Automotive catalytic converters are used extensively in the automotive industry to reduce toxic pollutants from vehicle exhausts. The flow across automotive exhaust catalysts is distributed by a sudden expansion and has a significant effect on their conversion efficiency. The exhaust gas is pulsating and flow distribution is a function of engine operating condition, namely speed (frequency), load (flow rate) and pressure loss across the monolith. The aims of this study are to provide insight into the development of the pulsating flow field within the diffuser under isothermal conditions and to assess the steady-state computational fluid dynamics (CFD) predictions of flow maldistribution at high Reynolds numbers. Flow measurements were made across an automotive catalyst monolith situated downstream of a planar wide-angled diffuser in the presence of pulsating flow. Cycle-resolved Particle Image Velocimetry (PIV) measurements were made in the diffuser and hot wire anemometry (HWA) downstream of the monoliths. The ratio of pulse period to residence time within the diffuser (J factor) characterises the flow distribution. During acceleration the flow remained attached to the diffuser walls for some distance before separating near the diffuser inlet later in the cycle. Two cases with J ~ 3.5 resulted in very similar flow fields with the flow able to reattach downstream of the separation bubbles. With J = 6.8 separation occurred earlier with the flow field resembling, at the time of deceleration, the steady flow field. Increasing J from 3.5 to 6.8 resulted in greater flow maldistribution within the monoliths; steady flow producing the highest maldistribution in all cases for the same Re. The oblique entry pressure loss of monoliths were measured using a one-dimensional steady flow rig over a range of approach Reynolds number (200 < Rea < 4090) and angles of incidence (0o < α < 70o). Losses increased with α and Re at low mass flow rates but were independent of Re at high flow rates being 20% higher than the transverse dynamic pressure. The flow distribution across axisymmetric ceramic 400 cpsi and perforated 600 cpsi monoliths were modelled using CFD and the porous medium approach. This requires knowledge of the axial and transverse monolith resistances; the latter being only applicable to the radially open structure. The axial resistances were measured by presenting uniform flow to the front face of the monolith. The transverse resistances were deduced by best matching CFD predictions to measurements of the radial flow profiles obtained downstream of the monolith when presented with non-uniform flow at its front face. CFD predictions of the flow maldistibution were performed by adding the oblique entry pressure loss to the axial resistance to simulate the monolith losses. The critical angle approach was used to improve the predictions, i.e. the oblique entry loss was limited such that the losses were assumed constant above a fixed critical angle, αc. The result showed that the perforated 600 cpsi monolith requires the entrance effect to be restricted above αc = 81o, while the losses were assumed constant above αc = 85o for the ceramic 400 cpsi monolith. This might be due to the separation bubble at the monolith entrance being restricted by the smaller hydraulic diameter of the perforated monolith thus limiting the oblique entry loss at the lower incidence angle.

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.

Thesis advisor: James P. Morken / This dissertation will present four main projects focused on stereoselective construction of borylated compounds as well as their applications in asymmetric syntheses. The first two projects describe the development of a catalytic conjunctive cross-coupling reaction. By merging three simple starting materials, an organolithium reagent, an organoboronate, and an organic electrophile, a synthetically valuable secondary boronate is furnished by the conjunctive cross-coupling in an efficient and enantioselective fashion. Next, this strategy is expanded to synthesize severely hindered tertiary boronates, a synthetic challenging but powerful building block to access a variety of quaternary stereocenters. The third project presents a platinum-catalyzed enantioselective diboration of alkenyl boronates to furnish a broad range of 1,1,2-tris(boronates) products. A deborylative alkylation of the 1,1,2-tris(boronates) leads to a variety of internal vicinal bis(boronates) with high diastereoselectivity. In the final chapter, a general and practical synthesis of alkenyl boronates via the boron-Wittig reaction is disclosed. Utilizing readily accessible geminal bis(boronates) and aldehydes, a broad range of disubstituted and trisubstituted alkenyl boronates are afforded with good yield and stereoselectivity. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

