High efficiency reactor and process

1. A process for endothermic chemical synthesis of HCN comprising:

(a) providing a reactor having an interior and a preheat zone for elevating the temperature of a feed gas to a first temperature, wherein said feed gas comprises at least one reactant, and wherein said preheat zone comprises a first heat pipe coated to inhibit the decomposition of said feed gas;

(b) providing a reaction zone containing a second heat pipe partially disposed in said reactor interior and coated with a first catalyst;

(c) flowing the preheated feed gas of step (a) to said reaction zone of step (b) and heating said preheated feed gas by contacting said preheated feed gas with the second heat pipe coated with the first catalyst;

(d) endothermically reacting the at least one reactant in said reaction zone to form at least one product at a temperature above about 1000° C.;

(e) withdrawing the at least one product comprising HCN from said reaction zone; and

(f) flowing said withdrawn product to a quench zone comprising a third heat pipe for cooling said at least one product, wherein said third heat pipe comprises a coating for inhibiting decomposition of said at least one product;

wherein the reactor pressure is at least 80 psia.

2. The process of claim 1 wherein one or more of the second and third coated heat pipes comprises an envelope having an interior, said heat pipe interior containing the working fluid, wherein said working fluid has a vapor pressure; and wherein the absolute pressure difference between a reactor pressure and said vapor pressure is sufficiently low to obtain stable heat pipe operating characteristics at said reactor temperature.

3. The process of claim 1 wherein said at least one reactant comprises ammonia and methane.

4. The process of claim 2 further comprising means to control said reactor pressure at a predetermined value.

5. The process of claim 2 wherein said working fluid comprises sodium.

6. The process of claim 2 wherein said pressure difference is less than about 1 atmosphere.

7. The process of claim 2 wherein said pressure difference is less than about 5 psi.

8. The process of claim 2 wherein said pressure difference is less than about 1 psi.

9. The process of claim 2 wherein said envelope comprises stainless steel or a stainless steel alloy.

10. The process of claim 1 wherein said reactor temperature is greater than about 1200° C.

11. The process of claim 2 further comprising means to control pressure of that portion of the envelope of said second heat pipe which is not disposed within said reactor.

12. The process of claim 1 wherein said first catalyst is disposed on at least a portion of an outer surface of said second heat pipe.

13. The process of claim 1 further comprising a ceramic sheath disposed around said second heat pipe, wherein said first catalyst is disposed on at least a portion of an outer surface of said ceramic sheath.

14. The process of claim 1 wherein said reactants flow substantially parallel to the longitudinal axis of said second heat pipe.

15. The process of claim 1 wherein said first heat pipe is partially disposed in said reactor interior, and wherein said reactants flow substantially parallel to the longitudinal axis of said first heat pipe.

16. The process of claim 1 , further comprising reducing the stress on the at least one heat pipe by reducing the absolute value of the differential between the reactor pressure and the pressure of the at least one heat pipe internal pressure.

17. A process for endothermic chemical synthesis of HCN comprising:

(a) providing a reactor having an interior and a preheat zone for elevating the temperature of a feed gas to a first temperature, wherein said feed gas comprises at least one reactant, and wherein said preheat zone comprises a first heat pipe coated to inhibit the decomposition of said feed gas;

(b) providing a reaction zone containing a second heat pipe partially disposed in said reactor interior and coated with a first catalyst;

(c) flowing the preheated feed gas of step (a) to said reaction zone of step (b) and heating said preheated feed gas by contacting said preheated feed gas with the second heat pipe coated with the first catalyst;

(d) endothermically reacting the at least one reactant in said reaction zone to form at least one product at a temperature above about 1000° C.;

(e) withdrawing the at least one product comprising HCN from said reaction zone; and

flowing said withdrawn product to a quench zone comprising a third heat pipe for cooling said at least one product, wherein said third heat pipe comprises a coating for inhibiting decomposition of said at least one product; and

wherein said at least one heat pipe comprises an envelope having an interior, said at least one heat pipe interior containing a sodium working fluid, wherein said working fluid has a vapor pressure; and wherein the reactor pressure on the exterior of the heat pipe (Po, measured in psia) when calculated as a function of the heat pipe working fluid temperature (T, measured in ° C.) satisfies the following equation:

Po=a Na T 3 −b Na T 2 +c Na T−d Na

wherein:

Po is in psia,

T is in the range of 1000 to 1300° C.,

a Na is equal to 1.2×10 −6 ,

b Na is equal to 2.7405×10 −3 ,

c Na is equal to 2.1643, and

d Na is in the range of 570 to 600.

and wherein varying the value of d Na from 570 to 600 defines an operating pressure band between the upper and lower limits of Po.