Graphene supported NiMo catalyst: A promising novel hydrocracking catalyst

The graphene nanosheet (GNS) is used as a catalyst support for various catalytic reactions. A comprehensive study of functionalized GNS (FGNS)-supported catalyst for the purpose of hydrocracking (HDC) process provides a guide to exploring the potential applications and discovering their superior properties. In this research, to study the effect of the support on the conversion and selectivity of n-hexadecane HDC process, experiments are carried out over a synthesized NiMo/FGNS (NMFG) and a commercial NiMo/Al₂O₃-SiO₂ (NMAS) catalysts in a fixed-bed reactor. The functional groups on the NMFG surface anchor and disperse active metals on the catalyst surface, and they enhance the HDC conversion and stability of NMFG catalyst. Moreover, results prove that, in comparison with the commercial catalyst, NMFG increases the HDC conversion of n-hexadecane about 48%, and decreases the coke deposition on its surface.     

Supported ruthenium catalyst as an effective catalyst for selective oxidation of toluene

The investigation comprised an evaluation of the use of the catalyst 1%Ru/TiO₂ in the liquid-phase conversion of toluene to benzyl alcohol and benzaldehyde. Transmission electron microscopy (TEM) and N₂ adsorption-desorption isotherms were deployed to delineate the properties of the supported catalysts. The findings indicated a good catalytic performance by 1%Ru/TiO₂ under green reaction conditions. This performance was deemed a consequence of the spread and loading of Ru on the TiO₂. The reaction conditions such as temperature, reaction time, type of support, catalyst preparation method, and activating quantity) were optimized to achieve superior reaction parameters. Catalyst produced via sol-immobilization has higher activity than the one prepared with the wet-impregnation method, which lead to a transformation rate of up to 9.5%, with the selectivity for benzyl alcohol at 92%.     

Tight bifunctional hierarchical catalyst

A new concept to prepare tight bifunctional catalysts has been developed, by anchoring CoMo(6) clusters on hierarchical ZSM-5 zeolites for simultaneous use in HDS and hydrocracking catalysis. The prepared material displays a significant improved activity in HDS catalysis compared to the impregnated counterpart.     

Lithium phosphate catalyst, III. New supported catalyst

Some new non-stoichiometric Li₃PO₄ supported on -Al₂O₃, -Al₂O₃, TiO₂ and SiO₂ are described as catalysts. The catalysts are used in the isomerization of propene oxide. The catalyst supported on SiO₂ is more active and selective to allyl alcohol than the catalysts described in the literature till now.

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, Li₃PO₄, -Al₂O₃, -Al₂O₃, TiO₂ SiO₂, . . , , SiO₂.

     

Cyclodextrin nanosponges: a potential catalyst and catalyst support for synthesis of xanthenes

The nanoporous framework of a cyclodextrin nanosponge was used as catalyst for accelerating the one-pot, three-component reaction of dimedone, aldehyde, and phenols for synthesis of xanthene derivatives. Moreover, the nanocavities of cyclodextrin nanosponges were exploited for immobilization of heteropolyacids through the wet impregnation method. This catalyst exhibited superior catalytic performance compared to the bare cyclodextrin nanosponge. Despite the good catalytic activity, the leaching of the catalytic species did not allow efficient recovery and reusability. To circumvent this problem, the cyclodextrin nanosponge was amine-functionalized prior to heteropolyacid immobilization. The results proved that the amine functionalities had an effective role in preserving the catalytic species and improving the reusability through decreasing the leaching time. This catalyst was used for synthesis of a variety of xanthenes in aqueous media. The catalytic amount of catalyst afforded the desired product in excellent yields and with a relatively short reaction time. The results suggested cyclodextrin nanosponge-based catalysts as potential candidates for promoting chemical reactions.     

Solid-phase luminescent catalyst immunoassay for human serum albumin with hemin as labeling catalyst

A solid-phase luminescent catalyst immunoassay is described for the determination of human serum albumin (HSA) in solution; hemin is used as a label which catalytically amplifies the sensitivity. The method is essentially a non-radioactive and non-enzymatic sandwich immunoassay. Anti-HSA antibody is covalently bound to a transparent plate, which then undergoes the immunochemical reaction with HSA in the test solution, and with the fixed amount of hemin-labeled anti-HSA antibody. After the two-step immunoreaction, the immunochemically-adsorbed hemin-antibody conjugate is quantified by means of the luminescence produced in a solution containing luminol and hydrogen peroxide. The luminescence intensity is correlated with the amount of HSA. The limit of detection for HSA is 1 ng ml^-1.     

Isocyanate–catalyst and hydroxyl–catalyst complex formation

As part of an investigation for evidence of isocyanate–catalyst and alcohol–catalyst complex formations, determinations of molecular weights were made by means of the freezing point depression of benzene solutions. Mixtures of 1-methoxy-2-propanol and dibutyltin dilaurate and mixtures of 1-methoxy-2-propanol and triethylamine both gave strong evidence of the formation of complexes. Complex formations were also detected when the alcohol was replaced by phenyl isocyanate. Significantly larger concentrations of the catalyst were involved in isocyanate complexes than were shown to be the case with the alcohol complexes. These results appear to be experimental evidence for the previously proposed ternary complex as an intermediate in the metal-catalyzed formation of urethanes.     

