Aldehyde Selectivity Research Articles

Catalytic properties of Ce-MCM-41 prepared with ceric ammonium nitrate in the liquid-phase oxidation of benzyl alcohol

This work reports the influence of microstructural features in the catalytic performance, reaction kinetics and stability of a cerium-modified MCM-41 material prepared with ceric ammonium nitrate (Ce-MCM-CAN) in the liquid-phase oxidation of benzyl alcohol with tert-butyl hydroperoxide (TBHP) as oxidant. All the mentioned features were compiled and compared to other two Ce-MCM-41 catalysts prepared with CeCl3·7H2O and Ce(NO3)3·6H2O (Ce-MCM-Cl and Ce-MCM-NO3, respectively). Ce-MCM-CAN sample has offered a unique catalytic profile and considerable resistance towards conversion of isomorphous cerium sites in inactive agglomerated CeO2. In a typical catalytic essay at 80 °C and 24 h, Ce-MCM-CAN sample attains 54.6% of conversion, with 47.4 and 25.9% of benzaldehyde selectivity and yield, respectively. Nonetheless, kinetic essays demonstrates that the reaction continues after 24 h, mainly by reducing the aldehyde's selectivity and favoring the formation of benzoic acid, whereas Ce-MCM-Cl and Ce-MCM-NO3 samples has product formation stagnated after 20 h. After four catalytic cycles, the deactivation of Ce-MCM-CAN sample occurs mainly after the first cycle (reduction of 19.8% in conversion) with little influence in TBHP efficiency, while the other two model catalysts deactivate progressively after each cycle (reduction of 33.3 and 23.6% in conversion for Ce-MCM-Cl and Ce-MCM-NO3 samples, respectively) with loss of oxidant usage. Overall, the long-range ordering and pre-existing non-framework CeO2 nanoparticles in Ce-MCM-CAN sample is responsible for decreasing the deactivation rate. Such properties emerge from the counterbalanced synergy between chaotropic nitrate anions and condensation between [Ce(OH)4] species with silicate anions.

Complexation effect between Cu-based catalyst and DESMP in acetylene hydration

Mercuric chloride catalysts are used to catalyze acetylene hydration for acetaldehyde production with high activity, but high toxicity limits its practical application. Here we present a phosphorus and sulfur ligands-complexed copper catalyst assessed for acetylene hydration. The optimum catalyst gave more than 94.0% acetylene conversion and 88.4% aldehyde selectivity at 10 h. After running for 20 h, the catalyst showed high stability. The conversion to acetylene remained stable at over 93.3% and the selectivity of aldehyde decreased from 92.2% to 79.7%. The accession of phosphorus and sulfur could be highly vigorous for the acetylene hydration reaction. All the catalysts were characterized by XRD, XPS, ICP, TPR, TEM, FT-IR and BET technologies. The results indicate that the selectivity of the catalysts is mainly improved by the P fragment of the ligands, and the S fragment of the ligands could restrain the loss of copper species to improve the stability of the catalysts.

The role of metal nodes on Rh coordinated MOFs for Hydroformylation of n-butene

In this work, three MOF-based materials with highly dispersed Rh(I) were synthesized for hydroformylation of n-butene, namely Rh(I)/UiO-66, Rh(I)/MOF-5 and Rh(I)/MIL-101. The defect sites on the metal nodes of MOFs promoted the anchoring of Rh as a single active site. A high-performance Rh(I)/MOF-5 catalyst was obtained with the n-butene conversion and pentanal selectivity of 96.4% and 85.8%, respectively. In addition, it showed a good stability in the recycling tests after five runs. XRD, TEM, XPS, in situ DRIRTS confirmed that the metal nodes in MOFs modified the activity of the coordinated Rh catalyst by influencing the adsorption strength of CO. Combing the DFT results, we predicted that Rh(I)/MOF-5 catalyst with suitable CO adsorption energy could reduce the reaction energy barrier in CO insertion process, which was the rate-determining step of overall reaction, thus improving the selectivity of total aldehydes. This work broadened the application of MOFs as catalyst supports and provided assistance for the development of heterogeneous catalysts in hydroformylation of olefins.

