Two-component Catalyst Research Articles

Synergistic catalytic conversion of nitrate into ammonia on copper phthalocyanine and FeNC two-component catalyst

Cu-based catalysts have been extensively studied to enhance the performance of the electrochemical nitrate reduction reaction (NO3–RR), while it is still a challenge to balance high ammonia (NH3) current density and Faradaic efficiency. Here, we incorporated nitrogen coordinated iron single atom catalyst (FeNC) with copper phthalocyanine (CuPc), denoted as CuPc/FeNC, for NO3–RR. Compared with the two individual catalysts, this two-component catalyst increases NH3 Faradaic efficiency and current density at low overpotentials, achieves efficient synergistic catalytic conversion. Experiments and theoretical calculations reveal that the enhanced electrochemical performance of CuPc/FeNC catalyst comes from the tandem process, in which NO2– is produced on CuPc and then transferred to FeNC and further reduced to NH3. In this exceptional tandem catalyst system, an outstanding NH3 Faradaic efficiency close to 100% was achieved at potentials greater than –0.35 V vs. RHE, coupled with a peak NH3 partial current density of 273 mA cm–2 at –0.57 V vs. RHE, effectively suppressing NO2– production across the entire potential range. This strategy provides a design platform for the continued advancement of NO3–RR catalysts.

Cobalt-manganese ion-exchanged clinoptilolite supported catalysts for n-hexane oxidation

Series of mono- and bi-component cobalt and manganese supported on ion-exchanged clinoptilolite catalysts were prepared by impregnation method. They were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FTIR), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The catalysts were tested in the reaction of complete oxidation of n-hexane. The highest catalytic activity was shown by the two-component catalyst containing 15 % of cobalt and 5 % of manganese oxides, which is due to the optimal ratio between the cation pairs Co2+/Co3+ and Mn3+/Mn4+ at Co/Mn = 1 on the surface calculated from XPS data and the presence of Co3O4.

Analysis of the Influencing Factors of the Efficient Degradation of Waste Polyurethane and Its Scheme Optimization.

This work proposes an efficient catalytic recovery and utilization method for waste polyurethane foam. This method uses ethylene glycol (EG) and propylene glycol (PPG) as two-component alcohololytic agents for the alcoholysis of waste polyurethane foams. For the preparation of recycled polyethers, the conditions of different catalytic degradation systems were catalyzed by duplex metal catalysts (DMC) and alkali metal catalysts, and a synergy with both was also used. The experimental method was adopted with the blank control group and was set up for comparative analysis. The effect of the catalysts on the recycling of waste polyurethane foam was investigated. The catalytic degradation of DMC and the alkali metal catalysts alone, as well as the synergistic effect of the two catalysts, was explored. The findings revealed that the NaOH and DMC synergistic catalytic system was the best, and that the system activity was high under a two-component catalyst synergistic degradation. When the amount of NaOH added in the degradation system was 0.25%, the amount of DMC added was 0.04%, the reaction time was 2.5 h, and the reaction temperature was 160 °C, the waste polyurethane foam was completely alcoholized, and the prepared regenerated polyurethane foam had high compressive strength and good thermal stability. The efficient catalytic recycling method of waste polyurethane foam proposed in this paper has certain guiding and reference values for the practical production of solid-waste-recycled polyurethane.

Synergistic Effect of Amorphous Ti(IV)-Hole and Ni(II)-Electron Cocatalysts for Enhanced Photocatalytic Performance of Bi2WO6

