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THE UNIVERSITY OF ALBERTA
DEHYDROGENATION OF n-PROPANOL AND PROPIONALDEHYDE
WITH A CHROMIA CATALYST
A THESIS
SUBMITTED TO THE FACULTY OF GRADUATE STUDIES
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE
OF MASTER OF SCIENCE IN CHEMICAL ENGINEERING
DEPARTMENT OF CHEMICAL AND PETROLEUM ENGINEERING
by
KENNETH THOMAS HANSEN, B.Sc.
EDMONTON, ALBERTA
JUNE, 1960
ABSTRACT
The vapor phase catalytic dehydrogenation of normal propanol and
propionaldehyde in a fluidized bed of chromic oxide on inactive alumina
was studied. The superheated vapors were used to fluidize the catalyst
of size range -40 mesh in a 2 inch I.D. reactor.
Operating conditions were varied over the following ranges:
Temperature - 375 to 525°C.
n-Propanol Feed Rate - 6.70 to 15.92 gm-moles/hr.
n-Propionaldehyde Feed Rate - 6.31 to 7.15 gm-moles/hr.
Superficial Linear Gas Velocities -0.175 to 0.398 ft/sec.
The experimental equipment consisted of a stainless steel reactor,
suitable for bed heights up to 40 inches, and associated preheating and
condensing assemblies. Chromatographic analytical methods were used for
quantitative determinations of reaction products.
Thermodynamic equilibrium constants have been determined for the
dehydrogenation of normal propanol and indicate that the reactions under¬
taken are thermodynamically feasible.
Conversions and reaction efficiencies of the reactions are presented.
These results show that low conversions were effected by the chromia catalyst
as compared to similar work by other investigators using zinc oxide catalyst.
The dehydrogenation of n-propanol was shown to follow a first order reaction
and reaction rate was found to vary with temperature as indicated by the
Arrhenius equation.
ACKNOWLEDGEMENTS
The author feels deeply indebted to Dr. D. B. Robinson of
the Department of Chemical and Petroleum Engineering, University of
Alberta, who directed the research program and whose efforts contributed
greatly to its success.
Acknowledgement is gratefully made to Dr. E. L. Tollefson of
Canadian Chemical Company Limited, for valuable discussions regarding
this study.
Appreciation is also expressed to Mr. D. Shaw, who assisted
with analyses, and to Mr. R. Kirby for his assistance during construction
of the apparatus.
The financial support provided by Canadian Chemical Company
Limited is gratefully appreciated.
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TABLE OF CONTENTS PAGE
LIST OF TABLES . iii
LIST OF FIGURES . iv
LIST OF PLATES . v
LIST OF SYMBOLS . v
INTRODUCTION . 1
THEORY .. 3
1. Dehydrogenation of Alcohols . 3
2. Fluidization . 6
3. Fluidized Catalytic Dehydrogenation of Alcohols . 8
EXPERIMENTAL PROCEDURE . 10
1. Experimental Apparatus . 10
(a) Reactor ... 10
(b) Preheater . 14
(c) Temperature Measurements . 15
(d) Pressure Measurements . 17
(e) Condensing System . 17
(f) Gas Sampling and Measurement . 18
(g) Alcohol and Propionaldehyde Feed System . 18
(h) Air and Nitrogen Purge System . 21
- ii -
PAGE
2 . Experimental Technique ....... 21
(a) Operation of Equipment .... 21
(b) Preparation of Catalyst . 22
(c) Analyses of Products ..... 22
i) Liquid Products . 22
ii) Gaseous Products ...•. 23
EXPERIMENTAL RESULTS .•... 26
1. Conversions and Reaction Efficiencies ... 26
2. Order of Reaction ..... 34
3. Thermodynamic Equilibria of Chemical Reactions . 36
4. Condition of Equipment ... 38
CONCLUSIONS . 40
1. Validity of Results .-. 40
2. Summary of Experimental Results . 40
BIBLIOGRAPHY . 43
APPENDICES. 44
A. Thermodynamic Study of Reaction Equilibria . 45
B. Sample Calculations . 50
C. Experimental Data . 53
.
Ill
LIST OF TABLES
TABLE • PAGE
I Analyses of Liquid Products ... 54
II Analyses of Gaseous Products . 55
III Operating Conditions and Material Accountabilities
Dehydrogenation of n-Propanol . 56
IV Operating Conditions and Material Accountabilities
Dehydrogenation of Propionaldehyde . 57
V Calculations of Conversions and Reaction Efficiencies
Dehydrogenation of n-Propanol . 58
VI Calculations of Conversions and Reaction Efficiencies
Dehydrogenation of Propionaldehyde . 59
VII Calculations of Log Concentration of Unchanged
n-Propanol and Time of Reaction
Dehydrogenation of n-Propanol . 60
VIII Calculations of Variation of the Rate of Dehydrogenation
of n-Propanol with Temperature
. Dehydrogenation of n-Propanol . 61
IX Calculations of Predicted Moles Hydrogen and
Actual Moles Hydrogen Evolved
Dehydrogenation of n-Propanol ...J. 62
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IV
LIST OF FIGURES
FIGURE PAGE
1 Schematic Apparatus Assembly . 11
2 Detailed Diagram of Reactor . 13
3 Wiring Diagram of Thermocouple System . 16
4 Detailed Diagram of Gas Sampling Apparatus . 19
5 Variation of n-Propanol Conversion with Temperature
Dehydrogenation of n-Propanol . 28
6 Variation of Propionaldehyde and Diethyl Ketone Reaction
Efficiencies with Reaction Temperature
Dehydrogenation of n-Propanol .:. 29
7 Variation of Propionaldehyde Conversion and Diethyl
Ketone Reaction Efficiency with Reaction Temperature
Dehydrogenation of Propionaldehyde . 31
8 Percentage Propionaldehyde Conversion
Dehydrogenation of n-Propanol and Propionaldehyde 33
9 Determination of Reaction Order
Dehydrogenation of n-Propanol . 35
10 Variation of Rate of Reaction with Temperature
Dehydrogenation of n-Propanol . 37
11 Comparison of Moles Hydrogen From Reactions:
n-PrOH-PrH + H 2
2n-PrOH — DEK + CO + 3H 2
With Actual Moles Hydrogen in Off Gas
Dehydrogenation of n-Propanol . 41
.
x 7
V
LIST OF PLATES
PLATE PAGE
1 Photograph of Experimental Equipment . 12
2 Gas Sampling Apparatus . 20
3 Microbellows Positive Displacement Pump . 20
4 Top View of Upper Catalyst Filter . 39
5 Bottom View of Upper Catalyst Filter . 39
LIST OF SYMBOLS
n-PrOH - Normal Propanol
PrH - Propionaldehyde
DEK - Diethyl Ketone
.
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1
INTRODUCTION
There have been extensive investigations of the dehydrogenation
of alcohols in fixed bed reactors (1,4,5,8). Several catalysts, mainly
of the metallic oxide type, have been studied and optimum conditions
and reaction selectivities reported. In the case of dehydrogenation of
alcohols utilizing the fluidized catalyst technique, very little similar
data is available (2,9).
The fluidized catalytic bed has definite advantages, particularly
for highly endothermic reactions such as the one undertaken in this study.
Fluidization provides a means of carrying out processes in which large
amounts of heat are released or required without the danger of local
overheating. Heat transfer coefficients for a fluidized bed are much
higher than normal gas film coefficients (7), due to the rapid circulation
of particles within the reactor. The high heat transfer rates in the
system coupled with a high thermal conductivity facilitates the uniform
control of temperature, making possible the attainment of isothermal
conditions. Isothermal conditions in a fluidized reactor may be of
particular value in cases where a reaction is very temperature sensitive,
i.e., favorable conditions can be maintained at the inlet without fear of
running into unfavorable conditions at the outlet of the bed. A much greater
solid surface for contacting the flowing medium is provided by the movement
of the fine solid particles in the fluidized bed than in fixed bed reactors.
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In cases where continuous regeneration and reactivation of the catalyst
are necessary because of fouling, the fluidized bed has proven to be of
considerable use.
Komarewsky and Coley (5) reported that primary alcohols of
n-carbon atoms are readily converted to symmetrical ketones of 2n-l
carbon atoms by vapor-phase contact with chromia catalysts. In view of
these results the dehydrogenation of n-propanol in a fluidized bed using
a chromic oxide catalyst on inactive alumina support was undertaken to
determine the extent to which the reaction to the symmetrical ketone,
diethyl ketone, could be promoted. Ketones and mixtures of ketones have
achieved commercial importance for selective solvent processes such as
the solvent dewaxing of lubricating oils.
Factors such as backmixing, which results in high concentrations
of products throughout a fluidized bed, and the variable quality of
fluidization can make reaction predictions uncertain.
