Chap10Lectures7N - Deactivation by Coking or fouling This...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
or fouling This mechanism is common in hydrocarbon Rxns: Carbonaceous (coke) material deposit on catalyst surface. Empirical C C = At n Deactivation by Coking C C = concentration of carbon on catalyst surface A & n = fouling parameters (can be functions of feed rate). The expression holds for variety of catalysts and feed streams.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
For East Texas light gas oil % coke = (min) 47 . 0 t Some other functionalities 1 1 + = p C C a 1 1 + = np p t A a For light Texas gas oil, cracked at 750 o F over a synthetic catalyst 2 / 1 6 . 7 1 1 t a + = t, sec Some others are C C e a 1 α - = C C a 2 1 1 + = Coking can be reduced at elevated pressures of 2000 – 3000 kPa & H-rich streams. Catalyst deactivated by coking can be regenerated via burning off carbon .
Background image of page 2
Deactivation by Poisoning Poisoning molecule is chemisorbed irreversibly on the active site. # of active sites decreases. Poisoning molecule may be reactant, product or impurity. Lead is used as anti-knock agent in gasoline. It is effective as octane enhancer, it poisons the catalytic after burner which converts NO x , CO and hydrocarbons in the exhaust. Thus, lead has to be removed from the gasoline.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Poison in the feed Poisoning molecule: Petroleum feed stock contain trace impurities such as S , Pb , etc which are too costly to remove. They poison the catalyst slowly. A + S A•S A•S B•S + C(g) B•S B + S P + S P•S Main reaction Poisoning reaction B B A A A A C K C K kC t a r + + = - 1 ) ( q m p d d a C k dt da r ' = - =
Background image of page 4
Let C P = concentration of poison in the gas C to = initial concentration of active sites C P•S = sites poisoned by P r P•S
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/17/2011 for the course CHEMICAL E 304 taught by Professor Darwish during the Spring '11 term at American University of Sharjah.

Page1 / 19

Chap10Lectures7N - Deactivation by Coking or fouling This...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online