Carbon capture by physical adsorption: Materials, experimental investigations and numerical modeling and simulations - A review

The Linear Driving Force (LDF) model for gas adsorption kinetics is frequently and successfully used for analysis of adsorption column dynamic data and for adsorptive process designs because it is simple, analytic, and physically consistent. Yet, there is a substantial difference in the characteristics of isothermal batch uptake curves on adsorbent particles by the LDF and the more rigorous Fickian Diffusion (FD) model. It is demonstrated by using simple model systems that the characteristics of the adsorption kinetics at the single pore or the adsorbent particle level are lost in (a) evaluating overall uptake on a heterogeneous porous solid, (b) calculating breakthrough curves from a packed adsorbent column, and (c) establishing the efficiency of separation by an adsorptive process due to repeated averaging of the base kinetic property. That is why the LDF model works in practice.

Why does the linear driving force model for adsorption kinetics work

In this minireview, we discuss the utility of heterogeneous carbons as catalysts for facilitating a broad range of synthetic transformations. While such materials are commonly used as supports for transition metals that are catalytically active, carbons that are free of metals are also capable of enabling useful chemical reactions. Carbon catalysts hold promise in the development of sustainable alternatives to existing metal-dependent processes, as well as the discovery of mechanisms and transformations that are altogether new. Spanning from the 1930s to the present day, we provide a broad overview of the utility of carbon to facilitate various oxidation, reduction, and bond forming processes. Lastly, we will present some challenges for the future of the field.

Carbocatalysis: Heterogeneous carbons finding utility in synthetic chemistry

Separation and purification of multicomponent gas mixtures by adsorption is an established process technology. Adsorptive process design requires accurate data on multicomponent gas adsorption equilibria, kinetics, and heats as input variables. These data often cannot be predicted by using today's models, particularly for complex practical systems where the gas mixtures have adsorbates of different sizes and polarities, and the adsorbent is energetically heterogeneous. There is a large volume of pure gas and some binary gas adsorption equilibrium and kinetic data in the published literature, but multicomponent adsorption data are rare. The data for heats of adsorption are only emerging. There is a desperate need to generate a multicomponent adsorption database for better understanding of the complex phenomenon, for seriously testing existing models, and for development of new models. Two recently developed methods called “isotope exchange technique” and “microcalorimetry for adsorption heats” are recommen...

Basic Research Needs for Design of Adsorptive Gas Separation Processes

Kinetic separation of methane—carbon dioxide mixture by adsorption on molecular sieve carbon

Air separation by pressure swing adsorption on a carbon molecular sieve

Adsorption and diffusion of nitrogen and oxygen in a carbon molecular sieve

Numerical simulation of a PSA system using a pore diffusion model

A numerical simulation of a pressure swing adsorption process is presented for a system in which a small concentration of an adsorbable component is separated from an inert carrier. Linear equilibrium and a linear rate expression are assumed. The model equations were solved by orthogonal collocation and by finite difference methods with consistent results. The theory is shown to provide a good representation of the experimental data of Mitchell and Shendalman (1973) for the system CO2-He-silica gel.

M.M. Hassan

Papers

Air separation by pressure swing adsorption on a carbon molecular sieve

Adsorption and diffusion of nitrogen and oxygen in a carbon molecular sieve

Numerical simulation of a PSA system using a pore diffusion model

Numerical simulation of a PSA system. Part I: Isothermal trace component system with linear equilibrium and finite mass transfer resistance

Pressure swing air separation on a carbon molecular sieve—II. Investigation of a modified cycle with pressure equalization and no purge