Initial Hydrogen Pressure Research Articles

Selective hydroconversion of ethanolyzed soluble portion from the ethanolysis of Hanglaiwan long flame coal extraction residue over highly active Ni/SAPO-34 catalyst

The ethanolyzed soluble portion (SPE) prepared from the ethanolysis of Hanglaiwan long flame coal (HLFC) extraction residue was converted to catalytically hydroconverted SPE (CHSPE) by the catalytic hydroconversion (CHC) over Ni10 %/SAPO-34 at 200 °C under an initial hydrogen pressure of 5 MPa for 24 h. The possible mechanisms for the origin and synergic effect of active hydrogen had been speculated according to the reactions of HLFC-related model compounds. H2 can be activated by Ni10 %/SAPO-34 to produce H···H, H+, and H-, the synergic effect of which leads to cleaving >C-O- bonds. After the CHC, arenes and heteroatom-containing aromatic compounds in SPE are converted to cyclanes, indicating that aromatic ring hydrogenation and heteroatom removal occur simultaneously during the CHC of SPE. The relative abundance (RA) of CH-containing species in CHSPE is larger than that in SPE, while the RAs of oxygen- and nitrogen-containing species in CHSPE are smaller than those in SPE. In addition, Ni10 %/SAPO-34 has excellent cyclability for the CHC of SPE, and the relative content of cyclanes decreases only by 17.4 % after five recycles. Undoubtedly, this investigation provides an effective strategy for directional upgrading of derived soluble portion from low metamorphic coals.

Solvent‐Free Efficient Hydrogenation of Levulinic Acid over Silicotungstic Acid Promoting the Activity of CuNiAl Catalysts: A Synergistic Effect

AbstractMulti‐metallic catalysts rely on the synergistic effect between metals to perform better catalytic effect in biomass hydrogenation experiments compared with mono‐metallic catalysts. A series of CuNiAl composite metal oxide catalysts promoted by silicotungstic acid (HSiW), which were prepared by co‐precipitation and impregnation methods, were characterized by powder X‐ray diffraction (XRD), N2‐physisorption, scanning electron microscope (SEM) and NH3 program temperature desorption (NH3‐TPD) and pyridine infrared adsorption (Py‐FTIR). Their catalytic performance was evaluated in the hydrogenation of levulinic acid (LA) to prepare γ‐valerolactone (GVL). The results showed that the addition of Cu could improve the hydrogenation activity of Ni, and the addition of HSiW could further increase the amount of acid sites in the catalysts. Both of them could enhance the conversion of LA to some extent. CuNiAl‐5SiW, the par excellence catalyst, relied on the synergistic interactions between metals as well as the Brønsted and Lewis acid active sites to show efficient hydrogenation performance. The CuNiAl‐5SiW catalyst demonstrated 96.9 % conversion of LA and more than 99 % selectivity to GVL under 2 hours of reaction time, 180 °C of reaction temperature, 3.0 MPa of initial hydrogen pressure and solvent‐free conditions.

Hydrogenation of phenol to cyclohexanone catalyzed by isolated Pd cations in the micropores of zeolite

Cyclohexanone is a key raw material for manufacturing nylon and other chemicals. The sustainable conversion of biomass-derived phenol to cyclohexanone meets the requirements of sustainable development goal but still be challenging. Herein, a catalyst containing isolated Pd cations in zeolite, namely Pd1/ZSM-5, is investigated for the partial hydrogenation of phenol to cyclohexanone. Under 140 °C and 1.5 MPa of initial hydrogen pressure, the conversion of phenol reaches 95.6% with the selectivity to cyclohexanone of 99.9%. Besides, the turnover rate (TOR) of partial hydrogenation of phenol reaches 382.7 h−1. The mild adsorption affinity of cyclohexanone on catalytic sites leads to the high selectivity. Moreover, as unveiled by surface reactivity of phenol monitored by in-situ infrared spectrum, the oxygen atom of phenol hydroxyl group is adsorbed on the Brönsted acid site of Pd1/ZSM-5 as the key reaction step. The reaction intermediate involves the partial hydrogenation of benzene ring of phenol.

