八角茴香中莽草酸提取工艺及抗氧化性研究

通过回流提取法、超声提取法、微波提取法对八角茴香中莽草酸的提取工艺进行优化。经过单因素与正交试验获得最佳提取工艺为微波提取方法下提取时间4 min、微波功率400 W、料液比1：20（g/mL）,莽草酸得率4.92％。用DPPH自由基捕获分光光度法对提取液莽草酸进行了研究,发现其对自由基清除率可达到12.71％,具有一定的抗氧化性。     

Phase formation of Mn-doped zinc silicate in water at high-temperatures and high-pressures

Phase formation of Mn-doped zinc silicate (Zn₂SiO₄:Mn²⁺, ZSM) in high-temperature and high-pressure water was studied by in situ observations with a hydrothermal diamond anvil cell (HDAC). Precursor was prepared with zinc oxalate dihydrate, manganese oxalate, and silica, where the Zn/Mn/Si molar ratio was 192/8/120 to 199/1/120. Conditions of particle formation were at temperatures up to 650 °C and at pressures up to 1250 MPa. Precursors dissolved at temperatures of 145–203 °C and needle-like particles formed through homogeneous nucleation at temperatures from 357 to 374 °C, close to the critical point of water. The needle-like particles grew at growth rates of 0.5–3.8 μm/s and were identified to be ZSM as evident from their green luminescence. ZSM synthesized in supercritical water (400 °C for 180 min) by batch reactions had comparable luminescence with that of ZSM produced by solid-state reaction (1200 °C for 240 min) using the same precursor. The key finding in this work is that the precursors can be made to dissolve in near-critical water and that this allows ZSM to form via a homogeneous nucleation process.     

Kinetics of the xylitol crystallization in hydro-alcoholic solution

Nývlt method was used to determine the kinetic parameters of commercial xylitol in ethanol:water (50:50 %w/w) solution by batch cooling crystallization. The kinetic exponents (n, g and m) and the system kinetic constant (B_N) were determined. Model experiments were carried out in order to verify the combined effects of saturation temperatures (40, 50 and 60 °C) and cooling rates (0.10, 0.25 and 0.50 °C/min) on these parameters. The fitting between experimental and calculated crystal sizes has 11.30% mean deviation.     

Additives assisted catalytic cyclo-dehydration of diethylene glycol in near-critical water

The additives assisted the cyclo-dehydration of diethylene glycol (DEG) reaction was studied in near-critical water (NCW). Zinc chloride (ZnCl₂) and sodium carbonate (Na₂CO₃) were selected to investigate their effects on the cyclo-dehydration of diol. The influences of reaction temperature, time, pressure, reactant/water ratio (r/w) and the concentration of additives on the product yield of the cyclo-dehydration of DEG were examined. The results showed that the final obtained product was primarily 1,4-dioxane, resulting from the cyclo-dehydration of DEG in NCW. The yield of 1,4-dioxane was only 9.84 wt.% in pure water by reacting at 340 °C for 240 min, but the maximum yield of 1,4-dioxane could reach as high as 50.89 wt.% in the solution of 0.50 wt.% ZnCl₂ at 340 °C for 120 min, and the conversion of DEG was 91.94 wt.%. The complete conversion of DEG was obtained in 1.00 wt.% ZnCl₂ at 340 °C for 120 min, but the yield of 1,4-dioxane was only 10.18 wt.%. In the case of Na₂CO₃, it did not have significant promotion effect on the cyclo-dehydration of DEG reaction. All these experimental results demonstrated that ZnCl₂ had the positive effects on the dehydration of DEG while Na₂CO₃ depressed the reaction. Based on these results, a possible reaction mechanism and pathway was proposed in NCW.     

Supercritical CO2 extraction of glycosides from Stevia rebaudiana leaves: Identification and optimization

The aim of this work was to optimize the glycoside composition of Stevia rebaudiana leaves using supercritical fluid extraction (SFE). A Box-Behnken statistical design was used to evaluate the effect of various values of pressure (150–350 bar), temperature (40–80 °C) and concentration of ethanol-water mixture (70:30) as co-solvent (0–20%) by CO₂ flow rate of 15 g min⁻¹ for 60 min. The most effective variables were co-solvent concentration (P < 0.005) and temperature (P ≤ 0.005). Evaluative criteria for both dependent variables (stevioside and rebaudioside A yields) in the model was assigned maximum. Optimum extraction conditions were elicited as 211 bar, 80 °C and 17.4% which yielded 36.66 mg/g stevioside and 17.79 mg/g rebaudioside A. Total glycosides composition were close to those obtained using conventional water extraction (64.49 mg/g) and a little higher than ethanol extraction (48.60 mg/g) demonstrating challenges for industrial scale application of SFE.     

