阅读说明：本技术 一种碳四炔烃选择加氢制丁二烯催化剂及制备方法和应用 (Catalyst for preparing butadiene by selective hydrogenation of carbon-tetra-alkyne, preparation method and application thereof ) 是由 王兰磊 白长城 刘保军 王江 孔祥明 张小锋 国欣 徐艳飞 梁健 张宏科 于 2019-10-21 设计创作，主要内容包括：本发明涉及一种碳四炔烃选择加氢制丁二烯催化剂及制备方法和应用。该催化剂包括ZrO<Sub>2</Sub>/CdO/Bi<Sub>2</Sub>O<Sub>3</Sub>复合载体和活性组分,活性组分组成包括：Pd或其氧化物、VIIB金属或其氧化物中的至少一种、La或其氧化物。本发明的催化剂可用于碳四炔烃选择加氢回收丁二烯的应用中,主要解决现有技术中存在的催化剂稳定性差、寿命短、炔烃选择性差以及丁二烯损耗过高的问题。(The invention relates to a catalyst for preparing butadiene by selective hydrogenation of carbon-tetraalkyne, a preparation method and application thereof. The catalyst comprises ZrO 2 /CdO/Bi 2 O 3 The carrier and active component, the active component composition includes: at least one of Pd or oxide thereof, VIIB metal or oxide thereof, La or oxide thereof. The catalyst can be used in the application of recovering butadiene by selective hydrogenation of carbon-tetrayne, and mainly solves the problems of poor catalyst stability, short service life, poor alkyne selectivity and high butadiene loss in the prior art.)

1. A catalyst for preparing butadiene by selective hydrogenation of C-C alkyne is characterized by comprising ZrO₂/CdO/Bi₂O₃The following contents of the composite carrier and the active component are based on the total mass of the catalyst, and ZrO is₂/CdO/Bi₂O₃The content of the composite carrier is 83.5-92.3%, and the content of the active component is 7.7-16.5%;

the active component comprises the following components:

pd or its oxide, the content is 0.05-0.8%, preferably 0.2-0.5% calculated by Pd element;

VIIB metal or at least one of oxides thereof, in terms of metal elements, in an amount of 0.2 to 6.0%, preferably 2.0 to 5.0%;

la or an oxide thereof in an amount of 0.1 to 4.0%, preferably 0.5 to 2.0% in terms of oxide form.

2. The catalyst according to claim 1, wherein the ZrO₂/CdO/Bi₂O₃The composite carrier takes the total mass of the catalyst as a reference, wherein the content of CdO is 1-10%, and preferably 1.0-4.0%; bi₂O₃The content of (A) is 0.1-5.0%, preferably 1.0-2.0%;

the ZrO₂/CdO/Bi₂O₃The total pore volume of the composite carrier is 0.3-0.9 mL/g, and the specific surface area is 90-180 m³(ii)/g; and/or

Said VIIB metal or oxide thereof, preferably Re or oxide thereof.

3. A process for preparing butadiene catalyst by selective hydrogenation of C-tetraalkyne according to claim 1 or 2, which comprises ZrO₂/CdO/Bi₂O₃CompoundingPreparing a carrier and loading an active component;

the ZrO₂/CdO/Bi₂O₃Preparing a composite carrier, namely preparing a carrier precursor by using a coprecipitation method, adding a pore-forming agent, an adhesive and water pressure strip forming, and aging, drying and roasting to obtain the composite carrier;

the active component is loaded by adopting an impregnation method, including equal-volume impregnation or excessive impregnation.

4. The production method according to claim 3, wherein the coprecipitation method produces a support precursor by: uniformly mixing soluble salts of zirconium, cadmium and bismuth with water, then coprecipitating the mixture with ammonia water, keeping the pH value of a reaction system at 3-6, reacting until the raw materials are exhausted, taking precipitates after the reaction is finished, and washing and drying the precipitates to obtain a carrier precursor;

preferably, the soluble salts of zirconium, cadmium and bismuth are one or more of nitrate and acetate; the soluble salt of zirconium is preferably zirconium nitrate, the concentration is preferably 3.0-4.0 mol/L, the soluble salt of cadmium is preferably cadmium acetate, the concentration is preferably 0.04-0.30 mol/L, the soluble salt of bismuth is preferably bismuth nitrate, and the concentration is preferably 0.02-0.25 mol/L;

preferably, the concentration of the used ammonia water is 1.0-4.5 mol/L, preferably 2.0-4.0 mol/L;

preferably, in the coprecipitation reaction process, soluble salt water solution of zirconium, cadmium and bismuth and ammonia water are dropwise added, and the dropping speed is controlled by the pH value of a reaction system, so that the pH value is kept at 3-6;

preferably, after the drying is completed, the carrier precursor is crushed into particles with the particle size of 80-120 meshes, preferably 100-120 meshes.

