WO1996015066A1

WO1996015066A1 - Recovery of chlorine from hydrogen chloride, with internal recycle of hydrogen chloride

Info

Publication number: WO1996015066A1
Application number: PCT/US1995/014736
Authority: WO
Inventors: Ronald G. Minet; Theodore T. Tsotsis; Sidney M. Benson; Max K. Mortensen
Original assignee: University Of Southern California
Priority date: 1994-11-14
Filing date: 1995-11-14
Publication date: 1996-05-23

Abstract

A process of recovering Cl2 from a stream of HCl (10) which comprises the steps of supplying an HCl stream (10) to a first fluidized bed of a carrier catalyst CuO (12) in a first reaction zone (11) to produce CuCl2, H2O, and heat; feeding the CuCl2 from the first zone (11) to a second reaction zone (16) via line (40); supplying O2 (17) to the second reaction zone (16) to react with CuCl2 in a second bed (15) at elevated temperature to produce CuO and Cl2; feeding the CuO from the second bed (15) to the first bed (12) via line (41); removing Cl2 from the second zone (16) via line (21) and recycling it via line (70) to the first reaction zone (11) for reaction with CuO at lower temperature to remove recycled HCl from the Cl2; recovering the Cl2 via line (23). A third fluidized bed is also disclosed.

Description

RECOVERY OF CHLORINE FROM HYDROGEN CHLORIDE, WITH INTERNAL RECYCLE OF HYDROGEN CHLORIDE

BACKGROUND OF THE INVENTION

This invention is useful in apparatus and process for the recovery of chlorine from waste or byproduct hydrogen chloride, by means of a multistage, continuous reaction process employing a combined catalytic carrier system. Hydrogen chloride is produced as a byproduct from many chemical processes, including production of titanium dioxide pigment, polyurethanes, vinyl chloride, organic chlorides, and many other useful and economically important substances. Typically, the chlorine used in the process is supplied from large-scale electrochemical plants by shipment via rail, truck or barge. The byproduct hydrogen chloride is collected and disposed of by sale at reduced price or by neutralization from some form of lime or caustic.

The described invention makes it possible to recycle the hydrogen chloride in an economical and environmentally sound manner to recover the chlorine for use in the primary process, thus materially reducing the quantity which must be shipped from outside, and at a cost which is significantly below the cost of fresh chlorine.

SUMMARY OF THE INVENTION

Basically, the process of continuously recovering chlorine from a stream of hydrogen chloride includes the steps: a) providing a first fluidized bed of carrier catalyst; cupric oxide in a first reaction zone, b) supplying hydrogen chloride in a first stream to the zone for reaction with cupric oxide to produce cupric chloride, water and heat, removing heat from the zone to maintain the required temperature, removing water from the zone, and removing cupric chloride from the zone, c) feeding the cupric chloride stream to a second reaction zone, providing a second fluidized bed of cupric chloride in the second reaction zone, and d) supplying oxygen in a third stream to the second zone for reaction with cupric chloride in the second bed at elevated temperatures to produce cupric oxide and chlorine, removing cupric oxide from the second bed for reuse as a catalyst to produce cupric chloride, and e) removing as a fourth stream the chlorine, which contains some hydrogen chloride, from the second bed and supplying said stream to the first fluidized bed in the first reaction zone to cause the recycled hydrogen chloride to react with the cupric oxide, and thus allow the chlorine product to leave the first reaction zone substantially free from hydrogen chloride, f) in an additional step a third reaction zone containing a third fluidized bed of cupric chloride can be provided which can be supplied with a fifth stream of oxygen and hydrogen chloride which will react to chemical equilibrium at elevated temperatures to produce chlorine, water and heat, and unconverted hydrogen chloride and oxygen, which will be removed as a sixth stream, to be supplied along the first stream of hydrogen chloride, and the fifth stream of chlorine to the first reaction zone fluidized bed, to react with cupric oxide resulting in additional production of chlorine product substantially free from hydrogen chloride.

This invention improves upon the disclosure of U.S. Patent 4,959,202, that disclosure incorporated herein by reference as background.

These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following specification and drawings, in which:

DRAWING DESCRIPTION Fig. 1 is a block flow diagram;

Fig. 2 is a material balance listing;

Fig. 3 is a tabulation of experimental results;

Fig. 4 is a tabulation of process economic factors;

Fig. 5 is a tabulation of process data; and Fig. 6 is a tabulation of process data.

