Format And Type Fonts CCHHEEMMIICCAALL EENNGGIINNEEEERRIINNGG TTRRAANNSSAACCTTIIOONNSS VOL. 45, 2015 A publication of The Italian Association of Chemical Engineering www.aidic.it/cet Guest Editors: Petar Sabev Varbanov, Jiří Jaromír Klemeš, Sharifah Rafidah Wan Alwi, Jun Yow Yong, Xia Liu Copyright © 2015, AIDIC Servizi S.r.l., ISBN 978-88-95608-36-5; ISSN 2283-9216 DOI: 10.3303/CET1545203 Please cite this article as: Zheksenbaeva Z.T., Tungatarova S.A., Baizhumanova T.S., Shaizada E., 2015, Development of technology for catalytic neutralization of toxic impurities of waste gas from industrial enterprises, Chemical Engineering Transactions, 45, 1213-1218 DOI:10.3303/CET1545203 1213 Development of Technology for Catalytic Neutralization of Toxic Impurities of Waste Gas from Industrial Enterprises Zauresh T. Zheksenbaeva, Svetlana A. Tungatarova*, Tolkyn S. Baizhumanova, Erdaulet Shaizada D.V. Sokolsky Institute of Organic Catalysis and Electrochemistry, 142, Kunaev str., Almaty, 050010, Republic of Kazakhstan tungatarova58@mail.ru The results of deep oxidation of toluene on polyoxide nickel-, copper-, chromium-containing catalysts supported on 2 % Ce/θ-Al2O3 are presented in the paper. Effect of process parameters (temperature, space velocity, concentration of toluene in a gaseous mixture) on the completeness conversion of toluene (to CO2 and H2O) on polyoxide catalyst has been studied. Polyoxide Ni-Cu-Cr catalyst supported on 2 % Ce/θ-Al2O3 in oxidation of toluene at space velocity of 5×10 3 h -1 , 723 - 773 K and 320 mg/m 3 toluene content in initial mixture provides 98.8 % toluene conversion to CO2. The presence of CeO2 crystals and X- ray amorphous clusters (d = 20 – 100 Å) of the oxides of metals of variable valence NiO, CuO, and solid solutions of metals CuO (NiO) on the surface of Ni-Cu-Cr/2 % Ce/θ-Al2O3 catalyst calcined at 873 K was installed by X-ray diffraction and electron microscopy. 1. Introduction The problem of chemical safety and sanitary air protection is particularly relevant due to the increase of harmful emissions of industrial enterprises, which have a strong toxic effect. Harmful emissions of the industrial enterprises (paint, furniture, cable, pharmaceutical, printing) and transport are the main pollutants of cities. Many chemical compounds (toluene, xylene, styrene, phenol, tricresol, mineral spirits, CO, etc.), which negatively affect the living organism and flora are harmful toxic emissions from industrial plants. Under the Kyoto agreement from December 1997, in addition to the United Nations Framework Convention on Climate Change (UNFCCC), developed countries and countries with economies in transition have to reduce or stabilize greenhouse gas emissions (Nikolaev, 2008). Large volumes of industrial emissions occur mainly in large cities, where their maximum permissible concentration (MPC) is much higher than the norm. The content of harmful emissions above the MPC in industrial workshops and atmospheric air in the cities cause a negative impact on living organisms and lead to various diseases thereby creates a threat to the safety of the environment (Jecha et al., 2013). Toluene, xylene and ethyl- benzene are major part of the solvents used in various industries, which are present in gaseous emissions (Brattoli et al., 2014). It is known that the sorption (adsorption, absorption) and deep oxidation (catalytic, thermal), as well as their combination are the main methods of utilization and neutralization of gas emissions from impurities of harmful volatile organic compounds. From the literature data (Popova et al., 2006), which presents an overview of methods and apparatuses of neutralization of toxic emissions follows that the most economical way to clean of gases with harmful emissions of complex composition is deep catalytic oxidation. Catalysts based on platinum group metals have high activity at low temperatures, durability, heat