The effect of temperature on the decomposition process of propane-butane mixture at high temperatures

. In the work, the composition of the starting materials and reaction products was checked by the chromatographic method. The purpose of the work is to study the effect of temperature on the decomposition process of the propane-butane mixture at high temperatures. Qualitative analysis was carried out by the method of "witnesses", and quantitative analysis was carried out by the method of internal normalization. Spatial composition analysis was performed on a DRON-4.0 (CuKa - radiation) diffractometer, particle size scanning electron microscopy ((JSM-6380 LV) Scanning Electron (Micscope) and emission electron microscopy (EMV-100BR)). The relative surface area was determined by the BET method. The total pore volume was calculated from the amount of nitrogen adsorbed at peak saturation. Pore size distribution was determined by the BJH (Barrett-Joyner-Halendr) method. The effect of temperature and exposure time on the decomposition of the propane-butane mixture at high temperatures was carried out under the following optimal conditions: the study of the effect of temperature on the yield of products was carried out with an exposure time of 0.12 seconds and a water vapour: reagent ratio of 0.4:1 and a temperature range of 700-900 ℃. The influence of various technological parameters on the process of decomposition of the propane-butane mixture under the influence of temperature in an airless place at high temperature was studied. The increase in temperature and the decrease in the time of the initial substance (reagent) in the reaction zone allows for increasing the output of ethylene from the propane-butane mixture, in which the optimum temperature for the production of lower molecular unsaturated hydrocarbons, i.e. ethylene, propy lene and butylene, is 850 ℃. The catalyst created for the decomposition of a propane-butane mixture


Introduction
Hydrocarbon gases, gasoline mixtures, gas condensates, catalytic reforming, and kerosenegas oil mixtures are considered raw materials of the thermal treatment process at high temperatures.
In countries with insufficient resources of gaseous and light liquid hydrocarbons, medium and heavy oil mixtures and even crude oil are used.Up to 70% of the total volume of ethylene is obtained from raw gas, 85-98% from gasoline and gas residue mixtures [1][2][3][4][5][6][7].
The choice of raw materials is determined by the purpose of heat treatment at high temperatures, as well as the availability of raw materials, their quantity and price.The efficiency of thermal treatment products at high temperatures depends on the quality of raw materials and the technological mode of the device.The choice of raw materials is of great importance and often has a decisive effect on the technical side.The propane-butane mixture is one of the main components of natural, petroleum-satellite gases and is a valuable organic raw material for the production of C2-C4 alkenes, arenes, etc. Zeolite catalysts can be the most promising for converting propane-butane mixture into alkenes and arenes, which show high activity and selectivity in dehydrogenation, decomposition, oligomerization, isomerization and dehydrocyclization reactions of various organic compounds [8,9].
It is generally accepted that the activity and selectivity of microporous zeolites determine their acidity properties and availability [10,11].
High-silica zeolites modified with gallium, zinc, molybdenum and rhenium are the most active [12,13] and selective in the conversion of lower C1-C6 alkanes to liquid hydrocarbons.For example, the maximum liquid hydrocarbon efficiency reached 56 wt.% at 550 ℃ during propane conversion on a 3% Zn/ZSM-5 catalyst.In addition, it was found that the methods of synthesis of high-silica zeolites and the methods of adding modifying additives to zeolite and their nature greatly affect the yield and selectivity of C2-C4 alkenes formation [14][15][16].
The effects of Zn/HZSM-5 synthesis methods on the formation of acidic sites and their catalytic properties were studied [17].
Today, one-step production of ethylene from natural gas (methane), catalytic aromatization of propane-butane mixtures, synthesis of lower alkenes and aromatic hydrocarbons, production of additives that increase the octane number based on synthesis gas from methane, and at the same time, methanol and taking dimethyl ethers and obtaining lower molecular olefins from them, i.e. ethylene, propylene and butylene, is of interest to world scientists.The main method of production of ethylene and propylene is thermal treatment at high temperatures and catalytic cracking processes.The growth rate of consumption of these expensive chemical products significantly exceeds the scale of their production, which forces us to look for other, cheaper and more convenient hydrocarbon raw materials.Such a raw material is natural gas, whose extraction and large-scale use have been predicted for a long time.The most popular and studied method of obtaining chemical products from natural gas is their production by pre-conversion of natural gas into synthesis gas (CО/H2) .

