RU2053018C1 - Method of preparing catalyst for hydrogenation of acetylene in ethane-ethylene fraction - Google Patents

Abstract

FIELD: catalysts. SUBSTANCE: aluminium oxide with specific surface 210-220 m²/g and mean pore radius

Description

 The invention relates to petrochemical synthesis, in particular to methods for preparing a catalyst for the selective hydrogenation of acetylene contained in the ethane-ethylene fraction (EEF).

; во втором слое катализатор, активированный при 300-550^оС, с размером кристаллитов до 45

. Кроме того, для повышения селективности и стабильности катализатора к исходной смеси в качестве компонента, препятствующего протеканию реакции полимеризации по радикальному механизму (т.е. для снижения выхода "зеленого масла"), добавляют окись углерода (0,008 мол.). Процесс очистки ЭЭФ ведут при объемной скорости 500-2500 ч^-1, 80^оС, молярном отношении H₂:C₂H₂ 3:1 и давлении 25 ат. В этих условиях содержание ацетилена в ЭЭФ на выходе из реактора не превышает 0,0002 об. Однако после 100 ч работы селективность процесса падает: заметно возрастает содержание этана (с 19 до 20,3% ) за счет протекания побочной реакции гидрирования этилена в этан. Кроме того, в продуктах реакции обнаружены олигомеры С₄-С₁₀ (0,2 мас. от общего количества пропущенного сырья), накопление которых в порах катализатора является одной из причин падения активности катализатора. Через 6 мес работы катализатор потерял селективность и резко снизилась его активность.It is known that the EEF of the gas of pyrolysis of hydrocarbon feedstock contains 0.4-2.2% acetylene, while its content in ethylene used for petrochemical synthesis should not exceed 0.0005 wt. When the content of acetylene in ethylene above the specified limit, the quality of the polymer obtained from ethylene decreases sharply, the service life of the catalyst decreases, and the operating conditions of the installation deteriorate [1]
A known method of preparing a catalyst for the hydrogenation of acetylene in EEF by impregnating alumina with a specific surface area of less than 100 m ² / g with a solution of palladium nitrate, chloride or acetylacetonate (0.1-0.5 wt. Pd), followed by activation at temperatures of 500-1100 ^about in an oxidizing and reducing environment at temperatures up to 200 ^C. [2] in order to improve selectivity of the process it is recommended to use the catalyst in reactors with two-layer packing: in the first layer catalyst activated in an oxidizing atmosphere at temperatures of 700-950 ^{° C,} containing palladium crystallites with an average size of 50-80

; in the second layer catalyst, activated at 300-550 ^C, with crystallite size of up to 45

. In addition, to increase the selectivity and stability of the catalyst, carbon monoxide (0.008 mol) is added to the initial mixture as a component that impedes the course of the polymerization by the radical mechanism (ie, to reduce the yield of "green oil"). EEF purification process is conducted at a space velocity of 500-2500 h ^-1, 80 ^{° C,} a molar ratio of H _2: C ₂ H ₂ of 3: 1 and a pressure of 25 atm. Under these conditions, the acetylene content in the EEF at the outlet of the reactor does not exceed 0.0002 vol. However, after 100 hours of operation, the selectivity of the process decreases: the ethane content appreciably increases (from 19 to 20.3%) due to the side reaction of hydrogenation of ethylene to ethane. In addition, C ₄ -C ₁₀ oligomers (0.2 wt.% Of the total amount of missed feed) were found in the reaction products, the accumulation of which in the pores of the catalyst is one of the reasons for the decrease in the activity of the catalyst. After 6 months of operation, the catalyst lost selectivity and its activity sharply decreased.

This method has the following disadvantages:
the need to restore the catalyst with hydrogen;
the need to use high temperatures (1100 ^C);
insufficient selectivity of the resulting catalyst, even under optimal conditions, the loss of ethylene due to side processes (hydrogenation of ethylene to ethane and oligomerization is 0.3%);
low productivity of the resulting catalyst; recommended volumetric rates of 500-2500 h ^-1 .

insufficiently long catalyst life;
the need to add carbon monoxide to the starting mixture.

