Unexpected crystal growth modifier effect of glucosamine as additive in the synthesis of SAPO-35

• Synthesis of SAPO-35 using glucosamine as modifier additive.
• Crystal size and morphology depend on glucosamine concentration in the gel.
• Addition of 0.5 wt% glucosamine to gel produces a 25-fold decrease in crystal size.
• Reduction of crystal size follows volcano shape curve vs. glucosamine concentration.

The synthesis of small-pore silicoaluminophosphate SAPO-35 (LEV) using hexamethyleneimine as organic template and glucosamine as additive is described for the first time. Pure SAPO-35 materials were obtained in short reaction times from gels containing up to 3 wt% glucosamine. The average crystal size varied in the range 2–50 μm and was found to depend strongly on the amount of glucosamine added to the synthesis gel. Thus, glucosamine shows a crystal growth modifier effect, providing a precise control on the crystal size, which allows to obtain crystals of SAPO-35 with the desired size.

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