Highly adaptable C3 fraction selective hydrogenation catalyst and its preparation method and application

Abstract

The present invention relates to a selective hydrogenation catalyst, and discloses a highly adaptable C3 fraction selective hydrogenation catalyst, a preparation method thereof, and an application thereof. The selective hydrogenation catalyst comprises a carrier and an active component supported on the carrier, wherein the active component comprises a main active component and a co-active component; the carrier is a modified alumina carrier, and the modified alumina carrier contains a modified metal element, wherein the modified metal element is selected from at least one of alkali metal elements, alkaline earth metal elements, and rare earth elements. The catalyst has the advantages of a wide range of applicable space velocity and strong resistance to MAPD fluctuations. Even when the reactor feed flow rate and components have strong fluctuations, the catalyst still exhibits higher catalytic activity and selectivity, and has a higher MAPD conversion rate and propylene selectivity. The catalyst preparation process is simple and can operate stably for a long period of time.

Description

Technical Field

[0001] The present invention relates to a selective hydrogenation catalyst, and more particularly to a highly adaptable C3 fraction selective hydrogenation catalyst, a preparation method thereof and an application thereof. Background Art

[0002] As the leading element of the petrochemical industry, ethylene plants play a crucial role in national economic and social development. Their production scale and technology represent the level of development of a country's petrochemical industry. Currently, tubular furnace steam cracking is the mainstream ethylene production technology. Typically, the cracked gas produced by hydrocarbon steam cracking contains 0.1%-0.5% (mol) acetylene and 0.2%-0.9% (mol) propyne and propadiene, with the acetylene content increasing with cracking depth. During the cracked gas separation process, acetylene is enriched in the C2 fraction, while propyne and propadiene are enriched in the C3 fraction. Because acetylenes and dienes can severely affect downstream olefin polymerization catalysts, industrial production has very strict requirements for their content in polymer-grade ethylene and polymer-grade propylene. For example, the current requirement for propyne and propadiene (MAPD) content in polymer-grade propylene is less than 5 ppm, respectively. At present, catalytic hydrogenation is the most commonly used method for removing MAPD from the three carbon fractions. The process is divided into gas phase hydrogenation and liquid phase hydrogenation. Among them, the liquid phase hydrogenation process is widely used due to its advantages such as high catalyst activity, low reaction temperature, high propylene selectivity, small amount of green oil production, and high liquid space velocity.

[0003] Most C3 liquid-phase selective hydrogenation catalysts consist of an Al2O3 support, an active component, Pd, and co-active components. Chinese patent application CN101906015A discloses a C3 fraction selective hydrogenation catalyst using an Al2O3 support with Pd and Ag contents of 0.2-0.5% and 0.2-1.4% of the support mass, respectively. This catalyst, produced by in-situ synthesis of layered composite metal hydroxides within the pores of the Al2O3 support, can achieve a certain degree of improved hydrogenation selectivity. However, this catalyst can only operate at high space velocities at low inlet MAPD levels. Chinese patent application CN100512955C utilizes an inert material coated with an Al2O3 coating as a support, with the main active component, Pd, and other co-active components loaded onto the Al2O3 coating. This catalyst, resulting in a catalyst for the selective hydrogenation of alkynes and dienes, improves the hydrogenation efficiency of the catalyst's active components to a certain extent. However, this invention is not suitable for operating conditions with large variations in space velocity and strong fluctuations in inlet MAPD levels.

[0004] In recent years, driven by ethylene plant expansion and the diversification of cracking feedstocks, C3 liquid-phase hydrogenation reactors have experienced frequent feed flow rate changes and significant composition fluctuations, severely impacting product control and yield. Therefore, developing C3 hydrogenation catalysts with a wide range of space velocity applications and robust tolerance to MAPD fluctuations has become a critical challenge in the industry, ensuring long-term, stable operation. Summary of the Invention

[0005] The present invention addresses the technical issues of existing C3 selective hydrogenation catalysts exhibiting poor tolerance to MAPD fluctuations and difficulty controlling the MAPD content at the C3 reactor outlet when facing changes in reactor feed flow and composition fluctuations. The invention provides a highly adaptable C3 fraction selective hydrogenation catalyst, its preparation method, and its application. The catalyst has advantages such as a wide applicable space velocity range and strong tolerance to MAPD fluctuations. Even with significant fluctuations in reactor feed flow and composition, the catalyst maintains higher catalytic activity and selectivity, resulting in higher MAPD conversion and propylene selectivity.

