What are the main industrial methods for producing benzaldehyde?

What are the main industrial methods for producing benzaldehyde?
Industrial benzaldehyde production relies primarily on toluene routes. The chlorination route involves side-chain chlorination to benzal chloride, followed by hydrolysis, yielding high-purity product (≥99.5%) but generating corrosive HCl and chlorine-containing waste. The liquid-phase oxidation route uses cobalt salts with bromide promoters and air, producing benzaldehyde as a byproduct in caprolactam or benzoic acid processes. This route yields chlorine-free product suitable for pharmaceuticals and fragrances, but suffers from low toluene conversion (below 20%) and over-oxidation to benzoic acid. China's capacity is around 65,000 tonnes annually, with major producers including Hubei Kelin Bolun and Wuhan Organic. The choice of process affects product purity, cost structure, and downstream application suitability.