Dual-template synthesis of nanostructured CoAPSO-34 used in methanol to olefins: Effect of template combinations on catalytic performance and coke formation

Methanol conversion to light olefins was investigated over SAPO-34 catalysts with Co introduction exploring the effect of different mixed templates. Applying mixed templates resulted in enhancement of catalyst life time and causing the reduction in catalyst preparation costs compared to those prepared with single template. Current research was focused on the synthesis of CoAPSO-34 catalysts with various mixtures of templates including TEAOH template. Three sets of mixed templates are taken into account for CoAPSO-34 synthesis, being TEAOH/TEA, TEAOH/DEA and TEAOH/morpholine with constant composition of 50%:50%. The catalysts were prepared via hydrothermal method and characterized with XRD, FESEM, PSD, TEM, EDX, BET and FTIR techniques. Nanostructured catalysts synthesized with TEAOH/DEA and TEAOH/morpholine mixtures exhibit high crystallinity evidenced by XRD analysis. TEAOH/TEA mixed template has the smallest particle size and the most uniform particle size distribution. Application of TEAOH/DEA and TEAOH/morpholine binary templates resulted in higher dispersion of Si and Co metals. Methanol to light olefins reaction was carried at different reaction temperatures. The stability test was conducted maintaining at constant temperature, molar feed ratio and GHSV to distinguish the effect of time on stream. In comparison, later emergence of DME in the products stream for the catalyst prepared with TEAOH/morpholine can be due to its higher crystallinity, better Si distribution and higher structural OH bands evidenced by XRD, EDX and FTIR techniques, respectively. Moreover, TGA, BET and FTIR techniques were implemented to characterize the coke deposit. (C) 2014 Elsevier B.V. All rights reserved.