CN117983274B - Method for preparing ultralow-content gold-ruthenium bimetallic catalyst by using continuous flow technology - Google Patents

Abstract

The invention relates to a method for preparing an ultralow-content gold-ruthenium bimetallic catalyst by utilizing a novel continuous flow technology, and belongs to the technical field of catalyst preparation technology and application technology. According to the invention, 1, 10-phenanthroline is used as a modifier to obtain a nitrogen-doped active carbon carrier, trace gold and ruthenium are used as co-active components, isopropanol with low polarity and low boiling point is used as a solvent, and a novel continuous flow preparation technology is utilized to obtain the ultralow-content gold and ruthenium bimetallic catalyst taking the nitrogen-doped active carbon as the carrier by optimizing the gold and ruthenium synthesis proportion, wherein the gold loading is 0.003wt% and the ruthenium loading is 0.06wt%, and the production efficiency and the catalytic performance of the catalyst are remarkably improved. The catalyst has excellent catalytic performance in the reaction of preparing chloroethylene by hydrochlorination of acetylene in a fixed bed, has low cost, no mercury pollution, simple and expandable preparation method and obvious industrial application value.

Description

Method for preparing ultralow-content gold-ruthenium bimetallic catalyst by using continuous flow technology

Technical Field

The invention belongs to the field of catalyst preparation technology and application, and particularly relates to a method for preparing an ultralow-content gold-ruthenium bimetallic catalyst by using a novel continuous flow technology.

Background

Continuous flow reactors (Continuous flow reactor, CFR) are a novel catalyst preparation technology, reactions taking place in channels with an inner diameter in the order of micrometers/millimeter. In chemical engineering, micro-continuous flow devices can play a unique role in controlling critical reaction parameters due to the tiny size of the reactor. The continuous flow reactor has a plurality of advantages, high mass and heat transfer efficiency, accurate control of reaction temperature, pressure and time, easier realization of integration and automation, and improved reaction efficiency, thus receiving attention of vast researchers.

Polyvinyl chloride (PVC) is one of five major engineering plastics (PVC, PE, PP, PS, ABS) in the world, accounting for over 16% of the total plastic demand, and is one of the most widely used thermoplastics in the medical care and medical equipment, electronics and automotive industries. In addition, it is also commonly used for construction and construction due to its physical properties and chemical resistance. The global consumption of PVC in 2021 was statistically over 4000 ten thousand tons, and it is expected that in 2026 the total consumption would rise to 5620 ten thousand tons.

Polyvinyl chloride (PVC) is obtained by free radical polymerization of Vinyl Chloride (VCM) monomers, and about 90% of the VCM production is used to produce PVC, and increasing PVC production necessitates increasing VCM production. The current method for producing VCM comprises an acetylene method, an ethylene oxychlorination method and an ethane oxychlorination method, wherein the acetylene hydrochlorination reaction has the advantage of one-step reaction, the vinyl technology has a plurality of reactions, the product yield is reduced, the separation step is complicated, and the acetylene hydrochlorination reaction is one of the most important synthetic routes in the VCM production due to the special lean oil and coal-rich energy structure in China. The catalyst system adopted by the traditional industrial acetylene method takes active carbon as a carrier and HgCl ₂ as an active center. Since HgCl ₂ is toxic and volatile, it is a serious threat to environmental safety and human health, and in 2013, the united nations environmental planning agency passed the water on mercury convention, aimed at limiting the use of mercury. Under the double constraints of mercury resource exhaustion and environmental protection policy, the development of a novel, green and efficient mercury-free catalyst is a key for realizing the green sustainable development of the polyvinyl chloride industry in China.

Mercury-free catalysts can be classified into metal-free catalysts and supported metal catalysts, and among many supported metal catalysts, noble metal catalysts are considered to be catalysts that are more promising for industrial applications because of their higher activity and stability. Hutchings et al have conducted an initial work to investigate the use of supported metal catalysts in hydrochlorination of acetylene. Several metal chlorides including Au ³⁺、Pt⁴⁺、Pd²⁺、Ru³⁺ and Bi ³⁺ are used as non-mercury catalysts for acetylene hydrochlorination, auCl ₃ is considered to be the best catalyst for replacing HgCl ₂ due to its higher activity, and RuCl ₃ is also becoming a significant research direction for the development of mercury-free catalysts for acetylene hydrochlorination due to lower cost and better activity.

