CN109926067B - A platinum-palladium-cobalt ternary metal hydrodearomatization catalyst and preparation method thereof - Google Patents

Abstract

The invention provides a platinum-palladium-cobalt ternary metal hydrogenation dearomatization catalyst and a preparation method. The catalyst preparation process adopts a method of step-by-step impregnation of active metal precursors. Specifically, the prepared carrier is used to impregnate the palladium-cobalt metal precursor first. , after reduction and post-treatment, and then impregnated with platinum and palladium metal precursors. The catalyst prepared by the method has high utilization rate of platinum, palladium and precious metal, strong synergistic catalyst ability, and the introduction of platinum and palladium leads to the enhancement of aromatics hydrogenation performance of non-precious metal cobalt. The catalyst is especially suitable for the hydrorefining process of deep dearomatization of feedstock oil with high sulfur content to prepare clean diesel oil, high-quality lubricating base oil and white oil.

Description

A platinum-palladium-cobalt ternary metal hydrodearomatization catalyst and preparation method thereof

technical field

The invention specifically relates to a platinum-palladium-cobalt ternary metal hydrogenation dearomatization catalyst and a preparation method.

Background technique

The deep hydrodearomatization technology is widely used in the refining and upgrading process of petroleum refining products. It mainly uses a reduced metal hydrogenation catalyst to deeply hydrogenate and saturate aromatic hydrocarbons in oil products, especially polycyclic aromatic hydrocarbons that are difficult to remove, to obtain Various products with excellent product performance and environmental protection requirements, such as diesel oil with high cetane index, jet fuel with low smoke point, lubricating oil base oil or white oil with good photothermal oxidation stability, etc.

From the perspective of reaction thermodynamics, low reaction temperature and high reaction pressure are beneficial to the hydrogenation saturation of aromatics to alkanes, which requires the prepared catalyst to have a good low-temperature hydrogenation activity. The VIII transition metals (such as nickel, cobalt, ruthenium, rhodium, palladium and platinum, etc.) in the reduced state all have the ability to saturate aromatic hydrocarbons. In contrast, non-precious metal nickel and cobalt-based catalysts have poor aromatics hydrogenation activities, but are inexpensive; precious metal ruthenium, rhodium, palladium, and platinum-based catalysts have good aromatics hydrogenation activities, but are expensive. Especially in the process of aromatics hydrorefining with complex sulfur-containing system, the synergistic catalysis of multiple precious metals is often used. Patents CN106466601A, CN1245204A, CN104826650B, US5391291A, US5393408, US5879539, etc. have reported that precious metal platinum-palladium bimetallic catalysts show good synergistic catalyst effect in the process of deep hydrogenation and saturation of aromatic hydrocarbons with sulfur system. Studies have shown that platinum-palladium alloy nanoparticles with strong electronic interactions exist on the surface of platinum-palladium bimetallic catalysts, platinum can transfer electrons to palladium, and the electron cloud structure on the surface of platinum-palladium metal is optimized, which is conducive to weakening metal active sites and sulfides. The bonding effect of bimetallic catalysts improves the anti-sulfur hydrogenation activity of bimetallic catalysts.

