Initial Hydrogen Pressure Research Articles

Conversion of Crude Palm Oil into Hydrocarbons over Commercial Raney Nickel

Crude palm oil was hydrotreated over commercial Raney nickel as a catalyst at 360 °C and an initial hydrogen pressure of 90 bar. After 5 h, a full conversion into n-alkanes with yields between 54 and 60% relating to the mass of the feedstock was achieved. The obtained products, consisting solely of hydrocarbons, mainly C15 and C17, possess an excellent compound distribution in the diesel range. Hence, their suitability as a replacement or blending component for diesel fuel according to methods given in EN 590 was tested. It can be shown that they are well-suited as blending components. For use as 100% diesel replacement, however, further upgrading, such as hydroisomerization, would be necessary.

Stabilized Ni-based catalysts for bio-oil hydrotreatment: Reactivity studies using guaiacol

The development of catalysts possessing high activity and high stability in the catalytic hydrotreatment of pyrolysis oils (bio-oil) is of great interest. NiCu bimetallic catalytic systems are very attractive for use in hydrotreatment process due to their low price and high activity in hydrogenation, hydrodeoxygenation and hydrocracking reactions. In the present work P-/Mo-containing agents were used to modify bimetallic catalytic system NiCu/SiO2–ZrO2 to improve its mechanical strength and stability in acidic medium. The modified catalysts were tested in hydrodeoxygenation (HDO) of guaiacol—a well-known model compound of bio-oil. HDO process has been carried out in an autoclave at 320°С, 17MPa initial hydrogen pressure, reaction time 1h. It was shown that phosphorus and molybdenum addition to the catalysts composition results in the decrease of guaiacol conversion and deoxygenation degree. The yield of undesirable gaseous reaction products (mainly methane) and coking of the catalyst were lower for the modified catalysts in contrast to the initial NiCu/SiO2–ZrO2 system. The catalysts treatment in glacial acetic acid at 118°C showed that modification by P and Mo gives a significant improvement of catalysts stability in acidic medium (mass loss decreases from 53 wt.% to 1 wt.%). Also a significant improvement of bulk crushing strength has been observed for PMo-modified samples (from 0.5MPa to 1.2MPa).

Hydrogen storage properties and mechanisms of Mg(BH4)2⋅2NH3–xMgH2 combination systems

• A composite system composed of Mg(BH 4 ) 2 ⋅2NH 3 and MgH 2 was prepared. • Ammonia release from Mg(BH 4 ) 2 ⋅2NH 3 is fully depressed in the presence of MgH 2 . • ∼13.9 wt% H 2 is released from Mg(BH 4 ) 2 ⋅2NH 3 –MgH 2 initiated at 70 °C. • The dehydrogenated sample can take up 3.7 wt% H 2 at 450 °C and 100 bar. The hydrogen storage properties and mechanisms of the Mg(BH 4 ) 2 ⋅2NH 3 – x MgH 2 combination systems were systematically investigated. The release of ammonia from pristine Mg(BH 4 ) 2 ⋅2NH 3 was completely depressed in the presence of MgH 2 . Approximately 13.9 wt% of hydrogen was released from the Mg(BH 4 ) 2 ⋅2NH 3 –MgH 2 combination system at a molar ratio of 1:1 with an onset temperature of 70 °C, which is 75 °C less relative to the onset temperature of pristine Mg(BH 4 ) 2 ⋅2NH 3 . In the initial dehydrogenation stage, the Lewis base H δ− in MgH 2 first attacks H δ+ in the NH 3 group of Mg(BH 4 ) 2 ⋅2NH 3 to release hydrogen and generate a MgBH 4 NH 2 compound. Further elevation of the operating temperature results in the decomposition of MgBH 4 NH 2 , releasing hydrogen to form MgH 2 and BN. Finally, MgH 2 decomposes to release the remaining hydrogen to produce Mg. In addition, the dehydrogenated product absorbed approximately 3.7 wt% hydrogen at 450 °C with an initial hydrogen pressure of 100 bar, which demonstrates the partial reversibility for hydrogen storage.