At present, most mercury-free catalysts take Activated Carbon (AC) as a carrier, and mainly because the activated carbon has the advantages of developed pore structure, large specific surface area, good adsorption performance and the like, but has poor hydrophilicity and low surface activity, and is easy to crush, coke and not easy to regenerate in the reaction. The nitrogen atoms (nitrogen-containing carbon materials) are introduced into the carbon material framework, so that the hydrophilicity and the surface activity of the traditional activated carbon can be improved, lone pair electrons can be provided, the surface polarity and the electron transmission performance of the activated carbon can be improved, and the physicochemical performance of the activated carbon can be effectively modulated, so that the reactivity of the activated carbon is enhanced.

Patent CN103623839A discloses a Ru-Ni-Cu trimetallic catalyst, the load of Ru is 1%, and the mol ratio of Ru, ni and Cu is 1:10:0.1. The conversion rate is 93% under the condition that the reaction temperature is 150 ℃ and the raw gas-material ratio V _(HCl)/V_(C2H2) =1.05; the selectivity of the chloroethylene reaches 99 percent. The invention has better catalytic activity when being used in acetylene hydrochlorination reaction, but has higher Ru content and high industrial cost.

Patent CN105056969B invented a trimetallic catalyst Au (0.45%) Cu (4%) TiO ₂ (9%)/C. Under the condition that the reaction temperature is 180 ℃, and the raw gas-material ratio V _(HCl)/V_(C2H2) =1.1, the conversion rate of acetylene reaches 95 percent. The invention has better catalytic activity and stability when being used in acetylene hydrochlorination reaction, but has higher gold loading, higher feeding of hydrogen chloride acetylene and excessively complicated preparation process.

Patent CN108246340a invented a AuTa/AC bimetallic catalyst with gold loading of 0.25% and tantalum loading of 5%. The catalyst is applied to acetylene hydrochlorination, the acetylene conversion rate reaches 86.7% under the condition that the reaction temperature is 150 ℃, the total space velocity is 770h ^-1, and the raw gas material ratio is V _(HCl)/V_(C2H2) =1.15, and the selectivity of vinyl chloride reaches 99.0%. The catalyst has better catalytic activity and stability, but the Au content is higher, and the industrial economic condition is not satisfied.

In summary, although the addition of the auxiliary metal effectively reduces the content of noble metal, the cost is still far higher than the industrial cost, and the multi-metal catalyst has the defects of excessively complicated synthesis steps and low acetylene conversion rate at a higher volume space velocity, and cannot realize industrial application. Under the condition of ensuring high catalytic activity, it is particularly important to seek a bimetallic synthesis method with low cost, simplicity and easy expansion, and a better foundation is provided for the industrial production of the catalyst.

Disclosure of Invention

The invention solves the technical problems that: provides a method for preparing an ultralow-content gold-ruthenium bimetallic catalyst by utilizing a novel continuous flow technology and application thereof. The method has the innovation points that Au load is greatly reduced to 0.003wt%, ru load is reduced to 0.06wt%, the optimal ratio of Au to Ru is regulated to 1:20, nitrogen doped carbon is used as a carrier, a novel continuous flow technology is utilized to prepare a bimetallic catalyst with ultralow content and high activity, under the condition that the acetylene airspeed is 170h ^-1,V_(C2H2)/V_(HCl) =1:1.05 and the reaction temperature is 180 ℃, the acetylene conversion rate can reach 90.7%, the vinyl chloride selectivity is greater than 99%, and the novel continuous flow technology ensures excellent catalytic performance while improving the production efficiency of the catalyst, thereby providing a unique and effective solution for industrially producing vinyl chloride with low cost and high efficiency.

In order to solve the technical problems of the invention, the technical proposal is as follows: a method for preparing ultralow-content gold-ruthenium bimetallic catalyst by using novel continuous flow technology and application thereof are characterized in that:

The catalyst is used in the reaction of preparing vinyl chloride by hydrochlorination of acetylene in a fixed bed, and the vinyl chloride is produced under the condition that the space velocity of the acetylene is 170h ^-1,V_(C2H2)/V_(HCl) =1:1.05 and the reaction temperature is 180 ℃, and the reaction route is as follows:

C₂H₂+HCl→C₂H₃Cl

The preparation method of the ultralow-content gold-based catalyst for the hydrochlorination of acetylene comprises the following steps of:

