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"METHANE"
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Seasonal dynamics and regional distribution patterns of CO.sub.2 and CH.sub.4 in the north-eastern Baltic Sea
Significant research has been carried out in the last decade to describe the CO.sub.2 system dynamics in the Baltic Sea. However, there is a lack of knowledge in this field in the NE Baltic Sea, which is the main focus of the present study. We analysed the physical forcing and hydrographic background in the study year (2018) and tried to elucidate the observed patterns of surface water CO.sub.2 partial pressure (pCO.sub.2) and methane concentrations (cCH.sub.4). Surface water pCO.sub.2 and cCH.sub.4 were continuously measured during six monitoring cruises onboard R/V Salme, covering the Northern Baltic Proper (NBP), the Gulf of Finland (GoF), and the Gulf of Riga (GoR) and all seasons in 2018. The general seasonal pCO.sub.2 pattern showed oversaturation in autumn-winter (average relative CO.sub.2 saturation 1.2) and undersaturation in spring-summer (average relative CO.sub.2 saturation 0.5), but it locally reached the saturation level during the cruises in April, May, and August in the GoR and in August in the GoF. The cCH.sub.4 was oversaturated during the entire study period, and the seasonal course was not well exposed on the background of high variability. Surface water pCO.sub.2 and cCH.sub.4 distributions showed larger spatial variability in the GoR and GoF than in the NBP for all six cruises. We linked the observed local maxima to river bulges, coastal upwelling events, fronts, and occasions when vertical mixing reached the seabed in shallow areas. Seasonal averaging over the CO.sub.2 flux suggests a weak sink for atmospheric CO.sub.2 for all basins, but high variability and the long periods between cruises (temporal gaps in observation) preclude a clear statement.
Journal Article
Dry Reforming of Methane over Dual Metal Oxide Al.sub.2O.sub.3 + MO.sub.x
The complex catalyst synthesis procedure is always a hurdle in the industrialization of catalysts. Industry eagerly needs catalysts for the dry reforming of methane, which can be prepared through straightforward, cheap processes by semi-skilled workers. Herein, dual metal oxide support 10 wt% MO.sub.x (M = Ti, Si, Zr, Y) & 90 wt% Al.sub.2O.sub.3 is prepared by just mixing mechanically and thereafter, catalytic active 5 wt% Ni is dispersed over the support by impregnation method. Metal oxide pairs in ZrO.sub.2 + Al.sub.2O.sub.3, TiO.sub.2-Al.sub.2O.sub.3, SiO.sub.2 + Al.sub.2O.sub.3, and Y.sub.2O.sub.3 + Al.sub.2O.sub.3 supports are non-interacting, partially-interacting, significantly interacting (through Si-O-Al) and highly interacting (with maximum covalence character) respectively. Ni dispersed over SiO.sub.2 + Al.sub.2O.sub.3 or Y.sub.2O.sub.3 + Al.sub.2O.sub.3 supports are strongly interacted, whereas Ni/Y.sub.2O.sub.3 + Al.sub.2O.sub.3 catalyst has oxide enrichment over the surface for potential oxidation of carbon deposit. The interacting nature of metal oxide pair in support, stability of active sites and extent of oxide enrichment over the surface confirms the following order of coke deposition, Ni/Y.sub.2O.sub.3 + Al.sub.2O.sub.3 (8%) < Ni/SiO.sub.2 + Al.sub.2O.sub.3 (17%) < Ni/TiO.sub.2-Al.sub.2O.sub.3 (38.2%) Ni/SiO.sub.2 + Al.sub.2O.sub.3 (55%) > Ni/TiO.sub.2-Al.sub.2O.sub.3 (50%) > Ni/ZrO.sub.2 + Al.sub.2O.sub.3 (47%).
Journal Article
Dry Reforming of Methane over Dual Metal Oxide Al.sub.2O.sub.3 + MO.sub.x Supported Ni Catalyst: A Simple and Practical Approach
The complex catalyst synthesis procedure is always a hurdle in the industrialization of catalysts. Industry eagerly needs catalysts for the dry reforming of methane, which can be prepared through straightforward, cheap processes by semi-skilled workers. Herein, dual metal oxide support 10 wt% MO.sub.x (M = Ti, Si, Zr, Y) & 90 wt% Al.sub.2O.sub.3 is prepared by just mixing mechanically and thereafter, catalytic active 5 wt% Ni is dispersed over the support by impregnation method. Metal oxide pairs in ZrO.sub.2 + Al.sub.2O.sub.3, TiO.sub.2-Al.sub.2O.sub.3, SiO.sub.2 + Al.sub.2O.sub.3, and Y.sub.2O.sub.3 + Al.sub.2O.sub.3 supports are non-interacting, partially-interacting, significantly interacting (through Si-O-Al) and highly interacting (with maximum covalence character) respectively. Ni dispersed over SiO.sub.2 + Al.sub.2O.sub.3 or Y.sub.2O.sub.3 + Al.sub.2O.sub.3 supports are strongly interacted, whereas Ni/Y.sub.2O.sub.3 + Al.sub.2O.sub.3 catalyst has oxide enrichment over the surface for potential oxidation of carbon deposit. The interacting nature of metal oxide pair in support, stability of active sites and extent of oxide enrichment over the surface confirms the following order of coke deposition, Ni/Y.sub.2O.sub.3 + Al.sub.2O.sub.3 (8%) < Ni/SiO.sub.2 + Al.sub.2O.sub.3 (17%) < Ni/TiO.sub.2-Al.sub.2O.sub.3 (38.2%) Ni/SiO.sub.2 + Al.sub.2O.sub.3 (55%) > Ni/TiO.sub.2-Al.sub.2O.sub.3 (50%) > Ni/ZrO.sub.2 + Al.sub.2O.sub.3 (47%). Graphical
Journal Article
Dry Reforming of Methane over Pyrochlore-Type Lasub.2Cesub.2Osub.7-Supported Ni Catalyst: Effect of Particle Size of Support
