Catalytic performance of Fe modified K/MO2C catalyst for CO hydrogenation

Fe modified and un-modified K/Mo2C were prepared and investigated as catalysts for CO hydrogenation reaction. Compared with K/Mo2C catalyst, the addition of Fe increased the production of alcohols, especially the C2+OH. Meanwhile, considerable amounts of C5+ hydrocar- bons and C2= -C4= were formed, whereas methane selectivity greatly decreased. Also, the activity and selectivity of the catalyst were readily affected by the reaction pressure and temperature employed. According to the XPS results, Mo4+ might be responsible for the production of alcohols, whereas the low valence state of Mo species such as Mo0 and/or Mo2+ might be account for the high activity and selectivity toward hydrocarbons.     

Promotion of Mn Doped Co/CNTs Catalysts for CO Hydrogenation to Light Olefins

With various contents, Mn was introduced into carbon nanotubes (CNTs) supported cobalt catalysts and the obtained Mn‐Co/CNTs catalysts were investigated for CO hydrogenation to light alkenes and characterized by N₂ adsorption, X‐ray diffraction (XRD), X‐ray photoelectron spectra (XPS), H₂ temperature programmed reduction (TPR), CO temperature programmed desorption (TPD) and transmission electron microscope (TEM). The results indicate that the addition of a small amount of Mn (0.3 wt%) to CNTs‐supported Co catalyst significantly increased the selectivity of C₂–C₄ olefins and decreased the selectivity of CH₄. However, with further addition of Mn to the cobalt catalysts, the CH₄ selectivity decreased obviously along with the increase of the C₅₊ selectivity. Compared with the unpromoted catalysts, the Mn‐promoted cobalt catalysts increased the C₂^?–C₄^?/C₂⁰–C₄⁰ molar ratio.     

Catalytic Oxidation of Methane to C2‐C4 Hydrocarbons over CeO2 Promoted W‐Mn/SiO2 Catalysts at Higher Pressure

CeO₂‐promoted Na‐Mn‐W/SiO₂ catalyst has been studied for catalytic oxidation of methane in a micro‐stainless‐steel reactor at elevated pressure. The effect of operating conditions, such as GHSV, pressure and CH₄/O₂ ratio, has been investigated. 22.0% CH₄ conversion with 73.8% C₂‐C₄ selectivity (C₂/C₃/C₄ = 3.8/1.0/3.6) was obtained at 1003 K, 1.5 × 10⁵ h^?;1 GHSV and 1.0 MPa. The results show: Elevated pressure disadvantages the catalytic oxidation of methane to C₂‐C₄ hydrocarbons. Large amounts of C₃ and C₄ hydrocarbons are observed. The unfavorable effects of elevated pressure can be overcome by increasing GHSV; the reaction is strongly dependent on the operating conditions at elevated pressure, particularly dependent on GHSV and ratio of CH₄/O₂. Analyses by means of XRD, XPS and CO₂‐TPD show that CO₂ produced from the reaction makes a weakly poisoning capacity of the catalyst; information of changeful valence on Ce and Mn was detected over the near‐surface of the Ce‐Na‐W‐Mn/SiO₂ catalyst; the existence of Ce³⁺/Ce⁴⁺ and Mn²⁺/Mn³⁺ ion couple supported that the reaction over the catalyst followed the Redeal‐Redox mechanism. Oxidative re‐coupling of C₂H₆ and CH₄ in gas phase or over surface of catalyst produces C₃ or C₄ hydrocarbons.     

