Title of Invention

"A CATALYTIC REACTOR FOR THE CATALYTIC CONVERSION OF A FEED STREAM"

Abstract Disclosed is an apparatus and process for controlling residence time in a reaction zone by adjusting the effect of reactor volume varying the elevation of feed introduction or the space velocity in a fluidized catalytic conversion reactor. Changing effective volume results in controllable residence time and/or space velocity. The effect of reactor volume may be changed by altering the space velocity the feed distributor elevation, diluent flow rate or the number of reaction subsections to which feed is distributed.
Full Text BACKGROUND OF THE INVENTION
[0001] The present invention relates to a catalytic reactor for the catalytic
conversion of a feed stream and generally to a catalytic conversion reactor and process utilizing a catalytic reaction zone with a controllable effective volume or space velocity.
[0002] In many catalytic reactions, it is important that reactants be well mixed with catalyst
to afford sufficient opportunity for the reactant to contact the catalyst Fluidized reactors have
been designed to ensure adequate mixing of catalyst and reactants. Fluidized reactors are
designed to ensure that the reactants are in contact with the catalyst for sufficient time to allow
for the reaction to proceed. However, in many catalyzed reactions the reactants should not
remain in contact with catalyst too long of overconversion can occur which can generate
undesirable byproducts and degrade product quality. This is especially true when the reaction
involves hydrocarbons of which overreaction can cause excess generation of coke, inhibiting
catalyst activity and selectivity.
[0003] Space velocity typically referred to as weight hourly space velocity (WHSV) is
crucial to ensuring that reactants and catalyst are in contact for the optimal duration. Space
velocity is a reaction condition mat is important when rapid reaction times are involved such as
monomolecular catalytic cracking reactions or rapid catalytic conversion reactions. The catalyst
and reactants need to make contact, but excessive contact time will cause additional undesirable
reaction to occur. Space velocity is calculated by Formula 1:


(Formula Removed)
where WHSV is the weight hourly space velocity, Mf is the mass flow rate of feed to the reactor
and mc is the mass of catalyst in the reactor. Space time is the inverse of space velocity. The
mass of catalyst, mc, can be determined by Formula 2:

(Formula Removed) (2)

where AP is the pressure drop over the height, h, of the reactor and V is the volume of the
reactor. The ratio of pressure drop and height is the catalyst density in the reactor:
(Formula Removed) (3)

[0004] Hence, combining Formulas 2 and 3:
(Formula Removed) (4)
Accordingly, both density, pc, and space velocity, WHSV, are functions of pressure drop, AP.
From Formula 4, the relationship of space velocity and volume is shown in Formula 5:
(Formula Removed) (5)
[0005] Catalyst flux is determined by Formula 6:
(Formula Removed) (6)

