CC BY
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AZ9RBAYCAN KIMYA JURNALI № 4 2017
UDC 661.21; 658.567; 669.054.8 PROCESSING OF GASEOUS SULPHUR CONTAINING INORGANIC COMPOUNDS
WITH EXTRACTION OF SULPHUR
S.T.Jafarova, E.B.Gahramanova, A.I.Agayev, M.M.Ahmadov
M.Nagiyev Institute of Catalysis and Inorganic Chemistry, NAS of Azerbaijan
rsevil 7@gmail.com Received 14.02.2017
The catalyst on the basis of red mud of aluminum production was developed and studied in target process for processing process of sulphur containing inorganic compounds (H2S+COS) by extraction of sulphur. The influence of mineralogical composition of red mud, component composition of catalysts, preliminary reduction processing on the activity was investigated. It was established that catalyst red mud-bentonite has a high working temperature range (225-3000C) at rate volumes of 500-1000 h-1. Under selected conditions the extraction process of sulphur was 90.9-93.7% at 1000 h-1.
Keywords: sulphur, red mud, sulphur gas.
Sulphur containing compounds (H2S, COS, SO2 and others) may belong to both technological gases of different productions (oil-refining, metallurgical and so on) and biogas. Only suphur dioxide is processed, during processing of which construction of production installations of sulphur is economically profitable.
Oxidizing catalytic method of processing hydrogen sulphide containing gases are based on that hydrogen sulphide is a reducer and can be easily oxidized, for example, till elementary sulphur by Claus reaction: 2H2S+SO2~3/nS„+2H2O.
Oxides of Al, Ti, Fe, alkali- and rare-earth elements with different additions are used as catalysts for this process [1, 2]. The principle of selecting catalysts for this redox process is based on mainly, modification of their acid-base properties [3].
All above-mentioned elements are in the section of the composition of aluminum production waste - red mud. Earlier we have studied the possibility of using catalysts prepared on the basis of red mud (RM) and layered montmorillonite - bentonite (RMB), in Claus reaction [4]. Due to availability and high activity of this catalyst it was expedient to perform more detailed investigations.
The aim of this work was the study of influence of different factors (temperature of process, component composition of catalyst, mineralogical composition of red mud) on oxidation process of hydrogen sulphide with sulphur dioxide using catalyst RMB.
Experimental part
Catalytic activity of catalyst RMB in oxidation reaction of hydrogen sulphide with sulphur dioxide was determined at atmospheric pressure in flow installation in quartz reactor with stationary layer of a catalyst. Sulphur containing gas mixture was obtained by reduction of sulphur dioxide with methane, thus obtained gas mixture, firstly, enter condenser (130-1500C), where gaseous sulphur was caught and only then it entered the Claus reactor. It is known that Claus reaction goes strictly according to stoi-chiometry and the best conditions for maximum yield of sulphur is observed at ratio of (H2S+COS)/SO2<2. That's why reduction process of sulphur dioxide with methane was performed in such way that in output of condenser gas mixture preferably comprises hydrogen sulphide and non-reacted sulphur dioxide in the ratio of ~2. To maintain such ratio of interacting components in Claus reactor it was necessary to support the ratio in the first reactor CH4/SO2 = 0.65-0.70. Before each experiment we performed standard testing of samples in reaction medium at 2500C for 4 h. Activity of catalysts was determined according to output of sulphur.
Results and discussion
Firstly, we conducted the researches on detection of activity of catalyst depending on temperature. The composition of gas entering to Claus knot is the following: hydrogen sulphide -13.16-13.8, sulphur dioxide - 6.58-6.6, carbon
oxysulphide - 0.9-0.11, hydrogen - 0.90-1.2, carbon monoxide - 1.94-2.3. Thus, the ratio of (H2S+COS)/SO2 was equal to 2.1. Results are given in Figure 1. As Figure shows slightly more output of sulphur is observed at 25 00C and at this temperature total yield of sulphur 96.8-90.9 % at volume rate of gas mixture 500-1000 h-1, correspondingly. As it is seen, catalyst has a wide working temperature range at different times of a contact. Study of the influence on activity of catalyst of gas load more than 1000 h-1, showed inexpediency of its growth. Correspondingly, 500-1000 h-1 is optimum for it the process.