Lithium cation as radical-polymerization catalyst

Density-functional theory (DFT) and ab initio (QCISD and CBS-RAD) calculations suggest that complexation of "naked" lithium cations to olefins favors the addition of alkyl radicals to the double bond over abstraction of an allyllic hydrogen atom. Thus, "naked" lithium cations in nonpolar solvents can catalyze the radical polymerization of olefins by favoring the chain-lengthening reaction over the competing hydrogen-atom extraction, which is competitive in the absence of metal ions. One putative initiation reaction, addition of triplet dioxygen to the double bond, is thermoneutral and has a very low barrier when the oxygen molecule is complexed to a lithium cation. An alternative process, abstraction of an allyllic hydrogen atom to generate the allyl and hydroperoxy radicals, is also strongly favored by complexation of the oxygen to the lithium cation but is less favorable than addition. These results support Michl's recent interpretation of experimentally observed alkene polymerization in the presence of lithium salts of hydrophobic carborane anions.     

Reduction of an aluminum-chromium-potassium catalyst

Conclusions In the case of reduction by carbon monoxide of a stabilized, and then oxidized aluminum-chromium-potassium catalyst, Cr²⁺ ions are formed primarily from chromium ions, present in the oxidized catalyst in a valence state higher than 3, and to a substantially lesser degree from ions present in the form of Cr³⁺.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2178–2181, October, 1974.     

Superoxide generator using polyaniline catalyst

A superoxide generator using a polyaniline catalyst was prepared. This apparatus was able to generate superoxide as 2.5 ppm of hydrogen peroxide concentration at an applied reduction current of −0.2 mA and at −0.25 V versus the saturated calomel electrode. Sterilizing of S. aureus and P. aeruginosa was confirmed by a cultivation test after 30 min of superoxide generation.     

Unique hydrogenation activity of supported tin catalyst: Selective hydrogenation catalyst for unsaturated aldehydes

Selective hydrogenation of unsaturated aldehydes, crotonaldehyde (CH₃CH=CHCH=O) and cinnamaldehyde (C₆H₅CH=CHCH=O), has been studied over SiO₂-supported monometallic Sn and bimetallic Rh---Sn catalysts in the liquid phase. Over a silica-supported monometallic Rh catalyst, Rh/SiO₂, no unsaturated alcohol (crotyl alcohol or cinnamyl alcohol) was formed, whereas considerable amounts of the corresponding saturated aldehyde and saturated alcohol were obtained. The selectivity to the unsaturated alcohol was improved over the Rh---Sn bimetallic catalyst. The selectivity to the corresponding unsaturated alcohol attained ca. 65% over the Rh---Sn bimetallic catalysts. On the other hand, The supported Sn catalyst showed markedly high selectivity to the unsaturated alcohols. The selectivity of the Sn/SiO₂, attained 95% to crotyl alcohol and 100% to cinnamyl alcohol, respectively. Although the conversion of each unsaturated aldehyde over Rh---Sn/SiO₂ catalysts was greater than that over Sn/SiO₂ catalysts, the selectivity of Sn/SiO₂ catalysts to the corresponding unsaturated alcohols was superior to that over Rh---Sn/SiO₂. The selectivity of Sn/SiO₂ was also compared with that of Rh---Sn/SiO₂ at a similar conversion of the unsaturated aldehydes. The selectivity of Sn/SiO₂ was significantly greater than that of the Rh---Sn bimetallic catalyst. These results indicate that the high selectivity over Sn/SiO₂ was ascribed not to low conversion but to intrinsic selectivity of the Sn catalyst.     

Cross-metathesis of vinyl aromatic heterocycles: comparison of Grubbs catalyst and Schrock catalyst

Metathesis of 2-vinyl aromatic heterocycles such as furan and thiophene has been investigated in the presence of a ruthenium-based Grubbs catalyst from a synthetic standpoint. The self-metathesis of 2-vinyl aromatic heterocycles was not successful. However, the cross-metathesis of these aromatic heterocycles with 1-octene occurred efficiently, but the selectivity of cross-metathesis product was very low, below 50%. The origin of the low selectivity of heterodimer formation was elucidated through metallacyclobutane intermediate mechanism, observations of carbenes by in situ ¹H NMR, and the reaction products. The effect of oxygen on the reaction behavior was also examined. Furthermore, the data obtained on the Grubbs catalyst were compared with those on a molybdenum-based Schrock catalyst.     

Single atom catalyst for electrocatalysis

Single atom catalyst (SAC) refers to a novel catalyst with the active metal atoms individually anchored on the support. Single atom catalysts present the unique appeal due to the high atomic availability and specific activity, as well as the high pathway selectivity. Herein, we summarized the classification, preparation, characterization, and application of single atom catalysts. Finally, the current bottlenecks and the outlooks of the SAC research are discussed.     

