L.D. Sharma

The determination of accessible Pt metal fraction in Pt–Sn/Al2O3 reforming catalyst

Abstract An attempt has been made to provide a simple method for the determination of accessible Pt metal fraction in Pt–Sn/Al 2 O 3 catalyst. The complications in Pt–Sn/Al 2 O 3 system arise mainly due to uncertainties involved in the oxidation states of tin: Sn 0 , Sn 2+ and Sn 4+ in the reduced catalyst. H 2 , O 2 chemisorption/titrations originally applied to Pt/Al 2 O 3 were extended to the Pt–Sn/Al 2 O 3 system. Two oxygen titration cycles OT1 and OT2 at room temperature were carried out using a dynamic pulse flow technique. Only part of the total Sn in the catalyst is reduced to Sn 0 (15%), which contributes to oxygen uptake. While OT1 is a linear function of the Sn content in the catalyst, the second oxygen titration OT2 gives the accessible Pt metal fraction only. It has been concluded that oxygen chemisorption/titrations at temperatures higher than ambient under dynamic conditions are not reliable for the determination of metal dispersions.

Preparation and characterization of MgO/Al2O3 mixed oxides support for hydrotreating catalysts

The characteristics of pure MgO, Al2O3 and three binary mixtures of MgO-Al2O3 were studied by determining their BET surface areas, micropore surface area, total pore volume, adsorption-desorption isotherms, the x-ray diffractogram, surface acidity and catalytic functionality for cumene cracking.The XRD results show that the incorporation of alumina into the magnesia beyond 50% renders it amorphous. Furthermore, the mixed oxide containing 50% magnesia and 50% alumina had the highest BET surface area of 200 m2/g and is the only mixed oxide with bimodal pores.The results of the acidity measurements and cumene cracking functionality indicates that strong acid sites are found only in mixed oxides containing more than 50% alumina.

Characterization of Al2O3-ZrO2 Mixed Oxide Supported Mo Hydrotreating Catalyst

Abstract A series of molybdenum catalysts supported on Al2O3–ZrO2 mixed oxide containing 50% ZrO2 and 50% Al2O3 were prepared by incipient wetness technique and characterized by BET surface area, X-ray diffraction, temperature programmed reduction and oxygen chemisorption. The catalytic activities for hydrodesulphurization (HDS), hydrogenation (HYD), and hydrocracking (HYC) were determined using thiophene, cyclohexene, and cumene as model compounds, respectively. Results indicate that up to 8 wt% Mo loading, the catalyst is well dispersed and crystallite growth occurred beyond this loading. Also both oxygen uptake and catalytic activities increase with Mo loading up to 8 wt% and then decreases at higher loading. A linear correlation was obtained between oxygen uptake and all catalytic activities and the correlation coefficients obtained suggest that the order of catalytic activities for HDS, HYD, and HYC is: HDS > HYD > HYC. Furthermore, the catalytic activities of the mixed oxide supported catalyst for HDS, HYD, and HYC were higher than those supported on pure alumina and pure zirconia. The incorporation of 3% Co on 8% Mo catalyst was determined to result in enhanced activity for HDS, HYD, and HYC.