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KINETICS OF THE NON-ISOTHERMAL DESORPTION OF ETHANOL ABSORBED ONTO CMS-3A
Nikola S. Jovancic3, Borivoj K. Adnadevicb, Jelena D. Jovanovicc
University of Belgrade, Faculty of Physical Chemistry, Belgrade, Republic of Serbia
a e-mail: [email protected],
ORCID iD: http://orcid.org/0000-0003-4917-9104 b e-mail: [email protected],
ORCID iD: http://orcid.org/0000-0002-9555-8191 c e-mail: [email protected], ORCID iD: http://orcid.org/0000-0002-7537-9591
https://dx.doi.org/10.5937/vojtehg65-12187
FIELD: Chemical Technology ARTICLE TYPE: Original Scientific Paper ARTICLE LANGUAGE: English
Abstract:
The kinetics of the desorption of ethanol previously absorbed onto carbon molecular sieves (CMS-3A) was studied using the non-isothermal thermogravimetric technique. The dependence of activation energy (Eaa) for a particular degree of desorption (a) was established. It was confirmed that the non-isothermal desorption of ethanol was a kinetically complex process. A novel mathematical model for the kinetics of non-isothermal desorption for the absorbed ethanol is established. This model is based on the proposed dependence of the specific desorption rate on time/temperature. The correlation dependences of the model parameters £> and n on heating rates were established. A general kinetic equation for the non-isothermal desorption of ethanol was developed. It was found that the specific desorption rate at every single heating rate increases, whereas Ea, decreases during the desorption process.
Key words: dependant, absorbers, molecular sieves, analytical models, model, zeolites, CMS-3A, kinetics, ethanol, desorption.
ACKNOWLEDGEMENT: This investigation was supported by the Ministry of Science and Technical Development of the Republic of Serbia through Project 172015OI.
Introduction
Bioethanol nowadays presents a main alternative source for the economic production of novel fuels and ethanol (Kosaric, et al, 2001). Ethanol is produced by fermentation of sugars obtained by hydrolyses of biomass. Three sources of biomass are commonly used: sugar, corn and lignocellulose materials. The most promising source is the lignocellulose biomass because it can use agricultural and forest residues and prevent the heated fuel-versus-food debate (Hashi, et al, 2010, pp.4628-4637). The only barrier for a broad application of production of ethanol is a high production cost (Kaminski, et al, 2008, pp.95-102).
Produced bioethanol contains a certain amount of water. The distillation process used for bioethanol separation and purification requires a large amount of energy which is approximately equal to 50% of the combustion energy of produced bioethanol (Fujita, et al, 2011, pp.869879). Selective ethanol adsorption on a hydrophobic material of the zeolite type is a way to reduce the energy consumption of this process, presently the most promising procedure for an energetically rational bioethanol production (Adnadjevic, Jovanovic, 2012, pp.761-768). The introduction of this new separation process for bioethanol production requires solving a novel problem of cheep and effective selective procedure of adsorbed ethanol desorption onto a zeolite type adsorbent. The key role in this solution is in the kinetics of ethanol desorption from the zeolite adsorbent. It was shown that the most effective adsorbents are carbon molecular sieves such as CMS - 3A. Knowing the kinetics of ethanol desorption can contribute to better and more economical production of bioethanol. Unfortunately, to the best of our knowledge, the literature data is sparse with data concerning this topic.
Fujita and co-workers investigated the kinetics of desorption of ethanol and water from various types of commercial zeolite (MSC-3A, 4A, -5A, -6A, -7A, HiSiV3000, ZSM-5 (Si02/Al03 =30), hydrophilic 5A) in the gaseous phase and evaluated the effectiveness of the proposed process (Fujita, et al, 2011, pp.869-879). The desorption of 1-buthanol from water solution adsorbed onto ZSM-5 with a high Si/Al ratio was discussed in the work of Saravanan et al. (Saravanan, et al, 2010, pp.68-69). Oudshoorn et al. investigated the desorption rate of 1- buthanol from zeolite CVB28014, CVB901 (Oudshoorn, et al, 2012, pp.167-172).
