REGENERATION METHOD AND APPLICATION OF NITROGEN-CONTAINING CARBON CATALYST

Abstract

A regeneration method of a nitrogen-containing carbon catalyst includes the following steps: roasting the nitrogen-containing carbon catalyst in a nitrogen-containing atmosphere to obtain a regenerated nitrogen-containing carbon catalyst. The method is a universal method, which is suitable for nitrogen-doped carbon catalysts and can be used to regenerate a nitrogen-containing carbon catalyst for producing vinyl chloride (VC) through 1,2-dichloroethane cracking. The method can greatly reduce the production cost of the catalyst and increase the service life of the catalyst, and a regeneration process thereof is fast, simple, and controllable, and does not require high temperatures.

Claims

1. A regeneration method of a nitrogen-containing carbon catalyst, comprising: roasting the nitrogen-containing carbon catalyst in a nitrogen-containing atmosphere to obtain a regenerated nitrogen-containing carbon catalyst.

2. The method according to claim 1, wherein the nitrogen-containing carbon catalyst is roasted in the nitrogen-containing atmosphere, and then cooled to obtain the regenerated nitrogen-containing carbon catalyst.

3. The method according to claim 1, wherein the nitrogen-containing carbon catalyst is roasted in the nitrogen-containing atmosphere, then the nitrogen-containing atmosphere is switched to an inert atmosphere, and the nitrogen-containing carbon catalyst is cooled to obtain the regenerated nitrogen-containing carbon catalyst.

4. The method according to claim 1, wherein the nitrogen-containing carbon catalyst comprises a nitrogen-doped carbon catalyst; in the nitrogen-containing carbon catalyst, a nitrogen element is doped in a carbon material through a covalent bond; and a mass fraction of the nitrogen element in the nitrogen-containing carbon catalyst is 0.1% to 20%.

5. The method according to claim 1, wherein a process of the roasting comprises: heating to a highest temperature of 300° C. to 850° C. at a heating rate of 0.1° C./min to 20° C./min, and keeping at the highest temperature for 0 min to 240 min.

6. The method according to claim 1, wherein a process of the roasting comprises: heating to a highest temperature of 300° C. to 800° C. at a heating rate of 0.1° C./min to 10° C./min, and keeping at the highest temperature for 0 min to 90 min.

7. The method according to claim 1, wherein nitrogen in the nitrogen-containing atmosphere is derived from at least one from the group consisting of ammonia and N.sub.2O.

8. The method according to claim 1, wherein the nitrogen-containing atmosphere is a mixed gas composed of a first gas and a second gas; the first gas is at least one from the group consisting of ammonia and N.sub.2O; and the second gas is an inert gas.

9. The method according to claim 8, wherein a mass fraction of the first gas in the mixed gas is 2% to 100%.

10. The method according to claim 8, wherein the inert gas is at least one from the group consisting of nitrogen, argon, and helium.

11. The method according to claim 1, wherein after the nitrogen-containing carbon catalyst is roasted in the nitrogen-containing atmosphere, a nitrogen content is increased by 3% to 150%.

12. A preparation method of a nitrogen-containing carbon catalyst, comprising: using the method according to claim 1 to prepare the nitrogen-containing carbon catalyst for 1,2-dichloroethane cracking to produce vinyl chloride (VC).

13. A method for producing VC through 1,2-dichloroethane cracking, comprising the following steps: vaporizing 1,2-dichloroethane to obtain vaporized 1,2-dichloroethane, and introducing the vaporized 1,2-dichloroethane into a reactor filled with a nitrogen-containing carbon catalyst; after the nitrogen-containing carbon catalyst is deactivated, switching a 1,2-dichloroethane-containing reaction atmosphere to a nitrogen-containing atmosphere for regeneration; and after the regeneration is completed, switching the nitrogen-containing atmosphere back to the 1,2-dichloroethane-containing reaction atmosphere.

14. The preparation method according to claim 12, wherein the nitrogen-containing carbon catalyst is roasted in the nitrogen-containing atmosphere, and then cooled to obtain the regenerated nitrogen-containing carbon catalyst.

