Conversion metal-impregnated zeolite catalysts

The use of bifunctional metal/zeolite catalysts for the conversion of synthesis gas (carbon monoxide and hydrogen) to gasoline range hydrocarbons has recently attracted much attention. For example, the combination of metal oxides with the medium pore ( 6A) zeolite ZSM-5 and the use of a metal nitrate impregnated ZSM-5 catalyst have been shown to produce gasoline range hydrocar-... 

Metal oxides on zeolites have also found use as redox catalysts. High-temperature (700-750 °C) dehydroaromatization of methane under nonoxidizing conditions has been explored with a number of zeolitic catalysts modified with transition metal ions. Although coke formation at these high temperatures is a problem, calcined molybdate-impregnated ZSM-5 shows unparalleled activity of up to 8 % methane conversion with 100 % selectivity towards aromatics. Surface studies of these Mo HZSM-5 catalysts indicate that M0O3 crystals are on the external zeolite surface [123]. 

Catalysts were contaminated with nickel and vanadium according to the method of Mitchell ( ), using metal naphthenates. Prior to blending, all contaminated materials were steamed (1450 F, 4 hrs, 90% steam, 10% air) to age the metals. The selectivity effects of the metals on the non-zeolitic component were determined by blending impregnated non-zeolitic components with 20% of the steamed, uncontaminated high activity zeolitic component such that the overall blend yielded 70% conversion. 

Rb+- and Cs+-impregnated X zeolites were found to exhibit the highest activity and selectivity in these transformations. A CsX zeolite treated with boric acid, for example, gave better than 50% overall selectivity in the formation of styrene and ethylbenzene (410°C, 60% conversion).275 Treatment of these catalysts with copper or silver nitrate resulted in further improvements in catalyst performance.276 The promoting role of these metals was suggested to be their involvement in dehydrogenation of methyl alcohol. 

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. 

High-yield catalytic conversion of glycerol into 1,2-propanediol without using an external H2 supply is possible on Pt impregnated NaY zeolites, characterized by extra-zeolitic metal clusters combined with traces of Bronsted acidity. A comparison is made with NaY zeolite supported Pt catalysts prepared by a conventional ion-exchange procedure. Both materials were characterized using SEM, XRD and CO chemisorption. 

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