Kinetics of the catalytic hydrodesulphurization reaction system; hydrogenolysis of thiophene

1980 ◽  
Vol 45 (10) ◽  
pp. 2728-2741 ◽  
Author(s):  
Pavel Fott ◽  
Petr Schneider
Keyword(s):  
Atmospheric Pressure ◽  
Active Sites ◽  
Flow Reactor ◽  
Kinetic Equations ◽  
Reaction System ◽  
Reaction Products ◽  
Molybdenum Catalyst ◽  
Cobalt Molybdenum Catalyst ◽  
Kinetics Of ◽  
Reaction Schemes

Kinetics have been studied of the reaction system taking place during the reaction of thiophene on the cobalt-molybdenum catalyst in a gradientless circulation flow reactor at 360 °C and atmospheric pressure. Butane has been found present in a small amount in the reaction products even at very low conversion. In view of this, consecutive and parallel-consecutive (triangular) reaction schemes have been proposed. In the former scheme the appearance of butane is accounted for by rate of desorption of butene being comparable with the rate of its hydrogenation. According to the latter scheme part of the butane originates from thiophene via a different route than through hydrogenation of butene. Analysis of the kinetic data has revealed that the reaction of thiophene should be considered to take place on other active sites than that of butene. Kinetic equations derived on this assumption for the consecutive and the triangular reaction schemes correlate experimental data with acceptable accuracy.

Kinetics of the catalytic hydrodesulphurization reaction system; hydrogenation of ethylene and butene

1980 ◽  
Vol 45 (10) ◽  
pp. 2742-2750 ◽  
Author(s):  
Pavel Fott ◽  
Petr Schneider
Keyword(s):  
Atmospheric Pressure ◽  
Active Sites ◽  
Flow Reactor ◽  
Reaction System ◽  
Circulation Flow ◽  
Kinetic Description ◽  
Molybdenum Catalyst ◽  
Cobalt Molybdenum Catalyst ◽  
Kinetics Of ◽  
Hydrogenation Of Ethylene

Hydrogenation has been studied of ethylene and butene in a circulation flow reactor on a cobalt-molybdenum catalyst at 360 °C and atmospheric pressure. The effect has been investigated of simultaneous hydrodesulphurization of thiophene on the hydrogenation. The results have confirmed that different active sites for hydrogenation and hydrodesulphurization must be considered in the kinetic description of simultaneous hydrogenation of ethylene and hydrodesulphurization of thiophene. For isolated hydrogenation of ethylene and butene the absence of hydrogen sulphide in the reaction mixture considerably enhances the hydrogenation activity of the catalyst due to the change of its state.

scholarly journals Different pathways of the formation of highly oxidized multifunctional organic compounds (HOMs) from the gas-phase ozonolysis of <i>β</i>-caryophyllene

2016 ◽  
Vol 16 (15) ◽  
pp. 9831-9845 ◽  
Author(s):  
Stefanie Richters ◽  
Hartmut Herrmann ◽  
Torsten Berndt
Keyword(s):  
Double Bond ◽  
Gas Phase ◽  
Organic Compounds ◽  
Atmospheric Pressure ◽  
Reaction System ◽  
Peroxy Radical ◽  
Closed Shell ◽  
Atmospheric Conditions ◽  
Reaction Products ◽  
Product Analysis

Abstract. The gas-phase mechanism of the formation of highly oxidized multifunctional organic compounds (HOMs) from the ozonolysis of β-caryophyllene was investigated in a free-jet flow system at atmospheric pressure and a temperature of 295 ± 2 K. Reaction products, mainly highly oxidized RO2 radicals containing up to 14 oxygen atoms, were detected using chemical ionization – atmospheric pressure interface – time-of-flight mass spectrometry with nitrate and acetate ionization. These highly oxidized RO2 radicals react with NO, NO2, HO2 and other RO2 radicals under atmospheric conditions forming the first-generation HOM closed-shell products. Mechanistic information on the formation of the highly oxidized RO2 radicals is based on results obtained with isotopically labelled ozone (18O3) in the ozonolysis reaction and from hydrogen/deuterium (H/D) exchange experiments of acidic H atoms in the products. The experimental findings indicate that HOM formation in this reaction system is considerably influenced by the presence of a double bond in the RO2 radicals primarily formed from the β-caryophyllene ozonolysis. Three different reaction types for HOM formation can be proposed, allowing for an explanation of the detected main products: (i) the simple autoxidation, corresponding to the repetitive reaction sequence of intramolecular H-abstraction of a RO2 radical, RO2  →  QOOH, and subsequent O2 addition, next forming a peroxy radical, QOOH + O2  →  R′O2; (ii) an extended autoxidation mechanism additionally involving the internal reaction of a RO2 radical with a double bond forming most likely an endoperoxide and (iii) an extended autoxidation mechanism including CO2 elimination. The individual reaction steps of the reaction types (ii) and (iii) are uncertain at the moment. From the product analysis it can be followed that the simple autoxidation mechanism accounts only for about one-third of the formed HOMs. Time-dependent measurements showed that the HOM formation proceeds at a timescale of 3 s or less under the concentration regime applied here. The new reaction pathways represent an extension of the mechanistic understanding of HOM formation via autoxidation in the atmosphere, as recently discovered from laboratory investigations on monoterpene ozonolysis.

