Critical roles of edge turbulent transport in the formation of high-field-side high-density front and density limit disruption in J-TEXT tokamak

This article presents an in-depth study of the sequence of events leading to density limit disruption in J-TEXT tokamak plasmas, with an emphasis on boudary turbulent transport and the high-field-side high-density (HFSHD) front. These phenomena were extensively investigated by using Langmuir probe and Polarimeter-interferometer diagnostics

Enhanced glucose production from cellulose and corn stover hydrolysis by molten salt hydrates pretreatment

Molten salt hydrates (MSHs) are remarkable in breaking through the recalcitrant structure of microcrystalline cellulose and raw biomass. After being pretreated in 60 wt% LiBr at 130 degrees C for 2 h, cellulose crystallinity as well as degree of polymerization (DP) decreased. It was found that 91.3% yield of pretreated cellulose was removed from MSHs by filteration followed by being hydrolyzed into glucose with a high yield of 75.3% by dilute acid under mild reaction conditions. The pretreatment process also works on raw corn stover hydrolysis. After being pretreated at 100 degrees C for 5 h, 88.4% yield of cellulose in biomass was recovered and can be hydrolyzed into 54.9% yield of glucose with dilute acid. It was found that the cellulose in corn stover can be easier degraded compared with microcrystalline cellulose during MSHs pretreatment, which dues to the formation of acetic acid from hemicellulose hydrolysis. The proposed pretreatment technique presents a promising potential for glucose production from biomass in a commercial way

Production of HMF from glucose using an Al3+-promoted acidic phenol-formaldehyde resin catalyst

An Al3+-modified formaldehyde-p-hydroxybenzenesulfonic acid resin catalyst (Al-SPFR) was synthesized through a hydrothermal method. N-2 adsorption-desorption experiment and acid-base titration revealed that the Al-SPFR catalyst had better texture properties and higher strong acid content than the previously prepared unmodified SPFR. The effects of reaction time and temperature, catalyst loading, and water content in water/GVL mixture were investigated for glucose dehydration using Al-SPFR as the catalyst. An HMF yield of 47.4% was obtained at 170 degrees C for 2 h in the biphasic GVL/H2O medium. Further performing a five-cycle experiment, the HMF yield initially decreased and then remained fairly constant, and the recyclability of the Al-SPFR was reasonable

Hydrocarbon Distribution of Cellulose Hydrogenolysis over Ru- MoOx/C Combined with HZSM-5

In this paper, acidic HZSM-5 coupled with the hydrodeoxygenation catalyst Ru-MoOx/C was applied for cellulose conversion to chain-mediated small-molecule alkanes in a water-containing biphasic solvent. The physicochemical properties of the binary catalyst Ru-MoOx/C were studied by an array of characterization methods. Meanwhile, the factors (such as the HZSM-5/Ru/MoOx ratio, reaction temperature, H-2 pressure, and volume ratio of the aqueous phase and organic phase) that influenced the yield of natural gas (CH4), liquefied petroleum gas (C-2-C-4 alkanes), and gasoline (C-3-C-6 alkanes) were thoroughly investigated, obtaining the highest CH4 yield of 56.1% and the highest C-5-C-6 alkane yield of 66.1% by adjusting the volume ratio of the aqueous phase and organic phase, respectively. Especially, a promising yield of C-2-C-4 alkanes (43.7%) was obtained via precisely tailoring C-C bond splitting. HZSM-5 in water was proved as the solid acid for hydrolyzing cellulose to glucose, followed by transferring to Ru-MoOx/C located at the water-oil interface for further hydrogenolysis to alkanes. The fact that small-molecule alkane distribution can be controlled by Lewis acid density over Ru-MoOx/C was clarified: the lower Lewis acid density proved C-1-C-4 alkane production, while a higher Lewis acid density favored C-5-C-6 alkane production

Efficient production of ethylene glycol from cellulose over Co@C catalysts combined with tungstic acid

Catalytic conversion of renewable cellulose, instead of fossil resources, to high-value ethylene glycol (EG) is of great significance for reducing considerable worries regarding the energy problem. However, the EG production from cellulose is dependent on Ni and Ru based catalysts. Herein, encapsulated Co@C catalyst was firstly applied for EG production from cellulose combined with tungstic acid (TA). The mixing of the two catalysts in different ratios was compared and well-controlled, and the highest 67.3% yield of EG can be achieved. TA is used mainly to promote both the cellulose hydrolysis and the retro-aldol reaction of glucose to glycolaldehyde. Co@C catalysts are responsible for the hydrogenation of glycolaldehyde to EG. Compared with traditional noble metals and composite catalysts, the inexpensive and easily synthesized Co@C catalysts could greatly reduce the cost of production of EG. The Co@C catalysts encapsulated with outside graphene layers can keep high stability for at least 6 runs

