Catalyst for carbon four alkylating raw material pretreatment, preparation method and pretreatment method

Abstract

The application discloses a kind of carbon four alkylation raw material pretreatment catalyst and preparation method and pretreatment method, belong to carbon four light hydrocarbon processing technical field.Its technical scheme is: carbon four alkylation raw material first enters extraction column and is extracted, water-washed carbon four alkylation raw material is extracted from top and enters catalytic rectification column, catalytic rectification column is divided into rectification section, reaction section and stripping section from top to bottom, catalyst of the application is placed in reaction section;Carbon four alkylation raw material enters reaction section, butadiene therein and hydrogen gas occur reaction, and 2-butene generated in the reaction process is removed constantly;Catalytic rectification column bottom is extracted and pretreated carbon four alkylation raw material.The pretreatment method of the application carries out corresponding desulfurization, denitrogenation, deoxidant and diene hydrocarbon etc.pretreatment before carbon four alkylation raw material enters alkylation device, meets the requirement of alkylation feed to raw material impurity, improves alkylation oil quality, reduces the material loss of alkylation process.

Description

Technical Field

[0001] This invention relates to the field of C4 light hydrocarbon processing technology, specifically to a catalyst for the pretreatment of C4 alkylation feedstock, its preparation method, and the pretreatment method. Background Technology

[0002] Alkylation is a crucial refining process, involving the reaction of isobutane with C4 olefins under a catalyst to produce alkylate (isooctane). Alkyate contains no olefins or aromatics, boasting high research octane and motor octane numbers, making it an ideal gasoline blending component. With increasingly stringent environmental regulations, gasoline standards have been introduced, imposing stricter requirements on olefin, aromatic, benzene, and sulfur content. Alkyate has thus emerged as a key component in the upgrading of petroleum products, possessing significant development potential.

[0003] In the alkylation process, whether liquid acid (sulfuric acid, hydrofluoric acid, ionic liquid) or solid acid is used as the catalyst, the composition and impurity content of the feedstock vary, significantly impacting the quality, yield, and acid consumption of the alkylation oil. Due to differences in crude oil source and processing technology, C4 feedstocks contain not only butadiene but also sulfides such as thiols, sulfides, and disulfides, as well as impurities such as nitrides, chlorides, oxygen-containing compounds, and heavy metals, all of which are poisons in the alkylation reaction and have a significant impact. During alkylation, butadiene in C4 reacts to form high-molecular-weight, viscous, acid-soluble oil (Aso) and heavy alkylation oil with very low octane numbers and high drying points, thus reducing the quality and yield of the alkylation oil and significantly increasing acid consumption and production costs. Sulfides, nitrides, chlorides, oxygen-containing compounds, and heavy metals significantly increase acid consumption for liquid acid catalysts and lead to catalyst deactivation for solid acid catalysts, severely impacting their lifespan. With the increase in residue blending in refinery catalytic cracking units and the emergence of new refining processes, the content of impurities such as butadiene and sulfides in C4 is on the rise. Therefore, it is essential to add corresponding removal measures to control impurities in C4 feedstock in order to ensure the operation of alkylation units.

[0004] The process for removing butadiene from C4 hydrocarbons typically employs selective hydrogenation. During hydrogenation, butadiene can be converted into mono-olefins, and 1-butene can be isomerized to 2-butene, increasing the octane number of the alkylate. The active metal for selective hydrogenation is usually a noble metal catalyst, primarily palladium. However, noble metal catalysts are highly sensitive to impurities in the feedstock; the presence of impurities can lead to decreased catalyst activity or even deactivation. Currently, refineries have dual-removal processes to remove hydrogen sulfide, mercaptans, and other sulfides, but due to process limitations, small amounts remain. While removing these impurities, new impurities, such as caustic soda, are also introduced. Reports have been published regarding how to address the impact of impurities on alkylation catalysts.

[0005] Patent CN 105601460 B provides a method for refining alkylation feedstock. The method involves passing the impurity-containing alkylation feedstock through a water washing tower, dehydration tower, desulfurization tower, dechlorination tower, denitrification tower, oxygen-containing compound removal tower, preheater, and selective hydrogenation reactor to obtain refined alkylation feedstock. This method effectively removes various impurities such as sulfides, nitrogen compounds, chlorides, and oxygen-containing compounds from the alkylation feedstock, significantly reducing the impurity content and preventing poisoning of the solid acid catalyst in subsequent alkylation reactions. It also improves the catalytic activity and lifespan of the solid acid catalyst in alkylation. The drawback is the high investment cost.