5. The method according to claim 4, wherein the drying process is temperature-programmed drying by: heating to 50-80 ℃ at a heating rate of 1-3 ℃/min, drying for 10-24 h, heating to 80-120 ℃ at a heating rate of 1-3 ℃/min, and drying for 6-10 h; and/or

The roasting method comprises the following steps: after drying, raising the temperature to 800-1200 ℃ at a heating rate of 5 ℃/min, and roasting for 4-8 h.

6. The preparation method according to claim 3, wherein the active component is loaded by: firstly, ZrO is firstly_2/CdO/Bi₂O₃VIIB metal is impregnated and loaded on the composite carrier, and Pd and La are impregnated and loaded after drying and roasting treatment; the specific loading method comprises the following steps:

1) ZrO 2 is mixed with₂/CdO/Bi₂O₃Soaking the composite carrier in a VIIB metal soluble salt aqueous solution for 8-10 h, then aging for 4-6 h, drying at 50-80 ℃ for 5-8 h after aging is completed, drying at 80-120 ℃ for 6-10 h, and finally roasting at 330-550 ℃ for 4-8 h to obtain a VIIB metal-loaded catalyst;

2) mixing a palladium soluble salt aqueous solution and a lanthanum soluble salt aqueous solution, adjusting the pH to 2-4 by using a nitric acid aqueous solution, then adding the VIIB metal-loaded catalyst prepared in the step 1) to impregnate for 5-10 h, and repeating the aging, drying and roasting processes in the step 1) to obtain the butadiene catalyst prepared by selective hydrogenation of C-C alkyne.

7. The preparation method as claimed in claim 6, wherein in step 1), the VIIB metal soluble salt is selected from soluble salts of rhenium element, preferably ammonium perrhenate and ammonium perrhenate; the concentration of the aqueous solution of the VIIB metal soluble salt is 0.04-2.20 mol/L, preferably 0.75-1.50 mol/L; and/or

In the step 2), the soluble salt of palladium is selected from palladium chloride and palladium nitrate, preferably palladium nitrate; the concentration of the soluble salt water solution of palladium is 0.01-0.13 mol/L, preferably 0.05-0.10 mol/L;

the soluble salt of lanthanum is selected from lanthanum nitrate and lanthanum acetate, preferably lanthanum nitrate; the concentration of the lanthanum soluble salt aqueous solution is 0.20-8.00 mol/L, preferably 0.70-4.00 mol/L;

the mass ratio of the soluble salt water solution of palladium to the soluble salt water solution of lanthanum is 0.7-7.0: 1, preferably 2.0 to 4.0: 1; and/or

In the step 1) and the step 2), the impregnation is carried out, wherein the mass ratio of the carrier to the impregnation liquid is 1: 1-3, and preferably 1: 1-1.5.

8. The preparation method according to any one of claims 3 to 7, wherein the catalyst for preparing butadiene by selective hydrogenation of carbon-tetrayne obtained in step 2) comprises a passivation treatment process, and the passivation method comprises the following steps: firstly, nitrogen containing hydrogen is used for reducing the carbon dioxide, the temperature of the reduction process is 200-500 ℃, the time is 4-8 h, and the gas hourly space velocity is 40-100 h^-1(ii) a Passivating for 4-8 h by using nitrogen containing oxygen, wherein the passivation temperature is 10-90 ℃, and the gas hourly space velocity is 70-160h^-1(ii) a And/or

The catalyst for preparing butadiene by selective hydrogenation of carbon-tetraalkyne comprises an activation process, and the activation method comprises the following steps: activating with nitrogen containing hydrogen at 80-150 deg.c for 2-5 hr.

9. The use of the catalyst for preparing butadiene by selective hydrogenation of C-tetraalkyne according to claim 1 or 2 or the catalyst for preparing butadiene by selective hydrogenation of C-tetraalkyne according to any one of claims 3 to 8, which is suitable for the selective hydrogenation of C-tetraalkyne in a feedstock containing C-tetraalkyne, in particular in a feedstock with a high content of C-tetraalkyne, for converting C-tetraalkyne into butadiene by hydrogenation;

the raw material composition containing the carbon tetraalkyne comprises one or more of butyne, vinyl acetylene, carbon tetraalkene and alkane; and/or

The raw material containing the carbon tetraalkyne is selected from a material containing the carbon tetraalkyne, which is a byproduct of an ethylene cracking process, preferably a material extracted from a lateral line after secondary extraction of a butadiene device in the ethylene cracking process, and the content of the carbon tetraalkyne is preferably 20-40% in percentage by mass.

