The ability to effectively remove sulphur from sulphur-poisoned NOx storage/reduction (NSR) catalysts, while minimizing associated fuel penalties and thermal degradation, is important for commercial application of NSR catalysts. As long as sulphur remains in the fuel or lubrication oil formulations, deactivation of NSR catalysts will persist. In an attempt to more fully understand the mechanism of sulphur removal and the associated operating conditions necessary to efficiently decompose sulphates, various gas compositions, temperatures and desulphation methodologies were applied to a commercially supplied catalyst. Experiments were conducted using a pilot scale plug flow catalytic reactor. FTIR spectroscopy and mass spectrometry were used to measure key sulphur species concentrations. Three groups of experiments were conducted. In the first, the effect of gas composition on the amount of sulphur removed from the catalyst was evaluated. In the latter two, high flow cycling desulphation and low flow cycling desulphation were compared. The most effective desulphation gas composition was achieved through the combination of high concentrations of H2, CO and C3H6 and also the inclusion of CO2 and H2O, which released up to 91% of the stored sulphur. The commercial catalyst tested is designed for a dual-leg process. Dual-leg systems are advantageous over single-leg systems in that engine modifications are unnecessary for catalyst regeneration, thereby minimizing losses in vehicle performance. It was found that under conditions appropriate for that application, catalyst desulphation is dominated by the amount of residual surface oxygen. Through the use of short lean phase cycling, to prevent oxygen saturation, the dual-leg application proved effective for sulphate removal, inducing 69% sulphur release compared to 51% when the surface was saturated with oxygen. Multiple stabilities of sulphur exist on the catalyst, which led to residual catalyst sulphates after many desulphations.

In emissions catalyst applications, an axial distribution of reaction, surface chemistry, and temperature all exist on or along the surface of the catalyst. Understanding these distributions is very important in developing physically relevant models of such systems. One focus of this work was developing a technique to obtain accurate temperature measurements from a catalyst during exothermic or endothermic reaction steps. IR thermography was tested as a method to evaluate spatial temperature distributions as a function of time on a diesel NOX adsorber catalyst. The technique proved accurate, relatively simple to interpret and operate, and efficient to the extent it can be used for data generation. As a continuation of the technique development, the temperature changes and gradients formed during simulated operation of a Pt/Ba/Al2O3 NOX adsorber catalyst (NAC) for diesel exhaust applications were monitored using IR thermography and standard thermocouples. NACs operate in a cyclic manner; during the lean phase, when the engine is in normal operation, the catalyst traps entering NOX; once the catalyst nears saturation, the catalyst is exposed to a rich exhaust phase, in reductant relative to oxygen, where the trapped NOX is reduced to N2; and finally the exhaust returns to the normally lean conditions thereby completing the cycle. During the rich phase, previous work has suggested that significant temperature changes might be occurring along the length of the catalyst. In this study, temporally and spatially resolved temperature distributions were obtained throughout the cycle in order to evaluate the significance of these temperature changes and their effects on the reaction chemistry. The effects of (1) reactor in the possible reaction pathways, (2) CO and O2 levels in the regeneration phase, (3) NO and NO2 as the source of NOX in the lean cycle and (4) nominal operating temperature on these temperature distributions were evaluated. The temperature gradient and distribution measurements are being used to characterize the reactions and as input into models.

