SELECTIVE CATALYTIC OXIDATION OF HYDROGEN SULFIDE FROM SYNGAS

In order to obtain a non-corrosive fuel gas (syngas), which is derived from coal by Integrated Gasification Combined Cycle (IGCC) technology and used in power plants, hydrogen sulfide (H2S), which is generated during the gasification process due to sulfur contained in coal, should be removed to protect instruments, especially turbines, from corrosion. To improve H2S removal efficiency and develop excellent regenerative catalyst, we conducted the following research. Simulated syngas was introduced into a fixed-bed quartz reactor where carbonaceous sorbents (which are excellent sorbents and have lower price) were positioned to capture H2S. Tail gases from the outlet of the reactor including H2S, COS, and SO2 were continuously monitored by a residual gas analyzer (or mass spectrometer) to determine the capacity of H2S uptake and selectivity of adsorption/oxidation by different sorbents. Carbonaceous materials including carbon black, graphite and activated carbon fibers (ACFs) were compared for the application in desulfurization. Rare earth metal oxides (La2O3 and CeO2) were investigated and used to modify ACFs due to their potential to effectively remove H2S and multicycle regenerative ability. Water vapor and temperature effects on H2S removal were studied. Functional groups on carbonaceous materials were determined and the mechanism of the promotion of H2S uptake by basic functional groups was proposed. Through the determination of activation energy of desorption of sulfur species from sulfided sorbents, it is concluded that chemisorption is the dominant mechanism at higher sulfurization temperature, while physisorption is the controlling process at lower temperature. At the temperature ranging from 110 to 170 ¡ãC, the best H2S-uptake capacity was obtained because chemisorption and physisorption are both present and water film on the surface of sorbents is ideally maintained. The observation of sulfurization and regeneration of sorbents and by-products related that nitrogen could only remove physically adsorbed H2S and hydroxide could, to some extent, restrain the formation of by-products (the reaction between COS or SO2 and hydroxide). ACFs modified by metal compounds showed excellent H2S-uptake capacity (up to 35 mg H2S/g Sorbent) in the 1st cycle but the capacity in the subsequent cycles were much lower than the 1st cycle because regeneration gas (nitrogen) could not recover the chemically adsorbed sulfur species

A Numerical Study of Porous-fluid Coupled Flow Systems with Mass Transfer

Ph.DDOCTOR OF PHILOSOPH

Macroporous Polymer-Derived Ceramic Monoliths for Cryogenic Applications Manufactured by Water-Based Freeze Casting

