Catalyst for selective hydrogenation of cracked gas, cracked gasoline or distillate oil thereof as well as preparation method and application of catalyst

Abstract

The invention provides a catalyst for selective hydrogenation of cracked gas, cracked gasoline or distillate oil thereof and a preparation method and application thereof.The catalyst comprises an aluminum oxide-titanium oxide composite oxide carrier and active components loaded on the aluminum oxide-titanium oxide composite oxide carrier, the pore volume of the composite oxide carrier is 0.2-0.8 mL / g, the pore diameter is 10-20 microns, the specific surface area is 90-150 m < 2 > / g, and the pore diameter of the composite oxide carrier is 10-20 microns. The active component is selected from one or more of transition metal, alkali metal and IVA group metal. The active components of the catalyst are high in dispersity, uniform in distribution and small in particle size, and the catalyst is high in low-temperature hydrogenation activity and good in stability.

Description

Technical Field

[0001] The invention relates to a catalyst for selective hydrogenation of cracked gas, cracked gasoline or its fraction oil, and a preparation method and application thereof. Background Art

[0002] Propylene is an important basic chemical raw material that can be used to produce polypropylene, acrylonitrile, propylene oxide, acrolein, acrylic acid, etc. Its downstream products are widely used in films, fibers, rubber, resins, coatings and other fields.

[0003] Propylene is usually obtained in petroleum cracking ethylene production units. The C3 fraction in the cracking gas usually consists of 93-96% propylene, 2.9-3.5% propane, and 1-5% propyne (MA) and propadiene (PD). MAPD is a toxic substance that affects downstream propylene applications. Therefore, to obtain high-purity propylene, MAPD must be removed first. Usually, MAPD in the C3 fraction is selectively hydrogenated to generate propylene, and there will also be certain side reactions to generate propane.

[0004] Industrial devices for removing MAPD from C3 fractions mainly include gas phase catalytic selective hydrogenation, liquid phase catalytic selective hydrogenation and catalytic distillation. At present, the liquid phase selective hydrogenation method is generally used in the market. This method has a simple process flow, low reaction temperature, low energy consumption, safety, environmental protection and easy operation. The selective hydrogenation of C3 fractions has high requirements for the selection of catalysts and the control of the reaction process. At present, the industrial C3 fraction selective hydrogenation catalyst is a loaded catalyst with precious metal palladium as the main active component and alumina as the carrier. Some also add additives such as silver, gold, and copper to improve propylene selectivity.

[0005] MAPD in the C3 fraction easily polymerizes into colloid at high temperature and precipitates on the catalyst surface, which quickly deactivates the catalyst and causes the catalyst to be frequently activated and regenerated. Therefore, it is hoped that the hydrogenation catalyst has a higher low-temperature activity and maintains an appropriate colloid capacity so that the activity of the polymer on the catalyst surface remains unchanged before being washed, thereby extending the service life of the catalyst, which is very important in industrial production. Summary of the invention

[0006] In view of this, in order to overcome at least one of the above problems existing in the prior art, the present invention proposes a catalyst for selective hydrogenation of pyrolysis gas, pyrolysis gasoline or its fractions, and a preparation method and application thereof.

[0007] The objectives of the present invention are achieved through the following technical solutions.

[0008] In a first aspect, the present invention provides a catalyst for selective hydrogenation of pyrolysis gas, pyrolysis gasoline or its fractions, wherein the catalyst comprises an alumina-titanium oxide composite oxide carrier and an active component supported thereon, the composite oxide carrier has a pore volume of 0.2 to 0.8 mL / g, a pore diameter of 10 to 20 μm, and a specific surface area of ​​90 to 150 m 2 / g, and the active component is selected from one or more of transition metals, alkali metals and IVA group metals.

[0009] According to the catalyst provided by the present invention, the surface of the composite oxide carrier has a coral 3D microscopic morphology. It is believed that in the alumina-titania composite oxide carrier of the present invention, titanium oxide is evenly distributed on the surface of alumina, and the surface of the carrier has a coral 3D microscopic morphology. The carrier can provide a higher specific surface area under the same pore size distribution and pore volume conditions, thereby having more active sites and stronger electron capture ability, greatly improving the low-temperature activity and stability of the catalyst, and ultimately improving the catalytic effect of TiO2 as an electron aid, and improving the hydrogenation performance of the catalyst.

[0010] According to the catalyst provided by the present invention, the content of titanium dioxide in the composite oxide support is 1 to 30 parts by weight based on 100 parts by weight of the composite oxide support. For example, the content of titanium dioxide in the composite oxide support can be 1 part by weight, 2 parts by weight, 5 parts by weight, 10 parts by weight, 12 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight or a range thereof.

[0011] In some embodiments, based on 100 parts by weight of the composite oxide support, the content of titanium dioxide in the composite oxide support is 5 to 25 parts by weight; and in some embodiments, the content of titanium dioxide in the composite oxide support is 5 to 20 parts by weight.