where toc is catalyst flux, Mc is the mass flow rate of catalyst and A is the cross sectional area of
the reactor. Additionally the product of height, h, and cross-sectional area, A, when constant, of
the reactor is the reactor volume, V:
(Formula Removed) (7)
[0006] The mass flow rate of feed, Mf, to the reactor is calculated by Formula 8:
(Formula Removed) (8)
where v^ is the superficial gas velocity of the feed, p^ is the density of the feed and A is the cross
sectional area of the reactor at which the velocity is measured. Hence, substituting Formulas 2, 7
and 8 into Formula 1 for constant cross-sectional reactor area yields formula 9:
(Formula Removed)
[0007] Residence time is a reaction condition that is important when the reaction is not as
rapid. The catalyst and reactaiits need to soak together to ensure catalyst and reactaiits are in
contact and for a sufficient period of tune to allow the reaction to occur. Residence time, Tr, is
calculated by Formula 10:
(Formula Removed)
where Qf is the actual volumetric flow rate of feed at reactor process conditions of temperature
and pressure. The volumetric flow rate, Qf, to the reactor is calculated by Formula 11:
(Formula Removed)(11)
Substituting Formulas 7 and 11 into Formula 10 for constant cross-sectional reactor area yields:
(12)
(Formula Removed)
In a fluidized catalytic reactor, the flow characteristics may be considered to assure space
velocity or residence time is optimal.
[0008] Two types of fluidization regimes typically used in fluidized catalytic reactors are a
transport flow regime and a bubbling bed. Transport flow regimes are typically used in FCC
riser reactors. In transport flow, the difference in the velocity of the gas and the catalyst, called
the slip velocity, is relatively low, typically less than 0.3 m/s (1.0 ft/s) with little catalyst back
mixing or hold up. Slip velocity is calculated by formula 9:
(Formula Removed)
where vs is the slip velocity, vf is the superficial gas velocity of the feed, vc is the catalyst
velocity and e is the void fraction of the catalyst. Another way to characterize flow regimes is by
slip ratio which is the ratio of actual density in the flow zone to the non-slip catalyst density in
the flow zone. The non-slip catalyst density is calculated by the ratio of catalyst flux to the
superficial gas velocity as in formula 10:
(Formula Removed)
where pcns is the non-slip catalyst density in the flow zone, superficial gas velocity of the feed. The slip ratio is proportional to the hold up of catalyst in the
flow zone. Typically, a slip ratio for a transport flow regime does not reach 2.5. Consequently,
the catalyst in the reaction zone maintains flow at a low density and very dilute phase
conditions. The superficial gas velocity in transport flow is typically greater than 3.7 m/s (12.0
ft/s), and the density of the catalyst is typically no more than 48 kg/m^ (3 Ib/ft^) depending on
the characteristics and flow rate of the catalyst and vapor. In transport mode, the catalyst-vapor
mixture is homogeneous without vapor voids or bubbles forming in the catalyst phase.
[0009] Fluidized bubbling bed catalytic reactors are also known. In a bubbling bed,
fluidizing vapor forms bubbles that ascend through a discernible top surface of a dense catalyst
bed. Only catalyst entrained in the vapor exits the reactor with the vapor. The superficial
velocity of the vapor is typically less than 0.5 m/s (1.5 ft/s) and the density of the dense bed is
typically greater than 480 kg/m^ (30 Ib/ft3) depending on the characteristics of the catalyst. The
mixture of catalyst and vapor is heterogeneous with pervasive vapor bypassing of catalyst.
[0010] Intermediate of dense, bubbling beds and dilute, transport flow regimes are turbulent
beds and fast fluidized regimes. US-A-4,547,616 discloses a turbulent bed used in a reactor for
converting oxygenates to olefins. In a turbulent bed, the mixture of catalyst and vapor is not
homogeneous. The turbulent bed is a dense catalyst bed with elongated voids of vapor forming
within the catalyst phase and a less discernible surface. Entrained catalyst leaves the bed with
the vapor, and the catalyst density is not quite proportional to its elevation within the reactor.
The superficial velocity is between 0.5 and 13 m/s (1.5 and 4.0 ids), and the density is typically
between 320 and 480 kg/m3 (20 and 30 lb/ft3) in a turbulent bed,
[0011] US-A-6,166,282 discloses a fast fluidized flow regime for oxygenate conversion.
Fast fluidization defines a condition of fluidized solid particles lying between the turbulent bed
of particles and complete particle transport mode. A fast fluidized condition is characterized by a
fluidizing gas velocity higher than that of a dense phase turbulent bed, resulting in a lower
catalyst density and vigorous solid/gas contacting. In a fast fluidized zone, there is a net
transport of catalyst caused by the upward flow of fluidizing gas. The superficial combustion gas
velocity for a fast fluidized flow regime is conventionally believed to be between 1.1 and 2.1
m/s (3.5 and 7 ft/s) and the density is typically between 48 and 320 kg/rn3 (3 and 20 lb/ft3).
Catalyst exits the reaction zone a small amount slower than the vapor exiting the reaction zone.
Hence, for a fast fluidized flow regime the slip velocity is typically greater than or equal to 0.3
m/s (1.0 ft/s) and the slip ratio is greater than or equal to 2.5 for most FCC catalysts. Fast
fluidized regimes have been used in FCC combustors for regenerating catalyst and in coal
gasification.
[0012] The conversion of hydrocarbon oxygenates to olefinic hydrocarbon mixtures is
accomplished in a fluidized catalytic reactor. Such oxygenates to olefins reactions are rapidly
catalyzed by molecular sieves such as a microporous crystalline zeolite and non-zeolitic
catalysts, particularly silicoaluminophosphates (SAPO). Numerous patents describe this process
for various types of these catalysts: US-A-3,928,483; US-A-4,025,575; US-A-4,252,479; US-A-
4,496,786; US-A-4,547,616; US-A-4,677,243; US-A-4,843,183; US-A-4,499,314; US-A-
4,447,669; US-A-5,095,163; US-A-5,191,141; US-A-5,126,308; US-A-4,973,792 and US-A-
4,861,938.
[0013] Th'e oxygenates to olefins catalytic process may be generally conducted in the
presence of one or more diluents which may be present in the hydrocarbon oxygenate feed in an
amount between 1 and 99 mol-%, based on the total number of rnoles of all feed and diluent
components fed to the reaction zone (or catalyst). Diluents include, but are not limited to,
helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, water, and hydrocarbons
such as methane, paraffins, aromatic compounds, or mixtures thereof. US-A-4,861,938 and USA-
4,677,242 particularly emphasize the use of a diluent combined with the feed to the reaction
zone to maintain sufficient catalyst selectivity toward the production of light olefin products,
particularly ethylene.
[0014] Another typical fluidized catalytic reaction is a fluidized catalytic cracking (FCC)
process. An FCC process is carried out by contacting the starting material whether it be vacuum
gas oil, reduced crude, or another source of relatively high boiling hydrocarbons with a catalyst
made up of finely divided or particulate solid material. The catalyst is fluidly transported by
passing gas through it at sufficient velocity to produce a transport flow regime. Contact of the oil
with the fluidized catalytic material catalyzes the cracking reaction. The cracking reaction
deposits coke on the catalyst. Catalyst exiting the reaction zone is spoken of as being "spent",
i.e., partially deactivated by the deposition of coke upon the catalyst. Coke is comprised of
hydrogen and carbon and can include other materials in trace quantities such as sulfur and
metals that enter the process with the starting material. Coke interferes with the catalytic activity
of the spent catalyst by blocking acid sites on the catalyst surface where the cracking reactions
take place. Spent catalyst is traditionally transferred to a stripper that removes adsorbed
hydrocarbons and gases from catalyst and then to a regenerator for purposes of removing the
coke by oxidation with an oxygen-containing gas. The regenerator may operate with a bubbling
bed, turbulent bed or fast fluidized flow regime. Such regenerators using a fast flow regime are
called combustors. However, in a regenerator or combustor, coke is burned from the catalyst.
The catalyst does not: provide a catalytic function other than with regard to oxidation. An
inventory of catalyst having a reduced coke content, relative to the spent catalyst in the stripper,
hereinafter referred to as regenerated catalyst, is collected for return to the reaction zone.
Oxidizing the coke from the catalyst surface releases a large amount of heat, a portion of which
escapes the regenerator with gaseous products of coke oxidation generally referred to as flue
gas. The balance of the heat leaves the regenerator with the regenerated catalyst. The fluidized
catalyst is continuously circulated between the reaction zone and the regeneration zone. The
fluidized catalyst, as well as providing a catalytic function in the reaction zone, acts as a vehicle
for the transfer of heat from zone to zone. The FCC processes, as well as separation devices used
therein are fully described in US-A-5,584,985 and US-A-4,792,437.
[0015] The above-described hydrocarbon catalytic conversion processes are sensitive to
underreaction and overreaction which both degrade product quality. Use of a fast fluidized flow
regime assures thorough mixing of catalyst and feed to catalyze the reaction. Hence, this
invention sought to provide an improved fluidized non-oxidative catalytic hydrocarbon
conversion process and apparatus that can provide a fast fluidized flow regime at adjustable flow
conditions that will enhance the conversion to the desired products. Additionally, this invention
sought to provide a reactor that can accommodate the varying demands on space velocity and
residence time based on different feed composition and desired products.
SUMMARY OF THE INVENTION
[0016] We have discovered a reactor and process for controlling die residence time in a
reaction zone by adjusting the space velocity within the volume of a catalytic reaction zone in a
fluidized catalytic reactor or varying the effective reaction volume. Space velocity is a function
of catalyst density. Space velocity and residence time is a function of the volume of the catalytic
reaction zone where catalyst and feed contact Therefore, it is possible to adjust the effective catalytic reactor volume or the space velocity through the catalyst circulation rate to achieve the desired residence time in the catalyst to feed contacting. This may be performed at highly effective gas-solid, mixing conditions. The catalyst circulation rate can be controlled based on the pressure drop in the reactor to maintain or achieve a desired space velocity. The volume of the catalytic reaction zone may be adjusted by changing .the flow rate of a minimally reactive diluent to the reactor, by changing a number of reactor subsections to which feed is delivered or by changing the elevation at which feed is delivered to the reactor section.
STATEMENT OF INVENTION
In accordance with the present invention there is provided a catalytic reactor for the catalytic conversion of a feed stream by contact with fluidized catalyst particles to produce a product stream, the reactor comprising a reaction section defining a catalytic reaction zone and a feed inlet communicating with the reaction zone a separation section for separating gaseous products from fluidized catalyst particles, the separation section defining a particle outlet for discharging fluidized catalyst particles and the separation section defining a gas recovery outlet for withdrawing the gaseous products from the separation section; a disengaging conduit extending from the reaction section to the separation section, in fluid communication with the reaction zone, for conducting the product stream and fluidized catalyst particles and defining a discharge opening for discharging the product stream and fluidized catalyst particles; at least one catalyst circulation pipe for conveying fluidized catalyst particles to the reaction section; a first feed conduit for adding feed to the catalytic reaction zone at a first elevation; and a catalyst control valve on the catalyst circulation pipe for controlling the rate at which catalyst particles are added to the reaction section and a pressure differential indicator with sensors at two elevations in the reaction section linked to the catalyst control valve .

BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic drawing of a fluidizcd catalytic reactor for use in the present
invention.
[0018] FIG. 2 is a schematic drawing of an alternative embodiment of the present invention.
[0019] FIG. 3 is a cross-sectional view taken along segment 3-3 in FIG. 2.
[0020] FIG. 4 is a schematic drawing of a further alternative embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] We have discovered a catalytic reactor that can be used to obtain thorough mixing of fluid reactants and particulate catalyst while contacting the catalyst and fluid reactants together for an adjustably optimal time. Hence, desirable reactions may occur without underreacting or overreacting to degrade the quality of the product composition for varying feeds and varying reactions. For example, in a fluidized catalytic reactor for upgrading-naphtha that may be obtained from an FCC cut, we have found that better mixing between the feed and the catalyst promotes hydrogen transfer reactions and catalytic cracking reactions while reducing the

undesirable generation of coke and dry gas. Use of a fast fluidized catalytic conversion zone
provides such thorough mixing, We have also found that in catalytic conversion of hydrocarbon
oxygenates to olefins, use of a fast fluidized zone significantly reduces catalyst inventory
compared to dense fluidized catalytic reactions. However, we have found that maintaining a fast
fluidized reaction zone may be difficult. Fast fluidized combustion zones have been attempted in
combustors for oxidizing coked catalyst from an FCC reactor zone but such combustors do not
involve nonoxidative catalytic conversion. The main concern in a combustion zone is that the
catalyst has sufficient residence time to burn off all of the coke. Fluidized catalytic conversion
reactors particularly hydrocarbon catalytic conversion processes bring with it other flow
considerations because the feed is the primary fluidization medium and the reactant that is
undergoing catalytic conversion to recoverable product. The selectivity and conversion of the
gas phase reaction must be optimized. Selectivity and conversion are functions of temperature,
residence time and space velocity. As indicated by Formulas 1 and 5, space velocity is related to
both catalyst and reactant feed flow rates and reactor volume. Formula 11 indicates that
residence time is related to reactor volume. Hence, this invention gives greater consideration to
the flow characteristics, space velocity and residence time in a fluidized catalytic conversion
reactor. Controlling these flow characteristics provides for achieving and maintaining a desired
fluidization regime, particularly a fast fluidized flow regime.
[0022] The present invention may be described with reference to a fluidized catalytic reactor
10 shown in FIG. 1. Although many configurations of the present invention are possible, one
specific embodiment is presented herein by way of example. All other possible embodiments for
carrying out the present invention are considered within the scope of the present invention.
[0023] In the embodiment of the present invention in FIG. 1, the catalytic reactor 10
comprises a reactor section 12 and a separation section 16 that may include a disengaging
section 14. The contacting of feed and catalyst occurs in the reactor section 12 of the catalytic
reactor 10. Control valves 18, 20 govern the rate of catalyst circulation to the reactor section 12.
The control valve 18 governs the flow rate of regenerated catalyst from a catalyst regenerator
through a regenerated catalyst pipe 24 to the reactor section 12, and the control valve 20 governs
the flow rate of recycled catalyst through a recycle spent catalyst pipe 26 to the reactor section
12. The catalyst flow rate through one or both of the control valves 18 and/or 20 is inversely
proportional to the space velocity of reactants through the reactor section 12. Relative settings of
the control valves 18, 20 are independently adjusted also to obtain the desired temperature and
mixture of the catalyst in the reactor section 12 that will contact the reactant feed. The multiple
recycle spent catalyst pipes 26 may be used to increase catalyst flux, and the recycle spent
catalyst pipes 26 may extend through the reactor 10 and particularly the reactor section 12.
[0024] In an embodiment, the regenerated catalyst from the regenerated catalyst pipe 24 and
the recycled catalyst from the recycle spent catalyst pipe 26 are mixed in a mixing pot 30 of the
reactor section 12. A minimally reactive or non-reactive diluent, such as steam, is distributed to
the mixing pot 30 through a nozzle 32 to mix the regenerated and recycled catalyst before it
contacts the feed. The mixing pot 30 enables adequate mixing and temperature equilibration of
recycled and regenerated catalyst before it is introduced to the feed. This assures that the hot
regenerated catalyst is moderated to a lower temperature by thorough mixing and direct heat
exchange with the cooler recycled catalyst which has not been heated by regeneration. All or a
part of the hot regenerated catalyst could cause thermal cracking or other undesirable byproduct
generation if it were allowed to contact the feed reactants without first undergoing thorough
moderation. In an embodiment which does not utilize a catalyst regenerator, the mixing pot
may not be necessary.
[3023] Feed reautaate which may include hydrocarbons are introduced through a line 36 to a
distributor 38 which distributes feed to the reactor section 12. The feed may be liquid that is
vaporized in the reactor or vapor, in embodiments. The flow rate of feed through the line 36 is
governed by a control valve 40. The setting of the control valve 40 also influences the space
velocity and residence time. The feed rate to the reactor section 12 is directly proportional to the
space velocity and inversely proportional to residence time.
[0026] Feed reactants from the distributor 38 contact fluidized catalyst ascending upwardly
from the mixing pot 30. The feed reactants may also include diluent as is necessary to provide
appropriate catalytic reaction conditions. In an embodiment, the feed reactants fluidize the
ascending catalyst to generate a fast fluidized bed in a catalytic reaction zone 22 of the reactor
section 12. It may be in practice that a dense bed forms at a base 42 of the reactor section 12
below the level at which all of the catalyst is fluidized by the incoming feed reactants in the
catalytic reaction zone 22. In an embodiment, the catalytic reaction zone 22 extends between the
distributor 38 and a top region 44, although catalytic activity may occur outside of the catalytic
reaction zone 22. The top region 44 of the reactor section 12 has a cross-sectional area that
decreases proportionally with height. The top region 44 may take the form of a frustoconical
section. The reducing cross-sectional area of the top region 44 serves to accelerate the mixture of
fluidized product and catalyst toward transport mode as they exit the reactor section 12 and enter
the transport conduit 46. The transport conduit 46 communicates the reactor section 12 with the
disengaging section 14. The transport conduit 46 may take the form of a riser. The transport
conduit 46 should have a smaller cross-sectional area than the reactor section 12. Consequently,
upon leaving the catalytic reaction zone 22 and the reactor section 12, the product fluids and
spent catalyst accelerate into a transport mode, thus giving the spent catalyst and product fluids
wfK9f
less lime to further react or crack into undesirable products. Entering transport mode also
prevents catalyst from falling out of entrainment with the product fluids.
[0027] Spent catalyst and product ascend from the reactor section 12 through the transport
conduit 46 to the disengaging section 14. The spent catalyst and vapor product exit through
discharge openings 48 (only one shown) in swirl tubes 50 to effect a primary, centripetal
separation of spent mixed catalyst from the vapor product. Separated spent mixed catalyst settles
into a dense bed 52 in the disengaging section 14. The spent mixed catalyst in the dense bed 52
is then in an embodiment stripped over a series of baffles 54 by use of a stripping medium such
as steam entering through stripping nozzles 58 in a stripping section 60 of the disengaging
section 14. In an embodiment, a first portion of the stripped spent catalyst exits the disengaging
section 14 through a spent catalyst pipe 62 at a flow rate that may be governed by a control
valve 64. The stripped spent catalyst may be delivered to the regenerator 66. The regenerator
may be shared with another fluidized catalytic system, such as an FCC system, in an
embodiment. Alternatively, the spent catalyst pipe 62 may deliver spent catalyst to another