DETAILED DESCRIPTION

The process of this invention makes use of a unique carrier catalyst system having metallic elements in the form of complex oxides and chlorides impregnated onto a carrier mass, such as alumina, silica, zeolite, or molecular sieve material of such a form as to be suitable for use in a multistage fluidized bed system. The chemical reactions are caused to take place in a series of steps which include: 1) 2HCl(g) + 1/2 O₂(g) Cl₂(g) + H₂O(g)

2) CuO(S) + HCl(g) Cu(OH)Cl(S)

3) 2Cu(OH)Cl(S) Cu-O C1₂(S) + H₂O(g)

4) Cu-OCl₂(S) CuO(S) + CuCl₂(S) 5) CuCl₂(S) CuCl(S) + 1/2 Cl₂(g)

6) 2CuCl(S) + 1/2 O₂(g) CuCl₂(S) + CuO(S)

These specific steps take place in specific reaction zones and within specific temperature ranges, as described on the block diagram, Fig. 1, and in the following steps:

SteEJL-Referring to Fig. 1, the stream 10 of hydrogen chloride, either anhydrous or containing water and process impurities, which might be present, is passed into reactor 11 through a fluidized bed 12 of carrier catalyst of copper oxides and copper chlorides with sodium chlorides, deposited on a suitable carrier in a 1: 1 molar ratio.

Reactions 2, 3, and 4 for the formation of complex chlorides take place at a temperature maintained in the range of 150° to 220°C. by providing a system 13 of heat transfer within the bed 12, which carries away the exothermic heat of reaction via, in a preferred arrangement, a heat exchanger 14 generating steam to improve the thermal economy of the process.

Chlorinated catalytic material is continuously withdrawn from the first reactor in paniculate form and transferred at 40 into the fluidized bed 15 in a second reactor 16 wherein step 2 takes place.

Step 2. In the second reactor, the above reactions 5 and 6 take place to convert the complex chlorides to cupric oxide and release chlorine gas. The fluidized bed in reactor 16 is blown with a gaseous mixture of oxygen and nitrogen ranging from 100% oxygen down to 20% oxygen entering the reactor at 17. The reactor 16 is maintained at a temperature between 300° and 360°C. by means of heat supplied through a system of heat transfer 19 within the fluidized bed.

One of die reactions taking place under the temperature conditions selected is the reverse of reaction (2) above, leading to the formation of a certain amount of hydrogen chloride (see Fig. 3 table) which must be removed from the gas exiting the second reactor, to improve the overall conversion of the feed hydrogen chloride to chlorine, and to avoid contamination of the chlorine product. This removal is accomplished by step 3, the recycle of hydrogen chloride to reactor 11 (see Fig. 5 table). A continuous stream of carrier catalyst containing cupric oxide is withdrawn through line 41 and returned to bed 12 in the first reactor.

Step 3. The total flow of hot gas from the second reactor containing chlorine, oxygen, nitrogen, and some small amount of hydrogen chloride is recycled at 70 through heat exchanger 22 and to the first reactor 11 and the fluidized bed 12, where the contained hydrogen chloride reacts with cupric oxide returned from the second reactor 16 through 41. At the temperature conditions selected for the first fluidized bed 12, 150° to 220°C, only the hydrogen chloride reacts, the oxygen, nitrogen, water, and chlorine passing through without change. See Fig. 5. Step 4.Effluent gases leaving the first reactor at 23 consist of chlorine, water, oxygen, and nitrogen, which pass off to heat exchange at 89, and to recovery system 50, for removal of water at 52, and chlorine product gas at 51. When operated as described, over 99% of die hydrogen chloride 10 entering the system is converted to chlorine product 51. Step 5. In another process step, overall thermal economy can be improved and capital cost can be decreased by adding a third reactor 31 to the system, which includes a fluidized bed 32 of catalytic carrier consisting of complex copper chlorides and sodium salts on a suitable carrier operating in a temperature range of 350° to 400°C, which reactor is supplied with streams of hydrogen chloride at 10a and oxygen 17g in a continuous flow. Note control valves 71-75 operable to enable step 5.

In this embodiment, most of the fresh feed hydrogen chloride flows to the third reactor 31 where 60% to 70% of the hydrogen chloride is converted to chlorine and water. Effluent gas at 33 from the third reactor contains chlorine, hydrogen chloride, water, oxygen, and inerts, which controllably passes through valve 75 and joins with the effluent gas 21 from second reactor 16 to flow at 70 through heat exchanger 22 and into first reactor 11 for complete recycle of hydrogen chloride and recovery of chlorine.