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THEORY
I . Dehydrogenation of Alcohols
The dehydrogenation of alcohols was first studied by Ipatieff,
who converted methyl, ethyl, Isopropyl, isobutyl, and isoamyl alcohols
to aldehydes and ketones using such catalysts as platinum tubes, zinc
rods, and brass turnings at suitable reaction temperatures. Later, the
majority of the studies of dehydrogenation utilized metallic oxides on
mixtures of these oxides as the catalyst. The preparation of ketones by
dehydrogenation of secondary alcohols over various catalysts has been
covered in standard reference books on catalysis.
Komarewsky and Coley (5) have found that primary alcohols of
n-carbon atoms are readily converted to symmetrical ketones of 2n-l carbon
atoms by vapor-phase contact with various catalysts. In the presence of
a chromia catalyst, these workers proposed a mechanism for the conversion
of the symmetrical ketones as follows:
1. Dehydrogenation of the alcohol to the aldehyde.
2. Aldol condensation of the aldehyde.
3. Removal of carbon monoxide from the -CHO group of the aldol leaving
a secondary alcohol.
4. Dehydrogenation of this alcohol to the corresponding ketone.
Komarewsky and Coley studied the dehydrogenation of primary
alcohols ranging from n-propanol to n-octadecyl alcohol. These dehydro¬
genations were performed in a fixed bed of chromic catalyst and at a
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temperature of 400°C. The molal conversion of reacted alcohol to ketone
exceeded 50 per cent in most cases. The mechanism proposed was supported
by an investigation of intermediates:
"In a preliminary consideration of the reaction mechanism,
aldehydes and aldols seem to be logical intermediates. It was
found that aldehydes undergo the same type of condensation,
producing yields considerably superior to those obtained from
the corresponding alcohol. When the aldols of n-buiylaldehyde
and n-heptaldehyde were subjected co the same reaction conditions,
excellent yields of ketone were produced directly by a catalytic
decomposition reaction. The order of conversion of the reactants
to ketones was aldol aldehyde alcohol."
To substantiate the aldol intermediate mechanism, a deuterium tracer
technique was employed and it showed that the intermediate forms did
exist.
A generalized theory of dehydrogenation of alcohols has been
reported by Church and Joshi (1). They have proposed that the reaction
proceeds through the formation of a complex between the alcohol and the
catalyst, M:
H H
R - C - H + 2M-R - C - H - M
6 - H O-H-M
Some generally accepted theories (1) concerning dehydrogenation
reactions are:
1. The reaction follows a pseudo first order reaction rate equation.
2. The energy of activation for dehydrogenation is constant for a
given catalyst but varies with the type and method of preparation
of it.
3. The reaction rate is dependent on temperature as stipulated by the
hypothesis of Arrhenius and is consistent with the constancy of the
energy of activation.
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4. The alcohol molecules are first adsorbed on the surface of the
catalyst with the hydroxyl groups parallel to the surface and the
rest of the molecules perpendicular to it.
5. The reaction velocity is independent of the pressure of the
system.
The fluid bed dehydrogenation of n-propanol was studied by
Tollefson (9) utilizing a zinc oxide on alumina catalyst. To explain
information obtained from mass spectrographic and infra-red analyses, the
following series of reactions were proposed:
1. C1I 3 - Cll 2 ~ CH 2 OH —CH 3 - CH 2 - c s = 0 + H 2
S H
propionaldehyde
z° /°
2. 2 CH 3 - CH 2 - -^ CH 3 - CH 2 - CH - CH - C '
n h OH CH 3 H
2 - methyl, 3 - hydroxy pentaldehyde
3. CH 3 - CH 2 - CH - C1I - C -a- CH 3 - CH 2 - CH = C - C + H 2 0
OH CH 3 H CH 3 H
2 - methyl penten - 2 - al
4. CH 3 - CH 2 - CH - CH - C -
dm 6 h 3 v h
CH 3 - CH 2 - CH - CH 2 - CH 3 -I- CO
OH
3 - pentanol
5. CH 3 - CH 2 - CIi - CH 2 - CH 3 —CH 3 - CH 2 - C - CH 2 - CH 3 + H 2
OH
diethyl ketone
6. CH 3 -
—C1I 2 = CH
pentene - 1
CH
d)H
ol
CH 2 - CH 3 + H 2
3
CHp - CH - CH 2 - CIi 3
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7. CH 3 - CH 2 - CH - CH 2 - CH 3 —► CH 3 - CH = CH - CH 2 - CH 3 + H 2 0
OH
pentene - 2
8. CO + H 2 0 —► C0 2 ■+■ H 2
9. CH 3 - CH 2 - CH 2 OH —CH 3 - CH = CH 2 -F H 2 0
Reactions 1, 2, 4, and 5 were reactions reported by Komarewsky
and Coley (5).
Neish (8) reported that the dehydrogenation of several alcohols
and glycols, in the gaseous state, was a first order process obeying
the Arrhenius relation for variation of rate with temperature. A porous
copper catalyst was found to be the most satisfactory in these experiments
which were carried out in a fixed bed reactor at temperatures of 180 to
370°C.
2. Fluidization
Since the introduction of the concept of fluidized solids by the
Standard Oil Development Company, there has been considerable development
and application of the technique. The unique properties of fluidized
catalytic beds have made several important industrial reactions feasible.
Fluidization describes an operation which pertains to a mode of
granular solids - fluid contacting. If a fluid passes upwards through a
bed of particles, the pressure drop will be the same as for downward flow
at low rates, but when the drag due to friction equals the apparent weight
of the particles, the bed starts to expand. This process continues
until the bed has assumed the loosest stable form of packing. If the
velocity is increased still further, the individual particles separate from
one another and become freely supported in the fluid and the bed is said
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to be fluidized. Solids in the fluidized state possess a degree of
mobility that is comparable to that of liquids.
Fluidized systems are extensively used because of the high rates
of heat transfer and the uniform temperature within the bed, and the
high coefficients for transfer from the bed to the walls of the containing
vessel. It is generally suggested that the presence of the particles near
the wall breaks up the laminar sub-layer which would normally provide a
resistance to heat transmission. Heat transfer characteristics of fluidized
beds internally and externally heated have been determined by Mickley and
Trilling (7). The coefficients were 3 to 70 times greater than in similar
tubes without particles. Radial and longitudinal temperature gradients
were shown to be virtually eliminated.
Summarizing, the chief advantages of the fluidized solids method
are: (6)
1. Continuous operation. Since spent solids are easily removed from
a system, continuous operation may result. The spent solids may
then be reactivated or replaced by fresh solids.
2. Flat temperature profiles. Intense particle and gas agitation in
the bed produces a uniform temperature distribution, longitudinally
as well as horizontally.
3. High heat transfer coefficients. The particle motion past the
heat transfer surfaces results in comparatively high wall to bed
heat transfer.
4. Relatively low pressure drops through the fluidized bed reactor.
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Chief disadvantages of the method are:
1. Concurrent solid and gas flow. In this way driving forces may
be adversely affected in physical operations.
2. Severe erosive damage to reactors and transfer accessories.
3. Requirements for catalyst recovery equipment because of eluiriation.
4. Attrition of the catalyst and its replacement cost.
Gilliland and Mason (3) investigated gas and solid mixing in
fluidized beds by tracer gas and heat flow methods and concluded that
backmixing of gas was relatively low in the small diameter reactors employed.
It was also concluded that for reactors with high aspect, i.e. L/D ratios,
reaction rate studies could be correlated on the basis of piston flow
neglecting mixing and that isothermal conditions of the fluidized bed
result from circulation of solids rather than from gas mixing.
3. Fluidized Catalytic Dehydrogenation of Alcohols
With the exception of petroleum refining fluidized catalyst
studies, the organic reactions carried out in fluidized catalyst beds
are relatively few. De Q. Jones (2) carried out the vapor phase catalytic
dehydrogenation of ethanol in a fluidized bed of reduced metallic copper.
Nitrogen was used to fluidize the fine solid particles of the catalyst
which were in the size range 104 - 208 microns, and were composed of
copper on crushed commercial Boileezers. Reactor temperatures were
varied over the range 225 to 385°C., and ethanol feed rate varied from
0.07 to 1.. 12 moles/hr. Results showed that low rate of alcohol feed and
temperature between 275 and 350°C. favored the formation of acetaldehyde,
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whereas high feed rates and lower temperatures, 225 to 260°C., effected
high conversions to ester. A maximum total conversion of 22.7 per cent
was obtained.
