Conversion of Dimethyl Ether to a Mixture of Liquid Hydrocarbons with Increased Triptane Content

The influence of the structural type and of the textural and acid properties of the zeolite on the catalyst selectivity in synthesis of a mixture of liquid hydrocarbons with increased content of isoalkanes from dimethyl ether was examined. The synthesis of liquid hydrocarbons enriched in triptane in the course of gasoline production from CO and H₂ via dimethyl ether in the presence of La-H-Y zeolite was performed for the first time. Excess hydrogen in the system and relatively short contact time of the catalyst with the feed favor an increase in the triptane yield. Additional modification with palladium leads to optimization of the acid properties of the La-H-Y zeolite and, as a consequence, to an increase in the triptane content of the gasoline from 2.0 to 9.4 wt %.

     

Synthesis of liquid hydrocarbons enriched with triptane via dimethyl ether conversion over combined catalyst

A combined catalytic system composed of catalysts with different functions was prepared. The catalyst for the synthesis of lower olefins based on is H-ZSM-5 zeolite modified with Mg, was mixed with the catalyst for alkylation of isobutane by olefins based on H-Y zeolite modified with La and Pd. In the presence of the combined system, liquid branched hydrocarbons were synthesized from dimethyl ether in a hydrogen medium at 340 °C and a pressure of 10 MPa. The effect of the composition of the combined catalyst on its selectivity to liquid hydrocarbons and, specifically, triptane was shown.

     

Optical and electrical properties of β-Tl<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Cu<Subscript>x</Subscript>InS<Subscript>2</Subscript> (0 ≤ <Emphasis Type="Italic">x</Emphasis> ≤ 0.015) single crystals

The peculiarities of fundamental optical absorption, thermally stimulated conductivity, and depolarization currents in β-Tl_{1 ? x} Cu_xInS₂ (0 ≤ x ≤ 0.015) single crystals have been investigated in the temperature range 4.2–300 K. It is found that the temperature coefficient of the band gap E _g changes near the temperature of the structural phase transition.     

Three-dimensional free-radical copolymerization of methyl methacrylate with diunsaturated monomers in the presence of an aromatic polyimide

The three-dimensional free-radical copolymerization of MMA with diunsaturated comonomers of various natures in the absence and in the presence of 4 wt % aromatic polyimide (η_inh = 0.38?1.02 dl/g) has been studied by isothermal calorimetry. It has been shown that, depending on the chemical nature of spacers separating double bonds of the comonomers, the kinetic curves of copolymerization may be divided into two groups, one of which is characterized by an almost complete absence of stationary portions. It has been demonstrated that the effects of the polyimide on the initial rate of copolymerization and on the parameters of the gel effect depend on the nature of diunsaturated comonomers and the molecular mass of the aromatic polyimide. The swelling of the polymer systems under study in toluene has been investigated, and the parameters of their network structure have been estimated. The irreversible flow deformation of the MMA copolymers with diunsaturated comonomers does not manifest itself up to a temperature corresponding to the onset of degradation of the copolymers. The incorporation of polyimide units improves the thermal stability of the copolymers.