Process for preparation of chlorine from hydrogen chloride

Abstract

The invention relates to a process for preparation of chlorine from hydrogen chloride comprising circulating a liquid melt comprising copper ions Cu.sup.n+ with n being a number in the range from 1 to 2, alkali cations and chloride ions Cl in a reactor system comprising three bubble lift reactors I, II and III, each comprising a reaction zone i, ii and iii respectively, wherein: (a) in the reaction zone i of the first bubble lift reactor I, a liquid melt comprising copper ions Cu.sup.n+, alkali cations and chloride ions Cl is contacted with oxygen at a temperature in the range from 395 to 405 C. so that the molar ratio Cu.sup.n+:Cu.sup.+ in the liquid melt increases, obtaining a liquid melt having an increased molar ratio Cu.sup.n+:Cu.sup.+ (b) the liquid melt obtained in (a) is circulated to the reaction zone ii in the second bubble lift reactor II, where the liquid melt is contacted with hydrogen chloride at a temperature in the range from 395 to 405 C. so that water is formed, obtaining a liquid melt being enriched in chloride anions (CI) compared to the liquid melt obtained according to (a); (c) circulating the liquid melt obtained in (b) to the reaction zone iii in the third bubble lift reactor III, which is operated at a temperature in the range from 420 to 430 C. so that chlorine (Cl.sub.2) is formed, wherein Cl.sub.2 is removed from the reaction zone iii and the third bubble lift reactor III respectively in gaseous form, leaving a liquid melt depleted of Cl-compared to the liquid melt obtained according to (b). The invention further relates to a reactor system comprising three bubble lift reactors I, II and III.

Claims

1. A process for preparation of chlorine from hydrogen chloride comprising circulating a liquid melt comprising copper ions Cu.sup.n+ with n being a number in the range from 1 to 2, alkali cations and chloride ions Cl-in a reactor system comprising three bubble lift reactors I, II and III, each comprising a reaction zone i, ii and iii respectively, wherein: (a) in the reaction zone i of the first bubble lift reactor I, a liquid melt comprising copper ions Cu.sup.n+, alkali cations and chloride ions Cl.sup. is contacted with oxygen (O.sub.2) at a temperature in the range from 395 to 405 C. so that the molar ratio Cu.sup.2+:Cu.sup.+ in the liquid melt increases, obtaining a liquid melt having an increased molar ratio Cu.sup.2+:Cu.sup.+ (b) the liquid melt obtained in (a) is circulated to the reaction zone ii in the second bubble lift reactor II, where the liquid melt is contacted with hydrogen chloride (HCl) at a temperature in the range from 395 to 405 C. so that water is formed, obtaining a liquid melt being enriched in chloride anions (Cl.sup.) compared to the liquid melt obtained according to (a); (c) circulating the liquid melt obtained in (b) to the reaction zone iii in the third bubble lift reactor III, which is operated at a temperature in the range from 420 to 430 C. so that chlorine (Ch) is formed, wherein Cl.sub.2 is removed from the reaction zone iii and the third bubble lift reactor III respectively in gaseous form, leaving a liquid melt depleted of Cl.sup. compared to the liquid melt obtained according to (b).

2. The process of claim 1, wherein the liquid melt depleted of Cl.sup. obtained in (c) is recirculated to (a).

3. The process of claim 1, wherein a liquid melt comprising copper ions Cu.sup.n+, alkali cations and chloride ions Cl.sup. with n being a number in the range from 1.5 to 2.0, is used as initial liquid melt at the start of the process and the process is started in step (c).

4. The process of claim 1, wherein the liquid melt comprising copper ions Cu.sup.n+, alkali cations and chloride ions Cl.sup. comprises as alkali cations one or more alkali cation(s) selected from the group of lithium cation, sodium cation and potassium cation.

5. The process of claim 4, wherein the one or more alkali cations comprise potassium cations.

6. The process of claim 4, wherein the liquid melt comprises Cu.sup.n+, potassium ions K.sup.+ and chloride ions Cl.sup. and is obtained or obtainable from a salt mixture having a molar ratio Cu.sup.n+:K.sup.+ in the range from 1:0.60 to 1:1.45.

7. The process of claim 6, wherein the salt mixture comprises Cu(II)Cl.sub.2 and KCl.

8. The process of claim 1, wherein (a), (b) and (c) are conducted in batch mode or continuously.

Description

SHORT DESCRIPTION OF FIGURES

(1) FIG. 1 shows the reactor system including three individual reactors I, II and III. In use, each reactor contained molten Cu salt species that circulate in the reactors continuously. Inlets and outlets for liquid melt and thus for melt circulation as well as the respective connection lines are indicated by arrows at the sides and between the reactors; gas inlets and gas outlets for gaseous components entering and leaving the reactors are indicated schematically at the bottoms and tops of the reactors. The reaction zones i, ii and iii in each reactor are not shown.

(2) FIG. 2 shows the build-up of all single reactors I, II and III in more detail, exemplarily for one reactor. The reactor design comprises three parts: main reactor (1), insert column (2), and an inlet tube (3) for delivering the gas-phase reagents in the reactor system. The main reactor (1) is equipped with a glass joint top with a gas inlet and a gas outlet for feeding and removing the gaseous reagents and products, as well as an inlet for liquid melt and an outlet for liquid melt (circulation). The insert column (2) separates the regions exposed to the gas bubbles, and lets the liquid flow back into the main reactor from the holes embedded on the top. The black arrows (.fwdarw.) in FIG. 2 show the melt direction in a single reactor, i.e. in a single bubble lift column. The dotted arrows indicate the direction of the gas flow.

(3) FIG. 3 shows a schematic top view of the reactor system, wherein the flow direction of the circulating melt is indicated by arrows.

(4) FIG. 4 shows a schematic side view of the reactor system, wherein the flow direction of the circulating melt is indicated by arrows. All three reactors I, II and III were placed in a heating medium system so that the top region of each reactor is embedded in the heating medium, wherein the outlets for liquid melt and at least a part of the connection lines are situated within the heating medium (4). All three reactors are further equipped with individual heating systems (F1, F2, F3), such as furnaces, so that a part of the bottom region of each reactor is surrounded by and in heat-transfer-contact with its individual heating system. As shown in FIG. 4, each individual heating system (F1, F2, F3) surrounds at least the part of each reactor's bottom region where the inlet for liquid melt is located. Preferably, for one reactor the outlet for liquid melt is situated between 5 to 10 mm higher than the outlets for liquid melt of the two remaining reactors in order to improve the flow between the reactors (not shown). The arrows at the top of each reactor indicate gas flow in and gas flow out.

(5) FIG. 5 shows the arrangement of the upper parts of the three bubble lift reactors in the heating mediumhere a sand bath. The top region of all three reactors are surrounded in the sand bath, so that the outlets for liquid melt and at least a part of the connection lines are within the sand bath. Heating bands (5) were wrapped in a large, horizontal triangle around the exterior of the connection lines and again in a smaller, horizontal triangle on the interior of the connecting line.

REFERENCE NUMBERS

(6) 1 main reactor 2 insert column 3 inlet tube 4 heating medium/sand bath 5 heating band(s) F1, F2, F3 individual heating systems/furnaces

CITED LITERATURE

(7) U.S. Pat. No. 2,418,930 Su S. et al., Ind. Eng. Chem. Res. 2018, 57, 7795-7801 Dissertation of Pavel Tokmakov: Untersuchung zur Chemie des Deacon-Prozesses in Salzschmelzen, 2018 U.S. Pat. No. 2,418,931 A