scholarly journals Deactivation and Regeneration of Mo/ZSM-5 Catalysts for Methane Dehydroaromatization

2009 ◽  
Vol 12 (1) ◽  
pp. 1 ◽  
Author(s):  
E.V. Matus ◽  
O.B. Sukhova ◽  
I.Z. Ismagilov ◽  
V.I. Zaikovskii ◽  
M.A. Kerzhentsev ◽  
...  
Keyword(s):  
Reaction Time ◽  
Reaction Temperature ◽  
Methane Conversion ◽  
Formation Rate ◽  
Space Velocity ◽  
Molybdenum Content ◽  
Stable Operation ◽  
Carbonaceous Deposits ◽  
Methane Dehydroaromatization ◽  
The Stability

The methane dehydroaromatization (DHA) was studied over a series of impregnated Mo/ZSM-5 catalysts with different molybdenum contents (1-10 wt.%). It was shown that total methane conversion was decreased by 30% during 12 h of DHA reaction. The benzene formation rate was increased from 0.5 to 13.9 mol C<sub>6</sub>H<sub>6</sub>/(g<sub>Mo</sub>·s) when the molybdenum content in the catalyst was lowered from 10 to 1 wt.%. The deactivated Mo/ZSM-5 catalysts were studied by a group of methods: N<sub>2</sub> adsorption, XRD, TGDTA, HRTEM and XPS. The content and condensation degree (C/H ratio) of the carbonaceous deposits was found to increase with an increase of either of the following parameters: molybdenum content (1-10 wt.%), reaction temperature (720-780 °C), space velocity (405-1620 h<sup>-1</sup>), reaction time (0.5-20 h). The stability of Mo/ZSM-5 catalysts in reaction-regeneration cycles was better when the time on stream was shorter. The regeneration conditions of deactivated Mo/ZSM-5 catalysts providing their stable operation under multiple reaction-regeneration cycles have been selected.

scholarly journals Acidic and Catalytic Properties of Mo-Containing Zeolite Catalysts for Non-Oxidative Methane Conversion

2017 ◽  
Vol 6 (3) ◽  
pp. 201 ◽  
Author(s):  
A.V. Vosmerikov ◽  
G.V. Echevsky ◽  
L.L. Korobitsyna ◽  
N.V. Arbuzova ◽  
L.M. Velichkina ◽  
...  
Keyword(s):  
Induction Period ◽  
Methane Conversion ◽  
Space Velocity ◽  
Zeolite Catalysts ◽  
Mechanical Mixing ◽  
Ammonium Heptamolybdate ◽  
Methane Dehydroaromatization ◽  
Conversion Of Methane ◽  
Benzene Toluene ◽  
The Stability

<p>The conversion of methane into benzene, toluene and naphthalene at the reaction temperature of 750 °C and gas hourly space velocity (GHSV) of 500-1500 h<sup>-1</sup> over zeolites modified via impregnation with ammonium heptamolybdate and mechanical mixing with Mo oxide and nanopowder is studied under non-oxidative conditions. It has been established that the highest methane conversion per one run and maximal yield of aromatic hydrocarbons are reached for the sample containing 4.0 mass.% the Mo nanopowder. The stability of Mo-containing zeolite catalysts in the process of methane dehydroaromatization at different GHSV has been studied and a characteristic presence of the induction period caused by the formation of active Mo forms both on the external surface and into the zeolite channels has been established. Both the duration of induction period and stable catalyst operation are decreasing with increasing of GHSV. It was demonstrated that acidic properties of a Mo-containing zeolite catalyst depend on the Mo concentration and method of its introduction.</p>

Bench-Scale Steam Reforming of Methane for Hydrogen Production

Catalysts ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 615 ◽  
Author(s):  
Hae-Gu Park ◽  
Sang-Young Han ◽  
Ki-Won Jun ◽  
Yesol Woo ◽  
Myung-June Park ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Reaction Temperature ◽  
Steam Reforming ◽  
Methane Conversion ◽  
Large Scale ◽  
Production Capacity ◽  
Space Velocity ◽  
Bench Scale ◽  
Steam Reforming Of Methane ◽  
Scale Reactor