Experimental and numerical study of temperature evolution and hydrogen desorption process on an amorphous alloy Mg50Ni50

In the present study, we explored the temperature evolution and hydrogen desorption properties of the Mg50Ni50 alloy through both numerical simulation and experimental analyses. Desorption kinetics characterization was carried out using the volumetric method, specifically employing a Sievert's-type apparatus to investigate solid-gas reactions. The experiments covered a temperature range from 313 K to 353 K, with an initial hydrogen pressure of 12 bar. Simultaneously, a mathematical approach was employed to numerically investigate the temperature evolution within the hydride bed. Using COMSOL Multiphysics as a simulator, a numerical simulation was conducted based on experimental data. The study examined the impact of cooling temperature on hydride temperature evolution. Results revealed that hydrogen desorption kinetics of the amorphous Mg50Ni50 alloy are more significant compared to those of Mg2Ni compounds. Moreover, the effect of the warming temperature on the equilibrium pressure can also be observed in the hydrogen desorption isotherm curves. The experimental study of the Mg50Ni50 alloy provided activation energy data, along with determination of hydride formation enthalpy and entropy. On the other hand, we showed that the hydride temperature is maximum at the hydride-hydrogen interface within the hydride center.

Selective hydroconversion of lignin-derived compounds over a Ni/hydroxyapatite

Catalytic hydroconversion (CHC) of lignin-derived compounds (LDCs) to cyclanes and cyclohexanol (CHII) promotes the value-added utilization of LDCs. Nevertheless, designing a highly active and selective catalyst for this purpose remains a challenge. Herein, Ni/hydroxyapatite (HAP) was fabricated by a slightly modified deposition–precipitation approach and employed for the CHC of benzyloxybenzene (BOB) and phenethoxybenzene (PEOB) under different conditions. Consequently, BOB was fully converted with CHII and methylcyclohexane (MCH) as the main products (MPs) in the yield of 94.8 and 100 % under the optimum conditions of 20 mg Ni15/HAP, 140 °C, 4 MPa H2, and 4 h, while complete conversion of PEOB to CHII and ethylcyclohexane (ECH) as MPs proceeded under initial hydrogen pressure of 4 MPa at 180 °C for 4 h. In addition, other lignin-related model compounds can also be selectively hydrogenated to cyclanes and CHII, suggesting the high activity and selectivity of Ni15/HAP. Meanwhile, based on the product distribution and Ni15/HAP characterization, relevant mechanisms were proposed. Specifically, BOB conversion to CHII and MCH via the >CH–O– bond cleavage induced by H− addition, abstraction of H+ by the resulting phenoxy anion from the catalyst surface, and benzene ring hydrogenation, whereas conversion of PEOB to CHII and ECH was similar to BOB. Furthermore, Ni15/HAP displays an excellent reusability.

Stable and selective multi-porous nickel nanoparticles catalysts for hydrocracking of dibenzyl ether supported by DFT studies

Preparation of clean fuel from biomass has a crucial significance on the development and utilization of renewable clean energy. In this study, a multi-stage porous mordenite supported nickel nanoparticles catalyst (Nix%/HMOR) was prepared, which showed that its acid content, acidity, porosity, specific surface area and metal dispersion were significantly improved while the crystallization strength was basically the same compared with microporous mordenite. In order to study the conversion mechanism of biomass energy, dibenzyl ether was selected as a typical lignin model compound. Under the condition of Ni10%/HMOR in n-hexane at 160 °C for 2 h under 5 MPa of initial hydrogen pressure, the conversion of dibenzyl ether was 100 % and the selectivity of methyl cyclohexane was 84.4 %, which manifested that Ni10%/HMOR had good activity in the selective hydrocracking process under mild conditions. Furthermore, density functional theory (DFT) was selected to study the activation energies of different reaction sites on dibenzyl ether bridge bonds and the recombination process of free radicals in the reaction process. It comes to a conclusion that the O atom on the C-O bridge bond is easier to be attacked by H*, and the C-O bond of the unsaturated aromatic ring is easier to break. During the recombination of free radicals, the two C-O bond breaking energy barriers of OMD are different, and H free radicals are more likely to attack the O atom in cyclohexane-methanol. It is conducive to the formation of stable compound 1 - (cyclohexylmethyl) − 1-methylcyclohexane and its isomers.