Closest to the proposed technical essence and the achieved result is a method of preparing a catalyst for the selective hydrogenation of acetylene compounds into ethylene by impregnating alumina (γ-Al ₂ O ₃ , specific surface area 200 m ² / g) with a solution of palladium chloride in concentrated hydrochloric acid in a weight ratio PdCl _2: Al ₂ O ₃ = 1: 19 for 10-12 hours, drying at ¹²⁰ ° C, processing alillovogo alcohol solution in an organic solvent (alcohol, acetone, ether, chloroform), drying and calcining in vacuo ^at 200 FROM for 3 h [3] The finished catalyst contains 3 wt. palladium.

The activity and selectivity of the catalyst prepared by this method are not high enough in the hydrogenation of acetylene in admixture with ethylene, namely the hydrogenation of a mixture of C ₂ H ₂ and C ₂ H ₄ in a ratio of 1: 100 at 70 ° ^C and a pressure of 1 atm ethylene loss for its hydrogenation to ethane was 5% and the residual content of C ₂ H ₂ 0.3%. After 1 h, the activity of the catalyst sharply decreased: the acetylene content in the mixture leaving the reactor increased from 0.3 to 0.7%
In addition, the disadvantages are:
use as a solvent of palladium chloride concentrated hydrochloric acid; high consumption of palladium (3% by weight of γ-Al ₂ O ₃ );
the duration of the stages of impregnation and drying, the need for a vacuum;
the use of organic solvents (alcohol, acetone, ether, chloroform) at the stage of impregnation of alumina with a solution of palladium chloride.

 The aim of the invention is to obtain a catalyst with increased activity, selectivity, performance and service life.

, проводят пропитку оксида алюминия по влагоемкости раствором хлорида палладия в разбавленной соляной кислоте и обработку ведут подкисленным уксусной кислотой 3-5%-ным водным раствором аллилового спирта с последующей промывкой водой для удаления избыточного спирта.The goal is achieved by the fact that in the method of preparing a catalyst for the hydrogenation of acetylene in ethane-ethylene fraction by impregnating alumina with a solution of palladium chloride in hydrochloric acid, drying, followed by treatment with an aqueous solution of allyl alcohol and drying, aluminum oxide with a specific surface area of 210-220 m ² / g and a pore radius of 65-85

the alumina is impregnated in moisture capacity with a solution of palladium chloride in dilute hydrochloric acid and the treatment is carried out with acidified acetic acid with a 3-5% aqueous solution of allyl alcohol, followed by washing with water to remove excess alcohol.

 The presence on the surface of the catalyst of small amounts of acrylic acid formed during the preparation of the catalyst in this way, and residual allyl alcohol contributes both to the drying of the finished catalyst at elevated temperatures and during the hydrogenation of acetylene, the formation of polymer compounds, the accumulation of which in the pores of the catalyst (the so-called "green oil") is one of the main reasons for the decline in catalyst activity.

 The use of alumina with a large pore size facilitates the removal of allyl alcohol and acrylic acid from the surface of the catalyst when washing it with water.

) и промывание катализатора водой обеспечивает полное удаление остаточного аллилового спирта и акриловой кислоты с поверхности катализатора, что приводит к получению высокоэффективного катализатора.Thus, the use for the preparation of a catalyst of aluminum oxide with a significant size of the average pore radius (65-85

) and washing the catalyst with water ensures complete removal of residual allyl alcohol and acrylic acid from the surface of the catalyst, resulting in a highly efficient catalyst.

 A decrease in the concentration of allyl alcohol below 3% is impractical, since this significantly slows down the formation of the active phase of the catalyst. An increase in the palladium content in the catalyst above 0.2% is also impractical, since when the palladium content was increased to 0.5%, the same EEF purification results were obtained as with 0.2% Pd.

