MPa H2 Research Articles

Alcohol production from fatty acids via Ni3Fe/Rutile: Revealing the role of oxygen vacancy and metal-support electronic density characteristics

Ni3Fe clusters anchored on rutile (R-TiO2) were synthesized by hydrothermal (HT), coprecipitation (CP) and impregnation (IM) methods, and the catalytic performance of different NiFe/R-TiO2 catalysts were investigated for hydrogenation of fatty acid into alcohol. Notably, HT-NiFe/R-TiO2 catalyst, with the highest specific surface area and Ni3Fe nanoparticles dispersion, exhibited the best hydrogenation activity towards alcohol production, with complete conversion and yield reach of 92.5 % at 4 MPa H2, 210 ℃ and 6 h. The structure–reactivity relationship was investigated by a series of catalysts characterization, DFT calculation and corroborated through hydrogenation performance evaluations. Anchoring Ni3Fe clusters onto highly dispersed basic site surfaces with different Ov concentrations can change the electron distribution and strength of the metal-support interaction, causing more stable adsorption of the H and acids molecular toward fatty alcohol production. This work provides further insight into the structure–activity of NiFe/TiO2 catalysts synthesized through different methods.

Enhanced hydrogen storage properties of Ti40-xV45Zr15Crx alloys by dual-phase nanostructures of eutectic and spinodal decomposition

Multi-principal elements alloys (MPEAs) with body center cubic (BCC) structure have shown great potential in hydrogen storage. However, the multi-cycle activation process and the high desorption temperature have inhibited their applications. In this study, the Ti40-xV45Zr15Crx (x = 1, 2, 3 at. %) alloys with three different BCC phases are synergized, and high hydrogenation capacities of over 2 wt% are achieved in the first hydrogen absorption. Owing to the formation of spinodal decomposition nanostructure in Ti38V45Zr15Cr2 alloy, 90 % of total hydrogen capacity is reached in 30s at 250 °C under 1 MPa H2, which indicates no incubation time is needed for activation. The Ti38V45Zr15Cr2 alloy also shows the highest reversible hydrogen storage capacity with fastest kinetics at 200 °C. The hydrogenation reaction is controlled by the 1D diffusion process of H atoms according to JMAK model. The spinodal decomposition structure can accelerate the decomposition of H2 molecules and the diffusion of H atoms by providing extra energy from large lattice distortion. The high-density interfaces in nano-eutectic structure can serve as active sites for the nucleation of hydrides and fast paths for the diffusion of H atoms.

Solvent-mediated selective hydroconversion of benzyloxybenzene over a Ni/β40 catalyst

During biomass conversion, solvent types often play an important role in determining product selectivity and reaction mechanisms. Nevertheless, solvent function remains poorly understood. Herein, Ni/β40 was prepared by a slightly modified deposition-precipitation method and used for the catalytic hydroconversion (CHC) of benzyloxybenzene (BOB) to dicyclohexylmethane (DCHM) or toluene and phenol mediated by solvent types. The results show that solvent types, atmospheres, and Ni20/β40 synergistically control product regulation. In n-hexane (H), DCHM was first produced with the selectivity of 94.5% under the optimum conditions (180 °C, 2 MPa H2, and 4 h). In isopropanol (IP), toluene and phenol were unique products under the optimal conditions (180 °C, 0.5 MPa H2, and 4 h). The characterizations of Ni20/β40 and variation of product distributions from the CHC of BOB demonstrates that BOB conversion to DCHM in H via the >CH-O- bond cleavage induced by H+ addition, benzylium addition to ortho and para positions of phenol, H…H transfer to the resulting 2-benzylphenol and 4-benzylphenol, dehydroxylation of 2-benzylcyclohexanol and 4-benzylcyclohexanol produced, together with benzene rings hydrogenation. By contrast, conversion of BOB to toluene and phenol in IP only depends on the cleavage of >CH-O- bond induced by H+ addition. Furthermore, Ni20/β40 exhibites splendid reusability.