The effects of reaction parameters, including reaction temperature and space velocity, on hydrogen production via steam reforming of methane (SRM) were investigated using lab- and bench-scale reactors to identify critical factors for the design of large-scale processes. Based on thermodynamic and kinetic data obtained using the lab-scale reactor, a series of SRM reactions were performed using a pelletized catalyst in the bench-scale reactor with a hydrogen production capacity of 10 L/min. Various temperature profiles were tested for the bench-scale reactor, which was surrounded by three successive cylindrical furnaces to simulate the actual SRM conditions. The temperature at the reactor bottom was crucial for determining the methane conversion and hydrogen production rates when a sufficiently high reaction temperature was maintained (>800 °C) to reach thermodynamic equilibrium at the gas-hourly space velocity of 2.0 L CH4/(h·gcat). However, if the temperature of one or more of the furnaces decreased below 700 °C, the reaction was not equilibrated at the given space velocity. The effectiveness factor (0.143) of the pelletized catalyst was calculated based on the deviation of methane conversion between the lab- and bench-scale reactions at various space velocities. Finally, an idling procedure was proposed so that catalytic activity was not affected by discontinuous operation.

Study on Bio-Fuels Drop Acid by [BSPy]HSO4 Catalytic Esterification

2013 ◽  
Vol 781-784 ◽  
pp. 2433-2437 ◽  
Author(s):  
Ai Hua Zhang ◽  
Zhi Hong Xiao ◽  
Liang Bo Zhang ◽  
Ru Kuan Liu ◽  
Wu Hong Zhong ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Reaction Time ◽  
Reaction Temperature ◽  
Acid Value ◽  
Esterification Reaction ◽  
Process Conditions ◽  
High Catalytic Activity ◽  
Brønsted Acidic Ionic Liquid ◽  
The Stability ◽  
Acid Esterification

Research on the synthesis of BrOnsted acidic ionic liquid by the method of solvent, the pyrolysis bio-fuel with cornus wisoniana oil drop acid esterification reaction, the catalyst dosage, reaction time and reaction temperature on the effects of the acid dropping and in the best optimization under the condition of the stability of the catalyst were investigated. The experimental results show that [BSPHSO4 with high catalytic activity, optimization of process conditions as follows: 1.2% of catalyst, reaction temperature 75 °C, reaction time of 70 min, acid value reduced to 2.0 mg KOH/g. By optimizing the cycle experiment, the stability of the catalyst performance is good, the catalytic activity is relatively stable.

Synthesis of Chitosan Grafted Ternary Polymerization

2010 ◽  
Vol 160-162 ◽  
pp. 1816-1821
Author(s):  
Yu Jie Wang ◽  
Juan Qin Xue ◽  
Wei Bo Mao ◽  
Ming Wu ◽  
Jing Xian Li
Keyword(s):  
Reaction Time ◽  
Reaction Temperature ◽  
Graft Copolymerization ◽  
Experimental Results ◽  
Optimal Synthesis ◽  
Synthesis Conditions ◽  
Graft Yield ◽  
The Stability

In this study, the graft copolymerization of acryalmide and acrylonitrile onto chitosan with K2S2O8-NaHSO3 initiator under N2 interaction is studied and the mechanism is discussed. Compared to the chitosan graft of acrylamide or acrylonitrile, the graft yield and graft efficiency of ternary polymerization increase significantly. The stability and reproducibility are also improved obviously. To be specific, the reaction time, the reaction temperature, the effect of the amount of materials, the concentration of K2S2O8, and the concentration of NaHSO3 on the graft yield and graft efficiency is investigated respectively. The C=C of acrylamide and the acrylonitrile react respectively with -NH2 and C6-OH of chitosan initiated by SO4-•. The experimental results show that the optimal synthesis conditions are given as follows: the reaction time is 6h, the reaction temperature is 60°C, the ratio of m(chitosan):m(acrylamide):m(acrylonitrile) is 1:7:5, the concentration of K2S2O8 is 4.5mmol/L, and the concentration of NaHSO3 is about 2.6mmol/L. Under such conditions the graft yield and graft efficiency can be up to 839.52% and 70.00%, respectively.

scholarly journals Environment-Friendly Deoxygenation of Non-Edible Ceiba oil to Liquid Hydrocarbon Biofuel: Process Parameters and Optimization Study

