Spelling suggestions: "subject:"[een] DIMETHYL ETHER"" "subject:"[enn] DIMETHYL ETHER""
11 |
Characterization of the Structure of Turbulent Non-premixed Dimethyl Ether Jet FlamesShen, Han 01 September 2015 (has links)
No description available.
|
12 |
SEMICONTINUOUS SEPARATION OF DIMETHYL ETHER FROM BIOMASSPascall, Alicia A. January 2013 (has links)
<p>Environmental concerns about greenhouse gas emissions and energy security are the main drivers for the production of alternative fuels from bio-based feedstock. Dimethyl ether has attracted interest of many researches and is touted as “A fuel for the 21<sup>st</sup> century” due to its versatility. However, the production of DME from biomass is dependent on the overall economics of its production.</p> <p>This thesis considers the application of semicontinuous distillation to improve the economics of the separation section in a biomass-to-DME facility. Semicontinuous distillation systems operate in a forced cycle to effect multiple separations using a single distillation column integrated with a middle vessel. The control system plays an integral role in the driving the forced cycle behaviour of the process in which no steady state exists.</p> <p>The separation section consists of a series of flash drums followed by a distillation train consisting of three (3) columns. In the first phase of this work, a semicontinuous system was developed to achieve the separation of the second and third distillation columns in the separation section. Rigorous models were used to simulate the semicontinuous system in which several control configurations were evaluated. The final control structure based on classic PI control was shown to achieve the specification objectives of the system and handle disturbances while avoiding weeping and flooding conditions. Optimization followed by an economic analysis showed that the semicontinuous system was economically preferable to the traditional continuous process for a range of DME production rates.</p> <p>Next, a semicontinuous system was developed to achieve the separation of the first and second distillation columns in the separation section. In this phase the application of semicontinuous distillation was extended to partial condenser configurations and the separation of biphasic mixtures. The control structure developed was effective in handling disturbance, attaining specification objectives while remaining with operational limits. An economic analysis, however, showed the traditional continuous configuration to be more economical for all DME production rates. Findings show that the operating cost is highly depending on the middle vessel purity so while uneconomical for this process it could result in favourable economics for less stringent purity specifications.</p> / Master of Applied Science (MASc)
|
13 |
Performance optimisation of a compression ignition engine fuelled on EthanolTeise, Heinrich Richardt 14 November 2006 (has links)
Student Number : 9506932W -
MSc research report -
School of Mechanical Engineering -
Faculty of Engineering and the Built Environment / In this research project, the performance and emissions of a conventional compression ignition engine fuelled on ethanol as main fuel and dimethyl ether as ignition promoter were investigated. Tests were first conducted on diesel fuel, then on ethanol fuel with dimethyl ether and compared. All tests for both fuelling techniques were conducted at the same engine speed and injector pressure. However, engine settings with specific reference to injection timing and injector pressure were optimised to suit diesel fuel, and were left unaltered when the engine was fuelled on ethanol and dimethyl ether. The injector nozzle configuration used for diesel fuel was a standard three-hole type nozzle, whereas for ethanol fuel with dimethyl ether a standard three-hole nozzle as well as a four-hole type nozzle was used. Also investigated was the effect a catalytic converter would have on exhaust emissions, from both fuelling techniques.
The performance results of ethanol/dimethyl ether fuel compared favourably to that of diesel fuel. The brake power attained for both fuelling techniques was approximately the same, however the only penalty incurred to this desired result was the simultaneous increase in the brake specific fuel consumption of ethanol/dimethyl ether fuel. The fuel conversion efficiency of ethanol/dimethyl ether fuel was also found to be lower than that of diesel fuel, this largely attributed to the difference in energy release patterns between the two fuels.
The emissions results obtained showed that ethanol/dimethyl ether fuel burns cleaner, mainly due to its chemical structure containing oxygen molecules. The NOx, THC, CO and CO2 emissions, produced before the catalytic converter, of ethanol/dimethyl ether fuel were lower than those of diesel fuel. The catalytic converter further produced lower emissions, with the four-hole type nozzle producing the most desired results. In terms of catalytic converter efficiency, THC and CO emissions were more readily removed compared to NOx. In addition, virtually no smoke emissions were detected for ethanol/dimethyl ether fuel combustion.