Integrated hydropyrolysis and vapor-phase hydrodeoxygenation process with Pd/Al2O3 for production of advanced oxygen-containing biofuels from cellulosic wastes

This study focuses on developing advanced oxygen-containing biofuels with high furan, cyclic ketone, and ethanol content from holocellulose and cellulosic wastes. To achieve this, we employed an integrated process that combined hydropyrolysis and vapor-phase hydrodeoxygenation using Pd/Al2O3 as a catalyst. In the first stage, the non-catalytic hydropyrolysis of hemicellulose resulted in furfural and acetic acid fractions that were effectively converted into furans, cyclic ketones, and ethanol in the second-stage reactor over Pd/Al2O3 under 0.3 MPa H2. We found that a hydropyrolysis temperature of 440 °C in the first stage reactor resulted in the highest yield of oxygen-containing biofuels (171.1 mg/g) with 89.2% hemicellulose conversion. However, increasing the hydrodeoxygenation temperature in the second stage reactor reduced the yield of oxygen-containing biofuels, and at 400 °C, excess deoxygenation led to hydrocarbon production. The Pd/Al2O3 catalyst demonstrated high stability during the vapor-phase hydrodeoxygenation of primary furfural and acetic acid intermediates, with only 2.1% coke formation after three reaction cycles. This scalable process enables the conversion of various cellulosic wastes into advanced oxygen-containing biofuels, with considerable total yields. Our findings suggest that this integrated process holds great promise for converting biomass waste into advanced oxygen-containing biofuels.

Dual grain size-effects on hydrogen-assisted fatigue crack growth in 1 GPa-class medium-carbon martensitic steel

The influence of prior austenite grain (PAG) size ranging from 6 to 90 μm on the fatigue crack growth (FCG) of a tempered 0.41%C lath martensitic steel was investigated in a 90 MPa H2 gas environment at ambient temperature. Under the presence of H, severe FCG accelerations accompanying intergranular (IG) cracking along PAG boundaries as well as quasi-cleavage (QC) fracture along martensite block boundaries and {011} crystallographic planes were systematically found. Smaller PAG mitigated the acceleration at a relatively high-stress intensity via suppressing IG cracking. However, PAG refinement instead escalated the acceleration at a low-stress intensity factor where QC facture prevailed. This inverse grain size effect was discussed in terms of the plasticity criterion in triggering QC and its possible dependence on the microstructural length scale.

Fully exposed Pd species on nanodiamond/graphene hybrid support for the efficient toluene hydrogenation reaction

AbstractLiquid organic hydrogen carriers have emerged as promising hydrogen storage systems, offering notable advantages over conventional storage and utilization efficiency methods. However, designing a catalyst that operates at low temperatures and remains cost‐effective poses a significant challenge. We successfully synthesized Pd species (single atoms, fully exposed clusters, and nanoparticles) on a nanodiamond/graphene (ND@G) hybrid support for toluene hydrogenation. The structure of as‐developed Pd catalyst was investigated by HAADF‐STEM, X‐ray absorption fine structure, Raman, XRD, XPS, and other characterizations. Remarkably, the Pdn/ND@G catalyst achieved a toluene conversion rate of 99.3% (100°C, 2.0 MPa H2) without loss of catalytic ability after 5 runs, which exhibited excellent catalytic performance and stable activity. Furthermore, the Pdn/ND@G catalyst exhibited an apparent activation energy as low as 62.36 ± 3.33 kJ mol−1 and an initial turnover frequency of 33.1 h−1 at 100°C. By adjusting the size and metal‐dependent effects, we have achieved enhanced catalytic performance for toluene hydrogenation, thus paving the way for the design of efficient liquid organic hydrogen storage catalysts.

NiCo/SiO2 nanospheres for efficient synergetic decarboxylation of fatty acids and upgrading of municipal sludge HTL bio-crude to biofuels