resistance and ability to operate stably at high space velocities. Conditions of deficit and high cost of platinum group metals lead to the need to develop new approaches to the creation of highly effective polyoxide catalysts that do not contain noble metals capable exhibit a high thermal stability and poison-resistance and sustainable in the long term operation (Tungatarova et al., 2014). Creation of catalysts for gas purification that do not contain noble metals or containing their small amounts is an important problem at the present time. The use of palladium catalysts with low metal content or 1214 catalysts based on mixed oxides is one of the most promising solutions to this problem. The data on studying the process of deep oxidation of toluene on polyoxide nickel-, copper-, chromium-containing catalysts are presented in this paper. Toluene as the main component of emissions the furniture, cable, footwear and other production has been chosen as model substance of neutralization. 2. Experimental Polyoxide catalysts were prepared by capillary impregnation of alumina modified with cerium by mixed aqueous solutions of metal nitrates by incipient wetness of carrier with subsequent drying under 453 – 473 K (4 – 5 h) and calcination at 873 K (1 – 1.5 h) in air. Ball θ-Al2O3 (manufactured by the Boreskov Institute of Catalysis SB RAS, Novosibirsk) diameter of 3 – 4 mm with surface area of 100 m 2 /g, bulk density of 0.80 g/cm 3 , the mechanical strength of 150 MPa and pore volume of 0.48 cm 3 /g was used as a carrier. θ- Al2O3 was modified by cerium oxide to stabilize the structure and thermal stability. It forms a surface perovskite CeAlO3 type with alumina that is stable up to 1,373 K (Zheksenbaeva et al., 2012). Previously, it was investigated the effect of ratio and concentration of elements on γ-Al2O3 on their efficiency in oxidation of 1 % CO and 0.5 % CH4 in air at space velocity 100×10 3 h -1 (Altynbekova et al., 2000). Variation of the components in mixture of elements allowed optimizing the chemical composition and ratio of elements in the mixed catalyst (in atomic ratio): Ni : Cu : Cr = 1 : 3 : 0.1. Catalyst composition corresponded to the stoichiometry of oxide in the spinel structure. It was shown that 7-10 % catalysts are optimal when the clusters of metal oxides are formed on the surface and complete uniform impregnation of granulated alumina is achieved. Toluene content before and after reaction was analyzed on the Crystal – 2000M chromatograph with a flame ionization detector (24.91 Hz) on a capillary column. Column temperature – 433 K, vaporizer temperature – 513 K, rate of hydrogen - 25 mL/min, rate of air - 250 mL/min. Catalytic activity of catalysts was determined in flow installation at deep oxidation of toluene in air at various temperatures (523 – 773 K), space velocities (5 - 15×10 3 h -1 ) and toluene concentration (320 mg/m 3 ) in the initial mixture (Tungatarova et al., 2012). The phase composition of catalysts was determined by X-ray diffractometer DRON-4.7, Co anode, 25 kV, 25 mA, 2θ – 5 - 80 o (XRD). The BET specific surface area was determined by adsorption method using an Accusorb instrument (Micromeritics, United States) at the low temperature adsorption of N2. The morphology, particle size, chemical composition of the Ni-Cu-Cr catalysts were investigated by a transmission electron microscope EM-125K at 80,000 magnification by the replica method with extraction using a microdiffraction. 