100 90 80 70 60 50
T3
i* -0 30 20
10
0
1'
1
Z 2
220
240
260
280
300
Temperature, C
Fig. 1. Temperature dependence of sulphur yields in products of oxidation reaction of H2S with sulphur dioxide at different volume rates: 500 (1, 2, 3) and 1000 (1', 2', 3') h-1: 1,1' - S, 2,2' - H2S, 3,3 ' - SO2.
At temperatures of the process 250-3 00° C and volume rate of 500 h-1 in products of reaction COS was absent which is probably explained with the fact that proposed catalyst comprises oxides of alkali and alkali earth metals, that according to literature data facilitates hydrolysis process of the compound. In the work [5] it is shown that at 180-4000C the catalyst comprising compounds Fe, Ni, Co, Cu, Zn, Cr and Mo, coated on Al2O3 or SiO2 or TiO2 combined with sulfates of Ca, Sr, Ba and Mg successfully converts this compound by the reaction:
2COS + SO2~ 2CO2 +1.5 S2 COS + H2O~ CO2 + H2S.
Catalysts with additionally included transition metals (Cr, Ni, Cu, Co) with amount of 6, 9, 12 mas% (when converted to metal oxide) were tested in obtaining of sulphur at 2500C and volume rate of gas mixture of 1000 h-1 (Figure 2).
ox
,ruh lp
lu
s f o
ld iel
£ -
2 3 1 2 3
1 2 3
Cr
Ni
Cu
Co
Fig. 2. Dependence of output of sulphur on catalysts modified by transition metals (Cr, Ni, Cu, Co) in oxidation of H2S sulphur dioxide at 2500C, volume rate of 1000 h-1 on concentration of introduced metals; 1 - 6, 2 - 9, 3 - 12%.
Comparison of the data shows that output of sulphur on the most active modified catalysts and sample of RMB without components is practically similar which is, probably, related to sufficient activity of components of RMB. Besides, after the first stage of Claus the ratio of non-reacted components (H2S/SO2) allows directing gas to the next stage of conversion.
For detection of the influence of component composition and thermal processing conditions of catalysts on oxidation process of hydrogen sulphide we prepared catalysts, the data (some physico-chemical characteristics, activity) of which are given in the Table 1. Activity was determined at 2500C and volume rate of gas mixture 1000 h-1.
To study synergetic effect we also prepared samples of catalysts on the basis of bentonite (natural) (Table 1). Yield of sulphur in this sample makes 75.6 %, which is 15.3% lower than in red mud. Considering that red mud comprises only 10 mas.% of bentonite, and then the influence on its activity can be neglected, however the effect on density of samples is significant.
To study the influence of additional amount of aluminum oxides on the structure of cata-
2
3
1
3
Table 1. Basic characteristics of catalysts
№ Component composition Thermal processing temperature, 0C (reduction with hydrogen at 450-5000C, 5 hours) £ й m <D Ё T3 О i £ сл Рн LOC, Yields of sulphur in reaction products, %
m 3 m <D 2 * СЛ Ö <D H % S H2S SO2
1 Bentonite 600 (-) 24 5.81 75.6 5.1 19.3
2 Red mud, 10% bentonite 450 (-) 450 (+) 1.10 23.75 3.11 90.9 93.7 5.8 6.5 3.3
3 Red mud, 10% bentonite,7% porophore 650 (+) 1.04 16.25 4.25 87.2 7.7 5.1
4 Red mud, НNO3, 10% Al(OH)3 600 (-) 1.05 3.32 6.7 87.2 3.8 8.96
5 Red mud, 10% bentonite, H3PO4 600 (-) 1.06 15.82 2.22 88.7 8.0 3.3
lyst we prepared samples of catalysts and Al(OH)3 with plasticizing component - HNO3 was added into their composition. As well as we obtained catalysts by adding H3PO4 in mixing stage.
As Table shows activity of these samples does not essentially differs from activity of a sample of red mud-bentonite, however, the change of component composition decreases density of samples which is not expedient.
According to the work [6] reductive processing of catalysts increases the activity. To detect this effect some samples were preliminarily reduced with hydrogen. As table shows reduction with hydrogen increases the activity of a catalyst up to 93.7%, since 7 mas.% of porophore in the composition of a sample decreases yield of sulphur to 6.5%.
Thus, the change of component composition of catalyst is inexpedient, but reductive processing increases yield of sulphur up to
94% at 1000 h-1, which can be compared with yield at 500 h-1.
