J.K. Gupta

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.

Acidity studies on titanium silicalites-1 (TS-1) by ammonia adsorption using microcalorimetry

Abstract Various titanium silicates (TS-1) synthesized following two different routes by conventional method and by sol-gel method have been characterized by microcalorimetric adsorption of ammonia. Calorimetric measurements of a basic probe (NH3) have shown that these solids were very acidic compared to a silicalite-1 sample. An introduction of a small amount of titanium creates acid sites of higher order in the medium strength range at low Ti contents (i.e., high Si/Ti ratios) in both sample prepared by conventional and sol gel methods. The sample prepared by sol-gel method (SGM) found to possess stronger acidity compared to conventional preparations and this especially so at higher titanium content. The molecular sieve with low titanium contents displayed acid strength distribution more similar to silicalite. The unavoidable presence of chlorine is found to be responsible for the observed higher acidity in incipient wetness impregnated samples.

Relationship between acidity and catalytic activity of chlorided alumina supported Pt-Sn catalysts

Abstract The acidity and acid strength distribution of chlorided γ-aluminas and mono and bimetallic catalysts containing Pt and Sn metals supported on a chlorided γ-Al 2 O 3 were measured by microcalorimetry and temperature programmed desorption (TPD) techniques. The addition of chlorine to γ-Al 2 O 3 creates new stronger acid sites. The total acid site density also increases with increasing chlorine content in the alumina support. The addition of tin to chlorided alumina suppresses the stronger acid sites. The catalytic activity for dehydration and dehydrogenation of 2-propanol on these catalysts was evaluated. A correlation between strong acid sites and dehydration activity was established.

Effect of method of preparation on hydrodesulphurization activity of Co- or Ni-promoted MoS2/SBA-15 catalysts

Abstract.Ordered mesoporous material SBA-15 was synthesized and used as a support for the preparation of molybdenum sulphide catalysts through precipitation from homogeneous solution (PFHS) technique with the Mo content varying from 2–12 wt%. The prepared catalysts were evaluated for thiophene hydrodesulphurization catalytic activities at 400°C. Catalysts prepared through PFHS method resulted in highly dispersed MoS2 catalysts, which were inferred from powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), low temperature oxygen chemisorptions (LTOC) and BET surface area analysis. The relationship between XPS intensity ratio, oxygen chemisorption and catalytic activities is discussed in terms of highly dispersed nano particles of MoS2 and its consequence in accommodating more promoted atoms at the edge sites. Figure.The ordered mesoporous material SBA-15 prepared using triblock polymer is used to prepare Mo, CoMo, and NiMo catalysts by PFHS technique. A comparison with γ-Al2O3-supported catalysts indicated that this support and preparation method combination increases the activities by about three times.

Effect of preparation method and the nature of sulfated mixed oxide catalysts on the acid strength distribution

Abstract The supports used for sulfated ZrO 2 , ZrO 2 -Al 2 O 3 , ZrO 2 -SiO 2 were prepared by ammonia hydrolysis and precipitation from homogeneous solutions (PFHS) methods. Microcalorimetric measurements of ammonia adsorption indicates the sulfation of metal oxides caused the enhancement of acid sites with ΔH > 130 kJ/mol. High acid strength distribution and surface area of ZrO 2 -Al 2 O 3 /SO 4 2 was obtained by sulfation of a support, prepared by PFHS method than the co-precipitation method but it was reverse in the case of ZrO 2 /SO 4 2 . Higher initial heat of adsorption, 178 kJ/mol was observed on ZrO 2 - Al 2 O 3 /SO 4 2 with low density of acid sites in which support was prepared by co-ppt. method. High surface area SO 4 2 /ZrO 2 -SiO 2 have the similar strength and distribution of acid sites present in sulfated zirconia with ΔH 158 kJ/mol. All the sulfated mixed oxides were amorphous at 620°C.