Bi2WO6 has become a common photocatalyst due to its advantages of simple synthesis and high activity. However, the defects of pure Bi2WO6 such as low light reception hinder its application in photocatalysis. In this study, based on the modification of Bi2WO6 with Ti(IV) as a cavity co-catalyst, new Ni- and Ti-doped nanosheets of Bi2WO6 (Ni/Ti-Bi2WO6) were prepared by a one-step wet thermal impregnation method and used for the photocatalytic degradation of tetracycline. The experimental results showed that the photocatalytic activity of Ni/Ti-Bi2WO6 modified by the two-component catalyst was significantly better than those of pure Bi2WO6 and Ti-Bi2WO6 modified with Ti(IV) only. The photocatalytic effect of Ni/Ti-Bi2WO6 with different Ni/Ti molar ratios was investigated by the degradation of TC. The results showed that 0.4Ni/Ti-Bi2WO6 possessed the best photocatalytic performance, with a degradation rate of 92.9% at 140 min TC. The results of cycling experiments showed that the catalyst exhibited high stability after five cycles. The scavenger experiment demonstrated that the h+ and O2− were the main reactive species. The enhanced photocatalytic activity of Bi2WO6 could be attributed to the synergistic effect between the Ti(IV) as a hole cocatalyst and Ni(II) as an electron cocatalyst, which effectively promoted the separation of photogenerated carriers.

Simple and Precision Approach to Polythioimidocarbonates and Hybrid Block Copolymer Derivatives

The advancement of polymeric materials relies heavily on the innovation in polymerization reactions. In this study, we have discovered alternating copolymerization of isothiocyanate (ITC) and epoxide, which results in a nearly unexploited sulfur-containing polymer, polythioimidocarbonate (PTC). Provided with a simple two-component catalyst, i.e., a Lewis pair consisting of triethylborane (Et3B) and excess phosphazene base (PB), the copolymerization starts from an alcohol and proceeds in a strictly alternating and highly chemoselective manner, yielding PTC with controlled molar mass and low dispersity, free of cyclic byproducts and ether linkages. The method applies well to a variety of ITCs and epoxides. It is also found with great excitement that the reaction on ITC is fully inhibited when the catalyst composition is inverted to have Et3B in excess, while homopolymerization of epoxide occurs selectively in this case. Density functional theory (DFT) calculation reveals that Et3B-alkoxide complexation is the key to suppressing the back-biting reaction during the copolymerization ([Et3B] < [PB]) and inhibiting the copolymerization ([Et3B] > [PB]). This unique “biased” feature is harnessed to develop a catalyst switch strategy for one-pot block copolymerization from the mixture of ITC and epoxide with either copolymerization or homopolymerization conducted first, resulting in tailor-made PTC-polyether block copolymers with reversible sequence structures. On the other hand, sequence-selective terpolymerization occurs from a mixture of phthalic anhydride, ITC, and epoxide, allowing the one-step synthesis of polyester-PTC block terpolymer. These results have highlighted the versatility of the method for exploring this uncharted area of polymers.

Ring-opening alternating copolymerization of epichlorohydrin and cyclic anhydrides using single- and two-component metal-free catalysts

Epichlorohydrin (ECH), a chloromethyl-carrying epoxide, is subject to alcohol-initiated ring-opening copolymerization with cyclic anhydrides using a mild phosphazene base (t-BuP1) or a Lewis pair comprising t-BuP1 and triethylborane as an organic/metal-free catalyst. The products exhibit controlled molar mass and strictly alternating sequence distribution without ether linkages though ECH is added in excess. The single-component organobase catalyst favors elevated reaction temperature (60 °C) and leads to broad molar mass distribution, especially at a relatively high catalyst loading, due to the nucleophilic substitution (NS) of the ECH chloromethyl groups by the chain-end carboxylate. This side reaction suspends the propagation of some chains and generates chloride anions that can reinitiate the copolymerization, thus leads to low-molar-mass byproducts. Meanwhile, the epoxy-ended copolymers may undergo chain-end ring opening to form high-molar-mass byproducts. On the other hand, the two-component catalyst allows for a wider range of reaction temperature (25–60 °C) and higher copolymerization rate. NS can be significantly delayed at room temperature with optimized catalyst loading and composition, resulting in narrowly distributed molar mass, ranging from 2 to 30 kg mol−1, at high or complete anhydride conversion. Interestingly, NS still occurs at the end of the copolymerization so that pendent- and end-group bifunctionalized polyester can be achieved in one synthetic step.

