Properties of a Nano CaO/Al₂O₃ CO₂ Sorbent

Abstract

This project studied the properties of nano CaO/Al2O3 as a high-temperature CO2 sorbent for its use in an adsorption enhanced reforming reaction. The sorbent containing nano CaCO3 precursors and aluminum oxide was prepared, and evaluation of the CO2 adsorption properties by a thermogravimetric analyzer, the results show that nano CaO/Al2O3 has a faster decomposition rate and has a higher CO2 adsorption ratio than micro CaO/Al2O3. The maximum adsorption ratio occurs at temperatures of 650 °C under a CO2 partial pressure of 0.33 atm. Durability studies show that the CO2 adsorption ratio remains at 68.3% after 50 cyclic runs under a carbonation temperature of 650 °C and calcination temperature of 800 °C, respectively. XRD, SEM, and BET were used for studying the change of micro characteristics of the CO2 sorbents before and after multiple carbonation−calcination runs. The results showed that the pore size of CaO/Al2O3 sorbents was enlarged and that a new substance (Ca12Al14O33) was formed even under a temperature of 800 °C for the function of keeping the compound stable and durable.

A Review of CO2 Capture by Absorption and Adsorption

“…SC-propane grafting apparatus. Lemonidou, 2008;Wu et al, 2008). Those obtained materials exhibited high adsorption capacities over 5 mmol/g in a temperature range from 600 and 700°C and long-term stability in cyclic runs which was attributed to the presence of Ca 12 Al 14 O 33 as the binder which inhibited the sintering of CaO particles.…”

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

“…limestone, dolomite), it makes sense to use the material over several cycles and to perform multiple regenerations before disposing of the used carbonate, so as to achieve genuine energy and CO 2 emissions reductions. Research efforts are taking place worldwide to understand the reasons for the loss of CO 2 capacity with repeated cycling and increase the durability of Ca-based CO 2 sorbent with this very aim [35][36][37][38][39][40][41][42][43]. Table 2 allows comparison of the minima of enthalpy changes of the urea-water system at 1 atm (and the temperatures at which they occur) with those of the urea-water-CaO system (with Ca:C=1), in kJ/mol of H 2 produced, alongside the H ratio, maxima of H 2 yield and of H 2 purity, also listed with their corresponding temperatures.…”

Chemical looping processes — particle characterization, ionic diffusion-reaction mechanism and reactor engineering

“…This is consistent with the SEM images that the hydration process breaks sintered sorbents into small pieces. Intra-particle spaces become larger with smaller grain size and thus become less CO 2 diffusion resistant (Wu et al 2008 ). Furthermore, it is found that hydration also alters the distribution of the surfaces in different orientations.…”

“…Furthermore, when the nano-CaCO 3 precursor was mixed with other materials, both nano-sorbents and support effects are integrated together. For example, nano-CaO/Al 2 O 3 yields a stable adsorption ratio of 68.3 % after 15 cycles (Wu et al 2008 ). In addition, Ca 12 Al 14 O 33 forms at a lower temperature for the reaction between nano-CaCO 3 and Al 2 O 3 .…”