[0012] According to the catalyst provided by the present invention, the pore volume of the composite oxide carrier is 0.3-0.4 mL / g; and / or the pore diameter is 12-16 μm; and / or the specific surface area is 105-130 m 2 / g.

[0013] According to the catalyst provided by the present invention, the transition metal is selected from one or more of Pd, Pt, Cu, Ag, and Au, preferably Pd and Ag; and / or the alkali metal is K or Rb; and / or the Group IVA metal is Sn or Pb.

[0014] According to the catalyst provided by the present invention, each active component can exist independently in the form of an atom or a compound, and preferably exists independently in the form of an oxide.

[0015] In the present invention, the catalyst is a Pd-Ag-Sn-K / TiO2-Al2O3 multi-metal supported catalyst. In some preferred embodiments, based on 100 parts by weight of the catalyst, the content of Pd is 0.1 to 1 parts by weight in terms of oxide; the content of Ag is 1 to 5 parts by weight in terms of oxide; the content of Sn or Pb is 0.1 to 2 parts by weight in terms of oxide; and the content of K or Rb is 0.1 to 2 parts by weight in terms of oxide.

[0016] In a second aspect, the present invention provides a method for preparing the above-mentioned catalyst, wherein the preparation method comprises:

[0017] S100, providing an alumina-titania composite oxide carrier;

[0018] S200, loading active components on the alumina-titania composite oxide carrier, comprising:

[0019] S210, pre-impregnating the alumina-titania composite oxide carrier with deionized water, filtering, and draining to obtain a pre-impregnated composite oxide carrier;

[0020] S220, impregnating the pre-impregnated composite oxide carrier with a metal salt solution of an active component, and obtaining the catalyst through reduction and calcination.

[0021] According to the preparation method provided by the present invention, step S100 comprises:

[0022] S110, adding a titanium salt solution and an alkaline solution to an aluminum salt solution in parallel at a temperature of 25° C. to 60° C., preferably 50° C. to 60° C., to obtain a composite oxide intermediate;

[0023] Preferably, step S110 includes:

[0024] S111, adding a titanium salt solution to an aluminum salt solution, optionally adding an alkaline solution in parallel, controlling the pH value to be 3 to 4, and staying for 5 to 20 minutes, preferably 10 to 15 minutes;

[0025] S112, adding alkaline solution to adjust the pH value to 9-10, and staying for 5-20 minutes, preferably 15-20 minutes;

[0026] S113, adding an acid solution to adjust the pH value to 7.5-8.5, and leaving for 5-20 minutes, preferably 6-10 minutes, to obtain a composite oxide intermediate;

[0027] S120, allowing the composite oxide intermediate obtained in step S110 to stand at a temperature of 80° C. to 150° C., preferably 80° C. to 95° C., for 20 to 60 minutes, preferably 20 to 40 minutes, to obtain a precipitate;

[0028] S130, washing, drying and calcining the precipitate obtained in step S120 to obtain an alumina-titania composite oxide carrier.

[0029] According to the preparation method provided by the present invention, the aluminum salt is a soluble aluminum salt, preferably one or more selected from aluminum sulfate, aluminum chloride, aluminum nitrate and organic aluminum salt; and / or the aluminum salt concentration is 0.5 to 2.5 mol / L.

[0030] According to the preparation method provided by the present invention, the titanium salt solution is an acid solution of a soluble titanium salt such as metatitanic acid, titanium sulfate, titanium tetrachloride, tetraethyl titanate, etc., such as a sulfuric acid solution; and / or the concentration of the titanium salt solution is 0.1 to 1.2 mol / L.

[0031] According to the preparation method provided by the present invention, the alkaline solution comprises an ammonium salt solution and an alkali solution. The ammonium salt is selected from one or more of ammonium bicarbonate, ammonium carbonate and an organic ammonium salt; and / or the concentration of the ammonium salt in the ammonium salt solution is 0.1 to 0.3 mol / L.

[0032] Similarly, the alkali solution is selected from one or more of ammonia water, sodium hydroxide, potassium hydroxide and organic base, and / or the concentration of the alkali solution is 0.2-15 mol / L.

[0033] In the present invention, the alkaline solution can be prepared from an ammonium salt solution and an alkali solution in a molar ratio of ammonium salt to alkali of 1 to 3:1.

[0034] According to the preparation method provided by the present invention, the acid in the acid solution is selected from one or more of sulfuric acid, nitric acid, hydrochloric acid and organic acid. Preferably, the concentration of the acid solution is 10-50wt%.

[0035] According to the preparation method provided by the present invention, wherein, washing the precipitate in step S130 includes washing with deionized water until acid radical ions are not detected.

[0036] According to the preparation method provided by the present invention, the drying conditions in step S130 include: a drying temperature of 80 to 150° C., preferably 100 to 120° C., and a drying time of 4 to 12 hours.

[0037] According to the preparation method provided by the present invention, the calcination conditions in step S130 include: a calcination temperature of 700 to 1000° C., preferably 800 to 900° C., and a calcination time of 4 to 12 hours.