In this alternate, the third reactor fluidized bed 32 is not circulated but remains constant as a catalyst in the reaction zone for the exothermic reaction, according to equation (1), (see Fig. 6) providing heat through heat exchanger system 34 to drive the endothermic reaction in the second reactor and other high-level energy requirements, such as steam turbines in the overall system, and eliminating the need for a high-temperature combustion system to heat the second reactor. Experimental work for the further development of this process was carried out to investigate various metallic systems and various carrier masses. The work included tests with manganese, iron and chromium, with sodium and potassium-based promoters. In some tests, the metals used were mixed with copper, as well as used alone. The copper content was varied from 5 to 18 weight percent of the total catalytic carrier mass. As a result of the various experiments, it was concluded that the most consistent and useful catalytic carrier system was copper oxides and copper chlorides blended with equalmolar sodium chloride on a zeolite base, which was also suitable for a base material in the fluid catalytic cracking of gas oil in commercial petroleum refineries. As an illustration of the stream compositions in a combination process for recovery of chlorine from hydrogen chloride, a block flow diagram and material balance is presented in Fig. 2. The calculated streams are based on more than 25 simulated experiments carried out with a one inch diameter by 36 inch long, tubular quartz reactor.

As an illustration of the economic factors for the invention, an engineering design was prepared for a plant processing 60,000 tons per year of anhydrous hydrogen chloride and an operating cost was determined based on zero value for the byproduct hydrogen chloride feed. These results, as shown in Fig. 4, indicate a chlorine recovery cost of $46 per ton (1994 data) with a chlorine selling price of $230 per ton on the then current market. Fig. 4 lists process economic factors in terms of typical plant investment and operating cost.

The overall system, as described, provides for essentially 100% conversion of hydrogen chloride to chlorine. The product chlorine can be produced as a liquid or a gas stream of 98% plus purity. No toxic or noxious effluent streams are produced to be released to the atmosphere or ground water. Energy requirements of less than 20% of the standard electrochemical process were realized, as well as significantly less than reported consumptions for alternate proposed chlorine recovery process. Fig. 2 shows material balance data.

The invention also embodies the two reactor process or method set forth below, wherein the designated chlorinator reactor is the same as reactor 11 in Fig. 1, and the designated oxidizer reactor is the same as reactor 16 in Fig. 1: a) providing at least two reactors, including a chlorinator reactor and an oxidizer reactor, and providing a fluidized bed of a carrier catalyst cupric oxide and cupric chloride in a reaction zone within the chlorinator reactor, b) supplying a stream of hydrogen chloride to d e chlorinator reactor, c) said stream reacting in the chlorinator reactor with said fluidized bed of carrier catalyst cupric oxide and cupric chloride at temperatures between 150° and 220 °C. exothermically to convert part of the cupric oxide to cupric chloride, and cupric hydroxychloride, thereby essentially eliminating the hydrogen chloride to produce a product stream including inerts and water, which is removed from die chlorinator reactor, and d) passing a stream of fluidized carrier catalyst containing cupric chloride , cupric hydroxy chloride, and residual cupric oxide from the chlorinator reactor to be supplied to die oxidizer reactor in a bed operating at temperatures between 300° and 380°C, wherein the oxidizer reactor is supplied with oxygen to fluidize the bed, and for endotheπnic reaction with cupric chloride and cupric hydroxy chloride to produce cupric oxide and a stream of chlorine, hydrogen chloride, inerts and oxygen and, e) feeding me carrier catalyst stream containing cupric oxide to die oxidizer reactor for reaction with hydrogen chloride, as defined in c), and f) supplying the stream of chlorine, hydrogen chloride, inerts and oxygen from the oxidizer reactor to the chlorinator reactor to cause the hydrogen chloride portion of the stream to react with the cupric oxide in die carrier catalyst at the operating temperature between 150° and 220°C, g) die product stream from the chlorinator reactor being chlorine rich but substantially free of hydrogen chloride, h) and wherein heat generated in the chlorinator reactor can be optionally used to supply heat for process use.

