CS245543B1 - Process for producing olefins by pyrolysis of hydrocarbons initiated by inorganic compounds - Google Patents

Abstract

The purpose of the solution is the production of olefins such as ethylene, propylene, 1,3-butadiene, isoprene, cyclopentadiene by pyrolysis of hydrocarbons from natural gas, oil and coal processing in the presence of nitrites and nitrates of metals of groups 1 and 2 of the periodic table and phosphorus pentasulfide in an amount of 0.001 to 2.0% by weight. This method valorizes the hydrocarbon raw material to a greater extent into the desired olefins alcohols than before. At the same time, coke formation is suppressed, thereby extending operating cycles. The solution can be used in the field of oil processing and petrochemicals.

Description

The invention relates to a method for producing olefins by pyrolysis of individual hydrocarbons or their mixture, which is initiated by substances of inorganic nature.

Until now, low-molecular olefins such as ethylene and propylene, together with the aromatics BTX, have been among the basic petrochemicals. Olefins are ^currently obtained to a decisive extent by thermal decomposition of hydrocarbons from natural and refinery gases, crude oil and coal processing. Pyrolysis of hydrocarbons to olefins takes place under harsh conditions that are very energy-intensive. Maximum ethylene yields in the case of pyrolysis of primary gasolines are achieved at temperatures of around 820 to 830 C and residence times below 0.3 seconds. Under these conditions, although the operation is in the optimal ethylene regime, the selectivity of the process decreases at the same time. This is manifested by a decrease in the formation, for example, of propylene, which is very desirable at this time, and an increase in the yields of undesirable methane, pyrolysis oil, tars and coke. Therefore, there is an intensive search for compounds that are capable of influencing the radical process of thermal decomposition of hydrocarbons in such a way that it is possible to work at lower temperatures. This would improve the kinetic parameters of the process and increase selectivity. Some nitrogen compounds are also among the compounds that have been studied for this purpose. The pyrolysis of hydrocarbons in the presence of ammonia is known; amines, nitro-, nitro compounds (AO ČSSR 190 747); sulfur-nitrogen compounds such as ammonium sulfide, thiourea, nitrothiophenol and thiazine (AO ČSSR 210 039). Despite the fact that these nitrogen compounds are characterized by high efficiency, their wider introduction on an operational scale is primarily hindered by availability and price.

The above-mentioned shortcomings are substantially eliminated by the method of producing olefins by pyrolysis of hydrocarbon raw materials in the presence of water vapor and inorganic compounds in the temperature range of 600 to 1,300 ° Celsius with a reaction time of less than 1 second, according to the invention, the essence of which consists in adding to the raw material before pyrolysis in an amount of 0.001 to 2.0 mass% nitrites, nitrates of metals of the first and second groups of the periodic table and phosphorus pentasulfide.

The invention achieves progress in that the hydrocarbon feed is utilized to a greater extent by the action of metal nitrites and nitrates. The speed and selectivity of the conversion are increased. Another benefit of the invention is the use of the effect of phosphorus pentasulfide, which effectively prevents the conversion of hydrocarbons to pyrocarbon, so that it is not deposited in the form of coke on the inner surface of the pyrolysis device. This allows for ^an increase in the period of continuous operation of pyrolysis furnaces and avoids the complex operation of burning coke from the furnace tubes. The accelerating effect of nitrites and nitrates in the pyrolysis of hydrocarbons results from their decomposition into nitric oxide and nitrogen dioxide. The molecules of both oxides have an odd number of electrons, so they are paramagnetic. By attacking the reactant molecules, they enable the formation of hydrocarbon radicals, especially in the initial phase of pyrolysis.

Phosphorus pentasulfide P2S5 decomposes under pyrolysis conditions into reaction intermediates that react with the inner surface of the reactor to form metal sulfides and phosphides, which have a passivating effect on coke formation.

The nature and properties of the additives determined the method of dosing into the pyrolysis system. Water-soluble compounds were dosed in the form of aqueous solutions and additives that are soluble in hydrocarbons were added to the hydrocarbon feed.

The subject matter of the invention is illustrated by examples of embodiments, without referring to the examples given.

