The Catalytic Behavior of Hydrochloric Acid Treated Neodymium Oxide. Isomerization of I-Pentene Andrew T. Welper and Howard F. Rase* Department of Chemical Engineering, The University of Texas at Austin. Austin, Texas 78712
Neodymium oxide was shown to b e h a v e similarly to aluminum oxide w h e n pretreated with HCI and used a s a catalyst for t h e isomerization of 1 -pentene. Skeletal isomerization and higher intrinsic activity are induced in both by HCI treatment.
The character and catalytic behavior of rare earth oxides have recently been demonstrated to parallel that of active alumina (Tosun and Rase, 1972). Surface hydroxyl groups and oxygen bridges have been shown to be the major active centers in each. These active species may be altered by pretreatment in various ways to obtain desired catalytic properties. The apparent similarity between neodymium oxide and alumina as shown by Tosun and Rase (1972) for ethanol dehydration encourages further study of rare earths on other important reactions for which substantial studies on alumina exist. The reaction system selected for the present investigation is the isomerization of 1-pentene. This is representative of one of the major classes of reactions occuring in such important processes as catalytic reforming and hydrocracking. It is in these processes where alumina has been extensively used as a carrier for the precious metallic component Pt or Pd while serving as the acid catalyst in these dual-functional catalysts. For this later purpose the alumina is treated with chlorides such as HC1 to maximize the acidic character (Ciapetta and Wallace, 1971; Giannetti, et al., 1970). Although one might expect similar behavior with neodymium oxide because of the already documented similarities in surface structure, it is by no means assured. The more than twice larger ionic radius of neodymium compared to aluminum ions produces major differences in geometry that may affect selectivity and activity. To test such possibilities the technique for activating commercial neodymium oxide described by Tosun (1971) was used for preparing samples with and without HCl treatment. The resulting activity and selectivity were then compared with HC1-treated and untreated activated alumina. Experimental Section Catalyst. Commerical neodymium oxide, manufactured by American Potash and Chemical Corp., Chicago, Ill., of 99.9% purity (0.170 other rare earth oxides) was transformed to the nitrate by treatment with nitric acid and thence to the hydroxide using ammonium hydroxide as described by Tosun (1971). After thorough washing, the hydroxide was air dried for 16 hr a t 120°C and then ground to particles 60 mesh or less in size. The powder was then calcined in an electric furnace a t 550°C for 10 hr, rapidly cooled, and stored under helium. This produced the porous active form of Ndz03 described by Tosun and Rase (1972) and was used both as untreated catalyst and as the catalyst subjected to pretreatment with gaseous HCl. The surface area was 18.6 m2/g. A low-soda y-alumina was a special sample prepared and supplied by Aluminum Company of America (Sample No. 58-C-7779) and used as received and also pretreated with HCl. The sodium content was