Reactions of 2,2-bis(trifluoromethyl)oxirane with alcohols under phase transfer catalysis

It was demonstrated that the reaction of 2,2-bis(trifluoromethyl)oxirane (1) with variety of alcohols could be successfully carried out under phase transfer catalysis conditions using sodium or potassium hydroxide as a base. For example, reaction of CH₃OH, C₂H₅OCH₂CH₂OH, HOCH₂CH₂OH with one or two moles of 1 in the presence of the catalyst [(C₄H₉)₄N⁺HSO₄⁻] gives the corresponding tertiary alcohols R[OCH₂C(CF₃)₂OH]_n (n=1 or 2) in 43-53% yield, along with some O[CH₂C(CF₃)₂OH]₂. Benzyl alcohol and phenol under similar conditions are less active, producing in the reaction with 1 the corresponding adducts ArOCH₂C(CF₃)₂OH in 31-35% yield. Fluorinated alcohols, such as CF₃CH₂OH, ClCF₂CH₂OH, HCF₂CF₂CH₂OH have much higher reactivity towards 1 giving ring opening products in 82-97% yield. Even in the reaction of hindered hexafluoro-iso-propanol the corresponding adduct was isolated in 43% yield. Surprisingly, the reaction of iso-propanol and epoxide 1, results in the formation of O[CH₂C(CF₃)₂OH]₂ as a major product, isolated in 56% yield. Possible mechanism for the formation of the last product was proposed.     

Impact of Water Molecules on the Isomerization of CH3S（OH）CH2 to CH3S（O）CH3： A Computational Investigation

The isomerization of CH3S（OH）CH2 to CH3S（O）CH3 in the absence and presence of water has been investigated at the G3XMP2//B3LYP/6-311 ＋ G（2df, p） level. The naked isomerization, the reaction without water, gives the high barrier height （21.56 kcal.mol^-1）. Three models are constructed to describe the water influence on the isomerization, that is, water molecules are the catalyst and the microsolvation, and water molecules act as the catalyst and microsolvation simultaneously. Our results show that the isomerization barrier heights of CH3S（OH）CH2 to CH3S（O）CH3 are reduced by 12.32, 11.04, and 7.80 kcal.mol^-1, respectively, when one, two, and three water molecules are performed as catalyst, in contrast to the naked isomerization. Moreover, the rate constants of the isomerization are calculated using the transition state theory with the Wigner tunneling correction over the temperature range of 240-425 K. We find that the rate constant of a single water molecule as the catalyst is 1.58 times larger than the naked isomerization at 325 K, whereas it is slower by 6 orders of magnitude when water molecule serves as the microsolvation at 325 K, compared to naked reaction. So the water-catalyzed isomerization of CH3S（OH）CH2 to CH3S（O）CH3 is predicted to be the key role in lowering the activation energy. The isomerization involving water molecules acting as mierosolvation is unfavorable under atmospheric conditions.     

In-Situ-Formed Potassium-Modified Nickel-Zinc Carbide Boosts Production of Higher Alcohols beyond CH4 in CO2 Hydrogenation

Ni-based catalysts have been widely studied in the hydrogenation of CO₂ to CH₄, but selective and efficient synthesis of higher alcohols (C₂₊OH) from CO₂ hydrogenation over Ni-based catalyst is still challenging due to successive hydrogenation of C1 intermediates leading to methanation. Herein, we report an unprecedented synthesis of C₂₊OH from CO₂ hydrogenation over K-modified Ni−Zn bimetal catalyst with promising activity and selectivity. Systematic experiments (including XRD, in situ spectroscopic characterization) and computational studies reveal the in situ generation of an active K-modified Ni−Zn carbide (K-Ni₃Zn₁C_0.7) by carburization of Zn-incorporated Ni⁰, which can significantly enhance CO₂ adsorption and the surface coverage of alkyl intermediates, and boost the C−C coupling to C₂₊OH rather than conventional CH₄. This work opens a new catalytic avenue toward CO₂ hydrogenation to C₂₊OH, and also provides an insightful example for the rational design of selective and efficient Ni-based catalysts for CO₂ hydrogenation to multiple carbon products.     

