Low H2 Pressure Research Articles

Tailoring the d‐band centers enables NiM alloy to be multifunctional site for tandem reductive amination

AbstractIntegrating multi‐step reactions through tandem catalysis offers potential for efficient chemical engineering processes, but designing an efficient tandem catalyst is challenging. Herein, we report tailoring the d‐band centers of Ni through alloying with a second metal (M = Fe/Co/Cu/Ga), which enables it to be multifunctional site for tandem reductive amination. A linear correlation of d‐band center with yield of primary amine product was observed. Density functional theory and experiments revealed the upshifted d‐band center strengthened the adsorption of Schiff base intermediate in advantageous di(C&N) mode, also narrowed the adsorption energy gap between NH3 and H2. Furthermore, the multifunctional nanoparticles provide a confined space with short diffusion pathway for NH3* and H* to timely react with Schiff base. As a result, the NiFe/AlOx with a d‐band center nearest to the Fermi level exhibited the highest primary amine yield of 96.2% with five consecutive reusability under extremely low H2 pressure, which is superior to other reported precious‐metal‐based catalysts.

Selective hydrodeoxygenation of guaiacol to phenol over CoFe/reduced graphene oxide

A reduced graphene oxide (rGO)-supported CoFe bimetallic catalyst (CoFe/rGO) was synthesized and used for hydrodeoxygenation of guaiacol to phenol (Ph). The CoFe/rGO catalyst without reduction pretreatment showed excellent catalytic performance, achieving 94.0 mol% conversion and 70.8 mol% selectivity to Ph at mild reaction temperature and low H2 pressure. The microstructure and chemical composition of the CoFe/rGO catalyst were characterized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and H2 temperature-programmed reduction (H2-TPR) characterization analysis. Co and Fe are supported on rGO in forms of the isolated metal atoms embedded in the rGO matrix and the CoFe oxide nanoparticles attached on rGO surface. Fe as a promoter weakens the hydrogenation activity of Co to benzene ring and dramatically improves the selectivity to Ph. The unique of rGO on constructing catalytic active sites and the synergistic effect of Co and Fe bimetals make CoFe/rGO an excellent catalyst.

Ru nanoparticles supported on various metal-modified (La, Zr, Cr, Ce and Ga) α-Al2O3 for the selective hydrogenolysis of lignin and its derived ethers

Controlling the C-O bond hydrogenolysis while suppressing the direct hydrogenation of aromatic rings in lignin-derived ethers is critical and challenging for the utilization of lignin. Herein, a series of metal-modified (La, Zr, Cr, Ce and Ga) α-Al2O3-supported Ru-based catalysts were synthesized for the conversion of diphenyl ether (DPE). The catalyst characterizations demonstrate that the metal modification cannot change the chemical valence of Ru but promotes the dispersion of Ru nanoparticles and adjusts the adsorption state of DPE. The results indicate that the metal modification inhibits the arenes hydrogenation at low temperatures but facilitates the C-O bond cleavage during heating (at low H2 pressures or an inert atmosphere). Ru-Cr/α-Al2O3 shows the highest reaction rate for DPE conversion at 1 MPa Ar and 200 °C. Moreover, Ru-Cr/α-Al2O3 not only efficiently converts different lignin model compounds by hydrogenolysis, but also achieves the controlled depolymerization of real lignin to generate guaiacols under mild conditions.

Microwave-Assisted Reductive Amination under Heterogeneous Catalysis for the Synthesis of β-Adrenergic Agonist and Related Structures

Reductive amination is a powerful tool in sustainable organic synthesis that allows chemists to access a wide range of valuable amine products using renewable feedstocks and mild reaction conditions, with minimal waste generation. Practical applications can be found in various fields, including pharmaceuticals, contributing to greener and more sustainable chemical processes. In this work, we present a heterogeneous (Rh and Pt) catalyzed protocol for the fast and efficient synthesis of ractopamine hydrochloride (β-adrenergic drug) under microwave-assisted reductive amination protocol starting from raspberry ketone and octopamine. Microwave (MW) successfully accelerated the hydrogenation reaction and reduced the reaction time from 13 h to only 3 h under mild conditions (50 °C at 10 bar). The best catalysts were Pt/C and Rh/C, which led to high conversion and selectivity towards ractopamine:HCl. Different solvents and ketone substrates were also experimented. Acetophenone, cyclohexanone, and 2-butanone reacted at lower H2 pressure (5 bar), and highest selectivity was observed with cyclohexanone (99%). These preliminary experiments may be useful for further process improvements in the synthesis of β-adrenergic agonists and related structures and underline the positive synergy between MW and heterogeneous catalysis.