With steadily increasing emissions regulations being imposed by government agencies, automobile manufacturers have been developing technologies to mitigate NOX emissions. Furthermore, there has been increasing focus on CO2 emissions. An effective approach for CO2 reduction is using lean burn engines, such as the diesel engine. An inherent problem with lean-burn engine operation is that NOX needs to be reduced to N2, but there is an excess of O2 present. NOX storage and reduction (NSR) is a promising technology to address this problem. This technology operates in two phases; where in the lean phase, normal engine operation, NOX species are stored as nitrates, and in a reductant rich phase, relative to O2, the NOx storage components are cleaned and the NOX species reduced to N2. In this study, the effects of reductant type, specifically CO and/or H2, and their amounts as a function of temperature on the trapping and reduction of NOX over a commercial NSR catalyst have been evaluated. Overall, the performance of the catalyst improved with each incremental increase in H2 concentration. CO was found ineffective at 200°C due to precious metal site poisoning. The addition of the H2 to CO-containing mixtures resulted in improved performance at 200°C, but the presence of the CO still resulted in decreased performance in comparison to activity when just H2 was used. At 300-500°C, H2, CO, and mixtures of the two were comparable for trapping and reduction of NOX, although the mixtures led to slightly improved performance. Although NSR technology is very efficient in reducing NOX emissions, a significant challenge that questions their long-term durability is poisoning by sulfur compounds inherently present in the exhaust. Therefore, during operation, NSR catalysts require an intermittent high-temperature exposure to a reducing environment to purge the sulfur compounds from the catalyst. This desulfation protocol ultimately results in thermal degradation of the catalyst. As a second phase of this study, the effect of thermal degradation on the performance of NSR technology was evaluated. The catalyst performance between a 200 to 500°C temperature range, using H2, CO, and a mixture of both H2 and CO as reductants was tested before and after different high-temperature aging steps. Tests included water-gas shift (WGS) reaction extent, NO oxidation, NOX storage capacity, oxygen storage capacity (OSC), and NOX reduction efficiency during cycling. The WGS reaction extent was affected by thermal degradation, but only at low temperature. NO oxidation did not show a consistent trend as a function of thermal degradation. The total NOX storage capacity was tested at 200, 350 and 500°C. Little change was observed at 500°C with thermal degradation and a steady decrease was observed at 350°C. At 200°C, there was also a steady decrease of NOX storage capacity, except after aging at 700°C, where the capacity increased. There was also a steady decrease in oxygen storage capacity at test temperatures between 200 and 500°C after each increase in thermal degradation temperature, except again when the sample was degraded at 700°C, where an increase was observed. In the cycling experiments, a gradual drop in NOX conversion was observed after each thermal degradation temperature, but when the catalyst was aged at 700°C, an increase in NOX conversion was observed. These data suggest that there was redispersion of a trapping material component during the 700°C thermal degradation treatment while the oxygen storage capacity data indicate redispersion of oxygen storage components. It therefore seems likely that it is these oxygen storage components that are becoming ‘‘activated’’ as trapping materials at low temperature.

The ability to effectively remove sulphur from sulphur-poisoned NOx storage/reduction (NSR) catalysts, while minimizing associated fuel penalties and thermal degradation, is important for commercial application of NSR catalysts. As long as sulphur remains in the fuel or lubrication oil formulations, deactivation of NSR catalysts will persist. In an attempt to more fully understand the mechanism of sulphur removal and the associated operating conditions necessary to efficiently decompose sulphates, various gas compositions, temperatures and desulphation methodologies were applied to a commercially supplied catalyst. Experiments were conducted using a pilot scale plug flow catalytic reactor. FTIR spectroscopy and mass spectrometry were used to measure key sulphur species concentrations. Three groups of experiments were conducted. In the first, the effect of gas composition on the amount of sulphur removed from the catalyst was evaluated. In the latter two, high flow cycling desulphation and low flow cycling desulphation were compared. The most effective desulphation gas composition was achieved through the combination of high concentrations of H2, CO and C3H6 and also the inclusion of CO2 and H2O, which released up to 91% of the stored sulphur. The commercial catalyst tested is designed for a dual-leg process. Dual-leg systems are advantageous over single-leg systems in that engine modifications are unnecessary for catalyst regeneration, thereby minimizing losses in vehicle performance. It was found that under conditions appropriate for that application, catalyst desulphation is dominated by the amount of residual surface oxygen. Through the use of short lean phase cycling, to prevent oxygen saturation, the dual-leg application proved effective for sulphate removal, inducing 69% sulphur release compared to 51% when the surface was saturated with oxygen. Multiple stabilities of sulphur exist on the catalyst, which led to residual catalyst sulphates after many desulphations.