reactor. A second portion of the stripped spent catalyst is withdrawn through the recycle spent
catalyst pipe 26 at a flow rate governed by the control valve 20 and is delivered to the mixing
pot 30 where it is mixed with regenerated catalyst delivered from the regenerated catalyst pipe
24. Product vapors and entrained spent catalyst exit from the disengaging section 14 through an
outlet 68 to the separation section 16 that contains at least one cyclone separator 70.
Alternatively, the separator section could comprise one or more cyclone separators 70 external
to the disengaging section 14 and with an inlet directly connected to the outlet 68 and a dipleg
72 directly connected to the disengaging section 14 or the reactor section 12 by appropriate
conduits. In an embodiment, the outlet 68 may be directly connected to the cyclone separators
70. The entrained spent catalyst is centripetally separated from product vapors in the cyclone
separators 70. Separated catalyst exits through the dipleg 72 into a dense catalyst bed 74 which
may be fluidized (not shown). In an embodiment, spent catalyst in the dense catalyst bed 74
enters into the stripping section 60 of the disengaging section 14 through ports 76. Alternatively,
the spent catalyst in the dense catalyst bed 74 may be removed through the pipes 26, 62 without
undergoing stripping. Product fluids are withdrawn from the cyclone separators 70 through
outlet conduits 78 and are recovered in a line 80.
[0028] Referring to the reactor 10 of the present invention shown in FIG. 1, the space
velocity may be changed in the reactor section 12 by increasing or decreasing the rate of
delivery of catalyst to the reactor section 12. This can be done by adjusting the control valve 20
to change the flow rate of spent catalyst through the recycle spent catalyst pipe 26 into the
mixing pot 30 and/or adjusting the control valve 18 to change the flow rate of regenerated
catalyst through the regenerated catalyst pipe 24 into the mixing pot 30 of the reactor section 12.
Increasing the catalyst flow rate through one or both of the control valves 18,20 into the reactor
section 12 decreases the weight hourly space velocity in the reactor section 12 while decreasing
the flow rate through one or both of the control valves 18, 20 increases the weight hourly space
velocity. The total flow rate of catalyst to the reactor section 12 through the pipes 24,26 is
directly proportional to catalyst flux.
[0029] Another way to control the weight hourly space velocity is to increase or decrease the
feed flow rate through the control valve 40 on the feed line 36. Increase of the feed flow rate is
directly related to the superficial velocity (vf). However, the feed flow rate is typically left
constant.
[0030] Lower superficial gas velocities have a greater tendency to generate a dense bed as
catalyst flux increases; whereas, higher superficial gas velocities have a lower tendency to
generate a dense bed as catalyst flux increases. The desired fast-fluidized flow regime in which
the greatest degree of mixing of catalyst and reactant occurs is moderated between a dense bed
condition at 320 kg/m3 (20 Ib/ft3) and a transport flow regime at 48 kg/m3 (3 lb/ft3). It is more
difficult to maintain a fast-fluidized flow at lower superficial gas velocity because the catalyst
tends to choke the reactant gas fed to the reactor, thereby jumping from a transport flow regime
to a dense bed. Furthermore, at extremely high superficial gas velocities, no increase in catalyst
flux will bring the flow regime out of transport. We have determined that a fast fluidized flow
regime can be maintained under the present invention with superficial velocities as low as 1.3
na/s (4 ft/s) and as high as 9.1 m/s (30 ft/s), which is higher than conventionally used, and with
catalyst fluxes as low as 15 kg/m2s (2.8 Ib/ft2s) and as high as 1100 kg/m2s (204.5 Ib/ft2s). In
an embodiment, a very controllable fast fluidized regime can be maintained under the present
invention with superficial velocities as low as 1.5 m/s (5 ft/s) and as high as 5 m/s (16 ft/s) and
with catalyst fluxes as low as 30 kg/m2s (5.6 Ib/ft2s) and as high as 325 kg/m2s (60.4 Ib/ft2s).
Under these conditions, catalyst flux can be increased or decreased to increase or decrease the
space velocity without disrupting the flow regime such that it chokes to a dense bed or
accelerates into a transport flow regime,
[0031] The subject invention is useful in a catalytic conversion reactor in which catalyst is
fluidized either by a fluidized feed or by a fluidizing diluent or both. Typically, the fluidized
feed has sufficient superficial velocity to entrain the catalyst or fluidize the catalyst as it enters
into the reactor. In an embodiment of the present invention, the addition of diluent can be
controlled to adjust the degree of fluidization in the reactor.
[0032] The space velocity in the reactor section 12 may be controlled as follows. The
pressure drop between two elevations in the reactor section 12 may be measured to monitor
catalyst density in the reactor, weight hourly space velocity or other reactor condition that is
proportional to space velocity. When desired to adjust the space velocity, either to maintain or
attain the last-iiuidized regime, to change resulting conversion or selectivity or to accommodate
a different feed composition, the control valve 20 can be opened relatively more or less to
change the catalyst flux which changes the space velocity accordingly.
[0033] FIG. 1 illustrates a control scheme for effectuating adjustments to space velocity. A
pressure sensor 92 is located at a relatively low elevation in the reactor section 12, and a
pressure sensor 94 is located at a relatively high elevation in the reactor section 12. In an
embodiment, at least one of the sensors, preferably the lower pressure sensor 92, should be in
the catalytic reaction zone 22. The pressure sensors 92, 94 transmit a pressure signal and/or
other data to a controller 96, which may comprise a pressure differential controller. A sensor 98
which may be on the line 36 or on the control valve 40 determines the flow rate of feed
therethrough by a suitable device and signals data to the controller 96. With the data, the
controller 96 determines the mass flow rate of feed to the reactor 10 through the control valve 40
and the mass of catalyst in the reactor section 12 from which the weight hourly space velocity is
determined. The flow rate of feed may be constant. The current weight hourly space velocity or
a parameter proportional thereto is compared to a set point which can be adjusted. If the space
velocity or proportional parameter does not match the set point, the controller 96 signals the
control valve 20 to open relatively more to lower the space velocity or to open relatively less to
increase the space velocity.
[0034] The temperature of the recycled spent catalyst in the recycle spent catalyst pipe 26 is
similar to the temperature in the reactor section 12. Hence, temperature in the reactor section 12
is controlled by the flow rate of hot regenerated catalyst in the regenerated catalyst pipe 24
through the control valve 18. A temperature sensor 101 in the catalytic reaction zone 22 or the
reactor section 12 signal temperature data to a controller 100 which may be a temperature
indicator controller. The controller 100 compares the temperature in the reactor section 12 to an
adjustable set point temperature and signals the control valve 18 to open relatively more if the,
reactor temperature is lower than the set point or to open relatively less if the reactor temperature
is higher than the set point. Suitable types, operation and locations of sensors and controller(s)
may vary consistently with ordinary skill in the art and the description herein.
[0035] The volume of the catalytic reaction zone 22 is proportional to residence time and
inversely proportional to space velocity as indicated by Formulas 5 and 10. The volume of the
catalytic reaction zone 22 may be adjusted and therefore residence time and space velocity may
be adjusted in the catalytic reaction zone 22 by adjusting the flow rate of a minimally reactive or
non-reactive diluent to the reactor section 12. Additional diluent may be added to the reactor
section 12 by a diluent line 102 at a rate governed by a control valve 104 through a nozzle
The effective reactor volume can be changed by adjusting the diluent rate to the reactor section
. 12 through the nozzle 106. If a smaller effective reactor volume is desired to provide a smaller
residence time or a larger space velocity, the control valve 104 should be opened relatively more
to allow a greater volumetric flow rate of diluent to the reactor section 12 from the diluent line
102. If a larger effective reactor volume is desired to increase residence time or reduce space
velocity, the control valve 104 should be opened relatively less to allow a smaller volumetric
