E2E2Q3Mak32
Among the sulfur species in petroleum fractions some of the methylated dibenzothiopenes are the most resistant compounds to hydrodesulfurization. Choose one of the staments below that best explains why some methylated dibenzothiophenes are resistant to hydrodesulfurization.
Methyl groups in some methylated dibenzothiphenes react with molybdenum found in the hydrodesulfurization catalyst.
Methyl groups introduce non-planarity to some methylated dibenzothiophenes.
Methyl groups in some methylated dibenzothiophenes react with hydrogen reducing the availability of hydrogen for hydrodesulfurization reactions.
Methyl groups increase the thermodynamic stability of some methylated dibenzothiophenes.
Methyl groups shield the sulfur atom in some methylated dibenzothiophenes.
Choose one of the statements below that represents a principal chemical change that takes place in Catalytic Reforming.
Aromatization
Carbon addition.
Hydrogen abstraction.
Carbon reduction.
Hydrogen oxidation.
One of the statements below most correctly completes the following sentence. Heavy naphtha can be reformed into high-octane number gasoline because
Its aromatic hydrocarbon content and iso-alkane contents are high.
Its sulfur content is high.
Its cycloalkane content is high.
It can be hydrotreated.
Its nitrogen content is low.
Thermal Severity Index relates most closely to the..
Thermodynamics of thermal cracking.
Kinetics of thermal cracking.
Equilibrium conversion in thermal cracking.
Mass transfer during thermal cracking.
Momentum transfer during thermal cracking.
Choose one of the statements below that would best complete the following sentence. Carbonium ions are made by
Adding protons to alkanes.
Adding protons to olefins.
abstracting protons from olefins.
Subtracting hydride ions from olefins.
Adding hydride ions to naphthenes.
Which one of the following processes does not normally reject carbon?
Catalytic Reforming
Visbreaking
Delayed Coking
Fluid Coking
Fluid Catalytic Cracking
Mark one of the statements below that is most likely to be a true statement.
Hydrogen abstraction from hydrocarbons is favored over beta-scission at lower pressures
High pressures during thermal cracking favors the formation of n-alkanes
Radical combination is a propagation step in free radical chain reactions.
High pressures during thermal cracking favors the formation of olefins.
Initiation of free radical chain reactions involves heterolytic bond cleavage.
Mark one of the choices below that is most likely to be a false statement to represent what happens as a result of disproportionation in visbreaking. Mark the false statement.
Production of fuel oil with a lower pour point than VDR.
Formation of coke on the surface of visbreaker coils
Breaking of C-C bonds in VDR molecules
Formation of light distillates from VDR.
Production of gasoline with a high octane number.
One of the phrases listed below to complete the following sentence makes a false statement. Mark the phrase that would make a false statement. Hydrocracking can be used to produce diesel fuel from LCO because
) it can process high-sulfur feedstocks.
It uses bifunctional catalysts
It is a hydrogen addition process
It can process highly aromatic feedstocks
It generates primarily a fuel with a high octane number.
A wet flue gas analysis in vol% from an FCC regenerator is as follows: N2: 80.00%, CO2:14.00%, CO: 2.00%, O2: 0.95%, and H2O: 3%, and SO2: 0.05%. What is the sulfur content (as wt%) of the coke burnt) in the regenerator? Assume that the coke burnt in the regenerator consists only of carbon, hydrogen, and sulfur, and that dry air is used for combustion of coke in the regenerator. Atomic weights: C:12; H:1; S: 32; O: 16. Choose the value below that is the closest to the correct answer below.
Sulfur content of the coke burnt is 3.0 wt%.
Sulfur content of the coke burnt is 5.0 wt%.
Sulfur content of the coke burnt is 1.0 wt%.
Sulfur content of the coke burnt is 4.0 wt%.
Sulfur content of the coke burnt is 2.0 wt%.
Choose one of the statements below that would correctly complete the following sentence. The fact that desirable hydrocracking reactions are promoted by low temperatures is explained by the principles of
Heat transfer
Kinetics.
Catalysis.
Thermodynamics.
Mass transfer.
Choose one of the phrases below that would correctly complete the following sentence. Hydrotreatment is a...
Generation process.
Separation process.
Conversion process
Supporting process.
Finishing process.
Which one of the following processes is usually the first process in a hydrotreatment sequence?
Hydrodesulfurization
Hydrodemetallation
Hydrodenitrogenation
Hydrodegeneration
Hydrodeconvolution
Choose one of the statements below that would correctly complete the following sentence. Hydrogen is used in the catalytic reforming process to.