Keeping that in mind, this work thoroughly investigates the kinetics of the non-isothermal desoprption of ethanol adsorbed onto carbon molecular
sieves (CMS-3A). Therefore, a kinetic model, kinetic complexity and the values of the kinetics parameters were determined and discussed.
Materials
The following materials were used: a carbon molecular sieve type 3A (CMS-3A), produced by Takeda Chem. Ind., Japan; ethanol 99.8 vol. % of p.a. purity purchased from Hemos, Belgrade, Serbia, and bidistilled water obtained from Hemofarm, Serbia. Before use, the CMS-3A was thermally activated at a temperature of 393 K for 2 hours, cooled and kept in a dessicator until use.
Characterization
by N2 (77 K) adsorption using a Micrometrics ASAP 2010 volumetric adsorption apparatus. The BET surface area was measured from the adsorption isotherms by applying the Brunauer-Emmett-Teller equation to calculate the micropore volume (Vmp ). The total volume (Vt) was obtained
at a relative pressure of 0.99. The pore size distribution (PSD) was obtained by the Horvath-Kawazoe analysis.
Sample preparation
in 01 CP CP
Materials and Methods <
01 OT 2 O o
T3
<u
.Q
.Q CO
<U
M—
O c o
CP
o tn <u
T3
The texture properties of the activated sample used were determined
E
o c <u
o <u
ro <u
Ethanol was absorbed onto the CMS-3A as follows. One gram of thermally activated CMS-3A was added to 50 mL of ethanol. Ethanol £ adsorption was undertaken for 24 hours. The ethanol adsorbed-CMS (CMS-ethanol) sample was separated from the ethanol excess by decantation. o The sample was kept in the exicator to prevent ethanol desorption.
Thermogravimetric measurements
The non-isothermal thermogravimetric curves were recorded using a TA Instruments SDT simultaneous TGA-DSC thermal analyzer, model 2960. These experiments were performed with the CMS-ethanol absorbed
samples weighing 20 ± 5 mg. The samples were placed in the platinum pans under (99.9995 vol. %) nitrogen flowing at a rate of 20 mL min-1. Four different heating rates (vh = 5, 10, 15 and 20 K min-1) were used in this
study. All experiments in this work were conducted in the temperature range from ambient temperature up to 400 K. For isothermal methods, it is necessary that the process of desorption is performed at a lower temperature range from ambient to 500K. The original mass loss versus temperature (TG) curves obtained at a constant heating rate were transformed into the degree of desorption (a) versus temperature curves by means of the following equation:
a
m0 - m
m0 - m
(1)
f
where m0, m and mf refer to the initial, actual and final mass of the sample.
Kissinger-Akahira-Sunose (KAS) method
The Kissinger-Akahira-Sunose method (Akahira, Sunose, 1971, pp.22-31) is the isoconversional integral method which uses Coats-Redfern approximation (Coats, Redfern, 1964, pp.1273-1278) of the temperature integral that leads to the equation:
r \
ln
v T2,
= ln
AR
RT
(2)
EaS (a)
where g(a)is the integral form of the selected kinetic model. For a =const., the plot of ln (n / T2) vs.T 1 should be a straight line the slope of which can be used to evaluate the apparent activation energy.
