The Rise of Trichlorides Enabling an Improved Chlorine Technology

Abstract

Chlorine plays a central role for the industrial production of numerous materials with global relevance. More recently, polychlorides have been evolved from an area of academic interest to a research topic with enormous industrial potential. In this minireview, the value of trichlorides for chlorine storage and chlorination reactions are outlined. Particularly, the inexpensive ionic liquid [NEt 3 Me][Cl 3 ] shows a similar and sometimes even advantageous reactivity compared to chlorine gas, while offering a superior safety profile. Used as a chlorine storage, [NEt 3 Me][Cl 3 ] could help to overcome the current limitations of storing and transporting chlorine in larger quantities. Thus, trichlorides could become a key technique for the flexibilization of the chlorine production enabling an exploitation of renewable, yet fluctuating, electrical energy. As the loaded storage, [NEt 3 Me][Cl 3 ], is a proven chlorination reagent, it could directly be employed for downstream processes, paving the path to a more practical and safer chlorine industry.

Polychlorides─A Safe and Convenient Alternative for Elemental Chlorine in Demonstration Experiments

“…of the electricity consumed in Germany is used for chlor-alkali electrolysis. 2 Thus, a "technical problem" like chlorine storage has serious implications for sustainability. TEMACl 3 is an ionic liquid, which minimizes the risk of uncontrolled release of toxic gases from leaks during transportation and storage (see Figure 1).…”

“…Riedel and co-workers have recently established that alkylammonium trichlorides could be a promising solution. 2,13 In particular, the commercially available triethylmethylammonium chloride [NEt 3 Me]Cl was found to be a suitable chlorine storage material, which forms the demonstrated that the trichloride [NEt 3 Me][Cl 3 ] shows a similar reactivity as elemental chlorine. However, it is an ionic liquid with a low chlorine vapor pressure (0.9 bar at 20 °C) that is safe and easy to handle.…”

“…However, it is an ionic liquid with a low chlorine vapor pressure (0.9 bar at 20 °C) that is safe and easy to handle. 2 For demonstration experiments in chemistry education, chlorine is often directly produced, e.g., by the comproportionation reaction of hydrogen chloride and hypochlorites. 14 The ionic liquid [NEt 3 Me][Cl 3 ] could be another, modern option to facilitate safe handling of chlorine.…”

“…Chlorine plays a significant role in both the chemical industry and chemistry education. Approximately 55% of all industrial chemicals are estimated to be dependent on chlorine chemistry. , In 2022, 97 million tons of chlorine were produced worldwide, with the mass of elemental chlorine serving as an indicator of a country’s chemical industry development . Chlorine is commonly used to represent the halogen group in many high school chemistry curricula, especially in relation to the properties and reactivity of the respective Group 17 elements, such as oxidation reactions. − …”

“…Thus, a safer alternative for the transport and storage of chlorine is necessary. Riedel and co-workers have recently established that alkylammonium trichlorides could be a promising solution. , In particular, the commercially available triethylmethylammonium chloride [NEt 3 Me]Cl was found to be a suitable chlorine storage material, which forms the corresponding trichloride [NEt 3 Me]­[Cl 3 ] when exposed to an atmosphere of chlorine gas. In recent work, it could be demonstrated that the trichloride [NEt 3 Me]­[Cl 3 ] shows a similar reactivity as elemental chlorine.…”