Selective front-end hydrogenation method for alkynes and/or dienes in C-2-fractions and C-3-fractions

The invention provides a selective front-end hydrogenation method for alkynes and/or dienes in C-2-fractions and C-3-fractions. The method comprises the steps that cracked gas material flow flowing out of the tower top of a front depropanizer and the tower top of a front dethanizer is mixed with hydrogen-rich gas material flow comprising carbonic oxide to obtain mixed hydrogen-rich cracked gas material flow with the stable content of the carbonic oxide, and then the mixed hydrogen-rich cracked gas material flow is subjected to a contact reaction with a palladium supported selective hydrogenation catalyst. Through the front-end hydrogenation method provided by the invention, temperature runaway and alkyne leakage of a hydrogenation reactor due to drastic fluctuation of the carbonic oxide in the cracked gas produced through a front system can be effectively avoided. Under the condition of high space speed, the activity and selectivity of the catalyst can be effectively improved through the method provided by the invention, and the using amount of catalyst active components is reduced.