Kinetic model
Desorption kinetics model
The ethanol desorption process is affected by many parameters such as temperature, time, pressure, ethanol concentration, pH of the solution, as well as the structural characteristics of carbon molecular sieves. The mathematical models of desorption presented bellow are based on the following assumptions listed below: (a) The desorption process is a kinetically complex process; (b) Leaving the molecules of a certain part of
the absorbed phase (desorption) leads to structural changes in the absorbed phase and its nearby surroundings (structural rearrangement); (c) The desorption rate is significantly higher than the structural rearrangement rate; (d) As a consequence of the above, the specific desorption rate (k ) is a function of both time (t) and temperature (T), which can be described by the equation:
p( t T
k = p L (3)
_
t
W
i.e
k = !-_
p( T - T0 ^
v_
(4)
where p and _ are the Weibull's parameters, To is the initial temperature
and vh is the heating rate; (e) the rate of desorption (dN / dt) is
proportional to the amount of the remaining molecules in the adsorbed phase. In this case, the desorption rate is given as:
dN k , A
dT=7t {N°- N) (5)
where N0 is the amount of the adsorbed molecules in the beginning of the
desorption process, and N is the amount of the desorbed molecules at T . Introducing Eq (4) into Eq (5) yields:
dN p
( T - T \p-1 1 1o
dT
vhV
vhV
(N0 - N)
The separation of the variables in equation (3) leads to:
N \
dN
(No - N) i vhv
I _p_( T - to ^
vhV
dT
(6)
(7)
The integration of equation (7) should be done in the limits of N from 0 to N and of T from To to T, to yield:
( n - N ^
ln = (8)
N0
vh_
The results is:
No - N
No
= exp
с t — t ^ __
V j.
Since: a = N / N0, equation (9) is transformed into the form:
a = 1 — exp
С t — t ^ __fo
V vbV j
(9)
(10)
Results and discussion
Figure 1 shows the thermogravimetric curves for the desorption of ethanol from CMS at various heating rates.
Am/m[%] 100959085-
80-
75-
280 300 320 340 360
Temperature/K
380
400
Figure 1 - The TG curves for the desorption of ethanol from CMS at various heating
rates: 5Kmin-1, •- 10Kmin-1 15Kmin"4- 20Kmin-1
Рис. 1
TG кривая десорбции этанола с CMS при разных скоростях нагревания: 5 K мин-1, •- 10 K мин-1 ▲- 15 K мин-1 ▼- 20 K мин-1 Слика 1 - TG крива десорпци]е етанола са CMS на различитим брзинама загрева^а: 5Kmin-1, •- 10Kmin-1A- 15Kmin"W- 20Kmin-1
As it can be seen from Figure 1, the TG curves for the desorption of ethanol at all investigated heating rates are of a complex sigmoid shape. As it is obvious from the TG curves, both the initial temperature (T) and
the final temperature (Tf), the reaction interval (AT = Tf -T) and the degree of asymmetry of the curves change with the change in the heating rates. Table 1 summarizes the effects of heating rates on the values of T, Tf AT and the residual (Am / m).
Table 1 - Data for the heating rates, initial temperatures, final temperatures, reaction intervals and percentage of residual masses for Fig.1 Таблица 1 - Значения температуры в начале десорбции, при завершении десорбции, температурного интервала и остаток массы в процентах Табела 1 - Вредности температуре почетка десорпци]е, температуре завршетка десорпци]е, температурског интервала и процентни остатак масе
vh [K/min] T [K] Tf [K] AT [K] Am / m [%]
5 305.63 344.59 38.96 76.04
10 308.09 358.63 50.54 76.97
15 310.54 366.65 56.11 77.72
20 312.29 373.73 61.44 78.02
As it is obvious from the results presented in Table 1, the increase of the
heating rate leads to the increase in the values of T, T, and AT, where the
' J
residual insignificantly varies within the experimental error. In order to preliminary determine the kinetic model of ethanol desorption, the shape of the dependence da/dt on a is analyzed. (Khawam, Flangan, 2005, pp.10073-10080). The dependence of da / dt on a is presented in Figure 2.
