Heterogeneous Catalytic Transfer Research Articles

Construction of ionic liquid-Pd/C based bifunction catalysts for the synthesis of UV-P

Adding light stabilizers to polymeric materials can inhibit or delay the light aging effect and improve the light resistance of materials. 2-(2′-Hydroxy-5′-methylphenyl) benzotriazole (UV-P), as a typical benzotriazole ultraviolet absorber, is widely used in various polymer synthetic materials and products owning to its outstanding oil resistance, color change resistance and low volatility. Currently, it is of great theoretical and practical significance to develop an environmentally friendly method to produce UV-P. Here, we introduce ionic liquids, tetra-butyl ammonium hydroxide, into the palladium-based catalyst, design a “transfer hydrogenation site - alkaline site” duel active center system, and investigate the physical and chemical properties and possible mechanism of this bifunction catalyst system. Such heterogeneous catalytic transfer hydrogenation method can remain 100% conversion and 93.86% selectivity. This bifunction catalyst also shows an outstanding stability when it was used for ten times, proving a green and efficient transfer hydrogenation method for the synthesis of UV-P.

Versatile functionalized mesoporous Zr/SBA-15 for catalytic transfer hydrogenation and oxidation reactions

Through this work, a family of sulfonamide functionalized mesoporous materials as sustainable heterogeneous catalysts has been successfully synthesized by employing sulfaguanidine, sulfathiazole, and sulfadiazine. The samples were fully characterized using a multitechnique approach. Such materials have proved to be highly versatile and catalytically active in both the advances in the hydrogenation of Levulinic acid through heterogeneous catalytic transfer hydrogenation (CTH) and oxidation reactions with a strong emphasis on discussing morphology and structure of versatile catalysts, plausible mechanism, and performance of the catalysts for biomass valorization of renewable feedstock. In particular, the prepared catalytic systems were tested in levulinic acid transformation into γ-Valerolactone, achieving a maximum conversion of 99% and a selectivity of 90% for the sulfaguanidine modified sample. The three nanocatalysts displayed good stability over four reuse cycles, and by considering the results of a hot filtration test, it is confirmed that the nature of the catalysis is heterogeneous as acid-base pairs and functionalized groups on catalytic activation of C–H and CO bonds for transfer hydrogenation of levulinic acid. Moreover, such samples also showed remarkable results in the oxidation of benzyl alcohol towards benzaldehyde, with conversion and selectivity values of 95% and 97%, respectively. The obtained catalytic results are highly promising for biomass upgrading processes, looking forward to a more sustainable future.

Recent advances in heterogeneous catalytic transfer hydrogenation/hydrogenolysis for valorization of biomass-derived furanic compounds

Catalytic transfer hydrogenation/hydrogenolysis can valorize renewable compounds derived from biomass. Different catalysts have the ability to transfer hydrogen from hydrogen-donor molecules thereby avoiding the use of hazardous gaseous hydrogen.

Synthesis and catalytic practicality of titania@ITO-grown nanoflakes: an excellent candidate for isopropanol conversion to acetone

Highly effective, remarkable and discerning isopropanol conversion to acetone has been achieved by a heterogeneous catalytic transfer oxidative hydrogenation of isopropanol using NaBH4 in the presence of active titanium oxide nanoflakes (TiO2 NFs) grown over ITO substrate for the first time followed by liquid-phase deposition protocol. Various sophisticated techniques were employed for the confirmation of well-shaped novel anatase nanoflakes, having small size and thickness of 5–10 and 30 nm, respectively, consequently providing high surface area and greater density active sites enable the particles to be extremely active for the catalytic reaction. These exceedingly active nanoflakes proved to be good candidate showing remarkably high heterogeneous catalytic efficiency by converting approximately 100% isopropanol to acetone within 40 s using 0.5 mg TiO2 NFs deposited over ITO surface. Various parameters are optimized, e.g., time, dose, concentration of reducing agent and isopropanol for this rapid and effective conversion. These synthesized nanoflakes are of finest choice in terms of cheapest source, high catalytic efficiency, exceptional reusability and good analytical practicality with maximum yield in very short time.