The hydroxyl radical reaction rate constant and atmospheric transformation products of 2‐propoxyethanol

The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of 2‐propoxyethanol (2PEOH, CH₃CH₂CH₂OCH₂CH₂(OH)). 2PEOH reacts with OH with a bimolecular rate constant of (21.4 ± 6.0) × 10⁻¹² cm³molecule⁻¹s⁻¹ at 297 ± 3 K and 1 atm total pressure, which is a little larger than previously reported [1]. Assuming an average OH concentration of 1 × 10⁶ molecules cm⁻³, an atmospheric lifetime of 13 h is calculated for 2PEOH. In order to more clearly define this hydroxy ether's atmospheric reaction mechanism, an investigation into the OH + 2PEOH reaction products was also conducted. The OH + 2PEOH reaction products and yields observed were: propyl formate (PF, 47 ± 2%, CH₃CH₂CH₂OC(O)H), 2 propoxyethanal (CH₃CH₂CH₂OCH₂C(O)H 15 ± 1%), and 2‐ethyl‐1,3‐dioxolane (5.4 ± 0.4%). The 2PEOH reaction mechanism is discussed in light of current understanding of oxygenated hydrocarbon atmospheric chemistry. The findings reported here can be related to other structurally similar alcohols and may impact regulatory tools such as ground‐level ozone‐forming potential calculations (incremental reactivity) [2]. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 315–322, 1999     

Adjusting the Reduction Potential of Electrons by Quantum Confinement for Selective Photoreduction of CO2 to Methanol

The production of CH₃OH from the photocatalytic CO₂ reduction reaction (PCRR) presents a promising route for the clean utilization of renewable resources, but charge recombination, an unsatisfying stability and a poor selectivity limit its practical application. In this paper, we present the design and fabrication of 0D/2D materials with polymeric C₃N₄ nanosheets and CdSe quantum dots (QDs) to enhance the separation and reduce the diffusion length of charge carriers. The rapid outflow of carriers also restrains self‐corrosion and consequently enhances the stability. Furthermore, based on quantum confinement effects of the QDs, the energy of the electrons could be adjusted to a level that inhibits the hydrogen evolution reaction (HER, the main competitive reaction to PCRR) and improves the selectivity and activity for CH₃OH production from the PCRR. The band structures of photocatalysts with various CdSe particle sizes were also investigated quantitatively to establish the relationship between the band energy and the photocatalytic performance.     

Synthesis and helicity of optically active poly(N‐propargylphosphonamidates) having chiral phosphorus center

Novel chiral N‐propargylphosphonamidate monomers (HC?CCH₂NHP(?O)R? O? menthyl, 1 : R = CH₃, 2 : R = C₂H₅, 3 : R = n‐C₃H₇, 4 : R = Ph) were synthesized by the reaction of the corresponding phosphonic dichlorides with menthol and propargylamine. Pairs of diastereomeric monomers 1 – 4 with different ratios were obtained due to the chiral P‐center and menthyl group. One diastereomer could be separated from another one in the cases of monomers 1 and 2 . Polymerization of 1 – 4 with (nbd)Rh⁺[η⁶‐C₆H₅B^?(C₆H₅)₃] as a catalyst in CHCl₃ gave the polymers with number‐average molecular weights ranging from 5000 to 12,000 in 65–85%. Poly( 1 )–poly( 4 ) exhibited quantitative cis contents, and much larger specific rotations than 1 – 4 did in CHCl₃. The polymers showed an intense Cotton effect around 325 nm based on the conjugated polyacetylene backbone. It was indicated that the polymers took a helical structure with predominantly one‐handed screw sense, and intramolecular hydrogen bonding between P?O and N? H of the polymers contributed to the stability of the helical structure. Poly( 1a ) and poly( 2a ) decreased the CD intensity upon raising CH₃OH content in CHCl₃/CH₃OH. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1515–1524, 2007     

A Robust Porous Metal–Organic Framework with a New Topology That Demonstrates Pronounced Porosity and High‐Efficiency Sorption/Selectivity Properties of Small Molecules

