Parent Catalyst Research Articles

Enhancing CO2 desorption performance in rich MEA solution by addition of SO42−/ZrO2/SiO2 bifunctional catalyst

A significant impediment to the widespread adoption of amine-based post-combustion technique for CO2 capture from flue gas is the huge energy demand for amine solvent regeneration. In this study, five novel bifunctional heterogeneous catalysts e.g., SO42−/ZrO2/SiO2 with different molar ratios of zirconia and SO42−/ZrO2 as a parent catalyst were synthesized and applied to evaluate their effectiveness in enhancing the CO2 desorption and solvent regeneration of 5M monoethanolamine solution with CO2 loading of 0.5 ± 0.01 mol CO2/mol monoethanolamine at 97 °C. The catalysts were characterized by Fourier transform-infrared spectrometry, pyridine-infrared spectroscopy, X-ray diffraction, N2-adsorption-desorption, and ammonia-temperature programmed desorption. The results demonstrated that these catalysts can significantly reduce the heat duty for CO2 desorption by 36.48% compared to without catalyst and enhance desorption rate by 35.1%. The results also showed that SO42−/ZrO2/SiO215% presented the highest efficiency compared to the other SO42−/ZrO2/SiO2 ratios and the super solid acid catalyst SO42−/ZrO2. Additionally, to investigate if the catalysts induce any unfavorable effects on the amine, the absorption of CO2 by regenerated amine solvent was studied. Finally, a reaction mechanism for the amine solvent regeneration with the synthesized catalyst e.g., SO42−/ZrO2/SiO2 was suggested.

Ball Milling Modified SAPO‐11 Based Catalysts for n‐Decane Hydroisomerization

AbstractBifunctional Pt/SAPO‐11 catalysts were prepared using as acid matrix the microporous silico‐aluminophosphate, SAPO‐11, synthesized under microwave radiation. After synthesis, the material was physically modified using a ball mill, changing the grinding time but keeping frequency constant. The metal function (0.5 wt.% Pt) was introduced through mechanical mixture with commercial Pt loaded alumina. The catalysts were characterized by several techniques: powder X‐Ray Diffraction, pyridine adsorption followed by infrared spectroscopy, low temperature N2 adsorption, Hg intrusion porosimetry and electronic microscopy (SEM). The characterization data show modifications of structural and textural properties of the samples as the milling time increases. The catalytic behaviour of Pt/SAPO‐11 materials was studied for hydroisomerization of long chain n‐alkanes, using n‐decane as model molecule, aiming to increase the production of mono‐branched isomers. The catalytic results show that, under optimized milling conditions (60 min; 50 Hz) the selectivity into mono‐branched isomers increased when compared with parent catalyst.

Electrochemically Driven Water Oxidation by a Highly Active Ruthenium-Based Catalyst.

The highly active ruthenium-based water oxidation catalyst [RuX (mcbp)(OHn )(py)2 ] [mcbp2- =2,6-bis(1-methyl-4-(carboxylate)benzimidazol-2-yl)pyridine; n=2, 1, and 0 for X=II, III, and IV, respectively], can be generated in a mixture of RuIII and RuIV states from either [RuII (mcbp)(py)2 ] or [RuIII (Hmcbp)(py)2 ]2+ precursors. The precursor complexes are isolated and characterized by single-crystal X-ray analysis, NMR, UV/Vis, EPR, and FTIR spectroscopy, ESI-HRMS, and elemental analysis, and their redox properties are studied in detail by electrochemical and spectroscopic methods. Unlike the parent catalyst [Ru(tda) (py)2 ] (tda2- =[2,2':6',2''-terpyridine]-6,6''-dicarboxylate), for which full transformation into the catalytically active species [RuIV (tda)(O)(py)2 ] could not be carried out, stoichiometric generation of the catalytically active Ru-aqua complex [RuX (mcbp)(OHn )(py)2 ] from the RuII precursor was achieved under mild conditions (pH 7.0) and short reaction times. The redox properties of the catalyst were studied and its activity for electrocatalytic water oxidation was evaluated, reaching a maximum turnover frequency (TOFmax ) of around 40 000 s-1 at pH 9.0 (from foot-of-the-wave analysis), which is comparable to the activity of the state-of-the-art catalyst [RuIV (tda)(O)(py)2 ].

