Synthesis of 3-methyl-3-buten-1-ol by supercritical CO2 in coordination with HZSM-5-catalyzed formaldehyde-isobutene Prins reaction.

The reaction solvent and catalyst play essential roles in the Prins reaction for the synthesis of 3-methyl-3-buten-1-ol (MBO) from formaldehyde and isobutene. The reactivity of the solid base-catalyzed Prins condensation reaction by formaldehyde and isobutene in supercritical CO2 was investigated using CsH2PO4-modified HZSM-5. We found that the alkaline sites of the alkali-loaded catalyst could extract the α-H on isobutene to generate olefin carbon-negative ions, while the supercritical CO2 with weak Lewis acidity could activate formaldehyde to carbon-positive ions, which can combine more easily with carbon-negative isobutene to react, thus improving the reactivity of the reaction system.

Mechanism of NCNTs Growth on Foamed Nickel and Thus-Prepared PS Hydrogenation High-Performance Carrier NCNTs@FN.

Traditional heterogeneous catalysts are affected in the catalytic hydrogenation of PS by the scale effect, viscosity effect, adhesion effect, and conformational effect, resulting in poor activity and stability. Monolithic Pd-CNTs@FN catalysts could eliminate or weaken the impact of these negative effects. We grew nitrogen-doped carbon nanotubes (NCNTs) on monolithic-foamed nickel (FN) and investigate their growth mechanism. Meanwhile, the feasibility of using the NCNTs@FN carrier for PS hydrogenation reaction was also verified. The growth of NCNTs on FN can be divided into 3 stages: initial growth stage, stable growth stage, and supersaturation stage. Finally, a three-layer structure of NCNT layer, dense carbon layer, and FN skeleton is formed. Two types of structures, nickel-doped carbon nanotubes (NiCNTs) and C-Ni alloy, are formed by combining C and Ni, while four nitrogen-doped structures, NPD, NPR, NG, and NO, are formed by C and N. The prepared carrier exhibited an extremely outstanding specific surface area (2.829 × 106 cm2/g) and strength (no NCNTs falling off after 24 h 500 rpm agitation), as well as high catalytic activity for PS hydrogenation after loaded with Pd (2.13 ± 0.95 nm), with a TOF of up to 27.6 gPS/(gPd•h). After 8 repetitions of the catalyst, there was no significant decrease in activity. This proves the excellent performance of Pd-NCNTs@FN in polymer hydrogenation reactions, laying a solid foundation for further research on the mechanism of NCNTs promoting PS hydrogenation and regulating the growth of NCNTs.

Intensification and Optimization of FAME Synthesis via Acid-Catalyzed Esterification Using Central Composite Design (CCD).

The acid-catalyzed pre-treatment esterification process is required for low-cost feedstock with high free fatty acids (FFAs) to avoid the saponification that occurs during alkali-catalyzed transesterification for the production of fatty acid alkyl esters (FAAE). Reverse hydrolysis in acid-catalyzed esterification causes a decrease in fatty acid methyl ester (FAME) yield. Therefore, the esterification process must be intensified. This study aims to develop and optimize a low-temperature intensification process to enhance biodiesel yield and reduce energy consumption. Three intensification systems were studied: co-solvent technique, co-solvent coupled with adsorption of water using molecular sieves, and entrainer-based continuous removal of water. The process variables of esterification reaction in co-solvents without the adsorption system were optimized by using central composite design (CCD). The study showed that the co-solvent without the adsorption system was effective in intensifying the FFA conversion (XFFA) at low temperatures, compared to the other two systems, due to the dilution effect at high co-solvent/entrainer amount required for sufficient vapors in the adsorption system. Optimized process variables have achieved 95% XFFA within 75 min at 55 °C, 20 mL/100 g of oil DEE, 9 MR, 3 wt % H2SO4, and 320-350 RPM in a co-solvent without the adsorption system.

Microenvironment Modulation of Metal-Organic Frameworks (MOFs) for Coordination Olefin Oligomerization and (co)Polymerization.

