Decomposition of Carbon Tetrachloride and Mono-Chlorobenzen by Using Basic Molten Salts

Abstract

The decomposition of simple organic chlorides (carbon tetrachloride, CCl 4 and mono-chlorobenzen, C 6 H 5 Cl) as the imitation substances of polychlorobiphenyls (PCBs) were investigated by using basic molten salts with a low melting point and oxidizing ability in order to establish a safe, simple and highly efficient decomposition process. CCl 4 or C 6 H 5 Cl was injected together with an inert carrier gas (Ar) into basic molten salts (KOH-K 2 CO 3 ) at 673-983 K, and the residual concentration in the exhaust was measured. The decomposition efficiency of CCl 4 strongly depended on the reaction temperature and the immersion depth of gas injection nozzle (related to the residence time of CCl 4 bubble in the molten salts). The decomposition efficiency reached to very high of 99.9% with KOH-20 mol% K 2 CO 3 at 973 K. On the other hand, the decomposition efficiency of C 6 H 5 Cl was not so high (97%) in the inert atmosphere condition applied in this study.

Mineralization of poly(tetrafluoroethylene) and other fluoropolymers using molten sodium hydroxide

“…It is also possible that the oxide ion reacts with the small molecules generated from the thermal degradation of PTFE to promote the formation of F − and CO 2 . It has also been found that molten MOH is a particularly effective agent for the decomposition of small organic compounds containing halogen or sulfur, such as CCl 4 , 27 chlorobenzene, 28 coal, 29 and even hazardous mixed organic waste. 30 Thus, as shown in eqn (6), if our system progresses ideally, PTFE can be processed without the generation of exhaust gases and can be efficiently mineralized.…”

“…For example, while hydroxide melts are believed to be fully dissociated, the formation of a "quasi-crystalline state" has also been described, in which a degree of order exists within the melt and dissociation is not complete. 27 Thus, at present, we do not have sufficient experimental evidence to understand the difference between the reactivities of molten NaOH and molten KOH toward PTFE. We recognize that this is an important subject to be addressed in the near future.…”

“…If the reaction proceeds to completion in a homogeneous aqueous solution, it is reasonable to assume that these results can be attributed to the different reactivities of the alkali metal hydroxides. Since the ionic radius of K + is larger than that of Na + , KOH is expected to be a stronger base and nucleophile than NaOH, 27 and the increased basicity and nucleophilicity could be expected to increase the reactivity of KOH. However, our reaction system is not aqueous, but is instead in the molten state.…”

Characteristics of Molten Salt Gasification of Waste PVC

“…Acidic gases such as HX and SO 2 are absorbed and neutralized by the molten salt, reducing the need for off-gas desulphurization and deacidification equipment [27]. The absence of chlorine in the exhaust gas inhibits the synthesis reaction of PCDD/F, leading to the decomposition and destruction of dioxin precursors in the molten salt, thereby eliminating the precursor synthesis pathway of PCDD/F [28,29]. Last but not least, molten salt has a high heat capacity, which helps to minimize the impact of temperature and feed fluctuations on the reaction process due to the thermally stable environment provided by the salt bath [30].…”

Decomposition Process for Polychlorobiphenyls by Means of Basic Molten Salts

“…[10][11][12][13][14] The advantages of utilization of molten salts are summarized as follows: (1) no dioxins are formed due to gas/liquid separation, and only simple harmless products (CO 2 and H 2 O) are emitted; (2) operation temperature is considerably lower than that in the conventional incineration, and the temperature control is easy because of the reaction in condensed phase; (3) decomposition treatment is carried out under atmospheric pressure; (4) handling of chlorine absorber (molten salts) is easy. The authors have studied the decomposition of carbontet-© 2012 ISIJ rachloride (CCl4) 3) and mono-, di-and tri-chlorobenzens 4) as a simple chlorinated organic compound prior to the decomposition of PCBs. As the results, CCl4 was destructed at high decomposition efficiency over 99.9% at relatively low temperature (673-973 K) without oxygen.…”