[0038] According to the preparation method provided by the present invention, the preparation method of the titanium salt aqueous solution comprises: dissolving a soluble titanium salt such as metatitanic acid, titanium tetrachloride, and tetraethyl titanate in a sulfuric acid solution to form a titanium salt solution.

[0039] According to the preparation method provided by the present invention, the pre-impregnation in step S210 includes: immersing the aluminum oxide-titanium oxide composite oxide carrier in deionized water of 1 to 1.5 times its volume for 0.3 to 1 hour.

[0040] According to the preparation method provided by the present invention, the metal salts of the active components are all soluble inorganic salts. For example, examples of inorganic salts of Pd include, but are not limited to, palladium chloride, palladium nitrate, palladium sulfate, etc.; examples of inorganic salts of Ag include, but are not limited to, silver nitrate, silver fluoride, silver chlorate, silver perchlorate, etc.; examples of inorganic salts of Sn include, but are not limited to, tin tetrachloride, tin dichloride, etc.; examples of inorganic salts of K include, but are not limited to, potassium nitrate and potassium chloride, etc.

[0041] According to the preparation method provided by the present invention, the metal salt solution is a deionized water solution of a metal salt.

[0042] According to the preparation method provided by the present invention, the concentration of the metal salt solution of the active component is 0.01-0.3 mol / L.

[0043] According to the preparation method provided by the present invention, the impregnation in step S220 can adopt a one-step impregnation method, that is, a mixed impregnation solution containing metal salt solutions of all active components is prepared, and the aluminum oxide-titanium oxide composite support is impregnated in a mixed solution of several metal salt solutions in one step. The impregnation in step S220 can also adopt a multi-step impregnation method.

[0044] In some embodiments, the impregnation in step S220 preferably adopts a two-step impregnation method. Specifically, step S220 specifically includes:

[0045] S221, impregnating the pre-impregnated composite oxide support with a first metal salt solution containing Sn salt and K salt, draining and drying to obtain a catalyst semi-finished product;

[0046] S222, using a second metal salt solution containing Ag salt and Pd salt to impregnate the catalyst semi-finished product, draining, reducing with hydrazine hydrate, filtering, washing, drying and calcining to obtain the catalyst.

[0047] Preferably, the immersion time in steps S221 and S222 is independently 0.5 to 4 hours.

[0048] Preferably, the amount of the first metal salt solution in step S221 and the second metal salt solution in step S222 are each independently 0.8 to 2.5 times the total pore volume of the composite oxide support.

[0049] Preferably, the amount of hydrazine hydrate used in step S222 is 1 to 2 times the volume of the composite oxide support, and / or the concentration is 30 to 40 wt%.

[0050] Preferably, the drying conditions in steps S221 and S222 independently include: a temperature of 80-150° C. and a time of 4 to 12 hours.

[0051] Preferably, the calcination conditions in step S222 include: a temperature of 700-1000° C. and a time of 4-8 hours.

[0052] Preferably, step S222 includes a reduction operation after calcination. More preferably, the reduction conditions include: hydrogenation temperature of 100-150°C, hydrogen pressure of 2.6-3.0 MPa, hydrogen flow rate of 35-65 ml / min, and reduction time of 6-8 h.

[0053] Of course, in the present invention, the metal salt solution of the active component can be loaded by conventional methods such as impregnation and spraying.

[0054] In a third aspect, the present invention further provides the use of the catalyst of the first aspect or the catalyst prepared by the method of the second aspect in the selective hydrogenation of pyrolysis gas, pyrolysis gasoline or its fractions, especially in the selective hydrogenation of C3 fractions.

[0055] In a fourth aspect, the present invention further provides a method for selective hydrogenation of pyrolysis gas, pyrolysis gasoline or its fractions, comprising: subjecting the pyrolysis gas, pyrolysis gasoline or its fractions to MAPD selective hydrogenation in the presence of the catalyst of the first aspect or the catalyst prepared by the method of the second aspect, wherein the fraction is preferably C3 fraction.

[0056] According to the method for selective hydrogenation of cracked gas, cracked gasoline or its fraction provided by the present invention, the conditions for selective hydrogenation include: reactor inlet temperature and reaction temperature are 20-50°C, hydrogen / (MA+PD) (mol)=1-2.5:1, pressure is 0.5-3.0MPa, material volume space velocity is 10-200h -1 .

[0057] In the present invention, the term "MA" means propyne, and the term "PD" means propadiene.

[0058] The present invention has the following advantages:

[0059] (1) In the catalyst of the present invention, titanium oxide and aluminum oxide are uniformly mixed and enriched on the surface of the oxide carrier, and the inventors surprisingly found that the surface microstructure of the composite oxide presents a coral-like 3D layered structure. The coral-like 3D layered structure can make the composite oxide have a higher specific surface area, thereby having more active sites and stronger electron capture ability, which helps to promote the catalytic effect of TiO2 as an electron auxiliary agent.

[0060] (2) The active components of the catalyst of the present invention have high dispersion, uniform distribution, and small particle size. The catalyst has high low-temperature hydrogenation activity and good stability.

