A Synergic Blend of Newly Isolated <Emphasis Type="Italic">Pseudomonas mandelii</Emphasis> KJLPB5 and [hmim]Br for Chemoselective 2° Aryl Alcohol Oxidation in H<Subscript>2</Subscript>O<Subscript>2</Subscript>: Synthesis of Aryl Ketone or Aldehydes via Sequential Dehydration-Oxidative C=C Cleavage

Abstract  

Pseudomonas mandelii KJLPB5 is reported for the oxidation of aryl alcohols in ionic liquid [hmim]Br (1-hexyl-3-methyl imidazolium bromide) with H₂O₂. With a slight alteration of reaction conditions, the developed protocol leads either to (i) chemoselective oxidation of 2° aryl alcohols over 1° and aliphatic counterparts or (ii) direct one pot-two step sequential conversion of 2° aryl alcohols into corresponding one or two carbons shorter aryl aldehydes through oxidative cleavage pathway, thus providing a new facet to metal-free oxidations. The key operational parameters such as substrate concentration, incubation temperature, incubation time, ionic liquid type and ionic liquid concentration are also optimized.     

Parametric study of pyrolysis and steam gasification of rice straw in presence of K<Subscript>2</Subscript>CO<Subscript>3</Subscript>

A parametric study of pyrolysis and steam gasification of rice straw (RS) was performed to investigate the effect of the presence of K₂CO₃ on the behavior of gas evolution, gas component distribution, pyrolysis/gasification reactivity, the quality and volume of synthetic gas. During pyrolysis, with the increase in K₂CO₃ content in RS (i) the instantaneous CO₂ concentration was increased while CO concentration was relatively stable; (ii) the yield of CO₂ and H₂ increased on the cost of CH₄. During steam gasification of RS, with the increase in K₂CO₃ content in RS (i) the instantaneous concentration of CO₂ and H₂ increased while instantaneous concentration of CO and CH₄ decreased; (ii) the yield of CO₂ and H₂ production and total yield increased; and (iii) yield of CO and CH₄ production followed the order: 9% K₂CO₃ RS<6% K₂CO₃ RS<raw RS<3% K₂CO₃ RS<water-leached RS. Water-leached RS showed the highest pyrolysis reactivity, while stream gasification reactivity was proportional to K₂CO₃ content in RS. The results of this study reveal that the presence of K₂CO₃ during pyrolysis and steam gasification of RS effectively improves production of H₂ rich gas.     

Gas-phase Photocatalytic Oxidation of Acrylonitrile on Sulphated TiO<Subscript>2</Subscript>: Continuous Flow and Transient Study

Abstract  

The gaseous products of photocatalytic oxidation (PCO) of acrylonitrile on sulphated P25 in concentrations from 10 to 100 ppm at 60 to 130 °C were CO₂, HCN and HNCO. This photocatalyst showed disproportionally improved performance at higher temperature and longer retention times. The temperature-programmed oxidation (TPO) after PCO disclosed possible reaction routes.     

In Situ FT-IR Study of Diesel Hydrocarbon Oxidation Over Pt/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalyst

Abstract  

The catalytic performance of Pt/Al₂O₃ for the total oxidation of a hydrocarbon mixture of n-decane and 1-methylnaphthalene was investigated by using in situ FT-IR spectroscopy. Although carbonate and/or carboxylate species were mainly detected under steady-state conditions, the formation of an acrylate species during the initial stage of the reaction was observed under transient conditions. Based on a comparison of the reaction and formation behavior of the acrylate species and CO₂ as a gaseous product, it was proposed that the total oxidation of the hydrocarbon mixture proceeds via the formation of an acrylate species as a reaction intermediate.     

Nanocasting Synthesis of Mesostructured Co<Subscript>3</Subscript>O<Subscript>4</Subscript> via a Supercritical CO<Subscript>2</Subscript> Deposition Method and the Catalytic Performance for CO Oxidation

Abstract  

We demonstrate a supercritical CO₂ (scCO₂) deposition method to synthesize mesostructured Co₃O₄ with crystalline walls using SBA-15 as the hard template. By variation of the scCO₂ pressure, randomly organized nanorods or a highly ordered mesoporous structure of Co₃O₄ is obtained after only one filling operation. The catalytic tests show that the randomly organized Co₃O₄ nanorods display excellent activity for CO oxidation with the complete conversion of CO even at room temperature, while neither the ordered mesoporous nor bulk Co₃O₄ is active at this low-temperature, demonstrating the important role of Co₃O₄ morphology in catalysis.     