The properties of supports (such as oxygen vacancies, oxygen species properties, etc.) significantly impact the anti-carbon ability due to their promotional effect on the activation of CO[sub.2] in dry reforming of methane (DRM). Herein, pyrochlore-type La[sub.2]Ce[sub.2]O[sub.7] compounds prepared using co-precipitation (CP), glycine nitrate combustion (GNC) and sol–gel (S-G) methods, which have highly thermal stability and unique oxygen mobility, are applied as supports to prepare Ni-based catalysts for DRM. The effect of the calcining temperature (500, 600 and 700 °C) on La[sub.2]Ce[sub.2]O[sub.7](CP) has also been investigated. Based on multi-technique characterizations, it is found that the synthesis method and calcination temperature can influence the particle size of the La[sub.2]Ce[sub.2]O[sub.7] support. Changes in particle size strongly modulate the pore volume, specific surface area and numbers of surface oxygen vacancies of the La[sub.2]Ce[sub.2]O[sub.7] support. As a result, the distribution of supported Ni components is affected due to the different metal–support interaction, thereby altering the activity of the catalysts for cracking CH[sub.4]. Moreover, the supports’ abilities to adsorb and activate CO[sub.2] are also adjusted accordingly, accelerating the removal of the carbon deposited on the catalysts. Finally, La[sub.2]Ce[sub.2]O[sub.7](CP 600) with an appropriate particle size exhibits the best catalytic activity and stability in DRM.
Journal Article
Principles of Correction for Long-Term Orbital Observations of Atmospheric Composition, Applied to AIRS v.6 CHsub.4 and CO Data
This study considers methods for assessing the quality of orbital observations, quantifying drift over time, and the application of correction methods to long-term series. AIRS v6 (IR-only) satellite methane (CH[sub.4]) and carbon monoxide (CO) total column (TC) measurements were compared with NDACC ground station data from 2003 to 2022. For CH[sub.4], negative trends were observed in the difference between satellite and ground measurements (AIRS-GR) at all 18 stations (mean drift: 1.69 × 10[sup.14] ± 0.31 × 10[sup.14] molecules/cm[sup.2] per day), suggesting a shift in the orbital spectrometer parameters is probable. The application of a dynamic correction based on this drift coefficient significantly improved the correlation with satellite data for both daily means and trends at all stations. In contrast, AIRS v6 CO measurements showed a strong initial correlation (R = 0.93 for the entire dataset, and R ~ 0.8–0.95 for separate stations) without systematic drift, i.e., the trends of AIRS-GR at individual sites were oppositely directed and statistically insignificant. Therefore, the AIRS v6 CO TC satellite product does not require additional correction within this method. The developed methodology for satellite data verification and correction is supposed to be universal and applicable to other long-term orbital observations.
Journal Article
Quantitative Analysis of Fracture Roughness and Multi-Field Effects for COsub.2-ECBM Projects
Carbon Dioxide-Enhanced Coalbed Methane (CO[sub.2]-ECBM), a progressive technique for extracting coalbed methane, substantially boosts gas recovery and simultaneously reduces greenhouse gas emissions. In this process, the dynamics of coalbed fractures, crucial for CO[sub.2] and methane migration, significantly affect carbon storage and methane retrieval. However, the extent to which fracture roughness, under the coupled thermal-hydro-mechanic effects, impacts engineering efficiency remains ambiguous. Addressing this, our study introduces a pioneering, cross-disciplinary mathematical model. This model innovatively quantifies fracture roughness, incorporating it with gas flow dynamics under multifaceted field conditions in coalbeds. This comprehensive approach examines the synergistic impact of CO[sub.2] and methane adsorption/desorption, their pressure changes, adsorption-induced coalbed stress, ambient stress, temperature variations, deformation, and fracture roughness. Finite element analysis of the model demonstrates its alignment with real-world data, precisely depicting fracture roughness in coalbed networks. The application of finite element analysis to the proposed mathematical model reveals that (1) fracture roughness ξ markedly influences residual coalbed methane and injected CO[sub.2] pressures; (2) coalbed permeability and porosity are inversely proportional to ξ; and (3) adsorption/desorption reactions are highly sensitive to ξ. This research offers novel insights into fracture behavior quantification in coalbed methane extraction engineering.
Journal Article
Influence of Depth on COsub.2/CHsub.4 Sorption Ratio in Deep Coal Seams
The present work aims to analyse the influence of present-day burial depths of coal seams on the sorption properties towards CH[sub.4] and CO[sub.2], respectively. For medium-rank coals located in the southwestern area of the Upper Silesian Coal Basin (USCB), the gravimetric sorption measurements were carried out with pure gases at a temperature of 30 °C. The variability of CO[sub.2]/CH[sub.4] exchange sorption and diffusivity ratios was determined. It was revealed that in coal seams located at a depth above 700 m, for which the sorption exchange ratio was the greatest, the process of CO[sub.2] injection for permanent storage was more beneficial. In the coal seams lying deeper than 700 m with a lower CO[sub.2]/CH[sub.4] sorption ratio, the CH[sub.4] displacement induced by the injection of CO[sub.2] (CO[sub.2]-ECBM recovery) became more favourable.
Journal Article