Non-catalytic Conditions Research Articles

Comparison of the effects of Na2CO3, Ca3(PO4)2, and NiO catalysts on the thermochemical liquefaction of microalga Spirulina platensis

This study investigated the effect of three types of catalysts on the yield of biocrude oil from thermochemical liquefaction (TCL) of the microalga, Spirulina platensis. TCL experiments were performed in a 1.8L batch reactor using an alkali metal catalyst (Na2CO3), an alkaline earth metal (Ca3(PO4)2), and a transition metal oxide (NiO) and compared with non-catalytic TCL results. Na2CO3 was found to increase biocrude oil yield resulting in 51.6% biocrude oil, which was ∼29.2% higher than under non-catalytic conditions and ∼71% and ∼50% higher than when using NiO and Ca3(PO4)2 catalysts, respectively. Presence of NiO and Ca3(PO4)2 increased yields of gaseous products. GC–MS analysis indicated critical differences in chemical composition of the biocrude oil obtained under different catalyst conditions. Biocrude oil from the catalyzed runs had greater abundance of monoaromatic compounds and lesser polyaromatic and aliphatic compounds than that of non-catalyzed reactions. TCL using Na2CO3 reported the lowest energy consumption ratio and recovered highest energy in the form of biocrude oil among all treatments. Algal biocrude oil had an energy density of 34–39MJkg−1 compared to 43MJkg−1 for petroleum crude, but had higher oxygen and nitrogen levels. In all cases, the solids conversion was more than 94%. Analysis of solids revealed that 40–60% of the initial catalysts were retained in the solid char.

Study of Turbulence-Radiation Interaction in Hypersonic Turbulent Boundary Layers

Studies of the turbulence-chemistry interaction (TCI) are performed in hypersonic turbulent boundary layers using direct numerical simulation (DNS) flow fields under typical hypersonic conditions representative of blunt-body and slender-body hypersonic vehicles, with supercatalytic and noncatalytic wall conditions in pure air. Nondimensional govern∂ � �

Degradation of diphenhydramine pharmaceutical in aqueous solutions by using two highly active TiO2 photocatalysts: Operating parameters and photocatalytic mechanism

In the present work the efficiency of a new TiO2 catalyst (ECT), synthesized by means of an optimized sol–gel method, is studied for degradation of an important pharmaceutical water pollutant, diphenhydramine (DP). Its activity is compared to P25, the benchmark catalyst, produced by Evonik Degussa Corporation, under different catalyst loadings (up to 2.00gL−1) and initial solution pH (3.0–11.0). The results show that DP is very stable under non-catalytic conditions but complete degradation and considerable mineralization (ca. 60–70%) under near UV to visible irradiation (∼50mWcm−2) can be achieved in 60min by selecting the appropriate TiO2 loading. ECT is significantly more active than the benchmark catalyst for loadings higher than 1.00gL−1 while the pseudo-first order rate constant increased with the initial solution pH from 3.0 to 11.0. The highest rate constant was obtained with ECT at pH 11 (173×10−3min−1 against 116×10−3min−1 for P25). Scavenger agents were used as a diagnostic tool for the analysis of the photocatalytic mechanism and it was possible to prove that holes were crucial active species participating in the photocatalytic mechanism as well as that ECT has a higher availability than P25 to generate reactive radicals, such as hydroxyl (HO•) and hydroperoxyl (HOO•) radicals.

ChemInform Abstract: A One‐Pot, Non‐Catalytic Approach to 1,2,4‐Benzothiadiazine‐11‐dioxides.

AbstractCondensation of o‐halobenzenesulfonyl chlorides with amidines and aminopyridine derivatives provides access towards a wide range of title benzthiadiazine dioxides under mild noncatalytic conditions.

Enhancement of Ethanol–Acetic Acid Esterification Under Room Temperature and Non-catalytic Condition via Pulsed Electric Field Application

The effects of pulsed electric fields (PEF) on esterification between ethanol and acetic acid were investigated in this paper. An ethanol–acetic acid model system was used and all experiments were conducted under moderate temperature and non-catalytic condition. The effects of various reaction conditions such as PEF intensity, temperature, reaction time as well as the molar ratio between reactants (ethanol and acetic acid) on the esterification efficiency were examined. Results from gas chromatography/mass spectrum analysis showed that the esterification was significantly enhanced by PEF treatment under appropriate conditions. A kinetic model for such esterification was established. It was identified that the reaction order of the ethanol–acetic acid estirification under PEF treatment was 2.0. The activation energy (E a) decreased significantly when a pulsed electric field was applied. The relationship between the applied PEF strength (E) and the activation energy change (ΔE a) can be expressed as ΔE a = 0.849E − 0.515 (R 2 = 0.975).

