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THERMODYNAMIC RESEARCH OF METHANOL STEAM REFORMING INTO HYDROGEN
IsmaylovaV.
PhD Student, Chemical technology faculty, Azerbaijan State Oil and Industry University, Baku, Azerbaijan
Baghiyev V.
Doctor of chemical science, Professor, Chemical technology faculty, Azerbaijan State Oil and Industry University, Baku, Azerbaijan
Abstract
A thermodynamic calculation of the reaction of steam conversion of methanol to hydrogen was carried out. It was established that the magnitude of the Gibbs energy change has a negative value, starting already from a temperature above 300 K. It was shown that the conversion of methanol to hydrogen reaches almost 100% even at a temperature of 500 K, i.e. the steam reforming reaction of methanol into hydrogen is thermodynamically favorable.
Keywords: methanol,hydrogen,methane,steam reforming, thermodynamic calculation
Introduction
From the periodic literature it is known that the reaction of steam conversion of organic compounds such as low molecular weight alcohols is one of the promising methods for producing hydrogen [1-4]. It is believed that methyl alcohol can be used as one of the preferred starting alcohols for steam conversion to hydrogen [5-7]. The prospect of using methyl alcohol as a feedstock is due to the fact that it is one of the most important large-scale products of the chemical industry [8, 9]. In this regard, in this article, identifying the possibility of using methyl alcohol as a feedstock, we performed a thermodynamic calculation of the reaction of steam conversion of methyl alcohol to hydrogen.
According to the authors of [10], the reaction of steam conversion of methyl alcohol proceeds in two stages according to the following general equation: CH3OH + H2O = CO2 + 3H2 CH3OH = CO + 2H2 CO + H2O = CO2 + H2
In addition to the main reaction, reactions of dehy-drogenation, dehydration and decomposition of alcohol can also occur with the formation of substances such as formaldehyde, dimethyl ether, methane, etc. These reactions are listed below:
2CH3OH ^ (CH3)2O +H2O 2CH3OH ^ CH4 +2H2 + CO2 CH3OH ^ CH2O+H2
In this regard, we carried out a thermodynamic calculation of these possible side reactions as well. Experimental
To carry out thermodynamic calculations, we took from the reference tables [11] the values of standard thermodynamic functions at a temperature of 298 K for the initial reagents and reaction products: changes in the enthalpy of formation of substances AH°298, absolute entropies S°298, and also the values of the coefficients entering into the equations describing the temperature dependence of the heat capacity of a given substance. The selected values of thermodynamic quantities are given in table 1.
Table 1
The values of the thermodynamic quantities of the starting reagents and reaction products of the
steam reforming of methanol.
Substance AH°298 S 298 Cp = f(T)
a b*103 c'*10-5 c*106
CH3OH -234800 281,38 10,99 204,70 0 -74,20
CH2O -166000 264,20 13,00 153,50 0 -53,70
C2H6O 52300 219,45 11,32 122,01 0 -37,90
CH4 -74850 186,27 14,32 74,66 0 -17,43
H2O -241810 188,72 30,00 10,71 0,33 0
CO -110530 197,55 28,41 4,1 -0,46 0
CO2 -393510 213,66 44,14 9,04 -8,54 0
H2 0 130,52 27,28 3,26 0,50 0
Results and discussions
Preliminary calculations showed that the methanol steam reforming reaction is endothermic and the change in the enthalpy of the reaction is 49300 Joules, and since the reaction proceeds with an increase in the number of moles, an increase in pressure leads to a shift of the reaction to the left.The change in the Gibbs energy of the chemical reaction was calculated according to the Temkin-Schwartzman equation:
AG0 = AH2098 - T (AaM0 + AbMx + AcM2 + Ac M_2)
Knowing also the value of the Gibbs energy change, we found the equilibrium constant from the equation:
AGt0 = -RTlnKp
Knowing the equilibrium constant, we determined the theoretical yield of hydrogen at various temperatures.