flow rate of diluent to the reactor section 12 from the line 102. Steam is a suitable diluent.
[0036] FIG. 2 shows another embodiment of the present invention which could be used to
replace the reactor section 12 in FIG. 1. All elements in FIG. 2 that are not modified from FIG. 1
retain the same reference numeral designation. Although one reactor section 12' may be used for
carrying out the purposes of this invention, the provision of a plurality of reactor subsections 84
with dedicated nozzles 88 and control valves 40' to govern the flow rate of feed to each of the
reactor subsections 84 may offer flexibility over use of a single reactor section 12. A plurality of
the reactor subsections 84 within a single reactor section 12' provides a greater degree of control
oi itisidciicc drue and iipace velocity. The embodiment in FIG. 2 provides greater flexibility
because the cross sectional area, and, therefore, the volume of a catalytic reaction zone 22' are
adjustable. Reactor cross-sectional area is inversely proportional to superficial gas velocity.
Superficial gas velocity is inversely proportional to residence time and directly proportional to
space velocity. Hence, residence time which is directly proportional to cross-sectional area and
space velocity which is inversely proportional to cross-sectional reactor area may be modified
by adjusting the flow rate or shutting off flow to one of the reactor subsections 84. The same
relationship applies to the reactor subsections 84 that do not have a constant cross-sectional area
because the volume of the catalytic reaction zone is proportional to residence time and inversely
proportional to space velocity as shown in Formulas 5 and 10.
[0037] Reactant feed is distributed by a line 36' at a flow rate governed by the control valves
40' through the nozzles 88 to the respective reactor subsections 84 in the reactor section 12'.
The reactor subsections 84 may be tubular with an open bottom end 90 communicating with a
dense catalyst bed 82 that forms in the reactor section 12'. Feed entering the reactor subsections
84 preferably pulls catalyst from the dense catalyst bed 82 into the reactor subsections 84 where
contacting occurs. The amount of catalyst pulled into the reactor subsection 84 for a given flow
rate of feed in the nozzle 88 will be proportional to the superficial velocity of the feed and the
height of a catalyst level 83 of the dense catalyst bed 82 which is controlled by the control
valves 18,20. Hence, the ratio of catalyst to feed, catalyst density, catalyst flux, space velocity,
and residence time in the reactor subsections 84, and therefore the reactor section 12', can all be
controlled by adjusting the elevation of the catalyst level 83 of the dense catalyst bed 82 and/or
adjusting or eliminating the flow rate of the feed through one or more of the control valves 40'.
[0038] The catalytic reaction zone 22' comprises the reactor subsection 84 from the bottom
end 90 to a top region 44'. In an embodiment, the catalytic reaction zone 22' comprises all of the
(Figure Removed0
reactor subsections 84 to which feed is distributed. The top region 44' of each of the reactor
subsections 84 has a reduced cross-sectional area that may take the form of frustoconical or
partial frustoconical sections. The reduced cross-sectional area of the top region 44' serves to
accelerate the mixture of vapor product and spent mixed catalyst as they exit the reactor
subsection 84. In an embodiment that is not shown, the top regions 44' may communicate with
outlet conduits which communicate the reactor subsections 84 with the transport conduit 46. In
such an embodiment, the outlet conduits should all have a smaller cross-sectional area than the
respective reactor subsection 84 and the transport conduit 46.
[0039] FIG. 3 is an upwardly looking cross-sectional view taken along segment 3-3 of the
reactor section 12'. Although, four reactor subsections 84 are shown in FIGS. 3 and 4, the
invention contemplates more or less, but more than one reactor subsection 84. In an
embodiment, the reactor subsections 84 may share common walls. In the embodiment shown in
FIGS. 2 and 3, a cross-sectional area of the transport conduit 46 may be less than the aggregate
cross-sectional area of all of the reactor subsections 84 that feed the transport conduit 46.
Additionally, in an embodiment, the cross-sectional area of the transport conduit 46 may be less
than that of a single reactor subsection 84, so that all but one of the reactor subsections 84 may
be shut off. Consequently, upon leaving the reactor subsection 84, the product vapor and spent
mixed catalyst accelerate into a transport mode through the top region 44', thus giving the spent
catalyst and product vapor little time to further react or crack into undesirable products. Entering
transport mode also prevents catalyst from falling out of entrainment with the product vapor.
[0040] The alternative embodiment of a reactor 10' of the present invention may be operated
similarly to the reactor 10, but greater flexibility is offered. The aggregate volume of catalytic
reaction zone 22' of the reactor section 12 comprising the on-stream reactor subsections 84 may
be varied which is an additional way to adjust the space velocity and the residence time. For
instance, by cutting off flow through two of the control valves 40' to two respective reactor
subsections 84, the volume of the catalytic reaction zone 22' is halved. The change in volume
will cancel out according to Formula 9. However, the halved cross-sectional area will double the
superficial velocity for the reactant feed at the constant flow rate through the line 36'. Moreover,
because the catalyst brought into the reactor subsections 84 is dependent on the flow of feed
thereto which has doubled for each reactor subsection remaining on-stream, the overall catalyst
flux will not substantially change. The doubled superficial velocity will draw double the catalyst
flux into each of the two reactor subsections 84 to compensate for the two reactor subsections
that have been shut off at the control valves 40'. Hence, the weight hourly space velocity will
increase. Similarly, the change in volume cancels out in Formula 12 while the velocity doubles.
Consequently, the shutting off of flow through the control valves 40' to two reactor subsections
84 results in a halving of the residence time in the reactor subsections 84.
[0041] Additionally, space velocity may be controlled by adjusting the catalyst flux as in the
reactor 10. The pressure drop between two elevations in the catalytic reaction zone 22' of the
reactor section 12 may be measured to monitor catalyst density in the reactor and weight hourly
space velocity. When desired to adjust the space velocity or a parameter proportional thereto,
without changing the flow rate through either of control valves 40', the control valve 20 can be
opened relatively more or less to change the height of the catalyst level 83. The height of the
catalyst level 83 is proportional to the amount of catalyst flux pulled into the reactor subsections
84 which changes the space velocity accordingly. FIG. 2 illustrates a control scheme for
effectuating adjustments to space velocity by changing flux. A pressure sensor 92' is located at a
relatively low elevation in the catalytic reaction zone 22 of each of the reactor subsections 84 or
at least in the one reactor subsection 84 that will always be on-stream, preferably above the
nozzle 88. A pressure sensor 94' is located at a relatively high elevation in the reactor section
12, in an embodiment, at a location where all of the outlets of the reactor subsections 84
converge, such as in the transport conduit 46, or in a single reactor subsection 84 that will
always be on-stream. The pressure sensors 92', 94' transmit a pressure .signal and/or other data
to the controller 96, which may comprise a pressure differential controller. Sensors 98' on each
of the branch lines from the line 36', on each control valve 40', on each of the nozzles 88 or on
the line 36' determine the flow rate of feed to the reactor section 12 by a suitable device and
signals data to the controller 96. With the data, the controller 96 determines the mass flow rate
of feed to the reactor 10 and the mass of catalyst in the catalytic reaction zone 22' comprising
the on-stream reactor subsections 84 from which the weight hourly space velocity is determined.
The flow rate of feed through the line 36' may be constant. The actual weight hourly space
velocity in the reactor section 12 is compared to a set point which can be adjusted. If the space
velocity does not match the set point, the controller 96 signals the control valve 20 to open
relatively more to lower the space velocity or to open relatively less to increase the space
