TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The first catalyst is chosen from vanadium pentoxide, molybdenum dioxide, titanium dioxide, selenium dioxide and palladium oxide. The second catalyst is chosen from palladium chloride-calcium chloride, stannic chloride, titanium sulfate and/or cerium chloride. The catalyst (C) is metal-rare earth oxide composite catalyst. The weight ratio of metal with respect to rare-earth is 1-2:100.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The plant straw is hydrolyzed with acid containing dilute sulfuric acid (0.5-1%). The hydrolysis is performed at 120-150 degrees C and pressure of 0.2-0.6 MPa for 1-3 hours. The step (b) involves (i) adding first catalyst and concentrated sulfuric acid to hydrolyzing liquid, adjusting concentration of the acid in the liquid and heating and stirring the liquid uniformly, (ii) adding concentrated nitric acid to the liquid while stirring for performing oxidation, until gas is not produced, and (iii) adjusting concentration of sulfuric acid in the obtained mixture. The oxidation is performed at 60-75 degrees C. The oxalic acid and methyl alcohol are esterified in presence of second catalyst. The esterification is performed at 70-90 degrees C and pressure of 6-8 MPa. The hydrocracking process is performed at 200-300 degrees C and pressure of 3-5 MPa for 0.5-1 hour. Preferred Composition: The weight ratio of the plant straw with respect to dilute sulfuric acid is 1:2-4. The concentration of sulfuric acid in the hydrolyzing liquid 50-60 %mass. The weight ratio of the first catalyst with respect to concentrated sulfuric acid is 0.05-0.1:100. The molar concentration of concentrated nitric acid is 10-15 mol/l. The weight ratio of concentrated nitric acid with respect to total sugar content of the hydrolyzing liquid is 1.5-3:1. The weight ratio of oxalic acid with respect to methyl alcohol is 1:2-4. The weight ratio of the catalyst (C) with respect to methyl alcohol is 1-2:100. The weight ratio of catalyst (C) with respect to dimethyloxalate is 1-1.5:100.