scholarly journals Different Pathways of the Formation of Highly Oxidized Multifunctional Organic Compounds (HOMs) from the Gas-Phase Ozonolysis of β-Caryophyllene

2016 ◽  
Author(s):  
Stefanie Richters ◽  
Hartmut Herrmann ◽  
Torsten Berndt
Keyword(s):  
Double Bond ◽  
Gas Phase ◽  
Organic Compounds ◽  
Atmospheric Pressure ◽  
Reaction System ◽  
Peroxy Radical ◽  
Closed Shell ◽  
Atmospheric Conditions ◽  
Reaction Products ◽  
Product Analysis

Abstract. The gas-phase mechanism of the formation of highly oxidized multifunctional organic compounds (HOMs) from the ozonolysis of β-caryophyllene was investigated in a free-jet flow system at atmospheric pressure and a temperature of 295 ± 2 K. Reaction products, mainly highly oxidized RO2 radicals, containing up to 14 oxygen atoms were detected using chemical ionization – atmospheric pressure interface – time-of-flight mass spectrometry with nitrate and acetate ionization. These highly oxidized RO2 radicals react with NO, NO2, HO22 and other RO2 radicals under atmospheric conditions forming the first-generation HOM closed-shell products. Mechanistic information on the formation of the highly oxidized RO2 radicals are based on results obtained with isotopically labeled ozone (18O3) in the ozonolysis reaction and from H/D exchange experiments of acidic H atoms in the products. The experimental findings indicate that HOM formation in this reaction system is considerably influenced by the presence of a double bond in the RO2 radicals primarily formed from the β-caryophyllene ozonolysis. Three different reaction types for HOM formation can be proposed allowing to explain the detected main products, i.e. (i) the simple autoxidation, corresponding to the repetitive reaction sequence of intramolecular H-abstraction of a RO2 radical, RO2 &amp;rightarrow; QOOH, and subsequent O2 addition forming a next peroxy radical, QOOH + O2 &amp;rightarrow; R'O2, (ii) an extended autoxidation mechanism additionally involving the internal reaction of a RO2 radical with a double bond forming most likely an endoperoxide, and (iii) an extended autoxidation mechanism including CO2 elimination. The individual reaction steps of the reaction types (ii) and (iii) are uncertain at the moment. From the product analysis it can be followed that the simple autoxidation mechanism accounts only for about one third of the formed HOMs. Time-dependent measurements showed that the HOM formation proceeds at a timescale of 3 s or less under the concentration regime applied here. The new reaction pathways represent an extension of the mechanistic understanding of HOM formation via autoxidation in the atmosphere, as recently discovered from laboratory investigations on monoterpene ozonolysis.

Kinetics and mechanism of the oxidation of 1-propane thiol by 2,6-dichlorophenolindophenol in acidic medium

1982 ◽  
Vol 60 (15) ◽  
pp. 1928-1932 ◽  
Author(s):  
M. Kashyap ◽  
K. K. Mishra ◽  
N. K. Pandey
Keyword(s):  
Kinetic Data ◽  
Acidic Medium ◽  
Reaction System ◽  
Activation Parameters ◽  
Molar Ratio ◽  
Water Medium ◽  
Reaction Products ◽  
Kinetics Of Oxidation ◽  
Acetone Water ◽  
Kinetics Of

