Catalysts characterisation

The reaction on the catalyst surface was followed by in situ i.r. spectroscopy using a Bruker IFS88 FTIR spectrometer for the characterisation of sorbed species and mass spectroscopy for the analysis of gas phase. The state of Pt was further investigated by in situ X-ray absorption spectroscopy (Daresbury, UK, beamline 9.1, transmission mode, Si(220) monochromator, Pt-Lj, edge). Details of catalyst characterisation techniques are reported elsewhere [13,14]. 

A variety of catalysts were used to examine the effect of changing pore size, metal crystallite size, and catalyst particle size. The catalyst characterisation is reported in Table 1. 

Metallocene catalysts show low r values, which allows easy incorporation of bulky cycloolefins into the growing copolymer chain. Surprisingly, the ethylene reactivity ratio in copolymerisation with cyclopentene in the presence of a (ThindCH2)2ZrCl2-based catalyst (r = 2.2) and in copolymerisation with norbornene in the presence of catalysts characterised by Cs and Ci symmetry (ri 3.4 and 3.1 respectively) is considerably lower than that for the copolymerisation of ethylene with propylene (r = 6.6 at 37 °C). Various catalysts produce copolymers of structures that are between statistical and alternating [468]. 

It has been found that the polymerisation of propylene oxide with catalysts characterised by an isolated metal atom surrounded by a porphyrin [49,50], Schiffs base [40,51] or calix[4]arene [41] moiety also proceeded by Cp—O bond cleavage. 

This manual has been prepared by the Commission on Colloid and Surface Chemistry including Catalysis of the IUPAC. It complements the Manual on Catalyst Characterisation which concerned nomenclature [1] and should be read in conjunction with this earlier manual. The Manual of Methods and Procedures for Catalyst Characterization provides details and recommendations concerning the experimental methods used in catalysis. The objective is to provide recommendations on methodology (rational approaches to preparation and measurements). It is not intended to provide specific methods of preparation or measurement, nor is it concerned with terminology, nomenclature, or standardization. 

Manual on Catalyst Characterisation, Pure Appl Chem 1991, 63, 1227... 

Catalyst characterisation was performed using thermal analysis and DRIFTS. Thermal analysis was performed using a NETZSCH 409 STA with a temperature ramp of 10°C/min. Acid site determination was performed using pyridine titration in conjunction with DRIFTS (Bruker Equinox 55 FTIR). Pyridine vapour was adsorbed over a period of 24 hours prior to recording the DRIFTS spectrum. 

The range of pore sizes important to good catalytic function are from around 1OA in the supported zeolite to perhaps 100,000 A (10 pm) in the zeolite/silica-alumina composite. The technique of gas adsorption is of little use beyond about 250A, so that by far the largest range of important pore sizes (and related interactions between pores which constitute the pore structure of the particle) are assessable only through the mercury porosimetry technique. Many practitioners in catalyst characterisation claim that... 

Garbowski, E. and Prahaud, H. (1994) in Catalyst Characterisation Physical Techniques for Solid Materials (eds B. Imelik and ).C. Vedrine), Plenum Press, New York, chap. 4. 

We have reported that (Al,Sb,V)204 is the active phase for propane ammoxidation in Al-rich Al-Sb-V-0 catalysts [5]. Figure 7 shows for a slurry preparation with Al Sb V = 21 5 1 the dependence of the catalytic performance with time-on-stream. The propane conversion and the selectivities show almost constant behaviour, indicating that the active structure is formed in the synthesis of the catalyst. Characterisation with FTIR, FT-Raman, XPS and X-ray diffraction before and after use in ammoxidation showed no difference [5]. 

The catalyst, characterised by BET, possessed a surface area of 12 m. g" with a dispersion of platinum, measured by pulse CO chemisorption of 35%. 

TPD experiments can be carried out either in ultra high vacuum or at ambient pressure under flow condition. Thus they can bridge the material and pressure gaps between surface science and heterogeneous catalysis. Despite the popularity of TPD as a catalyst characterisation method its application in kinetic analysis for porous samples is often being discouraged. There are indeed important methodical considerations such as the selection of the reactor model and the intrinsic kinetic model and the evaluation of mass transfer limitations. Furthermore, experimental data with sufficient information content should be collected in a carefully selected and standardised manner, since the pretreatment and the adsorption step prior to TPD significantly influence the TPD patterns. 

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