The dependence of da / dt on a shows a broad asymmetric peak with a clear maximum -amax. With the increase of the heating rate, the value of amax increases almost linearly. Since the dependence of da / dt on a has a complex shape, the dependence of Ea a on a is determined
by applying the KAS method. The dependence of Ea a on a is shown in Figure 3.
do/dt 0.5 -,
0.40.30.2-
0.1
0.0
0.0
0.2
0.4
0.6
0.8
1.0
О
Figure 2 - The dependence of do/dt on О at various heating rates: ■- 5 K min'V 10 K min-1 15 K min-1 ▼- 20 K min-1 Рис. 2- зависимость do/dt при разных скоростях нагревания: ■- 5 K мин-1,•- 10 K мин-1 15 K мин-1 ▼- 20 K мин-1
Слика 2 - зависност do/ dt на различитим брзинама загрева^а: ■- 5 K min'V 10 K min-1 ▲- 15 K min-1 ▼- 20 K min-1
E /kJmol-1 a 100-,
О
Figure 3 - The dependence of Eao on o Рис. 3 - Зависимость e ot о
Слика 3 - зависност ea o od o
80-
60-
40-
20
0.0 0.2 0.4 0.6 0.8 1.0
The values of Eaa decrease with the increase in the values of a. The
analysis of the shape of the dependence of Eaa on a clearly reveals two
characteristic shapes of changes in Eaa with the increasing a. In the range
of 0 < a < 0.25, Eaa decreases almost linearly with increasing the a values from ~100 kJ mol-1 to ~60 kJ mol-1. In contrast to this, when a > 0.25, the increase of a leads to concave decrease in the value Eaa from ~60 kJ
mol-1 to ~20 kJ mol-1. A complex shape of the dependence of Eaa on a , in
accordance with Vyazovkin's criteria (Vyazovkin, Linert, 1995, pp.109-118), indicates that the process of desorption of the ethanol from the CMS is a kinetics complex process which takes place through numerous elementary stages. In regard to that, the ability of a mathematical description of the kinetics of ethanol desorption with equation (10) was evaluated. Figure 4 presents the
dependence of ln[-ln(1 -a)~\ on ln
t - t
at different heating rates.
Figure 4- Dependence of ln[-ln(1 -a)] on
ln
T - T
at different heating rates:
■- 5 K min-1, •- 10 K min-1 15 K min-1 ▼- 20 K min-1
~T - T
Рис. 4 - Зависимость ln [-ln (1 -«)] от
ln
при разных скоростях нагревания:
■- 5 K мин-1, •- 10 K мин-1 ▲- 15 K мин-1 ▼- 20 K мин-1
T - T
Слика 4 - Зависност ln [-ln (1 -«)] од ln
на различитим брзинама загрева^а:
■- 5 K min-1, •- 10 K min-1 ▲- 15 K min-1 ▼- 20 K min-1
h
v
h
h
h
Table 2 - Values of the Weibull's parameters at different heating rates Таблица 2 - Значения параметров Вейбулла при разных скоростях нагревания Табела 2 - Вредности Ве]булових параметара на различитим брзинама загрева^а
vh [K/min] в r|[min]
5 2.35 7.57
10 2.47 4.69
15 2.63 3.47
20 2.82 2.95
Obviously, the dependencies of ln [-ln (1 -a)] on ln
t - tn
for all of
the investigated heating rates are linear. The values of the parameters ( and r were calculated based on the slopes and intercepts the
dependencies of ln [-ln (1 -a)] on ln
t - t,
. The effect of heating rates
on the Weibull's parameters ( and r is shown in Table 2.
As it can be seen from the results presented in Table 3, the increase in the heating rates leads to the increase in the values of the parameter ( while the values of the parameter r decrease. The found changes in the values of the parameters ( and r can be mathematically described by the expressions:
p(vh) = exp (0.827 + 0.05V, + 0.0003vh2) (11)
r{vh) = exp (2.658 - 0.143V, + 0.003v2 ) (12)
The mathematical expressions (11) and (12) enable to derive an equation which can successfully describe the kinetics of the investigated process as a function of temperature and heating rates:
da dT
РЫ
kn(vh)
(T - T0) vhn(vh)
P(yh-1 )
exp
P(vh)
T - To
v(vh)
(13)
Based on the knowledge on the values of the parameters f3 and ^ by using Eq (4), it is possible to calculate the values of a specific desorption rate for different temperatures at different heating rates. Figure 5 pre-
v
h
v
h
sents the dependence of the specific desorption rate with temperatures for different heating rates.