In this work, slurries of powder catalysts are washcoated on 22 mm diameter and 13 mm height cordierite monoliths. CeO2-ZrO2 (CZO) and CeO2-ZrO2- Al2O3 (CZAO) mixed oxides are synthesized by co-precipitation and sol-gel methods respectively, to be used as support materials of Pd and Rh metals. Metal loaded CZO is mixed with gamma phase alumina. Powder catalysts and their slurries are characterized by XRD, BET, ICP-MS and the monolithic catalysts are imaged by SEM. Catalytic activities of monolithic catalysts are tested in dynamic test system which is computerized and basically composed of gas flow control and conditioning units, split furnace, quartz reactor, mass spectrometer and CO analyzer. Gas mixture containing CO, C3H6, C3H8, NO, H2, O2, CO2, SO2, H2O and N2 is used to simulate the exhaust gas of gasoline vehicles. O2 is oscillated at 1 Hz frequency around the stoichiometric condition. Monolithic catalyst in the reactor is heated and cooled between 150 &ordm / C and 600 &ordm / C. Gas composition data from massspectrometer and CO analyzer and temperature data from thermocouple at the monolith entrance, are converted to conversion versus temperature graphs. Results of 26 activity tests are compared. Catalyst containing coimpregnated CZO support material with metals, showed the lowest loss of catalytic performance after exposure to SO2 during activity tests. Catalyst containing separately impregnated CZO support material, showed the highest resistance against thermal aging at 900 &ordm / C and 1000 &ordm / C, and even improved catalytic activity after aging. These catalysts showed higher resistances against the applied procedures than the commercial catalyst.

No description available.

In response to the increasingly widespread use of catalytic converters for meeting automotive exhaust emission regulations considerable attention is currently being directed towards improving their performance. Experimental analysis is costly and time consuming. A desirable alternative is computational modelling. This thesis describes the development of a fully integrated computational model for simulating monolith type automotive catalytic converters. Two commercial CFD codes, PHOENICS and STAR-CD, were utilised to implement established techniques for modelling the flow field in catalyst assemblies. To appraise the accuracy of the flow field predictions an isothermal steady flow rig was designed and developed. A selection of axisymmetric inlet diffusers and 180o expansions were tested, with the velocity profile across the monolith, the wall static pressure distribution along the inlet section and the total pressure drop across the assembly being measured. These datum sets were compared with predictions using a variety of turbulence models and solution algorithms. The closest agreement was achieved with a two-layer near wall approach, coupled to the fully turbulent version of the RNG k-ε model, and a nominally second order differencing scheme. Even with these approaches the predicted velocity profiles were too flat, the maximum velocity being as much as 17.5% too low. Agreement on pressure drops was better, the error being consistently less than 10%. These results illustrate that present modelling techniques are insufficiently reliable for accurate predictions. It is suggested that the major reason for the relatively poor performance of these techniques is the neglecting of channel entrance effects in the monolith pressure drop term. Despite these weaknesses it was possible to show that the model reproduces the correct trends, and magnitude of change, in pressure drop and velocity distributions as the catalyst geometry changes. The PHONETICS flow field model was extended to include the heat transfer, mass transfer and chemical reactions associated with catalysts. The methodology is based on an equivalent continuum approach. The result is a reacting model capable of simulating the three-dimensional distribution of solid and gas temperatures, species concentrations and flow field variables throughout the monolith mat and the effects that moisture has on the transient warm-up of the monolith. To assess the reacting model’s accuracy use was made of published light-off data from a catalyst connected to a test bed engine. Comparison with predicted results showed that the model was capable of reproducing the correct type, and time scales, of temperature and conversion efficiency behaviour during the warm-up cycle. From these predictions it was possible to show that the flow distribution across the monolith can significantly change during light-off. Following the identification, and subsequent modelling, of the condensation and evaporation of water during the warm-up process it was possible to show that, under the catalyst conditions tested, these moisture effects do not affect light-off times. Conditions under which moisture might affect light-off have been suggested. Although the general level of model accuracy may be acceptable for studying many catalyst phenomena, known deficiencies in the reaction kinetics used, errors in the flow field predictions, uncertainty over many of the physical constants and necessary model simplifications mean that accurate quantitative predictions are still lacking. Improving the level of accuracy will require a systematic experimental approach followed by model refinements.