Mild hydrogenolysis of lignin model compound and organosolv lignin over non-noble bimetallic Ni–Fe/TiN catalyst

Lignin is one of the most promising feedstocks for renewable aromatics production. Conversion of such feedstock into aromatics can be attained through catalytic hydrogenolysis. In this work, NixFey/TiN bimetallic catalysts were evaluated in the hydrogenolysis of both: (i) benzyl phenyl ether (BPE) as a model compound for lignin and (ii) real organosolv lignin feedstock under low temperature (150 °C) and low H2 pressure (12 bar). All bimetallic catalysts exhibited superior performance over single-component materials and were shown to compose of uniformly/highly dispersed and intimately mixed Ni and Fe nanoparticles. Among bimetallic materials, Ni5Fe2/TiN possesses the highest activity in BPE hydrogenolysis, which is comparable to that of a 5% Pd/C commercial catalyst while showing significantly higher aromatic selectivity. Ni5Fe2/TiN catalyst also outperformed Pd/C in hydrogenolysis of organosolv lignin, shown by its higher oil yield, greater content of phenolic monomers, and lower content of dimers. This material exhibited good stability in BPE conversion with no noticeable deactivation over 5 recycling cycles. XANES analysis suggests the electron transfer from Ni to Fe, which explains the superior activity observed with Ni5Fe2/TiN.

L-Lysine Stabilized FeNi Nanoparticles for the Catalytic Reduction of Biomass-Derived Substrates in Water Using Magnetic Induction.

The reduction of biomass-derived compounds gives access to valuable chemicals from renewable sources, circumventing the use of fossil feedstocks. Herein, we describe the use of iron-nickel magnetic nanoparticles for the reduction of biomass model compounds in aqueous media under magnetic induction. Nanoparticles with a hydrophobic ligand (FeNi3 -PA, PA=palmitic acid) have been employed successfully, and their catalytic performance is intended to improve by ligand exchange with lysine (FeNi3 -Lys and FeNi3 @Ni-Lys NPs) to enhance water dispersibility. All three catalysts have been used to hydrogenate 5-hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan with complete selectivity and almost quantitative yields, using 3 bar of H2 and a magnetic field of 65 mT in water. These catalysts have been recycled up to 10 times maintaining high conversions. Under the same conditions, levulinic acid has been hydrogenated to γ-valerolactone, and 4'-hydroxyacetophenone hydrodeoxygenated to 4-ethylphenol, with conversions up to 70 % using FeNi3 -Lys, and selectivities above 85 % in both cases. This promising catalytic system improves biomass reduction sustainability by avoiding noble metals and expensive ligands, increasing energy efficiency via magnetic induction heating, using low H2 pressure, and proving good reusability while working in an aqueous medium.

Highly Efficient Ruthenium-Catalyzed Semi-hydrogenation of Urea Derivatives to Formamides.

The utilization of CO2 as a non-toxic and cheap feedstock for C1 is a desirable route to achieve high value-added chemicals. In this context, we report a highly efficient ruthenium-catalyzed semi-hydrogenation reaction of CO2 -derived ureas. Various alkyl and aryl urea derivatives were successfully hydrogenated to obtain the corresponding recyclable amines and formamides (up to 97 % yield), highlighting the good substrate applicability of this method, which makes this method a sustainable alternative for the hydrogenation of CO2 to formamides in the presence of amines. In the meantime, we have discovered a new pathway that enables rapid hydrogenation of urea derivatives even at lower H2 pressure (<5 bar). This methodology might provide a new insight into the reduction functionalization of CO2 under mild pressure to form new C-N bond. Based on the control experiments and the observed intermediate products, we clarify the mechanism for selective semi-hydrogenation of ureas.

Harvesting alkyl phenols from lignin monomers via selective hydrodeoxygenation under ambient pressure on Pd/α-MoC catalysts

Alkyl phenol is an essential chemical intermediate that is in high demand in the chemical industry. The synthesis of alkyl phenols from lignin-derived molecules is one of the most promising routes for utilizing biomass resources. Herein, we report the catalytic hydrodeoxygenation (HDO) of dihydroeugenol (DHE) to alkyl phenols over a highly dispersed Pd/α-MoC catalyst with a substrate conversion of 98% and a selectivity of 96% to alkyl phenols. The Pd/α-MoC catalyst prepared by co-precipitation and temperature-programmed carbonization exhibits exceptional HDO activity under mild conditions with a low H2 pressure (1–10 bars). The characterizations of the catalyst suggest that Pd are highly dispersed on the α-MoC matrix. The reaction mechanism was investigated using the substrate scope experiments. Under ambient pressure, the abundant oxygen vacancies and acidity sites on Pd/α-MoC enable the selective hydrodeoxygenation of lignin monomers.

