Preparation method of catalyst carrier activated carbon for synthesizing vinyl acetate

Abstract

The invention discloses a preparation method of vinyl acetate synthesis catalyst carrier activated carbon, and relates to the technical field of activated carbon preparation. Comprising the following steps: carrying out crushing and washing treatment on a carbon-containing raw material with ash content of less than 5%; mixing with a certain proportion of oxidant solution, and standing for 6-24 hours; and grinding into powder with the particle size of less than 200-300 meshes, and then adding a binder and a catalytic promoter. The catalyst carrier activated carbon provided by the invention has more developed pore channels through which synthesis raw materials and product molecules can freely enter and exit, the strength and apparent density are higher, and the prepared catalyst carrier activated carbon is detected by adopting an ASAP2020 type full-automatic pore size distribution tester static liquid nitrogen adsorption method; the mesopore volume of the activated carbon with the pore diameter in the range of 1.5-5.0 nm is greater than 0.55 mL / g, and the total pore volume is greater than 1.0 mL / g; the filling density of the activated carbon is greater than 0.45 g / mL, and the abrasive resistance is greater than or equal to 96%.

Description

Technical Field

[0001] This invention belongs to the field of activated carbon technology, specifically relating to a method for preparing activated carbon as a catalyst carrier for the synthesis of vinyl acetate. Background Technology

[0002] Vinyl acetate, also known as vinyl acetate, and its derivatives are widely used in the manufacture of polyvinyl acetate and polyvinyl alcohol, and further processed for use in adhesives, coatings, vinylon fibers, textile processing, emulsions, resins, and films. It is one of the world's 50 most produced organic chemical raw materials. Currently, there are two main methods for the industrial production of vinyl acetate: the acetylene gas-phase method and the ethylene gas-phase method. In the acetylene process of vinyl acetate synthesis at a vinylon plant, the addition reaction between acetylene and acetic acid is carried out in the gas phase at 170℃–250℃, catalyzed by zinc acetate supported on the mesopores of activated carbon.

[0003] Currently, AC / ZnCl catalysts used in this field in China suffer from problems such as low activity, low yield per unit volume, poor mechanical strength, easy shedding of active components, and short deactivation cycle. The main reason is that the effective pore volume of the activated carbon support is small, the mechanical strength is poor, and the pore channels are prone to collapse, which damages the pore structure. This results in a high wear rate in the moving bed, leading to increased loss of hydroxyl groups on the catalyst and activated carbon surface, thereby reducing the catalyst's production capacity and service life.

[0004] To meet the higher requirements of the vinyl acetate synthesis industry for catalyst carrier activated carbon, it is necessary to provide a carrier activated carbon product with high strength, high and medium porosity, and high apparent density. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing activated carbon as a catalyst carrier for the synthesis of vinyl acetate, in order to solve the problems of small effective pore volume, poor mechanical strength, and easy collapse of pore channels in existing activated carbon carriers, which damages the pore structure.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing activated carbon as a catalyst carrier for the synthesis of vinyl acetate, comprising the following steps:

[0008] After crushing and washing bituminous or anthracite coal with an ash content of less than 5%, it is mixed with an oxidant solution, left to stand for 6-24 hours, and then ground to a fineness of less than 200-300 mesh to obtain powder.

[0009] Add a mixture of high-temperature coal tar, ferric chloride and ammonium citrate to the powder, mix well, knead for 40 min at a pressure of 7.0-10.0 MPa, and then carbonize at 250-650℃ for 50-90 min to obtain the kneaded material.

[0010] The kneaded materials were carbonized using steam as an activator at 880–950°C for 3–8 hours. Then, they were soaked in 3–5 wt% hydrochloric acid at 90–100°C for 2 hours, filtered, and washed with demineralized water to obtain activated carbon.

[0011] The catalyst carrier activated carbon has a mesopore volume greater than 0.55 mL / g, a total pore volume greater than 1.0 mL / g, a filling density greater than or equal to 0.45 g / mL, and an abrasion resistance ≥96% in the range of 1.5–5.0 nm.