Municipal sludge (MS) and derived HTL (hydrothermal liquefaction) bio-crude contains a large quantity of organics, including fatty acids, which may be a potential resource for producing biofuels via catalytic treatment. Herein, decarboxylation of fatty acids is chosen as the model reaction to screen a series of nickel-based bimetallic catalysts supported on homemade SiO2 nanospheres to investigate the synergetic effect. NiCo/SiO2 turned out with the best performance compared to NiCu-, NiZn-, NiMo- and NiFe/SiO2. An 83% conversion of stearic acid and an 84% selectivity of heptadecane via hydrothermal decarboxylation were achieved at 280 °C under 1 MPa H2. XPS results revealed the electron transfer from Co to Ni, leading to the formation of Niδ-, which is more accessible to bond with Cδ+ in the carboxyl group of fatty acids, thus facilitating the decarboxylation reaction. Compared to commercial SiO2, our homemade SiO2 showed a stronger carbon accumulation resistance, indicating a medium specific surface area was essential. Both the synergetic effect of NiCo bimetal and the carbon accumulation resistance of homemade SiO2 nanospheres contributed to the efficient hydrothermal decarboxylation. The NiCo/SiO2 catalyst was further applied for upgrading of MS HTL bio-crude to biofuels, and the theoretical higher heating value (HHV) was significantly improved from 34.4 to 37.2 MJ/kg, suggesting the potential application of converting MS bio-crude to biofuels.

In-situ construction of N-doped hollow carbon polyhedral cage anchored Co-Ni dual binding sites as nanoreactor for efficient real lignin oil hydrodeoxygenation

Rational design multifunctional nanoreactor with high activity under H2-free/low-H2 conditions for lignin hydrodeoxygenation reaction (HDO) is attractive for sustainable energy conversion. Here, strategy for in-situ assembly-etching was proposed to prepare N-doped hollow carbon polyhedral cage anchored Co-Ni dual binding sites as nanoreactors (CoxNiy/NC). Its unique and controllable hollow structure exhibits high content of pyridine-N as Lewis-base site for adsorption of substrate, and in adjacent nitrogen defect sites as active metal anchors enabled the Co2Ni1/NC to perform perfect the hydrodeoxygenation of real lignin oil. The conversion of lignin pyrolytic oil to cycloalkane products was achieved under 0.2 MPa H2 and 3 h, the yield of total liquid product and the cyclohexane were 87.8 wt% and 53.4 wt%, respectively. This research provides a novel way for upgrading raw bio-oil to high-value products under low energy consuming conditions.

Synergy between Ni3Sn2 alloy and Lewis acidic ReOx enables selectivity control of furfural hydrogenation to cyclopentanone

Selectivity controlling is a crucial and challenging issue for the hydrogenation of furfural (FAL) to cyclopentanone (CPO). Herein, Ni3Sn2-ReOx/TiO2 is synthesized via successive impregnation and exhibits full conversion and 92.5 % CPO selectivity under 3.0 MPa H2 at 140 °C, which are much higher than those of Ni/TiO2 and Ni3Sn2/TiO2. Characterizations show that Ni3Sn2 is the main active phase that remarkably restrains the over-hydrogenation of the furan ring, while ReOx plays an electrophile or Lewis acid site to activate C-OH of furfuryl alcohol and induces its rearrangement. DFT calculations verify that Sn doping weakens the furan ring adsorption on Ni3Sn2 and shifts its adsorption configuration, which consequently inhibits side reactions and favors the metal-acid (Ni3Sn2-ReOx) synergy. The catalyst is stable, recyclable and also active at even 0.5 MPa H2 and 80 °C. This study provides an advanced strategy for the rational design of superior catalysts for tuning product selectivity, with practical potential for upgrading biomass-derived platform molecules.

Preparation of SBA-15 supported Ru nanocatalysts by electrostatic adsorption-ultrasonic in situ reduction method and its catalytic performance for hydrogen storage of N-ethylcarbazole.

N-ethylcarbazole (NEC) is an ideal liquid organic hydrogen storage carrier. The development of efficient hydrogen storage catalysts can promote the large-scale application of this process. In this paper, SBA-15 supported Ru nanocatalysts (Ru/S15-SU) were synthesized by strong electrostatic adsorption (SEA)-ultrasonic in situ reduction method (UR). Ru/S15-SU was characterized by N2 adsorption-desorption, TEM, H2 temperature program reduction, FT-IR, XRD, and XPS analysis measures. The results showed that ultrafine Ru NPs were evenly distributed on the surface of SBA-15, and ultrasonic in situ reduction not only reduced Ru3+ to Ru0, but also produced a coordination effect between Ru and O, enhancing the interaction between Ru NPs and the carrier. Ru/S15-SU exhibited excellent catalytic performance in the hydrogenation reaction of NEC, and the hydrogen storage efficiency reached 99.31% at 130°C and 6 MPa H2 pressure, which is superior to that of commercial 5wt%Ru/Al2O3. The excellent catalytic hydrogenation performance can be attributed to the selective anchoring of ruthenium ions on the surface of SBA-15 via electrostatic adsorption, preventing the aggregation of Ru NPs and enhancing the interaction between SBA-15 and Ru NPs by ultrasonic in situ reduction. Ru/S15-SU had a lower NEC hydrogenation apparent activated energy (Ea) of 68.45 kJ/mol than 5wt%Ru/Al2O3 catalyst. This method provides a new approach for the green preparation of nanocatalysts without using any chemical reducing agents.

