NOVELTY - Modified zeolite catalyst (I) comprising noble metal incorporated pentasil zeolite based catalyst comprising zeolite (59-60 wt.%), pseudo extrude (39-40 wt.%), platinum (0.1-1 wt.%), and palladium (0-1 wt.%), is new.    USE - (I) is useful for: conversion of paraffins, olefins and aromatics in a mixed feedstock comprising fluid catalytic cracked gasoline into isoparaffins; and conversion of n-paraffins and naphthenes into branched paraffins. (I) is useful as gasoline blending stock.    ADVANTAGE - The octane number of the gasoline obtained is increased by 20-40% as compared to initial RON number. The hydro conversion of the feedstock results in an increase in octane number of 10-15 units of RON. The branched paraffins obtained in the final product is increased by 30-70% as compared to isoparaffins present in the feedstock. (I) has improved acidity and porosity. (I) provides significant level of isomerization product. (I) is eco-friendly. (I) enhances the formation of bulky iso-paraffins having high octane number. (I) reduces aromatics and olefins in the feedstock without any octane loss.    DETAILED DESCRIPTION - Modified zeolite catalyst (I) comprising noble metal incorporated pentasil zeolite based catalyst comprising zeolite (59-60 wt.%), pseudo extrude (39-40 wt.%), platinum (0.1-1 wt.%), and palladium (0-1 wt.%), where the catalyst has: silicon/aluminum ratio of 16-80; Brunauer-Emmett-Teller (BET) surface area of 200-350 m2/g; micropore area of 155-250 m2/g; external pore area of 90-135 m2/g, pore volume of 0.30-0.50 cc/g, acidity of 1.40-1.60 mmole/g catalyst; strong acidity (greater than 120 kJ/mol) of 0.40-0.60 kJ/mol; medium acidity (120-80 kJ/mol) of 0.45-0.50 kJ/mol; weak acidity (less than 80 kJ/mol) of 0.40-0.60 kJ/mol; and platinum dispersion of 60-80%, is new. INDEPENDENT CLAIMS are included for:    (1) the preparation of (I); and    (2) a process for the conversion of paraffins, olefins and aromatics in a mixed feedstock into isoparaffins, comprising feeding fluid catalytic cracked (FCC) gasoline having paraffin, iso-paraffin, olefin, naphthenes and aromatics into the fixed bed down flow reactor containing (I) comprising noble metals (0.1-1 wt.%), under hydrogen flow at 225-375 degrees C and 5-35 bar, at a space velocity of 1-6 hour-1, followed by cooling of the gaseous product at the reactor tail to obtain the desired product.