Although noble metal platinum-palladium bimetallic catalysts show good activity for deep hydrogenation of aromatic hydrocarbons, the proportion of platinum-palladium alloy nanoparticles in the traditional platinum-palladium catalyst preparation process is not high. Synergistic catalysis of platinum-palladium bimetallic catalysts. Patent CN1205316C discloses a method for preparing a multi-component metal hydrogenation saturated catalyst in which platinum palladium precious metal and non-precious metal are jointly supported on a carrier including porous silica-alumina, but the multi-component metal catalyst prepared by this method has non-precious metal components. The interaction force with noble metal components is weak, and the intrinsic hydrogenation activity of noble metal components is not significantly improved. Therefore, it is very important to develop non-precious metal-substituted or semi-substituted platinum-palladium aromatics hydrogenation catalysts with high hydrogenation activity to further enhance the synergistic catalytic effect of non-precious metal components and noble metal components through the regulation of catalyst preparation methods. significance.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for preparing a novel platinum-palladium-cobalt ternary metal hydrorefining dearomatization catalyst. The catalyst prepared by the method uses non-precious metal cobalt nanoparticles as anchor points and palladium nanoparticles as crystal seeds. In situ induction of platinum-palladium-cobalt ternary metal catalysts. The catalyst preparation process adopts the method of step-by-step impregnation of active metal precursors. Specifically, the prepared carrier is used to impregnate the palladium-cobalt metal precursor first, and after reduction and post-treatment, the platinum-palladium metal precursor is then impregnated. The catalyst prepared by the method has high utilization rate of platinum and palladium precious metals, strong synergistic catalyst ability, and the introduction of platinum and palladium leads to the enhancement of aromatics hydrogenation performance of non-precious metal cobalt. The catalyst is especially suitable for the hydrorefining process of deep dearomatization of feedstock oil with high sulfur content to prepare clean diesel oil, high-quality lubricating base oil and white oil.

To achieve the above object, the present invention adopts the following technical solutions:

A preparation method of an improved aromatic hydrocarbon deep hydrogenation saturated catalyst, the method specifically comprises the steps:

(a) Preparation of a silicon-alumina mixed oxide support;

(b) Prepare cobalt-palladium mixed precursor salt solution, and control the concentration of cobalt in the solution to be 1.0×10 ^-2 g/ml~3.0×10 ^-2 g/ml and the concentration of palladium to be 1.7×10 ^-3 g/ml Between ml ~1.0×10 ^-2 g/ml;

(c) impregnating the cobalt-palladium mixed precursor salt solution prepared in (b) on the support prepared in (a);

(d) subjecting the impregnated sample (c) to certain drying, roasting and reduction treatments;

(e) Prepare platinum-palladium mixed precursor salt solution, control the concentration of platinum in the solution to be 0.5×10 ^-3 g/ml ~ 6.7×10 ^-3 g/ml and the concentration of palladium to be 0.2×10 ^-3 g/ml Between ~1.0×10 ^-2 g/ml;

(f) dipping the sample obtained in (d) into the platinum-palladium mixed precursor salt solution prepared in (e);

(g) The sample impregnated in (f) is dried, calcined and reduced to a platinum-palladium-cobalt ternary metal catalyst.

Preferably, the alumina-silica component precursor of the carrier prepared in (a) can be at least two of alumina sol, silica sol, pseudo-boehmite, amorphous silica-alumina, and silica-alumina molecular sieves;

Preferably, the preparation method of the carrier in (a) can adopt the method of sol-gel or mechanical mixing, and the extruded shape of the carrier can be any one of three herbs, four-leaf clover, cylindrical and spherical;

Preferably, the mass fraction of oxides of metal components in the carrier prepared in (a) is: alumina 20-80%, silicon oxide 20-40%, and the sum of the total mass fractions is 100%;

Preferably, the cobalt salt precursor used in (b) can be any one of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate and cobalt oxalate; the palladium salt precursor can be palladium chloride, palladium nitrate, any one in ammonium palladate and tetraammine palladium nitrate;

Preferably, the weight ratio of the cobalt-palladium mixed salt solution used in (b) converted to cobalt and palladium is controlled between 6.0:1.0 and 3.0:1.0;

Preferably, (d) the drying treatment is performed at a temperature of 60-150°C for 1-12 hours, the calcination treatment is performed at a temperature of 350-550°C for 1-5 hours, and the reduction treatment is performed at a temperature of 200-400°C for 1-5 hours;

Preferably, the platinum salt precursor used in (e) can be any one of chloroplatinic acid, ammonium chloroplatinate, tetraammine platinum chloride and tetraammine platinum nitrate; the palladium salt precursor can be chloride any one in palladium, palladium nitrate, ammonium chloropalladate and tetraammine palladium nitrate;