Effects of Temperature and Initial Hydrogen Pressure on the Hydriding Properties of Zr9Ni11 Alloy

Abstract The hydriding properties of Zr 9 Ni 11 alloy at different temperatures (25∼150 °C) and various initial hydrogen pressures (10∼160 kPa) were investigated. The results show that with the increase of temperature, the equilibrium pressure of the Zr 9 Ni 11 alloy increases significantly, but its hydrogen absorption quantity decreases dramatically. When the temperature is less than 75 °C, the hydriding reaction rate of Zr 9 Ni 11 alloy increases with increasing of temperature; while the temperature is higher than 75 °C, the hydriding reaction rate of the alloy decreases with increasing of temperature. The initial hydrogen pressure has a great influence on the kinetic properties of the alloy. When the initial pressure is lower than 50 kPa, the hydriding reaction rate of the alloy increases obviously with the increase of the initial hydrogen pressure, and even in the case of relatively low pressure, the alloy can still absorb hydrogen dramatically. The hydrogen absorption quantity and the equilibrium pressure of the alloy increase with the increase of the initial hydrogen pressure. The samples of the alloy before and after hydrogenation were analyzed by XRD, SEM(EDS) and TEM(SAED). After several hydriding-dehydriding cycles, the surface of the alloy which is homogeneous and smooth before hydrogenation becomes rough and crannied, and the ratio of Zr and Ni on the surface is varied. It is also found the amorphous states might be increased and mischcrystal formed through hydriding-dehydriding cycles. Zr 9 Ni 11 alloy might be a promising candidate for extracting tritium according to our investigation.

Production of bio-hydrocarbons by hydrotreating of pomace oil

Olive pomace oil is a by-product from the olive oil industry that is still being used in the food industry as a low value vegetable oil. Crude olive pomace oil needs to be refined and is blended with virgin olive oils before being used as edible oil. The detection of toxic compounds led to more restricted legislation and to the search of alternative valorisation processes, such as hydrotreating to obtain bio-hydrocarbons. Hydrotreating of olive pomace oil at moderate temperatures (from 300 to 430°C) and in presence of initial hydrogen pressure of 1.1MPa led to triglycerides destruction and to their conversion into a large range of organic compounds with predominance to hydrocarbons. Even without any catalyst, conversions into hydrocarbons were always higher than 90% (v/v). Catalyst presence, such as: CoMo/Al2O3, FCC (fluid catalytic cracking) or HZSM-5 changed hydrogenated liquids composition. The highest content of alkanes was obtained with CoMo catalyst, while FCC and HZSM-5 led to the highest contents of aromatic compounds. The results obtained showed that olive pomace oil can be efficiently converted into bio-hydrocarbons with a wide range of applications. It was also studied the effect of pyrolysing olive pomace oil prior to its hydrotreating. Pyrolysis pre-treatment seems to have favoured hydrotreating process by promoting initial cracking reactions. Thus, it was possible to increase the production of liquid compounds with a higher content of light molecules. However, the advantages of using a more complex two steps process still need to be proven.

Reforming of Glycerol into Bio-Crude: A Parametric Study

AbstractThe reforming of glycerol was investigated using a micro-reactor in the presence of MoCoP/zeolite catalyst. The parameters which were investigated include initial hydrogen pressure, reaction temperature, residence time, and feedstock concentration. The liquid products were separated into water-soluble components and bio-oil by liquid-liquid extraction with water and ethyl acetate. The bio-oil, gaseous products, char, and unreacted glycerol were quantified relative to the initial mass of glycerol feed. The composition of the bio-oil was determined by GC/MS. The optimum conditions for the reforming of glycerol into bio-crude in the presence of MoCoP/zeolite catalyst were found to be: 300°C reaction temperature, 5 MPa initial hydrogen pressure, 60 min reaction time, and 100% glycerol feed. While dilution of the glycerol feedstock with water had a negative effect on bio-oil yield, reforming of pure glycerol produced the highest bio-oil yield (40 wt.% at 300°C, 1 h, and 5 MPa H2). The amount of char deposited on the catalyst decreased with extended reaction time, increased reaction temperature, and elevated initial hydrogen pressure.

