Energy efficient synthesis of boranes

Abstract

The reaction of halo-boron compounds (B—X compounds, compounds having one or more boron-halogen bonds) with silanes provides boranes (B—H compounds, compounds having one or more B—H bonds) and halosilanes. Inorganic hydrides, such as surface-bound silane hydrides (Si—H) react with B—X compounds to form B—H compounds and surface-bound halosilanes. The surface bound halosilanes are converted back to surface-bound silanes electrochemically. Halo-boron compounds react with stannanes (tin compounds having a Sn—H bond) to form boranes and halostannanes (tin compounds having a Sn—X bond). The halostannanes are converted back to stannanes electrochemically or by the thermolysis of Sn-formate compounds. When the halo-boron compound is BCl3, the B—H compound is B2H6, and where the reducing potential is provided electrochemically or by the thermolysis of formate.

Description

RELATED APPLICATIONS [0001] This application claims the benefit of copending U.S. Provisional Patent Application No. 60 / 771,739, filed Feb. 8, 2006 and entitled “Energy Efficient Synthesis of Boranes,” which is incorporated by reference herein.STATEMENT REGARDING FEDERAL RIGHTS [0002] This invention was made with government support under Contract No. DE-AC51-06NA25396 awarded by the U.S. Department of Energy. The government has certain rights in the invention.FIELD OF THE INVENTION [0003] The present invention relates generally to hydrogen storage, and more particularly to an energy efficient synthesis of boranes (boron compounds having at least one B—H bond). BACKGROUND OF THE INVENTION [0004] Hydrogen (H2) is currently the leading candidate for a fuel to replace gasoline / diesel fuel in powering the nation's transportation fleet. There are a number of difficulties and technological barriers associated with hydrogen that must be solved in order to realize this “hydrogen economy”. In...

AI Technical Summary

Benefits of technology

[0019] The invention also includes a method of forming halo-boron compounds suitable for reduction to boranes. The method involves reacting a boron compound selected from the group consisting of alcoholato-boron compounds, catecholato-boron compounds, amino-boron compounds, and anilino-boron compounds with a compound of the formula HX wherein X is selected from the group consisting of halogens; and thereafter separating a product halo-boron compound.

[0020] The invent

Problems solved by technology

In principle, this chemical storage system is attractive, but systems that have been developed to date involve either: (a) hydrolysis of high-energy inorganic compounds where the evolution of hydrogen is very exothermic (sodium borohydride / water as in the Millennium Cell's HYDROGEN ON DEMAND®, and lithium (or magnesium) hydride as in SAFE HYDROGEN®, for example), thus making the cost of preparing the inorganic compound(s) high and life-cycle efficiency low; or (b) dehydrogenation of inorganic hydride materials (such as Na3AlH6 / NaAlH4, for example) that release hydrogen when warmed but that typically have inadequate mass storage capacity and inadequate refueling rates.

Any heat that must be input to evolve the hydrogen represents an energy loss at the point of use, and any heat that is evolved along with the hydrogen represents an energy loss where the chemical storage medium is regenerated.

Either way, energy is lost, which diminishes the life-cycle efficiency.

Thus, most organic compounds are unsuitable for hydrogen storage, based on both life-cycle energy efficiency and delivery pressure considerations.

Thus, this endothermic hydrogen evolution reaction requires both a complex apparatus and high-grade heat, which diminishes the life-cycle energy efficiency for hydrogen storage.

Boranes have high hydrogen storage capacities and have attracted interest for use as hydrogen storage materials for transportation, but the difficulty of manufacturing borane compounds, and the life-cycle energy inefficiency of the chemical process presently used for their manufacture, has prevented their widespread use.

While convenient to practice on a small or intermediate laboratory or commercial scale, these reactions are not energy-efficient; the reaction of NaH with B(OCH3)3 is exothermic, and NaH is itself formed in the exothermic reaction of Na metal with H2, so overall, about 22 kcal of heat are released per B—H bond that is formed.

Their corrosive properties in combination with the difficulties of heat management make this process costly to practice.

Presently, there is no energy efficient means available for preparing boranes.

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