Carbon Nanotube Production From Ethylene in CO2/N2 Environments

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Chuanwei Zhuo ◽  
Henning Richter ◽  
Yiannis A. Levendis
Keyword(s):  
Elevated Temperatures ◽  
High Surface ◽  
Catalyst Support ◽  
Chemical Properties ◽  
Chemical Vapor ◽  
Abundant Species ◽  
Chemical Kinetic ◽  
Chemical Kinetic Model ◽  
Hydrogen Elimination ◽  
Experimental Findings

Carbon nanotubes (CNTs) have high surface areas and excellent mechanical, electrical, and chemical properties, thus they can be useful in applications related to extraction and conversion of energy. They can be readily produced from hydrocarbon feedstocks. In this work, ethylene, the most voluminously produced hydrocarbon, was used as a CNT feedstock. It was pyrolytically decomposed at elevated temperatures (984–1130 K) to generate CNTs, by catalytic chemical vapor deposition (CVD) on stainless steel substrates. To explore possible utilization of carbon dioxide, a typical combustion byproduct, the ethylene gas was introduced to a preheated CVD reactor at the presence of various amounts of CO2, in a balance of inert nitrogen gas. The ethylene pyrolyzates were assessed at the presence/absence of catalysts and CO2 to identify the gaseous carbon growth agents. Experimental findings were also contrasted to predictions of a detailed chemical kinetic model. It was found that whereas decomposition of ethylene was somewhat inhibited by CO2 at the presence of the catalyst support, its conversion to CNTs was promoted. CNTs consistently formed at 5% CO2. Maximum yields of CNTs occurred at 1130 K, whereas highest CNT quality was achieved at 1080 K. Hydrogen and 1,3-butadiene (C4H6) were experimentally found to be the most abundant species of ethylene thermal decomposition. This was in agreement with the model, which also highlighted the importance of unimolecular hydrogen elimination.

Characteristics and Applications of Nanostructured Nitrides Synthesized by Vapor Phase Reactions

2005 ◽  
Vol 876 ◽  
Author(s):  
Gerald Ziegenbalg ◽  
Carsten Pätzold ◽  
Ute Ŝingliar ◽  
Rico Berthold
Keyword(s):  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Vapor Phase ◽  
Elevated Temperatures ◽  
Catalyst Support ◽  
Chemical Properties ◽  
Molar Ratio ◽  
Basic Catalyst ◽  
Metal Chlorides ◽  
Amorphous Silicon Nitride

AbstractGas phase ammonolysis of volatile metal chlorides at elevated temperatures is a favorable way to produce nitride or oxynitride nanopowders. Their composition as well as the physico-chemical properties is determined by reaction temperature, molar ratio of the reactants and the residence time of the gases in the reaction zone. Both single and multi component powders can be obtained. Typical particle sizes are in the range of 50 to 350 nm. The specific surface can reach values up to 300 m2/g. Microporous analysis revealed the presence of pores with a diameter between 0.6 and 0.7 nm in amorphous silicon nitride. The powders can be used, depending on the characteristics, as catalyst or basic catalyst support. The paper gives an overview about vapor phase synthesis of single and multi component nitrides as well as the use of amorphous silicon nitride as a basic catalyst support for dehydrogenation of propane.

scholarly journals Methanediide Formation via Hydrogen Elimination in Magnesium versus Aluminium Hydride Complexes of a Sterically Demanding Bis(iminophosphoranyl)methanediide

2017 ◽  
Author(s):  
Christian P. Sindlinger ◽  
Samuel R. Lawrence ◽  
David B. Cordes ◽  
Alexandra M. Z. Slawin ◽  
Andreas Stasch
Keyword(s):  
Diethyl Ether ◽  
Elevated Temperatures ◽  
Chemical Properties ◽  
Molecular Structures ◽  
Hydride Complexes ◽  
Hydrogen Elimination ◽  
Sterically Demanding ◽  
Central Carbon ◽  
Acidic Compounds ◽  
H2 Elimination