Catalyst-free synthesis of lithium hydride at room temperature.

An organic solvent-assisted catalyst-free mechanochemical reaction is developed to synthesize lithium hydride at mild gas pressures and room temperature. Studies show that the formation of intermediates on the surface of bulk lithium metal is crucial for the synthesis of high purity (>98%) LiH. This provides a new strategy for the large-scale production of lithium-based hydrogen storage materials.

Hf4+-exchanged montmorillonite-boosted Pd-catalyzed reductive aminolysis of aryl ethers to efficiently synthesize cyclohexylamines

A robust and completely heterogeneous catalyst, Pd/Hf-MMT, was highly efficient for reductive aminolysis of aryl ethers to producce N-cyclohexyl-substituted amines at a low H2 pressure of 0.3 MPa without using any homogeneous acidic additives.

Cascade upcycling polystyrene waste into ethylbenzene over Fe2N @ C

Thermochemical conversion is one of the most effective ways to upcycle organic solid wastes into fuels and/or value-added chemicals. In this study, the tandem hydropyrolysis/hydrocracking of polystyrene (PS) to produce ethylbenzene was studied using metal nitrides as catalysts. Fe, N co-doped carbon-based catalyst (Fe2N @ C) with core-shell structure was synthesized. The experimental results showed that carbon doping significantly improved the catalytic performance of iron nitride. The yield of ethylbenzene obtained from Fe2N @ C catalysis was 81 wt%, which is much higher than that of Fe2N (63.3 wt%) and commercial iron nitride (FeN, 4.9 wt%) under the hydropyrolysis temperature of 480 ℃, hydrocracking temperature of 280 ℃, and low H2 pressure of 0.2 MPa. The high catalytic activity of Fe2N @ C is ascribed to the synergy of metal-based selective hydrogenation and acid site-mediated C-C bond activation. This work provides a flexible and efficient catalytic technology for the high-value utilization of polystyrene waste.

Metataxonomic characterization of an autochthonous and allochthonous microbial consortium involved in a two-stage anaerobic batch reactor applied to hydrogen and methane production from sugarcane bagasse

Enzymatically pre-treated sugarcane bagasse (SCB) was used as substrate for sequential production of hydrogen (H2) and methane (CH4). In stage I, SCB was used by autochthonous bacteria, such as Enterococcus (42.4 % relative abundance) and Paraclostridium (16.8 %) for H2 production (166.8 mL H2/L), while the metabolites accumulated at the end of this stage (9140.5 mg HAc/L) were used by allochthonous inoculum for CH4 production (870.8 mL CH4/L) in stage II. In stage II, hydrogenotrophic (Methanoculleus, 49.1 %) and acetoclastic (Methanosaeta, 15.5 %) archaeal genera were identified and considered important to maintain low H2 pressure in the system. According to gene inference, the hydrolysis of the SCB fiber was performed in both stages, as potential β-glucosidase and 1,4-β-xylosidase encoding genes were predicted. However, the energy metabolism of microbial populations differed, as potential genes involved in CH4 metabolism were predominant in phase II (39.0 %).

Hydrodeoxygenation of C3–4 polyols to C3–4 diols over carbon-supported bimetallic MgCu@C catalysts prepared from ion exchange resin

The selective hydrodeoxygenation (HDO) of C3–4 polyols (glycerol and erythritol) to value-added diol products was investigated over a series of Cu-based catalysts, namely, carbon-supported monometallic Cu@C and bimetallic MgCu@C prepared by using a weakly acidic cation-exchange resin as the carbon support precursors. High metal loading (> 50 wt%) and small metal particle size (< 15 nm) were realized by the catalyst prepared from ion-exchange resin. The addition of Mg decreased Cu particle size (10.0–13.5 nm) and improved metal dispersion. The largest metal surface area was achieved for the MgCu@C catalyst with Mg/Cu molar ratio of 1/9. Furthermore, HDO of C3–4 polyols was performed over the prepared catalysts at relatively low temperature (180 °C) under low initial H2 pressure (1.2 MPa). Over the MgCu@C catalyst with a nominal Cu/Mg atomic ratio of 9/1, a C3 polyol conversion of 94.0 C mol% was obtained with a high selectivity towards 1,2-propanediol (94.3 C mol%), while a low erythritol conversion of 18.75 C mol% with a selectivity toward butanediols of 43.0 C mol% was achieved after 360 h reaction. The different effects of the Mg addition on catalytic activity to C3 and C4 polyol HDO were likely attributed to the different reaction mechanism. The dehydration-hydrogenation mechanism was proposed for C3 HDO over Cu@C and MgCu@C, in which the addition of Mg species promoted the dehydration of glycerol to produce hydroxyacetone followed by the hydrogenation of hydroxyacetone to 1,2-propanediol.

