Zeolite catalysts in the reduction of NO_x in lean automotive exhaust gas conditions:behaviour of catalysts in activity, DRIFT and TPD studies

Abstract The aim of the thesis is to expand the knowledge of the catalytic properties of platinum-loaded zeolite catalysts in the reduction of NOx by hydrocarbons. The work is divided into three parts. First the recent literature of zeolite catalysts has been introduced, secondly the adsorption capacity, activity, and acidity of the catalysts have been studied by TPD and IR techniques, and thirdly the derived reaction mechanisms based on the obtained data are presented. Parent and 1 wt-% Pt-loaded ZSM-5, Beta, Y, and Ferrierite zeolite catalysts have been studied in the C3H6-assisted reduction of NO. The Pd/Al2O3-based catalyst was used as a reference material for the reaction mechanistic studies. Several experimental techniques (in situ DRIFT, activity measurements, CO chemisorption, N2 physisorption, TPD, and TEM) have been used for the characterisation of the catalysts properties. The IR technique was used as the main technique for the determination of activities, surface species, and the acidic properties of the zeolite-based catalysts. The activity studies carried out by the gaseous FTIR technique provide information on the desired reaction products as well as the undesired by-products. The detection and identification of the surface species as well as the reaction intermediates formed were done by the DRIFT method. The activity experiments indicate the effectiveness of the Pt-loaded zeolite catalysts. The reduction of NO was found to decrease in the order: Pt/Beta > Pt/Y > Pt/Ferrierite > Pt/ZSM-5 in the conditions with excess O2. Platinum can be concluded to have an effect on O2 and NO dissociation. Oxidation reactions of NO to NO2 and propene to CO2 were observed to be more intense over the platinum-loaded zeolites than over the parent zeolites. In this work the reaction mechanisms for the C3H6-SCR of NO were derived over the Pt-loaded zeolite as well as the Pd/alumina catalysts based on the data obtained by DRIFT and activity experiments. The kinetics for the NO reduction by CO over Pd/Al2O3 was also derived. With the methods employed, the mechanistic steps over the Pt-loaded zeolites and Pd/Al2O3-based catalysts could be derived quite precisely and easily for C3H6-SCR of NO. Reaction routes were determined to go via different formations of intermediates over the two catalysts, i.e. via organonitrogen and isocyanate routes, respectively. The IR techniques were discovered to be effective tools in applied engineering studies

Recent development in Power-to-X:part I — a review on techno-economic analysis

Abstract Power-to-X (P2X) pathways represent alternative storage technologies for utilization of surplus electricity from renewable energy sources (RES) and for greenhouse gas (GHG) emission reduction. These P2X pathways can be used to convert renewable surplus electricity and carbon dioxide from various sources into valuable products such as synthetic fuels and chemicals. Significant progress has been made in these processes towards replacement of conventional fossil fuel-based technologies in the recent years. In this paper the development of these novel technologies is reviewed, having a focus especially on the techno-economic analysis. Key performance indicators such as plant efficiency and production cost are discussed. Finally, knowledge gaps and future research outlook of P2X are highlighted

Preparation of granulated biomass carbon catalysts:structure tailoring, characterization, and use in catalytic wet air oxidation of bisphenol A

Abstract New carbonized biomass–metakaolin (PSD/MK_Fe) granular composite catalyst materials were manufactured for the catalytic wet air oxidation (CWAO) of bisphenol A (BPA). These catalysts were characterized using different analytical and spectroscopic techniques, and results showed that the catalysts’ final properties were influenced by the addition of metakaolin (MK), polyvinyl alcohol, boric acid, and iron. Under the optimal CWAO experimental conditions (p: 20 bar, T: 160 °C, initial pH: 5–6, c[catalyst]: 1.0 g/L), nearly complete BPA conversion (>98%) and total organic carbon (TOC) conversion of 70% were reached. A key factor behind the enhanced catalytic activity was high specific surface area, although catalytic activity was also affected by surface acidity. These results confirmed the high efficiency of the current BPA conversion process involving the use of the easily separable and reusable PSD/MK_Fe catalyst. Therefore, biomass composite catalysts can be regarded as efficient catalysts for the oxidation of BPA during the CWAO process

Process modelling and feasibility study of sorption-enhanced methanol synthesis

Abstract A sorption-enhanced process for hydrogenation of CO₂ to methanol was designed and investigated by mathematical modelling and techno-economic analysis. The modelling methodology combined dynamic modelling of the cyclic reactor operation with pseudo-steady state modelling of the overall process. With continuous adsorption of water in the sorption-enhanced process, highly pure methanol (>99%) was produced without downstream distillation. The dynamic reactor cycle was designed and optimized to maximize the methanol production rate. The cycle and the process were modelled in two reactor configurations: adiabatic and isothermal. Under the default cost assumptions for the raw materials (CO₂ 50 €/t, hydrogen 3000 €/t) the adiabatic configuration was found more competitive in terms of the overall methanol production cost, at 1085 €/t compared to 1255 €/t for the isothermal case. The cost estimate for the adiabatic case was found comparable to a reference process representing conventional CO₂ hydrogenation to methanol (1089 €/t). In addition to the methanol process, the developed modeling method has potential in the design of other sorption-enhanced processes

Vanadia–zirconia and vanadia–hafnia catalysts for utilization of volatile organic compound emissions

