NOVELTY - Preparing (M1) compounds of at least 8 carbon atom involves: catalytically reacting reactant stream of two reactants of hydrocarbon molecule with specific average oxygen to carbon ratio, with hydrogen in presence of acid condensation catalyst to produce product stream of water/several compounds containing at least eight carbon atoms e.g. alkanes of at least 8 carbons, where the acid condensation catalyst comprises an acidic support/heterogeneous acid catalyst of metal selected from palladium, platinum, copper, cobalt, ruthenium, chromium, nickel, silver and/or their alloy.    USE - For preparation compounds containing at least 8 carbon atom for preparing fuel product which is used for in jet fuel, diesel or heavy oil composition (claimed); in chemical applications, or as a neat fuel or blending component in jet fuel and diesel fuel, or as heavy oils for lubricant or fuel oil applications.    ADVANTAGE - The method maximize product yield and extend catalyst lifetime; has the ability to tailor the reactions to produce specific products of high demand or of higher commercial value; converts biomass and biomass-derived feedstocks to a greater quantity of heavier hydrocarbons useful in jet and diesel fuels, or as heavy oils for lubricant and/or fuel oil applications. The method is able to increase the production yield of greater than or equal to 8C compounds; uses combination of the first and second reactants in the reactant stream which helps to control the effects of water in the system and drives the reaction to produce the longer chain greater than or equal to 8C compounds. The combination of the reactants has the effect of increasing the reaction partial pressure for the reactants, while decreasing the partial pressure of water. The resulting product stream tends to have a greater yield of greater than or equal to 8C compounds as compared to systems not involving a second reactant.    DETAILED DESCRIPTION - Preparation (M1) compounds containing at least 8 carbon atom involves: providing a reactant stream comprising a first reactant and a second reactant; and catalytically reacting the reactant stream with hydrogen in the presence of an acid condensation catalyst to produce a product stream comprising water and several compounds containing at least 8 carbon atom, selected from alkanes, alkenes, cycloalkanes, cycloalkenes, alcohols, ketones, aryl, fused aryl, oxygenated aryl and/or oxygenated fused aryl containing at least 8 carbon atoms, where the acid condensation catalyst comprises an acidic support or a heterogeneous acid catalyst comprising a metal selected from palladium (Pd), platinum (Pt), copper (Cu), cobalt (Co), ruthenium (Ru), chromium (Cr), nickel (Ni), silver (Ag) and/or their alloy. The first reactant comprises at least one hydrocarbon molecule of formula CxHyOz and a first reactant average oxygen to carbon ratio of 0.2-1. The second reactant comprises at least one hydrocarbon molecule of formula CpHrOs and second reactant average oxygen to carbon ratio of less than or equal to 0.2. The number of carbon atoms in the reactant stream from the first reactant is greater than 10% of the total carbon atoms in the reactant stream, and the number of carbon atoms in the reactant stream from the second reactant is greater than 10% of the total carbon atoms in the reactant stream.    x=2-12 carbon atoms;    z=1-12 oxygen atoms;    p=2-7 carbon atoms;    s=0-1 oxygen atoms.    INDEPENDENT CLAIMS are included for the following:    (1) preparing fuel product involving: providing a reactant stream comprising the first reactant and the second reactant; catalytically reacting the reactant stream with hydrogen in the presence of an acid condensation catalyst to produce a product stream comprising water, several less than or equal to 7C compounds selected from less than or equal to 7C alkane, less than or equal to 7C alkene, less than or equal to 7C cycloalkane, less than or equal to 7C cycloalkene, less than or equal to 7C alcohol, less than or equal to 7C ketone and/or less than or equal to 7C aryl, and several compounds containing at least 8 carbon atoms selected from alkane, alkene, cycloalkane, cycloalkene, alcohol, ketone, aryl, fused aryl, an oxygenated aryl and/or oxygenated fused aryl containing at least 8 carbon atoms, where the acid condensation catalyst comprises an acidic support or a heterogeneous acid catalyst comprises metal selected from Pd, Pt, Cu, Co, Ru, Cr, Ni, Ag and/or their alloy; separating at least a portion of the compounds containing at least 8C from the product stream; catalytically reacting the separated compounds containing at least 8C in the presence of a finishing catalyst to produce a fuel product; and    (2) a jet fuel, diesel fuel or heavy oil composition comprising a fuel product produced by the method (M2).