3. Results and Discussion 3.1 Investigation of the activity of Ni-, Cu-, Cr-containing catalysts in the reaction of deep oxidation of toluene Figure 1 presents the data obtained in the oxidation of toluene in synthesized nickel-copper-chromium oxide catalysts at 723 K and space velocity 5×10 3 h -1 . The Figure 1 shows that the nickel-copper- chromium-containing polyoxide catalysts of the deep oxidation of toluene by activity are located in the following order: Ni-Cu-Cr/2 % Ce/-Al2O3 (98.8 %) > Ni-Cu-Cr/-Al2O3 (93 %) > Ni-Cu/2 % Се/-Al2O3 (85 %) > Ni-Cr/2 % Се/-Al2O3 (76 %) > Ni/2 % Се/-Al2O3 (57 %). Figure 1: The oxidation of toluene in air on oxide Ni-Cu-Cr containing catalysts: 1 - NiCuCr/2 % Ce/- Al2O3; 2 - NiCuCr/-Al2O3; 3 - NiCu/2 % Ce/-Al2O3; 4 - NiCr/2 % Ce/-Al2O3; 5 - Ni/2 % Ce/-Al2O3 1215 It should be noted that comparison of the activity of multicomponent Ni-Cu-Cr containing catalyst supported on alumina modified by cerium with catalyst supported on alumina without cerium showed that the conversion of toluene on the catalyst Ni-Cu-Cr/2 % Ce/θ-Al2O3 significantly higher (98.8 %) than on the Ni-Cu-Cr/θ-Al2O3 (93 %). Thus, the highest degree of conversion (up to 98.8 %) of toluene was determined on the multicomponent Ni-Cu-Cr/2 % Ce/θ-Al2O3 catalyst supported on alumina modified with cerium, the lowest - on Ni/2 % Ce/θ- Al2O3 contact. Methods of introducing the active components in composition of the Ni-Cu-Cr catalyst for the deep oxidation of toluene to CO2 and H2O were investigated. Methods of supporting of the catalytic active phase showed that sequential introduction the components are not optimal for efficiency of supported Ni-Cu-Cr catalyst. The best result was obtained by simultaneously introducing all components in the impregnation solution (see Table 1). Table 1: Effect of the method of introduction of active components into the Ni-Cu-Cr catalysts supported on Al2O3 on the efficiency in oxidation of toluene in air at 5×10 3 h -1 Method of introducing the components (Ni, Cu, Cr) The degree of conversion, %, at a temperature, K 523 573 673 723 Simultaneous (Ni, Cu, Cr) 73.0 89.0 94.0 98.8 Sequential (first Cr, then the sum of Ni and Cu) Sequential (first Ni, then the sum of Cr and Cu) Sequential (first Ni, then Cu and Cr) 56.0 52.0 50.0 66.0 62.0 61.0 80.0 78.0 75.0 91.0 85.0 82.0 Modification of catalysts with small additions of compound with basic character which are introduced into the impregnating solution (Na2CO3, KOH and NH4HCO3) is one way of obtaining the catalysts with uniform distribution of components. Effect of process parameters (temperature, space velocity, concentration of toluene in gaseous mixture) on the completeness conversion of toluene (to CO2 and H2O) on the Ni-Cu-Cr/2 % Ce/θ-Al2O3 polyoxide catalyst was studied. The degree of oxidation of toluene from the variation of space velocities at different temperatures on the Ni-Cu-Cr/2 % Ce/θ-Al2O3 catalyst are presented in Table 2. It can be seen that with the increase of space velocity from 5×10 3 to 15×10 3 h -1 degree of oxidation of toluene reduces from 98.5 to 89.3 %, respectively. Table 2: Effect of temperature and space velocity on the degree of conversion of toluene on the Ni-Cu-Cr/2 % Ce/θ-Al2O3 catalyst T, K Space velocity, ×10 3 h -1 5 10 15 Degree of conversion of toluene, % 523 73.7 81.0 82.1 573 623 673 723 773 89.5 94.7 97.5 98.5 98.8 85.7 90.5 91.5 93.5 95.2 83.8 85.7 89.3 89.3 89.3 Note: The concentration of toluene in the feed - 320 mg/m 3 Thus, degree of conversion of toluene to CO2 reaches the 98.5 – 98.8 % on the Ni-Cu-Cr/2 % Ce/θ-Al2O3 catalyst at a temperature of 723 – 773 K and space velocity 5×10 3 h -1 . Influence of concentration of toluene in the initial mixture to the efficiency of its conversion on the polyoxide catalysts of various compositions were studied. Table 3 shows that increasing the concentration of toluene from 100 to 320 mg/m 3 in the initial mixture with air leads to a slight decrease in the degree of conversion of toluene on the two component Ni-Cu/2 % Ce/θ-Al2O3 and Cu-Cr/2 % Ce/θ-Al2O3 catalysts. A noticeable decrease in activity among two component oxide catalysts were found on the nickel-chromium- containing catalyst from 76.6 to 73.0 %. Ni-Cu-Cr/2 % Cr/θ-Al2O3 catalyst was the most stable. 