Abstract
Activated carbons of resorcinol-formaldehyde aerogels (AC-RFA) were prepared and mixed with multiwall carbon nanotubes (MWCNTs) with various ratios. Samples were characterized by different techniques. The novelty of the study is in evaluating the effect of uniformity of carbon nanocomposites on their performance for the adsorption of CH4 and CO2 gases as well predicting the separation of their mixtures. The results indicated that, by increasing the percentage of MWCNTs into the sample, its structural uniformity and order ascend. The capacities of CH4 and CO2 by adsorption were measured at various temperatures, and were correlated with the extended dual site Langmuir (DSL) model. Overall, results showed that the adsorption capacity of MWCNTs towards gases is relatively very low compared to that of activated carbons. The DSL model was utilized to forecast the separation of the binary CO2/CH4 mixed gas based on knowledge of single component adsorption isotherm parameters. Adsorption equilibrium data of the CO2/CH4 binary gas mixture was forecasted at different temperatures by DSL model in accordance with the perfect-negative (PN) or perfect-positive (PP) behaviors on the heterogeneous surface of the adsorbent.
Highlights
Methane (CH4 ) and carbon dioxide (CO2 ) gases coexist often in nature, forming gas mixtures, such as natural gas, biofuel gas, landfill gas, coal bed methane, etc. [1,2,3,4,5].Separation of CO2 gas from CO2 /CH4 mixed binary gas is a core and strategic target in enhancing the gas purity and efficiency
The peak at 2623 cm−1 (G00 -peak) for multiwall carbon nanotubes (MWCNTs) in Figure 3 refers to an overtone of the D-peak [38]
The impact of temperature on the adsorption/desorption isotherms of gases was conducted on the sample of medium composition (S50)
Summary
Separation of CO2 gas from CO2 /CH4 mixed binary gas is a core and strategic target in enhancing the gas purity and efficiency. The existence of CO2 impurity within CH4 gas reduces its heating value and leads to pipeline corrosion, especially if moisture is found [6]. CO2 and CH4 gases are key players in the amassing of greenhouse gases, and subsequently in the augmented global warming crisis [7]. The greenhouse warming impact of CH4 is 21 times bigger than that of CO2 [8]. Owing to the strong augmentation in the cost of oil and recent rigorous ecological regulations, there is a noticeable rise in the extraction of natural gas as a strong competent source of energy [9]. It is desired to establish efficient techniques for removing CO2 gas from natural gas
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