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CHEMICAL PROBLEMS 2023 no. 2 (21) ISSN 2221-8688
UDC 544.478.12
DEPENDENCE OF THE ACTIVITY OF Ce-Zn-O CATALYSTS IN THE REACTION OF THE CONVERSION OF ETHANOL INTO ACETONE ON THE ACIDIC PROPERTIES
OF THE SURFACE
T.Ch. Taghi, I.J. Ahmadova, V.L. Baghiyev
Azerbaijan State Oil and Industry University, Azadlyg 20, Baku, AZ-1010, Azerbaijan e-mail: [email protected]
Received 25.02.2023 Accepted 08.04.2023
Abstract: The reaction of ethanol conversion to acetone on binary cerium-zinc oxide catalysts has been studied. It has been established that the reaction products of the conversion of ethyl alcohol on binary cerium-zinc oxide catalysts are ethylene, acetaldehyde, acetone, carbon dioxide and, at high temperatures, destructive decomposition products. The highest yield of acetone is observed on samples rich in zinc at temperatures of the order of 450-550°C, while catalysts rich in cerium are active in the reaction of dehydration of ethanol to ethylene. In this work, the acid properties of cerium-zinc oxide catalysts were evaluated by their activity in the isomerization of butene-1 to trans and cis butenes-2. It was found that cerium-rich catalysts are active in butene-1 isomerization reaction. The activities of cerium-zinc oxide catalysts in the reactions of the conversion of ethanol to acetone and the isomerization of butene-1 into trans and cis butenes-2 are compared. It was found that the reaction of the conversion of ethanol to acetone proceeds on the centers of the basic nature, and the formation of ethylene proceeds on the centers of the acidic nature.
Keywords: Ethanol, acetone, binary catalysts, butene-1 isomerization, zinc oxide, cerium oxide. DOI: 10.32737/2221-8688-2023-2-146-152
Introduction
Acetone is one of the most important monomers widely used in the chemical industry. One of the possible methods for obtaining acetone is the reaction of the vapor phase conversion of ethanol [1, 2]. The promise of this method for obtaining acetone lies in the fact that ethanol is a renewable raw material and is obtained in large quantities from vegetable raw materials [3,4]. In this regard, the creation of active and selective catalysts for this process is a very important issue for the chemical industry. It is known from periodic literature that catalysts based on zinc oxide exhibit a high activity of the reaction of the conversion of ethanol to acetone [5, 6]. In this regard, we previously studied the effect of cerium oxide on the activity of zinc oxide in the reaction of the conversion of ethanol to acetone [7]. It was
found that binary cerium-zinc catalysts exhibit a fairly high activity in the reaction of the conversion of ethanol to acetone. It is known that the surface properties of the catalyst affect their catalytic activity. One of the surface properties of a catalyst that can have a strong influence on their activity is acid-base properties [8-10]. To assess the acid-base properties of a surface under conditions close to real catalytic reactions, some catalytic reactions are widely used as model ones [11-13]. Due to the ease of implementation, the measurement of the activity of catalysts for the reaction of isomerization of butene-1 to cis and trans butenes-2 is most often used for these purposes [14, 15]. Earlier, we studied the acid surface properties of binary tungsten-containing catalysts by their activity in the reaction of
CHEMICAL PROBLEMS 2023 no. 2 (21)
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isomerization of butene-1 into trans and cis butenes-2 [16]. A continuation of these studies is the present paper where, we compared the activity of cerium-zinc oxide catalysts in the
reactions of the conversion of ethanol to acetone and the isomerization of butene-1 into trans and cis butenes-2.
Experimental technique
Binary cerium-zinc oxide catalysts of various compositions were prepared by coprecipitation of aqueous solutions of cerium and zinc nitrates. The resulting mixture was evaporated at 95-100°C, dried at 100-120°C, and calcined at 250-350°C until nitrogen oxides were completely released. The resulting solid mass was calcined at 700oC for 10 hours. Thus, we synthesized nine binary cerium-zinc oxide catalysts of various compositions from Ce-Zn=1-9 to Ce-Zn=9-1. The activity of the synthesized catalysts in the reaction of the conversion of ethanol to acetone was studied on a flow unit with a quartz reactor in the temperature range of 250-700°C. The volumetric feed rate of the raw material was 1800 h-1. The ratio of ethanol : steam : nitrogen was 1:1:8. The reactor was loaded with 5 ml of the studied catalyst 1.0-2.0 mm in size, and its activity in the ethanol steam reforming reaction
was studied. The yields of ethanol conversion products, as well as the amount of unreacted ethanol, were determined on a chromatograph with a flame ionization detector and a 2-m column filled with a specially treated Polysorb-
1 sorbent. The amount of carbon dioxide formed was determined on a chromatograph with a 6-meter column filled with a Celite sorbent coated with Vaseline oil. The isomerization reaction of butene-1 to butene-2 was carried out at a feed space velocity of 1200 h-1, in the temperature range of 150-400°C. The reactor was loaded with 5 ml of a catalyst with grains of 1 -2 mm, and a reaction mixture of butene-1 and nitrogen was fed. The ratio of butene-1 to nitrogen was 1:9. The analysis of the mixture of unreacted butene-1 and the resulting trans and cis butenes-
2 was carried out by chromatography using a 5-meter column filled with celite coated with Vaseline oil.