Development of a metal hydride hydrogen compressor with high-pressure hydrogen storage alloys

Single- and double-stage metal hydride hydrogen compressors (MHHC) were developed using two series of metal hydrides of AB5-based La0.5Ce0.5Ni5-xAlx (x = 0, 0.1, 0.2) alloys and AB2-based Ti1-yZryMn0.8Cr1.2 (y = 0.05, 0.1, 0.2) alloys. In single-stage mode, La0.5Ce0.5Ni5 and Ti0.9Zr0.1Mn0.8Cr1.2 alloys could produce hydrogen pressures of 117 atm and 132 atm, respectively, at 100 °C. When the temperature was raised to 140 °C, both alloys could produce hydrogen pressures of 200 atm. The Ti0.9Zr0.1Mn0.8Cr1.2 alloy exhibited higher hydrogen discharging pressure and faster kinetics than those of the La0.5Ce0.5Ni5 alloy. A pair of alloys were used for a double-stage MHHC (first stage: Ti0.9Zr0.1Mn0.8Cr1.2; second stage: Ti0.95Zr0.05Mn0.8Cr1.2). The initial hydrogen pressure of 50 atm increased to 245 atm when the working temperature was raised from 25 °C to 100 °C, which provides an opportunity for designing a compact and simple MHHC.

Hydrodecyclization of Naphthenes over Iridium-Containing Zeolite Catalysts

The study investigates the hydrodecyclization of decalin over zeolite catalysts. The synthesized catalysts were characterized using a combination of physicochemical methods, such as TEM, SEM, low-temperature nitrogen adsorption/desorption, and XPS. The zeolite structure was found to have a major effect on the hydrodecyclization process. This process involves the isomerization of one ring followed by the opening of that ring. Incorporating iridium into the catalysts promoted the production of branched hydrocarbons. When testing the process in the temperature range of 300–400°C and at an initial hydrogen pressure of 50 atm, the Ir/BEA catalyst exhibited the highest activity: at 350°C the decyclization of decalin exceeded 50%.

Uncovering the Hydrocracking Efficiency of Iron-Based Catalysts: A Novel Approach to Asphaltene Transformation in Iranian Heavy Oil

In the quest for optimal asphaltene conversion, this study investigated a range of cost-effective and easily accessible catalyst precursors, targeting both high yields of lighter products and minimal coke formation. The hydrocracking experiments were conducted within a 10 ml bomb-type reactor equipped with a reciprocating stirrer operating at a reciprocation rate of 200 times per minute. The experiments were performed at a temperature of 425°C for a duration of 90 minutes, with an initial hydrogen pressure of 100 bar. The outcomes of each experiment were assessed in terms of liquid products, coke production and C5- gas products. To analyze the Iranian heavy asphaltene, Nuclear Magnetic Resonance (1H NMR), Gel Permeation Chromatography (GPC) and elemental analysis were employed. Gas products were characterized using Gas Chromatography (GC). The investigation aimed to identify the catalyst precursor mixture that would maximize asphaltene conversion while minimizing coke production. A series of catalyst precursors, encompassing FeSO4·H2O, its binary mixtures with metal oxides (Fe2O3, Al2O3, CaO, SiO2), and combinations of Fe2O3, Al2O3, and SiO2 with elemental sulfur, were evaluated. The experimental results demonstrated that the toluene-soluble fraction (TSF), which includes the middle distillate portion, could be increased to a maximum of 56% while concurrently reducing the coke yield to 19%, down from the initial 36.9% when no precursor was used.

Ceria supported nickel nanoparticles for catalytic hydroconversion of lignin-related model compounds

The combination method of impregnation, desiccation, and subsequent reduction with H2 was applied to prepare Nix/CeO2. Each catalyst was characterized with multiple tools and its catalytic performance for the catalytic hydroconversion (CHC) of lignin-related model compounds (LRMCs) containing oxybis(methylene)dibenzene (OBMDB) and guaiacol was evaluated. Over Ni14%/CeO2, OBMDB was completely converted into methylcyclohexane under initial hydrogen pressure (IHP) of 3 MPa at 200 °C for 2 h. The complete conversion of guaiacol to cyclohexanol (CHII) was realized under IHP of 4 MPa at 200 °C for 3 h. Additionally, H2 can be activated to H⋯H, H+, and H− over Ni14%/CeO2. H+ is attracted by oxygen atom in OBMDB, leading to the cleavage of >CH2-O- bond to produce phenylmethanol (PM) and benzylium, which is subsequently comminated with H− to produce toluene. Next, H⋯H transfers to toluene and PM resulting in the hydrogenation of benzene rings (BRs) to produce methylcyclohexane and cyclohexylmethanol followed by the dehydration to form methylcyclohexane. BR in guaiacol was hydrogenated by H⋯H transfer to produce 2-methoxycyclohexan-1-one (MCHI) and 2-methoxycyclohexan-1-ol (MCHII) in sequence and subsequent demethoxylation of them to generate cyclohexanone (CHI) and CHII, respectively. Finally, H⋯H transfers to CHI to produce CHII.