пропитывают по методу влагоемкости 0,95 л раствора 3,0 г PdCl₂ в разбавленной соляной кислоте (рН 4) в течение 0,5 ч, при этом раствор полностью впитывается носителем. Весовое соотношение PdCl₂:Al₂O₃ равно 1:300. После пропитки образец подсушивают при 110-115^оС 2 ч, охлаждают до комнатной температуры и отрабатывают его 0,8 л 3%-ного раствора аллилового спирта, подкисленного уксусной кислотой до рН 3. После этого катализатор промывают 4,5 л воды и сушат на воздухе 2 ч, постепенно повышая температуру до 140^оС. Содержание палладия в этом образце 0,2% Готовый катализатор после охлаждения до комнатной температуры загружают в реактор плотной установки тонкой очистки ЭЭФ. При пропускании над этим катализатором сырья с объемной скоростью 4500 ч^-1 при температуре 60^оС и объемном соотношении водород:ацетилен 2:1 получают этан-этиленовую смесь, содержащую лишь следы ацетилена т.е. <0,0001%), убыль этилена не превышает 0,01% В те же условиях проведения реакции при повышении объемной скорости подачи сырья до 5000 ч^-1 получают этан-этиленовую смесь, содержащую менее 0,0001% ацетилена, убыль этилена при этом не превышает 0,01% Катализатор после испытаний в течение 3500 ч сохраняет первоначальную активность. Результаты испытаний представлены в таблице.PRI me R 1.5 l (900 g) γ-Al ₂ O ₃ with a granule size of 3-5 mm, a specific surface area of 210-220 m ² / g and an average pore radius of 65-85

they impregnate 0.9 g of a solution of 3.0 g of PdCl ₂ in dilute hydrochloric acid (pH 4) for 0.5 h, using the method of moisture capacity, while the solution is completely absorbed by the carrier. The weight ratio of PdCl ₂ : Al ₂ O ₃ is 1: 300. After impregnation the sample was dried at 110-115 ^{C for} 2 hours, cooled to room temperature and 0.8 l fulfill its 3% allyl alcohol solution acidified with acetic acid to pH 3. Thereafter the catalyst was washed with 4.5 L water and dried in air for 2 hours, gradually raising the temperature to 140 ^о С. The palladium content in this sample is 0.2%. The finished catalyst, after cooling to room temperature, is loaded into the reactor of a dense EEF fine purification plant. When passed over this catalyst with a feedstock hourly space velocity of 4500 hr ^-1 at ⁶⁰ ° C and the volume ratio of hydrogen to acetylene of 2: 1 was prepared ethane-ethylene mixture containing only traces of acetylene i.e. <0.0001%), ethylene loss does not exceed 0.01%. Under the same reaction conditions, with an increase in the volumetric feed rate to 5000 h ^-1 , an ethane-ethylene mixture containing less than 0.0001% acetylene is obtained, while ethylene loss does not exceed 0.01%. The catalyst, after testing for 3500 hours, retains its original activity. The test results are presented in the table.

As can be seen from the example and the results shown in the table, the proposed method has the following advantages:
the carrier impregnation time is reduced by 48-50 times;
reduced palladium consumption by 15 times;
consumption of allyl alcohol is reduced by 5-7 times;
reduced working temperature of the resulting catalyst at 20-30 ^{° C;}
significantly increased catalyst service life;
the catalyst is highly efficient.

The resulting catalyst for the selective hydrogenation of acetylene in EFF has the following advantages:
higher activity and selectivity: the space velocity of 4500-5000 h ^-1 and a temperature of 60 ° ^C the residual acetylene content of not more than 0.0001% ethylene losses do not exceed 0.01%
low palladium content (0.2 wt.);
the service life of the catalyst significantly exceeds the service life of the catalyst prepared in a known manner: the proposed catalyst after testing for 3500 hours retains its original activity and selectivity without increasing the initial temperature (60 ^about C). The high degree of ethylene purification achieved on this catalyst leads to a significant increase in the quality of ethylene-based petrochemical synthesis products (for example, polyethylene).

 The proposed method does not require capital costs and changes in existing technology.

Claims (1)

METHOD FOR PREPARING THE CATALYST FOR HYDROGENING ACETHYLENE IN ETHANEETHYLENE FRACTION by impregnating alumina with a solution of palladium chloride in hydrochloric acid, drying, followed by treatment with an allyl alcohol solution and drying, characterized in that, in order to obtain a catalyst with increased activity and selective services, use alumina with a specific surface area of 210-220 m ² / g and an average pore radius of 65-85 A, impregnation is carried out by the moisture capacity of a solution of palladium chloride in dilute salt ki the slot and processing is carried out with an acidified 3-5% solution of allyl alcohol, followed by washing with water to remove excess alcohol.

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