1216 Table 3: Effect the content of toluene in the initial mixture with air on degree of its conversion on the various catalysts Catalysts Concentration of toluene, mg/m 3 100 320 Degree of conversion of toluene,% 5%Cu-Cr/2%Ce/θ-Al2O3 68.0 67.9 5%Ni-Cr/2%Ce/θ-Al2O3 5%Ni-Cu/2%Се/θ-Al2O3 9%Ni-Cu-Cr/2%Ce/θ-Al2O3 76.6 85.0 98.5 73.0 84.0 98.8 Note – T – 723 K; GHSV - 5×10 3 h -1 Thus, the optimal conditions of deep oxidation of toluene on oxide Ni-, Cu- and Cr-containing catalysts over 2 % Ce/θ-Al2O3 were determined. Degree of conversion of toluene reaches 98.5 – 98.8 % on the Ni- Cu-Cr/2 % Ce/θ-Al2O3 catalyst at temperatures of 723 – 773 K, GHSV - 5×10 3 h -1 and the concentration of toluene in the initial mixture with air – 100 - 320 mg/m 3 . 3.2 The study of polyoxide catalysts based on Ni-, Cu-, Cr- on 2 % Ce/θ-Al2O3 by X-ray diffraction analysis Table 4 shows the results of determination of the phase composition of initial 2 % Ce/θ-Al2O3 and Ni-Cu-Cr catalysts on 2 % Ce/θ-Al2O3 after preparation under the following conditions: heating temperature - 873 K for 1 h, duration of heating - 5 h at 873 K in air with a consequent increase in temperature to 1,473 K and holding at this temperature for 5 h. Reflections from θ-Al2O3, α-Al2O3 and CeO2 (quantitative evaluation was carried out by reflexes 2.31 Ǻ, 1.74 Ǻ, 1.91 Ǻ, respectively) are present in 2 % Ce/θ-Al2O3, as well as in the carrier. Figure 2 shows dependence of the intensity of CeO2 (1.91 Å), α-Al2O3 (1.74 Å), Ni(Cu)Al2O4 (1.43 Å) and surface area from heating temperature of the Ni-Cu-Cr/2 % Ce/θ-Al2O3 catalyst in air. Intense reflections from the CuO and less intense reflections from the NiO except CeO2 and θ-Al2O3 phases are observed in roentgenograms of the Ni-Cu-Cr/2 % Ce/θ-Al2O3 heated at 873 K. Not only crystallization of CeO2 occurs as a result of heating of the Ni-Cu-Cr/2 % Ce/θ-Al2O3 catalyst but the content of α-Al2O3 increases sharply, starting from 1,273 K. Significant decrease in the total surface of catalysts takes place due to this process at heating. CeO2 crystallization process occurs to a lesser degree due to the low content of cerium (only in the carrier). Promotion of the Ni-Cu-Cr catalyst by Pt and Pd also contributes the phase transformations in catalyst under heating. Weak reflections from the NiО, Ce6O11 as well as NiAl10O16 are available in the X-ray data except crystal CeO2, α-Al2O3, CuO, Ni(Cu)Al2O4. Thus, based on the XRD data the presence of CeO2 crystals and X-ray amorphous clusters (d = 20 – 100 Å) of oxides of variable valence metals NiO, CuO as well as solid solutions of metals CuO (NiO) was recorded during the synthesis of catalyst after heating at 873 K on the carrier surface. Figure 2: Dependence of the intensity of CeO2 (1.91 Å), α-Al2O3 (1.74 Å), Ni(Cu)Al2O4 (1.43 Å) reflexes and the surface area from heating temperature in air for the catalyst Ni-Cu-Cr/2 % Ce/θ-Al2O3: 1 - Cu(Ni)Al2O4 (reflex 1.43 Å), 2 - relative content of α-Al2O3 (reflex 1.74 Å), 3 - relative content of CeO2 (reflex 1.91 Å), 4 - surface area Phase transformations occur in the Ni-Cu-Cr catalyst upon heating in air above 1,273 K. Metal oxides react with alumina to form an aluminate MeAl2O4 type with d = 200 – 1,000 Å. Wherein the surface decreases sharply to 2.5 m 2 (Grigor’eva et al., 2002). 1217 Table 4: Results of the XRD analysis of polyoxide Ni-Cu-Cr catalysts supported on 2 % Ce/θ-Al2O3 Catalysts Promoter, % Theating, K CeO2, 1.91 Å -Al2O3, 1.74 Ǻ -Al2O3, 2.31 Ǻ NiAl2O4, CuAl2O4, 1.43 Ǻ Less intensive phase Ni1Cu3Cr0.1 873 13 37 10 - CuO (2.51, 2.31, 1.85) NiO (2.08, 2.42, 1,48) 1,273 58 158 5 90 1,473 30 120 3 105 0.3 Pt 873 10 9 22 - CuO, Al2O3 (2.12), NiO (2.42) 0.1 Pt 873 14 20 - - CuO, Al2O3 (2.12), Ce6O11, Cr5O12 (3.57) 0.1 Pt 1,073 26 20 10 10 CuO, NiO, Ce6O11, Al2O3 0.3 Pt 1,473 52 166 5 70 0.05 Pd 873 20 13 7 7 CuO, Ce6O11, Al2O3 (2.12) 0.05 Pd 1,273 45 148 2 55 Pd (2.25) 0.05 Pd 1,473 60 177 5 105 NiAl10O16 (1.99) 3.3 The study of