F:Highly flammable;111-43-3Relevant articles and documents
Improving carbon retention in biomass conversion by alkylation of phenolics with small oxygenates
Nie, Lei,Resasco, Daniel E.
, p. 14 - 21 (2012)
Alkylation of phenolics with alcohols is an efficient way to retain carbon from small oxygenates in the liquid products of pyrolysis bio-oil. In this contribution, we have investigated the alkylation of m-cresol with several alkylating agents over H-Beta zeolite. The alkylation activity follows the sequence 2-propanol > propylene > 1-propanol. In all cases, propylene is the actual alkylation agent since the alcohols dehydrate at a faster rate than the rate of alkylation. A two-stage process is proposed to convert fractions of bio-oil rich in small aldehydes and ketones together with phenolics. In the first stage, aldehydes and ketones are selectively hydrogenated to alcohols. In the second stage, the resulting alcohols alkylate the phenolic compounds and get incorporated into the upgraded liquid. To illustrate this concept, two consecutive catalyst beds have been used. The first bed contains a metal catalyst for the selective hydrogenation. Among several catalysts investigated, Cu/SiO2 and Pt-Fe/SiO2 were found to exhibit good selectivity to hydrogenate the aldehyde and ketone, respectively, while preserving the aromatic ring of the phenolic compound. The second bed contains an H-Beta zeolite for the alkylation stage.
Low-temperature rhodium-catalyzed dehydration of primary alcohols promoted by tetralkylammonium and imidazolium halides
Dowson, George R. M.,Shishkov, Igor V.,Wass, Duncan F.
, p. 4001 - 4003 (2010)
Rhodium complexes, promoted by imidazolium or tetraalkylammonium halide salts, catalyze the dehydration of primary alcohols with good conversion and selectivity.
Dehydration Pathways of 1-Propanol on HZSM-5 in the Presence and Absence of Water
Zhi, Yuchun,Shi, Hui,Mu, Linyu,Liu, Yue,Mei, Donghai,Camaioni, Donald M.,Lercher, Johannes A.
, p. 15781 - 15794 (2015)
The Br?nsted acid-catalyzed gas-phase dehydration of 1-propanol (0.075-4 kPa) was studied on zeolite H-MFI (Si/Al = 26, containing minimal amounts of extra framework Al moieties) in the absence and presence of co-fed water (0-2.5 kPa) at 413-443 K. It is shown that propene can be formed from monomeric and dimeric adsorbed 1-propanol. The stronger adsorption of 1-propanol relative to water indicates that the reduced dehydration rates in the presence of water are not a consequence of the competitive adsorption between 1-propanol and water. Instead, the deleterious effect is related to the different extents of stabilization of adsorbed intermediates and the relevant elimination/substitution transition states by water. Water stabilizes the adsorbed 1-propanol monomer significantly more than the elimination transition state, leading to a higher activation barrier and a greater entropy gain for the rate-limiting step, which eventually leads to propene. In a similar manner, an excess of 1-propanol stabilizes the adsorbed state of 1-propanol more than the elimination transition state. In comparison with the monomer-mediated pathway, adsorbed dimer and the relevant transition states for propene and ether formation are similarly, while less effectively, stabilized by intrazeolite water molecules.
General Ether Synthesis under Mild Acid-Free Conditions. Trimethylsilyl Iodide Catalyzed Reductive Coupling of Carbonyl Compounds with Trialkylsilanes to Symmetrical Ethers and Reductive Condensation with Alkoxysilanes to Unsymmetrical Ethers
Sassaman, Mark B.,Kotian, Kirtivan D.,Prakash, G. K. Surya,Olah, George A.
, p. 4314 - 4319 (1987)
Facile synthesis of symmetrical ethers is achieved by either trimethylsilyl triflate or trimethylsilyl iodide catalyzed reductive coupling of carbonyl compounds (aldehydes and ketones) with trialkylsilanes.The method was also extended to the trimethylsilyl iodide catalyzed preparation of unsymmetrical ethers by reductive condensation (of carbonyl compounds) with alkoxysilanes.The scope and limitations of the reactions are discussed with emphasis on diastereoselectivity.
Kinetics and site requirements of ether disproportionation on γ-Al2O3
DeWilde, Joseph F.,Bhan, Aditya
, p. 361 - 369 (2015)
Abstract Measured rates of methyl propyl ether (MPE), an asymmetric ether, conversion on γ-alumina at 623 K verify that hydration rates are negligible compared to disproportionation rates below 2.0 kPa of water. Steady state kinetic measurements establish that diethyl ether (DEE) disproportionation rates possess reaction orders between 0 and 1. A mechanism for DEE disproportionation in which ethanol monomers and reactive ethoxy species are the primary surface species is consistent with measured pressure dependencies. The intrinsic rate constant of DEE disproportionation is nearly identical to that of unimolecular ethanol dehydration, revealing the similarity in the rate-limiting steps of these two reactions. In-situ pyridine titration studies verify that DEE disproportionation and unimolecular ethanol dehydration possess similar site requirements and densities (0.3 and 0.2 sites nm-2, respectively) while bimolecular ethanol dehydration occurs on a separate pool of catalytic sites.
