• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 48
  • 24
  • 19
  • 8
  • 5
  • 3
  • 2
  • 1
  • 1
  • Tagged with
  • 129
  • 26
  • 22
  • 16
  • 13
  • 13
  • 12
  • 11
  • 10
  • 10
  • 9
  • 9
  • 9
  • 9
  • 9
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Research on the pollutants of catalytic oxidation for gasoline and emission reduction of bio-diesel fuel

Yang, Hung-wen 12 January 2010 (has links)
How effective would the implementation of biodiesel fuel in reducing emissions caused by automobiles and motorcycles in the densely populated regions? The goal of this research is targeted at determining the most proficient methods in depleting the harmful substances emitted from refueling stations and the efficiency of biodiesel fuel in emissions reduction. The initial stages in the research involved the use of aluminum oxide and molecular sieve, which would act as active metals for copper and manganese. Impregnation and solgel method of catalytic production were utilized with 12 sets of oxidized copper, and molecular sieve catalysts, totaling at 24 sets. With results from the primary testing, initial selection of impregnation production methods based on its conversion rate had a carrying capacity of 20% CuMn/ oxidized copper catalyst (Cu: Mn ratio at 1:1), and a 20% CuMn/molecular sieve catalyst (Cu: Mn ratio of 1:1) with the solgel method. The two exogenous tests were not only found to be the most efficient rate of conversion as base standards, but were also found to be the most competent method to date. Approximate calculations from the two catalytic testing showed that CuMn/oxidized copper catalyst conversion are less affected by variation in concentration density. Furthermore, the CuMn/oxidized copper and CuMn/molecular sieve catalysts faced a positive conversion rate when reacted with a decreased space velocity, but leveled off once it reached a specific level. Moreover, the two catalysts also faced an increased conversion rate when conducted with an increase in oxygen concentration, and reached maximized efficiency at 30% concentration. Secondary stage of the research focuses on operational efficiency of the biodiesel fuel, with emphasis on its pollutant emissions and economical standpoint. The initial testing concluded that not only did the fuel has a lower cost in reducing greenhouse gas emission than alternative energy sources, but it can also reduce SOx emissions by 7,200kg, 23 metric tons of PM10, and 262,400 metric tons of CO2 annually when applied with B2 fuel. Pollution reduction assessment indicated that if all diesel powered automobiles utilized the B10 biodiesel fuel, then it¡¦s estimated that it would have an annual THC reduction rate of 2.83x102 metric tons, 1.98x103 tons in COs, 4.56x103 in NOx, and 5.66x101 metric tons in PM gases. Furthermore, if the B20 fuel cells were incorporated, then it¡¦s estimated to have an annual reduction rate of 2.83x102 metric tons in THC, 2.83x103 metric tons of CO, 1.14x103 metric tons of NOx, and 1.16x102 metric tons of PM. Results from the beta stage testing indicated that if B10 fuel were incorporated into all diesel powered automobiles, with a budget of NT$1million would result in an annual reduction rate of 0.57 metric tons of THC, 9.12 metric tons of NOx, 0.11 metric tons of PM and a totaled 9.8 metric tons of reduction. Furthermore, if B20 were implemented, again with NT$1 million budget, we would expect to see annual reductions of 0.06 metric tons of THC, 0.25 metric tons of NOx, 2.51 tons of PM gases, totaling at 2.81 metric tons of reductions.
2

Properties of glass/polypropylene composites manufactured by weaving of pre-preg tapes and other routes

Al-Zubaidy, Majeed Nahee Shail January 2001 (has links)
This thesis reports a study on the melt impregnation and weaving of glass/PP pre-preg tapes into sheet for use as the precursor for pressed thermoplastic composite products, and a comparison of the properties attainable with those achievable by other comparable routes. Melt impregnation has been used successfully to manufacture well-impregnanted tapes of polypropylene and glass fibres, with and without coupling agent. It appears that weaving could be an economically viable process for converting unidirectional tape into a press-formable pre-preg.
3

Supercritical carbon dioxide processing for the extraction and delivery of flax bioactives