Tollefson (9) determined conversions, reaction efficiencies
and products when n-propanol was dehydrogenated over zinc oxide on
inactive alumina in the fluidized state. The dehydrogenation was
investigated at superficial gas velocities of 0.2, 0.3 and 0.4 ft./sec.
and at reaction temperatures of 375, 425, 475, and 525°C. using a
1.70 inch diameter fluidized bed 10 inches high. A maximum conversion
of 95 per cent was obtained at a superficial gas velocity of 0.2 ft./sec.
and a temperature of 525°C. The maximum diethyl ketone reaction efficiency
of 15 per cent was obtained at these same conditions. The dehydrogenation
of secondary butanol was also studied by the above investigator utilizing
similar catalysts and conditions as for the dehydrogenation of n-propanol.
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EXPERIMENTAL PROCEDURE
1. Experimental Apparatus
A schematic diagram and a photograph of the experimental equipment
appear in Figure I and Plate I respectively. The equipment used is
similar to that used by Tollefson (9) for his study of the dehydrogenation
of secondary butanol.
(a) Reactor
Figure 2 is the detailed diagram of the reactor. It was
constructed of Type 316 stainless steel except for the low carbon
steel lap joint flanges. A 4 foot section of 2 inch standard pipe
was used as the main reactor section enlarging into a 2 foot section
of 4 inch diameter disengaging zone. The catalyst support grid plate
consisted of a circular section of 1/8 inch porous stainless steel
supplied by Micrometals Company. The grid plate was recessed into
the flange in the lower reactor. The disengaging section was provided
with a baffle plate and porous stainless steel filter to eliminate
carry-over of the catalyst into the condensing system.
Pressure taps were located 1.5 inches above the lower grid
plate of the reactor and in the disengaging zone. To prevent catalyst
from moving into the manometer lines, small porous stainless steel
filters were fitted into the pressure taps.
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FIGURE I - SCHEMATIC APPARATUS ASSEMBLY
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PLATE 1 - PHOTOGRAPH OF EXPERIMENTAL EQUIPMENT
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FIGURE 2 - DETAILED DIAGRAM OF REACTOR
14
Heat was supplied to the reactor by two 1000 watt heaters
controlled by 1 KVA variable transformers. The heaters consisted of
20 feet of 20 gauge nichrome electrical resistance wire strung on
porcelain insulating beads. The winding was supported with a coating
of Saurereisen No. 29 refactory cement. Electrical terminals were
constructed with 14 gauge nichrome wire strung on beads and cemented
in place by refactory cement. A 10 ampere ammeter and 10 ampere fuses
were included in each heater circuit. Asbestos insulation was used
as a cover for the reactor winding and the entire 2 inch reactor
section was sheathed with corrugated aluminum sheeting.
The disengaging zone and upper flange heater consisted of
18 feet of 20 gauge nichrome resistance wire controlled by a 1 KVA
variable transformer. Loose flake asbestos and fibreglass insulation
was placed over the upper flange, but the disengaging zone was left
uninsulated.
(b) Preheater
A 3 foot section of 1 inch Schedule 40 stainless steel
pipe was threaded into the side outlet of a tee at the lower end of
the reactor. Liquid alcohol was admitted through a 1/4 inch O.D.
stainless steel tube silver soldered into a 1 inch stainless steel
cap threaded to the 1 inch pipe.
A 20 foot, 20 gauge nichrome resistance heater constructed
and controlled similarly to the reactor heaters supplied heat required
to vaporize the liquid alcohol and heat the vapors to the desired level
of temperature. Asbestos insulation sheathed with aluminum sheeting
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was used as preheater insulation. The lower reactor tee fitting
was insulated with loose flake asbestos held in place with a formed
sheet aluminum cover.
(c) Temperature Measurements
A single iron-constantan thermocouple was installed to
measure vapor temperature in the preheater. A two hole ceramic
insulator fitted into a 1/8 inch I.D. thin wall stainless steel tube
supported the wires. The tube was silver soldered into a standard
stainless 1 inch plug, extending the thermocouple junction 6 inches
into the preheater when threaded into the lower reactor tee fitting.
Temperature measurement in the reactor was accomplished by
positioning an eight point thermocouple string from the upper tee
fitting of the reactor to within 1 inch of the grid plate. A diagram
of the thermocouple system appears in Figure 3. A common constantan
wire extended to the lowest point of the thermocouple string; the
iron wires extended to thermocouple junction points along the constantan
wire. The thermocouple wires were insulated by using 1/8 inch O.D.
2 hole ceramic insulators. The entire string was placed in a 3/8
inch I.D. thin wall stainless steel tube which was soldered into a
1 inch stainless steel plug. The ends of the thermocouple wires were
attached to a nine-point junction to facilitate thermocouple dis¬
connection during removal of the thermocouple tube from the reactor.
A single cold junction was held at the ice point to provide a
reference potential. All thermocouples were connected to a Leeds and
Northrup twelve-point recorder. A Leeds and Northrup Potiable
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Potentiometer connected to the remaining three recorder junctions
was used for calibration of the recorder.
The longitudinal temperature gradient of the bed, as indicated
by reactor thermocouples, was controllable to approximately 2.5°C.
at steady state conditions. This temperature variation increased
considerably at superficial linear gas velocities below 0.175 ft./sec.
(d) Pressure Measurement
Pressures were measured at two points, immediately above the
grid plate and in the disengaging zone. Filters were placed in each
line to eliminate the flow of catalyst into the manometer. Copper
tubing was used to connect pressure taps to two mercury manometers
installed in the control panel.
The pressure drop across the fluidized bed was essentially
constant at 2.5 inches of mercury for all superficial linear gas
velocities used in this study. The absolute pressure varied with
gas velocity due to increased pressure drop across the upper catalyst
trap at higher gas velocities.
(e) Condensing System
Two condensers of identical construction were used to condense
hot gaseous products from the reactor. Each condenser was constructed
by placing a nine tube bundle in a 2 foot, 2 inch I.D. copper shell.
The tube bundle consisted of 1/4 inch copper tubing. The upper
condenser was water cooled and situated immediately above the final
condenser which was cooled by refrigerated ethylene glycol-water
solution. The refrigerated coolant, circulated by means of a small
F
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18
centrifugal pump, was maintained at -16°C. A liquid product
receiver was located below the final condenser together with an
exit for uncondensed gases.
(f) Gas Sampling and Measurement
Figure 4 and Plate 2 show the apparatus used for gas sampling.
A Redmond Model 3554, Type L, diaphragm pump was installed to boost
gas pressure in glass sample bombs to 6 psig. The additional gas
sample was necessary to provide sufficient gas for chromatographic
analyses. Sample bombs were fitted with Burrell check valves for
direct insertion into a Burrell Model K-2 Kromotog.
An oil filled wet test meter provided with a bypass was used
to measure the volume of the uncondensed off gas.
(g) Alcohol and Propionaldehyde Feed System
A calibrated Lucite tube served as a feed reservoir for a
Research Appliances Model 1000, stainless steel, 3/4 inch microbellows
positive displacement pump (Plate 3). The discharge line of the pump
led to a metering needle valve located close to the preheated inlet.
This allowed the feed to be shut off at the metering valve, limiting
the amount of alcohol remaining in the preheater to a minimum. A
pressure gauge located in the pump discharge line assisted in control
of the metering valve.
The Lucite feed tube was replaced by a calibrated glass tube
during Runs 26 to 31 as Lucite was dissolved by the propionaldehyde
feed used in these runs.
J.
• i- • • i w it ; i. . .
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7; . xi : x J '• ...
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r • • • . •
• ■ ■ 1 ... v .. \ . 1. . ....... S.. O'. .
.. .. ... J . ; , . .
. 7 :: .......
... .. .. .' . j . . • . n , . . ,•..
7 .. / ... .. . X • . > ; .
•7. / /. 3 _ i -■■. _ .0 > *. . 1 . .. i
■ v .. . ■.. _ '• .' ■ ... ;• • . : : ! i i. .. ..... ...;• ,.
■
To W«t
Test
Meter
19
FIGURE 4 - PETAILED DIAGRAM OF GAS SAMPLING APPARATUS
20
PLATE 3 - MICROBELLOWS POSITIVE DISPLACEMENT PUMP
21
(h) Air and Nitrogen Purge System
For initial startup and reactivation of catalyst, an air
and nitrogen purge system was connected to the preheater. The purge
gas flowed through a calibrated rotameter, then into a needle valve
located near the preheater inlet. The low volume between the needle
valve and preheater inlet insured that little alcohol backed up into
the purge line during a run.