10. The use according to claim 9, characterized in that the hydrogenation reaction is carried out under the conditions: the temperature is 20-60 ℃, the inlet temperature of the reactor is 35-50 ℃, and the preferred temperature is 40-45 ℃; the liquid hourly space velocity is 7-20 h^-1Preferably 9h^-1(ii) a The reaction pressure is 0.5 to 2.5MPa (G), preferably1.1MPa (G); the hydrogen/alkyne molar ratio is 1 to 4, preferably 1.6 to 2.5, and most preferably 1.8 to 2.0.

Technical Field

The invention relates to a catalyst for preparing butadiene by selective hydrogenation of carbon tetraalkyne, belonging to the technical field of petrochemical industry, in particular to a catalyst for preparing butadiene by selective hydrogenation of carbon tetraalkyne contained in a material after extraction of a butadiene device, a preparation method and application thereof.

Background

The ethylene cracking gas contains a large amount of carbon tetrahydrocarbons and cracked gasoline besides diene. The cracking gas can separate out four carbon components in the separation process of the ethylene device, and then the cracking gas enters a butadiene device to carry out deep separation on the four carbon raw materials. The carbon four raw material contains isobutene, normal butane, isobutene, vinyl acetylene, butyne and other substances besides butadiene and 1-butene, the butadiene can be separated from the raw material after secondary extraction, alkyne substances in the raw material can be gradually enriched in the butadiene material, a butadiene device can generally extract the alkyne-rich material from a lower tower of a second extraction tower through a lateral line, the total content of alkyne-rich materials in the material reaches about 30 percent, and the carbon four alkyne, especially vinyl acetylene, is a very flammable and explosive substance, so the material is very dangerous, the industrial application value is very low, the quality of butadiene products is influenced, and a treatment method generally adopted in industry is to reduce the alkyne concentration of the material by mixing butane or butene and other materials in a stream, and then sending the stream to a torch for incineration treatment. Taking a set of butadiene device with 5.4 ten thousand tons/year as an example, the quantity of alkyne materials (mainly butyne and vinyl acetylene) sent to a torch system is as high as 757 tons/year, and the danger of explosion of alkyne exists while huge material waste is caused. Therefore, how to reduce the risk of alkyne and effectively utilize it is a new direction of current research. The popular research direction is to use a high-selectivity catalyst to selectively convert carbon tetraalkyne into butadiene, 1-butene and a small amount of butane, so that alkyne impurities in butene materials can be removed, waste can be changed into valuable, corresponding alkene is converted, and the economic benefit of the operation of the full-flow zero-emission improving device is further realized.

There are two main processes for hydrogenation of carbon tetraalkyne. One is a pre-hydrogenation scheme, the main process flow of which is to hydrogenate the carbon four feedstock from the ethylene plant to 1-butene and butadiene prior to two-stage extraction, and selectively hydrogenate the butynes and vinyl acetylenes therein while avoiding hydrogenation of olefins in the feedstock. The technical difficulty of the method is that the handling capacity of the catalyst is large, alkyne in the raw material must be reduced to below 20ppm, simultaneously olefin loss cannot exceed 1%, vinyl acetylene and butadiene in the raw material belong to conjugated diene, the chemical stability is poor, and if the selectivity of the catalyst is poor, butadiene and vinyl acetylene are very easy to hydrogenate simultaneously, so unnecessary loss is caused, and therefore the used catalyst must have stability and high selectivity simultaneously.

The other technology is a post-hydrogenation scheme, namely, after the C-C raw material is subjected to secondary extraction, the alkyne-rich butadiene raw material which is extracted from the side line of the second extraction lower tower is hydrogenated. After the alkyne is hydrogenated into olefin, the olefin is sent back to an extraction tower for feeding, and the hydrogenation process is completed. The process has the greatest advantages of reducing the treatment capacity of the hydrogenation catalyst and avoiding economic loss caused by excessive hydrogenation of butadiene due to change of working conditions. However, 20-30% of alkyne is enriched in the butadiene material extracted from the side line, so if the operation is careless, the explosion risk is very high. Meanwhile, the materials are all active alkyne, alkene and alkane substances, and a small amount of water, acetonitrile, dimers and heavy components are mixed in the materials, so that the selectivity requirement on the catalyst is high, the poisoning resistance requirement on the catalyst is strict, and the application of the catalyst in the industry is limited, so that the research on the catalyst in the industry is relatively less at present.