Hydrogen storage characteristics of Ti45Zr38Ni17−xCox (x=4, 8) alloy and quasicrystal powders produced by mechanical alloying

Abstract The effect of substitution of Co for Ni on hydrogen storage characteristics of Ti–Zr–Ni/Co powders (Ti45Zr38Ni17−xCox (x = 4, 8)) produced by mechanical alloying (MA) was investigated. The final product after MA was amorphous for all the powders, but subsequent annealing caused the formation of the icosahedral quasicrystal (i) phase with a Ti2Ni type crystal and a C14 like Laves phases. The amount of i-phase decreased, and reversely those of Ti2Ni and the Laves phases increased with increasing the amount of Co. After hydrogenation at 573 K and at an initial hydrogen pressure of 3.8 MPa, the maximum hydrogen concentration for the annealed powders reached was about 58 at%, and all the phases in the powders transformed to metallic hydrides ((Zr,Ti)H2, Ni(Zr,Ti)H3 and Co(Zr,Ti)H3). Because of the formation of several hydrides, accelerated hydrogen desorption occurred at several temperatures. The activation energies for hydrogen desorption varied from about 70 kJ/mol to 180 kJ/mol.

Non-catalytic hydropyrolysis of microalgae to produce liquid biofuels

Non-catalytic hydropyrolysis of Chlorella pyrenoidosa was studied by using a stainless-steel batch reactor at different temperature (150–450°C), time (5–120min) and initial hydrogen pressure (1atm–8MPa), aiming to find how these parameters affect the product (oil, gas and solid) yields and properties of the hydropyrolysis oil (HPO). Temperature was the most influential factor to the relative amount of each product and properties of the HPOs. The hydrogen favored the stabilization of the active intermediates but cannot guarantee to produce HPOs in higher hydrogen at its higher initial pressure. The HPO, which showed much difference in component strongly depending on the reaction conditions, mainly consisted of aromatics and straight-chain hydrocarbons, amides, amines, nitriles and carboxylic acids at moderate temperatures. The main gas products detected during the hydropyrolysis were unreacted H2, CO2, CO and CH4. About 85% of energy originally present in the microalgae was recovered as oil under the optimal conditions.

Hydroconversion of an atmospheric residue with a dispersed catalyst in a batch reactor: Kinetic modeling including vapor–liquid equilibrium

A kinetic model was proposed to describe the atmospheric residue hydroconversion with a dispersed catalyst in a batch reactor. The model, taking into account the gas–liquid mass transfer, includes hydrogen and five lumps: remaining residue (>510°C), VGO (350–510°C), distillate (180–350°C), naphtha (40–180°C), and gas. Vapor–Liquid Equilibrium (VLE) was determined by performing an adiabatic flash with PROII software.Atmospheric residue fractions reacted with active hydrogen species (activated by dispersed MoS2 catalysts in-situ generated from a precursor) to give lighter fractions, such as naphtha and gas oil were produced with almost no coke formation. The experiments of atmospheric residue hydroconversion were performed under the reaction conditions of 420 or 430°C, an initial partial pressure of hydrogen of 15MPa, and different reaction times.Stoichiometric coefficients, kinetic parameters and the mass transfer coefficient (kLa) were estimated using a nonlinear least-squares regression of the experimental results. The calculated apparent activation energies and the contribution of hydrogen concentration via the Hatta number in liquid phase on hydroconversion were discussed.