multicomponent oxide catalysts based on NiCuCr over 2 % Ce/θ-Al2O3 by electron microscopy The morphology of the Ni-Cu-Cr catalysts was examined by a transmission electron microscopy at increasing components in the Ni-Cu-Cr catalyst. It was found that single, double and triple metal oxides are formed during complication of composition of the Ni-Cu-Cr catalysts, the particle size of which decreases from 50 - 80 Å (Ce/Al2O3) to 20 - 30 Å (Ni-Cu-Cr). From the data of electron microscopy and microdiffraction (Table 5) is seen that the catalysts contain mainly nanoparticles of oxides (20 – 100 Ǻ) and mixtures thereof, as well as larger, dense particles of aluminates AB2O4 and ABO3 types with size of 200 – 300 Ǻ after heating at 873 K. When introducing of the Pt or Pd in Ni-Cu-Cr catalyst was also formed two types of particles: fine oxides (60 – 150 Ǻ) and larger aluminates in the case of promotion by Pd with d > 1,000 Ǻ, especially by heating to 1,473 K. Most of the particles is finely dispersed at promotion by platinum, which grow in size to 200 – 500 Ǻ after heating at 1,473 K due to formation of aluminates and chromates. The relative content of large particles of metals aluminates in the Ni-Cu-Cr catalysts increases at promotion by Pt and Pd, and at the high-temperature heating. Table 5: Data of electron microscopy studies of polyoxide Ni-Cu-Cr catalysts supported on 2 % Ce/θ-Al2O3 Catalysts Theating, K Particle size, Ǻ Diffraction data Ni1-Cu3-Cr0,1 873 1,473 20 – 30 20 – 100 > 200 NiCr2O4, CuCrO4, CuAl2O4, CuAlO4, NiAl2O4, CrO2, Cr2O3,CuAlO2, AlCu, NiCrO4, Cr2O3 CuAl2O4, NiAl2O4, CeAlO3 Ni1-Cu3-Cr0,1+Pd 873 100 oxides of Cu, Ni, Cr; CeO2 200 – 500 (flakes) aluminates of Cu, Ni; CuCr2O4, PdO, Ce2O3, CrO2, NiCrO3 CuAl2O4, CuCr2O4, 1,473 > 1,000 NiCrO3, CeAlO3, oxides of Cu, Ni, Cr, NiAl26O42Cu2O, Ni2O Ni1-Cu3-Cr0,1+Pt 873 60 - 150 oxides of Cu, Ni, Cr, Pt Cu2O, Ni2O, PtO, NiAl2O3 1,473 200 – 500 (dispersion, enlargement) CuAl2O4, CrO4, Cr2O3, Ni2O3 Cu2O, Pt, NiCrO4, Ni2O Thus, nanoparticles of metal oxides or their mixtures are formed in the initial oxide Ni-Cu-Cr catalyst after decomposition of metals nitrate at 873 K according to electron microscopy and microdiffraction. Process of interaction of elements with the carrier θ-Al2O3 to form larger aluminates of copper and nickel AB2O4 or ABO3 types occurs with increasing temperature (Komashko et al., 2002). 1218 4. Conclusions Polyoxide supported Ni-Cu-Cr/2 % Ce/θ-Al2O3 catalyst with desired properties for deep oxidation of hydrocarbons - toluene, xylene, styrene, ethyl acetate, butyl acetate, isobutanol, formaldehyde, acetone, ethanol and others who have severe toxic effects on a living organism and flora was developed. It has been shown that the synthesized polyoxide Ni-Cu-Cr catalyst supported on 2 % Ce/θ-Al2O3 provides 98.8% toluene conversion to CO2 at space velocity of 5×10 3 h -1 , temperature of 723 – 773 K and 320 mg/ m 3 content of toluene in the feed mixture. By X-ray diffraction and electron microscopy was established the presence of CeO2 crystals and X-ray amorphous clusters (d = 20 - 100 Å) of the oxides of transition metals NiO, CuO, as well as solid solutions of metals CuO (NiO) on the surface of Ni-Cu-Cr/2 % Ce/θ-Al2O3 catalyst prepared by impregnation method and calcined at 873 K. Phase transformations occur in the Ni-Cu-Cr catalyst at heating above 1,273 K in air: metal oxides react with alumina with the formation of aluminates MeAl2O4 type with d = 200 – 1,000 Å with simultaneous decrease of specific surface area. References Jecha D., Martinec J., Brummer V., Stehlík P., Leštinský P., 2013, Modernization of unit for elimination of VOCs by catalytic oxidation, Chemical Engineering Transactions, 35, 745-750. Nikolaev S., 2008, Kyoto Protocol and joint implementation projects, Energy: Economics Technology, and Ecology, 6, 30-36 (in Russian). 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