Combination of precipitation and ultrasound irradiation methods for preparation of lanthanum-modified Y zeolite nano-catalysts used in catalytic cracking of bulky hydrocarbons

Abstract In the present study, lanthanum-containing HY nano-catalysts were prepared using three different techniques including wet impregnation, precipitation, and new precipitation-ultrasonic methods for the sake of catalysts performance promotion through improvement of rare earth dispersion on zeolite. The synthesized nano-catalysts were characterized by means of XRD, N2 adsorption-desorption, TEM, NH3-TPD, FE-SEM and EDX dot-Mapping techniques. Furthermore, amount and type of deposited coke over the spent nano-catalysts were investigated using TGA and FT-IR analyses, respectively. N2 adsorption-desorption analysis showed that the textural properties of zeolite were acceptably preserved in the prepared nano-catalyst with precipitation-ultrasonic method. TEM and EDX dot-Mapping analyses indicated that using ultrasonic irradiation led to synthesis well-dispersed and smaller size lanthanum species over the Y zeolite. Obtained results from the catalytic performance of nano-catalysts revealed that compared with impregnation and precipitation methods, using precipitation-ultrasonic technique not only led to achievement of significantly higher gasoline yield (increase 41% in comparison to parent catalyst), but also efficient decrease in density, viscosity and molecular weight of liquid product were obtained. In addition, application of precipitation-ultrasonic method moderated the acidity strength of zeolite. It led to increased nano-catalyst life time and less coke formation.

Efficient Removal of Diclofenac from Pharmaceutical Wastewater Using Impregnated Zeolite Catalyst in Heterogeneous Fenton Process

In this study, we report removal of Diclofenac (DCF) through heterogeneous Fenton process using Fe-ZSM-5 catalyst. The parent catalyst was prepared by hydrothermal technique. Fe species were introduced by wet impregnation. Characterization of the catalysts was carried out using XRD, FT-IR, FE-SEM, N2 adsorption-desorption, NH3-TPD, and acidimetric-alkalimetric titration. The bimetallic catalyst had the high crystallinity (81.2%), specific surface area (291.8 m2g-1) and uniform spherical morphology. Effect of pH, temperature, catalyst concentration, and H2O2 concentration on DCF removal efficiency was investigated. The results showed that the optimum conditions were reaction temperature of 25 oC, H2O2 concentration of 10mM, pH level of 3, and catalyst concentration of 2g L-1 which resulted in the highest DCF removal (97%). The catalyst was applied in the sequence cycles at the optimum reaction conditions which had no significant change in the catalytic performance. The prepared catalyst showed the high potential for the treatment of the pharmaceutical wastewater due to the high efficiency and stability.

Conversion of Cow Manure Pyrolytic Tar Under FCC Conditions Over Modified Equilibrium Catalysts

Changes were produced by means of alkaline lixiviation in the porosity of an equilibrium commercial FCC catalyst formulated to maximize the yield of middle distillates, in order to improve its performance in the conversion of tar from the pyrolysis of cow manure into hydrocarbons. The pyrolysis was produced at 650 °C in a fixed bed reactor and the tar was catalytically upgraded, comparing the performances of the parent and modified catalysts under realistic FCC conditions, in a CREC Riser Simulator reactor at 550 °C during 10 s, catalyst to reactant relationships being 3, 5 and 8. The alkaline treatment increased both acidity and average mesopore size of the commercial catalyst, thus favoring the diffusion process of the bulkiest oxygenated molecules in tar. The modified catalyst was more effective in deoxygenating tar (conversions up to 87.5% and deoxygenation up to 74.6%), producing more hydrocarbons and coke than the parent catalyst. According to the chemical nature of the pyrolitic tar from cow manure, a high proportion of paraffins derived from the primary cracking of its components were observed among the product hydrocarbons in the gasoline range over both catalysts.

