Page 296 - Principles of Catalyst Development

INDEX 287

Semiconductors (cont.) Spinel (cont.)
doping of, 39 reactions between, 108
electronic band structure of, 63, 67 Spheres
intrinsic, 63 manufacture of, 129
n-type, 65 pressure drop with, 10
oxides, 28 Stability, of silica gels, 100
p-type, 65 Steam cracking, 242
sulfides, 28 Steam reforming, 242
types of, 66 catalyst requirements for, 30
Sensitivity, 241 coking in, 221
Shape selectivity collapse of pores in, 195
in coking, 212 deactivation in, 189
in zeolites, 75, 78, 80 loss of mechanical strength in, 192
Shift reaction, 241 of methane, 24
Side chain, 241 of naphtha. 20, 193
Silica loss of potassium in, 48, 193
gels, 33, 100 process demands on, 43
recipe for, 259 loss of silica in, 43
as spheres, 129 Straight run gasoline, 242
as a structural promoter, 193 Substitute natural gas (SNG), 21, 28, 242
surface area of, 148 Sulfides
Silica alumina as catalysts, 70
acidity of, 168 as semiconductors. 66
acid sites in, 73 Sulfiding. of hydrodesulfurization catalysts,
carbonium ion reactions with, 74 120
coking on, 211 Supersaturation, in sol precipitation, 97
manufactured as spheres, 129 Supports
metal porphorin contamination in, 218 function of. 28
particle size distribution, 143 metal interactions with, 60
potassium promotion of, 214 oxides as. 31
preparation of. 106 Surface
recipe for, 260 accessibility. 162
Silver, reactions catalyzed by, 62 dilution in alloys. 59
Sintering mechanisms in catalyst design. 89
of colloidal metals, 29 metal sites. 61
in deactivation, 194 morphology, 158
mechanisms of, 195 structure of, 161
of supports, 195 Surface area
Skeletal density, 141 apparatus for measuring. 149. 150. 151
Small angle x-ray scattering, 160 external. 12
Smoke point, 241 importance of. 9
Sodium, as a promoter, 36 measurement of. 9
Solid acids, reactions catalyzed by, 27, 75 nomenclature. II
Sols Surface diffusion. 16
adsorption of, 109 Synthesis gas. 242
gelation of. 101
preparation of, 97
Sour or sweet crude, 241 Tahlets. pressure drop with. 10
Specific rate, 172 Tamm temperature. 29
Spinel Temperature programmed reduction (TPR),
AI 20 3 as a defect, 105 140