[0006] One of the objects of the present invention is to provide a selective hydrogenation catalyst, comprising a carrier and an active component supported on the carrier, wherein the active component comprises a main active component and a co-active component; the carrier is a modified alumina carrier, and the modified alumina carrier contains a modified metal element, and the modified metal element is selected from at least one of alkali metal elements, alkaline earth metal elements and rare earth elements.

[0007] In a preferred embodiment of the present invention, the modified alumina contains α-phase in its crystal form, wherein the α-phase crystal form accounts for no less than 70%, preferably 70%-80%.

[0008] The α-phase crystal form and proportion are detected by X-ray diffraction (XRD).

[0009] The specific surface area, bulk density, pore volume, etc. of the modified alumina support can be selected within a wide range. In a preferred embodiment of the present invention, the specific surface area of the modified alumina support is 5-120 m 2 / g, preferably 20-100m 2 / g, and / or, the bulk density is 0.4-1.0 g / mL, preferably 0.6-0.8 g / mL; and / or, the pore volume is 0.25-1 mL / g, preferably 0.35-0.95 mL / g.

[0010] In a more preferred embodiment of the present invention, the specific surface area of the modified alumina support is 5-120m 2 / g, preferably 20-100m 2 / g, the bulk density is 0.4-1g / mL, preferably 0.6-0.8g / mL. Further preferably, the specific surface area of the modified alumina carrier is 5-120m 2 / g, preferably 20-100m 2 / g, the bulk density is 0.4-1g / mL, preferably 0.6-0.8g / mL; the pore volume is 0.25-1mL / g, preferably 0.35-0.95mL / g.

[0011] According to the present invention, the specific surface area is measured according to GB / T-5816-1995 Catalyst and Adsorbent Surface Area Determination Method; the pore volume is obtained according to the maximum nitrogen adsorption capacity of the sample; and the bulk density is measured according to NB / SH / T 0958-2017 Molded Catalyst and Catalyst Support Mechanical Vibration Bulk Density Determination Method.

[0012] According to the present invention, the shape of the catalyst includes but is not limited to granular, spherical, flake, toothed ball, strip, clover and the like.

[0013] According to the present invention, the total mass of the modified metal elements can be selected within a wide range. In a preferred embodiment of the present invention, the total mass of the modified metal elements in the modified alumina support accounts for 0.01-1.5% by mass of the modified alumina support, preferably 0.01-1.2% by mass; for example, it can be 0.01% by mass, 0.05% by mass, 0.1% by mass, 0.2% by mass, 0.3% by mass, 0.4% by mass, 0.5% by mass, 0.6% by mass, 0.7% by mass, 0.8% by mass, 1% by mass and 1.2% by mass, as well as any value between 0.01% by mass and 1.2% by mass, and any interval between two values. Further preferably, the total mass of the modified metal elements in the modified alumina support accounts for 0.05-0.15% by mass of the modified alumina support.

[0014] According to the present invention, there are multiple options for the modified metal elements, such as K, Ca, Mg, Sr, Ba, Ce and La. In a preferred embodiment of the present invention, the modified metal elements contained in the modified alumina are selected from one or more of K, Ca, Mg, Ce and La.

[0015] In a more preferred embodiment of the present invention, the modified alumina support is prepared by loading a precursor of at least one modifying metal element onto the alumina support and performing a first calcination. In this preferred embodiment, the resulting catalyst exhibits higher catalytic activity and selectivity, including higher MAPD conversion and propylene selectivity, even under conditions with significant fluctuations in reactor feed flow and composition.

[0016] The inventors of the present invention believe through research that the modified metal elements in the present invention change the physical and chemical properties of the alumina carrier to a certain extent, so that the catalyst prepared from the modified alumina carrier has the above-mentioned advantages.

[0017] According to the present invention, MAPD is a mixture of methyl acetylene (MA) and propadiene (PD).

[0018] According to the present invention, the main active component can be selected from a variety of options, and the modified alumina carrier of the present invention has technical effects. In a preferred embodiment of the present invention, the main active component is Pd.

[0019] According to the present invention, the co-active component can be selected from a variety of options, all of which have the same technical effect when using the modified alumina support of the present invention. In a preferred embodiment of the present invention, the co-active component is at least two of Ag, Cu, Au, Zn, Ga, and a rare earth element; preferably, at least two of Ag, Ga, La, and Ce.

