ES2957057A2 - Dehydrogenation catalyst having ring-type metal distribution - Google Patents

Abstract

Dehydrogenation catalyst having a ring-type metal distribution. The present invention relates to a dehydrogenation catalyst, which is a spherical platinum catalyst containing tin and potassium components and is used for dehydrogenation catalysis of light hydrocarbons in a range of C3 to C5, such as propane and butane, in wherein the platinum component is absent on the surface of the catalyst and is present in the form of a ring with a predetermined thickness at a certain depth from the surface of the catalyst. In the catalyst according to the present invention, the tin component is present in the form of an eggshell only to a certain depth from the surface of the catalyst and the potassium component is distributed uniformly throughout the catalyst.

Description

DESCRIPTION

Dehydrogenation catalyst having a ring-type metal distribution

Technical field

The present disclosure relates to a dehydrogenation catalyst and, more specifically, to a spherical platinum catalyst containing tin and potassium components used for the catalytic dehydrogenation of C3 to C5 light hydrocarbons, such as propane, butane, and the like. The catalyst has a ring-shaped metal distribution where a platinum component is not present on the surface of the catalyst but is present within the catalyst, in the form of a ring with a predetermined thickness at a predetermined depth from the surface of the catalyst. In the catalyst according to the present disclosure, the tin component is present in the form of an eggshell where the tin component is present in a region from the surface to a predetermined depth, and the potassium component is uniformly distributed throughout the catalyst. .

Background of the technique

Light olefins are materials used for various commercial purposes related to raw materials for plastics, synthetic rubber, medicines, chemicals, and the like and can be produced by the following dehydrogenation of light hydrocarbons.

Paraffin (CnH2n+2) ←→ Olefin (CnH2n) Hydrogen (H2)

For catalysts that catalyze the dehydrogenation of light hydrocarbons, spherical-shaped carriers having micropores, such as gamma/theta/alpha alumina, zeolite, silica, spinel-type metal aluminate, and the like, are mainly used. These materials have a satisfactory effect on coke resistance or product selectivity. However, when the amount of coke accumulated on the catalyst gradually increases as the reaction progresses, the micropores become clogged with coke. Furthermore, the active metals present in the pores eventually cannot participate in the reaction and become inactive. Therefore, a carrier structure capable of reducing secondary reactions, such as cracking and the like, and coke deposition, is required. On the other hand, the loss of active metals is also an important factor in the decrease in the conversion rate. In particular, in the case of using a fluidized reactor, the loss of active metals can cause the surface of the catalyst to crack or wear due to abrasion that occurs between the catalyst and the catalyst while the catalyst flows, or abrasion that occurs between the catalyst and the reactor. Furthermore, as illustrated in Figure 1, when the amount of the active metal on the catalyst surface is high, the catalyst surface may be clogged with coke generated by a successively occurring cracking reaction. Therefore, a ring-shaped catalytic structure having a shape in which no active metal is present on the surface can resolve such deficiencies.

Divulgation

technical problem

An objective of the present disclosure is to avoid a decrease in mass transfer by suppressing the surface coke deposition that inevitably occurs on a catalyst used for the dehydrogenation of light hydrocarbons, as well as to reduce the loss of platinum active sites due to the abrasion resulting from a fluidized bed reactor.

Technical solution

The above objective can be achieved by a catalyst used for the dehydrogenation of light hydrocarbons, the catalyst having a form in which the platinum is distributed within a ring-shaped spherical carrier with a thickness in a range of 200 um to 500 um a a depth in a range of 30 um to 200 um from the surface of the carrier. Without limitation, in the catalyst of the present disclosure, an eggshell tin component may be present where the tin component is present in a region from the surface of the catalyst to a predetermined depth, and a potassium component may be present. be supported uniformly inside the carrier.

The present disclosure is characterized by providing a spherical platinum catalyst containing tin and potassium components used for the catalytic dehydrogenation of light hydrocarbons. The platinum component is not present on the surface of the catalyst, but is present within the catalyst, in the form of a ring with a predetermined thickness at a predetermined depth from the surface of the catalyst. Without limitation, the tin component may be present in an eggshell form where the tin component is present in a region from the surface of the catalyst to a predetermined depth, and the potassium component may be distributed uniformly throughout the catalyst. Preferably, to form a ring-shaped structure, the predetermined depth can be set in a range of 30 um to 200 um, and the predetermined thickness can be set in a range of 200 um to 500 um.