Catalytic hydroconversion of guaiacol and a poplar lignin derivate to cyclanes over Ni20%/β25

Upgrading lignin derivatives (LDs) to cyclanes by catalytic hydroconversion facilitates the value-added utilizations. Ni20%/β25 was prepared via a deposition-precipitation method and used for catalytically hydroconverting guaiacol and a poplar lignin derivate (PLD). Guaiacol was completely converted to cyclohexane (CH) as the main product in the yield of 93.3 mol% at 220 °C under initial hydrogen pressure of 4 MPa for 2 h, while the PLD was significantly converted to cyclanes over Ni20%/β25 for 8 h. Density functional theory combined with experiments explained the related mechanisms, i.e., H2 was activated to H…H, which was split to relatively mobile H+ and immobile H- over Ni20%/β25. H…H transfer to benzene ring (BR) leads to BR hydrogenation and subsequent H+ transfer to the oxygen atom in -OCH3 and -OH connected to the hydrogenated BR induces the demethoxylation and dehydroxylation.

Catalytic hydroconversion of a cotton stalk-derived soluble portion over Ni/sepiolite

Catalytic hydroconversion (CHC) of a lignin-derived soluble portion to value-added chemicals is of great significance. Ni/sepiolite was successfully prepared via a impregnation method and used for the CHC of a cotton stalk-derived soluble portion (CSDSP). Cyclanes and cyclohexanols are the main products with total relative content of 64.7% from the CHC of CSDSP over Ni/sepiolite. To better understand the reaction mechanism, the CHC of oxydibenzene (ODB), benzyloxybenzene (BOB), and guaiacol over Ni/sepiolite were investigated. They were completely converted at 240 °C under 4 MPa of initial hydrogen pressure. According to the resulting products, H…H and H+ are the main active hydrogen species in the CHC and H+ transfer induces the cleavage of -CH2-O- bond in BOB followed by hydrogenating benzene ring (BR), while the CHC of ODB and guaiacol proceeds via the hydrogenation of BR and subsequent cleavage of -CH2-O- bond.

Novel synthesis of LaH2 and La2O3 through mechanochemistry and sintering

Some hydrogen storage materials have been created by a mechanochemical method utilizing ball milling and hydrogen gas. This study developed a novel method for employing hydrogen gas in a ball milling process followed by sintering to dissociate La(OH)3 into La2O3 and produce LaH2. This study aimed to sinter and mill La(OH)3 in a planetary ball with hydrogen, determine the underlying sub-reaction pathways, and characterize the resultant products. The materials characterization was performed through XRD, PSA, DSC/TGA, and SEM-EDS. The rate of hydrogen pressure decrease during ball milling was from 0.0037 to 0.0049 bar/h. The longer the ball milling time, the higher the amount of LaH2. The resulting intermediate compounds after ball milling were LaH2, La, and H2O2, whose composition variations depended upon the initial hydrogen pressure and milling time. LaH2 and La2O3 were the final products following sintering, whose compositions varied depending on the intermediate compounds and their susceptibility to oxygen.

Hydrogen storage properties of the TiVFeZr multicomponent alloy with C14-type laves phase structure

In this work, the structure and hydrogen storage properties of the TiVFeZr multicomponent alloy with C14-type Laves phase structure was comprehensively investigated. This alloy presents fast hydrogen storage kinetics at room temperature with high hydrogen storage capacity, absorbing H/M = 1.5 (2.41 wt%) in less than 100 s under initial hydrogen pressure of 20 bar. This is one of the highest hydrogen storage capacities among the Laves phase alloys reported to date. The formed hydride is highly stable, which needs temperatures above to 550 °C to completely desorb hydrogen. The high hydrogen storage capacity of this alloy as well as the high stability of the formed hydride are discussed in terms of the high fraction of hydride forming elements in the C14-type Laves phase structure.

