It is used to produce plasticizer in the plastics industry, to produce the paper treatment agent in the paper-making industry, to produce the insulating varnish, the white enamel varnish and the varnish in the coating industry, to produce long-acting sulfonamide in the medical industry, to produce unsaturated polyester resin and alkyd resin in the synthetic industry, to produce fumaric acid and tetrahydrofuran in the organic industry.