Hydrocarbon compounds from methanol

Since it was first reported in 1976 that protonated ZSM-5 zeolites are excellent catalysts for conversion of methanol (and many other oxygenated compounds ) into hydrocarbons in the C - C q range the catalyst and the reactions have been intensely studied. Several aspects of the reactions leading to hydrocarbon formation from methanol or dimethyl ether over H-ZSM-5 or other protonated zeolites still remain unclear. In particular the first OC bond formation has been debated, and several mechanisms proposed (ref. 1). 

Rectisol A process for removing sulfur compounds from gas mixtures resulting from the partial oxidation of hydrocarbons, based on physical absorption in methanol at low temperatures. Originally developed in 1951 by Lurgi Gesellschaft fur Warmetechnik for the SASOL coal gasification plant... 

Surfaces with oil or grease contamination should be cleaned by an organic solvent such as methanol or acetone in an ultrasonic cleaner. It is also important to avoid touching the cleaned specimen with bare hands because fingerprints contain volatile hydrocarbon compounds. Sometimes a dark mark occurs on a well-cleaned specimen. This might result from hydrocarbon contamination from a dirty vacuum system. Hydrocarbons escaping from the diffusion pump oil into the SEM chamber can also contaminate a specimen under electron beam. 

Our analytical procedure consists of stepwise acetone extraction followed by cyclohexane. Subsequently, the acetone-soluble fraction is partioned between hexane/aqueous ethanol (12,15), and the soluble components are freed of solvents and determined gravimetrically. For lack of specific nomenclature, the botanochemicals isolated by this technique have been referred to as "whole plant oil," "polyphenol," and "polymeric hydrocarbon." Actually, components from these extracts need to be further characterized. However, petroleum refinery processes may be sufficiently insensitive to allow use of carbon-hydrogen rich compounds represented by a broad spectrum of structures. For example, consider the diverse chemicals ranging from methanol to natural rubber which have been converted to gasoline (16). Thus, chemical species may be important if chemical intermediates are being generated but may be nonconsequential for production of fuels, solvents, carbon black, and other basic chemicals. 

Several companies are developing the manufacture and use of dimethyl ether, CH3OCH3, as an efficient and clean alternative to diesel fuel [Chemical and Engineering News, 1995 (May 29), 37-39]. Much of this interest in dimethyl ether and other related compounds is focused on minimizing C—C bonds in fuels in order to limit formation of polycyclic aromatic hydrocarbons see A Word About... Polycyclic Aromatic Hydrocarbons and Cancer on page 136. Show how dimethyl ether could be synthesized from methanol. 

Hydrocarbon synthesis from syngas (Fischer-Tropsch reactions) can be carried out over the catalysts prepared from Co- and Cu-containing LDHs. The products include methane, higher paraffins, and olefins as well as methanol. The loading of Co and Cu determines the selectivity for each compound. For instance, Co-rich catalysts give more paraffins, while Co-poor ones lead to methanol (615). 

The first hydrocarbon described from the B race was a C34 compound called botryococcene (31 one of the most widespread members of the botryococcene family as demonstrated by subsequent studies. Due to its large predominance in the total hydrocarbon fraction isolated from some strains, ca 90%, no additional purification was needed for identification of the C34 compound. This simple case, however, occurs rarely and isolation of pure or at least enriched fractions of the other botryococcenes was required. This purification was obtained by reversed-phase HPLC using analytical columns and by repeated injections of botryococcene mixtures various eluents such as acetone-acetonitrile 2 3 (52), acetonitrile (55) and acetone-methanol 3 2 were used 34). This technique was however ineffective for separation of hydrocarbons exhibiting only regio- and (or) stereo-isomerism of double bonds. 

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