Conversion of levulinic acid and its esters to 1,5-dimethyl-2-pyrrolidone over a nonnoble metallic Ni@CeOx catalyst.

1,5-dimethyl-2-pyrrolidone (MNMP), as a highly efficient green solvent, can be obtained from biomass-derived levulinic acid and its esters with 100% conversion and 96.8% yield over a 10% Ni@CeOx catalyst at 140 °C, 2 MPa H2, 8 h, and with water as the solvent. Structure-property correlation investigations were performed with diverse characterization methods, including BET, XRD, XPS, TEM, HAADF-STEM, H2-TPR, NH3-TPD, CO2-TPD and FT-IR, and the results revealed that the excellent catalytic performance of the 10% Ni@CeOx catalyst was mainly resulted from the strong interaction between Ni and CeOx, which formed more catalytic active sites and contributed to higher reductive amination efficiency. Besides, the 10% Ni@CeOx catalyst had a chemisorption effect on LA. This was also the key to the excellent catalytic activity of the 10% Ni@CeOx catalyst. The 10% Ni@CeOx catalyst exhibited great stability throughout 6 reaction runs and excellent catalytic efficiency in the kilogram scale preparation of MNMP. This work provides a low-cost, efficient, and environmentally friendly heterogeneous catalytic system for the production of MNMP.

Exceptional catalytic effect of novel rGO-supported Ni-Nb nanocomposite on the hydrogen storage properties of MgH2

The design of an excellent active catalyst to improve the sluggish kinetic and thermodynamic properties of magnesium hydride (MgH2) remains a great challenge to achieve its practical application. In this study, a novel Ni-Nb/rGO nanocomposite catalyst was successfully prepared by one-spot hydrothermal and subsequent calcination methods. The novel Ni-Nb/rGO nanocomposite exhibits an exceptional catalytic effect on improving MgH2 sorption properties. Specifically, the onset desorption temperature of MgH2 + 10 wt% Ni-Nb/rGO composite is reduced to 198 °C, much lower than that of undoped MgH2 (330 °C). Interestingly, the composite can release 5.0, 5.9, and 6.0 wt% H2 within 10 min at 245, 260, and 275 °C, respectively. Furthermore, the dehydrogenated MgH2 + 10 wt% Ni-Nb/rGO composite starts to absorb hydrogen even at room temperature with approximate 2.75 wt% H2 uptake at 75 °C under 3 MPa H2 pressure within 30 min and exhibits excellent stability by maintaining 6.0 wt% hydrogen content after 20 cycles at 300 °C. Chou's model suggests that the de/hydrogenation kinetics of Ni-Nb/rGO-modified MgH2 switches from surface penetration model to diffusion model at lower temperatures. Additionally, the activation energies (Ea) for the de/hydrogenation of MgH2 + 10 wt% Ni-Nb/rGO are reduced to 57.8 kJ/mol and 33.9 kJ/mol, which are significantly lower than those of undoped MgH2. The work demonstrates that the addition of a novel ternary Ni-Nb/rGO catalyst is an effective strategy to not only boost the sorption kinetics of MgH2 but also maintain its cycling property.