Results and discussions
The results of the experiments showed that the reaction products of the conversion of ethyl alcohol on binary cerium-zinc oxide catalysts are ethylene, acetaldehyde, acetone, carbon dioxide and, at high temperatures, destructive decomposition products. We have studied the effect of temperature on the yields of reaction products. As an example, Table 1 shows the results of a study of the oxidation reaction of ethanol on the catalyst Ce-Zn=2-8. As can be seen, the conversion of ethanol on this catalyst begins at a temperature of 300°C. At this temperature, 0.8% acetaldehyde is
formed. With increasing temperature, the yield of acetaldehyde increases and at 400°C reaches its maximum value of 8.8%, after which it decreases to 2.8% at 450°C. The formation of ethylene and acetone begins at 350°C, their yields at this temperature are 1.2% and 3.1%, respectively. With an increase in the reaction temperature, the yield of acetone passes through a maximum at a temperature of 500°C (63.7%). The yield of carbon dioxide increases throughout the studied temperature range and at 550°C is 9.9%. The ethanol conversion on this sample reaches 89.8% at 550°C.
Table 1. Conversion of ethanol to acetone on the catalyst Ce-Zn=2-8
Temperature, °C Yie lds of the reaction products, % Selectivity by acetone, % Conversion, %
CO2 C2H4 CH3CHO CH3COCH3
300 0 0,8 0 0 0,8
350 1,2 0 6,3 3,1 29,3 10,6
400 2,5 1,1 8,8 13,3 51,8 25,7
450 8,1 9,9 2,8 47,5 69,5 68,3
500 9,5 14,5 0 63,7 72,6 87,7
550 9,9 23,9 55,2 61,5 89,8
The activity of binary cerium-zinc oxide catalysts also depends on the atomic ratio of cerium to zinc. Table 2 shows the dependences of the yields of the reaction products of the vapor phase conversion of ethanol on the Ce/Zn atomic ratio at a temperature of 350°C. As can be seen from Table 2, with an increase in the atomic ratio of cerium to zinc, the yield of acetone at first does not change, and then, starting from the Ce-Zn=6-4 sample, it begins to increase and reaches 27.3% for the Ce-Zn=8-2 sample. The yield of acetaldehyde decreases
A different picture of the dependence of the yields of ethanol conversion products on the composition of the catalysts is observed at higher temperatures. Table 3 shows the dependences of the yields of reaction products on the Ce/Zn atomic ratio in catalyst samples at 500°C. As can be seen from Figure 3, the dependences of ethanol conversion and acetone yield on the atomic ratio of cerium to zinc have two maxima on the catalysts Ce-Zn=2-8 and Ce-
with an increase in the atomic ratio of cerium to zinc, and its formation is practically not observed on samples with a Ce/Zn atomic ratio above 4/6. The yields of carbon dioxide and ethylene increase with an increase in the atomic ratio of cerium to zinc. It can be seen from the obtained results that at 350°C the maximum yields of carbon dioxide and ethylene are 7.3 and 5%, respectively. The maximum conversion of ethanol at a given temperature is observed on a sample with a ratio of Ce-Zn=8-2 and reaches 38.3%.
Zn=7-3. The maximum conversion of ethanol is observed on the sample Ce-Zn=2-8 and is 87.7%. The highest yield of acetone is also observed on the Ce-Zn=2-8 sample and is equal to 63.7%. The yield of carbon dioxide slightly increases with an increase in the atomic ratio of cerium to zinc and varies between 8.1% and 14.7. Ethylene yield tends to increase with increasing Ce/Zn atomic ratio and varies from 14.5% to 37.8%.