[0006] Patent CN 1621396 A provides a method for the selective hydrogenation removal of trace amounts of diolefins from C4 alkylation feedstock. The method involves contacting the C4 alkylation feedstock containing trace amounts of diolefins with a magnetic noble metal catalyst in a fluidized bed. The catalyst consists of a spherical support and one or more noble metal active components selected from palladium, platinum, ruthenium, and rhodium. The spherical support is composed of alumina and magnetic particles, with the magnetic particles consisting of a SiO2 coating layer and an iron-containing core. Under the influence of a magnetic field, the catalyst can be easily separated and recovered from the reaction products. A drawback is that the feedstock only considers post-etherification C4 and low-sulfur materials, lacking broad applicability.

[0007] Patent CN 107118072 A discloses a method for producing isomeric C8 alkanes from C4 fractions. The process involves the refinery's C4 fraction first entering a propane removal tower, then a heavy component removal tower, where it is separated into light and heavy components. 2-Butene is separated from the heavy components. Butadiene in the light components is hydrogenated to 1-butene and 2-butene, which are then isomerized to 1-butene. n-Butane is separated from the heavy components and isomerized to isobutane. 1-Butene reacts with isobutane to produce isomeric C8 alkanes. This method maximizes the utilization of the C4 fraction and removes most impurities, but it is energy-intensive.

[0008] Patent CN 206624800 U discloses an apparatus for refining isooctane into alkylation feed gas. Utilizing the differences in boiling points and solubility of different components in the feed gas, an additional isooctane refining and alkylation feed gas operation unit is added. Isooctane is used as an absorbent to remove organic sulfur and organic chlorine from the C4 feed gas after etherification, effectively solving the problem of catalyst deactivation in the 1,3-butadiene catalytic hydrogenation. The disadvantages are that using isooctane as an absorbent for impurity removal results in isooctane loss, and the recompression of C4 gas increases additional energy consumption.

[0009] In summary, the processes disclosed in the prior art mainly involve adsorbents or raw material extraction processes. Although some processes solve the problem of the impact of impurities in raw materials on alkylation catalysts, there are still problems such as complex processes, high investment, and high energy consumption. Therefore, it is necessary to develop a new pretreatment method to adapt to raw materials from various sources and improve the flexibility and industrial feasibility of alkylation units. Summary of the Invention

[0010] The object of the present invention is to solve the technical problems existing in the prior art, such as complex impurities in C4 alkylation raw materials, long purification process flow, high investment, and easy loss or inactivation of alkylation catalysts. A pretreatment method for removing impurities from raw materials of different sources is provided. At the same time, a new selective hydrogenation catalyst is provided, which can better adapt to impurities. This method is applicable to the C4 fraction in light hydrocarbons generated by processes such as oil refining and ethylene cracking. Before entering the alkylation unit, corresponding pretreatment such as desulfurization, denitrification, deoxidation, and diolefin removal is carried out to meet the requirements of alkylation feed for raw material impurities, improve the quality of alkylated oil, and reduce the material loss of the alkylation process.

[0011] The technical solution of the present invention is as follows:

[0012] On the one hand, the present invention provides a catalyst for pretreatment of C4 alkylation raw materials, characterized in that the catalyst is loaded with the main active component Pd and the co-active component La or Ce on a mixed-phase alumina carrier with δ-phase as the main phase.

[0013] Preferably, in the alumina carrier, δ-phase alumina accounts for 80-95 wt%, and the rest is γ-phase alumina.

[0014] Preferably, the content of the main active component Pd in the catalyst is 0.05-0.5 wt%, preferably 0.1-0.3 wt%; the content of the co-active component La or Ce is 0.05-3.0 wt%, preferably 0.1-2.0 wt%.

[0015] Preferably, the specific surface area of the alumina carrier is 30-300 m² / g, preferably 50-200 m² / g; the specific pore volume is 0.2-0.8 ml / g, and the pore radius is 5.0-15 nm (nitrogen adsorption method).

[0016] Preferably, the catalyst has an annular structure, and several ribs are radially arranged inside. The ribs are in the shape of a "rice" character or a "cross", making the catalyst a multi-ribbed wheel-shaped cylinder; the catalyst particle size is 6-30 mm to meet the process requirements of uniform mixing with dumped packing or being used as an independent separation-capable packing; the catalyst particles have a high specific surface area of the fluid as a packing, which is 200-500 m 2 / m 3 .

