Plasma and catalytic processes for methane and carbon dioxide activation

CH4 in CO2 sta najvplivnejša toplogredna plina. Njuno koncentracijo v atmosferi bi lahko znižali preko pretvorbe tako na mestu izpusta kot tudi zajetih plinov iz ozračja. Zato je nujno potreben razvoj novih procesov in tehnologij, ki bi omogočale tovrstno pretvorbo z visoko energetsko učinkovitostjo in sintezo uporabnih produktov z dodano vrednostjo. Doktorsko delo je razdeljeno na tri sklope, kjer se v vsakem od njih preučuje določen tovrstni proces: Povratno reakcijo vodnega plina, suhi reforming metana in delno oksidacija metana. V sklopu povratne reakcije vodnega plina je bila narejena sinteza petih bakrovih katalizatorjev na različnih nosilcih, ki so bili preučeni z različnim analitskimi tehnikami, pomerjena pa je bila tudi njihova aktivnost in kinetika reakcije pri različnih obratovalnih temperaturah, tlakih, pretokih in razmerjih reagentov. Razviti so bili tudi trije različni matematični modeli reaktorja, ki so vključevali snovni transport in kinetiko površinske reakcije na katalizatorju. Iz modelov so bili dobljeni novi vpogledi v snovni transport, prilagodile pa so se tudi reakcijske konstante za izboljšanje napovedne moči. V sklopu suhega reforminga metana je bil le-ta preučevan v plazemskem reaktorju z iskro, kjer se je študirala kinetika procesa pri uporabi čiste plazme in souporabi plazme in nikljevih katalizatorjev pri različnih obratovalnih pogojih (temperatura, moč plazme, pretok plina, razmerje reagentov), kjer je imela dodaten poudarek stabilnost obratovanja v prisotnosti nalaganja ogljika. Tudi v tem delu je bil narejen matematični model, ki je upošteval fluidno dinamiko v reaktorju. V zadnjem sklopu se je raziskovala delna oksidacija metana s kisikom v plazemskem reaktorju z dielektrično pregrado, kjer so se formirali tekoči produkti kot so metanol, formaldehid ter mravljinčna in ocetna kislina. Kinetika je bila izmerjena pri različnih pogojih (razmerje reagentov, pretok plina), preučil pa se je tudi širok spekter različnih katalizatorjev v kombinaciji s plazmo, in sicer različnih čistih zeolitov ter katalizatorjev na osnovi kovin kot so Pd, Fe in Mo.CH4 and CO2 are the most impactful greenhouse gases. Their atmospheric concentration could be lowered via conversion of the gases collected at the emission site or captured from the atmosphere. The development of new technologies for such conversion with high energy efficiency and useful products is crucial. The PhD thesis is divided into three parts, each dedicated to the study of one such promising process: reverse water-gas shift reaction, dry reforming of methane and partial oxidation of methane. In the reverse water-gas shift section, synthesis of five different copper-based catalysts with different supports was carried out. The catalysts were characterised with different analytical techniques and had their activity measured at different operating temperatures, pressure, gas flow rates and reagent ratios. Three different reactor mathematical models were developed, taking into account the mass transport as well as the catalytic surface reactions. New insights regarding mass transport were obtained, and numerical regression of the reaction constants was performed in order to increase the model accuracy. Methane dry reforming reaction was studied in a spark plasma reactor. Reaction kinetics were studied both in pure plasma and plasma-catalytic modes of operation, the latter utilising Ni-based structured alumina foam catalysts, under different operating conditions (temperatures, plasma powers, gas flow rates, reagent ratios) and special attention was paid to stability under coke-deposition conditions. A three-dimensional mathematical model was developed for this process using fluid dynamics. Methane partial oxidation was carried out with different reagent ratios and total gas flow rates. In addition, a multitude of different catalytic materials were coupled with plasma, such as pure zeolites and metal-based catalysts (Pd, Fe and Mo)