(1) Preparing a gold precursor solution: 0.1082g of chloroauric acid HAuCl ₄·4H₂ O, wherein Au is more than or equal to 47.5% of solid is dissolved in isopropanol of an organic solution, and the solution is prepared into HAuCl ₄·4H₂ O solution through oscillation and ultrasound, wherein Au is as follows: 1mg/mL;

(2) Preparing ruthenium precursor solution: 0.2780g of ruthenium trichloride RuCl ₃ solid was dissolved in deionized water and prepared into RuCl ₃ solution by shaking and ultrasound, ru:2.7070mg/mL;

(3) Preparing a nitrogen-doped carbon carrier: 3g of active carbon is weighed and placed in a beaker containing 25mL of deionized water, and 1.5mL of glacial acetic acid is added under stirring at normal temperature for 30min; weighing 25mL of deionized water, weighing 1.0g of 1, 10-phenanthroline and 1.5mL of 30% hydrogen peroxide, sequentially adding into the beaker, and continuously stirring for 24 hours under normal temperature and darkness; filtering, and drying in a 90 ℃ oven for 12-24 hours; in a tube furnace, keeping the flow rate of nitrogen at 50mL/min, and heating to 900 ℃ at the heating rate of 5 ℃/min for calcination for 1h to obtain a nitrogen modified carbon carrier;

(4) Preparing a catalyst by a continuous flow method:

The continuous flow device is formed by assembling a peristaltic pump, a magnetic stirrer, a polytetrafluoroethylene tee joint, a polytetrafluoroethylene pipeline and a collecting device; inlet end pipelines of the two peristaltic pumps are respectively led into the container A, B, outlet end pipelines of the two peristaltic pumps are connected with two ends of a polytetrafluoroethylene tee joint, a lower interface of the tee joint is connected with the polytetrafluoroethylene pipeline, and finally, the outlet ends of the polytetrafluoroethylene pipeline are fixed above the collecting container C;

Taking 3g of the nitrogen-doped carbon carrier prepared in the step (3), placing the carrier in a container A, adding 15mL of isopropanol into the carrier A, and continuously stirring the carrier; adding the HAuCl ₄·4H₂ O solution prepared in the step (1) and the RuCl ₃ solution prepared in the step (2) into isopropanol according to a proportion to prepare 15ml of solution, placing the solution into a container B, and continuously stirring; then preparing a catalyst through a continuous flow device, and finally completing collection in a container C; the ratio of Au to Ru is 1:20. the gold loading in the prepared bimetallic catalyst is 0.003wt% and the ruthenium loading is 0.06wt%

(5) The prepared catalyst is placed in a forced air drying oven to be dried for 12-24 hours.

Preferably, the activated carbon in step (3) is 200 mesh activated carbon that has not been pretreated.

Preferably, the firing conditions in step (3) are: the flow rate of nitrogen is 50mL/min, and the temperature is raised to 900 ℃ at the heating rate of 5 ℃/min for calcination for 1h, so as to obtain the nitrogen-doped carbon carrier.

Preferably, the theoretical nitrogen loading in step (3) is 3.9wt%.

Preferably, in step (4) low polarity low boiling point isopropanol is used as solvent, HAuCl ₄·4H₂ O solution and RuCl ₃ solution are mixed in 15ml isopropanol at room temperature and stirred using a magnetic stirrer for 1h.

Preferably, in the continuous flow device in the step (4), peristaltic pumps are firstly adjusted to respectively sample two paths to the same position of a tee joint, two pump switches are simultaneously started after the same flow rate (1 mL/min) is set, two liquids are mixed, and finally, the collected catalyst is placed in a blast drying box at 90 ℃ for drying for 12-24 hours.

Preferably, the specific steps are as follows:

(1) Filling a catalyst: a layer of quartz cotton with the thickness of 10mm is padded at the middle position of a quartz reaction tube with the diameter of 10mm, a catalyst is added into the reaction tube, the catalyst is ensured to be smooth, and then a layer of quartz cotton with the thickness of 10mm is padded;