Preferably, (e) the weight ratio of the platinum and palladium precursor salt solutions converted into platinum and palladium is controlled between 0.2:1.0 and 2.0:1.0;

Preferably, when (c) and (f) impregnate the carrier, the aging temperature is controlled at 20-120°C, and the aging time is controlled at 1-12 hours;

Preferably, (f) the impregnation of the carrier is carried out under the protection of vacuum or inert gas (such as nitrogen);

Preferably, in (g), the drying treatment is performed at a temperature of 60-150 °C for 1-12 hours, the roasting treatment is performed at a temperature of 350-550 °C for 1-5 hours, and the reduction treatment is performed at a temperature of 250-400 °C for 1-5 hours;

Preferably, the catalyst obtained in (g) has a total noble metal loading of platinum and palladium of 0.3-1.0 wt%, and a cobalt metal loading of 0.5-3.0 wt%.

When the above catalyst is applied to the hydrorefining of raw oil, the reaction conditions are as follows: the reaction temperature is 190-350° C., the reaction pressure is 14-18 MPa, the space velocity is 0.3-1.0 h ^-1 , and the volume ratio of hydrogen to oil is 500-800.

The advantages of the present invention are: the catalyst preparation process prepared by the method adopts a step-by-step impregnation method, that is, the prepared carrier is first impregnated with the cobalt-palladium metal precursor mixed solution, and then treated after reduction and then impregnated with the platinum-palladium metal precursor. In the first step, the cobalt-palladium mixed solution is impregnated, and the introduction of palladium in the reduction process can promote the reduction of cobalt. The obtained reduced samples can provide cobalt nanoparticles as anchoring sources and palladium nanoparticles as seeds. Because of the high surface free energy and electrochemical displacement of metal nanoparticles, the platinum-palladium solution impregnated in the second step can be further induced to contain platinum. The form of palladium alloy is dispersed on the surface of the catalyst support. The catalyst prepared by the method has a high concentration of platinum-palladium alloy nanoparticles, and mostly exists in the form of palladium as the core and platinum as the shell, and has strong synergistic catalytic ability. In addition, the introduction of platinum and palladium also further improves the aromatics hydrogenation performance of non-precious metal cobalt. In the platinum-palladium-cobalt three-way catalyst prepared by the method, the platinum-palladium-cobalt active metal exhibits a good synergistic catalytic effect, and is suitable for the removal of aromatics from the feedstock oil with high sulfur content. The invention provides a preparation method of an aromatic hydrocarbon deep hydrorefining catalyst with strong raw material adaptability, and the preparation process is simple, good in reproducibility and convenient for industrial production.

Detailed ways

The preparation method and application of the present invention will be further described below in conjunction with specific examples, but the specific embodiments described herein are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

The specific surface area and pore volume of the catalyst material of the present invention are measured by a low-temperature liquid nitrogen adsorption method.

Example 1

130 grams of amorphous silica-alumina (pore volume 0.9 mL/g, specific surface area 490m ² /g, dry basis 80%), 60 grams pseudoboehmite (dry basis 70%, pore volume 0.7 mL/g, specific surface area 280m ² /g), 4.5 grams of succulent powder was put into a rolling machine and mixed and ground, and 170 grams of dilute nitric acid solution (the mass of nitric acid contained was 3% of the dry basis weight of pseudo-boehmite) was added and rolled into a paste. , the extruded strands (about 1.6 mm in diameter) were dried at 120 °C for 12 hours, and then calcined at 500 °C for 4 hours to obtain the carrier SCAT.