A review of plasma-assisted catalytic conversion of gaseous carbon dioxide and methane into value-added platform chemicals and fuels

CO(2) and CH(4) contribute to greenhouse gas emissions, while the production of industrial base chemicals from natural gas resources is emerging as well. Such conversion processes, however, are energy-intensive and introducing a renewable and sustainable electric activation seems optimal, at least for intermediate-scale modular operation. The review thus analyses such valorisation by plasma reactor technologies and heterogeneous catalysis application, largely into higher hydrocarbon molecules, that is ethane, ethylene, acetylene, propane, etc., and organic oxygenated compounds, i.e. methanol, formaldehyde, formic acid and dimethyl ether. Focus is given to reaction pathway mechanisms, related to the partial oxidation steps of CH(4) with O(2), H(2)O and CO(2), CO(2) reduction with H(2), CH(4) or other paraffin species, and to a lesser extent, to mixtures' dry reforming to syngas. Dielectric barrier discharge, corona, spark and gliding arc sources are considered, combined with (noble) metal materials. Carbon (C), silica (SiO(2)) and alumina (Al(2)O(3)) as well as various catalytic supports are examined as precious critical raw materials (e.g. platinum, palladium and rhodium) or transition metal (e.g. manganese, iron, cobalt, nickel and copper) substrates. These are applied for turnover, such as that pertinent to reformer, (reverse) water–gas shift (WGS or RWGS) and CH(3)OH synthesis. Time-on-stream catalyst deactivation or reactivation is also overviewed from the viewpoint of individual transient moieties and their adsorption or desorption characteristics, as well as reactivity

Synthesis of a Cu/ZnO Nanocomposite by Electroless Plating for the Catalytic Conversion of CO2 to Methanol

The process of methanol synthesis based on the hydrogenation of CO2 was investigated over binary Cu/ZnO catalyst materials, prepared by applying a novel electroless plating fabrication method. The activity of the produced catalytic samples was determined at temperature range between 200 and 300 °C and the feedstock conversion data were supplemented with a detailed microstructure analysis using high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD) and Cu and Zn K-edge, X-ray absorption near-edge structure (XANES) measurements and extended X-ray absorption fine-structure (EXAFS) measurements. It was confirmed that the disorder in the Cu crystallites created unique geometrical situations, which acted as the additional reactive centres for the adsorption of the reactant molecule species. Copper and zinc structural synergy (spill-over) was also demonstrated as being crucial for the carbon dioxide’s activation. EXAFS and XANES results provide strong evidence for surface alloying between copper and zinc and thus the present results demonstrate new approach applicable for explaining metal–support interactions

Adaptable reactors for resource- And energy-efficient methane valorisation (ADREM) benchmarking modular technologies

Following the global trend towards increased energy demand together with requirements for low greenhouse gas emissions, Adaptable Reactors for Resource- and Energy-Efficient Methane Valorisation (ADREM) focused on the development of modular reactors that can upgrade methane-rich sources to chemicals. Herein we summarise the main findings of the project, excluding in-depth technical analysis. The ADREM reactors include microwave technology for conversion of methane to benzene, toluene and xylenes (BTX) and ethylene; plasma for methane to ethylene; plasma dry methane reforming to syngas; and the gas solid vortex reactor (GSVR) for methane to ethylene. Two of the reactors (microwave to BTX and plasma to ethylene) have been tested at technology readiness level 5 (TRL 5). Compared to flaring, all the concepts have a clear environmental benefit, reducing significantly the direct carbon dioxide emissions. Their energy efficiency is still relatively low compared to conventional processes, and the costly and energy-demanding downstream processing should be replaced by scalable energy efficient alternatives. However, considering the changing market conditions with electrification becoming more relevant and the growing need to decrease greenhouse gas emissions, the ADREM technologies, utilising mostly electricity to achieve methane conversion, are promising candidates in the field of gas monetisation.Complex Fluid Processin