NOVELTY - Preparation of silane involves simultaneously reducing and oxidizing alkoxysilane in presence of catalyst to obtain gaseous silane which is purified by adsorption and a liquid product containing tetra-alkoxysilane which is extracted with alcohol, which are hydrolyzed to silica sol and alcohol.    USE - For preparing high purity silane used for forming thin layer semiconductor structures, including critical parts of integrated circuits. High purity polysilicon and single crystal silicon produced from high purity silane are applied in the field of electronics, such as in infrared receivers and nuclear radiation detectors. Solar grade silicon produced from high purity silane is used in photovoltaic solar cell production. Tetra-alkoxysilane extracted from liquid products is used as absorber.    ADVANTAGE - High purity silane is obtained. Energy required for extracting alcohol from condensed products, in the preparation of high purity silane, is very less. The process of preparing high purity silane requires low temperature and eliminates the break-up of silicon-hydrogen bonds in di- and tri-alkoxysilane. This increases the output of silane. Purification of alkoxysilanes is simple and the products are practically free from impurities. The process generates no wastes and thus is ecologically safe. The unreacted alcohol from silicon-alcohol reaction and the active part of catalyst in simultaneous oxidation and reduction reaction are reused. The method employed reduces consumption of raw materials due to recycling of alcohol, reuse of catalyst and increase in output of silane.    DETAILED DESCRIPTION - Preparation of silane involves forming an alkoxysilane by reacting silicon and alcohol at high temperature, separating and purifying the product, followed by simultaneously reducing and oxidizing the purified alkoxysilane at a temperature between -20 to 40 degreesC for 1-50 hours, in presence of a catalyst. A mixture containing gaseous silane and a liquid which contains a portion of catalyst, tetra-alkoxysilane and an impurity compound containing silicon-hydrogen bond are obtained. The gaseous silane is purified by adsorption and the liquid product is mixed with alcohol to extract tetra-alkoxysilane which is then hydrolyzed to produce silica sol and alcohol.