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Title: Green catalyst preparation using electrochemical and mechanochemical techniques
Author: Taylor, Sarah Frances Rebecca
ISNI:       0000 0004 2745 300X
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2012
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The conventional method for synthesis of supported metal catalysts is a multi step reaction that produces large amounts of waste. The focus of this work has been to look at alternative methods of catalyst production which eliminate or lower the number of steps and therefore waste produced. The aim of the project was to synthesise supported metal catalysts by alternative (greener) techniques and then to test these catalysts alongside conventional catalysts for improved and novel activity. It was proposed that catalysts could be synthesized by a novel electrochemical route where the pure metal is electrochemically oxidized into solution to form a transient soluble complex. This complex is then reduced electrochemically/electrolessly and the metal is deposited onto a support with the ligand of the complex being recovered in solution for subsequent cycles. The development of such a system was studied for gold using ionic liquids, the stripping and depositing of gold was demonstrated using dicyanamide ligand ([DCAn but attempts to prove the recyclability of the ligand were not successful. However during these studies a set of active gold catalysts where prepared by the electroless deposition of gold from H[AuCI4].3H20 in [C4mim][NTf2] onto silica and titania. The activity of these catalysts was compared to standard wet impregnated catalysts, interestingly the preparation method was found to control the selectivity of the reaction. The standard catalysts showed activity for the oxidation of benzyl alcohol in toluene whereas the catalysts prepared by electroless deposition from ionic liquids showed Friedel-Crafts alkylation of benzyl alcohol with toluene. This is the first time that heterogeneously supported gold catalysts have been found to be active in Friedel--Crafts alkylations. Ag/AI203 and PtlAI203 catalysts have been prepared by means of solvent-free mechanochemistry using a ball mill. Remarkable catalytic activity was observed using a Ag/AI203 catalyst by ball milling (Ag20) for octane-SCR, compared with a conventionally prepared Ag/AI203 catalyst (wet impregnation) the ball milled catalyst shows an increase in activity with a reduction in the light off temperature of -150°C and NOx conversion below 200°C which is the first time this has been achieved in the absence of hydrogen.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available