The current academic application of selective hydrogenation catalysts for acetylene hydrocarbon or olefin hydrocarbon is the palladium catalyst and non-noble metal catalyst. As is well known, the performance research of palladium catalysts on selective hydrogenation of diene is very common, and the academic research in recent years finds that the palladium catalysts can obtain better selectivity on alkyne in butadiene materials through proper modification, and can be completely suitable for industrial application of selective hydrogenation of alkyne; as for non-noble metal catalysts, one type is a copper-based catalyst, and the catalyst has good selectivity on carbon four-alkyne, but the alkene and alkyne in the raw materials are easy to generate polymerization reaction due to high reaction temperature required in the catalytic process, so that the active site of the catalyst is blocked, and the service life of the Cu-based catalyst is shortened. The other kind of non-noble metal catalyst is Ni catalyst with low cost and poor alkyne selectivity, and is only suitable for use as assistant to regulate and control the performance of catalyst. In comparison, the Pd-based catalyst has mild operating conditions and better selective activity for alkyne, and on this basis, the Pd-based catalyst can be modified by adding an additive to improve the selectivity and anti-poisoning performance thereof, and is most suitable as an alkyne hydrogenation catalyst.

Based on the above facts, there is a widely recognized need in the academia to modify Pd-based catalysts to improve the overall catalytic performance of Pd-based catalysts as alkyne hydrogenation catalysts. The modification method is mainly characterized in that a modification auxiliary agent is introduced, the activity of Pd is passivated, and the type and structure of a carrier are improved, so that the interaction of Pd and alkyne is improved, and the selective activity of the Pd on a target product butadiene is improved. CN108927173A reports a catalyst for selective hydrogenation of alkyne, which regulates the acidity of a catalyst carrier by introducing Mg, Li and Ag auxiliaries into a Pd catalyst taking alumina as the carrier, thereby improving the activity and stability of the catalyst. CN102249838A indicates that the selectivity of Pd is related to the exposed active sites on the carrier, and it uses ionizing radiation and adds free radical cleaning agent to control the crystal face state of Pd sites during the preparation of the catalyst, so as to achieve the purpose of increasing its selectivity to alkyne, and its selectivity to alkyne can reach 74.11% at most, but this invention does not give a detailed description of its lifetime. CN108863699A is prepared by adding Li and Ni auxiliary agents in the preparation process of an alumina carrier and adding Mo, K and other auxiliary agents in the process of Pd co-impregnationThe palladium-molybdenum catalyst with the crystal form and the nickel-containing alumina carrier obtains better selective activity, but the selected hydrogenation raw material is simpler, and the anti-poisoning performance of the catalyst under the condition of heavy component/acetonitrile is not considered. CN108863696A on the basis of the catalyst, the auxiliary agent K is replaced by Ag, and the reaction temperature is 25-100 ℃, the pressure is 0.6-2.5 MPa, and the liquid hourly space velocity is 15-25 h^-1Under the working condition, the alkyne removal rate can reach 99.97%, but the butadiene is greatly lost, and the butadiene is removed from 10.01% to 0.0094% of the raw material. The catalyst disclosed in CN102886262A uses Ni-Cu bimetallic active elements, wherein the Ni content is 10-20%, the Cu content is 3-10%, and the rest is an alumina carrier. The selectivity of the catalyst to EA (butyne) and VA (vinyl acetylene) can reach 90 percent and 84.1 percent, but the catalyst also has great loss to butadiene, and the butadiene of the catalyst is reduced by 67.5 percent in the whole reaction process. At present, the research on the modifying assistants Ag and Cu is very extensive, for example, as described in patents US4547600, US6717022, CN1090997 and the like, the loss of Pd can be effectively inhibited, the service life of the catalyst is prolonged, but the addition of Ag also reduces the catalytic activity and the processing capacity of the catalyst on raw materials; the copper additive needs higher reaction temperature, so that coking in raw materials is serious, and the stability of the catalyst is reduced. In addition, in the prior art, an impregnation method is generally used for loading active components and auxiliaries, but the active components are distributed unevenly due to the fact that the surface and internal pore channels of the carrier are complex and the impregnation process is improper, and if the added auxiliaries are excessive, the pore channels can be blocked, particularly, the elements in IB families and IVA families, such as Ag, Cu, Si, Sn and the like are added, and the content of the elements is far higher than that of the main active components, so that the catalytic activity is not obviously improved. In addition, experimental research also finds that most of the modification aids in the prior art have strong inhibition effect on the activity of the catalyst, especially elements such as Cu, Ag and Ni, and the addition of the elements can have large inhibition effect on the activity of the catalyst or can be unfavorable for the selectivity of the catalyst, so that the unit consumption of the catalyst is increased.