velocity. Temperature in the reactor section 12 is controlled by the flow rate of hot regenerated
catalyst in the regenerated catalyst pipe 24 through the control valve 18. Temperature sensors
101' in the catalytic reaction zone 22' signal temperature data to the controller 100 which may
be a temperature indicator controller. The temperature sensor 98' may instead be in the dense
catalyst bed 82 in the reactor section 12'. The controller 100 compares the temperature in the
reactor section 12' to a set point temperature and signals the control valve 18 to open relatively
more if the reactor temperature is lower than the set point or to open relatively less if the reactor
temperature is higher than the set point. Locations of sensors, operation of controller(s) may
vary consistent with ordinary skill in the art and the description herein.
[0042] Some or all of the reactor subsections 84 may be operated under different conditions,
such as temperature, space velocity or residence time to achieve the desired reactor flow
couditiouo itiid proUuci: composition. Similarly, superficial feed velocity in one, some or all of
the reactor subsections 84 may be different. Under this embodiment, the lower pressure sensors
92' will have to be in each reactor subsection 84 and the upper pressure sensor 94' will have to
be where all outlets of reactor subsections converge or in each reactor subsection 84. Moreover,
under this embodiment, the sensors 98' will have to be on each branch of the line 36' or on each
of the control valves 40'.
[0043] FIG. 4 shows another embodiment of the present invention which could be used to
replace the reactor section 12 in FIG. 1 or 12' in FIG. 2. All elements in FIG. 4 that are not
modified from FIG. 1 retain the same reference numeral designation. A reactor section 12" of
FIG. 4 includes a plurality of reactant feed distributors 38a-38d all at different heights in the
reactor section 12". Although four reactant feed distributors 38a-38d may be used for carrying
out the purposes of this invention, more or less may be used, but more than one. Each reactant
feed distributor 38a-38d is fed by a respective feed line 36a-36d in communication with a main
feed line 36". A plurality of control valves 40a-40d are each dedicated to less than all of the
plurality of reactant feed distributors 38a-38d to separately govern the flow of feed to the
plurality of reactant feed distributors. In an embodiment, each control valve 40a-40d is dedicated
to each respective reactant feed distributor 38a-38d and feed line 36a-36d to separately govern
the flow rate of reactant feed therethrough. A sensor 99 which may be on the main feed line 36"
or sensors 98a-98d which may be on the respective lines 36a-36d or on the respective control
valves 40a-40d determines the flow rate of feed therethrough by a suitable device and signals
data to the controller 96. A catalytic reaction zone 22a-22d is the volume in the reactor section
12" that is above the respective reactant feed distributor 38a-38d up to the top region 44. In the
reactor section 12", the reactor volume of the catalytic reaction zone 22a-22d is inversely
proportional to the elevation of the reactant feed distributor 38a-38d.
[0044] The provision of a plurality of the reactant feed distributors 38a-38d with the
dedicated control valves 40a 40d to govern the flow rate of feed to the reactor section 12 may
offer flexibility over use of a single reactant feed distributor to control residence time and space
velocity. The embodiment in FIG. 4 provides greater flexibility because the volume of the
catalytic reaction zone 22a-22d is adjustable. Formula 5 indicates that space velocity is inversely
proportional to reactor volume. Formula 10 indicates that residence time is directly proportional
to reactor volume. Although there will be a catalyst density gradient over the reactor height
which will change with the changing height of the distribution of the reactant stream, the reactor
volume of the catalytic reaction zone will change more significantly upon a change in feed
distributor elevation.
[0045] If it is desired to reduce the residence time and/or increase the space velocity in the
reactor section 12', the flow to the lower reactant feed distributor 38a-38c through the dedicated
control valve 40a-40c would be shut off and flow to the higher reactant feed distributor 38b-38d
through the dedicated control valve 40b-40d would be opened. Similarly, if it is desired to
increase the residence tune and/or decrease the space velocity in the reactor section 12', the flow
to the higher reactant feed distributor 38b-38d through the dedicated control valve 40b-40d
would be shut off and flow to the lower reactant feed distributor 38a-38c through the dedicated
control valve 40a-40c would be opened.
[0046] The top region 44 of the reactor sections 12' have a reduced cross-sectional area that
may take the form of frustoconical section. The reduced cross-sectional area of the top region 44
serves to accelerate the mixture of vapor product and spent mixed catalyst as they exit the
reactor section 12". Consequently, upon leaving the reactor subsection 84, the product vapor
and spent mixed catalyst accelerate into a transport mode through the top region 44, thus giving
the spent catalyst and product vapor less time to further react or crack into undesirable products.
Entering transport mode also prevents catalyst from felling out of entrainment with the product
vapor,
[0047] .Additionally, space velocity may be controlled by adjusting the catalyst flux as in the
reactor 10. The pressure drop between two elevations in the catalytic reaction zone 22a-22d of
the reactor section 12 may be measured to monitor catalyst density in the reactor and weight
hourly space velocity. When desired to adjust the space velocity or a parameter proportional
thereto, without changing the elevation of the operating reactant feed distributor 38a-38d, the
control valve 20 can be opened relatively more or less to change the catalyst flux to the reactor
section 12" which changes the space velocity accordingly. FIG. 4 illustrates a control scheme
for effectuating adjustments to space velocity by changing flux which is similar to that for FIG.
1. Although only one is shown, the pressure sensors 92' will be located at a point slightly above
every reactant feed distributor 38a-38d in the respective reaction zone 22a-22d. The pressure
sensor 94 is located at a relatively high elevation in the reactor section 12'. The pressure sensors
92', 94' transmit pressure signals and/or other data to the controller 96, which may comprise a
pressure differential controller. The sensor 99 determines the flow rate of feed through to the
applicable reactant feed distributor 38a-38d by a suitable device and signals data to the
controller 96. With the data, the controller 96 determines the mass flow rate of feed to the
reactor 10 through the reactant feed distributors 38a-38d and the mass of catalyst in the reactor
section 12 from which the weight hourly space velocity is determined. The flow rate of feed
through the line 36" may be constant. The actual weight hourly space velocity in the reactor
section 12" is compared to a set point which can be adjusted. If the space velocity does not
match the set point, the controller 96 signals the control valve 20 to open relatively more to
lower the space velocity or to open relatively less to increase the space velocity to come closer
to the desired space velocity. Temperature in the reactor section 12 is controlled by the flow rate
of hot regenerated catalyst in the regenerated catalyst pipe, 2.4 through the control valve 18 based
on a signal from a temperature sensor (not shown) in the catalytic reaction zone 22a-22d to the
controller 100 similar to the control scheme shown in FIG, 1. Suitable locations, types and
operation of sensors and controller(s) may vary consistent with ordinary skill in the art and the
description herein.
[0048] It is also contemplated that one or more distributors 38a-38d may operate at the same
time at the same or different flow rates to provide desired benefits. Additionally, if diluent
through the nozzle 32 is not sufficient to fluidize catalyst up to the higher reactant feed
distributor 38a-38d, a lower distributor may have to always operate to some degree to fluidize
catalyst up to the primarily operational reactant feed distributor 38a-38d. Lastly, a retractable
distributor (not shown) or a transport conduit with a telescopically retractable inlet end (not
shown) may be used to accomplish the present invention.
[0049] Accordingly, the present invention provides for the adjustment of reactor flow
parameters of residence time, volume and space velocity to meet particular needs in response to
differences in feed composition or desired product slate and to achieve and maintain an .
appropriate fluidization regime.