A one-pot, non-catalytic approach to 1,2,4-benzothiadiazine-1,1-dioxides

Condensations of o-halo-substituted benzenesulfonyl chlorides with 2-aminopyridines and amidines may give the corresponding 1,2,4-benzothiadiazine-1,1-dioxides under mild, non-catalytic conditions in nearly quantitative yields. The successful one-pot cyclization depends on three factors: (i) the nature of the o-halogen, (ii) the electronic character of the benzene ring substituent, and (iii) the steric load around the amidine unit. O-Fluorobenzenesulfonyl chlorides bearing methylcarboxyl- or nitro-group and o-chloro- and o-bromobenzenesulfonyl chlorides bearing nitro-group are reactive enough to give the desired 1,2,4-benzothiadiazine-1,1-dioxides in a one-pot base-promoted reaction. In all other cases, open-chain sulfonylated amidine intermediates are isolated. The latter are converted to the title compounds either in the presence of potassium carbonate or upon the addition of a copper(I) catalyst.

Catalytic activity and stability of multiwalled carbon nanotubes in catalytic wet air oxidation of oxalic acid: The role of the basic nature induced by the surface chemistry

Different chemical and thermal treatments (nitric acid at boiling temperature, liquid-phase urea treatment at 200°C, and gas-phase thermal treatment with nitrogen at 600°C) were applied to multiwalled carbon nanotubes (MWCNTs) in order to produce materials with different textural and chemical properties. Nitrogen adsorption isotherms, temperature programmed desorption, pHpzc (point of zero charge), elemental analysis and X-ray photoelectron spectroscopy were used to characterize these materials. The chemical and thermal treatments have influence on the materials pHpzc, which decreases upon nitric acid treatment and increases with urea or gas-phase thermal treatments. The original and modified MWCNTs, without any impregnated metal, were investigated as catalysts in the catalytic wet air oxidation (CWAO) process, using oxalic acid as model compound at 140°C and 40bar of total pressure. Oxalic acid is very stable under non-catalytic conditions but can be totally degraded in less than 30min in the presence of MWCNTs. The rate of oxidation of oxalic acid depends on the chemical properties of MWCNTs, the apparent initial first-order rate constants being lower for the MWCNTs with a marked acid character. The textural properties of MWCNTs are stable in cyclic CWAO experiments, but a decrease of their basic character leads to the reduction of their catalytic activity, even if this activity is still high with reused catalysts (nearly total oxalic acid degradation in 45min and complete mineralization in 120min). Therefore, MWCNTs without any impregnated metal, especially those of more basic character, are very active catalysts for CWAO, their activity strongly depending on the stability of their surface chemistry.

Coupled ZnO/TiO<sub>2</sub> Nanorods Deposited in the Pores of Expanded Graphite Prepared by Microwave Irradiation

Expanded graphite (EG) was prepared by microwave irradiation at 1000W for 60s. The growth of coupled ZnO/TiO2 nanonods in the pores of EG by using hydrolysis method without harsh conditions was investigated and their microstructure was studied by scanning electron microscopy (SEM). Results show that pores of EG, which can load catalytic nanoparticles, is the physical base for growth of catalytic nanorods. The active edges of graphene of freshly EG is a key factor for the growth of coupled ZnO/TiO2 nanorods under non-catalytic and normal temperature and pressure conditions.

Directed synthesis of tertiary phosphine chalcogenides with pyridine and hydroxy functions

Secondary phosphine chalcogenides react with pyridine-2-, pyridine-3-, and pyridine-4-carbaldehydes under mild noncatalytic conditions (22–43°C, 1–8.5 h) to form in 81–98% yield functional tertiary phosphine chalcogenides containing pyridine and hydroxy functions.

