Process for cyanic acid production

• US 5,882,618 A
• Filed: 04/28/1997
• Issued: 03/16/1999
• Est. Priority Date: 04/28/1997
• Status: Expired due to Fees

• Current Assignee: Air Liquide Large Industries U S LP (L'Air Liquide SA)
• Original Assignee: Air Liquide America LP (Mitsubishi Chemical Group Corp.)
• Inventors: Bhatia, Sandeep, Gezer, Metin
• Primary Examiner(s): LANGEL, WAYNE A
• Application Number:
  US08/845,849
• Time in Patent Office: 687 Days
• Field of Search: 423/376, 423/379
• US Class Current: 423/376
• CPC Class Codes: C01C 3/0212 from hydrocarbons and ammonia in the presence of oxygen, e.g. the Andrussow-process
• CPC Class Codes: C01C 3/0216 characterised by the catalyst used

Abstract

Provided is a process for the production of hydrogen cyanide by reacting methane, ammonia and oxygen in the presence of a catalyst. The process, more specifically, comprises first establishing a temperature for the catalyst in the reaction using air as a source for oxygen. This essentially establishes the gauze temperature of the plant. Additional oxygen is then provided to the reaction to provide oxygen enrichment of the reaction feed, while also adjusting the amount of ammonia and methane reactants in the reaction feed such that the volume percent of the ammonia and methane is above the upper flammability limit and the temperature of catalyst is maintained within 50° C. of the temperature of the catalyst originally established as the fixed gauze temperature of the plant. The process of the present invention allows one to increase production of hydrogen cyanide while maintaining safe operation and not sacrificing catalyst performance in return. In particular, the process of the present invention has applicability to existing plants which need to be improved with regard to hydrogen cyanide production. The process would allow one to take the existing plant, optimize production, capacity and selectivity, while operating safely without adversely affecting catalyst performance.

Claims

1. A process for the production of hydrogen cyanide by reacting methane, ammonia and oxygen in the presence of a catalyst, the process comprising

(i) establishing a temperature for the catalyst in the reaction using air as a source for oxygen, and

(ii) providing additional oxygen to the reaction to provide oxygen enrichment of the reaction feed, while also adjusting the amount of ammonia and methane reactants in the reaction feed such that the volume percent of the ammonia and methane is above the upper flammability limit, with the methane/ammonia ratio after adjustment being in the range of from about 50 to 98% of the methane/ammonia ratio used in establishing (i), and the temperature of the catalyst is within 50°

C. of the temperature of the catalyst established in (i).

2. The process of claim 1, wherein the temperature of the catalyst in (i) is about 1100°

C.

3. The process of claim 1, where the temperature of the catalyst after the adjustment of feed reactants is within 5 to 10°

C. of the temperature of the catalyst established in (i).

4. The process of claim 1, wherein the methane to ammonia ratio after adjustment is in the range of about 85 to 96% of the methane to ammonia ratio used in establishing (i).

5. The process of claim 1, wherein the ammonia to oxygen ratio after adjustment is from 5 to 50% greater than the ammonia/oxygen ratio used in establishing (i).

6. The process of claim 5, wherein the ammonia/oxygen ratio after adjustment is from 10 to 25% greater than the ammonia/oxygen ratio used in establishing (i).

7. The process of claim 1, wherein the oxygen added is added as oxygen enriched air with the oxygen enrichment being such that the oxygen comprises about 24 volume percent of the total oxygen plus air, the sum of the ratios of methane/air plus ammonia/air is greater than 0.40.

8. The process of claim 1, wherein oxygen is added to the feed as pure oxygen.

9. The process of claim 8, wherein the oxygen is injected using an oxygen injector having radial vanes which cause a deflection of oxygen to flow substantially radially into the flow of air with a tangential component.

10. The process of claim 1, wherein the oxygen added is added as oxygen enriched air.

11. The process of claim 1, wherein the oxygen enrichment is such that the oxygen comprises up to 25 volume % of the oxygen plus air in the feed.

12. The process of claim 1, wherein the oxygen enrichment is such that the oxygen comprises up to 40 volume % of the oxygen plus air in the reaction feed.

13. The process of claim 1, wherein the oxygen enrichment is such that oxygen comprises about 24 volume percent of the oxygen plus air total.

16. A reaction for preparing sodium cyanide which comprises reacting hydrogen cyanide with sodium hydroxide, the process comprising preparing the hydrogen cyanide by the process of claim 1, and reacting the hydrogen cyanide with sodium hydroxide.

14. A process for the production of hydrogen cyanide by reacting methane, ammonia and oxygen, in the presence of a catalyst, where air is a source for oxygen, the process comprising enriching the feed with oxygen by an amount of oxygen greater than that provided by air alone, adjusting the amount of ammonia and methane reactants in the reaction feed such that the volume % of the ammonia and methane is above the upper flammability limit, with the methane/ammonia ratio after adjustment being in the range of from about 50 to 98% of the methane/ammonia ratio prior to adjustment, and that the sum of the ratios CH₄ /air plus NH₃ /air is greater than 0.40 and the temperature of the catalyst is within 50°

C. of the catalyst temperature for a reaction where air is the sole source of oxygen.

15. The process of claim 14, wherein the temperature of the catalyst is about 1100°

C.

17. A process for the production of sodium cyanide by reacting hydrogen cyanide with sodium hydroxide, the process comprising preparing the hydrogen cyanide by the process of claim 14, and reacting the hydrogen cyanide product with sodium hydroxide.