| abstract |
A catalyst comprising a high surface area porous silica containing 1-10% by weight of an alkali metal (expressed as metal), in which the catalyst contains a boron compound as a modifying element in such an amount that the catalyst contains a total of 0.39 to 3.9 gram atoms of said boron modifying element per 100 moles of silica, said modifying element compound being dispersed in the pores of said silica and wherein the porous silica of high surface area is selected of gel silicas, precipitated gel silicas and agglomerated pyrogenic silicas. |