15. The preparation method according to claim 12, wherein the nitrogen-containing carbon catalyst is roasted in the nitrogen-containing atmosphere, then the nitrogen-containing atmosphere is switched to an inert atmosphere, and the nitrogen-containing carbon catalyst is cooled to obtain the regenerated nitrogen-containing carbon catalyst.

16. The preparation method according to claim 12, wherein the nitrogen-containing carbon catalyst comprises a nitrogen-doped carbon catalyst; in the nitrogen-containing carbon catalyst, a nitrogen element is doped in a carbon material through a covalent bond; and a mass fraction of the nitrogen element in the nitrogen-containing carbon catalyst is 0.1% to 20%.

17. The preparation method according to claim 12, wherein a process of the roasting comprises: heating to a highest temperature of 300° C. to 850° C. at a heating rate of 0.1° C./min to 20° C./min, and keeping at the highest temperature for 0 min to 240 min.

18. The preparation method according to claim 12, wherein a process of the roasting comprises: heating to a highest temperature of 300° C. to 800° C. at a heating rate of 0.1° C./min to 10° C./min, and keeping at the highest temperature for 0 min to 90 min.

19. The preparation method according to claim 12, wherein nitrogen in the nitrogen-containing atmosphere is derived from at least one from the group consisting of ammonia and N.sub.2O.

20. The preparation method according to claim 12, wherein the nitrogen-containing atmosphere is a mixed gas composed of a first gas and a second gas; the first gas is at least one from the group consisting of ammonia and N.sub.2O; and the second gas is an inert gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG. 1 is an outside view of a nitrogen-containing carbon catalyst sample supported by silica gel (Fresh-Cat#);

[0048] FIG. 2 is a schematic diagram illustrating the raw material conversion rates of the regenerated catalysts obtained in Example 1 and Comparative Example 1 that change with the reaction time; and

[0049] FIG. 3 is a schematic diagram illustrating the raw material conversion rates of the regenerated catalysts obtained in Examples 2, 3, and 4 that change with the reaction time.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] The present application will be described in detail below with reference to examples, but the present application is not limited to these examples. Those skilled in the art can adjust the regeneration conditions using the method provided in the present application according to actual needs to obtain different regeneration effects.

[0051] Unless otherwise specified, the raw materials and catalysts in the examples of the present application are all purchased from commercial sources. Unless otherwise specified, the test methods are all conventional methods, and the instrument settings are all those recommended by manufacturers.

[0052] The silica gel spheres are 80-120 mesh white coarse-pored microsphere silica gel purchased from Shandong Dongying Yiming New Material Co., Ltd.

[0053] Analysis methods in the examples of the present application are as follows:

[0054] A nitrogen content is determined by an EA3000 element analyzer of Leeman.

[0055] An EDC conversion rate and the VC selectivity are analyzed and determined through a fixed bed reactor, where EDC is carried by nitrogen into the reactor under bubbling, with a nitrogen flow rate of 2.5 ml/min, a bubbling temperature of 5° C., a catalyst filling amount of 0.2 g, and a bed residence time of 18.1 s.

[0056] In the present application, when a regenerated catalyst is used for EDC cracking to produce VC, there is an induction period in the reaction, and during the induction period, the conversion rate gradually increases over time and is stable after 3 days.

[0057] The conversion rate and selectivity in the examples of the present application are calculated as follows:

[0058] In the examples of the present application, the EDC conversion rate and the VC selectivity are calculated based on the number of moles:

EDC conversion rate=EDC consumed by a reaction (mol)/EDC introduced into a reactor (mol)×100%

VC selectivity=VC produced by a reaction (mol)/sum of all products produced by the reaction (mol)×100%

[0059] Preparation of a Nitrogen-Containing Carbon Catalyst Sample:

[0060] 200 mL of furfuryl alcohol was added to a 1,000 mL beaker at room temperature, then 2.00 g of oxalic acid was added under stirring, and after the oxalic acid was dissolved, 300 mL of xylene was added; then 500 mL of coarse-pored microsphere silica gel was added to the beaker, and the beaker was placed in a 20° C. water bath to conduct impregnation for 6 h; excess liquid was removed through filtration, and then the silica gel was placed in a 1,000 mL beaker; and a polymerization reaction was conducted for 12 h in a 60° C. water bath, the temperature was raised to 90° C., and a polymerization reaction was further conducted for 12 h.