A Potential Approach to Launch Hypervelocity Projectiles up to 10 km/s Based on Two-stage Gas Gun Facilities

On the basis of Sandia's third-stage launcher, a new scheme of hypervelocity launchers is brought forward for purpose of propelling a one-gram-weight projectile in the shape of sphere or cylinder upwards of 10km/s. It includes an assembly of a sabot, a projectile and a steel impactor, and a hypervelocity launcher (HVL) that is attached to the muzzle end of two-stage light gas gun (LGG). With a specially designed sabot for LGG, the projectile together with the ring-shaped impactor being fixed on the sabot is first driven by LGG to a speed of 6-7km/s. The projectile will gain the secondary acceleration in the HVL synchronously controlled by the high-speed impactor.Three kinds of designs are put forth for a HVL with propelling media of explosive, epoxy resin, or hydrogen respectively. To accomplish the sabot/projectile separation and secondary driven of the projectile, enormous computations have been performed to attain an optimized configuration of the sabot and the HVL. For the launcher using explosive, the projectile is driven by gas productions resulted from strong detonation. It is illustrated by simulations that a 1.03g spherical projectile of 2024 alloy can be accelerated from an injection velocity of 6km/s (LGG launching speed) to 9.6km/s without extremely large deformation and spall damage. To launch a cylindrical projectile with constrained deformation, an improved design for HVL is achieved with adoption of a secondary impactor and an epoxy resin ring in place of explosive. It is capable of propelling a cylindrical projectile from 6km/s towards 8km/s by converging gas production of decomposition of epoxy. In the third design for a HVL, a pressure container with hydrogen is embedded in the tube of a HVL in an attempt to drive a projectile with hydrogen. Preliminary simulations reveal that a projectile (chunk plate) is possible to be accelerated towards 10.6km/s at initial hydrogen pressure of 7MPa, and towards 12km/s at an increased pressure of 20MPa. Enormous efforts are still required, however, to put this scheme into practice.

Guaiacol hydrodeoxygenation kinetics with catalyst deactivation taken into consideration

The hydrodeoxygenation of guaiacol, a compound modeling bio-oil, has been investigated. Experiments have been carried out in an autoclave at 280, 320, and 360°C and an initial hydrogen pressure of about 17 MPa using a Ni-Cu/SiO2-ZrO2-La2O3 catalyst. A formal kinetic model of the first stage of guaiacol hydrodeoxygenation is suggested. It is assumed that the reaction is first-order with respect to both guaiacol and hydrogen. The model takes into account the deactivation of the catalyst and the decrease in the concentration of the deactivating compounds due to their hydrogenation. A possible cause of deactivation is the formation of coke and heavy intermediates, as well as the competitive adsorption of intermediate products of guaiacol conversion on the active sites of the catalyst. The parameters with which the model satisfactorily fits the observed dependence of the guaiacol concentration on the reaction time have been determined.

Structural characteristics and mechanism of hydrogen-induced disproportionation of the ZrCo alloy

The intermetallic compound ZrCo was prepared, and its hydrogen-induced disproportionation in hydrogen desorption processes was investigated. The hydrogenation-dehydrogenation thermodynamics of the ZrCo alloy was evaluated by pressure-composition isotherm measurements at different temperatures. The kinetic processes of hydrogen-induced disproportionation at different temperatures under certain pressures were detailedly studied. The disproportionation rate of the ZrCo alloy increased with the increases of temperature and initial hydrogen pressure under experimental conditions. However, the maximum attainable extent of disproportionation did not change much with an increase in temperature or initial hydrogen pressure. The crystallographic structure analysis of the ZrCo alloy combining with its corresponding dehydrogenation kinetic curves under the conditions of an initial hydrogen pressure of 0.2 MPa and a temperature of 723 K indicated that the basic process of disproportionation reactions was composed of four stages: rapid dehydrogenation of ZrCoH3, equilibrium of dehydrogenation, simultaneity of dehydrogenation and disproportionation, and completion of disproportionation.

