Experimental investigation of secondary reactions of intermediates in delayed coking

We report an experimental investigation of secondary reactions of intermediates in delayed coking. Thermal cracking reactions of intermediates, for example coker naphtha (C₅ ~180?°C), light coker gas oil (LCGO, 180?C350?°C), middle coker gas oil (MCGO, 350?C440?°C), and heavy coker gas oil (HCGO, >440?°C), were investigated. The results reveal that cracking of coker naphtha and LCGO is low under these experimental conditions. Thermal cracking MCGO exceeds that of LCGO. Among all the intermediates, thermal cracking is greatest for HCGO. The secondary reactions of HCGO produce not only gas and liquid products, but also coke. This increase in the yields of gas and coke is attributed to secondary reactions of HCGO and MCGO. Inhibition of the secondary reactions of intermediates results in a greater yield of liquid.     

AGET ATRP of water‐soluble PEGMA: Fast living radical polymerization mediated by iron catalyst

In this work, living radical polymerizations of a water‐soluble monomer poly(ethylene glycol) monomethyl ether methacylate (PEGMA) in bulk with low‐toxic iron catalyst system, including iron chloride hexahydrate and triphenylphosphine, were carried out successfully. Effect of reaction temperature and catalyst concentration on the polymerization of PEGMA was investigated. The polymerization kinetics showed the features of “living”/controlled radical polymerization. For example, M_n,GPC values of the resultant polymers increased linearly with monomer conversion. A faster polymerization of PEGMA could be obtained in the presence of a reducing agent Fe(0) wire or ascorbic acid. In the case of Fe(0) wire as the reducing agent, a monomer conversion of 80% was obtained in 80 min of reaction time at 90 °C, yielding a water‐soluble poly(PEGMA) with M_n = 65,500 g mol^?1 and M_w/M_n = 1.39. The features of “living”/controlled radical polymerization of PEGMA were verified by analysis of chain‐end and chain‐extension experiments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

The effect of phosphate buffer solutions on uniconazole complexation with hydroxypropyl-β-cyclodextrin and methyl-β-cyclodextrin

The inclusion complexes of uniconazole [(E)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-lyl)-1-penten-3-ol, UCZ] with two cyclodextrin derivatives, hydroxypropyl-β-cyclodextrin (HP-β-CD) and methylated-β-cyclodextrin (Me-β-CD), were prepared and characterized by ¹H NMR and FT-IR. The phase solubility of UCZ and HP-β-CD, UCZ and Me-β-CD, which displays the ability of CDs complexation and solubilization, was studied in aqueous solutions and phosphate buffer solutions (PBS) with different property pH values (6.2, 7.2, 8.0). The solubility results indicated that the pH of PBS showed more enhancement on the interaction of HP-β-CD and UCZ than Me-β-CD with the increasing pH value, and the optimal pH value for complexation of UCZ and HP-β-CD, UCZ and Me-β-CD was at 8.0 and at 7.2, respectively. These were also determined by UCZ release behavior and dissolution studies of the complexes in solid state.     

Fabrication of a sol–gel derived microporous zirconia membrane for nanofiltration

This paper reports the fabrication and nanofiltration properties of a sol–gel derived microporous zirconia membrane. Effects of synthesis parameters, including hydrolysis time, hydrolysis temperature, hydrolysis ratio and chelating agent dopant, on the state and size of polymeric zirconia sol, were investigated. Highly reproducible and stable zirconia sol after refluxing at 40 °C for 180 min, with an average particle size of approximately 8.6 nm, was synthesized with a recipe of [Zirconium n-propoxide]: [Diethanolamine]: [1-propanol]: [H₂O] being 1: 2.2: 28.7: 9.4 (in molar ratio). The sol was subsequently used for the fabrication of microporous ZrO₂ membranes onto alumina supported mesoporous γ-Al₂O₃ layers. ZrO₂ membranes with molecular weight cut-off (MWCO) of 354, 1,195, corresponding to the pore size of 0.94 and 1.75 nm, were successfully fabricated. Ionic retention properties of such ZrO₂ membranes with respect to electrolyte solutions, like MgCl₂, CaCl₂, NaCl and Na₂SO₄, were also determined. Effects of parameters such as concentration of salt solutions and trans-membrane pressure on retention rates of microporous ZrO₂ membranes were studied in detail. Results showed that zirconium n-propoxide derived microporous ZrO₂ membranes exhibited comparatively high retention rates towards divalent ions like Mg²⁺ and Ca²⁺, while much lower retention rates were observed for mono-valent ion (Na⁺) in the present study, which are the characteristics of nanofiltration membranes.     

Tuner design and RF test of a four-rod RFQ

A mini-vane four-rod radio frequency quadruple (RFQ) accelerator has been built for neutron imaging. The RFQ will operate at 201.5 MHz, and its length is 2.7 m. The original electric field distribution along the electrodes is not flat. The resonant frequency needs to be tuned to the operating value. And the frequency needs to be compensated for temperature change during high power RF test and beam test. As tuning such a RFQ is difficult, plate tuners and stick tuners are designed. This paper will present the tuners design, the tuning procedure, and the RF properties of the RFQ.