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Mammadova Salima Huseyn, PhD., student, the Faculty of Chemical Engineering Azerbaijan State Oil and Industry University E-mail: bvl_ok@rambler.ru Garaybayli Samira Aslan, Engineer, the Faculty of Chemical Engineering Azerbaijan State Oil and Industry University
Baghiyev Vagif Lachin, Professor, department of chemistry and chemical materials engineering Azerbaijan State Oil and Industry University E-mail: Vagif_bagiev@yahoo.com
THERMODYNAMIC EVALUATION OF ETHANOL CONVERSION ROUTES
Abstract: The work is devoted to the thermodynamic study of ethanol conversion routes. It was shown that the reaction of dehydrogenation of ethanol to ethyl acetate is exothermic and proceeds with a volume increasing. It was found that for the selective conversion of ethanol to ethyl acetate. the dehydrogenation reaction must be carried out in the temperature range 200-250 ° C.
Keywords: thermodynamics. ethanol. acetone. ethylene. ethyl acetate.
In recent years. an increasing number of chemical To conduct thermodynamic calculations. we compounds are derived from ethanol in the industry took from the reference tables the values of the [1; 2; 3]. This is because ethanol is produced in large standard thermodynamic functions at a tempera-quantities from biomass and in the future. it will be ture of 298K. We took thermodynamic functions one of the main sources of raw materials for the chem- for the initial reactants and reaction products for ical industry. One of the possible ways of converting example changes in the enthalpy of formation of the ethanol is the reaction of its dehydrogenation to form substances AH0. absolute entropies S0 and also the ethyl acetate. Various undesirable reactions can also values of the coefficients entering into the equations take place with the formation of ethylene. acetone. describing the temperature dependence of the heat etc. In order to identify possible optimal conditions capacity of the substance. for obtaining ethyl acetate. we carried out thermody- Results and discussions
namic calculations of the reaction of dehydrogenation The dehydrogenation of ethanol to ethyl acetate
of ethanol to ethyl acetate. as well as possible reactions proceeds according to the following reaction. of formation of undesirable side reactions. 2C2H5OH = CH3COOC2H5 + 2H2
Method of calculation The formation of reaction by-products. namely
Calculation of the change in the isobar of the acetone. ethylene and acetic aldehyde. proceeds ac-chemical reaction was carried out according to the cording to the following reactions. Temkin-Shvartsman equation: 2C2H5OH + H20 CH3COCH3 + C02 + 4H2
AGT = AH2098 - T(AaM0 + AbM1 + AcM2 + Ac'M_2) C2H5OH = C2H4 +H20
Section 6. Chemistry
C2H5OH = ch3CHO +H2 The values of thermodynamic quantities dependence of the chosen for calculations (enthalpy AH0. absolute entropies S0 values of the heat capacity temperature coefficients) are given in Table 1.
Carried out calculations showed that the value of changing in the enthalpy of the reaction is -9430 J. i.e. the reaction is exothermic. and since the reaction proceeds with an increase in the number of moles. an increasing in pressure leads to a shift of the reaction to the left.
Table 1.- The thermodynamic values of the initial reactants and reaction products
Substance AH298 S298 Cp = f(T)
a b*103 c'*10-5 c*106
C2H5OH -234800 281.38 10.99 204.70 0 -74.20
CH3COOC2H5 -479030 259.41 8.67 303.1 0 -115.8
C,H,0 -166000 264.20 13.00 153.50 0 -53.70
C^ 52300 219.45 11.32 122.01 0 -37.90
CH3COCH3 -217570 294.93 22.47 201.80 0 -63.50
C02 -393510 213.66 44.14 9.04 -8.54 0
H2 0 130.52 27.28 3.26 0.50 0
H20 -241810 188.72 30.00 10.71 0.33 0
Carried out calculations showed that the value of changing in the enthalpy of the reaction is -9430 J. i.e. the reaction is exothermic. and since the reaction proceeds with an increase in the number of moles. an increasing in pressure leads to a shift of the reaction to the left.
The calculated Gibbs energy values are shown in (Table 2) below. It is seen that as the reaction temperature increases. the Gibbs energy for the reaction of ethyl acetate formation increases from 3.3 kJ at 300 K to 14.9 kJ at 600 K. It should be
mation reaction in the entire studied temperature range have a negative value. Gibbs energy of other products as seen from table 2 decrease and at temperatures above 550 K have negative values. This indicates that at these temperatures high yields of acetone. acetic aldehyde and ethylene should be observed. A comparison of the Gibbs energy values for all reactions suggests that in order to reduce the yields of ethylene. acetone and acetic aldehyde. the dehydrogenation of ethanol must be carried out at temperatures below 500K or up to 250 ° C.
noted that the Gibbs energies for the acetone for-
Table 2.- Thermodynamically calculated values of Gibbs energy for the reaction of formation of ethyl acetate. ethylene. acetic aldehyde and acetone.
Reactions of alcohol conversion into: Gibbs Energy. AG. Kj.
300 350 400 450 500 550 600
ethyl acetate 3.3 5.3 7.3 9.2 11.1 13.0 14.9
acetic aldehyde 34.8 29.1 23.2 17.3 11.3 5.2 -.90
Acetone -185.2 -193.8 -202.8 -212.0 -221.6 -231.5 -241.5
ethylene 7.2 0.9 -5.6 -12.1 -18.6 -25.2 -31.8
Conclusions 2. For the selective conversion of ethanol to eth-
1. The reaction of dehydrogenation of ethanol yl acetate. the dehydrogenation reaction must be
to ethyl acetate is exothermic and proceeds with in- carried out in the temperature range 200-250 ° C. creasing volume.
References:
1. Dapeng Liu, Yan Liu, Eileen Yi Ling Goh, Christina Jia Ying Chu, Chuandayani Gunawan Gwie,Jie Chang. Armando Borgna. Catalytic conversion of ethanol over ZSM-11 based catalysts. Applied Catalysis - A: General.- Volume 523.- 2016.- P. 118-129.
2. Hala R. Mahmoud. Highly dispersed Cr2O3-ZrO2 binary oxide nanomaterials as novel catalysts for ethanol conversion. Journal of Molecular Catalysis A: Chemical.- Volume 392.- 2014.- P. 216-222.
3. Filek U., Kirpsza A., Micek-Ilnick A., Lalika E., Bielanski A. Ethanol conversion over cesium-doped mono- and bi-cationic aluminum and gallium H3PW12040 salts. Journal of Molecular Catalysis A: Chemical.- Volume 407.- 2015.- P. 152-162.
