KR102035471B1 - Preparation of dehydrogenation catalysts having superior selectivity - Google Patents

Abstract

In the present invention, a spherical alumina, gamma-alumina, is subjected to heat treatment and acid treatment to phase-change into gamma-alumina, theta-alumina or mixed alumina of theta-alumina and alpha-alumina having bimodal pore characteristics, and then a mixture of strontium oxide and alumina. (SrO + Al ₂ O ₃ ) and strontium alumina (SrAl ₂ O ₄ ) relates to a method for producing a dehydrogenation catalyst comprising the step of preparing a composite alumina carrier coexisting, strontium doped alumina dehydrogenation according to the present invention The catalyst is increased in stability and can operate under harsh process conditions with high temperature and high pressure, as well as an increase in selectivity and lifetime.

Description

Preparation of dehydrogenation catalysts having superior selectivity

The present invention relates to a method for producing a dehydrogenation catalyst which is capable of operating under severe conditions by doping strontium to alumina in which porosity is controlled and improving selectivity, stability, and lifespan.

As catalysts for dehydrogenation of hydrocarbon gases, platinum-based catalysts in which platinum and tin are supported on an alumina (Al ₂ O ₃ ) carrier and chromium-based catalysts mainly composed of chromium dioxide (Cr ₂ O ₃ ) are known. . Platinum-based dehydrogenation catalysts have been widely used because of their excellent dehydrogenation catalyst activity and stability and long catalyst life. As the carrier of the catalyst, alumina, silica, zeolite and the like are used in various ways. As the properties required for such a dehydrogenation catalyst, the content of the active ingredient, the type of promoter, the dispersion of the active ingredient, the type of carrier, the pore characteristics of the carrier, the acidity of the carrier, etc. should be considered. In particular, the dispersity of the active ingredient plays an important role in the initial activity of the catalyst, and when used for a long time in the process, the sintering of the active metal components proceeds, so that the dispersibility is lowered and eventually the activity is lowered. do. Therefore, there is a need for a method for preparing a catalyst having a high degree of active ingredient dispersion. In general, the dehydrogenation catalyst is prepared by the room temperature / elevated adsorption support method. First, chloroplatinic acid, hydrochloric acid and nitric acid are dissolved in distilled water, and then a fixed amount of carrier is added. After stirring sufficiently at room temperature, drying and heat treatment are performed. Thereafter, the component used as a promoter is dissolved in distilled water and adsorbed and supported in the same manner as platinum.

In recent years, in order to increase propylene productivity and lower raw units, there is a need for a catalyst capable of further increasing propylene selectivity. In order to control the performance of the catalyst such as conversion, selectivity, stability, and lifetime of the alumina-based catalyst, as a promoter in addition to the platinum component, tin, germanium, lead, titanium, gallium, indium, zinc, arsenic, manganese, mercury, etc. It is known to use metals. It is also known to use metals such as potassium, sodium, lithium, cerium, etc. in order to suppress side reactions such as cracking and hydrogenolysis to increase the performance and life of the catalyst. These existing catalysts are rapidly deactivated and have poor reaction stability under harsh operating conditions to maximize yields. In addition, the strontium doped catalyst used in the existing propane dehydrogenation reaction has a limitation in maximizing low dispersion and yield of platinum due to low specific surface area and simple pore distribution. On the other hand, the strontium supported catalyst prepared by the coprecipitation method is difficult to apply to the actual moving bed (moving bed) process because it is difficult to form a sphere due to the characteristics of the slurry.

The present invention is to solve the problems of the prior art as described above, one object of the present invention is strontium doped with strontium in the pore properties of the strontium is possible to operate in harsh conditions and improved selectivity, stability and lifespan It is to provide a method for producing this doped dehydrogenation catalyst.

Another object of the present invention is to provide a strontium doped dehydrogenation catalyst having excellent selectivity and dispersion.