2021 ◽  
Author(s):  
Nur Hafawati Binti Abdullah ◽  
Nurul Asikin Asikin-Mijan ◽  
Yun Hin Taufiq-Yap ◽  
Hwai Chyuan Ong ◽  
Hwei Voon Lee
Keyword(s):  
Reaction Time ◽  
Reaction Temperature ◽  
Fossil Fuels ◽  
Liquid Hydrocarbon ◽  
Coke Deposition ◽  
Catalyst Loading ◽  
Product Analysis ◽  
Spent Catalyst ◽  
Catalyst Reusability ◽  
The Stability

Abstract Non-edible Ceiba oil has feasibility as a sustainable biofuel resource in tropical countries that act as alternative to a portion of the fossil fuels used today.Catalytic deoxygenation of the Ceiba oil (high O/C ratio) was conducted to produce hydrocarbon biofuel (high H/C ratio)over NiO-CaO5/SiO2-Al2O3catalyst with aims of high diesel selectivity and catalyst reusability. In the present study, Box-Behnken experimental design was used to evaluate and optimize liquid hydrocarbon yieldby considering following reaction factors: catalyst loading (1-9 wt.%), reaction temperature (300 - 380°C) and reaction time (30 -180 min). It was discovered that the optimum yield for hydrocarbon fractionsn-(C8 – C20) was 77% under deoxygenation condition of 5 wt.% catalyst loading, reaction temperature of 340°C within 105 min. Besides, deoxygenationmodel indicated that interaction effects of catalyst loading-reaction time influence the deoxygenation activity greatly. Based on the product analysis, oxygenated species(e.g. CO2 and CO) were removed mainly via decarboxylation/decarbonylation (deCOx) pathways. The NiO-CaO5/SiO2-Al2O3 catalyst is stable for five consecutive runs with hydrocarbon fractions within range of 66-75% and n-(C15+C17) selectivity of 64-72% as well. The stability profile of NiO-CaO5/SiO2-Al2O3 catalyst indicated that the catalyst able to maintain deoxygenation reactivity throughout five cycles with hydrocarbon yield of 66-75% and n-(C15+C17) selectivity of 64–72 %. However, coke deposition was noticed for the spent catalyst after several times of usage, which due to the high reaction temperature above 300 oC.

scholarly journals Carbonization and Regeneration of Mo/ZSM-5 Catalysts for Methane Dehydroaromatization

2017 ◽  
Vol 7 (2) ◽  
pp. 115 ◽  
Author(s):  
Z.R. Ismagilov ◽  
L.T. Tsikoza ◽  
E.V. Matus ◽  
G.S. Litvak ◽  
I.Z. Ismagilov ◽  
...  
Keyword(s):  
Methane Concentration ◽  
Stable Operation ◽  
Reaction Conditions ◽  
Catalyst Synthesis ◽  
Synthesis Conditions ◽  
Carbonaceous Deposits ◽  
Oxidative Treatment ◽  
Treatment Conditions ◽  
Methane Dehydroaromatization ◽  
Mo Content

<p>The character of carbonaceous deposits formed during methane dehydroaromatization reaction in the presence of Mo/ZSM-5 catalysts was studied by differential thermal analysis. The dependence of the concentration and condensation degree (C/H ratio) of the carbonaceous deposits on the catalyst synthesis conditions (Mo content = 1-10%, Si/Al ratio in the initial H-ZSM-5 = 17-45) and reaction conditions (feed flow rate = 405-1620 h<sup>-1</sup>, methane concentration = 90-98%, reaction temperature = 720-780 °C) was investigated. The oxidative treatment conditions of carbonized Mo/ZSM-5 catalysts providing stable operation of the catalysts under multiple reaction-oxidative treatment cycles were selected.</p>

Tyrosine-Selective Bioconjugation with Iminoxyl Radicals

2020 ◽  
Author(s):  
Katsuya Maruyama ◽  
Takashi Ishiyama ◽  
Yohei Seki ◽  
Kounosuke Oisaki ◽  
Motomu Kanai
Keyword(s):  
Reaction Time ◽  
Steric Hindrance ◽  
Room Temperature ◽  
Water Soluble ◽  
Light Irradiation ◽  
Sodium Ascorbate ◽  
Iminoxyl Radical ◽  
Short Reaction Time ◽  
Modified Peptides ◽  
The Stability

A novel Tyr-selective protein bioconjugation using the water-soluble persistent iminoxyl radical is described. The conjugation proceeded with high Tyr-selectivity and short reaction time under biocompatible conditions (room temperature in buffered media under air). The stability of the conjugates was tunable depending on the steric hindrance of iminoxyl. The presence of sodium ascorbate and/or light irradiation promoted traceless deconjugation, restoring the native Tyr structure. The method is applied to the synthesis of a protein-dye conjugate and further derivatization to azobenzene-modified peptides.

