Different efficiency toward the biomimetic aerobic oxidation of benzyl alcohol in microchannel and bubble column reactors: Hydrodynamic characteristics and gas–liquid mass transfer

The selective aerobic oxidation of benzyl alcohol to benzaldehyde has attracted considerable attention because benzaldehyde is a high value-added product. The rate of this typical gas–liquid reaction is significantly affected by mass transfer. In this study, CoTPP-mediated(CoTPP: cobalt(II) mesotetraphenylporphyrin) selective benzyl alcohol oxidation with oxygen was conducted in a membrane microchannel(MMC) reactor and a bubble column(BC) reactor, respectively. We observed that 83% benzyl alcohol was converted within 6.5 min in the MMC reactor, but only less than 10% benzyl alcohol was converted in the BC reactor. Hydrodynamic characteristics and gas–liquid mass transfer performances were compared for the MMC and BC reactors. The MMC reactor was assumed to be a plug flow reactor,and the dimensionless variance was 0.29. Compared to the BC reactor, the gas–liquid mass transfer was intensified significantly in MMC reactor. It could be ascribed to the high gas holdup(2.9 times higher than that of BC reactor), liquid film mass transfer coefficient(8.2 times higher than that of BC reactor), and mass transfer coefficient per unit interfacial area(3.8 times higher than that of BC reactor). Moreover,the Hatta number for the MMC reactor reached up to 0.61, which was about 15 times higher than that of the BC reactor. The computational fluid dynamics calculations for mass fractions in both liquid and gas phases were consistent with the experimental data.

Controlled release and enhanced antibacterial activity of salicylic acid by hydrogen bonding with chitosan

Microcapsules of salicylic acid （SA） with chitosan were prepared by spray drying method. Various analytical methods were used to characterize the nature of microcapsules. Fourier-transform infrared spectroscopy （FTIR） confirmed the presence of intermolecular interactions between chitosan and SA. Particle size analysis showed that the average size ofmicrocapsules ranged from 2 to 20 pro, Scanning electron microscopy （SEM） studies indicated that the microspheres were spherical and had a relatively smooth surface. Microbiological assay of antibacterial activity for SA and its microcapsules was measured using different bacterial strains. It was found that the antibacterial activity of SA was improved after the formation of microcapsules. The in vitro release profile showed that the microcapsules could control SA release from I h to 4 h. Kinetic studies revealed that the release pattern follows Korsmeyer-Peppas mechanism. Enhanced antibacterial activity of the SA micro- capsules was attributed to the synergistic effects of intermolecular hydrogen-bonding interactions N-H...O and O-H...O=C between SA and chitosan. It was also confirmed by quantum chemical calculation.

Tissue Culture and Rapid Propagation System of Roselle(Hibiscus sabdariffa L.)

[Objectives]This study was conducted to establish a tissue culture and rapid propagation system of roselle(Hibiscus sabdariffa L.)[Methods]A tissue culture and rapid propagation experiment was carried out with roselle plants as materials to study the suitable explants,the best disinfection method,the best growth medium,the best rooting medium and the transplanting and domestication method of roselle.[Results]The lateral buds of roselle were the best explants.Sterilizing with 0.1%mercuric chloride for 7 min showed a contamination rate of 5%and achieved a survival rate of 90%.With MS as the basic medium,adding 1.0 mg/L 6-BA and 0.5 mg/L IBA could obtain the best effect of bud induction.The medium with the highest proliferation rate was MS+6-BA 0.5 mg/L+BA 0.1 mg/L.On the basis of 1/2MS,adding 0.5 mg/L NAA+0.5 mg/L IBA could make adventitious buds root fastest and most,and greatly improve the propagation coefficient.And 1∶1 perlite rock:peat soil was the best transplanting substrate,with which the transplanting survival rate reached 95%.[Conclusions]This study provides technical reference for rapid cultivation and large-scale planting of roselle.

Activity promotion of Rh_(1)Ca_(x)/Al_(2)O_(3) single-atom catalyst in 1-octene hydroformylation:a volcano curve exists between Ca adding ratio and catalytic activity

Single-atom catalysts(SACs)are considered the best candidates for olefin hydroformylation due to their combined advantages of homogeneous and heterogeneous catalysts.Unlike conventional organo-phosphine modification,Rh SAC is modified by introducing Ca,resulting in a significant increase in activity(maximum~5.7-fold)and stability.Furthermore,a volcano curve between Ca addition ratio and catalytic activity is found.Introducing Ca significantly increases activity by decreasing the energy barrier,but excessive Ca decreases activity due to hindering substrate adsorption and reaction.