[0020] According to the present invention, the content of the main active component in the selective hydrogenation catalyst has a wide selection range. In a preferred embodiment of the present invention, the content of the main active component in the selective hydrogenation catalyst is 0.005-1% by mass, preferably 0.05-0.5% by mass, based on the mass content of the element, relative to the total mass of the selective hydrogenation catalyst. For example, it can be 0.05% by mass, 0.08% by mass, 0.1% by mass, 0.15% by mass, 0.2% by mass, 0.3% by mass, 0.4% by mass, 0.5% by mass, and any value or any interval between 0.05% by mass and 0.5% by mass.

[0021] According to the present invention, the content of the co-activating component in the selective hydrogenation catalyst can be selected within a wide range. In a preferred embodiment of the present invention, the content of the co-activating component in the selective hydrogenation catalyst is 0.01-10% by mass, preferably 0.01-5% by mass, calculated as the mass content of the element, relative to the total mass of the selective hydrogenation catalyst. For example, the co-activating component can be 0.01% by mass, 0.05% by mass, 0.08% by mass, 0.1% by mass, 0.5% by mass, 1% by mass, 1.5% by mass, 2% by mass, 2.5% by mass, 3% by mass, 4% by mass, 5% by mass, or any value or range between 0.01% and 5% by mass.

[0022] In a more preferred embodiment of the present invention, the support is a modified alumina support preferred in the present invention, the primary active component is Pd, and the co-active components are at least two of Ag, Cu, Au, Zn, Ga, and a rare earth element, preferably at least two of Ag, Ga, La, and Ce. The content of the primary active component in the selective hydrogenation catalyst is 0.005-1% by mass, preferably 0.05-0.5% by mass, and the content of the co-active component is 0.01-10% by mass, preferably 0.01-5% by mass, relative to the total mass of the selective hydrogenation catalyst, calculated by elemental mass content. In this preferred embodiment, the catalyst exhibits higher catalytic activity and selectivity even when the reactor feed flow rate and composition fluctuate significantly, and has higher MAPD conversion and propylene selectivity.

[0023] A second object of the present invention is to provide a method for preparing the selective hydrogenation catalyst described above, comprising loading a main active component precursor and a co-active component precursor on a modified alumina carrier, followed by drying and performing a second calcination; the modified alumina carrier is prepared by modifying alumina with at least one of the modifying metal elements.

[0024] In a preferred embodiment of the present invention, the loading method includes spraying or dipping; preferably, the main active component precursor and the co-active component precursor are first formulated into a main active component and a co-active component precursor solution, and then the main active component precursor and the co-active component precursor are loaded onto the carrier by spraying or dipping; the spraying or dipping can be carried out in a one-step method or a step-by-step method; preferably, it is carried out by spraying.

[0025] According to the present invention, during dipping or spraying, there is no particular limitation on the concentration of the main active component and the concentration of the auxiliary active component in the active component precursor solution. The present invention can be achieved as long as spraying or immersion is facilitated.

[0026] According to the present invention, the drying temperature has a wide selection range. In a preferred embodiment of the present invention, the drying temperature is 50-200° C., preferably 60-150° C., and the drying time is 3-48 hours, preferably 5-24 hours.

[0027] According to the present invention, the temperature of the second roasting can be selected within a wide range. In a preferred embodiment of the present invention, the temperature of the second roasting is 300-600° C., preferably 400-500° C., and the time is 2-10 h, preferably 4-8 h.

[0028] According to the present invention, the preparation process of the alumina carrier includes the steps of powder kneading, extrusion molding, green embryo drying, high temperature roasting, etc. Alkali metals, alkaline earth metals, and rare earth elements can be added by adding corresponding soluble compounds at any step of the preparation of the alumina carrier.

[0029] In a more preferred embodiment of the present invention, the preparation method of the modified alumina carrier comprises the following steps: kneading alumina powder, extruding, drying the green embryo, and performing the first calcination, and adding a solution containing at least one of the modified metal precursors at any stage before the first calcination treatment, preferably at the powder kneading stage or after the green embryo is dried, and then performing the next step to obtain the modified alumina carrier.

[0030] Preferably, the conditions for drying the raw embryo include: a temperature of 80-150° C. and a time of 6-24 hours;

[0031] Preferably, the conditions for the first calcination include: a temperature of 900-1200° C. and a time of 4-10 h.