2. Experimental Technique
(a) Operation of Equipment
Fluidization of the catalyst bed was initiated by flowing air
through the bed at the rate of 4 - 5 cu. ft. per hour. This was con¬
tinued during the heating of the reactor to the desired level which
required 4 to 5 hours. When the reactor temperature was at the
desired point, nitrogen was flowed through the reactor to purge the
air from the system. This eliminated a potential explosive mixture
which could result from the hydrogen produced from the reaction and
the oxygen in the purging air. The nitrogen purge was continued for
15 minutes. After purging, the liquid feed pump was started and
alcohol or propionaldehyde metered into the preheater. The microbellows
feed pump could be adjusted for flow rates from 30 to 1500 mis./hr. by
varying the stroke of the bellows. Back pressure of 10 - 15 psig was
maintained in the discharge line by the adjustment of the metering
valve. After startup, the level in the feed reservoir was checked
over a period of time and final adjustments made to the pump to
achieve the flow rate desired.
i:<: g :r. ' • . r
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: i ..: :a
... ...v ...
I
22
When steady state conditions had been established, a one hour
run was made. At 30 minutes an uncondensed gas sample was taken and
pressured to 6 psig. The amount of feed, volume of off gas, weight
of liquid sample, reactor pressures and temperatures were recorded.
A liquid sample was taken from the liquid product and placed in
tightly stoppered bottles which were refrigerated until chromatographic
analyses were performed.
(b) Preparation of Catalyst
The chromic oxide on inactive alumina used in this study
was prepared by impregnating inactive alumina (Norton Company) with
chromium nitrate (Cr(N0 3 ) 2 •9H 2 0) in aqueous solution. The catalyst
was dried and decomposed at 700°C. in a fluidizing air stream.
The amount of chromic oxide on the inactive alumina was calcu¬
lated to be 6.3 per cent. A size analysis of the catalyst showed the
size distribution to be:
Size Range Weight %
+ 40
0
- 40
+
60
6.7
- 60
+
100
26.4
- 100
-1-
200
44.0
- 200
22.8
(c ) Analyses of Products
i) Liquid Products
Liquid compositions were determined by analyses using
a Burrell Model K-2 Kromotog gas chromatograph. Initially, several
column packings and operating conditions were studied in an attempt
t, J. $1 >■
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23
to find a column or columns which would give a satisfactory
separation of components. As many minor fractions were found to
exist in the liquid products, particularly during high reaction
temperature runs, this selection of a suitable column was difficult.
A 2 1/2 meter, Apiezon L grease on crushed firebrick column was
found to give satisfactory separation of the major components, namely
pentene, propionaldehyde, n-propanol, and diethyl ketone. The minor
fractions gave overlapping peaks in some cases; attempts to identify
them gave little success. The minor fractions were classed as
"other" in the analyses.
The following chromatographic conditions were used.
Column: 2 1/2 meter, Apiezon L on Firebrick.
Column Temperature: 130°C.
Carrier Gas: Hydrogen at 75 cc/min.
Detector Current: 200 milliamperes.
Sample: 5 microliters.
Quantitative determinations were made by assuming
that the area under any peak was proportional to the weight per cent
of that particular component in the sample. This method, while
unsound for analyses requiring a high degree of precision, provides
a relatively easy means of quantitative analyses to a reasonable
accuracy (10). In any case, a change from sample to sample is
readily detected despite the fact that the absolute percentage value
may be in error. Areas under the peaks were measured by use of a
planimeter.
ii) Gaseous Products
A Burrell Model K-2 Kromotog gas chromatograph similar
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24
to the one used for liquid analyses was used for quantitative
analyses of the uncondensed gaseous products.
Listed below are the columns and conditions used
and the separations achieved on each:
1.
Column -
2 1/2 meter, Linde Sieve
Column Temperature
Room temperature
Carrier Gas -
Helium at 40 cc-./min.
Detector Current -
180 milliamperes
S amp1e -
3 cc.
Separation -
Hydrogen, Oxygen, Nitrogen, Carbon Monoxide
2.
Column -
2 1/2 meter, Linde Sieve
Column Temperature
Room temperature
Carrier Gas -
Nitrogen at 40 cc./min.
Detector Current -
160 milliamperes
Sample -
3 cc .
Separation -
Hydrogen
3.
Column -
2 1/2 meter, Apiezon M on Firebrick
Column Temperature
70°C.
Carrier Gas -
Helium at 40 cc./min.
Detector Current -
190 milliamperes
S amp 1 e -
3 cc.
Separation -
Hydrogen, Oxygen, Nitrogen CO (one peak),
Carbon Dioxide, Propylene, Propionaldehyde,
n-Propanol, "other".
To perform
the above three determinations from one
s amp 1 e
it was necessary to
pressurize the glass sample bombs to
6 psig
. as discussed in the
equipment section. In addition, the
pressure in the bomb was found to be convenient for flushing the
gas sampling system installed in the Burrell Kromotog.
Calibration runs were made to improve the hydrogen
determination. As a result, this analysis is considered to be
the most accurate of the gaseous quantitative analyses. A similar
calibration was attempted for carbon monoxide, however, poor cali¬
bration reproducibility was experienced. The poor reproducibility
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. :
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25
obtained for carbon monoxide determinations would indicate that
the Linde Sieve column was possibly not inert to this component.
No attempts were made to determine more satisfactory means of
analyzing for carbon monoxide. The remainder of the gas was
quantitatively analyzed by assuming that peak height was proportional
to the volume per cent of that particular component in the sample.
As in the case of analyses of liquid products, several unidentified
components were classed as "other".
26
EXPERIMENTAL RESULTS
1. Conversion and Reaction Efficiencies
The analyses of liquid and gaseous products appear in Table I and
II in the Appendix. Tables III and IV show the operating conditions and
material accountabilities of Runs 8 to 25 and Runs 26 to 31 respectively.
Calculated conversions and reaction efficiencies appear in Tables V and
VI.
Results from Runs 1 to 7, associated with the startup of equip¬
ment were considered unreliable and are not reported as data. During
this period, analytical techniques and operating methods for the equipment
were established.
The following definitions were used in the preparation of Tables V
and VI.
(a) Dehydrogenation of n-propanol
% n-PrOH Conversion = Moles n-PrQH Fed - Moles n-PrOH in Product
Moles n-PrOH Fed
x 100
7 a PrH Reaction Efficiency = Moles PrH in Product x ^qq
Moles n-PrOH converted
°L Diethyl Ketone Efficiency = 2 x Moles DEK in Product x ^qq
Moles n-PrOH converted
7o PrH Conversion = Moles n-PrOH converted - Moles PrH in Product x -^qq
Moles n-PrOH converted
(b) Dehydrogenation of Propionaldehyde
7. PrH Conversion = Moles PrH Fed - Moles PrH in Product .
Moles PrH Fed
7o Diethyl Ketone Efficiency = 2 x Moles DEK in Product x ]_qq
Moles PrH converted
. ;
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: . ...... .. :: .... .. , y, \
■ • ' ' - * - : ■■ . '. . J ;. . - . .. . . y ,, ; .; ;
> • v, - 0 ; J.’ h
: - * • •• A ......a-. . i .. (. c '.
27
% Material Accountability = Weight of Products x ^.00
Weight of Feed
Figure 5 shows the percentage n-propanol conversion for different
operating temperatures and superficial linear gas velocities. While there
is a marked improvement in percentage conversion from 0.3 to 0.2 ft./sec.
superficial gas velocity, no difference was detected between the 0.3 and
0.4 ft./sec. velocities. The superficial linear gas velocity is calculated
on the basis of moles n-propanol fed through an empty reactor at reaction
temperature and pressure. The actual gas velocity through the bed will
vary with the extent of conversion of the n-propanol fed since the main
reactions occurring are accompanied by an increase of volume. A complete
sample calculation of superficial linear gas velocity is included in the
Appendix.
The percentage conversions of n-propanol shown in Figure 5 compare
very closely to results of Tollefson (9) over the same temperature range.
It must be noted, however, that the zinc oxide on inactive alumina catalyst
bed used by the above investigator was only 10 inches high so that the
contact time experienced for runs reported herein was much greater.
In Figure 6, a plot of propinnaldehyde and diethyl ketone reaction
efficiencies is given for the reaction conditions studied. In this case, the
propionaldehyde reaction efficiencies reported by Tollefson (9) are
approximately 20 per cent higher than reaction efficiencies reported in this
study; the diethyl ketone efficiencies are quite similar. For reasons
mentioned above, it appears that conversions and reaction efficiencies
obtained in this study are considerably lower than dehydrogenation performed
.
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FIGURE
28
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N0ISb3AN00 "lONVdOdd %
REACTION TEMPERATURE
29
30
in fluidized beds using zinc oxide catalyst. Recent work by Tollefson (9)
has shown that catalyst containing a high concentration of chromia does
not improve the results obtained in fluidized bed alcohol dehydrogenations.