One aspect of the present invention for achieving the above object,

Spherical gamma-alumina (γ-Al ₂ O ₃ ) was subjected to heat treatment and acid treatment to heat treatment and acid treatment of gamma-alumina (γ-Al ₂ O ₃ ), theta-alumina (θ-Al ₂ O ₃ ) or theta- Mixed alumina (θ-Al ₂ O ₃ with alumina and alpha-alumina + phase shift to α-Al ₂ O ₃ ); Phase-shifted gamma-alumina, theta-alumina, or mixed alumina of theta-alumina with alpha-alumina, strontium nitrate, a precursor of strontium oxide (SrO)

preparing a composite alumina carrier in which a mixture of strontium oxide and alumina (SrO + Al ₂ O ₃ ) and strontium alumina (SrAl ₂ O ₄ ) coexist in an aqueous solution of (strontium nitrate) (Sr (NO ₃ ) ₂ ) ; And it relates to a method for producing a strontium-doped alumina dehydrogenation catalyst comprising the step of calcining the composite alumina carrier at a temperature of 700 to 1200 ℃.

Another aspect of the present invention relates to a dehydrogenation catalyst capable of operating under the harsh process conditions produced by the process, having a selectivity of 94 to 99% by weight and an average coke production of 0.5 to 10% by weight / hr.

The strontium-doped alumina dehydrogenation catalyst according to the present invention can be operated even in harsh process conditions having a high H ₂ / C ₃ ratio and a high temperature and high pressure condition by increasing the stability by doping strontium to the alumina in which pore characteristics are controlled. In addition, the selectivity and lifespan are improved. In addition, it is economical because a dehydrogenation catalyst can be produced at low process cost since no complicated process is required.

Hereinafter, the manufacturing method of the dehydrogenation catalyst by this invention is demonstrated in detail.

In order to prepare a strontium-doped alumina dehydrogenation catalyst according to the present invention, first, spherical alumina, gamma-alumina, under heat treatment and acid treatment under optimized conditions, is characterized by bisodal porosity (Meso) and macro (Macro). Phase change is carried out with gamma-alumina, theta-alumina or mixed alumina of theta-alumina and alpha-alumina having the characteristic. The gamma-alumina, theta-alumina, or mixed alumina carrier of theta-alumina and alpha-alumina thus prepared was supported in an aqueous solution of strontium nitrate (Sr (NO ₃ ) ₂ H ₂ O), which is a precursor of strontium oxide (SrO). A composite alumina carrier having a mixture of strontium oxide and alumina (SrO + Al ₂ O ₃ ) or strontium aluminate (SrAl ₂ O ₄ ) coexists by adsorbing support method. Subsequently, firing at a temperature of 700 to 1200 ° C. produces a strontium-doped alumina dehydrogenation catalyst.

In the present invention, the acid treatment is, for example, supported by spherical commercial alumina in a solution of distilled water of hydrochloric acid and nitric acid, stirred at 25 rpm for 2 to 3 hours at room temperature, and 25 rpm for 2 to 3 hours at 70 to 90 ℃ Stir. Then, dried by rotating at 25 rpm for 2 to 3 hours at 80 ℃ under reduced pressure. Dry for 14-16 hours in an oven at 100-110 ° C. for complete drying and heat treatment for 2-4 hours in a 700 ° C. furnace. Solutions usable in the acid treatment of the present invention include hydrochloric acid, nitric acid, sulfuric acid, etc. The acid treatment concentration may be used in 0.01M to 1M relative to the alumina carrier. When the concentration of the acid solution is less than 0.01M, the alumina pores are insignificant, and there is no effect of mass transfer. When the concentration of the acid solution exceeds 1M, the pores are shaved too much and the strength is weak, making it difficult to use as a process catalyst.

The amount of strontium oxide in the supporting process is 0.001 to 1.0 mole based on the total amount of alumina. If the amount of strontium oxide is less than 0.001 mole or more than 0.1 mole based on the total amount of alumina, the selectivity, stability, and lifetime of the dehydrogenation catalyst may be reduced. If the firing temperature is less than 700 ℃ or more than 1200 ℃ may reduce the selectivity, stability, and life of the catalyst.