Using a conventional equal volume impregnation method, a mixed solution of CoCl ₂ (analytical grade) and PdCl ₂ (analytical grade) (converted to the weight ratio of cobalt and palladium in the cobalt-palladium mixed salt solution is 5.31:1.00) is immersed in the carrier. On SCAT, aging at 50°C for 3 hours, then drying at 120°C for 10 hours, calcining at 500°C for 3 hours, and hydrogen reduction at 300°C for 3 hours to obtain MCAT-1 sample; continue to use equal volume impregnation method, PdCl ₂ The mixed solution of (analytical grade) and H ₂ PtCl ₆ (analytical grade) (the weight ratio of platinum and palladium in the platinum-palladium mixed salt solution converted to platinum and palladium is 0.75:1.00) was impregnated on the carrier MCAT-1 under vacuum conditions, 50 Aging at ℃ for 3 hours, then drying at 120 ℃ for 10 hours, calcination at 500 ℃ for 3 hours, and hydrogen reduction at 350 ℃ for 3 hours to obtain CAT-1 catalyst. In the prepared catalyst, the metal loadings of the final platinum, palladium and cobalt relative to the carrier are controlled at 0.12wt%, 0.32wt% and 0.85wt% respectively.

Example 2

Using the conventional method of equal volume impregnation, the mixed solution of Co(NO ₃ ) ₂ (analytical grade) and PdCl ₂ (analytical grade) (the cobalt-palladium mixed salt solution is converted into a weight ratio of cobalt and palladium is 5.31:1.00 ) was immersed on the carrier SCAT, aged at 50°C for 3 hours, then dried at 120°C for 10 hours, calcined at 500°C for 3 hours, and treated with hydrogen reduction at 300°C for 3 hours to obtain the MCAT-2 sample; continue to use the method of equal volume impregnation , the mixed solution of PdCl ₂ (analytical grade) and H ₂ PtCl ₆ (analytical grade) (the weight ratio of platinum and palladium converted into platinum-palladium mixed salt solution is 0.75:1.00) was immersed in the carrier MCAT- 2, aging at 50°C for 3 hours, then drying at 120°C for 10 hours, calcination at 500°C for 3 hours, and hydrogen reduction at 350°C for 3 hours to obtain CAT-2 catalyst. In the prepared catalyst, the metal loadings of the final platinum, palladium and cobalt relative to the carrier are controlled at 0.12wt%, 0.32wt% and 0.85wt% respectively.

Example 3

Using the conventional method of equal volume impregnation, the mixed solution of Co(NO ₃ ) ₂ (analytical grade) and PdCl ₂ (analytical grade) (the cobalt-palladium mixed salt solution converted into the weight ratio of cobalt and palladium is 4.25:1.0 ) was immersed on the carrier SCAT, aged at 50°C for 3 hours, then dried at 120°C for 10 hours, calcined at 500°C for 3 hours, and treated with hydrogen reduction at 300°C for 3 hours to obtain the MCAT-3 sample; continue to use the method of equal volume impregnation , the mixed solution of PdCl ₂ (analytical grade) and [Pt(NH ₃ ) ₄ ] (NO ₃ ) ₂ (analytical grade) (the weight ratio of platinum-palladium mixed salt solution converted to platinum and palladium is 1.00:1.00) Impregnated on the carrier MCAT-3 under vacuum conditions, aged at 50°C for 3 hours, then dried at 120°C for 10 hours, calcined at 500°C for 3 hours, and treated with hydrogen reduction at 350°C for 3 hours to obtain CAT-3 catalyst. In the prepared catalyst, the metal loadings of the final platinum, palladium and cobalt relative to the carrier are controlled at 0.12wt%, 0.32wt% and 0.85wt% respectively.

