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In this work, a comparative study on methanol to olefins (MTO) kinetics in fixed and fluidized bed reactors was conducted. Based on the analysis of experimental observations, a modeling approach that can be used to simulate both reactor configurations was proposed. The coke deposition was shown responsible for the difference of product selectivities for these two reactor configurations. In a fluidized bed reactor, the distribution of the coke deposition is spatially uniform, and evolves with time on stream. However, the coke deposition shows a distribution along the bed height in a fixed bed reactor, and olefins conversions were taken into consideration to account for the selectivity changes with time on stream. With the proposed model, we established a linkage between fixed bed reactors and fluidized bed reactors through coke deposition. By use of this model, it is possible to predict the performance of MTO reaction over SAPO-34 catalyst in fluidized bed reactor with experimental data obtained in fixed bed reactor, or verse vice. [ABSTRACT FROM AUTHOR]

Light olefins including ethylene and propylene are important chemical materials, and a diversity of production technologies have been applied in industrial processes. An index called Olefins Production Security Index (OPSI) is proposed for quantifying the performance of techno-economics and security for different olefins production routes. The results show that Coal via Methanol to Olefins (CMTO) and Coal via Methanol to Propylene (CMTP) routes have the higher security rank in terms of raw materials supply and reasonably good economic performance compared with the Nature Gas via Fischer–Tropsch Synthesis to Olefins (NFTO) and Deep Catalytic Cracking (DCC) routes. Carbon Dioxide via Methanol to Olefins (CDMTO) and Carbon Dioxide via Methanol to Propylene (CDMTP) routes have lower carbon dioxide emissions but higher direct production costs. Basically, CMTO, CMTP, and Nature Gas via Methanol to Olefins (NMTO) routes have the top OPSI grades, which means they are more competitive than other routes in terms of security. We also identify the shortcomings of each olefins production route with regard to the security through sensitivity analysis. It is expected the proposed framework plays a role in searching the most suitable production route for light olefins from the viewpoint of security. [Display omitted] • Light olefins production routes are evaluated against techno-economics and security. • Olefins Production Security Index (OPSI) is proposed. • OPSI considers effects of raw materials, energy, technology, economy, and CO 2. • OPSI can be genetically extended to other industrial productions chain. [ABSTRACT FROM AUTHOR]

Attrition of catalyst in a fluidized bed reactor is an inevitable issue especially in a commercial unit. Methanol to olefins (MTO) is becoming one of the main stream technologies for light olefins production. The attrition of MTO catalyst, however, received little attention. This study is focused on the attrition behavior of MTO catalyst in jet cup at high temperature. The influence of test time, inlet gas velocity, and temperature on MTO catalyst attrition was studied. It is found that the Gwyn formulation can well represent the relation between attrition index and test time. Our results show that jet cup can retrieve results quantitatively comparable to high velocity gas jets method while significantly shortening test time. It is also found that the inlet gas velocity has considerable influence on the MTO catalyst attrition, and the relation between inlet gas velocities and attrition index can be described by a power index of 3.7. Similar to high velocity gas jets experiments the attrition index manifests a maximum with the increase of temperature. But the temperature corresponding to the maximum attrition index shifts from 300 °C in high velocity jets tests to 100 °C in jet cup experiments. An analysis based on SEM pictures indicates that the transition of attrition mechanism is responsible for this shift. An empirical correlation has been presented for MTO catalyst attrition in jet cup, which shows good agreement with experimental data for inlet gas velocity from 88 to 158 m/s, and temperature from 100 to 500 °C. [ABSTRACT FROM AUTHOR]

The air jets method proved to be an important tool for assessing attrition propensity of fluidized bed catalyst in the laboratory, but the influence of test temperature and test time has seldom been considered. This paper focuses on the influence of test temperature and test time on the attrition mechanism of methanol to olefins (MTO) catalyst in high velocity air jets. The attrition time was prolonged to 144 h in current study. It has been found that test time should be carefully chosen in order to achieve an equilibrium attrition rate. A short test time is not sufficient to understand the attrition mechanism. Test temperature affects the attrition mechanism significantly. At room temperature the abrasion and fragmentation were found coexisting while at 500 °C the abrasion is dominant. The abrasion of MTO catalyst at 500 °C results in a severe generation of superfine powder that is hard to capture by downstream cyclones, which is in accordance with the findings in industrial MTO unit. Apparently the attrition test at room temperature cannot reflect the generation of superfine powder. Both test time and test temperature should be carefully considered when the air jets method is used in the attrition study in laboratory. [ABSTRACT FROM AUTHOR]