[0012] The effective pore size of the activated carbon used in the synthesis of vinyl acetate is in the range of 1.5–5.0 nm. Currently, commercially available activated carbons have a high proportion of pores (micropores) in the range of 0.6–1.5 nm, resulting in insufficient effective pore volume (only about 0.3 mL / g), low strength (80–90%), and low apparent density (0.38–0.42 g / mL), which no longer meets the ever-increasing application demands. Compared with existing technologies, in the preparation of activated carbon using this invention, a mixture of high-temperature coal tar, ferric chloride, and ammonium citrate plays a crucial synergistic role, with the combination of ferric chloride and ammonium citrate further enhancing this effect. High-temperature coal tar, acting as a binder, effectively binds bituminous or anthracite powder together, providing a foundation for subsequent kneading and molding. Simultaneously, it participates in the construction of the carbon skeleton during carbonization, contributing to improved material structural stability. The synergistic effect of ferric chloride and ammonium citrate is even more pronounced. Ferric chloride, as a Lewis acid catalyst, promotes the reconstruction of the carbon skeleton and the development of pores in the raw materials during carbonization and activation, accelerating the transformation from micropores to mesopores. Ammonium citrate, on the one hand, forms a stable complex with ferric chloride, regulating its catalytic activity and preventing excessive loss of the ordered carbon structure due to overly vigorous reactions. On the other hand, the gases and residues produced by its decomposition can further optimize the pore structure and increase the proportion of mesopores. When these three components work together, the high-temperature coal tar ensures the formability of the material and the basic construction of the carbon skeleton, while the synergy of ferric chloride and ammonium citrate precisely controls the direction of pore development. This accelerates the expansion of micropores into mesopores while reducing the loss of carbon material. Ultimately, the resulting activated carbon has a significantly increased mesopore volume of over 0.55 mL / g in the 1.5–5.0 nm range, a total pore volume exceeding 1.0 mL / g, a filling density of over 0.45 g / mL, and an abrasion resistance of no less than 96%. This not only meets the requirements for effective pores in the synthesis of vinyl acetate but also takes into account high yield and high strength, with overall performance far exceeding that of commercially available products.

[0013] Furthermore, the oxidant is at least one of hydrogen peroxide, potassium permanganate, ammonium persulfate, sodium hypochlorite, and sodium percarbonate, and the content of the oxidant in bituminous coal or anthracite is 5 to 20 wt%.

[0014] Compared with existing technologies, the hydrogen peroxide and potassium permanganate introduced in the preparation process, at a dosage of 5-20 wt% of bituminous or anthracite coal, work synergistically with the initial raw material pretreatment. The oxidant, through oxidation, can pre-alter the chemical structure of the coal raw material, breaking some stable carbon-hydrogen bonds and aromatic ring structures, and introducing oxygen-containing functional groups (such as carboxyl and hydroxyl groups) onto the surface of coal particles. This not only enhances the interaction between the raw material and the subsequently added high-temperature coal tar, ferric chloride, and ammonium citrate mixture, improving the material's binding performance, but also promotes pore germination and expansion during subsequent carbonization and activation stages. Simultaneously, the moderate oxidation by the oxidant can regulate the reactivity of the raw material, making the subsequent carbonization and activation processes easier to control. Combined with the directional regulation of pore structure by ferric chloride and ammonium citrate, the formation of effective mesopores of 1.5-5.0 nm is further optimized, reducing the proportion of ineffective micropores. This increases the effective pore volume of activated carbon while ensuring its structural strength and filling density. Working together with other components, it ultimately improves the overall performance of the product.

[0015] Furthermore, the high-temperature coal tar content accounts for 30-50 wt% of the bituminous or anthracite coal; the content of the mixture of ferric chloride and ammonium citrate accounts for 1.0-6.0 wt% of the bituminous or anthracite coal; and the ratio of ferric chloride to ammonium citrate is (0.5-3.0):(1-10).