[0032] In a preferred embodiment of the present invention, the modified metal element precursor is selected from the water-soluble metal salt of the corresponding metal element; preferably one or more of the nitrate, chloride, and acetate of the corresponding metal element; further preferably one or more of the nitrate and acetate of the corresponding metal element.

[0033] According to the present invention, there is no particular limitation on the concentration of the solution of the modified metal precursor, and the present invention can be achieved as long as it is conducive to uniform dispersion.

[0034] According to the present invention, there are multiple options for the alumina powder. In a preferred embodiment of the present invention, the alumina powder includes pseudo-boehmite powder; preferably, the alumina powder includes pseudo-boehmite powder, and at least one of trihydrate alumina powder, fast-release alumina powder and composite phase alumina powder; further preferably, the total mass of trihydrate alumina powder, fast-release alumina powder and composite phase alumina powder accounts for 0-30% by mass of the total mass of the alumina powder, preferably 0-20% by mass.

[0035] A third object of the present invention is to provide a selective hydrogenation catalyst prepared by the preparation method described above.

[0036] A fourth object of the present invention is to provide a method for selective hydrogenation of a C3 fraction, comprising contacting the C3 fraction with the aforementioned selective hydrogenation catalyst under hydrogenation reaction conditions.

[0037] According to the present invention, the finished catalyst obtained by the present invention needs to be reduced before use, preferably by passing hydrogen in a reactor.

[0038] According to the present invention, the range of selection of hydrogenation conditions is relatively wide. Preferably, the pressure is 1.9-2.3 MPa, the reaction temperature is 28-45°C, and the C3 material space velocity is 40-140 hr -1In this preferred embodiment, the catalyst has higher catalytic activity, higher MAPD conversion rate and better propylene selectivity.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The catalyst has the advantages of wide applicable range of space velocity and strong resistance to MAPD fluctuation. -1 and lower, up to 100hr -1 and higher) and strong MAPD fluctuations (the inlet MAPD content is as low as 1.5 mol% and lower, and as high as 3.6 mol% and higher), the catalyst still exhibits high catalytic activity and selectivity, and has high MAPD conversion rate and propylene selectivity.

[0041] The inventors of the present invention believe that the above advantages are due to the fact that the modified alumina support has a pH value more suitable for the selective hydrogenation reaction of the C3 fraction, and the prepared catalyst produces low green oil and can operate stably for a long period of time.

[0042] Moreover, the modified alumina carrier of the present invention is used in combination with active components, preferably two auxiliary active components, which greatly improves the catalyst's ability to resist MAPD fluctuations and broadens the catalyst's applicable space velocity range. The catalyst exhibits excellent performance when faced with changes in reactor feed flow and component fluctuations.

[0043] (2) The C3 fraction selective hydrogenation catalyst prepared by the present invention can better control the outlet MAPD content when the reactor feed composition fluctuates and the feed flow rate changes, ensuring smooth and normal production operation and long-term stable operation;

[0044] (3) The catalyst preparation method is simple, easy, green and environmentally friendly, and can be produced on a large scale industrially. DETAILED DESCRIPTION

[0045] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0046] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0047] Test example

[0048] In the following examples, the α-phase crystal form and proportion are determined by XRD; the specific surface area is determined according to GB / T-5816-1995 Catalyst and Adsorbent Surface Area Determination Method; the pore volume is obtained based on the maximum nitrogen adsorption capacity of the sample; and the bulk density is determined according to NB / SH / T 0958-2017 Molded Catalyst and Catalyst Support Mechanical Vibration Bulk Density Determination Method.

[0049] Example 1

[0050] A mixed powder consisting of 90% pseudo-boehmite powder and 10% fast-dealumina powder was prepared. During the kneading step, a corresponding amount of cerium nitrate hexahydrate was added. After thorough kneading, the mixture was extruded and pelletized to obtain particles with a diameter of 4-6 mm. The particles were dried at 120°C for 12 hours and calcined at 1180°C for 6 hours to obtain a 0.1% Ce-modified alumina support S1.

[0051] After testing, it was verified that the carrier crystal form in Example 1 contained α phase, of which the α phase accounted for >70%, or 76%. The specific surface area of the modified alumina carrier was 23.6m 2 / g, and the bulk density is 0.73g / mL.