The majority of commercial polyolefins are produced by coordination polymerization using early or late transition metal catalysts. Molecular catalysts containing these transition metals (Ti, Zr, Cr, Ni, and Fe, etc.) are loaded on supports for controlled polymerization behavior and polymer morphology in slurry or gas phase processes. Within the last few years, metal-organic frameworks (MOFs), a class of unique porous crystalline materials constructed from metal ions/clusters and organic ligands, have been designed and utilized as excellent supports for heterogeneous polymerization catalysis whose high density and uniform distribution of active sites would benefit the modulations of molecular weight distributions of high-performance olefin oligomers and (co)polymers. Impressive efforts have been made to modulate the microenvironment surrounding the active centers at the atomic level for improved activities of MOFs-based catalysts and controlled selectivity of olefin insertion. This review aims to draw a comprehensive picture of MOFs for coordination olefin oligomerization and (co)polymerization in the past decades with respect to different transition metal active centers, various incorporation sites, and finally microenvironment modulation. In consideration of more efforts are needed to overcome challenges for further industrial and commercial application, a brief outlook is provided.

[Acupoint injection combined with Vitalstim electrical stimulation for post-stroke dysphagia:a randomized controlled trial].

OBJECTIVE: To observe the clinical efficacy of acupoint injection combined with Vitalstim electrical stimulation for post-stroke dysphagia. METHODS: A total of 98 patients with dysphagia after first stroke were randomized into an acupoint injection group (35 cases, 2 cases dropped off), an electrical stimulation group (31 cases, 3 cases dropped off) and a combination group (32 cases, 3 cases dropped off). Injection of mecobalamin into Tunyan point, Vitalstim electrical stimulation and the combination of injection of mecobalamin into Tunyan point and Vitalstim electrical stimulation were applied respectively in the 3 groups, once a day, 10 times as one course, 2 courses were required. Before and after treatment, the tongue muscle thickness and video fluoroscopic swallowing study (VFSS) score were observed in the 3 groups. RESULTS: After treatment, the tongue muscle thickness was decreased (P<0.05), the VFSS scores were increased (P<0.05) compared with before treatment in the 3 groups, and the variation of tongue muscle thickness and VFSS score in the combination group was greater than the acupoint injection group and the electrical stimulation group (P<0.05). CONCLUSION: Both acupoint injection of mecobalamin and Vitalstim electrical stimulation have therapeutic effect on dysphagia after stroke, and the two have synergistic effect.

Simple and sensitive determination of trace nitrite in water by zero-crossing first-derivative synchronous fluorescence spectrometry using 6-amino-1,3- naphthalenedisulfonic acid as a new fluorescent probe.

A new fluorescent probe, 6-amino-1,3-naphthalenedisulfonic acid (ANDSA), has been developed for the determination of trace nitrite in different waters. This probe is based on the selective reaction of nitrite with ANDSA in hydrochloric acid solution to form the corresponding diazonium acid in sodium hydroxide solution at room temperature. The diazonium acid produced has high fluorescence intensity at 488 nm (excitation at 367 nm), whereas ANDSA has high fluorescence intensity at 465 nm (excitation at 354 nm). The synchronous fluorescence (Δλ = 121 nm) spectrum and the first-derivative synchronous fluorescence spectrum of diazonium acid greatly overlapped with those of ANDSA. The zero-crossing method was used to measure the first-derivative value (dF/dλ) of the first-derivative spectra, in which physical separation of excess ANDSA was unnecessary. The zero-crossing point was located at 351.2 nm for ANDSA, at which dF/dλ of diazonium acid was proportional to the nitrite concentration. Therefore, dF/dλ at 351.2 nm was selected as the analytical signal. Under the optimized experimental conditions, the signal intensity was linear over a nitrite concentration range of 0.006-0.075 mg L-1, with a correlation coefficient better than 0.9994. The limit of detection was 2.1 µg L-1 for the determination of nitrite by the proposed method. The relative standard deviation of the method for the determination of nitrite in real water samples was below 2.45%, and the corresponding recoveries were between 95.7% and 104.1%. The validity of the proposed method was further confirmed by comparison with the reference method with use of the t test. Graphical abstract ANDSA reacts with nitrite to form diazonium acid with higher fluorescence intensity. For ANDSA, dF/dλ was zero at 351.2 nm, whereas dF/dλ of diazonium acid at 351.2 nm was close to the maximum value.

