Commercial Nickel Catalyst Research Articles

Valorization of hemicellulosic sugars to sugar alcohols by Raney nickel mediated hydrogen transfer

The versatility of the pathway to produce polyols from sugars through catalytic transfer hydrogenation (CTH) using commercial Raney nickel catalysts and 1,4-butanediol as hydrogen source has been explored. The results reveal that the nickel purity of the catalyst is a key parameter in process selectivity and presents the CTH route as a promising alternative to conventional hydrogenation processes, effective for the complete valorization of the sugar platform, including hexoses, pentoses and disaccharides. The study uncovers a significant influence of sugar structure on the resulting reactions, with threo-configured sugars displaying enhanced selectivity, while erythro-configured sugars demonstrate elevated conversion rates and the production of a broader spectrum of sugar alcohol isomers. Furthermore, a computational study, using density functional theory (DFT) calculations, has been carried out to describe the performance of the disaccharides and correlate it with their activity in the reaction media.

Preparation and performance evaluation of hydrogen-producing catalysts for diesel reforming

Ru/Al2O3 catalyst was prepared by standard impregnation method. The catalytic reforming performance of Ru/Al2O3 and commercial high nickel/low nickel catalysts on commercial No.0 diesel oil was studied. The regeneration method of carbon-deposited catalyst was also discussed. The results show that commercial low nickel catalyst has poor catalytic activity and stability for diesel, and increasing the water-carbon ratio can slightly improve the conversion rate of diesel. Increasing the reforming reaction temperature and adding methanol additives can effectively improve the catalytic activity of commercial high nickel catalysts. Ru/Al2O3 is a potential catalyst for diesel reforming, reducing the reforming reaction temperature can effectively prevent the catalyst from high temperature hydrolysis deactivation. Hydrogen peroxide has a good regeneration effect on Ru/Al2O3 catalyst.

Relationship between the deterioration of bleachability index (DOBI) value and hydrogenation performance for the hydrogenation of split‐crude palm oil (s‐CPO) in the oleochemical industry

AbstractA major cause of premature catalyst deactivation in the catalytic hydrogenation of fatty acids is the presence of impurities in the feedstock. With more oleochemical plants shifting to opportunistic crude palm oil (CPO) as their feedstock, the feedstock quality becomes an important factor in their procurement process. For CPO, the impurities level can be coarsely estimated by the deterioration of bleaching index (DOBI). A high DOBI value (e.g. DOBI > 2.99) indicates good quality CPO and ease in processing, while low DOBI value implies low level of carotene and/or high level of oxidised sludge oil, both of which could be detrimental to the processing of CPO. In our work, unsplit CPO feedstocks with varying DOBI value were directly hydrogenated in a laboratory‐scale pressure reactor with the presence of commercial nickel catalysts. Experimental results showed that catalyst deactivation was linked to DOBI value, where decreasing DOBI led to faster catalyst deactivation. For example, iodine value (IV) < 1.0 can be achieved for CPO with high DOBI value (2.97) after 150 min, and IV of 5–7 and IV > 20 were achieved for medium DOBI value (2.57–2.68) and low DOBI value (2.24), respectively. For CPO with low DOBI value (2.24), doubling the catalyst dosage ensured that the hydrogenated product met the low IV specification. This work showed that identifying the CPO with DOBI value presents an indicator to the manufacturer to find the right CPO tailored to the existing processes to maximise profitability.

Silica Modulation of Raney Nickel Catalysts for Selective Hydrogenation

Selective hydrogenation over earth-abundant metal catalysts is challenging but particularly valuable for practical applications in heterogeneous catalysis. Herein, we demonstrate that the catalytic selectivity of the commercial Raney nickel catalyst can be greatly tuned by modulation of the nickel surface by silica. Using quinoline hydrogenation as a model, we show that the silica-modified Raney nickel catalysts exhibit good activity, excellent selectivity, and long stability, whereas the undesired overhydrogenation reactions are effectively hindered. In contrast, the pristine Raney nickel catalyst shows inferior selectivity for the targeted product. Mechanistic studies confirm a positive role of silica to facilitate the desorption of 1,2,3,4-tetrahydroquinoline from the catalyst surface, thus enhancing the product selectivity.