k / min-
3.2-,
280
300
320
340
360
380
400
Temperature / K
Figure 5 - Dependence of k on temperature at different heating rates: ■- 5 K min-1, •- 10 K min-1 ▲- 15 K min-1 ▼- 20 K min-1 Рис. 5- Зависимость k от температуры при различных скоростях нагревания
■- 5 K мин-1, •- 10 K мин-1 ▲- 15 K мин-1 ▼- 20 K мин-1 Слика 5- Зависност k од температуре на различитим брзинама загрева^а
■- 5 K min-
•- 10 K min-1 ▲- 15 K min-1 ▼- 20 K min"
The increase in temperature leads to the increase in the values of the specific desorption rate at all of the investigated heating rates. Also, the increase in the heating rates at all investigated temperature values leads to the increase in the values of the specific desorption rate. The established dependencies of k on T allow applying the Arrhenius equation to calculate the values of activation energies at different temperatures for different heating rates. The dependence of Ea on temperature at the investigated heating rates is presented in Figure 6.
E / kJmol"
a
200-
150-
100-
50-
280
320
360
400
Temperature / K
Figure 6 - The dependence of Ea on temperature at different heating rates:
■- 5 K min-1, •- 10 Kmin-1 15 K min-1 ▼- 20 K min-1 Рис. 6 - Зависимость Ea от температуры при различных скоростях нагревания ■- 5 K мин-1, •- 10 K мин-1 ▲- 15 K мин-1 ▼- 20 K мин-1
Слика 6 - Зависност Ea од температуре на различитим брзинама загрева^а: ■- 5 K min-1, •- 10 Kmin-1 15 K min-1 ▼- 20 K min-1
The Ea value decreases with the increasing temperature at all of the investigated heating rates. The two characteristic shapes of changes of EaTwith increasing T are obvious. In the range of 290 <T < 315 K, the
dependence Ea T on T almost linearly decreases with increasing temperature, whereas at temperatures 315 <T < 400 K, the value of Ea decreases concavely with increasing temperature. At a particular value of temperature, the value of Ea increases with the increase in the heating rate. Based
on the dependence of Ea on temperature at a particular heating rate, it is
0
possible to get the dependence of Ea a on a for that heating rate. Figure 7 presents the dependence of Ea a on a for different heating rates.
E / kJmol"1
a
200
150
100-
50
~o!o~
0.2
0.4
—i— 0.6
—i— 0.8
—i— 1.0
a
Figure 7- Dependence of Ea a on a for different heating rates Рис. 7 - Зависимость ea от a при различных скоростях нагревания Слика 7 - Зависност Ea a од a на различитим брзинама загрева^а The curves of the dependence of Ea a on a at all investigated heating rates are of similar shapes. The curves of the dependence of Ea aon a show two different shapes of changes of the dependence of Ea a on a. The two characteristic shapes of changes of Ea awith increasing a are obvious. For the range of values 0 < a < 0.2, the dependence Ea aon a linearly decreases with increasing a. For the values of a > 0.2, the values of Ea a decrease concavely with increasing Ea a .The comparison of
the shapes of the dependences of ea on a at different heating rates with
the dependence of Ea a on a obtained by the isoconversion method (Fig
3) clearly shows their mutual similarity, especially at extremely low and high degrees of desorption. The found similarity confirms physical reality of the previously suggested model for the non-isothermal desorption based on the assumption about the changes in the values of the specific rate of
7 7
CO
I
O) Ю CO
p. p
< CO
I
CO ^
о
o
d e or s a
e f o n
io ptr
or
s e d
"(0 E
e
in
k:
"го
t
e
Ю
n a
>
o
desorption with temperature. Since with the increasing temperature the specific rate of desorption increases more rapidly than the rate of internal rearrangement of ethanol's molecules in the absorbed phase, the activation energy decreases, the kinetics complexity changes and the specific rate of desorption increases.
