The influence of a small amount of maleic acid on crystal deposition phenomena of methacrylic acid in melt crystallization

Crystal deposition phenomena were investigated in the suspension melt crystallization of an organic acid. Methacrylic acid was used as the target substance, a certain amount of methanol was used as the solvent, and the effect of a small amount of maleic acid by-produced in methacrylic acid synthesis was focused on. Batch crystallizations were carried out on a laboratory scale using various concentrations of maleic acid. In the presence of maleic acid, a certain deviation from equilibrium of the pure binary system was observed in the final composition of mother liquor. Moreover, nevertheless the final temperature in the crystallizer was same, the amount of crystal deposition in the presence of maleic acid was smaller than in the absence of maleic acid. It was suggested that the final amount of crystal deposition decreased in the presence of maleic acid. Additionally, it was observed that the obtained crystal size was smaller in the presence of maleic acid. Hence, a simplified kinetic analysis of crystal deposition rates was carried out to make the effect of maleic acid clear. Consequently, it was suggested that the cause of the above-mentioned phenomena was the existence of the maleic acid concentration dependent pseudo-liquidus line.

► Crystallization phenomena of methacrylic acid melt were investigated.
► The effect of a small amount of maleic acid was focused on.
► A certain deviation from equilibrium was observed in the presence of maleic acid.
► A simplified kinetic analysis of crystal deposition rates was carried out.
► Maleic acid seems to affect the crystal deposition rate and the liquidus line.