Coke deposits formation and products selectivities for the MTG process in a fluidized bed reactor

107

The influence of reaction conditions in the transformation of methanol into gasoline (temperature, time on stream, and contact time) on the deposition and nature of coke (composition, H/C ratio) and on its location in the porous structure of a H-ZSM5 zeolite-based catalyst has been studied in an isothermal fixed-bed integral reactor. The distribution of the coke within the porous structure of the catalyst is similar to that proposed for other reactions on H-ZSM5 zeolites, and the highly hydrogenated character of coke and its instability is noteworthy. Coke deposition has been related to catalyst acidic site deterioration and to a kinetic model for catalyst deactivation in an integral reactor.

Section: Coke Depositionsupporting

confidence: 78%

Deposition and Characteristics of Coke over a H-ZSM5 Zeolite-Based Catalyst in the MTG Process

Benito

Gayubo

Aguayo

et al. 1996

107

“…This would be expected considering that longer space time leads to higher conversion of oxygenates. However, for T ≥ 635 K, it is visible that the molar fraction of ethylene passes through a maximum that is characteristic of an intermediate species, in accordance with observation made by other authors. ,, A similar behavior was observed for propylene, Figure C, except that the maximum is already observed at T = 623 K.…”

Section: Resultssupporting

confidence: 91%

“…Their molar fraction goes through a maximum, in accordance with observations made by other authors. 22,25,29,41 The steady increase at a low conversion level is comparable to the results shown by Marti ́nez-Espi ́n et al 2 A decrease of the olefins fraction is observed at an oxygenate conversion value higher than 0.75, in agreement with observations made by ref 22. In addition, it is shown that the molar fraction of ethylene is higher than that of propylene in the complete range of experimental conditions, in accordance with other results reported in the literature.…”

Section: Industrial and Engineering Chemistry Researchmentioning

confidence: 99%

DME-to-Hydrocarbon over an MFI Zeolite: Product Selectivity Controlled by Oxygenates under the Kinetic Regime

Ortega

Kolb

2019

The influence of process variables on the DME-to-hydrocarbon (DtH) conversion has been assessed. The reaction was studied at atmospheric pressure, over an MFI zeolite (H-ZSM-5, SiO2/Al2O3 = 58), in a gradientless recycle reactor, under the kinetic regime, and process variables in the range of 598–648 K and space time in the range of 0.008–0.040 h kgcat kgDME –1. The results showed that DME and methanol are not in equilibrium, that the cis-/trans-C4 olefins are in equilibrium with each other but not with the 1-butene, while C5 + hydrocarbons are favored at high oxygenates conversion. Finally, it was observed for the first time, to best of the knowledge of the current authors, that under kinetically controlled conditions, the selectivity to main groups of products can be described by the oxygenates conversion (x oxy), independently of the process conditions, which means that the x oxy controls the process selectivity independently of reaction temperature and space time.

“…One of the consequences of catalyst deactivation, together with methanol conversion decrease with time on stream, is the evolution of selectivity, so that light olefin yield (ethylene, propylene, and butenes) increases with time on stream, while heavier hydrocarbon yield (mainly aromatics and paraffins) decreases (Liederman et al, 1978;Edwards and Avidan, 1986;Pop et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

Concentration-Dependent Kinetic Model for Catalyst Deactivation in the MTG Process

Benito

Gayubo

Aguayo

et al. 1996

From experimental results obtained in a wide range of operating conditions (temperature and contact time) in an isothermal fixed-bed integral reactor, the usefulness of the model of Schipper and Krambeck (Chem. Eng. Sci. 1986, 41, 1013−1019) for simulating the operation has been proven in the 300−375 °C range. The validity of a deactivation kinetic model dependent on the composition of the three lumps for the MTG process (oxygenates, light olefins, and the rest of the products) has been proven, for a wide interval of compositions of the lumps. These compositions correspond to different states of catalyst deactivation. The use of this model in the simulation of the integral reactor avoids noticeable errors inherent to the nonconsideration of the effect of composition on the deactivation.