Comin, Lauren Unknown Date
No description available.
4

Bearing capacity of cohesionless soil after the dynamic compaction

Chung, Young-Jun January 2000 (has links)
No description available.
5

Selective CO Adsorption Separation from CO2 via Cu-modified Adsorbents

Abbassi, Maria 18 May 2021 (has links)
CO2 capture and conversion appears to be a prominent solution to mitigate greenhouse gas emissions (GHG) and global warming issue. Among different CO2 conversion approaches, CO2 hydrogenation via reverse water gas shift (RWGS) reaction is one of the most promising technology to convert CO2 to CO. Subsequently, CO is transformed to value added chemicals or liquid fuels. To improve the overall CO2 conversion for RWGS reaction, product separation and recycling is being proposed. In this research, adsorption separation technology has been explored to selectively separate CO from CO2 in RWGS using pressure swing adsorption (PSA) process. To investigate the adsorption capacity and selectivity of CO, different porous materials have been identified for CO separation. In this research, activated carbons, ordered mesoporous silica, and metal organic framework materials were studied. Equilibrium isotherms of CO and CO2 were measured in a gravimetric system at a temperature of 25 °C for pressures up to 20 bar. Preliminary adsorption isotherm results had shown an insufficient CO uptake and low selectivity level compared to CO2, thus not justifying their application for CO separation. Herein, to improve the CO adsorption capacity and selectivity, Cu-based adsorbents were developed using copper (II) chloride (CuCl2) as a precursor to synthesize six different adsorbents. The adsorbents were prepared using two different synthesis methods; the modified polyol method for reduction and nanoparticle deposition of Cu (I) ions, and thermal monolayer auto-dispersion method. Furthermore, different copper (II) loadings were investigated to determine the monolayer dispersion capacity of CuCl2 on the support. The modified adsorbents by copper salt exhibited significantly high CO uptake with large CO/CO2 selectivity, reversing the results obtained before adsorbent modification. Thus, Cubased adsorbents are promising materials for CO separation and recovery from a gaseous mixture containing CO2.
6

Modification and Characterization of Nafion Perfluorinated Ionomer Membrane for Polymer Electrolyte Fuel Cells

Ahmad Nazir, Nadzrinahamin 29 July 2011 (has links)
No description available.
7

Development of Spherical Ni-Co/MgAlO Bimetallic Catalyst for CO2 Reforming of CH4

2012 January 1900 (has links)
Carbon dioxide reforming, or drying reforming, of methane can now be used in new applications such as landfill gas utilization where CO and CH need to be converted to a mixture of CO and H, called synthesis gas or syn-gas. A novel Ni-Co/AlMgO bimetallic powder catalyst was developed in previous research for dry reforming of methane (DRM) process which can eliminate carbon deposition. But it is difficult242x to apply this loose-powder catalyst in industrial scale. The procedure of making spherical Ni-Co/AlMgOx bimetallic catalyst supported on BASF CSS-350 alumina balls (BASF Catalysts LLC) using impregnation method with different impregnation steps and calcination steps is explained in this thesis. For every batch of preparation, the concentration of metal solution was calculated based on different impregnation steps. BET (Brunauer-Emmett-Teller) analysis, compressive strength test, XANES (X-ray Absorption Near-Edge Structure) measurement and ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis are conducted to understand the physical and chemical properties of the catalyst. It is found that both impregnation steps and calcination steps have great influence on the performance of the prepared catalyst samples. Among all the catalysts prepared, BF-4-0.25(MgNiCo)-C, which was made by using 4 impregnation-calcination cycles, shows the best activity and stability for 160 h time-on stream (TOS) under the reaction condition of 0.10 g catalyst loading, 750 oC, ambient pressure, GHSV=100,000 ml/gc·h, and CH4/CO2/N2 = 1/1/1. The CH4 conversion started at 66.7% and slowly dropped to 52.8% after 160 hours. I I BF-4-0.25(MgNiCo)-C spherical catalyst shows lower reaction rate compared to the loose powder format but shows compatible or higher activity to other two reported catalysts in similar compositions. Most importantly, it is a shaped catalyst ready for industrial use.
8

Imprégnation forcée de fluides dans des milieux poreux / Forced impregnation of fluids into porous media