八角特色资源加工利用产业发展现状

八角是我国特色天然植物资源,广泛用于香精香料、食品和医药领域。综述了八角资源量、分布情况及利用部位：世界上85%以上的八角资源产自中国的广西和云南,全国八角种植总面积47.27万公顷,八角干果年均产量约20.69万t,以果实和枝叶利用为主。介绍了八角干果、茴油等初级产品和八角油树脂、茴脑、草蒿脑、莽草酸、茴香醛等深加工产品,以及其加工工艺、质量要求和检测方法。分析了干果加工、茴油提取、精深加工和其他高价值有效成分提取等八角加工利用产业的发展现状、趋势,指出目前八角加工利用产业存在以干果原料直接食用为主、深加工利用比例很少、精深加工技术和新产品开发严重滞后等问题,并提出未来八角加工利用产业的建议与对策：提升精深加工技术、扩大新产品开发和拓宽产品应用面。     

Dehydration of lactic acid to acrylic acid in high temperature water at high pressures

Reaction of lactic acid was investigated with a flow apparatus in water at high temperatures (450 °C) and high pressures (40–100 MPa). The major products obtained from the reaction of lactic acid were acrylic acid, acetaldehyde, and the minor products were acetic acid and propionic acid. The maximum selectivity of acrylic acid was 44% at 23% lactic acid conversion that was obtained at 450 °C, 100 MPa and a residence time of 0.8 s. The reaction kinetics could be modeled by considering two pathways defined as a dehydration pathway to acrylic acid and a combined reaction pathway that consisted of decarboxylation and decarbonylation to acetaldehyde. The data and the kinetic analysis consistently show that both dehydration and the combined decarboxylation and decarbonylation reactions continue to be promoted in supercritical water as pressure (water density) increases. However, high water densities increase the selectivity of the dehydration reaction.     

Continuous Hydrolysis of Cuphea Seed Oil in Subcritical Water

Cuphea seed oil (CSO) is a source of decanoic acid which is useful in the preparation of estolide lubricants among other applications. Decanoic acid and other free fatty acids (FFA) can be hydrolyzed from CSO using a catalyst like KOH, followed by neutralization with HCl and extraction with hexane. This procedure, however, uses caustic materials, hazardous solvents and generates waste salt streams. This study investigated the use of water without catalysts to hydrolyze CSO in a continuous flow tubular reactor. Parameters such as the interaction of pressure and temperature, temperature, water to cuphea oil fatty acid residue (H₂O:COFAR) molar ratio, and flow rate were examined. The lowest conversions of CSO to FFA were at the lowest temperature (i.e., 300 °C) and the hydrolysis was ca. 90% at 350 °C and 13.8 MPa and ca. 80% at 365 °C and 13.8 MPa. Hydrolysis increased with pressure and leveled off at 13.8 MPa. Hydrolysis increased with temperature and leveled off at ca. 330 °C. The optimal H₂O:COFAR molar ratio was found to be 6:1. Conversion rates were inversely proportional to flow rate with 95% conversion at the lowest flow rate (i.e., 0.25 mL/min) corresponding to the longest residence time (i.e., ca. 45.2 min). These results demonstrate a continuous subcritical water process for hydrolyzing CSO to FFA that is effective, requires no catalysts and does not generate a waste salt stream.     

