Nature of the description:

  Benzoic acid as a scaly or needle-like crystals, with the smell of benzene or formaldehyde, flammable. The relative density of 1.2659. Melting point 122.4 ℃, boiling point 249 ℃, the refractive index of 1.504. Steam volatile. Flash point (closed cup) 121-123 ℃. Slightly soluble in water, soluble in ethanol, methanol, ether, chloroform, benzene, toluene, carbon disulfide, carbon tetrachloride, and turpentine. Rapid sublimation at 100 ℃, can be volatile with water vapor at the same time. Acid often free acid, ester or its derivatives in the form of widely distributed in nature. For example, benzoic acid and gel in order to free the form of benzyl ester; in some plants the leaves and stem bark of the free form; in flavor to methyl or benzyl ester form; in ma niu in its the form of hippuric acid derivatives.

 Production methods:

  Initially by dry distillation of gum benzoin or alkaline hydrolysis, or by the hippuric acid hydrolysis. Methods of industrial production of benzoic acid liquid phase air oxidation of toluene, sub-benzyl trichloro hydrolysis and decarboxylation of phthalic anhydride method three, and air oxidation of toluene liquid the most common. Toluene and air pass into the cobalt naphthenate catalyst containing reactor, the reaction temperature is 140-160 ℃, operating pressure 0.2-0.3MPa under the conditions of the reaction of benzoic acid, the unreacted toluene steam to crude acid, and then by vacuum distillation, crystallization products. With phthalic anhydride decarboxylation method refining the final product is not easy, but high production costs, not only in quantities of pharmaceutical products to the manufacturing process used. Toluene chlorination products unfit for food. Acid for industrial use, food, medicine, etc. with different specifications. Food grade should meet GB1901-80, content of 99.5%, melting point 121-123 ℃, also oxide, easily carbide, chlorine compounds, residue on ignition, heavy metals, arsenic and other quality indicators regulated. Consumption of raw materials fixed: toluene 1140kg / t, Cobalt 4kg / t. In addition, the production of benzene, toluene, formaldehyde can be by-product acid.