Saving energy upon water removal in drying by making the α-polymorph of L-glutamic acid

Shaping particle size distribution of a metastable polymorph in additive-assisted reactive crystallization by the Taguchi method

“…They display an endotherm in the range of 207 to 211 °C owing to melting, which is 8 to 10 °C higher than α-GLU. 40…”

“…For each parameter, three levels were set to construct a 3-level L9 orthogonal array in Table 2: (1) addition rates of H 2 SO 4 (aq) of 0.5, 1, and 2 mL s −1 , (2) reaction temperatures of 25, 35, and 45 °C, (3) agitation rates of 400, 500, and 600 rpm, and (4) concentrations of l -PHE of 1.04, 2.60, and 5.20 × 10 −2 M. Those levels were defined based on our preliminary studies or some previous results in the literature. 40,53,54 The range of agitation rates from 400 to 600 rpm was within the operating limit of the agitator we used, while the formed crystals of l -GLU were not suspended well or uniformly throughout a stirred batch crystallizer under agitation below 400 rpm. In other words, good macromixing ( i.e.…”

“…α-GLU is a metastable polymorph, yet it is favorable in the manufacturing process. Due to its prismatic shape and less affinity to hydrogen bonding with water, it is much easier to separate α-GLU crystals from the mother liquor after crystallization, and to be handled for downstream operations of filtration and drying 39,40 As compared to needle-or rod-like β-GLU, 33% of drying energy could be saved in the case of α-GLU. 40 Supersaturation, the driving force for crystallization, is created by means of evaporation, cooling, and antisolvent addition.…”

“…α-GLU is a metastable polymorph, yet it is favorable in the manufacturing process. Due to its prismatic shape and less affinity to hydrogen bonding with water, it is much easier to separate α-GLU crystals from the mother liquor after crystallization, and to be handled for downstream operations of filtration and drying 39,40 As compared to needle- or rod-like β-GLU, 33% of drying energy could be saved in the case of α-GLU. 40…”