Glycolic acid high-pressure synthesis

High-Pressure Synthesis of Glycolic Acid from Formaldehyde, Carbon Monoxide, and Water in Presence of Nickel, Cob t, and Iron Catalysts... 

Encouraged by the interesting results obtained in the high-pressure synthesis of acetic acid from methanol and carbon monoxide using nickel, cobalt, and iron halides as catalysts (5-7), the synthesis of glycolic acid from formaldehyde, carbon monoxide and water has been studied using various nickel, cobalt, and iron catalysts. 

In the direct conversion homogeneous catalysts could be applied to provide oxygenates. Potential applications exist for alcohols, acids and esters. Alcohol synthesis is a favorable way to upgrade synthesis gas because of its positive thermodynamics. A number of homogeneous catalysts are known to convert CO/H2 to alcohols. Most remarkable is the high-pressure homogeneous reduction of CO in the work by Union Carbide aimed at an industrial synthesis of ethylene glycol [8]. 

BHET formation is conducted at temperatures of 200 to 250 °C to achieve reasonable reaction rates. The activation energies of the two reactions are of the order of 25 000-30 000 cal/mol [4, 5], The BHET formation is usually conducted under pressure to keep the ethylene glycol in the liquid state. Terephthalic acid is slurried with ethylene glycol for the esterification reaction. Dimethyl terephthalate is dissolved in ethylene glycol and BHET for a liquid-phase transesterification reaction. The synthesis of BHET is driven to this material by the removal of water or methanol. The reactions are reversible at reasonable rates if the concentrations of water or methanol reactants are held high. 

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