Table 3. Dependences of the yields of ethanol conversion products on the atomic ratio of cerium to
zinc. T= 500^
Atomic ratio Ce/Zn 1:9 2:8 3-7 4:6 5:5 6:4 7:3 8:2 9:1
Reaction products Reaction product yields, %
CO2 8,9 9,5 8,1 13,1 9,8 13,4 14,7 13,7 12,2
C2H4 20,3 14,5 22,1 30,5 21,9 34,2 37,8 36,4 35,5
CH3CHO 0 0 6 0 0 0 0 0 0
CH3COCH3 46,9 63,7 40,4 27,3 24,6 24,8 30,4 22,1 15,3
Selectivity by acetone, % 61,6 72,6 52,7 38,5 43,7 34,3 36,6 30,6 23,8
Conversion 76,1 87,7 76,6 70,9 56,3 72,4 82,9 72,2 64,3
Table 2. Dependences of the yields of the products of ethanol conversion on the atomic ratio of
cerium to zinc. Т= 350^
Atomic ratio Ce/Zn 1:9 2:8 3-7 4:6 5:5 6:4 7:3 8:2 9:1
Reaction products Reaction product yields, %
CO2 0 1,2 0,7 3,2 2,6 2,8 4,2 6,3 7,3
C2H4 0 0 0 0 0 1,2 2,3 3,7 5
CH3CHO 8,9 6,3 5,5 0 0 0 0 0 0
CH3COCH3 3,5 3,1 5,4 3,3 2,8 11,2 11,7 27,3 21,9
Selectivity by acetone, % 28,2 29,2 28,4 50,8 51,9 73,7 64,3 71,3 64,0
Conversion 12,4 10,6 11,6 6,5 5,4 15,2 18,2 38,3 34,2
Thus, the conducted studies have shown that the highest yield of acetone is observed on samples rich in zinc at temperatures of the order of 450-550°C. Cerium-rich catalysts are active in the dehydration of ethanol to ethylene.
It is known that the acid-base properties of solid catalysts in heterogeneous catalysis affect their activity and selectivity in many catalytic reactions [16-18]. In this regard, we evaluated the acidic properties of cerium-zinc oxide catalysts by their activity of butene-1 isomerization reaction into trans and cis butenes-2. Figure 1 shows the results of a study
at a temperature of 450°C of the butene-1 isomerization reaction on the studied catalysts. It can be seen that on samples with the atomic ratio Ce-Zn=1-9 and Ce-Zn=2-8, the yields of trans and cis butenes-2 are 3.4 and 3.1%, respectively. With a further increase in the atomic ratio of cerium to zinc, the yields of trans and cis butenes-2 increase and starting from the Ce-Zn=7-3 sample, a sharp increase in the yields of butenes-2 up to almost 50% is observed. It should be noted that the ratio of the yields of trans and cis butenes-2 is approximately equal to unity.
Fig.1. Dependences of the degree of isomerization of butene-1 to butenes-2 on the atomic ratio of
cerium to zinc. T=450°C.
Fig.2. Dependences of the yields of ethanol conversion products on the degree of isomerization of
butene-1 to butenes-2. Т=450°С
In paper [15] it is assumed that the total surface acidity is determined by the total rate of butene-2 formation. At the same time, according to [19] the formation of trans-butene-2 occurs on the Bronsted centers, and the formation of cis-butene-2 on the Lewis acid centers. Thus, based on the results obtained we can say that the isomerization rate of butene-1 (total surface acidity) on cerium-zinc oxide catalysts with increasing atomic ratio of cerium to zinc increases and the surface has approximately the same number of Bronsted and Lewis centers (yields of trans and cis butenes-2 are approximately equal).
Dependences of yields of ethanol conversion reaction products on butene-1
isomerization degree to butenes-2, i.e. on total surface acidity of binary cerium-zinc oxide catalysts are presented in Figure 2. As can be seen from Fig. 2 increasing the activity of cerium-zinc oxide catalysts in butene-1 isomerization reaction (with increase of total acidity) ethylene yield increases, while acetone yield and total ethanol conversion decreases. This suggests that increasing surface acidity leads to a decrease in the reaction rate of vapor-phase conversion of ethanol to the target product - acetone. Based on this, we can say that the reaction of the conversion of ethanol to acetone proceeds on the centers of the basic nature, and the formation of ethylene proceeds on the centers of the acidic nature.