[0017] Secondly, this invention provides a method for preparing the catalyst for the pretreatment of the above-mentioned C4 alkylation raw materials. The method involves preparing a metal salt solution from the carbonate, nitrate, or chloride salts of the main active component and the co-active component. An organic acid (formic acid, acetic acid, or oxalic acid, etc.), nitric acid, or hydrochloric acid is added to make the solution acidic, preventing the metal salt solution from hydrolyzing and precipitating under alkaline conditions. An alumina support is impregnated in an aqueous solution at room temperature to 60°C. After impregnation, it is dried at 100 to 300°C and then calcined at 300 to 600°C for 3 to 6 hours to obtain the catalyst. During molding, the binder and pore-expanding agent used are known substances, and the amount added is based on the weight of the alumina support. Preferably, the amount of pore-expanding agent added is 2 to 4 wt%, and the amount of binder added is 1 to 3 wt%.

[0018] Thirdly, this invention also provides a method for pretreating C4 alkylation feedstock using the aforementioned catalyst. The C4 alkylation feedstock from upstream units or tank farms first enters the lower part of an extraction tower for extraction, where it comes into countercurrent contact with demineralized water entering from the upper part of the extraction tower. This extraction removes water-soluble impurities such as metal ions, alkali nitrogen compounds, and oxygen-containing compounds (methanol, ether, etc.). The demineralized water is the continuous phase, while the C4 alkylation feedstock is the dispersed phase. The material collected from the bottom of the extraction tower is sent to a wastewater treatment unit. The extracted C4 alkylation feedstock is then separated and dehydrated by a coalescer before entering a catalytic distillation tower. The internal components of the extraction tower are sieve plates or packing, with a theoretical extraction stage number > 2. The washed C4 alkylation feedstock enters the catalytic distillation tower, which is divided into a rectification section, a reaction section, and a stripping section from top to bottom. The reaction section contains the aforementioned catalyst for hydrogenating butadiene and isomerizing 1-butene to 2-butene. The C4 alkylation feedstock enters from the top of the reaction section, while hydrogen enters from the bottom, contacting the feedstock from bottom to top. Butadiene in the feedstock reacts with hydrogen to form butene. 1-Butene isomerizes to 2-butene under hydrogen conditions, and the generated 2-butene is continuously removed during the reaction. The top fraction of the catalytic distillation column, containing hydrogen, C3 hydrocarbons, oxygen-containing compounds (dimethyl ether, methanol, water, etc.), light sulfides (hydrogen sulfide, carbonyl sulfide, light thiols, etc.), and a small amount of isobutane, is collected and sent to the flare network. The bottom fraction, free of butadiene and other impurities, is the C4 alkylation feedstock that meets the requirements of the alkylation unit.

[0019] Preferably, the C4 alkylation feedstock is first processed in a C5 removal tower before entering the extraction tower. When the C4 alkylation feedstock contains impurities such as C5 components and heavy sulfides, it is necessary to process the C4 alkylation feedstock in a C5 removal tower to remove C5 components, components with boiling points higher than C5, and heavy sulfides before it enters the extraction tower for further processing.

[0020] Preferably, the operating conditions of the five-column decarbonization column are: pressure 0.3–1.0 MPa, top temperature 40–90°C, and reflux ratio 0.2–3.0; the operating conditions of the extraction column are: pressure 0.3–0.6 MPa, temperature ambient to 60°C, and oil-water volume ratio 3–20:1; the operating conditions of the catalytic distillation column are: pressure 1.0–1.8 MPa, top temperature 40–60°C, and reflux ratio 20–50; and the operating conditions of the reaction section of the catalytic distillation column are: pressure 0.4–2.0 MPa, temperature 40–90°C, and C4 liquid hourly space velocity 5–30 h⁻¹. -1 The molar ratio of hydrogen to butadiene is 1.0 to 5.0. If the molar ratio is too low, butadiene will not be completely removed; if it is too high, a side reaction of olefin hydrogenation to form alkanes will occur.

