Experimental evaluation of adsorption technology for CO2 capture from flue gas in an existing coal-fired power plant

Activated carbons from biomass-based sources for CO2 capture applications

In an ever-growing attempt to reduce the excessive anthropogenic CO₂ emissions, several CO₂ capture technologies have been developed in recent years. Adsorption using solid carbonaceous materials is one of the many promising examples of these technologies. Carbon-based materials, notably activated carbons, are considered very attractive adsorbents for this purpose given their exceptional thermal stability and excellent adsorption capacities. More importantly, the ability to obtain activated carbons from agricultural wastes and other biomass that are readily available makes them good candidates for several industrial applications ranging from wastewater treatment to CO₂ adsorption, among others. Activated carbons from biomass can be prepared using various techniques, resulting in a range of textual properties. They can also be functionalized by adding nitrogen-based groups to their structure that facilitates faster and more efficient CO₂ capture. This review provides a detailed overview of the recent work reported in this field, highlighting the different preparation methods and their differences and effects on the textual properties such as pore size, surface area, and adsorption performance in terms of the CO₂ adsorption capacity and isosteric heats. The prospect of activated carbon functionalization and its effect on CO₂ capture performance is also included. Finally, the review covers some of the pilot-plant scale processes in which these materials have been tested. Some identified gaps in the field have been highlighted, leading to the perspectives for future work.

Enrichment of Hydrogen from a Hydrogen/Propylene Gas Mixture Using ZIF-8/Water-Glycol Slurry

In this work, zeolitic imidazolate framework-8 (ZIF-8), a subclass of metal organic frameworks (MOFs), was dispersed in a water-glycol solution to form a porous slurry. Using this porous slurry, a tail gas mixture containing hydrogen/propylene was separated. Experiments were performed to investigate the effects of using only the solid ZIF-8 material, a ZIF-8/water slurry, a ZIF-8/glycol slurry, or a ZIF-8/water-glycol slurry on the selectivity of the separation. The experimental results show that the slurry made from ZIF-8/water-glycol (20%) achieves good gas separation. The respective influences of the solid content, initial pressure, and temperature on the separation performance were also investigated in detail. We found that lower temperature, a ZIF-8 mass fraction of 20 wt %, and a higher operation pressure are suitable for the recovering of hydrogen from a H2/C3H6 mixture. The selectivity of C3H6 over H2 reaches 128 at 680 kPa initial pressure. The slurries were completely reusable for at least three cycles. The structure of the ZIF-8 material was not altered after repeated separation, meaning the material can likely be reused more than three times on an industrial scale.

Development Trends in Porous Adsorbents for Carbon Capture

Accumulation of greenhouse gases especially CO2 in the atmosphere leading to global warming with undesirable climate changes has been a serious global concern. Major power generation in the world is from coal based power plants. Carbon capture through pre- and post- combustion technologies with various technical options like adsorption, absorption, membrane separations, and chemical looping combustion with and without oxygen uncoupling have received considerable attention of researchers, environmentalists and the stake holders. Carbon capture from flue gases can be achieved with micro and meso porous adsorbents. This review covers carbonaceous (organic and metal organic frameworks) and noncarbonaceous (inorganic) porous adsorbents for CO2 adsorption at different process conditions and pore sizes. Focus is also given to noncarbonaceous micro and meso porous adsorbents in chemical looping combustion involving insitu CO2 capture at high temperature (>400 °C). Adsorption mechanisms, material characteristics, and synthesis methods are discussed. Attention is given to isosteric heats and characterization techniques. The options to enhance the techno-economic viability of carbon capture techniques by integrating with CO2 utilization to produce industrially important chemicals like ammonia and urea are analyzed. From the reader's perspective, for different classes of materials, each section has been summarized in the form of tables or figures to get a quick glance of the developments.

Graphene nanosheets as novel adsorbents in adsorption, preconcentration and removal of gases, organic compounds and metal ions

Due to their high adsorption capacities, carbon-based nanomaterials such as carbon nanotubes, activated carbons, fullerene and graphene are widely used as the currently most promising functional materials. Since its discovery in 2004, graphene has exhibited great potential in many technological fields, such as energy storage materials, supercapacitors, resonators, quantum dots, solar cells, electronics, and sensors. The large theoretical specific surface area of graphene nanosheets (2630 m(2)·g(-1)) makes them excellent candidates for adsorption technologies. Further, graphene nanosheets could be used as substrates for decorating the surfaces of nanoparticles, and the corresponding nanocomposites could be applied as novel adsorbents for the removal of low concentrated contaminants from aqueous solutions. Therefore, graphene nanosheets will challenge the current existing adsorbents, including other types of carbon-based nanomaterials.