[0061] (3) The catalyst of the present invention has cheap and readily available raw materials and is suitable for industrial production of a C3 fraction selective hydrogenation catalyst. The catalyst has a specific structure, TiO2 is evenly dispersed on the surface of the carrier, the catalyst has good low-temperature activity, and high hydrogenation activity at high space velocity. The catalyst is used for hydrogenation of C2 and C3 fractions, has a high conversion rate and hydrogenation selectivity, effectively removes MAPD from the C3 fraction, and has a good industrial application prospect. In addition, compared with existing catalysts, the hydrogenation catalyst provided by the present invention has higher low-temperature activity and hydrogenation activity at high space velocity in the field of C3 fraction hydrogenation. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is the SEM image of the aluminum oxide-titanium oxide composite oxide prepared in Example 1. DETAILED DESCRIPTION

[0063] The present invention will be further described below in conjunction with specific embodiments, but they do not constitute any limitation to the present invention.

[0064] Example 1

[0065] Prepare 1L of deionized aluminum sulfate solution with a concentration of 0.42mol / L; prepare 0.5L of dilute sulfuric acid solution of titanic acid with a concentration of 0.19mol / L; mix 0.6L of 0.38mol / L ammonium bicarbonate solution and 0.25L of 1.75mol / L ammonia water to obtain a mixed alkaline solution with a pH of 11.5±0.5; prepare 0.5L of 30wt% dilute sulfuric acid solution.

[0066] At normal pressure and a temperature of 55°C, add all the dilute sulfuric acid solution of metatitanic acid to a deionized aluminum sulfate solution, and add part of the mixed alkali solution in a stream, keep the pH value of the mixed solution within the range of 3.5±0.5, stop adding the mixed alkali solution, and stir vigorously for 15 minutes; continue to add the mixed alkali solution to make the pH value = 9.5±0.5, stop adding the mixed alkali solution, and stay within this range for 15 minutes; add dilute sulfuric acid to adjust the pH value to 8.0±0.5, and stay for 10 minutes; raise the temperature to 92°C and maintain for 20 minutes; filter, wash the filter cake repeatedly 5 times with 20 times the volume of deionized water, dry the washed filter cake at 110°C for 6 hours, and calcine at 850°C for 5 hours to obtain an aluminum oxide-titanium oxide composite oxide with a TiO2 content of 15.0%.

[0067] Example 2

[0068] Prepare 1L of deionized aluminum nitrate solution with a concentration of 0.8mol / L; prepare 0.38L of dilute sulfuric acid solution of titanium sulfate with a concentration of 0.2mol / L; mix 0.6L of 0.38mol / L ammonium bicarbonate solution and 0.25L of 1.75mol / L ammonia water to obtain a mixed alkaline solution with a pH of 11.5±0.5; prepare 0.5L of 35wt% dilute nitric acid solution.

[0069] At normal pressure and a temperature of 60°C, add all the dilute sulfuric acid solution of titanium sulfate to a deionized aluminum nitrate solution, and add part of the mixed alkali solution in a stream, keep the pH value of the mixed solution within the range of 3.5±0.5, stop adding the mixed alkali solution, and stir vigorously for 15 minutes; continue to add the mixed alkali solution to make the pH value = 9.5±0.5, stop adding the mixed alkali solution, and stay within this range for 15 minutes; add dilute nitric acid solution to adjust the pH value to 8.0±0.5, and stay for 10 minutes; raise the temperature to 85°C and maintain for 40 minutes; filter, wash the filter cake repeatedly 5 times with 20 times the volume of deionized water, dry the washed filter cake at 110°C for 6 hours, and calcine at 950°C for 5 hours to obtain an aluminum oxide-titanium oxide composite oxide with a TiO2 content of 12.3%.

[0070] Example 3

[0071] Prepare 1L of deionized aluminum sulfate solution with a concentration of 0.44mol / L; prepare 0.5L of dilute sulfuric acid solution of titanic acid with a concentration of 0.15mol / L; mix 0.6L of 0.38mol / L ammonium bicarbonate solution and 0.25L of 1.75mol / L ammonia water to obtain a mixed alkaline solution with a pH of 11.5±0.5; prepare 0.5L of 25wt% dilute sulfuric acid solution.

[0072] At normal pressure and a temperature of 50°C, add all the dilute sulfuric acid solution of metatitanic acid to a deionized aluminum sulfate solution, and add part of the mixed alkali solution in a stream, keep the pH value of the mixed solution within the range of 3.5±0.5, stop adding the mixed alkali solution, and stir vigorously for 15 minutes; continue to add the mixed alkali solution to make the pH value = 9.5±0.5, stop adding the mixed alkali solution, and stay within this range for 15 minutes; add dilute sulfuric acid to adjust the pH value to 8.0±0.5, and stay for 10 minutes; raise the temperature to 100°C and maintain for 30 minutes; filter, wash the filter cake repeatedly 5 times with 20 times the volume of deionized water, dry the washed filter cake at 110°C for 6 hours, and calcine at 950°C for 5 hours to obtain an aluminum oxide-titanium oxide composite oxide with a TiO2 content of 9.1%.