In an attempt to obtain a further understanding of the mechanism
of dehydrogenation of n-propanol, Runs 26 to 31 were conducted using
propionaldehyde feed (88.2 per cent propionaldehyde). Komarewsky and
Coley (5) proposed that the aldehydes were intermediates in the dehydro¬
genation of alcohols. Komarewsky's work showed that dehydrogenation of
aldehydes gave higher conversions to ketones than did dehydrogenation of
corresponding alcohols. Figure 7 shows the total percentage conversion
and diethyl ketone reaction efficiency for the range of operating conditions
chosen -- 0.2 ft./sec. linear superficial velocity and 375, 425, 475, and
525°C.
While reaction efficiency to diethyl ketone was slightly higher
during runs using propionaldehyde feed, the total percentage conversion
is very low compared to the n-propanol dehydrogenation. Despite the higher
conversions to ketone reported by Komarewsky and Coley (5) when using
aldehyde feed, these results are quite plausible. The total conversion
of n-propanol includes the conversion to propionaldehyde as well as
propionaldehyde to diethyl ketone and other unidentified products. In Runs
26 to 31, the total conversion includes only the conversion from aldehyde
to ketone and other products; apparently the more difficult reaction to
complete. Figure 7 shows that the diethyl ketone efficiency was favored
by increasing temperature, a conclusion which is not apparent from the
dehydrogenation of n-propanol (Figure 6).
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FIGURE
31
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A0N3I0I333 NOIIDV 3 d >130% B N0ISd3AN0D H^d %
32
To achieve a more satisfactory means of comparing the
dehydrogenation of n-propanol and propionaldehyde, propionaldehyde
conversions from the n-propanol dehydrogenation were calculated. This
conversion was defined as the percentage moles of propionaldehyde converted
to diethyl ketone and "other" from the moles propionaldehyde available
for reaction. The moles propionaldehyde available for reaction was
estimated from the conversion of n-propanol, i.e. this assumes that all
n-propanol converted goes through the propionaldehyde intermediate and
that no "other" compounds are formed directly from n-propanol. The
propionaldehyde percentage conversions is then calculated as:
% PrH Conversion = Moles n-PrOH converted - Moles Prll in Product x -^qq
Moles n-PrOH converted
Propionaldehyde conversion from Runs 8 to 25 are shown in Figure 8.
In addition, the conversion from propionaldehyde dehydrogenations. Runs
26 to 31, is included. The propionaldehyde conversion of Runs 26 to 31
is considerably lower than conversion obtained in Runs 8 to 25 over the
temperature range 375 to 475°C. Conversions for Runs 8 to 25 show a
minimum at 450°C. for all superficial linear velocities studied. It is
proposed that the presence of the aldehyde depresses the activity of
the catalyst and that higher temperatures favor higher conversions of
propionaldehyde to diethyl ketone. At the lowest temperature studied,
375°C., only small amounts of propionaldehyde are formed, but as the
temperature increases the propionaldehyde concentration increases lowering
the catalyst activity. As the reaction temperature increases, this reduced
catalyst activity is offset by the effect of reaction temperature on conversion
For Runs 26 to 31, the propionaldehyde concentration is fixed by the feed
• \ ' ; '
: . . ..
V..; r.: ;
:) .
i ... . .. ; :
. • • .
\
(.
• <: :
. r: : \ ; ... : .: . . c •
/
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■
c. ;;..j
J
/■ ■. l: v. .
i J • .
c
i i
i.
i :
Vj
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A .
c
33
REACTION TEMPERATURE
*
34
composition and the curve reflects only the influence of temperature on
propionaldehyde conversion.
The effect of propionaldehyde on catalyst activity was also
encountered by Neish (8), who stated that:
"One might be tempted to conclude .•. that the primary
alcohol group required more energy for activation than the
secondary alcohol group. This is misleading, however, since
in reality the primary group is dehydrogenated just about as
readily as the secondary. The differences observed are
caused by reversible combination of the products of dehydro¬
genation with the catalyst,* The aldehydes show a marked
tendency to lower the activity of the catalyst as does diacetyl,
while the simple methyl ketones have little or no effect."
2. Order of Reaction
Previous investigations (1,8) have shown that the dehydrogenation
of alcohols over many catalysts followed a first order rate equation.
Also, the same investigators found that all alcohols studied obeyed
the Arrhenius relation for variation of rate with temperature.
Neish (8) plotted log C, the fraction unchanged, versus
t, time of reaction and obtained linear plots for one temperature indicating
that the reaction was of the first order type. A similar calculation was
o
performed for the n-propanol dehydrogenation at 375, 425, 475, and 525 C.
(Table VII). A constant fluidized bed height was assumed for calculation
of reaction time. The plots (Figure 9) indicate that a first order
reaction was experienced in this study.
* Catalysts studied by Neish were copper and nickel on various
supports prepared by several methods.
35
C£
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Q —I
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HO J d u Q39NVH0Nn NOIJLVU1N39N00 903
T I'M E OF REACTION ~ SECONDS
36
The rate constant, k, is defined by the familiar expression:
2.303 1
k = t log c
where t and C are reaction time and fraction unchanged. Table VIII
shows the calculation of log k for the four reaction temperatures
studied. The plot of log k versus Js is shown in Figure 10. The
linear relation between log k and was found to hold indicating that
the reaction rate constant is dependent on temperature as indicated by
the Arrhenius equation.
The calculations described above are not strictly true since
the formation of products in the reactor does not occur instantaneously.
Actually, the composition of the gas varies along the reactor as products
are formed according to the first order relation. Another assumption
used is that backmixing in the fluid bed is negligible. No attempt
was made to account for these deviations from the idealized case.
3. Thermodynamic Equilibria of Chemical Reactions
For the purpose of the thermodynamic analysis, reaction equilibrium
constants for two reactions were considered:
PrOH -PrH + H 2 -- (1)
2PrOH ——► DEK + CO + 3H 2 ..-.. (2)
Calculations of the equilibrium constants, K a , for reaction temper¬
atures of 375, 425, 475, and 525°C. for each of these reactions are shown
in the Appendix. Since complete thermodynamic properties of diethyl ketone
were not available, estimates were made to determine the free energy of
-
.
: t j, .3 _ . : .. .' :
. . .
. > : ’ J .Kg 1 tt... .
. ffi.., 1 ;. t#i, *
; _Jp.Ci'l ,jl1;,
/ : . . ii. 1 ^ i
, . ... : .1 • ■' ■ : ..
■ U i ■ v
. : ... . :. . .
r- ■ ; :
37
1.25 1.30 1.35 1.40 1.45 1.50 1.55
38
formation and heat of formation for this reaction product. Heat capacities
of n-propanol, propionaldehyde, and diethyl ketone were similarly estimated.
For the temperature range considered, the natural logarithm of
equilibrium constants varied from 1.97 to 3.16 for reaction (1) and from
14.9 to 21.0 for reaction (2). This would indicate the reactions must
proceed essentially to completion before equilibrium is reached. The
equilibrium constants increased with increasing temperature showing that
both reaction equilibria are favored by a rise in temperature.
The low conversions obtained in this work indicate that rate is the
controlling factor as complete conversion would occur if the reactants
could be activated in some way.
4. Condition of Equipment
Upon completion of runs reported herein, the upper reactor
was inspected for cleanliness. Fine catalyst and carbon were deposited
on the bottom of the screen and baffle.. The top of the screen was
covered with a tacky carbon-like deposit. Photographs of the conditioning
of the upper catalyst filter are shown in Plates 4 and 5.
.
: 1
.. .V
-
' j
r
< .;j) •' i... , - I’ - '/
. (
39
<%
PLATE 4
|
- TOP VIEW OF UPPER CATALYST FILTER
PLATE 5 - BOTTOM VIEW OF UPPER CATALYST FILTER
- 40
CONCLUSIONS
1. Validity of Results
Considering the two main overall reactions of the dehydrogenation
of n-propanol,
PrOH - 5 - PrH + H 2
2Pr0H—DEK + CO -!- 3H 2
the hydrogen evolved can be predicted knowing the moles propionaldehyde
and diethyl ketone in the product. As discussed in the analytical
methods section, the hydrogen analyses are regarded as the most reliable
of the gaseous analyses. Calculations of predicted moles hydrogen versus
actual moles hydrogen is given in Table IX; a plot is shown in Figure 11.
This plot shows fair agreement with the theoretical prediction, indicating
a reasonable accuracy of analyses.
Material accountabilities of Runs 8 to 25 range from 93.6 to
108.0 per cent; Runs 26 to 31 ranged from 88.0 to 108.5 per cent. Runs
26 to 31, the dehydrogenation of propionaldehyde, were shortened to
30 minutes which could account for the greater range of material accounta¬
bility experienced.
