe ions in the sample is comparable to Fe-sil-12900 catalyst, as well as... 

Xyloflning [Xylol refining] A process for isomerizing a petrochemical feedstock containing ethylbenzene and xylenes. The xylenes are mostly converted to the equilibrium mixture of xylenes the ethylbenzene is dealkylated to benzene and ethylene. This is a catalytic, vapor-phase process, operated at approximately 360°C. The catalyst (Encilite-1) is a ZSM-5-type zeolite in which some of the aluminum has been replaced by iron. The catalyst was developed in India in 1981, jointly by the National Chemical Laboratory and Associated Cement Companies. The process was piloted by Indian Petrochemicals Corporation in 1985 and commercialized by that company at Baroda in 1991. 

Destruction of N20 can be carried out at lower temperatures by adding a reductant. In this case an iron-containing zeolite catalyst is used for the selective catalytic reduction of N20 using hydrocarbons as a reductant. The catalyst did not deactivate in a 2000-hour test under demanding conditions (450°C, 6% H20). Hydrocarbons such as propane (or LPG) and methane (widely available as natural gas) can be used as the reducing agent221. 

We have prepared the Fe Pc/ zeolite catalyst and used in the aerobic oxidation of 1-octene and cyclohexene. Zeohte-encapsulated iron phthalocyanine proved to be an active and stable catalyst in the oxidation of hydroquinone and in the triple catdytic oxidation of 1-octene and cyclohexene. Product distribution, selectivity and yield were similar to those obtained with free iron phthalocyanine. No decrease in catalytic activity was observed during the catalytic reaction. The zeohte-encapsulated complex is easier to handle than the non-supported one, it can be removed from the reaction mixture by simple filtration and it can be reused in several subsequent catalytic runs with similar catalytic activity. 

Large amounts of styrene are commercially produced by dehydrogenation of ethylbenzene (EB) in the presence of steam using iron oxide-based catalysts. Carbon dioxide, small amounts of which are formed as a by-product in the ethylbenzene dehydrogenation, was known to depress the catalytic activity of commercial catalyst [7,8]. However, it has been recently reported that several examples show the positive effect of carbon dioxide in this catalytic reaction [5,9,10]. In this study, we investigated the effect of carbon dioxide in dehydrogenation of ethylbenzene over ZSM-5 zeolite-supported iron oxide catalyst. 

Among zeolite-supported iron oxide catalysts the highest catalytic activity was obtained in the case of 5.0 wt.% loading of iron oxide... 

We presented a facile route for the modification of zeolites and for the preparation of bifunctional catalysts possessing both acidic and hydrogenation functions via solid-solid reaction. Branched and higher hydrocarbons were obtained over such modified composite catalysts. Sodium migration from the surface of the iron-based catalyst to the zeolite during the solid-solid reaction accounts for the change of catalytic activity. XRD measurements exhibited evidence for Na migration. 

Langhendries et al [5.74] analyzed the liquid phase catalytic oxidation of cyclohexane in a PBMR, using a simple tank-in-series approximate model for the PBMR. In their -reactor the liquid hydrocarbon was fed in the tubeside, where a packed bed of a zeolite supported iron-pthalocyanine catalysts was placed. The oxidant (aqueous butyl-hydroperoxide) was fed in the shellside from were it was extracted continuously to the tubeside by a microporous membrane. The simulation results show that the PBMR is more efficient than a co-feed PBR in terms of conversion but only at low space times (shorter reactors). A significant enhancement of the organic peroxide efficiency, defined as the amount of oxidant used for the conversion of cyclohexane to the total oxidant converted, was also observed for the PBMR. It was explained to be the result of the controlled addition of the peroxide, which gives low and nearly uniform concentration along the reactor length. 

There is considerable interest in isomorphous substitution of aluminium in the zeolite framework by other elements and some papers have described the synthesis of MFI zeolites containing boron, gallium, titanium and iron as lattice elements (ref.1-3). The replacement of Al ions with the ions of another element can modify both the acidity and pore size features of the zeolite (ref.4, 5), resulting in modification of the catalytic property of zeolite catalysts (ref.6-8). 

Fe-FER, Fe-BEA, and Fe-MFI catalysts prepared by the proposed method provide for high catalytic activity in all three test reactions, i.e. NO oxidation (see Fig. 4), SCR of NO by propane (see Fig. 5), and N2O decomposition, showing 50 % conversion of N2O at 350 °C for all three iron-zeolite samples with Fe/Al value of about 0.05. For the same iron content activity of the Fe-MFI sample in NO oxidation is lower in comparison with Fe-FER and Fe-BEA samples, both reaching the equilibrium NO2/NO composition for temperature above 300°C. In the SCR reaction the picture is more complex, with Fe-MFI showing higher activity at lower temperatures and then decreasing at temperatures above 350°C. Significantly, the selectivity of the process, i.e. the... 

