Catalyst Mixture Research Articles

Catalytic Performance of Bimetallic Systems (Cu-Fe, Cu-Mn, Fe-Mn) Based on Spherical MCM-41 Modified by Template Ion-Exchange in NH3-SCR Process

Mesoporous silica of MCM-41 type with spherical morphology was modified with copper, iron, or manganese as well as pairs of these metals by template ion-exchange (TIE) method. The obtained samples were characterized with respect to their structure (XRD), morphology (SEM-EDS), textural parameters (low-temperature N2 sorption), surface acidity (NH3-TPD), transition metal loadings (ICP-OES), their deposited forms (UV-vis DRS) and reducibility (H2-TPR). The catalytic performance of monometallic and bimetallic samples in the selective catalytic reduction of NO with ammonia (NH3-SCR) was tested. The best catalytic results presented a bimetallic copper-manganese sample, which was significantly more active than the mechanical mixture of monometallic copper and manganese catalysts. The synergistic cooperation of manganese and copper species is possibly related to charge relocation between them, resulting in activation of the catalyst in oxidation of NO to NO2, which is necessary for the fast NH3-SCR reaction.

Production of Brake Pad from Epoxy Resin: From Polymerization Concept to the Experiment with Analysis of Mechanical Properties

The purpose of this study was to determine the effect of variations in the use of catalysts on the performance of brake pads. The performance testing is compressive strength and puncture strength. The resin is formed from a mixture of Bisphenol A-epichlorohydrin and cycloaliphatic amine. Based on the results of the study, it was found that brake pads with samples B and C had better performance. The hardness values of samples A, B, and C are 307.4; 331.1; and 334.3 N, respectively. The ratio of resin and catalyst mixture affects the performance of the brake pad. The more catalysts added, the faster the hardening process. It is hoped that this research can be the basis for developing brake pads.

DEHYDROALKYLATION OF BENZENE WITH PROPANE ON MECHANICAL MIXTURES OF CATALYSTS

The conversion of C6H6 : C3H8 mixtures on mixed catalysts (MMC) composed of the metal oxide catalysts M,ReOx/Al2O3 (Pt or Ni -0.5 wt.%, Re-1.0 wt.%) and zeolites Y, МOR, and ZSM-5 in the H form was studied. The products of benzene dehydroalkylation by propane and propane dehydrogenation products are formed at 200–400°C. It has been shown that C3H8 is activated on the metal oxide catalysts and C6H6 interacts with the zeolites yielding the C6H7+ intermediate, which acts as an agent of proton transfer from a zeolite to a metal catalyst, and another intermediate C9H13+ . Cumene, alkylbenzenes, and propene are formed as a result of the conversion . Acomparison of the results of the conversion of these mixtures on the composite catalysts with different zeolites shows that the formation of cumene and propene is thermally controlled and the formation of the other products is kinetically controlled. It has been concluded that the coupling of the redox properties of the metal oxide catalysts with the acid–base properties of the zeolite catalysts facilitates the low–temperature transformations of the C6H6 : C3H8 mixtures. Keywords: dehydroalkylation, dehydrogenation, benzene, propane, mechanical mixture of catalysts, zeolite isopropylbenzene, propylene

Methanolysis of Poly(lactic Acid) Using Catalyst Mixtures and the Kinetics of Methyl Lactate Production

Polylactic acid (PLA) is a leading bioplastic of which the market share is predicted to increase in the future; its growing production capacity means its end-of-life treatment is becoming increasingly important. One beneficial disposal route for PLA is its chemical recycling via alcoholysis. The alcoholysis of PLA leads to the generation of value-added products alkyl lactates; this route also has potential for a circular economy. In this work, PLA was chemically recycled via methanolysis to generate methyl lactate (MeLa). Four commercially available catalysts were investigated: zinc acetate dihydrate (Zn(OAc)2), magnesium acetate tetrahydrate (Mg(OAc)2), 4-(dimethylamino)pyridine (DMAP), and triazabicyclodecene (TBD). Dual catalyst experiments displayed an increase in reactivity when Zn(OAc)2 was paired with TBD or DMAP, or when Mg(OAc)2 was paired with TBD. Zn(OAc)2 coupled with TBD displayed the greatest reactivity. Out of the single catalyst reactions, Zn(OAc)2 exhibited the highest activity: a higher mol% was found to increase reaction rate but plateaued at 4 mol%, and a higher equivalent of methanol was found to increase the reaction rate, but plateaued at 17 equivalents. PLA methanolysis was modelled as a two-step reversible reaction; the activation energies were estimated at: Ea1 = 25.23 kJ∙mol−1, Ea2 = 34.16 kJ∙mol−1 and Ea-2 = 47.93 kJ∙mol−1.

