The growth and characterisation of supported metal catalysts prepared by novel chemical vapour deposition methods
A novel TCVD procedure was employed for the preparation for thepreparation of supported gold catalysts using dimethyl goldacetylacetonates Me 2 Au(acac) as the volatile precursor. Preliminaryexperiments on the use of TCVD for the preparation of coppercatalysts from copper acetylacetonate Cu(acac) were also performed.The reactor design and the preparation protocol employed were usedfor the first time during current investigation. The impact ofcalcination conditions, system vacuum along with different pretreatmentshave been reported for better understanding of TCVDprocedure.Similarly CCVD have been presented for the first time as analternative procedure for the preparation of highly effective,uniformly dispersed supported Au, Cu and Ag catalysts, usingenvironment friendly(HAuC! 4 , Cu(NO 3 )2, AgNO 3 ) cost effective,readily available precursors. The most important parameters like rateof nebulization, frequency of mixing, total number of passes,equivalent ratio, and the growth temperature along with their impacton resulting catalysts is also presented.A significant part was also dedicated to compare liquid phasemethods with thermal and combustion chemical vapour depositionwith focus on the liquid phase methods in general and depositionprecipitation in particular. The effects of variant reaction conditions,like pH of precipitation, effects of support, and the influence of otherrelated parameters will also be discussed.Particular attention was given to CO oxidation reactor whichwas constructed specifically for the present work. Also described arethe analysis of the gold silver or copper contents of the catalysts andoperation of the CO oxidation reactor (including the safety procedure with regard to CO reactor). For catalyst characterisation variousanalytical techniques used in this present work were X-ray diffraction(XRD), scanning electron microscopy (SEM), and atomic absorption(AA) analysis.Based on present investigation TCVD procedure can beregarded as effective as DP for the preparation of highly activeAu/TiO 2 (T 50 239K) catalysts. The novelty of TCVD lies in its abilityto successfully anchor Au on inert (A1 2 O 3 ) supports. An interestingfeature of present study was the successful use of a high and lowsurface area supports the samples prepared using the high surface areasupport like TiO 2 were more active than the lower surface area. Forsupported silver and copper catalysts the samples prepared by CCVD,when compared with traditional preparation procedures were noticedto equally effective. Therefore presenting CCVD as an alternativeprocedure for traditional supports like TiO 2 in general and inertsupports i.e., A1 2 O 3 , SiO 2 , in particular. During present work we wereunable to prepare highly active supported Au catalysts, possibly duechloride impurities.Finally based on large number of experiments TCVD and CCVDcan be regarded as highly effective, innovative, alternativepreparation procedure with enormous potential for the surfacetreatment of powders in general and catalysts in particular.
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