[0052] 5 mL of palladium nitrate solution containing 50 mg Pd / mL was measured, and 0.79 g of silver nitrate and 0.52 g of gallium nitrate hydrate were added to the palladium nitrate solution. The solution was diluted to 60 mL with deionized water and sprayed onto 100 g of modified alumina support S1. The sprayed sample was dried at 120°C for 6 h and calcined at 450°C for 8 h to obtain a catalyst with a Pd content of 0.25% by mass, an Ag content of 0.5% by mass, and a Ga content of 0.1% by mass.

[0053] Example 2

[0054] Using the same mixed powder as in Example 1, a corresponding amount of cerium nitrate hexahydrate was added during the powder kneading step. After thorough kneading, the mixture was extruded and pelletized to obtain particles with a diameter of 4-6 mm. The particles were dried at 80°C for 24 hours and calcined at 1180°C for 6 hours to obtain a 0.15% by mass Ce-modified alumina support S2.

[0055] 5 mL of palladium nitrate solution containing 50 mg Pd / mL was measured, and 0.71 g of silver nitrate and 0.52 g of gallium nitrate hydrate were added to the palladium nitrate solution. The solution was diluted to 60 mL with deionized water and sprayed onto 100 g of modified alumina support S2. The sprayed sample was dried at 120°C for 6 h and calcined at 450°C for 8 h to obtain a catalyst with a Pd content of 0.25% by mass, an Ag content of 0.45% by mass, and a Ga content of 0.1% by mass.

[0056] Example 3

[0057] Using the same mixed powder as in Example 1, a corresponding amount of cerium nitrate hexahydrate was added during the powder kneading step. After thorough kneading, the mixture was extruded and pelletized to obtain particles with a diameter of 4-6 mm. The particles were dried at 150°C for 6 hours and calcined at 1180°C for 6 hours to obtain a 0.05% by mass Ce-modified alumina support S3.

[0058] 5 mL of palladium nitrate solution containing 50 mg Pd / mL was measured, and 0.79 g of silver nitrate and 0.78 g of gallium nitrate hydrate were added to the palladium nitrate solution. The solution was diluted to 60 mL with deionized water and sprayed onto 100 g of modified alumina support S3. The sprayed sample was dried at 120°C for 6 h and calcined at 450°C for 8 h to obtain a catalyst with a Pd content of 0.25% by mass, an Ag content of 0.5% by mass, and a Ga content of 0.15% by mass.

[0059] Example 4

[0060] Using the same mixed powder as in Example 1, alumina powder was thoroughly kneaded, extruded, and pelletized to obtain particles with a diameter of 4-6 mm. These particles were dried at 120°C for 12 hours, sprayed with an aqueous solution of lanthanum nitrate hexahydrate containing the appropriate amount, dried, and calcined at 1180°C for 6 hours to obtain alumina support S4 modified with 0.2% La by mass.

[0061] 6 mL of palladium nitrate solution containing 50 mg Pd / mL was measured, and 0.79 g of silver nitrate and 0.31 g of cerium nitrate hexahydrate were added to the palladium nitrate solution. The solution was diluted to 60 mL with deionized water and sprayed onto 100 g of modified alumina support S4. The sprayed sample was dried at 120°C for 6 hours and calcined at 450°C for 8 hours to obtain a catalyst with a Pd content of 0.3% by mass, an Ag content of 0.5% by mass, and a Ce content of 0.1% by mass.

[0062] Example 5

[0063] According to the same method as in Example 1, a corresponding amount of potassium nitrate was added to the powder kneading step of the alumina carrier to obtain a 0.1% by mass K-modified alumina carrier S5.

[0064] 4 mL of palladium nitrate solution containing 50 mg Pd / mL was measured, and 0.79 g of silver nitrate and 0.31 g of cerium nitrate hexahydrate were added to the palladium nitrate solution. The solution was diluted to 62 mL with deionized water and sprayed onto 100 g of modified alumina support S5. The sprayed sample was dried at 120°C for 6 h and calcined at 450°C for 8 h to obtain a catalyst with a Pd content of 0.2% by mass, an Ag content of 0.5% by mass, and a Ce content of 0.1% by mass.

[0065] After testing, it was verified that the carrier crystal form of this embodiment contained α phase, wherein the α phase crystal form accounted for >70%.

[0066] Comparative Example 1

[0067] The method for preparing the modified alumina support S1 is the same as that of Example 1, except that cerium nitrate hexahydrate is not added, and the alumina support S6 without any additive modification is prepared.