Example 1

The experiments were carried out in stainless steel flow-through tubular reactors in the temperature range of 600 to 1300 °C. The pressure ranged from 0.05 to 0.5 MPa, preferably from 0.1 to 0.2 MPa, the residence time was less than 1 s. The operation was carried out in the presence of water vapor in an amount of 20 to 300% of the hydrocarbon feed. Hydrocarbons and petroleum fractions with a boiling point of 30 to 400 °C were pyrolyzed individually, especially light and heavy primary gasoline, gasoline from catalytic reforming after extraction of aromatics (raffinate), kerosene and gas oils.

The effect of inorganic additives was investigated in the pyrolysis of n-heptane and primary gasoline. The rate constant from the first-order equation was used to determine the initiation effect of metal nitrites, nitrates and phosphorus pentasulfide. The results from the pyrolysis of n-heptane are given in Table 1 and from the pyrolysis of primary gasoline in Table 2,

TABLE 1

Effect of metal nitrites and nitrates on the pyrolysis of n-heptane

Temperature, °C 700 H2O ratio 3 Withdrawal period, with 0.074 0.068 0.130 0.052 Amount of ingredient, wt.% 0 1.0 0.92 0.68 Additive — NaNOz On the knife KNO3 Pyrolysis rate, s' ⁴ 3.47 3.85 3.85 3.92 Selectivity (moles of ethylene/ /100 moles of reactant' n-C7 119.4 144.2 157.4 145.6

TABLE 2

The effect of NaNCú and Mg(NO3)2 on the pyrolysis of primary gasoline (b.p. 34 to 125 °C) Temperature, ^C C 780 Ratio HzO/raw material 0.5 Withdrawal period, with 0.19 Amount of ingredient, wt.% 0 1.0 0.08 Additive — NaNOz P2S5 Amount of pyrogas, % wt. 83 86 84 Yield, % wt. Methane 10.1 11.3 10.8 Ethylene 22.2 27.4 24.6 Propylene 14.1 15.6 13.1

Example 2

The effect of phosphorus pentasulfide on coke formation was monitored during the pyrolysis of gasoline raffinate in a tubular reactor without the presence of water vapor. During the pyrolysis of gasoline raffinate alone at 820 °C, 0.83 g of coke was formed within three hours. During the pyrolysis of gasoline raffinate containing 0.5 wt. % P2S5, only 0.12 g of coke was formed within the same period of time. The result indicates a significant inhibitory effect of phosphorus pentasulfide on coke formation.

Claims (2)

245543 TABLE 1 Effect of metal nitrites and nitrates on n-heptane pyrolysis Temperature, ° C 700 Ratio H2O 3 Holding time, s 0.074 0.068 0.130 0.052 Additive amount,% wt. 0 1,0 0,92 0,68 Additive - NaNO2 NO KNO3 Pyrolysis rate, s'4 3,47 3,85 3,85 3,92 Selectivity (moles of ethylene / / 100 moles of reacted n-C7 119,4 144 , 2 157.4 145.6 TABLE 2 Effect of NOx and Mg (NO3) 2 on pyrolysis of primary gasoline (tv 34 to 125 ° C) Temperature, CIC 780 H 2 O / raw material ratio 0.5 Retention time, s 0.19 Additive amount,% wt 0 1.0 0 , 08 Additive - NaNO2 P2S5 Amount of pyrolysis,% wt 83 86 84 Yield,% wt Methane 10.1 11.3 10.8 Ethylene 22.2, 27.4 24.6 Propylene 14.1 15.6 13, EXAMPLE 2 The phosphorous pentasulphate on the formation of the oxycoke was observed in the pyrolysis of the naphtha-naphtha in a tubular reactor without the presence of water vapor, and 0.83 g of coke was obtained by pyrolysis of the benzine raffinate alone at 820 DEG C. for three hours. which contained 0.5% by weight of P2S5, only 0.12 g of coke was produced in the same time, indicating a marked inhibitory effect of phosphorous sulphide on the formation of coke PR ED Μ ET Process for the production of olefins by pyrolysis of hydrocarbons initiated by inorganic compounds in the presence of aqueous vapor in the temperature range of 000 to 1300 QC pr with a reaction time of less than 0.5 seconds characterized by the addition of nitrites, metal nitrates first and second groups of the periodic table to the feedstock prior to pyrolysis, and the sulfur and phosphorous .