The kinetics of oxidation of 1-propanethiol by 2,6-dichlorophenolindophenol have been studied in acetone–water medium and in the presence of phosphate buffer. The principal reactants interact in a molar ratio of 2:1 forming disulphide and dihydroindophenol. The reaction follows second order kinetics in indophenol while the order is unity in thiol. The rate increases linearly on increasing [H+]. The rate of oxidation increases on increasing the ionic strength as well as the dielectric constant of the reaction system. The addition of reaction products has no effect on the rate. Activation parameters have been evaluated and a suitable mechanism consistent with kinetic data is suggested.

scholarly journals Is Mass Transfer in Secondary Organic Aerosol Particles Intrinsically Slow? Equilibration Timescales of Engine Exhaust and α-Pinene SOA Under Dry and Humid Conditions

2018 ◽  
Author(s):  
Khairallah Atwi ◽  
Mohamad Baassiri ◽  
Mariam Fawaz ◽  
Alan Shihadeh
Keyword(s):  
Atmospheric Pressure ◽  
Flow Reactor ◽  
Organic Aerosol ◽  
Vapor Concentration ◽  
Smog Chamber ◽  
Atmospheric Conditions ◽  
Engine Exhaust ◽  
Clean Air ◽  
Ambient Particle ◽  
Kinetics Of

Abstract. Semi-volatile secondary organic aerosols (SOA) comprise a major fraction of ambient particle pollutants. The partitioning of SOA in the atmosphere has commonly been assumed to be fast enough that it could be computed solely from thermodynamic equilibrium considerations e.g., using Raoult's Law. This simplifying assumption has been called into question by recent studies of single SOA particles evaporating in a zero-vapor concentration environment, which reported unexpectedly slow evaporation relative to atmospheric timescales. In this work we directly investigated the phase equilibration kinetics of systems of SOA particles under realistic atmospheric conditions. SOA was generated in an oxidation flow reactor (OFR) from engine exhaust or α-pinene and mixed with clean air in an atmospheric pressure smog chamber (32 °C) to induce evaporation. The evolution of the particle size distribution was monitored over time as the aerosol system returned to phase equilibrium under different particle concentrations (2.5 and 5 µg m−3) and humidity conditions (

scholarly journals Enhanced Selective Production of Arenes and Regenerating Rate in Aryl Ether Hydrogenolysis over Mesoporous Nickel in Plug-Flow Reactors

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 904
Author(s):  
Chunming Zheng ◽  
Dongxue Wang ◽  
Xudong Hu ◽  
Chao Ma ◽  
Xuan Liu ◽  
...  
Keyword(s):  
Surface Area ◽  
Active Sites ◽  
Flow Reactor ◽  
High Surface ◽  
High Surface Area ◽  
Reaction System ◽  
Aryl Ether ◽  
General Applicability ◽  
Ordered Mesoporous ◽  
Catalytic Cleavage

Ordered mesoporous nickel (mesoNi) was successfully synthesized with a hard templating method by using KIT-6 ordered mesoporous silica as a template. With small-angle X-ray diffraction (SAXRD), transmission electron microscopy (TEM) and N2 sorption technique, the mesoporous structures of synthesized catalysts were characterized with desired high surface area (84.2 m2·g−1) and narrow pore size distribution. MesoNi exhibited outstanding catalytic cleavage activity for lignin model compounds (benzyl phenyl ether, BPE) with high selectivity of arenes in the flow reactor system. MesoNi also showed higher regeneration rates than non-porous ones, which were confirmed from deactivation and regeneration mechanism studies in the flow reaction system with varied high temperature and pressure. The adsorbed poisoning species on the mesoporous Ni surface were analyzed and phenol could be the main poisoning species. The excellent catalytic cleavage performance of mesoNi originates from their unique mesoporous structure, which offers high surface area and Ni active sites. The outstanding catalytic performance shows that this process provides a promising candidate for improved lignin valorization with general applicability.

Kinetics of methyl tert. butyl ether synthesis in gaseous phase

1990 ◽  
Vol 55 (4) ◽  
pp. 1033-1037 ◽  
Author(s):  
Alena Hejtmánková ◽  
Karel Jeřábek ◽  
Karel Setínek
Keyword(s):  
Kinetic Equation ◽  
Metal Ions ◽  
Gaseous Phase ◽  
Atmospheric Pressure ◽  
Active Sites ◽  
Methyl Tert Butyl Ether ◽  
Iron Ions ◽  
Butyl Ether ◽  
Ether Synthesis ◽  
Kinetics Of

Kinetics of methyl tert.butyl ether synthesis from methanol and isobutene was measured in gaseous phase at 85 °C and atmospheric pressure on macroreticular ion exchanger catalyst containing strongly acidic functional groups SO3H and on the same catalyst partially neutralized by sodium and iron ions. The form of the best Langmuir-Hinshelwood type kinetic equation suggests absorption of the reactants in the polymer mass causing ìswellingî of it and influencing the accessibility of active sites by the reactants. Neutralization of the catalyst by metal ions suppresses this effect.