Experimental part
Catalysts created for high-temperature decomposition of propane-butane mixture with mesoporous zeolite obtained by chemical treatment of bentonite contain saturated hydrocarbons from methane to butane and hydrocarbons of the ethylene series from ethylene to butylene.The gas products of the decomposition of propane-butane mixtures were analyzed by gas-liquid chromatography according to GOST 26703-93 under the following optimal conditions: a Kristallux-4000 M chromatograph with a thermal conductivity detector.The separation of С1-С6 hydrocarbons and carbon dioxide was carried out in a column filled with Porapak Q. Conditions for analyzing hydrocarbon content and carbon dioxide in gaseous products of propane-butane mixtures: The carrier gas is helium, and its consumption is 30 ml/min, the column length is 3 m, the column diameter is 3 mm, the detector current is 130 mA, the detector temperature is 220 ℃, and the evapourator temperature is 150 ℃.The analysis of inorganic gaseous products of the conversion of propane-butane mixtures was carried out under the following optimal conditions: the carrier gas is helium, its flow rate is 40 ml/min, the column length is 3 m, the column diameter is 3 mm, the detector current is 120 mA, the detector temperature is 80 ℃, the evapourator temperature is 70 ℃, the column temperature is 70 ℃.Synthesis products were analyzed by gas-liquid chromatography with a flame-ionization detector under the following optimal conditions: Tsvetochrom -15% Lestosil in 545 with the size of stationary liquid phase particles 0.250-0.315nm, glass column 2x0.004 m in size, column temperature 100 ℃, carrier consumption of gas-nitrogen flow is 30 ml/min.Qualitative analysis was carried out by the method of "witnesses", and quantitative analysis was carried out by the method of internal normalization.Spatial composition analysis was performed on a DRON-4.0(CuKa -radiation) diffractometer, particle size scanning electron microscopy ((JSM-6380 LV) Scanning Electron (Micscope) and emission electron microscopy (EMV-100BR)).The relative surface area was determined by the BET method.The total pore volume was calculated from the amount of nitrogen adsorbed at peak saturation.Pore size distribution was determined by the BJH (Barrett-Joyner-Halendr) method.

Checking the acidity centre of catalysts
The acidic characteristics of the samples were studied by the method of thermoprogrammed desorption of ammonia in the automatic chemisorption analyzer USGA-101.For this, a sample of 0.12-0.125g was placed in a quartz reactor and treated as follows: The temperature was raised to 500 ℃ in a helium flow (20 ml/min) at a rate of 20 ℃/min.Heating at this temperature was continued for 1 hour and cooled to 60 ℃.The sample was then kept in a stream of ammonia-nitrogen mixture for 15 min to saturate it with ammonia, and then the sample was cleaned of physically adsorbed ammonia in a stream of helium (30 mL/min) at 100℃ for 1 h.The temperature was then reduced to 60 ℃, and the sample was linearly heated at a rate of 8 ℃/min to 750 ℃ in a helium stream (30/min).The released ammonia was recorded in a catharometer detector.According to this model, one ammonia molecule is adsorbed on one acidic site.Therefore, the amount of desorbed ammonia is equal to the amount of acid centre in the sample.Decomposition of propane-butane mixture conversion at high temperature in the absence of air was carried out under the following optimal conditions: reaction temperature in the range of 600-900 ℃, volume velocity 750-2000 h -1 , exposure time 0.12-0.48seconds, water vapour: initial substance (reagent) 0.2 in a ratio of -0.6:1.CrF3*CoF2*5%NiF2*2%ZrO2*8%Na2SO4 and %CoO*5%NiO*2%ZrO2*8%Na2SO4 were used as catalysts for propane-butane mixture decomposition at high temperatures.Zn, Cr, Ni, Co, Fe, Mg, Mn, H3BO3, and H3PO4 were used as modifiers.The effect of temperature and exposure time on the decomposition of the propane-butane mixture at high temperatures was carried out under the following optimal conditions: the study of the effect of temperature on the yield of products was carried out with an exposure time of 0.12 seconds and a water vapour: reagent ratio of 0.4:1 and a temperature range of 700-900 ℃.The results of the studies are presented in Table 4.It can be seen from Table 4 obtained from the experimental studies and presented that when the temperature is increased from 700 ℃ to 900 ℃, the yield of ethylene produced by the conversion of the propane-butane mixture increases with increasing temperature and reaches the highest value at the temperature of 900 ℃.At the same time, the yield of propylene resulting from the conversion of the propane-butane mixture reaches its highest value at a temperature of 800 ℃, and when the temperature is further increased, the yield of propylene sharply decreases due to the increase in the rate of breaking of bonds between carbon and hydrogen compared to the rate of breaking of bonds between carbon and hydrogen.The results of the research show that with the increase in the process temperature, the conversion rate of the propane-butane mixture increases, along with the yield of side products -hydrogen and methane.