|
14 |
A comparative study of the combustion characteristics of a compression ignition engine fuelled on diesel and dimethyl etherLopes, Paulo Miguel Pereira 28 February 2007 (has links)
Student Number : 9707408V -
MSc(Eng) research report -
School of Mechanical, Industrial and Aeronautical Engineering -
Faculty of Engineering and the Built Environment / This research is an investigation into the performance and combustion characteristics of
a two-cylinder, four-stroke compression ignition engine fuelled on diesel and then on
dimethyl ether (DME). Baseline tests were performed using diesel. The tests were then
repeated for dimethyl ether fuelling. All DME tests were performed at an injection
opening pressure of 210 bar, as recommended for diesel fuelling. The tests were all
carried out at constant torque with incremental increases in speed and an improved
method of measuring the DME flow rate was devised. It was found that the engine’s
performance characteristics were very similar, regardless of whether the engine was
fuelled on diesel or DME. Brake power, indicated power and cylinder pressure, during
the highest loading condition of 55 Nm, were virtually identical for diesel and DME
fuelling, with the most significant finding being that the engine was more efficient when
fuelled on DME than when fuelled with diesel. Another interesting finding was that the
energy release of diesel decreases with increasing load, whilst the energy release of
DME increases with increasing load. At the highest loading condition of 55 Nm, the
energy release of DME was approximately 210 joules higher than that of diesel. This
investigation concluded that DME may definitely be a suitable substitute fuel for diesel.
|
15 |
Développement et optimisation de catalyseurs à base de cuivre pour la synthèse de méthanol et de diméthyléther à partir de CO2 / Development and optimization of copper-based catalysts for the methanol and dimethyl ether synthesis from CO2L'Hospital, Valentin 11 September 2018 (has links)
Diminuer les émissions de CO2, principal gaz à effet de serre, constitue un des enjeux majeurs de notre ère actuelle. De nombreuses mesures existent déjà mais sont encore insuffisantes. C’est dans ce cadre que le projet ANR DIGAS a vu le jour. Durant ces travaux, des matériaux catalytiques composés de CuO/ZnO/ZrO2 ont été développés par coprécipitation classique et ont été testés sous une pression de 50 bar pour la synthèse de méthanol à partir de l’hydrogénation de CO2. Ces catalyseurs ont ensuite été optimisés à l’aide d’un système développé au laboratoire : la synthèse microfluidique en continu. Elle a permis de rendre les catalyseurs plus homogènes et ainsi plus efficaces. Le catalyseur le plus performant a, par la suite, été couplé à un catalyseur acide, une zéolithe ZSM5, pour permettre la synthèse directe de diméthyléther (DME) à partir de l’hydrogénation de CO2. Dans le cas de la synthèse de méthanol ainsi que pour la synthèse de DME, les catalyseurs développés sont compétitifs et plus performants que les catalyseurs actuellement sur le marché. / Reducing CO2 emissions, the main greenhouse gas, is one of the major challenges of our current era. Many measures already exist but are still insufficient. It is in this context that the ANR project called DIGAS was funded. During this work, catalytic materials composed of CuO/ZnO/ZrO2 were developed by classical coprecipitation and tested under a pressure of 50 bar for the methanol synthesis from CO2 hydrogenation. Then, these catalysts were optimized using a system developed in the laboratory: microfluidic continuous synthesis. It has made the catalysts more homogeneous and thus more efficient. The most efficient catalyst was subsequently coupled to a ZSM5 zeolite to allow direct dimethyl ether (DME) synthesis from the CO2 hydrogenation. In the case of methanol as well as for DME synthesis, the developed catalysts are competitive and more efficient than the catalysts currently on the market.
|
16 |
Kinetic Studies For Dimethyl Ether And Diethyl Ether ProductionVarisli, Dilek 01 September 2007 (has links) (PDF)
Fast depletion of oil reserves necessitates the development of novel alternative
motor vehicle fuels. Global warming problems also initiated new research to develop new
fuels creating less CO2 emission. Nowadays, dimethyl ether (DME) and diethyl ether
(DEE) are considered as important alternative clean energy sources. These valuable
ethers are produced by the dehydration reaction of methanol and ethanol, respectively,
in the presence of acidic catalysts. Besides DEE, ethylene which is very important in
petrochemical industry, can also be produced by ethanol dehydration reaction.
