MPa N2 Research Articles

Near IR Raman laser beams generated by 1064 nm pumped Stimulated Raman Scattering (SRS) of pressurized nitrogen

Nitrogen is a nonflammable, nonexplosive and cheap Raman active gas. N2 has a vibrational Raman shift of 2330 cm −1, and there are no other Raman active media with a similar Raman shift. Therefore, the SRS of N2 plays an essential role in expanding the spectral range of Raman lasers. In this work, a pulsed 1064 nm laser was used as a pump source, and by the first and second Stokes SRS of pressurized N2, 1415 nm and 2110 nm laser beams were generated. By optimizing N2 pressure and focus configuration, the maximum pulse energies of 1415 nm and 2110 nm Raman lasers reached 109.9 mJ and 22.5 mJ, respectively. Their corresponding peak powers obtained were 20.7 MW and 4.4 MW, respectively. Comparing the thresholds of H2 (hydrogen) and N2, the first Stokes (S1) Raman gain coefficient of 1.5 MPa N2 was estimated to be about 1/9 of H2.

High Performing and Stable Cu/NiAlOx Catalysts for the Continuous Catalytic Conversion of Ethanol into Butanol

AbstractThe catalytic conversion of ethanol into butanol is one of crucial reactions in biorefinery for the production of renewable fuels and chemicals. The development of highly durable non‐noble metal‐based catalysts is of great significance but poses big challenges. Herein, we prepared a series of NiAl‐hydrotalcite derived Cu/NiAlOx catalysts via the hydrothermal precipitation method. Cu addition to the system shows an enhanced reactivity in the continuous catalytic conversion of ethanol into butanol. The 0.75 %Cu/NiAlOx catalyst afford a sustained ethanol conversion of ∼35 % and butanol selectivity of ∼45 % within 1000 h at 250 °C, 3 MPa N2. Complementary characterization studies reveal that Cu addition into the catalysts could not only provide redox sites for facilitating the dehydrogenation/hydrogenation processes, but also modulate the base/acid property for suppressing the side reactions. The excellent stability might stem from the enhanced interaction between Cu and Ni species, as evidenced by EDX‐mapping and H2‐TPR. We believe this work will help to rational design and develop of high‐performing and durable non‐noble metal catalysts for ethanol coupling to higher alcohols.

Preparing high-entropy ceramic films from high-entropy alloy substrate

High-entropy ceramic films with good anti-wear, anti-radiation, anti-corrosion and anti-oxidation performance are attractive for the application in extreme environments such as high temperature, high strength and strong radiation. This paper reported an alternative way to produce high-entropy ceramic films by in-situ nitridation or oxidation of high-entropy alloy substrates. Nitride and oxide high-entropy ceramic films of (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)N and (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)O2 were prepared by heat treatment of high-entropy alloy (Ti0.2Zr0.2V0.2Nb0.2Ta0.2) in 0.1 MPa N2 and air atmosphere, respectively. For the high-entropy ceramic films, except for a small amount of oxides impurity, the solid solutions (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)N and (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)O2 with a simple face-centered cubic and tetragonal crystal structure were the major products and showed homogeneous element distribution. The porous (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)O2 film about 5.5 μm thick has a hardness of 19.8 GPa, modulus of 378 GPa and critical load value of 55.3 mN. And (Ti0.2Zr0.2V0.2Nb0.2Ta0.2)N film about 850 nm thick is relatively dense and exhibits a hardness of 36.7 GPa, modulus of 635 GPa and critical load value of 90.8 mN.

Study on the catalytic activity of char-based Fe–Co–K catalyst for volatiles reforming during biomass pyrolysis

