Effect of methanol dilution on H-ZSM-5 zeolite deactivation in the process of light olefin formation

Conversion of methanol in the presence of H₂O, O₂, H₂, CO, CO₂ and He was studied at 733 K on H-ZSM-5 zeolite. The effect of diluent on the selectivity to light olefins and resistance to coking of H-ZSM-5 were observed. Among the diluents studied only water exerts a promoting effect on prolonged activity of the catalyst. Some explanations of the deactivation process are given.

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H₂O, O₂, H₂, CO, CO₂ He H-ZSM-5 733K. H-ZSM-5. . .

     

A column packing for isothermal gas chromatographic analysis of C1−C5 paraffins and monoolefins and dimethyl ether

Summary An analytical GC method was developed which uses a single packed column consisting of three packings in series prepared with the following liquid phases: dimethyl sulfolane, propylene carbonate, and silver nitrate. This system provides satisfactory resolution of mixtures of C₁–C₅ hydrocarbons and dimethyl ether obtained when converting methanol to gasoline. Due to the high capacity of the column it is possible to inject larger sample amounts permitting trace analysis.     

Application of hitherto unexplored macrocyclization strategies in the epothilone series: novel epothilone analogs by total synthesis

A total synthesis of Epothilone 490 and a synthesis of 11-hydroxy dEpoB utilizing a vinyl-boronate cross-metathesis followed by a Suzuki macrocyclization. A mild route to reach aldehydes from terminal olefins, anticipating Nozaki-Kishi macrocyclization is described.     

Synthesis of Some Biologically Active Cyclopente-Nones using New Organophosphorus Reagents

Abstract

The use of organic phosphorus and sulfur compounds in the general synthesis of biologically active functionalized cyclopentenones is presented.     

Analysis of flammability and smoke emission of rigid polyurethane foams modified with nanoparticles and halogen-free fire retardants

Using one-step method, rigid polyurethane foams were made, modified with developed fire retardant systems containing halogen-free flame retardants and nanofillers in the form of multi-walled carbon nanotubes or nanoscale titanium dioxide. The materials were subjected to a test using a cone calorimeter and smoke-generating chamber, and selected samples were further analyzed via thermogravimetry and oxygen index. Moreover, the products of thermal degradation of selected samples were identified using gas chromatography with mass spectrometer. Conducted flammability tests confirmed the presence of a synergistic effect between the used nanofillers and halogen-free flame retardants. It has been observed that the carbonized layer, the formation of which favored the presence of nanoadditives, inhibits the combustion process. Furthermore, nanofillers influenced favorably reduction in the amount and the number of occurring products of thermal degradation.     

Application of the additive increments method to the calculation of chemical shift of olefinic protons in aromatic olefines: Additive increments for para and meta substituents in the aromatic ring

Additive increments for para and meta substituents in the aromatic ring were calculated on the basis of 332 examples of chemical shifts and were correlated with Hammett's constants. Examples of calculation of chemical shifts of olefinic protons in substituted aromatic olefines by means of the increments are given.     

Reaction of 5,5-diphenyl-2-thiohydantoin with 1,3-dibromopropane : Crystal and molecular structure of 2,3,4,5-tetrahydro-6,6-diphenylimidazo [2, 1-b]-thiazine-7 (6H)-one

The reaction between the potassium salt of 5,5-diphenyl-2-thiohydantoin (1) and 1,3-dibromopropane carried out in DME under anhydrous conditions has been found to give two isomeric diphenylimidazothiazines 2 and 3. When the reaction of 1 with 1,3-dibromopropane was performed in protic solvents (EtOH, HOH, NaOH) 2 and 3-(3-mercaptopropyl) - 5,5 - diphenylthiohydantoin (4) were formed. The latter is the product of hydrolysis of 3 taking place under the reaction conditions. 2,3,4,5 - Tetrahydro - 6,6 - diphenylimidazo [2,1-b] - thiazine - 7 (6H) - one (2) crystallises in space group P2₁/n with a =10.812(3), b =14.905(7), c =9.885(4) Å, β = 104.91(2)°. The 5-membered ring in 2 is planar whereas the 6-membered thiazine ring adopts the sofa conformation.     

Organosulphur compounds—XVIII: A new and general synthesis of ketene s,s- and o,s-thioacetals based on the horner-wittig reaction

A new and general synthesis of ketene S,S-thioacetals (1) and ketene O.S-thioacetals (6) which involves the Horner-Wittig reaction of carbonyl compounds with the metallated S,S- and O,S-thioacetals of formyl-phosphonates (4 and 5) is described. The Horner-Wittig reaction of 4 with aromatic aldehydes can be carried out under two-phase conditions. The generation of the carbanions from 4 and 5 as well as the course of their reaction with carbonyl compounds were studied by the low temperature ³¹P NMR spectroscopy. It was found that S,S-thioacetals of formylphospbonates (4) are very easily metallated in contrast to O,S-thioacetals of formyl-phosphonates (5) which form the lithium derivatives only on treatment with t-butyllitnium. No evidence was obtained from ³¹P NMR spectra supporting the formation of the lithium derivatives of 0,0-acetals of formyl-phosphonates (12).