[0021] Preferably, the catalytic distillation column has multiple reaction sections, with the catalyst randomly packed in each section, either independently or uniformly mixed with the packing material. A liquid distributor is located above each reaction section, through which the C4 alkylation feedstock enters the reaction section. A hydrogen feed distribution pipe is located below each reaction section, through which hydrogen enters the reaction section. Separation trays are provided between adjacent reaction sections. Furthermore, the catalytic distillation column has 60 theoretical plates, with 15-30 theoretical plates in the rectification section, 5-10 theoretical plates in the reaction section, and 25-30 theoretical plates in the stripping section.

[0022] Inside the catalytic distillation column, upward-flowing gaseous hydrogen passes through the reaction section, while downward-flowing liquid C4 alkylation feedstock, after being distributed, enters the reaction section and undergoes hydrogenation and isomerization reactions under the action of a catalyst to produce butene. Simultaneously, most of the 1-butene isomerizes to 2-butene. The reactants are separated in the reaction section, with high-boiling-point 2-butene continuously moving out, disrupting the chemical equilibrium between 1-butene and 2-butene, thus increasing the conversion rate and isomerization rate, resulting in deep conversion of 1-butene. Heat and mass transfer occurs between the gas and liquid phases in the reaction section; the heat of reaction and isomerization heat can be used for the vaporization of some materials, making efficient use of heat and improving the economy of the catalytic distillation column. The reaction structure is simple, the catalyst loading and unloading are convenient, and the reactants are in direct contact with the catalyst, which is more conducive to the reaction.

[0023] The reaction section is located below the feed inlet. Light sulfides (such as methanethiol, hydrogen sulfide, carbonyl sulfide, etc.) and oxygen-containing compounds (alcohols, ethers, etc.) flow towards the top of the column at the feed inlet, thereby reducing their contact with the hydrogenation catalyst in the reaction section below and reducing the possibility of them affecting the activity and lifespan of the hydrogenation catalyst.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. The method of this invention, through treatments such as removal of C5 components, extraction, and selective hydrogenation, can remove most of the impurities such as sulfides, nitrides, chlorides, oxygen-containing compounds, heavy metals, and dienes from the C4 alkylation feedstock, thereby improving the quality of the alkylation oil and reducing the consumption of liquid acid catalyst in the alkylation unit. For solid acid alkylation, it can effectively reduce the total amount of impurities entering the adsorption unit, extending the adsorbent operating cycle and the service life of the solid acid catalyst.

[0026] 2. The hydrogenation catalyst selected in this invention has better adaptability to small amounts of oxygen-containing compounds and light sulfides (such as thiols), and can maintain high hydrogenation activity at lower temperatures. The reasons may be: (1) Although the co-active components lanthanum or cerium are transition metals, they have the properties of alkaline earth metals in some aspects. The presence of lanthanum oxide / cerium oxide reduces the acidity of the catalyst surface and reduces the adsorption of sulfides; (2) The co-active components lanthanum or cerium can reduce the particle size of palladium crystals and increase their dispersion, which is conducive to palladium loading onto the support and avoids sintering and agglomeration during the calcination process, thereby improving the activity of the catalyst; (3) The co-active components are electron donors, which regulate the electron density of palladium and weaken the adsorption of sulfides; (4) The catalyst support is regulated so that the most probable pore size is in a suitable range to reduce the entry of oxygen-containing compounds such as alcohols and ethers, sulfides, etc. into the catalyst channels.

[0027] 3. This invention utilizes a catalytic distillation column to selectively hydrogenate and remove butadiene. This not only leverages the separation capabilities of the reaction section to fractionate impurities harmful to the hydrogenation catalyst, but also disrupts the chemical equilibrium between 1-butene and 2-butene, increasing the isomerization rate of 1-butene. The heat generated from the hydrogenation reaction and the isomerization of 1-butene can be used for component separation, reducing steam consumption in the distillation reaction. The use of liquid material within the catalytic distillation column for flushing reduces carbon buildup on the catalyst surface, extending the lifespan of the selective hydrogenation catalyst.

[0028] 4. The catalyst of the present invention adopts a multi-ribbed wheel structure, which not only has a good gas and liquid dispersion effect, but also increases the specific surface area of ​​the catalyst and the contact area of ​​the material on the catalyst surface. It has a good separation ability, ensures the distribution of liquid material on the catalyst surface, improves the hydrogenation effect, and simplifies the filling method. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the structure of the present invention.

[0031] Figure 2 It is a schematic structural view of the reaction section of the catalytic distillation column of the present invention.

[0032] Figure 3 It is a schematic structural view of the catalyst of the present invention.