Conclusion
The non-isothermal desorption of ethanol absorbed onto CMS-3A is a kinetically complex process. Kinetic's complexity of the desorption of ethanol is a consequence of the changes in the specific rate of desorption and activation energy with temperature. The conversion kinetics curves of the non-isothermal desorption of ethanol, at all heating rates, can be entirely mathematically described by the suggested model. The correlation dependences of the parameters of the kinetics model on heating rates are established. A general kinetics equation of the non-isothermal desorption of ethanol is developed. It was found that the value of the specific desorption rate of ethanol, at every single heating rate, increases with the increase in temperature, whereas the activation energy decreases. The functional dependences of activation energy on time for each heating rate were determined. The results obtained by this work can be used to enhance the knowledge of the desorption kinetics of ethanol, wich is a key factor for its more economical production.
Symbols
Ea [kJ mol-1] activation energy
E,a [kJ mol-1] activation energy at a
EaT [kJ mol-1] activation energy at T
V^ Vmp [cm3g-1] micropore volume
V [cm3g-1] total volume
d [nm] average pore size
m [g] the initial mass of the sample
m [g] actual mass of the sample
mf [g] final mass of the sample
Am / m [%] percentage of residual mass
g (a) integral form of the selected
kinetic mode
T [K] temperature h-01
T-1 [K-1] inverse temperature CD LO
T [K] initial temperature at TG 01 cp
Tf [K] final temperature at TG < 01
AT [K] reaction interval OT 2
R [J mol-1K-1] universal gas constant (8.314 ) O £
k [min-1] specific desorption rate "c o
t [min] time T3 <u _Q
To [K] initial temperature O tn
dN / dt rate of desorption ro "o
amount of the adsorbed c ro
No molecules in the beginning -C <u
of the desorption process 15
N amount of the desorbed molecules at o
temperature p o
vh [K min-1] heating rate <D T3
Greek symbols (B E <D
a a [-] degree of desorption .c o
«max [-] maximum degree of desorption £Z o
P [-] Weibull's parameter c <u
r [min] Weibull's parameter M— O
Abbreviations </) O +-<
CMS-3A Carbon molecular sieves type 3A c
CMS-ethanol Ethanol adsorbed carbon molecular sieves "(C
PSD Pore size distribution <D
TG Thermogravimetric curve -±
KAS method Kissinger-Akahira-Sunose method ■<J ;o
MSC-3A Molecular Sieving Carbon type 3A c ro >
MSC-4A Molecular Sieving Carbon type 4A o
MSC -5A Molecular Sieving Carbon type 5A
MSC -6A Molecular Sieving Carbon type 6A
MSC -7A Molecular Sieving Carbon type 7A
HiSiV3000 Silicalite zeolite
ZSM-5 Zeolite Socony Mobil-5
CVB28014 Zeolite ammonium ZSM-5
CVB901 Zeolite H-SDUSY
CM <D
</) tf>
LO CD
"o >
o CM
of
UJ
a. z> O
o <
o
X
o
LU
H ^
a. <
H
<
CD >o
X LU H O
O >
References
Adnadjevic, B., & Jovanovic, J., 2012. Kinetics of Isothermal Ethanol Adsorption onto a Carbon Molecular Sieves under Conventional and Microwave heating. Chemical Engineering Technology, 34(4), pp.761-768. Available at: http://dx.doi.org/10.1002/ceat.201100153.
Akahira, T., & Sunose, T., 1971. Trans. Joint Convention of Four Electrical Institutes. Research Report, Chiba Institute of Technology, 16(246), pp.22-31.
Coats, A.W., & Redfern, J.P.,1964. Kinetic Parameters from Thermogravimetric Data. Nature, 201(4914), pp.68-69. Available at: http://dx.doi.org/10.1038/201068a0.
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Hashi, M., Tezel, F.H., & Thibault, J., 2010. Ethanol Recovery from Fermentation Broth via Carbon Dioxide Stripping and Desorption. Energy & Fuels, 24(9), pp.4628-4637.