2. Summary of Experimental Results
1. The dehydrogenation of n-propanol in a fluidized chromia on inactive
alumina catalyst has been studied and conversions and reaction
efficiencies plotted for a range of reaction temperatures and
e •
Ci :■ i
, i .. i.i J
t i. \ •. w. -• 7. ..
_ , ...... . , r 7 ,
. • . - . - : . - . .. r -
J c i .. . j :: ,. ' . .
1
.
; . ■ ; ; •
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41
_j
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rn
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C>J
o
MOLES HYDROGEN IN OFF GAS
42
superficial linear gas velocities. Indications are that
the chromia on inactive alumina catalyst used in this work is
a less desirable dehydrogenating catalyst than reported by other
workers.
2. A similar dehydrogenation of propionaldehyde has been performed
for one superficial linear gas velocity. The use of a
propionaldehyde feed resulted in slightly improved conversions to
diethyl ketone, however, there is evidence that the presence of
the aldehyde tends to lower the overall activity of the catalyst.
3. The dehydrogenation of n-propanol was shown to follow a first
order reaction and the reaction rate was found to vary with
temperature as indicated by the Arrhenius equation.
4. Thermodynamic equilibrium constants have been determined at
temperatures for the reactions considered in this study. The
high values of equilibria constants obtained would indicate that
the dehydrogenation of n-propanol to propionaldehyde and diethyl
ketone is thermodynamically feasible and that the reaction warrants
further study.
5. The equipment used in this study functioned satisfactorily with
adequate and sensitive control of reaction temperature over the
superficial linear gas velocities studied.
-
: O . 7
V. :
. . : ' .
• - •' :
■- .■■■ jll i
f >V i*rr
: ; '
.
. . • .. . •
■ ■ ... • . 1 '■ ,
.
r. 7 7
.. ...
...
■
- - .. V ., ,
' ■
•i
. ' •
' . ' ;
- 43
BIBLIOGRAPHY
1. Church, J. M. and H. K. Joshi., Ind.. Eng. Chem. , A3, 1804, (1951).
2. De Q. Jones, H. K., M.Sc. Thesis, Univ, of Toronto, (1959).
3. Gilliland, E. R. and E. A. Mason., Ind. Eng. Chem., 44, 218, (1952).
4. Ipatieff, V. N. et al., Ind. Eng. Chem., 41., 1802, (1949).
5. Komarewsky, V. I. and J. R. Coley., J. Am. Chem. Soc., 63 _, 700, 3269,
(1941).
6. Leva, M., Chemical Engineering, 289, October, (1957).
7. Mickley, H. S. and C. A. Trilling., Ind. Eng. Chem., 41, 1135, (1949).
8. Neish, A. C., Can. Journal of Research, 23B, 49, (1945).
9. Tollefson, E. L., Private Communication, November, (1959).
Warren,' G. W. et al. , Analytical Chem., 31., 1626, (1959).
10 .
0
- *
. 1
.
44
APPENDICES
A. THERMODYNAMIC STUDY OF REACTION EQUILIBRIA
B. SAMPLE CALCULATIONS
C. EXPERIMENTAL DATA
- 45
A. THERMODYNAMIC STUDY OF REACTION EQUILIBRIA
- 46
Thermodynamic Study of Reaction Equilibria
For the purpose of this thermodynamic analysis of the
dehydrogenation of n-propanol, the two following reactions were considered:
ch 3 - ch 2 - CH 2 0H (g)^rCH 5 - CH 2 - C* (g) + h 2 (g) - (1)
H
2CH 3 - GH 2 - CH 2 OH (g)^Z«rCH 3 - CH 2 - C - CH 2 - CH 3 (g)
0
+ CO (g) + 3H 2 (g) -.— (2)
To perform the calculations for the determination of reaction
equilibrium constants for each reaction, it was necessary to determine the
free energy of formation (A F )> heat of formation (AH), and specific
heat (Gp), of the reactants and products.
The free energy of formation of diethyl ketone was estimated using
the emperical group contribution method of J. W. Anderson, G. H. Beyer, and
K. M. Watson.* A similar method** was used to estimate the heat of formation
of diethyl ketone. Specific heats of n-propanol, propionaldehyde, and
diethyl ketone were determined using a group contribution proposed by
Anderson, Beyer, and Watson.*** The remaining thermodynamic properties
were obtained from Perry.****
*
Reid,
R. C., and T. K. Sherwood, "The Properties of Gases and Liquids",
p. 129, McGraw-Hill Book Company, Inc., New York, (1958).
kk
Ibid.
, p. 117.
kkk
Ibid.
, p. 152.
kkkk
Perry
, J. H., "Chemical Engineers 1 Handbook", 220, 238, McGraw-Hill
Book Company, Inc., New York, (1950).
o
£
- 47
Heats of formation and free energies of formation for reactants
and products of the two reactions considered are shown below.
Component
n-propanol (g)
propionaldehyde (g)
diethyl ketone (g)
carbon monoxide (g)
Ah A F
kcal./mole kcal./mole
@ 25°C.
@ 25°C.
- 61.17
- 49.15
-63.0
- 26.42
- 38.83
- 33.96
-34.6
- 32.81
The following heat capacity expressions were used in the
calculations:
n-propanol
3 ^ 2
Cp = 4.69 + 68.32 x 10 T - 23.84 x 10 T
propionaldehyde
3 6 2
Cp = 5.13 + 27.46 X 10 T - 6.61 x lo" T
diethyl ketone
Cp = 7.98 + 84.29 x 10 _3 T + 27.35 x IQ -6 ! 2
carbon monoxide
Cp = 6.60 + 1.20 x 10 T
hydrogen
Cp = 6.62 + 0.8 x 10 _3 T
The equilibrium constant, Ka, was expressed as a function of
absolute temperature using the following relationships:
- 48
In Ka
✓D T
A H°
RT2
where AH?
and, A C p
.c
J298
C p dT
- Ah 298
= Cp (products) - Cp (reactants)
For reaction (1),
H 2 93 = -49.15 - (-61.17) = 12.02 kcal./mole
A C p = 6.86 - 40.05 x 10‘ 3 T + 17.23 x 10~ 6 T 2
RT In Ka x = 2.87 x lO'S? 2 + 6.86 In T - _ 2.02 x 10"^T + C
where C is the constant of integration.
To establish a value for the constant of integration, Ka x can be
calculated at 298°K. using the free energy of formation data available
at that temperature.
A F° = - RT In Ka
R
where,A F° = F? (products) - F? (reactants)
In the case of reaction (1),
AFr = 33.96 - (-38.83) = 4.87
- RT In Ka = 4.87
This
In Ka = -8.22 at 298°K.
establishes the lower limit,
In Ka>j,
A o
Ah t
RT 2
in the expression,
dT
.
1 \
:> ■-
:: I
c -
.
,
y. . . ■: >
. ...
k
>
s ...' .. ■■ ■ .: i:-j
' - . ■
.
- 49
Finally, for reaction (1),
R (In Ka x + 8.22) = “ 11500
“2 6 2
+ 6.86 In T - 2.02 x 10 T + 2.87 x 10 T
298
where T is the reaction temperature in °K.
Similarly for reaction (2),
A ^298 = 33.0 kcal./mole
Ac p = 25.05 - 48.72 x 10 _3 T + 75.03 x 10
R In Ka 2 = 25.05 In T - 2.42 x 10 _2 T + 1.25 x 1Q" 5 T 2
AFr = 10.3 kcal./mole
In Ka = -17.4 at 298°K.
6 2
T
27036
T
r -2 -52
R (In Ka 2 + 17.4) = I 25.05 In T - 2.42 x 10 T + 1.25 x 10 T
27036
T
Equilibrium constants for reaction (1) and (2) are shown below
for the temperatures studied for the dehydrogenation of n-propanol.
o
Temperature C.
In Ka n
In Ka ;
375
1.97
14.9
425
2.47
17.2
475
2.88
19.2
525
3.16
21.0
c
>
.
L
t i .1
s
50
B. SAMPLE CALCULATIONS
51
Sample Calculations - Run 12
1. Superficial Linear Gas Velocity
Sup . Gas Vel. f t.
3
359 ft
= feed rate
sec. hr.
EL. X 0.804 S22-s x 1 lb - x 1 lb -
ml. 453 gms. 60 lb.
mole
Reactor Temp °R 29 .92 in. Hg
lb. mole
1 hr.
3600 sec.
492°R
_ l _
Reactor Area ft^
x
Reactor Pressure in. Hg
Reactor Area = 2.175 x 10 ^ ft^
Sup. Gas Vel. ft. _ £ ee( j rate ml s. Reactor Temp °R
sec. hr. Reactor Press, in Hg.
Run 12 - Reactor Temp. = 425°C. = 1257°R.
