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The ruthenium catalyst can be utilized at high pressures, the operation resulting in wax yields.  With increasing pressure, the yield and molecular weight of the paraffins formed are increased.  Some experiments have been made at 1000 atms. pressure, but no life test has been made under these conditions.  A two-year life test has been carried out using this catalyst at 100 atms.

Ruthenium does give carbonyls but these seem to decompose readily with H2 without loss of metal.  The catalyst is more susceptible to sulfur poisoning.  Thus, with 1.0 g. S/100 cu.m. of synthesis gas, poisoning is produced in a few weeks.  (Contraction is educed by 1/2 in 3 weeks).  0.3 g. S/100 cu.m. of gas gives poisoning in a few months, while no poisoning is obtained when the S concentration is less than 0.01 g. S/100 cu.m. of synthesis gas.  This tendency to undergo poisoning by such small amounts of S is not exhibited by iron, nickel or cobalt catalysts.  The last three catalysts are different in the respect that sulfides are actually formed throughout the catalyst, and 20-30% of the metal has to be converted to the sulfide in order to show poisoning.