Spray-dried zeotype/clay nanocatalyst for methanol to light olefins in fluidized bed reactor: Comparison of active and non-active filler

Abstract

Methanol to light olefins (MTO) process utilizes a fluidized bed reactor which is preferable from various points of view. In order to implement the catalysts in fluidized beds, they need to be prepared in fluidizable shape to achieve the fluidization of particulate solids. Fluidizable catalysts have at least three major components including filler, binder and zeolite or zeotype. The filler is mostly a clay which is incorporated into the catalyst in order to dilute its activity. Kaolin was used in fluidizable catalysts preparation. Its activation was studied as a chemical treatment method. Filler was called active matrix/filler in case it was treated with inorganic acids. Physiochemical properties were studied by different techniques such as XRD, SEM, EDX, FTIR, BET and NH3-TPD. Furthermore, TGA and NH3-TPD analyses were applied in order to characterize the used catalysts. MTO activity tests were done in a fixed and fluidized bed reactor. Pore volume and surface area increased with acid treatment consideration. By the implementation of kaolin which was already treated with acid, the intensity of acid sites was increased. MTO reaction results indicates that the catalyst with active filler has the ability to convert methanol to desired light olefins and it enhances the corresponding performance in terms of making induction period shorter. Coking rates with the simplified assumption of uniform coke formation during the catalyst life time can put a light on defining the dominant cycle according to the dual cycle mechanism. Increasing WHSV in fluidized bed reactor results in further aging of organic species according to the aromatic cycle. Resultantly, the catalyst with active matrix owning higher density of active centres deactivates earlier in fluidized bed due to the increased rate of reaction in whole catalyst bed. Furthermore, uniform occurrence of the MTO reaction in the whole catalyst bed in fluidized bed accelerates the deactivation of the catalyst with active matrix.