[0073] Example 4

[0074] Prepare 1L of deionized water solution with a concentration of 0.9mol / L aluminum chloride; prepare 0.5L of dilute sulfuric acid solution of titanium tetrachloride with a concentration of 0.12mol / L; mix 0.6L of 0.38mol / L ammonium bicarbonate solution and 0.25L of 1.75mol / L ammonia water to obtain a mixed alkaline solution with a pH of 11.5±0.5; prepare 0.5L of 15wt% dilute hydrochloric acid solution.

[0075] At normal pressure and a temperature of 25°C, all the titanium tetrachloride solution is added to the aluminum chloride aqueous solution, and part of the mixed alkali solution is added in parallel to maintain the pH value of the mixed solution within the range of 9.5±0.5, stop adding the mixed alkali solution, and stir vigorously for 20 minutes; continue to add the mixed alkali solution to make the pH value = 9.5±0.5, stop adding the mixed alkali solution, and stay within this range for 20 minutes; add dilute hydrochloric acid to adjust the pH value to 8.0±0.5, and stay for 10 minutes; raise the temperature to 80°C and maintain for 40 minutes; filter, wash the filter cake repeatedly 5 times with 20 times the volume of deionized water, dry the washed filter cake at 120°C for 6 hours, and calcine at 700°C for 5 hours to obtain an aluminum oxide-titanium oxide composite oxide with a TiO2 content of 5.2%.

[0076] Example 5

[0077] Prepare 1L of deionized water solution with a concentration of 0.39mol / L aluminum sulfate; prepare 0.5L of anhydrous ethanol solution of tetraethyl titanate with a concentration of 0.15mol / L; mix 0.6L of 0.38mol / L ammonium bicarbonate solution and 0.25L of 1.75mol / L ammonia water to obtain a mixed alkaline solution with a pH of 11.5±0.5; prepare 0.5L of a 50wt% dilute sulfuric acid solution.

[0078] At normal pressure and a temperature of 50°C, all the tetraethyl titanate solution is added to an aqueous aluminum sulfate solution, and part of the mixed alkali solution is added in parallel to maintain the pH value of the mixed solution within the range of 3.5±0.5, stop adding the mixed alkali solution, and stir vigorously for 20 minutes; continue to add the mixed alkali solution to adjust the pH value to 9.5±0.5, stop adding the mixed alkali solution, and stay within this range for 20 minutes; add dilute sulfuric acid to adjust the pH value to 8.0±0.5, and stay for 10 minutes; raise the temperature to 110°C and maintain for 40 minutes; filter, wash the filter cake repeatedly 5 times with 20 times the volume of deionized water, dry the washed filter cake at 150°C for 6 hours, and calcine at 1000°C for 5 hours to obtain an aluminum oxide-titanium oxide composite oxide with a TiO2 content of 20.2%.

[0079] Comparative Example 1

[0080] Prepare 1L of deionized aluminum sulfate solution with a concentration of 0.42mol / L; prepare 0.5L of dilute sulfuric acid solution of titanic acid with a concentration of 0.19mol / L; mix 0.6L of 0.38mol / L ammonium bicarbonate solution and 0.25L of 1.75mol / L ammonia water to obtain a mixed alkaline solution with a pH of 11.5±0.5; prepare 0.5L of 30wt% dilute sulfuric acid solution.

[0081] At normal pressure and 55°C, three solutions of aluminum sulfate deionized water, titanic acid dilute sulfuric acid solution and mixed alkali solution were co-precipitated in parallel. The flow rate of the mixed alkali solution was controlled until all the solutions were added. The reaction solution was allowed to stand at 70°C for 30 minutes, filtered, and washed repeatedly 5 times with deionized water 20 times the volume of the filter cake. Finally, the washed filter cake was dried at 110°C for 6 hours and calcined at 850°C for 5 hours to obtain a titanium oxide-aluminum oxide composite.

[0082] Standards for Titanium Oxide-Aluminum Oxide Composite Supports

[0083] 1. Specific surface area and pore volume

[0084] The specific surface area and pore volume of the carrier were determined using the ASAP 2020 adsorption instrument (N2 adsorption-desorption method) from Mack Instruments, USA. Specifically, the carrier sample was degassed at 623K for 4 hours before the test, nitrogen was adsorbed at liquid nitrogen temperature, the sample data was processed using AMSM software, and the specific surface area of ​​the sample was obtained using the Brunauer-Emmet-Teller (BET) method. The average pore size was obtained based on the nitrogen adsorption isotherm curve using the Barrett-Joyner-Halenda (BJH) method, and the pore volume was obtained using the P / Po single-point desorption curve. The results are shown in Table 1.

[0085] 2. Determination of Al2O3 and TiO2 content in carrier

[0086] UV-2100 ultraviolet spectrophotometer was used to measure the components in the carrier. The results are shown in Table 1.

