A sustainable valorization of neopentyl glycol salt waste containing sodium formate via bipolar membrane electrodialysis

Abstract

Neopentyl glycol (NPG) is an important organic compound that has numerous applications. The standard preparation route via the formate sodium method is cramped by the generation of a large amount salt waste and the high consumption of acid, base and water. In this study, a sustainable valorization of NPG waste salt was developed using bipolar membrane electrodialysis (BMED). This technique allowed the direct conversion of NPG waste salt into high value formic acid and soda, which could be used as raw feeds for upstream hydrogenation and neutralization processes. To verify the feasibility of BMED for neopentyl glycol production, effects of current density and feed salt concentration on the separation performance were investigated. The conversion rates of formate salt were almost 100% for all the experiments. Current efficiency decreased with an increase in current density and the energy consumption increased with an increase in current density. A lowest energy consumption of 6.08 kWh·kg−1 was obtained at the current density of 100 A·m−2. The BMED performances were enhanced when the feed salt concentration increased from 0.1 mol·L−1 to 0.4 mol·L−1, but the performance decreased when the feed concentration further increased to 0.5 mol·L−1. The total process cost of BMED process was estimated at $1.304·kg−1 HCOOH under the optimal experimental condition. By considering the benefit of recycled formic acid and soda, the total running cost was about -$115.5 for produce 1 tons of NPG. The revenue of recycled chemicals was greater than the total process cost of the BMED process. Naturally, BMED is a sustainable, cost-effective, environment friendly technology for the valorization of NPG salt waste.