A robust porous metal–organic framework (MOF), [Co₃(ndc)(HCOO)₃(μ₃‐OH)(H₂O)]_n ( 1 ) (H₂ndc=5‐(4‐pyridyl)‐isophthalic acid), was synthesized with pronounced porosity. MOF 1 contained two different types of nanotubular channels, which exhibited a new topology with the Schlafli symbol of {4².6⁵.8³}{4².6}. MOF 1 showed high‐efficiency for the selective sorption of small molecules, including the energy‐correlated gases of H₂, CH₄, and CO₂, and environment‐correlated steams of alcohols, acetone, and pyridine. Gas‐sorption experiments indicated that MOF 1 exhibited not only a high CO₂‐uptake (25.1 wt % at 273 K/1 bar) but also the impressive selective sorption of CO₂ over N₂ and CH₄. High H₂‐uptake (2.04 wt % at 77 K/1 bar) was also observed. Moreover, systematic studies on the sorption of steams of organic molecules displayed excellent capacity for the sorption of the homologous series of alcohols (C₁–C₅), acetone, pyridine, as well as water.     

The hydroxyl radical reaction rate constant and atmospheric transformation products of 2-butanol and 2-pentanol

The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of +2-butanol (2BU, CH₃CH₂CH(OH)CH₃) and 2-pentanol (2PE, CH₃CH₂CH₂CH(OH)CH₃). 2BU and 2PE react with OH yielding bimolecular rate constants of (8.1±2.0)×10⁻¹² cm³molecule⁻¹s⁻¹ and (11.9±3.0)×10⁻¹² cm³molecule⁻¹s⁻¹, respectively, at 297±3 K and 1 atmosphere total pressure. Both 2BU and 2PE OH rate constants reported here are in agreement with previously reported values [1–4]. In order to more clearly define these alcohols' atmospheric reaction mechanisms, an investigation into the OH+alcohol reaction products was also conducted. The OH+2BU reaction products and yields observed were: methyl ethyl ketone (MEK, (60±2)%, CH₃CH₂C((DOUBLEBOND)O)CH₃) and acetaldehyde ((29±4)% HC((DOUBLEBOND)O)CH₃). The OH+2PE reaction products and yields observed were: 2-pentanone (2PO, (41±4)%, CH₃C((DOUBLEBOND)O)CH₂CH₂CH₃), propionaldehyde ((14±2)% HC((DOUBLEBOND)O)CH₂CH₃), and acetaldehyde ((40±4)%, HC((DOUBLEBOND)O)CH₃). The alcohols' reaction mechanisms are discussed in light of current understanding of oxygenated hydrocarbon atmospheric chemistry. Labeled (¹⁸O) 2BU/OH reactions were conducted to investigate 2BU's atmospheric transformation mechanism details. The findings reported here can be related to other structurally similar alcohols and may impact regulatory tools such as ground level ozone-forming potential calculations (incremental reactivity) [5]. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 745–752, 1998     

Electron‐rich O=PR3 compounds: Catalysts for alcohol silylation

The catalytic effect of a group of R₃P=O compounds was studied in a mild procedure for the silylation of primary alcohols, secondary alcohols, hindered secondary alcohols, and of hindered phenols in the presence of t‐butyldimethylsilyl chloride (TBDMSCl) and t‐butyldiphenylsilyl chloride (TBDPSCl). It was found that R₃P=O is an efficient catalyst in such reactions when R is a good electron‐donating group, such as Me₂N or n‐Bu and as an NMe(CH₂) moiety in N(CH₂CH₂NMe)₃P=O ( 3 ). However, R₃P=O is a weak or ineffective catalyst when R is a poor electron‐donating group, such as Ph or O‐n‐Bu or as a CH₂N‐o‐CH₂C₅H₄N moiety in N(CH₂CH₂N‐o‐CH₂C₅H₄N)₃P=O. Compound 3 , synthesized by oxidation of commercially available N(CH₂CH₂NMe)₃P, displayed the best catalytic properties for alcohol silylation in terms of efficiency, stability, and safety. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:21–26, 2001     