Recent advances in the production of γ‐valerolactone from biomass‐derived feedstocks via heterogeneous catalytic transfer hydrogenation

Abstractγ‐valerolactone (GVL) is an important intermediate chemical with a wide range of applications as fuel, fuel additive and as a green solvent which has received a great deal of attentions from both academia and industry. This review aims to summarise the advances in conversion of renewable feedstocks into GVL through heterogeneous catalytic transfer hydrogenation (CTH) with a strong emphasis on discussing preparation, characterisation and performance of the catalysts in order to provide a better understanding of various catalytic systems and also to compare them in terms of catalytic performance. © 2017 Society of Chemical Industry

Heterogeneous Catalytic Transfer Partial-Hydrogenation with Formic Acid as Hydrogen Source Over the Schiff-Base Modified Gold Nano-Catalyst

The catalytic hydrogenation transformation with gaseous hydrogen in liquid phase always refers to a harsh condition and over-hydrogenation, and it is highly desired to develop new methods with partial-hydrogenation at mild condition. Herein, a heterogeneous catalytic transfer partial-hydrogenation strategy with formic acid as hydrogen source was developed over the Schiff-base modified gold nano-catalysts. The Au/Schiff-SiO2 catalyst was successfully prepared by one pot aldimine condensation and NaBH4 reduction of a gold precursor. The characterization results indicated that the gold nanoparticles with an average size below 2 nm were highly dispersed over the Schiff-base modified silica support. Such Schiff-based gold nano-catalysts exhibits excellent activity and partial-hydrogenation selectivity, with a high yield (>99%) for phenylacetylene partial-hydrogenation and achieving a 75% chemoselectivity for imines at a relative low temperature and atmospheric pressure. More importantly, the excess of formic acid can be removed by the direct dissociation of formic acid over Au/Schiff-SiO2 catalyst with CO2 emission into atmosphere, which leads to a hydrogen source as clean as hydrogen gaseous, but with a much more high activity and selectivity under mild reaction process.

Heterogeneous Catalytic Transfer Hydrogenation as an Effective Pathway in Biomass Upgrading

Reducing oxygen content in biomass-derived feedstocks via hydrodeoxygenation (HDO) is a key step in their upgrading to fuels and valuable chemicals. Organic molecules, e.g., alcohols and formic acid, can donate hydrogen to reduce the substrate in a process called catalytic transfer hydrogenation (CTH). Although it is practiced far less frequently than molecular-hydrogen-based HDO processes, CTH has been proven to be an efficient and selective strategy in biomass upgrading in the last two decades. In this paper, we present a selective review of recent progress made in the upgrade of biomass-derived feedstocks through heterogeneous CTH, with a focus on the mechanistic interpretation. Hydrogenation and cleavage of C═O and C–O bonds, respectively, are the two main categories of reactions discussed, owing to their importance in the HDO of biomass-derived feedstocks. On acid–base catalysts, Lewis acid–base pair sites, rather than a single acid or base site, mediate hydrogenation of carbonyl groups with alcohols...

Electrocatalytic measurement of H2O2 concentration using bis(N-2-methylphenyl alicyldenaminato)copper(II) spiked in a carbon paste electrode

The electrochemical behavior of a bis( N -2-methylphenyl-salicyldenaminato)copper(II) complex spiked in a carbon paste electrode (BMPSCu-CPE) and its electrocatalytic reduction of H 2 O 2 were examined using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry. Cyclic voltammetry was used to study the redox properties of BMPSCu-CPE at various potential scan rates. The apparent charge transfer rate constant and the transfer coefficient for the electron transfer between BMPSCu and the carbon paste electrode (CPE) were 1.9 ± 0.1 s –1 and 0.43, respectively. BMPSCu-CPE had excellent electrocatalytic activity for H 2 O 2 reduction in 0.1 mol/L phosphate buffer solution (pH 5.0), and it decreased the overpotential by 300 mV as compared to CPE alone. The diffusion coefficient and kinetic parameters such as the heterogeneous catalytic electron transfer rate constant and electron transfer coefficient for the reduction of H 2 O 2 at the BMPSCu-CPE surface were also determined using electrochemical methods. Differential pulse voltammetry showed two linear dynamic ranges of 1.0–10.0 and 10.0–300.0 μmol/L and a detection limit of 0.63 μmol/L H 2 O 2 . The BMPSCu-CPE has excellent reproducibility and long term stability, and it was successfully applied for the determination of H 2 O 2 in two pharmaceutical samples: an antiseptic solution and a hair dying cream. A Cu(II) complex (BMPSCu) used for the electrocatalytic reduction of H 2 O 2 gave excellent activity. It successfully detected H 2 O 2 in two pharmaceutical samples.

