The present invention discloses a two-step process for the ring opening of aromatics and naphthenic C6+ ring containing compounds (e.g. tetrahydro-6-naphthalene, propyl benzene, methylcyclohexane, methylcyclohexanol) and catalysts which can be used in that process. An important novelty of this invention is that the ring opening is accomplished in two separate steps in such a way that both steps can be operated under different process conditions (i.e. different pressure, temperature and throughput) to maximize the formation of high molecular weight paraffins and minimize carbon loss. This process consists of a first reactor loaded with Pt and/or Pd catalysts containing an acid catalyst to convert the C6 ring containing compounds into C5 ring containing compounds; a ring contraction step. The second reactor contains a metal catalyst such as Ir/Al2O3 to convert the C5 ring containing compounds into paraffins highly valuable for diesel and jet markets; a C5- ring opening step. Proof of concept was successfully demonstrated with model compounds and real bio-oils. First, methylcyclohexane and methylcylohexanol were used as model naphthenic compounds. We successfully demonstrated that methylcyclohexane can be converted into desired products (i.e. alkylcyclopentane and C7 paraffins) with a remarkable selectivity of 93% using a 1%Pt/HZSM22 catalyst operating while operating under mild conditions (320 degrees C, 20 bars). The alkylcyclopentane compounds are then converted in a second reactor into (iso)heptane using an Ir/Al2O3 catalyst while operating at 280 degrees C-320 degrees C and 20 bars. For this novel two step process, ~50% yield toward C7 paraffins ( see Figure 1) and about 70% yield toward C5-C7 paraffins was obtained while conducting the ring contraction step at 320 degrees C, 20 bars with a 1%Pt/HZSM22 catalyst whereas the C5-ring opening step was operating at 280 degrees C, 20 bars with a 1% Ir/Al2O3 catalyst. Comparatively, for the conventional one step process operated at 320 degrees C, 20 bars with a 1%Ir/Al2O3 catalyst, only 27% yield of C7 paraffins was obtained due to significant cracking. The ring contraction followed by the C5-ring opening was found to be key in avoiding undesirable cracking reactions. Proof of concept was also demonstrated with model compounds found in Hydrothermal liquefaction bio-oils. Table 3 presents the composition of the liquid hydrocarbons feed and product obtained after ring-contraction step. The aromatics (e.g. phenanthrene, pyrene) are fully converted into cyclohexanes and cyclopentanes demonstrating that this technology can be applied to multi-rings/ aromatics compounds found in HTL bio-oils. The two-step process was then applied to real bio-oils. The gasoline fraction of a hydrotreated fast-pyrolysis oil (pine wood) was used as feedstock. As shown in Table 4 the feedstock contains mainly aromatics ( 31%), branched cyclohexanes (21%) and branched cyclopentanes (15%). The ring opening product contains mainly (iso) paraffins/ olefins (56%) and cyclohexanes (28%). These results indicate that the aromatics were fully converted into branched cyclohexanes and a fraction of the branched cyclohexanes was either converted into cyclopentanes or (iso)paraffins and olefins. The cyclopentanes product from the first reactor/ step were converted into (iso)paraffins and olefins in the second reactor/ step. Proof of concept