[Post-stroke dysphagia treated with acupoint injection combined with neural electrical stimulation].

OBJECTIVE: To observe the effect differences on post-stroke dysphagia among acupoint injection combined with neural electrical stimulation, acupoint injection, neural electrical stimulation, and swallowing training respectively, so eligible intervention can be applied to this kind of disease. METHODS: One hundred and eight-three patients of post-stroke dysphagia were randomized into a comprehensive treatment group (42 cases), an acupoint injection group (44 cases), a neural electrical stimulation group (49 cases) and a swallow training group (48 cases) and were treated with the comprehensive therapy of acupoint injection and neural electrical stimulation, acupoint injection, neural electrical stimulation and swallowing training separately. The treatments for 10 days made one session. There were 3 days at the interval among treatment sessions and 3 sessions were required totally. The cases in those treatment groups were blankly controlled with the other 47 patients of post-stroke dysphagia. All the patients received basic rehabilitation treatment. The modified water swallowing test was conducted to assess the efficacy before treatment, 10 days after treatment and 30 days after treatment in each group separately. The clinical efficacy, score of water swallowing test and improvement in water swallow test were compared among the groups. RESULTS: After 10-day treatment, the differences in efficacy and score of water swallow test were not significant in each group (all P > 0.05). After 30-day treatment, the effective rate (94.29%, 33/35) in the comprehensive treatment group was apparently better than 68.75% (22/32) in the acupoint injection group, 80.00% (32/40) in the neural electrical stimulation group, 67.50% (27/40) in the swallowing training group and 42.86% (12/28) in the blank group separately. The score in water swallow test in the comprehensive treatment group was lower than that in each of the other groups (1.37 ± 0.60 vs 2.03 ± 1.00, 1.90 ± 0.90, 2.20 ± 0.72, 2.71 ± 0.90, all P < 0.05). The differences in the effective rate and score in water swallow test were not significant among the acupoint injection group, neural electrical stimulation group and swallowing training group (all P > 0.05), which indicated that the improvement in swallowing function in the comprehensive treatment group was significantly superior to the other groups (all P < 0.05). CONCLUSION: The comprehensive therapy of acupoint injection and neural electrical stimulation achieves the much better efficacy on post-stroke dysphagia.

Study of the anomalous sorption behavior of CO2 into poly(methyl methacrylate) films in the vicinity of the critical pressure and temperature using a quartz crystal microbalance (QCM).

The anomalous solubility maximum of CO2 in polymer thin films in the vicinity of the critical temperature and pressure has not yet been clearly understood when the quartz crystal microbalance (QCM) technique has been used to determine the micromass change. In this study, the adsorption of CO2 on the surface of bare polished and unpolished crystals at different pressures and temperatures was investigated using the QCM technique to illustrate why a plot of the true frequency shift as a function of temperature and pressure can intuitively exhibit the adsorption behavior of CO2 on bare crystals. The sorption of CO2 into a PMMA film at different temperatures, pressures, and PMMA film thicknesses was also investigated. An accurate solubility for CO2 in the PMMA film could be obtained by an improved data correction method from the linear relation between the true frequency shift and the polymer film mass, and the anomalous solubility maximum could be corrected by this method. The mechanism of nonabsorbed CO2 transitorily staying in the interspace between the PMMA film and the crystal surface can be explained by the morphology change of the PMMA film. The assumption of "passerby CO2" was satisfactorily confirmed to explain the anomalous sorption behavior of CO2 into PMMA films in the vicinity of the CO2 critical temperature and pressure, and this assumption could be valid for other CO2-polymer thin film systems.