Revalorization of CO2 for methanol production via ZnO promoted carbon nanofibers based Cu-ZrO2 catalytic hydrogenation

Abstract A series of novel carbon nanofibers (CNFs) based Cu-ZrO2 catalysts were synthesized by deposition precipitation method. To investigate the influence of promoter, catalysts were loaded with 1, 2, 3 and 4 wt% ZnO and characterized by ICP-OES, HRTEM, BET, N2O chemisorption, TPR, XPS and CO2-TPD techniques. The results revealed that physicochemical properties of the catalysts were strongly influenced by incorporation of ZnO to the parent catalyst. Copper surface area (SCu) and dispersion (DCu) were slightly decreased by incorporation of ZnO promoter. Nevertheless, SCu and DCu were remarkably decreased when ZnO content was exceeded beyond 3 wt%. The catalytic performance was evaluated by using autoclave slurry reactor at a pressure and temperature of 30 bar and 180 °C, respectively. The promotion of Cu-ZrO2/CNFs catalyst with 3 wt% of ZnO enhanced methanol synthesis rate from 32 to 45 g kg−1 h−1. Notably, with the ZnO promotion the selectivity to methanol was enhanced to 92% compared to 78% of the un-promoted Cu-ZrO2/CNFs catalyst at the expense of a lowered CO2 conversion. In addition, the catalytic activity of this novel catalyst system for CO2 hydrogenation to methanol was compared with the recent literature data.

Synthesis of highly crystalline nanosized HZSM-5 catalyst employing combined hydrothermal and sonochemical method: Investigation of ultrasonic parameters on physico-chemical and catalytic performance in methanol to propylene reaction

Nanostructured HZSM-5 catalysts were synthesized using sonochemical and hydrothermal techniques. The central composite experimental design method was applied to investigate the effects of three critical preparation variables including ultrasound power, irradiation time, and sonication temperature on the structure of the prepared catalysts. The catalysts were characterized by XRD and FE-SEM techniques. The catalytic performance of the selected catalysts was also evaluated in methanol conversion to propylene reaction. The results showed that higher crystallinity and lower particle size were obtained by increasing the above-mentioned factors. The maximum relative crystallinity and minimum mean particle size were obtained as 55.5% and 62.4 nm, respectively, under the optimal conditions of ultrasound power (231 W), irradiation time (21.2 min), and sonication temperature (42.7 °C). The mean particle size of the parent and sonicated HZSM-5 nanocatalysts which were prepared using 48 and 4 h crystallization in autoclave, were 893 and 62.4 nm, respectively. The optimum sonicated catalyst showed higher selectivities to propylene (C3=, 36.8%) and lower selectivity to total heavy hydrocarbons (C5+, 16.1%) compared to the parent catalyst. These results strongly suggest that a nanocatalyst with smaller particle size and higher crystallinity can be obtained in a lower crystallization time using ultrasound method which shows better performance in methanol to propylene reaction.

Production of light olefins from methanol over modified H-ZSM-5: effect of metal impregnation in high-silica zeolite on product distribution

Improvement of H-ZSM-5 catalyst to convert methanol to light olefins was studied in this research. High-silica H-ZSM-5 zeolite (Si/Al = 200) was prepared by a hydrothermal method and modified by impregnation with different promoters (Cs, Mg, Ag, Mn, Fe, Ni, Ir, or P). The parent and modified catalysts were characterized using X-ray diffraction (XRD) analysis, inductively coupled plasma (ICP) spectrometry, scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) measurements, Fourier-transform infrared (FT-IR) spectroscopy, and NH3-temperature programmed desorption (TPD) measurements. Performance tests were performed for all samples in a fixed-bed reactor at 480 °C, 1 bar, and methanol weight hourly space velocity (WHSV) of 0.9 h−1, using feed with methanol to water weight ratio of unity. The results revealed that the parent catalyst was stable during the impregnation process and that the promoted catalysts exhibited nearly the same crystallinity and BET surface area compared with the parent sample. The acidity of the catalysts was decreased after impregnation of promoters except for Ag. It was found that the propylene selectivity was strongly dependent on the structure, texture, and acidic properties of the catalysts, being affected by the type of promoter. The phosphorus- and iron-promoted H-ZSM-5 catalysts showed high propylene selectivity (45.7 % and 43.7 %, respectively) and good catalytic stability, which was attributed to the moderate density and distribution of acidic sites over these catalysts.

