The answer lies here:
Industrially, silane is produced from metallurgical grade silicon in a two-step process. In the first step, powdered silicon is reacted with hydrogen chloride at about 300 °C to produce trichlorosilane, HSiCl3, along with hydrogen gas, according to the chemical equation:
Si + 3 HCl → HSiCl3 + H2
The trichlorosilane is then boiled on a resinous bed containing a catalyst which promotes the formation of silane and silicon tetrachloride according to the chemical equation:
4 HSiCl3 → SiH4 + 3 SiCl4
The most commonly used catalysts for this process are metal halides, particularly aluminium chloride. This is referred to as a redistribution reaction, which is a double displacement involving the same central element. It may also be thought of as a disproportionation reaction even though there is no change in the oxidation number for silicon (Si has a nominal oxidation number IV in all three species). However, the utility of the oxidation number concept for a covalent molecule, even a polar covalent molecule, is ambiguous. The silicon atom could be rationalized as having the highest formal oxidation state and partial positive charge in SiCl4 and the lowest formal oxidation state in SiH4 since Cl is far more electronegative than is H.
An alternative industrial process for the preparation of very high purity silane, suitable for use in the production of semiconductor grade silicon, starts with metallurgical grade silicon, hydrogen, and silicon tetrachloride and involves a complex series of redistribution reactions (producing byproducts that are recycled in the process) and distillations. The reactions are summarized below:
Si + 2 H2 + 3 SiCl4 → 4 SiHCl3
2 SiHCl3 → SiH2Cl2 + SiCl4
2 SiH2Cl2 → SiHCl3 + SiH3Cl
2 SiH3Cl → SiH4 + SiH2Cl2
The silane produced by this route can be thermally decomposed to produce high-purity silicon and hydrogen in a single pass.
Still other industrial routes to silane involve reduction of SiF4 with sodium hydride (NaH) or reduction of SiCl4 with lithium aluminum hydride (LiAlH4).
Another commercial production of silane involves reduction of silicon dioxide (SiO2) under Al and H2 gas in a mixture of NaCl and aluminum chloride (AlCl3) at high pressures:
3SiO2 + 6H2 + 4Al → 3SiH4 + 2Al2O3
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In short, you get some free hydrogen from chemically processing sand. So yes, theoretically you can turn sand into fuel, but the hydrogen comes from the hydrochloric acid used to process the sand, NOT The sand itself. While silane gas is flammable, you probably wouldn't want to put it in your car, even in liquid form, as the silicon buildup would invariably destroy your engine. And let's not even talk about the effects of molecular silicon dust being inhaled in huge quantities.
Also, lithium aluminum hydride, featured in this process, has been researched for use in storing hydrogen in fuel cells. Check that out here: https://en.wikipedia.org/wiki/Lithium_aluminium_hydride#Hydrogen_storage