1245.    ---------------.  [GREAT BRITAIN FUEL RESEARCH BOARD.] Synthesis of Methane.  6^th Annual Rept., 1944-45, pp. 18-32.

        Since the 5^th report (see abs. 1224) a medium-scale plant has been designed to allow purification from S compounds of the synthesis gas, the modification of the proportions of H₂ and CO in the gas, and the division of the gas into streams for evaluation of a number of variables including pressure, each stream carrying about 250 cu. ft. of gas per hr.  Methods were recorded in the 5^th report for controlling the heat of reaction by (1) recirculation of gas, (2) the use of rod-shaped catalysts over which streamline conditions of flow were maintained, so that the rate of diffusion of gas to the surface of the catalyst controlled the rate of reaction by giving a natural distribution over a wide surface, and (3) the use of forced distribution by means of a perforated feed pipe extending over a length of catalyst surface.  Using methods (2) and (3), life periods of over 2,000 hr. were maintained at gas velocities of 2,000 vol. per vol. of catalyst per hr., and with method (3) it was possible to use a synthesis gas as low as 1.0 in H₂ : CO ratio, and to avoid C deposition for 2,700 hr.  Some study of the reactions involved in C deposition were made.  Variations have been made with some success in the composition of the standard Ni catalyst, with the object of preventing deposition of C.  Further studies have also been made of the increases in temperature over the catalyst surface and of the connection between this temperature and loss of activity due to sintering.  Little success has been obtained in employing MoS as a CH₄-forming catalyst resistant to poisoning by S, but the potentialities are so great that the work will be continued.  Experimental details are given in tabular and graphic form on the effect of additions to the catalyst of S, Mn, and Al on C deposition; S up to 0.2% of the Ni and Al in excess were favorable in their effect.  Mn favored C deposition.  The X-containing catalyst resists sintering less effectively than does the Al-containing catalyst.  Other experiments studied the influence of space velocity, control temperature, and size of catalyst granule upon the maximum temperature developed in a column of granulated catalyst at atmospheric pressure with dissipation of reaction heat.  The mechanism of C deposition on the Ni catalyst involves the formation of NiC by the reaction between CO and Ni at 200° and the subsequent breakdown of this into Ni and C.  The Fuel Research Station has studied the effect of the carrier on C deposition on catalysts of Ni-ThO₂-MgO-kieselguhr and has concluded that a kieselguhr with low specific surface area promotes the most rapid C deposition.  Calcination of the kieselguhr is best carried out at 700°-800°.  It was also found that the effect of heating the catalyst in H₂ was to decrease the activity for CH₄ synthesis and to increase the tendency to deposit C.  The addition of small proportions of P and S reduces its tendency to C deposition but increases the rate of deterioration; the addition of 0.2% S as NiSO₄ reduced the rate of C deposition with process gas H₂:CO = 1.5:1 from 0.462% to 0.157%, but reduced the active life with gas of H₂:CO=3.0:1 and space velocity 3,700 vol. per vol. per hr. from 1,700-910 hr.