Mechanistic Investigation of Enhanced Catalytic Selectivity toward Alcohol Oxidation with Ce Oxysulfate Clusters.

Ceria-based materials have been highly desired in photocatalytic reactions due to their redox properties and strong oxygen storage and transfer ability. Herein, we report the structures of one CeCe70 oxysulfate cluster and four MCe70 clusters (M = Cu, Ni, Co, and Fe) with the same Ce70 core. As noted, single-crystal X-ray diffraction confirmed the structures of CeCe70 and the MCe70 series, while Raman spectroscopy indicated an increase in oxygen defects upon the introduction of Cu and Fe ions. The clusters catalyzed the oxidation of 4-methoxybenzyl alcohol under ultraviolet light. CuCe70 and FeCe70 exhibited enhanced reactivity compared to CeCe70 and improved aldehyde selectivity compared to control experiments. In comparison with their homogeneous congeners, the CeCe70/MCe70 clusters altered the location of radical generation from the bulk solution to the clusters' surfaces. Mechanistic studies highlight the role of oxygen defects and specific transition metal introduction for efficient photocatalysis. The mechanistic pathway in this study provides insight into how to select or design a highly selective catalyst for photocatalysis.

Simple and low–cost transition metal-free borophosphate glass catalyst for aromatic alcohol oxidation by sodium hypochlorite

The oxidation of primary and secondary alcohols to their respective aldehydes/ketones is one of the most important reactions in fine chemistry due to the industrial application of these products. Based on this, a large number of new catalysts and oxidants have been tested using this reaction as a catalytic model, mainly looking for a process that ensures high aldehyde selectivity. In this paper, we have used moisture stable borophosphate glass doped with 10 mol% Al2O3 as a heterogeneous catalyst in the oxidation of sodium hypochlorite, an effective, greener, and low-cost oxidant, using acetonitrile as solvent under mild conditions. The glass catalyst mass and the particle size were evaluated, as were the reaction temperature and oxidant amount, to determine the ideal reaction conditions where the conversions achieved 87.0 mol% for 1-phenylethanol to acetophenone and 79.4 mol% for benzyl alcohol to benzaldehyde, with benzaldehyde selectivity above 95%. Although sodium hypochlorite is a strong oxidant, benzaldehyde was the main product of the oxidation of benzyl alcohol due to the formation of a biphasic organic-aqueous system that protects the aldehyde from oxidation and allows the reaction to occur without the use of a phase transfer catalyst (PTC). HPLC analysis of both phases showed that alcohols, aldehyde, and ketone were mostly present in the organic phase (concentrations above 98.7%). During the reaction, a small amount of alcohol is transferred to the aqueous phase, where the oxidation took place. Once formed, the products are transferred back to the organic phase. ICP-OES analysis indicates that borophosphate glass acts in the reaction by partially releasing phosphate-based groups, reducing the pH of hypochlorite to 9. In this sense, borophosphate glasses prove to be a simple and inexpensive alternative for the development of new catalysts.

Sustainable and Selective Aerobic Oxidative C–C Bond Cleavage of Vicinal Diols under Near-Room-Temperature Condition

The selective oxidative C–C bond cleavage is essential for the production of functional molecules. Herein, a sustainable and efficient heterogeneous catalytic protocol is developed to facilitate the aerobic oxidative C–C bond cleavage, in which the selective conversion of vicinal diols to the corresponding aldehydes was achieved under a near-room-temperature condition with NH3-treated cobalt catalysts. Hydrobenzoin was selectively transformed to generate benzaldehyde with the solid ComOn/C–N catalyst, where the conversion and product selectivity reached 96.7 and 99.0% under an oxygen atmosphere, respectively. Further investigations revealed that the high catalytic activity of the catalyst is contributed to numerous oxygen defects, which lead to efficient generation of active 1O2 species. Moreover, the ComOn/C–N catalyst still exhibited a very high catalytic activity after it was continuously recycled five times. Finally, the oxidative cleavages of the C–C bond in the different 1,2-diols were also studied where more than 96.5% conversion of substrates and 99% selectivity of aldehydes were acquired under the optimal conditions.

