Simultaneous effects of water, TEAOH and morpholine on SAPO-34 synthesis and its performance in MTO process

Abstract

Simultaneous effects of water, tetraethyl ammonium hydroxide (TEAOH) and morpholine in the initial gel are investigated under hydrothermal synthesis of the SAPO-34 molecular sieve. Physicochemical properties of synthesized catalysts were characterized by techniques of XRD, SEM, BET, ICP, FTIR and NH3-TPD. A TEAOH increment causes a reduction of crystallinity and particle size, and an increase of strong acid site. Increasing water at a high TEAOH intensifies the concentration and the strength of the weak and the strong acid site. Controlling the properties of the synthesis catalysts improves the light olefins yield and the lifetime. The best catalyst was synthesized with 1.71 mol of TEAOH, 0.29 mol of morpholine and 85.61 mol of water, which it has a propylene of 15.46 (g/100gMeOH), an ethylene of 15.07 (g/100gMeOH), a total olefins yield of 32.32 (g/100gMeOH), and a lifetime of 21.12 (gMeOH/gCat). This is due to both the optimum intracrystalline diffusion path length and the optimum strong acidity.