The invention also embodies die three reactor process or method as set forth below, wherein the described first reactor is the same as reactor 31 in Fig. 1; the designated second reactor is the same as reactor 11 in Fig. 1; and the designated third reactor is die same as reactor 16 in Fig. 1: a) providing first, second and diird reactors, and providing a fluidized bed of a carrier catalyst cupric oxide and cupric chloride in a reaction zone widiin the second reactor, b) supplying hydrogen chloride and oxygen to react exothermically in the first reactor to produce a stream of chlorine and water, at elevated temperatures between 300° and 400°C, and also unreacted hydrogen chloride and oxygen which is removed from the first reactor and flow to die second reactor and, c) the stream reacting in the second reactor with the fluidized bed of carrier catalyst cupric oxide and cupric chloride at temperatures between 150° and 220°C. exothermically to convert part of die cupric oxide to cupric chloride, and cupric hydroxychloride, thereby essentially eliminating the hydrogen chloride to produce a product stream of chlorine, water, inerts and oxygen which is removed from the second reactor, and d) passing a stream of the fluidized carrier catalyst containing cupric chloride, cupric hydroxy chloride, and residual cupric oxide from the second reactor to be supplied to die diird reactor in a bed operating at temperatures between 300° and 380°C, wherein die diird reactor is supplied widi oxygen to fluidize d e bed, and for endotheπnic reaction with cupric chloride and cupric hydroxy chloride to produce cupric oxide and a stream of chlorine, hydrogen chloride and oxygen and, e) feeding d e carrier catalyst stream containing cupric oxide to the second reactor for reaction with hydrogen chloride, as defined in c), and f) supplying the stream of chlorine, hydrogen chloride, inerts and oxygen from the diird reactor to the second reactor to cause the hydrogen chloride component of that stream to react with the cupric oxide in die carrier catalyst at operating temperatures between 150° and 220°C, and g) die product stream from the second reactor which contains chlorine, water and oxygen being chlorine rich but substantially free of hydrogen chloride, h) and wherein heat generated in die first reactor exothermic reaction can be optionally used to supply heat for process use.

In the above, the reactor 16 may be divided into two temperature zones. A gas stream from the hot zone at temperatures between 300° and 380°C. passes through the fluidized catalytic carrier maintained at between 150° and 220 °C, to cause die hydrogen chloride present in the gas to react with the cupric oxide in the catalytic carrier, thereby producing an effluent product stream which contains chlorine, oxygen and water but is free of hydrogen chloride.

As stated in die disclosure of U.S. Patent 4,959,202, the processes can be carried out using a catalytic carrier where manganese oxides and chlorides are substituted for copper, with good results, where a chlorination temperature in me range of 250°- 350°C, and an oxidation temperature of about 400°-450°C.

Iron oxides and chlorides can also be substituted.

Heat recovery and chlorine recovery from the product stream can be carried out as described in U.S. Patent 4,959,202.

Claims

WE CLAIM:

1. In a process of recovering chlorine from a stream of hydrogen chloride, the steps that include: a) providing at least two reactors, including a chlorinator reactor and an oxidizer reactor, and providing a fluidized bed of a carrier catalyst cupric oxide and cupric chloride in a reaction zone within the chlorinator reactor, b) supplying a stream of hydrogen chloride to the chlorinator reactor, c) said stream reacting in the chlorinator reactor with said fluidized bed of carrier catalyst cupric oxide and cupric chloride at temperatures between 150° and 220°C. exodiermically to convert part of the cupric oxide to cupric chloride, and cupric hydroxychloride, thereby essentially eliminating the hydrogen chloride to produce a product stream including inerts and water, which is removed from said chlorinator reactor, and d) passing a stream of said fluidized carrier catalyst containing cupric chloride, cupric hydroxy chloride, and residual cupric oxide from said chlorinator reactor to be supplied to the oxidizer reactor in a bed operating at temperatures between 300° and 380°C, wherein said oxidizer reactor is supplied widi oxygen to fluidize said bed, and for endodiermic reaction with cupric chloride and cupric hydroxy chloride to produce cupric oxide and a stream of chlorine, hydrogen chloride, inerts and oxygen and, e) feeding said carrier catalyst stream containing cupric oxide to die oxidizer reactor for reaction with hydrogen chloride, as defined in c), and f) supplying the stream of chlorine, hydrogen chloride, inerts and oxygen from die oxidizer reactor to the chlorinator reactor to cause the hydrogen chloride portion of d e stream to react with the cupric oxide in die carrier catalyst at the operating temperature between 150° and 220°C, g) said product stream from the chlorinator reactor being chlorine rich but substantially free of hydrogen chloride, h) and wherein heat generated in die chlorinator reactor can be optionally used to supply heat for process use.