Review of Calixarene-Derivatives in Transition Metal Chemistry

The survey depicts the combination of large-scale monodentate phosphites in response to PCl3/NEt3 with p-tert-butyl calix[4]-(OH)3-OR, where R contains an oxygen-containing substituent (R = CH2P(O)Ph2, -CH2CO2Et, -CH2C(O)NEt2, -CH2CH2OMe). These funnel-shaped calissarenes have a phosphorus particle bridging three phenolic oxygen atoms, and are incredibly steady in NaOH-aqueous arrangement due to the cone point being more noteworthy than 180°. Upon response with transition metal particles, these phosphites shape either P monodentate complexes or expansive P,O chelate complexes including the oxygen atom of the R group. The reactivity of four different ligands in the rhodium-catalyzed hydroformylation of octene was examined. The general trend is that a bulkier phosphite ligand leads to a slower reaction rate. The ligand-to-base ratios ranged from 1.4 to 3.6, and the highest straight aldehyde selectivity was observed when the carboxylate group was CH2CO2Et.

Selective Electrooxidation of Biomass‐Derived Alcohols to Aldehydes in a Neutral Medium: Promoted Water Dissociation over a Nickel‐Oxide‐Supported Ruthenium Single‐Atom Catalyst

AbstractThe biomass‐derived alcohol oxidation reaction (BDAOR) holds great promise for sustainable production of chemicals. However, selective electrooxidation of alcohols to value‐added aldehyde compounds is still challenging. Herein, we report the electrocatalytic BDAORs to selectively produce aldehydes using single‐atom ruthenium on nickel oxide (Ru1‐NiO) as a catalyst in the neutral medium. For electrooxidation of 5‐hydroxymethylfurfural (HMF), Ru1‐NiO exhibits a low potential of 1.283 V at 10 mA cm−2, and an optimal 2,5‐diformylfuran (DFF) selectivity of 90 %. Experimental studies reveal that the neutral electrolyte plays a critical role in achieving a high aldehyde selectivity, and the single‐atom Ru boosts HMF oxidation in the neutral medium by promoting water dissociation to afford OH*. Furthermore, Ru1‐NiO can be extended to selective electrooxidation of a series of biomass‐derived alcohols to corresponding aldehydes, which are conventionally difficult to obtain in the alkaline medium.

Selective Electrooxidation of Biomass-Derived Alcohols to Aldehydes in a Neutral Medium: Promoted Water Dissociation over a Nickel-Oxide-Supported Ruthenium Single-Atom Catalyst.

The biomass-derived alcohol oxidation reaction (BDAOR) holds great promise for sustainable production of chemicals. However, selective electrooxidation of alcohols to value-added aldehyde compounds is still challenging. Herein, we report the electrocatalytic BDAORs to selectively produce aldehydes using single-atom ruthenium on nickel oxide (Ru1 -NiO) as a catalyst in the neutral medium. For electrooxidation of 5-hydroxymethylfurfural (HMF), Ru1 -NiO exhibits a low potential of 1.283 V at 10 mA cm-2 , and an optimal 2,5-diformylfuran (DFF) selectivity of 90 %. Experimental studies reveal that the neutral electrolyte plays a critical role in achieving a high aldehyde selectivity, and the single-atom Ru boosts HMF oxidation in the neutral medium by promoting water dissociation to afford OH*. Furthermore, Ru1 -NiO can be extended to selective electrooxidation of a series of biomass-derived alcohols to corresponding aldehydes, which are conventionally difficult to obtain in the alkaline medium.

Study on the Staged and Direct Fast Pyrolysis Behavior of Waste Pine Sawdust Using High Heating Rate TG-FTIR and Py-GC/MS.

