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F SC 432 Midterm Key
answers to the midterm exam
38
Chemical Engineering
Undergraduate 4
12/19/2012

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Cards

Term
T/F?
crude oil contains olefins
Definition
False
Term
T/F?
crude oil contains heteroatoms like S, N, and O
Definition
True
Term
T/F?
crude oil contains inorganic gases
Definition
True
Term
T/F?
crude oil contains metals such as Ni and V
Definition
True
Term
T/F?
crude oil contains naphthenes
Definition
True
Term
name two organic gases that are typically found in crude oil
Definition
CH4 (methane)
C2H6 (ethane)
Term
T/F?
Iso-alkanes have higher boiling points than n-alkanes with the same carbon number
Definition
False
Term
T/F?
Organic sulfur compounds tend to concentrate in the higher boiling fractions of crude oil
Definition
True
Term
T/F?
Boiling point of hydrocarbons decreases with the increasing carbon number
Definition
False
Term
T/F?
Vapor pressure (RVP) is not an important property of gasoline
Definition
False
Term
T/F?
Naphthenes have lower densities than n-alkanes with the same carbon number
Definition
False
Term
Crude oil is generally classified as heavy or light according to ___
Definition
API gravity
Term
Characterization factors are calculated using ___ of crude oil
Definition
physical properties
Term
What is the octane number n-heptane?
Definition
0
Term
ASTM distillation temperatures of a light gas oil (at 95%vol) and a heavy gas oil (at 5%vol) obtained in an atmospheric distillation column are 580°F (i.e.,95% vol of LGO distilled) and 585°F(i.e., 5%vol HGO distilled), respectively. Mark the correct statement below.
Definition
95% LGO at 580 F & 5% HGO at 585 F

5 F ASTM gap

(gap because HGO BP range is above the LGO range, which is expected)
Term
T/F?
Disproportionation in visbreaking does NOT involve Formation of coke on the surface of visbreaker coils
Definition
False
Term
T/F?
Disproportionation in visbreaking does NOT involve Formation of light distillates from VDR
Definition
False
Term
T/F?
Disproportionation in visbreaking does NOT involve Production of fuel oil with a lower pour point than that of VDR
Definition
False
Term
T/F?
Disproportionation in visbreaking does NOT involve breaking of C-H bonds
Definition
True
Term
The two principal strategies used in upgrading heavy fractions of crude oil are ___ and ___
Definition
carbon rejection
hydrogen addition
Term
T/F?
Fluid coking can process VDR with higher sulfur contents
Definition
True
Term
T/F?
Fluid coking produces only fuel coke
Definition
True
Term
T/F?
Delayed coking is used more frequently than fluid coking in the US refineries.
Definition
True
Term
T/F?
Fluid coking is a semi-continuous process
Definition
False
Term
T/F?
Flexi-coking process is a variation of fluid coking
Definition
True
Term
Thermal cracking is carried out in two different reactors because...
A. the conversion in a single reactor is not sufficient.
B. one reactor could have a fixed-bed configuration.
C. thermal reactivity of n-paraffins depends on the chain length.
D. it is a continuous process.
E. It is a semi-continuous process.
Definition
thermal reactivity of n-paraffins depends on the chain length
Term
T/F?
Radical combination is a propagation step in free radical chain reactions
Definition
False
Term
T/F?
Hydrogen abstraction from hydrocarbons is favored over beta-scission at lower pressures
Definition
False
Term
T/F?
High pressures during thermal cracking favors the formation of n-alkanes
Definition
True
Term
T/F?
Low pressures during thermal cracking favors the formation of n-alkanes
Definition
False
Term
T/F?
Initiation of free radical chain reactions involves heterolytic bond cleavage
Definition
False
Term
Thermal cracking processes in US refineries have been replaced by catalytic cracking processes because...
Definition
the isomerization of free radicals is very slow
Term
A similar concept for providing heat for cracking reactions was used in what two processes?
Definition
fluid coking
FCC
Term
Which two processes used a similar concept (using multiple reactors) to provide continuity of feedstock flow round the clock.
Definition
delayed coking
fixed-bed catalytic cracking
Term
on a TBP plot (TBP vs. vol % distilled), the line for the crude with the largest light and middle distillate yield would be...
Definition
lowest in the low BP range
Term
on a TBP plot (TBP vs. vol % distilled), the line for the crude with the most aromatic light and middle distillate yield would be...
Definition
highest in the low BP range
Term
on a crude oil ternary diagram, the cheapest crude would be
Definition
closest to the top point (most aromatic)
Term
on a crude oil ternary diagram, the most expensive crude would be
Definition
closest to the bottom left point (most paraffinic)
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