The conversion of carbon monoxide and hydrogen to produce a mixture of low molecular weight hydrocarbons which, on a methane-free basis, contain a predominance of C.sub.2 -C.sub.6 paraffins is achieved using as the catalyst a rare earth metal promoted layered complex metal silicate composition characterized as having repeating units of the structural formula[(1-x)Ni.sup.a + xRu.sup.6 ].sub.n (OH).sub.4 Si.sub.2 O.sub.5.wH.sub.2 Owhere x is a number from 0 to 1, this number expressing the atomic fraction of the metals nickel and ruthenium; a is the valence of nickel; b is the valence of ruthenium; n is a number equal in value to that defined by the ratio6/[a(1-x) + bx]and w is a number ranging from 0 to 4. A rare earth promoted nickel chrysotile is the preferred catalyst.