Liquefaction chemistry

Fundamental studies of coal liquefaction have shown that the structure of solvent molecules can determine the nature of liquid yields that result at any particular set of reaction conditions. One approach to understanding coal liquefaction chemistry is to use well-defined solvents or to study reactions of solvents with pure compounds which may represent bond-types that are likely present in coal [1,2]. It is postulated that one of the major routes in coal liquefaction is initiation by thermal activation to form free radicals which abstract hydrogen from any readily available source. The solvent may, therefore, function as a direct source of hydrogen (donor), indirect source of hydrogen (hydrogen-transfer agent), or may directly react with the coal (adduction). The actual role of solvent thus becomes a significant parameter. 

Retrograde Diels-Alder reactions are unlikely reactions in coal liquefaction chemistry due, again, to the lack of suitable molecular structures. Decomposition of cyclohexene to ethylene and 1,3-butadiene, for instance, is 40 kcal/mol endothermic and at 450°C proceeds at a rate such that the half-life of cyclohexene is 13 hours (11a). For tetralin to react by an analogous reaction, resonance stability would be lost, and the reaction would be many orders of magnitude slower than cyclohexene. 

John William Lord Rayleigh (1842-1919 Nobel Prize for chemistry 1904) and Sir William Ramsay (1852-1916 Nobel Prize for physics 1904). Isolated by liquefaction of air and identified as a new element by spectral analysis. 

It accumulates during the liquefaction of air, and is a common and popular protective gas in chemistry and metal- A. Argon lasers have many versatile lurgy, for example, in electrowelding. in, eseaKh and... 

R. P. Skowronski, J. J. Ratto and L. A. Heredy, "Deuterium Tracer Method for Investigating the Chemistry of Coal Liquefaction", Annual Report, 1977, Rockwell International,... 

Numerous implications on the fundamental chemistry of coal liquefaction can be drawn from the observed reaction of solvent isomerization and adduction. The literature indicates that... 

The physical chemistry underlying the liquefaction of a gas is surprisingly complicated, so we shall not return to the question until Chapter 5. 

O Brien, T.F. White, I.F. (1998) Process engineering considerations in chlorine compression and liquefaction. In Modern Chlor-Alkali Technology, Vol. 7 (ed. S. Sealey), pp. 202-213. Society of Chemical Industry, London and Royal Society of Chemistry, Cambridge. 

Pyrolysis and liquefaction products are in need of substantial treating processes, the chemistry of which is not yet very well understood. There is also a need and an opportunity to improve the selectivity of Fischer-Tropsch type processes. 

Makino, E. Coal liquefaction, in Ullmann s Encyclopedia of Industrial Chemistry, 7th ed., CRC Press, Boca Raton, Fla, 2005. 

From the analysis of the results on the preliquefaction chemistry, it was found that the preliquefaction process results in reduction of carboxyl groups, partial crosslinking of the structure and some bond breaking resulting in hi er chloroform extractables. The effect of this preliquefaction process on subsequent liquefaction is a high yields of liquids. 

Whitehurst, D. D. Mitchell, T. O. Faicasiu, M. Coal Liquefaction-The Chemistry and Technology ofThermal Processes (Academic Press 1980, N.Y.), pp. 207-272 and references cited therein. 

The chemistry of coat liquefaction Is less well understood and how studies of this matter are Interpreted depends to some extent on how the "molecular" structure of coal Is perceived. 

The chemistry of a third group of conversion techniques -i.e., partial conversion methods which skim hydrocarbon gases and/or liquids from the coal and leave a char suitable for use as a boiler fuel or gasification feedstock - is. If anything, even more speculative than the chemistry of liquefaction. 

This paper touches on the chemistry of coal gasification and liquefaction comments on the current status of conversion processes and the influence of coal properties on coal performance in such processes and examines the contributions which coal conversion could make towards attainment of Canadian energy self-sufficiency. Particular attention is directed to a possible role for the medium-btu gas in long-term supply of fuel gas to residential and industrial consumers to linkages between partial conversion and thermal generation of electric energy and to coproduction of certain petrochemicals, fuel gas and liquid hydrocarbons by carbon monoxide hydrogenation. 

Equations of state (EOS) offer many rich enhancements to the simple pV = nRT ideal gas law. Obviously, EOS were developed to better calculate p, V, and T, values for real gases. The point here is such equations are excellent vehicles with which to introduce the fact that gases cannot be really treated as point spheres without mutual interactions. Perhaps the best demonstration of the existence of intermolecular forces that can also be quantified is the Joule-Thomson experiment. Too often this experiment is not discussed in the physical chemistry course. It should be. The effect could not exist if intermolecular forces were not real. The practical realization of the effect is the liquefaction of gases, nitrogen and oxygen, especially. 

In preceding sections, fundamental coal chemistry, liquefaction mechanisms, solvent and catalyst characteristics were summarized briefly. In the following three sections, the roles and improvements in solvents and catalysts in multistage liquefaction processes are reviewed in more detail on the basis of recent progress in this area. 

The ability to cool (and eventually liquefy) gases by adiabatic expansion underlies industrial gas liquefaction processes. Adiabatic cooling of gaseous nozzle-jet expansions is also an important technique in modem molecular beam and mass spectrometric research. Thermodynamicist John Fenn, winner of the 2002 Nobel Prize in Chemistry, pioneered many of the techniques of adiabatic nozzle-beam cooling. 

The methods of fractional liquefaction and distillation have very many similar and important applications in the chemistry of gases. 

---