[0033] In the figure, 1 - decarbonized pentane tower, 2 - extraction tower, 3 - coalescer, 4 - catalytic distillation column, 41 - rectifying section, 42 - reaction section, 421 - liquid distributor, 422 - separating tray, 423 - hydrogen feed distribution pipe, 43 - stripping section, 6 - rib. Specific embodiments

[0034] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0035] Embodiment 1

[0036] The preparation process of the hydrogenation catalyst in this embodiment is as follows: Weigh 100 g of pseudo - boehmite and 4 g of pore - forming agent, mix them evenly, add 2 g of a solution containing a binder, and after kneading, extrude them into the eight - rib wheel shape (such as the "rice" shape shown) of the present invention in a mold. The catalyst particle size is φ8×8 mm, put it into a muffle furnace, and calcine it at 1000 °C for 4 h to form an alumina support. Weigh palladium chloride and lanthanum nitrate, and add them to water with hydrochloric acid respectively to prepare a metal solution. Weigh the alumina support by weight, immerse it in the metal solution at room temperature, dry it at 200 °C, and then calcine it at 500 °C for 3 h to obtain the hydrogenation catalyst of this embodiment. Figure 3 shown.

[0037] After XRD detection, the δ - phase alumina in the alumina support accounts for 95 wt%, and the rest is γ - phase alumina. The specific surface area of the support is 180 m² / g, the specific pore volume is 0.6 ml / g, the pore radius is 9 nm (nitrogen adsorption method), the loaded Pd metal content is 0.2 wt%, and the La metal content is 1.5 wt%. [[ID=一]]

[0038] According to Figure 1-2 the process flow shown, using catalytic C4 as the raw material, the raw material composition is shown in Table 1 - 1, the impurity sulfide composition in the raw material is shown in Table 1 - 2, and the impurity oxygen - containing compound composition is shown in Table 1 - 3.

[0039] Feed stream I enters the decarbonylation tower, which operates at a pressure of 0.5 MPa, a top temperature of 54°C, and a reflux ratio of 0.5. At the top of the tower, C4 stream II, after C5 removal, is obtained, containing <5 ppm of heavy sulfides such as dimethyl disulfide and <0.1% of C5. C4 stream II then enters the bottom of the extraction tower, which operates at a pressure of 0.4 MPa, a temperature of 40°C, and an oil-to-water volume ratio of 20:1. After countercurrent extraction with water, the extracted C4 stream contains <1 ppm of alkali nitrogen compounds and metal ions.

[0040] The C4 feed stream V, after most metal ions and alkali nitrides have been removed, is collected from the top of the extraction column and enters the catalytic distillation column. The catalytic distillation column operates at a pressure of 1.0 MPa, a top temperature of 54°C, and a reflux ratio of 50. Hydrogen enters the column from the bottom of the reaction section and contacts the C4 feed stream from bottom to top within the reaction section. The catalytic distillation column has one reaction section. Under the action of the hydrogenation catalyst, hydrogen reacts with butadiene to produce butene. The 1-butene component isomerizes to 2-butene under hydrogen conditions. Through distillation separation, the 2-butene generated in the reaction is rapidly discharged downwards from the reaction section, breaking the butene double bond isomer equilibrium within the reaction section, allowing the 1-butene in the reaction section to undergo a deeper reaction. The top of the column yields a stream VII containing C3, water, hydrogen, and a small amount of light components such as methanethiol. The bottom of the column yields a high-quality C4 alkylation feed stream VIII, which is purified and free of impurities such as butadiene, sulfides, and oxygen-containing compounds. The composition of feed and impurities in each stream is shown in Tables 1-4 and 1-5.

[0041] The hydrogenation catalyst loading in the reaction section was set at 200 ml, and the hydrogenation liquid hourly space velocity (LHSV) was 10 h⁻¹. -1 The hydrogen-diene ratio was 2.5 mol / mol, the temperature was 70℃, and the pressure was 1.0 MPa. Dienes were removed from the feedstock, and the content of dienes in the post-reaction material was <100 ppm, with a 1-butene isomerization rate ≥85%.