Reactor Press. = 3.0 +27.5 = 30.5 in. Hg.
Feed Rate = 620 mis./hr.
x 8.25 x 10
-6
Sup. Gas Vel. ft. = mis. x 1257 .. R x 8-25 x 10
hr. 30.5 in.Hg.
-6
sec,
= 0.209 ft.
sec.
2. Material Accountability - Run 12
Vol. of n-Propanol Fed = 620 mis.
O
Vol. Off Gas = 2.35 ft @ 70°F, 1 atm.
Wt. Liquid Product = 446 gms.
Analysis of Gas:
h 2
= 46.7
(Volume or
CO
= 2.0
mole 7o)
C0 2
= 4.5
c 3
= 38.7
PrH
= 1.1
n-PrOH
= 1.9
Unknown
= 5.0
! ,
" V
<L'.
.
; c
c. .
■ ■ ■ i \
V
3
L
52
Volume of Off Gas at S.T.P.
492 27.5
X 530 X 29.9
2.01 ft .
= 2.01 ft" 3
x 28.32
litres = 56.9 litres
f t 3
Moles of gas
= 56.9 _
22.4
2.54 gm-moles.
Component
Mole 7 0
Moles
M.Wt. Weight (gm;
h 2
46.7
1.19
2 2.4
CO
2.0
0.05
28 1.4
co 2
4.5
0.11
44 4.8
C 3~
38.7
0.98
42 41-.1
PrH
1.1
0.03
58 1.7
n-PrOH
1.9
0.05
60 3.0
Unknown
5.0
0.13
40* 5.1
59.5
* Note:
Assumed
Molecular Weight
Total Wt.
of Products = 59.5 + 446 = 505.5 ;
Wt. of Feed = 620
mis. x 0.80 x = 498 ;
7 , Material Accountability
— Pr g' is - - - x 100
Wt. Feed
505.5 (100 )
498
= 101.5 7 .
C . «1 t. :
53
C. EXPERIMENTAL DATA
54
TABLE I
ANALYSES OF LIQUID PRODUCTS (WEIGHT %)
DEHYDROGENATION OF n-PROPANOL AND PROPIONALDEHYDE WITH A FLUIDIZED
CHROMIC OXIDE ON INACTIVE ALUMINA CATALYST
Run No.
Pentene PrH n-PrOH DEK Other
n-Propanol Feed
8
33.5
50.3
9 .40
6.6
9
•JU
A
53.2
20.6
10.90
5.3
10
*
52.9
19.6
12.30
15.2
11
0.50
6.8
83.6
0.70
8.5
12
0.67
18.0
70.0
2.35
8.0
13
1.12
32.9
55.8
2.50
7.6
14
0.85
59.9
19.8
10.00
9.5
15
0.34
3.9
90.2
0.80
4.8
16
0.78
12.3
79.2
. 1.84
5.9
17
0.26
4.4
89.7
0.65
5.0
18
0.71
14.9
77.9
2.12
4.4
19
0.71
53.4
31.9
6.70
7.6
20
0.83
34.9
55.9
3.10
5.6
21
0.85
32.1
57.4
3.50
6.3
22
0.70
56.5
27.1
8.00
7.7
24
1.05
19.6
62.0
4.10
13.1
25
0.60
37.6
42.5
8.50
11.0
Propionaldehyde Feed
26
84.0
0.70
15.3
27
83.7
1.20
15.1
28
75.0
3.60
21.4
29
59.5
11.00
29 .2
30
86.6
0.40
13.0
31
83.8
0.80
15.4
PrH Feed Stock
88.2
11.8
* Not determined
;."ju j. ' .
■ ■ ■ i
■/....: r
... (
J
r
L
55
TABLE II
ANALYSES OF GASEOUS PRODUCTS (VOLUME %)
DEHYDROGENATION OF n-PROPANOL AND PRO PIONALDEHYDE WITH A FLUIDIZED
CHROMIC OXIDE ON INACTIVE ALUMINA CATALYST
Run No.
H2
CO
COp
C 3
PrH
n-PrOH
Unknown
n-Propanol Feed
11
59.0
0.5
2.3
31.9
0.5
0.7
6.2
12
46.7
2.0
4.5
38.7
1.1
1.9
5.0
13
37.8
2.7
6.3
44.5
1.5
2.8
4.4
14
44.0
3.0
6.9
37.6
1.3
3.1
4.1
15
70.0
0.6
1.7
21.7
0.3
0.7
5.0
16
57.2
1.5
2.9
31.4
0.7
1.5
4.8
17
70.0
0.8
2.0
21.0
0.4
1.4
4.5
18
58.2
1.8
3.4
30.6
0.8
1.9
3.2
19
43.3
3.0
8.4
37.7
1.2
2.5
3.9
20
54.3
3.3
5.4
31.8
1.0
2.2
2.0
21
43.5
3.6
6.9
39.4
1.3
2.9
2.5
22
50.5
3.5
7.6
31.6
1.0
3.3
2.5
24
61.5
3.1
3.7
27.0
0.8
1.6
2.3
25
53.5
4.0 .
5.3
31.5
1.1
2.8
1.8
Propionaldehyde Feed
26
36.0
25.0
28.8
5.1
1.9
3.3
27
33 ..5
35.0
21.2
5.4
1.6
3.4
28
32.5
49.0
*
*
n
29
32.5
46.0
12.5
3.3
1.0
4.7
30
35.0
25.0
32.9
4.0
2.7
2.8
31
34.0
34.0
22.2
3.9
0.4
5 .5
Not determined
56
TABLE III
OPERATING CONDITIONS AND MATERIAL ACCOUNTABILITIES
DEHYDROGENATION OF n-PROPANOL WITH A FLUIDIZED CHROMIC OXIDE
ON INACTIVE ALUMINA CATALYST
Wt. of Material
Run No.
Reactor
Temp
°C
Feed
Rate
mis./hr.
Reactor
Press
in.Hg.
Lin. Gas
Velocity
ft./sec.
Vol. of
Off Gas
ft 3 @ NTP
Liquid
Prods.
gms.
Account'
ability
7
/o
8
475
587
2.75
0.212
4.72
350
9
525
590
3.50
0.226
8.77
271
*
10
554
520
3.50
0.206
9.85
203
11
375
680
3.00
0.212
0.76
529
99.6
12
425
620
3.00
0.209
2.35
446
101.5
13
475
573
3.25
0.205
4.19
357
105.0
14
525
500
3.50
0.190
6.90
188
93.6
15
375
1030
3.25
0.327
0.72
819
101.0
16
425
875
3.40
0.293
2.15
663
100.8
17
375
1300
3.85
0.398
1.11
1023
99 .4
18
425
1190
4.40
0.386
3.29
901
101.5
19
525
1025
5.75
0.362
13.40
521
108.0
20
475
1135
5.15
0.386
7.95
742
101.1
21
475
855
4.50
0.296
6.47
549
106.0
22
525
.820
5.25
0.296
11.10
374
99.5
24
425
550
3.50
0.184
2.10
398
99.1
25
475
537
3.75
0.191
4.83
317
99.1
* Gas analyses not determined
57
TABLE IV
OPERATING CONDITIONS AND MATERIAL ACCOUNTABILITIES
DEHYDROGENATION OF PROPIONALDEHYDE WITH A FLUIDIZED CHROMIC OXIDE
ON INACTIVE ALUMINA CATALYST
Run No.
Reactor
Temp .
°C
Feed
Rate
mis./hr.
Reactor
Press.
in.Hg.
26
375
584
3.25
27
425
544
3.25
28
475
515
3.50
29
525
447
4.00
30
375
580
■3.50
31
425
536
3.50
Lin. Gas
Velocity
ft. / sec.
Vol. of
Off Gas
ft 3 (a NTP
Wt. of
Liquid
Prods.
gms .
Material
Account¬
ability
%
0.190
0.205
407
88.0
0.190
0.348
408
95.6
0.191
1.435
366
99 .5
0.175
3.920
218
93.1
0.187
0.154
456
108.5
0.186
0.328
393
93.1
: 'iT.ilM
w i
c
CALCULATIONS OF CONVERSIONS AND REACTION EFFICIENCIES
58
d
o
•H
CO
. o
M3
M0
m
t—1
m
MO
CTN
m
in
O
in
m
H
Ed
Pi
c n
p
CD S'?
o
CO
CO
00
cn
CM
CM
MO
MO
1-1
o
00
oo
>p
CP
>
m
M3
1^-
MO
m
in
nO
MO
m
MO
m
m
NO
m
m
d
<3
o
H
o
<3
u
<3
ti
is
o
H
•H
4-J
o
E3
o
d
d
CD
i—1
00
CM
Mt
on
00
CM
i—1
MO
m
in
cn
in
m
t-'-
<i
0)
•H S'?
