catalyst deactivation
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Fuel ◽  
2022 ◽  
Vol 312 ◽  
pp. 122910
Author(s):  
Enara Fernandez ◽  
Laura Santamaria ◽  
Maite Artetxe ◽  
Maider Amutio ◽  
Aitor Arregi ◽  
...  

2022 ◽  
Vol 429 ◽  
pp. 132206
Author(s):  
G. Abdulkareem-Alsultan ◽  
N. Asikin-Mijan ◽  
Laith K. Obeas ◽  
Robiah Yunus ◽  
Siti Zulaika Razali ◽  
...  

Catalysts ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 98
Author(s):  
Galina Y. Nazarova ◽  
Elena N. Ivashkina ◽  
Emiliya D. Ivanchina ◽  
Maria Y. Mezhova

Changes in the quality of the feedstocks generated by involving various petroleum fractions in catalytic cracking significantly affect catalyst deactivation, which stems from coke formed on the catalyst surface. By conducting experimental studies on feedstocks and catalysts, as well as using industrial data, we studied how the content of saturates, aromatics and resins (SAR) in feedstock and the main process variables, including temperature, consumptions of the feedstock, catalyst and slops, influence the formation of catalytic coke. We also determined catalyst deactivation patterns using TG-DTA, N2 adsorption and TPD, which were further used as a basis for a kinetic model of catalytic cracking. This model helps predict the changes in reactions rates caused by coke formation and, also, evaluates quantitatively how group characteristics of the feedstock, the catalyst-to-oil ratio and slop flow influence the coke content on the catalyst and the degree of catalyst deactivation. We defined that a total loss of acidity changes from 8.6 to 30.4 wt% for spent catalysts, and this depends on SAR content in feedstock and process variables. The results show that despite enriching the feedstock by saturates, the highest coke yields (4.6–5.2 wt%) may be produced due to the high content of resins (2.1–3.5 wt%).


Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 596
Author(s):  
Javier Torres-Liñán ◽  
Ramiro Ruiz-Rosas ◽  
Juana María Rosas ◽  
José Rodríguez-Mirasol ◽  
Tomás Cordero

A Zr-loaded P-containing biomass-derived activated carbon (ACPZr) has been tested for methanol dehydration between 450 and 550 °C. At earlier stages, methanol conversion was complete, and the reaction product was mainly dimethyl ether (DME), although coke, methane, hydrogen and CO were also observed to a lesser extent. The catalyst was slowly deactivated with time-on-stream (TOS), but maintained a high selectivity to DME (>80%), with a higher yield to this product than 20% for more than 24 h at 500 °C. A kinetic model was developed for methanol dehydration reaction, which included the effect of the inhibition of water and the deactivation of the catalyst by coke. The study of stoichiometric rates pointed out that coke could be produced through a formaldehyde intermediate, which might, alternatively, decompose into CO and H2. On the other hand, the presence of 10% water in the feed did not affect the rate of coke formation, but produced a reduction of 50% in the DME yield, suggesting a reversible competitive adsorption of water. A Langmuir–Hinshelwood reaction mechanism was used to develop a kinetic model that considered the deactivation of the catalyst. Activation energy values of 65 and 51 kJ/mol were obtained for DME and methane production in the temperature range from 450 °C to 550 °C. On the other hand, coke formation as a function of time on stream (TOS) was also modelled and used as the input for the deactivation function of the model, which allowed for the successful prediction of the DME, CH4 and CO yields in the whole evaluated TOS interval.


Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 219
Author(s):  
Verónica Torregrosa-Rivero ◽  
María-Salvadora Sánchez-Adsuar ◽  
María-José Illán-Gómez

A series of BaMnO3 solids (BM-CX) were prepared by a modified sol-gel method in which a carbon black (VULCAN XC-72R), and different calcination temperatures (600 °C–850 °C) were used. The fresh and used catalysts were characterized by ICP-OES, XRD, XPS, FESEM, TEM, O2-TPD and H2- TPR-. The characterization results indicate that the use of low calcination temperatures in the presence of carbon black allows decreasing the sintering effects and achieving some improvements regarding BM reference catalyst: (i) smaller average crystal and particles size, (ii) a slight increase in the BET surface area, (iii) a decrease in the macropores diameter range and, (iv) a lower temperature for the reduction of manganese. The hydrogen consumption confirms Mn(III) and Mn(IV) are presented in the samples, Mn(III) being the main oxidation state. The BM-CX catalysts series shows an improved catalytic performance regarding BM reference catalyst for oxidation processes (NO to NO2 and NO2-assisted soot oxidation), promoting higher stability and higher CO2 selectivity. BM-C700 shows the best catalytic performance, i.e., the highest thermal stability and a high initial soot oxidation rate, which decreases the accumulation of soot during the soot oxidation and, consequently, minimizes the catalyst deactivation.


