Yangcheng Lu

Absorption and desorption of gaseous toluene by an absorbent microcapsules column.

Heavy solvents absorption appears to be very attractive in recovering of volatile organic compounds (VOCs) from industrial tail gas. Their high viscosities make good dispersion required but difficult to reduce mass transfer resistance. Microencapsulation techniques provide a candidate solution. In this paper, vapor pressures for toluene+poly(dimethylsiloxane) (PDMS) mixtures were measured at temperature ranging from 273.2K to 343.2K. Polyacrylonitrile (PAN) hollow microspheres, prepared by orifice dispersion plus solvent extraction method, was used to immobilize PDMS. The capacity was adjusted from 2.3g to 9.3g PDMS/g PAN by addition of cyclohexane in PDMS during solvent impregnation. The breakthrough curves of column packed with PDMS/PAN microcapsules were determined, indicating shapes close to ideality, high absorption efficiencies and considerable absorption capacities before breakthrough. The influence of operational temperature, concentration of feed and gas feed flow rate on the absorption process were investigated as well. A mathematical model, suitable for dilute gas absorption process, was used to simulate the breakthrough curves. This model has proved to be useful to fit curves and analyze the absorption kinetics of PDMS/PAN microcapsules column. After absorption, the column can be regenerated completely by gas stripping. Enrichment of toluene was founded by increasing desorption temperature. Through absorption and desorption by turns, the stability of PDMS/PAN microcapsules column was verified.

Synthesis of single-crystal dendritic iron hydroxyl phosphate as a Fenton catalyst

In this work, the single-crystal dendritic iron hydroxyl phosphate is synthesized via a facile and well-controlled hydrothermal process without any additional surfactant or template. The morphology of the product at various scales is characterized by scanning electron microscopy and transmission electron microscopy. The phase and crystal structure is determined and carefully confirmed by using X-ray powder diffraction, high resolution transmission electron microscopy and selected area electron diffraction combined with thermal analysis comprehensively. A reasonable self-template route, as well as the precipitation–dissolution–recrystallization process is revealed according to the time dependence of morphology, crystal structure, zeta potential and precipitate amount. Finally, the single-crystal dendrite is tested as a Fenton catalyst for the degradation of phenol, a typical advanced oxidation process (AOP). Attributed to the perfect crystal structure and the hierarchical architecture, this novel catalyst presents numerous advantages including remarkable catalytic activity over a wide pH range (e.g., pH = 3–8), outstanding cycle performance (no observation of activity loss in five runs), and extremely low leaching iron concentration (below 0.5 mg L−1).

Micromixing enhanced synthesis of HRPIBs catalyzed by EADC/bis(2-chloroethyl)ether complex

In this work, a micromixing module was utilized in the polymerization of isobutylene (IB) initiated by tert-butyl chloride (t-BuCl) and catalyzed by ethylaluminum dichloride (EADC)/bis(2-chloroethyl)ether (CEE) complex for the synthesis of highly reactive polyisobutylene (HRPIB). Better micromixing performance resulted in HRPIB with narrower molecular weight distribution, where the PDI could be decreased from 3.5 without micromixing module to 2.5 or less. The polymerization rate also increased while the molecular weight and content of exo-olefin end groups of HRPIBs could be adjusted conveniently by the ratio of CEE to EADC and monomer concentration. A dynamic mechanism was proposed to explain the effects of micromixing on the enhanced HRPIB synthesis.

Back Extraction of HCl from TOA Dissolved in N-Octanol by Aqueous Ammonia in a Microchannel Device

Abstract To recover the extractant in the preparation of KH2PO4 using the extraction method, studies for the back extraction of HCl by aqueous ammonia from TOA (trioctylamine) dissolved in n-octanol were conducted. First, the reaction of HCl back extraction from TOA in n-octanol with aqueous ammonia was examined in shaking flasks and the equilibrium of this reaction was validated. The equilibrium constant of the stripping reaction was determined in the temperature range of 297.7-318.2 K and the reaction enthalpy was found to be -17.8 kJ/mol indicating that the stripping reaction was exothermic. Then kinetic experiments were performed in a microchannel device with the elimination of mass transfer limitations, as demonstrated by the experimental results. A kinetic model was established to obtain the forward and backward interfacial reaction rate constants with the help of the obtained equilibrium constant of the stripping reaction. This model described the measured data well and predicted correctly the change of HCl concentration in the oil phase along with the residence time in our experiments. Furthermore, the activation energy for the forward (8.21 kJ/mol) and backward (26.0 kJ/mol) reaction was determined and subsequently the forward and backward interfacial reaction rate constants were determined in the temperature range of 298.7-313.2 K.

Continuous Removal of Lead from Aqueous Solutions by Ca(II) Imprinted Chitosan Microspheres Packed Column

The continuous removal of lead from aqueous solutions by Ca(II) imprinted chitosan (Ca(II)-CS) microspheres packed column is carefully investigated in this work. The modified dose-response model and the Thomas model are exploited to evaluate dynamic behaviors of breakthrough curves. The results show 0.257 min of space time is enough for a Ca(II) imprinted chitosan microspheres packed column to realize deep purification of water containing Pb(II). The Thomas rate constants are higher than 3 mL min-1 mg-1. The Modified dose-response model is feasible to predict the breakthrough curve. The reusability is confirmed during a multi-cycle adsorption-desorption process.

Cationic polymerization of isobutylene catalysed by AlCl3 with multiple nucleophilic reagents

In this work, by exploiting the perfect performances of microflow reactors in mixing and residence time control, we systematically investigated the cationic polymerization of isobutylene (IB) catalysed by AlCl3 with multiple nucleophilic reagents, isopropyl ether (iPr2O) and ethyl benzoate (EB). Through properly introducing iPr2O and EB, the polymerization of IB could produce PIBs with a narrow molecular weight distribution (PDI 40 000 g mol−1), and a high content of exo-olefin (w > 70%) at relatively high temperatures (−30 °C), during which most of the monomer conversion (>70%) could be fulfilled within 0.5 s and the chain scission mainly takes place after seconds. The expression [2[EB] + [iPr2O]]/[AlCl3] being equal to 1 is recognized as a quantitative criterion for achieving these outcomes, corresponding to H+iPr2OAlCl3(OH)− initiating polymerization with inhibited chain transfer by introducing EB(AlCl3)n, but eliminating free AlCl3. Increasing the flow capacity in a certain microflow system provides the potential to increase the molecular weight further and facilely tailor it for particular applications. This work verifies the various functions of multiple nucleophilic reagents and their ability to break the trade-off of conversion rate and propagation chain stability in cationic polymerization and develop new functional products of PIBs.

Effects of Ether on the Cationic Polymerization of Isobutylene Catalyzed by AlCl3

In this work, we prepared different initiator solutions containing ether and AlCl3 by changing the addition sequence of ingredients, studied the interactions between ether and AlCl3 from the evolution of the Fourier transform infrared (FTIR) spectra by comparison, and investigated the catalytic performances of AlCl3 affected by ether for isobutylene polymerization. We observed that different preparation methods of initiator solutions could lead to two kinds of interactions between ether and H2O/AlCl3 in hexane. The strong interaction could stabilize carbenium ions and seriously decrease the catalytic performance, whereas the weak interaction could promote isomerization and proton elimination. Moreover, we found that the preparation method of initiator solutions was not a critical factor in CH2Cl2. Finally, a universal mechanism based on the AlCl3-involved interactions in different solvents was proposed to understand the effects of ether on the cationic polymerization catalyzed by AlCl3 thoroughly.