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Khawam, A., & Flanagan, R.D., 2005. Complementary use of model-free and modelistic methods in the analysis of solid-state kinetics. J Phys Chem B, 109(20), pp.10073-80. pmid:16852219.
Kosaric, N., Vardar-Sukan, F., & Pieper, H.J., 2001. The Biotechnology of ethanol: Classical and Future Application. In: M. Roehel Ed., Weinheim: Wiley - VCH.
Oudshoorn, A., van der Wielen, L.A.M., & Straathof, A.J.J., 2012. Desorption of butanol from zeolite material. Biochemical Engineering Journal, 67, pp.167-172.
Saravanan, V., Waijers, A.D., Ziari, M., & Noordemeer, M.A., 2010. Recovery of 1-butanol from aqueous solutions using zeolite ZSM-5 with a high Si/Al ratio; suitability of a column process for industrial applications. Biochemical Engineering Journal, 49, pp.33-39.
Vyazovkin, S., & Linert, W., 1995. Thermaly induced reactions of solids, isokinetic relationship of nonisothermal decomposition of solids. Chem Phys, 193, pp.109-118.
НЕИЗОТЕРМИЧЕСКАЯ КИНЕТИКА ДЕСОРБЦИИ ЭТАНОЛА, АБСОРБИРОВАННОГО НА УГЛЕРОДНОМ МОЛЕКУЛЯРНОМ СИТЕ ОМБ-ЭА
Никола С. Йованчич, Боривой К. Аднаджевич, Елена Д. Йованович Университет в Белграде, Факультет физической химии, г. Белград, Республика Сербия
ОБЛАСТЬ: химические технологии
ВИД СТАТЬИ: оригинальная научная статья
ЯЗЫК СТАТЬИ: английский
Резюме:
В данной статье описаны проведенные исследования по кинетике десорбции эталона, абсорбированного на углеродном молекулярном сите ОМБ-ЭА. Главным источником биоэтанола являются: сахар, кукуруза и лигноцеллюлозные материалы. Выработанный биоэтанол содержит определенное количество воды. Для его очистки используются различные сеперационные методы, которые в настоящий момент еще недостаточно испытаны. Главная проблема очистки биоэтанола заключается в высокой стоимости процедуры и больших затратах энергии -на 50% превышающих производимую биоэтанолом энергию. Селективная адсорбция этанола на цеолите значительно снижает затраты энергии при производстве, но, к сожалению, данный метод требует много времени. В целях улучшения кинетики десорбции могут применятся различные технологии, однако они на сегодняшний день недостаточно испытаны. Одним из самых практичных и наиболее экономичных методов очистки биоэтанола является десорбция этанола на углеродном молекулярном сите, при этом вода остается на поверхности углеродного молекулярного сита. С учетом того, что данный метод недостаточно испытан, необходимо полагаться на знания о кинетике десорбции этанола на цеолитах. Хотя на сегодняшний день опубликовано малое количество научных работ, посвященных исследованиям кинетики десорбции этанола на цеолитах. В данной работе применена неизотермическая термогравиметрическая техника. В ходе исследования была утверждена полная зависимость энергии активации от степени десорбции, а также установлена модель процесса десорбции. Данная модель основана на полной зависимости скорости десорбции от времени и температуры. Благодаря применению данной модели можно повлиять на скорость процесса десорбции и энергию активации с температурой. Математическая модель, описанная в данной работе основана на полной зависимости скорости процесса десорбции и энергии активации от
температуры. Данная модель также отражает последовательность этапов процесса десорбции. Настоящая модель кинетики процесса десорбции этанола может значительно улучшить технологию производства биоэтанола и уменьшить производственные затраты.
Ключевые слова: зависимость, абсорбенты, молекулярные сита, аналитические модели, модели, цеолиты, ОМБ-ЭА, кинетика, этанол, десорбция.