Delbos, Aline 21 October 2010 (has links)
Cette thèse porte sur les capacités d'extraction d'une mousse déposée sur un support poreux dans le but d'y déloger un contaminant ayant imprégné la porosité. Nous avons donc considéré l'imprégnation forcée de fluides dans un pore unique, étudiée pour deux cas particuliers : (i) lors de l'impact d'une goutte de liquide à l'aplomb d'un pore unique vertical cette situation visant à modéliser l'imprégnation du poreux par le contaminant, et (ii) lors de l'aspiration d'une mou sse liquide à travers le pore qui illustre la compétition d'aspiration entre la mousse et le poreux. Dans chaque cas, le diamètre du pore est inférieur à celui des gouttes ou des bulles.Pour le premier cas, nous nous sommes intéressés au volume et à la profondeur d'imprégnation pour des surfaces hydrophiles et hydrophobes. Nous établissons les diagrammes d'imprégnation en fonction du diamètre du pore et de la vitesse d'impact et un travail de modélisation nous permet de déterminer les limites entre les différentes régions de ces digrammes.Pour le second cas, nous montrons que lors de l'aspiration, la mousse entre dans le pore uniquement dans un domaine bien déterminé dans le diagramme fraction liquide, rapport de taille pore/bulle et débit d'aspiration. En dehors de ce domaine, l'aspiration peut faire entrer soit le gaz seul, soit le liquide seul. La encore, un travail de modélisation nous permet de prédire les limites des différentes zones du diagramme. Dans une dernière partie, nous revenons à un problème pratique d'imprégnation sur support textile et quantifions les capacités d'extraction d'une mousse dans cette configuration dans le but d'y déloger un contaminant / This thesis is about the ability of foam to extract a pollutant trapped in a fabric. We studied the forced impregnation of fluids into a single pore, in two particular cases : (i) when a liquid droplet impact vertically on the pore (this situation corresponds to the model of the impregnation of the pollutant into the fabric), and (ii) when a foam is sucked through a pore, which illustrate the competition between the suction on the foam and those of the porous media. For each case, the diameter of the pore is smaller than the diameter of droplet or bubble. At first, we studied the volume and how deep penetrates the liquid penetrates, for hydrophobic and hydrophilic surfaces. We established diagrams of impregnation as a function of the pore diameter and impact velocity, and a model determines the limits between the different areas of the diagram. For the second case, we showed that during the suction, the foam go into the pore only for one delimited area of the diagram liquid fraction, ration pore diameter / bubble diameter. Out of this area, suction force solely liquid or solely gas into the pore. Again, a model determines the limits between the different areas of the diagram. Finally an applied part of our work is about the ability of foam to extract a pollutant trapped in a fabric
9

