PROCESS FOR HYDROGENATION LIQUID FRACTIONS C 3

Liq. 3C fractions are selectively hydrogenated in the trickling liq. phase in the presence of a supported Pd catalyst fixed in a tubular reactor. The catalyst packing consists of 2 superimposed layers. In the bottom layer, the catalyst contains 0.5-5 wt.% Pd and opt. 5 wt.% Ag, Cu, Ni, Fe, Cr, Mo, W, Zn and/or Cd, in metallic or oxide form, as promoters, on a macroporous, Al oxide-contg. support having specific surface max. 50 m2/g and SiO2 content 10 wt.%. The top layer catalyst contains 0.1-1 wt.% Pd on a macroporous Al2O3 support having specific surface max. 25 m2/g. Over 50 pore vol. % consists of pores having radii >500 angstroms. Total catalyst bed level is 2-6 (3-5) m. Bed level ratio of bottom to top catalyst layers is 0.5-10 (1.5-7). Ratio of an internal catalyst tube dia. to catalyst blank dia., level or length is 4-30. The 3 C crude fraction contains 9 (3.5-7) wt.% propyne + propadiene. Hydrogenation takes place in reactor without recycling the hydrogenated 3 C fraction, at 5-50 degrees C under pressure 10-35 kp/cm2, at a total catalyst bed charge with liq. 3 C fraction 40 (5-25) kg/l. hr. Molar ratio N2 : total C3H4 cpds. is 1-10 (1.2-2). The reaction gas contains >=70 (85) vol.% H2. The catalysts allow high process selectivity, do not coke and have long service-life. Propyne and propadiene can be degraded down to 10 ppm, i.e. C3H4 conversion can reach =99%.