Investigating the Influence of Fe Speciation on N2O Decomposition Over Fe\u2013ZSM-5 Catalysts

The influence of Fe speciation on the decomposition rates of N2O over Fe–ZSM-5 catalysts prepared by Chemical Vapour Impregnation were investigated. Various weight loadings of Fe–ZSM-5 catalysts were prepared from the parent zeolite H-ZSM-5 with a Si:Al ratio of 23 or 30. The effect of Si:Al ratio and Fe weight loading was initially investigated before focussing on a single weight loading and the effects of acid washing on catalyst activity and iron speciation. UV/Vis spectroscopy, surface area analysis, XPS and ICP-OES of the acid washed catalysts indicated a reduction of ca. 60% of Fe loading when compared to the parent catalyst with a 0.4 wt% Fe loading. The TOF of N2O decomposition at 600 °C improved to 3.99 × 103 s−1 over the acid washed catalyst which had a weight loading of 0.16%, in contrast, the parent catalyst had a TOF of 1.60 × 103 s−1. Propane was added to the gas stream to act as a reductant and remove any inhibiting oxygen species that remain on the surface of the catalyst. Comparison of catalysts with relatively high and low Fe loadings achieved comparable levels of N2O decomposition when propane is present. When only N2O is present, low metal loading Fe–ZSM-5 catalysts are not capable of achieving high conversions due to the low proximity of active framework Fe3+ ions and extra-framework ɑ-Fe species, which limits oxygen desorption. Acid washing extracts Fe from these active sites and deposits it on the surface of the catalyst as FexOy, leading to a drop in activity. The Fe species present in the catalyst were identified using UV/Vis spectroscopy and speculate on the active species. We consider high loadings of Fe do not lead to an active catalyst when propane is present due to the formation of FexOy nanoparticles and clusters during catalyst preparation. These are inactive species which lead to a decrease in overall efficiency of the Fe ions and consequentially a lower TOF.

A Recyclable Hydrophobic Anchor‐Tagged Asymmetric Amino Thiourea Catalyst

AbstractA novel, recyclable, thiourea‐based asymmetric organocatalyst containing a hydrophobic anchor has been developed. The chemical nature of the hydrophobic anchor contributes to the desirable characteristics of the recyclable catalyst. The hydrophobic anchor‐tagged thiourea catalyst is highly soluble in less polar solvents, which is compatible with amino thiourea catalyst‐mediated asymmetric reaction conditions, but sparingly soluble in polar solvents used for the recycle process. This asymmetric catalyst delivers a catalytic performance comparable to that of a parent catalyst and can be readily recycled from reactions.

Application of silica-supported Ir and Ir-M (M = Pt, Pd, Au) catalysts for low-temperature hydrodechlorination of tetrachloromethane

Herein, it is presented a catalytic system for gas-phase hydrodechlorination of tetrachloromethane at low temperature and atmospheric pressure, using iridium supported on silica as parent catalyst. Iridium electronic configuration is suitable to catalyse the hydrodechlorination reactions, however, it has been rarely used in this reaction to date. The catalytic abilities were significantly improved when a second transition metal was added. Catalysts' stability and selectivity to the desired products (i.e. C1-C4 hydrocarbons) improved compared to conventional activation in hydrogen when catalysts were activated shortly with microwave irradiation. Microwave irradiation of catalysts favourably influences the homogeneity of the metallic active phase, both in terms of the size of metal crystals and the homogeneity of bimetallic systems. Addition of platinum to the ‘parent’ iridium catalyst improved its catalytic properties and decreased deactivation. Fresh and spent catalysts were comprehensively characterized using several techniques (BET, CO-chemisorption, XRD, XPS, electron microscopy and mass spectrometry) to determine structure-activity relationships and potential causes for catalyst deactivation. No significant changes in crystalline size or bimetallic phase composition were observed for spent catalysts (with the exception of Ir-Pd catalysts which underwent bulk carbide during the reaction).

