Wei Bai

Barium sulphate catalyzed dehydration of lactic acid to acrylic acid

Dehydration of lactic acid was performed over various metal sulphates. BaSO4 was found to show an efficient activity for dehydration of lactic acid to acrylic acid due to the moderate acidity on its surface. Under the optimal conditions, 99.8% lactic acid conversion and 74.0% acrylic acid selectivity were achieved over the BaSO4 catalyst.

Strontium pyrophosphate modified by phosphoric acid for the dehydration of lactic acid to acrylic acid

The dehydration of lactic acid to acrylic acid over strontium catalysts was investigated. Strontium catalysts were prepared by a precipitation method. The catalysts were calcined at 500 °C for 6 hours in an air atmosphere and characterized by SEM for morphological features, by XRD for crystal phases, by FTIR for structure, by N2 sorption for specific surface area, and by the Hammett indicator method for acidity. As for bare strontium catalysts, the types of anions have significant effects on the activity due to the acidity difference of corresponding strontium salts. Among the tested anions, the pyrophosphate anion displayed an excellent catalytic performance. Adjusting the impregnated involatile acid concentration and immersion time can change the acidity of the catalysts, resulting in a higher catalytic activity. The dehydration of lactic acid is sensitive to the surface acidity of the catalysts. Moderate acidity of the catalysts can efficiently catalyze the dehydration of lactic acid to acrylic acid. Under the optimal reaction conditions, 100% lactic acid conversion and 72.2% selectivity to acrylic acid were achieved over the phosphoric acid impregnated strontium pyrophosphate catalyst.

Poly(para-Dioxanone)/Inorganic Particle Composites as a Novel Biomaterial

In this work, poly(para-dioxanone) (PPDO) was mixed with 1% (by weight) calcium carbonate (CaCO(3)), beta-tricalcium phosphate (beta-TCP), or calcium sulphate dihydrate (CSD) by solution co-precipitation. Samples were compression molded into bars using a platen-vulcanizing press. The morphology, thermal and mechanical properties, and crystalline structure of the composites were investigated using differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy, and X-ray diffraction. All results suggest that three types of inorganic particle in this system promote the crystallinity of PPDO and act as an effective nucleating agent: the relative degree of crystallinity of PPDO increased from 30.74% to 100%, and the crystallization temperature of PPDO was increased by 18 degrees C. On the other hand, the mechanical properties of PPDO were changed by the presence of inorganic particles: the tensile strength of PPDO/CSD increased by 11.46%.

Efficient and selective conversion of lactic acid into acetaldehyde using a mesoporous aluminum phosphate catalyst

Although acetaldehyde is a very important compound and has been utilized as a useful synthon for various important chemicals, it has been synthesized in industry through a petroleum route until now. Herein, we have successfully developed a sustainable route using a heterogeneous catalyst. In the presence of mesoporous aluminum phosphate (MAP3), the decarbonylation reaction of lactic acid proceeded efficiently, with 100% lactic acid conversion and ∼92% acetaldehyde selectivity. The catalyst shows high stability for at least 248 h. The unprecedented catalytic performance is due to rich medium acidic sites existing on the catalyst surface.

Preparation and characterization of biodegradable poly(D,L-lactide) and surface-modified bioactive glass composites as bone repair materials

In order to improve filler dispersion and phase compatibility between poly(d,l-lactide) (PDLLA) and inorganic bioactive glass (BG) particles, and to enhance the mechanical properties of PDLLA/BG composites, the silane coupling agent 3-glycidoxypropyltrimethoxysilane (KH570) was used to modify the surface of BG particles (represented by KBG). The structure and properties of PDLLA/BG and PDLLA/KBG composites were investigated by mechanical property testing and scanning electron microscopy (SEM). This study demonstrated that the Guth and Gold models can be combined to predict the Young’s modulus of the composites. The Pukanszky modulus showed that the interaction parameter B of PDLLA/KBG composites was higher than that of the PDLLA/BG, which indicates that there is a higher interfacial interaction between the PDLLA and KBG. The composites were incubated in simulated body fluid (SBF) at 37°C to study the inxa0vitro degradation and bioactivity of the composites and to detect bone-like apatite formation on their surfaces.

A dual-cocatalyst-loaded Au/BiOI/MnOx system for enhanced photocatalytic greenhouse gas conversion into solar fuels

Photocatalysis is a green and economical method to convert greenhouse gases such as carbon dioxide (CO2) for environmental remediation and solar fuel generation. In a semiconductor photocatalyst system, cocatalysts play a very important role. They are not only redox-active sites but also can be used to improve the separation efficiency of photo-induced carriers. In this work, a dual-cocatalyst-loaded Au/BiOI/MnOx photocatalyst was prepared to enhance the photocatalytic reduction activity for the conversion of greenhouse gases (CO2) into solar fuels. The as-prepared BiOI, Au/BiOI, MnOx/BiOI and Au/BiOI/MnOx were characterized by using X-ray diffraction patterns (XRD), the Brunauer–Emmett–Teller (BET) method, transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS) and X-ray photoelectron spectroscopy (XPS). The photocatalytic reduction results showed that Au/BiOI/MnOx had higher activity than pure BiOI, MnOx–BiOI, Au–BiOI and other BiOI-based photocatalysts for solar fuel generation. Photocurrent and electrochemical impedance (EIS) spectroscopy revealed that the efficient photo-induced carrier separation efficiency of Au/BiOI/MnOx induced the high photocatalytic activity.