In the first part of this study, the catalytic activity of tungstophosphoric acid
(TPA), silicotungstic acid (STA) and molybdophosphoric acid (MPA), which are well-known
heteropolyacids were tested in ethanol dehydration reaction. The activities of other solid
acid catalysts, such as Nafion and mesoporous aluminosilicate, were also tested in the
dehydration reaction of ethanol. In the case of DME production by dehydration of
methanol, activities of STA, TPA and aluminosilicate catalysts were tested. Among the
heteropolyacid catalysts, STA showed the highest activity in both ethanol and methanol
dehydration reactions. With an increase of temperature from 180oC to 250oC, Ethylene
selectivities increased while DEE selectivities decreased. Ethylene yield values over 0.70
were obtained at 250oC. The presence of water in the feed stream caused some reduction
in the activity of TPA catalyst. Very high DME yields were obtained using mesoporous
aluminosilicate catalyst at about 450oC.
The surface area of heteropolyacids are very low and they are soluble in polar
solvents such as water and alcohols. Considering these drawbacks of heteropolyacid
catalysts, novel mesoporous STA based high surface area catalysts were synthesized
following a hydrothermal synthesis route. These novel catalysts were highly stable and
they did not dissolve in polar solvents. The catalysts containing W/Si ratios of 0.19
(STA62(550)) and 0.34 (STA82(550)) have BJH surface area values of 481 m2/g and 210
m2/g, respectively, with pore size distributions ranging in between 2-15 nm. These
catalysts were characterized by XRD, EDS, SEM, TGA, DTA, DSC, FTIR and Nitrogen
Adsorption techniques and their activities were tested in ethanol dehydration reaction.
Calcination temperature of the catalysts was shown to be a very important parameter for
the activities of these catalysts. Considering the partial decomposition and proton lost of
the catalysts over 375oC, they are calcined at 350oC and 550oC before testing them in
ethanol dehydration reaction. The catalysts calcined at 350oC showed much higher
activity at temperature as low as 180oC. However, the catalysts calcined at 550oC
showed activity over 280oC. Ethylene yield values approaching to 0.90 were obtained at
about 350oC with catalysts calcined at 350oC. DEE yield past through a maximum with an
increase in temperature indicating its decomposition to Ethylene at higher temperatures.
However, at lower temperatures (< / 300oC) Ethylene and DEE were concluded to be
formed through parallel routes. Formation of some acetaldehyde at lower temperatures
indicated a possible reaction path through acetaldehyde in the formation of DEE. DRIFTS
results also proved the presence of ethoxy, acetate and ethyl like species in addition to
adsorbed ethanol molecules on the catalyst surface and gave additional information
related to the mechanism.
|
17 |
Nanocomposite Nafion And Heteropolyacid Incorporated Mesoporous Catalysts For Dimethyl Ether Synthesis From MethanolCiftci, Aysegul 01 August 2009 (has links) (PDF)
The need for alternative transportation fuels is rising with the rapid depletion of oil reserves and the simultaneous growth of the world& / #8217 / s population. Production of dimethyl ether, a non-petroleum derived attractive fuel-alternate for the future, is a challenging research area. Different routes and various solid-acid catalysts are being developed in order to achieve the most efficient way of synthesizing this potential diesel alternative fuel. The focus of heterogeneous catalysis is to convert renewable feed stocks to valuable chemicals. Nafion resin and heteropolyacid compounds are active acidic catalysts with significantly low surface areas, which act as a strong barrier limiting their catalytic activity. Synthesizing solid-acid catalysts by incorporation of nonporous active compounds into mesoporous silicate structured materials opens a door to producing valuable chemicals by heterogeneous catalysis.
The objective of this work was to synthesize and characterize nafion and heteropolyacid incorporated nanocomposite catalysts and to catalyze DME synthesis
by dehydration of methanol at different temperatures. The interactions of methanol and DME with these catalysts were also investigated by in situ FT-IR.
Silicotungstic acid (STA)/Silica and Tungstophosphoric acid (TPA)/Silica catalysts were synthesized by following a one-pot hydrothermal route. These mesoporous catalysts had surface area values of 143-252 m2/g. The STA/SiO2 nanocomposite catalyst having a W/Si atomic ratio of 0.33 showed the highest activity, with a DME selectivity approaching to 100% and a methanol conversion of 60% at 250° / C at a space time of 0.27 s.g.cm-3. Effects of W/Si atomic ratio and the synthesis procedure on the performance of these novel materials were investigated.