Decarboxylation of dialkyl carbonates to dialkyl ethers over alkali metal-exchanged faujasites
Selva, Maurizio,Fabris, Massimo,Perosa, Alvise
, p. 863 - 872 (2011)
Non-toxic DAlCs, especially lighter dimethyl- and diethyl-carbonate, are regarded as very green alkylating reagents, particularly when coupled with metal-exchanged Y- and X-faujasites as catalysts. These reactions are selective, free from wastes or byproducts, and often require no additional solvent other than the carbonate. Nonetheless, this paper demonstrates that the operating temperature and the nature of the faujasite must be carefully chosen in order to avoid DAlC decomposition. In fact, at temperatures ranging from 150 to 240°C, faujasites can promote decarboxylation of light DAlCs to the corresponding ethers CH3OCH3 and CH3CH 2OCH2CH3 plus CO2. Heavier DAlCs (dipropyl- and dioctyl-carbonate) undergo a similar decomposition pathway, followed by further reactions to the corresponding alcohols (n-propanol and n-octanol) and alkenes [propylene and octene(s)]. These transformations not only consume DAlCs, but also give rise to dangerously flammable ethers, as well as undesirable alcohols, alkenes and CO2. The present work reports an original investigation of the decarboxylation of DAlCs on faujasites with the aim of providing operative boundaries to the experimental conditions to minimise unwanted decomposition. The reaction is strongly affected by the nature of the catalyst: the more basic zeolites, NaX and CsY, are by far more active systems than NaY and LiY. However, solid K2CO3 proves to be rather inefficient. The temperature also plays a crucial role: for example, the onset of the decarboxylation of DMC requires a temperature of ～30°C lower than that for DEC and DPrC. Overall, awareness that certain zeolites cause decomposition of DAlCs under conditions similar to the ones used for DAlC-promoted alkylations allows determination of the correct experimental boundaries for a safer and more productive use of DAlCs as alkylating agents. The Royal Society of Chemistry.
INTRAMOLECULAR COORDINATION BETWEEN MAGNESIUM AND OXYGEN IN CYCLIC ORGANOMAGNESIUM COMPOUNDS
Freijee, F. J. M.,Wal, G. Van Der,Schat, G.,Akkerman, O. S.,Bickelhaupt, F.
, p. 229 - 238 (1982)
Association measurements in THF solution reveal that cyclic organomagnesium compounds capable of intramolecular coordination between magnesium and a suitably located oxygen atom in the ring exist exclusively as monomers in THF solution, whereas their oxygen-free analogues have a high tendency to dimerize; 1-oxa-5-magnesacyclooctane (I), 1-oxa-6-magnesacyclodecane (II), its dibenzoanalogue III, and the corresponding di-Grignard reagents IIB and IIIB were investigated.A thermochemical investigation of I-III yielded more quantitative information; the intramolecular coordinative O-Mg bond has been found to be stronger than the intermolecular bond to THF.The ring strain in these compounds is discussed.
The adsorption and reaction of alcohols on TiO2 and Pd/TiO 2 catalysts
Bahruji, Hasliza,Bowker, Michael,Brookes, Catherine,Davies, Philip R.,Wawata, Ibrahim
, p. 66 - 73 (2013)
The decomposition of alcohols (methanol, ethanol, n-propanol, i-propanol) on TiO2 and Pd/TiO2 catalysts has been studied using temperature programmed desorption. The alcohols mainly decompose via a dehydration pathway on TiO2 catalysts, with no evidence for reactions involving α CC scission or dehydrogenation. However, the reaction pathway was fundamentally altered by the presence of Pd nanoparticles, and products of α CC scission became dominant due to decarbonylation pathways. For the reaction with ethanol, there was no evidence of the dehydration product ethylene even though the surface is mainly composed of titania, indicating that diffusion of alkoxy species from the support to the Pd occurs efficiently during TPD. However, competing dehydration reactions did occur on Pd/TiO2 in the cases of n-propanol and i-propanol decomposition which is postulated to be due to more limited diffusivity of the bulkier alkoxides.
Reduction of Propanoic Acid over Pd-Promoted Supported WOx Catalysts
Kammert, James D.,Brezicki, Gordon,Miyake, Naomi,Stavitski, Eli,Davis, Robert J.
, p. 314 - 325 (2020)
Silica-, titania-, and zirconia-supported tungsten oxide catalysts were synthesized by wetness impregnation techniques. When promoted with Pd, these materials catalyzed the reduction of propanoic acid to 1-propanol at 433 K with a selectivity of up to 92 % (13.5 % conversion) in atmospheric pressure of H2. Over Pd-promoted WOx/TiO2, the observed orders of reaction were 0.2 in H2 and 0.7 in propanoic acid, and the apparent activation energy was 54 kJ mol?1. In situ X-ray absorption spectroscopy of Pd-promoted WOx/SiO2 revealed a slight reduction of the W from +6 to an average oxidation state of about +5 during H2 treatment above 473 K. In situ infrared spectroscopy indicated the catalyst surface was covered mostly by propanoate species during reaction. For comparison, supported phosphotungstic acid was also evaluated as a catalyst under identical conditions, but the resulting high acidity of the catalyst was deleterious to alcohol selectivity.
On the miscibility of ethers and perfluorocarbons. An experimental and theoretical study
Babiak, Peter,Němcová, Adriana,Rulí?ek, Lubomír,Beier, Petr
, p. 397 - 401 (2008)
Despite their significant polar character, some organic ethers such as diethyl ether were found to be miscible with perfluorocarbon solvents. Solubilities of various ethers in perfluorocarbons and miscibility temperatures were determined. These properties were found to be greatly dependent on the polarity but also size and shape of the ether molecule. Theoretical calculations of the miscibility temperatures of organic solvents and perfluorocarbons using COSMO-RS method were correlated with experimental data. Considering the difficulties in the accurate description of the macroscopic properties, such as miscibility temperatures, from the first principles, the agreement between experimental and theoretical data is reasonable.