(2) Before the reaction: the whole pipeline is purged for 60min at the flow rate of N ₂ of 20mL min ^-1 to remove air and moisture in the system, and meanwhile, the temperature is controlled to be increased to 150 ℃ at 5 ℃/min and maintained for 30min, and then increased to 180 ℃ at 5 ℃/min; then, introducing hydrogen chloride at a flow rate of V=20 mL/min for 30min, then introducing reaction gas at a flow rate of V _C2H2＝16mL/min,V_HCl =16.8 mL/min for 10min, ensuring that the catalyst is in the gas atmosphere of acetylene and hydrogen chloride, then reducing the flow rate of the reaction gas at a ratio of V _C2H2/V_HCl =1:1.05, and starting detection after maintaining the reaction gas at the reaction flow rate for ten min;

(3) After the reaction: the gas phase product was first passed through an absorber flask containing NaOH solution to remove excess HCl, and then analyzed on-line by gas chromatography GC-9790 ii to evaluate acetylene conversion and selectivity to VCM.

The beneficial effects of the invention are as follows:

Compared with other methods, the method greatly reduces the preparation cost, improves the production efficiency and the catalytic performance, reduces the human error, and has simpler operation and expandability. The carrier is modified by taking 1, 10-phenanthroline as an active carbon organic surface modifier, a proper low-polarity low-boiling point organic solvent is selected, meanwhile, the content of Au and Ru in the catalyst is greatly reduced, the ratio of Au to Ru is optimal to be 1:20, and the ultralow-content gold-ruthenium bimetallic catalyst is prepared by utilizing a novel continuous flow technology, wherein the gold load is 0.003wt% and the ruthenium load is 0.06wt%. The production cost is effectively saved; compared with a single metal catalyst with the same economic cost, the bimetallic catalyst prepared by the invention has more excellent catalytic performance on acetylene hydrochlorination reaction, and is suitable for industrial production.

(1) The catalyst takes nitrogen doped active carbon as a carrier, gold and ruthenium as main active components, and isopropanol as a solvent. Isopropanol is a typical low-boiling point and low-polarity organic solvent, and can be mutually dissolved with water and various organic solvents, so that the industrial production cost is low. The low-polarity organic solvent can better wet the hydrophobic active carbon, so that the active components are more rapidly and uniformly distributed on the surface of the carrier, the dispersity of Au and Ru is effectively improved, the aggregation of the active components is relieved, and the catalytic efficiency of the active components is further improved.

(2) The carrier used in the invention is activated carbon doped with 1, 10-phenanthroline as a nitrogen source. Under the same conditions, the nitrogen-doped carbon carrier can stabilize the active center by changing the electronic environment of the active carbon, improve the catalytic activity and reduce the deactivation rate.

(3) Compared with a single metal catalyst under the same economic cost, the bimetallic catalyst has more excellent catalytic activity, the synergistic effect of Au, ru and N and the special proportion of AuRu promote the activity improvement, and further realize the cost reduction.

(4) The continuous flow preparation technology used in the invention has the advantages of simple operation, environmental protection, energy consumption reduction, mass production under zero human error and provides a simple and efficient preparation path for industrial application.

(5) As can be seen from table 1, example 1 has more excellent catalytic activity than comparative example 1 under the same conditions, indicating that the novel continuous flow preparation technology can replace the conventional impregnation technology to become a new approach for industrial application. Examples 1 and 6 are novel continuous flow technology prepared bimetallic catalysts with 0.02% Au/NAC and 0.08% Ru/NAC (economic cost ratio of Au and Ru is about 4:1), under the condition that the reaction temperature is 180 ℃, the acetylene conversion rate is 70.6% and 87.2% respectively, and the vinyl chloride selectivity is higher than 99%, examples 2-5 examine the bimetallic catalysts AuRu/NAC prepared by the same economic cost and different Au and Ru ratios, it is known that example 4 has optimal catalytic activity for AuRu (1:20)/NAC synthesized by Au: ru=1:20, under the condition that the reaction temperature is 180 ℃, the acetylene conversion rate is 90.7% respectively, the vinyl chloride selectivity is higher than 99%, the acetylene conversion rate is increased by about 20% compared with example 1, and the acetylene conversion rate is increased by 3.5% compared with example 6.

In a word, the method of the invention obviously improves the activity and stability of the catalyst by reducing the content of the bimetal, preparing the proportion of the bimetal and combining with the nitrogen-doped carbon carrier and utilizing the novel continuous flow preparation technology. Compared with a single metal catalyst, the bimetallic catalyst synthesis method in the technology can show excellent catalytic activity and can be applied to industry.