2022 ◽  
pp. 398-424
Author(s):  
S. S. E. H. Elnashaie ◽  
S. S. Elshishini

Catalysts ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 51
Author(s):  
Pavel Čičmanec ◽  
Jiří Kotera ◽  
Jan Vaculík ◽  
Roman Bulánek

The catalytic activity of zeolites is often related to their acid–base properties. In this work, the relationship between the value of apparent activation energy of ethanol dehydration, measured in a fixed bed reactor and by means of a temperature-programmed surface reaction (TPSR) depending on the amount of ethanol in the zeolite lattice and the value of activation energy of H/D exchange as a measure of acid–base properties of MFI and CHA zeolites, was studied. Tests in a fixed bed reactor were unable to provide reliable reaction kinetics data due to internal diffusion limitations and rapid catalyst deactivation. Only the TPSR method was able to provide activation energy values comparable to the activation energy values obtained from the H/D exchange rate measurements. In addition, for CHA zeolite, it has been shown that the values of ethanol dehydration activation energies depend on the amount of ethanol in the CHA framework, and this effect can be attributed to the substrate clustering effects supporting the deprotonation of zeolite Brønsted centers.


Energies ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 308
Author(s):  
Thabang W. Selalame ◽  
Raj Patel ◽  
Iqbal M. Mujtaba ◽  
Yakubu M. John

Heavy petroleum industries, including the fluid catalytic cracking (FCC) unit, are useful for producing fuels but they are among some of the biggest contributors to global greenhouse gas (GHG) emissions. The recent global push for mitigation efforts against climate change has resulted in increased legislation that affects the operations and future of these industries. In terms of the FCC unit, on the riser side, more legislation is pushing towards them switching from petroleum-driven energy sources to more renewable sources such as solar and wind, which threatens the profitability of the unit. On the regenerator side, there is more legislation aimed at reducing emissions of GHGs from such units. As a result, it is more important than ever to develop models that are accurate and reliable, that will help optimise the unit for maximisation of profits under new regulations and changing trends, and that predict emissions of various GHGs to keep up with new reporting guidelines. This article, split over two parts, reviews traditional modelling methodologies used in modelling and simulation of the FCC unit. In Part I, hydrodynamics and kinetics of the riser are discussed in terms of experimental data and modelling approaches. A brief review of the FCC feed is undertaken in terms of characterisations and cracking reaction chemistry, and how these factors have affected modelling approaches. A brief overview of how vaporisation and catalyst deactivation are addressed in the FCC modelling literature is also undertaken. Modelling of constitutive parts that are important to the FCC riser unit such as gas-solid cyclones, disengaging and stripping vessels, is also considered. This review then identifies areas where current models for the riser can be improved for the future. In Part II, a similar review is presented for the FCC regenerator system.


2022 ◽  
pp. 134620
Author(s):  
Songbo He ◽  
Hero Reinder Goldhoorn ◽  
Zhuorigebatu Tegudeer ◽  
Anshu Chandel ◽  
Andre Heeres ◽  
...  

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 53
Author(s):  
Kai Miao ◽  
Tan Li ◽  
Jing Su ◽  
Cong Wang ◽  
Kaige Wang

Catalytic hydropyrolysis via the introduction of external hydrogen into catalytic pyrolysis process using hydrodeoxygenation catalysts is one of the major approaches of bio-oil upgrading. In this study, hydrodeoxygenation of acetone over Mo/HZSM-5 and HZSM-5 were investigated with focus on the influence of hydrogen pressure and catalyst deactivation. It is found that doped MoO3 could prolong the catalyst activity due to the suppression of coke formation. The influence of hydrogen pressure on catalytic HDO of acetone was further studied. Hydrogen pressure of 30 bar effectively prolonged catalyst activity while decreased the coke deposition over catalyst. The coke formation over the HZSM-5 and Mo/HZSM-5 under 30 bar hydrogen pressure decreased 66% and 83%, respectively, compared to that under atmospheric hydrogen pressure. Compared to the test with the HZSM-5, 35% higher yield of aliphatics and 60% lower coke were obtained from the Mo/HZSM-5 under 30 bar hydrogen pressure. Characterization of the spent Mo/HZSM-5 catalyst revealed the deactivation was mainly due to the carbon deposition blocking the micropores and Bronsted acid sites. Mo/HZSM-5 was proved to be potentially enhanced production of hydrocarbons.


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