USOO890697OB2

(12) United States Patent (10) Patent No.: US 8,906,970 B2

Gamlin (45) Date of Patent: *Dec. 9, 2014
(54) FISCHER-TROPSCH PROCESS IN A RADAL (58) Field of Classification Search
REACTOR USPC .......................................... 518/700, 707, 706
(75) Inventor: Timothy Douglas Gamlin, London See application file for complete search history.
(GB) (56) References Cited
(73) Assignee: Davy Process Technology Limited, U.S. PATENT DOCUMENTS
London (GB)
(*) Notice: Subject to any disclaimer, the term of this 5,545,674. A * 8/1996 Behrmann et al. ............ 518,715
patent is extended or adjusted under 35 6,323,248 B1 11/2001 Mart et al.
U.S.C. 154(b) by 0 days. FOREIGN PATENT DOCUMENTS
This patent is Subject to a terminal dis
claimer. EP 1300 190 A1 4/2003

(21) Appl. No.: 13/579,973 (Continued)

(22) PCT Fled: Feb. 6, 2012 OTHER PUBLICATIONS

(86) PCT NO.: International Search Report and Written Opinion issued in PCT/
GB2012/050256, dated May 2, 2012.
S371 (c)(1), (Continued)
(2), (4) Date: Oct. 2, 2012
(87) PCT Pub. No.: WO2O12/146903 Primary Examiner — Jafar Parsa
Assistant Examiner — Medhanit Bahta
PCT Pub. Date: Nov. 1, 2012 (74) Attorney, Agent, or Firm — Armstrong Teasdale LLP
(65) Prior Publication Data (57) ABSTRACT
US 2014/O187653 A1 Jul. 3, 2014 In a process for converting synthesis gas to higher hydrocar
(30) Foreign Application Priority Data bons in a tubular reactor, reactants are introduced through an
inlet of the reactor. The reactants are passed downwardly
Apr. 27, 2011 (GB) ................................... 1107070.3 through at least one tube to an upper Surface of a catalyst
carrier where they pass into a passage defined by an inner
(51) Int. C. perforated wall of a catalyst container before passing radially
CD7C I/04 (2006.01) through the catalyst bed towards the perforated outer wall.
B65D 6/00 (2006.01) Reaction occurs as the synthesis gas contacts the catalyst.
(Continued) Unreacted reactant and product is passed out of the container
through a perforated outer wall thereof and then upwardly
(52) U.S. C.
between a skirt and an outer wall of the container, followed by
CPC ............... C07C I/041 (2013.01); B01J 8/0214 being directed over the end of the skirt and downwardly
(2013.01); B01J 8/0285 (2013.01); B01.J between the skirt and the reactor tube where heat transfer
8/0415 (2013.01); B01.J.8/067 (2013.01); B01.J takes place. These steps are repeated for any Subsequent
19/2485 (2013.01); C10G 2/341 (2013.01); catalyst carrier, then product is removed from an outlet of the
B01J 2208/00814 (2013.01); B01J 2219/00038 reactOr.
(2013.01); B01.J 2219/0004 (2013.01)
USPC ............................ 518/706; 518/700; 518/707 24 Claims, 5 Drawing Sheets
 US 8,906,970 B2
Page 2

(51) Int. Cl. EP 1818094 A1 8, 2007

BOI. 8/02 (2006.01) WO 201OO694.86 A2 6, 2010
WO 201104.8361 A1 4/2011
BOI. 8/06 (2006.01) WO WO 201104.8361 A1 * 4, 2011
BOI. 8/04 (2006.01)
BOI, I/24 (2006.01)
CIOG2/00 (2006.01) OTHER PUBLICATIONS
(56) References Cited International Preliminary Report on Patentability and Written Opin
FOREIGN PATENT DOCUMENTS ion for PCT/GB2012/050256 dated Nov. 7, 2013; 7 pages.
EP 1623755 A1 2/2006 * cited by examiner
U.S. Patent Dec. 9, 2014 Sheet 1 of 5 US 8,906,970 B2
U.S. Patent Dec. 9, 2014 Sheet 2 of 5 US 8,906,970 B2
U.S. Patent Dec. 9, 2014 Sheet 3 of 5 US 8,906,970 B2