C−C Bond Formation in Syngas Conversion over Zinc Sites Grafted on ZSM‐5 Zeolite

Despite significant progress achieved in Fischer–Tropsch synthesis (FTS) technology, control of product selectivity remains a challenge in syngas conversion. Herein, we demonstrate that Zn²⁺‐ion exchanged ZSM‐5 zeolite steers syngas conversion selectively to ethane with its selectivity reaching as high as 86 % among hydrocarbons (excluding CO₂) at 20 % CO conversion. NMR spectroscopy, X‐ray absorption spectroscopy, and X‐ray fluorescence indicate that this is likely attributed to the highly dispersed Zn sites grafted on ZSM‐5. Quasi‐in‐situ solid‐state NMR, obtained by quenching the reaction in liquid N₂, detects C₂ species such as acetyl (‐COCH₃) bonding with an oxygen, ethyl (‐CH₂CH₃) bonding with a Zn site, and epoxyethane molecules adsorbing on a Zn site and a Brønsted acid site of the catalyst, respectively. These species could provide insight into C?C bond formation during ethane formation. Interestingly, this selective reaction pathway toward ethane appears to be general because a series of other Zn²⁺‐ion exchanged aluminosilicate zeolites with different topologies (for example, SSZ‐13, MCM‐22, and ZSM‐12) all give ethane predominantly. By contrast, a physical mixture of ZnO‐ZSM‐5 favors formation of hydrocarbons beyond C₃₊. These results provide an important guide for tuning the product selectivity in syngas conversion.     

Dichiral [4.4.3.01,5]tridecane copper(II) cluster derived from a tripodal ligand having unsymmetrical podands and the linker: Synthesis,structure, surface grafting and catalytic aspects

Pseudo‐atranes have a significant role in catalysis; however, obtaining chiral pseudo‐atranes for covalent functionalization of heterogeneous catalytic surfaces is very challenging. Herein, synthesis of a chiral tripodal amine [N{CH (CH₂Ph)CH₂OH}{CH₂(4? Br? C₆H₃OH)}{CH₂(2? CHO? 4? Me? C₆H₂OH)}] ( 1 ) and a dichiral [4.4.3.0^1,5]tridecane copper(II) cluster, that is, (Cu[N{CH (CH₂Ph)CH₂OH}{CH₂(4? Br? C₆H₃O)}{CH₂(2? CHO? 4? Me? C₆H₂O)}])₂ ( 2 ) is described. The compounds are characterized by elemental analyses, Fourier transform infrared (FT‐IR) spectroscopy, mass spectrometry and single‐crystal X‐ray crystallography (for 2 ). The compound 2 is the first example of chiral pseudo‐copper(II)atrane in which three unsymmetrical arms (two phenolic and a chiral ethanolic arm) are fused via Cu? N transannular bond. The free ? CHO group present in one of the tricyclic arms of the 2 is tested as a linker to load it on 3‐aminopropyltriethoxysilane‐functionalized magnetic nanosilica for catalytic applications. The loading of 2 on magnetic nanosilica through ? CHO was confirmed by FT‐IR spectroscopy, and the 2 ‐loaded magnetic nanosilica ( Fe ₃ O ₄ @SiO ₂ /2 ) was characterized by powder X‐ray diffraction, vibrating sample magnetometry, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and elemental mapping. The Fe ₃ O ₄ @SiO ₂ /2 was found highly efficient, retrievable, eco‐friendly and green catalyst for obtaining β‐amino alcohols in excellent yields in an aqueous medium. Overall, present work is the first report on synthetic, structural and catalytic aspects of dichiral cluster of copper(II)atrane possessing unsymmetrical tricyclic arms.     

A Long‐Lived Mononuclear Cyclopentadienyl Ruthenium Complex Grafted onto Anatase TiO2 for Efficient CO2 Photoreduction

This work shows a novel artificial donor–catalyst–acceptor triad photosystem based on a mononuclear C₅H₅‐RuH complex oxo‐bridged TiO₂ hybrid for efficient CO₂ photoreduction. An impressive quantum efficiency of 0.56 % for CH₄ under visible‐light irradiation was achieved over the triad photocatalyst, in which TiO₂ and C₅H₅‐RuH serve as the electron collector and CO₂‐reduction site and the photon‐harvester and water‐oxidation site, respectively. The fast electron injection from the excited Ru²⁺ cation to TiO₂ in ca. 0.5 ps and the slow backward charge recombination in half‐life of ca. 9.8 μs result in a long‐lived D⁺–C–A^? charge‐separated state responsible for the solar‐fuel production.     

