TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Gas: The oxidizing gas is air. Preferred Catalyst: The alcohol modification catalyst contains rhodium and/or platinum, and additives (0.1-5%) consisting of alkali metal, iron, and/or cerium. The alkali metal is sodium, potassium and/or cesium.    TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Arrangement: The catalyst-performance decrement detector is an ethylene detector. The catalyst regenerator has an oxidizing-gas supplier (70) and a catalyst-regeneration controller. The alcohol modification catalyst is regenerated by supply of oxidizing gas. The catalyst-regeneration controller is equipped with a catalyst-exit temperature detector. The supply of oxidizing gas is carried out while change of catalyst-exit temperature is greater than 20 degrees C/second and is stopped when change of catalyst-exit temperature is less than 10 degrees C/second. The catalyst-regeneration controller is equipped with an alcohol-supply controller and a steam-supply controller. When the detector detects performance decrement of catalyst, after stopping supply of alcohol by the alcohol-supply controller and supply of steam by steam-supply controller, the oxidizing gas is supplied and the catalyst is regenerated. The catalyst-regeneration controller is the catalyst-exit temperature detector. An inert-gas supplier (80) and an inert-gas supply controller are provided. The heat supplier has an inlet and an exit for heat supply gas with respect to the modification reactor. The catalyst-performance decrement detector detects the temperature of gas inlet (41) and gas outlet (43) of heat supplier. When the gas-outlet temperature of heat supply gas is higher than gas-inlet temperature, the catalyst is regenerated. The oxidizing gas is supplied at a temperature range from room temperature to 500 degrees C. The oxidizing gas is supplied such that the catalyst-exit temperature does not exceed 800 degrees C. The oxidizing gas is supplied for every preset time.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Alcohol: The alcohol is ethanol or mixed alcohol of ethanol.