Microwave‐assisted synthesis and bulk polymerization of 3‐aminophthalic anhydride as an AB‐type monomer for the formation of linear and cyclic polyimides

Abstract3‐Aminophthalic anhydride was synthesized in high purity by heterogeneous catalytic transfer hydrogenation of 3‐nitrophthalic acid. The reduction was carried out in a one‐pot reaction under microwave conditions, using 4‐methyl‐1‐cyclohexene as a source of hydrogen, in short reaction times. By microwave‐assisted polymerization of the resulting AB‐type amino anhydride monomer in bulk, linear and cyclic polymers consisting of amic acid and imide units were formed. Copyright © 2012 Society of Chemical Industry

Photosensitizers for photodynamic therapy: One-pot heterogeneous catalytic transfer reduction of porphyrins

A number of new porphyrin-based photosensitizers have been developed for Photodynamic Therapy (PDT) in recent years. Chlorins, which are a reduced form of porphyrins, show better potential of application since they have a stronger absorption band on the red region of the visible spectrum and, hence, a deeper penetration into tissues. We found that by using heterogeneous catalytic transfer reduction (CTR), meso-tetraphenylporphyrin (TPP) could be hydrogenated, although in modest yields, to meso-tetraphenylchlorin (TPC) in a single reaction step. Best reaction conditions were attained using formic acid or sodium phosphinate/water as hydrogen donors, tetrahydrofuran (THF) or toluene as solvent and 10% palladium on charcoal as catalyst.

Suspension catalysis in a liquid–liquid capillary microreactor

Suspended catalyst particles in two phase slug flow could be an alternative technique for using heterogeneous catalysts in microreactors, which has so far mainly been restricted to immobilised solid catalysts, either in micro-fixed-beds or catalytically coated wall reactors. The hydrodynamic and particle behaviour in slug flow was analysed using fluorescent particles and particles of typical catalyst supports in various biphasic liquid–liquid systems. Typically, the circulations only encompassed the anterior section of the slug and depended on the properties of the liquid–liquid system and, in particular, on the slug velocity. Silicon dioxide or aluminum oxide particles suspended in the aqueous phase follow the internal circulation streamlines almost exactly, while carbon-based particles suspended in the continuous organic phase formed a contiguous cap around the rear end of the dispersed aqueous slug. The principle of suspension catalysis was demonstrated experimentally for a heterogeneous catalytic transfer hydrogenation of m-nitrotoluene with aqueous potassium formate.

Formation of epoxide-amine oligo-adducts as OH-functionalized initiators for the ring-opening polymerization of ε-caprolactone

Epoxide-amine oligo-adducts were synthesized via a one-pot microwave assisted heterogeneous catalytic transfer hydrogenation. Accordingly, 4-nitroanisole was reduced under microwave conditions to give 4-aminoanisole which reacted immediately with the diglycidyl ether of bisphenol A in an addition polymerization reaction to yield oligo(amino alcohol)s. The hydroxy groups of the new formed oligomers were used as the initiator for the ring-opening polymerization of ε-caprolactone to produce a graft copolymer.

Water-improved heterogeneous transfer hydrogenation using methanol as hydrogen donor over Pd-based catalyst

The heterogeneous catalytic transfer hydrogenation (CTH) of styrene and nitrobenzene over Pd-based catalyst using methanol as hydrogen donor was investigated in a fixed-bed reactor. With the increase of the molar ratio of water to methanol from 0 to 1, the conversions of styrene and nitrobenzene are increased from 26.3% and 7.1% to 100% and 31.9%, respectively, and the selectivity of aniline is increased from 22.0 to 94.5 mol%. The presence of water improves the hydrogen transfer from methanol to styrene or nitrobenzene through the quick reaction of water with formaldehyde, formed from the dehydrogenation of methanol, into formic acid, which is an excellent hydrogen donor for the CTH of unsaturated organics. In the presence of water, methanol is a better hydrogen donor than isopropanol, n-propanol and ethanol, because water cannot easily react with acetone, propionaldehyde, and acetaldehyde formed from isopropanol, n-propanol, and ethanol, respectively. Additionally, the hydrogen atom utilization of the methanol donor in the presence of water is higher than the other donors, hydrogen atom in a part of water can also be utilized for the reduction of unsaturated organics.