Self-adhesive ionomers for durable low-temperature anion exchange membrane electrolysis

Low-temperature water electrolysis using an anion conductive polymer electrolyte has several potential advantages over other technologies, however, the fabrication of durable alkaline electrodes remains a challenge. Detachment of catalysts results in the loss of electrochemical surface area. Simple mixtures of ionomer and catalyst can suffer from poor catalyst adhesion because only physical adhesion is used to bind the components together. A family of chemically bonded, self-adherent, hydroxide conducting ionomers were synthesized and tested under alkaline electrolysis conditions with nickel ferrite anode electrocatalysts and platinum-nickel cathode catalyst. The ionomers are based on hydroxide conducting poly(norbornene) polymers used as the solid polymer electrolyte in alkaline fuel cells and electrolyzers. The synthesized terpolymer ionomers have been functionalized to provide pendant sites for covalent chemical bonding of bis(phenyl)-A-diglycidyl ether to the ionomer, catalyst, and porous transport layer. The electrodes show excellent adhesion between the catalyst particles, porous transport layer and ionomer, as determined by adhesion measurements and electrolysis performance. The AEM electrolyzer had stable voltage performance under high current density (1 A/cm2 at 1.83 V (67% voltage efficiency)) for extended time periods (>600 h) without degradation.

Impact of Mono- and Dual-Sized α-Fe2O3 Catalyst Mixtures on the Thermochemical Processing of Pinewood for Upgraded Liquid Chemicals

The incorporation of mono-sized particle catalysts in real industrial systems for biomass conversion is a significant challenge, hence the impact of individual α-Fe2O3 catalysts with varying non-ideal spherical sizes of 54 nm (FS054), 221 nm (FS221), and ∼2 µm (FSm002) as well as dual-sized mixtures (FS054-FS221 and FS221-FSm002) were considered in the catalytic upgrading of pinewood pyrolysis vapors. The size variation of the α-Fe2O3 catalyst revealed a substantial effect on the product distribution. Although the yield of phenols shows a decrease by almost a factor of two irrespective of the catalyst particle size, the FS221 catalyst demonstrates the most potent effect on reducing phenols through decarboxylation reactions. Considering the role of the catalyst on the individual phenolics, the FS221 catalyst reveals higher selectivity towards the reduction of 2-methoxyphenol, isoeugenol, and eugenol, whereas the application of FS054 catalysts displays a stronger impact on the decrease of creosol and other phenols. Both FS054 and FS221 catalysts showed the highest effectiveness in reducing the relative yield of 2-methoxy-4-vinylphenol. Applying a dual-size mixture (FS054-FS221) shows a synergetic effect, simultaneously decreasing the content of phenols, acids, and aldehydes followed by a strong CO2 release attributed to competitive decarbonylation reactions of aldehydes. The appearance of γ-Fe2O3 small fraction was revealed in the powders with mono-(FS221) and dual particle size (FS054-FS221 and FS221-FSm002), whereas the FS054 and FSm002 catalysts demonstrate good chemical and phase stability.

