SAPO-11 component of Pt/SAPO-11-Al2O3 catalysts displays relatively low hydrothermal stability in hydrotreating of vegetable oils that produces water during the process. Application of XRD, HRTEM, NH3 TPD, TPO, H-2 pulse chemisorptions and Si-29 MAS NMR revealed that the reason for hydrothermal deactivation of SAPO-11 is partially reversible desilication of its framework. This results in gradual loss of acidity and catalytic activity in isomerization of normal paraffins - products of oil deoxygenation. Addition of amine surfactant hexadecylamine to SAPO-11 crystallization gel at HDA/Al2O3 ratio of similar to 0.6 strongly increases the hydrothermal stability of SAPO-11. This translates in stable operation of Pt/SAPO-11-Al2O3 catalyst in hydrotreating of soybean oil yielding >99% deoxygenation and producing liquid organic product with cloud point < -35 degrees C containing 15 wt% monoaromatics. The stabilizing effect of HDA is a sequence of increasing the relative content of Si(nAl(4-n)Si) tetrahedra with n = 3-4 displaying higher resistance to hydrothermal desilication. (C) 2015 Elsevier Inc. All rights reserved.