Hydrodesulphurization mechanism of thiophene and tetrahydrothiophene on a cobalt molybdenum catalyst

1980 ◽  
Vol 58 (5) ◽  
pp. 479-484 ◽  
Author(s):  
José M. Pazos ◽  
Paulino Andréu
Keyword(s):  
Reaction Mechanism ◽  
Ring Opening ◽  
Contact Time ◽  
Active Sites ◽  
High Pressures ◽  
Catalyst Activity ◽  
Fresh Catalyst ◽  
Molybdenum Catalyst ◽  
Cobalt Molybdenum Catalyst ◽  
Sulphur Uptake

The hydrodesulphurization mechanism of thiophene and tetrahydrothiophene has been developed at high pressures and over a broad range of temperature and contact time on a commercial CoMo—Al2O3 catalyst. The influence of the pretreatment on the catalyst activity and stability was also studied. The pretreatment with a mixture of H2 and H2S was found to be the most convenient. It was found that the sulphur uptake of the fresh catalyst increases with temperature and that an excess of sulphur in the catalyst leads to an initial higher activity.The thiophene reaction seems to occur simultaneously by two pathways: one consists of ring opening, and the second is yielding tetrahydrothiophene. The latter is the slowest step. The tetrahydrothiophene reacts faster than the thiophene and its reaction mechanism involves mainly the rupture of the C—S bond. However, thiophene was detected in small concentrations, showing the contribution of a second route for the tetrahydrothiophene hydrodesulphurization. Experiments carried out with benzene seem to indicate the existence of three different kinds of active sites in the catalyst: desulphurization, aromatics hydrogenation, and olefin saturation sites.On a élaboré le mécanisme d'hydrodésulfurisation du thiophène et du tétrahydrothiophène à haute pression et sur une large échelle de température et de temps de contact avec une catalyseur commercial mixte: CoMo—Al2O3. On a également étudié la stabilité ainsi que l'influence d'un traitement préalable sur l'activité du catalyseur. On a trouvé que le traitement préalable, par un mélange de H2 et de H2S, est celui qui convient le mieux. On a constaté que la fixation de soufre sur le catalyseur frais augmente avec la température et que l'excès de soufre sur le catalyseur conduit à une activité initiale plus forte.

scholarly journals Thermal Decomposition of Nitrated Tri-n-Butyl Phosphate in a Flow Reactor

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Lalit K. Patil ◽  
Vilas G. Gaikar ◽  
Shekhar Kumar ◽  
U. Kamachi Mudali ◽  
R. Natarajan
Keyword(s):  
Thermal Decomposition ◽  
Atmospheric Pressure ◽  
Flow Reactor ◽  
Degradation Products ◽  
Reaction Pathway ◽  
Operating Conditions ◽  
Purex Process ◽  
Power Law Model ◽  
Reaction Products ◽  
Instrumental Methods

Tri-n-butyl phosphate (TBP) is a universal nuclear extractant, commercially used in the PUREX process for the last 60 years. However, it is prone to nitration and thermal degradation, and as a consequence a red-oil event may be initiated under several operating conditions resulting in severe pressurization of vessel/cell if venting is inadequate. In this work, an attempt was made to understand the reaction pathway of thermal decomposition of nitrated TBP in a flow reactor at atmospheric pressure. Many reaction products were identified and quantified by instrumental methods like HPLC-RI and GC-TCD. The experimental data was analysed with a power law model and the apparent rate constants were estimated. The activation energy for thermal decomposition of nitrated TBP, assuming an Arrhenius type of temperature dependency, was estimated to be 47.39 ± 0.25 kJ·mol−1. The effect of both varying temperature and concentration of nitric acid on conversion of TBP into degradation products and products distribution was experimentally studied. Based on the experimental observations, a reaction mechanism framework for thermal decomposition of nitrated TBP is proposed.

Sign in / Sign up

Export Citation Format

Share Document