Cage-shaped [P(W3O10)4]3- nanoclusters deposited carbon nitride to construct a dual-functional catalyst for photocatalytic mineralization wastewater and dye detector

In this work, [P(W3O10)4]-g-C3N4 composite catalyst is prepared from phosphotungstic acid and thin-layer carbon nitride at high temperature, which can efficiently remove Rhodamine B (RhB) organic wastewater by photocatalysis. The results of UV–vis, TPC, PL and EIS tests show that the introduction of [P(W3O10)4]3- increases the light absorption range of the g-C3N4 and prolongs the recombination time of photogenerated electrons and holes. The degradation efficiency of g-C3N4 and the [P(W3O10)4]-g-C3N4 catalyst are compared and analyzed, and the corresponding active species (O2·-) is proposed. The new catalyst can decolor and mineralize the RhB solution in a short time, and its degradation rate and mineralization rate are 98.0% and 81.0%, respectively. Interestingly, [P(W3O10)4]-g-C3N4 catalyst and RhB solution mixture can be used as a chili powder dye detector. Its special performance can be attributed to the dissociation of the composite catalyst under acid conditions, and the newly formed H3PW12O40 combines with the RhB solution to change color. In short, a dual-function catalyst is synthesized to remove water pollution, and its advantages such as high efficiency, rapidity and strong practicability are worthy of attention.

Hydrogen Storage in Complex Metal Hydrides NaBH4: Hydrolysis Reaction and Experimental Strategies

Worldwide, hydrogen is gaining ground since it is a promising alternative energy source to conventional fuels, which include fossil fuel. Thus, numerous techniques to generate hydrogen have been suggested. This literature review describes the challenges and obstacles identified through a series of the publications that target the hydrolysis of sodium borohydride. This review present several catalysts and reactor systems for the generation of hydrogen gas using the hydrolysis of sodium borohydride, selecting articles in the literature that show a promising future for this technology, although some challenges lie ahead. Sodium borohydride has been widely considered as a low-cost hydrogen storage material with high gravimetric hydrogen capacity of about 10 wt.%. However, its thermodynamic stability seriously hinders the application of sodium borohydride to obtain hydrogen. The performances of the reviewed systems of sodium borohydride hydrolysis include analysis from both the thermodynamic and kinetic points of view. The feasibility of an efficient hydrogen generation system, where a mixture of sodium borohydride and catalysts is hydrolyzed, is considered. This review aims to provide a useful resource to aid researchers starting work on the generation of hydrogen gas using the hydrolysis of sodium borohydride, so they can select the catalysts and reactor systems that best suit them. Thus far, no single catalyst and reactor system can simultaneously meet all of the required standards for efficient practical applications.

Self-Assembly Ultrathin Fe-Terephthalic Acid as Synergistic Catalytic Platforms for Selective Hydrogenation

Self-Assembly Ultrathin Fe-Terephthalic Acid as Synergistic Catalytic Platforms for Selective Hydrogenation

Effect of a Metallocene Catalyst Mixture on CNT Yield Using the FC-CVD Process

This work studies synthesis of carbon nanotube (CNT) sheet using the high temperature (1400 °C) floating catalyst chemical vapor deposition (FC-CVD) method. Three metallocenes—ferrocene, nickelocene, cobaltocene—and their combinations are used as precursors for metal catalysts in the synthesis process. For the carbon source, an alcohol fuel, a combination of methanol and n-hexane (9:1), is used. First, the metallocenes were dissolved in the alcohol fuel. Then, the fuel mixture was injected into a tube furnace using an ultrasonic atomizer with Ar/H2 carrier gas in a ratio of about 12/1. The synthesis of CNTs from a combination of two or three metallocenes reduces the percentage of metal catalyst impurity in the CNT sheet. However, there is an increase in structural defects in the CNTs when using mixtures of two or three metallocenes as catalysts. Furthermore, the specific electrical conductivity of the CNT sheet was highest when using a mixture of ferrocene and cobaltocene as the catalyst. Overall, the multi-catalyst method described enables tailoring certain properties of the CNT sheet. However, the standard ferrocene catalyst seems most appropriate for large-scale manufacturing at the lowest cost.

N,N-Dimethylbenzimidazolium iodide as an Efficient Catalyst for a Green Reaction of Intermolecular Stetter Reaction in Water

N,N-dimethylbenzimidazolium iodide in the presence of NaOH catalyst intermolecular Stetter reaction in water was developed to afford the desired 1,4-addition products in satisfactory to good yields, although aroin products occurred competitively. The benzimidazolium salt catalyst and NaOH mixture can be reused several times without significant loss of efficiency.