Water-catalyzed gas-phase hydrogen abstraction reactions of CH3O2 and HO2 with HO2: a computational investigation

The gas-phase hydrogen abstraction reactions of CH(3)O(2) and HO(2) with HO(2) in the presence and absence of a single water molecule have been studied at the CCSD(T)/6-311++G(3d,2p)//B3LYP/6-311G(2d,2p) level of theory. The calculated results show that the process for O(3) formation is much faster than that for (1)O(2) and (3)O(2) formation in the water-catalyzed CH(3)O(2) + HO(2) reaction. This is different from the results for the non-catalytic reaction of CH(3)O(2) + HO(2), in which almost only the process for (3)O(2) formation takes place. Unlike CH(3)O(2) + HO(2) reaction in which the preferred process is different in the catalytic and non-catalytic conditions, the channel for (3)O(2) formation is the dominant in both catalytic and non-catalytic HO(2) + HO(2) reactions. Furthermore, the calculated total CVT/SCT rate constants for water-catalyzed and non-catalytic title reactions show that the water molecule doesn't contribute to the rate of CH(3)O(2) + HO(2) reaction though the channel for O(3) formation in this water-catalyzed reaction is more kinetically favorable than its non-catalytic process. Meanwhile, the water molecule plays an important positive role in increasing the rate of HO(2) + HO(2) reaction. These results are in good agreement with available experiments.

Reforming of bioethanol over Ni/Al 2O 3 and Ni/CeZrO 2/Al 2O 3 catalysts in supercritical water for hydrogen production

Bioethanol was reformed in supercritical water (SCW) at 500 °C and 25 MPa on Ni/Al 2O 3 and Ni/CeZrO 2/Al 2O 3 catalysts to produce high-pressure hydrogen. The results were compared with non-catalytic reactions. Under supercritical water and in a non-catalytic environment, ethanol was reformed to H 2, CO 2 and CH 4 with small amounts of CO and C2 gas and liquid products. The presence of either Ni/Al 2O 3 or Ni/CeZrO 2/Al 2O 3 promoted reactions of ethanol reforming, dehydrogenation and decomposition. Acetaldehyde produced from the decomposition of ethanol was completely decomposed into CH 4 and CO, which underwent a further water–gas shift reaction in SCW. This led to great increases in ethanol conversion and H 2 yield on the catalysts of more than 3–4 times than that of the non-catalytic condition. For the catalytic operation, adding small amounts of oxygen at oxygen to ethanol molar ratio of 0.06 into the feed improved ethanol conversion, at the expense of some H 2 oxidized to water, resulting in a slightly lower H 2 yield. The ceria–zirconia promoted catalyst was more active than the unpromoted catalyst. On the promoted catalyst, complete ethanol conversion was achieved and no coke formation was found. The ceria–zirconia promoter has important roles in improving the decomposition of acetaldehyde, the enhancement of the water–gas shift as well as the methanation reactions to give an extremely low CO yield and a tremendously high H 2/CO ratio. The SCW environment for ethanol reforming caused the transformation of gamma–alumina towards the corundum phase of the alumina support in the Ni/Al 2O 3 catalyst, but this transformation was slowed down by the presence of the ceria–zirconia promoter.

The Co-liquefaction of Elbistan Lignite and Biomass. Part II: The Characterization of Liquefaction Products

This study examines the effects of various process parameters regarding separately and co-liquefaction in a nitrogen gas medium under catalytic and non-catalytic conditions of Elbistan lignite and various biomass samples, the direct use of which is inconvenient both economically and ecologically. According to the obtained results, the optimum process parameters are as follows: The particle size is 1.5 mm, liquid/solid ratio is 3/1, reaction time is 90 min, and reaction temperature is 400°C. Fe2O3 has been selected as the most suitable catalyst type and waste paper as the most suitable biomass type. At 3/1 liquid/solid ratio, as a result of the liquefaction studies, which are made through using fresh and recycled solvent, the obtained total conversions are 90.2 and 88.4%, oil + gas conversions are 59.3 and 57.6%. Elemental analyses have been made in order to gain information on the structure of the preasphaltene and chars, which are obtained as a result of the liquefaction of Elbistan lignite separately and together with paper under catalytic conditions. According to the results of the elemental analysis, chars and preasphaltenes may not be used as fuel. However, as preasphaltenes have high content of both carbon and hydrogen, their re-liquefaction under catalytic and non-catalytic conditions separately or together with the biomass, and the co-liquefaction of the char with the biomass or burning it in a fluidized bed may be recommended. According to the results of gas chromatography/mass spectrometry analyses of the oils obtained as a result of liquefaction, the oils basically consist of various components, such as naphthalene and its derivatives, tetraline and derivatives, indene, butylated-hydroxytoluen, binaphtalene, and indole.