L-Isoleucine-catalyzed Michael Synthesis of N-Alkylsuccinimide Derivatives and Their Antioxidant Activity Assessment

N-Substituted succinimides having different alkyl groups were prepared by the reaction of N-substituted maleimide with aldehydes. A two-component catalyst system composed of an amino acid (l-isoleucine) and a base (KOH) was used to facilitate reaction of the α-hydrogen-containing aldehyde with N-substituted maleimide. With 20 mol % catalyst/cocatalyst, good results in term of the reaction time and yield (892-99%) of products containing contiguous quaternary and tertiary stereogenic centers were obtained. The CHN elemental analyses of N-substituted succinimides indicated appreciable purity. Structural assessment of the synthesized N-substituted succinimides was carried out by 1H and 13C NMR spectroscopy. The products exhibited excellent antioxidant and mild antimicrobial activities.

Supercritical water gasification of microalgae over a two-component catalyst mixture

Supercritical water gasification (SCWG) of the microalga Chlorella pyrenoidosa was examined with a catalyst mixture of Ru/C and Rh/C in a mass ratio of 1:1. The influences of temperature (380–600°C), water density (0–0.197g/cm3), and catalyst loading (0–20wt%) on the yields and composition of the gaseous products and the gasification efficiency were examined. The temperature and water density significantly affected the SCWG of the microalgae. The hydrogen gasification efficiency was more dependent on the temperature, while the carbon gasification efficiency was more dependent on the water density. The gaseous products mainly consisted of CH4, H2, CO, and CO2, with smaller amounts of C2-C3 hydrocarbons. CH4 made up half of the mole fraction of the gaseous products under most reaction conditions. A synergistic effect between Ru/C and Rh/C existed during the SCWG of the microalgae, and this effect favored the production of CH4. The role of the catalyst mixture became indistinct at higher temperatures. Hydrogen atoms from the water were transferred to the gaseous products during the SCWG, leading to hydrogen gasification efficiencies that exceeded 100%. The main components of the bio-oil were aromatics and nitrogen-containing compounds, and the main aromatics consisted of azulene and anthracene. The nitrogen-containing compounds are potential poisons to the catalyst mixture.

Copper-Stabilized Si/Au Nanowhiskers for Advanced Nanoelectronic Applications.

We report here the growth and functional properties of silicon-based nanowhisker (NW) diodes produced by the vapor–liquid–solid process using a pulsed laser deposition technique. For the first time, we demonstrate that this method could be employed to control the size and shape of silicon NWs by using a two-component catalyst material (Au/Cu ≈ 60:1). During the NW growth, copper is distributed on the outer surface of the NW, whereas gold sticks as a droplet to its top. The length of NWs is defined by the total amount of copper in the catalyst alloy droplet. The measurements of the electrical transport properties revealed that in contact with the substrate, individual NWs demonstrate typical I–V diode characteristics. Our approach can become an important new tool in the design of novel electronic components.

Titanium-catalyzed [6π+2π]-cycloaddition of Si-containing alkynes to bis(1,3,5-cycloheptatriene-7-yl)alkanes

The reaction between Si-containing alkynes and bis(1,3,5-cycloheptatriene-7-yl)alkanes in the presence of the two-component catalyst Ti(acac)2Cl2-Et2AlCl, led to the selective formation of mono- and bis-adducts – {9-[4-(2,4,6-cycloheptatrienyl)alkyl]-8-alkyl(phenyl)bicyclo[4.2.1]nona-2,4,7-triene-7-yl}(trimethyl)silanes and bis(7-trimethylsilyl-8-alkyl(phenyl)bicyclo[4.2.1]nona-2,4,7-triene-7-yl)alkanes in 78–86% yield. The structures of the obtained cycloadducts were confirmed by 1H and 13C NMR spectroscopy.