To understand the fast pyrolysis kinetics and product evolution of waste pine sawdust, high heating rate thermogravimetry-Fourier transform infrared (TG-FTIR) was used to obtain the kinetic parameters and the chemical groups formed during the pyrolysis process, while pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was used to investigate the detailed compositions of products under the staged (seven stages from 300 to 600 °C) and direct fast pyrolysis process. Spectral bands were identified for acids, alcohols, aldehydes, aromatics, esters, ethers, hydrocarbons, ketones, phenols, and sugars. Research found that the apparent activation energy for fast pyrolysis is much higher than that of slow pyrolysis. The evolution of CO2 is the major deoxygenation route. Cracking mainly occurred at the 450 °C stage with phenols, ketones, aldehydes, and sugars as the main products. The product distributions for different stages are significantly different; the selectivity of aldehydes decreased, while phenols showed an upward trend with an increase in pyrolysis temperature. Ketones and sugars reached their peak values at 450 °C. The changes in the molecular composition of each stage helped to understand the pyrolysis process. Compared with the staged pyrolysis, the direct pyrolysis process had higher selectivity of acids, aldehydes, esters, and sugars and lower selectivity of phenols, ketones, and alcohols.

Activity, Selectivity and Initial Degradation of Iron Molybdate in the Oxidative Dehydrogenation of Ethanol

AbstractIron molybdate catalysts are applied in the industrial FormOx process to produce formaldehyde by oxidative dehydrogenation (ODH) of methanol. Only few studies are available about the applicability of iron molybdate catalysts for the ODH of ethanol to produce acetaldehyde. Herein, an iron molybdate synthesized by co‐precipitation (p) and an iron molybdate prepared by a ball‐milling solid‐state synthesis (bm) are applied as ethanol ODH catalysts. Both materials show attractive acetaldehyde selectivites of >90 % (280 °C: p‐Fe2(MoO4)3: YAcH=90.3 %; bm‐Fe2(MoO4)3: YAcH=60.4 %) and a stable performance. The bulk composition and crystal structure could be confirmed by various characterization techniques and is maintained during ethanol ODH. XPS reveals an enrichment of Mo on the catalyst surface which is slightly decreasing after the catalytic tests. This observation could be a first sign of long‐term deactivation like known from methanol ODH. Comparing the performance of both materials, p‐Fe2(MoO4)3 shows higher activity and aldehyde selectivity. We propose the higher Mo/Fe surface ratio and the lower acidity to be the reasons for these differences.

Droplet Flow Assisted Electrocatalytic Oxidation of Selected Alcohols under Ambient Condition.

This study reports using a droplet flow assisted mechanism to enhance the electrocatalytic oxidation of benzyl alcohol, 2-phenoxyethanol, and hydroxymethylfurfural at room temperature. Cobalt phosphide (CoP) was employed as an active electrocatalyst to promote the oxidation of each of the individual substrates. Surface analysis of the CoP electrocatalyst using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), as well as electrochemical characterization, revealed that it had excellent catalytic activity for each of the substrates studied. The combined droplet flow with the continuous flow electrochemical oxidation approach significantly enhanced the conversion and selectivity of the transformation reactions. The results of this investigation show that at an electrolysis potential of 1.3 V and ambient conditions, both the selectivity and yield of aldehyde from substrate conversion can reach 97.0%.

Influence of the framework on the catalytic performance of Rh-supported Zr-MOFs in the hydroformylation of n-alkenes

Three large pore crystalline zirconium-based metal-organic frameworks (Zr-MOFs) of different pore sizes (6–18 Å) and structure were synthesized and used for the preparation of the Rh-supported catalysts Rh@UiO-66, Rh@UiO-67, and Rh@MOF-808. The materials were characterized by XRD, FTIR, SEM/TEM, XPS, and nitrogen adsorption/desorption measurements. The catalytic performance was studied in the hydroformylation of olefins to the corresponding aldehydes. A series of n-alk-1-enes of different chain length was used to study the influence of the pore size and structure. The results show that the Zr-MOF-based catalysts are very active and show high aldehyde selectivity. The superior catalytic properties are assigned to the presence of highly dispersed active Rh sites located at the isolated zirconia moieties and the enhanced accessibility of sites via the large pores. Nevertheless, marked differences in the catalytic performance of the catalysts are observed, which are assigned to the different accessibility of Rh located at various secondary building units.