Example 4

Using the conventional method of equal volume impregnation, the mixed solution of Co(NO ₃ ) ₂ (analytical grade) and PdCl ₂ (analytical grade) (the cobalt-palladium mixed salt solution converted into the weight ratio of cobalt and palladium is 3.27:1.00 ) was immersed on the carrier SCAT, aged at 50°C for 3 hours, then dried at 120°C for 10 hours, calcined at 500°C for 3 hours, and treated with hydrogen reduction at 300°C for 3 hours to obtain the MCAT-4 sample; continue to use the method of equal volume impregnation , the mixed solution of PdCl ₂ (analytical grade) and H ₂ PtCl ₆ (analytical grade) (the weight ratio of platinum-palladium mixed salt solution converted to platinum and palladium is 2.00:1.00) was immersed in the carrier MCAT- 4, aging at 50°C for 3 hours, then drying at 120°C for 10 hours, calcination at 500°C for 3 hours, and hydrogen reduction at 350°C for 3 hours to obtain CAT-4 catalyst. In the prepared catalyst, the metal loadings of the final platinum, palladium and cobalt relative to the carrier are controlled at 0.12wt%, 0.32wt% and 0.85wt% respectively.

Comparative Example 1

Using the conventional equal volume impregnation method, the solution of Co(NO ₃ ) ₂ (analytical grade) was impregnated on the carrier SCAT, aged at 50°C for 3 hours, then dried at 120°C for 10 hours, and calcined at 500°C for 3 hours. The MCAT-5 sample was obtained by hydrogen reduction treatment at 400 °C for 3 hours; the method of equal volume impregnation was continued, and the mixed solution of PdCl ₂ (analytical grade) and H ₂ PtCl ₆ (analytical grade) was immersed in the carrier MCAT-5 under vacuum conditions. 5, aged at 50°C for 3 hours, then dried at 120°C for 10 hours, calcined at 500°C for 3 hours, and treated with hydrogen reduction at 350°C for 3 hours to obtain CAT-5 catalyst. In the prepared catalyst, the metal loadings of the final platinum, palladium and cobalt relative to the carrier are controlled at 0.12wt%, 0.32wt% and 0.85wt% respectively.

Comparative Example 2

Using the conventional method of equal volume impregnation, the mixed solution of Co(NO ₃ ) ₂ (analytical grade) H ₂ PtCl ₆ (analytical grade) (the cobalt-platinum mixed salt solution is converted into a weight ratio of cobalt and palladium is 14.17 : 1.0) Impregnated on the carrier SCAT, aged at 50°C for 3 hours, then dried at 120°C for 10 hours, calcined at 500°C for 3 hours, and treated with hydrogen reduction at 300°C for 3 hours to obtain MCAT-6 samples; continue to use equal volume impregnation method, the mixed solution of PdCl ₂ (analytical grade) and [Pt(NH ₃ ) ₄ ] (NO ₃ ) ₂ (analytical grade) (the platinum-palladium mixed salt solution is converted into a weight ratio of platinum and palladium is 0.19: 1.00) Impregnated on the carrier MCAT-6 under vacuum conditions, aged at 50°C for 3 hours, then dried at 120°C for 10 hours, calcined at 500°C for 3 hours, and reduced in hydrogen at 350°C for 3 hours to obtain CAT-6 catalyst. In the prepared catalyst, the metal loadings of the final platinum, palladium and cobalt relative to the carrier are controlled at 0.12wt%, 0.32wt% and 0.85wt% respectively.

Comparative Example 3

Using the conventional method of equal volume impregnation, a mixed solution containing Co(NO ₃ ) ₂ (analytical grade) PdCl ₂ (analytical grade) and H ₂ PtCl ₆ was impregnated on the carrier SCAT, aged at 50 °C for 3 hours, and then subjected to 120 The CAT-7 catalyst was obtained by drying at ℃ for 10 hours, calcining at 500 ℃ for 3 hours, and hydrogen reduction at 350 ℃ for 3 hours. In the prepared catalyst, the metal loadings of the final platinum, palladium and cobalt relative to the carrier are controlled at 0.12wt%, 0.32wt% and 0.85wt% respectively.