[0068] 5 mL of palladium nitrate solution containing 50 mg Pd / mL was diluted to 60 mL with deionized water and sprayed onto 100 g of alumina support S6. The sprayed sample was dried at 120°C for 6 h and calcined at 450°C for 8 h to obtain a catalyst with a Pd content of 0.25% by mass.

[0069] Comparative Example 2

[0070] The catalyst was prepared in the same manner as in Example 1, except that the alumina carrier was not modified during the preparation process. Instead, cerium nitrate hexahydrate was added to a palladium nitrate solution, and a solution containing silver nitrate, palladium nitrate, gallium nitrate, and cerium nitrate was sprayed onto the unmodified alumina powder carrier in accordance with the method of Example 1.

[0071] Comparative Example 3

[0072] A catalyst was prepared in the same manner as in Example 1, except that equal amounts of silver nitrate, gallium nitrate, palladium nitrate solution, and cerium nitrate hexahydrate in Example 1 were added during the powder kneading step of the alumina carrier. A catalyst precursor was prepared in the same manner as in Example 1, and then dried at 120°C for 6 h and calcined at 450°C for 8 h to obtain a catalyst.

[0073] Comparative Example 4

[0074] The modified alumina support S1 prepared in the same manner as in Example 1 was used.

[0075] 5 mL of palladium nitrate solution containing 50 mg Pd / mL was diluted to 60 mL with deionized water and sprayed onto 100 g of alumina support S1. The sprayed sample was dried at 120°C for 6 h and calcined at 450°C for 8 h to obtain a catalyst with a Pd content of 0.25% by mass.

[0076] Comparative Example 5

[0077] The modified alumina support S1 prepared in the same manner as in Example 1 was used.

[0078] 5 mL of palladium nitrate solution containing 50 mg Pd / mL was measured, and 0.79 g of silver nitrate was added to the palladium nitrate solution. The solution was diluted to 60 mL with deionized water and sprayed onto 100 g of modified alumina support S1. The sprayed sample was dried at 120°C for 6 hours and calcined at 450°C for 8 hours to obtain a catalyst with a Pd content of 0.25% by mass and an Ag content of 0.5% by mass.

[0079] Experimental Example 1

[0080] The reaction was evaluated using an adiabatic bed. 92 mL of each catalyst prepared in Example and Comparative Example was reduced for 8 h under the conditions of normal hydrogen pressure, temperature of 100 ° C, and hydrogen flow rate of 300 mL / min. The reactor pressure was 2.0 MPa, the inlet temperature was 36 ° C, and the C3 material space velocity was 70 hr -1 The feedstock was introduced at a hydrogen-to-acetylene ratio of 1.2-2.0 for the test. The feedstock composition was 5.4 mol% propane, 91 mol% propylene, 2.0 mol% propyne, and 1.6 mol% propadiene. The gas compositions at the feed and discharge were measured by gas chromatography. The conversion and selectivity of MAPD were calculated as follows:

[0081]

[0082]

[0083] The evaluation results are shown in Table 1.

[0084] Table 1

[0085] catalyst MAPD conversion rate (%) Selectivity (%) Example 1 99.2 87.2 Example 2 99.4 86.9 Example 3 99.1 87.5 Example 4 99.7 82.1 Example 5 98.6 84.9 Comparative Example 1 67.9 46.3 Comparative Example 2 79.2 72.7 Comparative Example 3 5.8 3.6 Comparative Example 4 83.7 59.2 Comparative Example 5 81.3 74.5

[0086] Experimental Example 2

[0087] The evaluation conditions were the same as those in Experimental Example 1. The raw material composition was 5.3 mol% propane, 91.7 mol% propylene, 1.7 mol% propyne, and 1.3 mol% propadiene. The evaluation results are shown in Table 2.

[0088] Table 2

[0089] catalyst MAPD conversion rate (%) Selectivity (%) Example 1 99.6 85.3 Example 2 99.7 84.9 Example 3 99.4 85.2 Example 4 99.9 76.5 Example 5 99.2 79.4 Comparative Example 1 82.5 44.6 Comparative Example 2 86.1 70.7 Comparative Example 3 6.6 2.9 Comparative Example 4 95.1 57.6 Comparative Example 5 89.3 73.8

[0090] Experimental Example 3

[0091] The evaluation conditions were the same as those in Experimental Example 1. The raw material composition was 8.9 mol% of propane, 89.6 mol% of propylene, 0.7 mol% of propyne, and 0.8 mol% of propadiene. The evaluation results are shown in Table 3.