Drawings

FIG. 1 conversion of acetylene in hydrochlorination of acetylene with the catalysts of examples 1-6

FIG. 2 catalyst examples 1-6 vinyl chloride selectivity in acetylene hydrochlorination FIG. 3 continuous flow apparatus schematic

Detailed Description

Example 1 catalyst preparation

3G of 200 mesh Activated Carbon (AC) was weighed and placed in a beaker containing 25mL of deionized water, and 1.5mL of glacial acetic acid was added at room temperature with stirring for 30min; weighing 25mL of deionized water, weighing 1g of 1, 10-phenanthroline and 1.5mL of hydrogen peroxide (30%), sequentially adding into the beaker, and continuously stirring for 24 hours under normal temperature and darkness; filtering, and drying in a 90 ℃ oven for 12-24 hours; in a tube furnace, maintaining the flow rate of nitrogen to be 25-50 mL/min, and heating to 900 ℃ at the heating rate of 5 ℃/min for calcination for 1h to obtain NAC.

Weighing 3g NAC, placing in a container A, adding 15mL isopropanol to the container A, and continuously stirring; adding 600 mu L of HAuCl ₄·4H₂ O solution prepared in the step (1) into isopropanol to prepare 15ml of solution, placing the solution into a container B, and continuously stirring; then preparing a catalyst through a continuous flow device, and finally completing collection in a container C; and then dried in a blast drying oven at 90 ℃ for 12 hours. And after the drying is finished, sealing and storing.

The catalyst was named 0.02% au/NAC.

Comparative example 1 catalyst preparation

3G of 200 mesh Activated Carbon (AC) was weighed and placed in a beaker containing 25mL of deionized water, and 1.5mL of glacial acetic acid was added at room temperature with stirring for 30min; weighing 25mL of deionized water, weighing 1g of 1, 10-phenanthroline and 1.5mL of hydrogen peroxide (30%), sequentially adding into the beaker, and continuously stirring for 24 hours under normal temperature and darkness; filtering, and drying in a 90 ℃ oven for 12-24 hours; in a tube furnace, maintaining the flow rate of nitrogen to be 25-50 mL/min, and heating to 900 ℃ at the heating rate of 5 ℃/min for calcination for 1h to obtain NAC.

3G NAC is weighed and tiled in a mortar, 600 mu LHAuCl ₄·4H₂ O (IPA) solution prepared in the step (1) is added into 6mL isopropanol to prepare a solution, then dropwise and uniformly dropwise added into nitrogen-doped carbon, and the mixture is quickly ground clockwise after the dropwise addition is finished until the surface of the catalyst is smooth. Then transferred to a petri dish and dried in a forced air drying oven at 90℃for 12h. And after the drying is finished, sealing and storing.

The catalyst was named 0.02% au/NAC impregnation.

Example 2 catalyst preparation

3G of 200 mesh Activated Carbon (AC) was weighed and placed in a beaker containing 25mL of deionized water, and 1.5mL of glacial acetic acid was added at room temperature with stirring for 30min; weighing 25mL of deionized water, weighing 1g of 1, 10-phenanthroline and 1.5mL of hydrogen peroxide (30%), sequentially adding into the beaker, and continuously stirring for 24 hours under normal temperature and darkness; filtering, and drying in a 90 ℃ oven for 12-24 hours; in a tube furnace, maintaining the flow rate of nitrogen to be 25-50 mL/min, and heating to 900 ℃ at the heating rate of 5 ℃/min for calcination for 1h to obtain NAC.

Weighing 3g NAC, placing in a container A, adding 15mL isopropanol to the container A, and continuously stirring; adding 156 mu LHAuCl ₄·4H₂ O solution prepared in the step (1) and 578 mu LRuCl ₃ solution prepared in the step (2) into isopropanol according to the ratio of Au to Ru=1:10 to prepare 15mL solution, placing the solution into a container B, and continuously stirring; then preparing a catalyst through a continuous flow device, and finally completing collection in a container C; and then dried in a blast drying oven at 90 ℃ for 12 hours. And after the drying is finished, sealing and storing.

The catalyst was named AuRu (1:10)/NAC with an Au loading of 0.0052% and a Ru loading of 0.052%.