Supercritical CO2 extraction of essential oil from yarrow

Essential oil was extracted from yarrow flowers (Achillea millefolium) with supercritical CO₂ at pressure of 10 MPa and temperatures of 40–60 °C, and its composition and yield were compared with those of hydrodistillate. The yield of total extract, measured in dependence on extraction time, was affected by extraction temperature but not by particle size of ground flowers. CO₂-extraction of cuticular waxes was lowest at 60 °C. Major essential oil components were camphor (26.4% in extract, 38.4% in distillate), 1,8-cineole (9.6% in extract, 16.2% in distillate), bornyl acetate (16.7% in extract, 4.3% in distillate), γ-terpinene (9.0% in extract, 9.4% in distillate), and terpinolene (7.6% in extract, 3.9% in distillate). Compared to hydrodistillation, the yield of monoterpenes was lower due to their incomplete separation from gaseous CO₂ in trap but the yield of less volatile components like monoterpene acetates and sesquiterpenes was higher. Hydrolysis of γ-terpinene and terpinolene, occuring in hydrodistillation, was suppressed in supercritical extraction, particularly at extraction temperature of 40 °C.     

Chitosan-conjugated thermo-responsive polymer for the rapid removal of phenol in water

Chitosan-conjugated thermo-responsive polymers (PNIPAAm-CSs) containing 2.0–8.7% (w/w) chitosan were readily synthesized by the condensation of chitosan and poly(N-isopropylacrylamide-co-acrylic acid) with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. PNIPAAm-CSs were water-soluble at 30 °C, while they deposited above the lower critical solution temperature (LCST, ca. 34 °C in 50 mM sodium phosphate, pH 6.8). Tyrosinase-induced phenol oxidation was performed in the dilute aqueous polymer solution at 30 °C for the rapid binding of oxidized compounds to the amino moiety of PNIPAAm-CS. By heating and shaking the solution, the polymer containing highly concentrated oxidized compounds deposited and agglutinated to a condensed coagulate. Increasing polymer concentration and chitosan content in the polymer increased the removal of phenol and its oxidized compounds. When 1.0 g of PNIPAAm-CS containing 8.7% chitosan was employed for treating 1 l of contaminated water, the concentration of phenol (19 mg l⁻¹) was reduced below the detection limit (0.08 mg l⁻¹) within 2 h.     

Effect of sintering on the catalytic activity of a Pt based catalyst for CO oxidation: Experiments and modeling

The goal of this paper was to make the link between sintering of a 1.6% Pt/Al₂O₃ catalyst and its activity for CO oxidation reaction. Thermal aging of this catalyst for different durations ranging from 15 min to 16 h, at 600 and 700 °C, under 7% O₂, led to a shift of the platinum particle size distributions towards larger diameters, due to sintering. These distributions were studied by transmission electron microscopy. The number and the surface average diameters of platinum particles increase from 1.3 to 8.9 nm and 2.1 to 12.8 nm, respectively, after 16 h aging at 600 °C. The catalytic activity for CO oxidation under different CO and O₂ inlet concentrations decreases after aging the catalyst. The light-off temperature increased by 48 °C when the catalyst was aged for 16 h at 600 °C. The CO oxidation reaction is structure sensitive with a catalytic activity increasing with the platinum particle size. To account for this size effect, two intrinsic kinetic constants, related either to platinum atoms on planar faces or atoms on edges and corners were defined. A platinum site located on a planar face was found to be 2.5 more active than a platinum site on edges or corners, whatever the temperature. The global kinetic law {r (mol m⁻² s⁻¹) = 103 × exp(−64,500/RT)[O₂]^0.74[CO]^−0.5)} related to a reaction occurring on a platinum atom located on planar faces allows a simulation of the CO conversion curves during a temperature ramp. Modeling of the catalytic CO conversion during a temperature ramp, using the different aged catalysts, allows prediction of the CO conversion curves over a wide range of experimental conditions.     

Supercritical carbon dioxide extraction of sesquiterpenes from valerian root

Supercritical carbon dioxide extraction of sesquiterpenes from valerian root was investigated. Extractions from cultivar Arterner züctung and two wild grown valerian subspecies were performed. The influence of extraction conditions on extraction yield and chemical composition of obtained extracts was investigated at temperatures from 40 °C to 50 °C and pressures from 10 MPa to 20 MPa. Chemical composition of obtained extracts was analyzed by GC/FID and GC/MS methods. The influence of particle size on extraction process was investigated at 40 °C and 10 MPa. The major constituents of supercritical extracts were valerianol, valerenal, bornyl acetate and kessanyl acetate. Optimal extraction conditions for the cyclopentanoid sesquiterepenes isolation, referred to the content of cyclopentanoid sesquiterpenes in extract, were found to be 50 °C and 15 MPa. Extract obtained from the cultivar was characterized by the higher content of cyclopentanoid sesquiterpenes, as well as valerenal comparing to extracts from wild grown species. At 40 °C and 20 MPa 19.6% of cyclopentanoid sequiterpenes isolated with methanol can be extracted. At 40 °C and 10 MPa, 17.4% of cyclopentanoid sequiterpenes isolated with methanol can be extracted. However, the extract obtained with methanol was characterized by the high content (42.51%) of unwanted isovaleric as well as by the lower content of cyclopentanoid sequiterpenes than the extracts obtained with supercritical carbon dioxide. The process of supercritical extraction was influenced by particle size. In order to simulate the process, mathematical model on the secretory structure scale was derived. Results of the model showed good agreement with the experimental data.     