Hydrogen storage properties of LiBH4 destabilized by SrH2

In this work, we have succeeded in destabilizing LiBH4 by the addition of SrH2, via the reaction 6LiBH4+SrH2→SrB6+6LiH+10H2 with a theoretical hydrogen capacity of 9.1wt.%. According to the van’t Hoff and Arrhenius equations, the dehydrogenation enthalpy change and activation energy for the LiBH4/SrH2 system were experimentally determined to be 48kJ/mol H2 and 64kJ/mol, respectively. Both are remarkably reduced in comparison with the pristine LiBH4, which is responsible for the improved dehydrogenation property of the LiBH4/SrH2 system. The dehydrogenated products SrB6+6LiH can be rehydrogenated to form LiBH4 and LiSrH3 at 723K under an initial hydrogen pressure of 8.0MPa.

The Effect of Technological Parameter on the Co-liquefaction of Coal with Lignin

The co-liquefaction of coal with lignin was studied by minisize high pressure reactor, tetralin and Fe2O3 were used as solvent and catalyst, and the study was focused on the reaction temperature, initial pressure of hydrogen and mixture ratio of lignin with coal. The results showed that the reaction temperature, the initial pressure and mixture ratio has the important influence on the conversion rate of coal, the oil production rate in the process of co-liquefaction with coal and the lignin. Effect of co-liquefaction is best in reaction temperature 440°C, initial pressure 9Mpa, mixture ratio of lignin and coal for 2∶8, the conversion rate of coal and the oil production rate respectively achieves 87.66% and 50.39%.

Experimental study on bio-oil upgrading over [formula omitted] catalyst in supercritical ethanol

The effects of reaction conditions, including the initial hydrogen pressures (0.5MPa, 2.0MPa), the mass ratios of ethanol to bio-oil (5:1, 3:1, 2:1, 1:1) and reaction temperatures (260°C, 280°C, 300°C) on catalytic upgrading of fast pyrolysis bio-oil were investigated in this work. Experiments were carried out in supercritical ethanol with bifunctional 5%Pt/SO42-/ZrO2/SBA-15 catalyst. The physical properties and organic compounds of upgraded bio-oil were compared and the mass and energy balance of certain upgrading processes were studied. The results showed that higher initial hydrogen pressure (2.0MPa) could inhibit coke formation effectively. Increasing mass ratio of ethanol to bio-oil (5:1, 3:1) was helpful for desired products formation and heating value improvement as well as lower coke yield. With the rising temperature, the heating value of upgraded bio-oil increased, but the amount of desired products reduced and the formation of coke became much more serious.

In situ measurement of alternating current magnetic susceptibility of Pd–hydrogen system for determination of hydrogen concentration in bulk

An alternating current magnetic susceptometer for use as a hydrogen gauge for hydrogen-storage materials was designed and developed. The experimental system can simultaneously measure the hydrogen equilibrium pressure and the magnetic susceptibility of metal hydrides. The background voltage of the susceptometer was stabilized for a long period of time, without any adjustments, by attaching an efficient compensation circuit. The performance of the susceptometer at a static hydrogen concentration was demonstrated by measuring the magnetic susceptibility of a Pd-hydrogen system under equilibrium conditions. The in situ measurement of the magnetic susceptibility of Pd during hydrogen absorption was carried out using the susceptometer. Since the in situ magnetic susceptibility obtained at a lower initial hydrogen pressure agreed with the magnetic susceptibility measured at a static hydrogen concentration, the susceptometer could be used to determine the hydrogen concentration in Pd in situ. At a higher initial hydrogen pressure, enhancement of the magnetic susceptibility was observed at the beginning of hydrogen absorption because the magnetic moments induced by the large temporary strain generated in the Pd affected the magnetic susceptibility.

