Alcohol Catalyst Research Articles

Effects of atom arrangement and thickness of Pt atomic layers on Pd nanocrystals for electrocatalysis

Depositing ultrathin Pt layer on less expensive substrates is an effective way to increase the catalytic activity and utilization efficiency of Pt catalyst in direct alcohol fuel cells. In this study, electrocatalytic properties of Pt atomic layer on Pd nanocrystals (NCs) was studied by changing the thickness of Pt layers and the surface structure of Pd NCs. We prepared 1–5 atomic Pt layers on {730}-faceted tetrahexahedral Pd nanocrystals (THH Pd@Ptn NCs) and on {111}-preferential Pd NCs. For both cases, Pt monolayer has a strong electronic effect from Pd NCs, while Pt bilayers have a moderate effect. In comparison with the {111}-preferential Pd@Ptn NCs, the THH Pd@Ptn NCs exhibit about 3 times higher catalytic activity towards ethanol electrooxidation. It has measured that the THH Pd@Pt2 NCs exhibit the highest catalytic activity amongst all THH Pd@Ptn (n = 1–5) NCs and THH Pt NCs, which is interpreted by a synergy of electronic effect and surface atom arrangement effect.

Bimetallic Mn–Co Oxide Nanoparticles Anchored on Carbon Nanofibers Wrapped in Nitrogen-Doped Carbon for Application in Zn–Air Batteries and Supercapacitors

The exploration and rational design of cost-effective, highly active, and durable catalysts for oxygen electrochemical reaction is crucial to actualize the prospective technologies such as metal–air batteries and fuel cells. Herein manganese cobalt oxide nanoparticles anchored on carbon nanofibers and wrapped in a nitrogen-doped carbon shell (MCO/CNFs@NC) is successfully prepared. Benefiting from the synergistic effect between the core nanoparticles and nitrogen-doped carbon shell, MCO/CNFs@NC catalyst exhibits oxygen reduction reaction (ORR) activity with comparable onset potential (1.00 V vs RHE) and half-wave potential (0.76 V vs RHE) which is only about 40 mV lower than that of the state of art Pt/C catalyst. Furthermore, the MCO/CNFs@NC catalyst exceeds the Pt/C catalyst by a great margin in terms of stability in alkaline media. Additionally, MCO/CNFs@NC catalyst is strongly tolerant to methanol crossover, promising its applicability as cathode catalyst in alcohol fuel cells. Moreover, MCO/CNFs@NC catalyst exhibits the oxygen evolution reaction (OER) activity with low overpotential of 0.41 V at the current density of 10 mA cm–2 and ORR/OER potential gap (ΔE) as low as 0.88 V, suggesting its strong bifunctionality. The Zn–air battery based on MCO/CNFs@NC catalyst is found to deliver a specific capacity of 695 mA h g–1Zn and an energy density of 778 W h kg–1Zn at a current density of 20 mA cm–2. The mechanically rechargeable Zn–air battery based on MCO/CNFs@NC catalyst is also found to function continually by only reloading the consumed Zn anode and electrolyte. Furthermore, the electrically rechargeable battery based on MCO/CNFs@NC catalyst is found to function for more than 220 cycles with negligible loss of voltaic efficiency. Moreover, MCO/CNFs@NC is found to display a supercapacitive nature with a good discharge capacity of 478 F g–1 at a discharge current density of 1 A g–1.

Origins of Stereoselectivity in Chiral Aminoalcohol Catalysis of Oxyallyl Cation-Indole Reactions.

The enantioselective coupling of indoles with racemic α-tosyloxy ketones mediated by a chiral amino alcohol catalyst is studied with density functional theory (DFT) calculations. The addition of indole to an oxyallyl cation intrinsically favors the (S,S) and (R,R) stereoisomeric products through electrostatic interactions in the transition state. Our model shows that the enantioselectivity is controlled by the cyclohexane moiety of the catalyst; selectivity diminishes upon removal of the cyclohexane ring. Substitution to enhance the enantioselectivity of this reaction is proposed.