[0042] Table 1-1 Raw Material Composition

[0043]

[0044] Table 1-2 Sulfide Composition in Raw Materials

[0045]

[0046] Table 1-3 Composition of oxygen-containing compounds in raw materials

[0047] composition methanol MTBE dimethyl ether tert-Butanol water wt, % - - - - 0.01

[0048] Table 1-4 Raw material composition of each logistics stream

[0049]

[0050] Impurity composition in each stream of Table 1-5

[0051]

[0052] Stream VIII represents the final product after pretreatment. As can be seen from Table 1-4 and 1-5, the method of this embodiment can remove impurities such as C5, most sulfides, basic substances, oxygen-containing compounds, heavy metals, etc. and diolefins in the C4 alkylation raw material. The C4 alkylation raw material pretreated by this embodiment meets the impurity requirements for entering the alkylation unit.

[0053] Example 2

[0054] For the hydrogenation catalyst of this embodiment, 100 g of pseudo-boehmite and 3 g of pore-forming agent are weighed and mixed evenly, and 3 g of a solution containing a binder is added. After kneading, it is extruded into the shape of an eight-rib wheel of the present invention (such as the "rice" shape shown Figure 3 ). The catalyst particle size is φ6×6 mm, and it is placed in a muffle furnace and calcined at 900 °C for 4 h to form an alumina support. Palladium chloride and cerium nitrate are taken, and a small amount of nitric acid is added to water respectively to prepare a metal solution. The alumina support is weighed and impregnated in the metal solution at room temperature, dried at 200 °C, and then calcined at 400 °C for 3 h to obtain the hydrogenation catalyst of this embodiment.

[0055] After XRD detection, δ-phase alumina in the alumina support accounts for 85 wt%, and the rest is γ-phase alumina. The specific surface area of the support is 180 m² / g, the specific pore volume is 0.4 ml / g, the pore radius is 8 nm (nitrogen adsorption method), the loaded Pd metal content is 0.2 wt%, and the Ce metal content is 1.2 wt%.

[0056] According to the Figure 1-2 shown process flow, catalytic etherified C4 is used as raw material stream II, the raw material composition is shown in Table 2-1, the impurity sulfides in the raw material are shown in Table 2-2, and the impurity oxygen-containing compounds are shown in Table 2-3.

[0057] Feed stream II, containing low levels of heavy sulfides, bypasses the C5 decarbonylation tower and directly enters the bottom of the extraction tower. The extraction tower operates at a pressure of 0.4 MPa and a temperature of 40°C, with an oil-to-water volume ratio of 3:1. After countercurrent extraction with water, the methanol content in the C4 feed is <50 ppm. Stream V, having removed most metal ions and basic substances, is collected from the top of the extraction tower and enters the catalytic distillation tower. The catalytic distillation tower operates at a pressure of 1.8 MPa, a top temperature of 66°C, and a reflux ratio of 50. Hydrogen enters the tower from the bottom of the reaction section, contacting the C4 feed from bottom to top. Under the action of the hydrogenation catalyst, hydrogen reacts with butadiene to produce butene. The 1-butene component is isomerizes to 2-butene under hydrogen conditions. Stream VII, containing C3, dimethyl ether, methanol, water, hydrogen, and small amounts of methanethiol, is collected from the top of the tower. The purified, high-quality C4 alkylation feed stream VIII is obtained from the bottom of the tower. The butadiene content is <100ppm, sulfides ≤15ppm, methanol-free, dimethyl ether <40ppm, and water <50ppm. The composition of raw materials and impurities in each stream is shown in Tables 2-4 and 2-5.

[0058] The hydrogenation catalyst was loaded with 200 ml of catalyst and mixed with similarly sized dispersed stainless steel θ-ring packing material to form two reaction sections, separated by structured packing. The hydrogenation liquid space velocity was 15 h⁻¹. -1 The hydrogen-diene ratio is 4.0 mol / mol, the temperature is 92–100 °C, and the pressure is 1.80 MPa. Dienes are removed from the feedstock, and the content of dienes in the post-reaction material is <100 ppm, with a 1-butene isomerization rate ≥90%.

[0059] Table 2-1 Raw Material Composition

[0060]

[0061] Table 2-2 Sulfide Composition in Raw Materials

[0062]

[0063] Table 2-3 Composition of oxygen-containing compounds in raw materials

[0064] composition methanol MTBE dimethyl ether tert-Butanol water wt, % 0.0103 0.0077 0.1603 0.0013 0.047

[0065] Table 2-4 Composition of each stream

[0066]

[0067] Table 2-5 Composition of Impurities in Each Stream

[0068]

[0069] Logistics VIII represents the final product after pretreatment. As can be seen from Tables 2-4 and 2-5, the method of this embodiment can remove most of the impurities such as sulfides, basic substances, oxygen-containing compounds, heavy metals, and dienes from the C4 alkylation feedstock. The C4 alkylation feedstock pretreated by this embodiment meets the impurity requirements for entering the alkylation unit.