Conclusions
• The highest yield of acetone is observed on samples rich in zinc at temperatures of the order of 450-550°C, while catalysts rich in cerium are active in the reaction of dehydration of ethanol to ethylene. Thus, the highest yield of acetone (63.7%) is observed on the sample Ce-Zn=2-8, while the maximum yield of ethylene (36.4%) is observed on the catalyst Ce-Zn=8-2.
• With increasing total acidity of cerium-zinc
oxide catalysts (with increasing yields of trans and cis butenes-2) ethylene yield increases, while acetone yield and total ethanol conversion decreases. Based on this we can say that the reaction of conversion of ethanol to acetone proceeds on the centers of basic nature, while the formation of ethylene proceeds on the centers of acid nature.
References
1. Adriana F.F.de Lima, Carla R.Moreira, Odivaldo C.Alves, Roberto R.de Avillez, Fatima M.Z.Zotin, Lucia G.Appel. Acetone synthesis from ethanol and the Mars and Van Krevelen mechanism using CeO2 and AgCeO2 nanostructured catalysts. Applied Catalysis A: General, 2021, Volume 611, 117949
2. R.Sreerama Murthy, P.Patnaik, P.Sidheswaran, M.Jayamani. Conversion of ethanol to acetone over promoted iron oxide catalysis. Journal of Catalysis, 1988, Volume 109, Issue 2, Pages 298-302
3. Danilo JoseCarvalho, Ricardo Roquetto Moretti, Jorge Luiz Colodette, Waldir Antonio Bizz. Assessment of the self-sustained energy generation of an integrated first- and second-generation ethanol production from sugarcane through the characterization of the hydrolysis process
residues. Energy Conversion and Management, 2020, Volume 203, 112267
4. Amisha Patel, Amita R.Shah. Integrated lignocellulosic biorefinery: Gateway for production of second-generation ethanol and value-added products. Journal of Bioresources and Bioproducts, 2021, Volume 6, Issue 2, Pages 108-128
5. Tsuyoshi Nakajima, Kozo Tanabe, Tsutomu Yamaguchi, Isao Matsuzaki, Shozi Mishima. Conversion of ethanol to acetone over zinc oxide—calcium oxide catalyst optimization of catalyst preparation and reaction conditions and deduction of reaction mechanism. Applied Catalysis, 1989, Volume 52, Issue 3, Pages 237-248
6. Malik M.Mohammed, Nisreen Sabti Mohammed Ali, Hayder A.Alalwan, Alaa H.Alminshid, Haydar A.S.Aljaafari. Synthesis of ZnO-CoO/Al2O3
nanoparticles and its application as a catalyst in ethanol conversion to acetone. Results in Chemistry, 2021, Volume 3, 100249
7. Taghi T.Ch., Baghiyev V.L. Ethanol conversion to acetone on binary Ce-Zn-O catalysts. The Austrian Journal of Technical and Natural Sciences, 2022, N5-6, pp 62-65
8. S.Valange, A.Beauchaud, J.Barrault, Z.Gabelica, M.Daturi, F.Can, Lanthanum oxides for the selective synthesis of phytosterol esters: Correlation between catalytic and acid-base properties, Journal of Catalysis, Volume 251, Issue 1, 2007, Pages 113-122
9. Enrico Sartoretti, Chiara Novara, Angelica Chiodoni, Fabrizio Giorgis, Marco Piumetti, Samir Bensaid, Nunzio Russo, Debora Fino. Nanostructured ceria-based catalysts doped with La and Nd: How acid-base sites and redox properties determine the oxidation mechanisms. Catalysis Today, 2022, Volumes 390-391, Pages 117-134
10. Motoi Sasaki, Kunio Suzuki, Asima Sultana, Masaaki Haneda, Hideaki Hamada. Effect of Acid-Base Properties on the Catalytic Activity of Pt/Al2O3 Based Catalysts for Diesel NO Oxidation. Topics in Catalysis, 2013, Volume 56, pages 205209.
11. M. Guisnet, Model reactions for characterizing the acidity of solid catalysts. Accounts of chemical research, 1990, v.23, N11, p.392-398
12. G. Bourdillon, C. Gueguen, M. Guisnet, Characterization of acid catalysts by means of model reactions: I acid strength necessary for the catalysis of various hydrocarbon reactions. Applied Catalysis, 1990, v.61, 123-139
13. D. Martin, D. Duprez, Evaluation of the acid-base surface properties of several oxides and supported metal catalysts by means of model reactions. Journal of molecular catalysis A, 1997, v.118, 113128
14. Jacques C. Védrine. Acid-base characterization of heterogeneous catalysts: an up-to-date overview, Research on Chemical Intermediates, 2015, v.41, p. 9387-9423.