Example 3 catalyst preparation

3G of 200 mesh Activated Carbon (AC) was weighed and placed in a beaker containing 25mL of deionized water, and 1.5mL of glacial acetic acid was added at room temperature with stirring for 30min; weighing 25mL of deionized water, weighing 1g of 1, 10-phenanthroline and 1.5mL of hydrogen peroxide (30%), sequentially adding into the beaker, and continuously stirring for 24 hours under normal temperature and darkness; filtering, and drying in a 90 ℃ oven for 12-24 hours; in a tube furnace, maintaining the flow rate of nitrogen to be 25-50 mL/min, and heating to 900 ℃ at the heating rate of 5 ℃/min for calcination for 1h to obtain NAC.

Weighing 3g NAC, placing in a container A, adding 15mL isopropanol to the container A, and continuously stirring; adding the 114 mu LHAuCl ₄·4H₂ O solution prepared in the step (1) and the 633 mu LRuCl ₃ solution prepared in the step (2) into isopropanol according to the ratio of Au to Ru=1:15 to prepare 15mL solution, placing the solution into a container B, and continuously stirring; then preparing a catalyst through a continuous flow device, and finally completing collection in a container C; and then dried in a blast drying oven at 90 ℃ for 12 hours. And after the drying is finished, sealing and storing.

The catalyst was named AuRu (1:15)/NAC with an Au loading of 0.0038% and a Ru loading of 0.057%.

Example 4 catalyst preparation

3G of 200 mesh Activated Carbon (AC) was weighed and placed in a beaker containing 25mL of deionized water, and 1.5mL of glacial acetic acid was added at room temperature with stirring for 30min; weighing 25mL of deionized water, weighing 1g of 1, 10-phenanthroline and 1.5mL of hydrogen peroxide (30%), sequentially adding into the beaker, and continuously stirring for 24 hours under normal temperature and darkness; filtering, and drying in a 90 ℃ oven for 12-24 hours; in a tube furnace, maintaining the flow rate of nitrogen to be 25-50 mL/min, and heating to 900 ℃ at the heating rate of 5 ℃/min for calcination for 1h to obtain NAC.

Weighing 3g NAC, placing in a container A, adding 15mL isopropanol to the container A, and continuously stirring; adding 90 mu LHAuCl ₄·4H₂ O solution prepared in the step (1) and 666 mu LRuCl ₃ solution prepared in the step (2) into isopropanol according to the mass ratio of Au to Ru=1:20 to prepare 15mL solution, placing the solution into a container B, and continuously stirring; then preparing a catalyst through a continuous flow device, and finally completing collection in a container C; and then dried in a blast drying oven at 90 ℃ for 12 hours. And after the drying is finished, sealing and storing.

The catalyst was named AuRu (1:20)/NAC with an Au loading of 0.003% and a Ru loading of 0.06%.

Example 5 catalyst preparation

3G of 200 mesh Activated Carbon (AC) was weighed and placed in a beaker containing 25mL of deionized water, and 1.5mL of glacial acetic acid was added at room temperature with stirring for 30min; weighing 25mL of deionized water, weighing 1g of 1, 10-phenanthroline and 1.5mL of hydrogen peroxide (30%), sequentially adding into the beaker, and continuously stirring for 24 hours under normal temperature and darkness; filtering, and drying in a 90 ℃ oven for 12-24 hours; in a tube furnace, maintaining the flow rate of nitrogen to be 25-50 mL/min, and heating to 900 ℃ at the heating rate of 5 ℃/min for calcination for 1h to obtain NAC.

Weighing 3g NAC, placing in a container A, adding 15mL isopropanol to the container A, and continuously stirring; adding 75 mu LHAuCl ₄·4H₂ O solution prepared in the step (1) and 694 mu LRuCl ₃ solution prepared in the step (2) into isopropanol according to the ratio of Au to Ru=1:25 to prepare 15mL solution, placing the solution into a container B, and continuously stirring; then preparing a catalyst through a continuous flow device, and finally completing collection in a container C; and then dried in a blast drying oven at 90 ℃ for 12 hours. And after the drying is finished, sealing and storing.

The catalyst was named AuRu (1:25)/NAC with an Au loading of 0.0025% and a Ru loading of 0.0625%.

Example 6 catalyst preparation

3G of 200 mesh Activated Carbon (AC) was weighed and placed in a beaker containing 25mL of deionized water, and 1.5mL of glacial acetic acid was added at room temperature with stirring for 30min; weighing 25mL of deionized water, weighing 1g of 1, 10-phenanthroline and 1.5mL of hydrogen peroxide (30%), sequentially adding into the beaker, and continuously stirring for 24 hours under normal temperature and darkness; filtering, and drying in a 90 ℃ oven for 12-24 hours; in a tube furnace, maintaining the flow rate of nitrogen to be 25-50 mL/min, and heating to 900 ℃ at the heating rate of 5 ℃/min for calcination for 1h to obtain NAC.

