Hydrodechlorination of 4-Chloro-2-Aminophenol into a Recyclable Product Using Ni- and Cu-Based Catalysts

Abstract

The 4-chloro-2-amino phenol (4C2AP) bearing wastewater is produced while manufacturing dyes and pharmaceutical ingredients. Ni-and Cu-based cost-effective catalysts were developed, typically characterized, and subjected to hydrodechlorination (HDC) of 4C2AP. The role of reducing agents, concentration, pH of wastewater, presence of salt, reaction temperature, catalyst reuse, and the kinetics was investigated. A selective makeover of 2-amino phenol (2AP) was analyzed by HPLC, LCMS, and NMR. A complete HDC of 4C2AP with remarkable selectivity (98%) toward 2AP was achieved using a Ni 0 catalyst and NaBH 4 at room temperature. It is observed that the alkaline condition, the presence of salt, and a high reaction temperature favor the HDC process. A maximum of 1 g L −1 of the Ni 0 loading is found to be sufficient to dechlorinate the pollutant. It can be concluded that the catalytic HDC is a technically viable and inexpensive process for the conversion of 4C2AP into a valuable product, 2AP.

Optimizing hydrothermal dechlorination of PVC in a SS-316 reactor: From chemistry knowledge to material considerations

“…Water is considered a weak oxidative agent at room temperature, but as its temperature and pressure rise, it gains more oxidizing strength. Accordingly, water is expected to act as a moderate nucleophile in the HTDC environment driving dechlorination via the OH substitution (S N 2) mechanism proposed by a multitude of researchers [24,36,38]. However, in stark contrast, CHN results show a merely opposite trend in the solid samples of the HTDC test in the present work, which prompted us to reconsider the mechanism through which water takes part in the HTDC of PVC (see Section 3.4 ).…”

“…It worsens when the chlorine leaks into an aqueous solution, forming hydrochloric acid. Thus, HTDC of PVC or any other Cl-containing organic moieties [24,25] inevitably involves corrosion, so the condition of the reactor wall must be monitored as precisely as the chlorine removal rate.…”

“…Regarding heterogeneous catalysts, the initial research focused on Pd-based catalysts supported primarily on well-known substrates such as Alumina [22]. Later, to replace the overpriced Pd particles, some catalysts based on Fe/Ni and copper were developed, with Ni being the most effective in the dechlorination of PVC liquid phase under mild conditions, such that after a significant reaction time (more than 5 h), all the chlorine is transferred into the aqueous product [23][24][25].…”

Catalytic dechlorination of 1,2-DCA in nano Cu0-borohydride system: effects of Cu0/Cun+ ratio, surface poisoning, and regeneration of Cu0 sites

“…They also act as successful coatings by providing stability to nanoparticle suspensions. Moreover, organic acids and alcohols can also be used as a H 2 source in catalytic reduction treatments 10 , 15 .…”