Substituted bis(iminophosphoranyl)methanes are CH acidic compounds that can form complexes with formally dianionic central carbon centres. The reaction of H2C(Ph2P=NDip)2 (≡ H2L), Dip = 2,6-diisopropylphenyl, with one equivalent of di-n-butylmagnesium afforded the methanide complex [HLMgnBu] 1. Treatment of complex 1 with phenylsilane in aromatic solvents at elevated temperatures afforded the methanediide complex [(LMg)2] 2 presumably via the MgH intermediate [(HLMgH)n] (n = 1 or 2). The reaction of 1 with LiAlH4 in diethyl ether yielded the AlH complex [HLAlH2] 3. Alternatively, this complex was also obtained from the reaction of H2L with AlH3∙NMe3. The molecular structures of [HLMgnBu] 1, [(LMg)2] 2, and [HLAlH2] 3 are reported. Complex 3 shows no sign of H2 elimination to a methanediide species at elevated temperatures in contrast to the facile elimination of the putative reaction intermediate [(HLMgH)n] (n = 1 or 2) to form [(LMg)2] 2. The chemical properties of complex 2 were investigated and this complex appears to be stable against coordination with strong donor molecules.

In Situ microscopy of the anodic etching of silicon

1995 ◽  
Vol 53 ◽  
pp. 232-233
Author(s):  
Frances M. Ross ◽  
Peter C. Searson
Keyword(s):  
Composite Structures ◽  
High Surface ◽  
High Surface Area ◽  
Chemical Properties ◽  
Selective Etching ◽  
Silicon On Insulator ◽  
Second Phase ◽  
Porous Layers ◽  
New Class ◽  
Porous Semiconductors

Porous semiconductors represent a relatively new class of materials formed by the selective etching of a single or polycrystalline substrate. Although porous silicon has received considerable attention due to its novel optical properties1, porous layers can be formed in other semiconductors such as GaAs and GaP. These materials are characterised by very high surface area and by electrical, optical and chemical properties that may differ considerably from bulk. The properties depend on the pore morphology, which can be controlled by adjusting the processing conditions and the dopant concentration. A number of novel structures can be fabricated using selective etching. For example, self-supporting membranes can be made by growing pores through a wafer, films with modulated pore structure can be fabricated by varying the applied potential during growth, composite structures can be prepared by depositing a second phase into the pores and silicon-on-insulator structures can be formed by oxidising a buried porous layer. In all these applications the ability to grow nanostructures controllably is critical.

scholarly journals The chemistry of cool circumstellar envelopes

1987 ◽  
Vol 122 ◽  
pp. 551-552
Author(s):  
L.A.M. Nejad ◽  
T. J. Millar
Keyword(s):  
Kinetic Model ◽  
Chemical Kinetic ◽  
Time Dependent ◽  
Circumstellar Envelopes ◽  
Chemical Kinetic Model ◽  
Ion Molecule Reactions ◽  
Cool Stars

We have developed a time-dependent chemical kinetic model to describe the chemistry in the circumstellar envelopes of cool stars, with particular reference to IRC + 10216. Our detailed calculations show that ion-molecule reactions are important in the formation of many of the species observed in IRC + 10216.

scholarly journals Photocatalytic Decolorization of Methyl Red on Nanoporous Anodic ZrO2 of Different Crystal Structures

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 215
Author(s):  
Ewa Wierzbicka ◽  
Karolina Syrek ◽  
Klaudia Mączka ◽  
Grzegorz D. Sulka
Keyword(s):  
Photocatalytic Activity ◽  
Photocatalytic Performance ◽  
Elevated Temperatures ◽  
Aqueous Electrolyte ◽  
High Surface ◽  
High Surface Area ◽  
Methyl Red ◽  
Self Organized ◽  
Photocatalytic Decolorization ◽  
Perfect Adhesion

High surface area, self-organized nanoporous ZrO2 arrays with perfect adhesion to the Zr substrate were synthesized by anodization in an aqueous electrolyte containing (NH4)2SO4 and NH4F. The obtained semiconductor materials were tested as photocatalysts for decolorization of the methyl red (MR) as a model azo dye pollutant. It was demonstrated that as-synthesized anodic ZrO2 anodic layers are already crystalline and, therefore, do not require further thermal treatment to provide a high photocatalytic performance. However, photocatalytic efficiency could be improved by annealing at a relatively low-temperature of 350 °C. Higher annealing temperatures caused a gradual drop of photocatalytic activity. The photocatalytic behavior was correlated with the crystal phase transformation in anodic ZrO2. It was found that higher photocatalytic activity was observed for the tetragonal phase over the monoclinic phase (predominant at elevated temperatures). It results from the optimal and complex electronic structure of annealed ZrO2 with three different energy states having absorption edges at 2.0, 4.01 and 5.28 eV.

