Kinetic Modeling of Methanol Transformation into Olefins on a SAPO-34 Catalyst

Abstract

A kinetic model for the methanol to olefins (MTO) process on a catalyst based on a silicoaluminophosphate SAPO-34 has been proposed. The model takes into account four individual steps for the production of ethene, propene, butenes, and remaining hydrocarbons (pentenes + paraffins). The kinetic parameters have been obtained by experimentation in an isothermal fixedbed reactor, in the 623-748 K range. In virtue of the results, it has been proven that the water introduced in the feed (required for attenuation of coke deactivation) inhibits olefin formation. This inhibition is taken into account in the kinetic model.

Mathematical modeling of multi-bed adiabatic reactor for the Methanol-to-Olefin process

“…Because of the deactivation attenuation effect, co-feeding water proved to be a good choice and attracted the attention of many scholars [9,10]. Alwahabi [11] also gave a detailed discussion focusing on this issue.…”

“…The catalyst turns into fast deactivation stage afterwards, which gives a notable decrease of oxygenated conversion. Because a first order global reaction rate is found [7,9,12], the kinetic model of methanol consumption is proposed as Eq. 3, as the reaction remains in a stationary stage.…”

“…Adopting Bos's kinetic results, Soundararajan performed a circulating fluidized reactor simulation, and investigated different process conditions. Gayubo [9] introduced a more simplified reaction model, with which water addition for deactivation attenuation was studied. Alwahabi [10] developed very detailed reaction kinetics based on the single-event theory in terms of SAPO-34 catalyst with the consideration of the coke formation which was assumed to be the result of large molecules trapped inside the catalyst cavities.…”

Methanol‐to‐Hydrocarbons

“…Evidence for intracrystalline diffusion limitations has been found at crystal sizes >2.5 µm [59,60] and for intraparticle diffusion limitations for particles >1 mm [57]. This may be the reason why the reported activation energies vary over a broad range from 35 to 90 kJ mol −1 [58,[61][62][63].…”

“…Their reactor model suggests that the circulating fast fluidized-bed reactor and a turbulent fluidized-bed reactor are the most promising reactor systems for MTO and that a certain carbon content on the catalyst is required to obtain maximum yield of light olefins. Chen et al [61] and Gayubo et al [63] applied a similar approach and introduced activation energies and competing adsorption to describe the effect of temperature and water on selectivity and deactivation. Gayubo et al found that the reaction network could be reduced to four parallel reactions without losing accuracy even at conversions up to almost 100%.…”