Advantageous effects

In the dehydrogenation catalyst according to the present disclosure, the platinum active component is not present on the surface of the catalyst, but is present within the catalyst, in the form of a ring with a predetermined thickness while separating inward from the surface. When dehydrogenation is performed using such a ring-type catalyst, the deactivation rate of the catalyst is reduced in a durability test while the same level of activity is obtained, compared to that of existing catalysts containing a component active present in a non-ring form. Therefore, even after 24 hours of an abrasion test, an equal or greater level of activity is shown.

Description of the drawings

Figure 1 is a schematic diagram illustrating pore clogging by coke in catalysts in which an active component is present or not present on the surface;

Figure 2 is a diagram of EPMA images showing the distribution of active components in a catalyst; and

Figure 3 is a graph showing changes in conversion rate over time.

best way

A ring-type active metal catalyst, according to the present disclosure, is a catalyst to which a porous alumina carrier is applied. The catalyst has a form in which platinum, tin and potassium are introduced. The platinum is distributed in a thickness in the range of 200 um to 500 um at a depth in the range of 30 um to 200 um from the surface of the carrier. Additionally, potassium is evenly distributed throughout the interior of the wearer.

The catalyst herein refers to a spherical catalyst, which has a form in which an active component and/or an auxiliary metal is supported on a spherical carrier. The active component present in the form of a ring or ring-type means that the active component is present in a predetermined thickness while separating inward from the surface of the catalyst, which is distinguished from the tin component present in the form of an eggshell. The eggshell shape is distinguished from the ring shape by the fact that the eggshell shape with a predetermined thickness is present in a region from the surface of the catalyst to the center of the catalyst, and the thickness thereof is forms directly from the surface of the catalyst. As used herein, platinum is primarily described as the active component, and the auxiliary metal is exemplified by the tin and potassium components. However, the present disclosure is not limited thereto, and metallic components having the same purpose and function as understood by those skilled in the art can be easily applied to the present disclosure.

The ring-type platinum catalyst having a unique structure according to the present disclosure can be prepared approximately by the following steps.

1) Preparation of mixed platinum-tin solution: While preparing mixed platinum-tin solution by mixing solution of platinum precursor and tin precursor, platinum easily precipitates in air due to high reducing capacity of tin . To prevent precipitation of platinum, hydrochloric acid, an inorganic acid, is added in an amount in the range of 10% by weight to 20% by weight of the mixed platinum-tin solution. Furthermore, to prepare a stable mixed solution, alcohol, for example, ethylene glycol, which is dihydroxy alcohol, is added in an amount in the range of 5% by weight to 10% by weight of the prepared catalyst, and deionized water is used as a solvent. .

2) Uniform impregnation of porous alumina carrier with platinumtin mixed solution: A porous alumina carrier heat treated at a temperature in the range of 900 °C to 1060 °C in a baking oven is used to control the pore size and the pore volume. The heat-treated carrier was impregnated with the mixed platinum-tin solution prepared using a spray carrier method.

3) Immobilization of metal on carrier: After impregnation, a drying process is carried out in a dryer at a temperature of 120 °C or higher for 12 hours or more, followed by firing in an atmosphere of air at a temperature in the range of 400 °C to 700 °C to immobilize the metals on the carrier.

4) Alkali metal support and immobilization: An alkali metal is supported to prevent side reactions from occurring due to acidic sites left on the porous alumina carrier. The potassium is supported in pores within the carrier using a spray support method, dried in a dryer at a temperature of 120 °C or higher for 12 hours or more, and subjected to firing in an air atmosphere at a temperature in the range of 400 °C to 700 °C to immobilize potassium in the carrier.

5) Reduction: After immobilizing the alkali metal, a reduction process is carried out using hydrogen gas at a temperature in the range of 400 °C to 600 °C to obtain the final catalyst. During the reduction process, when the temperature is 400 °C or lower, metal oxidation species may not be completely reduced. When the temperature is above 600 °C, aggregation and sintering of metal particles may occur, thereby reducing the number of active sites.