Weighing 3mg of NAC, holding in container a, adding 15mL of isopropanol thereto, and stirring continuously; adding 888 mu LRuCl ₃ solution prepared in the step (1) into isopropanol to prepare 15mL solution, placing the solution into a container B, and continuously stirring; then preparing a catalyst through a continuous flow device, and finally completing collection in a container C; and then dried in a blast drying oven at 90 ℃ for 12 hours. And after the drying is finished, sealing and storing.

The catalyst was named 0.08% Ru/NAC.

The evaluation process and conditions of the catalyst are as follows:

(1) Filling a catalyst: and a layer of quartz cotton with the thickness of 10mm is padded in the middle of a quartz reaction tube with the diameter of 10mm, a catalyst is added into the reaction tube, the catalyst is ensured to be smooth, and then a layer of quartz cotton with the thickness of 10mm is padded.

(2) Before the reaction: the entire tube was purged at a flow rate of N ₂ of 20mL min ^-1 for 60min to remove air and moisture from the system while controlling the temperature to rise to 150℃at 5℃per min and hold for 30min, and then to rise to 180℃at 5℃per min. Then, hydrogen chloride was introduced at a flow rate of v=20 mL/min for 30min, then a reaction gas was introduced at a flow rate of V (C ₂H₂) =16 mL/min and V (HCl) =16.8 mL/min for 10min, the catalyst was ensured to be in a gas atmosphere of acetylene and hydrogen chloride, then the reaction gas flow rate was reduced at a ratio of V (C ₂H₂)/V (HCl) =1:1.05, and the detection was started after holding at the reaction flow rate for ten minutes.

(3) After the reaction: the gas phase product was first passed through an absorber flask containing NaOH solution to remove excess HCl and then analyzed on-line by gas chromatography (GC-9790 ii) to evaluate acetylene conversion and selectivity to VCM.

TABLE 1 test of hydrochlorination Activity of acetylene

As can be seen from table 1, example 1 has more excellent catalytic activity than comparative example 1 under the same conditions, indicating that the novel continuous flow preparation technology can replace the conventional impregnation technology to become a new approach for industrial application. Examples 1 and 6 are novel continuous flow technology prepared bimetallic catalysts with 0.02% Au/NAC and 0.08% Ru/NAC (economic cost ratio of Au and Ru is about 4:1), under the condition that the reaction temperature is 180 ℃, the acetylene conversion rate is 70.6% and 87.2% respectively, and the vinyl chloride selectivity is higher than 99%, examples 2-5 examine the bimetallic catalysts AuRu/NAC prepared by the same economic cost and different Au and Ru ratios, it is known that example 4 has optimal catalytic activity for AuRu (1:20)/NAC synthesized by Au: ru=1:20, under the condition that the reaction temperature is 180 ℃, the acetylene conversion rate is 90.7% respectively, the vinyl chloride selectivity is higher than 99%, the acetylene conversion rate is increased by about 20% compared with example 1, and the acetylene conversion rate is increased by 3.5% compared with example 6.

The invention is not limited to the specific technical solutions described in the above embodiments, and all technical solutions formed by adopting equivalent substitution are the protection scope of the invention.

Claims (1)

1. A method for preparing an ultralow-content gold-ruthenium bimetallic catalyst by using a continuous flow technology is characterized by comprising the following steps of:

The catalyst is used in the reaction of preparing vinyl chloride by hydrochlorination of acetylene in a fixed bed, and the vinyl chloride is produced under the condition that the space velocity of the acetylene is 170h ^-1,V_(C2H2)/V_(HCl) =1:1.05 and the reaction temperature is 180 ℃, and the reaction route is as follows:

C₂H₂+HCl→C₂H₃Cl

Wherein the preparation of the ultralow-content gold-ruthenium bimetallic catalyst by utilizing a continuous flow technology comprises the following steps:

(1) Preparing a gold precursor solution: 0.1082g of chloroauric acid HAuCl ₄·4H₂ O, wherein Au is more than or equal to 47.5% of solid is dissolved in isopropanol of an organic solution, and the solution is prepared into HAuCl ₄·4H₂ O solution through oscillation and ultrasound, wherein Au is as follows: 1mg/mL;