Simple and sensitive synchronous- fluorescence method for the determination of trace bisphenol S based on its inhibitory effect on the fluorescence quenching reaction of rhodamine B.

An inhibitory kinetic fluorimetric method is reported for the determination of trace bisphenol S (BPS). The proposed method is based on the inhibitory effect of BPS on the fluorescence quenching of rhodamine B (RhB) caused by potassium bromate in a dilute phosphoric acid medium. Under the optimal conditions of the experiment, the detection limit for BPS was 0.021 mg/L, and the linear range of determination was from 0.035 mg/L to 0.750 mg/L. The relative standard deviations of 11 measurements for 0.20 mg/L and 0.40 mg/L BPS solutions were 2.74 % and 1.87 %, respectively. The method was successfully applied to the determination of bisphenol S derived from commercially available plastic film samples in hot water. A possible reaction mechanism of the inhibitory effect of BPS on the fluorescence quenching of RhB was proposed.

[Study on effect of oil-bearing solution environment of Caryophylli Flos and other traditional Chinese medicines on system flux and oil recovery rate].

The membrane enrichment process of traditional Chinese medicine volatile oil is environmental friendly and practical, with a good application prospect. In this article, oil-bearing solutions of eight traditional Chinese medicines, namely Caryophylli Flos, Schizonepetae Herba, Eupatorii Herb, Acori Talarinowii Rhizoma, Magnoliae Flos, Chrysanthemum indicum, Cyperi Rhizoma and Citri Reticulatae Pericarpium Viride, were taken as the experimental system. Under unified conditions (membrane: PVDF-14W, temperature: 40 degreeC, pressure: 0. 1 MPa, membrane surface speed: 150 r min- 1), trans-membrane was conducted for above eight oil-bearing solutions to explore the effect of their oil-bearing solution environment on system flux and oil recovery rate. The results showed that systems with smaller pH had a lower flux, without significant effect on oil recovery rate. Greater differences between the surface tension of solutions and that of pure water contributed to a lower oil recovery rate. The conductivity had no notable effect on membrane enrichment process. Systems with high turbidity had a lower flux, without remarkable effect on oil recovery rat. Heavy oils showed lower flux than light ones, but with a slightly higher oil recovery rat. Systems with higher viscosity had a lower flux than those with lower viscosity. Except for Magnoliae Flos volatile oil, all of the remaining volatile oils showed a much higher oil recovery rat than systems with high viscosity. The above results could provide data support and theoretical basis for the industrialization of membrane enrichment volatile oil technology.

Introduction of ß-cyclodextrin into poly(aspartic acid) matrix for adsorption and time-release of ibuprofen.

Biodegradable copolymers with molecule inclusion ability was prepared by introduction of ß-cyclodextrin into poly(aspartic acid) matrices. The ibuprofen loading and dissolution properties of poly(aspartic acid)-ß-cyclodextrin were investigated.

Shape complexity and fractality of fracture surfaces of swelled isotactic polypropylene with supercritical carbon dioxide.

We have investigated the fractal characteristics and shape complexity of the fracture surfaces of swelled isotactic polypropylene Y1600 in supercritical carbon dioxide fluid through the consideration of the statistics of the regions embedded in the contours at different height of fracture landscapes (also called islands in the literature) of binary scanning electronic micrography images. The probability density functions of the areas A, perimeters L, and shape complexities C (defined by L/2 sqrt piA) of islands are shown to follow power laws p(A) approximately A-(muA+1), p(L) approximately L-(muL+1) and p(C) approximately C-(nu+1), with the scaling ranges spanning over two orders. The perimeter and shape complexity scale respectively as L approx. A(D/2)and C approx. A(q) in two scaling regions delimited by A approximately equal to 10(3). The fractal dimension and shape complexity increase when the temperature decreases. In addition, the relationships among different power-law scaling exponents muA, muB, nu, D, and q have been derived analytically, assuming that A, L, and C follow power-law distributions.