Benzoic Acid is an aromatic alcohol that exists naturally in many plants and is a common additive to food, drinks, cosmetics, and other products. It acts as a preservative by inhibiting both bacteria and fungi.
Methods of Manufacturing
1. Initially benzoin dry distillation or alkaline hydrolysis in the system can also be obtained from hippuric acid hydrolysis. The industrial production methods of benzoic acid are toluene liquid phase air oxidation, benzyl benzyl trichlorohydrin, and phthalic anhydride decarboxylation, while the toluene liquid air oxidation is the most common. Toluene and air into a reactor containing cobalt naphthenate catalyst in the reaction temperature 140-160 C, operating pressure 0.2-0.3MPa under the conditions of reaction to generate benzoic acid, by steaming the unreacted toluene was rough Benzoic acid, and then vacuum distillation, recrystallization was finished. The phthalic anhydride decarboxylation method is not easy to refine the final product, and high production costs, only in the small batch of medicine and other products used in the manufacturing process. The product of the chlorination of toluene is not suitable for use in food. Benzoic acid is for industrial use, food, medicine, and other different specifications. Food grade should be consistent with GB1901-80, the content of 99.5% or more, the melting point of 121-123 ℃, and easy oxide, easy carbide, chlorine compounds, burning residue, heavy metals, arsenic content, and other quality indicators were provided. Consumption of raw materials fixed: toluene 1140kg / t, cobalt naphthenate 4kg / t. In addition, the production of benzaldehyde from toluene can be a by-product of benzoic acid.
2. Although benzoic acid can be obtained by the chlorination of toluene and phthalic acid decarboxylation method, at home and abroad is widely used in industrial production methods for toluene as raw material liquid catalytic oxidation of air. The catalyst (cobalt acetate, cobalt naphthenate, or cobalt acetate) of toluene and air were continuously pumped into the oxidation tower (or kettle), and then 140-165 ℃ and 0.3-0.4MPa pressure oxidation of benzoic acid. The top of the tower tail gas is condensed and activated carbon adsorption method to recover toluene after the venting; tower reactor reaction liquid is often the initial pressure recovery unreacted toluene, benzyl alcohol and benzaldehyde and other light components, and then vacuum distillation of benzoic acid; Toluene and other return oxidation tower, toluene single-pass conversion rate can be controlled at 35% or more. Domestic consumption per ton of benzoic acid toluene is 1025-1500kg, cobalt naphthenate is about 4kg; foreign toluene consumption of 820kg per ton.
3. By benzyl chloride oxidation in crude, washed with cold water, and then recrystallized in hot water.4. The use of hydrolysis and hydrogenation. Hydrolysis: Phthalic anhydride as raw material, by hydrolysis, decarboxylation derived. Chlorination: toluene as raw material, derived by chlorination hydrolysis.5. Tobacco: pOR, 18, 26, 41, 43, 44; FC, 9, 18, 40, 59; BU, 26, 56.