Dense Ru single-atoms integrated with sulfoacids for cellulose valorization to isosorbide

Metal-acid bifunctional catalysts are the unity of two opposites (metal-acid repelling) for cellulosic biomass valorization to isosorbide. It is challenging to improve the selectivity of metal hydrogenation catalysts and their synergism with acids for catalytic hydrolysis and dehydration to achieve substantial isosorbide. Herein, dense Ru single-atoms (10.1 wt% of Ru SAs) are anchored on sulfoacid-functionalized hollow mesoporous carbon shells, designed by assembling silica and 8-hydroxyquinoline-modified chitosan (HQ-CTS) through in situ Stöber templating strategy before pyrolysis and acid treatment. Based on X-ray absorption fine structure and computational modeling results, the structure of Ru SAs is determined as RuN4, which is more selective for a transitional glucose hydrogenation to sorbitol than Ru001 of Ru clusters. A lower-energy barrier of 1.21 (0.72) eV is delivered over RuN4 (Ru001) for glucose hydrogenation (isomerization). These Ru SAs are integrated with sulfoacids (SO3H) but resistent against acids, rendering enhanced isosorbide yield in water as compared to Ru clusters, via a one-pot cascade reaction under harsh conditions (220 °C, 6 MPa H2). The elaborately fabricated dense Ru SAs and sulfoacids, achieved by varying the addition time of HQ-CTS during the in situ Stöber templating process, improve the synergism of glucose hydrogenation with cellulose hydrolysis and sorbitol dehydration. This study provides a new idea for rational design of high-performance metal-acid bifunctional catalysts toward one-pot conversion of cellulose to isosorbide.

Anchoring Co on CeO2 nanoflower as an efficient catalyst for hydrogenolysis of 5-hydroxymethylfurfural

Developing economical and efficient catalysts to accelerate sustainable fabrication of value-added chemicals and fuels from biomass remains a challenging task. Herein, Co species anchored on CeO2 nanoflowers catalyst, Co/CeO2-NF, were synthesized for catalyzing the efficient selective hydrodeoxygenation (HDO) of 5-hydroxymethylfurfural (HMF). Co/CeO2-NF exhibited high 2,5-dimethylfuran (DMF) yield of 99 % at 160 °C, 2 MPa H2 within 5 h, and afforded excellent catalytic performance and stability after 5 times of reuse. The combination of various structural characterization and catalytic experiments reveals that the outstanding activity of Co/CeO2-NF stems from the unique nano-flower structure with high content oxygen vacancies, desired acid property, the high dispersed cobalt species and strong metal-support interaction. This study not only provides insight into the selective HDO of HMF, but also inspires the design of cheap heterogeneous catalysts for the HDO of renewable biomass to high-value-added chemicals.

Reactant enrichment in hollow void of Pt NPs@MnOx nanoreactors for boosting hydrogenation performance.

In confined mesoscopic spaces, the unraveling of a catalytic mechanism with complex mass transfer and adsorption processes such as reactant enrichment is a great challenge. In this study, a hollow nanoarchitecture of MnOx-encapsulated Pt nanoparticles was designed as a nanoreactor to investigate the reactant enrichment in a mesoscopic hollow void. By employing advanced characterization techniques, we found that the reactant-enrichment behavior is derived from directional diffusion of the reactant driven through the local concentration gradient and this increased the amount of reactant. Combining experimental results with density functional theory calculations, the superior cinnamyl alcohol (COL) selectivity originates from the selective adsorption of cinnamaldehyde (CAL) and the rapid formation and desorption of COL in the MnOx shell. The superb performance of 95% CAL conversion and 95% COL selectivity is obtained at only 0.5MPa H2 and 40min. Our findings showcase that a rationally designed nanoreactor could boost catalytic performance in chemoselective hydrogenation, which can be of great aid and potential in various application scenarios.

One-pot synthesis of 2,5-bis(propoxymethyl)furan from 5-hydroxymethylfurfural by using the supported copper catalyst and hierarchical pore ZSM-5 zeolite

The highly-efficient conversion of 5-hydroxymethylfurfural (HMF) to 2,5-bis(propoxymethyl)furan was achieved via the one-pot route, which were performed by the combination of supported copper catalyst and hierarchical pore ZSM-5 zeolite. Among the supported copper catalyst, the Cu/Al2O3 catalyst exhibited the excellent activity and selectivity in the hydrogenation of HMF, obtaining a 98.7% yield of BHMF at 100 °C for 6 h under 2.5 MPa of H2. The reason might be attributed to that the highly dispersed copper particles and relatively weaker acid sites, which improved the hydrogenation activity of catalyst and suppressed the occurrence of side reaction. In the one-pot synthesis of BPMF, the Cu/Al2O3 catalyst and HP-ZSM-5 zeolite were responsible for HMF hydrogenation and BHMF etherification, respectively, and the competition between them is negligible. This work provides a simple route to produce furanic diether from HMF.