Microwave-assisted extraction of chlorogenic acid from flower buds of Lonicera japonica Thunb.

An efficient microwave-assisted extraction (MAE) technique has been developed to recover chlorogenic acid from flower buds of Lonicera japonica Thunb. The yield of chlorogenic acid rapidly reached 6.14% within 5 min under the optimal MAE conditions, i.e. 50% ethanol as extraction solvent, 1:10 (w/v) of the solid/liquid ratio and 60 °C of extraction temperature. The MAE showed obvious advantages in terms of short duration and high efficiency to recover chlorogenic acid from raw plant materials in comparison with conventional heat-reflux extraction. The mechanism of the enhanced extraction by microwave assistance was discussed by observing cell destruction of plant material after MAE treatment by scanning electron microscopy. The results showed that the plant materials were significantly destroyed due to the cell rupture after MAE treatment.     

Optimization of supercritical CO2 extraction of Anastatica hierochuntica

Response surface methodology (RSM) was applied to optimize the variables affecting the supercritical carbon dioxide (SC-CO₂) extraction of non-polar compounds from Anastatica hierochuntica using the Central Composite Design technique (CCD). Independent variables were temperature (32–46 °C) and pressure (22–46 MPa). Dependent variables were the percentage of the content of hexadecanoic acid, 9,12-octadecadienoic acid, heneicosane and heptacosane. Pressure was the most significant parameter that affected the content of the compounds. The hexadecanoic and 9,12-octadecadienoic content decreased while heneicosane and heptacosane increased with pressure. A number of choices can be run either at low pressure and low temperature or at low pressure and high temperature in order to optimize extraction of the selected compounds. Extraction either at low temperature (33 °C) and low pressure (25.6 MPa), or at high temperature (42 °C) and low pressure (22.0 MPa) maximized the yield of hexadecanoic, 9,12-octedecanoic, heneicosane and heptacosane.     

The role of particle size on the electrochemical properties at 25 and at 55 °C of the LiCr0.2Ni0.4Mn1.4O4 spinel as 5 V-cathode materials for lithium-ion batteries

The role of the particle size on the electrochemical properties at 25 and at 55 °C of the LiCr_0.2Ni_0.4Mn_1.4O₄ spinel synthesized by combustion method has been determined. Samples with different particle size were obtained by heating the raw spinel from 700 to 1100 °C, for 1 h in air. X-ray diffraction patterns revealed that all the prepared materials are single-phase spinels. The main effect of the thermal treatment is the remarkable increase of the particles size from 60 to 3000 nm as determined by transmission electron microscopy. The electrochemical properties were determined at high discharge currents (1C rate) in two-electrode Li-cells. At 25 and at 55 °C, in spite of the great differences in particle size, the discharge capacity drained by all samples is similar (Q_dch ≈ 135 mAh g⁻¹). Instead, the cycling performances strongly change with the particle size. The spinels with Φ > 500 nm show better cycling stability at 25 and at 55 °C than those with Φ < 500 nm. The samples heated at 1000 and 1100 °C, with high potential (E ≈ 4.7 V), elevate capacity (Q ≈ 135 mAh g⁻¹), and remarkable cycling performances (capacity retention after 250 cycles >96%) are very attractive materials as 5V-cathodes for high-energy Li-ion batteries.     