Macroporous SiOC ceramics were prepared by a water-based freeze casting process, using polysiloxanes as precursors and silica sol as water phase and binder. The obtained porous monoliths have anisotropic porous structure and thermal and mechanical properties. The macroporous SiOC aimed at cryogenic applications which involve mass transport and thermal transport processes. The first part of the thesis focuses on manufacturing macroporous monoliths, in which process the surface characteristics of preceramic polymers in terms of hydrophobicity/hydrophilicity were modified to be used in the water-based freeze casting process. Two approaches were chosen for the surface modification. The first approach to modify the wettability of the precursor was pyrolysis of hydrophobic methyl phenyl polysiloxanes (H44) in inert gas at low temperature, by which hybrid ceramic materials (H44-derived filler) were generated. Depending on the pyrolysis temperatures, the surface characteristics can be varied from hydrophobic to hydrophilic. H44-derived fillers obtained by pyrolyzing methyl phenyl polysiloxane at 600 degree Celsius were hydrophilic enough to be used as solid phase in water-based process. The influence of solid loading, freeze temperatures and pyrolysis temperatures on porosity and specific surface areas were investigated. The combination of polymer derived filler materials with freezing casting method resulted in the trimodal pore structure (micro/meso/macropore) at pyrolysis temperature of 600 to 700 degree Celsius. Even at pyrolysis temperature of 1000 degree Celsius, the specific surface area was be as high as 74 square meter per gram. The pore shape can be tailored from lamellar to tubular depending on freezing temperatures. The second approach to modify the wettability was to introduce more hydrophilic groups to the hydrophobic methyl polysiloxane (MK) by cross-linking with (3-Aminopropyl)triethoxysilane (APTES). The molar ratios between MK and APTES and pyrolysis temperature led to different amounts of aminopropyl groups in the cross-linked products, which altered the basicity and hydrophilicity. For both approaches, besides the surface characteristics, surface charges also account for stable suspension to prepare final homogenous monoliths. Filler material prepared with MK: APTES molar ratio of 1:1, pyrolyzed at 600 degree Celsius was applicable for freeze casting considering the wettability and suspension stability. The monolith prepared with MK-APTES derived filler had also a hierarchical micro/meso/macroporous structure. The vapor adsorption indicated that the high content of silica sol improved the hydrophilicity greatly, and pyrolysis temperature also influenced the hydrophilicity to a minor degree. Notably, the silica sol is responsible for the formation of mesopores. The second part of the thesis was to investigate the mechanical and thermal properties of the obtained unidirectional porous SiOC ceramics prepared with MK and H44 at cryogenic and room temperatures. The compressive strength of monoliths was investigated both in air (293 Kelvin) and in liquid nitrogen (77 Kelvin). The influence of both liquid and cryogenic temperature on compressive strength was investigated. The compressive strength of monoliths showed not only anisotropy, but also a significant increase in liquid nitrogen. This increase may be due to the liquid nitrogen trapped inside the porous structures and cryogenic temperature. The linear thermal expansion coefficients (CTE), thermal conductivity and specific heat capacity of porous SiOC, were studied from cryogenic to room temperature. Both monoliths show anisotropic linear expansion coefficients, with the parallel direction having almost twice the shrinkage of the perpendicular direction. The monolith prepared with H44 showed thermal shrinkage twice as much as that prepared with MK and APTES, which might be due to the composition differences and measurement condition. The thermal conductivities of both monoliths made from two precursors showed anisotropic features and similar values. The minimum and maximum values for thermal conductivity are 0.2 and 0.9 Watts per meter per Kelvin. Thermal conductivities and specific heat capacities displayed an upward trend from low temperature to room temperature. It was assumed that the maximum heat conductivities of these materials were determined mainly by the macroporosity and the thermal conductivity of the hybrid material

A Method for Identifying the Key Performance Shaping Factors to Prevent Human Errors during Oil Tanker Offloading Work

Acknowledgments: The authors would like to appreciate the experts and the engineers working in the Beihai Oil Terminal for their constructive supports during the development of this work. The authors would also like to thank the editors and the anonymous reviewers for their valuable comments.Peer reviewedPublisher PD

China actively promotes CO2 capture, utilization and storage research to achieve carbon peak and carbon neutrality