The influence of diaphragm rupture rate on spontaneous self-ignition of pressurized hydrogen: Experimental investigation

Influence of rupturing process on a diffusion self-ignition of hydrogen was studied experimentally at a pulse discharge into an open channel filled with air. Self-ignition of hydrogen occurred at a contact surface of the jet of hydrogen. Required temperatures for self-ignition were reached due to heating the air by a shock wave which appears as a result of the non-stationary discharge of hydrogen from the high pressure vessel. Initial pressure of hydrogen was varied from 3 to 14 MPa. Rupture duration of a diaphragm was measured. Rupture rate of the diaphragm was determined by an intensity of light, passing through the diaphragm. Formation of a shock wave flow structure at the pulse discharge of compressed hydrogen into the channel with air was studied, and ignition delays of hydrogen were determined. Correlation between rupture duration of the diaphragm and ignition delays are given. Comparison of experimental results with the previous numerical ones was carried out.

Hydrogenation of rapeseed oil for production of liquid bio-chemicals

The main objective of rapeseed oil hydrogenation tests was the production of liquid bio-chemicals to be used as renewable raw material for the production of several chemicals and in chemical synthesis to substitute petroleum derived stuff. As, hydrogenation of vegetable oils is already applied for the production of biofuels, the work done focused in producing aromatic compounds, due to their economic value. The effect of experimental conditions on rapeseed oil hydrogenation was studied, namely, reaction temperature and time with the aim of selecting the most favourable conditions to convert rapeseed oil into liquid valuable bio-chemicals. Rapeseed oil was hydrogenated at a hydrogen initial pressure of 1.10MPa. Reaction temperature varied in the range from 200°C to 400°C, while reaction times between 6 and 180min were tested. The performance of a commercial cobalt and molybdenum catalyst was also studied. The highest hydrocarbons yields were obtained at the highest temperature and reaction times tested. At a temperature of 400°C and at the reaction time of 120min hydrocarbons yield was about 92% in catalyst presence, while in the absence of the catalyst this value decreased to 85%. Hydrocarbons yield was even higher when the reaction time of 180min was used in the presence of catalyst, as the yield of 97% was observed. At these conditions hydrocarbons formed had a high content of aromatic compounds, around 50%. For this reason, the viscosity values of hydrogenated oils were lower than that established by EN590, which together with hydrogenated liquids composition prevented its use as direct liquid fuel to substitute fossil gas oil for transport sector. However, hydrocarbons analysis showed the presence of several valuable compounds that encourages their use as a raw material for the production of several chemicals and in chemical synthesis.

Controlled hydrogenation of aromatic compounds by platinum nanowire catalysts

Aromatic hydrogenation to form cyclohexane derivatives is one of the most important steps in both the petrochemical industry, for clean diesel fuel generation, and the pharmaceutical industry, for safe drug synthesis. We report herein, pure ultra-thin Pt nanowire catalysts with no supporting matrix and their high activities towards the hydrogenation of aromatic compounds (>99% conversion, 1 MPa initial hydrogen pressure, 70 °C). The catalysts can also be recycled up to 40 times with no loss in activity.

Hydrogen Incorporation and Storage in Well-Defined Nanocrystals of Anatase Titanium Dioxide

Hydrogen incorporation into well-defined nanocrystals of anatase titanium dioxide (TiO2) has been investigated by a combination of experimental studies and density functional theory (DFT) calculations. The hydrogenation of TiO2 nanocrystals was determined at 450 °C with an initial hydrogen pressure of 7.0 MP, and storage capacities of 1.0 wt % and 1.4 wt % were achieved for nanocrystals with predominant (001) and (101) surface terminations, respectively. X-ray diffraction and Raman spectroscopy measurements indicate that the TiO2 crystal structure is very well preserved during the hydrogenation. DFT calculations show that hydrogen occupies the interstitial sites between titanium–oxygen octahedra and the energy barrier for hydrogen incorporation through the anatase (101) surface is lower than that through (001).