2. The method of claim 2 wherein the oxidized reactor is divided into two temperature zones, and wherein a gas stream from the hot zone at temperatures between

300° and 380°C. passes tiirough the fluidized catalytic carrier maintained at between 150° and 220°C, to cause the hydrogen chloride present in the gas to react with the cupric oxide in the catalytic carrier, thereby producing an effluent product stream which contains chlorine, oxygen and water but is free of hydrogen chloride.

3. The method of claim 1 wherein said cupric oxide in said stream defined in e) of claim 1 is removed from said oxidizer reactor.

The method of claim 1 including supplying heat to said oxidizer reactor.

The metiiod of claim 1 including removing chlorine from said product stream.

6. The metiiod of claim 1 wherein said heat generated in die chlorinator reactor is supplied to said oxidizer reactor.

7. The method of claim 1 wherein said catalytic carrier is selected from the group consisting of alumina, zeolite, silica, and molecular sieve material.

8. The method of claim 1 including transferring heat from the stream of chlorine, hydrogen chloride, inerts, and oxygen flowing from me oxidizer reactor to die chlorinator reactor.

9. The method of claim 1 including controlling the supply of hydrogen chloride and oxygen to die reactors.

10. In a process of recovering chlorine from a stream of hydrogen chloride, the steps that include: a) providing first, second and third reactors, and providing a fluidized bed of a carrier catalyst cupric oxide and cupric chloride in a reaction zone witiiin the second reactor, b) supplying hydrogen chloride and oxygen to react exothermically in d e fluidized bed of carrier catalyst cupric chloride, and cupric oxide in the first reactor to produce a stream of chlorine and water, at elevated temperatures between 300 and 380°C, and also unreacted hydrogen chloride and oxygen which is removed from die first reactor and flow to die second reactor and, c) said stream reacting in the second reactor with said fluidized bed of carrier catalyst cupric oxide and cupric chloride at temperatures between 150° and 220°C. exodiermically to convert part of the cupric oxide to cupric chloride, and cupric hydroxychloride, diereby essentially eliminating the hydrogen chloride to produce a product stream of chlorine, water, inerts and oxygen which is removed from said second reactor, and d) passing a stream of said fluidized carrier catalyst containing cupric chloride, cupric hydroxy chloride, and residual cupric oxide from said second reactor to be supplied to said diird reactor in a bed operating at temperatures between 300° and 380 °C, wherein said diird reactor is supplied with oxygen to fluidize said bed, and for endodiermic reaction with cupric chloride and cupric hydroxy chloride to produce cupric oxide and a stream of chlorine, hydrogen chloride and oxygen and, e) feeding said carrier catalyst stream containing cupric oxide to the second reactor for reaction with hydrogen chloride, as defined in c), and f) supplying the stream of chlorine, hydrogen chloride, inerts and oxygen from die diird reactor to die second reactor to cause die hydrogen chloride component of mat stream to react with die cupric oxide in die carrier catalyst at said operating temperatures between 150° and 220°C, and g) said product stream from the second reactor which contains chlorine, water and oxygen being chlorine rich but substantially free of hydrogen chloride, h) and wherein heat generated in die first reactor exothermic reaction can be optionally used to supply heat for process use.

11. The metiiod of claim 10 wherein the third reactor is divided into two temperature zones, and wherein a gas stream from the hot zone at temperatures between 300° and 380°C. passes through the fluidized catalytic carrier maintained at between 150° and 220°C. to cause the hydrogen chloride present in die gas to react with the cupric oxide in the catalytic carrier, thereby producing an effluent product stream which contains chlorine, oxygen and water but is free of hydrogen chloride.

12. The method of claim 10 wherein said cupric oxide in said stream defined in e) of claim 10 is removed from said diird reactor.

13. The method of claim 10 including supplying heat to said oxidizer reactor.

14. The method of claim 10 including removing chlorine from said product stream.

15. The method of claim 10 wherein said heat generated in d e first reactor is supplied to said diird reactor.

16. The metiiod of claim 10 including transferring heat from the third reactor to the second reactor.

17. The method of claim 10 including controlling the supply of hydrogen chloride and oxygen to die reactors.