Alumina by calcination, reactor

Dehydration Catalysts. In the production of amines from alcohols and ammonia or from alcohols and various amines, catalysts prepared by dehydrating alumina or silica gel are generally used. For specific reactions, these catalysts are promoted with various metals, their oxides or salts. For example, a dehydration catalyst has been made by incorporating aluminum phosphate in alumina gel prior to dehydrating the gel. An amination catalyst made by treating absorptive alumina with calcium and copper nitrates, followed by calcination and then reduction with hydrogen in a vapor-phase reactor, was used to produce an excellent yield of mono-methylaniline from aniline and methanol. ... 

Catalysts - A commercial Raney nickel (RNi-C) and a laboratory Raney nickel (RNi-L) were used in this study. RNi-C was supplied in an aqueous suspension (pH < 10.5, A1 < 7 wt %, particle size 0.012-0.128 mm). Prior to the activity test, RNi-C catalyst (2 g wet, 1.4 g dry, aqueous suspension) was washed three times with ethanol (20 ml) and twice with cyclohexane (CH) (20 mL) in order to remove water from the catalyst. RCN was then exchanged for the cyclohexane and the catalyst sample was introduced into the reactor as a suspension in the substrate. RNi-L catalyst was prepared from a 50 % Ni-50 % A1 alloy (0.045-0.1 mm in size) by treatment with NaOH which dissolved most of the Al. This catalyst was stored in passivated and dried form. Prior to the activity test, the catalyst (0.3 g) was treated in H2 at 250 °C for 2 h and then introduced to the reactor under CH. Raney cobalt (RCo), a commercial product, was treated likewise. Alumina supported Ru, Rh, Pd and Pt catalysts (powder) containing 5 wt. % of metal were purchased from Engelhard in reduced form. Prior to the activity test, catalyst (1.5 g) was treated in H2 at 250 °C for 2 h and then introduced to the reactor under solvent. 10 % Ni and 10 % Co/y-Al203 (200 m2/g) catalysts were prepared by incipient wetness impregnation using nitrate precursors. After drying the samples were calcined and reduced at 500 °C for 2 h and were then introduced to the reactor under CH. 

The catalyst bed was a coated wall reactor using commercial CuZnAl catalyst. An alumina sol was used to enhance the adhesion of the catalyst to the channel walls. After the shims were washed thoroughly, the alumina adhesion layer was deposited using an alumina sol (NYACOL AL20DW colloidal alumina, PQ Corporation) and then dried at 60 °C. To decrease the surface tension of the wash-coat solvent, small amounts of 2-propanol were added to a catalyst slurry of ICI Synetix 33—5 catalyst, with 20 wt % alumina sol and water. The catalyst was calcined at 350—400 °C for 2 h after air-drying. Before testing, the catalyst was reduced by flowing H2/N2 over it at 280 °C. 

Capping. Capped silica-alumina was prepared by vapor phase transfer of hexamethyldisilazane (> 99.5%, Aldrich) onto calcined silica-alumina until there was no further uptake, as indicated by stabilization of the pressure. The reactor was evacuated and the material heated to 350°C under dynamic vacuum for 4 h to remove ammonia produced during the capping reaction. 

Entrained flow reactor (riser) This is a fluidized-bed reactor in which the solid is entrained by the fluid phase and is recycled throughout the operation (Figure 3.9). Some applications of this reactor type are the modem FCC process and the calcination of alumina hydrate. 

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