Effect of temperature
When compared with similar yields of products resulting from temperature changes, the catalyst created for the decomposition process of the propane-butane mixture at high temperatures in the presence of a catalyst 5%CoO*5%NiO*2%ZrO2*8%Na2SO4 as a result of the conversion of the propane-butane mixture into lower molecular unsaturated hydrocarbons, i.e. ethylene, propylene and an increase in the total yield of butylene was observed.It was determined that the yield of propylene depends on the increase of the process temperature in the optimal catalyst with the content of 5%CoO*5%NiO*2%ZrO2*8%Na2SO4.In the case of transfer of the process, the formation of propylene occurs only at temperatures above 650 ℃.As a result of the catalytic conversion of the propane-butane mixture, propylene is formed at a temperature of 610 ℃ in an optimal catalyst with a composition of 5%CoO*5%NiO*2%ZrO2*8%Na2SO4.As a result of research, it was found that the rate of decomposition reactions increases when the temperature rises above 710 ℃.As the temperature of the process increases, the yield of substances such as hydrogen and methane increases.However, in the presence of a catalyst designed for the decomposition process of 5%CoO*5%NiO*2%ZrO2*8%Na2SO4 propanebutane mixture at high temperatures, the conversion of the propane-butane mixture has a low yield of solids.The residual matter is mainly formed on the outer surface of the catalysts created for the decomposition process of the propane-butane mixture at high temperatures due to the limited diameter of the mesoporous zeolite channels.
Therefore, the increase in the temperature of the process did not affect the qualitative composition of the products but changed their quantity.

Effect of exposure time
Effect of exposure time of 0.12, 0.24 and 0.48 seconds and water vapour: starting substance ( reagent) was conducted in the temperature range of 600-800 ℃ when the ratio = 0.4:1.The results of the research are presented in Figures 1-8.
Figure 1 shows the data describing the dependence of the initial substance (reagent) conversion rate on exposure time as a result of the high-temperature transformation of the propane-butane mixture on an optimal catalyst with a composition of 5%CoO*5%NiO*2%ZrO2*8%Na2SO4.The data presented in Figure 1 shows that the reaction time increased from 0.12 to 0.48 seconds in the conversion rate of the reagent.At the same time, the highest value of the propane-butane mixture conversion rate of 90.03% was observed at 0.48 seconds of reaction time, i.e., at the reaction time between the catalyst and the reactants and a temperature of 800 ℃.The data presented in Figure 2, similar to the data obtained from the experimental studies presented in Figure 1, show that the conversion rate of the starting substance (reagent) increased with increasing process temperature and exposure time from 0.12 to 0.48 seconds.The highest value of the propane-butane mixture conversion rate of 87.75% was observed at the reaction time of 0.48 seconds, i.e., during the reaction time between the catalyst and the reactants and at a temperature of 800 ℃. the initial substance (reagent) conversion level on exposure time as a result of the hightemperature transformation of the propane-butane mixture in an optimal catalyst with a composition of 5%CrF3*5%CoO*NiO*ZrO2*Na2SO4.Figures 3-5 show the dependence of ethylene, propylene yield, and C2-C4 yield on exposure time as a result of the high-temperature conversion of the propane-butane mixture on an optimal catalyst with a composition of 5%CrF3*5%CoO*NiO*ZrO2*Na2SO4.The data obtained as a result of experimental studies and presented in Figure 3 shows that the increase in exposure time to 0.12 ÷ 0.48 seconds and the temperature range of 610÷750 ℃ increases the yield of ethylene.The highest yield of ethylene at 800 ℃ was: 35.78% in 0.12 seconds, 35.50% in 0.24 seconds, and 32.34% in 0.48 seconds.In Figure 4, in the presence of 5%CrF3*5%CoO*NiO*ZrO2*Na2SO4 catalyst, the highest yield of propylene at a temperature of 600÷750 ℃ was recorded at a reaction time of 0.24 seconds.At 800 ℃, the highest yield of propylene was 18.12% at an exposure time of 0.12 seconds.At the same time, the highest yield of propylene was 15.12% at 0.24 second exposure time and 12.24% at 0.48 second exposure time.The data presented in the experimental study results in Figure 5 shows that the yield of saturated hydrocarbons from ethane to butane was higher in the temperature range of 600-750 ℃ at 0.24 s exposure time compared to the results at 0.12 s and 0.48 s exposure time.
As the temperature increased to 800 ℃, the highest yield of saturated hydrocarbons from ethane to butene was reached at 0.12 second reaction time, i.e. at the reaction time between the catalyst and the reactants and was 57.48%.At the same time, the highest yield of lower molecular unsaturated hydrocarbons, namely ethylene, propylene and butylene, is 52.70% at the reaction time of 0.24 seconds (that is, during the reaction time between the catalyst and the reactants); 46.13% at the reaction time of 0.48 seconds (that is, during the reaction time between the catalyst and the reactants).The greatest catalytic activity of the catalyst created for the decomposition of the 5%CoO*5%NiO*2%ZrO2*8%Na2SO4 propane-butane mixture at high temperatures was shown in the temperature range of 600-750 ℃, during the reaction time of 0.24 seconds, that is, during the reaction time between the catalyst and the reactants.With an increase in temperature to 800℃, the increase in the catalytic activity of the catalyst created for the process of breaking down the 5%CoO*5%NiO*2%ZrO2*8%Na2SO4 propane-butane mixture at high temperatures was recorded at 0.12 seconds of exposure time, that is, during the interaction between the catalyst and the initial substances entering the reaction.According to the data obtained as a result of experimental studies presented in Fig. 6, at 0.24 seconds of reaction time (that is, during the reaction time between the catalyst and the reactants) the yield of ethylene is 33.94%; 31.46% at 0.48 second reaction time (i.e.reaction time between catalyst and reactants).The data presented on the results of the experimental study in Figure 7 shows that the highest yield of propylene was observed at the exposure time of 0.24 seconds in the temperature range of 600-750 ℃.Increasing the temperature to 800 ℃ led to an increase in the propylene yield, but the highest propylene yield of 18.06% was achieved at 0.12 seconds of reaction time, i.e., the reaction time between the catalyst and the reactants.The highest yield of propylene was 16.00% at the reaction time of 0.24 seconds, that is, during the reaction between the catalyst and the reactants, and it was 12.11% at the reaction time of 0.48 seconds, that is, during the reaction between the catalyst and the reactants.From the experimental data presented in Figure 8, it can be seen that increasing the exposure time from 0.12 to 0.24 and 0.48 seconds in the temperature range of 600-750 ℃ led to an increase in the total yield of saturated hydrocarbons from ethane to butene.During the reaction time of 0.24 seconds, i.e. during the reaction between the catalyst and the reactants, the highest yield of lower molecular unsaturated hydrocarbons, namely ethylene, propylene and butylene at 800 ℃ is 55.16%, during the 0.12 second reaction time, i.e. the reaction between the catalyst and the reactants.and 0.48 seconds of reaction time, i.e., during the reaction time between the catalyst and the reactants, were 52.79% and 45.76%, respectively.