Catalytic synergistic effect of bis-ZSM-5 zeolite with different crystal sizes for xylene isomerization

High-performance xylene isomerization catalysts were prepared by physical mixing of two types of ZSM-5 after reasonable modification. Here, SZ/LZ catalysts were prepared by simple physical mixing of two modified Pt–3Si/SZ-5 and Mo/LZ-5 with different crystal sizes. The catalytic performance of the catalysts was evaluated in the mixed xylene isomerization reaction on a fixed bed. The catalysts were characterized by XRD, BET, SEM, TEM, XPS, Py-IR, NH 3 -TPD and probe molecular reactions. The results demonstrated that the deposition of silica finely adjusted the size of the pore opening and passivated the acid sites on the external surface of the SZ-5 zeolite. The loading of MoO 3 reduced the distribution of acidic site density of LZ-5. The reaction sites of ethylbenzene, m-xylene and o-xylene were precisely distributed by the 2SZ/8LZ catalyst. Optimizing the mixing ratio and reaction temperature of the catalysts further improved their synergistic catalysis. High EB conversion rate (74.9%), high PX yield (23.3%) and low xylene loss (1.41%) were obtained by controlling the reaction path of ethylbenzene, m-xylene and o-xylene. High performance xylene isomerization catalysts (2SZ/8LZ) were obtained by a simple mixture of the dealkylation catalyst (Pt–3Si/SZ-5) and the isomerization catalyst (Mo/LZ-5). It demonstrates excellent catalytic activity in mixed xylene isomerization reactions. • The SiO 2 deposition effectively covers the acidic sites on the external surface and adjusts the pore-opening size. • The modification of MoO 3 reduces the acidic site density of LZ-5 with large crystal size and improves the MX and OX isomerization activity. • The ethylbenzene conversion rate, xylene loss rate and PX yield of 2SZ/8LZ reached 74.9%,1.41% and 23.3% at 380 °C, respectively.

A new catalyst mixture for synthesis of 1,3,5‐trioxane

AbstractBACKGROUNDA new catalyst mixture, namely trifluoromethanesulfonic acid + N‐methylimidazolium trifluoromethanesulfonate (CF3SO3H + [mim][CF3SO3]), is developed to overcome long‐standing problems of commercial catalysts and catalytic distillation for 1,3,5‐trioxane synthesis. CF3SO3H serves as a catalyst to accelerate the main reaction and [mim][CF3SO3] serves as an extractive distillation agent to promote phase separation. Unlike the conventional design methods whose purpose is to increase catalytic activity and selectivity, this catalyst mixture is designed to significantly enhance phase separation.RESULTSCompared to commercial catalysts, the new catalyst mixture significantly increases product concentration in distillate, and significantly decreases byproduct concentration in reaction liquid phase and volatilization loss of reactant in reaction liquid phase. This catalyst mixture also considerably decreases corrosion rate and salting out effect of catalyst.CONCLUSIONSOur design approach is of general significance for catalytic distillation. As a real example, it is used to markedly improve the performances of commercial catalysts for 1,3,5‐trioxane synthesis. © 2021 Society of Chemical Industry (SCI).

Hydrocracking of Di-and Triaromatic Hydrocarbons to Monoaromatics over Mixed Bi-functional Catalysts