Synthesis and characterization of nano-sized nickel catalyst supported on SiO2–Al2O3

support on thecatalytic activity of nickel catalyst. The reaction used in this studywas the hydrogenation of p-nitrophenol into p-aminophenol.p-Aminophenolisconsideredtobeveryimportantintermediateinthemanufactureofmanyanalgesicandantipyreticdrugs,suchasparacetamol,acetanilide,phentacin,...etc.[9–15].Itisalsousedasadeveloper in photography (under trade names of activol or azol), inaddition of its use in chemical dye industries [16].There are several methods used in the preparation of p-aminophenolfromp-nitrophenolsuchas:(1)metal/acidreduction[17], (2) catalytic hydrogenation [18], (3) electrolytic reduction[19], (4) homogeneous catalytic transfer hydrogenation [20], and(5) heterogeneous catalytic transfer hydrogenation, etc.Among all previously mentioned methods, direct catalytichydrogenation of p-nitrophenol to p-aminophenol becomes themost important one. This is because it could be an efficient routefor synthesis [15]. Raney nickel [21], nano-sized nickel [22] andseveral noble metal catalysts, such as Pd/C [15], have been used ascatalysts for this reaction. Due to their lowest cost and highercatalytic activity, supported nickel catalysts, are widely used insuch reactions [15–21].Although nickel catalyst is used in hydrogenation reactions[23–29], only few recent researches have been carried out onhydrogenation of p-nitrophenol over nano-sized supported nickelmetal catalyst [10,30,31].The present investigation reports the results of an intensivestudy on preparation and characterization of nano-sized metallicnickel supported on SiO

Mechanistic insight into the heterogeneous catalytic transfer hydrogenation over Cu/Al 2O 3: Direct evidence for the assistant role of support

The catalytic transfer hydrogenation (CTH) between alcohol and alkene was investigated over Cu/Al 2O 3 catalyst via mechanical mixture of the supported catalyst and the pure support. It is found that the CTH activities are highly depended on the amount and acid/basic properties of the mechanically mixed support, clearly indicating the assistant role of support. In addition, only alkene with high activity of hydrogenation can really act as hydrogen acceptor. Based on these, a new bifunctional reaction pathway is proposed. Alcohol dehydrogenates to form alkoxide on Al 2O 3 surface (R 1CH(OH)R 2 → R 1CH(O)R 2 + H), and H atom migrates to the metallic Cu patches via reverse hydrogen spillover, while extraction of α-hydrogen forming ketone (R 1CH(O)R 2 → R 1C(O)R 2 + H) occurs on Cu or Cu–Al 2O 3 interface. On the metallic Cu patches, alkene hydrogenates yielding alkane (R 3CH = CHR 4 + 2H → R 3CH 2CH 2R 4). This mechanism can give a better explanation for the observed acceleration or deceleration role of hydrogen acceptor to alcohol dehydrogenation.

Efficient and chemoselective reduction of carbonyl compounds with supported gold catalysts under transfer hydrogenation conditions

A new heterogeneous catalytic transfer hydrogenation (CTH) system, consisting of a non-flammable supported Au catalyst along with 2-propanol as the hydrogen donor, was proven to be effective for chemoselective reduction of a wide range of aromatic ketones and aldehydes to the corresponding alcohols.

Heterogeneous Catalytic Transfer Hydrogenation in Peptide Synthesis

AbstractFor Abstract see ChemInform Abstract in Full Text.

Heterogeneous Catalytic Transfer Hydrogenation of Aromatic Nitro and Carbonyl Compounds over Cobalt(II) Substituted Hexagonal Mesoporous Aluminophosphate Molecular Sieves.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Reductive Cleavage of Azo Compounds Catalyzed by Commercial Zinc Dust and Hydrazinium Monoformate as a New Hydrogen Donor for Heterogeneous Catalytic Transfer Hydrogenation.

Reductive Cleavage of Azo Compounds Catalyzed by Commercial Zinc Dust and Hydrazinium Monoformate as a New Hydrogen Donor for Heterogeneous Catalytic Transfer Hydrogenation.

Heterogeneous catalytic transfer hydrogenation of aromatic nitro and carbonyl compounds over cobalt(II) substituted hexagonal mesoporous aluminophosphate molecular sieves

Catalytic transfer hydrogenation of aromatic nitro and carbonyl compounds was carried out using novel cobalt(II) substituted hexagonal mesoporous aluminophosphate molecular sieves. The catalyst showed excellent yield with good recycling capability.