NOVELTY - Identifying upgrading catalysts from compositions (A) containing the following components: (a) platinum (Pt), iridium (Ir) or its mixtures; and (b) a large-pore zeolite, comprises: (1) reacting decalin with hydrogen, in the presence of one of the catalytic compositions, at a temperature ranging from 250 to 380 degrees C and a pressure equal to 5.2 MPa; (2) calculating indices; and (3) comparing the indices.    USE - The processes are useful for identifying upgrading catalysts from compositions containing Pt and/or Ir, and large-pore zeolite; and for upgrading hydrotreated hydrocarbon mixtures (all claimed).    ADVANTAGE - The catalytic compositions selected can be used in an upgrading process of hydrotreated hydrocarbon mixtures for obtaining high-quality diesel fuels with a reduced density. Additionally, the catalysts are active in processes for enhancing the fuel quality of hydrotreated hydrocarbon mixtures.    DETAILED DESCRIPTION - Identifying upgrading catalysts from compositions (A) containing the following components: (a) platinum (Pt), iridium (Ir) or its mixtures; and (b) a large-pore zeolite having a crystalline lattice composed of silica and an oxide YOX selected from alumina, boron oxide and its mixtures, where the negative charges present in the crystalline lattice are neutralized by one or more cations of metals Me selected from alkaline metals, alkaline-earth metals and lanthanoids, and x moles of hydrogen ions per mole of aluminum and/or boron, where x ranges from 0.04 to 0.65, where the method comprises: (1) reacting decalin with hydrogen, in the presence of one of the catalytic compositions, at a temperature ranging from 250 to 380 degrees C and a pressure equal to 5.2 MPa; (2) calculating: for the compositions A(Ir) the I(Ir) index, where: A(Ir) is a catalytic composition (A) where the metal (a) is Ir or a mixture of Ir and Pt where the iridium moles are greater than or equal to the Pt moles, and I(Ir) corresponds to the ratio SelC4/SelC2, where SelC4 and SelC2 are the selectivity to C4 hydrocarbons and C2 hydrocarbons respectively, obtained in the reaction of step (1), for the compositions A(Pt) the I(Pt) index where: A(Pt) is a catalytic composition (A) where the metal (a) is Pt or a mixture of Pt and Ir where the Pt moles are greater than the Ir moles, and I(Pt) corresponds to the ratio SelC4/SelC5, where SelC4 and SelC5 are the selectivity to C4 hydrocarbons and to C5 hydrocarbons respectively, obtained in the reaction of step (1); and (3) comparing the I(Ir) index obtained for the compositions of the A(Ir) type within the range 0.2-10.0 and comparing the I(Pt) index obtained for the compositions of the A(Pt) type within the range 1.3-2.4, the catalytic compositions of the type A(Ir) and A(Pt), whose relative indexes respectively fall within the ranges, including the extremes, being active. INDEPENDENT CLAIMS are:    (1) a process for upgrading hydrotreated hydrocarbon mixtures comprising reacting the mixtures with a catalytic composition (A) comprising the following components: (a) Pt, Ir or its mixtures; and (b) a large-pore zeolite having a crystalline lattice composed of silica and an oxide YOX selected from alumina, boron oxide and its mixtures, where the negative charges present in the crystalline lattice are neutralized by one or more cations of metals Me selected from alkaline metals, alkaline-earth metals and lanthanoids, and x moles of hydrogen ions per mole of aluminum and/or boron, where x ranges from 0.04 to 0.65, where the catalytic composition: when the metal (a) is Ir or a mixture of Ir and Pt where the iridium moles are greater than or equal to the Pt moles, is characterized by an I(Ir) index ranging from 0.2 to 10.0, where the index corresponds to the ratio SelC4/SelC2, where SelC4 and SelC2 are the selectivity to C4 hydrocarbons and to C2 hydrocarbons respectively, obtained, by the catalytic composition, in the reaction of decalin with hydrogen at a temperature ranging from 250 to 380 degrees C, at a pressure of 5.2 MPa; when the metal (a) is Pt or a mixture of Pt and Ir where the Pt moles are greater than the Ir moles, is characterized by an I(Pt) index ranging from 1.3 to 2.4, where the I(Pt) index corresponds to the ratio SelC4/SelC5, where SelC4 and SelC5 are the selectivity to C4 hydrocarbons and the selectivity to C5 hydrocarbons respectively, obtained by the catalytic composition, in the reaction of decalin with hydrogen at a temperature ranging from 250 to 380 degrees C, at a pressure of 5.2 MPa; or a process for upgrading hydrotreated hydrocarbon mixtures comprising reacting the mixtures with a catalytic composition comprising then following components: (a) Ir or Pt; and (b) a Beta zeolite having a crystalline lattice composed of silica and an oxide YOX selected from alumina, boron oxide and its mixtures, where the negative charges present in the crystalline lattice are neutralized by one or more cations of metals Me selected from alkaline metals, alkaline-earth metals and lanthanoids, and x moles of hydrogen ions per mole of aluminum and/or boron, where x ranges from 0.45 to 0.65 or x is higher than or equal to 0.17 and lower than 0.45; and    (2) a catalytic composition comprising the following components: (a) Ir or Pt; and (b) a Beta zeolite having a crystalline lattice composed of silica and an oxide YOX selected from alumina, boron oxide and its mixtures, where the negative charges present in the crystalline lattice are neutralized by one or more cations of metals Me selected from alkaline metals, alkaline-earth metals and lanthanoids, and x moles of hydrogen ions per mole of aluminum and/or boron, where x ranges from 0.45 to 0.65, or x is higher than or equal to 0.17 and lower than 0.45.