Thermogravimetric analysis of coking during dry reforming of methane

Nickel-based catalysts used for dry reforming of methane (DRM) suffer from coking and sintering, which hinders the broad application of the process in the industry. Thermogravimetric analysis was employed to investigate coking on a commercial nickel catalyst with an anti-coking additive (CaO). It was found that the catalyst sintered at temperatures between 850 and 900 °C, which resulted in permanent catalyst deactivation. For the tested Ni/CaO–Al2O3 catalyst, the coking and carbon gasification rates are equal at the temperatures of 796–860 °C, depending on the heating rate (5–20 K/min). Significant differences in the temperatures related to the maxima on TG curves for various heating rates follow from DRM kinetics. This work reveals that the coking rate is lower at higher temperatures. After 50 min, the weight gains amount to about 20% and 40% at 800 °C and 600 °C, respectively. Lower sample weight gains were observed at higher temperatures for a methane decomposition reaction over the Ni/CaO catalyst, unlike for the second tested catalyst – activated carbon. For the nickel catalyst, the reaction order for methane decomposition is 0.6 in the temperature range 640–800 °C, while the sign of the activation energy changes at 700 °C. The elaborated kinetic equation predicts the initial CH4 decomposition rate with 15% accuracy.

Development of a kinetic model for CO2 methanation over a commercial Ni/SiO 2 catalyst in a differential reactor

Development of a kinetic model for CO2 methanation over a commercial nickel catalyst was performed to consider pathways of CO2 conversion via Sabatier and RWGS reactions. H2/CO2 ratio in the feed gas composition was varied at the stoichiometry of the Sabatier reaction assuming a fictitious CO2 conversion of 0 to 0.7. Non-stochiometric gas feeding and the addition of product gases, i.e., methane and steam, were also considered to examine reaction orders and inhibition effects. The kinetic tests were carried out at 300–350 °C and 0.1–0.9 MPa. GHSV corresponded to 37,494 h−1. The stable activity was achieved by forcibly stressing the catalyst under the equilibria at 500 °C for 35 h. The kinetic measurements were conducted at an isothermal differential fixed bed reactor in the absence of heat and mass transport limitations. The methanation reaction was first fitted with the power law and LH approaches by considering the Sabatier reaction. Then, the RWGS reaction was added to consider CO formation using the power law models. The results showed a better fitting of experimental observations by using the LH expression with the formation of formyl as RDS and the power law model with inhibiting influence of water.

Kinetic study of thermocatalytic decomposition of methane over nickel supported catalyst in a fluidized bed reactor

ThermoCatalytic Decomposition of methane (TCD) offers an interesting route to convert natural gas into hydrogen and functional carbon. In this study the reaction kinetics of TCD is studied for a nickel supported catalyst using a special fluidized bed reactor. The effect of operating conditions such as temperature, concentrations of methane and hydrogen and space velocity (SV) was studied on a commercial nickel catalyst on a silica support. The performance of the catalyst was evaluated in terms of three parameters: maximum reaction rate, lifetime and carbon yield. Values up to and in excess of 70gC/gcat and 12h (at 550 °C and 70vol.% CH4-5vol.% H2) have been achieved for carbon yield and lifetime, respectively. The carbon product has fish bone structure. Our study has revealed that at lower temperatures and in the presence of small amounts of hydrogen (≤10%) a higher carbon yield is obtained. Lower concentration of methane (higher concentration of the inert) lowers the reaction rate, the lifetime and therefore the carbon yield. A dual kinetic approach has been adopted to determine maximum reaction rate and the associated deactivation factor. The kinetic parameters were estimated for the temperature range of 550-600 °C.