Nickel and potassium co-modified β-Mo2C catalyst for CO conversion

Nickel and potassium co-modified -Mo2C catalysts were prepared and used for CO hydrogenation reaction. The major products over -Mo2C were C1–C4 hydrocarbons, only few alcohols were obtained. Addition of potassium resulted in remarkable selectivity shift from hydrocarbons to alcohols at the expense of CO conversion over -Mo2C. Moreover, it was found that potassium enhanced the ability of chain propagation with a higher C2+OH production. Modified by nickel, -Mo2C showed a relatively high CO conversion, however, the products were similar to those of pure -Mo2C. When co-modified by nickel and potassium, -Mo2C exhibited high activity and selectivity towards mixed alcohols synthesis, and also the whole chain propagation to produce alcohols especially for the stage of C1OH to C2OH was remarkably enhanced. It was concluded that the Ni and K had, to some extent, synergistic effect on CO conversion.     

Efficient organotin catalysts for urethanes: kinetic and mechanistic investigations

Dibenzyltin bis(2‐ethylhexanoate) 1 (4‐Y C₆H₄CH₂)₂Sn(OC(O)R¹)₂ [Y = H, 1a; MeO, 1b; Cl, 1c; Me, 1d; and R¹ = MeCH₂CH₂CH₂CH(Et) ] were synthesized either from the reaction of corresponding dibenzyltin dichlorides with silver 2‐ethylhexanoate or from the reaction of dibenzyltin oxides with 2‐ethylhexanoic acid. Compound 1a was further utilized as a catalyst for the reaction of mono‐ and di‐isocyanates [PhNCO, CH₃C₆H₃‐2,4‐(NCO)₂ and OCN(CH₂)₆NCO] with alcohols (primary, secondary, tertiary, cyclohexcyl, alkyl, allyl, benzyl and aryl) leading to the formation of the corresponding urethanes. The catalytic efficiencies of 1 vis‐à‐vis industrially known organotin catalysts have been determined through kinetic studies for the reaction of PhNCO and n‐BuOH at various temperatures. Compounds 1a, 1c and 1d show higher efficiency than dibutyltin bis(2‐ethylhexanoate). FTIR studies further provide mechanistic insights into the catalytic cycle, which comprises pre‐coordination of isocyanate to tin(IV), formation of stannyl carbamate and generation of dibenzyl(alkoxy)carboxylate as the active catalyst. Copyright © 2000 John Wiley & Sons, Ltd.     

Axial base‐controlled catalytic activity,oxidative stability and product selectivity of water‐insoluble manganese and iron porphyrins for oxidation of styrenes in water under green conditions

A series of water‐insoluble iron(III) and manganese(III) porphyrins, FeT(2‐CH₃)PPCl, FeT(4‐OCH₃)PPCl, FeT(2‐Cl)PPCl, FeTPPCl, MnT(2‐CH₃)PPOAc, MnT(4‐OCH₃)PPOAc, MnT(2‐Cl)PPOAc and MnTPPOAc, in the presence of imidazole (ImH), F^?, Cl^?, Br^? and acetate were used as catalysts for the aqueous‐phase heterogeneous oxidation of styrenes to the corresponding epoxides and aldehydes with sodium periodate. Also, the effect of various reaction parameters such as reaction time, molar ratio of catalyst to axial base, type of axial base, molar ratio of olefin to oxidant and nature of metal centre on the activity and oxidative stability of the catalysts and the product selectivity was investigated. Higher catalytic activities were found for the iron complexes. Interestingly, the selectivity towards the formation of epoxide and aldehyde (or acetophenone) was significantly influenced by the type of axial base. Furthermore, Br^? and ImH were found to be the most efficient co‐catalysts for the oxidation of olefins performed in the presence of the manganese and iron porphyrins, respectively. The optimized molar ratio of catalyst to axial base was different for various axial bases. Also, the order of co‐catalyst activity of the axial bases obtained in aqueous medium was different from that reported for organic solvents. The use of a convenient axial base under optimum reaction catalyst to co‐catalyst molar ratio in the presence of the manganese porphyrin gave the oxidative products with a conversion of ca 100% in a reaction time of less than 3 h. However, the catalytic activity of the iron porphyrins could not be effectively improved by increasing the catalyst to co‐catalyst molar ratio.     

