摘要:
Zeolites exchanged with lithium, rubidium, cesium cations and trivalent cations are prepared by first partially, fully or excessively ion-exchanging a sodium-containing zeolite, a potassium-containing zeolite or a sodium- and potassium-containing zeolite with trivalent cations, then calcining the partially, fully or excessively trivalent cation-exchanged zeolite, and then ion exchanging the calcined zeolite with lithium rubidium, cesium cations, thereby replacing hydrogen and any sodium and/or potassium cations remaining in the zeolite with lithium, rubidium, cesium cations, whereby trivalent cations present in the zeolite will not be substantially replaced by the lithium ions.
摘要:
A catalyst composition comprises at least one first layer of a catalytically active metal dispersed on an inert carrier first support and at least one second layer of a reduced metal catalyst consisting essentially of a noble or transition metal supported on or in a stable inorganic metal oxide washcoat on a second support, the first layer having a greater thermal stability than the second layer. The catalyst compositions may be used to catalyse the partial oxidation of hydrocarbons, particularly C 1 to C 4 hydrocarbons, to form synthesis gas mixtures of carbon monoxide and hydrogen. The first layer may, for example, comprise rhodium supported on alumina. The second layer may comprise a porous partially stabilised zirconia monolith having a ceria wash coat supporting a rhodium metal catalyst.
摘要:
Sodium X zeolite containing little or no sodium A zeolite as by-product, is prepared by direct synthesis from a uniform, substantially potassium ion free aqueous reaction / mixture comprising silica, alumina and sodium ions, the concentration of the components in the reaction mixture being such that the silica/alumina molar ratio is in the range of about 2.1:1 to about 3.0:1, the sodium oxide/silica ratio is in the range of about 1.2:1 to about 2.5:1 and the water / sodium oxide molar ratio is greater than about 35:1. The crystallization step is carried out by maintaining the reaction mixture at a temperature below about 70° C, but preferably equal to or above 50° C for the duration of the crystallization step. Preferably, the ratios of components in the solutions used to make the reaction mixture are such that in the reaction mixture the silica/alumina molar ratio will be in the range of about 2.25:1 to about 2.4:1; the sodium oxide to silica molar ratio will be in the range 1.6:1 to about 1.9:1; and the water to sodium oxide molar ratio will be greater than about 60:1. The reaction mixture is preferably prepared as a hydrogel.
摘要:
Zeolites exchanged with lithium, rubidium, cesium cations and trivalent cations are prepared by first partially, fully or excessively ion-exchanging a sodium-containing zeolite, a potassium-containing zeolite or a sodium- and potassium-containing zeolite with trivalent cations, then calcining the partially, fully or excessively trivalent cation-exchanged zeolite, and then ion exchanging the calcined zeolite with lithium rubidium, cesium cations, thereby replacing hydrogen and any sodium and/or potassium cations remaining in the zeolite with lithium, rubidium, cesium cations, whereby trivalent cations present in the zeolite will not be substantially replaced by the lithium ions.
摘要:
A composite zeolite product is prepared by crystallizing a sodium ion- or sodium ion- and potassium ion-containing alumina-silica hydrogel under conditions which result in the production of a zeolitic composite which contains both zeolite type A and zeolite type X crystal domains. The composite is ion exchanged with divalent cations. In a preferred embodiment, calcium ions constitute a substantial number of the composite's exchangeable cations and the type X portion of the composite zeolite product has a silicon-to-aluminum atomic ratio in the range of 0.9 to less than 1.15. The composite is a nitrogen oxide- and hydrocarbon-selective adsorbent which can be incorporated into an atmospheric air prepurification plant downstream of a water vapor-selective adsorbent and a carbon dioxide-selective adsorbent.
摘要:
Zeolites exchanged with lithium, caesium or rubidium cations and polyvalent cations (e.g. pure earths or Group III cation) are prepared by first partially ion-exchanging a sodium-containing zeolite, a potassium-containing zeolite or a sodium- and potassium-containing zeolite with polyvalent cations, then heat-treating the partially polyvalent cation-exchanged zeolite, then ion exchanging the heat-treated zeolite with ammonium cations, and then reacting the ammonium cation-exchanged zeolite with a water-soluble lithium compound under conditions which result in the removal of ammonia from the reaction zone.
摘要:
Zeolites exchanged with lithium ions and, optionally, with polyvalent cations are prepared by ion-exchanging a sodium-containing zeolite, a potassium-containing zeolite or a sodium- and potassium-containing zeolite with ammonium ions, thereby replacing the sodium and/or potassium ions with ammonium ions, and then reacting the ammonium ion-exchanged zeolite with a water-soluble lithium compound under conditions which result in the removal of ammonia from the reaction zone. Polyvalent ions, which may be present in the zeolite undergoing ion-exchange, will not be substantially replaced by the ammonium or lithium ions.