Simplified Microwave Assisted Solvothermal One Pot Synthesis of Highly Active Nickel-Iron Layered Double Hydroxide as Oxygen Evolution Reaction Catalyst

The increasing demand for solar fuels and hydrogen as most promising energy carrier requires new materials for electro-catalytic splitting of water or the back-transformation of hydrogen into electricity. Especially, the oxygen electrode caused by sluggish kinetics is hampering progress for cheap hydrogen made by electrolysis. Moreover the low abundance and the high costs of current highly active noble metal catalysts require new developments for novel cheap and abundant materials. Therefore we have developed a new two-component catalyst system consisting of Nickel-Iron layered double hydroxide (NiFe-LDH) and Fe-N doped carbon material (Fe-N-C) as non noble bifunctional catalyst for the oxygen electrode in alkaline unitized reversible fuel cells/electrolyzers (URFC). The combination of NiFe-LDH known as most active non-noble catalyst for the oxygen evolution reaction (OER) in alkaline media and Fe-N-C known as highly active catalyst for the oxygen reduction reaction (ORR) resulted in a combined overpotential with their respective advantages. Highly crystalline NiFe-LDH was prepared by a simple and time-saving microwave assisted solvothermal synthesis route. The crystallinity was confirmed by X-ray diffraction (XRD) spectroscopy and Transmission electron microscopy (TEM) verified morphological characteristics. Rotating Ring disk (RRDE) measurement revealed high selectivity for the multi-component catalyst. We further investigated the behaviour in a membrane based reversible electrolyzer using an anion exchange membrane (AEM, Tokuyama A201). Compared to noble catalyst systems such as Iridium and Platinum the membrane electrode assembly (MEA) measurements proved the ability to compete and supported the initial high activities.

Utilization of Solar Fuels By Implementation of Nife-LDH and Fe-N-C As Bifunctional Catalyst for the Oxygen Reduction Reaction and the Oxygen Evolution Reaction

The increasing demand for solar fuels and hydrogen as most promising energy carrier requires new materials for electro-catalytic splitting of water or the back-transformation of hydrogen into electricity. Especially, the oxygen electrode caused by sluggish kinetics is hampering progress for cheap hydrogen made by electrolysis. Moreover the low abundance and the high costs of current highly active noble metal catalysts require new developments for novel cheap and abundant materials. Therefore we have developed a new two-component catalyst system consisting of Nickel-Iron layered double hydroxide (NiFe-LDH) and Fe-N doped carbon material (Fe-N-C) as non noble bifunctional catalyst for the oxygen electrode in alkaline unitized reversible fuel cells/electrolyzers (URFC). The combination of NiFe-LDH known as most active non-noble catalyst for the oxygen evolution reaction (OER) in alkaline media and Fe-N-C known as highly active catalyst for the oxygen reduction reaction (ORR) resulted in a combined overpotential with their respective advantages. NiFe-LDH was prepared by a simple and time-saving microwave assisted solvothermal synthesis route. The crystallinity was confirmed by X-ray diffraction (XRD) spectroscopy and Transmission electron microscopy (TEM) verified morphological characteristics. Rotating Ring disk (RRDE) measurement revealed high selectivity for the multi-component catalyst. We further investigated the behaviour in a membrane based reversible electrolyzer using an anion exchange membrane (AEM, Tokuyama A201). Compared to noble catalyst systems such as Iridium and Platinum the membrane electrode assembly (MEA) measurements proved the ability to compete and supported the initial high activities.

An efficient bifunctional two-component catalyst for oxygen reduction and oxygen evolution in reversible fuel cells, electrolyzers and rechargeable air electrodes

We report RDE and MEA performance of an active and stable non-precious, two-phase bifunctional oxygen reduction and evolution (ORR and OER) electrocatalyst for use in unitized reversible fuel cell/electrolyzers or rechargeable metal–air batteries.

First examples of the synthesis of macroaluminahetero(N,S)cycles with the participation of metallo(Ti,Zr)cene catalysts

An efficient method is developed for the selective synthesis of 4-aryl-2,6,8,11-tetraethyl-1,7-dithia-4-aza-2,6,8,11-tetraaluminacycloundecanes via the reaction of 3-aryl-1,5,3-dithiazepanes with EtAlCl2 involving the participation of a two-component catalyst based on Cp2TiCl2 and Cp2ZrCl2.