Fe3+ doped amorphous Co2BOy(OH)z with enhanced activity for oxygen evolution reaction

Achieving efficient oxygen evolution reaction (OER) is crucial for advancing energy storage and conversion technologies. Several methodologies have been developed to expedite the OER process. However, producing catalysts with excellent performance still remains challenging. Herein, we successfully achieve an enhanced OER performance in amorphous (Co1-xFex)2BOy(OH)z (x = 0, 10, 20, 30, 40 and 50%) by improving electrode kinetics. The incorporation of Fe3+ not only improves the charge transfer rate, but also modulates the absorption ability of Fe3+ ions to hydroxyl, as evidenced by the decrease of 3d electron density from the Mössbauer measurement. As a consequence, (Co0.7Fe0.3)2BOy(OH)z shows a superior electrocatalytic performance with a current density of 10 mA cm-2 at an overpotential of 308 mV and a Tafel slope of 39 mV dec−1, which are smaller than those observed for undoped parent catalyst Co2BOy(OH)z and commercial IrO2. Moreover, (Co0.7Fe0.3)2BOy(OH)z catalyst has a high stability in OER electrocatalytic process. The current density still remains about 70% after continuous electrocatalytic reaction for 12 h. (Co0.7Fe0.3)2BOy(OH)z used as anode also catalyzes overall water splitting reaction to give a current density of 20 mA cm-2 at 1.62 V when taking Pt/C catalyst as cathode. The present study provides an effective approach to design new metal-based electrocatalystsby introducing foreign cation to alter outer electron density and further modulating the electrochemical activity.

Base-free Asymmetric Transfer Hydrogenation of 1,2-Di- and Monoketones Catalyzed by a Chiral Iron(II) Hydride.

The chiral iron(II) hydride complex [FeH(CNCEt3)(1a)](BF4) (3, 1a is a chiral macrocycle with an (NH)2P2 donor set) catalyzes the base-free transfer hydrogenation (ATH) of prochiral ketones and the hemireduction of benzils to the corresponding benzoins using iPrOH as hydrogen donor. Ketones give the same excellent enantio-selectivity (up to 99% ee) as the parent catalyst [Fe(CNCEt3)2(1a)](BF4)2 (2), which is only active upon treatment with NaOtBu. Benzoins, whose labile stereocenter is known to undergo racemization under basic conditions, are formed in up to 83% isolated yield with enantioselectivity as high as 95%.

Catalytic Enhancement of SAPO-34 for Methanol Conversion to Light Olefins Using in Situ Metal Incorporation

Parent and MeAPSO-34 (Me = Cu, Ca, and W) catalysts were synthesized for methanol conversion to more valuable products such as light olefins. The effect of metal presence on the catalytic performance and physicochemical properties were investigated. The comprehensive characterizations, XRD, EDX, FESEM, FTIR, N2-BET, NH3-TPD, and DR UV–vis, have been applied to characterize the metal modified SAPO-34. Even though the crystallinity of MeAPSO-34s decreased compared to that of parent SAPO-34, the diffusion and acidity properties were improved. Good activity and selectivity for olefin production were observed for all synthesized catalysts. Metal incorporation to the framework of SAPO-34 enhanced the catalytic lifetime and propylene yield. The methanol conversion was stable for 1 h over MeAPSO-34 with W/F = 6.6 g h/mol at 350 °C and 1 bar. The deactivation rate was higher for the parent SAPO-34 as compared to MeAPSO-34. CaAPSO-34 favored propylene production, while CuAPSO-34 favored ethylene.

Combining traditional 2D and modern physical organic-derived descriptors to predict enhanced enantioselectivity for the key aza-Michael conjugate addition in the synthesis of Prevymis™ (letermovir).

Quantitative structure-activity relationships have an extensive history for optimizing drug candidates, yet they have only recently been applied in reaction development. In this report, the predictive power of multivariate parameterization has been explored toward the optimization of a catalyst promoting an aza-Michael conjugate addition for the asymmetric synthesis of letermovir. A hybrid approach combining 2D QSAR and modern 3D physical organic parameters performed better than either approach in isolation. Using these predictive models, a series of new catalysts were identified, which catalyzed the reaction to provide the desired product in improved enantioselectivity relative to the parent catalyst.

Tuning nano-nickel selectivity with tin in flow hydrogenation of 6-methyl-5-hepten-2-one by surface organometallic chemistry modification

Chemoselective flow hydrogenation of 6-methyl-5-hepten-2-one was performed over nano-nickel catalysts. The parent catalyst composed solely of nickel nanoparticles grafted on the polymeric resin exhibited high activity and selectivity towards CC bond saturation but its modification with small quantities of tin significantly increased its ability to perform CO bond hydrogenation. The post-synthetic modification of the parent catalyst was achieved by surface organometallic chemistry approach and performed in the same flow micro-reactor, which was used for the catalytic studies, providing a methodology for online modification of parent catalysts.