We claim:
1. A catalytic reactor (10) for the catalytic conversion of a feed stream by contact with fluidized
catalyst particles to produce a product stream, the reactor comprising:
a reaction section (12) defining a catalytic reaction zone (22) and a feed inlet communicating with the reaction zone;
a separation section (16) for separating gaseous products from fluidized catalyst particles, the separation section defining a particle outlet for discharging fluidized catalyst particles and the separation section defining a gas recovery outlet (68) for withdrawing the gaseous products from the separation section;
a disengaging conduit (46) extending from the reaction section to the separation section, in fluid communication with the reaction zone, for conducting the product stream and fluidized catalyst particles and defining a discharge opening (48) for discharging the product stream and fluidized catalyst particles;
at least one catalyst circulation pipe (26) for conveying fluidized catalyst particles to the reaction section;
a first feed conduit (38) for adding feed to the catalytic reaction zone at a first elevation; and
a catalyst control valve (20) on the catalyst circulation pipe for controlling the rate at which catalyst particles are added to the reaction section and a pressure differential indicator (96) with sensors (92, 94) at two elevations in the reaction section linked to the catalyst control valve .
2. The reactor as claimed in claim 1 wherein the first feed conduit (38a) and at least one
additional feed conduit (38b) provide at least part of a plurality of feed distributors at different
elevations in the reactor section; and
a plurality of feed control valves (40a, 40b) govern the flow of feed to each of the distributors and each of the feed control valves is dedicated to less than all of the plurality of feed distributors to separately govern the flow of feed to the plurality of feed distributors.
3. The catalytic reactor as claimed in claim 2 wherein each of the control valves is dedicated to
only one of the feed distributors.