In emissions catalyst applications, an axial distribution of reaction, surface chemistry, and temperature all exist on or along the surface of the catalyst. Understanding these distributions is very important in developing physically relevant models of such systems. One focus of this work was developing a technique to obtain accurate temperature measurements from a catalyst during exothermic or endothermic reaction steps. IR thermography was tested as a method to evaluate spatial temperature distributions as a function of time on a diesel NOX adsorber catalyst. The technique proved accurate, relatively simple to interpret and operate, and efficient to the extent it can be used for data generation. As a continuation of the technique development, the temperature changes and gradients formed during simulated operation of a Pt/Ba/Al2O3 NOX adsorber catalyst (NAC) for diesel exhaust applications were monitored using IR thermography and standard thermocouples. NACs operate in a cyclic manner; during the lean phase, when the engine is in normal operation, the catalyst traps entering NOX; once the catalyst nears saturation, the catalyst is exposed to a rich exhaust phase, in reductant relative to oxygen, where the trapped NOX is reduced to N2; and finally the exhaust returns to the normally lean conditions thereby completing the cycle. During the rich phase, previous work has suggested that significant temperature changes might be occurring along the length of the catalyst. In this study, temporally and spatially resolved temperature distributions were obtained throughout the cycle in order to evaluate the significance of these temperature changes and their effects on the reaction chemistry. The effects of (1) reactor in the possible reaction pathways, (2) CO and O2 levels in the regeneration phase, (3) NO and NO2 as the source of NOX in the lean cycle and (4) nominal operating temperature on these temperature distributions were evaluated. The temperature gradient and distribution measurements are being used to characterize the reactions and as input into models.

With steadily increasing emissions regulations being imposed by government agencies, automobile manufacturers have been developing technologies to mitigate NOX emissions. Furthermore, there has been increasing focus on CO2 emissions. An effective approach for CO2 reduction is using lean burn engines, such as the diesel engine. An inherent problem with lean-burn engine operation is that NOX needs to be reduced to N2, but there is an excess of O2 present. NOX storage and reduction (NSR) is a promising technology to address this problem. This technology operates in two phases; where in the lean phase, normal engine operation, NOX species are stored as nitrates, and in a reductant rich phase, relative to O2, the NOx storage components are cleaned and the NOX species reduced to N2. In this study, the effects of reductant type, specifically CO and/or H2, and their amounts as a function of temperature on the trapping and reduction of NOX over a commercial NSR catalyst have been evaluated. Overall, the performance of the catalyst improved with each incremental increase in H2 concentration. CO was found ineffective at 200°C due to precious metal site poisoning. The addition of the H2 to CO-containing mixtures resulted in improved performance at 200°C, but the presence of the CO still resulted in decreased performance in comparison to activity when just H2 was used. At 300-500°C, H2, CO, and mixtures of the two were comparable for trapping and reduction of NOX, although the mixtures led to slightly improved performance. Although NSR technology is very efficient in reducing NOX emissions, a significant challenge that questions their long-term durability is poisoning by sulfur compounds inherently present in the exhaust. Therefore, during operation, NSR catalysts require an intermittent high-temperature exposure to a reducing environment to purge the sulfur compounds from the catalyst. This desulfation protocol ultimately results in thermal degradation of the catalyst. As a second phase of this study, the effect of thermal degradation on the performance of NSR technology was evaluated. The catalyst performance between a 200 to 500°C temperature range, using H2, CO, and a mixture of both H2 and CO as reductants was tested before and after different high-temperature aging steps. Tests included water-gas shift (WGS) reaction extent, NO oxidation, NOX storage capacity, oxygen storage capacity (OSC), and NOX reduction efficiency during cycling. The WGS reaction extent was affected by thermal degradation, but only at low temperature. NO oxidation did not show a consistent trend as a function of thermal degradation. The total NOX storage capacity was tested at 200, 350 and 500°C. Little change was observed at 500°C with thermal degradation and a steady decrease was observed at 350°C. At 200°C, there was also a steady decrease of NOX storage capacity, except after aging at 700°C, where the capacity increased. There was also a steady decrease in oxygen storage capacity at test temperatures between 200 and 500°C after each increase in thermal degradation temperature, except again when the sample was degraded at 700°C, where an increase was observed. In the cycling experiments, a gradual drop in NOX conversion was observed after each thermal degradation temperature, but when the catalyst was aged at 700°C, an increase in NOX conversion was observed. These data suggest that there was redispersion of a trapping material component during the 700°C thermal degradation treatment while the oxygen storage capacity data indicate redispersion of oxygen storage components. It therefore seems likely that it is these oxygen storage components that are becoming ‘‘activated’’ as trapping materials at low temperature.