Cu-Co nanoparticles supported on nitrogen-doped carbon: An efficient catalyst for hydrogenation of 5-hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan

Production of the 2,5-Bis(hydroxymethyl)furan (BHMF) has important scientific value and strategic significance for the development of new biodegradable polyester materials. Herein, Cu-Co/NC composites containing bimetallic nanoparticles in nitrogen-doped carbon were produced by the calcination of zeolitic imidazolate frameworks (ZIFs). They featured a cubic Cu-Co core and a porous structure derived from the ZIFs. The surface morphology, surface area, and composition of the catalysts were analyzed by scanning electron microscopy (SEM), transmission electron microscope (TEM), thermogravimetric (TG) analysis, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), CO2-temperature program desorption (CO2-TPD), and N2 adsorption-desorption isotherms. A conversion of 93.7% of 5-hydroxymethylfurfural (HMF) with a BHMF selectivity of 92.4% was achieved using the Cu0.04Co1/NC-450 catalyst at a relatively low reaction temperature and H2 pressure. This outstanding catalytic performance was ascribed to the high dispersion of Co nanoparticles in the NC framework, forming Co-Nx species. We found that the synergistic catalysis of Cu-Co sites due to electron transfer contributed to the increase in the BHMF selectivity during HMF hydrogenation. The intensity of the XRD peaks corresponding to metallic Co decreased as the calcination temperature increases, which results in agglomeration of Co nanoparticles (NPs), and reduces the catalytic activity in HMF hydrogenation. Additionally, the conversion of HMF during hydrogenation remained stable after using Cu0.04Co1/NC-450 for ten cycles.

Synergistic Effects of Earth-Abundant Metal–Metal Oxide Enable Reductive Amination of Carbonyls at 50 °C

Reductive amination of carbonyls to primary amines is of importance to the synthesis of fine chemicals; however, this reaction with heterogeneous catalysts containing earth-abundant metals under mild conditions remains scarce. Here, we show that the nickel catalyst with mixed oxidation states enables such synthesis of primary amines under low temperature (50 °C) and H2 pressure (0.9 MPa). The catalyst shows activity in both water and toluene. The high activity likely results from the formation of small (ca. 4.6 nm) partially oxidized nickel nanoparticles (NPs) homogeneously anchored onto the silica and their synergistic effect. Detailed characterizations indicate stabilization of NPs through strong metal support interaction via electron donation from the metal to support. We identify that the support endowed with an amphoteric nature shows better performance. This strategy of making small metal-metal oxide NPs will open an avenue toward the rational development of efficient catalysts that would allow for other organic transformations under mild reaction conditions.

Highly efficient syntheses of 2,5-bis(hydroxymethyl)furan and 2,5-dimethylfuran via the hydrogenation of biomass-derived 5-hydroxymethylfurfural over a nickel–cobalt bimetallic catalyst

The hydrogenation of furan derivatives is of great scientific and strategic significance because the molecular diversity of the hydrogenation products ensures the efficient utilization of biomass resources. In this study, an inexpensive and magnetically separable bimetallic catalyst (NixCoy) was synthesised via solid-phase grinding. The catalyst exhibited efficient catalytic activity towards the hydrogenation of 5-hydroxymethylfurfural (HMF) into 2,5-bis(hydroxymethyl)furan (BHMF) and 2,5-dimethylfuran (DMF) at a low reaction temperature and H2 pressure. Further, the 93.1% and 80.1% selectivities of BHMF and DMF with a full conversion of HMF were obtained under the optimal conditions by controlling the temperature, respectively. Furthermore, the as-prepared catalysts were characterized via the thermogravimetry–derivative thermogravimetry (TG-DTG), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and N2 adsorption–desorption isotherm techniques. Additionally, the synergistic catalytic effect of the hydrogenation sites in the Ni and Co metals, as well as the Lewis acid sites in NiO and CoO promoted the conversion of HMF into BHMF and DMF. Thereafter, the possible synergistic catalytic mechanism was proposed based on the characterization of the catalyst and the experimental results.