In this study, we present selective hydrocracking of poly (di and tri) aromatic compounds to monoaromatics, such as benzene, toluene, and xylenes (BTX), over a mixture of Pt/Al2O3 and Y zeolites. The polyaromatic compounds feed is a combined simulated model feed, which is similar to light cycle oil (LCO) in composition. The feed is processed in a fixed bed reactor over a catalyst mixture: in the first step, selective hydrogenation of di and tri-aromatic compounds occurs in the presence of Pt/Al2O3 catalyst, followed by conversion of selective hydrocracking of partial hydrogenated polyaromatic hydrocarbons into BTX-rich stream over Y zeolite. The structural properties and Pt dispersion of Pt/Al2O3 were studied by X-ray powder diffraction (XRD) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The acidity of Y zeolite with different SiO2/Al2O3 ratios (SAR) was studied by temperature-programmed desorption of NH3 (NH3-TPD). In addition, the textural properties of catalysts were determined using the N2 adsorption and desorption method. Different parameters such as the effect of temperature, effect of weight hourly space velocity (WHSV), different SAR of Y zeolite, Pt/Al2O3, and Y zeolite wt% ratios, and paraffin concentration were investigated. The maximum BTX yield of ~28 wt.% was obtained at 450°C, WHSV-0.7 h-1, H2 pressure 60 bar, Pt/Al2O3, and Y zeolite ratios of 1:2 (wt%) at Y zeolite SAR of 80. These results suggest that the yield of BTX strongly depends on the hydrogenation function (Pt/Al2O3) and acidity function of Y zeolite. Furthermore, the concentration of paraffin plays a key role in the conversion of diaromatics and triaromatics and desired products of BTX formation.

Cryogenic blackbody calibration source for superconducting terahertz detectors

Blackbody radiation source has been widely used as a calibration source for terahertz (THz) radiometers in recent decades with the applications of THz detection technology in the fields of aerospace, astronomy and remote sensing. We develop a THz blackbody calibration source capable of working in the cryogenic environment and having adjustable radiation power for the calibration of THz superconducting detectors. The ideal blackbody source has an emissivity and absorptivity of 1 and the reflectance coefficient is used to indirectly characterise the performance of the developed blackbody source. In this work, we use a mixture of epoxy, catalyst, carbon black and glass beads as blackbody absorbing material. The real part and imaginary part of the complex dielectric constant of Berkeley blackbody material are extracted from the THz time-domain spectra, and its reflection coefficient is measured. We use this material to design a conical blackbody radiation source , and simulate it as well. The simulation result show that it has low reflectivity below –35 dB in a frequency range of 0.2–0.5 THz. We fabricate a conical blackbody radiation source that is mounted in a dilution refrigerator, and use filters and light-guiding systems to make the detector for measuring the radiation by the THz light of a specific wavelength. The radiation power can be tuned by changing its temperature. The relationship between radiation power and temperature shows a power tuning range of 10<sup>–12</sup>–10<sup>–9</sup> W in the frequency range of 0.2–0.5 THz with a minimum power value of 2.13 × 10<sup>–12</sup> W. The designed blackbody radiation source can meet the calibration requirements of THz superconducting detectors, and will contribute to the development and application of highly sensitive THz radiometers.

Photothermal polymerization of benzoxazines

Visible irradiation of mixtures of benzoxazine monomers and metal salt catalysts leads to extensive photothermal polymerization, which allows the preparation of complex polybenzoxazine featuresviaphotolithography.

Improving Catalytic Activity in the Electrochemical Separation of CO2 Using Membrane Electrode Assemblies

The direct electrochemically driven separation of CO2 from a humidified N2, O2, and CO2 gas mixture was conducted using an asymmetric membrane electrode assembly (MEA). The MEA was fabricated using a screen-printed ionomer bound Pt cathode, an anion exchange membrane (AEM), and ionomer bound IrO2 anode. Electrocatalyst materials were physically and chemically characterized prior to inclusion within the electrode. Electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) measurements using a rotating disk electrode (RDE) were used to quantify the catalytic activity and determine the effects of the catalyst-to-ionomer ratio. Catalysts were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface analysis, and (dynamic light scattering) DLS to evaluate catalyst structure, active surface area, and determine the particle size and bulk particle size distribution (PSD). The electrocatalyst layer of the electrodes were fabricated by screen printing a uniformly dispersed mixture of catalyst, dissolved anionic ionomer, and a solvent system onto an electrode supporting gas diffusion layer (GDL). Pt-IrO2 MEAs were fabricated and current-voltage relationships were determined using constant-current measurements over a range of applied current densities and flow rates. Baseline reaction kinetics for CO2 separation were established with a standard set of Pt-IrO2 MEAs.

