Chemisorption of carbon dioxide on sodium oxide promoted alumina

Abstract

New equilibrium and column dynamic data for chemisorption of carbon dioxide from inert nitrogen at 250, 350, and 4508C were measured on a sample of sodium oxide promoted alumina, which was found to be a reversible chemisorbent for CO 2 . The equilibrium chemisorption isotherms were Langmuirian in the low pressure region (p CO 2 \2.0 kPa) with a large gas-solid interaction parameter. The isotherms deviated from the Langmuirian behavior in the higher pressure region. A new analytical model which simultaneously accounted for Langmuirian chemisorption of CO 2 on the adsorbent surface and additional reaction between the gaseous and sorbed CO 2 molecules was used to describe the measured equilibrium data. The heats of CO 2 chemisorption and the additional surface reaction were, respectively, 64.9 and 37.5 kJ/mol. The column breakthrough curves for CO 2 sorption from inert N 2 on the chemisorbent as well as the desorption of CO 2 from the chemisorbent by N 2 purge at 3508C could be described by the linear driving force (LDF) model in conjunction with the new sorption isotherm. The same LDF mass transfer coefficients can be used to describe both sorption and desorption processes. The CO 2 mass transfer coefficients were (i) independent of feed gas CO 2 concentration in the range of the data at a given temperature, and (ii) a weak function of temperature. The ratio of the mass transfer zone length to the column length was very small due to highly favorable CO 2 sorption equilibrium. Several sequential cyclic CO 2 sorption-desorption column dynamic tests were conducted to demonstrate the apparent stability of the material.

In Situ XRD Detection of Reversible Dawsonite Formation on Alkali Promoted Alumina: A Cheap Sorbent for CO2 Capture

“…Nevertheless such high breakthrough capacities complete very well the information gathered by the structural study reported herein and support the proposed pathway under relatively high pressure and temperature. In contrast, previous studies on CO 2 sorption on alkali-promoted alumina carried out at ordinary pressure [30] or relative high CO 2 pressure without steam [31] have revealed much lower CO 2 capacities. …”

Monitoring Solid Oxide CO2 Capture Sorbents in Action

“…A new analytical model for these sorbents was derived by Lee et al to describe the deviation from conventional Langmuirian equilibrium chemisorption isotherms. [4] This model, though it described the data well, assumed, without experimental proof, that there is one single type of adsorption site and that deviations from the Langmuir model are due to complexing between the gas and already chemisorbed CO 2 molecules. These sorbents have been donated by Air Products and Chemicals, Inc. to Lehigh University for further development.…”

“…[1] Lee et al has recently studied two promising high temperature chemisorbents for the water-gas-shift-SER (WGS-SER), a K 2 CO 3 -promoted hydrotalcite and a Na 2 O-promoted alumina. [1,[4][5][6][7] The chemisorbents were originally developed by Air Products and Chemicals, Inc. to produce fuel-cell-grade hydrogen by steam methane reforming. [8][9][10][11] These chemisorbents offer (i) reversible sorption of CO 2 in the presence of steam, H 2 , and CO, (ii) relatively fast CO 2 sorption and desorption kinetics, (iii) moderate heats of sorption (~20-65 kJ mol À1 ), (iv) acceptable cyclic working capacity, (v) nearly infinite selectivity of CO 2 chemisorption over gases like CO, steam, N 2 , and CH 4 at 200-500 8C, and (vi) thermal stability under WGS reaction conditions.…”

Novel Sorption Enhanced Reaction Process for Simultaneous Production of CO2 and H2 from Synthesis Gas Produced by Coal Gasification

“…The compression ratio in the two compressors were 2.0 and 1.73 to raise the pressure to 140 atm and the power consumption of each compressor was calculated from (31) where m is the CO 2 flow rate (kg/s), C p is the gas phase specific heat (C p = 0.85 kJ/kg K -1 ), T in is the gas inlet temperature (T in = 310.9 K), R is the compression ratio, γ is the specific heat ratio (γ CO2 =1.287), and η is the compressor efficiency (η = 0.75). The cost of electricity is $0.10 per kWhr and the cost of electrical energy for CO 2 compression was calculated.…”