Ni–Re alloy catalysts on Al2O3 for methane dry reforming

Methane reforming with CO2 is still of great interest due to growing demand creating a continuous need for new hydrogen sources. The main difficulty in this reaction is the deactivation of the catalyst due to the formation of carbon deposits on its surface. Herein, a series of commercial nickel catalysts supported on α-Al2O3 and modified with different amounts of rhenium (up to 4 wt%) was investigated. It was revealed that Re addition causes the formation of Ni–Re alloy during high temperature reduction, which was confirmed in deep XRD and STEM studies. The addition of Re positively influences not only the stability of the catalyst, but also increases its activity in the DRM reaction carried out in a Tapered Element Oscillating Microbalance (TEOM). The formation of Ni–Re alloy played a significant role in enhancing the properties of the catalyst.

Nickel-Fe3O4 Magnetic Nanoparticles Supported on Multiwalled Carbon Nanotubes: Effective Catalyst in Suzuki Cross Coupling Reactions

Nickel-Fe3O4 nanoparticles supported on multi-walled carbon nanotubes (Ni-Fe3O4/MWCNTs) were synthesized by mechanical grinding of a sample of nickel salt, Fe3O4 and MWCNTs using a ball-mill mixer. The preparation method allows for bulk production of Ni-Fe3O4 nanoparticles at room temperature without the necessity of any solvent or chemical reagent. The nanoparticles prepared by this method exhibit small particles size of 5–8 nm with uniform dispersion of nickel nanoparticles on the surface of multi-walled carbon nanotubes. The Ni-Fe3O4/MWCNTs demonstrated remarkable catalytic activity for Suzuki cross coupling reactions of functionalized aryl halides and phenylboronic acids with excellent turnover number and turnover frequency (e.g., 76,000 h−1) using Monowave 50 conventional heating reactor at 120 °C within a very short reaction time of 15 min. The catalyst is air-stable and exhibits easy removal from the reaction mixture due to its magnetic properties, recyclability with no loss of activity, and significantly better performance than the other well-known commercial nickel catalyst. The Ni-Fe3O4/MWCNTs nanoparticles were fully characterized by a variety of spectroscopic techniques including X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). Since nickel offers similar properties to other more expensive transition metals including the most widely used palladium counterpart in cross coupling catalysis, this work demonstrates a promising lower-cost, air-moisture stable and efficient alternative catalyst based on nickel nanoparticles for cross coupling reactions.

Flexible Hybrid Process for Combined Production of Heat, Power and Renewable Feedstock for Refineries

A flexible combined heat, power and fuel production concept, FlexCHX, is being developed for managing the seasonal mismatch between solar energy supply and the demand for heat and power characteristic of northern and central Europe. The process produces an intermediate energy carrier (Fischer-Tropsch (FT) hydrocarbon product), which can be refined to transportation fuels using existing refineries. The FlexCHX process can be integrated into various combined heat and power (CHP) production systems, both industrial CHPs and communal district heating units. In the summer season, renewable fuels are produced from biomass and hydrogen; the hydrogen is produced from water via electrolysis that is driven by low-cost excess electricity from the grid. In the dark winter season, the plant is operated only with biomass in order to maximise the production of the much-needed heat, electricity and FT hydrocarbons. Most of the invested plant components are in full use throughout the year with only the electrolysis unit being operated seasonally. The catalytic reformer plays a key role in this process by converting tars and light hydrocarbon gases into synthesis gas (syngas) and by bringing the main gas constituents towards equilibrium. Developmental precious metal catalysts were used, and an optimal reformer concept was established and tested at pilot scale. Reforming results obtained at pilot gasification tests with commercial nickel catalysts and with the developed precious metal catalysts are presented.

Catalyst Deactivation by Carbon Deposition: The Remarkable Case of Nickel Confined by Atomic Layer Deposition

AbstractIn hydrocarbon reforming processes, coke formation on the catalyst usually reduces reaction rates. We show that when subjected to thermal treatment, a commercial nickel catalyst, overcoated with alumina, ALD exhibited both higher activity per g Ni and higher carbon formation rates than an uncoated catalyst. During the temperature‐programmed reaction in a CH4+CO2 atmosphere, the uncoated catalyst deactivated rapidly from carbon buildup, but the overcoated catalyst displayed an increase in catalytic activity per g Ni, despite generating two times the surface carbon. The unexpected phenomenon was investigated via TEM/EDS, TGA/DSC, SEM, XRD and Raman spectroscopy. We hypothesize that this may be due to (a) formation of a thicker than expected ‘quasi‐ALD’ overcoat of amorphous alumina, (b) crystallization of ALD overcoat into nanofibers that act as secondary supports for migrating Ni, and (c) the ability of ALD overcoat to isolate carbon as carbon nano‐onions (CNOs).