[0070] Comparative Example 1

[0071] Using Example 6 of Publication No. CN108865243B as a comparison, a palladium-molybdenum selectively enhanced catalyst was used. Nickel-based boehmite was used as a support, mixed with nitric acid, phosphoric acid, lithium citrate, calcium nitrate, and water, kneaded, extruded, dried at 110°C, and calcined at 1040°C for 4 hours to obtain the support. Palladium chloride, molybdenum oxide, and potassium carbonate were prepared as an active component impregnation solution. The pH of the solution was adjusted, and the prepared impregnation solution was impregnated onto the support. After 30 minutes, the excess solution was removed, and the catalyst was washed with distilled water, aged, dried at 120°C for 4 hours, and calcined at 550°C for 4 hours to obtain the catalyst. Its active metal content was 0.32% palladium, 1% nickel, 1.42% molybdenum oxide, 1.45% lithium oxide, and 5.1% phosphorus oxide.

[0072] Taking the optimal data example 6 provided by the patent as an example, the experimental raw material was a mixed C4 mixture with a butadiene content of 0.17%. A fixed-bed pilot-scale apparatus was used, and the mixture was reduced at 100°C for 6 hours under a hydrogen atmosphere. The reaction inlet temperature was 50°C, the reaction pressure was 1.3 MPa, and the liquid hourly space velocity was 9.5 h⁻¹. -1 The molar ratio of hydrogen to butadiene was 3.5. The reaction results showed that the butadiene removal rate was 98.7% and the 1-butene isomerization rate was 70% after hydrogenation. Since there was no purification process, the content of impurities other than butadiene remained unchanged before and after the hydrogenation reaction.

[0073] As can be seen from Comparative Example 1 and Examples 1-2, the pretreatment method of the present invention features high removal rates of impurities such as sulfides, nitrides, oxides, and dienes, a simple process, and a high 1-butene isomerization rate. The butadiene hydrogenation catalyst has high activity, efficiently removing dienes through selective hydrogenation of the C4 feedstock, while simultaneously breaking the 1-butene isomerization equilibrium through catalytic distillation, significantly improving the 1-butene isomerization rate. The catalyst structure allows the hydrogenation catalyst to maintain separation efficiency during hydrogenation, and the scouring of the catalyst surface by the liquid in the column helps extend the catalyst's lifespan and simplifies the packing structure of the reaction section. The pretreatment method of the present invention can also be used in non-alkylation purification processes.

[0074] Comparative Example 2

[0075] Using catalyst B from patent CN1238239A as a comparison, a palladium-based selective hydrogenation catalyst was prepared according to its preparation steps. The palladium content was 0.2%, the co-active component was gold with a content of 0.02%, and the catalyst particle size was φ2.2×3~5mm. Catalytic C4 (composition of raw material 1 is shown in Table 1-1) and post-etherified C4 (composition of raw material 2 is shown in Table 2-1) were used as raw materials, respectively, at a reaction pressure of 1.5MPa, a temperature of 50℃, and a space velocity of 10h⁻¹. -1 The molar ratio of hydrogen to butadiene was 2.5. The catalyst prepared in Example 2 of this invention was reacted under the same process conditions, and the results are shown in Table 3.

[0076] Table 3 shows the operating results of the catalysts in Comparative Example 2 and Example 2.

[0077]

[0078] As shown in Table 3, after hydrogenation, the butadiene residue in feedstock 1 of Comparative Example 2 was 0.002%, and the butadiene residue in feedstock 2 was 0.0017%, with butadiene removal rates of 99.1% and 99.3%, respectively, and 1-butene isomerization rates of 59.7% and 56.2%, respectively. In contrast, under the same process conditions, the catalyst of Example 2 of this invention showed undetectable butadiene residue, a 100% butadiene removal rate, and 1-butene isomerization rates of 68.5% and 67.7%, respectively. Therefore, under the same feedstock conditions, the catalyst of this invention exhibits better activity.