Temperature-programmed desorption/pulse surface reaction (tpd/tpsr) studies of CH4, C2H6, C2H4, and CO over a cobalt/MWNTs catalyst

Summary Temperature-programmed desorption (TPD) of CH₄, C₂H₆, C₂H₄, and CO and temperature-programmed pulse surface reactions (TPSR) of CH₄, C₂H₆, C₂H₄, CO, and CO/H₂ over a Co/MWNTs catalyst have been investigated. The TPD results indicated that CH₄ and C₂H₆ mainly exist as physisorbed species on the Co/MWNTs catalyst surface, whilst C₂H₄ and CO exist as both physisorbed and chemisorbed species. The TPSR results indicated that CH₄ and C₂H₆ do not undergo reaction between room temperature and 450^oC. Pulsed C₂H₄ can be transformed into CH₄ at 400 ^oC whilst pulsed CO can be transformed into CO₂ at 100 or 150^oC. In gaseous mixtures of CO and H₂ containing excess CO, the products of pulsed reaction were CH₃CHO and CH₃OH. When the ratio of CO and H₂ was 1:2, pulsed CO and H₂ were transformed into CH₃CHO, CH₃OH and CH₄. In H₂ gas flow, pulsed CO was transformed into a mixture of CH₃CHO and CH₄ between 200 and 250^oC and was transformed into CH₄ only above 250^oC.     

Kinetics of the gas‐phase reactions of hydroxyl radicals with C1–C6 aliphatic alcohols in the presence of ammonium sulfate aerosols

The effects of ammonium sulfate aerosols on the kinetics of the hydroxyl radical reactions with C₁–C₆ aliphatic alcohols have been investigated using the relative rate technique. P‐xylene was used as a reference compound for the C₂–C₆ aliphatic alcohols study, and ethanol was used as a reference compound for the methanol study. Two different aerosol concentrations that are typical of polluted urban conditions were tested. The total surface areas of aerosols were 1400 μm² cm^?3 (condition I) and 3400 μm² cm^?3 (condition II). Results indicate that ammonium sulfate aerosols promote the ethanol/OH radical and 1‐propanol/OH radical reactions as compared to the p‐xylene/OH radical reaction. The relative rate of the ethanol/·OH reaction versus the p‐xylene/·OH reaction increased from 0.19 ± 0.01 in the absence of aerosols to 0.24 ± 0.01 and 0.26 ± 0.02 under aerosol conditions I and II, respectively. The relative rate of the 1‐propanol/·OH reaction versus the p‐xylene/·OH reaction increased from 0.45 ± 0.03 in the absence aerosols to 0.56 ± 0.02 and 0.55 ± 0.03 under aerosol conditions I and II, respectively. However, significant changes in the relative rates of the 1‐butanol/·OH, 1‐pentanol/·OH, and 1‐hexanol/·OH reactions versus the p‐xylene/·OH reaction were not observed for either aerosol concentration. The relative rates of the methanol/·OH reaction versus the ethanol/·OH reaction were identical in the absence and presence of aerosols. These results indicate that ammonium sulfate aerosols promote the methanol/·OH reaction as much as the ethanol/·OH reaction (as compared to the p‐xylene/·OH reaction). © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 422–430, 2001