scholarly journals Performance of Alternative Methane Reforms Based on Experimental Kinetic Evaluation and Simulation in a Fixed Bed Reactor

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1479
Author(s):  
Augusto Knoelchemann ◽  
Deivson C. S. Sales ◽  
Marcos A. M. Silva ◽  
Cesar A. M. Abreu
Keyword(s):  
Comparative Evaluation ◽  
Carbon Deposition ◽  
Catalyst Deactivation ◽  
Fixed Bed ◽  
Reaction Rates ◽  
Fixed Bed Reactor ◽  
Methane Reforming ◽  
Kinetic Evaluation ◽  
Alternative Processes ◽  
Al2o3 Catalyst

A comparative evaluation of alternative methane reforming processes as an option to steam reforming was performed by carrying out simulations of operations in a fixed bed reactor with a Ni (4.8 wt.%/γ-Al2O3) catalyst at 1023 K under 1.0 bar. Methane reforms, including processing with carbon dioxide (DRM, CH4/CO2), autothermal reform (ATRM, CH4/H2O/O2), and combined reform (CRM, CH4/CO2/H2O/O2) had their operations predicted based on experimental data developed to represent their kinetic behavior, formalized with mechanisms and parametric quantifications. The performance of fixed bed reactor operations for methane conversions occurred with different reaction rates in the three alternative processes, and comparatively the orders of magnitude were 102, 10−1, and 10−4 in CRM, ATRM, and DRM, respectively. According to each process, the methane conversions were oriented towards the predominant productions of hydrogen or carbon monoxide, indicating the kinetic selectivities of H2, 86.1% and CO, 59.2% in CRM and DRM, respectively. Considering the possibility of catalyst deactivation by carbon deposition, its predicted yields are low due to the slow stages of its production and due to its simultaneous consumption through interactions with O2, CO2, and H2O, reflecting favorably in additional productions of H2 and CO.

scholarly journals Condensation By-Products in Wet Peroxide Oxidation: Fouling or Catalytic Promotion? Part II: Activity, Nature and Stability

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 518 ◽  
Author(s):  
Asunción Quintanilla ◽  
Jose L. Diaz de Tuesta ◽  
Cristina Figueruelo ◽  
Macarena Munoz ◽  
Jose A. Casas
Keyword(s):  
Catalyst Deactivation ◽  
Fixed Bed ◽  
Reaction Rates ◽  
Fixed Bed Reactor ◽  
Intrinsic Activity ◽  
Peroxide Oxidation ◽  
Air Oxidation ◽  
Carbonaceous Deposits ◽  
Wet Peroxide Oxidation ◽  
By Products

The deposition of condensation by-products onto the catalyst surface upon wet peroxide and wet air oxidation processes has usually been associated with catalyst deactivation. However, in Part I of this paper, it was demonstrated that these carbonaceous deposits actually act as catalytic promoters in the oxygen-assisted wet peroxide oxidation (WPO-O2) of phenol. Herein, the intrinsic activity, nature and stability of these species have been investigated. To achieve this goal, an up-flow fixed bed reactor packed with porous Al2O3 spheres was used to facilitate the deposition of the condensation by-products formed in the liquid phase. It was demonstrated that the condensation by-products catalyzed the decomposition of H2O2 and a higher amount of these species leads to a higher degree of oxidation degree The reaction rates, conversion values and intermediates’ distribution were analyzed. The characterization of the carbonaceous deposits on the Al2O3 spheres showed a significant amount of condensation by-products (~6 wt.%) after 650 h of time on stream. They are of aromatic nature and present oxygen functional groups consisting of quinones, phenols, aldehydes, carboxylics and ketones. The initial phenol concentration and H2O2 dose were found to be crucial variables for the generation and consumption of such species, respectively.

scholarly journals Hydrodeoxygenation (HDO) of Aliphatic Oxygenates and Phenol over NiMo/MgAl2O4: Reactivity, Inhibition, and Catalyst Reactivation