Inhibit isomerization reactions
Promote aromatization reactions.
Inhibit coking on catalysts.
Promote cyclization reactions.
Inhibit hydrocracking reactions.
Choose one of the statements below that would correctly complete the following sentence. The fact that desirable hydrocracking reactions are promoted by low temperatures is explained by the principles of ..
Thermodynamics
Heat transfer.
Kinetics.
Catalysis.
Mass transfer.
Choose one of the statements below that correctly describes polymerization.
Polymerization produces iso-olefins in the naphtha boiling range to obtain high-octane number gasoline.
Polymerization produces iso-alkanes and iso-olefins to obtain high-octane number gasoline.
Polymerization produces aromatics to obtain high-octane number gasoline.
Polymerization is a free radical process.
Polymerization is a hydrogen addition reaction.
Fluid coking would produce higher liquid yields and lower coke yields because, compared to delayed coking, fluid coking operates at
Higher recycle rates
Lower steam flow rates.
Higher pressures for longer time periods.
Lower fractionation temperatures
Higher temperatures for shorter time periods.
Choose on of the statements below that would best complete the following sentence. Thermal cracking processes in the U. S. Refineries have been replaced by catalytic cracking processes because..
The isomerization of free radicals is very slow.
The initiation of free radical chain reaction is slow.
The termination of free radical chains is fast.
The free radical reactions produce more aromatics in gasoline.
Hydrogen abstraction by free radicals is very slow.
Choose whether the following statement is true or false. Hydrogen consumption in hydrotreatment processes is minimized because the sole purpose of a hydrotretment is to remove heteroatoms, not to cause any change in hydrocarbon composition, except for saturation of the unsaturated C-C bonds in desired hydrogenation reactions.
True
False
Choose one of phrases below that would most correctly complete the following sentence. Removal of nitrogen (HDN) may be used as a pretreatment process in a refinery in order to protect
Neutral catalysts.
Metal catalysts.
Liquid catalysts.
Acid catalysts.
Base catalysts.
Choose one of the statements below that does not represent the FCC process.
FCC is a carbon rejection process.
FCC produces high-octane number gasoline in high yields.
FCC is an exothermic process.
FCC produces olefins in the gasoline boiling range.
FCC uses acidic catalysts.
Conducting hydrodesulfurization (HDS) of feedstocks before hydrodemetallation (HDM) may be advantageous because hydrogen sulfide produced in HDS can be used to remove the metals as metal sulfides in HDM.
True
False
Mark the false statement below.
Alkylation is the opposite of cracking considering the change in molecular size during the process.
Alkylate has a higher octane number than polymerate.
Alkylate is currently favored over reformate in the U.S. Refineries because of environmental regulations on gasoline.
Alkylate has a high aromatic hydrocarbon content.
Alkylation requires highly concentrated acid as catalyst.
One of the statements below most correctly completes the following sentence. Catalytic Reforming is no longer considered as a highly favorable process in the U.S. Refineries because of..
Decreasing heavy naphtha yields from distillation.
Competition for platinum by the fuel cell industry.
Decreasing hydrogen demand.
Increasing sulfur contents of heavy naphtha
Regulatory limits on the aromatic content of gasoline.
Choose one of the statements below that would best complete the following sentence. Thermal cracking cannot produce branched-chain alkanes from n-alkanes because..
Carbon disproportionation will not be favorable.
Secondary and tertiary radicals are not significantly more stable than primary primary radicals.
) beta-scission is faster than hydrogen abstraction.
Hydrogen abstraction is faster than beta-scission.
Olefins are less reactive than naphthenes.
Considering the reaction conditions in coil and soaker visbreaking, for a VDR with a high asphaltenes content, soaker visbreaking (rather than coil visbreaking) would provide a preferred option for easier and more economical maintenance of the coils in the furnace.
True
False
Choose one of the statements below that correctly answers the following question. Which reaction involving free radicals most effectively increases the alkane yield in thermal cracking of gas oils?
None of the above.
Hydrogen abstraction.
Isomerization.
Beta scission.
Disproportionation.
Choose one of the statements below that is most likely a FALSE statement.
Carbenium ions can be made on Bronsted acid sites
Carbenium ions can be made on Lewis acid sites on a catalyst.
Carbonium ions can be made made on Lewis acid sites on a catalyst.
Carbonium ions can be made on Bronsted acid cites on a catalyst.