НЕИЗОТЕРМНА КИНЕТИКА ДЕСОРПЦШЕ ЕТАНОЛА АДСОРБОВАНОГ НА УГ^ЕНИЧНОМ МОЛЕКУЛСКОМ СИТУ ОМБ-ЭА
Никола С. иованчи^, Бориво\ К. Адна^еви^, Jелена Д. иованови^ Универзитет у Београду, Факултет за физичку хеми]у, Београд, Република Срби]а
ОБЛАСТ: хеми]ске технологи]е
ВРСТА ЧЛАНКА: оригинални научни чланак
иЕЗИК ЧЛАНКА: енглески
Сажетак:
У овом раду проучавана jе кинетика десорпцие етанола претходно адсорбованог на угъеничном молекулском ситу CMS-3A. Главни извори биоетанола су ферментабилни шеЯери, кукуруз и лигноцелулозни отпадни материал. Произведени биоетанол садржи одре^ену количину воде, а да би се пречистио користе се разне сепарационе методе ще jош нису довоъно испитане. Главни проблем при пречишЯаваъу биоетанола jе висока цена, као и знатан утрошак енергие щи представка више од 50% енергие щу биоетанол производи. Селективна адсорпциа етанола са зеолита знатно сма^уjе утрошак енергие при производъи. Нажалост, ова метода jе веома спора. Ради побоъшаъа кинетике десорпцие користе се различите технике, ще нису довоъно испитане. иедну од практичниих и jефтиниjих метода ща се користи при пречишЪаваъу биоетанола представка десорпциа етанола са угъеничног молекулског сита, при чему вода остаjе задржана на угъеничном молекулском ситу. Ме^утим, ова метода ние довоъно испитана, а ради побоъшаъа производи (брзине производи) потребно jе познавати кинетику десорпцие етанола са зеолита. Мало jе научних радова и литературе щи проучаваjу кинетику десорпцие (брзину десорпцие) етанола са зеолита За одре^иваъе кинетике десорпцие у овом раду jе коришЯена неизотермна термогравиметриска техника.
Установлена je комплексна зависност eHepeuje активацще од степена десорпц^е, као и математички модел по щем се ££
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© 2017 Авторы. Опубликовано в «Военно-технический вестник / Vojnotehnicki glasnik / Military Technical Courier» (www.vtg.mod.gov.rs, втг.мо.упр.срб). Данная статья в открытом доступе и распространяется в соответствии с лицензией «Creative Commons» (http://creativecommons.org/licenses/by/3.0/rs/).
© 2017 Аутори. Обjавио Воjнотехнички гласник / Vojnotehnicki glasnik / Military Technical Courier (www.vtg.mod.gov.rs, втг.мо.упр.срб). Ово jе чланак отвореног приступа и дистрибуира се у складу са Creative Commons licencom (http://creativecommons.org/licenses/by/3.0/rs/).
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десорпц^а одиграва. Oeaj модел заснован je на комплексноj зависности брзине десорпц^е од времена и температуре. Због комплексности модела долази до промене брзине десорпц^е и ^ енерг^е активац^е са температуром. Математички модел установлен у овом раду заснива се на комплeксноj зависности брзине десорпц^е и енерг^е активац^е од температуре и и показуje на ко\и начин се десорпц^а одиграва у неколико ступъева. Познаваъе кинетике процеса десорпц^е етанола може допринети болоj и економичнио производи биоетанола.
Клучне речи: зависност, апсорбенти, молекулска сита, аналитички модели, модели, зеолити, CMS-3A, кинетика, етанол, 1о десорпци]а.
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Paper received on / Дата получения работы / Датум приема чланка: 24.10.2016. Manuscript corrections submitted on / Дата получения исправленной версии работы / ^ Датум достав^а^а исправки рукописа: 28.11.2016. о
Paper accepted for publishing on / Дата окончательного согласования работы / Датум ® коначног прихвата^а чланка за об]ав^ива^е: 30.11.2016.
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© 2017 The Authors. Published by Vojnotehnicki glasnik / Military Technical Courier (www.vtg.mod.gov.rs, втг.мо.упр.срб). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/rs/).
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