In summary, the butadiene selective hydrogenation catalysts developed at present still have many technical problems, and the industrial implementation schemes are few. The carrier is mainly alumina, and the modification auxiliary agent is selected from various types and usage, but the reaction activity and stability of Pd can be effectively improved, and particularly, the catalyst with better effect on the hydrogenation selectivity of carbon four is still less. Therefore, the catalyst with high activity, high selectivity and good stability for preparing butadiene by selective hydrogenation of the C-tetraalkyne is found, and the catalyst has extremely important significance for the application of separating and purifying the four extracted C components and the like.

Disclosure of Invention

One of the technical problems to be solved by the invention is to provide a catalyst for preparing butadiene by selective hydrogenation of carbon tetraalkyne aiming at the problems of low hydrogenation selectivity of carbon tetraalkyne, large consumption of diolefin and low catalytic activity of the existing catalyst on the carbon tetraalkyne in a butene raw material and a preparation method thereof.

The second technical problem to be solved by the invention is to provide an application method of the catalyst, and particularly, under the condition of the catalyst, tail gas obtained from a lateral line after secondary extraction of a butadiene device in an ethylene cracking process is used as a raw material, and carbon tetraalkyne in the tail gas is converted into butadiene through selective hydrogenation. The catalyst has strong coking resistance, can still keep high hydrogenation activity particularly in raw materials containing dimers and heavy components, and can reduce the loss of dialkene caused by deep hydrogenation.

In order to solve the problems, the technical scheme adopted by the invention is as follows:

the invention provides a catalyst for preparing butadiene by selective hydrogenation of carbon tetraalkyne, which comprises ZrO₂/CdO/Bi₂O₃The following contents of the composite carrier and the active component are based on the total mass of the catalyst, and ZrO is₂/CdO/Bi₂O₃The content of the composite carrier is 86.5-92.3%, and the content of the active component is 7.7-13.5%;

the active component comprises the following components:

pd or its oxide, the content is 0.05-0.8%, preferably 0.2-0.5% calculated by Pd element;

VIIB metal or at least one of oxides thereof, in terms of metal elements, in an amount of 0.2 to 6.0%, preferably 2.0 to 5.0%;

la or an oxide thereof in an amount of 0.1 to 4.0%, preferably 0.5 to 2.0% in terms of oxide form.

Catalyst of the invention, the ZrO₂/CdO/Bi₂O₃Composite support, ZrO₂(zirconia) as a main carrier component, CdO (cadmium oxide) and Bi₂O₃(bismuth oxide) as a support modifier. Based on the total mass of the catalyst, the content of CdO is 1-10%, preferably 1.0-4.0%; bi₂O₃The content of (B) is 0.1 to 5.0%, preferably 1.0 to 2.0%.

Preferably, the ZrO₂/CdO/Bi₂O₃The composite carrier has a total pore volume of 0.3-0.9 mL/g and a specific surface area of 90-180 m³/g。

The catalyst of the present invention, said VIIB metal or oxide thereof, is preferably Re (rhenium) or an oxide thereof.

The invention also provides a preparation method of the catalyst for preparing butadiene by selective hydrogenation of carbon tetraalkyne, which comprises the steps of ZrO₂/CdO/Bi₂O₃Preparing a composite carrier and loading an active component.

In the production method of the present invention, the ZrO₂/CdO/Bi₂O₃The composite carrier is prepared by the following method: firstly, preparing a carrier precursor by using a coprecipitation method, then adding a pore-forming agent, an adhesive and water to perform isostatic pressing molding, and aging, drying and roasting to obtain the catalyst.

Further, the above-mentioned ZrO₂/CdO/Bi₂O₃Preparing a composite carrier, wherein a carrier precursor is prepared by the coprecipitation method, and the preferable method comprises the following steps: and uniformly mixing soluble salts of zirconium, cadmium and bismuth with water, then coprecipitating with ammonia water, keeping the pH value of a reaction system at 3-6 (preferably 4-5) for reaction until the raw materials are exhausted, taking precipitates after the reaction is finished, washing with water, and drying (the drying environment is at 60-80 ℃) to obtain the carrier precursor.