Process optimization of spent catalyst regeneration under microwave and ultrasonic spray-assisted

In this work, the activated carbon loaded with zinc acetate dihydrate and used for catalyst in the polyvinyl alcohol and adhesive production process, was regenerated by microwave heating under ultrasonic spray atmosphere to recover the adsorption capacity of the spent catalyst. The effects of regeneration temperature, regeneration time and water mist flow rate on the adsorption ability of methylene blue (MB) and yield of activated carbon were researched systematically. The experiment results indicated that a promising adsorption capability via ultrasonic spray regeneration was developed for the spent catalyst, corresponding to Brunauer-Emmett-Teller (BET) surface area of 1263m2/g and total pore volume of 1.28mL/g under optimum conditions. The spent catalyst was also regenerated under the CO2 and N2 atmosphere, which indicated that the better pore structure was obtained under ultrasonic spray conditions. The physico-chemical properties of the activated carbon were measured by N2 adsorption, Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscopy (SEM). The results showed that the chemical groups of activated carbons changed after regeneration and before and the spent catalyst can be regenerated commendably by microwave and ultrasonic spray-assisted.

Direct synthesis of Pt-free catalyst on gas diffusion layer of fuel cell and usage of high boiling point fuels for efficient utilization of waste heat

Gas diffusion layers (GDL) and electrocatalysts are integral parts of fuel cells. It is, however, a challenging task to grow Pt-free robust electrocatalyst directly on GDL for oxygen reduction reaction (ORR) – a key reaction in fuel cells. Here, we demonstrate that boron-doped carbon nanotubes (BCNTs) grown directly on gas-diffusion layer (which avoid the need of ionomer solution used for catalyst loading) can be used as efficient Pt-free catalyst in alcohol fuel cells. Increase in boron concentration improves the electrochemical ORR activity in terms of onset and ORR peak positions, half-wave potentials and diffusion-limited current density that ensure the optimization of the device performance. The preferential 4e− pathway, excellent cell performance, superior tolerance to fuel crossover and long-term stability makes directly grown BCNTs as an efficient Pt-free cathode catalyst for cost-effective fuel cells. The maximum power density of the fuel cell is found to increase monotonically with boron concentration. In addition to the application of BCNTs in fuel cell, we have introduced the concept of hot fuels so that waste heat can effectively be used and external power sources can be avoided. The fuel is passed through a hot bath for the realization of hot fuel which eventually increases the operating temperature of the cell (for example: 60°C for methanol and 80°C for ethyleneglycol, avoids the requirement of heating arrangement) and hence, the performance. Overall, different strategies to design ultimate fuel cells for their commercial adoption and effective utilization of waste heat have been outlined.

An Asymmetric, Catalytic (4 + 3) Cycloaddition Reaction of Cyclopentenyl Oxyallylic Cations.

Treatment of 2-tosyloxycyclopentanone with substituted furans in the presence of a chiral amino alcohol catalyst and K2HPO4 results in the formation of (4 + 3) cycloaddition products with enantioselectivities that exceed 90% in certain cases.

A Diamino Alcohol Catalyzed Enantioselective Crossed Aldol Reaction of Acetaldehyde with Isatins – A Concise Total Synthesis of Antitumor Agents

Enantioselective crossed aldol reactions of isatin derivatives and acetaldehyde have been developed with a series of simple diamino alcohol catalysts to afford 3‐substituted 3‐hydroxyindolin‐2‐ones in high chemical yields (up to 95 %) and optical purities (up to 92 % ee). The synthetic potential of the present protocol has been demonstrated by concise, enantioselective, protecting‐group‐free, and transition metal‐free total syntheses of antitumor and antiviral agents with the tryptanthrin architecture, that is, phaitanthrin B and cephalanthrin A, along with the biologically active indolidine alkaloids chimonamidine and donaxaridine as well as the formal synthesis of CPC‐1. The highly enantioselective outcome of this catalytic crossed aldol reaction was evaluated by calculating the Gibbs free energies of the possible transition states.

Hybrid‐Type Squaramide‐Fused Amino Alcohol Organocatalysts for Enantioselective Nitro‐Aldol Reaction of Nitromethane with Isatins

A series of hybrid‐type squaramide‐fused amino alcohol (SFAA) catalysts were synthesized, and their catalytic efficiency in the enantioselective nitro‐aldol reaction of various isatins with nitromethane has been described. This transformation afforded chiral 3‐substituted 3‐hydroxyoxindoles in excellent chemical yields (up to 99 %) with high enantioselectivities (up to 95 % ee). The resulting chiral 3‐hydroxyoxindoles can be further used as synthetic precursors for the synthesis of several natural products that have a broad spectrum of fascinating biological activities.