Aerobic oxidation of aldehydes to acids with N-hydroxyphthalimide derivatives

The N-hydroxyphthalimide derivative-mediated aerobic oxidation of a selection of aldehydes to the corresponding carboxylic acids in air is described. This reaction proceeds via rearrangement of the Creigee (carboxylic peracid) intermediate and/or by the treatment of H2O and/or sulfides. Optimization of reaction conditions established NHNPI (14) as a mild catalyst for the oxidation reaction in MeCN under an atmosphere of air.

Confinement of atomically dispersed Rh catalysts within porous monophosphine polymers for regioselective hydroformylation of alkenes

Precisely controlling the regioselectivity with monophosphine ligand is a long-standing challenge in hydroformylation. Herein, we describe the one-pot encapsulation of single-atom Rh catalysts within porous monophosphine polymers for regioselective heterogeneous hydroformylation of alkenes. The optimized catalyst (Rh@POP-PTBA-HA-50) shows remarkable enhancement of regioselectivity compared with the combination of Rh(CO)2(acac) and monophosphine ligand (PTBA), and the linear aldehyde selectivity increases from 62% to 92%. In addition, this catalyst shows excellent catalytic activity (one run TON at least 60,000) and good stability. Detailed studies reveal that the encapsulation of atomically dispersed Rh catalysts within porous monophosphine polymers may endow the catalysts with high regioselectivity, while the encirclement of metal active species by abundant but dispersive phosphine ligand would strengthen the stability of the catalysts through multiple-sites-coordination. The present study provides meaningful insights for designing heterogeneous catalysts with good regioselectivity, and merging the advantages of homogeneous and heterogeneous catalysis.

Effectively Regulating the Microenvironment of Atomically Dispersed Rh through Co and Pi to Promote the Selectivity in Olefin Hydroformylation.

In the study of heterogeneity of homogeneous processes, effective control of the microenvironment of active sites is a reliable means to improve the selectivity of products. Here, we develop a high-performance Rh-based atomically dispersed catalyst for olefin hydroformylation by controlling the electronic environment and spatial distribution of active metals on the supports, which is achieved through wet impregnation of Rh on ZnO modified with Pi and Co. Various characterizations demonstrate that Co weakens Rh-CO interactions and Pi promotes the formation of atomically dispersed Rh, which thereby improves the selectivity of linear aldehydes in hydroformylation. This strategy of rationally designing the local microenvironment of active metals is important to optimize the catalytic performance.

Co‐Ni‐P‐B catalyzed hydroformylation of long linear α olefins

AbstractBACKGROUNDAs indirect liquefaction of coal has been carried out in megaton scale, extension of the Fischer‐Tropsch synthesis products has received renewed interest. Hydroformylation provides a way for the transformation of alkenes to aldehydes. Homogeneous rhodium complex catalysts are efficacious but expensive and not easy to recover and reuse. Heterogeneous catalysts are desired to enable their easy separation. Amorphous four‐component non‐precious metal catalysts were prepared using facile reduction and their activity toward hydroformylation of long linear α olefins was investigated.RESULTSObtained Co‐Ni‐P‐B presented uniform nanoparticles that were well‐dispersed Co with more electrons, attributing to isolation and electron transfer among the four components. The Co, Ni, P, and B were in both atomic states and oxidation states. The Co in Co‐Ni‐P‐B was shown to be electron‐enriched with enhanced catalytic activity. Co‐Ni‐P‐B displayed good catalytic activity for hydroformylation of linear C6, C8, C10, or C12 α olefins, and the highest activity for 1‐octene. The conversion of 1‐octene and the selectivity of C9 aldehydes reached 99.62% and 96.30%, respectively. The ratio of nonanal to isononanal was 1.44. The selectivity for isomeric products was 3.70%. There existed an appropriate four‐component ratio for hydroformylation of 1‐octene owing to synergistic effects among the Co, Ni, P, and B. Co‐Ni‐P‐B exhibited good reusability.CONCLUSIONAmorphous four‐component Co‐Ni‐P‐B prepared by facile reduction showed good catalytic performance toward hydroformylation of long linear C6, C8, C10, or C12 α olefins due to synergistic effects among the Co, Ni, P, and B. © 2021 Society of Chemical Industry (SCI).