Catalytic hydrogenation of lignin-derived aldehydes over bimetallic PdNi/hydrotalcite catalyst under mild conditions

Selective conversion of lignin derivatives into value-added chemicals benefits to develop sustainable chemical engineering and material manufacturing. In this work, a hydrotalcite-supported PdNi bimetallic catalyst was synthesized by introducing Ni to promote Pd dispersion and adjust the charge distribution of the active center, which was used for the catalytic hydrogenation of lignin-derived aldehydes in water under mild conditions. At 30 ℃ and 2 MPa H2, PdNi/HT achieved 99 % of vanillin (VAN) conversion with 100 % selectivity of vanillyl alcohol (VAL), and most of the typical lignin-derived aldehydes could be hydrogenated over this catalyst. This catalyst was steady and could be recycled at least five runs. The introduction of Ni and the nanosheet structure of HT improved the dispersion of the metal particles, significantly reducing the metal particle size. Besides, the Pdδ−–Niδ+ pair and the basic sites of HT facilitated the H2 activation and the adsorption of the aldehyde groups of lignin-derived aldehydes on the catalyst surface, enhancing the hydrogenation efficiency and selectivity.

Al-Doped Core-Shell-Structured Ni@Mesoporous Silica for Highly Selective Hydrodeoxygenation of Lignin-Derived Aldehydes.

Selective deoxygenation of chemicals using non-noble metal-based catalysts poses a significant challenge toward upgrading biomass-derived oxygenates into advanced fuels and fine chemicals. Herein, we report a bifunctional core-shell catalyst (Ni@Al3-mSiO2) consisting of Ni nanoparticles closely encapsulated by the Al-doped mesoporous silica shell that achieves 100% vanillin conversion and >99% yield of 2-methoxy-4-methylphenol under 1 MPa H2 at 130 °C in water. Due to the unique mesoporous core-shell structure, no significant decrease in catalytic activity was observed after 10 recycles. Furthermore, incorporating Al atoms into the silica shell significantly increased the number of acidic sites. Density functional theory calculations reveal the reaction pathway of the vanillin hydrodeoxygenation process and uncover the intrinsic influence of the Al sites. This work not only provides an efficient and cost-effective bifunctional hydrodeoxygenation catalyst but also offers a new synthetic protocol to rationally design promising non-noble metal catalysts for biomass valorization or other widespread applications.

Decarboxylative - Dimerization of levulinic acid using spent Li-ion battery electrode material with lithium nickel cobalt manganese oxide as a catalyst

A low cost catalyst prepared by pyrolyzing electrode coating material from spent Li-ion battery cells was shown as an effective catalyst for the decarboxylative - dimerization of levulinic acid to a mixture of C6 and C9 fuel precursors. The highest levulinic acid conversion of 94% was observed with 10% (w/w) catalyst loading under 1.24 MPa H2 at 140 °C, 15 h. A reaction scheme was proposed to explain the novel transformation producing C9 lactone products and C6 unsaturated alcohol product through a decarboxylative pathway followed by the aldol dimerization of levulinic acid.

Improving catalytic performance and reusability of flower-like Co-B-P amorphous alloy nanobelts for the selective hydrogenation of furfural in water

Herein, active, low-cost, stable, and sustainable amorphous alloy Co-B-P nanobelts (NBs) are synthesized for the selective hydrogenation of furfural (FFR) to furfuryl alcohol (FFA) in H2O. The Co-B-P NBs are flower-like bundles of ultrathin nanosheets obtained by reducing Co ions in a layered liquid crystal using double-reducing agents at room temperature. The specific surface area, hydrogen adsorption capacity, surface states, and FFR selective hydrogenation performance of the Co-B-P NB catalyst can be modified via low-temperature plasma treatment. The treatment does not change the amorphous structure of Co-B-P NBs. In H2O, Co-B-P NBs treated with plasma at an appropriate power and time exhibit 100% FFR conversion and 95.8% FFA selectivity within 80 min at 80 °C and 1.2 MPa H2 pressure. Moreover, plasma treatment can be used to regenerate Co-B-P NB catalysts. The catalytic activity of Co-B-P NB catalysts can be restored using plasma treatment when it decreases because of their oxidation after several hydrogenation cycles.