Liquid phase aerobic oxidation of benzyl alcohol by using manganese ferrite supported-manganese oxide nanocomposite catalyst

This study illustrates for the first time the performance of nano-manganese ferrite supported-manganese oxide catalyst in benzyl alcohol (BzOH) oxidation without employing any oxidizing agent other than the air present in the reactor. The magnetic catalyst displayed moderate activity but 100% selectivity in conversion to benzaldehyde (BzH) under mild conditions. Compared to the other heterogeneous MnOx-based systems, the catalyst deserves attention in that an enhancement of the activity can be achieved by tuning the core-shell composition which plays a synergistic role in the catalytic reaction.

ChemInform Abstract: Oxy‐Allyl Cation Catalysis: An Enantioselective Electrophilic Activation Mode.

AbstractUsing a new amino alcohol catalyst, the enantioselective conversion of racemic α‐tosyloxy ketones into optically enriched α‐indolic carbonyls in the presence of electron‐rich indole nucleophiles is investigated.

Effect of Temperature on Creep behavior of Poly(vinyl chloride) Loaded with Single Walled Carbon Nanotubes

Single walled carbon nanotubes (SWCNTs) were synthesized using alcohol catalyst chemical vapor deposition ACCVD method using ethanol and were characterized with TEM. The prepared SWCNTs were incorporated with different concentrations in Poly(vinyl chloride) with different concentrations. The effect of both SWCNTs concentrations and temperature on creep and creep recovery of PVC were studied. Burger’s model was applied to the region of creep and material parameters like instantaneous elastic modulus, Voigt elastic modulus and viscosity, Newtonian viscosity and linear thermal expansion coefficient were calculated at different concentrations of SWCNTs and different temperatures. These parameters were found to have a maximum at 1 wt % of SWCNTs and also found to decrease with increasing temperature. The recovery relaxation time was calculated and the activation energy of chains upon heating was calculated and samples containing 5 wt% of SWCNTs was found to have a maximum of 0.36 eV.

Oxy-Allyl Cation Catalysis: An Enantioselective Electrophilic Activation Mode.

A generic activation mode for asymmetric LUMO-lowering catalysis has been developed using the long-established principles of oxy-allyl cation chemistry. Here, the enantioselective conversion of racemic α-tosyloxy ketones to optically enriched α-indolic carbonyls has been accomplished using a new amino alcohol catalyst in the presence of electron-rich indole nucleophiles. Kinetic studies reveal that the rate-determining step in this S(N)1 pathway is the catalyst-mediated α-tosyloxy ketone deprotonation step to form an enantiodiscriminant oxy-allyl cation prior to the stereodefining nucleophilic addition event.

Theoretical and experimental studies of 1,5,7-triazabicyclo[4.4.0]dec-5-ene-catalyzed ring opening/ring closure reaction mechanism for 5-, 6- and 7-membered cyclic esters and carbonates

The ring-opening polymerizations (ROP) of five-, six-, and seven-membered ring cyclic substrates, as well as the transesterification of acyclic esters, with 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst precursor in the presence of methanol as an initiator were investigated using density functional theory calculations at the B3LYP/6–311G(d) level of theory. The calculated energy barriers for the ROP are in the range from 12.5 to 21.5 kcal/mol. By analyzing the energy profiles, the overall polymerization process can be classified into exergonic for trimethylene carbonate, tetramethylene carbonate, caprolactone and 1,4-dioxane-2,5-dione, almost athermic for valerolactone, energetically unfavorable for 1,4-dioxanone, and thermodynamically forbidden for ethylene carbonate and gamma-butyrolactone. The study of the kinetics of ROP of cyclic substrates and transesterification of acyclic esters using the TBD—benzyl alcohol catalyst demonstrated that the experimentally determined rate constants for the reactions of cyclic substrates are qualitatively correlated with the calculated activation barriers. It was also experimentally found that TBD efficiently catalyzes the irreversible cyclization to give ethylene carbonate and gamma-butyrolactone, the catalyst productivity being 2–3 orders of magnitude higher than that of conventional basic catalysts. The obtained results confirm that the donor–acceptor mechanism is common for different ester-type substrates.