Sustainable production of acetaldehyde from lactic acid over the carbon catalysts

The synthesis of acetaldehyde from lactic acid over the carbon material catalysts was investigated. The carbon materials were characterized by scanning electron microscopy for morphologic features, by X-ray diffraction for crystal phases, by Fourier transform infrared spectroscopy for functional group structures, by N2 sorption for specific surface area and by ammonia temperature-programed desorption for acidity, respectively. Among the tested carbon catalysts, mesoporous carbon displayed the most excellent catalytic performance. By acidity analysis, the medium acidity is a crucial factor for catalytic performance: more medium acidity favored the formation of acetaldehyde from lactic acid. To verify, we compared the catalytic performance of fresh activated carbon with that of the activated carbon treated by nitric acid. Similarly, the modified activated carbon also displayed better activity due to a drastic increase of medium acidity amount. However, in contrast to fresh carbon nanotube, the treated sample displayed worse activity due to decrease of medium acidity amount. The effect of reaction temperature and time on stream on the catalytic performance was also investigated. Under the optimal reaction conditions, 100% lactic acid conversion and 91.6% acetaldehyde selectivity were achieved over the mesoporous carbon catalyst.

Production of propionic acid via hydrodeoxygenation of lactic acid over FexOy catalysts

The gas-phase hydrodeoxygenation of LA to propionic acid over Fe and its oxides was firstly investigated under various conditions. The catalysts were characterized by nitrogen adsorption–desorption, XRD, FT-IR, H2-TPR and SEM. Fe3O4 as active species was confirmed. Due to that reason, Fe2O3 can be efficiently transformed in situ to Fe3O4 under an atmosphere containing hydrogen derived from decarboxylation/or decarbonylation reaction of lactic acid, which offers the most excellent catalytic performance. The catalyst is sensitive to reaction temperature. LA conversion and its consumption rate increased with an increase of reaction temperature. Similarly, propionic acid selectivity also increased with reaction temperature in the range of 360–390 °C. But with further enhancement of reaction temperature from 390 to 400 °C, it drastically decreased since the formation rate of propionic acid reduced at 400 °C. The catalyst displayed an excellent adaptability in a wide range of LA LHSV except for 1.3 h−1. More importantly, at high LA LHSV of 26.3 h−1, the catalyst offered a satisfactory stability within 100 h on stream. Under the optimal reaction conditions, 96.7% of LA conversion and 46.7% of propionic acid selectivity were achieved.

Cellular responses to electrospun membranes made from blends of PLLGA with PEG and PLLGA-b-PEG.

Control of cellular responses is crucial for the use of electrospun membranes in biomedical applications, including tissue engineering or biomedical devices. However, it is still unclear whether adhesion and proliferation of fibroblasts is stimulated or inhibited on polyethylene glycol (PEG)-modified electrospun membranes. In this study, poly(L-lactide-co-glycolide) (PLLGA)-PEG copolymer and pure PEG were blended with PLLGA, and then electrospun onto nonwoven membranes. The effects of blending of PLLGA-PEG or pure PEG on the adsorption of proteins, and further on the adhesion and proliferation of L929 fibroblasts on the electrospun membranes were investigated. Addition of PLLGA-PEG or PEG significantly improved the hydrophilicity of the electrospun membranes. Pure PEG had no obvious effects on the growth of L929 fibroblasts; in contrast, PLLGA-PEG significantly inhibited the adsorption of proteins and the proliferations of the cells on the electrospun membranes. In response to diminished protein adsorption, mRNA expression of genes related to cell adhesion and migration was up-regulated. The limited effects of pure PEG were probably caused by its preferential dissolution, whereas membrane-confined PLLGA-PEG displayed excellent performance on the inhibition of protein adsorption and cell proliferation.

Microwave-assisted ring-opening polymerization of poly (glycolic acid-co-lactic acid) copolymers

Abstract The microwave-assisted synthesis of poly(glycolic acid-co-lactic acid) (PGLA) copolymers by ring-opening polymerization of glycolide (GA) and L-lactide (L-LA) was studied. The microwave irradiation time and feed ratios on the molecular weights, as well as the thermal properties of the copolymers were discussed. These copolymers were characterized by 1H-NMR, GPC and DSC. It was found that the largest molecular weight ([η]: 0.8745 dL/g) of PGLA5050 was obtained at the irradiation time of 5 min. The color of the copolymers changed from white to light brown, and the yield was higher with the extension of the irradiation time. The molar component ratio of GA in PGLA (FG) was higher than the initial GA feed ratio (nGA) in the raw materials. As the nGA content increased, the glass transition temperature (Tg) of the copolymers decreased and the melting temperature (Tm) of the copolymers increased.