[0092] Table 3

[0093] catalyst MAPD conversion rate (%) Selectivity (%) Example 1 99.9 82.1 Example 2 99.9 81.7 Example 3 99.8 83.9 Example 4 99.9 73.3 Example 5 99.7 76.2 Comparative Example 1 98.6 41.3 Comparative Example 2 98.9 69.0 Comparative Example 3 10.7 2.3 Comparative Example 4 99.5 53.2 Comparative Example 5 99.2 71.6

[0094] As can be seen from Tables 1, 2, and 3, in the C3 fraction selective hydrogenation reaction, the C3 fraction selective hydrogenation catalyst prepared by the present invention can ensure that the outlet MAPD content is within the acceptable range, regardless of whether the inlet MAPD concentration is at a high value (3.6 mol%) or a low value (1.5 mol%), while maintaining high selectivity. Compared with the comparative example, the C3 fraction selective hydrogenation catalyst prepared by the present invention can well control the outlet MAPD content when the reactor feed composition fluctuates, ensuring stable and normal production operation.

[0095] Experimental Example 4

[0096] The C3 material space velocity is 20hr -1 , and the rest of the evaluation conditions are the same as those in Experimental Example 1. The evaluation results are shown in Table 4.

[0097] Table 4

[0098] catalyst MAPD conversion rate (%) Selectivity (%) Example 1 99.9 78.6 Example 2 99.8 80.6 Example 3 99.9 81.5 Example 4 99.9 75.3 Example 5 99.9 75.9 Comparative Example 1 89.5 43.7 Comparative Example 2 95.1 66.3 Comparative Example 3 7.3 2.7 Comparative Example 4 98.2 53.1 Comparative Example 5 96.8 67.4

[0099] Experimental Example 5

[0100] The C3 material space velocity is 100hr -1 , and the rest of the evaluation conditions are the same as those in Experimental Example 1. The evaluation results are shown in Table 5.

[0101] Table 5

[0102] catalyst MAPD conversion rate (%) Selectivity (%) Example 1 98.3 89.2 Example 2 98.5 88.7 Example 3 98.2 89.3 Example 4 99.1 87.5 Example 5 98.0 89.9 Comparative Example 1 59.7 50.1 Comparative Example 2 71.8 76.3 Comparative Example 3 3.2 3.9 Comparative Example 4 75.6 63.1 Comparative Example 5 73.7 79.9

[0103] It can be seen from Table 1, Table 4 and Table 5 that in the selective hydrogenation reaction of C3 fraction, -1 Within the range, the C3 fraction selective hydrogenation catalyst prepared by the present invention can ensure that the outlet MAPD content is within the qualified value and maintain high selectivity under both high and low space velocity conditions. Compared with the comparative example, the C3 fraction selective hydrogenation catalyst prepared by the present invention can well control the outlet MAPD content when the reactor feed flow rate changes, ensuring stable and normal production operation.

Claims

1. A selective hydrogenation catalyst comprising a carrier and an active component supported on the carrier, wherein the active component comprises a main active component and a co-active component; the carrier is a modified alumina carrier, the modified alumina carrier contains a modifying metal element, and the modifying metal element contained in the modified alumina is selected from one or more of K, Ca, Mg, Ce and La; The modified alumina contains an α phase in its crystal form, wherein the α phase accounts for no less than 70%; The main active component is Pd; The auxiliary active components are at least two of Ag, Cu, Au, Zn, Ga, and rare earth elements; The total mass of the modified metal elements in the modified alumina support accounts for 0.01-1.5% by mass of the modified alumina support; The preparation method of the modified alumina support comprises the following steps: The modified alumina support is obtained by kneading alumina powder, extruding, drying the green body, and first calcining, and adding a solution containing at least one modified metal precursor at any stage before the first calcination treatment and then performing the next process.

2. The selective hydrogenation catalyst according to claim 1, wherein: The modified alumina contains α phase in its crystal form, wherein the α phase accounts for 70%-80%.

3. The selective hydrogenation catalyst according to claim 1, characterized in that: The specific surface area of the modified alumina carrier is 5-120m 2 / g; and / or, A bulk density of 0.4-1 g / mL; and / or, The pore volume is 0.25-1 mL / g.

