Alkenes, separation from gases

Benzyl- and methyltriarylphosphonium salts bound to 2% and 8% cross-linked, and to 20% cross-linked macroporous, polystyrene undergo Wittig reactions in good yield with both aldehydes and ketones. The Wittig reaction has been carried out under gas-liquid phase-transfer catalytic conditions using solid potassium carbonate as the base. An advantage of the procedure is that the alkene product separates from the phosphine oxide. Unprotected phenolic aldehydes can be converted into alkenes by Wittig reactions provided two moles of base are used. ... 

The gas condensate phase is composed of C3 and heavier alkanes and alkenes, present in the gas phase at reservoir conditions, that condense due to the temperature and pressure drop in the well string during production or in flowlines and production facilities. The gas condensate phase can occur in gas wells, flowlines, and in crude oil well gas processing facilities after separation of gas from the crude... 

The results presented here demonstrate several points. Although the facilitated transport of alkenes in a pervaporative mode is not quite as productive as in a condensed phase mode, the separation is still highly effective for both alkene-alkene separations and alkene-paraffin separations. The requirement, however, is that the membrane must be swept with a water-saturated gas. This requirement at first may seem cumbersome due to consumption of a sweep gas and the presence of water with the collected permeate. However, the separation of water from hexenes is trivial and one can easily envision a system which recirculates a non-condensing sweep gas such as heliiun or nitrogen. The alkene-saturated water condensed from the sweep stream could also be recycled after thawing and separating from the organics. 

The oxidation of terminal alkenes with an EWG in alcohols or ethylene glycol affords acetals of aldehydes chemoselectively. Acrylonitrile is converted into l,3-dioxolan-2-ylacetonitrile (69) in ethylene glycol and to 3,3-dimetho.xy-propionitrile (70) in methanol[28j. 3,3-Dimethoxypropionitrile (70) is produced commercially in MeOH from acrylonitrile by use of methyl nitrite (71) as a unique leoxidant of Pd(0). Methyl nitrite (71) is regenerated by the oxidation of NO with oxygen in MeOH. Methyl nitrite is a gas, which can be separated easily from water formed in the oxidation[3]. 

Raffinate-II typically consists of40 % 1-butene, 40 % 2-butene and 20 % butane isomers. [RhH(CO)(TPPTS)3] does not catalyze the hydroformylation of internal olefins, neither their isomerization to terminal alkenes. It follows, that in addition to the 20 % butane in the feed, the 2-butene content will not react either. Following separation of the aqueous catalyts phase and the organic phase of aldehydes, the latter is freed from dissolved 2-butene and butane with a counter flow of synthesis gas. The crude aldehyde mixture is fractionated to yield n-valeraldehyde (95 %) and isovaleraldehyde (5 %) which are then oxidized to valeric add. Esters of n-valeric acid are used as lubricants. Unreacted butenes (mostly 2-butene) are hydroformylated and hydrogenated in a high pressure cobalt-catalyzed process to a mixture of isomeric amyl alcohols, while the remaining unreactive components (mostly butane) are used for power generation. Production of valeraldehydes was 12.000 t in 1995 [8] and was expected to increase later. 

Mosandl A, Schubert V, Stereoisomeric flavor compounds XXXVII Enantiomer separation of l-alken-3-yl esters and their chirality evaluation from essential oils using multidimensional gas chromatography (MDGC),/ Essen Oil Res 2 121— 132, 1990. 

Bromine monofluoride or iodine monofluoride can be prepared from the corresponding elements in trichlorofluoromethane at — 781 and — 45 C,2,3 respectively. The compounds are unstable and decompose at low temperatures, iodine monofluoridc at — 14 C2,3 and bromine monofluoride, in part, even at — 78 C.1 Therefore, they are used, without separation and purification, in Freon solutions at low temperatures or, most frequently, as stoichiometric mixtures bromine trifluoride/bromine and iodine pentafluoride/iodine. A solution of iodine monofluoride, obtained by bubbling nitrogen-diluted fluorine gas into a suspension of iodine in trichlorofluoromethane at — 75 C, was used for addition to alkene C = C bonds. The reaction is regioselective and in most cases obeys the Markovnikov rule.4 Iodine monofiuoride prepared in situ reacts quite efficiently with steroidal alkenes.4... 

The true catalytically-active species is probably HCo(CO)3, a 16-electron complex. This intermediate results from 18-electron HCo(CO)4, 1, which in turn ultimately comes from Co(0) or Co(II), via Co2(CO)s, in the presence of a 1 1 mixture of CO and H2 (synthesis gas).16 Sometimes 1 is prepared in a separate step and introduced to the alkene in the presence of synthesis gas this allows the subsequent hydroformylation to be run at a lower temperature (90-120 °C rather than the usual 120-170 °C). The dissociation step to form the active catalyst occurs with a relatively high activation energy, and it is, of course, inhibited by a high concentration of CO (the overall rate law for hydroformylation typically shows the concentration of CO with a negative exponent, n, where 0 > n > -1). The reaction is run, however, under very high pressure (200-300 bar) to stabilize HCo(CO)3 and later intermediates in the catalytic cycle, thus demonstrating a balance in reaction conditions between the formation of sufficient HCo(CO)3 for hydroformylation to occur at a reasonable rate and the enhancement of the stability of catalytic intermediates.17 Calculations indicate that the preferred geometry... 

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