It is known that red mud has an unstable composition, since it is obtained from bauxites with variable composition. Due to unstable composition of red mud samples for preparing catalysts it is necessary to study the influence of different mineralogical composition on the properties of catalysts. For this purpose during investigations we took samples of red mud which were obtained in plants of different years and samples of red mud were prepared and comparative activity of samples in the process was studied. Identical results were obtained, despite various mineralogical composition of red mud. Results of X-ray phase analysis of one of the sample, which showed the activity identical to the other and comprised a compound which was absent in others, were presented in Figure 3.
29
Figure 3. Results of X-ray phase analysis of sample of RMB:
1 - Fe1.696Tio22sO3, 2 - Nao.765(Feo.785Sio.2i5)O2, 3 - Ca3Al2O6, 4 -Al(OH, F)3, 5 - NaU5AlU5Si0,85O4, 6 - Na-Al-Si-O-OH-H2O, 7 -1.0Na2OAl2O31.68SiO21.73H2O
Thus, interpretation of results of X-ray phase analysis shows that this sample comprises, mainly, the compound of iron, aluminum and titanium. Difference of this sample is the presence of phase Al(OH, F)3 under the number 4. Study of comparative characteristics of physico-chemical parameters and catalytic properties of this sample with other samples showed their similarity. This is, probably, explained by the fact that stable basic components of red mud-oxides of iron, aluminum and titanium have catalytic action. High catalytic activity of the sample comprising Al(OH, F)3 conforms to the results of the work [7] in which for this process authors suggest catalytic system Al2O3-AlF3 containing aluminum oxide from 0 to 100%.
Detected PPM
S 4033660 100695
K 2506 208
Ti 498 44
Not Detected
P < 1 66560
CI < 5835
Ca (445
Cr < 26
Mn < 37
Fe ( 86
Co <14
Ni <31
Thus, inconstancy of the composition of RM does not have a negative effect on physico-chemical parameters and catalytic properties of samples of catalysts which is a very important factor.
Catalyst worked for more than 400 h in Claus process at 2500C, CH4/S02=0.65-0.70, volume rate 1000 h-1, and with nitrogen purging after each reactor shutdown without decreasing the activity.
Figure 4 shows an image of elementary sulphur which was obtained in the process and its X-ray-fluorescent spectrometric analysis. Thus, quality of sulphur is equal to the quality of sulphur of 99.85 GOST 127-76.
Fig. 4. Image and results of X-ray-fluorescent spectrometry of sulphur; Ka, Kb - spectral lines of K-series.
Energy, keV
In order to give more concise idea of high activity of the catalyst which was prepared by us, comparative characteristics of catalytic properties of the sample and literature data are presented in the table 2. Investigation of the surface of red mud-bentonite showed that samples have internal channel surface, for example, like in zeolites, that's why comparison of activities in reduction reaction of sulphur dioxide with hydrogen sulphide was conducted also with zeolites.
Activity of clinoptilolite tuff which was modified with iron, is comparable with the activity of the sample of red mud-bentonite. However, its obtaining requires a number of stages and it is not non-waste (nitrogen oxides are thrown into atmosphere), which is not expedient. The sample of red mud-bentonite shows the highest activity while preserving high productivity of the process, preparation process of samples is simple and without hazardous emissions into atmosphere.
Table 2. Comparative characteristics of catalytic activity of samples in oxidation reaction of hydrogen sulphide with sulphur dioxide at 2500C
Sample Modifier (reductive processing) Volume rate, h-1 Yield of sulphur, in % Literature
- (+) 1000 93.7
RMB - (-) 1000 90.9
- (-) 500 96.8
Bauxite of Tikhvinsky deposit - 500 94.4 [9]
Bauxite of Turgay deposit - 890 90 [8]
High-alumina cement - 500 86.7 [6]
Clinoptilolite tuff - 1000 83.3 [6]
Clinoptilolite tuff 10 weight % Fe (+) 1000 93.4 [6]
Thus, on the basis of industrial waste from processing of aluminum containing raw material -red mud it is possible to prepare a catalyst for oxidation process of hydrogen sulphide with sulphur dioxide. To prepare catalysts we selected the preparation technique which is non-waste and based on mechanical mixing of different components excluding hazardous emissions into atmosphere.
References
1. Pat. EP1295848A1. Process for the selective oxidation of H2S to elemental sulphur /Gastec N.V., Berben Pieter Hildegardus, Borsboom Johannes, Geus John Wilhelm, Lagas Jan Adolf. 2003.