Propylene epoxidation coupled with furfural oxidation over Pt(Ⅱ) TPP porphyrin with molecular oxygen

The development of green route for preparing propylene oxide(PO)with molecular oxygen is of significance both in academic and industrial.In this work,propylene epoxidation coupled with furfural oxidation catalyzed by platinum meso-tetraphenylporphyrin(Pt(Ⅱ)TPP)has been developed.Propylene conversion and PO selectivity reached up to 56%and 83%,respectively.Meanwhile,furfural was almost completely converted to furoic acid.Based on operando characterizations and electron paramagnetic resonance(EPR)tests,a mechanism involved high-valent Pt species was proposed.This work is expected to provide a potential application prospects for producing PO and furoic acid simultaneously in chemical industry.

Enhanced performance for propane dehydrogenation through Pt clusters alloying with copper in zeolite

Metal alloys have been widely applied for heterogeneous catalysis,especially alkane dehydrogenation.However,the catalysts always suffer from sintering and coke deposition due to the rigorous reaction conditions.Herein,we described an original approach to prepare a catalyst where highly dispersed Pt clusters alloying with copper were encapsulated in silicalite-1(S-1)zeolite for propane dehydrogenation(PDH).The introduction of Cu species significantly enhances the catalytic activity and prolongs the lifetime of the catalyst.0.1Pt0.4CuK@S-1 exhibits a propane conversion of 24.8%with 98.2%selectivity of propene,and the specific activity of propylene formation is up to 32 mol·gPt^(−1)·h^(−1)at 500℃.No obvious deactivation is observed even after 73 h on stream,affording an extremely low deactivation constant of 0.00032 h^(−1).The excellent activity and stability are ascribed to the confinement of zeolites and the stabilization of Cu species for Pt clusters.

Furfural Reduction via Hydrogen Transfer from Supercritical Methanol

Furfural derived from biomass hemicelluloses is an important intermediate for biofuels and chemicals. In order to further upgrade, furfural is usually reduced into 2-methyl furan that is more stable and useful. In this work, furfural was reduced by CuZnAl, CuMgAl, Cu2Cr2O5, CuNiAl as catalysts in a supercritical methanol without external H2 source. The best yield of 2-methyl furan was achieved among the H2 free furfural process reported as high as 74%. And the catalytic behaviors were discussed under difierent catalysts and temperatures conditions.

Quasi-continuous synthesis of cobalt single atom catalysts for transfer hydrogenation of quinoline

Improving the transfer hydrogenation of N-heteroarenes is of key importance for various industrial pro-cesses and remains a challenge so far.We reported here a microcapsule-pyrolysis strategy to quasi-continuous synthesis S,N co-doped carbon supported Co single atom catalysts(Co/SNC),which was used for transfer hydrogenation of quinoline with formic acid as the hydrogen donor.Given the unique ge-ometric and electronic properties of the Co single atoms,the excellent catalytic activity,selectivity and stability were observed.Benefiting from the quasi-continuous synthesis method,the as-obtained cata-lysts provide a reference for the large-scale preparation of single atom catalysts without amplification ef-fect.Highly catalytic performances and quasi-continuous preparation process,demonstrating a new and promising approach to rational design of atomically dispersed catalysts with maximum atomic efficiency in industrial.

Synthesis of Nitrogen-doped Carbon Supported Cerium Single Atom Catalyst by Ball Milling for Selective Oxidation of Ethylbenzene

Through screening Ce precursors and pyrolysis temperatures[Ce(acac)3 as Ce precursors and pyrolysis at 900°C],zeolitic imidazolate framework-8(ZIF-8)derived nitrogen-doped carbon supported cerium single atom catalyst(Ce_(1)/NC)is successfully prepared by ball milling method.The Ce_(1)/NC catalyst exhibits exceptional catalytic performance in the selective oxidation of saturated C―H bonds in aromatic compounds,e.g.,91%conversion and 99%selelctivity can be achieved in the oxidation of ethylbenzene to acetophenone under mild reaction conditions.

Manganese porphyrin-mediated aerobic epoxidation of propylene with isoprene: A new strategy for simultaneously preparing propylene epoxide and isoprene monoxide

The direct epoxidation of propylene by O_(2) is a significant and challenging topic. The key factor for this homogeneous aerobic epoxidation is the activation of molecular oxygen under mild conditions. In this work,the aerobic epoxidation of propylene catalyzed by manganese porphyrins was achieved in the presence of isoprene. Isoprene contains an allyl methyl group, and the α-H can be easily removed to achieve the activation of molecular oxygen. The conversion of propylene was 38% and the selectivity toward propylene oxide(PO) was up to 87%. The role of isoprene was demonstrated, and a plausible mechanism was proposed. The protocol reported herein is expected to provide a strategy for the simultaneous preparation of propylene oxide and isoprene monoxide.