Abstract 647: SeriMabs: N-terminal serine modification enables modular, site-specific payload incorporation into antibody-drug conjugates (ADCs)

Abstract Site-specific incorporation of cell-killing agents into cancer-targeting antibodies is an active area of innovation in the field of ADCs. We have developed a highly modular site-specific conjugation platform employing N-terminal serine engineered antibodies (SeriMabs), using ligation chemistry orthogonal to lysine and cysteine modification which typically employs maleimide containing linkers. Humanized IgG1 antibodies were engineered with N-terminal serine residues on either the light or heavy chain, with the precise position optimized for quantitative conversion to the corresponding glyoxyl aldehyde in the presence of sodium periodate. The aminooxy functional group of the heterobifunctional linker N-[(aminooxy)acetyl]-3-[(3-nitro-2-pyridinyl)dithio]-L-alanine was condensed with the aldehyde group on the antibody using 4-amino phenethyl alcohol catalyst, yielding a stable oxime bond under conditions that fully maintain antibody integrity. The dithiopyridine groups were then reacted with thiol-containing maytansinoid or IGN cell-killing agents, yielding disulfide-linked SeriMab ADCs with exactly 2 payload molecules per antibody, as determined by MS analysis, in > 90% yield and with a monomer content of > 98%. Conjugation of payload was found to be selective for the N-terminal serine based on MS/MS analysis. The site-specific ADCs were found to bind to their target antigens with affinity similar to the corresponding lysine-conjugated ADCs, and FcRn binding (pH 5.8) of the SeriMab ADCs were comparable to lysine-conjugated controls. DGN462, our proprietary DNA-acting IGN payload used in our preclinical candidate IMGN779, was conjugated to SeriMabs against two targets, and in both cases, high, antigen-specific in vitro potency was noted. The oxime linkage used in the serine site-specific conjugates was found to be stable at pH 5.5 and pH 7.4 in buffer, as little detectable payload was released over 4 days at 37°C. SeriMab antiFRα-DGN462 (2 DGN462 molecules per Ab) demonstrated potent, dose-dependent antitumor activity against NCI-H2110 non-small cell lung cancer xenografts in SCID mice. SeriMab antiFRα-DGN462 was highly active at a single injection dose of 50 and 25 μg/kg (DGN462 dose) with a minimal efficacious dose (MED) of 10 μg/kg. We have developed a modular method for preparing site-specific, disulfide-linked ADCs with good biochemical characteristics, through an optimized N-terminal serine engineered IgG, using the same thiol containing effector payloads employed in our lysine-conjugation platform. Citation Format: Luke Harris, Daniel Tavares, Lingyun Rui, Erin Maloney, Alan Wilhelm, Juliet Costoplus, Katie Archer, Megan Bogalhas, Lauren Harvey, Rui Wu, Xuan Chen, Xiangyang Xu, Sonia Connaughton, Lintao Wang, Kathleen Whiteman, Olga Ab, Erica Hong, Wayne Widdison, Manami Shizuka, Michael Miller, Jan Pinkas, Thomas Keating, Ravi Chari, Nathan Fishkin. SeriMabs: N-terminal serine modification enables modular, site-specific payload incorporation into antibody-drug conjugates (ADCs). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 647. doi:10.1158/1538-7445.AM2015-647

Effects of methanol co-feeding in ethanol synthesis from syngas using alkali-doped MoS2 catalysts

Gasification of biomass to syngas followed by catalytic conversion of syngas over mixed alcohol catalysts is an alternative pathway to produce bioethanol. Significant improvements in catalyst and process development need to be achieved to make this process commercially attractive. It is known that ethanol is produced from methanol by means of a CO insertion mechanism in the case of mixed alcohol MoS2 catalysts. Thus, an improvement in the industrial process could be to recycle methanol produced in the reactor. This paper examines experimentally the influence of methanol co-feeding for a wide range of methanol concentration in the feed at different reaction temperatures. The results reveal that CO conversion and productivity of ethanol and higher alcohol increase linearly with methanol concentration in the feed for a given reaction temperature, while hydrocarbon productivity increases exponentially. Therefore, there is a trade-off between increasing alcohol productivity and the selective conversion of methanol to alcohols. When the concentration of methanol in the feed changes from 0% to 8%mole concentration, ethanol and higher alcohol productivity increase more than two-fold. The addition of methanol has a positive influence in the ethanol selectivity only at low methanol content in the feed.

Conducting polymer-supported palladium nanoplates for applications in direct alcohol oxidation

Nanostructured materials play a critical role in the catalysis of various relevant reactions in fuel cells, resulting in enhanced intrinsic electroactivity with high surface area, superior conductivity and better mass transport. The catalytic activity and stability of Pd nanoplates (Pd-NPLs) for the oxidation of ethanol were studied by using cyclic voltammetry and chronoamperometry. The poly(diphenylbutadyine) (PDPB) polymer nanofiber can be used as support to enhance the catalytic activity of Pd nanoplates for the oxidation of ethanol. The chronoamperometric response confirms the better activity and stability of the nanofiber-based support compared to commercial nafion (5 wt%). The nanofiber morphology of the poly(diphenylbutadyine) polymer helps in the effective dispersion of the Pd nanoplates, facilitating an easier access of ethanol molecules to the catalytic sites. The dispersion of the Pd nanoplates within the polymer nanofibers is connected with an enhancement of the catalytic activity. These results show that the polymer-supported Pd nanoplate based hybrid structure is a promising anode catalyst in direct alcohol fuel cells (DAFCs).