15. Michel Guisnet, Ludovic Pinard. Characterization of acid-base catalysts through model reactions. Catalysis Reviews, 2018, v.60, i.3, p. 337-436.
16. Aghayeva K.X., Baghiyev V.L. Investigation of the isomerization reaction of butene-1 to butenes-2 on binary tungsten-containing catalysts. Chemical Problems, 2022, v. 20, # 3, pp. 256-260
Ce-Zn-O KATALiZATORLARININ AKTiVLiYiNiN ETANOLUN ASETONA CEVRiLMOSi REAKSiYASINDA S9THiN TUR§U XÜSUSiYY9TL9RlND9N
ASILILIGI
T.£. Tagi, i.C. Ohmadova, V.L. Bagiyev
Azdrbaycan Dövldt Neft vd Sdnaye Universiteti, Azadliq 20, Baki, AZ-1010, Azdrbaycan [email protected]
Xülasa: Binar serium-sink oksid katalizatorlari üzarinda etanolun asetona 9evrilmasi reaksiyasi öyranilmi§dir. Müayyan edilmi§dir ki, etil spirtinin binar serium-sink oksid katalizatorlari üzarinda 9evrilmasi reaksiyasinin mahsullari etilen, sirka aldehidi, aseton, karbon qazi va, yüksak temperaturlarda, destruktiv par9alanma mahsullaridir. Asetonun an yüksak 9iximi sinkla zangin olan nümunalarda 450-550oC temperatur araliginda mü§ahida olunur, halbuki seriumla zangin olan katalizatorlar etanolun etilena dehidratasiyasi reaksiyasinda aktivdir. Bu i§da serium-sink oksid katalizatorlarinin tur§u xüsusiyyatlari buten-1-in trans va sis buten-2-ya izomerla§masi reaksiyasinda aktivliyina göra qiymatlandirilmi§dir. A§kar edilmi§dir ki, seriumla zangin
katalizatorlar buten-1-in izomerla§ma reaksiyasinda aktivdir. Serium-sink oksin katalizatorlarinin etanolun asetona 9evrilmasi reaksiyasinda va buten-1-in trans va sis buten-2-уэ izomerla§masi reaksiyasinda aktivliyi müqayisa olunmu§dur. A§kar edilmi§dir ki, etanolun asetona 9evrilmasi reaksiyasi asas tabiatli, etilenin alinmasi isa tur§u tabiatli markazlarda gedir.
A?ar sözlar: Etanol, aseton, binar katalizatorlar, buten-1-in izomerla§masi, sink oksid, natrium oksid.
ЗАВИСИМОСТЬ АКТИВНОСТИ Ce-Zn-O КАТАЛИЗАТОРОВ В РЕАКЦИИ ПРЕВРАЩЕНИЯ ЭТАНОЛА В АЦЕТОН ОТ КИСЛОТНЫХ СВОЙСТВ
ПОВЕРХНОСТИ
Т.Ч. Таги, И. Дж. Ахмедова, В.Л. Багиев
Азербайджанский государственный университет нефти и промышленности, Пр. Азадлыг 20, Баку, AZ-1010, Азербайджан e-mail: [email protected]
Аннотация: Изучена реакция превращения этанола в ацетон на бинарных церий-цинк оксидных катализаторах. Установлено, что продуктами реакции превращения этилового спирта на бинарных церий-цинк оксидных катализаторах являются этилен, уксусный альдегид, ацетон, углекислый газ и при высоких температурах продукты деструктивного разложения. Наибольший выход ацетона наблюдается на образцах, богатых цинком, при температурах порядка 450-550°С, в то время как катализаторы, богатые церием, активны в реакции дегидратации этанола в этилен. В работе оценены кислотные свойства церий-цинк оксидных катализаторов по их активности в реакции изомеризации бутена-1 в транс и цис бутены-2. Найдено, что катализаторы, богатые церием, активны в реакции изомеризации бутена-1. Сопоставлена активность церий-цинк оксидных катализаторов в реакциях превращения этанола в ацетон и изомеризации бутена-1 в транс и цис бутены-2. Найдено, что реакция превращения этанола в ацетон протекает на центрах основной природы, а образование этилена протекает на центрах кислотной природы.
Ключевые слова: Этанол, ацетон, бинарные катализаторы, изомеризация бутена-1, оксид цинка, оксид церия.
