CN117000273A - Ultralow mercury catalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a preparation method of an ultralow-mercury catalyst, which takes active carbon as a carrier, takes 0.58-1.16wt% of elemental selenium loaded on the carrier as an anchoring agent, and takes 2-4wt% of mercury chloride as a catalytic component. The acetylene hydrochlorination catalyst is prepared by vacuumizing, selenium deposition and mercury chloride deposition, and has the technical advantages of good thermal stability, high catalytic conversion rate and long service life by utilizing the physical vapor deposition and utilizing the strong adsorption effect of selenium and mercury.

Description

An ultra-low mercury catalyst and preparation method

Technical field

The invention belongs to the field of acetylene hydrochlorination catalysts, and specifically relates to an ultra-low mercury catalyst and a preparation method.

Background technique

Mercury is a heavy metal, commonly known as "mercury", and a toxic substance. On January 19, 2013, the United Nations Environment Program adopted the Minamata Convention, an international convention aimed at controlling and reducing mercury emissions on a global scale, and made detailed provisions on the specific emission restriction range to reduce the impact of mercury on the environment and human health. Damage, the Convention came into effect on August 16, 2017. As the first party to join the Convention, China will begin to implement various provisions of the Convention nationwide and assume performance responsibilities and tasks. Regarding the production process of calcium carbide polyvinyl chloride, the Convention proposes many According to the management requirements, including that by 2020, the mercury usage per unit product of calcium carbide process polyvinyl chloride will be reduced by 50% compared with 2015, the Environmental Protection Foreign Cooperation Center of the Ministry of Environmental Protection and the United Nations Industrial Development Organization (UNIDO) officially launched the "Global Environmental Fund—China PVC Production Mercury Reduction and Minimization Demonstration Project", which officially came into effect in January 2018. After the project is implemented, enterprises are required to use no more than 48g/tPVC of mercury in PVC products, and enterprises are encouraged to Minimize mercury usage.

The main reasons for the deactivation of the acetylene hydrochlorination catalyst are: ① Sublimation of mercury chloride, which is a molecular crystal with a melting point of 277°C and a boiling point of 302°C. The temperature of the converter used for the catalytic reaction is 100-180°C. During the reaction process, a large amount of mercury chloride will sublimate into the catalytic conversion reaction system, and the catalyst will lose activity. ② Carbon deposition. During the catalytic reaction, acetylene and vinyl chloride monomers will be deposited on the surface of the catalyst in the form of self-polymers, covering the active sites of the catalyst and causing catalyst deactivation.

The patent application number 202210516350.8 discloses a highly stable low-mercury catalyst for acetylene hydrochlorination and its preparation method, which includes the following components: activated carbon is used as a carrier, 3 to 5wt% of mercury is loaded on the carrier, and 0.6 to 5wt % of selenium. The preparation method mainly uses active selenium to efficiently anchor mercury chloride molecules. Active selenium can be prepared by in-situ reduction of selenic acid or selenious acid with sulfur dioxide. The strong adsorption between elemental selenium and mercury and the bonding effect of chlorine are used to Mercury chloride molecules provide efficient anchoring. This method is to dissolve the selenium source in water to make a solution, use the excessive impregnation method to immerse it with activated carbon in a water bath at 60-80°C for more than 10 hours, add mercuric chloride solution to the solution, and use the reduction effect of sulfur dioxide to stabilize the selenium and mercury in the solution. Valence, synthesis of selenium-modified low-mercury catalysts. Since this technology is synthesized in liquid phase, there are problems such as few active sites, low dispersion, and low catalytic conversion rate.

Contents of the invention

In order to solve the problems existing in the prior art, the present invention provides an ultra-low mercury catalyst and a preparation method, which can further reduce the mercury content, have high active sites and high catalytic rate.

In order to achieve the object of the present invention, the technical solutions of the present invention are as follows:

An ultra-low mercury catalyst, activated carbon is used as a carrier, 0.58-1.16wt% of elemental selenium is loaded on the carrier as an anchoring agent, and 2-4wt% of mercury chloride is used as a catalytic component.

The above-mentioned ultra-low mercury catalyst uses activated carbon as a carrier, and the carrier is loaded with 0.72-1.02wt% elemental selenium as the anchoring agent, and 2.3-3.5wt% mercury chloride as the catalytic component.