A modified furnace, which burns diesel oil is adopted to study the combustion characteristics and the pollution of the exhausting products under certain designing and operating conditions. The different equivalence ratios and swirl numbers can be obtained by adjusting the flow rate of both axial air and tangential air. The controlling ranges of the various experimental parameters include the equivalence ratios from 0.8 to 1.1, the jet oil pressures from 7 kg/cm² to 9 kg/cm², the open angles of the plate 0¢X and 45¢X, the swirl numbers from 0 to 1.0, the flow rates of the recirculated flue gas from 0% to 12%. The effects of the controlling variables on the combustion characteristics and the formations of pollutants within combustion chamber are studied in this reseach. A photographic technology is used to study the flame structures for helping us to understand the behaviors of the flame under various operating conditions. Under the equivalence ratios from 0.8 to1.1, the concentrations of the average NO and CO decrease, at the lower equivalence ratio. However, the concentrations of the average NO and temperature increases monotonously when jet oil pressure increases. The plate open angle 45¢X is useful for the mixing of both fuel and air, so that the open angle of the plate have important effects on both the temperature of combusion gas and the formation of pollutant NO. When the plate open angle 45¢X and the swirl number is 0.6, the flow rate of NO in the exhaust duct is the lowest. At equivalence ratio 0.8, the average NO concentration in exhaust duct decrease, when the flow rate of the recirculated flue gas increase. Our experiments display that the optimized operating condition is at the plate open angle 45¢X, the swirl number 1.0 and the recirculation rate of the flue gas 12%. NO can be reduced to 32% in this condition, and heat efficiency is reduced only about 3.7%, so we can achieve the request of reducing efficiency to much, the formation of pollutant without influencing the combustion. Under the condition of swirl number 0 and the open angle of the plate at 0¢X and 45¢X the color of the flame in the primary combustion region are white-yellow. In the other hand, at the swirl number 1.0, the color of the flame out of the primary combustion region at the swirl number 1.0 exhibits the red color due to the formation of CO2 and water vapor. The red color region at the swirl number 1.0 is much larger than that at the swirl number 0.

Emissions of oxides of nitrogen (NOx) from combustion devices is a topic of tremendous current importance. The bulk of the review of NOx emissions has been in the field of turbulent jet flames. However laminar jet flames have provided much insight into the relative importance of NOx reaction pathways in non premixed combustion for various flame conditions. The existing models include detailed chemistry kinetics for various species involved in the flame. These detailed models involve very complex integration of hundreds of chemical reactions of various species and their intermediates. Hence such models are highly time consuming and also normally involve heavy computational costs. This work proposes a numerical model to compute the total production of NOx in a non-premixed isolated circular laminar jet flame. The jet consists of the fuel rich inner region and the O2 rich outer region. The model estimates both thermal NOx and prompt NOx assuming single step kinetics for NOx formation and a thin flame model. Further the amount of air entrainment by jet depends upon the Sc number of fuel. The higher the Sc number, the higher is the air entrained which lowers the flame temperature and hence NOx formation. With increasing Sc number, flame volume increases which leads to an increase in the NOx formation. The effect of the Sc number variation on the net production of NOx and flame structure is also investigated. The effect of equilibrium chemistry for CO2 <-> CO + 1/2 O2 and H2O <-> H2 +1/2 O2 on total NOx emission is studied. Also the effect of both CO2 and H2O equilibrium is considered simultaneously and the net x NO formation for propane is 45 ppm. The split between pre-flame and post-flame regions is also investigated. For Propane, 96% of NO emissions occur in the pre-flame region and about 4% in the post-flame region. The model predictions are compared with experimental values of NOx missions reported elsewhere.

