Zeolite-supported iron catalysts

It is concluded from the characterization studies, that the extraction technique which we have employed for the preparation of zeolite-supported iron catalysts results in the formation of highly dispersed, small particle-sized Y-Fe2°3 on the support surface and, in addition, a small amount ( 1%) of iron present as a spe-... 

The basis of the demonstration can be based on already published data on the surface reaction between NOz and adsorbed organic compounds. Yokoyama and Misono have shown that the rates of N02 reduction over zeolite or silica are proportional to the concentration of adsorbed propene [29], whereas Il ichev et al. have demonstrated that N02 reacts with pre-adsorbed ethylene and propylene on H-ZSM-5 and Cu-ZSL-5 to form nitro-compounds [30], Chen et al [2-4] have observed the same nitrogen-containing deposits on MFI-supported iron catalysts. The question on the pairing of nitrogen atoms is not considered here. 

H.-Y. Chen, X. Wang, and W. M. H. Sachtler, Reduction of NO c over zeolite MFI supported iron catalysts Nature of active sites, Phys. Chem., Chem. Phys. 2, 3083-3090 (2000). 

Series of zeolite-supported iron-containing catalysts with weight percent iron (% Fe) varying from 1 to 17% Fe have been prepared from Fe3(CO) 2 and the synthetic zeolites ZSM-5, mordenite and 13X by an extraction technique. The zeolites ZSM-5 and mordenite were used in the acid form, 13X in the sodium form. 

Carbon dioxide was proposed as an oxidant in dehydrogenation of ethylbenzene over zeolite-supported iron oxide catalyst, which was highly dispersed in zeolite matrix. The dehydrogenation was mainly proceeded under the oxidative pathway in the presence of carbon dioxide. The presence of carbon dioxide contributed to remarkable enhancement not only in dehydrogenation activity of catedyst but also of its coke resistance. 

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. 

Zeolite-supported iron oxide catalysts were prepared by precipitation of aqueous suspension of Fe(II) hydroxide in slightly alkaline solution at 333 K under N2 atmosphere. 

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

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. 

Selective oxidation of alkenes on a zeolite supported iron phthalocyanine catalyst... 

Chang JS, ParkSE, Park MS (1997) Beneficial effect of carbon dioxide in dehydrogenation of ethylbenzene to styrene over zeolite-supported iron oxide catalyst. Chem Lett 26 1123-1124... 

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. 

The efficiency and selectivity of a supported metal catalyst is closely related to the dispersion and particle size of the metal component and to the nature of the interaction between the metal and the support. For a particular metal, catalytic activity may be varied by changing the metal dispersion and the support thus, the method of synthesis and any pre-treatment of the catalyst is important in the overall process of catalyst evaluation. Supported metal catalysts have traditionally been prepared by impregnation techniques that involve treatment of a support with an aqueous solution of a metal salt followed by calcination (4). In the Fe/ZSM-5 system, the decomposition of the iron nitrate during calcination produces a-Fe2(>3 of relatively large crystallite size (>100 X). This study was initiated in an attempt to produce highly-dispersed, thermally stable supported metal catalysts that are effective for synthesis gas conversion. The carbonyl Fe3(CO) was used as the source of iron the supports used were the acidic zeolites ZSM-5 and mordenite and the non-acidic, larger pore zeolite, 13X. 

The one-stage synthesis of linear ot-olctlns has been investigated by the Mobil Oil Corporation using zeolite supported catalysts [140]. As is shown in Table VIII. iron on SiOj gave only 16% linear a olefins. ITic same catalyst on Na ZSM-5 led to a 48% selectivity of linear Of olefins.. An increase of iron content in the catalyst enhanced the conversion, promoting with potassium raised the selectivity up to 67% (140]. 

Several methods such as powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and BET isotherms from N2 adsorption-desorption were selected to characterize iron oxide in zeolite-supported catalysts. 

The selective synthesis of lower olefms(C2 - C4) by the CO2 hydrogenation over Iron catalysts promoted with Potassium and supported on ion exchanged(H, K) Zeolite-Y... 

The zeolite-encaped iron phthalocyanine catalyst was used to oxidize hydro-quinone to benzoquinone, 1-decene to 2-decanone and cyclohexene to 1-acetoxy-2-cyclohexene. The free iron phthalocyanine catalyst was also used for the same oxidation reactions, and the results were compared with those obtained employing the supported catalyst. 

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. 

Group 1 alkali metals (including potassium) are poisons for cobalt catalysts but are promoters for iron catalysts. Catalysts are snpported on high-surface-area binders/supports such as silica, alumina, and zeolites (Spath and Dayton, 2003). Cobalt catalysts are more active for FTS when the feedstock is natnral gas. Natnral gas has a high H2 to carbon ratio, so the water-gas-shift is not needed for cobalt catalysts. Iron catalysts are preferred for lower quality feedstocks such as coal or biomass. 

The Mittash catalyst is unsupported because iron is cheap and the alumina promoter warrants a high specific surface area. This situation is different with Ru catalysts, which are usually prepared on either oxide or carbon supports. Loading of zeolites with small Ru particles offers an interesting alternative but with lower activity, however (44,45). Pioneering work was performed by Ozaki and co-workers (46), who presented an alkali-promoted Ru catalyst on a carbon support with an activity superior to that of the conventional Fe catalyst operated at identical conditions. Further development of this type of catalyst (47) led to a material that has recently been installed in an industrial plant (Ocelot, Canada). Apart from lower capital costs, this plant also operates with reduced energy consumption, and replacement of the iron catalysts by Ru-based ones remains an interesting option for the future. 

---