In the coprecipitation method, the soluble salts of zirconium, cadmium and bismuth are one or more of nitrate, acetate and the like; the soluble salt of zirconium is preferably zirconium nitrate, the concentration is preferably 3.0-4.0 mol/L, the soluble salt of cadmium is preferably cadmium acetate, the concentration is preferably 0.04-0.30 mol/L, the soluble salt of bismuth is preferably bismuth nitrate, and the concentration is preferably 0.02-0.25 mol/L.

The concentration of ammonia water used for coprecipitation is 1.0-4.5 moL/L, preferably 2.0-4.0 moL/L. And (3) preferably dropwise adding soluble salt water solution of zirconium, cadmium and bismuth and ammonia water in the precipitation reaction process, and controlling the dropwise adding speed through the pH value of a reaction system to keep the pH value at 3-6.

Preferably, after the drying is completed, the carrier precursor is crushed into particles with the particle size range of 80-120 meshes, and preferably 100-120 meshes.

Further, the above-mentioned ZrO₂/CdO/Bi₂O₃Preparing a composite carrier, wherein the drying process needs temperature programming and drying, and the preferable scheme is as follows: heating to 50-80 ℃ at a heating rate of 1-3 ℃/min (preferably 1 ℃/min), and drying for 10-24 h; and then heating to 80-120 ℃ at a heating rate of 1-3 ℃/min (preferably 1 ℃/min), and drying for 6-10 h. It should be noted that direct drying (e.g. 120 ℃, 12h) may cause collapse of the pore structure of the zirconia carrier due to the surface tension effect of water, so that the specific surface area is small, and therefore, the drying process of the carrier according to the present embodiment needs to be performed at 50-80 ℃ for a long time to increase the specific surface area.

Further, the above-mentioned ZrO₂/CdO/Bi₂O₃Preparing a composite carrier, and roasting, wherein the preferable scheme is as follows: after drying, raising the temperature to 800-1200 ℃ at a heating rate of 5 ℃/min, and roasting for 4-8 h.

ZrO of the above₂/CdO/Bi₂O₃In the preparation method of the composite carrier, the adhesive is not particularly limited, and includes but is not limited to sesbania powder and/or polyvinyl alcohol; the pore former is also not particularly limited, including but not limited to citric acid.

The mass ratio of the carrier precursor to the adhesive, the pore-forming agent and the water is 1.00: 0.01-0.10: 0.10-0.40: 0.50-1.00. In more detail, the mass ratio of the carrier precursor to the adhesive, the pore-forming agent and the water can be 1.00:0.03:0.50:0.67, for example.

In the preparation method of the present invention, the active ingredient may be supported by an optional impregnation method, such as an equal-volume impregnation or an excess impregnation, but the present invention is not limited thereto, and an equal-volume impregnation method is preferred. In the active components of the catalyst, Pd is a main active component, VIIB metal and La are auxiliary agents, and according to the characteristics of different types of active components, the preferable loading scheme is as follows: firstly, ZrO is firstly_2/CdO/Bi₂O₃VIIB metal is impregnated and loaded on the composite carrier, and Pd and La are impregnated and loaded after the treatment of drying, roasting and the like, wherein the specific loading method comprises the following steps:

1) ZrO 2 is mixed with₂/CdO/Bi₂O₃Soaking the composite carrier in a VIIB metal soluble salt aqueous solution for 8-10 h (preferably equal-volume soaking), then aging for 4-6 h, drying at 50-80 ℃ for 5-8 h after aging is completed, drying at 80-120 ℃ for 6-10 h, and finally roasting at 330-550 ℃ for 4-8 h to obtain a VIIB metal-loaded catalyst;

2) mixing a palladium soluble salt aqueous solution and a lanthanum soluble salt aqueous solution, adjusting the pH to 2-4 by using a nitric acid aqueous solution with the concentration of 15-25 g/L, then adding the catalyst loaded with the VIIB metal prepared in the step 1) to impregnate for 5-10 h (preferably equal-volume impregnation), and repeating the aging, drying and roasting processes in the step 1) to obtain the catalyst for preparing butadiene through selective hydrogenation of C-C alkyne.

In the step 1), the VIIB metal soluble salt is selected from soluble salts of rhenium elements, preferably ammonium perrhenate, ammonium perrhenate and the like; the concentration of the aqueous solution of the VIIB metal soluble salt is 0.04-2.20 mol/L, preferably 0.75-1.50 mol/L.

In the step 2), the soluble salt of palladium is selected from palladium chloride, palladium nitrate and the like, preferably palladium nitrate; the concentration of the soluble salt water solution of palladium is 0.01-0.13 mol/L, preferably 0.05-0.10 mol/L.