This work studied the catalytic activity of char-loaded Fe, Co, and K catalyst for the reforming of volatiles of biomass pyrolysis in a two-stage fixed-bed reactor under 0.1 MPa N2 and 800 °C, reforming temperature 600 °C. The results showed that the addition of Co do not exhibit the desired catalytic activity and the yield of H2 decreased from 163.08 mL/g (9Fe/Char) to 152.30 mL/g (9Fe0.5Co/Char). While, with the addition of K, the catalytic activity of Fe–Co-based catalyst was improved, and the H2 yield increased from 95.16 mL/g(raw pine needle)to 179.10 mL/g (9Fe0.5Co0.4K/Char). In addition, K do not enhance the catalytic activity of Co. The characterization results showed that the addition of K favorable the formation of the active phase Fe3O4, that helped to increase the H2 yield. Which due to K combined with oxygen-containing functional groups and captured O to form lattice oxygen (K(O∗)), transferred to the oxygen vacancy of Fe (Fe( )) through intermetallic interaction, and finally formed Fe3O4. Co is easily oxidized to form Co3O4, and it is not possess catalytic activity. The addition of K promoted the oxidation of Co, which leads to the loss of catalytic activity. The study developed a low-cost Fe–Co–K/Char catalyst exhibits a promising application in the catalytic reforming of biomass pyrolysis to hydrogen-rich gas.

Effect of precipitating agents for the preparation of Fe-based catalysts on coal pyrolysis: Effect of Ba and Mg additives

In this work, the effect of Fe catalysts prepared with four precipitating agents (ammonia, urea, KOH and NaOH) on the catalytic pyrolysis of coal (BC) was investigated using a fixed-bed reactor under 0.1 MPa N2 and 700 °C. The results indicated that the precipitating agent significantly affected the activity of the Fe catalyst (5 wt%). Concretely, the Fe catalysts obtained with ammonia (Fe-X1) and urea (Fe-X2) as precipitating agents showed low activity was attributed to the small size of the particles blocked the pores of the coal, making it difficult for Fe species to be reduced. The Fe catalysts obtained with NaOH (Fe-X3) and KOH (Fe-X4) as precipitating agents showed good catalytic activity. However, the final metal Fe phase in Fe-X3 catalyst had a large particle size and aggregation. The Fe-X4 catalyst facilitated the preferential consumption of small defective structures and the removal of small aromatic rings, and the catalyst particles were uniformly dispersed and showed the best catalytic activity. Accordingly, the Fe-X4 catalyst had the highest total conversion (56.79 wt%) and H2 yield (93.66 ml/g) in coal pyrolysis. Moreover, Mg and Ba enhanced the activity of the Fe catalyst, which was attributed to the fact that Mg and Ba promoted the dispersion of Fe and prevented the formation of Fe-O-Si from the original Si in the coal, and the effect of Mg was greater than that of Ba.

Inverse-Tunable Red Luminescence and Electronic Properties of Nitridoberylloaluminates Sr2-x Bax [BeAl3 N5 ]:Eu2+ (x=0-2).

The nitridoberylloaluminate Ba2[BeAl3N5]:Eu2+ and solid solutions Sr2−x Ba x [BeAl3N5]:Eu2+ (x=0.5, 1.0, 1.5) were synthesized in a hot isostatic press (HIP) under 50 MPa N2 atmosphere at 1200 °C. Ba2[BeAl3N5]:Eu2+ crystallizes in triclinic space group P1‾ (no. 2) (Z=2, a=6.1869(10), b=7.1736(13), c=8.0391(14) Å, α=102.754(8), β=112.032(6), γ=104.765(7)°), which was determined from single‐crystal X‐ray diffraction data. The lattice parameters of the solid solution series have been obtained from Rietveld refinements and show a nearly linear dependence on the atomic ratio Sr : Ba. The electronic properties and the band gaps of M 2[BeAl3N5] (M=Sr, Ba) have been investigated by a combination of soft X‐ray spectroscopy and density functional theory (DFT) calculations. Upon irradiation with blue light (440–450 nm), the nitridoberylloaluminates exhibit intense orange to red luminescence, which can be tuned between 610 and 656 nm (fwhm=1922–2025 cm−1 (72–87 nm)). In contrast to the usual trend, the substitution of the smaller Sr2+ by larger Ba2+ leads to an inverse‐tunable luminescence to higher wavelengths. Low‐temperature luminescence measurements have been performed to exclude anomalous emission.