The mixing ratio of theta-alumina and alpha-alumina in the mixed alumina may be 99: 1 to 95: 5 of theta-alumina: alpha-alumina depending on the heat treatment temperature and time. The ratio of theta-alumina: alpha-alumina is, for example, 100: 0 when heat treated at 1050 ° C. for 2 hours, 100: 0 when heat treated at 1060 ° C. for 2 hours, and 100: 0, when heat treated at 1070 ° C. for 99 hours: When heat treated at 1, 1080 ℃ for 2 hours, 99: 1, heat treated at 1090 ℃ for 2 hours, 95: 5, heat treated at 1100 ℃ for 2 hours, 87:13, and the time to maintain firing also affects the phase ratio.

The alumina carrier is gamma phase, theta phase of alumina, or mixed alumina of theta phase and alpha phase, and preferably has a crystallinity of 90% or more. In the case of gamma-alumina, the side reactions due to the acid point of alumina itself are large, the alumina crystallinity is changed during the reaction, and the specific surface area is reduced, but the support of strontium can reduce the acid point of itself and has a negative effect. Can be prevented. In the case of alpha-alumina, the low specific surface area lowers the dispersibility of the metal and decreases the active area of the entire metal, thereby showing low catalytic activity. The alumina carrier may be a gamma phase, theta phase, or mixed alumina with theta phase and alpha phase depending on the heat treatment temperature and time.

The alumina carrier has a specific surface area of 50 to 170 m 2 / g, and has meso pores of 5 to 100 nm and macro pores of 0.1 to 20 μm. If the specific surface area of the carrier is less than 50 m 2 / g, the dispersibility of the metal active component is lowered. If the specific surface area is more than 170 m 2 / g, the gamma crystallinity of the alumina is kept high, thereby increasing the side reaction. In addition, the volume of the pores of the carrier and the size of the pores are the major factors that determine the mass transfer coefficients of the reactants and products.In the case of fast chemical reactions, the diffusion resistance of the material determines the overall reaction rate, so that the structure of the large pores Is advantageous for keeping the activity of the catalyst high. Therefore, the use of a carrier having a large pore size is insensitive to the accumulation of coke, and the high mass transfer rate results in high reaction activity even with an increase in the liquid hourly space velocity (LHSV).

The catalyst has a high degree of dispersion when supporting the active ingredient, and the development of meso and macro pores has an effect of increasing the material transfer rate. That is, when the size of the pores present in the catalyst is large, it becomes insensitive to the decrease in activity due to coke generated on the catalyst, and even if the liquid space velocity is increased due to the high mass transfer rate, high reaction activity is exhibited.

In the present invention, platinum is used as the main metal, and an auxiliary metal is selected from the group consisting of tin, germanium, gallium, indium, strontium and manganese, and tin is particularly preferable. As the halogen component, one selected from the group consisting of chlorine, phosphorus and fluorine is used, and chlorine is particularly preferable.

The catalyst according to the present invention can be prepared by adjusting the amount of the halogen component to 0.1 to 3.0% by weight relative to the total weight of the catalyst. If the content of halogen is less than 0.1% by weight, the formation of coke on the catalyst is rapidly increased, the coke regeneration of the catalyst is low, the platinum dispersity is low during catalyst regeneration, and if the content of halogen is more than 3.0% by weight, Poisoning of noble metals lowers the activity of the catalyst. That is, the halogen component, in particular chlorine, is combined with the aluminum element of the alumina carrier to attenuate the characteristics of the Lewis acid possessed by the alumina itself, thereby facilitating the desorption of the product, thereby suppressing the formation of coke. The formation of coke is adsorbed on the carrier itself and the reaction is complete, or the main product / by-product produced at the active site is spill-over, accumulated in the carrier and finally produced through an additional coke formation reaction. Degradation of the product to facilitate the desorption of the product can reduce the amount deposited on the carrier to reduce coke production. In addition, in the direction of reducing the scattering point inherent in the crystallinity of the alumina, the same scattering effect is reduced by changing from the properties of gamma to theta or alpha. Chlorine is also used to control the sintering of platinum during the catalyst regeneration process.

The catalyst preparation solution usable in the present invention may use one or more organic solvents selected from hexane, benzene, acetone, toluene and xylene, but is not necessarily limited thereto. The evaporation rate of the catalyst preparation solution is stirred at 30 to 100 rpm for 1 to 3 hours at room temperature, and then dried by rotating at 30 to 100 rpm for 1 to 3 hours at a reduced pressure.