Roles of Nanostructured Bimetallic Supported on Alumina-Zeolite (AZ) in Light Cycle Oil (LCO) Upgrading

Light cycle oil (LCO) is one of the major products in Fluid catalytic cracking (FCC) processes, and has drawbacks such as high aromatics, sulfur, and nitrogen contents, and low cetane number (CN). Hydro-upgrading is one of the most typical processes for LCO upgrading, and alumina-zeolite (AZ) is an effective hydrotreating catalyst support. This paper examined the effects of different bimetallic catalysts (CoMo/AZ, NiMo/AZ, and NiW/AZ) supported by AZ on hydro-upgrading of both model compounds and real LCO. CoMo/AZ preferred the direct desulfurization (DDS) route while the NiMo/AZ and NiW/AZ catalysts favored the desulfurization route through hydrogenation (HYD). The presence of nitrogen compounds in the feed introduced a competitive adsorption mechanism and reduced the number of available acid sites. Aromatics were partially hydrogenated into methyltetralines at first, and then further hydrogenated, cracked, and isomerized into methyldecalins, monocyclic, and methyltetralines isomers. CoMo/AZ is the best hydrodesulfurization (HDS) catalyst for the model compounds at low H2 pressure (550 psi) and for LCO at lower temperature (573 K), while NiMo/AZ performs the best for LCO at higher temperature (648 K). NiMo/AZ is the best hydrodenitrogenation (HDN) catalyst for LCO. The hydrodearomatization (HDA) performances of NiMo/AZ and NiW/AZ improved significantly and overwhelmingly higher than that of the CoMo/AZ when the H2 pressure was increased to 1100 psi.

Synergistic Effect of Ni/W/Cu on MgAl2O4 for One-Pot Hydrogenolysis of Cellulose to Ethylene Glycol at a Low H2 Pressure.

Nickel and tungsten, combined with copper, were incorporated into a magnesium aluminum spinel to form a multifunctional catalyst (Ni–W–Cu/MgAl2O4). Characterization results suggested that the adjacent Cu not only facilitated the reduction of W6+ to W5+ with substantial oxygen vacancies but also promoted the reducibility of the Ni species. Besides, the incorporation of Ni, W, and Cu into the support enhanced the catalytic acidity, as well as the L acid sites. The catalyst exhibited a strong synergistic effect between the three metals and the support, resulting in higher catalytic activity for the one-pot hydrogenolysis of cellulose to ethylene glycol. High cellulose conversion (100%) and ethylene glycol yield (52.8%) were obtained, even under a low H2 pressure of 3 MPa.

Low-temperature catalytic upgrading of waste polyolefinic plastics into liquid fuels and waxes

A new low-temperature catalytic upgrading of waste polyolefinic plastics to valuable chemicals such as liquid fuels and waxes by a heterogeneous catalyst is presented. CeO2-supported Ru (Ru/CeO2) acted as an effective and reusable heterogeneous catalyst, showing much higher activity than other metal-supported catalysts in hydrogenolysis of low-density polyethylene, and the catalyst worked even under mild reaction conditions such as low temperature of 473 K and low H2 pressure of 2 MPa, providing liquid fuel (C5-C21) and wax (C22-C45) in 77 % and 15 % yields (total 92 % yield), respectively. This catalyst was applicable to hydrogenolysis of various low-density polyethylenes, high-density polyethylene, polypropylene to provide the valuable chemicals (liquid fuel + wax) in high yields (83–90 %). Furthermore, a commercial plastic bag and waste polyethylenes could be transformed to the valuable chemicals in high yields (91 % and 88 % yields).

An iron corrosion-assisted H2-supplying system: a culture method for methanogens and acetogens under low H2 pressures

H2 is an important fermentation intermediate in anaerobic environments. Although H2 occurs at very low partial pressures in the environments, the culture and isolation of H2-utilizing microorganisms is usually carried out under very high H2 pressures, which might have hampered the discovery and understanding of microorganisms adapting to low H2 environments. Here we constructed a culture system designated the “iron corrosion-assisted H2-supplying (iCH) system” by connecting the gas phases of two vials (one for the iron corrosion reaction and the other for culturing microorganisms) to achieve cultures of microorganisms under low H2 pressures. We conducted enrichment cultures for methanogens and acetogens using rice paddy field soil as the microbial source. In the enrichment culture of methanogens under canonical high H2 pressures, only Methanobacterium spp. were enriched. By contrast, Methanocella spp. and Methanoculleus spp., methanogens adapting to low H2 pressures, were specifically enriched in the iCH cultures. We also observed selective enrichment of acetogen species by the iCH system (Acetobacterium spp. and Sporomusa spp.), whereas Clostridium spp. predominated in the high H2 cultures. These results demonstrate that the iCH system facilitates culture of anaerobic microorganisms under low H2 pressures, which will enable the selective culture of microorganisms adapting to low H2 environments.