[0087] 3. SEM analysis

[0088] The morphology of the carrier was observed using a FEI QUANTA 200 scanning electron microscope. The sample was coated on a conductive adhesive after grinding, and gold was sprayed on the surface using an ion sputtering instrument, and then observed after drying.

[0089] Table 1 Analysis data of titanium oxide-aluminum oxide composite

[0090] <![CDATA[TiO2 content (wt%)]]> <![CDATA[BET(m 2 / g)]]> Pore ​​volume (mL / g) Average pore size (μm) Example 1 15.0％ 110 0.39 15.6 Example 2 12.3％ 112 0.38 15.4 Example 3 9.1％ 120 0.38 15.7 Example 4 5.2％ 130 0.39 15.8 Example 5 20.2％ 105 0.38 14.8 Comparative Example 1 14.3％ 53 0.31 15.0

[0091] It can be seen from Table 1 that the titanium oxide-aluminum oxide composite prepared in the present invention has a significantly high specific surface area (small particle size) and a relatively high pore volume.

[0092] Further, Figure 1 The SEM image of the aluminum oxide-titanium oxide composite oxide prepared in Example 1 is shown. Figure 1 It can be seen that the surface of the composite oxide support prepared in Example 1 has a coral 3D microscopic morphology, and through SEM configured EDS, TiO2 is uniformly dispersed on the support surface. Similar to Example 1, the surfaces of the composite oxide supports of Examples 2-5 also have a coral 3D microscopic morphology, and TiO2 is uniformly dispersed on the support surface, but the composite oxide support prepared in Comparative Example 1 does not have such a morphology. It is believed that the coral-like 3D layered structure can make the composite oxide have a higher specific surface area.

[0093] Example 6

[0094] Prepare a mixed solution of tin and potassium (first metal salt solution): weigh 1.21 g of tin tetrachloride and 1.06 g of potassium chloride, and dissolve them in 0.2 L of deionized water, wherein the concentration of tin tetrachloride is 0.02 mol / L and the concentration of potassium chloride is 0.07 mol / L.

[0095] Prepare a mixed solution of palladium and silver (second metal salt solution): weigh 0.63 g of palladium nitrate and 1.88 g of silver nitrate, dissolve them in 0.2 L of deionized water to prepare a mixed solution, wherein the concentration of palladium nitrate is 0.01 mol / L, and the concentration of silver nitrate is 0.06 mol / L.

[0096] Take 100 g of the titanium oxide-aluminum oxide composite prepared in Example 1, pre-soak it with 160 mL of deionized water for 0.5 h, filter and drain the water, immerse it in the above prepared tin and potassium mixed solution, take it out after 1 h, drain it, and dry it at 100° C. for 4 h to obtain a catalyst semi-finished product.

[0097] The semi-finished catalyst was immersed in the palladium and silver mixed solution prepared above and taken out after 45 minutes. It was reduced with 145 ml of 40% hydrazine hydrate for 1 hour, the acid radical ions were washed with deionized water, dried at 120°C for 6 hours, and then roasted at 700°C for 4 hours. The roasted product was reduced for 6 hours under the conditions of hydrogenation temperature of 110°C, hydrogen pressure of 3.0MPa, and hydrogen flow rate of 40mL / min to obtain Pd-Ag-Sn-K / TiO2-Al2O3 catalyst A. The catalyst composition is shown in Table 2.

[0098] Example 7

[0099] Prepare a mixed solution of tin, potassium and silver: weigh 0.62g of tin tetrachloride, 0.78g of potassium chloride and 1.28g of silver nitrate, and dissolve them in 0.2L of deionized water, wherein the concentration of tin tetrachloride is 0.01mol / L, the concentration of potassium chloride is 0.05mol / L, and the concentration of silver nitrate is 0.04mol / L.

[0100] Prepare palladium solution: weigh 0.63 g of palladium nitrate and dissolve it in 0.2 L of deionized water, wherein the concentration of palladium nitrate is 0.01 mol / L.

[0101] 100 g of the titanium oxide-aluminum oxide composite prepared in Example 1 was pre-soaked in 160 mL of deionized water for 0.5 h, filtered and drained, and then immersed in the mixed solution of tin, potassium and silver prepared above, taken out after 1 h, drained, and dried at 110° C. for 6 h to obtain a semi-finished catalyst.

[0102] The semi-finished catalyst was immersed in the palladium solution prepared above and taken out after 45 minutes. It was reduced with 145 ml of 30% hydrazine hydrate for 1 hour, the acid radical ions were washed with deionized water, dried at 130°C for 4 hours, and then calcined at 850°C for 4 hours. The calcined product was reduced for 6 hours under the conditions of hydrogenation temperature of 100°C, hydrogen pressure of 3.0 MPa, and hydrogen flow rate of 40 mL / min to obtain Pd-Ag-Sn-K / TiO2-Al2O3 catalyst B.

[0103] Examples 8-10

[0104] The catalyst preparation method is the same as that of Example 6, except that the amount of the active component salt in the first metal salt solution and the second metal salt solution is adjusted to prepare catalysts C, D and E, respectively.