[0061] 500 mL of the treated coarse-pored silica gel spheres was taken and put into a quartz tube of a rotary tube furnace, and nitrogen was introduced at a flow rate of 250 mL/min for 4 h to replace the air and dry the impregnated pellets spheres. In the rotary tube furnace, under the protection of nitrogen, the silica gel spheres were heated to 150° C. at 1° C./min and kept at the temperature for 3 h, then heated to 450° C. and kept at the temperature for 3 h, and then cooled to room temperature.

[0062] After the cooling under nitrogen, the nitrogen flow rate was changed to 45 mL/min, and an ammonia flow rate was 320 mL/min; gas replacement was conducted before a temperature rise; the silica gel spheres were heated to 800° C. at 5° C./min and kept at the temperature for 1.5 h; the introduction of ammonia was stopped, and the nitrogen flow rate was changed to 250 mL/min; and the silica gel spheres were cooled to 600° C. and kept at the temperature for 1.5 h, and then naturally lowered to room temperature. A mass percentage of nitrogen in the supported nitrogen-containing carbon material was 6.1%. The appearance of the sample was shown in FIG. 1, which was recorded as Fresh-Cat#.

[0063] EDC was charged under bubbling into a fixed bed reactor filled with the catalyst, with a reactor temperature of 250° C. and an EDC residence time (GHSV) of 18.1 s. Test results showed that an EDC conversion rate was 13%, and the VC selectivity was 99%. After 45 days of reaction, the EDC conversion rate was 10%, and the VC selectivity was 98%. A deactivated sample was recorded as 45d-Cat#.

REGENERATION EXPERIMENT

Example 1

[0064] The deactivated catalyst 45d-Cat# was placed in a mixed atmosphere of ammonia and nitrogen, heated from room temperature to 800° C., and subjected to a reaction for 1.5 h at 800° C.; and then the atmosphere was switched to nitrogen, and a product was naturally cooled to room temperature. A rate of the heating was 5° C./min, and a mass fraction of the ammonia was 50%, which was recorded as NH.sub.3-1#. An evaluation process of the regenerated catalyst was the same as the above process. An EDC conversion rate was 15%. A mass percentage of nitrogen in the supported nitrogen-containing carbon material was 14.1%. The EDC conversion rate changed with the reaction time, as shown in FIG. 2. The VC selectivity was 99%. It can be seen from FIG. 2 that a conversion rate of the regenerated catalyst during an induction period has reached more than 16%, which is better than a conversion rate of the fresh catalyst (13%); and during the induction period, the conversion rate gradually increases over time, and a stabilized conversion rate is higher than 16%, indicating that the performance of the catalyst can be restored through the regeneration process and the restored performance is better than the performance of the fresh catalyst. However, if the temperature is raised in an inert atmosphere and then a nitrogen-containing atmosphere (Comparative Example 1) is introduced, the conversion rate and selectivity of the catalyst will both decrease.

Comparative Example 1

[0065] This comparative example was basically the same as Example 1, except that the deactivated catalyst was first placed in a nitrogen atmosphere and heated from room temperature to 800° C.; and then the nitrogen atmosphere was switched to a mixed atmosphere of ammonia and nitrogen, and a reaction was conducted for 1.5 h. A product was recorded as DB-1#. A mass percentage of nitrogen in the supported nitrogen-containing carbon material was 17.6%. A catalyst evaluation process was the same as the above process, and the reaction was conducted at 250° C. An EDC conversion rate was 3%, and the VC selectivity was 92%. The EDC conversion rate was shown in FIG. 2. It can be seen that, although a mass content of nitrogen in the supported nitrogen-containing carbon material increases in the catalyst treated by this method, the regeneration of the catalyst cannot be achieved due to the different treatment order. This is because in an atmosphere without ammonia, the catalyst is irreversibly destroyed at a high temperature, and it is difficult to regenerate the catalyst even if an ammonia-containing gas is then introduced.