Copper catalyst activation driven by photoinduced electron transfer: a prototype photolatent click catalyst

PET cat. While the copper(II) tren ketoprofenate precatalyst 1 (see picture) is inactive at room temperature in methanol, it is quantitatively and rapidly reduced to its cuprous state upon light irradiation to provide a highly reactive click catalyst. By simply introducing air into the reaction medium the catalysis can be switched off and then switched on again by bubbling argon followed by irradiation.     

Perfluorinated membranes as catalyst supports

The perfluorinated polymer Nafion and porous PTFE/Nafion composite membranes have been employed as supports for nickel complexes or for platinum and palladium metal particles. The resultant materials have been employed as catalysts in various olefin conversion processes. Supported platinum and palladium metal systems were evaluated as catalysts for the hydrogenation of cyclohexene. Rates of reaction are better than those of commercially available catalysts; turnover numbers in excess of 6000 have been obtained with no poisoning apparent. Catalysts may be regenerated many times. The reduction rate approaches a limit at high pressures of hydrogen and has an activation energy of 13 kJ mol^?1 in neat cyclohexene. Nafion was employed as a strong acid cocatalyst to activate and then support a nickel complex catalyst. The resultant catalyst was active for double-bond-shift isomerization.     

Silver as acrolein hydrogenation catalyst: intricate effects of catalyst nature and reactant partial pressures

The hydrogenation of acrolein over pure and supported silver has been investigated with a focus on the influence of catalyst structure and reaction pressure (mbar to 20 bar range) on activity and selectivity. An onset of formation of allyl alcohol beyond 100 mbar reaction pressure (at 250 degrees C) is ascribed to a change in adsorption geometry upon increasing coverage. Smaller silver particles (in the nanometer range), the proximity of a reducible oxide component as well as high pressure lead to enhanced allyl alcohol formation; the selectivity to the other main product propionaldehyde is reduced. The silver dispersion changed depending on the reaction pressure. Moreover, the presence of oxygen, most likely as subsurface oxygen, and the presence of defects are of paramount importance for the catalytic behaviour. The considerable changes of the silver catalysts under reaction conditions and the pressure dependence call for in situ measurements to establish true structure-activity/selectivity relationships for this system.     

Constructing catalyst knowledge networks from catalyst big data in oxidative coupling of methane for designing catalysts

Designing high performance catalysts for the oxidative coupling of methane (OCM) reaction is often hindered by inconsistent catalyst data, which often leads to difficulties in extracting information such as combinatorial effects of elements upon catalyst performance as well as difficulties in reaching yields beyond a particular threshold. In order to investigate C₂ yields more systematically, high throughput experiments are conducted in an effort to mass-produce catalyst-related data in a way that provides more consistency and structure. Graph theory is applied in order to visualize underlying trends in the transformation of high-throughput data into networks, which are then used to design new catalysts that potentially result in high C₂ yields during the OCM reaction. Transforming high-throughput data in this manner has resulted in a representation of catalyst data that is more intuitive to use and also has resulted in the successful design of a myriad of catalysts that elicit high C₂ yields, several of which resulted in yields greater than those originally reported in the high-throughput data. Thus, transforming high-throughput catalytic data into catalyst design-friendly maps provides a new method of catalyst design that is more efficient and has a higher likelihood of resulting in high performance catalysts.

Catalyst data created through high-throughput experimentation is transformed into catalyst knowledge networks, leading to a new method of catalyst design where successfully designed catalysts result in high C₂ yields during the OCM reaction.     

A phase separable polycarbonate polymerization catalyst

Polyisobutylene is shown to be a nonpolar phase tag that separates a highly colored salen Cr(III) complex from products but is otherwise kinetically similar to a low molecular weight salen Cr(III) complex in polycarbonate formation by Cr(III)-catalyzed copolymerization of CO2 and cyclohexene oxide.     

Dynamic effectiveness factor for catalyst particles

The effectiveness factor (EF) is a nondynamic concept that has been demonstrated to be useful for the analysis and design of reaction-diffusion systems (e.g., catalyst particles). The aim of this paper is to introduce a dynamic EF factor (DEF) concept that extends the existing nondynamic one. In the first step, the standard EF is interpreted as a scaling factor that transforms total reaction rates from surface/bulk to catalyst particle conditions. Through the use of Fourier transform (i.e., frequency domain) to deal with time variations, the above interpretation is extended to dynamic conditions by defining the DEF as a linear operator transforming total reaction rate signals from surface/bulk to catalyst particle conditions. It is shown that the classical nondynamic EF concept is recovered in the steady-state limit of the DEF definition. Interestingly, the DEF can be easily computed from the nondynamic EF expressions by introducing a complex Thiele modulus. Results show that for reaction-diffusion processes where the diffusion mechanism is governed by Fick's law the magnitude of the DEF decreases with the frequency. This means that the best reaction rate performance is obtained when the process operates at steady-state (i.e., nondynamic) conditions. However, when a diffusion model with relaxation time is assumed to hold, resonant peaks at nontrivial frequencies can be displayed. Physically, this behavior implies that dynamic (e.g., periodic) operation of the reaction-diffusion process can yield better performance when compared with its nondynamic counterpart.