There is an overview of secondary methods for NOX removal from stationary sources in the first part of master’s thesis. There are well known methods as SCR o SNCR, but also new and experimental ones. An accent is putting on catalytic filtration, especially on cloth filter, which will be used for experiments. An important part of master’s thesis is a project of new experimental unit for experiments with cloth and ceramic catalytic filters as well as with a bit of cloth filtration material. Unit has compact proportions, high-class measurement and control and wide application spectra. Other advantages of this equipment are fast and easy cleaning and installation. This unit, called INTEQ II, can be used in plants or in laboratories. There is prediction model created together with new technology. It enables calculation of efficiency at catalytic filters with variable conditions without many experiments. This model is elaborate and will be finished with dates from measuring. There in only summary of planned experiments in this thesis, because measurements at new unit have not done yet. Experiences with operations at unit INTEQ I were used for proposal of new equipment and for experiments planning.

Research in the field of NOX abatement has grown significantly in the past two decades. The general trend has been to develop new catalysts with complex materials in order to meet the stringent environmental regulations. The master’s thesis deals with the cleaning flue gases through a filter element which is from porous ceramics. There is catalyst implemented for NOx reduction throug the method of selective catalytic reduction in the filter element. There is also description of experimental unit for flue gas cleaning. Part of the thesis is creation of prediction model which allows to predict efficiency reduction in the filtration device operating conditions with some accuracy.

No description available.

Due to the widespread application of pesticides and herbicides in agricultural industries, these substances have been highlighted as emerging contamination of natural ground and surface water resources. Conventional water treatment processes are only effective in removing emerging contaminants in water. The mechanism of degradation of organic impurities present in water using ozone is known to either directly involve the ozone molecule or to occur by the indirect effect of free hydroxyl radicals (•OH). The latter are produced in the radical chain reaction of ozone decomposition. A series of experiments were carried out to investigate the effects of particle sizes of nano-ZnO catalysts on removal of atrazine (ATZ). Nano-ZnO catalysts increase the rate of ozone decomposition and atrazine removal by production of hydroxyl radicals as oxidative intermediates. However, different particle sizes have a minimal effect on the rate of ozone decomposition and atrazine removal. It is believed that molecular ozone is adsorbed on the surface of nano-ZnO followed by the oxidation of the ozone molecule. This leads to the production of OH radicals. Therefore, it is reasonable to assume that reaction is carried out in the bulk of the solution and the rate is independent of catalyst’s surface area. This is probably the reason for similar reaction rates of different particle sizes of nano-Zno catalysts. Additionally three different metal oxides (ZnO, Mn2O3 and Fe2O3) loaded on ƴ-alumina and ƴ-alumina (metal oxide-free) were used in catalytic ozonation of aquatic atrazine samples. The findings substantiate the strong influence of molecular ozone on degradation of ATZ and the partial involvement of hydroxyl radicals in the mechanism. Based on adsorption studies, atrazine has a low affinity towards adsorption on the surface of the catalysts. It is logical to assume that ozone reacts with the hydroxyl groups of the catalyst to form a highly reactive metal-ozone complex. This layer could react with a molecule of atrazine through an electron-transfer mechanism. The residual concentration of ATZ and total organic carbon (TOC) were determined by High Performance Liquid Chromatography (HPLC) and Total Organic Carbon (TOC) analyses.