A new adsorbent based on potassium carbonate (K 2 CO 3 ) supported on modified γ-Al 2 O 3 has been developed in this work. It has shown excellent multicycle stability with adsorption and regeneration at 55 and 130 °C, respectively. The support (γ-Al 2 O 3 ) is stabilized by thermal treatment and alkali treatment with hydroxide, followed by calcination. The excellent regeneration characteristics are due to minimal interactions between the support and reactants during CO 2 adsorption. This is due to acidity reduction of the support responsible for the formation of stable species, for example, KAl(CO 3 ) 2 (OH) 2 . Various physicochemical characteristics have been studied to understand the adsorption and regeneration behavior of the adsorbents over multiple cycles. The effects of operating parameters, such as adsorption temperature, thermal dehydration of support material, and gas hourly space velocity (GHSV), during regeneration have also been studied. The CO 2 adsorption capacities are found to be in the range of 2.3−2.6 mmol of CO 2 /g of adsorbent (10−11.4 wt % CO 2 ), which also shows good stability after multicycle tests. The developed adsorbents also show high attrition resistance and, thus, can be effectively used in commercial application for CO 2 capture.
The effect of the preparation method on the CO 2 adsorption capacity of K 2 CO 3 /Al 2 O 3 adsorbents is examined. The multi-step impregnation (MI) method enables uniform dispersion of active species (K 2 CO 3 ) in the broad macropores without blocking narrower mesopores. This facilitates higher loading of accessible K 2 CO 3 for CO 2 adsorption and, hence, higher adsorption capacity. The single-step impregnation (SI) method suffers from blockage of narrower mesopores by excessive growth of K 2 CO 3 . This limits the CO 2 accessibility toward active species in the porous structure because of the formation of larger active species aggregates. For 50 wt % K 2 CO 3 /Al 2 O 3 prepared by MI and SI methods, the maximum CO 2 adsorption capacity at CO 2 partial pressure of 8 kPa is found to be 3.12 and 2.1 mmol/g, respectively. The regeneration efficiency of 50MI and 50SI are observed to be nearly 65 and 56%, respectively, at 130°C in multi-cycle testing. The experimental data for CO 2 adsorption were described by the Langmuir isotherm, and the isosteric heat as a function of fractional coverage of the adsorbent was evaluated by means of the van't Hoff equation. The isosteric heat showed a decreasing trend with an increase in the surface coverage of the adsorbent. From the results, it is concluded that the adsorbent prepared by the MI method shows better performance because of its tunable textural and morphological properties to achieve higher CO 2 adsorption capacity.
Straight chain C10 to C13 di-olefins were selectively hydrogenated to increase the mono-olefins content in the feed to alkylation reactor in the process of production of Linear Alkyl Benzene (LAB). The reaction was carried out in a liquid phase up-flow fixed bed reactor at temperature of 448-503 °K and pressure of 1.08-1.96 MPa, which keeps hydrogen dissolved in the hydrocarbon feed. Under the above process conditions the reactor will be virtually two phase (solid-liquid) instead of three phase (solid-liquid-vapour). Kinetics of hydrogenation of straight chain C10 to C13 di-olefins on nickel alumina (Ni/Al2O3) catalyst was studied in the temperature range of 458-488 °K. The reaction scheme considered includes two consecutive hydrogenation reactions. Various rate models based on the modified Power Law, Horiuti-Polanyi mechanism & proposed by Somers. A.; were derived for the two consecutive hydrogenation reactions and subjected to model discrimination. Parameter estimation was done utilizing the Levenberg-Marquardt Algorithm for global convergence using MATLAB software. Out of the various models tested, rate model based on power law with modification fitted the data well. The estimated rate constants of the best model are thermodynamically sound and statistically consistent.
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