Abstract Utilization is a sustainable and interesting alternative for the destructive treatment of volatile organic compounds due to avoided CO₂ emission. This work concentrates on the development of active and sulfur-tolerant catalysts for the utilization of contaminated methanol. Impregnated and sol–gel prepared vanadia–zirconia and vanadia–hafnia catalysts were thoroughly characterized by N₂ sorption, analytical (S)TEM, elemental analysis, XRD and Raman spectroscopy, and their performances were evaluated in formaldehyde production from methanol and methanethiol mixture. The results showed higher activity of the sol–gel prepared catalysts due to formation of mono- and polymeric vanadia species. Unfortunately, the most active vanadia sites were deactivated more easily than the metal-mixed oxide HfV₂O₇ and ZrV₂O₇ phases, as well as crystalline V₂O₅ observed in the impregnated catalysts. Metal-mixed oxide phases were formed in impregnated catalysts through formation of defects in HfO₂ and ZrO₂ structure during calcination at 600 °C, which was evidenced by Raman spectroscopy. The sol–gel prepared vanadia–zirconia and vanadia–hafnia catalysts were able to produce formaldehyde from contaminated methanol with high selectivity at temperature around 400 °C, while impregnated catalysts required 50–100 °C higher temperatures

Characterization of mineral wool waste chemical composition, organic resin content and fiber dimensions:aspects for valorization

Abstract Despite mineral wool waste is only a small fraction of total construction and demolition waste (CDW) by mass, it requires large transportation and landfilling capacities due to its low bulk density, and its utilization remains low compared to other CDW types. It is essential to understand the physical and chemical properties of this waste fraction in order to utilize it, e.g. as fiber reinforcement in composites or as supplementary cementitious material. Here, we provide a chemical and physical characterization of 15 glass wool and 12 stone wool samples of different ages collected from various locations across Europe. In addition, the chemical compositions of 61 glass and stone wool samples obtained from the literature are presented. Glass wool samples show little variation in their chemical composition, which resembles the composition of typical soda-lime silicate glass. Stone wool presents a composition similar to basaltic glass but with variability between samples in terms of calcium, magnesium, and iron content. Potentially toxic elements, such as Cr, Ba, and Ni, are present in mineral wools, but in low concentrations (<0.2%). Both wool types contain organic resin, which may decompose into smaller molecular fragments and ammonia upon heating or contact with alkaline solution. Mineral wool wastes have relatively similar length and width distributions, despite the age and type of the mineral wool. Overall, both mineral wool waste types have homogenous chemical and physical properties as compared to many other mineral wastes which makes their utilization as a secondary raw material promising

Regeneration of sulfur-poisoned Pd-based catalyst for natural gas oxidation

Abstract Sulfur deactivation and regeneration behavior of the Pd/Al₂O₃ catalyst has been investigated via experimental characterization and density functional theory (DFT) simulations. During the sulfur exposure, PdO crystallites grow slightly while bulk Al₂(SO₄)₃ forms on the support. DFT calculations indicate that SOₓ species interact strongly with the catalyst surface making it chemically inactive in agreement with the experimental results. During the regeneration treatment (CH₄ conditions), PdO particles reduce, Al₂(SO₄)₃ is partially removed, and the activity for CH₄ conversion is increased. No full recovery can be observed due to remaining Al₂(SO₄)₃, the formation of encapsulating sulfur species, and the partial reduction of PdO particles. To reoxidize Pd, the catalyst is further regenerated (O₂ conditions). The resulting CH₄ conversion is at the same level than with the regenerated catalyst. Thus, a small amount of Al₂(SO₄)₃ appears to have a stronger effect on the performance than the state of Pd

Modelling and cost estimation for conversion of green methanol to renewable liquid transport fuels via olefin oligomerisation

Abstract The ambitious CO₂ emission reduction targets for the transport sector set in the Paris Climate Agreement require low-carbon energy solutions that can be commissioned rapidly. The production of gasoline, kerosene, and diesel from renewable methanol using methanol-to-olefins (MTO) and Mobil’s Olefins to Gasoline and Distillate (MOGD) syntheses was investigated in this study via process simulation and economic analysis. The current work presents a process simulation model comprising liquid fuel production and heat integration. According to the economic analysis, the total cost of production was found to be 3409 €/tfuels (273 €/MWhLHV), corresponding to a renewable methanol price of 963 €/t (174 €/MWhLHV). The calculated fuel price is considerably higher than the current cost of fossil fuels and biofuel blending components. The price of renewable methanol, which is largely dictated by the cost of electrolytic hydrogen and renewable electricity, was found to be the most significant factor affecting the profitability of the MTO-MOGD plant. To reduce the price of renewable fuels and make them economically viable, it is recommended that the EU’s sustainable transport policies are enacted to allow flexible and practical solutions to reduce transport-related emissions within the member states

Random networks of core-shell-like Cu-Cu₂O/CuO nanowires as surface plasmon resonance-enhanced sensors

Abstract The rapid oxide formation on pristine unprotected copper surfaces limits the direct application of Cu nanomaterials in electronics and sensor assemblies with physical contacts. However, it is not clear whether the growing cuprous (Cu₂O) and cupric oxides (CuO) and the formation of core-shell-like Cu-Cu₂O/CuO nanowires would cause any compromise for non-contact optical measurements, where light absorption and subsequent charge oscillation and separation take place such as those in surface plasmon-assisted and photocatalytic processes, respectively. Therefore, we analyze how the surface potential of hydrothermally synthetized copper nanowires changes as a function of time in ambient conditions using Kelvin probe force microscopy in dark and under light illumination to reveal charge accumulation on the nanowires and on the supporting gold substrate. Further, we perform finite element modeling of the optical absorption to predict plasmonic behavior of the nanostructures. The results suggest that the core-shell-like Cu-Cu₂O/CuO nanowires may be useful both in photocatalytic and in surface plasmon-enhanced processes. Here, by exploiting the latter, we show that regardless of the native surface oxide formation, random networks of the nanowires on gold substrates work as excellent amplification media for surface-enhanced Raman spectroscopy as demonstrated in sensing of Rhodamine 6G dye molecules