近临界水中水解鱼蛋白制备氨基酸

The hydrolysis technology and reaction kinetics for amino acids production from fish proteins in subcritical water reactor without catalysts were investigated in a reactor with volume of 400 ml under the conditions of reaction temperature from 180-320℃, pressure from 5-26 MPa, and time from 5-60 rain. The quality and quantity of amino acids in hydrolysate were determined by bioLiquid chromatography, and 17 kinds of amino acids were obtained. For the important 8 amino acids, the experiments were conducted to examine the effects of reaction temperature, pressure and time on amino acids yield. The optimum conditions for high yield are obtained from the experimental results. It is found that the nitrogen and carbon dioxide atmosphere should be used for leucine, isoleucine and histidine production while the air atmosphere might be used for other amino acids. The reaction time of 30 rain and the experimental temperature of 220℃, 240℃ and 260℃ were adopted for reaction kinetic research. The total yield of amino acids versus reaction time have been examined experimentally. According to these experimental data and under the condition of water excess, the macroscopic reaction kinetic equation of fish proteins hydrolysis was obtained with the hydrolysis reaction order of 1.615 and the rate constants being 0.0017, 0.0045 and 0.0097 at 220℃, 240℃ and 260℃ respectively. The activation energy is 145.1 kJ·mol^- 1.     

Response Surface Analysis and Modeling of Flaxseed Oil Yield in Supercritical Carbon Dioxide

Supercritical fluid extraction of flaxseed oil with carbon dioxide was performed. Effects of particle size, pressure, temperature and the flow rate of supercritical carbon dioxide (SC-CO₂) were investigated. Response surface methodology was used to determine the effects of pressure (30–50 MPa), temperature (50–70 °C) and SC-CO₂ flow rate (2–4 g/min) on flaxseed oil yield in SC-CO₂. The oil yield was represented by a second order response surface equation (R ² = 0.993) using the Box-Behnken design of experiments. The oil yield increased significantly with increasing pressure (p < 0.01), temperature (p < 0.05) and SC-CO₂ flow rate (p < 0.01). The maximum oil yield from the response surface equation was predicted as 0.267 g/g flaxseed for 15 min extraction of 5 g flaxseed particles (particle diameter <0.850 mm) at 50 MPa pressure and 70 °C temperature, with 4 g/min solvent flow rate. Total extraction time at these conditions was predicted as 22 min.     

The enantioselective hydrolysis of racemic naproxen methyl ester in supercritical CO2 using Candida rugosa lipase

The enantioselective hydrolysis of racemic naproxen methyl ester by Candida rugosa lipase (CRL) was studied in aqueous buffer solution/isooctane reaction system in the presence of supercritical CO₂. The effects pressure (75–160 bar), temperature (32–42 °C) and reaction time (0.5–12 h) on the enantiomeric excesses of the product (ee_p) and the substrate (ee_s), enantiomeric ratio (E), conversion (x) and enzyme activity were investigated in a batch reactor system. The highest enantiomeric ratio achieved at 120 bar of pressure, 37 °C of temperature and 2 h of reaction time was E = 193 with x = 41.3%, ee_p = 97.9% and ee_s = 68.8%. CRL remained active at least for 12 h at 37 °C and 120 bar in supercritical CO₂ medium. Furthermore, enantiomeric ratio increased with increasing reaction time and reached the value of E = 236 with ee_p = 98.2%, ee_s = 70.0% and x = 41.6% after 12 h of hydrolysis.     

NOx adsorption and diesel soot combustion over La2O3 supported catalysts containing K, Rh and Pt

In this work we report results of NOx adsorption and diesel soot combustion on a noble metal promoted K/La₂O₃ catalyst. The fresh-unpromoted solid is a complex mixture of hydroxide and carbonate compounds, but the addition of Rh favors the preferential formation of lanthanum oxycarbonate during the calcination step. K/La₂O₃ adsorbs NOx through the formation of La and K nitrate species when the solid is treated in NO + O₂ between 70 and 490 °C. Nitrates are stable in the same temperature range under helium flow. However, they become unstable at ca. 360 °C when either Rh and/or Pt are present, the effect of Rh being more pronounced. Nitrates decompose under different atmospheres: NO + O₂, He and H₂. The effect of Rh might be to form a thermally unstable complex (Rh–NO⁺) which takes part both in the formation of the nitrates when the catalyst is exposed to NOx and in the nitrates decomposition at higher temperatures. Regarding soot combustion, nitrates react with soot with a temperature of maximun reaction rate of ca. 370 °C, under tight contact conditions. This temperature is not affected by the presence of Rh, which indicates that the stability of nitrates has little effect on their reaction with soot.