Catalytic Upgrading of Ethanol to 1-Butanol Biofuel Additive Using Pd/MgO-Al2O3 and Bimetallic Pd-Cu/MgO-Al2O3 Mixed Oxide Catalysts

Catalytic conversion of ethanol to 1-butanol was studied over MgO-Al2O3 mixed oxide-based catalysts. Relationships between acid-base and catalytic properties and the effect of active metal on the hydrogen transfer reaction steps were investigated. The acid-base properties were studied by temperature-programmed desorption of CO2 and NH3 and by the FT-IR spectroscopic examination of adsorbed pyridine. Dispersion of the metal promoter (Pd, Pt, Ru, Ni) was determined by CO pulse chemisorption. The ethanol coupling reaction was studied using a flow-through microreactor system, He or H2 carrier gas, WHSV = 1 gEtOH·gcat.-1·h-1, at 21 bar, and 200-350 °C. Formation and transformation of surface species under catalytic conditions were studied by DRIFT spectroscopy. The highest butanol selectivity and yield was observed when the MgO-Al2O3 catalyst contained a relatively high amount of strong-base and medium-strong Lewis acid sites. The presence of metal improved the activity both in He and H2; however, the butanol selectivity significantly decreased at temperatures ≥ 300 °C due to acceleration of undesired side reactions. DRIFT spectroscopic results showed that the active metal promoted H-transfer from H2 over the narrow temperature range of 200-250 °C, where the equilibrium allowed significant concentrations of both dehydrogenated and hydrogenated products.

C and Si delta doping in Ge by CH3SiH3 using reduced pressure chemical vapor deposition

Simultaneous synthesis of enantiomerically pure ( S)-amino acids and ( R)-amines using α/ω-aminotransferase coupling reactions with two-liquid phase reaction system

Vapor-phase transformations of furfural in H(2) over a series of Pt nanoparticles (NPs) with various particle sizes (1.5-7.1 nm size range) and shapes (rounded, cubes, octahedra) encapsulated in poly(vinylpyrrolidone) (PVP) and dispersed on MCF-17 mesoporous silica were investigated at ambient pressure in the 443-513 K temperature range. Furan and furfuryl alcohol (FFA) were two primary products as a result of furfural decarbonylation and hydrogenation reactions, respectively. Under conditions of the study both reactions exhibited structure sensitivity evidenced by changes in product selectivities, turnover rates (TORs), and apparent activation energies (E(A)'s) with Pt particle size and shape. For instance, upon an increase in Pt particle size from 1.5 to 7.1 nm, the selectivity toward FFA increases from 1% to 66%, the TOR of FFA production increases from 1 × 10(-3) s(-1) to 7.6 × 10(-2) s(-1), and E(A) decreases from 104 kJ mol(-1) to 15 kJ mol(-1) (9.3 kPa furfural, 93 kPa H(2), 473 K). Conversely, under the same experimental conditions the decarbonylation reaction path is enhanced over smaller nanoparticles. The smallest NPs (1.5 nm) produced the highest selectivity (96%) and highest TOR values (8.8 × 10(-2) s(-1)) toward furan formation. The E(A) values for decarbonylation (∼62 kJ mol(-1)) was Pt particle size independent. Furan was further converted to propylene via a decarbonylation reaction, but also to dihydrofuran, tetrahydrofuran, and n-butanol in secondary reactions. Furfuryl alcohol was converted to mostly to 2-methylfuran.

Intermolecular cross-pinacol coupling reaction between aliphatic and aromatic aldehydes by using heterodinuclear hemisalen complexes 1cis with vanadium(V) and titanium(IV) on a hexaarylbenzene scaffold is reported. Our ligand design is based on the individual activation of two aldehydes by vanadium and titanium, which are positioned with a suitable space on the rigid scaffold. Ligands such as 1cis were synthesized by Diels-Alder addition and decarbonylation reaction, followed by condensation of dialdehyde 3cis with various aminophenols. The influence of the substituents on the ligands on the pinacol coupling reaction was investigated. As a result, the reductive coupling reaction between aliphatic and aromatic aldehydes by using a catalytic amount of 1cis in the presence of Me3 SiCl and Zn provided the corresponding cross-coupled 1,2-diol in good yields with high cross-selectivity.