The above-mentioned ultra-low mercury catalyst uses activated carbon as a carrier, and uses physical vapor deposition method to load 0.84-0.90wt% elemental selenium as the anchoring agent and 2.5-2.8wt% mercury chloride as the catalytic component on the carrier.

In the above-mentioned ultra-low mercury catalyst, the material ratio of selenium element to mercury element is 1:1.

A method for preparing an ultra-low mercury catalyst, which adopts a physical vapor deposition method and includes the following steps:

(1) Vacuuming: Preheat the physical vapor deposition system to 80°C, and evacuate the entire system to a vacuum degree of 6×10-3_6×10-4Pa;

(2) Selenium deposition: Turn on the selenium heater and heat the elemental selenium temperature to 700-800°C to obtain selenium gas. The activated carbon in the physical vapor deposition system is used as a deposition matrix, and the selenium gas is allowed to deposit on the activated carbon for 1-5 hours;

(3) Mercury chloride deposition: Turn on the mercury chloride heater, heat the mercury chloride to 300-400°C, and the mercury chloride gas will be deposited on the activated carbon after selenium deposition for 1-5 hours.

In the above-mentioned ultra-low mercury catalyst preparation method, the system preheating temperature is 80°C, and the system vacuum degree is 8×10-3_4×10-4Pa.

In the above-mentioned ultra-low mercury catalyst preparation method, the selenium element is heated to a temperature of 730-770°C, and the deposition time is 2-4 hours.

According to the above-mentioned ultra-low mercury catalyst preparation method, the mercury chloride is heated to 320-380°C, and the deposition time is 2-4 hours.

Beneficial effects: Compared with the existing technology, the present invention has the following advantages:

(1) The present invention uses physical vapor deposition of selenium and mercury chloride, which has more active sites, higher dispersion and higher catalytic conversion rate. Mercury chloride is a molecular crystal and is prone to sublimation at high temperatures during actual use, resulting in the sublimation of the catalytically active component mercuric chloride and deactivation of the catalyst. The method of combining selenium and mercuric chloride can effectively inhibit the sublimation problem of mercuric chloride. Extend catalyst service life.

(2) The present invention uses physical vapor deposition of selenium and mercury chloride. The deposition process is carried out in a closed environment, no waste water is generated, and the production process does not pollute the environment.

(3) The strong adsorption of selenium and mercury is used to increase the thermal stability of the catalyst, effectively inhibit the sublimation of mercury chloride, and extend the service life of the catalyst.

(4) Compared with preparing catalysts in the liquid phase, preparing catalysts in the liquid phase is likely to cause agglomeration problems between molecules. The present invention uses physical vapor deposition to prepare ultra-low mercury catalysts, and gaseous molecules migrate to the In the matrix, the catalytically active components are evenly dispersed, which can effectively overcome the problem of agglomeration between mercury chloride molecules. The molecular utilization rate is high, the dispersion is large, and the catalytic conversion rate is high. Compared with the in-situ deposition method, the present invention not only improves the catalytic conversion Through research and analysis of the preparation process of physical vapor deposition method, the process parameters were optimized to further reduce the mercury content in the obtained catalyst, but the catalytic effect, stability, service life, etc. were not reduced, thus improving the quality of the catalyst.

Using the same mercury chloride content, the comparison of the conversion rates of catalysts prepared by the liquid phase method and the physical vapor deposition method is as follows:

Detailed ways

The present invention will be further described below with reference to the examples and comparative examples, but they are not used as a basis for limiting the present invention.

Example 1: An ultra-low mercury catalyst, activated carbon is used as a carrier, and 0.58-1.16wt% of elemental selenium is loaded on the carrier as an anchoring agent, and 2-4wt% of mercury chloride is used as a catalytic component.

Even better, activated carbon is used as a carrier, and 0.72-1.02wt% of elemental selenium is loaded on the carrier as an anchoring agent, and 2.3-3.5wt% of mercury chloride is used as a catalytic component.

Even better, activated carbon is used as a carrier, and 0.84-0.90wt% elemental selenium is loaded on the carrier as an anchoring agent and 2.5-2.8wt% mercury chloride is used as a catalytic component through physical vapor deposition.

Even better, the amount ratio of selenium to mercury is 1:1.