[0016] Compared with existing technologies, the synergistic effect formed by high-temperature coal tar, ferric chloride and ammonium citrate in a specific ratio is crucial for optimizing the performance of activated carbon. High-temperature coal tar, comprising 30–50 wt% of bituminous or anthracite coal, serves as a binder. Its dosage ensures that the powdered material forms a stable plastic body during kneading, meeting the molding requirements under pressure of 7.0–10.0 MPa. Furthermore, it provides sufficient carbon source replenishment for the carbon skeleton during carbonization through appropriate cracking and condensation, reducing structural collapse. Meanwhile, a mixture of ferric chloride and ammonium citrate, comprising 1.0–6.0 wt% in a ratio of (0.5–3.0):(1–10), enhances the effect through a precise catalytic and regulatory mechanism. The Lewis acidity of ferric chloride promotes the cross-linking and rearrangement of aromatic structures in coal, accelerating the transformation of micropores into mesopores. Ammonium citrate not only buffers the catalytic intensity by forming coordination compounds with ferric chloride, preventing the strength reduction caused by excessive etching of the carbon structure, but also further unblocks pore channels with the nitrogen-containing gas produced by its decomposition. The synergistic ratio of the two ensures the appropriateness and directionality of the catalytic effect. This multi-component ratio allows the binding and carbon replenishing effects of high-temperature coal tar to complement the catalytic and regulatory effects of ferric chloride-ammonium citrate. While accelerating the formation of effective mesopores (1.5–5.0 nm), it minimizes the loss of ordered carbon, ultimately achieving a comprehensive performance improvement in activated carbon with a mesopore volume exceeding 0.55 mL / g, a total pore volume exceeding 1.0 mL / g, a filling density ≥0.45 g / mL, and an abrasion resistance ≥96%. This perfectly meets the dual requirements of vinyl acetate synthesis for carrier porosity and mechanical properties. Detailed Implementation

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, it should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0018] Example 1

[0019] 5000g of bituminous coal with an ash content of less than 3% after crushing and jigging is sprayed and stirred with a mixed solution containing 225g each of hydrogen peroxide and ammonium persulfate, and then left to stand for 9 hours. The mixture is then ground to 200 mesh. A mixture of 30% high-temperature coal tar and 4% ferric chloride and ammonium citrate (ferric chloride to ammonium citrate ratio 1:4) is added to the mixture. The mixture is kneaded in a kneader at 7MPa for 40 minutes, then shaped by a hydraulic granulator. The shaped material is then carbonized in a rotary carbonization furnace at 280℃ for 60 minutes. It is then activated in an activation furnace at 910℃ for 4.5 hours with steam. After soaking in 4% hydrochloric acid at 100℃ for 2 hours, the mixture is filtered out and then washed with demineralized water.

[0020] Example 2

[0021] 5000g of bituminous coal with an ash content of less than 3% after crushing and jigging is sprayed and stirred with a mixed solution containing 600g of sodium percarbonate, then left to stand for 12 hours. The mixture is then ground to a fineness of less than 200 mesh. A mixture of 40% high-temperature coal tar, 3% ferric chloride, and ammonium citrate (ferric chloride to ammonium citrate ratio 1:3) is added to the mixture. The mixture is kneaded in a kneader at 8MPa for 40 minutes, then shaped by a hydraulic granulator. The shaped material is then carbonized in a rotary carbonization furnace at 320℃ for 60 minutes. It is then activated in an activation furnace at 920℃ with steam for 5.5 hours. After soaking in 4% hydrochloric acid at 100℃ for 2 hours, the mixture is filtered out and then washed with demineralized water.