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 521 ◽  
Author(s):  
Trine Marie Hartmann Dabros ◽  
Mads Lysgaard Andersen ◽  
Simon Brædder Lindahl ◽  
Thomas Willum Hansen ◽  
Martin Høj ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Ethylene Glycol ◽  
Active Sites ◽  
Carbon Deposition ◽  
Catalyst Deactivation ◽  
Fixed Bed ◽  
Complex Mixture ◽  
Fixed Bed Reactor ◽  
Hydrogenation Reactions ◽  
Pyrolysis Of Biomass

This study provides new insights into sustainable fuel production by upgrading bio-derived oxygenates by catalytic hydrodeoxygenation (HDO). HDO of ethylene glycol (EG), cyclohexanol (Cyc), acetic acid (AcOH), and phenol (Phe) was investigated using a Ni-MoS2/MgAl2O4 catalyst. In addition, HDO of a mixture of Phe/EG and Cyc/EG was studied as a first step towards the complex mixture in biomass pyrolysis vapor and bio-oil. Activity tests were performed in a fixed bed reactor at 380–450 °C, 27 bar H2, 550 vol ppm H2S, and up to 220 h on stream. Acetic acid plugged the reactor inlet by carbon deposition within 2 h on stream, underlining the challenges of upgrading highly reactive oxygenates. For ethylene glycol and cyclohexanol, steady state conversion was obtained in the temperature range of 380–415 °C. The HDO macro-kinetics were assessed in terms of consecutive dehydration and hydrogenation reactions. The results indicate that HDO of ethylene glycol and cyclohexanol involve different active sites. There was no significant influence from phenol or cyclohexanol on the rate of ethylene glycol HDO. However, a pronounced inhibiting effect from ethylene glycol on the HDO of cyclohexanol was observed. Catalyst deactivation by carbon deposition could be mitigated by oxidation and re-sulfidation. The results presented here demonstrate the need to address differences in oxygenate reactivity when upgrading vapors or oils derived from pyrolysis of biomass.

scholarly journals Effect of CO2 partial pressure on dry reforming of ethanol for hydrogen production

2018 ◽  
Vol 1 (1) ◽  
pp. 6-10
Author(s):  
Fahim Fayaz ◽  
Ahmad Ziad Sulaiman ◽  
Sharanjit Singh ◽  
Sweeta Akbari
Keyword(s):  
Partial Pressure ◽  
Fixed Bed ◽  
Dry Reforming ◽  
Fixed Bed Reactor ◽  
Bet Surface Area ◽  
Impregnation Method ◽  
X Ray Diffraction ◽  
Co2 Partial Pressure ◽  
Temperature Programmed ◽  
Al2o3 Catalyst

The effect of CO2 partial pressure on ethanol dry reforming was evaluated over 5%Ce-10%Co/Al2O3 catalyst at = PCO2 = 20-50 kPa, PC2H5OH = 20 kPa, reaction temperature of 973 K under atmospheric pressure. The catalyst was prepared by using impregnation method and tested in a fixed-bed reactor. X-ray diffraction measurements studied the formation of Co3O4, spinel CoAl2O4 and CeO2, phases on surface of 5%Ce-10%Co/Al2O3 catalyst. CeO2, CoO and Co3O4 oxides were obtained during temperature–programmed calcination. Ce-promoted 10%Co/Al2O3 catalyst possessed high BET surface area of 137.35 m2 g-1. C2H5OH and CO2 conversions was improved with increasing CO2 partial pressure from 20-50 kPa whilst the optimal selectivity of H2 and CO was achieved at 50 kPa.

scholarly journals Analysis and Model-Based Description of the Total Process of Periodic Deactivation and Regeneration of a VOx Catalyst for Selective Dehydrogenation of Propane

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1374
Author(s):  
Andreas Brune ◽  
Andreas Seidel-Morgenstern ◽  
Christof Hamel
Keyword(s):  
Catalyst Deactivation ◽  
Process Development ◽  
Coke Formation ◽  
Fixed Bed ◽  
Reaction Network ◽  
Fixed Bed Reactor ◽  
Side Reactions ◽  
Model Based ◽  
Total Process