Catalytic upgrading of pretreated algal oil with a two-component catalyst mixture in supercritical water

Single-component catalysts present opportunities and challenges for upgrading crude algal bio-oil in supercritical water. Herein, we report the coordination of the action of two heterogeneous catalysts to upgrade pretreated algal oil to a hydrocarbon-rich fuel. The activities of several different catalyst mixtures for hydrothermal hydrodeoxygenation and hydrodenitrogenation of pretreated algal oil at 400°C for 4h were determined in a batch reactor. The yield of upgraded oil produced using each catalyst mixture ranged from a low of 63.2wt.% in the Ru/C+Rh/γ-Al2O3-catalyzed reaction to a high of 77.2wt.% in the Ru/C+Mo2C-catalyzed reaction. Coke production was controlled in the presence of most of the two-component catalyst mixtures under these hydrothermal conditions. All the two-component mixtures exhibited excellent performance with respect to deoxygenation, denitrogenation, and, in particular, desulfurization. Ru/C+Mo2C, Ru/C+Pt/γ-Al2O3, and Ru/C+Pt/C performed best with respect to deoxygenation, denitrogenation, and desulfurization and produced upgraded oils with O, N and S contents of 0.1, 1.8, and 0.065wt.%, respectively. The upgraded oil produced with Ru/C+Mo2C retained 89.7% of the heating value of the original pretreated oil and contained 98.5% of the material boiling below 450°C. The upgraded oils consisted mainly of saturated hydrocarbons, which accounted for no less than 40% of the total peak area for the majority of the oils. Thus, we view the two-component catalyst mixture as a promising strategy for upgrading bio-oils derived from microalgae.

An efficient method for the synthesis of cyclic carbonates from CO2 and epoxides using an effective two-component catalyst system: Polymer-supported quaternary onium salts and aqueous solutions of metal salts

A highly efficient method for the synthesis of cyclic carbonates from carbon dioxide and epoxides in the presence of polymer-supported quaternary onium salts (PS-Q+X−) and aqueous solution of metal salts under mild conditions, is described. In comparison with conventional homogeneous catalysts, immobilized tributylmethylammonium chloride (PS-TBMAC) is a recyclable, effective catalyst for the studied reaction. The presence of an aqueous solution of zinc iodide as a co-catalyst enhances significantly the catalytic activity of PS-TBMAC. Using this two-component catalyst system (polymer-supported quaternary onium salts and aqueous solution of metal salts), the reaction of CO2 with selected epoxides can be conducted with high product yield (71–91%) and selectivity (97–99%) under mild reaction conditions (temperature 110°C and initial CO2 pressure 0.9MPa). Propylene carbonate was obtained in the best yield (91%). In addition, the advantages of this method include a short reaction time, solvent-free conditions, and an easy separation of catalyst system.

Hydrothermal catalytic processing of pretreated algal oil: A catalyst screening study

We herein report on the catalytic processing of pretreated algal oil that was produced from the hydrothermal liquefaction of Chlorella pyrenoidosa. The activities of 5% Pt/C, 5% Pd/C, 5% Ru/C, 5% Pt/C (sulfided), Mo2C, MoS2, alumina, CoMo/γ-Al2O3 (sulfided), Ni/SiO2–Al2O3, HZSM-5, activated carbon, and Raney-Ni for hydrothermal hydrodeoxygenation and hydrodenitrogenation of the pretreated algal oil at 400°C were determined. Ru/C showed the best performance for deoxygenation and Raney-Ni was the most suitable catalyst for denitrogenation. The upgraded oil from the Ru/C catalyzed reaction contained the highest hydrocarbon content, the highest fraction of material boiling below 400°C, and the highest higher heating value (45.1MJ/kg). All of the metal catalysts produced freely flowing upgraded oil. The combination of Ru/C and Raney Ni, which showed very good deoxygenation and denitrogenation of the oil, produced upgraded oil that retained 86% of the heating value in the original pretreated oil. This upgraded oil was also produced in a higher yield (77.2wt.%) and with lower gas (9.4wt.%), coke (15.6wt.%) and water-soluble products yields (2.1wt.%) than from either catalyst alone. These results indicate that a two-step biocrude treatment strategy (noncatalytic treatment followed by catalytic upgrading) and a two-component catalyst bed in the second step represents an intriguing option for the hydrothermal catalytic upgrading of algal biocrude.

