Route map for 100％completion of solid-state reactions
Although thermodynamics tells us that solid-state reactions without solution will not stop until 100％com-pletion,they may stop far before the exhaust of reactants because of the difficulty of mass transfer among the solid particles.To solve this problem,the author has publicized a novel technique called the less solvent solid-state reac-tion(LSR),which makes small parts of the solid reactants dissolve and react in a small amount of solvent,thus mak-ing the reaction proceed faster and more complete in a stirred reactor.Consequently,LSR could make some of the industrial processes greener.By using numerical calculating and charting of its Gibbs energies with respect to its extent of reaction,this paper proves that(i)an LSR is a combination of a reaction thermodynamically equivalent to a solution-free solid-state reaction in the middle and semi-solution reactions at both ends.Although the LSR does reach an equilibrium eventually,it goes much further to the 100％completion than the solution reaction;if the sol-vent is removed gradually at the ending period of the reaction,the LSR can be pushed to 100％completion;(ii)for the consecutive reactions,it is possible to get the sole intermediate product by controlling the molar ratio of the reac-tants as its stoichiometric ratio;(iiD it is possible to make an LSR with near-zero negative △,Gmϴ 100％completed by using more solvent or using the solid products as seeds;(ⅳ)it is the dissolution speed of reactants,the speed of chem-ical reaction,and crystallization speed of products,rather than the solubilities of the substances that control the speed of an LSR.Measures for 100％completion and selection of LSRs of non-spontaneous or coexisting competi-tive reactions are also discussed.
less solvent solid-state reactionsolid-state reactionsolution reactionGibbs energygreener chemistry100％conversion
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