2. Pat. 2840295 France. Procede d'elimination du soufre d' un charge contenant de H2S et du benzene, toluene et/ou xylenes / Nedez Christopher, Chapat Jean Francois, Ray Jean Louis. 2003.
3. Pat. 650945. Switzerland. Catalyseur de Claus a base d'oxide de sodium, son procede de fabrication et son d' utilization /Goodboy Kenneth Poul. 1985.
4. Kahramanova Y.B., Ahmadov M.M, Jafarova S.T, Agayev A.I. Study of catalysts synthesized on the
basis of industrial wastes in CH4/SO2 and H2S/SO2 reactions // Azerb. chem. j. 2016. No 1. Р. 74-78.
5. Pat. 2632626 France. Procede pour ameliorer le rendement soufre d' un ensemble de production de soufre a partir d'un gaz acide renferment H2S, ledit ensemble comportant une d'epuration / Kvasnikoff Georqes, Philippe Andre, Unirin Robert. 1989.
6. Ахмедов М.М., Ибрагимов А.А., Аллахверди-ева Х.В., Касимова Н.М. Исследование каталитической активности природного и модифицированного клиноптилолита в процессе Клауса // Азерб. хим. журн. 2004. № 3. С. 22-25.
7. Kowalans. Catalytic activity of the Al2O3-AlF3 system in the Claus reaction // Acta Chim. J. 1983. 114. № 3-4. Р. 255-259.
8. Адливанкина М.А., Кельцев Н.В., Торогешни-ков Н.С., Шумяцкий Ю.И. Изучение каталитической активности цеолитов и боксита в процессе прямого окисления // Тр. Моск. химико-технол. ин-та им. Д.И.Менделеева. 1969. № 60. С. 123-126.
9. Агаев А.И. Получение элементарной серы каталитическим восстановлением кислородсодержащих и влажных сернистых газов: Дис. ... канд. хим. наук. Баку: ИНФХ АН Азерб. ССР. 1987. 164 с.
KUKURDUN QAZVARi KUKURD TЭRKiBLi QEYR^UZVi BiRLЭ§MЭLЭRiNDЭN ЕМАЬ1
YOLU тЭ BЭRPASI
S.T.Cэfэrova, Y.B.Qэhramanova, АЛ.А§ауеу, M.M.Эhmэdov
КикшЛэгЫЬЬ qeyri-uzvi Ыг1э§тэ1эпп кикиМип д1хап1та51 Пэ gedэn ета11 prosesi идип gil-torpaq istehsahnm tu11antlsl о1ап qlrmlzl §1ат эsasmda kata1izator hazlr1anml§ уэ tэdqiq о1ипти§йш\ Qlrmlzl §1атт minera1oji tэrkibi, kata1izator1aпn бncэdэn redшksiya o1шnma1anmn уэ котропеШ: tэrkib1эri on1aпn aktiу1iyinэ tэsiri tэdqiq edi1mi§dir. Миэууэп edi1mi§dir ki, qlrmlzl §1am-bentonit katalizatoru hэcmi surэt (500-1000) s-1 olduqda geni§ temperatшr diapazonunda (225-300)0С ^1эуш Prosesin apan1masl идип seдi1mi;J §эгаМэ kukurdun дlxlml hэcm surэi 1000 s-1 oldugda 90.9-93.7% :Э§Ы1 edir.
Адаг sдzlэr: ЫЫЫ, qlrmm §1ат, ЫЫЫ qazl.
ПЕРЕРАБОТКА СЕРОСОДЕРЖАЩИХ НЕОРГАНИЧЕСКИХ СОЕДИНЕНИЙ
С ИЗВЛЕЧЕНИЕМ СЕРЫ
С.Т.Джафарова, Е.Б.Гахраманова, А.И.Агаев, М.М.Ахмедов
Для процесса переработки серосодержащих неорганических соединений с извлечением серы разработан и исследован в целевом процессе катализатор на основе красного шлама глиноземного производства. Исследовано влияние минералогического состава, компонентного состава катализатора, восстановительной обработки на активность. Установлено, что катализатор красный шлам-бентонит имеет широкий температурный диапазон (225-300)0С работы при объёмных скоростях (500-1000) ч-1. При выбранных условиях проведения процесса извлечение серы при объемной скорости 1000 ч-1 составило 90.9-93.7%.
Ключевые слова: сера, красный шлам, сернистый газ.