Catalytic pyrolysis of pine needle biomass over Fe–Co–K catalyst for H2-rich syngas production: Influence of catalyst preparation

In this work, the effects of preparation methods of Fe–Co–K catalysts on biomass pyrolysis were studied in a fixed bed reactor under 0.1 MPa N2 and 700 °C. The results showed that Fe–Co bimetallic catalyst has better activity than Fe. the yields of H2 and CO increased from 84.90 ml/g and 63.94 ml/g (Fe) to 98.42 ml/g and 85.43 ml/g (Fe + Co) prepared by co-impregnation, respectively, and the CO2 yield was 276.94 ml/g. The preparation of Fe∗ + Co∗ catalyst by co-precipitation could not only improve the yields of H2 (138.23 ml/g) and CO (89.75 ml/g), but also reduce the CO2 yield (225.19 ml/g). In the Fe∗ + Co∗ catalyst system, the addition of 0.6 wt% K increased the yields of H2 and CO to 153.85 ml/g and 107.80 ml/g. Characterization proved that the crystallinity of Co3Fe7 in Fe∗+Co∗ was stronger than that of Fe + Co, and the addition of Co facilitates the reduction of Fe, K promoted the dispersion of Fe∗ + Co∗ and enhanced the catalytic activity. This study provided theoretical support for increasing the yields of H2 and CO while reducing the CO2 yield.

Effects of alkali and alkaline earth metals of inherent minerals on Fe-catalyzed coal pyrolysis

In this work, the effects of alkali and alkaline earth metals (AAEM (K, Na, Ca and Mg)) on Fe (5 wt%) loaded-coal pyrolysis were conducted using the fixed-bed reactor at 700 °C with 0.1 MPa N2. The coal was pretreated by HCl and HF aqueous solutions (De-2 coal). These effects were investigated with AAEM additive into Fe loaded De-2 coal. The results indicate that K, Na, Ca and Mg (0.1 wt%-1.5 wt%) enhanced the catalytic effect of Fe catalyst, leading to the high H2 selectivity (59.34 ml/g →85.94 ml/g), as well as the low yield toward CO2 (157.50 ml/g →148.62 ml/g), and the catalytic activity follows the order of Na ≈ K > Ca > Mg. Characterization results reveal that the inherent AAEM promote the reduction of Fe species and the dispersion of Fe particles. The reason for that was AAEM combined with oxygen-containing functional group generated C–O-AAEM and COO-AAEM, and released active oxygen sites to activate carbon sites, leading to Fe catalyst bound with active oxygen sites formed iron oxide and Fe-(O)–C on char surface. This study was helpful to understand the promotion mechanism of AAEM on Fe catalyzed coal pyrolysis.

Valorization of lignin in native corn stover via fractionation-hydrogenolysis process over cobalt-supported catalyst without external hydrogen

• We presented a modified method that provides the hydrogen source in the reaction with a mixed solvent of alcohol, acid and water, replacing the original method that directly provides a hydrogen source with external hydrogen. • In addition, a new cobalt supported on nitrogen doped carbon catalyst preparation method (one-pot) was presented . • The role of the alcohol to acid and water mixed solvent not only extract lignin fragments from the matrix but also provide the hydrogen source. • Cobalt which has electronic interaction with the nitrogen reformed alcohols to obtain hydrogen and stabilized lignin intermediates during the reaction by hydrogenation of active bonds. Nearly complete delignification (91%) and high yield of target monomers (23.8%) can be obtained under the conditions (5wt% Co/Ac-N_one-pot, 10:1:1mixture solvent consist of isopropanol/water/formic acid, 235 °C, 200 min, 0.1 MPa N2), and the selectivity of target monomers was 85%. The (hemi) cellulose section is also used efficiently, and a considerable part is converted into compounds such as glucose and furfural alcohol, which realizes the effective utilization of the three components of lignocellulose. Circulation experiment of catalyst was performed directly without any operation of the residue, and it could maintain 90% activity in the first four cycles. Lignin, which represents the most abundant renewable aromatic biomass resource on the earth, is promising as an alternative for the production of chemicals. We presented a modified method that provides the hydrogen source in the reaction with a mixed solvent of alcohol, acid and water, replacing the original method that directly provides a hydrogen source with external hydrogen. In addition, a new cobalt supported on nitrogen doped carbon catalyst preparation method (one-pot) was presented. We proposed one-step method in which corn stover lignin is converted to target monomers over Co/AC-N_one-pot catalyst and mixed solvent. The role of the alcohol to acid and water mixed solvent not only extract lignin fragments from the matrix but also provide the hydrogen source. Cobalt which has electronic interaction with the nitrogen reformed alcohols to obtain hydrogen and stabilized lignin intermediates during the reaction by hydrogenation of active bonds. Different kinds of nitrogen including pyridinic and pyrrolic nitrogen functional groups plays a critical role in stabilizing Co. Nearly complete delignification (91%) and high yield of target monomers (23.8%) can be obtained under the conditions (5wt% Co/Ac-N_one-pot, 10:1:1mixture solvent consist of isopropanol/water/ formic acid, 235 °C, 200 min, 0.1 MPa N 2 ), and the selectivity of target monomers was 85%. Circulation experiment of catalyst was performed directly without any operation of the residue, and it could maintain 90% activity in the first four cycles.

