Suleymanova G.N., Efendi A.C., Novruzov N.N.
STUDY OF THE ACTIVITIES OF NEW CATALYTIC SYSTEMS IN THE OXIDATIVE DEHYDROGENATION REACTION OF METHANOL *
Аннотация:
as we mentioned, many catalytic systems are active in the oxidative dehydrogenation and dehydration reactions of methanol, but the number of catalysts capable of purposefully converting methanol into formaldehyde is relatively limited. Most catalytic systems are highly active in the conversion of methanol to formaldehyde. In this regard, as can be seen from the analysis of literature materials, there is a need to create a number of new catalytic systems
Ключевые слова:
methanol, formaldehyde, zirconium, vanadium, molybdenum, alloy, catalysts
Introduction. The fact that our country has large hydrocarbon reserves makes it important to purchase important organic compounds that are widely used based on them. In recent times, especially the discovery and commissioning of new oil and gas fields, many production areas have been created based on this raw material base. In this regard, the commissioning of the "Methanol" plant with a large production capacity in our republic is commendable.
In addition to the sale of methanol as a raw material, which is a product of the methanol plant, it is considered appropriate to convert it into very valuable substances, including very valuable dimethoxymethane, widely used formaldehyde, acetic acid, dimethyl ether, dimethyl carbonate, methyl tributyl ether, and methyl formate as an additive to fuels.
Synthesis, selection and determination of activity of new catalytic systems for catalytic oxidation of methanol to formaldehyde, dimethyl ether and other valuable compounds are considered to be urgent problems. Synthesis of new catalytic systems based on vanadium, molybdenum, zirconium, cobalt, iron for the conversion of methanol to formaldehyde, determination of their activity and kinetic regularities of the process.
Methanol (СH3OH), which can be obtained from the conversion of natural gas, has a large reserve in our country, so there is a methanol plant with a production capacity of about 600,000 tons. Recently, metal oxides (Ni, Co, Sb, V) deposited on various carriers (Al2O3, SiO2, MgO), which are widely used for the thermocatalytic decomposition of methane, have shown high activity.
Currently, the production of formaldehyde from methanol is carried out with the presence of Ag and iron-molybdate catalysts. Various catalytic systems and alloys containing metallic Ag and silver allow the oxidative dehydrogenation of formaldehyde at high temperature (950–1000 K) and pressure. The main disadvantages of these processes are that they are carried out at high temperature and pressure, although the conversion of methanol is very low. In order to perform the dehydrogenation of methanol to formaldehyde, many catalytic systems containing copper were obtained and their activities were tested. Although it was possible to increase the stability of the catalyst by adding Zn, Se to the catalyst, the conversion of methanol at 900 K did not exceed 10–15%, although the yield of formalin reached 60–68%.
Experimental part. Based on the known information, a number of catalysts were synthesized and brief information about their initial activities was given. Initially, in order to obtain alloys of V, Mo, Fe with Zr with different composition, their samples were taken at different atomic weights and melted together in the furnace. For example: Az(Zr)=91.224, Az(Mo)=95.94, M(ZrMo2)=91.224+2.95.94=283.104 for obtaining ZrMo2 intermetallics. In this composition, Mo=67.8%, Zr=32.2%. After synthesizing catalyst alloys, modern physico-chemical analysis methods were used to determine the composition of their samples. Initially, all samples were studied by irradiation of their composition using the RFA method of X-ray phase analysis.
In order to determine the activities of the obtained alloy and other catalyst samples, we place their amounts of 0.2 g and 0.3 g in pulse and open flow reactors, respectively. The experiment in the device operating in the open flow mode is carried out in the following sequence. By means of a stream of purified nitrogen (1), methanol vapors are supplied to the mixer (5), which enters the purified oxygen (1) by passing through the saturator (4). The temperature of the mixer is maintained at a constant temperature by a thermostat (10). Then, this mixture enters the reactor placed in the heating furnace (11) and is heated to the reaction temperature, and a stationary mode is obtained for 20-30 minutes. After that, the reaction products from the reactor are directed to the analysis by taking a sample for the chromatograph by means of a six-pass faucet. The other part of the reaction products is released and collected. The reaction temperature in the reactor is regulated by means of a thermocouple placed there. At the same time, the flow rate is regulated by controlling the O2:N2 ratio, the methanol flow rate, and the PCH:PO2 ratio.
Catalyst samples were analyzed by X-ray diffraction (XRD) using Rigoku Mini Flex 600 (K 1.5 4060 Å) CuK α-irradiating Ni-filter and diffractometer Bruker "D2 Phaser" as well as CuK α-irradiating DRON-2 device.
Based on the results of the X-ray diffractometric analysis, it can be said that zirconium is mainly present in the oxidized phase on the surface of the catalysts (Figure 1).
As can be seen from the X-ray image (Fig. 1), peaks 2θ=30.00 in the X-ray image of the initially synthesized ZrV0.3 sample (Fig. 1 a), 35.70, 51,590, 62.30, 67.50, which can be in both monoclinic and tetragonal structure of ZrO2. ZrO2 (JCPDS:37-1434, 17-923) 2θ=32.00, 35,680, 40.09, 54,750 peaks indicate the presence of metallic zirconium (JCPDS%5-665). Thus, in this initial sample, mainly metallic Zr and m-ZrO2, t-ZrO2 are observed, and vanadium oxides are generally absent. Only after treatment with O2 in air for 1 h at 873 K, phase changes occur in the sample (Figure 1 b, Tables 1–2), which leads to a decrease in catalytic activity.
Номер журнала Вестник науки №4 (73) том 3
Ссылка для цитирования:
Suleymanova G.N., Efendi A.C., Novruzov N.N. STUDY OF THE ACTIVITIES OF NEW CATALYTIC SYSTEMS IN THE OXIDATIVE DEHYDROGENATION REACTION OF METHANOL // Вестник науки №4 (73) том 3. С. 581 - 591. 2024 г. ISSN 2712-8849 // Электронный ресурс: https://www.вестник-науки.рф/article/13999 (дата обращения: 19.05.2024 г.)
Вестник науки СМИ ЭЛ № ФС 77 - 84401 © 2024. 16+