Synthesis of Highly Active Nano-Sized Pt/CeO<Subscript>2</Subscript> Catalyst via a Cerium Hydroxy Carbonate Precursor for Water Gas Shift Reaction

Abstract  

A novel precipitation/digestion route has been developed to synthesize crystalline cerium hydroxy carbonate (CHC: Ce(OH)CO₃) by using an equimolar quantity of cerium nitrate (Ce(NO₃)₃·6H₂O) and mixed precipitants (KOH + K₂CO₃) at room temperature. Nano-sized CeO₂ supports could be prepared by the pre-calcination of CHC at 400 °C for 4 h. A highly active water gas shift (WGS) catalyst, 1 wt.% Pt/CeO₂ catalyst showed almost equilibrium CO conversion with 100% CO₂ selectivity at 320 °C even at the gas hourly space velocity (GHSV) of 45,625 h⁻¹.     

Incorporation of Metal Ions into Silica-Grafted Imidazolium-Based Ionic Liquids to Efficiently Catalyze Cycloaddition Reactions of CO<Subscript>2</Subscript> and Epoxides

Abstract  

A variety of imidazolium-based ionic liquids (ILs) have been widely developed to effectively catalyze the cycloaddition reactions of CO₂ and epoxides. To further improve the catalytic performance of those IL catalysts, we incorporated various metal chlorides (CoCl₂, NiCl₂, CuCl₂, ZnCl₂, and MnCl₂) into silica-grafted 1-methyl-3-[(triethoxysilyl)propyl] imidazolium chloride to produce a series of heterogeneous catalysts. Catalytic reaction tests demonstrated that the incorporation of such metal ions can significantly enhance the catalytic reactivity of the silica-grafted ILs towards cycloaddition reactions of CO₂ and epoxides that produce cyclic carbonates in solvent-free conditions. In addition, the effects on the catalytic reactivity of reaction parameters including reaction time, reaction temperature and CO₂ pressure were investigated.     

Simplified synthesis of K<Subscript>2</Subscript>CO<Subscript>3</Subscript>-promoted hydrotalcite based on hydroxide-form precursors: Effect of Mg/Al/K<Subscript>2</Subscript>CO<Subscript>3</Subscript> ratio on high-temperature CO<Subscript>2</Subscript> sorption capacity

Hydrotalcite was synthesized from hydroxide-form precursors to prepare a novel high-temperature CO₂ sorbent, and the effect of Mg/Al ratio on CO₂ sorption was studied. To enhance the CO₂ sorption capacity of the sorbent, K₂CO₃ was coprecipitated during the synthetic reaction. X-ray diffraction analysis indicated that the prepared samples had a well-defined crystalline hydrotalcite structure, and confirmed that K₂CO₃ was successfully coprecipitated in the samples. The morphology of the hydrotalcite was confirmed by scanning electron microscopy, and N₂ adsorption analysis was used to estimate its surface area and pore volume. In addition, thermogravimetric analysis was used to measure its CO₂ sorption capacity, and the results revealed that the Mg: Al: K₂CO₃ ratio used in the preparation has an optimum value for maximum CO₂ sorption capacity.     

Chemical Vapor Deposition of Pd(C<Subscript>3</Subscript>H<Subscript>5</Subscript>)(C<Subscript>5</Subscript>H<Subscript>5</Subscript>) to Synthesize Pd@MOF-5 Catalysts for Suzuki Coupling Reaction

Abstract  

The highly porous metal organic framework MOF-5 was loaded with the metal–organic compound [Pd(C₃H₅)(C₅H₅)] by metal–organic chemical vapor deposition (MOCVD) method. The inclusion compound [Pd(C₃H₅)(C₅H₅)]@MOF-5 was characterized by powder X-ray diffraction (PXRD), Fourier-transform infrared (FT-IR) spectroscopy, and solid-state nuclear magnetic resonance spectroscopy. It was found that the host lattice of MOF-5 remained intact upon precursor insertion. The –C₃H₅ ligand in the precursor is easier to lose due to the interaction between palladium and the benzenedicarboxylate linker in MOF-5, providing a possible explanation for the irreversibility of the precursor adsorption. Pd nanoparticles of about 2–5 nm in size was formed inside the cavities of MOF-5 by hydrogenolysis of the inclusion compound [Pd(C₃H₅)(C₅H₅)]@MOF-5 at room temperature. N₂ sorption of the obtained material confirmed that high surface area was retained. In the Suzuki coupling reaction the Pd@MOF-5 materials showed a good activity in the first catalytic run. However, the crystal structure of MOF-5 was completely destroyed during the following reaction runs, as confirmed by PXRD, which caused a big loss of the activity.     