Example 2

[0066] The deactivated catalyst was placed in a mixed atmosphere of ammonia and nitrogen and heated from room temperature to 550° C., then the atmosphere was immediately switched to nitrogen, and a product was naturally cooled to room temperature. A rate for the heating was 5° C./min, and a mass fraction of the ammonia was 25%, which was denoted as NH.sub.3-2#. A mass percentage of nitrogen in the supported nitrogen-containing carbon material was 6.5%. An evaluation process of the regenerated catalyst was the same as the above process, and the reaction was conducted at 250° C. An EDC conversion rate was 12%, as shown in FIG. 3; and the VC selectivity was 99%. After the induction period, a stabilized EDC conversion rate was higher than 13%.

Example 3

[0067] This example was different from Example 2 in that a mass fraction of ammonia was 75%, which was recorded as NH.sub.3-3#; a mass percentage of nitrogen in the supported nitrogen-containing carbon material was 6.3%; an evaluation process of a regenerated catalyst was the same as the above process, and the reaction was conducted at 250° C.; an EDC conversion rate was 11%, as shown in FIG. 3; and the VC selectivity was 99%. After the induction period, a stabilized EDC conversion rate was higher than 13%.

Example 4

[0068] This example was different from Example 3 in that the temperature was kept at 550° C. for 1 h, which was recorded as NH 3-4#; a mass percentage of nitrogen in the supported nitrogen-containing carbon material was 6.9%; an evaluation process of a regenerated catalyst was the same as the above process, and the reaction was conducted at 250° C.; an EDC conversion rate was 10%, and the reaction performance was shown in FIG. 3; and the VC selectivity was 99%. After the induction period, a stabilized EDC conversion rate was higher than 13%.

[0069] FIG. 3 is a schematic diagram illustrating the raw material conversion rates of the regenerated catalysts obtained in Examples 2, 3, and 4 that change with the reaction time.

Example 5

[0070] This example was different from Example 2 in that a heating rate was 0.1° C./min.

Example 6

[0071] This example was different from Example 2 in that a heating rate was 10° C./min.

Example 7

[0072] This example was different from Example 2 in that a mass fraction of ammonia was 2%.

Example 8

[0073] This example was different from Example 2 in that a mass fraction of ammonia was 5%.

Example 9

[0074] This example was different from Example 2 in that a mass fraction of ammonia was 15%.

[0075] The regenerated catalysts in Examples 5 to 9 were evaluated by the same evaluation process as in Example 2, and the reaction was conducted at 250° C. After the induction period, the VC selectivity was 99%, and the EDC conversion rate was higher than 13%.

Example 10

[0076] This example was different from Example 3 in that the highest temperature for regeneration was 300° C.; after the regeneration, a mass percentage of nitrogen in the supported nitrogen-containing carbon material was 6.4%; an evaluation reaction was conducted at 250° C.; and an EDC conversion rate was 8%, and the VC selectivity was 99%. After the induction period, a stabilized EDC conversion rate was higher than 13%.

Example 11

[0077] This example was different from Example 3 in that the highest temperature for regeneration was 600° C.; after the regeneration, a mass percentage of nitrogen in the supported nitrogen-containing carbon material was 6.6%; an evaluation reaction was conducted at 250° C.; and an EDC conversion rate was 15%, and the VC selectivity was 99%. After the induction period, a stabilized EDC conversion rate was higher than 15%.

[0078] It can be seen that the regeneration method of the present application is very convenient and efficient, for example, in Example 2, a very short residence time can achieve prominent regeneration performance. The regeneration method of the present application is very economical, for example, in Example 7, excellent regeneration performance can be achieved at a relatively low ammonia concentration, which can greatly reduce the regeneration cost.

[0079] The above examples are merely few examples of the present application, and do not limit the present application in any form. Although the present application is disclosed as above with preferred examples, the present application is not limited thereto. Some changes or modifications made by any technical personnel familiar with the profession using the technical content disclosed above without departing from the scope of the technical solutions of the present application are equivalent to equivalent implementation cases and fall within the scope of the technical solutions.