was also demonstrated with the diesel fraction of a hydrotreated fast-pyrolysis oil (oak wood). Composition of the feed and the ring opening product are presented in Table 5. As seen in Table 5, the feed contains mainly aromatics (39.8%) , organic and oxygenated cyclic compounds ( 37.1%) that are converted predominantly into branched cyclohexanes (45.6%) and C8+ (iso) parrafins (31.9%). Table1. Conversion, selectivity and yield for the PNNL two step process Process conditions for C5-ring opening stepa Methylcyclohexane conversion (%) Selectivities (%) Yield (%) C7 paraffins Temperature (C) Pressure (bars) GHSV (h-1) C1-C6 MCPb C7 paraffins DMCPb toluene 280 20 22257 87.9 25.2 17.3 54.7 1.8 1.0 48.1 280 20 4181 72 20.8 18.5 51.5 7.9 1.3 37.1 280 20 1203 95.9 30.6 15.8 51.1 1.6 0.9 49 300 20 4181 86.7 27.2 17.5 52.3 2.1 1.0 45.3 320 20 8489 88.3 31.8 16.2 48.8 2.1 1.0 43.1 320 20 4152 100 52.9 10.6 34.6 1.0 0.8 34.6 For the ring contraction step, T = 320 degrees C, P = 20 bars, GHSV = 2500h-1. b. MCP stands for methylcyclopentane, DMCP stands for dimethylcyclopentane Table 2. Products distribution for the one step process. T = 320 degrees C, P = 20 bars, conversion = 100% Process Catalyst Selectivity (%) C1-C6 paraffins C7 paraffins C6-C7 cyclic paraffins Toluene 1-step carbocation route 1%Pt/HZSM22 84.6 3.5 11.1 0.8 1-step Hydrogenolysis route 1%Ir/Al2O3 72.5 26.5 1 0 Unconventional 1-step route 1%Pt/HZSM22+ 1%Ir/Al2O3 58.9 28.5 12.6 0 Table 3. Products obtained from the ring-contraction of a mixture of model compounds found in hydrothermal liquefaction bio-oil. Compounds GC-MS mass % Feed Product C3-C5 (iso)paraffins - 6.7 C6-C7 (iso)paraffins 45.5 48.4 C8+ (iso)paraffins 12.9 2.8 Branched cyclopentanes - 18.5 Branched cyclohexanes - 17.3 Aromatics* 38.5 - Oxygenated compounds 3.4 0.8 Other cyclic compounds - 3.8 T= 280 degrees C, P=320 psig, LHSV=0.9 hr-1, H2(95%/N2) = 120sccm, catalyst = 1% Pt/HY720. *Aromatics consist of phenanthrene, pyrene, propylbenzene, 2-methyl-naphthalene, dimethyl-naphthalene. Table 4. Ring-Opening of the gasoline fraction of a hydrotreated fast-pyrolysis bio-oil. Compounds GC-MS (mass %) Feed Product C3-C5 (iso)paraffins/olefins 2.4 3.2 C6-C7 (iso)paraffins/olefins 6.7 28.9 C8+ (iso)paraffins/olefins 13.1 24.1 Branched cyclopentanes 15.3 11.1 Branched cyclohexanes 21.3 28.4 Aromatics 31.1 - Oxygenated compounds 5.8 1.3 Other cyclic compounds 4.3 2.4 Reaction conditions for the 1 step: T = 320 degrees C, P = 300 psig, H2 (95%/N2) = 36 sccm, LHSV = 0.16 hr-1, catalyst is 1% Pt/HZSM-22. Reaction conditions for the 2nd step: T = 320 degrees C, P = 300 psig, H2 (95%/N2) = 36 sccm, LHSV = 0.3 hr-1, catalyst is 1% Ir/Al2O3. Table 5. Ring-Opening of the diesel fraction of a hydrotreated fast-pyrolysis bio-oil. Compounds GC-MS (mass %) Feed Product C3-C5 (iso)paraffins - 2.9 C6-C7 (iso)paraffins - 9.3 C8+ (iso)paraffins 6.6 31.9 Branched cyclopentanes 1.5 6.5 Branched cyclohexanes 8.1 45.6 Aromatics* 39.8 1.1 Organic and Oxygenated compounds** 37.1 1.2 Others 6.9 1.5 Reaction conditions for the 1 step: T = 300 degrees C, P = 300 psig, H2 (95%/N2) = 32 sccm, LHSV = 0.03 hr-1, catalyst is 1% Pt/HY901. Reaction conditions for the 2nd step: T = 280 degrees C, P = 300 psig, H2 (95%/N2) = 32 sccm, LHSV = 0.15 hr-1, catalyst is 1% Ir/Al2O3. * e.g. ethyl-tetrahydro-naphthalene **mainly cyclic oxygenates compounds such as phenolics.