Subunit Movements in Single Membrane-bound H+-ATP Synthases from Chloroplasts during ATP Synthesis

Subunit movements within the H(+)-ATP synthase from chloroplasts (CF(0)F(1)) are investigated during ATP synthesis. The gamma-subunit (gammaCys-322) is covalently labeled with a fluorescence donor (ATTO532). A fluorescence acceptor (adenosine 5'-(beta,gamma-imino)triphosphate (AMPPNP)-ATTO665) is noncovalently bound to a noncatalytic site at one alpha-subunit. The labeled CF(0)F(1) is integrated into liposomes, and a transmembrane pH difference is generated by an acid base transition. Single-pair fluorescence resonance energy transfer is measured in freely diffusing proteoliposomes with a confocal two-channel microscope. The fluorescence time traces reveal a repetitive three-step rotation of the gamma-subunit relative to the alpha-subunit during ATP synthesis. Some traces show splitting into sublevels with fluctuations between the sublevels. During catalysis the central stalk interacts, with equal probability, with each alphabeta-pair. Without catalysis the central stalk interacts with only one specific alphabeta-pair, and no stepping between FRET levels is observed. Two inactive states of the enzyme are identified: one in the presence of AMPPNP and one in the presence of ADP.

Multi‐Product Classes Obtained from Allylation of α‐Halo Ketones with Allylzinc Bromide

An efficient, one-pot synthesis procedure for the preparation of allylic epoxides, aldehydes and homoallylic alcohols (see scheme) has been described. The three industrial products were synthesized by the reaction of allylzinc bromide with α-halo ketones under non-catalytic conditions with p-toluenesulfonic acid and ytterbium triflate as catalysts, respectively. Feasible reaction mechanisms and intermediates leading to the correlating products are discussed.

Reaction of secondary phosphine chalcogenides with 2,2,2-trichloroacetaldehyde

The nucleophilic addition of secondary phosphine chalcogenides to 2,2,2-trichloroacetaldehyde proceeds under mild noncatalytic conditions (12–25dgC, 15–90 min) with the formation of functional tertiary phosphine chalcogenides, containing hydroxy groups in up to 98% yield. Using the method of concurrent reactions the reactivity of secondary phosphine chalcogenides in this reaction was shown to decrease in the order: (PhCH2CH2)2P(O)H ≫ (PhCH2CH2)2P(S)H > (PhCH2CH2)2P(Se)H, and the secondary bis[2-(2-pyridyl) ethyl]-phosphine oxide was more reactive than bis(2-phenethyl)phosphine oxide.

Synthesis of Boltorn 1,2,3‐triazole dendrimers by click chemistry

AbstractSecond‐, third‐, and fourth‐generation hyperbranched aliphatic polyols namely Boltorn® H20, Boltorn H30, and Boltorn H40 were endcapped with azido and activated acetylenic groups in good to excellent yields (75–95%) following an acid catalyzed procedure. The resultant terminally functionalized dendritic azido and acetylenic groups undergo 1,3‐dipolar cycloaddition using methyl (or ethyl) propiolate and benzyl azide, respectively, under catalytic or noncatalytic conditions below 40 °C to yield 1,2,3‐triazole dendrimeric polymers in 82–95% yield, under extremely mild conditions that could be applied for compounds sensitive to acid, base, or heat. The dendritic azido and activated acetylenic derivatives may act as novel scaffolds to tune the mechanical properties of different polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3748–3756, 2009

Carbon nanotube growth in the pores of expanded graphite by chemical vapor deposition

The growth of carbon nanotubes (CNTs) in the pores of expanded graphite by chemical vapor deposition with and without a catalyst was investigated and their microstructure was studied by scanning electron microscopy. Results show that pores of the expanded graphite, which can load catalyst particles, is the physical base for the growth of CNTs. Co(NO 3) 2 is better than Fe(NO 3) 3 and Ni(NO 3) 2 when used to immerse expanded graphite. The optimum catalyst concentration is 0.025 mol/L Co(NO 3) 2. The active edges of graphenes of freshly expanded graphite is a key factor for the growth of CNTs under non-catalytic conditions.