R&D of a Hydraulic Hydrogen Compression System for Refuelling Stations

Abstract The article presents a hydraulic hydrogen compression solution designed to serve as a booster compressor. It can be adapted to changing parameters of the inlet pressure of hydrogen and allows stabilising the hydrogen accumulation process in the high-pressure storage. The main results of this study were obtained using a numerical model developed to explore the thermodynamic processes that occur during the hydraulic compression of hydrogen. The modelling was carried out using COMSOL Multiphysics® 6.0 software with the CFD and heat transfer modules. The compression chamber in the form of a cylinder with a volume of 1.14 l and wall thickness of 5 mm was used in the computational model. The aim of these simulations was to investigate the temperature change limits of hydrogen, cylinder walls and working fluid, as well as to estimate the actual value of pressure inside the cylinder. The considered process of pressure increase in the cylinder chamber was modelled as a continuous change of volume filled with working fluid with discrete time step of 0.01 s, taking into account the increase of temperature inside the cylinder. The derived modelling results for different durations of compression stroke ts from 0.5 to 20.0 s were presented. The curves of energy consumption and temperature rise during the compression process were calculated for initial hydrogen pressures P1 = 3.0, 10.0, 15.0 and 20.0 MPa and compression ratio Kc = 5.0. The results of simulation of thermodynamic processes and their analysis allowed estimating energy consumption in the system of hydraulic compression and determining conditions which would lead to the increase in efficiency of hydrogen compression operation systems under consideration.

Investigation on the catalytic performance of magnetic copper ferrite nanoparticles in the catalytic hydroconversion of Hanglaiwan long flame coal

Magnetic copper ferrite (CuFe2O4) was prepared by hydrothermal synthesis method and used for the catalytic hydroconversion (CHC) of Hanglaiwan long flame coal (HLFC) in cyclohexane under 1 MPa of initial hydrogen pressure (IHP) at 300 °C for 4 h. The total yield of soluble portion (SP) from the CHC is 33.7 wt%, significantly being higher than that (10.5 wt%) from the non-CHC (NCHC) under the same conditions. The main compounds detected in SPCHC (for CHC) are arenes and oxygen-containing organic compounds (OCOCs). Benzyloxybenzene (BOB), 2-(benzyloxy)naphthalene (BON), oxybis(methylene)dibenzene (OBMDB), oxydibenzene (ODB), and 2,2′-oxydinaphthalene (ODN) were used as HLFC-related model compounds to investigate the catalytic activity of CuFe2O4 and understand the CHC mechanism of HLFC. According to the model reactions, CuFe2O4 activates H2 to biatomic active hydrogen (H…H) and splits H…H to mobile H+ and immobile H-. H+ addition to oxygen atoms (OAs) in >C-O- bridged bonds (BBs) cleaves the BBs and releases SP during the CHC of HLFC.

Determination of Optimal Conditions for Catalytic Hydrogenation of Oil Sludge (Atasu-Alashankou)

The optimal conditions of catalytic hydrogenation of oil sludge (Atasu-Alashankou) and the change in the kinematic viscosity of the fraction to 350℃ from the studied factors using the method of probabilisticdeterministic planning were experimentally determined. During the hydrogenation process of oil sludge, the maximum total yield of light fractions reached 62.1 %, and the kinematic viscosity decreased from 2.2 to 1.2 mm2/s. It was established the initial hydrogen pressure and the amount of added nanocatalyst microsilicate with cobalt (catalyst 1) have the greatest influence on the yield of the middle fraction from oil sludge under experimental conditions. It was shown that catalyst 1 increases the yield of diesel fraction components during the hydrogenation process of oil sludge. For the first time, we established the individual and group chemical composition of the fraction up to 350℃ before and after processing. The use of nanocatalyst 1 in amounts of 1.2–1.5 % led to an increase in the yield of the fraction up to 350℃ and diesel fraction components. This is due to the yield of paraffinic hydrocarbons increasing from 57.6 (initial fraction) to 80.7 %, as well as a decrease in aromatic hydrocarbons from 14.1 to 12.9 % and polycyclic aromatic hydrocarbons from 9.56 to 4.3 %.