Analysis is performed using an electron probe X-ray microanalyzer (hereinafter referred to as EPMA) to confirm the distribution of the metallic active material on the catalyst according to the present disclosure. Furthermore, to perform the abrasion that occurs between the catalyst and the catalyst in a fluidized reactor, or the abrasion that occurs between the catalyst and the reactor, an abrasion test is carried out by introducing and rotating the catalyst and SUS type balls. in a plastic bottle. On the other hand, to evaluate the dehydrogenation performance, a hydrocarbon having 2 to 5 carbon atoms, including paraffin, isoparaffin and alkyl aromatic compounds, is diluted with hydrogen, the hydrocarbon preferably having 3 to 4 carbon atoms, to perform the dehydrogenation with a gas phase reaction under the conditions: a temperature in the range of 500 °C to 680 °C, preferably at 570 °C, a pressure in the range of 0 atm to 2 atm, preferably at 1.5 atm, and a liquid hourly space velocity (LHSV) of paraffinic hydrocarbons in the range of 1 h-1 to 40 h-1.

Example 1

A bead-type alumina carrier was heat treated at a temperature of 1050 °C for use. Heat-treated alumina has the following physical properties: a specific surface area of 95 m2/g, a pore volume of 0.4 cm3/g, and an average pore size of 12 nm. Chloroplatinic acid was used as a platinum precursor, and tin chloride was used as a tin precursor. 0.2% by weight of tin chloride and 6% by weight of ethylene glycol, with respect to the total weight of the catalyst, and hydrochloric acid were mixed in an amount corresponding to 10% of the total solution. Next, 0.4% by weight of chloroplatinic acid, based on the total weight of the catalyst, was added to prepare a mixed platinum-tin solution, which was added to and dissolved in deionized water in an amount corresponding to the pore volume. total of the bearer. Next, the heat-treated alumina carrier was impregnated with the mixed platinum-tin solution prepared using a spray support method. The supported platinum-tin composition was dried at a temperature of 120 °C for 12 hours and then subjected to a heat treatment process at a temperature of 550 °C for 3 hours in an air atmosphere to immobilize the active metal. Subsequently, 0.8 wt% potassium nitride, based on the total weight of the catalyst, was once again supported in the internal pores of alumina containing platinum and tin, using a spray support method. Furthermore, the supported metal composition was dried at a temperature of 120 °C for 12 hours and then subjected to a heat treatment process at a temperature of 550 °C for 3 hours to prepare a supported metal catalyst. A catalytic reduction process was performed to raise the temperature to 550 °C gradually in an air atmosphere, and the elevated temperature was then maintained in a hydrogen atmosphere for 1 hour to prepare the catalyst.

Comparative example 1

While alumina heat treated in the same manner as in Example 1 was used as a carrier, a comparative catalyst was prepared by a method of sequentially introducing platinum, tin and potassium. Using chloroplatinic acid as a platinum precursor, a solution in which 0.4% by weight of platinum, with respect to the total weight of the catalyst, and hydrochloric acid in an amount corresponding to 10% by weight of the total solution were mixed, was diluted with deionized water in an amount corresponding to the total pore volume of the carrier, and then introduced into the carrier using a spray support method. The supported platinum composition was subjected to the drying and heat treatment processes in the same manner as in Example 1 to immobilize the active metal. Next, using tin chloride as tin precursor once again, a solution in which 0.2% by weight of tin, with respect to the total weight of the catalyst, and the same amount of hydrochloric acid as in step platinum introduction was supported in the same way. The solution was then subjected to drying and heat treatment processes. Next, 0.8% by weight of potassium nitride, with respect to the total weight of the catalyst, and nitric acid were mixed in an amount corresponding to 1% of the total solution and diluted with deionized water to be introduced in the same way. , followed by undergoing drying and firing. Catalyst reduction was carried out by raising the temperature to 550 °C gradually in an air atmosphere, and the elevated temperature was then maintained in a hydrogen atmosphere for one hour to prepare the catalyst.