Changes in the Secondary and Tertiary Structures of Secreted Phospholipase A2 upon Activation

Activation of human pancreatic phospholipase A2 (PLA2) in the presence of DPPC/DPPG (7:3) vesicles was induced by a temperature shift from 4 to 38 oC. PLA2 activity was monitored by changes in fluorescence of bis-Pyrene-PC (2.5 mol % in the membranes), while simultaneous far- and near-UV circular dichroism (CD) spectra identified changes in the secondary and tertiary structures of the protein in real time. The 4-to-38 oC temperature shift caused dramatic changes in both bis-Pyrene-PC fluorescence and the protein CD spectra. The monomer fluorescence signal of bis-Pyrene-PC rapidly increased and the excimer signal decreased, demonstrating PLA2 activation. Drastic weakening in the α-helical CD signal of the protein, i.e., a 20% decrease in the n-π* transition intensity at 222 nm, was detected upon enzyme activation. The α-helical signal exhibited a significantly smaller change upon a similar temperature shift under non-catalytic conditions (1 mM EGTA), while little changes were detected in the absence of lipid. Strong changes in the tertiary structure during PLA2 activation were also identified. Initially, at 4 oC, the near-UV CD spectra showed a weak negative band around 280 nm. Upon a shift to 38 oC, strong positive CD bands rapidly developed around 250 and 280 nm, implying significant changes in the conformation and/or the microenvironment of Tyr and Trp side chains of PLA2, possibly accompanied with a global tertiary structure perturbation associated with deformation of the abundant disulfide bonds in the protein. These experiments provide new information on the structure-function relationship of PLA2 by near-simultaneous measurements of PLA2 activity and its secondary and tertiary structures.

Surface-catalyzed singlet oxygen production on iodine oxide films

Enhanced production of singlet oxygen, O2(a1Δg), was observed by reaction of O2/He discharge effluents on an iodine oxide film surface in a microwave discharge-flow reactor at 320K. We observed a two-fold increase in the O2(a) yields over discharge-generated amounts for non-catalytic conditions. The iodine oxide surface appears to catalyze the heterogeneous reaction to form O2(a) with high collision efficiency. The observed catalytic effect could significantly benefit the development of electrically driven oxygen–iodine laser systems, and may also have implications for the chemistry of atmospheric iodine oxide aerosol.

Anatomy of a Simple Acyl Intermediate in Enzyme Catalysis: Combined Biophysical and Modeling Studies on Ornithine Acetyl Transferase

Acyl-enzyme complexes are intermediates in reactions catalyzed by many hydrolases and related enzymes which employ nucleophilic catalysis. However, most of the reported structural data on acyl-enzyme complexes has been acquired under noncatalytic conditions. Recent IR analyses have indicated that some acyl-enzyme complexes may be more flexible than most crystallographic analyses have implied. OAT2 is a member of the N-terminal nucleophile (Ntn) hydrolase enzyme superfamily and catalyzes the reversible transfer of an acetyl group between the alpha-amino groups of ornithine and glutamate in a mechanism proposed to involve an acyl-enzyme complex. We have carried out biophysical analyses on ornithine acetyl transferase (OAT2), both in solution and in the crystalline state. Mass spectrometric studies identified Thr-181 as the residue acetylated during OAT2 catalysis; (13)C NMR analyses implied the presence of an acyl-enzyme complex in solution. Crystallization of OAT2 in the presence of N-alpha-acetyl-L-glutamate led to a structure in which Thr-181 was acetylated; the carbonyl oxygen of the acyl-enzyme complex was located in an oxyanion hole and positioned to hydrogen bond with the backbone amide NH of Gly-112 and the alcohol of Thr-111. While the crystallographic analyses revealed only one structure, IR spectroscopy demonstrated the presence of two distinct acyl-enzyme complex structures with carbonyl stretching frequencies at 1691 and 1701 cm(-1). Modeling studies implied two possible acyl-enzyme complex structures, one of which correlates with that observed in the crystal structure and with the 1691 cm(-1) IR absorption. The second acyl-enzyme complex structure, which has only a single oxyanion hole hydrogen bond, is proposed to give rise to the 1701 cm(-1) IR absorption. The two acyl-enzyme complex structures can interconvert by movement of the Thr-111 side-chain alcohol hydrogen away from the oxyanion hole to hydrogen bond with the backbone carbonyl of the acylated residue, Thr-181. Overall, the results reveal that acyl-enzyme complex structures may be more dynamic than previously thought and support the use of a comprehensive biophysical and modeling approach in studying such intermediates.