Inorganic chemistry

Semester 1

Catalyst

Increases rate of reaction toward equilibrium without being appreciably consumed in the process. Cant make a thermodynamically forbidden reaction possible. Can accelerate thermodynamically allowed reaction my providing lower energy pathway (lower ea). Can enhance chemo/stereo/regio selectivity.

Steps for heterogeneous catalysis

Molecular adsorption, dissociative adsorption, surface diffusion, surface reaction, absorbed product, product desorption.

Catalyst activity

“The rate at which a catalyst causes the reaction to proceed to chemical equilibrium.” Must be expressed in specific terms of temp, conc, pressures etc as all can affect rate.

Space time yield

“quantity of product formed per unit time per unit volume of the reactor”

Turnover number (TON) / Turnover frequency (TOF)

“The number of molecules that react per site per unit time”

Selectivity

“A measure of the extent the catalyst accelerates the rate to produce the desired product”

Catalyst deactivation

“a catalyst may lose its activity or its selectivity for a variety of reasons:”

Functionality

“Type of reaction that a catalyst will promote e.g. oxidation or reduction, hydrogenation, dehydrogenation etc.”

Poisoning

“occurs when an impurity in the feed stream adsorbs onto an active site. Desorption may occur depending on the strength of the bonding, hence some poisoning may be permanent.” type of deactivation. have to break chemical bonds to get rid of

Fouling

“is where active sites are blocked by impurities. For example, carbonaceous or metal oxides can block the entrance to pores, hence reducing the active surface area.” can be cleaned (sludge)

Sintering and migration

Types of deactivation. “is where a breakdown of the supported structure occurs, which inevitably leads to a loss of surface area.”

Loss of active species

Loss of active species