Spinocerebellar ataxia type 7 (SCA7) is an autosomal dominant neurodegenerative disorder caused by a CAG trinucleotide expansion in the SCA7 gene resulting in progressive ataxia and retinal dystrophy. SCA7 belongs to a group of neurodegenerative disorders called polyglutamine (polyQ) diseases, that share the common feature of glutamine tract expansions within otherwise unrelated proteins. Common suggested mechanisms by which polyQ expanded proteins induce toxicity include aggregation and induction of oxidative stress.  In this work we examined the connection between oxidative stress, aggregation and toxicity in SCA7 disease. We show that expression of the SCA7 disease protein, ataxin-7 (ATXN7), results in elevated levels of ROS and oxidative stress which in turn lead to toxicity. Our results also revealed that the oxidative stress further contributes to mutant ATXN7 aggregation. Moreover, we show, for the first time, that the major source of the elevated ROS in mutant ATXN7 cells is the increased activation of NOX1 enzymes. Interestingly, our results further revealed that the increased level of NOX1 activity together with altered p53 function leads to a metabolic shift in mutant ATXN7 expressing cells. Treatments with antioxidants, a NOX1 specific inhibitor or NOX1 knock-down, all decreased the ROS level, restored the metabolic shift and ameliorated the mutant ATXN7 induced toxicity. Taken together, we conclude that mutant ATXN7 activate NOX1 enzymes which results in oxidative stress, increased mutant ATXN7 aggregation, metabolic dysfunction and toxicity. NOX1 specific inhibition could thus be a potential therapeutic strategy for SCA7. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

An integrated NOx adsorption-reduction process has been proposed in this study for the treatment of flue gases under lean-burn conditions by decoupling the adsorption and reduction into two different zones. The hypothesis has then been validated in a novel internal circulating fluidized bed. The adsorption and reaction performance of Fe/ZSM-5 for the selective catalytic reduction (SCR) of NOx with propylene was investigated in a fixed bed reactor. The fine Fe/ZSM-5(Albemarle) catalyst showed reasonable NOx adsorption capacity, and the adsorption performance of the catalyst was closely related to the particle size and other catalyst properties. Fe/ZSM-5 catalyst was sensitive to the reaction temperature and space velocity, and exhibited acceptable activity when O₂ concentration was controlled at a low level. Water in the flue gas was found to slightly enhance the reactivity of Fe/ZSM-5(Albemarle), while the presence of CO₂ showed little effect. SO₂ severely inhibited the reactivity of Fe/ZSM-5(Albemarle), and the deactivated catalyst could be only partially regenerated. Configurations of the reactor influenced the hydrodynamic performance significantly in a cold model internal circulating fluidized bed (ICFB) reactor. For all configurations investigated, the high gas bypass ratio from the annulus to draft tube (RAD) and low draft tube to annulus gas bypass ratio (RDA) were observed, with the highest RDA associated with the conical distributor which showed the flexible and stable operation over a wide range of gas velocities. Solids circulation rates increased with the increase of gas velocities both in the annulus and the draft tube. Gas bypass was also studied in a hot model ICFB reactor. The results showed that the orientation of perforated holes on the conical distributor could be adjusted to reduce RAD and/or enhance RDA. Coarse Fe/ZSM-5(PUC) and fine Fe/ZSM-5(Albemarle) catalysts were used in an ICFB and a conventional bubbling fluidized bed to test the NOx reduction performance. Coarse Fe/ZSM-5(PUC) catalyst showed poor catalytic activity, while fine Fe/ZSM-5(Albemarle) catalyst exhibited promising NOx reduction performance and strong inhibiting ability to the negative impact of excessive O₂ in the ICFB reactor, proving that the adsorption-reduction two-zone reactor is effective for the NOx removal from oxygen-rich combustion flue gases.