Zeolites are well suited for the preparation of encapsulated complexes by virtue of the large supercages. Metallo-phthalocyanines encaged in zeolites have been proposed as enzyme mimics [7,8 Zeolite-encapsulated iron phthalocyanine catalysts have been used in hydrocarbon oxidations it was found that the resistance of the zeolite-encaged complexes against oxidative destruction by far exceeded that of free iron phthaTocyanines [9,10]. In the present work, zeolite-encaged phthalocyanine catalysts were studied in the triple catalytic oxidation of olefins. 

The zeolite-encapsulated iron phthalocyanine catalyst was also active in this reaction and the catalytic activity was similar to that of the free complex. After the injection of a new portion of hydroquinone, the catalyst showed almost the same activity as in the first run, indicating that there was no catalyst deactivation during the reaction. The supported catalyst can be filtered off and used in new experiments. 

The zeolite-encapsulated iron phthalocyanine catalyst exhibited a similar behavior. When the oxygen uptake in the first run had ceased, 1-decene was injected into the reactor (second run), and the oxygen uptake was measured again. A similar rate was measured in the second run as in the first one, i.e. the catalytic activity did not decrease during the oxidation reaction, in spite of the presence of the strong acid HCIO4 in the reaction mixture. 

In the last years a great interest was paid to the catalytic properties of iron-containing zeolites that show interesting activities in different industrial reactions. The Fe-BEA zeolite is reported to be a good catalyst in the vapour phase alkylation processes [1], the Fe-TON zeolite shows very high activity and selectivity in the olefin isomerization [2, 3]. Finally, new applications of zeolitic catalysts in the partial oxidation catalysis, such as the Solatia Inc. processes for benzene hydroxylation to phenol using Fe-MFI, open a novel route for the use of zeolites in oxidation processes [4, 5]. On the other hand, the catalytic properties of the metal-modified MOR type zeolite in the isomerization process are well known. 

Ammonia may likewise be used as reductant for selective catalytic reduction of NOx species. For this application, metal-exchanged zeolite catalysts offer new opportunities to reduce NOx emissions from lean-bum engine via the NH3-SCR process. Iron-exchanged ZSM-5 has received much attention because of its promising activity and stability in the NH3-SCR process. Correlating catalytic activities with the concentration of mononuclear and binuclear Fe species shows that both types of Fe ions and even small metal clusters are active sites for SCR,... 

The presence of thallium(0) led to an increase in activity and selectivity of metallic palladium catalysts supported on silica in aldose oxidation reactions. However, silica-supported thallium(0) had no activity by itself (entry 3). ° Similarly, the bimetallic catalyst platinum-thallium/ZSM-5, prepared by impregnation of thallium sulfate and chloroplatinic acid on Zeolite Socony Mobil-5 (ZSM-5), showed greater selectivity in propane aromatisation and almost the same catalytic activity as monometallic thallium/ZSM-5 (entry 4). Similar comparison of vanadium-caesium-copper and vanadium-caesium-copper-thallium catalysts supported on TiOa.SiC demonstrated that addition of thallium improved the catalytic activity in partial oxidation of p-tert-butyltoluene to p-tert-butyl-benzaldehyde (entry The application of solid-supported thallium-based catalysts in different processes includes (a) iron-thallium catalysts in carbon monoxide hydrogenations to form hydrocarbons and alcohols, and catalytic reforming of... 

The preparation procedure of iron zeolites strongly influences the nature and distribution of iron species in the catalyst and the catalytic performance. Catalysts were prepared by hydrothermal synthesis, liquid-ion exchange, and chemical vapor deposition containing molar Fe/Al ratios in the range of 0.26-1. Activation in steam of the isomorphously substituted iron zeolite leads to superior propylene yields (22-25%) as compared to iron zeolites prepared by liquid-ion exchange and chemical vapor deposition (9-16%), with propylene selectivities around 40%. Iron impurities (170 ppm Fe) in steamed commercial H-ZSM-5 induce relatively low conversions of propene and N2O, but lead to a propylene selectivity of 90%. Mononuclear Fe sites are crucial for ODHP as iron species in large clusters enhance deep oxidation. ... 

Iron-modified zeolites (Fe/ZSM-5) are highly efficient catalysts for a wide range of important processes than include the selective oxidation of benzene with N O (the Panov reaction) [37], catalytic decomposition of N O [38], selective catalytic reduction (SCR) of NOx [39], and many others. These unique properties stem from the presence of specific extra-framework iron-containing cationic species in the micropores of ZSM-5 zeolite [40]. Because of a very heterogeneous iron speciation in the zeolite catalyst, the direct determination of the catalytically active iron species and the mechanism of the catalytic reaction by experimental methods was not possible. The exact speciation will obviously depend on such parameters as the Fe loading, the method of iron introduction, and the history of the sample (calcination, reduction, etc.). Many studies have indicated that the reactivity of Fe/ZSM-5 for the selective benzene oxidation is mainly associated with the presence of highly dispersed Fe + extraframework cations [41]. On the contrary, the high catalytic activity in the N O decomposition... 

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