Global climate change is a common challenge facing mankind, which has evolved from a scientifific issue into a global economic and political issue of universal concern to the international community. Temperature increase, sea level rise, extreme weather and climate events caused by the climate change are becoming more and more prominent. The scientifific understanding of climate change in the international community has been deepening. The Intergovernmental Panel on Climate Change (IPCC, 2014) further strengthened the scientific conclusion that human-induced climate change is more than 95% likely to be attributed to emissions of greenhouse gases from human activities.The United Nations Climate Change Summit (held in September 2014) pointed out that climate change threatens the hard-won peace, prosperity and opportunities of all mankind, and that no one and no country is immune to its impact. Controlling global warming within 2℃ is an urgent and severe challenge faced by mankind in dealing with climate change. The awareness of all countries on the issue of climate change is gradually increasing. The 26th Conference of the Parties (held in November 2021 in Glasgow, UK) urged all countries to achieve the net zero carbon emissions by around 2050, and step up efforts to reduce carbon emission before 2030. Therefore, taking active measures to cope with climate change becomes the common aspiration and urgent need of all countries.Mitigating greenhouse gas emissions (represented by CO2) has become the consensus of the world. In September 2020, Chinese President Xi Jinping pledged at the General Debate of the 75th Session of The United Nations General Assembly that China aims to peak its CO2 emissions before 2030 and achieve carbon neutrality before 2060 (i.e., dual carbon goals), which demonstrates the responsibility of a major country.CO2 Capture, Utilization, and Storage (CCUS) is considered as an effective technology directly achieving carbon emissions mitigation, and has attracted widespread attention of the international community (Metz et al., 2005). The implementation of CCUS projects began in the 1970s, and was mainly carried out in the United States, Canada and some European countries. Those projects mainly focused on CO2 enhanced oil recovery, whereas projects with the pure purpose of CO2 sequestration are relatively rare due to their poor economy.CCUS projects in China started relatively late, and most of them were gradually implemented after 2000 (Guo et al., 2014). The initial technical routes of these projects were similar to those of projects carried out in European and American countries, which began with the geological sequestration of CO2 and enhanced oil recovery. In the past decade, CCUS projects in China began to develop in a diversified way, and there emerged a variety of carbon dioxide capture, storage and utilization technologies, including pre-combustion capture of power plants, CO2 chemical and biological utilization, etc.The realization of the dual carbon goals not only requires revolutionary changes in industrial technology, but also largely depends on the formulation of relevant policies and capital investment. The National Natural Science Foundation of China launched a special research program “Major Basic Science Issues and Countermeasures for National Carbon neutrality” in 2021 to meet the needs of basic science research for the national carbon neutrality strategy. Focusing on the two core issues of “carbon emission mitigation” and “carbon sink increase”, the special program includes a total of 28 research projects, with an average funding of about 3 million RMB per project.This special research program aims to reveal the oceans and terrestrial carbon sinks, the process mechanism, evolution trend and its mutual feedback mechanism with the climate system, delineate the geological process of carbon sequestration and the effectivity of fixing carbon. The program also has goals to increase the potential of CO2 storage, to assess the technology risk and management mode, to analyze the economic transformation, the optimal pathway, climate control, international cooperation management and policy issues. Interdisciplinary integration research is needed to condense key basic science issues and solutions for serving the national carbon-neutral strategy.It is foreseeable that China will further increase investment in realizing a carbon emission peak and its carbon-neutral strategy in the future. This is also a great opportunity for the development of CCUS-related technologies. The contribution of CCUS technology in carbon emission mitigation is generally low today. For instance, even in Norway, which has the highest proportion of carbon emissions treated by CCUS, the value is less than 5% (Cai et al., 2020). However, as the guaranteed technology of carbon peak strategy, the contribution ratio of CCUS in carbon emission mitigation is expected to significantly increase in the future.Although the CCUS technology has been implemented for many years and many projects have been carried out, there are still many challenges to be solved, such as:(i) CCUS related technology development and cost control The CCUS technology includes capture, transportation, utilization and storage, all of which need to consume a lot of energy. At present, the cost of the CCUS projects is still high. It is estimated that the cost of the whole CCUS process will be 150-540 RMB per ton of CO2 by 2025, of which CO2 capture cost accounts for more than two thirds of the total cost, about 100-480 RMB/ton. In comparison, the cost of CO2 sequestration is 50-60 RMB/ton, while the cost of CO2 transportation is very low, less than 1 RMB/ton (Cai et al., 2021). Obviously, the wider promotion of CCUS projects in the future largely depends on the further development of CO2 capture technology and the rapid reduction of cost.(ii) Effect of long-term CO2-water-rock interaction on rock structure and mechanical properties In the process of CO2 geological storage and utilization, the injected CO2 will inevitably change the pH of formation water, breaking the original water-rock balance and inducing a new water-rock reaction. Thus, the rock structure and mechanical properties of the caprock are likely to be changed over time, which affects the safety of the storage reservoirs. The current studies mostly focus on the effect of CO2-water-rock interaction on the leakage channels (porosity and permeability) of the caprock (Credoz et al., 2009; Liu et al., 2020). However, the study on the change of rock mechanical properties caused by chemical reactions requires further research attention. A few previous studies only simply correlated the evolution of rock mechanical properties with porosity, but without considering the influence of changes in mineral composition induced by CO2-water-rock interaction on the rock mechanical properties (Agarwal, 2019). Therefore, it is necessary to further deepen the relevant investigation and build a comprehensive rock mechanical parameter evolution model considering the changes of porosity, mineral composition and content, and other factors (Tian et al., 2019).(iii) CO2 leakage monitoring and risk assessment methods The leakage risk of CO2 after injection has been one of the main concerns, which directly affects the safety and feasibility of CCUS technology (Bachu, 2008). At this point, the construction of a CO2 leakage monitoring system is particularly important. However, the CO2 leakage process is usually characterized by sudden occurrence and weak surface response. Therefore, a single monitoring method is difficult to ensure the reliability of monitoring. In the future, it is necessary to combine various monitoring methods with their respective advantages.For a long-term (more than 100 years) CO2 leakage risk assessment, the most commonly used method at present is to employ the reactive transport modelling. However, due to the large time scale, parameter uncertainty and the difficulty of validation, the predicted results have high uncertainty. Some natural CO2 gas reservoirs have existed for more than thousands of years (Jonathan et al., 2018). Taking natural CO2 gas reservoirs as a natural analogue of CO2 geological sequestration can solve the problem that long-term simulated results are difficult to verify, thereby improving the reliability of long-term risk assessment (Xu et al., 2019). AcknowledgementThis work was performed in support of the National Natural Science Foundation of China (Grant Nos. 42141013 and 41772247). Conflict of interest The authors declare no competing interest.Open Access This article is distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Cited as: Xu, T., Tian, H., Zhu, H., Cai, J. China actively promotes CO2 capture, utilization and storage research to achieve carbon peak and carbon neutrality. Advances in Geo-Energy Research, 2022, 6(1): 1-3. https://doi.org/10.46690/ager.2022.01.0