[0105] Comparative Example 2

[0106] The catalyst preparation method is the same as that of Example 6, except that the composite oxide selected from Comparative Example 1 is used as a carrier to prepare Catalyst F.

[0107] Analysis of active components of catalyst

[0108] The active metal content in the catalyst was determined by ICP atomic emission spectrometer, and the test standard was: JYT015 General Rules for Inductively Coupled Plasma Atomic Emission Spectrometry. The Optima 8300 full-spectrum direct-reading ICP spectrometer from PerkinElmer (PE) of the United States was used. The instrument had a step grating, a solid-state detector, a dual-path dual solid-state detector in the ultraviolet and visible regions, and a flat-plate plasma technology to ensure that the instrument had the lowest argon consumption. The active component content of each catalyst is shown in Table 2.

[0109] Table 2 Composition of each catalyst

[0110]

[0111] As can be seen from Table 2, the titanium oxide-aluminum oxide composite prepared in the present invention can load more active ingredients, has more active sites and stronger electron capture ability, which helps to promote the catalytic effect of TiO2 as an electron auxiliary agent.

[0112] Application Examples

[0113] This application example is the application of the catalyst in the selective hydrogenation reaction of C3 fraction. The composition of the raw materials used in this application example is shown in Table 3.

[0114] Table 3 Composition of raw materials for selective hydrogenation of C3 fraction

[0115]

[0116]

[0117] This application example uses the fixed bed pilot evaluation device of Tuochuan Scientific Research Equipment Co., Ltd., loaded with 50mL of catalyst, to carry out the selective hydrogenation reaction of the C3 fraction.

[0118] Reaction conditions: reaction pressure is 3.0 MPa, hydrogen / (MA+PD) (mol) = 1:1, material space velocity: 100 h-1, reactor inlet temperature is 25°C.

[0119] Catalysts A, B, C, D, E, and F were evaluated under the same conditions, and the selective hydrogenation results are shown in Table 4.

[0120] Table 4 Results of selective hydrogenation of C3 fraction

[0121]

[0122] Among them, MAPD conversion rate = (MAPD in feedstock - MAPD in product) / (MAPD in feedstock); MAPD selectivity = (propylene in product - propylene in feedstock) / (MAPD in feedstock - MAPD in product).

[0123] It can be seen from Table 3 that the catalyst of the present invention can be used for hydrogenation of C3 fraction and has high conversion rate and hydrogenation selectivity.

[0124] Any numerical value mentioned in the present invention, if there is only an interval of two units between any minimum value and any maximum value, includes all values ​​from the minimum value to the maximum value each time increasing by one unit. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is declared to be 50-90, in this specification it means that 51-89, 52-88... and 69-71 and 70-71 are specifically listed. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 can be appropriately considered as a unit. These are just some specially specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0125] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A catalyst for selective hydrogenation of pyrolysis gas, pyrolysis gasoline or its fractions, wherein: The catalyst comprises an aluminum oxide-titanium oxide composite oxide carrier and an active component loaded thereon, wherein the composite oxide carrier has a pore volume of 0.2 to 0.8 mL / g, a pore diameter of 10 to 20 μm, and a specific surface area of ​​90 to 150 m 2 / g, and the active component is selected from one or more of transition metals, alkali metals and IVA group metals.

2. The catalyst according to claim 1, characterized in that Based on 100 parts by weight of the composite oxide support, the content of titanium dioxide in the composite oxide support is 1 to 30 parts by weight, preferably 5 to 25 parts by weight, and more preferably 5 to 20 parts by weight; and / or, the pore volume of the composite oxide carrier is 0.3-0.4 mL / g; and / or, the pore diameter is 12-16 μm; and / or, the specific surface area is 105-130 m 2 / g.

3. The catalyst according to claim 1 or 2, characterized in that The transition metal is selected from one or more of Pd, Pt, Cu, Ag, and Au, preferably Pd and Ag; And / or, the alkali metal is K or Rb; and / or, the Group IVA metal is Sn or Pb; Preferably, based on 100 parts by weight of the catalyst, the content of Pd in ​​the catalyst is 0.1 to 1 parts by weight in terms of oxide; the content of Ag is 0.1 to 5 parts by weight in terms of oxide; the content of Sn or Pb is 0.1 to 2 parts by weight in terms of oxide; and the content of K or Rb is 0.1 to 2 parts by weight in terms of oxide.

4. The method for preparing the catalyst according to any one of claims 1 to 3, wherein: The preparation method comprises the following steps: S100, providing an alumina-titania composite oxide carrier; S200, loading active components on the alumina-titania composite oxide carrier, comprising: S210, pre-impregnating the alumina-titania composite oxide carrier with deionized water, filtering, and draining to obtain a pre-impregnated composite oxide carrier; S220, impregnating the pre-impregnated composite oxide carrier with a metal salt solution of an active component, and obtaining the catalyst through reduction and calcination.