Hierarchical Fe–Sn/Beta catalyzes the conversion of glucose to methyl lactate

Bimetallic modified Fe–Sn/Beta was synthesized and examined as a solid acid catalyst for the transformation of glucose into methyl lactate in methanol. The catalysts were characterized by a combined characterization techniques i.e. X-ray fluorescence spectroscopy, N2 physisorption, powder X-ray diffraction, X-ray photoelectron spectroscopy, NH3 temperature-programmed desorption, and pyridine adsorption Fourier transform infrared spectroscopy. A high yield of methyl lactate of 67% was achieved upon conversion of 0.3 g glucose in 24 g methanol over 0.15 g catalyst at 220 ℃ under 2 MPa N2 for 6 h. The recyclability of the catalyst was also investigated, and the conversion of glucose remained constant; conversely, the yield of methyl lactate decreased slightly in five catalytic runs. The excellent catalytic performance of Fe–Sn/Beta was attributed to the presence of large amounts of Lewis acid sites. Besides, the rich mesoporosity in Fe–Sn/Beta improved mass transfer rates in the conversion of glucose to alkyl lactates.

Efficient conversion of cellulose to lactic acid over yttrium modified siliceous Beta zeolites

The selective one-pot synthesis of lactic acid (LA) from cellulose, and further the raw biomass, on heterogeneous catalysts is the key point for the development of biorefinery technology. Herein, we reported an yttrium (Y) modified siliceous Beta zeolites catalyst via two-step post-synthesis for highly efficient conversion of cellulose to LA. Under condition of 220 °C and 2 MPa N2, the cellulose could be transformed to LA with a yield of 49.2 % within 30 min, and the substrate can be extended to various raw biomass. It was demonstrated that the dealumination and modification of Y can efficiently modulate the acidity on the surface of zeolite. The dehydration products HMF and other derivatives were suppressed, and the yield of LA was correlated in line with the acid amount, which were attributed to the increased Lewis acidity originated by Y incorporation. These results contribute to the development of the green and efficient synthesis of bio-chemicals.

Microstructures and mechanical properties of the bilayer functionally graded WC-TiC-Ni/Co cemented carbides

The nitridation of the WC-TiC-Ni/Co cemented carbides successfully yielded a bilayer-graded structure that consists of face center cubic-rich outer and coarse grain intermediate layers. The sintered carbides were nitrided at 1723 K under 4 MPa N2 for 90 min. The bilayer gradient showed a unique microstructure combination of element distribution and grain features. The graded microstructures contributed to the hardness and fracture toughness of the outer layer, intermediate layer, and inner region. The fracture mode of the intermediate layer was mainly a transgranular fracture, which increased the fracture toughness of the intermediate layer. The fracture mechanism of the inner region was a combination of the intergranular and transgranular fractures; however, the primary mechanism was intergranular fracture. The correlations among the binder phase composition, microstructure, and mechanical properties were investigated to determine the gradient structure characterization of the bilayers of the functionally graded cemented carbides.

