Xylene

About: Xylene is a research topic. Over the lifetime, 7168 publications have been published within this topic receiving 110696 citations. The topic is also known as: Xylen & Xileno.

Hierarchical and comparative kinetic modeling of laminar flame speeds of hydrocarbon and oxygenated fuels

Abstract: The primary objective of the present endeavor is to collect, consolidate, and review the vast amount of experimental data on the laminar flame speeds of hydrocarbon and oxygenated fuels that have been reported in recent years, analyze them by using a detailed kinetic mechanism for the pyrolysis and combustion of a large variety of fuels at high temperature conditions, and thereby identify aspects of the mechanism that require further revision. The review and assessment was hierarchically conducted, in the sequence of the foundational C0–C4 species; the reference fuels of alkanes (n-heptane, iso-octane, n-decane, n-dodecane), cyclo-alkanes (cyclohexane and methyl-cyclo-hexane) and the aromatics (benzene, toluene, xylene and ethylbenzene); and the oxygenated fuels of alcohols, C3H6O isomers, ethers (dimethyl ether and ethyl tertiary butyl ether), and methyl esters up to methyl decanoate. Mixtures of some of these fuels, including those with hydrogen, were also considered. The comprehensive nature of the present mechanism and effort is emphasized.

Selective alkylation of toluene with methanol to produce para-xylene

Abstract: Toluene has been alkylated with methanol over ZSM-5-class zeolite catalysts to produce xylenes and water. A near equilibrium mixture containing 24% of the para isomer was usually observed. Production of over 90% para isomer in the xylene product was achieved when the catalyst was modified by impregnation with phosphorus and with boron compounds. para-Xylene selectivity was also enhanced by coking and coating the catalyst surface with heat-stable polymers. A controlled reduction in the effective dimensions of the catalyst pore openings, and/or channels, along with deactivation of acidic surface sites, has been proposed as a mechanism for the selective production of p-xylene.

A Pseudomonas thrives in high concentrations of toluene

Abstract: TOLUENE, like many organic sovents, is highly biotoxic and kills most microorganisms at low concentrations (0.1% v/v). It is often used therefore to sterilize microbial cultures and lyse bacterial cells in the assay of bacterial enzymes1–3. The physiological basis of such solvent toxicity, however, remains poorly characterized. Although some microorganisms, including Pseudomonas4–6 , Achromobacter4 and Nocardia7 , can assimilate toluene, their toler-ance for the solvent is less than 0.3% (v/v). We report here the discovery of a variant strain of Pseudomonas putida which is capable of growing in media culture containing more than 50% (v/v) toluene or high concentrations of cyclohexane, xylene, styrene and heptanol. By studying this unusually tolerant strain we show that the relative toxicities of different solvents are determined by their polarities.

Composition of oils derived from the batch pyrolysis of tyres

Abstract: A nitrogen purged static-bed batch reactor was used to pyrolyse 3 kg batches of shredded scrap tyres at temperatures between 450 and 600°C. The oils were trapped in a series of condensers and the derived gases analysed off-line by packed column gas chromatography. The oil yield was found to decrease with increasing final pyrolysis temperature and the yield of product gases increased. The fuel properties of the condensed oil including, calorific values, ultimate analyses, flash point, moisture content, fluorine and chlorine contents were determined. The concentration of polycyclic aromatic hydrocarbons (PAH) and lighter aromatic hydrocarbons were determined. The results showed that the derived tyre oils had fuel properties similar to those of a light petroleum fuel oil. The influence of pyrolysis temperature showed an increase in the aromatic content of the oils with increasing temperature, with a consequent decrease in aliphatic content. The total PAH content of the oils were found to increase from 1.5 to 3.5 wt.% of the total oil as the pyrolysis temperature was increased from 450 to 600°C. Biologically active compounds such as methylfluorenes, tri- and tetra-methylphenanthrenes and chrysene were identified in significant concentrations. The results of gas analysis supported a Diels–Alder mechanism of alkane dehydrogenation to alkenes, followed by cyclisation and aromatisation. Limonene was identified as a major component of the oils, representing 3.1 wt.% at 450°C falling to 2.5 wt.% total oil at 600°C. Significant quantities of light aromatics such as benzene, toluene, xylene and styrene were also found.