HBX-Mediated Migration of HBV-Replicating HepG2 Cells: Insights on Development of Hepatocellular Carcinoma

Hepatitus B virus (HBV) is a major cause of the development of hepatpcellular carcinoma (HCC). One of the significant characteristics of tumor progression is cell migration which is reflective of cytoskeletal dynamics. The Rho GTPases contribute to a multiple cellular processes, including the cellular cytoskeletal reorganization and motility. It has been found that some Rho GTPases have oncogenic activity and can promote cancer cell invasion. Here we discuss one of the Rho GTPases, Rac1 can be activated by HBV replication and such activation results in the high motility of HBV-replicating cells. The enhanced cell motility can be interestingly alleviated by the mutation at the sites of proline rich domain located in HBX. Our findings may provide new insights on the mechanism of HCC development associated with chronic HBV infection

Rheological properties of polyurethane-based magnetorheological gels

© 2019 Zhang, Li, Wang and Wang. The paper tests the influence of mass fractions of carbonyl iron particles (CIPs) on the rheological properties of magnetorheological (MR) gels. Polyurethane-based MR gels with different weight fraction of CIPs, i.e., 40, 60, and 80%, were firstly prepared by mechanical mixing, respectively. The changes of shear stress and viscosity with shear rate under different magnetic flux density were tested and analyzed. It was found that the shear stress increases with mass fraction under magnetic flux density. The viscoelastic properties of MRGs were achieved by oscillatory shear measure. The effects of strain amplitude and frequency on viscoelastic of MRGs under different magnetic flux density were measured and analyzed. The study results shown that the elastic characteristics become more obvious with the increase of CIPs mass fraction. However, it has opposite effect on the viscous properties of materials