Steam Conversion of Propane in a Membrane Reactor with a Commercial Nickel Catalyst

The propane conversion in a membrane reactor with NIAP–03-01 commercial Ni catalyst at temperatures of 673, 723, 773, and 823 K, feed space velocities of 1800 and 3600 h–1, and steam/propane ratios of 5 and 7 was studied. The Н2 removal through the membrane leads to an increase in the conversion of the feed to Н2 and СО2 formed by the water-gas shift reaction. The conversion in this reaction increases when the rate of the Н2 recovery through the membrane is increased by the permeate evacuation. In the temperature interval 773–823 K, the feed conversion is 100%, and about 90% of high-purity Н2 is recovered from the reaction mixture. An increase in the feed/catalyst contact time leads to a decrease in the feed conversion to the target products and to an increase in the rate of carbon deposit formation. The regularities of the steam conversion of propane in a membrane reactor are similar to those found previously for n-butane with the same catalyst and under the same conditions.

Continuous flow semi-hydrogenation of alkynes using 3D printed catalytic static mixers

The semi-hydrogenation of 2-methyl-3-butyn-2-ol and 2-butyne-1,4-diol over three sets of catalytic static mixers coated with commercial and non-commercial palladium and nickel catalysts has been investigated and optimised over a range of conditions, achieving excellent results of up to 87 % in alkene yield, selectivities above 90 % and space-time yields of up to 3.0 kg L−1 h−1. We investigated the effects of process parameters including pressure, temperature, residence time and concentration on the rate and selectivity of hydrogenation for the different catalytic static mixers tested. The most prominent influence was observed for changes in reactor pressure, whereby higher values result in an increase in conversion but a decrease in selectivity.

Easy Method for the Transformation of Levulinic Acid into Gamma-Valerolactone Using a Nickel Catalyst Derived from Nanocasted Nickel Oxide.

Different nickel catalysts have been tested for the transformation of levulinic acid into γ-valerolactone using an easy hydrothermal method, taking advantage of the properties of the high temperature water. A metallic nickel catalyst derived from NiO synthesized by a nanocasting procedure can achieve a productivity to γ-valerolactone, which is two orders of magnitude higher than that obtained by a commercial nickel catalyst. This nanocasted metallic nickel catalyst has shown bifunctionality as it is capable of activating water as the source for hydrogen and undertaking the further hydrogenation step. In contrast with metallic nickel, nickel oxide has shown to be incapable of transforming levulinic acid into γ-valerolactone.

Hydrogenation of plant oil over a palladium catalyst supported on activated diatomite

A possibility of lowering the formation of trans-isomers during hydrogenation of plant oil over a low-loaded palladium catalyst supported on activated diatomite was studied. The comparison to the commercial nickel catalyst led to establish that the activated diatomite is a promising support of the catalyst for hydrogenation of plant oil. Palladium particles of 2–10 nm in size (3–6 nm particles predominated) were shown to be uniformly distributed over the support surface. It was shown experimentally that the Pd catalyst was more active and selective at low temperature than the nickel catalyst to provide two-fold decrease in the concentration of trans-isomers in the hydrogenated fat.

Whisker carbon formation in catalytic steam reforming of biomass gasification gas

Whisker carbon formation in the steam reforming of biomass gasification gas was studied in a laboratory scale reactor using two commercial nickel catalysts, precious metal catalyst and inert materials. The synthetic feed gas contained ethylene, tar model compounds and H2S as impurities. Whisker carbon was formed below the reaction temperature of 700 °C on an calcium-doped nickel catalyst and below 850 °C on an undoped nickel catalyst when the feed gas contained no sulfur. With the addition of more than 50 ppmv of H2S in the feed gas, the whisker carbon formation was inhibited. Thermodynamic calculations were carried out to estimate the upper limit temperature for the whisker carbon formation but the calculations did not correlate well with the experimental results. One of the probable explanations for this was the high concentration of unsaturated C2+ hydrocarbons in the feed gas.