The soluble salt of lanthanum is selected from lanthanum nitrate and lanthanum acetate, preferably lanthanum nitrate; the concentration of the lanthanum soluble salt aqueous solution is 0.20-8.00 mol/L, preferably 0.70-4.00 mol/L.

The mass ratio of the soluble salt water solution of palladium to the soluble salt water solution of lanthanum is 0.7-7.0: 1, preferably 2.0 to 4.0: 1.

in the step 1) and 2), the impregnation is carried out, wherein the mass ratio of the carrier to the impregnation liquid is 1: 1-3, preferably 1: 1-1.5, and most preferably 1: 1.3.

Preferably, in the preparation method of the present invention, the catalyst for preparing butadiene by selective hydrogenation of carbon-tetrayne obtained in step 2) further comprises a passivation treatment process. The catalyst of the present invention, which needs to be passivated for storage, is generally passivated by the following methods in the embodiments of the present invention: firstly, nitrogen (the volume content of hydrogen is 1-5%) containing a certain proportion of hydrogen is used for reducing the hydrogen, and the specific working conditions of the reduction process are as follows: the temperature is 200-500 ℃, the time is 4-8 h, and the gas hourly space velocity is 40-100 h^-1. Then passivating for 4-8 h by using nitrogen (the volume content of oxygen is 5-10%) containing a certain proportion of oxygen, wherein the passivating temperature is 10-90 ℃, and the gas hourly space velocity is 70-160h^-1And the reduction and passivation processes both comprise a temperature programming step.

Before the catalyst is put into use, some active elements in the catalyst are generally reduced to a metal form. The alkyne selective hydrogenation butadiene catalyst of the invention also needs to be activated before use, and one of the adopted activation methods is as follows: activating with nitrogen containing hydrogen in a certain proportion (the volume concentration of hydrogen is preferably 1-5%), wherein the activation temperature is 80-150 ℃, and the activation time is 2-5 h.

The invention also provides the application of the catalyst for preparing butadiene by selective hydrogenation of carbon tetraalkyne, which is suitable for the selective hydrogenation reaction of carbon tetraalkyne in raw materials containing carbon tetraalkyne, in particular in raw materials with high content of carbon tetraalkyne, and the carbon tetraalkyne is converted into butadiene through the hydrogenation reaction.

In the application, the raw material containing the carbon tetraalkyne comprises one or more of butyne, vinyl acetylene, carbon tetraalkene and alkane; the carbotetraalkynes include butyne, vinylacetylene, and the like.

Further, the raw material containing the carbon tetraalkyne is selected from a material containing the carbon tetraalkyne, which is a byproduct of an ethylene cracking process, preferably a material extracted from a side line after secondary extraction of a butadiene device in the ethylene cracking process, wherein the content of the carbon tetraalkyne is preferably 20-40% in terms of mass percentage, and the rest components are mainly C4 alkene and C4 alkane, such as butane, propadiene, butadiene, isobutene, 1-butene, 2-butene and the like, and in addition, the raw material also contains a small amount of impurity water, acetonitrile and the like.

The catalyst is suitable for single-stage bed, double-stage bed or other types of isothermal fixed bed reactors.

Further, the hydrogenation reaction is carried out under the conditions of: the temperature is 20-60 ℃, the inlet temperature of the reactor is 35-50 ℃, and the preferred temperature is 40-45 ℃; the liquid hourly space velocity is 7-20 h^-1Preferably 9h^-1(ii) a The reaction pressure is 0.5-2.5 MPa (G), preferably 1.1MPa (G); the hydrogen/alkyne molar ratio is 1 to 4, preferably 1.6 to 2.5, and most preferably 1.8 to 2.0.

After the hydrogenation reaction is finished, the removal rate of carbon tetraalkyne in the system can reach more than 90 wt%, the selectivity to butadiene can reach more than 56 wt%, the content of carbon tetraalkyne after the reaction can be reduced to less than 2 wt%, and the total consumption rate of olefin is not higher than 0.4 wt%, so that the aim of basically not consuming mono/diolefin is achieved, and the hydrogenation catalyst has high application value.