A method for preparing an ultra-low mercury catalyst, which adopts a physical vapor deposition method and includes the following steps:

(1) Vacuuming: Preheat the physical vapor deposition system to 80°C, and evacuate the entire system to a vacuum degree of 6×10 ^-3 -6×10 ^-4 Pa;

(2) Selenium deposition: Turn on the selenium heater and heat the elemental selenium temperature to 700-800°C to obtain selenium gas. The activated carbon in the physical vapor deposition system is used as a deposition matrix, and the selenium gas is allowed to deposit on the activated carbon for 1-5 hours;

(3) Mercury chloride deposition: Turn on the mercury chloride heater, heat the mercury chloride to 300-400°C, and the mercury chloride gas will be deposited on the activated carbon after selenium deposition for 1-5 hours.

Even better, the system preheating temperature is 80°C and the system vacuum degree is 8×10 ^-3 -4×10 ^-4 Pa.

Better yet, the heating temperature of the selenium element is 730-770°C, and the deposition time is 2-4 hours.

Better yet, heat the mercuric chloride to 320-380°C with a deposition time of 2-4 hours.

Example 2

An ultra-low mercury catalyst preparation method, the steps are as follows: (1) Vacuuming: preheat the system to 80°C, and use a diffusion pump to evacuate the entire system to a vacuum degree of 6×10 ^-3 Pa; (2) Selenium deposition: heating The temperature of the selenium element reaches 750°C, and the deposition time of selenium gas on the carrier activated carbon is 4 hours; (3) Mercury chloride deposition: Heat the mercury chloride to 350°C, and the mercury chloride gas is deposited on the above-mentioned selenium-deposited activated carbon. The deposition time is In 5 hours, an acetylene hydrochlorination catalyst was prepared, with a mercury chloride content of 3.8%, a selenium content of 1.1%, and an activated carbon content of 95.1%.

The catalyst is used for the catalytic reaction of acetylene hydrochlorination. The set temperature is 170°C, the molar ratio of acetylene to hydrogen chloride is 1:1.1, the acetylene spatial flow rate is 200h ^-1 , the acetylene conversion rate is 98.5%, and the selectivity is 99.8%.

Example 3

An ultra-low mercury catalyst preparation method, the steps are as follows: (1) Vacuuming: preheat the system to 80°C, and use a diffusion pump to evacuate the entire system to a vacuum degree of 6×10 ^-3 Pa; (2) Selenium deposition: heating The temperature of the selenium element reaches 700°C, and the deposition time of selenium gas on the carrier activated carbon is 5 hours; (3) Mercury chloride deposition: Heat the mercury chloride to 320°C, and the mercury chloride gas is deposited on the above-mentioned selenium-deposited activated carbon. The deposition time is In 3 hours, an acetylene hydrochlorination catalyst was prepared, with a mercury chloride content of 3.4%, a selenium content of 0.98%, and an activated carbon content of 95.62%.

The catalyst is used for the catalytic reaction of acetylene hydrochlorination. The set temperature is 170°C, the molar ratio of acetylene to hydrogen chloride is 1:1.1, the acetylene spatial flow rate is 200h ^-1 , the acetylene conversion rate is 98.3%, and the selectivity is 99.8%.

Example 4

An ultra-low mercury catalyst preparation method, the steps are as follows: (1) Vacuuming: preheat the system to 80°C, and use a diffusion pump to evacuate the entire system to a vacuum degree of 6×10 ^-3 Pa; (2) Selenium deposition: heating The temperature of the selenium element reaches 600°C, and the selenium gas is deposited on the carrier activated carbon for 3 hours; (3) Mercury chloride deposition: Heat the mercury chloride to 300°C, and the mercury chloride gas is deposited on the above-mentioned selenium-deposited activated carbon. The deposition time is In 2.5 hours, an acetylene hydrochlorination catalyst was prepared, with a mercury chloride content of 3.0%, a selenium content of 0.87%, and an activated carbon content of 96.13%.

The catalyst is used for the catalytic reaction of acetylene hydrochlorination. The set temperature is 170°C, the molar ratio of acetylene to hydrogen chloride is 1:1.1, the acetylene space flow rate is 200h ^-1 , the acetylene conversion rate is 98.1%, and the selectivity is 99.7%.