Energy-minimization multiscale based mesoscale modeling and applications in gas-fluidized catalytic reactors

2019 ◽  
Vol 35 (8) ◽  
pp. 879-915 ◽  
Author(s):  
Bona Lu ◽  
Yan Niu ◽  
Feiguo Chen ◽  
Nouman Ahmad ◽  
Wei Wang ◽  
...  
Keyword(s):  
Energy Minimization ◽  
Fluid Model ◽  
Scale Up ◽  
Flow Characteristics ◽  
Chemical Kinetic ◽  
Mesoscale Modeling ◽  
Catalytic Reactors ◽  
Chemical Kinetic Model ◽  
Starting Point ◽  
Wide Range

Abstract Gas-solid fluidization is intrinsically dynamic and manifests mesoscale structures spanning a wide range of length and timescales. When involved with reactions, more complex phenomena emerge and thus pose bigger challenges for modeling. As the mesoscale is critical to understand multiphase reactive flows, which the conventional two-fluid model without mesoscale modeling may be inadequate to resolve even using extremely fine grids, this review attempts to demonstrate that the energy-minimization multiscale (EMMS) model could be a starting point to develop such mesoscale modeling. Then, the EMMS-based mesoscale modeling with emphasis on formulation of drag coefficients for different fluidization regimes, modification of mass transfer coefficient, and other extensions are discussed in an attempt to resolve the emerging challenges. Its applications with examples of development of novel fluid catalytic cracking and methanol-to-olefins processes prove that the mesoscale modeling plays a remarkable role in improving the predictions in hydrodynamic behaviors and overall reaction rate. However, the product content primarily depends on the chemical kinetic model itself, suggesting the necessity of an effective coupling between chemical kinetics and flow characteristics. The mesoscale modeling can be believed to accelerate the traditional experimental-based scale-up process with much lower cost in the future.

Simulation of HCCI Combustion Characteristics for Low RON Gasoline Surrogate Fuels

2014 ◽  
Vol 694 ◽  
pp. 54-58
Author(s):  
Ling Zhe Zhang ◽  
Ya Kun Sun ◽  
Su Li ◽  
Qing Ping Zheng
Keyword(s):  
Equivalence Ratio ◽  
Chemical Kinetic ◽  
Combustion Characteristics ◽  
Material Strength ◽  
Inlet Temperature ◽  
Compression Ignition Engine ◽  
Chemical Kinetic Model ◽  
Hcci Engine ◽  
Surrogate Fuels ◽  
Inlet Conditions

A reduced chemical kinetic model (103species and 468 reactions) for new low-RON(research octane number) gasoline surrogate fuels has been proposed. Simulations explored for ignition delay time have been compared with experimental data in shock tubes at pressure of 10atm-55 atm and temperatue of 600-1400 K (fuel/air equivalence ratio=0.5,1.0,2.0 and EGR rate=0, 20%). The simulation data presented 15% enlargement compared with experiments showed applicability of the new kinetic mode in this work. A combustion simulation model has been build for HCCI(homogeneous charge compression ignition) engine with Chemkin-pro. The effects of different air inlet temperature, inlet pressure, engine speed and the fuel air equivalence ratio on the combustion characteristics of the fuel were researched. The results indicated the combustion in an HCCI engine worked sufficiently with lean mixtures and low speed. Meanwhile the material strength could be influenced when the inlet conditions changed. This helps to promote the low-RON gasoline surrogate fuel application in the HCCI engine.

Sign in / Sign up

Export Citation Format

Share Document