Comparative study of aliphatic alcohols electrooxidation on zero-valent palladium complex for direct alcohol fuel cells

In this paper, bis (dibenzylidene acetone) palladium (0), Pd (DBA)2, was used as an effective catalyst for the electrooxidation of different aliphatic alcohols such as ethylene glycol (EG), ethanol (EtOH), glycerol (Gly), methanol (MeOH)) in the alkaline media. The activity and stability of Pd (DBA)2 were assessed for the electrooxidation of the mentioned alcohols using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA). Pd (DBA)2 exhibited significantly high anodic current density and lower onset potential in EtOH oxidation compared to EG, Gly and MeOH. CV and CA results demonstrated that Pd (DBA)2 is still active even after 200 CV cycles. The tolerance of Pd (DBA)2 against poisoning intermediate products in case EtOH was higher than other mentioned alcohols. Finally, Pd (DBA)2 successfully employed as an anode catalyst in a passive air breathing direct alcohol fuel cell (DAFC). The maximum power density (MPD) of 30, 31, 25 and 18 mW cm−2 were achieved for EG, EtOH, Gly and MeOH, respectively. These results indicated that Pd (DBA)2 can be a promising anode catalyst for DAFCs.

Enantioselective Diels-Alder reaction of 1,2-dihydropyridines with aldehydes using β-amino alcohol organocatalyst.

The enantioselective Diels-Alder reaction of 1,2-dihydropyridines with aldehydes using an easily prepared optically active β-amino alcohol catalyst was found to provide optically active isoquinuclidines, an efficient synthetic intermediate of pharmaceutically important compounds such as oseltamivir phosphate, with a satisfactory chemical yield and enantioselectivity (up to 96%, up to 98% ee). In addition, the obtained highly optically pure isoquinuclidine was easily converted to an optically active piperidine having four successive carbon centers.

Molybdenum(VI) dioxo complexes for the epoxidation of allylic alcohols and olefins

Several molybdenum(VI) dioxo complexes have been investigated as catalyst precursors for allylic alcohol epoxidation using mainly hydrogen peroxide as oxidant. All catalysts proved to be efficient and selective for the epoxidation of allylic alcohols provided the olefins were rather electron rich. Indeed, electron poor substrates could be converted selectively into the corresponding unsaturated aldehydes. A chiral dioxomolybdenum complex based on an optically pure tridentate Schiff base ligand was synthesized and characterized. Though that complex provided an efficient epoxidation catalyst for allylic alcohols and olefins, no chiral induction was observed. During the X-ray diffraction analysis, the cooling at 100 K led to the appearance of super-lattice reflections on diffraction patterns reflecting an ordering of the structure. Instead of one organometallic species observed at 298 K, three similar complexes of the same molecular structure could be observed in the asymmetric unit at 100 K.

Enantiopure Isotactic PCHC Synthesized by Ring-Opening Polymerization of Cyclohexene Carbonate

The ring-opening polymerization (ROP) of racemic trans-cyclohexene carbonate (rac-CHC) and enantiopure trans-(R,R)-CHC is successfully carried out with various catalyst systems. Poly(cyclohexene carbonate) (PCHC) with a slight isotactic bias (Pm = ca. 60–76%) is obtained by ROP of rac-CHC catalyzed by zinc diaminophenolate, zinc β-diketiminate, yttrium bis(phenolate), or 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in combination with an alcohol as a co-initiator. Purely isotactic PCHC is synthesized for the first time via ROP of enantiopure (R,R)-CHC with a zinc/benzyl alcohol catalyst system. All reactions proceed without decarboxylation, affording well-defined PCHCs with Mn,NMR up to 17 000 g mol–1 and ĐM = ca. 1.2. Purely isotactic PCHC is semicrystalline, with Tg = 130 °C, Tc = 162 °C, and Tm = 248 °C. DFT computations further highlight the significant favorable impact of the trans-cyclohexane ring-strain to enable the ROP of CHC, as opposed to meso-CHC which is unreactive.