The invention relates to a catalyst for preparing butadiene by selective hydrogenation of carbon tetraalkyne, which adopts ZrO₂/CdO/Bi₂O₃Composite support, ZrO₂As main component of carrier, CdO and Bi₂O₃Is a carrier modifier. Main component ZrO of carrier₂The carrier has acid-base dual active centers, can well play a synergistic effect with loaded active component elements through reasonable regulation and control, and increases the uniform dispersion effect of the active elements on the surface of the carrier. With ZrO in the support₂And the catalyst can effectively dissociate and adsorb hydrogen to generate ZrOH and ZrH, so that the chemical adsorption and utilization of the catalyst on the hydrogen are further improved, and the hydrogenation reaction efficiency is improved. In addition, CdO and Bi are introduced into the carrier₂O₃As a carrier modifier, some kinds of cadmium soluble salts (such as cadmium acetate) are easy to form spinel oxides under the high-temperature roasting, a coated composite cadmium oxide carrier with a remarkable limited domain structure can be constructed, and the carrier not only can promote the main active element Pd to be in the high-temperature roasting stateThe dispersion on the surface of the catalyst can also effectively inhibit ZrO₂Reduction of specific surface area and abrasion during the reaction due to high-temperature calcination and during long-term reaction. And the assistant Bi₂O₃The addition of the catalyst not only has the functions of controlling the removal of the butylene α -H and inhibiting the excessive hydrogenation of the butadiene, but also can effectively adjust the acidity and alkalinity of the catalyst so as to inhibit ZrO₂The activity of the acid center of the catalyst can prevent olefin and alkyne from polymerizing at the surface acid center to generate green oil, colloid and the like to block the pore channel of the catalyst, and influence the activity, stability and service life of the catalyst.

In the active component loaded by the catalyst, Pd is a main active component, and VIIB element and La are promoters.

Because the main active component Pd is easy to generate a complex with the raw material under the long-term reaction state, the complex is lost in the catalytic process, and the VIIB element (such as Re) of the cocatalyst component is introduced, so that the electronic action between the Pd and the carrier is changed, the interaction between the Pd and the carrier is enhanced, the loss of the Pd element is reduced, and the stability and the service life of the catalyst are further improved. In addition, because Pd has strong hydrogenation catalytic activity and poor selectivity for hydrogenation of carbon tetraalkyne, and is very easy to catalyze olefin to deeply hydrogenate to generate alkane and consume butadiene, the catalyst provided by the invention forms an alloy similar to a solid solution type by adding the catalyst promoter component La and Pd, La can preferentially occupy the side, edge or step position on the Pd crystal phase, and modifies the defect position on the active site of the Pd which is easy to generate side reaction, so that the lattice structure of Pd or an oxide thereof is effectively improved, the poisoning resistance of the catalyst on a dimer and a heavy component can be improved, the catalytic activity of the catalyst on the reaction of producing alkane by hydrogenation of monoolefin, the deep hydrogenation capability of Pd on monoolefin is inhibited, and the hydrogenation selectivity of carbon tetraalkyne is improved.

The technical scheme of the invention has the beneficial effects that: the catalyst of the invention can effectively improve the selectivity of hydrogenation of carbon tetraalkyne to butadiene, and the conversion rate of the carbon tetraalkyne reaches more than 90%, and can also effectively reduce the loss of olefin and improve the anti-poisoning performance of the catalyst on components. Even under the condition of improving the flux of raw materials, the loss of Pd element in the catalyst can be reduced, and good catalytic activity and hydrogenation selectivity to carbon tetraalkyne can be maintained for a long time. In addition, the catalyst has strong coking resistance and good long-period running stability, and 500h online evaluation results show that the selectivity and activity of the catalyst are basically unchanged, the online running is stable, and the operation requirement of recovering butadiene by selective hydrogenation of carbon tetraalkyne in tail gas of an alkyne distillation tower unit of a butadiene device can be met.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention in any way.

The feed used in the following examples was taken from the side of the lower column of the carbon four-unit two-stage extraction column of the ethylene cracking process (S & W process flow) and the composition is detailed in table 1.

TABLE 1

Composition of raw materials	In specific wt/%)
		Water (W)	1.20
1-butene	0.04
		2-butene	15.40
1, 3-butadiene	15.02
		1, 2-butadiene	0.14
Butyne	4.16
		Vinyl acetylene	26.72
1-pentene	4.16
		N-butane	22.93
Acetonitrile	4.62
		Heavy fraction	5.30

For the catalyst for preparing butadiene by selective hydrogenation of carbon-tetraalkyne, the performance of the catalyst is evaluated by acetylene hydrocarbon removal rate and butadiene selectivity after hydrogenation reaction.

Wherein, the content of the residual alkyne is directly tested by using an Agilent 7890B gas chromatography, and the test method adopts the composition determination SH-T1141092 analysis of industrial cracking carbon four.

Butadiene selectivity was calculated using the following formula:

note: in the following examples, all chemical reagents used were analytical reagents unless otherwise specified; all references to gas concentrations are molar.