Adsorption–desorption characteristics of methyl ethyl ketone with modified activated carbon and inhibition of 2,3-butanediol production

Figures & data

Figure 1. Experimental setup for continuous AC adsorption–desorption process.

Table 1. Characteristics of the ACs evaluated.

Original carbon	AC-1	AC-2	AC-3	AC-4	ACF
Ignition point (ºC)	498	504	524	505
Ash content (%)	2.56	7.33	10.22	6.59
pH (50ºC)	8.9	4.8	9.3	7.2
Specific surface areas (m^2/g)	1209	1343	1155	1178	1318
Pore volume (cm^3/g)	0.53	0.84	0.65	0.59	0.55
Average pore diameter (Å)	19.72	24.97	22.57	20.79	16.8

Figure 2. Percentages of functional groups in original ACs.

Figure 3. Composition of ash content in original ACs.

Table 2. Characteristics of two adsorbates tested.

Adsorbate	Formula	Molecular weight (g/mol)	Boiling point at 1atm (ºC)	Vapor pressure at 20ºC (mmHg)	Molecular diameter^a (Å)	Polarity index^a	Density at 25ºC (g/mL)
MEK	CH3COC2H5	72.11	79.6	71	5.25	4.7	0.81
Toluene	C6H5CH3	92.14	110.6	22	5.68	2.4	0.87

Note: ^aLee et al., 2008.

Table 3. Original carbon, modifier, and impregnation solvent used.

Carbon number	Original carbon	Modifier	The original carbon (g)/modifier (g)/solvent (mL)
Im-1	AC-1	Ethanolamine	100/3.1/H2O (50)
Im-2	AC-1	Ethylene diamine	100/3.5/H2O (200)
Im-3	AC-1	MgO	100/3/H2O (200)
Im-4	AC-1	KNO3	78.1/3/H2O (200)
Im-5	AC-1	Ethanolamine	100/6.2/H2O (50)
Im-6	AC-1		350ºC, nitrogen, 4 hr
Im-7	AC-1	O3	200 ppm, 6 L/min

Note: AC-1, TAKETA- G₂.

Table 4. Adsorption capacity and average BDO concentration in the desorbed solvent with various ACs evaluated.

Original carbon	AC-1	AC-2	AC-3	AC-4	AC-1*	ACF
Saturated adsorption capacity (wt%) g/g AC	29.3	24.9	20.8	26.0	26.8	31.7
Average working capacity (wt%) g/g AC	22.5	17.3	15.1	19.5	16.5	17.4
Average length of adsorption zone (mm)	90	179	129	110	107	305
Average BDO concentration in the desorbed solvent (wt%)	0.123	0.119	0.104	0.111	0.199	0.06

Note: The BDO concentration of the original MEK solvent is 0.023%.

*The desorption temperature is controlled at 110ºC.

Figure 4. BDO concentration in desorbed solvents of AC-1, AC-2, AC-3, and AC-4.

Figure 5. Effects of desorption temperature (100ºC or 130ºC) on BDO concentration of the recovered solvent with AC-1 as adsorbent.

Table 5. Effect of various commercial modifiers on ignition point.

Modifier	Ignition point of AC-1 (ºC)	Ignition point of the modified AC (ºC)	Ignition point changes
Ethanolamine (Im-1)	498	502	+4
EDA (Im-2)	498	501	+3
MgO (Im-3)	498	510	+12
KNO3 (Im-4)	498	470	–28

Table 6. Comparison of AC desorption performance and BDO concentrations with different modifier loadings.

Item	Modifier/AC (g/g)	Saturated adsorption capacity (wt%)	Average working capacity (wt%)	Average length of adsorption zone (mm)	Average BDO concentration in the desorbed solvent (wt%)	Specific surface areas (m^2/g)	Pore volume (cm^3/g)	Ave. pore diameter (Å)
AC-1	—	29.3	22.5	90	0.123	1209	0.53	19.72
Im-1	3.1/100	27.6	20.8	86	0.112	1140	0.49	17.37
Im-5	6.2/100	20.7	9.6	164	0.075	1162	0.51	17.48

Note: The BDO concentration of the original MEK solvent was 0.023%.

Figure 6. Comparison of BDO concentrations in the desorbed solvents of AC-1 and two types of modified carbons.

Figure 7. Comparison of BDO concentrations in the desorbed solvents achieved with modified ACs (Im-6, Im-7).

Figure 8. Oxygen-containing functional groups contents in original ACs and modified AC (Im-6 and Im-7).

Figure 9. BDO concentrations of the recovered solvents with alternate MEK and toluene feedings.

Figure 10. Effects of N₂ as the desorption medium on BDO concentration.

Figure 11. Comparison of BDO concentrations in N₂ desorbed solvents for original carbon AC-1 and modified carbon Im-2 by mixed feeding (MEK 2,000 ppm + toluene 2,000 ppm), and BDO concentration in air-desorbed solvent for AC-1 by feeding 4,000 ppm MEK.

Lee, S.W., J.K. Cheon, H.J. Park, and M.G. Lee. 2008. Adsorption characteristics of binary vapors among acetone, MEK, benzene, and toluene. Korean J. Chem. Eng. 25:1154–59. doi:10.1007/s11814-008-0190-3

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