Process for preparing furfural by using agricultural by-products of high and crude fiber plants

The invention discloses a process for preparing furfural by using agricultural by-products of high and crude fiber plants. The process includes the steps of 1) conducting pretreatment of raw materials; 2) hydrolyzing pretreated raw materials in a hydrolyzing tank, and using an acid catalyst formed by mixing sulfuric acid and phosphoric acid during the hydrolytic process; 3) introducing high-temperature steam into the hydrolyzing tank, heating up the hydrolyzing tank, and conducting gap stripping for hydrolysis products of furfural; and 4) feeding gas stripped furfural to into a furfural phase splitter to obtain coarse furfural and furfural residues. According to the process, the acid catalyst combining the sulfuric acid and the phosphoric acid is used for hydrolyzing the raw materials, and the hydrolytic process is assisted by ultrasonic treatment simultaneously, so that the productivity of the furfural is improved, the residue amount of the sulfuric acid is a little, the production of sulfur oxides in the subsequent activating process of furfural residues is reduced, and the environmental pollution is reduced. Besides, the invention also provides a process for producing activated carbon adsorbents by using the furfural residues. The process includes the steps of drying the furfural residues, screening, roasting, hardening activating and steam curing, the obtained activated carbon specific surface is large, the iodine value is high and the adsorption capacity is high.