Synthesis and characterization of a K/K<Subscript>2</Subscript>CO<Subscript>3</Subscript>-based solid superbase as a catalyst in propylene dimerization

A novel solid superbase 3%K/K₂CO₃ was prepared by loading metallic potassium on K₂CO₃. The optimized preparation conditions included a loading time of 1.5 h, loading temperature of 150 °C, loading amount of 3wt% and average carrier size of 120 μm. Under the optimum conditions, the conversion of propylene is about 60% with the selectivity of dimers 98.5% and the selectivity of 4MP1 86.3%. In addition, the superbase 3%K/K₂CO₃ has a base strength of H _?≥37, and the concentration of basic sites of H _?≥35 is approximately 0.3mmol·g _CAT ^?1 . The microcrystal of metallic potassium was determined using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). It was assumed that the oxygen species, which are adjacent to lattice defects, such as the crystalline corners, edges and vacancies of metallic potassium micro-crystals, constituted the superbasic sites.     

Heterogeneous Enantioselective Hydrogenation of Hydroxy-substituted (<Emphasis Type="Italic">E</Emphasis>)-2,3-diphenylpropenoic Acids over Pd/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Modified by Cinchonidine

Abstract  

The enantioselective hydrogenation of (E)-2,3-diphenylpropenoic acids substituted by hydroxyl group has been studied over Pd/Al₂O₃ catalyst modified by cinchonidine. The effect of the acidic hydroxyl substituents was compared with that of the methoxy group in the same position. The para-hydroxyl substituent on the 3-phenyl ring had similar effect on the enantioselectivity as the methoxy group, whereas the meta positioned decreased the optical purity of the saturated acid. This was explained by different origin of the increase in the enantioselectivity obtained in the presence of electron releasing substituents in these positions. Although, the para-hydroxyl group on the 2-phenyl ring had beneficial influence on the enantioselectivity of the hydrogenation of the mono-substituted acid, in the presence of fluorine or hydroxyl group on the 3-phenyl ring the effect of the two substituents was not additive. This study demonstrated that the cinchonidine-modified Pd catalyst is appropriate for the preparation of several hydroxy-substituted 2,3-diphenylpropionic acids in good optical purities, extending the scope of this catalytic system to new types of versatile chiral building blocks.     

Low-temperature CO oxidation of Pt/Al<Subscript>0.1</Subscript>Ce<Subscript>0.9</Subscript>O<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> catalysts: Effects of supports prepared with different precipitants

We prepared 0.1Al-0.9Ce supports using various precipitants such as NH₄OH, KOH, NaOH, K₂CO₃, and Na₂CO₃ to prepare Pt-based CO oxidation catalysts. Of the studied catalysts, the Pt/0.1Al-0.9Ce_NH₄OH catalyst showed the optimum activity for CO oxidation. Catalysts prepared with carbonate-form precipitants revealed relatively lower activity than carbonate-free precipitants. A temperature at 50% CO conversion of all samples was observed in the low-temperature region in the presence of water vapor because of the promotional effect of the water-gas shift reaction. Several characterization results revealed that catalytic activity was related to oxygen capacity and Pt dispersion was attributable to precipitant nature.     

Temperature programmed desorption of oxygen from Pd films interfaced with Y<Subscript>2</Subscript>O<Subscript>3</Subscript>-doped ZrO<Subscript>2</Subscript>

The origin of the effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) or Electrochemical Promotion was investigated via temperature-programmed-desorption (TPD) of oxygen, from polycrystalline Pd films deposited on 8 mol%Y₂O₃–stabilized–ZrO₂ (YSZ), an O²⁻ conductor, under high-vacuum conditions and temperatures between 50 and 250 °C. Oxygen was adsorbed both via the gas phase and electrochemically, as O²⁻, via electrical current application between the Pd catalyst film and a Au counter electrode. Gaseous oxygen adsorption gives two adsorbed atomic oxygen species desorbing at about 300 °C (state β₁) and 340–500 °C (state β₂). The creation of the low temperature peak is favored at high exposure times (exposure >1 kL) and low adsorption temperatures (T_ads < 200 °C). The decrease of the open circuit potential (or catalyst work function) during the adsorption at high exposure times, indicates the formation of subsurface oxygen species which desorbs at higher temperatures (above 450 °C). The desorption peak of this subsurface oxygen is not clear due to the wide peaks of the TPD spectra. The TPD spectra after electrochemical O²⁻ pumping to the Pd catalyst film show two peaks (at 350 and 430 °C) corresponding to spillover O_ads and according to the reaction:

Epoxidation of Propylene on a [Ag<Subscript>14</Subscript>O<Subscript>9</Subscript>] Cluster Representing Ag<Subscript>2</Subscript>O (001) Surface: A Density Functional Theory Study

Abstract  

Density functional theory calculations were employed to study partial oxidation of propylene on a [Ag₁₄O₉] cluster representing Ag₂O (001) surface for which positive effect for ethylene oxide formation has been reported in our earlier work at the same level of theory (Fellah et al., Catal Lett 141:762, 2011). Propylene oxide (PO), propanal, acetone and П-allyl radical formation reaction mechanisms were investigated. Π-allyl formation path and two propylene adsorption paths resulting in PO formation are competing reactions on silver oxide (001) surface because of their comparable activation barriers (9, 8 and 9 kcal/mol, respectively) while Π-allyl formation path is generally a more favorable path on Ag (111) surface as reported in previous theoretical literature. SO₂ adsorption calculations indicate that silver oxide has lower Lewis basicity relative to oxygen atom adsorbed on silver. Calculations also showed that surface oxygen atom of Ag₂O (001) has a higher spin density compared to that of oxygen atom adsorbed on Ag (111), which indicates that oxygen atom on Ag₂O (001) cluster has a more radical character.     

CO<Subscript>2</Subscript> capture using aqueous solutions of K<Subscript>2</Subscript>CO<Subscript>3</Subscript>+2-methylpiperazine and monoethanolamine: Specific heat capacity and heat of absorption

The specific heat capacity, heat of CCO₂ absorption, and CCO₂ absorption capacity of aqueous solutions of potassium carbonate (K₂CO₃)+2-methylpiperazine (2-MPZ) and monoethanolamine (MEA) were measured over various temperatures. An aqueous solution of K₂CO₃+2-MPZ is a promising absorbent for CCO₂ capture because it has high CCO₂ absorption capacity with improved absorption rate and degradation stability. Aqueous solution of MEA was used as a reference absorbent for comprison of the thermodynamic characteristics. Specific heat capacity was measured using a differential scanning calorimeter (DSC), and heat of CCO₂ absorption and CCO₂ absorption capacity were measured using a differential reaction calorimeter (DRC). The CCO₂-loaded solutions had lower specific heat capacities than those of fresh solutions. Aqueous solutions of K₂CO₃+2-MPZ had lower specific heat capacity than those of MEA over the temperature ranges of 303-353 K. Under the typical operating conditions for the process (CCO₂ loading=0.23mol-CCO₂·mol^?1-solute in fresh solution, T=313 K), the heat of absorption (?ΔHabs) of aqueous solutions of K₂CO₃+2-MPZ and MEA were approximately 49 and 75 kJ·mol-CO₂, respectively. The thermodynamic data from this study can be used to design a process for CCO₂ capture.     

CO<Subscript>2</Subscript> methanation and co-methanation of CO and CO<Subscript>2</Subscript> over Mn-promoted Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

A series of Mn-promoted 15 wt-% Ni/Al₂O₃ catalysts were prepared by an incipient wetness impregnation method. The effect of the Mn content on the activity of the Ni/Al₂O₃ catalysts for CO₂ methanation and the comethanation of CO and CO₂ in a fixed-bed reactor was investigated. The catalysts were characterized by N2 physisorption, hydrogen temperature-programmed reduction and desorption, carbon dioxide temperature-programmed desorption, X-ray diffraction and highresolution transmission electron microscopy. The presence of Mn increased the number of CO₂ adsorption sites and inhibited Ni particle agglomeration due to improved Ni dispersion and weakened interactions between the nickel species and the support. The Mn-promoted 15 wt-% Ni/Al₂O₃ catalysts had improved CO₂ methanation activity especially at low temperatures (250 to 400 °C). The Mn content was varied from 0.86% to 2.54% and the best CO₂ conversion was achieved with the 1.71Mn-Ni/Al₂O₃ catalyst. The co-methanation tests on the 1.71Mn-Ni/Al₂O₃ catalyst indicated that adding Mn markedly enhanced the CO₂ methanation activity especially at low temperatures but it had little influence on the CO methanation performance. CO₂ methanation was more sensitive to the reaction temperature and the space velocity than the CO methanation in the co-methanation process.

