TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The acid catalyst is a mineral or organic acid having a negative logarithm of acid dissociation constant (pKa) in water of below 3.75. The hydrogenation catalyst is a homogeneous catalyst or a heterogeneous catalyst. The source of hydrogen is a hydrogen gas that is contacted with the cellulosic material in a countercurrent manner.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The cosolvent is a solvent having a polarity of log P less than 1. The co-solvent comprises at least part of the liquefied product, which part of the liquefied product comprises one or more polar solvents.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The product comprises 20-80 wt.% of one or more monomeric compounds; 20-80 wt.% of one or more oligomeric compounds that are liquid at ambient temperature (20 degrees C) and pressure (1 bar absolute); and 0-25 wt.% of tar. The weight ratio of the monomeric compound(s) to the oligomeric compound(s) is 4:1-1:4. The product comprises tetrahydropyranic monomers and/or oligomers. The second product obtained in step (b) comprises one or more tetrahydropyranic monomers and/or oligomers. EXAMPLE - Birch wood (particle size of less than 4 mm, semidried at 105 degrees C) (3.3 g) was loaded into a 60 ml autoclave together with palladium on carbon catalyst (0.1 g), water (21 g), acetic acid (9 g), and sulfuric acid (0.1 g). The autoclave was sealed, pressurized to 50 bar of hydrogen (H2) and heated to a temperature of 200 degrees C. Subsequently the H2 pressure was adjusted to 80 bar. After a reaction time of 90 minutes, the autoclave was cooled to room temperature (20 degrees C) and opened and appropriate samples were taken. The total product, including liquid, tar, insoluble humins and catalyst, was removed from the autoclave. The total product was subsequently filtered over a filter to produce a filtrate and a filter cake. The filter cake was washed with acetone and dried under vacuum (200 mbar) at 50 degrees C overnight. A fraction of dissolved oil (a mixture of monomeric and oligomeric compounds) was dried under vacuum.