Example 5

An ultra-low mercury catalyst preparation method, the steps are as follows: (1) Vacuuming: preheat the system to 80°C, and use a diffusion pump to evacuate the entire system to a vacuum degree of 6×10 ^-4 Pa; (2) Selenium deposition: heating The temperature of the selenium element reaches 660°C, and the deposition time of the selenium gas on the carrier activated carbon is 4 hours; (3) Mercury chloride deposition: Heat the mercury chloride to 300°C, and the mercury chloride gas is deposited on the above-mentioned selenium-deposited activated carbon. The deposition time is In 3.5 hours, an acetylene hydrochlorination catalyst was prepared, with a mercury chloride content of 2.8%, a selenium content of 0.82%, and an activated carbon content of 96.39%.

The catalyst is used for the catalytic reaction of acetylene hydrochlorination. The set temperature is 170°C, the molar ratio of acetylene to hydrogen chloride is 1:1.1, the acetylene space flow rate is 200h ^-1 , the acetylene conversion rate is 98.1%, and the selectivity is 99.7%.

Example 6

An ultra-low mercury catalyst preparation method, the steps are as follows: (1) Vacuuming: preheat the system to 80°C, and use a diffusion pump to evacuate the entire system to a vacuum degree of 6×10 ^-4 Pa; (2) Selenium deposition: heating The temperature of the selenium element reaches 680°C, and the deposition time of the selenium gas on the carrier activated carbon is 4 hours; (3) Mercury chloride deposition: Heat the mercury chloride to 380°C, and the mercury chloride gas is deposited on the above-mentioned selenium-deposited activated carbon. The deposition time is In 4 hours, an acetylene hydrochlorination catalyst was prepared, with a mercury chloride content of 2.5%, a selenium content of 0.73%, and an activated carbon content of 96.77%.

The catalyst is used for the catalytic reaction of acetylene hydrochlorination. The set temperature is 170°C, the molar ratio of acetylene to hydrogen chloride is 1:1.1, the acetylene space flow rate is 200h ^-1 , the acetylene conversion rate is 98.1%, and the selectivity is 99.7%.

Comparative Example

The catalyst was prepared using the method of patent application number 202210516350.8, the temperature was 170°C, the acetylene spatial flow rate was 200h ^-1 , the acetylene conversion rate was 85%, and the selectivity was 99%.

Claims (8)

1. An ultra-low mercury catalyst, characterized in that: activated carbon is a carrier, 0.58-1.16wt% elemental selenium is loaded on the carrier as an anchoring agent, and 2-4wt% mercury chloride is a catalytic component. 2. An ultra-low mercury catalyst according to claim 1, characterized in that: activated carbon is a carrier, and 0.72-1.02wt% of elemental selenium is loaded on the carrier as an anchoring agent, and 2.3-3.5wt% of mercury chloride is loaded on the carrier. As a catalytic component. 3. An ultra-low mercury catalyst according to claim 2, characterized in that: activated carbon is a carrier, and 0.84-0.90wt% elemental selenium is loaded on the carrier through physical vapor deposition method as an anchoring agent, and 2.5-2.8 wt% mercury chloride is the catalytic component. 4. An ultra-low mercury catalyst according to claim 1, characterized in that: the material ratio of selenium element to mercury element is 1:1. 5. The preparation method of an ultra-low mercury catalyst according to any one of claims 1 to 4, characterized in that the method used is a physical vapor deposition method, which includes the following steps: (1) Vacuuming: Preheat the physical vapor deposition system to 80°C, and evacuate the entire system to a vacuum degree of 6×10 ^-3 _{_} 6×10 ^-4 Pa; (2) Selenium deposition: Turn on the selenium heater and heat the elemental selenium temperature to 700-800°C to obtain selenium gas. The activated carbon in the physical vapor deposition system is used as a deposition matrix, and the selenium gas is allowed to deposit on the activated carbon for 1-5 hours; (3) Mercury chloride deposition: Turn on the mercury chloride heater, heat the mercury chloride to 300-400°C, and the mercury chloride gas will be deposited on the activated carbon after selenium deposition for 1-5 hours. 6. The preparation method of an ultra-low mercury _catalyst according to claim 5, characterized in that the system preheating temperature is 80°C and the system vacuum is 8×10 ^-3_4 ×10 ^-4 Pa. 7. The preparation method of an ultra-low mercury catalyst according to claim 5, characterized in that the heating temperature of selenium element is 730-770°C, and the deposition time is 2-4 hours. 8. The preparation method of an ultra-low mercury catalyst according to claim 5, characterized in that the mercury chloride is heated to 320-380°C, and the deposition time is 2-4 hours.