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Crystal structure of new compound (Rb,K)<Subscript>2</Subscript>Cu<Subscript>3</Subscript>(P<Subscript>2</Subscript>O<Subscript>7</Subscript>)<Subscript>2</Subscript>

A new compound of (Rb,K)₂Cu₃(P₂O₇)₂ is obtained by high-temperature reactions from a mixture of RbNO₃, KNO₃, Cu(NO₃)₂, and (NH₄)₄P₂O₇. The crystal structure was solved by direct methods and refined to R ₁ = 0.056 for 5022 independent reflections. The compound belongs to a rhombic crystal system, P2₁2₁2₁, Z = 8, a = 9.9410(7) Å, b = 13.4754(6) Å, c = 18.6353 (3) Å, and R = 0.056. The basis of the structure is a complex copper-phosphate skeleton of the composition of [Cu₃(P₂O₇)₂]^2–, which can be regarded as consisting of two types of heteropolyhedral layers parallel to the (001) plane. The layers are alternated with each other, forming a frame, in the cavities of which the positions of alkali cations are located, statistically populated with K⁺ and Rb⁺ ions. Based on the refined populations of the positions of alkali cations, an exact chemical formula of the compound can be written as Rb_1.28K_0.72Cu₃(P₂O₇)₂. The compound is the most complex among those known to this day of the composition of A₂ ^IB₃ ^II(P₂O₇)₂ (A = Li, Na, K, Rb, or Cs; B = Ni, Cu, or Zn).     

TiO<Subscript>2</Subscript>/Ni Inverse-Catalysts Prepared by Atomic Layer Deposition (ALD)

Abstract  

Atomic layer deposition (ALD) was used to deposit TiO₂ on Ni particles, and the catalytic activity of Ni for CO₂ reforming of methane (CRM) was evaluated. In the presence of TiO₂ islands on Ni surfaces, the onset temperature of the CRM reaction was lower than that of bare Ni. During the CRM reaction, carbon was deposited on the surface of bare Ni, which reduced the catalytic activity of the surface with time, and TiO₂ islands were able to remove carbon deposits from the surface. When the Ni surface was completely covered with TiO₂, the catalytic activity disappeared, demonstrating that tuning of the TiO₂ coverage on Ni is important to maximize the activity of the CRM reaction.     

Oxygen Isotope (<Superscript>18</Superscript>O<Subscript>2</Subscript>) Evidence on the Role of Oxygen in the Plasma-Driven Catalysis of VOC Oxidation

Abstract  

This paper reports isotopic evidence on nonthermal plasma-induced fixation of gas-phase oxygen on the surface of several catalysts such as TiO₂, Ag/TiO₂, Ag/γ-Al₂O₃ and Ag/MS-13X at atmospheric-pressure. On-line mass spectrometric analysis and stoichiometric comparison of reactants and products revealed that the fixed surface oxygen can be activated by nonthermal plasma. The fixed ¹⁸O by nonthermal plasma survived for a certain period of time (about 30 min), and involved in the formation of isotope-exchanged oxygen (¹⁸O¹⁶O) and isotope containing CO _x (CO and CO₂).     

Synthesis and study of novel catalysts based on hollandite K<Subscript>2</Subscript>Ga<Subscript>2</Subscript>Ti<Subscript>6</Subscript>O<Subscript>16</Subscript>

The results of experimental studies of synthesis of the hollandite phase K₂Ga₂Ti₆O₁₆ using initial mixtures of different dispersion compositions obtained by two methods, i.e., mechanical dispersion (MD) (followed by solid-phase sintering) and sol-gel method (Pechini method, MP), are reported. The catalytic properties of the obtained materials in the reactions of carbon monoxide (CO) and hydrogen (H₂) oxidation have been determined. It has been demonstrated that an increase in the catalytic activity in the CO oxidation reaction is observed on the samples obtained using the sol-gel method, in which the hollandite phase content is higher and crystallization is more complete. The samples obtained using the MD method are characterized by a low porosity and activity in comparison with those produced by the Pechini method.