The anaerobic treatment of a ligno-cellulosic substrate offering little natural pH buffering capacity

1998 ◽  
Vol 38 (4-5) ◽  
pp. 29-35 ◽  
Author(s):  
C. J. Banks ◽  
P. N. Humphreys
Keyword(s):  
Ph Control ◽  
Anaerobic Treatment ◽  
Buffering Capacity ◽  
Single Stage ◽  
Stable Operation ◽  
Reactor Performance ◽  
Two Stage ◽  
Ph Buffering ◽  
Stage System ◽  
The Stability

The stability and operational performance of single stage digestion with and without liquor recycle and two stage digestion were assessed using a mixture of paper and wood as the digestion substrate. Attempts to maintain stable digestion in both single stage reactors were unsuccessful due to the inherently low natural buffering capacity exhibited; this resulted in a rapid souring of the reactor due to unbuffered volatile fatty acid (VFA) accumulation. The use of lime to control pH was unsatisfactory due to interference with the carbonate/bicarbonate equilibrium resulting in wide oscillations in the control parameter. The two stage system overcame the pH stability problems allowing stable operation for a period of 200 days without any requirement for pH control; this was attributed to the rapid flushing of VFA from the first stage reactor into the second stage, where efficient conversion to methane was established. Reactor performance was judged to be satisfactory with the breakdown of 53% of influent volatile solids. It was concluded that the reactor configuration of the two stage system offers the potential for the treatment of cellulosic wastes with a sub-optimal carbon to nitrogen ratio for conventional digestion.

scholarly journals Stability Analysis of Different Regulation Modes of Hydropower Units

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1933
Author(s):  
Xinran Guo ◽  
Yuanchu Cheng ◽  
Jiada Wei ◽  
Yitian Luo
Keyword(s):  
Stable Operation ◽  
Rotor Speed ◽  
Frequency Range ◽  
Power Regulation ◽  
Normal Frequency ◽  
Dynamic Performances ◽  
Negative Damping ◽  
The Stability ◽  
Regulation Mode ◽  
Water Inertia

The dynamic characteristics of hydropower unit governing systems considerably influence the stability of hydropower units and the connected power system. The dynamic performances of hydropower units with power regulation mode (PRM) and opening regulation mode (ORM) are different. This paper establishes a detailed linear model of a hydropower unit based on the Phillips–Heffron model. The damping characteristic and stability of two regulation modes with different water inertia time constants TW were analyzed. ORM tended to provide negative damping, while PRM often provided positive damping in the major parts of the frequency range within the normal frequency oscillations when TW was large. Eigenvalue analysis illustrated that PRM has better stability than ORM. To validate the analysis, a simulation under two typical faults WAS conducted based on a nonlinear model of a hydropower unit. The simulation results illustrated that the responses of units with PRM are more stable in terms of important operating parameters, such as output power, rotor speed, and power angles. For hydropower units facing challenges in stable operation, PRM is recommended to obtain good dynamic stability.

scholarly journals Asymmetry underlies stability in power grids

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ferenc Molnar ◽  
Takashi Nishikawa ◽  
Adilson E. Motter
Keyword(s):  
Symmetry Breaking ◽  
Real World ◽  
Power Grids ◽  
Stable Operation ◽  
World Systems ◽  
Symmetric State ◽  
Network Systems ◽  
Additional Improvement ◽  
The Stability ◽  
General Method

AbstractBehavioral homogeneity is often critical for the functioning of network systems of interacting entities. In power grids, whose stable operation requires generator frequencies to be synchronized—and thus homogeneous—across the network, previous work suggests that the stability of synchronous states can be improved by making the generators homogeneous. Here, we show that a substantial additional improvement is possible by instead making the generators suitably heterogeneous. We develop a general method for attributing this counterintuitive effect to converse symmetry breaking, a recently established phenomenon in which the system must be asymmetric to maintain a stable symmetric state. These findings constitute the first demonstration of converse symmetry breaking in real-world systems, and our method promises to enable identification of this phenomenon in other networks whose functions rely on behavioral homogeneity.

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