5. The preparation method according to claim 4, wherein Step S100 includes: S110, adding a titanium salt solution and an alkaline solution to an aluminum salt solution in parallel at a temperature of 25° C. to 60° C., preferably 50° C. to 60° C., to obtain a composite oxide intermediate; Preferably, step S110 includes: S111, adding a titanium salt solution to an aluminum salt solution, optionally adding an alkaline solution in parallel, controlling the pH value to be 3 to 4, and staying for 5 to 20 minutes, preferably 10 to 15 minutes; S112, adding alkaline solution to adjust the pH value to 9-10, and staying for 5-20 minutes, preferably 15-20 minutes; S113, adding an acid solution to adjust the pH value to 7.5-8.5, and leaving for 5-20 minutes, preferably 6-10 minutes, to obtain a composite oxide intermediate; S120, allowing the composite oxide intermediate obtained in step S110 to stand at a temperature of 80° C. to 150° C., preferably 80° C. to 95° C., for 20 to 60 minutes, preferably 20 to 40 minutes, to obtain a precipitate; S130, washing, drying and calcining the precipitate obtained in step S120 to obtain an alumina-titania composite oxide carrier.

6. The preparation method according to claim 5, characterized in that: The aluminum salt is selected from one or more of aluminum sulfate, aluminum chloride, aluminum nitrate and organic aluminum salt; and / or, the aluminum salt concentration is 0.5 to 2.5 mol / L; and / or, the titanium salt solution is an acid solution of metatitanic acid, titanium sulfate, titanium tetrachloride or tetraethyl titanate, such as a sulfuric acid solution; and / or, the concentration of the titanium salt solution is 0.1 to 1.2 mol / L; and / or, the alkaline solution comprises an ammonium salt solution and an alkali solution; preferably, the ammonium salt is selected from one or more of ammonium bicarbonate, ammonium carbonate and an organic ammonium salt; and / or, the concentration of the ammonium salt in the ammonium salt solution is 0.1-0.3 mol / L; and / or, the alkali solution is selected from one or more of ammonia water, sodium hydroxide, potassium hydroxide and an organic base, and / or, the concentration of the alkali solution is 0.2-15 mol / L; and / or, the alkaline solution is prepared from the ammonium salt solution and the alkali solution according to a molar ratio of ammonium salt to alkali of 1-3:1; And / or, the acid in the acid solution is selected from one or more of sulfuric acid, nitric acid, hydrochloric acid and organic acid; and / or, the concentration of the acid solution is 10-50wt%.

7. The preparation method according to claim 5 or 6, characterized in that: The drying conditions in step S130 include: a drying temperature of 80 to 150° C., preferably 100 to 120° C., and a drying time of 4 to 12 hours; And / or, the calcination conditions in step S130 include: a calcination temperature of 700 to 1000° C., preferably 800 to 900° C., and a calcination time of 4 to 12 hours.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The pre-impregnation in step S210 includes: immersing the aluminum oxide-titanium oxide composite oxide support in deionized water of 1 to 1.5 times its volume for 0.3 to 1 hour; And / or, step S220 specifically includes: S221, impregnating the pre-impregnated composite oxide support with a first metal salt solution containing Sn salt and K salt, draining and drying to obtain a catalyst semi-finished product; S222, impregnating the semi-finished catalyst product with a second metal salt solution containing Ag salt and Pd salt, draining, reducing with hydrazine hydrate, filtering, washing, drying and calcining to obtain the catalyst; Preferably, the amount of the first metal salt solution in step S221 and the second metal salt solution in step S222 are each independently 0.8 to 2.5 times the total pore volume of the composite oxide support; Preferably, the amount of hydrazine hydrate used in step S222 is 1 to 2 times the volume of the composite oxide support, and / or the concentration is 30 to 40 wt%; Preferably, the drying conditions in steps S221 and S222 independently include: a temperature of 80-150° C. and a time of 4 to 12 hours; Preferably, the calcination conditions in step S222 include: a temperature of 700 to 1000° C. and a time of 4 to 8 hours; Preferably, step S222 includes a reduction operation after calcination; more preferably, the reduction conditions include: hydrogenation temperature of 100-150°C, hydrogen pressure of 2.6-3.0 MPa, hydrogen flow rate of 35-65 ml / min, and reduction time of 6-8 h.

9. Use of the catalyst according to any one of claims 1 to 3 or the catalyst prepared by the preparation method according to any one of claims 4 to 8 in the selective hydrogenation of pyrolysis gas, pyrolysis gasoline and its fractions, especially in the selective hydrogenation of C3 fractions.

10. A method for selective hydrogenation of pyrolysis gas, pyrolysis gasoline or its fractions, comprising: The pyrolysis gas, pyrolysis gasoline or its fraction is subjected to MAPD selective hydrogenation in the presence of the catalyst according to any one of claims 1 to 3 or the catalyst prepared by the preparation method according to any one of claims 4 to 8, wherein the fraction is preferably C3 fraction; Preferably, the conditions for selective hydrogenation include: reactor inlet temperature and reaction temperature of 20-50°C, hydrogen / (MA+PD) (mol) = 1-2.5:1, pressure of 0.5-3.0 MPa, material volume space velocity of 10-200 h -1 .

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