Nanocomposite Nafion/SiO2 solid-acid catalysts having high surface area values (595-792 m2/g) and narrow pore size distributions (4.3 nm) were successfully synthesized by a one-pot hydrothermal procedure. Effects of the modifications in the synthesis procedure concerning the surfactant removal, nafion loading, etc. were investigated based on the characterization results and activity tests. Nafion was observed to be uniformly distributed within these mesoporous catalysts. Nafion resin was also impregnated into aluminosilicate and & / #945 / -alumina, but one-pot synthesis was concluded to be better for obtaining well dispersed, nafion incorporated active catalysts. The Nafion/Silica catalyst synthesized by a nafion/silica weight ratio of 0.15 and washed with 2M sulfuric acid-ethanol solution exhibited the highest activity due to its highest Brö / nsted, as well as Lewis acidity. A methanol conversion of 40% at 300° / C, 0.27 s.g.cm-3 and DME selectivity values approaching to 100% over 180° / C were very promising for the synthesis of this green fuel alternate over the new catalysts synthesized.
|
18 |
Dimethyl Ether (dme) Synthesis Using Mesoporous Sapo-34 Like Catalytic MaterialsDemir, Hakan 01 August 2011 (has links) (PDF)
In 21st century, researchers make great effort of finding a clean transportation fuel to
diminish the severe effects of conventional transportation fuel combustion such as global
warming and air pollution. Dimethyl ether is considered as a strong fuel alternative due to its
good burning characteristics and environmentally friendly properties. In order to produce
dimethyl ether, different synthesis routes and solid acid catalysts are being utilized. SAPO-34 is
an aluminophosphate based catalyst having moderate acidity. This property makes it a good
candidate for the synthesis of dimethyl ether. However, SAPO-34 has microporous structure
causing diffusion limitations.
The objective of this study is to synthesize, characterize mesoporous SAPO-34 like
catalytic materials and test the activity of them in methanol dehydration reaction. The benefit of
obtaining mesoporous structure is that the diffusion limitations can be eliminated.
Mesoporous SAPO-34 like catalysts were synthesized through hydrothermal synthesis
route. BET surface areas of these catalysts were 117-133 m2/g. All methanol dehydration
reactions were carried out at a space time of 0.14 s.g/cm3. By using mesoporous SAPO-34 like
catalysts, the highest methanol conversion was 48% obtained at 550° / C with DME selectivity and
yield values of 1 and 0.49, respectively. Since utilizing microporous SAPO-34 catalyst gave
higher methanol conversion, 67%, at lower temperature, 250° / C, with dimethyl ether selectivity
of around 1, mesoporous SAPO-34 like catalysts are not suitable for this reaction.
|
19 |
Zr And Silicotungstic Acid Incorporated Silicate Structured Mesoporous Catalysts For Dimethyl Ether SynthesisOrman, Sultan 01 August 2011 (has links) (PDF)
Due to high consumption rates of petroleum derived fuels and environmental regulations, significant search has been initiated for the development of environmental friendly and efficient fuels, which were derived from more abundant feedstocks. Dimethyl ether (DME), as having a good combustion quality and high cetane number, is an efficient alternative for diesel fuel. With improved combustion quality, the emissions from DME used engines are greatly decreased. DME synthesis can be carried out via two different methods / methanol dehydration on acidic catalysis and syn-gas conversion on bifunctional catalysis.
In this study, the aim is to synthesize acidic catalysts using direct hydrothermal synthesis method for DME synthesis as using methanol as feed stock via dehydration and to characterize these materials.
The support of the synthesized materials comprises of MCM-41 structure and silicotungstic acid (STA) and metals (Zr / Ni / Cu) were incorporated into the MCM-41 structure during synthesis. Two different techniques were used to extract the surfactant (CTMABr) from catalyst matrix. First one is the conventional calcination technique (at 350° / C) and the second is supercritical fluid extraction (at various operating conditions) with methanol modified CO2. The effect of metal loading on extraction performance is analyzed through characterizations of Ni and Cu incorporated materials. In addition, The effect of operation parameters on catalyst properties are also investigated with performing extraction at different pressures for different durations. By changing the type of metal incorporated into the catalyst, the extraction performance is also monitored. The characterization results indicated that, SFE process is also a promising method for surfactant removal.
The activities of zirconium added catalysts are tested in methanol dehydration reaction towards DME. It is concluded that the conversion of methanol and selectivity of DME in presence of extracted samples are lower (maximum yield -0.54- obtained at 450° / C with sceSZ1) compared to the calcined materials (maximum yield -0.80- obtained at 300° / C with cSZ6). This result can also be foreseen by DRIFTS analysis of pyridine adsorbed samples. The acid sites of extracted materials are not as strong as in the calcined catalysts.
|
20 |
Electro-catalysis of Oxygen Reduction on Platinum-Bismuth Alloy Nanoparticles and a Study of Nafion Ionomer ImpactFang, Junchuan 05 October 2021 (has links)
No description available.
|
Page generated in 0.0328 seconds