Pi
CD
CM
ON
ON
in
o
CON
r-
o
NO
i—1
CM
w
•H
1-1
i—1
i—1
>
X
MP
M
w
MP
H
o
CD
O
<3
3
H
d
o
kO
s
•H
a
o
•u
d
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CD
w
cd
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m
<r
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m
m
on
00
m
i—i
CM
m
m
o
i—1
m
m
Q
<d
<J B-S
M
Pi
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l-1
m
CON
nO
MO
l—1
MO
m
cn
cn
ON
ON
i—1
i—i
X
MP
CO
CM
cn
<fr
cn
CO
CO
in
•d-
m
<{■
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m
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s
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00- <t
00
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cn
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NO
CM
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Q
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p
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CD g-S
CM
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o
oo
r^.
MO
o
o
in
CM
MO
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<1-
<!■
00
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00
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i—1
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m
CON
1—1
CM
1-1
CM
00
m
m
00
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NO
M
1
d
Q
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o
P
Pi
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CD
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r—1
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p CD
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cn
i—l
cn
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m
ON
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ON
M
I—1
CP >
33
o
i d
NO
nO
r—4
cn
MO
i—1
CM
CM
o
00
MO
ON
cn
S
d o
1 —1
hJ
u
O
CP
Ed
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CO
o
CM
nO
o
i—1
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1-1
CM
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m
I—1
m
o
o
Pi
01
P TO
00
ON
ON
I—1
CO
M0
r*-
00
ON
CM
<t
o
CO
CM
Cl,
i—1
CP 0)
1
o
1 MP
nO
ON
00
nO
CO
i—i
m
CO
m
i—1
T—1
r^.
c
Pp
o
£
d
i—l
i—i
i—i
t—1
i—i
i—1
t—1
1—1
/-~N
X
CM
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M0
CM
<t
ON
MO
CM
00
CM
m
CO
00
00
3
CO
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<t
ON
CM
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T—1
r-
CM
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MO
CM
<1*
00
i—i
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CD
w
CO
cn
CM
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1-1
1—1
CM
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1-1
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CM
CM
CM
cn
1—1
CO
H
1 - 1
a
H
o
o
O
o
o
O
o
O
o
O
o
O
o
O
O
o
o
o
<3
£3
3
'w'
w
o
4-J
o
o
Ed
Pi
Q
0
O
cn
MO
CON
O
CM
CM
CON
LO
CO
o
NO
o
m
o
CM
m
T3
P
ON
On
MO
cn
CM
cn
MO
CM
r-
cn
r-
CM
1 - 1
CM
X
O
CP
td
P
0
CM
o
O
m
CO
O
CM
00
m
i—i
CM
NO
m
i — i
-d-
CM
w
CP
d
1 - 1
i — 1
i — i
Q
T3
•H
d
CT*
H-pJ
CM
00
in
CM
CTN
cn
<1“
m
1 — 1
00
CO
a>
MO
in
m
•H
P
O
00
MO
cn
o
ON
m
r^-
CO
<t*
o
NO
CO
o
CP
o
13
CM
CM
r—1
O
l — 1
CM
T—1
o
T—1
o
CM
CO
cn
i—l
CM
00
ON
o
r—1
CM
cn
LO
M0
1^*
00
o
i—1
CM
-4-
m
8
pi
i — 1
r—1
1 - 1
l—1
1 - 1
i — 1
r—1
1—1
1—1
i—i
CM
CM
CM
CM
CM
59
TABLE VI
CALCULATION OF CONVERSIONS AND REACTION EFFICIENCIES
DEHYDROGENATION OF PROPIONALDEHYDE WITH A FLUIDIZED CHROMIC OXIDE
ON INACTIVE ALUMINA CATALYST
Liquid Product (Moles)
Run No. PrH DEK
Moles Moles
PrH PrH
Fed* Converted
PrH
Conversion
7 .
DEK
Efficiency
7
_ fo _
26
5.90
0.032
7.15
1.25
17.5
5.1
27
5.90
0.057
6.66
0.76
11.4
15.0
28
4.75
0.154
6.31
1.56
24.8
19.7
29
2.24
0.279
5.48
3.24
59.1
17 .2
30
6.81
0.021
7.12
0.41
5.8
10.2
31
5.87
0.037
6.59
0.92
14.0
7.8
* Based on fraction of propionaldehyde in feed
TV .
, ' L'
:r '
■ }
. ; O' .;
; f!
I - :*
.1
60
TABLE VII
CALCULATIONS OF LOG CONCENTRATION OF UNCHANGED n-PROPANOL
AND TIME OF REACTION
DEHYDROGENATION OF n-PROPANOL WITH A FLUIDIZED CHROMIC OXIDE
ON INACTIVE ALUMINA CATALYST
Run No.
Reactor
Temp.
°C
Time of
Reaction
secs.
Moles
n-PrOH
fed
Moles
n-PrOH
in Prod .
Fraction
Unchanged
C
Log 10 C
11
375
14.15
9.10
7.37
0.812
1.910
15
375
9.18
13.80
12.29
0.890
1.948
17
375
7.54
17.42
15.33
O'. 880 •
1.944
12
425
14.35
8.31 '
5.20
0.626
1.796
16
425
10.25
11.71
8.75
0.746
1.872
18
425
7.77
15.92
11.70
0.734
1.865
24
425
16.30
7.37
4.12
0,560
1.748
8
475
14.15
7.87
2.94
0.374
1.572
13
475
14.60
7.67
3.32
0.433
1.636
20
475
7.77
15.21
6.90
0.453
1.654
21
475
10.10
11.45
5.25
0.459
1.661
25
475
15.70
7.20
2.25
0.312
1.494
9
525
13.30
7.92
0.93
0.117
1.068
14
525
15.80
6.70
0.62
0.093
2.966
19
525
8.30
13.75
2.76
0.200
1.300
22
525
10.10
11.00
1.70
0.155
1.189
61
TABLE VIII
CALCULATIONS OF VARIATION OF THE RATE OF DEHYDROGENATION OF n-PROPANOL
WITH TEMPERATURE
DEHYDROGENATION OF n-PROPANOL WITH A FLUIDIZED CHROMIC OXIDE
ON INACTIVE ALUMINA CATALYST
Run No.
Fraction
Unchanged
C
Time of
Reaction
secs .
Reaction Rate
Constant
k
A x 103
Logio
11
0.812
14.15
0.0146
1.545
2.164
15
0.890
9.18
0.0129
1.545
2.110
17
0.880
7 .54
0.0169
1.545
2.227
12
0.626
14.35
0.0325
1.430
2.512
16
0.746
10.25
0.0285
1.430
2.454
18
0.734
7.77
0.0395
1.430
2.596
24
0.560
16.30
0.0356
1.430
2.550
8
0.374
14.15
0.0700
1.350
2.846
13
0.433
14.60
0.0575
1.350
2.759
20
0.453
7.77
0.1020
1.350
1.008
21
0.459
10.10
0.0772
1.350
2.887
25
0.312
15.70
0.0740
1.350
2.868
9
0.117
13.30
0.1600
1.250
1.206
14
0.093
15.80
0.1510
1.250
1.178
19
0.200
8.30
0.1940
1.250
1.288
22
0.155
10.10
0.1850
1.250
1.266
62
TABLE IX
CALCULATION OF PREDICTED MOLES HYDROGEN AND ACTUAL MOLES HYDROGEN EVOLVED
DEHYDROGENATION OF n-PROPANOL WITH A FLUIDIZED CHROMIC OXIDE
ON INACTIVE ALUMINA CATALYST
Run No.
Liquid
Prll
moles
Product
DEK
moles
Moles PrH
-f
3(moles DEK)
Per Cent
Il 2 in Off
Gas
Vol. of
Off Gas
ft 3
H 2 in
Off Gas
moles
11
0.62
0.046
0.75
59.0
0.76
0.44
12
1.39
0.122
1.75
46.7
2.35
1.32
13
2.03
0.104
2.34
37.8
4.19
1.90
14
1.94
0.219
2.60
44.0
6.90
3.65
15
0.55
0.076
0.78
70.0
0.72
0.60
16
1.41
0.142
1.83
57.2
2.15
1.48
17
0.78
0.078
1.01
70.0
1.11
0.89
18
2.33
0.222
3.00
58.2
3.29
2.30
19
4.79
0.405
6.01
43.3
13.40
6.95
20
4.46
0.268
5.26
54.3
7.95
5.17
21
3.04
0.224
3.71
43.5
6.47
3.38
22
3.64
0.348
4.69
50.5
11.10
6.71
24
1.35
0.188
1.91
61.5
2.10
1.55
25
2.05
0.314
2.99
53.5
4.83
3.10
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