Nonaqueous gel casting using multicomponent concentrated slurries through Michael additive reaction for fabricating silicon nitride dense ceramics

A novel gel casting system using nonaqueous, multicomponent, and concentrated slurries was designed for manufacturing Si3N4 dense ceramics with complex structures. The proposed process involves the dispersion of reagent particles in α-terpineol aided by the saturated adsorption of polyethyleneimine partially complexed with oleic acid (PEI-OA) as well as the addition of small amounts of multifunctional acrylates (MAs). The occurrence of the Michael additive reaction between the MAs and the remaining amines of PEI-OA fixed on the reagent particles resulted in a gradual increase in the viscosity of the slurry until its solidification. Using the Si3N4/α-terpineol slurry as a model system, the effects of processing parameters such as OA complex ratio, particle volume fraction, and MA structures on the solidification behaviors were systematically investigated. A slurry having higher particle concentration which was treated with PEI-OA comprised from lesser OA ratio found to effectively solidify within 2 h when mixed with MA having larger number of acryloyl group per molecule. The proposed gel casting process was then applied to the multicomponent Si3N4–Y2O3–Al2O3–TiO2–AlN/α-terpineol system. The gel casted complex structured green compacts were successfully densified up to 98% by liquid phase sintering at 1750 °C under 0.9 MPa N2 gas pressure.

Synthesis of Nitride Zeolites in a Hot Isostatic Press

The recently introduced nitridophosphate synthesis in a hot isostatic press (HIP) enabled simple access to large‐scale product quantities starting from exclusively commercially available starting materials. Herein, we show that this method is suitable for the synthesis of highly condensed functional nitridophosphates, as well. Hence, the syntheses of the nitridophosphate zeolites Ba3P5N10 X (X=Cl, Br) are presented as proof of concept for this innovative access. Furthermore, samples of unprecedented Sr3P5N10 X (X=Cl, Br) were prepared and characterized to demonstrate the advantages of this synthetic approach over commonly used methods. Luminescence investigations on Eu2+‐doped samples of AE 3P5N10 X (AE=Sr, Ba; X=Cl, Br) were carried out and characteristics of observed emission bands are discussed.

Oil shale in situ catalytic conversion over clin/SBA-15 composites under subcritical water

The massive reserves of oil shale in China offer the potential to lessen energy dependence on conventional sources. A novel oil shale in situ upgrading process over mineral-based clin/SBA-15 catalysts has been proposed, and catalytic pyrolysis behavior was intensively studied. Clinoplilolite was chosen for clin/SBA-15 preparation. The apparent activation energy Ea of hexadecane cracking on clin/SBA-15(3.0) is 90.37 kJ/mol that is 35 kJ/mol less than that of thermal cracking. DSC curves of n-C16 conversion under 3 MPa N2 reveals that the cracking peak temperature was declined to 365 °C and 372 °C from 417 °C (thermally) on clin/SBA-15 and kaolin/SBA-15, respectively. The extracted kerogen was converted at 280 °C with a biphasic solvent (water and decalin) to mimic the hydrocarbon generation process, and the products were mainly concentrated in C9, C10 and C11. Oil shale conversion was carried out at 280 °C under subcritical water. Non-catalytic converted products mainly contains hydrocarbons (34.01 %), long-chain fatty acids (esters), alcohol, and ketones. Catalytically produced oil have a strongly aliphatic nature, and the hydrocarbon yield is up to 70.50 % for clin/SBA-15. The clin/SBA-15 played a remarkable role on H/C ratio rising (1.98–2.08) and O/C ratio declining (0.10 to 0.04) because of the catalytic decarboxylation. Clin/SBA-15 showed no activity decay on seven-day oil shale aqueous conversion test.