4. The selective hydrogenation catalyst according to claim 1, characterized in that: The specific surface area of the modified alumina carrier is 20-100m 2 / g; and / or, A bulk density of 0.6-0.8 g / mL; and / or, The pore volume is 0.35-0.95 mL / g.

5. The selective hydrogenation catalyst according to claim 1, characterized in that: The total mass of the modified metal elements in the modified alumina support accounts for 0.01-1.2 mass % of the modified alumina support.

6. The selective hydrogenation catalyst according to any one of claims 1 to 5, characterized in that: The auxiliary active components are at least two of Ag, Ga, La and Ce.

7. The selective hydrogenation catalyst according to any one of claims 1 to 5, characterized in that: The content of the main active component in the selective hydrogenation catalyst is 0.005-1% by mass relative to the total mass of the selective hydrogenation catalyst, calculated as the mass content of the element; and / or, Calculated by the mass content of the element, the content of the co-activating component in the selective hydrogenation catalyst is 0.01-10 mass % relative to the total mass of the selective hydrogenation catalyst.

8. The selective hydrogenation catalyst according to any one of claims 1 to 5, characterized in that: The content of the main active component in the selective hydrogenation catalyst is 0.05-0.5% by mass relative to the total mass of the selective hydrogenation catalyst, calculated as the mass content of the element; and / or, Calculated by the mass content of the element, the content of the co-activating component in the selective hydrogenation catalyst is 0.01-5 mass % relative to the total mass of the selective hydrogenation catalyst.

9. A method for preparing the selective hydrogenation catalyst according to any one of claims 1 to 8, comprising loading a main active component precursor and a co-active component precursor on a modified alumina support, followed by drying and performing a second calcination; The modified alumina carrier is prepared by modifying alumina with at least one of the modifying metal elements.

10. The preparation method according to claim 9, characterized in that: The loading method includes spraying or dipping; and / or, the drying temperature is 50-200°C and the drying time is 3-48 h; And / or, the second calcination temperature is 300-600° C. and the time is 2-10 hours.

11. The preparation method according to claim 9, characterized in that: The loading method includes spraying or dipping: first, the main active component precursor and the auxiliary active component precursor are prepared into a main active component and auxiliary active component precursor solution, and then the main active component precursor and the auxiliary active component precursor are loaded onto the carrier by spraying or dipping; and / or, the drying temperature is 60-150°C and the drying time is 5-24 h; And / or, the second calcination temperature is 400-500° C. and the time is 4-8 h.

12. The preparation method according to any one of claims 9 to 11, characterized in that: The preparation method of the modified alumina support comprises the following steps: The modified alumina support is obtained by kneading alumina powder, extruding, drying the green body, and first calcining, and adding a solution containing at least one modified metal precursor during the powder kneading stage or after the green body is dried, and then performing the next step.

13. The preparation method according to claim 12, characterized in that: The conditions for drying the raw embryo include: a temperature of 80-150° C. and a drying time of 6-24 h; and / or, The first calcination conditions include: temperature of 900-1200° C. and time of 4-10 h.

14. The preparation method according to claim 12, characterized in that: The modified metal element precursors are selected from water-soluble metal salts of corresponding metal elements; and / or, The alumina powder includes pseudo-boehmite powder.

15. The preparation method according to claim 12, characterized in that: The modified metal element precursors are selected from water-soluble metal salts of the corresponding metal elements, such as nitrates, chlorides, and acetates of the corresponding metal elements; and / or, The alumina powder includes pseudo-boehmite powder and at least one of alumina trihydrate powder, fast-desorption alumina powder and composite phase alumina powder.

16. The preparation method according to claim 12, characterized in that: The modified metal element precursors are selected from water-soluble metal salts of corresponding metal elements, and are one or more of nitrates and acetates of corresponding metal elements.

17. The selective hydrogenation catalyst prepared according to the preparation method according to any one of claims 9 to 16.

18. A method for selective hydrogenation of a C3 fraction, comprising contacting the C3 fraction with the selective hydrogenation catalyst according to any one of claims 1 to 8 and 17 under hydrogenation reaction conditions.

19. The method for selective hydrogenation of a C3 fraction according to claim 18, characterized in that: The pressure is 1.9-2.3 MPa, the reaction temperature is 28-45℃, and the C3 material space velocity is 40-140hr -1 ; Hydrogen-acetylene ratio 1.2-2.2.

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