Selective Gas-Phase Functionalization of SiO2 and SiNx Surfaces with Hydrocarbons.

Selective functionalization of dielectric surfaces is required for area-selective atomic layer deposition and etching. We have identified precursors for the selective gas-phase functionalization of plasma-deposited SiO2 and SiNx surfaces with hydrocarbons. The corresponding reaction mechanism of the precursor molecules with the two surfaces was studied using in situ surface infrared spectroscopy. We show that at a substrate temperature of 70 °C, cyclic azasilanes preferentially react with an -OH-terminated SiO2 surface over a -NHx-terminated SiNx surface with an attachment selectivity of ∼5.4, which is limited by the partial oxidation of the SiNx surface. The cyclic azasilane undergoes a ring-opening reaction where the Si-N bond cleaves upon the reaction with surface -OH groups forming a Si-O-Si linkage. After ring opening, the backbone of the grafted hydrocarbon is terminated with a secondary amine, -NHCH3, which can react with water to form an -OH-terminated surface and release CH3NH2 as the product. The surface coverage of the grafted cyclic azasilane is calculated as ∼3.3 × 1014 cm-2, assuming that each reacted -OH group contributes to one hydrocarbon linkage. For selective attachment to SiNx over SiO2 surfaces, we determined the reaction selectivity of aldehydes. We demonstrate that aldehydes selectively attach to SiNx over SiO2 surfaces, and for the specific branched aliphatic aldehyde used in this work, almost no reaction was detected with the SiO2 surface. A fraction of the aldehyde molecules reacts with surface -NH2 groups to form an imine (Si-N═C) surface linker with H2O released as the byproduct. The other fraction of the aldehydes also reacts with surface -NH2 groups but do not undergo the water-elimination step and remains attached to the surface as an aminoalcohol (Si-NH-COH-). The surface coverage of the grafted aldehyde is calculated as ∼9.8 × 1014 cm-2 using a known infrared absorbance cross-section for the -C(CH3)3 groups.

Engineering Thermostability in Artificial Metalloenzymes to Increase Catalytic Activity

Protein engineering has shown widespread use in improving the industrial application of enzymes and broadening the conditions they are able to operate under by increasing their thermostability and solvent tolerance. Here, we show that protein engineering can be used to increase the thermostability of an artificial metalloenzyme. Thermostable variants of the human steroid carrier protein 2L, modified to bind a metal catalyst, were created by rational design using structural data and a 3DM database. These variants were tested to identify mutations that enhanced the stability of the protein scaffold, and a significant increase in melting temperature was observed with a number of modified metalloenzymes. The ability to withstand higher reaction temperatures resulted in an increased activity in the hydroformylation of 1-octene, with more than fivefold improvement in turnover number, whereas the selectivity for linear aldehyde remained high up to 80%.

A novel biphasic and recyclable system based on formamide for the hydroformylation of long-chain alkenes with water-soluble phosphine rhodium catalyst

Abstract A simple and recyclable biphasic rhodium catalytic system for the hydroformylation of long-chain alkenes is performed with the presence of Rh/TPPTS (trisodium tris(m-sulfophenyl)phosphine) in highly polar formamide for the first time. This work investigated the phase behavior of 1-octene, 1-nonanal and formamide, as well as the factors affecting the catalytic performance and catalyst recovery. Two phases were fully separated with distinct interface, allowing facile recycle of catalyst-containing formamide solution by decantation. Hydroformylation could be carried out under mild condition with turnover frequency and aldehyde selectivity up to 950 h−1 and 97 %, respectively. The catalyst could be reused for at least 40 runs without obvious activity and selectivity decline. No extra rhodium or TPPTS was needed during the cycle runs, and the average rhodium loss for each cycle was as low as 0.02 wt%. This system has also been successfully applied to the hydroformylation of crude higher α-olefins with high conversion and rhodium reservation, which were just distilled from Fischer-Tropsch synthesis with 64.7∼81.0 % fraction.