As described above, the dehydrogenation catalyst according to the present invention is operable under harsh process conditions, has a selectivity of 94 to 99% by weight, and an average coke production amount of 0.5 to 10% by weight, superior selectivity to conventional catalysts and It has a degree of dispersion. In addition, it is high in strength and resistant to external impact, and there is no structural change due to heat or change in the properties of the active substance.

The catalyst according to the present invention preferably has a volume density of 0.5 to 0.8 g / cc, and the volume density of the catalyst is a factor for determining the total amount of active catalyst of the catalyst introduced into the process by determining the filling amount of the catalyst introduced into the process. The catalyst according to the present invention preferably has a strength of 15 to 70 N, and increases the strength so that the catalyst has less rigidity in regeneration or circulation of the catalyst. If the strength of the catalyst is less than 15N it is easily broken and difficult to apply to the continuous reaction system.

Hereinafter, a method for preparing a dehydrogenation catalyst according to the present invention will be described in more detail with reference to Examples. However, this is only for the purpose of illustrating the present invention and the protection scope of the present invention should not be construed as being limited thereto.

Example  1: Dehydrogenation Catalyst Preparation

15 g of spherical alumina purchased from Sasol, Germany, having a gamma crystallinity, an average diameter of 1.65 mm, and a packing density of 0.56 g / ml, was used in a catalyst synthesis. Heat deformation for 2 hours. Subsequently, it was supported on a solution mixed with 0.5 g of hydrochloric acid, 0.05 g of nitric acid, and 32 g of distilled water, stirred at 25 rpm for 1.5 hours at room temperature, and then stirred at 25 rpm for 1.5 hours at 80 ° C. Thereafter, the mixture was dried by rotating at 25 rpm for 1.5 hours at 80 ° C under reduced pressure. For complete drying it was dried for 15 hours in a 105 ℃ oven, heat-treated for 3 hours in a 700 ℃ heating furnace transformed into theta phase. As a result of measuring the crystallinity of theta alumina by X-ray analysis, theta crystallinity was 90% or more. Using the heat-treated and acid-treated theta-alumina carrier, a catalyst was prepared by the room temperature / temperature adsorption support method. Sr nitrate (Sr (NO ₃ ) ₂ ), a precursor of strontium oxide (SrO), was dissolved in distilled water, and then heat-strained and acid-treated with theta-alumina. The supporting solution was dried using a rotary evaporator, and stirred at 25 rpm for 1.5 hours at room temperature, and then dried by rotating at 25 rpm for 1.5 hours at 80 ° C under reduced pressure. For complete drying it was dried for 15 hours in a 105 ℃ oven, and fired for 2 hours in a 700 ℃ heating furnace. In this case, the amount of strontium oxide is 0.001 mol based on the total amount of alumina.

Example  2: Dehydrogenation Catalyst Preparation

A catalyst was prepared in the same manner as in Example 1 except that gamma-alumina heat-treated and acid-treated as a carrier was used and the amount of strontium oxide was 0.1 mole based on the total amount of alumina.

Comparative example  1: Dehydrogenation Catalyst Preparation

A dehydrogenation catalyst was prepared using a general adsorption supporting method. A chloroplatinic acid _{(H 2 PtCl 6 · H 2} O, 99.95%, Aldrich) 0.53 g, hydrochloric acid (HCl,> 35%, JUNSEI ) 0.2143 g, nitric acid _{(HNO 3, 70%, Yakuri} ) 0.0536 g of distilled water 24 g After melting, 0.8 g of alumina was added thereto to carry it. The supporting solution was dried using a rotary evaporator, and stirred at room temperature for 1.5 hours and 25 rpm, and then dried under reduced pressure for 1.5 hours at 25 rpm, dried in an oven for 15 hours, and heated at 600 ° C. for 3 hours. . Then, 10 g of tin and platinum-supported alumina was added to 12.1136 g of distilled water in which 0.1933 g of potassium nitrate (KNO ₃ ,> 99%, Sigma-Aldrich) and 0.1629 g of hydrochloric acid (HCl,> 35%, JUNSEI) were dissolved. It was. The supporting liquid was dried using a rotary evaporator, and stirred at room temperature for 1.5 hours and 25 rpm, and then dried under reduced pressure for 1.5 hours at 25 rpm, dried in an oven for 15 hours, and heat treated in a 600 ° C. heating furnace for 3 hours. Was prepared. The particle size of the prepared platinum was 10 ~ 30 nm.