In situ polymerisation of stereospecific propylene nanocomposites blends. Optimising mechanical properties

Isotactic (iPP) and syndiotactic (sPP) polypropylene composites and their blends containing different amounts of nanosepiolite as cocatalyst support were prepared via in-situ polymerisation using different metallocene catalysts to find out improvements in the mechanical properties in comparison with traditional PP nanocomposites obtained by melt.The results showed that the amount of nanoclay significantly affects the catalytic activity of the Cs-symmetry catalyst, obtaining nanocomposites with important microstructural changes: increased molecular weight and syndiotactic sections, narrower molecular weight distributions and increased crystallinity. The particular ordering of the crystalline sections of the sPP observed in the WAXS patterns was the main reason for the dramatic changes in the thermal and mechanical properties of the obtained nanocomposites. Although the nanocomposites obtained with catalyst mixtures maintained certain thermal properties of the iPP, these did not translate into improved mechanical properties due to the loss of crystallinity and the preference for the synthesis of syndiotactic configurations.

Heavy Oil Residue Upgrading With Iron Based Catalysts Under High Hydrogen Pressure

In this study, effective and easily accessible cheap catalysts that assist converting heavy oil residue to lighter products with high yield are investigated. Hydrocracking experiments were carried out in a 10 ml stainless steel bomb-type reactor with up and down stirrer at 200 times of reciprocation per minute. The catalyst mixture provided the minimum coke yield was investigated. FeSO4.H2O, the binary mixtures of FeSO4.H2O with metal oxides (Fe2O3, Al2O3, CaO, SiO2) and the mixtures Fe2O3, Al2O3 and SiO2 with elementary sulphur were used as catalyst. Experiments were conducted at 425 0C for 90 minutes with the initial pressure 100 bar H2. The amount of coke, liquid products and C5- gas products were calculated for each experiment. Gel Permeation Chromatography (GPC), Nuclear Magnetic Resonance (1H NMR) and elemental analysis were used for Iranian heavy oil residue. Differential Scanning Calorimeter (DSC) was used to analyze the catalyst. According to the results, minimum coke yield is achieved by FeSO4.H2O+SiO2 catalyst. Although minimum coke yield achieved with FeSO4.H2O+SiO2, middle distillate containing toluene soluble fraction (TSF) was maximized with Fe2O3+Al2O3+Sulphur catalyst mixture. In addition, the product selectivity in the reactions with the least coke formation showed selectivity in the direction of the formation of gas and light products, not in the direction of liquid product formation.

Applications of Ionic Liquids in Green Catalysis: A Review of Recent Efforts

: Ionic Liquids (ILs) in their neoteric form have emerged to be a potential ‘green’ alternative to traditional Volatile Organic Compounds (VOCs) as solvents in different fields of industries and academia. Recent investigations on the development of multi-faceted applications of ionic liquids have revealed that they really stand for “environmentally-benign” solvents as far as their impact on the ecology is concerned. This caused them to be an exciting and lucrative subject to explore more and more, and many research groups are involved in the manifestation of their inherent undisclosed legacy. Recently, there has been a huge jump in search of an alternative to conventional metal catalysts in academia as well as in industries due to their pollution-evoking roles. Scientists have explored multiple numbers of homogeneous or heterogeneous mixtures of catalysts incorporating ionic liquids to reduce the extent of contamination in our global environment produced due to catalytic synthesis and chemical transformations. In this review, we have put our concentration on some beneficial and recently explored aspects of the successful implementation of Ionic Liquids in different forms in several fields of catalysis as a ‘green’ alternative catalyst/co-catalyst/solvent for catalysis to replace or minimize the lone and hazardous use of metal and metallic compounds as catalysts as well as chemicals like mineral acids or VOCs as solvents. Here, our study focuses on the inevitable role of ILs in several catalytic reactions like cycloaddition of CO2, electrolytic reduction of CO2, biocatalytic or enzymatic reactions, some of the important organic conversions, and biomass to biofuel conversion as catalysts, cocatalysts, catalyst activator, and solvents.