Effect of water vapour: reagent (starting substance) ratio
Study of the effect of water vapour: reagent ratio during high-temperature conversion of propane-butane mixture with 5%CoO*5%NiO*2%ZrO2*8%Na2SO4 at a given exposure time of 0.12 seconds, in the temperature range from 600 to 800 ℃ was carried out in the ratio of water vapour: initial substance (reagent) 0.2-0.6:1.Figures 9-12 show the results of the research.In Fig. 9, the catalyst created for the high-temperature decomposition of the propanebutane mixture in 5%CoO*5%NiO*2%ZrO2*8%Na2SO4 shows the conversion rate of the reagent (starting substance) as a result of the high-temperature transformation of the propane-butane mixture: water vapour: 0.2-0.6:1 of the starting substance (reagent) data describing the dependence on the ratio and exposure time of 0.12 seconds are presented.From the experimental data shown in Figure 9, it can be seen that the highest conversion rate of the propane-butane mixture was 82.13% at 800 ℃ when the water vapour: reagent ratio was 0.2-0.6:1.At the same temperature and water vapour: reagent (starting material) ratios of 0.4:1 and 0.6:1, the conversion rate was 78.58% and 38.68%, respectively.Figures 10-12 present data describing the dependence of the total yield of lower molecular unsaturated hydrocarbons, i.e., ethylene, propylene, and butylene, on the ratio of water vapour: initial substance (reagent) of 0.2-0.6:1as a result of the hightemperature transformation of the propane-butane mixture in the 5%CoO*5%NiO*2%ZrO2*8%Na2SO4 catalyst.The data presented in Figure 10 shows that the highest yield of ethylene was obtained at a water vapour: reagent (initiator) ratio of 0.4:1 over the entire temperature range of 600-800 ℃.At 800℃, the highest yield of ethylene was: 35.78% water vapour: reagent ratio 0.4:1, 29.76% water vapour: reagent ratio 0.2:1, and 16, 49% water vapour: initial substance (reagent) in a ratio of 0.6:1.From the data obtained as a result of experimental studies presented in Figure 11, it can be seen that the highest yield of propylene at the ratio of water vapour: starting substance (reagent) of 0.2:1 and the temperature of 600÷800 ℃ was as follows: 19.01%water steam: starting substance (reagent) in the ratio of 0.2:1, 18.05% water steam: starting substance (reagent) in the ratio 0.4:1 and 9.61% water steam: starting substance (reagent) in 0, in a ratio of 6:1.From the data presented in Figure 12, it can be seen that the highest yield of lower molecular unsaturated hydrocarbons, ie, ethylene, propylene, and butylene, was obtained at a water vapour: reagent ratio of 0.4:1.At a temperature of 800 ℃, the highest yield of lower molecular unsaturated hydrocarbons, i.e. ethylene, propylene and butylene, was 57.48%.The highest yield of lower molecular unsaturated hydrocarbons, i.e., ethylene, propylene, and butylene, is 56.16% at a temperature of 800 ℃ and water vapour: reagent ratio of 0.2:1 and water vapour: reagent ratio of 0.6 in the ratio: 1 -28.10%.