Catalytic process for methane production from atmospheric carbon dioxide utilizing renewable energy

Kinetics of CO2 methanation reaction over the commercial nickel catalyst NKM-2V was studied in a perfectly mixed reactor at T=250–350°C. It has been shown for the stoichiometric mixture of CO2 and H2 that both the catalyst activity and CO2 conversion increase with temperature. The decrease in CO2:H2 ratio at T=300°C have led to the rise of CO2 conversion to methane. The composite material K2CO3/Al2O3, which is a promising solid absorbent for direct CO2 capture from ambient air, has been synthesized and studied in the temperature-swing adsorption cycles. It has been shown that the increase in the adsorber temperature from 200 to 325°C during the thermal regeneration step enhances the utilization extent of the composite sorbent in the cycle with the total CO2 uptake rising from 1.9 to 4.4wt.%. The process combining thermal regeneration of the composite sorbent in hydrogen atmosphere at T=325°C and CO2 methanation reaction over the commercial nickel catalyst NKM-2V at T=425°C has been studied using the catalytic reactor connected to the outlet of the adsorber. It has been demonstrated that it is possible to transform CO2 into methane with conversion >99%.

Carbon nanotube-supported Ni–CeO2 catalysts. Effect of the support on the catalytic performance in the low-temperature WGS reaction

The low temperature water-gas shift (WGS) reaction has been studied over two commercial multiwall carbon nanotubes-supported nickel catalysts promoted by ceria. For comparison purposes, activated carbon-supported catalysts have also been studied. The catalytic performance and the characterization by N2 adsorption analysis, powder X-ray diffraction (XRD), temperature-programmed reduction with H2 (TPR-H2), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analysis showed that the surface chemistry has an important effect on the dispersion of ceria. As a result, ceria was successfully dispersed over the carbon nanotubes (CNTs) with less graphitic character, and the catalyst afforded better activity in WGS than the catalyst prepared over massive ceria. Moreover, a 20 wt.% CeO2 loading over this support was more active than the analogous catalyst with a 40 wt.% loading. The ceria nanoparticles were smaller when the support was previously oxidized, however this resulted in a decrease of the activity.

Activation of a cement-containing nickel catalyst for ammonia dissociation

The activation behavior of the KDA-10A (NIAP-13-02) commercial cement-containing nickel catalyst at temperatures of up to 750°C has been investigated by temperature-programmed reduction, hightemperature X-ray diffraction, and activation dynamics methods. The catalyst activation dynamics has been studied at 600, 650, 700, and 750°C. At 700–750°C and a heat treatment time of 6.0 h, the catalyst is almost completely activated. The high degrees of nickel dispersion and high catalytic activities observed at 700–750°C indicate a high thermal stability of the catalyst. A shortened catalyst activation procedure is recommended for industrial implementation.

Oxidative steam reforming of pyrolysis oil aqueous fraction with zirconia pre-conversion catalyst

Hydrogen was produced via steam reforming and oxidative steam reforming of a pyrolysis oil aqueous fraction, which was obtained via fractional condensation. The steam reforming experiments were carried out using a commercial nickel catalyst with and without a zirconia monolith as a pre-conversion catalyst. Addition of oxygen, which was examined at four different oxygen-to-carbon ratios, resulted in linearly decreasing H2 yields using both catalyst combinations. The combined effect of the zirconia pre-conversion catalyst and the oxygen addition did, however, slow down the rate at which the H2 yield decreased during the 4 h experiments. A long term experiment at the previously determined optimal conditions showed that the H2 yield decreased clearly more rapidly than carbon conversion. The decrease in the H2 yield was accompanied by a decrease in the selectivity towards CO2, and consequent increases in the selectivities of CO, CH4 and C2 hydrocarbons. These changes indicated that the catalyst was continuously losing its activity towards the reforming of hydrocarbons and conversion of CO via the water-gas shift reaction.