High-temperature liquid water: a viable medium for terephthalic acid synthesis

Area of Science:

• Chemical Engineering
• Green Chemistry
• Catalysis

Background:

• Traditional p-xylene oxidation uses acetic acid, posing environmental concerns.
• Dense water offers a more sustainable solvent alternative for chemical synthesis.

Purpose of the Study:

• To investigate the partial oxidation of p-xylene in dense water.
• To evaluate the impact of oxygen and catalyst parameters on terephthalic acid yield.

Main Methods:

• Experiments were conducted in a 440 mL Hastelloy batch reactor.
• Varying temperatures (250-380°C), catalyst concentrations (MnBr2, CoBr2, ZrBr4, Mn(OAc)2), and oxygen levels were tested.
• Oxygen consumption and product formation (terephthalic acid, COx) were monitored.

Main Results:

• Manganese bromide (MnBr2) proved to be the most effective catalyst.
• Optimal terephthalic acid yields (>80%) were achieved at 300°C with specific reactant concentrations and short reaction times (5-15 min).
• Supplemental oxygen injection mid-reaction boosted terephthalic acid yield.

Conclusions:

• High yields of terephthalic acid are achievable using p-xylene oxidation in dense water.
• Optimized conditions using MnBr2 offer a highly efficient and environmentally benign alternative to conventional methods.
• The process demonstrates minimal byproduct formation under optimal conditions.