Effect of temperature on fracture toughness of an amorphous poly(ether-ether ketone) film using essential work of fracture analysis

Lipid Structure and Composition Control Consequences of Interleaflet Coupling in Asymmetric Vesicles

Three different fluoro-terminated hyperbranched poly(ether ketone)s (FHBPEKs) with variable degrees of branching and their linear analogous poly(ether ketone) (LPEK) whose chemical structure and molecular weight were similar to those of the FHBPEKs were synthesized. Cyano-terminated hyperbranched poly(ether ketone), CHBPEK, in which the terminal groups of FHBPEK were modified with cyanophenol was also prepared as a reference. The local relaxation and motion of the three FHBPEKs, in conjunction with their hyperbranched structure and the degrees of branching, were characterized by the solid-state 1H pulsed wide-line NMR spectroscopy and compared to that of the linear counterpart, LPEK. From the measurements of the spin−lattice relaxation times in the rotating frame, T1ρ's, over the temperature range 140−400 K, the correlation times, τc's, and the corresponding activation energies, Ea's, were determined, providing a direct evaluation for the local molecular motion. FHBPEKs were found to be structurally heterogeneous because they had two different motions throughout the system; with aid of the τc results of CHBPEK, each was assigned as originating from the linear and from the terminal/branched portion, respectively. In contrast, LPEK exhibited single relaxational and motional behavior, indicating that it was structurally homogeneous. The molecular mobility of the linear portion of FHBPEKs was higher than that of LPEK and enhanced with increasing degree of branching in the entire range of experimental temperatures. For the terminal/branched portion of the FHBPEKs, the local mobility was little affected by the degree of branching, especially at the temperature range from 140 K to room temperature, but increased afterward as was for the linear portion.

Effect of Promoters on Pt/Sio2 Catalysts for the N-Alkylation of Sterically Hindered Anilines in the Vapor Phase

Effects of Ti, Nb and Zr doping on thermoelectric performance of β-FeSi 2

Cross-electrophile coupling (XEC) reactions are widely employed to rapidly construct C(sp2)-C(sp3) bonds from available substrates. Key elementary steps of the reaction, such as oxidative addition and radical coupling, have been individually investigated with discrete complexes, but no studies exist that probe these and other key steps along the reaction pathway from a single, synthetically relevant platform. This work leverages the accessibility of persistent organonickel complexes to benchmark the effects of electronic and steric parameters of complexes and substrates on the rates of oxidative addition, the stabilities of organonickel intermediates, and the rates of radical coupling. Insights into the rates of oxidative addition help to rationalize synthetic limitations that are frequently encountered in Ni-catalyzed methodologies. Finally, the aggregate effects of the independently studied steps were evaluated by measuring the overall yields of the combinatorial coupling reactions. These insights established guidelines for selecting Ni complexes for XEC reactions of substrates that are challenging to couple.

Effect of temperature on work of fracture parameters in poly(ether-ether ketone) (PEEK) film

3.22 Carbonylation and Decarbonylation Reactions

Herein, we reported Lewis acid- or Brønsted acid-promoted intramolecular C(sp2)-C(sp2) bond cleavage and a novel C(sp2)-C(sp2) bond-forming cascade reaction to synthesize the acridine motif. The metal-free oxidation of the alkyne motif generated the in situ ketone group extracted via a decarbonylation reaction. The mechanistic studies revealed that the electrophilic N-iodo species triggered key decarbonylation reactions via consecutive dearomatization/aromatization reactions. In addition, we exploited this acid-promoted C-C bond activation system with internal alkynes to synthesize bis(heteroaryl) ketones.

We present a detailed investigation of the design characteristics and performance of a novel reactor system, termed the hybrid adsorbent−membrane reactor (HAMR), for hydrogen production. The HAMR concept, originally proposed by our group1,2 for esterification reactions, couples the reaction and membrane separation steps with adsorption on the membrane feed or permeate side. The HAMR system investigated previously involved a hybrid pervaporation membrane reactor and integrated the reaction and pervaporation steps through a membrane with water adsorption. Coupling reaction, pervaporation, and adsorption significantly improved the performance. In this paper, we investigate a new HAMR system involving a hybrid packed-bed catalytic membrane reactor coupling the methane-steam-reforming reaction through a porous ceramic membrane with a CO2 adsorption system. The present HAMR system is of potential interest to pure hydrogen production for proton exchange membrane (PEM) fuel cells for various mobile and stationary applications. The reactor characteristics have been investigated for a range of temperature and pressure conditions relevant to the aforementioned applications. The HAMR system exhibits enhanced methane conversion, hydrogen yield, and product purity and shows good promise for reducing the hostile operating conditions of conventional methane−steam reformers and for meeting the product purity requirements for PEM operation.