Themethanol to olefins (MTO) process has been successfully commercializedin China and will potentially become an important route for lightolefins production. In this work, a modeling approach is presentedfor MTO fluidized bed reactor design and operation optimization. Thetwo-fluid model (TFM) where the solid phase shear viscosity and solidphase pressure are derived from kinetic theory of granular flow hasbeen used to model the solid–gas two-phase flows. The interphasedrag force is calculated by either the traditional Gidaspow modelor a recently developed EMMS-bubble model. The simulation study hasbeen performed for a fluidized bed reactor in a 16 kt/a DMTO unit.It has been shown that the Gidaspow model cannot predict a stabledense bed, while the EMMS-bubbling model could simulate the solidfraction distribution in the reactor reasonable well. A reaction modelbased on the simple MTO reaction kinetics has been implemented totest the effectiveness of the model approach. The simulation resultsshow that the methanol is converted rapidly just above the gas inlet.The selectivity of ethylene and propylene however are underpredicted,while the selectivity of CO2and other products are overestimated.It is suggested that a further extension of the EMMS model to a turbulentfluidized bed is important in order to get more quantitative results.Also the MTO reaction kinetics for a commercial DMTO catalyst, inwhich the coke formation kinetics should be included, is highly desired. [ABSTRACT FROM AUTHOR]

In the methanol-to-olefins (MTO) process, coke deposition is closely related to the selectivity of light olefins. Previous simulations of different-sized MTO reactors using two-fluid model (TFM) combined with the EMMS (energy minimization multi-scale)-based drag well predict the hydrodynamic behaviors but poorly predict the product distribution of large reactors due to the unreasonable prediction in coke distribution. In this study, the TFM integrated with the EMMS-based drag is still employed, but the solid phase is treated as a mixture of a series of species with different coke contents. Because the coke content depends on the age of catalyst particles inside the reactor, a continuous stirred tank reactor (CSTR) model mimicking turbulent fluidization while considering the age distribution of catalysts is established to predict the initial coke distribution for speeding up simulation. Compared with the previous simulation without consideration of coke distribution, this approach increases the computational time by a factor of 36% and shows no influence on hydrodynamic predictions, but the reaction quantities such as methanol conversion, mass fractions of gaseous products and selectivity of light olefins, are better predicted. [ABSTRACT FROM AUTHOR]

The methanol to olefins (MTO) process opens an economical and important route to produce light olefins. The design of MTO reactor borrows ideas from the reaction–regeneration configuration of the modern fluid catalytic cracking (FCC) units. However, their hydrodynamic behaviors are quite different in the sense that the fluidized bed for MTO reactions operates in different flow regime from that of FCC, calling for new modeling for scale-up. In addition, the coke deposited on catalysts greatly affects the MTO reaction while its generation is very slow. It normally takes tens of minutes or even hours for catalysts to reach the desired level of coke content. Time-dependent computational fluid dynamics (CFD) simulation of such a long process poses a big challenge to reactive multiphase flow modeling. To speed up it, we try to integrate the classic chemical reaction engineering (CRE) model with CFD. In particular, the continuous stirred tank reactor (CSTR) model is established to estimate the steady state distribution of coke content, which is then set as the initial distribution for CFD simulation to shorten the time to reach the steady state of reactive flows. Comparison with experimental data shows good agreement and also great speed-up ratio compared to traditional CFD simulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A population balance model is proposed for describing the evolution of coke content. • The PBM and multiscale CFD are efficiently combined to simulate an industrial-scale MTO reactor. • The primary light olefins and their selectivity are better predicted. • The relaxation time for expressing the effects of induction period in catalysts are considered. The coke distribution over shape-selective catalysts in fluidized bed reactors is critical to the selectivity of target products. A population balance model (PBM) is developed in this study to describe the evolution of coke distribution due to both reactions and circulation of catalysts. The PBM is coupled with multiscale computational fluid dynamics (CFD) to simulate a methanol-to-olefins fluidized bed reactor. A wide, uneven distribution of coke content can thus be predicted. The mass fractions of the desired products, ethylene and propylene, show better agreement with the experimental data than those without PBM. And the selectivity ratio of ethylene to propylene is also better predicted. Furthermore, the relaxation time of fresh catalyst is considered to express the effects of the induction period in MTO reactions. The reasonable prediction suggests that coupling PBM with multiscale CFD is helpful to understand MTO reactors and may find more application with respect to its optimization and scale-up. [ABSTRACT FROM AUTHOR]