A method for producing a selective hydrogenation catalyst for hydrogenating a highly unsaturated hydrocarbon to an unsaturated hydrocarbon comprising contacting an inorganic catalyst support with a chlorine-containing compound to form a chlorided catalyst support and adding palladium to the chlorided catalyst support to form a supported-palladium composition. A selective hydrogenation catalyst for hydrogenating a highly unsaturated hydrocarbon to an unsaturated hydrocarbon formed by the method comprising contacting an inorganic catalyst support with a chlorine-containing compound to form a chlorided catalyst support and adding palladium to the chlorided catalyst support to form a supported-palladium composition. A method of selectively hydrogenating a highly unsaturated hydrocarbon to an unsaturated hydrocarbon comprising contacting the highly unsaturated hydrocarbon with a selective hydrogenation catalyst composition produced by contacting an inorganic catalyst support with a chlorine-containing compound to form a chlorided catalyst support and adding palladium to the chlorided catalyst support to form a supported-palladium composition.

A method for producing a selective hydrogenation catalyst for hydrogenating a highly unsaturated hydrocarbon to an unsaturated hydrocarbon comprising contacting an inorganic catalyst support with a chlorine-containing compound to form a chlorided catalyst support and adding palladium to the chlorided catalyst support to form a supported-palladium composition. A selective hydrogenation catalyst for hydrogenating a highly unsaturated hydrocarbon to an unsaturated hydrocarbon formed by the method comprising contacting an inorganic catalyst support with a chlorine-containing compound to form a chlorided catalyst support and adding palladium to the chlorided catalyst support to form a supported-palladium composition. A method of selectively hydrogenating a highly unsaturated hydrocarbon to an unsaturated hydrocarbon comprising contacting the highly unsaturated hydrocarbon with a selective hydrogenation catalyst composition produced by contacting an inorganic catalyst support with a chlorine-containing compound to form a chlorided catalyst support and adding palladium to the chlorided catalyst support to form a supported-palladium composition.

Modified zeolites may include a microporous framework including a plurality of micropores having diameters of less than or equal to 2 nm. The microporous framework may include at least silicon atoms and oxygen atoms. The modified zeolite may include a plurality of mesopores having diameters of greater than 2 nm and less than or equal to 50 nm, wherein the plurality of mesopores are ordered with cubic symmetry. The modified zeolite may include a plurality of zirconium hydride moieties each bonded to at least two bridging oxygen atoms, wherein a zirconium atom of the zirconium hydride is bonded to the bridging oxygen atom, and wherein the bridging oxygen atom bridges the zirconium atom of the zirconium hydride moiety and a silicon atom of the microporous framework.

An adsorbent for passive NO.sub.x adsorption includes a small pore zeolite having an eight-ring framework structure and a non-noble metal ion doped in the framework structure. An exhaustion system comprising the adsorbent and a method for preparing the adsorbent are also addressed.

An adsorbent for passive NO.sub.x adsorption includes a small pore zeolite having an eight-ring framework structure and a non-noble metal ion doped in the framework structure. An exhaustion system comprising the adsorbent and a method for preparing the adsorbent are also addressed.