Table 2 below shows the calculated Gibbs energy at various temperatures for the reactions of the steam
conversion of methyl alcohol into hydrogen, formaldehyde and dimethyl ether, methane and carbon monoxide. It can be seen that in the entire temperature range studied, the Gibbs energy change for the main reaction, namely the formation of hydrogen, has negative values and their values increase with increasing reaction temperature, which indicates a high possibility of a hydrogen formation reaction. A similar dependence is obtained for the reaction of the conversion of methanol to methane. For this reaction, the change in the Gibbs energy in the entire studied temperature range is negative. Table 2 also shows that over the entire temperature range studied, the Gibbs energy change for the dimethyl ether formation reaction exceeds 200 kJ, which indicates that the reaction is almost completely shifted to the left, i.e. ether is practically not formed.The table also shows that the possibility of a methanol dehydro-genation reaction with the formation of formaldehyde increases with increasing reaction temperature.
Table 2
The calculated Gibbs energy at various temperatures for various reactions occurring in the steam reform-
Methanol conversion reactions Gibbs energy, AG, kJ.
300 400 500 600 700 800 900
CHsOH+H2O=CO2+3H2 -3,7 -22,1 -41,6 -61,8 -82,5 -103,6 -125,0
CHBOH=CO+2H2 24,82 2,31 -21,09 -45,06 -69,39 -93,96 -118,7
CO+H2O=CO2+H2 -28,54 -24,41 -20,44 -16,66 -13,02 -9,52 -6,15
2CHSOH=(CH3)2O+H2O 224,73 226,94 228,88 230,66 232,30 233,86 235,35
2CHbOH=CH4+2H2+CO2 -120,8 -139,6 -159,3 -179,6 -200,4 -221,4 -242,6
CHsOH=CH2O+H2 52,23 40,99 29,34 17,44 5,37 -6,81 -19,05
Table 3 shows the dependences of the calculated theoretical yields of methyl alcohol conversion reaction products.
Table 3
The calculated values of theoretically possible degrees of conversion at various temperatures for various _reactions _ occurring in the steam reforming reaction of methanol._
Methanol conversion reactions Theoretically possible degrees of conversion of the starting reagents in per- centageof unit
300 400 500 600 700 800 900
CHsOH+H2O=CO2+3H2 0,66 0,95 0,99 1 1 1 1
CHBOH=CO+2H2 0,02 0,52 1 1 1 1 1
CO+H2O=CO2+H2 1 0,98 0,92 0,84 0,75 0,67 0,60
2CHSOH=(CH3)2O+H2O 0 0 0 0 0 0 0
2CHbOH=CH4+2H2+CO2 1 1 1 1 1 1 1
CHsOH=CH2O+H2 0 0 0,03 0,17 0,53 0,86 0,96
As can be seen from table 3, the theoretically possible yields of hydrogen, carbon monoxide, and formaldehyde increase with increasing reaction temperature and reach almost 100% at a temperature of 900 K. Table 3 also shows that the theoretically possible yields of methane,diethyl ether in the entire methanol studied are 0 and 100%, respectively.
Thus, based on the thermodynamic calculations, it can be said that it is prefereble to carry out the steam reforming of methanol into hydrogen at temperatures above 600 K.
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RESEARCH OF COMPLEX FORMATION IN THE ME - PGMG SYSTEM
Obushenko T.
Senior Lecturer National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute» Tolstopalova N.
PhD, Associate Professor National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute»
Matusevych I.
Student National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute»
ДОСЛ1ДЖЕННЯ КОМПЛЕКСОУТВОРЕННЯ У СИСТЕМ1 МЕ -ПГМГ
Обушенко T.I.
старший викладач Нацюнальний технгчний унгверситет Украши «Кшвський полтехтчний унгверситет гменг1горя Сгкорського»
Толстопалова Н.М.
Кандидат техтчних наук, доцент Нацюнальний технгчний унгверситет Украши «Кшвський полтехтчний унгверситет гменг 1горя Сгкорського»
Матусевич I.B. студентка
Нацюнальний технгчний унгверситет Украши «Кшвський полтехтчний унгверситет гменг 1горя Сгкорського»
Abstract
Interactions of biocide reagent polyhexamethyleneguanidine (PGMG) with heavy metal ions were studied in this work. Researches were made on model solutions with the concentrations of heavy metals 10-1 mol/dm3 - 10-2 mol/dm3. Composition of the complex compound of metals with PGMG was established.
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