[0022] Example 3

[0023] 5000g of bituminous coal with an ash content of less than 3% after crushing and jigging is sprayed and stirred with an aqueous solution containing 400g of potassium permanganate, then left to stand for 14 hours. The mixture is then ground to a fineness of less than 300 mesh. A mixture of 50% high-temperature coal tar, 2% ferric chloride, and ammonium citrate (ferric chloride to ammonium citrate ratio 1:2.7) is added to the mixture. The mixture is kneaded in a kneader at 9MPa for 40 minutes, then shaped by a hydraulic granulator. The shaped material is then carbonized in a rotary carbonization furnace at 400℃ for 70 minutes. It is then activated in an activation furnace at 920℃ for 4.8 hours under steam supply. After soaking in 3% hydrochloric acid at 95℃ for 2 hours, the mixture is filtered out and then washed with demineralized water.

[0024] Example 4

[0025] 5000g of anthracite with an ash content of less than 3% after crushing and jigging is sprayed and stirred with a mixed solution containing 400g sodium hypochlorite and 200g ammonium persulfate. After standing for 10 hours, it is ground to less than 300 mesh. Then, 45% of the total amount of bituminous coal high-temperature coal tar, 1% of the total amount of bituminous coal ferric chloride and ammonium citrate are added. The ratio of ferric chloride to ammonium citrate is 1:4.4. The mixture is kneaded in a kneader at 10MPa for 40 minutes, shaped by a hydraulic granulator, and carbonized in a rotary carbonization furnace at 280-550℃ for 65 minutes. It is then activated in an activation furnace at 920℃ with steam for 5 hours. After soaking in 5% hydrochloric acid at 90℃ for 2 hours, it is filtered out and washed with demineralized water.

[0026] Example 5

[0027] 5000g of anthracite with an ash content of less than 3% after crushing and jigging is sprayed and stirred with a mixed solution containing 300g of sodium percarbonate and 400g of ammonium persulfate. After standing for 8 hours, it is ground to less than 200 mesh. Then, a mixture of 50% high-temperature coal tar and 5% ferric chloride and ammonium citrate (ferric chloride to ammonium citrate ratio 1:5) is added. The mixture is kneaded in a kneader at 8MPa for 40 minutes, shaped by a hydraulic granulator, and carbonized in a rotary carbonization furnace at 400℃ for 70 minutes. It is then activated in an activation furnace at 910℃ for 5 hours with steam supply. After soaking in 4% hydrochloric acid at 100℃ for 2 hours, it is filtered out and washed with demineralized water.

[0028] Example 6

[0029] 5000g of bituminous coal with an ash content of less than 3% after crushing and jigging is sprayed and stirred with a mixed solution containing 200g hydrogen peroxide, 150g sodium percarbonate and 150g ammonium persulfate, and then left to stand for 8.5h. The mixture is then ground to less than 200 mesh. A mixture of 35% high-temperature coal tar and 3.5% ferric chloride and ammonium citrate (ferric chloride to ammonium citrate ratio 1:5) is added to the mixture. The mixture is kneaded in a kneader at 8MPa for 40min, then formed by a hydraulic granulator. The formed material is then carbonized in a rotary carbonization furnace at 500℃ for 70min, and activated in an activation furnace at 910℃ for 4.5h under steam supply. The mixture is then soaked in 4% hydrochloric acid at 100℃ for 2h, filtered out, and then washed with demineralized water.

[0030] Comparative Example 1

[0031] BPL4×10 type activated carbon for catalyst carrier in vinyl acetate synthesis (USA).

[0032] Comparative Example 2

[0033] Domestically produced carrier activated carbon.

[0034] Comparative Example 3

[0035] Taking Example 2 as an example, the difference from Example 2 is that ammonium citrate is used to replace ferric chloride in equal amounts.

[0036] Comparative Example 4

[0037] Taking Example 2 as an example, the difference from Example 2 is that ferric chloride is used to replace ammonium citrate in an equal amount.

[0038] Comparative Example 5

[0039] Taking Example 2 as an example, the difference from Example 2 is that a mixture of ferric chloride and ammonium citrate is used to replace the high-temperature coal tar in equal amounts.

