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DMTM

Recently, the spectral study of DMTM(TCNQ)2 phase transition was performed [60]. The salt is a quarter-filled organic semiconductor containing segregated chains of TCNQ dimers and DMTM counterions. This material undergoes an inverted Peierls transition, which has tentatively been explained in terms of a crystal-field distortion. It was shown that the experimental values of unperturbed phonon frequencies and e-mv coupling constants are nearly independent of temperature. The dimer model fails to reproduce the phonon intensities and line shapes and underestimates the coupling constants, whereas the CDW model produces better results... [Pg.260]

A still more singular case than MEM(TCNQ)2 is provided by DMTM(TCNQ)2, a salt of the same family (DMTM = dimethylthimor-pholinium) [19,40]. This salt is also found to undergo a first-order phase transition, at Tc = 272 K but below Tc, the electrical conductivity increases... [Pg.335]

A preliminary investigation of the efficacy of the synthesis of 4-(4,6-dimethoxy-l,3 5-triazin-2-yl)-4-methylmor-pholinium (DMTMM) chloride <1998JOC4248> evidenced the formation of methyl chloride in a demethylation side reaction, which decreased the yield and caused contamination of the final products (Scheme 1) <1999TL5327>. The demethylation product from DMTMM was isolated and identified unequivocally as 4-(4,6-dimethoxy-l,3,5-triazin-2-yl)morpholine (DMTM) by X-ray diffraction. [Pg.206]

This interest induced a number of reviews on the subject [31,33—38]. However, these reviews primarily dealt with the catalytic oxidation of methane, reflecting the traditional focus on catalytic technologies and the lack, at that time, of a dear understanding of the real mechanism of the DMTM process. With the exception of [31], they contained no new original data or conclusions, being based predominantly on compilations of previous results. [Pg.2]

Since then, dozens of experimental works have been published. The most evident and widespread drawbacks of some of these papers, especially in the early period, which significantly complicate their analysis, are an incomplete presentation of the experimental conditions and the practice of simultaneously changing several experimental parameters. It may be supposed that, in the absence of clear ideas about the reaction mechanism, some researches practiced "random" (rather than time-consuming systematic) search for optimal conditions of methanol production. Such approach significantly depreciates the results and, in some, cases makes their analysis and inclusion in the common pool of DMTM data practically impossible. [Pg.2]

A vast body of interesting but contradictory data published in recent years and a new level of theoretical understanding of the DMTM mechanism motivated us to perform a new comprehensive analysis of the process. Such analysis showed that the potentialities of the DMTM process is high enough but needs serious elaboration. [Pg.3]

The most reliable experimental data on DMTM used in this analysis are summarized in Appendixes I and II. Note that many of the figures in the monograph, while plotted based on data from the cited original papers, are not necessarily present in these papers. [Pg.3]

Appendix I contains a summary of the experimental conditions and the results of the most informative (in our opinion) works on DMTM, an analysis of which enabled to draw most of the subsequent conclusions. Looking ahead and anticipating the results of the analysis, it is worthwhile to note that flow-reactor experiments on the DMTM, prototypes of real industrial processes, caimotbe viewed as studying one and the same process. It is necessary to consider three fundamentally different groups of experiments, investigating, strictly speaking, and... [Pg.3]

In works focused on practical applications, the yield of liquid DMTM products is often characterized not by the selectivity of their formation or their concentration, but by the mass per unit volume of gas mixture passed through the reactor. The results of such works are summarized in Appendix II. It should be borne in mind that, the liquid phase is usually separated from the postreaction gas—liquid mixture by cooling it with ambient-temperature water. In this case, according to phase equilibrium calculations, the exhaust gas can carry away 5—15% of the methanol produced and an even a larger fraction of formaldehyde [51]. Therefore, the actual yield of oxygenates may exceed the corresponding experimental values. A more complete methanol extraction, with a carried-away amount of less than 1%, requires cooling the exhaust gas to a temperature dose to 0°C. [Pg.4]

To provide the reader with the entire scope of data and facts about this process alongside with their comprehensive analysis, the chapters 2 through 4 discuss the products of DMTM, the main parameters of the process and the influence of gas composition on its behavior. These chapters present some imique data in this resped, some from sources difficult to access or published only in Russian. [Pg.4]

Chapters 5 through 9 are devoted to the peculiarities of the DMTM mechanism and the most important consequences ensuing from them. These chapters provide a basic theoretical imderstanding of the main features of this complex branched-chain oxidation process. The reader will find explanations of some imusual and imobvious features of the process and an in-depth analysis of its characteristics and possibilities. [Pg.4]

Chapter 10 examines the partial oxidation of heavier homologues of methane. It is the most rapidly developing direction in the modem studies of the DMTM process, motivated by the need to effectively process associated oil gases and heavier components of natural gas. [Pg.4]

The major gas-phase products of the DMTM process are carbon oxides and hydrogen, with the yield of carbon monoxide at high pressmes being several times that of carbon dioxide. The main pathways of formation of carbon dioxide in this process are apparently not directly related to carbon monoxide, since according to a number of studies, carbon dioxide is formed before carbon monoxide in the induction period [54]. With rising temperature, the yields of ethane and ethylene increase rapidly. [Pg.7]

Although methane oxidation is a complex branched-chain reaction, the ratio of the major DMTM products for t) ical conditions can be illustrated by the following gross reaction scheme, which reflects the fundamental nonselectivity of the gas-phase process ... [Pg.7]

The fact that formaldehyde, along with methanol, is the principal product of the DMTM process has been demonstrated in many studies, but then it is quickly removed by secondary reactions. Formaldehyde, dominating at low pressures, probably due to some specific features of the oxidation mechanism, remains present in significant quantities at high pressures as well, in both gas-phase and catalytic processes. [Pg.8]

In early studies of the DMTM process, the composition of the products was carefully analyzed, and a large number of various oxygen-containing and oxygen-free hydrocarbon oxidation products were separated and identified. In the later works, the focus was largely on the yield and kinetics of formation of the main products. Therefore, the scardty of information on byproducts in contemporary works seems to reflect a decline in interest in their formation in this process. However, in part, it may also be assodated with the changeover to more rigid conditions and shorter reaction times, which is less favourable for their formation. [Pg.14]

Below are listed the organic compounds observed in various works concerning the DMTM process ... [Pg.14]

Dimethyl ether (DME) is rarely detected in the DMTM products however, in [73], it was reported to be formed on a reduced copper surface, along with other products of methanol decomposition. [Pg.14]

FIGURE 2.14 Dependence of the CH3OH selectivity on the CH4 conversion obtained from fast-flow experiments with t, < 20 s and P > 30 atm (based on the data from Appendix I). The dashed line is the trend of experimental data, whereas the solid line represents the results of kinetic simulations of the gas-phase DMTM process at P = 100 atm and T = 420 °C [89]. (For colour version of this figure, the reader is referred to the online version of this book.)... [Pg.19]


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See also in sourсe #XX -- [ Pg.2 , Pg.335 ]




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DMTM Process

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