Study Of Recovery Of Acetic Acid From Furfural Wastewater And Furfural Production From Xylose Mother Liquor

Furfural, produced from hydrolysis of biomass, is an important chemical product and is widely used. The amount of furfural produced in our country is the largest in the world now. However, wastewater pollution and low furfural yield affect the consistent development of the whole furfural industry. The paper discusses these critical problems for furfural industry.Furfural wastewater, in which concentration of acetic acid is about 2%, can severely destroy environment if there is no treatment. Now a few factories have adopted biological treatment, which has some disadvantages such as high cost in the treatment and being incapable of recovering the acetic acid in furfural wastewater. Recovery of acetic acid in furfural wastewater will benefit our society both in environment and economy. In this paper, some high boiling point extractants were adopted for recovery of acetic acid from furfural wastewater. Firstly, the distribution ratio and viscosity of extractant with different compositions were determined in order to investigate the effects of composition of extractant on those parameters and decide on composition of extractant. Secondly, extraction experiments were done in impulse packed extractor with extractant of optimum composition and furfural wastewater from Tieling in Liaoning province (concentration of acetic acid 1.65%), Wuji in Hebei province (2.84%) and Xuanhua in Hebei province (1.43%).Effects of phase ratio, impulse time and pressure, and concentration of acetic acid in wastewater on extraction efficiency were investigated. It is concluded that, for furfural wastewater with different concentrations of acetic acid, the extraction efficiency can reach 99% when phase ratio is proper and impulse time and pressure is 3 s, 0.04MPa, respectively. Thirdly, in order to protect the extractant, batch vacuum distillation was selected to recover extractant for recycle. Acetic acid aqueous solution can be obtained from the top of the tower and the concentration of acetic acid is around 60%. In this paper two-stage process of furfural production was researched. Currently furfural factories in our country adopt one-stage process by sulfuric acid, which leads to low conversion around 50% and a mass of residues .What's more, the catalyst, sulfuric acid can not be recovered. In the two-stage process of furfural production, furfural yield can be increased by optimizing the reaction conditions of the second stage (dehydration of pentose to form furfural). And choosing acetic acid as catalyst can accomplish the recycle of acetic acid due to the recovery of acetic acid from furfural wastewater. In this paper, the mother liquor, which is a by-product in crystal xylose production, was chosen as feed and acetic acid as catalyst to study the effects of reaction time, temperature, concentration of acetic acid and concentration of pentose in xylose mother liquor on furfural yield. When the pentose concentration in mother liquor is 16.92%, the optimum furfural yield is 80.4% when reaction time, temperature, concentration of acetic acid is 375min, 180℃, 4.5%, respectively .