Estudo da impregnação a vácuo de trealose como crioprotetor em morangos

Kunsler, Nicole Luíse Froehlich January 2017 (has links)
Embora o congelamento apresente vantagens em relação a outros métodos de conservação de alimentos, o mesmo causa alterações sensoriais, principalmente em produtos de origem vegetal. O morango, uma fruta muito apreciada e com formas variadas de consumo, tem comportamento sazonal e apresenta como fator limitante para o congelamento sua estrutura frágil e sensível ao processo, o que causa alterações sensoriais. Tais alterações podem ser minimizadas com a incorporação de crioprotetores, como a trealose, um dissacarídeo que vem se destacando pelo seu efeito crioprotetor em produtos congelados e desidratados. O principal objetivo deste trabalho foi verificar o efeito crioprotetor da trealose incorporada através da impregnação a vácuo em soluções de diferentes concentrações (100, 300 e 500 g/L) em morangos submetidos ao congelamento e descongelamento. As condições de impregnação foram de 5 min, aplicando pressão de -650 mmHg e 10 min de tempo de relaxamento. As alterações provocadas pelo processo de impregnação bem como a verificação do efeito crioprotetor da trealose foram identificadas através de análise de cromatografia líquida de alta eficiência (High Performance Liquid Chromatography- HPLC), análise colorimétrica, análise de textura, determinação do teor de sólidos solúveis, determinação do teor de umidade e perda de massa (perda por gotejamento). Os resultados mostraram que a concentração da solução de trealose exerce influência significativa no teor de umidade, teor de sólidos solúveis e teor de trealose. As amostras tratadas com soluções mais concentradas não sofreram desidratação após descongelamento. O teor de trealose, após descongelamento, permaneceu constante em todas as amostras tratadas. Todas as amostras tiveram a mesma perda de massa após descongelamento (perda por gotejamento), porém a composição da massa diferiu entre elas. Amostras tratadas com a solução mais concentrada perderam sólidos enquanto que as amostras tratadas com a menos concentrada, perderam água. Na análise de textura, a introdução da trealose não influenciou a força máxima de pico nas amostras impregnadas. Após descongelamento, todas as amostras, exceto a tradada com solução de 500 g/L, sofreram amolecimento. A parte externa dos morangos não sofreu alterações de cor devido à introdução da trealose nem devido ao congelamento e descongelamento. Na parte interna dos frutos, ocorreram variações no parâmetro L* devido à impregnação e no parâmetro b*, devido ao congelamento e descongelamento. / Although freezing offers advantages to others food conservations process, it causes sensorial changes, mostly in vegetables products. The strawberry, a quite appreciated fruit, shows different ways of use, has seasonal behavior and is limited to freezing due the sensorial changes caused by its fragile structure to freezing process. These sensorial changes can be minimized by the incorporation of cryoprotectors, as trehalose, that is known by its cryoprotector effect during freezing and dehydration. The aim of this work was to verify the trehalose cryoprotector effect in frozen and thawed strawberries introduced by vacuum impregnation with different solutions (100, 300 and 500 g/L). The impregnation conditions were 5 min of applying pressure of -650 mmHg and after atmospheric pressure was restored, the sample was maintained within the solution for 10 min (these conditions were obtained from previous experiments). The alterations caused by the vacuum impregnation and the verification of the cryoprotector effect of trehalose were identified by High Performance Liquid Chromatography (HPLC), color analysis, texture analysis, soluble solids content, moisture content and drip loss. The results have shown that concentration of the trehalose solution had a significant influence on the moisture content, soluble solids and trehalose content of impregnated strawberries. The samples treated with more concentration solutions did not dehydrated after thawing. The trehalose content was the same in all treated samples after thawing. All the samples showed the same drip loss due to thawing although the composition of the mass was different among the samples. Samples treated with the most concentration solution lost trehalose while the sample treated with the least concentration solutions lost water. The introduction of trehalose did not affect the maximum peak force of the impregnated samples. The freezing and the thawing process caused the softening of the samples. This effect was not observed on the sample treated with solution of 500 g/L. The introduction of trehalose did not cause significant differences in all color parameters measured on the outside of the strawberries after impregnation and thawing. In the inside of the samples, there were variation in the L* parameter caused by the vacuum impregnations and in the b* parameter caused by the freezing and thawing process.
10

The Study of Catalytic Oxidation of Isopropyl Alcohol in an Air Stream over Honeycomb Catalyst

Huang, Shi-wei 29 June 2004 (has links)
ABSTRACT Isopropyl Alcohol (denoted as IPA) is a valuable chemical product, which is used in the chemical industry such as synthetic resin, essential oils and surface paint. Moreover, factory of the production of photography and electronics are also the user of IPA.IPA is the typical pollutant emitted from those industrial processing . It is known to be causing severe irritation and burns and is suspected to have long-term effects such as bronchitis. This study was to investigate the effect on conversion, deactivation of long-term test, selectivity of product and kinetics in oxidation of IPA over Cu and Cu/Ce catalysts supported on ceramic honeycomb. The explanation of results can be divided into several major parts as follows: 1. In the of selection catalyst, we find that 20%Cu/Ce catalysts prepared by wet- impregnation has the best conversion and selectivity. 2. The conversion of IPA in catalytic reaction is increased with the increasing both of reaction temperature and influent concentration of oxygen but decreased with the going up of initial concentration of IPA, space velocity and relative humidity. 3. In the catalyst stability of long-term test, Cu/Ce catalysts had a good stability after 7 days reaction in heterogeneous reactor. The tests such as XRD, SEM and EA were also determined to verify the stability from surface of catalyst. 4. Two kinetic models, Power rate law and Mars-Van Krevelen model were used to fit the kinetic data of the decomposition of IPA. Power rate law is suitable to describe the catalytic decomposition of IPA under the operation range in this work.

Page generated in 0.1041 seconds