Carbenium ions are made by adding protons to olefins.
Changing (i.e., increasing, or decreasing the value of) one of the reaction parameters listed below would not satisfy the two objectives of the catalytic reforming process simultaneously: 1) Promoting dehydrocyclization reactions, while 2) Inhibiting hydrocracking reactions. Choose from the list below which parameter would create this conflict.
Hydrogen / hydrocarbon ratio
Changing none of the listed parameters would create a conflict in meeting the two objectives of catalytic reforming simultaneously.
Space Velocity
Temperature
Pressure
It is given that the true octane numbers of a reformate and a straight run gasoline are 90 and 60, respectively. Based on this information, only one of the following statements is true. Mark the true statement below.
The true octane number of any blend cannot be calculated from the given information.
The blending octane number of the 50/50 blend of the two products would be 75.
The mean octane number (MON) of the 50/50 blend of the two products is 75.
The posted octane number (PON) of the 50/50 blend of the two products is 75.
The true octane number of the 50/50 blend of the two products would be 75.
Choose one of the statements below that would best complete the following sentence. Carbenium ions are made by..
Subtracting hydride ions from olefins.
Adding hydride ions to naphthenes.
Abstracting protons from olefins.
Adding electrons to alkanes.
Adding protons to olefins.
Which pair of the following pairs of processes uses a similar concept for providing heat to carry out the desired cracking reactions?
Catalytic Dewaxing and Fluid Coking
Fluid Coking and Thermal Cracking
Fluid Coking and Fluid Catalytic Cracking
Visbreaking and Fluid Coking
Delayed Coking and Fluid Catalytic Cracking
Mark one of the choices below that is most likely to be a false statement to represent what happens as a result of disproportionation in visbreaking. Mark the false statement.
Breaking of C-C bonds in VDR molecules.
Production of fuel oil with a lower pour point than VDR.
Formation of light distillates from VDR.
Formation of coke on the surface of visbreaker coils.
Production of gasoline with a high octane number.
Choose one of the statements below that most correctly completes the following sentence. At least two drums are used in the delayed coking process in order to..
Delay the coking reactions.
Fractionate the coking products.
Increase the coke quality.
Increase the coke yield.
Ensure the continuity of VDR flow.
One of the statements below is a false statement. Mark the false statement.
Fluid coking is used more frequently than delayed coking in the US refineries.
Fluid coking can theoretically process heavy VDR with high sulfur contents that may not be a preferred feedstock for delayed coking.
Fluid coking produces only fuel coke.
Flexi-coking process is a variation of fluid coking process.
Fluid coking is a continuous process.
Choose one of the statements below that most correctly represents the FCC process.
FCC is a hydrogen addition process.
FCC uses basic catalysts to generate carbocations for producing high-octane number gasoline in high yields.
FCC uses transition metal catalysts for effective hydrogenation/dehydrogenation reactions.
FCC is a carbon sequestration process to reduce the emissions of CO during catalyst regeneration.
FCC is a carbon rejection process.
Choose one of the statements given below that most correctly completes the following sentence. To obtain the highest yield of alkanes in a thermal cracking process, the refiners would choose to run the reactor at relatively..
Low space velocity.
High temperature.
Low pressure.
High flow rates.
High pressure.
Choose one of the statements below that would best complete the following sentence. Catalytic cracking produces branched-chain alkanes because..
Secondary and tertiary carbocations are more stable than primary carbocations.
Secondary and tertiary free radicals are less stable than primary free radicals.
Acid catalysts accelerate the cracking reactions.
FCC is a well integrated process.
Olefins are less reactive than naphthenes.
A wet flue gas analysis in vol% from an FCC regenerator is as follows: N2: 80%, CO2:14%, CO:2%, O2:1%, and H2O: 3%. What is the hydrogen content (as wt%) of the coke burnt) in the regenerator? Assume that the coke burnt in the regenerator consists only of carbon and hydrogen. Choose the correct answer below.
Hydrogen content of the coke burnt is 5.6 wt%.
Hydrogen content of the coke burnt is 4.6 wt%.
Hydrogen content of the coke burnt is 7.5 wt%.
Hydrogen content of the coke burnt is 6.5 wt%.
Hydrogen content of the coke burnt is 3.0 wt%.
Choose one of the following statements that best completes the following sentence. The principal upgrading strategy used in coking processes is..
Hydrogen abstraction.
Hydrogen addition.
Carbon rejection.
Carbon oxidation.
Carbon addition.
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