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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Synthesis and Characterisation of Nanomaterial Catalysts Made Using Continuous Hydrothermal Flow Reactors

Author: BOLDRIN, Paul

Year: 2008

Supervisor(s): Asa Barber

Continuous Hydrothermal Flow Synthesis (CHFS) methods have been developed for the production of nano-ceramic particles (<100 nm). Briefly, deionised water is pumped under pressure (24 MPa) through a pre-heater which heats the water up to 450°C. A metal ion feed is mixed with the superheated water, and nanoparticles are precipitated. The suspension is cooled and passes through the back pressure regulator where it is collected. Catalytic testing on certain powders for activity in the hydrogenation of nitrobenzene to aniline has been performed.

The temperature, pressure, feed rates and concentrations of reagents can affect the composition of the products, particle size, shape and surface area. This basic system has been developed to allow for use of oxidants, reductants, pH modifiers, surfactants, and their effect has been described. A high throughput version of the system, capable of producing dozens of samples per day, has also been developed and tested.

A number of methods for producing catalysts using CHFS have been developed. These include nickel alumina catalysts produced by reduction of CHFS produced nickel-aluminium layered double hydroxides, deposition of CHFS produced NiO particles on alumina supports, co-crystallisation of platinum group metals with ceria, zirconia or titania supports in the CHFS system, or use of ceria, zirconia or titania as supports to produce catalysts by incipient wetness. In particular, some of the catalysts produced from layered double hydroxides showed good activity compared to a commercially available nickel-alumina catalyst. Platinum-titania catalysts showed good activity compared to equivalent commercially available catalysts.