(2) Preparing ruthenium precursor solution: 0.2780g of ruthenium trichloride RuCl ₃ solid is dissolved in deionized water, and is prepared into RuCl ₃ solution by shaking and ultrasonic treatment, ru:2.7070mg/mL;

(3) Preparing a nitrogen-doped carbon carrier: 3g of active carbon is weighed and placed in a beaker containing 25mL of deionized water, and 1.5mL of glacial acetic acid is added under stirring at normal temperature for 30min; weighing 25mL of deionized water, weighing 1.0g of 1, 10-phenanthroline and 1.5mL of 30% hydrogen peroxide, sequentially adding into the beaker, and continuously stirring for 24 hours under normal temperature and darkness; filtering, and drying in a 90 ℃ oven for 12-24 hours; in a tube furnace, keeping the flow rate of nitrogen at 50mL/min, and heating to 900 ℃ at the heating rate of 5 ℃/min for calcination for 1h to obtain a nitrogen modified carbon carrier;

(4) Preparing a catalyst by a continuous flow method:

The continuous flow device is formed by assembling a peristaltic pump, a magnetic stirrer, a polytetrafluoroethylene tee joint, a polytetrafluoroethylene pipeline and a collecting device; inlet end pipelines of the two peristaltic pumps are respectively led into the container A, B, outlet end pipelines of the two peristaltic pumps are connected with two ends of a polytetrafluoroethylene tee joint, a lower interface of the tee joint is connected with the polytetrafluoroethylene pipeline, and finally, the outlet ends of the polytetrafluoroethylene pipeline are fixed above the collecting container C;

Taking 3g of the nitrogen-doped carbon carrier prepared in the step (3), placing the carrier in a container A, adding 15mL of isopropanol into the carrier A, and continuously stirring the carrier; adding the HAuCl ₄·4H₂ O solution prepared in the step (1) and the RuCl ₃ solution prepared in the step (2) into isopropanol according to the mass ratio of Au to Ru=1:20 to prepare 15ml solution, placing the solution into a container B, and continuously stirring; then preparing a catalyst through a continuous flow device, and finally completing collection in a container C; the gold loading in the prepared catalyst is 0.003wt% and the ruthenium loading is 0.06wt%;

(5) Drying the prepared catalyst in a blast drying oven for 12-24 hours;

in the step (3), the theoretical nitrogen load of the 1, 10-phenanthroline is 3.9wt%;

in the step (4), the mass ratio of Au to Ru is 1:20, a step of;

in the continuous flow device in the step (4), peristaltic pumps are firstly regulated to respectively sample two paths to the same position of a tee joint, two pump switches are simultaneously started after the same flow rate is set to be 1mL/min, two liquids are mixed, and finally, the collected catalyst is placed in a blast drying box at 90 ℃ for drying for 12-24 hours;

The specific steps of the reaction for preparing chloroethylene by hydrochlorination of acetylene on a fixed bed by using the catalyst are as follows:

(1) Filling a catalyst: a layer of quartz cotton with the thickness of 10mm is padded at the middle position of a quartz reaction tube with the diameter of 10mm, a catalyst is added into the reaction tube, the catalyst is ensured to be smooth, and then a layer of quartz cotton with the thickness of 10mm is padded;

(2) Before the reaction: the whole pipeline is purged for 60min at the flow rate of N ₂ of 20mL min ^-1 to remove air and moisture in the system, and meanwhile, the temperature is controlled to be increased to 150 ℃ at 5 ℃/min and maintained for 30min, and then increased to 180 ℃ at 5 ℃/min; then, introducing hydrogen chloride at a flow rate of V=20 mL/min for 30min, then introducing reaction gas at a flow rate of V _C2H2＝16mL/min,V_HCl =16.8 mL/min for 10min, ensuring that the catalyst is in the gas atmosphere of acetylene and hydrogen chloride, then reducing the flow rate of the reaction gas at a ratio of V _C2H2/V_HCl =1:1.05, and starting detection after maintaining the reaction gas at the reaction flow rate for ten min;

(3) After the reaction: the gas phase product was first passed through an absorber flask containing NaOH solution to remove excess HCl, and then analyzed on-line by gas chromatography GC-9790 ii to evaluate acetylene conversion and selectivity to VCM.