Experimental example

The distribution of the metallic active material confirmed by EPMA is shown in Figure 2. In the case of Example 1, the platinum is not distributed in a region from the surface to a distance of approximately 100 um, but is observed to have a shape with a predetermined thickness of 300 um at a depth of 100 um from the surface. In contrast, it was confirmed that the tin was distributed in an eggshell shape in which the tin component is distributed in a region with a predetermined thickness that varies directly from the surface. In the case of the comparative example, the platinum and tin were uniformly distributed in a region that goes directly from the surface to the interior. Depending on the reagent and concentration, the platinum component may be present in the form of a ring with a thickness in the range of 200 um to 500 um at a depth in the range of 30 um to 200 um from the surface of the carrier.

The dehydrogenation of propane was carried out by charging a fixed bed catalytic reactor with the catalyst according to the present disclosure. The composition of the reaction gas in the reactor has a volume ratio of hydrogen and propane of 0.61, and 95 ppm of the entire gas is composed of H2S gas to prevent corrosion of the SUS reactor. After raising the temperature to 607 °C in a hydrogen atmosphere at a heating rate of 6 °C per minute, propane dehydrogenation proceeds while adding propane and hydrogen at the predetermined ratio described above. The conversion rate and selectivity are calculated by analyzing the product gas using gas chromatography.

Table 1 summarizes the results of the analysis of propane dehydrogenation at an initial stage and after 12 hours.

[Table 1]

The initial conversion rates of the catalysts of the example and the comparative example were 36.5 and 36.2, respectively, which were at the same level, but were 35.1 and 34.5, respectively, when 12 hours had elapsed. , causing the separation to widen. In the case of propylene selectivity, the initial values were 88.9% and 89.2%, respectively, and even after 12 hours of reaction, a similar level of difference was observed. In the case of the comparative example, after 12 hours of reaction, a reduction in the yield of propylene is notably shown, which is determined to be due to coke depositing on the platinum distributed directly from the surface, thereby clogging the active sites and blocking the reaction gas from reaching the interior. On the contrary, in the case of the example, it is confirmed that the platinum active sites are not exposed to the outside, so the reduction in activity due to coke deposition is small. Figure 3 is a graph showing changes in conversion rate over time. It is observed that the catalyst of the example allows achieving a high conversion rate and maintaining the high conversion rate for 12 hours.

To evaluate the post-abrasion activity of the example and the comparative example prepared according to the present disclosure, an abrasion test was performed. 50 g of each catalyst were collected and placed in an empty container along with 50 g of SUS type balls. The container was then placed in a rotation tool so that the container continued to rotate while the catalyst surface was damaged. This operation lasted 10 days. As a result, it was confirmed that the average catalyst size was reduced by 7% to 8% in both the example and the comparative example. The dehydrogenation of propane was performed using the catalyst subjected to the abrasion test, as described above, for 12 hours, and the results were compared with those before undergoing the abrasion test. Results are shown in table 2.

[Table 2]

There was no difference in the activity of the catalyst according to the example, but it was confirmed that the conversion rate in the case of the catalyst, according to the comparative example, decreased significantly. In the case of the example, loss of platinum caused by the abrasion test is avoided because the platinum is present at a predetermined depth of at least 100 um from the surface. However, in the case of the comparative example, it can be inferred that such results were obtained due to the damaged surface as well as the reduced number of platinum active sites.

Claims (4)

1. Dehydrogenation catalyst which is a spherical platinum catalyst comprising tin and potassium components used for the catalytic dehydrogenation of light hydrocarbons, the catalyst having a ring-shaped metal distribution where the platinum component is not present on the surface of the catalyst but is present within the catalyst, in the form of a ring with a predetermined thickness at a predetermined depth from the surface of the catalyst. 2. Catalyst of claim 1, wherein the tin component is present in the form of an eggshell wherein the tin component is present in a region from the surface to a predetermined depth. 3. Catalyst of claim 1, wherein the potassium component is uniformly distributed throughout the catalyst. 4. Catalyst of any one of claims 1 to 3, wherein the predetermined depth is in a range of 30 um to 200 um, and the predetermined thickness is in a range of 200 um to 500 um.