Optimal design modeling of an energy system for a near-zero energy restaurant with green hydrogen energy storage systems

In this research, we want to analyze the consumed energy of an nZEB restaurant in a typical city to anticipate tourists. The energy of this restaurant is supplied through solar panels and electricity grids and we use the hydrogen storage tool because of its advantages to store energy. In this regard, Using the Fanger model, the thermal comfort of passengers was assessed, the energy consumption rate was obtained for the refrigerator, HVAC, lights, and systems, and the consumed water of the restaurant is supplied. Trnsys software was used for this simulation, and the transient performance of the mentioned nZEB in a year is evaluated by Trnsys software. PV panels are used to supply the consumed electricity of the building, A tank stores hydrogen and the extra produced electricity that can be used as needed if sunlight is scarce or electricity is needed. A solar collector is used to generate hot water, and a water tank is used to store the generated hot water. A heat pump is used to supply the cooling load and heating. The consumed hot water by the dwellers is supplied using the stored hot water. With the help of MATLAB software, the Fanger model is used to evaluate the thermal comfort of dwellers. The energy and performance of the restaurant refrigerator are obtained by TRNSYS and EES software. The results show that a significant part of the restaurant's electricity is supplied using 140 PV panels with 0.89 area. In addition, the initial hydrogen pressure tank was lower than the final hydrogen pressure tank. In this regard, energy for the heat pump, refrigerator, light, pump, fan, and compressors is supplied well. Using 16 square meters of solar collectors, the building gets its hot water. Furthermore, the restaurant's air conditioning system provides thermal comfort throughout the year. As a result, using the building roof area for ZEB can significantly reduce the greenhouse gas emissions of Doha.

Specific cleavage of >CH-O-bonds in benzyloxybenzene and poplar lignin over nickel supported on a nitrogen-doped carbon material

Nickel supported on a nitrogen-doped carbon material (NDCM) was successfully prepared and used for catalyzing the hydroconversion of benzyloxybenzene (BOB) and poplar lignin (PL). Over Ni/NDCM, BOB was completely converted to toluene and phenol in the yields of 75.5 and 73.1 mol%, respectively, under initial hydrogen pressure (IHP) of 2 MPa at 240 °C for 2 h. The adsorption energies (AEs) of different systems were calculated using the density functional theory. The AEs of H2 on Ni (111), Ni (200), and Ni (220) crystal planes are −1.26, −1.27, and − 1.28 eV, respectively, indicating that Ni (111) crystal plane is the most active for splitting H2 to mobile H+ and immobile H−, the higher absolute value of AE (−2.5 eV) of BOB on Ni/NDCM facilitates BOB hydrocracking. Moreover, Ni/NDCM could promote the cleavage of >CH-O- bonds in PL to produce more phenols.

Branched-chain biofuels derived from hydroisomerization of palm olein using Ni/modified beta zeolite catalysts for biojet fuel production

To overcome mass transfer limitation and adjust zeolite's acidity, the modification of beta zeolite via etching with hydrofluoric acid/ammonium fluoride (HF/NH4F) solution was revealed and the modified beta zeolite was then applied as a support of nickel (Ni) catalysts used for hydroisomerization of palm olein. HF/NH4F solution containing 0.25 M HF concentration was appropriate to enlarge original existing intercrystalline mesopores of beta zeolite (beta-0.25), which resulted to the higher pore volume. The Ni/beta-0.25 catalyst also exhibited the better Ni dispersion and lower acidity. These features suppressed overcracking and provided 43.4 wt% bio-jet fuel yield with 22.1 wt% iso-alkanes fraction when hydroisomerization was operated under 40 bar initial hydrogen (H2) pressure at 340 °C for 5 h. At 0.75 M HF concentration, the excessive leaching of aluminum species out of the zeolite framework provided beta-0.75 with very low acidity, which was ineffective to convert molecules of palm olein to bio-jet fuel range. Initial H2 pressure at 40 bar was sufficient to activate the hydroisomerization of palm olein over Ni/beta-0.25 catalyst to produce liquid biofuel containing iso−/n-alkane ratio of 2.61. The liquid biofuel/Jet A-1 blend at 50% (v/v) had freezing point and gross heating value of −58.9 °C and 43.7 MJ/kg, respectively.