Conclusion
Thus, as a result of research on the dependence of the yield of lower olefins, i.e. lower molecular unsaturated hydrocarbons, i.e. ethylene, propylene and butylene, and the degree of conversion of the initial substance (reagent) on the ratio of water vapour: as a result of the high-temperature transformation of the propane-butane mixture in an acceptable catalyst containing 5%CoO*5%NiO*2%ZrO2*8%Na2SO4, we came to the following conclusion It can be concluded that the ratio of water vapour: starting substance (reagent) from 0.2:1 to 0.4:1 does not increase the conversion level of the starting substance (reagent), but by reducing the process of formation of lower molecular unsaturated hydrocarbons, i.e. ethylene, propylene and leads to an increase in the yield of butylene.
Increasing the steam: reagent ratio to 0.6:1 did not increase the yield of lower olefins or increase the conversion rate of the propane-butane mixture in the 5%CoO*5%NiO*2%ZrO2*8%Na2SO4 propane-butane mixture catalyst developed for the high-temperature cracking process of mesoporous zeolite.In this regard, the optimal ratio of water vapours: initial substance (reagent) was calculated to be 0.4:1.

Fig. 1 .
Fig. 1.Dependence of reaction time on the reaction time of initial substance (reagent) conversion rate as a result of the high-temperature transformation of the propane-butane mixture in an optimal catalyst containing 5%CrF3*5%CoO*NiO*ZrO2*Na2SO4

Fig. 3 .
Fig. 3. Dependence of reaction time on the reaction time of initial substance (reagent) conversion rate as a result of the high-temperature transformation of the propane-butane mixture in an optimal catalyst containing 5%CrF3*5%CoO*NiO*ZrO2*Na2SO4

E3SFig. 5 .
Fig. 5. Dependence of reaction time on the yield of olefins from ethylene to butylene as a result of the high-temperature conversion of the propane-butane mixture on an optimal catalyst with a composition of 5%CrF3*5%CoO*NiO*ZrO2*Na2SO4

Fig. 6 .
Fig. 6.Dependence of exposure time of ethylene yield as a result of the high-temperature conversion of the propane-butane mixture on an optimal catalyst containing 5%CoO*5%NiO*2%ZrO2*8%Na2SO4

Fig. 7 .
Fig. 7. Dependence of exposure time of propylene yield as a result of the high-temperature conversion of the propane-butane mixture on optimal catalyst containing 5%CoO*5%NiO*2%ZrO2*8%Na2SO4

Fig. 8 .
Fig. 8. Dependence of reaction time on the total yield of olefins from ethylene to butylene as a result of the high-temperature conversion of the propane-butane mixture on an optimal catalyst containing 5%CoO*5%NiO*2%ZrO2*8%Na2SO4

Fig. 12 .
Fig.12.Dependence of reagent (starting material): water ratio on the total yield of olefins from ethylene to butylene in the high-temperature conversion of the propane-butane mixture in an optimal 5%CoO*5%NiO*2%ZrO2*8%Na2SO4 catalyst

Table 1 .
The composition of the propane-butane mixture

Table 2 .
Physico-chemical and physicomechanical properties of catalysts created for the decomposition process of the propane-butane mixture at high temperatures

Table 3 .
Properties of catalysts created for the process of decomposition of the propane-butane mixture at high temperatures

Table 4 .
Effect of temperature on the high-temperature decomposition of propane-butane mixtures