Physical mixture of Ag/Al2O3 and Zn/ZSM-5 as an active catalyst component for selective catalytic reduction of NOx with n-C10H22

The activity of single and two-component catalyst systems consisting of a partial oxidation catalyst and a reduction catalyst (Ag/Al2O3), were investigated for selective catalytic reduction (SCR) of nitrogen oxides (NOx) with n-decane (HC) as a reductant. The single component Ag/Al2O3 catalyst showed a maximum NOx conversion of 28% at 400°C and formation of minor amounts of hydrocarbon cracking products. Co-presence of partial oxidation catalyst, especially metal/ZSM-5, along with Ag/Al2O3 enhanced the NOx conversion of the composite catalysts. Among the composite catalysts, Zn/ZSM-5–Ag/Al2O3 combination led to the most increase in NOx conversion. It was identified that the n-decane can be more effectively converted, on Zn/ZSM-5, to smaller hydrocarbons (such as ethene, propane and propene) intermediates. These in situ generated intermediates were found to enhance the NOx conversion of Zn/ZSM-5–Ag/Al2O3 composite catalysts. Catalyst optimization showed that the NOx conversion increased with increase in zinc loading of up to 5wt% in ZSM-5 and by increasing Zn/ZSM-5 content in the composite mixture catalyst. A combination of 17mg of Ag/Al2O3 and 33mg of 5%Zn/ZSM-5 led to the most active catalyst showing a maximum NOx conversion of about 67% at 400°C.

Ti-catalyzed [6π + 2π] cycloadditions of allenes with 1,3,5-cycloheptatriene

The reaction between 1,2-dienes and 1,3,5-cycloheptatriene in the presence of the two-component catalyst, TiCl 4–Et 2AlCl leads to the regioselective formation of endo-bicyclo[4.2.1]nona-2,4-diene derivatives in yields of up to 80%.

NiMo/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Promoted Hybrid Catalysts of Nanosized Alumina and Beta Zeolite for Hydrocracking with Isomerization

An efficient catalyst is desired to produce lighter isoparaffins from heavy n-paraffins by isomerization and hydrocracking, which are environmentally friendly processes for producing high-octane fuel. This paper assesses the suitability of a catalyst consisting of beta zeolite and nanosized (i.e., 5-50 nm; hereafter ns) alumina particles for isomerization and hydrocracking of large n-paraffins. The catalytic performances of three catalysts, namely an alumina-supported metal catalyst (NiMo/γ-Al2O3), a two-component catalyst (ns Al2O3–beta zeolite), and a three-component catalyst (NiMo/γ-Al2O3–ns Al2O3–beta zeolite) for an isothermal reaction with n-hexadecane were evaluated. The results reveal that the conversion and selectivity are improved by increasing the number of components in a catalyst. Specifically, the three-component catalyst exhibits superior catalytic performance between 225 and 350 °C due to concerted effect of the three components. We investigated the effect of the SiO2/Al2O3 molar ratio of beta zeolite on the performance of three-component catalysts and found that beta zeolite with a SiO2/Al2O3 molar ratio of 25 has a higher activity and cracking selectivity with high isoparaffin selectivity of the cracked products (hereafter iso-selectivity) than three-component catalysts with SiO2/Al2O3 molar ratios of 16, 50, and 150; this indicates that there is an optimum SiO2/Al2O3 molar ratio of zeolite in the three-component catalyst.The three-component catalyst composed of NiMo/γ-Al2O3, ns Al2O3, and dealuminated beta zeolite had a high conversion and iso-selectivity. Its catalytic performance is more suitable for producing isoparaffins of gasoline fraction than these of three three-component catalysts composed of ns Al2O3 and non-dealuminated beta zeolite, ns SiO2 and non-dealuminated beta zeolite, or ns SiO2 and dealuminated beta zeolite. Acid treating was found to remove extra-framework aluminum and amorphous alumina from the beta zeolite surface to make Si–OH. It produced reformed acid sites between the Si–OH of the external zeolite surface and ns Al2O3 surfaces, which consequently improved the isomerization and cracking activities due to the acid sites existing at nanopores.