Hydrotalcites catalyst characterization

In another study, Mg-Al hydrotalcite catalysts with different Mg A1 molar ratios (0.6, 1.4, 2.2, 3.0) were characterized by microcalorimetry using CO2 in the gas phase and benzoic acid in toluene [95]. The calcined Al-rich sample (Mg A1 molar ratio of 0.6) possesses Lewis acid sites similar in strength to those found on AI2O3, but stronger than those found on the Mg-rich hydrotalcites. The liquid-phase basicity microcalorimetry measurements with benzoic acid in toluene correlated very well with the catalytic achvity for Michael addihons. 

Resini, C., Montanari, T., Barattini, L., et al. (2009). Hydrogen production by ethanol steam reforming over Ni catalysts derived from hydrotalcite-like precursors. Catalyst characterization, catalytic activity and reaction path, Appl.Catal. A Gen., 355, pp. 83-93. 

Turco M, et al. Production of hydrogen from oxidative steam reforming of methanol -I. Preparation and characterization of Cu/ZnO/Al2C>3 catalysts from a hydrotalcite-like LDH precursor. J Catal. 2004 228(l) 43-55. 

Narayanan, S. and Krishna, K. (1998). Hydrotalcite-supported palladium catalysts Part I preparation, characterization of hydrotalcites and palladium on uncalcined hydrotalcites for CO chemisorption and phenol hydrogenation. Appl. Catal. A 174, 221. 

The main purpose of this chapter is to review the applications of thermal analysis and calorimetric techniques to the study of catalysts such as oxides, heteropolyanions, hydrotalcites, layered silicates and microporous or mesoporous molecular sieves. A brief summary of studies that made use of calorimetry to characterize crystaUine or amorphous oxides and related materials is also presented. 

High-concentration NjO has been decomposed catalytically with four metal oxide systems which contain s, p, ti-block elements. In all cases, the decomposition reaction can be treated as first order with respect to partial pressure of N O, considering that decomposition product O2 exhibits no or little inhibition effect on the reaction. Optimal preparation conditions for the catalysts have been explored. In particular, chemical interaction between surface metals and carriers has been investigated. The catalysts have been characterized by various analytical techniques and general material issues have also been addressed. Among the four systems studied, Ru/AljOj and Mg-Co mixed oxides give best catalytic performance. For example, approximately 6 moles of NjO per kg of the hydroxide/hydrotalcite can be decomposed at 350°C within an hour. 

Magnesium-aluminium hydrotalcites are prepared with Mg/Al atomic ratios 2-7 and characterized by XRD, DTA, surface area measurements and acidity-basicity measurements. The tert-butylation of phenol is carried out on the calcined magnesium-aluminium hydrotalcites using isobutanol in the temperature range of350-500°C. The major products of this reaction are O-tert-butyl phenol and 2-tert-butyl phenol. Along with the normal alklyated products 0-butenyl phenol and 2-butenyl phenols are also obtained. A correlation between the product distribution and the nature of acid-base properties of the catalyst is studied. 

In this work, we studied the deactivation of Mg-Al mixed oxides in the gas phase oligomerization of acetone. We prepared and characterized calcined Mg-Al hydrotalcites with Mg/Al atomic ratios of 1-9. The effect of composition on both the surface and catalytic properties and the catalyst deactivation was investigated by combining several characterization methods with catalytic data. 

Rao et al. have developed a methodology based on simple condensation of ketones (methyl ethyl ketone and five-, six-, seven-membered cyclic ketones) with malononitrile and sulfur in presence of calcined Mg-Al hydrotalcite as heterogeneous catalyst (Scheme 66) [86]. Mg-Al hydrotalcites (Mg Al=4 l) having high basic properties, have been used as a mixed oxides precursor. The catalyst was fully characterized by XRD, thermogravimetry, and BET surface area measurements. The ratio of M(ll) and M(III) ions in calcined hydrotalcite was estimated by inductively coupled plasma emission spectrometry measurements. 

Mg-Al hydrotalcites (HTC) as heterogeneous base catalyst was studied for transesterification of soybean oil with methanol. It was found that oil to methanol ratio of 1 12 at a temperature of 60-65° C with 2.5% of catalyst and reaction time of 4 h were the optimized conditions. The characterization of the catalyst by (X-ray dilTraction) XRD pattern showed that MgO was the main substance present in the structure [59], Mg-Al hydrotalcite derived catalyst... 

Wang, S. H., Wang, Y. B., Dai, Y. M., and Jehng, J. M. Preparation and characterization of hydrotalcite-like compounds containing transition metal as a solid base catalyst for the transesterification /rp/ierf Catal A General 439 40,135-141 (2012). 

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