P-type conductivity and damage recovery in implanted GaN annealed by rapid gyrotron microwave annealing

We demonstrate p-type activation of GaN doped by Mg ion implantation, and in situ during metalorganic chemical vapor deposition through sequential short-duration gyrotron microwave heating cycles at temperatures of 1200–1350 °C. GaN is implanted with 1019 cm−3 Mg ions, capped with AlN, and annealed under 3 MPa N2 overpressure in 5 s heating cycles for less than 60 s total using a high-power gyrotron microwave heating source. Through I–V characterization, photoluminescence spectroscopy, and Raman spectroscopy, we study the evolution of electrical properties, optically active point defects, and material strain in response to implantation and annealing. For Mg-implanted samples, increasing annealing temperature is characterized by an increase in the PL substitutional Mg-related peak (UVL) relative to the shallow-donor vacancy-related peak (GL2). Through comparison of implanted and in situ doped samples, it is demonstrated that the origin of compensating VN lies primarily in implantation rather than degradation from the annealing process. Transmission line measurements and diode I–V measurements show a sheet resistance of 1083 kΩ/□ and a hole concentration of 1.23 × 1015 cm−3, respectively, in the Mg-implanted material annealed at 1350 °C. We conclude that temperature-cycled gyrotron annealing at 1350 °C decreases implant-induced compensating point defects and activates Mg to obtain selective p-type conduction.

Illuminating Nitridoberylloaluminates: The Highly Efficient Red-Emitting Phosphor Sr2[BeAl3N5]:Eu2+

The nitridoberylloaluminate Sr2[BeAl3N5]:Eu2+ was obtained through reaction of the binary nitrides in a hot isostatic press under a pressure of 50 MPa N2 and a temperature of 1400 °C. The crystal s...

Subcritical CO2 shows no effect on liquid hot water pretreatment of poplar wood

Pretreatment of lignocellulosic biomass is required for many biorefinery processes. Previous studies have described hydrolysis of hemicelluloses by using liquid hot water (LHW) pretreatment. We evaluated the effect of carbonic acid originating from pressurized carbon dioxide during LHW pretreatment of poplar. The conditions applied covered temperatures from 120 to 200 °C, pretreatment times from 5 to 240 min and pressures from 1.0 to 2.2 MPa CO2 or N2. The pressure and the type of gas (CO2 or N2) did not have an effect on production of acetic acid, which functioned as a marker of progress of biomass hydrolysis. Results suggested that the presence of carbonic acid in the process does not significantly contribute to acidification. Deacetylation of lignocellulosic biomass can be achieved by LHW pretreatment irrespective of pressure and of gas type used, at the conditions tested.

Chlorella to fuel conversion on amphiphilic SO3H-SBA-15 catalysts: Pyrolysis characteristics and kinetics

The aim of this work was to propose a novel process to make Chlorella pyrolyzed and in situ upgraded to fuel over amphiphilic SO3H-SBA-15 catalysts. This strategy is developed to build a Pickering emulsion system through the w/o (water/decalin) droplets. Chlorella catalytic pyrolysis has been conducted under the different heating rates to get the activation energy 166 kJ/mol (α = 0.5) according to the kinetic-free model. Palmitic acid, as a model compound, was employed for TG and DRIFTS analysis to elucidate the pyrolysis and deoxygenation reaction pathway. n-hexadecane pyrolysis at 3 MPa N2 illustrated the peak cracking temperature declining from thermally 422 °C to catalytically 413 °C. N2 physisorption of the fresh and post-reaction catalysts indicated that there is little catalyst decay. With improved thermal stability and hydrophobicity, the SO3H-SBA-15 catalysts showed enhanced performance for Chlorella pyrolysis, and revealed the promising application for better fuel production in aqueous conversion.

Effects of MgSiN2 addition and post-annealing on mechanical and thermal properties of Si3N4 ceramics

Si3N4 ceramics with 10 mol% (MgSiN2+Y2O3) additives were prepared by sintering at 1900 °C for 8 h in 1 MPa N2 atmosphere. Both the bending strength and thermal conductivity of the ceramics increase with increasing content of MgSiN2, and reached 689 MPa and 97 Wm−1K−1 with the addition of (7 mol% MgSiN2 + 3 mol% Y2O3). The bending strength and thermal conductivity were enhanced to 698 MPa and 105 Wm−1K−1 by post annealing at 1400 °C for 20 h. By annealing at 1600 °C, the thermal conductivity could be further improved to 117 Wm−1K−1, but the strength decreased to be 517 MPa. From the experimental results, adding more MgSiN2 and increasing the annealing temperature are helpful to improve the thermal conductivity, by reducing the grain boundary phase and increasing the grain size.