Continuous-Flow Hydrogenation of D-Xylose with Bimetallic Ruthenium Catalysts on Micrometric Alumina

Continuous-flow hydrogenation of D-xylose to xylitol was evaluated with pristine and silver modified ruthenium supported on micrometric alumina. The original size of alumina support is required for direct use in flow hydrogenation since it prevents setup clogging. The parent ruthenium catalyst shows high activity and selectivity to the desired product. However, there was an evident competition between adsorption of substrate and product desorption, and ruthenium nanoparticles aggregation. In situ modification of the parent catalyst with silver improved catalysts stability and minimize the competitive adsorption behavior between reactant and product.

Phosphate Ester Bond Hydrolysis Promoted by Lanthanide-Substituted Keggin-type Polyoxometalates Studied by a Combined Experimental and Density Functional Theory Approach.

Hydrolytic cleavage of 4-nitrophenyl phosphate (NPP), a commonly used DNA model substrate, was examined in the presence of series of lanthanide-substituted Keggin-type polyoxometalates (POMs) [Me2NH2]11[CeIII(PW11O39)2], [Me2NH2]10[CeIV(PW11O39)2] (abbreviated as (CeIV(PW11)2), and K4[EuPW11O39] by means of NMR and luminescence spectroscopies and density functional theory (DFT) calculations. Among the examined complexes, the Ce(IV)-substituted Keggin POM (CeIV(PW11)2) showed the highest reactivity, and its aqueous speciation was fully determined under different conditions of pD, temperature, concentration, and ionic strength by means of 31P and 31P diffusion-ordered NMR spectroscopy. The cleavage of the phosphoester bond of NPP in the presence of (CeIV(PW11)2) proceeded with an observed rate constant kobs = (5.31 ± 0.06) × 10-6 s-1 at pD 6.4 and 50 °C. The pD dependence of NPP hydrolysis exhibits a bell-shaped profile, with the fastest rate observed at pD 6.4. The formation constant (Kf = 127 M-1) and catalytic rate constant (kc = 19.41 × 10-5 s-1) for the NPP-Ce(IV)-Keggin POM complex were calculated, and binding between CeIV(PW11)2 and the phosphate group of NPP was also evidenced by the change of the chemical shift of the 31P nucleus in NPP upon addition of the POM complex. DFT calculations revealed that binding of NPP to the parent catalyst CeIV(PW11)2 is thermodynamically unlikely. On the contrary, formation of complexes with the monomeric 1:1 species, CeIVPW11, is considered to be more favorable, and the most stable complex, [CeIVPW11(H2O)2(NPP-κO)2]7-, was found to involve two NPP ligands coordinated to the CeIVcenter of CeIVPW11 in the monodentate fashion. The formation of such species is considered to be responsible for the hydrolytic activity of CeIV(PW11)2 toward phosphomonoesters. On the basis of these findings a principle mechanism for the hydrolysis of NPP by the POM is proposed.

Effects of p‐ and n‐type Doping in Inorganic Fullerene MoS2 on the Hydrogen Evolution Reaction

AbstractIn this report, a systematic study of the effects of p‐ and n‐type doping of the inorganic fullerene (IF) MoS2 on the efficiency of the hydrogen evolution reaction (HER) is described. Active edge site enriched IF‐MoS2, promoted by strategically introducing Nb (p‐type) and Re (n‐type) dopants (below 500 ppm), enables facile HER over a range of pH values. Experimental results suggest that although Nb‐doping on IF‐MoS2 leads to better electrocatalytic HER activity in an alkaline medium with an onset potential difference of 80 mV, Re‐doping gives excellent activity in an acidic medium. The present work presents a systematic study of HER activity by finely tuning the activity in different electrolyte media with varied pH values through deliberate doping of the parent catalyst with p‐ and n‐ type materials. The doped IF‐MoS2 catalysts exhibit excellent catalytic activity even with sea water as an electrolyte.