Production of liquid fuel intermediates from furfural via aldol condensation over Lewis acid zeolite catalysts

Aldol condensation reactions between furfural and acetone can be used to produce liquid fuel intermediates. It was found that tin-containing zeolites with MFI (Sn-MFI) and BEA* (Sn-Beta) framework structures are effective for C-C bond formation via the aldol condensation reactions between furfural and acetone. Aldol condensation between furfural and acetone produced two main products, 4-(2-furyl)-3-buten-2-one (FAc) and 1,5-di-2-furanyl-1,4-pentadien-3-one (F2Ac). Although both these catalysts were active for the aldol condensation reactions, different selectivities to aldol products were observed over Sn-MFI and Sn-Beta. FAc and F2Ac were formed over the Sn-Beta catalyst with selectivities to FAc of 40% and F2Ac of 22%, respectively. In contrast, only FAc was produced over Sn-MFI. The variation in selectivity is likely due to different pore geometries of Sn-Beta and Sn-MFI, suggesting that Sn-MFI exhibits shape selectivity for aldol condensation between furfural and acetone. In addition, it was found that the addition of water to the reaction system can also affect the product selectivity, leading to the aldol product exclusively being FAc over Sn-Beta

Lignin-first depolymerization of native corn stover with an unsupported MoS2 catalyst

The lignin-first biorefinery method appears to be an attractive approach to produce phenolic chemicals. Herein, corn stover was employed for the production of phenolic monomers using an unsupported non-noble MoS2 catalyst. The yield of phenolic monomers was enhanced from 6.65% to 18.47% with MoS2 at 250 degrees C and about 75% lignin was degraded with more than 90% glucan reserved in the solid residues. The Fourier-Transform Infrared (FT-IR) and heteronuclear single quantum coherence-nuclear magnetic resonance (H-1-C-13 HSQC-NMR) characterization suggested that the cleavage of the beta-O-4, gamma-ester and benzyl ether linkages were enhanced, promoting the delignification and the depolymerization of lignin. The catalyst performance was relatively effective with 14.30% phenolic monomer yield after the fifth run. The effects of the reaction temperature, the initial hydrogen pressure, the dosage of catalyst, and the reaction time were investigated. The model reactions were also proposed for the potential mechanism study. This work provides some basic information for the improvement of the graminaceous plant lignin-first process with a non-noble metal catalyst

Dehydration of glucose to 5-hydroxymethylfurfural and 5-ethoxymethylfurfural by combining Lewis and Bronsted acid

In this work, glucose was transformed into 5-hydroxymethylfurfural (HMF) and 5-ethoxymethylfurfural (EMF) in the presence of AlCl3 center dot 6H(2)O and a Bronsted solid acid catalyst (PTSA-POM). GVL (gamma-valerolactone)-water and ethanol-water solvent systems were evaluated in the dehydration reaction of glucose into HMF and EMF, respectively. Water content and dosage of AlCl3 center dot 6H(2)O were examined in the conversion of glucose into HMF, and some valuable chlorides (FeCl3 center dot 6H(2)O, NiCl2 center dot 6H(2)O, CrCl3 center dot 6H(2)O etc.) were also used in contrast with AlCl3 center dot 6H(2)O. Some different organic solvents were added to the ethanol-water system to explore whether it would be beneficial to the generation of EMF. A high yield of HMF (60.7%) was obtained at 140 degrees C within 60 min in GVL-water (10:1) solvent system, and total yield 42.1% of EMF and HMF (30.6% EMF, 11.5% HMF) was achieved at 150 degrees C after 30 min in an ethanol-water (9 : 1) solvent system

Efficient conversion of lactic acid to alanine over noble metal supported on Ni@C catalysts

Alanine (Ala), regarded as the building block for protein synthesis, has been widely used in the field of food processing, pharmaceutical, and bio-based plastic industries. Containing plenty of oxygenic functional groups, biomass-derived chemicals are proper for Ala synthesis in an economic and green way via amination. In this work, lactic acid (LA) derived from renewable biomass and waste glycerol (the major by-product of biodiesel industry) was used to produce Ala. Here, a series of magnetic catalysts M/Ni@C (M = Ru, Pt, Pd, Ir, and Rh) were synthesized by ethylene glycol reduction of metal M supported on encapsulated Ni@C. Compared with catalysts based on other M metals, Ru/Ni@C catalysts exhibited extraordinary efficiency with 91.4% selectivity for Ala synthesis from LA (63.7% yield of Ala and 69.7% conversion of LA). The results of experiments and catalyst characterization indicated that the doping of M metals could improve the dehydrogenation ability of catalysts, as well as the ability of NH3 adsorption, facilitating the reaction towards Ala. Overall, this study provides an efficient chemo-catalytic way for the production of Ala from biomass-derived substrates