Development of a Continuous Lactulose Process: Separation and Purification

We developed a continuous pilot plant process to produce lactulose from lactose using boric acid to boost the conversion to about 75%. The process consists of three reactors (two continuous stirred tank reactors followed by a tubular reactor), pH adjustment, a crystallizer—filter—evaporator recycle initial separation section, and a chromatographic purification system to produce lactulose containing less than 1–5 ppm of boric acid. The continuous process operates at 0.53 kg/min (20% solids) through the reactors and about 0.3 kg/min (55% solids) out of the initial separation section. The chromatographic separation is at the prep scale with a flow rate of 2.0 mL/min. The final product is a 55% solids syrup containing no detectable boric acid.