This study intends to provide insights into various aspects related to the reaction kinetics of the VOx catalyzed propane dehydrogenation including main and side reactions and, in particular, catalyst deactivation and regeneration, which can be hardly found in combination in current literature. To kinetically describe the complex reaction network, a reduced model was fitted to lab scale experiments performed in a fixed bed reactor. Additionally, thermogravimetric analysis (TGA) was applied to investigate the coking behavior of the catalyst under defined conditions considering propane and propene as precursors for coke formation. Propene was identified to be the main coke precursor, which agrees with results of experiments using a segmented fixed bed reactor (FBR). A mechanistic multilayer-monolayer coke growth model was developed to mathematically describe the catalyst coking. Samples from long-term deactivation experiments in an FBR were used for regeneration experiments with oxygen to gasify the coke deposits in a TGA. A power law approach was able to describe the regeneration behavior well. Finally, the results of periodic experiments consisting of several deactivation and regeneration cycles verified the long-term stability of the catalyst and confirmed the validity of the derived and parametrized kinetic models for deactivation and regeneration, which will allow model-based process development and optimization.

scholarly journals Supercritical Transesterification of Palm Oil and Hydrated Ethanol in a Fixed Bed Reactor with a CaO/Al2O3 Catalyst

Energies ◽  
2012 ◽  
Vol 5 (4) ◽  
pp. 1062-1080 ◽  
Author(s):  
Ruengwit Sawangkeaw ◽  
Pornicha Tejvirat ◽  
Chawalit Ngamcharassrivichai ◽  
Somkiat Ngamprasertsith
Keyword(s):  
Palm Oil ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Al2o3 Catalyst

Modeling of Low-Temperature Reduction of Metal Oxide in Hydrogen Treatment System for Severe Accidents in Nuclear Power Plants

2020 ◽  
Author(s):  
Kotaro Nakamura ◽  
Masashi Tanabe ◽  
Satoru Abe ◽  
Takashi Mawatari ◽  
Takao Nakagaki
Keyword(s):  
Water Vapor ◽  
Metal Oxide ◽  
Nuclear Power ◽  
Elevated Temperatures ◽  
Fixed Bed ◽  
Reaction Rates ◽  
Numerical Calculations ◽  
Treatment System ◽  
Fixed Bed Reactor ◽  
Hydrogen Treatment

Abstract At the Fukushima Daiichi nuclear power plant, zirconium in the fuel rod cladding reacted with water vapor at elevated temperatures due to a loss of cooling water, resulting in the production of a large amount of hydrogen. This hydrogen leaked from the reactor vessel and accumulated in the top of reactor building, eventually leading to an explosion. A hydrogen treatment system that re-oxidizes hydrogen to water vapor is one of the effective methods to prevent such an explosion. A prominent re-oxidation method is via a fixed bed reactor packed with metal oxide pellets. The advantages of this method are its relatively fast oxidation rate without external oxygen/air injection. In this study, experiments and complementary numerical calculations were performed on the hydrogen re-oxidation reaction by metal oxides. The oxidation of hydrogen by copper oxide is modeled by 5 interacting, elementary reactions consisting of 6 chemical species. Experiments were performed using two packed bed set-ups, with measurement of inlet/outlet gas composition and pre/post-analysis of solid composition used to determine constants of the individual reaction rates for numerical calculations. From these reaction constants, the temporal behavior of the outlet gas was predicted.

scholarly journals Investigation on the simultaneous removal of COS, CS2 and O2 from coke oven gas by hydrogenation on a Pd/Al2O3 catalyst

2020 ◽  
Vol 10 (9) ◽  
pp. 2961-2969
Author(s):  
Eva Kamp ◽  
Holger Thielert ◽  
Olaf von Morstein ◽  
Sven Kureti ◽  
Norman Schreiter ◽  
...  
Keyword(s):  
Fixed Bed ◽  
Coke Oven ◽  
Fixed Bed Reactor ◽  
Organosulfur Compounds ◽  
Simultaneous Removal ◽  
Coke Oven Gas ◽  
Al2o3 Catalyst

Simultaneous hydrogenation of organosulfur compounds and O2 by Pd/Al2O3 catalyst was studied in a fixed bed reactor and by DRIFTS.

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