Application Of Boron Affinitv Technology In The Separation Of Bio-based 1,2,4-butanetriol

1,2,4-Butanetriol(BT)is an important bulk chemical with high value,which is widely applied in many fields,such as medicine,materials,daily chemicals,energy,and other fields.Compared with the traditional chemical synthesis method to produce BT,the biological fermentation method has the advantages of mild reaction conditions,low cost,and environmental protection.However,the lack of efficient,green,and economical separation and purification researches has become the main factor restricting the large-scale industrial production and utilization of BT.Boron affinity separation is an efficient technology for separating bio-based chemicals.The process of separating hydrophilic BT in fermentation broth based on the boron affinity has not been reported yet.This dissertation takes the separation and purification of BT in the fermentation broth as the starting point,a boron affinity separation system was established,the mechanism of the boron affinity was studied,the two processes of the reactive extraction and solid-phase extraction based on boron affinity was developed,the separation parameters were optimized,and the feasibility of the two processes was analyzed.Firstly,the mechanism of the boron affinity was studied by fluorescence spectroscopy and quantum chemistry calculations.Through the analysis of the binding constant,thermodynamic function,and weak intramolecular interaction,it was concluded that:(1)Compared with butanediol,ionized phenylboronic acid(PBA)was easier to bind with BT,and the boron affinity was an exothermic reaction,which can proceed spontaneously at room temperature;(2)The boronic acid group preferentially recognizes the ortho-dihydroxy group under alkaline conditions and preferentially recognizes the meta-dihydroxy group under acidic conditions;(3)The ionized PBA and BT have a larger binding constant under alkaline conditions,ranging from 4.4 M-1 under neutral conditions to 7.2 M-1 under alkaline conditions.Based on the reaction mechanism of PBA and BT,a new type of reactive extraction system suitable for BT separation in the simulated solution was constructed.The influence of diluent,extractant,co-extractant,BT concentration,solution pH,and coexisting impurities on the reactive extraction were studied.The extractant and co-extractant have a significant effect on the reactive extraction efficiency.A reactive extraction system with dichloromethane as diluent,4-Biphenylboronic acid(4-BiPBA)as the extractant,and Aliquat(?)336(A336)as the co-extractant were determined.The reactive extraction efficiency for the BT solution with a concentration of 30 g/L reached 87.4%after optimizing the separation parameters.Secondly,the optimized parameters were applied to the fermentation broth.To eliminate the influence of soluble impurities in the fermentation broth on the reactive extraction efficiency,the effects of pretreatment methods on deproteinization and decolorization were investigated.It was determined that the activated carbon adsorption and isoelectric point precipitation method were used to pretreat the fermentation broth,and the protein removal efficiency and decolorization efficiency were 90.8%and 93.3%,respectively.The pretreated fermentation broth was used to separate BT by reactive extraction,and the extraction efficiency was 90.9%.BT was stripped with the hydrochloric acid(HCl)solution.After the extractant and diluent were recycled five times,the reactive extraction efficiency and the concentration of BT after stripping stabilized at 50.0%and 85.9 g/L,and the purity of BT reached 93.1%.Finally,in order to avoid the loss of the extractant,avoid the use of A336 and high-concentration hydrochloric acid,and simplify the separation steps.The extractant was synthesized through Friedel-Crafts reaction to synthesize a boron affinity super-crosslinked solid-phase extraction adsorbent(HCP)with high specific surface area,rich in micropores and mesopores,which was used for solid-phase extraction to separate BT in solution.The effects of pH,metal cations,coexisting impurities,temperature,and other factors on the adsorption performance were studied,and the adsorption mechanism was analyzed by X-ray photoelectron spectroscopy(XPS).The adsorption isotherm and kinetic experiments show that the adsorption process belongs to monolayer adsorption,and the adsorption kinetics belongs to the pseudo-second-order model.The maximum adsorption capacity calculated by the fitting results was 148.2 mg/g.Through multiple cycles of adsorption and desorption experiments,HCP could maintain a high adsorption capacity(102.0 mg/g),indicating that HCP has a good recycling performance.Comparing the two boron affinity separation processes,the boron affinity solid-phase extraction avoids the loss of extractant,does not need A336 and high-concentration hydrochloric acid.BT can be separated and recovered through column penetration adsorption,alcohol desorption,and distillation.The boron affinity solid-phase extraction is expected to realize the separation of BT in fermentation broth in an efficient way.