Experimental Example : Dehydrogenation of Dehydrogenation Catalyst

In order to confirm the performance of the dehydrogenation catalyst according to the present invention, the following experiment was performed.

2.4 ml of the catalysts prepared in Examples 1 and 2 and Comparative Example 1 were respectively filled in a quartz reactor having a volume of 7 ml, and then a mixed gas of propane and hydrogen was supplied to dehydrogenation, respectively. At this time, the ratio of hydrogen and propane was fixed at 1: 1, and the dehydrogenation reaction was performed while maintaining the reaction temperature at 620 ° C., the absolute pressure at 1.5 atm, and the liquid space velocity at 15 hr ⁻¹ . The gas composition after the reaction was analyzed by gas chromatography connected with the reaction apparatus to determine the propane conversion and the propylene selectivity in the product after the reaction.

The conversion, selectivity, and yield at 5 hours after the start of the reaction are shown in the table.

division Conversion rate (% by weight) Selectivity (% by weight) Average Coke Production (wt% / hf) Example 1 36.9 95.2 1.8 Example 2 36.3 94.9 3.2 Comparative Example 1 35.8 94.9 3.5

As shown in Table 1, Examples 1 and 2 of the present invention are superior to the reaction selectivity and propane conversion rate compared to the comparative example. In addition, it was found that the average amount of coke produced for 5 hours was reduced in the Examples compared to the Comparative Examples.

Although the present invention has been described in detail with reference to preferred embodiments of the present invention, the present invention is not limited to the above-described embodiments, and many modifications are made by those skilled in the art to which the present invention pertains within the scope of the technical idea of the present invention. This possibility will be self-evident.

Claims (7)

Spherical gamma-alumina (γ-Al ₂ O ₃ ) was subjected to heat treatment and acid treatment, followed by heat treatment and acid treatment of gamma-alumina (γ-Al ₂ O ₃ ), and heat treatment and acid treatment of theta-alumina (θ-Al ₂ O ₃ ). ₃ ) or phase shifting the mixed alumina (θ-Al ₂ O ₃ + α-Al ₂ O ₃ ) of theta-alumina and alpha-alumina heat treated and acid treated; A mixture of strontium oxide and alumina (SrO +) was supported by a phase-shifted gamma-alumina, theta-alumina, or a mixed alumina of theta-alumina and alpha-alumina in an aqueous solution of strontium nitrate (Sr (NO ₃ ) ₂ ). Preparing a strontium composite alumina carrier having Al ₂ O ₃ ) and strontium aluminate (SrAl ₂ O ₄ ) coexisting; And calcining the strontium composite alumina carrier at a temperature of 700 to 1200 ° C., when the mixed alumina is immersed in an aqueous solution of strontium nitrate, the amount of strontium oxide is 0.001 to 0.1 mole based on the total amount of alumina. A method for producing a strontium-doped alumina dehydrogenation catalyst, characterized in that 94 to 99% by weight, the average coke production amount is 0.5 to 10% by weight.
The method of claim 1, wherein the heat-treated and acid-treated gamma-alumina, theta-alumina, or mixed alumina has bimodal pore characteristics.
According to claim 1, wherein the acid treatment is carried out by stirring the spherical gamma-alumina in hydrochloric acid or nitric acid aqueous solution at room temperature, and then heated to 70 to 90 ℃; Drying by rotating under reduced pressure; And a step of further drying at 100 to 110 ° C. A method for producing a strontium-doped alumina dehydrogenation catalyst.
The method of claim 3, wherein the concentration of the acid solution during the acid treatment is 0.01M to 1M relative to the alumina carrier.
delete The method of claim 1, wherein the mixed alumina has a theta crystallinity of 90% or more.
Strontium-doped, characterized in that prepared by the method of any one of claims 1 to 4, 6, the selectivity is 94 to 99% by weight, the average coke production is 0.5 to 10% by weight / hr Alumina dehydrogenation catalyst.