[0079] Comparative Example 3

[0080] Using catalyst B from patent CN1238239A as a comparison, a palladium-based selective hydrogenation catalyst was prepared according to its preparation steps. The palladium content was 0.2%, the co-activating component was gold with a content of 0.02%, and the catalyst particle size was φ2.2×3~5mm. The catalyst was loaded into a catalytic distillation column, which was 3m high and 25mm in diameter. The raw materials were as shown in Table 2-1, and the feed rate was 400ml / h with a reflux ratio of 50. Distillation was performed under the same process conditions as the catalyst prepared in Example 2 of this invention, and the results are shown in Tables 4-1 and 4-2.

[0081] Table 4-1 Comparison of feedstock composition after catalyst operation between Comparative Example 3 and Example 2

[0082]

[0083]

[0084] Table 4-2 Comparison of impurity composition after catalyst operation between Comparative Example 3 and Example 2

[0085]

[0086] As can be seen from Tables 4-1 and 4-2, the catalyst of Example 2 of the present invention has a better distillation separation effect and separation efficiency for light and heavy components of C4 hydrocarbons when performing C4 distillation in a catalytic distillation column compared with the hydrogenation catalyst of Comparative Example 3.

[0087] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the invention should also be covered within the protection scope of the invention. Therefore, the protection scope of the invention should be determined by the scope of the claims.

Claims

1. A catalyst for the pretreatment of C4 alkylation feedstock, characterized in that, The catalyst is a mixed-phase alumina support with δ phase as the main phase on which the main active component Pd and the auxiliary active component La or Ce are loaded; in the alumina support, δ phase alumina accounts for 80-95 wt%, and the remainder is γ phase alumina.

2. The catalyst for pretreatment of C4 alkylation feedstock as described in claim 1, characterized in that, The catalyst has a Pd content of 0.05–0.5 wt% as the main active component and a La or Ce content of 0.05–3.0 wt% as the co-active component.

3. The catalyst for pretreatment of C4 alkylation feedstock as described in claim 1, characterized in that, The specific surface area of ​​the alumina carrier is 30–300 m². 2 / g; pore volume is 0.2~0.8mL / g, pore radius is 5.0~15nm.

4. The catalyst for pretreatment of C4 alkylation feedstock as described in claim 1, characterized in that, The catalyst has a ring-shaped structure with several radial ribs inside.

5. The method for preparing the catalyst for pretreatment of C4 alkylation feedstock as described in any one of claims 1-4, characterized in that, The main active component and the carbonate, nitrate or chloride of the auxiliary active component are prepared into an aqueous solution, and organic acid, nitric acid or hydrochloric acid are added to make the aqueous solution acidic; the alumina support is impregnated in the aqueous solution at room temperature to 60°C, then dried at 100 to 300°C, and then calcined at 300 to 600°C for 3 to 6 hours to obtain the final product.

6. A method for pretreating C4 alkylation feedstock using the catalyst according to any one of claims 1-4, characterized in that, The C4 alkylation feedstock first enters an extraction tower for extraction. The washed C4 alkylation feedstock is then collected from the top of the tower and enters a catalytic distillation tower. The catalytic distillation tower is divided into a rectification section, a reaction section, and a stripping section from top to bottom. The reaction section contains the catalyst described in any one of claims 1-4. The reaction section is located below the feed inlet. The C4 alkylation feedstock enters the reaction section, where butadiene reacts with hydrogen, and the generated 2-butene is continuously removed during the reaction. The pretreated C4 alkylation feedstock is collected from the bottom of the catalytic distillation tower.

7. The method as described in claim 6, characterized in that, Before entering the extraction tower, the C4 alkylation feedstock is first processed in the C5 decarbonization tower.

8. The method as described in claim 7, characterized in that, The operating conditions for the five decarbonization towers are: pressure 0.3–1.0 MPa, top temperature 40–90 °C, and reflux ratio 0.2–3.0; the operating conditions for the extraction towers are: pressure 0.3–0.6 MPa, temperature between ambient and 60 °C, and oil-water volume ratio 3–20:1; the operating conditions for the reaction section of the catalytic distillation towers are: pressure 0.4–2.0 MPa, temperature 40–90 °C, and C4 alkylation feedstock volume hourly space velocity 5–30 h⁻¹. -1 The molar ratio of hydrogen to butadiene is 1.0 to 5.

0.

9. The method as described in claim 6, characterized in that, The catalytic distillation column is equipped with multiple reaction sections, and a liquid distributor is installed above each reaction section. The C4 alkylation feedstock enters the reaction section through the liquid distributor; a separation tray is installed between two adjacent reaction sections.

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