Pressure-change absorption separation method for ethylene and hydrogen from refining plant dry gas

The invention relates to a method used to separate ethylene and hydrogen at the same time from the dry gas of an oil refinery, in particular to a method used to separate ethylene and hydrogen from the dry gas of an oil refinery through pressure swing adsorption. The method is carried out according to the following: the first step: elimination of carbon dioxide is completed; the second step: dehydration is completed; the third step: the extraction of ethylene is realized through pressure swing adsorption; and the fourth step: the recovery of hydrogen is finished through pressure swing adsorption. The method has the advantages that: both ethylene and hydrogen are separated from the dry gas of an oil refinery along with better separation effect, a simple flow and low energy consumption; the raw material adopted by the method has low price and adapts well to the raw gas of the dry gas of an oil refinery; valuable resource is obtained from waste gas and is used to further manufacture subsequent products with high added value; meanwhile, the method reduces atmospheric emission to protect the environment and has a long service life of equipment, low operating cost and lower cost; moreover, the method is especially suitable to make the raw material of a propionaldehyde production device which adopts water-soluble rhodium-phosphine complex compound as catalyst.