THE deposition of active agents onto adsorbentshas been employed widely to provide catalysts of increased activity, improved stability, greater selectivity, more convenient physical form, and lower cost (11). The development of a simple method for measuring surface areas of porous materials (1) provided a basis for correlating information on the action of adsorbents in this application. This work was undertaken to examine the relation of adsorbent area to catalyst activity for molybdena impregnated onto activated alumina as a catalyst for the dehydrocyclization of n-heptane to toluene. This reaction was reported with a variety of catalysts prepared in diverse manners on a number of supports (4, 5, 7, 9, 14, 15). investigation of the reaction mechanism indicates that an initial dehydrogenation is followed by cyclization and further dehydrogenation (S, 17, 18). Carbon skeleton rearrangement can take olace on a chromia-alumina catalyst (10). MATERIALS, APPARATUS, AND ANALYSISThe activated aluminas were products of the Aluminum Ore Company. The activated alumina F series analyzed: 2% loss on ignition, 0.1% Na20, 0.1% Si02, 0.05% FeA, and 0.7% Cl.The activated alumina H series analyzed: 4% loss on ignition, 0.1% Na»0, 7% Si02, 0.2% Fe203, '.3% CaO, 0.2% MgO, and 0.3% S03. Activated aluminas of the H series have one and a half to three times the surface area and pore volume, and more uniform pore widths as determined by sorption, than do those of the F series. Molybdena was obtained as Baker's Analyzed ammonium molybdate: 83% MoOs, 0.01% SO,, all other reported impurities less than 0.01%. Ammonia was Baker's Analyzed (meeting A.C.S. standards). The n-heptane, supplied by Westvaco Chlorine Products Company, had boiling point 98,42 °C., freezing point -90.65°C ., d^°0 .68371 gram per ml., and 21.38766. Tank hydrogen passed over hot copper and dried with activated alumina was used for catalyst reduction.Catalysts were prepared as follows: Ammonium paramolybdate was dissolved in distilled water (0.5 ml. per gram of alumina in the completed catalyst), and the quantity of concentrated ammonia necessary to convert the paramolybdate to the normal molybdate was added. The solution was boiled and the alumina added immediately wdth vigorous stirring. The excess water was removed by drying at 70-90°C. under overhead heat, with occasional stirring. "When the alumina appeared dry, in 4-6 hours, the sample was calcined 16 hours at 500°C.

The heat stability in dry air of molybdena-alumina catalysts has been measured as a function of alumina type, alumina area, and molybdena concentration.

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Only one series of experimental data on the hydrogen sorption of alumina is available in the literature. H. S. Taylor1"reported the sorption at 650 mm. and 445 and 525°to be of the order of 0.2 ml. STP/g. for an alumina formed by heating the precipitate from treating aluminum nitrate with ammonia. The heat of sorption was about 27,500 cal. per mole, sorption was reversible, and no water was formed during sorption and desorption. Th. Schoon and H. Klette2 did not give quantitative data but reported verification of the "stairlike form of the adsorption isotherm'' for hydrogen on a number of materials including alumina.The present work presents values of hydrogen sorption on various forms of alumina in the temperature range 400 to 900°, and in the pressure range 9 to 620 mm.