Fabrication of MoS2 microflowers for hydrogenation of nitrobenzene

MoS2 microflowers with the size of 3.9-5.8 mu m in diameter, which is constructed by nanosheets, are hydrothermally synthesized using sodium diethyldithiocarbamate trihydrate as the sulfur source. Studies on the hydrothermal process reveal that the temperature plays crucial roles in determining the crystal phase of MoS2. It is found that the higher temperature favors the reduction of Mo (VI) to Mo (IV). The obtained MoS2 microflowers are highly active and selective for hydrogenation of nitrobenzene into aniline. Compared with commercial MoS2, the higher percentage of coordinative unsaturated Mo sites on MoS2 microflowers offer a relatively higher catalytic activity. (c) 2017 Elsevier B.V. All rights reserved

Mild Hydrogenation of alpha-Pinene Catalyzed by Ru Nanoparticles Loaded on Boron-doped Amphiphilic Core-Shell Mesoporous Molecular Sieves

Highly dispersed and stable catalysts comprising Ru nanoparticles supported on boron-doped amphiphilic core-shell mesoporous molecular sieves (MMS-C@MMS-NH2/B/Ru) with alkyl-modified hydrophobic silica core and NH2-functionalized hydrophilic silica shell are successfully prepared for use in hydrogenation of alpha-pinene for the first time. Dodecyl-modified MMS-C-12@MMS-NH2/B/Ru exhibits the best catalytic activity under mild hydrogenation conditions. The abundant -NH2 functional groups on the molecular sieve surface and their amphipathy allow the sieves to facilitate attachment of more Ru nanoparticles, and to simplify their dispersion in the water-organic reaction medium. Moreover, B-doped molecular sieves may adjust their acidity to meet the needs of alpha-pinene hydrogenation. Under mild reaction conditions (25 degrees C, 1 MPa H-2, and 1 h), alpha-pinene can be completely converted with 99 % selectivity to cis-pinane, because every nanocomposite is equivalent to a microreactor. The catalytic activity does not change much over 5 cycles, indicating that Ru nanoparticles are stably loaded on the molecular sieves

Biomimetic Robust Starch Composite Films with Super-Hydrophobicity and Vivid Structural Colors

The starch composite films (SCFs) will be one of the best alternative packaging materials to petroleum based plastic films, which mitigates white pollution and energy consumption. However, weak mechanical stability, water resistance, and dyeability has hindered the application of SCFs. Herein, a bioinspired robust SCFs with super-hydrophobicity and excellent structural colors were prepared by fiber-reinforcement and assembling SiO2/Polydimethylsiloxane (PDMS) amorphous arrays on the surface of SCFs. The properties of the designed SCFs were investigated by various methods including scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), a tensile test, contact angle (CA) test, and an optical test. The results showed that the obtained SCFs possessed a higher tensile strength (55.17 MPa) attributed to the formed abundant hydrogen bonds between the molecular chains of the starch, cellulose fiber, and polyvinyl alcohol. Benefiting from the nanostructure with rough surface which were modified by materials with low surface free energy, the contact angle and sliding angle of the film reached up to 154° and 2°, respectively. The colors which were produced by the constructive interference of the coherent scattered light could cover all of the visible regions by tuning the diameters of the SiO2 nanoparticles. The strategy in the present study not only reinforces the mechanical strength and water resistance of SCFs but also provides an environmentally friendly way to color the them, which shows unprecedented application potential in packaging materials of the starch composite films

Selective mercury(ii) detection in aqueous solutions upon the absorption changes corresponding to the transition moments polarized along the short axis of an azobenzene chemosensor

A completely water soluble azobenzene chemosensor 1 for selective detection of Hg2+ was synthesized. Taking advantage of the absorption changes corresponding to the transition moments polarized along the short axis of an azobenzene, 1 showed characteristic UV-Vis signal changes in the band around 240 nm for Hg2+ in wide pH ranges, which also showed good tolerance to various metal ions and photoirradiation. Upon addition of Hg2+ into the solution of 1, a favored formation of trans-1 was observed, which is attributed to an intramolecular coordination of the PEG chain and Nβ to Hg2+ confirmed by a control experiment test.\ua0\ua9 The Royal Society of Chemistry 2020

Co-Production of Isoprene and Lactate by Engineered <i>Escherichia coli</i> in Microaerobic Conditions

Lactate and isoprene are two common monomers for the industrial production of polyesters and synthetic rubbers. The present study tested the co-production of D-lactate and isoprene by engineered Escherichia coli in microaerobic conditions. The deletion of alcohol dehydrogenase (adhE) and acetate kinase (ackA) genes, along with the supplementation with betaine, improved the co-production of lactate and isoprene from the substrates of glucose and mevalonate. In fed-batch studies, microaerobic fermentation significantly improved the isoprene concentration in fermentation outlet gas (average 0.021 g/L), compared with fermentation under aerobic conditions (average 0.0009 g/L). The final production of D-lactate and isoprene can reach 44.0 g/L and 3.2 g/L, respectively, through fed-batch microaerobic fermentation. Our study demonstrated a dual-phase production strategy in the co-production of isoprene (gas phase) and lactate (liquid phase). The increased concentration of gas-phase isoprene could benefit the downstream process and decrease the production cost to collect and purify the bio-isoprene from the fermentation outlet gas. The proposed microaerobic process can potentially be applied in the production of other volatile bioproducts to benefit the downstream purification process

Comparative Study of the Structure of Hydroproducts Derived from Loblolly Pine and Straw Grass

The structural characteristics of products derived from the hydrothermal carbonization (HTC) of loblolly pine (LP) and straw grass (SG) were investigated via solid-state cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS ¹³C NMR), heteronuclear single-quantum correlation nuclear magnetic resonance (HSQC-NMR), and solution ¹³C NMR and ³¹P NMR techniques. Results revealed that after HTC, hydrochars from both LP and SG mainly consisted of a combination of lignin, furfural, and condensed polyaromatic structures with a high level of fixed carbon content and higher heating value (HHV). Hydrochar from LP exhibited a higher aryl to furan ratio, and those from SG contained more aliphatic functional groups. Solution ¹³C NMR and HSQC revealed that both liquid chemicals were condensed polyphenolic structures with aliphatic groups that exist mainly in the form of side chains. Although the LP products exhibited a higher proportion of aromatic structures, the types of polyphenol and aliphatic C–H were more diverse in the SG products. Results also indicated that reactions such as chain scission and condensation occurred during hydrothermal carbonization processes. Overall, HTC was found to be an effective refinery treatment for converting different waste biomass into valuable energy materials and chemicals

Stability and activity of cellulase modified with polyethylene glycol (PEG) at different amino groups in the ionic liquid [C₂OHmim][OAc]

<p>Polyethylene glycol (PEG), as a suitable tool to improve enzyme stability, such as monomethoxyl-polyethylene glycol aldehyde (mPEG-ALD) and monomethoxyl-polyethylene glycol succinimide (mPEG-SPA), has been appended at the ε-amino group of lysine or the N-terminal α-amino acid residue of commercial cellulase. The modified cellulases thus obtained are designated as Cell-ALD and Cell-SPA, respectively. The stabilities and activities of these modified cellulases have been studied in the ionic liquid [C₂OHmim][OAc]. Cell-ALD showed excellent stability and activity in [C₂OHmim][OAc], such as the activity of Cell-ALD 5k (molecular weight of ALD is 5000), which can reach above 80% of its original value after remaining in [C₂OHmim][OAc] for 24 h, and outstanding performance in the hydrolysis of natural cellulose.</p