4. The catalytic reactor as claimed in any of claims 1 to 3 wherein the reaction section comprises a catalyst mixing zone (30) belew the reaction zone in fluid communication with the circulation pipe.
5. The catalytic reactor as claimed in claim 5 wherein the catalyst circulation pipe is in communication with the separation section and an additional catalyst circulation pipe (24) with one end in communication with a catalyst regenerator has a control valve (18) governed by the temperature in the reactor section.
6. The catalyst reactor as claimed in any of claims 1 to 3 wherein the reaction section comprises a plurality of discrete reactor sections (84$ and a reactant feed line (36') is in communication with each reactor section through one of the feed control valves (40') to separately regulate feed to each reactor section.
7. A catalytic reactor for the catalytic conversion of a feed stream by contact with fluidized catalyst particles to produce a product stream, substantially as hereinbefore described with reference to the foregoing description and accompanying drawings.



Documents:

2699-DELNP-2005-Abstract-(22-08-2008).pdf

2699-delnp-2005-abstract.pdf

2699-delnp-2005-assignment.pdf

2699-DELNP-2005-Claims-(22-08-2008).pdf

2699-delnp-2005-claims.pdf

2699-DELNP-2005-Correspondence-Others-(22-08-2008).pdf

2699-delnp-2005-Correspondence-Others-(27-08-2008).pdf

2699-DELNP-2005-Correspondence-Others-(28-08-2008).pdf

2699-delnp-2005-correspondence-others.pdf

2699-delnp-2005-correspondence-po.pdf

2699-DELNP-2005-Description (Complete)-(28-08-2008).pdf

2699-delnp-2005-description (complete)-22-08-2008.pdf

2699-delnp-2005-description (complete).pdf

2699-DELNP-2005-Drawings-(22-08-2008).pdf

2699-delnp-2005-drawings.pdf

2699-DELNP-2005-Form-1-(22-08-2008).pdf

2699-delnp-2005-form-1.pdf

2699-delnp-2005-form-13-(27-08-2008).pdf

2699-delnp-2005-form-13.pdf

2699-delnp-2005-form-18.pdf

2699-DELNP-2005-Form-2-(22-08-2008).pdf

2699-delnp-2005-form-2.pdf

2699-DELNP-2005-Form-26-(27-08-2008).pdf

2699-delnp-2005-form-26.pdf

2699-DELNP-2005-Form-3-(22-08-2008).pdf

2699-delnp-2005-form-3.pdf

2699-delnp-2005-form-5.pdf

2699-DELNP-2005-GPA-(22-08-2008).pdf

2699-DELNP-2005-Others-Document-(27-08-2008).pdf

2699-DELNP-2005-Others-Documents-(22-08-2008).pdf

2699-delnp-2005-pct-101.pdf

2699-delnp-2005-pct-210.pdf

2699-delnp-2005-pct-220.pdf

2699-delnp-2005-pct-401.pdf

2699-delnp-2005-pct-notification.pdf

2699-DELNP-2005-Petition-137-(27-08-2008).pdf

2699-DELNP-2005-Petition-138-(27-08-2008).pdf


Patent Number 223009
Indian Patent Application Number 2699/DELNP/2005
PG Journal Number 44/2008
Publication Date 31-Oct-2008
Grant Date 02-Sep-2008
Date of Filing 20-Jun-2005
Name of Patentee UOP LLC
Applicant Address 25 EAST ALGONQUIN ROAD, DES PLAINES, ILLINOIS 60017-5017, U.S.A.
Inventors:
# Inventor's Name Inventor's Address
1 LOMAS, DAVID A. UOP LLC,25 EAST ALGONQUIN ROAD, DES PLAINES, ILLINOIS 60017-5017, U.S.A.
2 MILLER, LAWRENCE, W. UOP LLC,25 EAST ALGONQUIN ROAD, DES PLAINES, ILLINOIS 60017-5017, U.S.A.
PCT International Classification Number B01J 8/28
PCT International Application Number PCT/US03/041203
PCT International Filing date 2003-12-19
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10327,279 2002-12-20 U.S.A.
2 10/327,214 2002-12-20 U.S.A.