Comparative Example 4

Using the conventional equal volume impregnation method, the mixed solution of PdCl ₂ (analytical grade) and H ₂ PtCl ₆ (analytical grade) was impregnated on the carrier SCAT, aged at 50 °C for 3 hours, and then dried at 120 °C for 10 hours, 500 calcination treatment at ℃ for 3 hours, and hydrogen reduction treatment at 350 ℃ for 3 hours to obtain CAT-8 catalyst. In the prepared catalyst, the final metal loading of platinum and palladium relative to the carrier was controlled at 0.20wt% and 0.40wt% respectively.

The above CAT-1 to CAT-8 catalysts were used in the evaluation of hydrorefining performance of No. 1 feedstock oil, No.2 feedstock oil and No.3 feedstock oil (see Table 1 for the physical properties of the feedstock oils). The evaluation operating conditions are: 30 mL of catalyst (the particles are crushed to 14-20 mesh size) and 60 mL of quartz sand (14-20 mesh) are mixed and packed, the reaction temperature is 190-250 °C, the space velocity is 0.5 h ^-1 , and the volume ratio of hydrogen to oil is 700 .

The physicochemical properties of the above catalysts are shown in Table 2 and the properties of the hydrogenated oil products corresponding to the performance evaluation are shown in Tables 3 to 5.

Table 1 Physical parameters of hydrogenation feedstock oil

The physicochemical properties of the catalysts prepared in Table 2

Table 3 Properties of No. 1 Hydrogenated Oil

Table 4 Properties of No. 2 Hydrogenated Oil

Table 5 Properties of No. 3 Hydrogenated Oil

Three different feedstock oils were selected to investigate the performance of the prepared catalysts. The evaluation results showed that using non-precious metal cobalt nanoparticles as anchor points and palladium nanoparticles as seeds, the in-situ induced platinum-palladium-cobalt ternary metal catalyst has excellent performance. The anti-sulfur and deep dearomatization performance is especially suitable for the production of high-quality white oil from lubricating oil fractions. The catalyst prepared by this method still shows good deep hydrotreating performance under the condition that the platinum content can be reduced by 40% and the palladium content can be reduced by 20% by using a low amount of non-precious metal cobalt.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (1)

1. A preparation method of a platinum-palladium-cobalt ternary metal hydrogenation dearomatization catalyst is characterized by comprising the following steps:

(1) placing 130 g of amorphous silica-alumina, 60 g of pseudo-boehmite and 4.5 g of sesbania powder into a rolling machine for mixing and rolling, adding 170 g of dilute nitric acid solution, wherein the mass of the nitric acid is 3% of the dry basis weight of the pseudo-boehmite, rolling into paste, drying extruded strips at 120 ℃ for 12 hours, and roasting at 500 ℃ for 4 hours to obtain a carrier SCAT;

(2) the CoCl is impregnated by a conventional method with equal volume ₂ And PdCl ₂ The mixed solution of (A) is impregnated on a carrier SCAT, and the weight ratio of cobalt to palladium in the cobalt-palladium mixed salt solution is 5.31: 1.00, aging at 50 ℃ for 3 hours, then drying at 120 ℃ for 10 hours, roasting at 500 ℃ for 3 hours, and reducing with hydrogen at 300 ℃ for 3 hours to obtain an MCAT-1 sample; continuously adopting an equal-volume impregnation method to prepare PdCl ₂ And H ₂ PtCl ₆ The mixed solution of (a) was impregnated on the support MCAT-1 under vacuum, and the weight ratio of platinum to palladium in the platinum-palladium mixed salt solution was 0.75: 1.00, aging at 50 ℃ for 3 hours, then drying at 120 ℃ for 10 hours, roasting at 500 ℃ for 3 hours, and reducing at 350 ℃ for 3 hours to obtain the catalyst The final metal loading of platinum, palladium and cobalt in the prepared catalyst was controlled at 0.12wt%, 0.32wt% and 0.85wt% respectively relative to the carrier.