[0040] Comparative Example 6

[0041] Taking Example 2 as an example, the difference from Example 2 is that high-temperature coal tar is used to replace the mixture of ferric chloride and ammonium citrate in equal amounts.

[0042] Performance testing

[0043] Performance testing of the activated carbon adsorbent obtained in the examples: specific surface area was determined by the BET method, pore size distribution and pore volume were determined by the static liquid nitrogen adsorption method (Cranston-Inkley method) using an ASAP2020 fully automatic pore size distribution meter, and abrasion resistance and apparent density were determined by the methods specified in GB / T7702-2008.

[0044] The main physical properties of the activated carbon used as a catalyst carrier for vinyl acetate synthesis prepared by the method of this invention are shown in the table below.

[0045]

[0046]

[0047] As can be seen from the data in the table above, the overall performance of the activated carbon prepared by the method of this invention is far superior to that of commercially available domestic carrier activated carbon, and also better than similar products from the United States.

[0048] Comparative Examples 3 and 4 replaced ferric chloride with an equal amount of ammonium citrate and ferric chloride with an equal amount of ammonium citrate, respectively. The mesopore volume and total control volume of the activated carbon prepared were much smaller than those of the activated carbon prepared in the embodiments of the present invention. This may be because when ferric chloride or ammonium citrate is present alone, it is impossible to coordinate and accurately control the pore development direction, resulting in poor activated carbon quality.

[0049] Comparative Example 5 replaced high-temperature coal tar with an equal amount of a mixture of ferric chloride and ammonium citrate, and Comparative Example 6 replaced the mixture of ferric chloride and ammonium citrate with an equal amount of high-temperature coal tar. The mesopore volume and total pore volume of the activated carbon prepared in the end were much smaller than those of the activated carbon prepared in the embodiments of the present invention. This may be because the conversion process from micropores to mesopores cannot be accelerated when using high-temperature coal tar alone or when using the mixture of ferric chloride and ammonium citrate alone. This also proves the synergistic effect among the three.

[0050] The various embodiments described in this specification are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing activated carbon as a catalyst carrier for the synthesis of vinyl acetate, characterized in that, Includes the following steps: After crushing and washing bituminous or anthracite coal with an ash content of less than 5%, it is mixed with an oxidant solution, left to stand for 6-24 hours, and then ground to a fineness of less than 200-300 mesh to obtain powder. Add a mixture of high-temperature coal tar, ferric chloride and ammonium citrate to the powder, mix well, knead for 40 min at a pressure of 7.0-10.0 MPa, and then carbonize at 250-650℃ for 50-90 min to obtain the kneaded material. The kneaded materials were carbonized using steam as an activator at 880–950°C for 3–8 hours. Then, they were soaked in 3–5 wt% hydrochloric acid at 90–100°C for 2 hours, filtered, and washed with demineralized water to obtain activated carbon. The catalyst carrier activated carbon has a mesopore volume greater than 0.55 mL / g, a total pore volume greater than 1.0 mL / g, a filling density greater than or equal to 0.45 g / mL, and an abrasion resistance ≥96% in the range of 1.5–5.0 nm.

2. The method for preparing activated carbon as a catalyst carrier for the synthesis of vinyl acetate according to claim 1, characterized in that, The oxidant is at least one of hydrogen peroxide, potassium permanganate, ammonium persulfate, sodium hypochlorite, and sodium percarbonate, and the content of the oxidant is 5-20 wt% of bituminous coal or anthracite.

3. The method for preparing activated carbon as a catalyst carrier for the synthesis of vinyl acetate according to claim 1, characterized in that, The high-temperature coal tar content accounts for 30-50 wt% of the bituminous or anthracite coal; the content of the mixture of ferric chloride and ammonium citrate accounts for 1.0-6.0 wt% of the bituminous or anthracite coal; and the ratio of ferric chloride to ammonium citrate is (0.5-3.0):(1-10).

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