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1. 2
FISCHER-TROPSCH PROCESS IN A RADAL It has also been proposed to reduce the carbon monoxide to
REACTOR hydrogen ratio in the reactant gas to improve the mass transfer
of the carbon monoxide to the centre of the catalyst particle.
The present invention relates to a process for the conver Whilst this does improve the catalyst selectivity, the reaction
sion of carbon monoxide and hydrogen (synthesis gas) to kinetics are slowed which can lead to various problems such
liquid hydrocarbon products in the presence of a Fischer as carbide formation which has to be removed periodically.
Tropsch catalyst. A further problem is that reduced catalyst cannot generally
In the Fischer-Tropsch synthesis reaction a gaseous mix be used in fixed bed reactors so equipment has to be in place
ture of carbon monoxide and hydrogen is reacted in the pres to cater for initial reduction to allow for regeneration of the
ence of a catalyst to give a hydrocarbon mixture having a 10 catalyst if required. In some cases this requires the reactor
relatively broad molecular weight distribution. The product is vessel design conditions to be considerably in excess of the
predominantly straight chain, Saturated hydrocarbons which normal operating conditions thereby increasing capital costs.
typically have a chain length of more than 2 carbonatoms, for An alternative approach is to carry out the reaction in a
example, more than 5 carbon atoms. bubble slurry reactor. In this arrangement, Small catalyst par
The ability to build hydrocarbons from synthesis gas is an 15 ticles, such as those of 150 um or less, are Suspended in the
attractive alternative to production of the hydrocarbons by hydrocarbon product and are agitated by the injection of
cracking oil. This approach to hydrocarbon make has reaction gas at the bottom of the reactor. The gas becomes
increased as oil production has struggled to keep up with highly dispersed throughout the reactor and So, in theory, the
increasing demand for high quality fuel and will increase mass transfer area from gas to catalyst is very large. Addi
further as oil reserves diminish and those reserves become tionally, as the catalyst diameter is low, the mass transfer and
more carbon rich. heat transfer resistances within the catalyst particle are also
It is therefore desirable to optimise the Fischer-Tropsch low. Since the catalyst surface area is relatively large the heat
process. Several approaches to this have been made and these transfer from catalyst particle to fluid is high so that the
have generally been directed at reactor design or at the cata particles can be maintained at approaching fluid temperature
lyst formulation. One of the major issues with the process is 25 conditions. The high heat evolution in the reaction can be
that the heat evolved by the reaction is very substantial being, managed with internal or external coils in which water is
for example, approximately twice that produced by the reac vaporised. Thus in theory, carrying out the process in a bubble
tion to produce methanol for the equivalent conversion of slurry reactor offers various advantages.
carbon oxides. However, in practice there can be significant mass transfer
One approach to handling the high heat evolved is to carry 30 resistances in the bubble slurry reactors such that high water
out the reaction in a fixed bed reactor. In this arrangement, partial pressures can be experienced inside the catalyst par
catalyst pellets are loaded inside tubes of an axial reactor. ticles. Workers have reported issues such as catalyst oxidation
Cooling medium, Such as vaporising water, is Supplied and catalyst damage due to hydrothermal attack of the cata
around the tubes. Reactant gases are then passed through the lyst Support structures. In addition, catalyst attrition can be a
tubes where they contact the catalyst and the Fischer-Tropsch 35 significant problem which can lead to product purity and
reaction takes place. The heat evolved is transferred through catalyst loss issues caused by the difficulty of arranging
the tube wall to the surrounding cooling medium. In view of adequate separation of very Small particles from the product.
the need to control the heat within the tube, the size of the Further cobalt based Fischer-Tropsch catalysts can be sus
tubes is limited to allow the heat to pass readily from the ceptible to poisoning by even very low levels of impurities
centre of the tubes to the walls where heat exchange occurs. 40 Such as Sulphur species. This is a particular issue in bubble
Generally therefore the tubes have a diameter of less than slurry reactors since, if the synthesis gas includes poisons, all
about 40 mm to ensure the required level of heat transfer and the catalyst within the reactor will be exposed to the poison
to prevent the catalyst located towards the centre of the tube whereas in fixed bed reactors the first catalyst to be exposed to
overheating and thermal runaway occurring. The Small size of the poison tends to act as a guard bed for Subsequent catalyst.
the tubes contributes to the high cost of construction of these 45 It will therefore be understood that bubble slurry reactors
reactOrS. provide a challenging environment for catalysts and therefore
Even at the small tube size the catalyst particles have to be long catalyst charge lives are difficult to achieve leading to
relatively small in order to ensure reasonable mixing and heat frequent or continuous removal of spent catalyst and replace
transfer. In addition careful selection of conditions such as ment with fresh catalyst charge which results in reduced
Superficial velocity and gas hourly space Velocity has to be 50 average production per unit of catalyst and increases the cost
made in order to maintain the required heat transfer and of operating the system.
manage the conversion of the reactant gases at a reasonable Further, in order to optimise the operation of the bubble
overall pressure drop. slurry reactor, it has to be relatively tall in order to achieve the
For tubes approaching the upper size limit, it has been required level of agitation and mass transfer. Sufficient liquid
proposed to use larger catalyst particle sizes and to incorpo 55 has to be contained in the reactor to accommodate the catalyst
rate gas and/or liquid recycles to enhance the tube cooling. at concentrations in the region of 20 to 30 weight percent
However, this approach has some disadvantages since there is which results in a large volume of contained liquid. When
significant resistance to mass transfer in Fischer-TropSch these reactors are operating, the gas holdups within the slurry
catalyst particles where the reactants and lighter products are also significant. This requires extra reactor capacity to
have to travel through wax. This leads to the selectivity to 60 accommodate the slurry bed in the gassed state. To accom
unwanted lighter products increasing and the generation of modate this, the reactors are generally of the order of 60 m in
further unwanted heat at the centre of the particle. height. Such large reactors are heavy which makes them
In an attempt to address these problems so-called "egg expensive and difficult to deploy. If the plant site is not proxi
shell' catalysts have been proposed in which the surface of a mate to a substantial waterway, the transport issues of Such a
Support is impregnated. However, these catalysts provide less 65 large reactor become critical.
active catalyst per unit volume of the reactor and therefore More recently, it has been suggested that a so-called micro
reduce the productivity, and hence economics, of the process. channel reactor can be used to improve the Fischer-Tropsch
 US 8,906,970 B2
3 4
reaction system by process intensification. Key to this a skirt extending upwardly from the perforated outer wall
approach is to carry out the reaction in narrow channels of the annular container from a position at or near the
between the plates of a steam raising reactor. In this arrange bottom surface of said container to a position below the
ment high heat transfer coefficients and high specific produc location of a seal; and
tivities can be achieved. This approach also enables mass a seal located at or near the top Surface and extending from
transfer resistances to be minimised by using highly active the container by a distance which extends beyond an
catalysts on extended Surfaces. outer Surface of the skirt, said process comprising:
These micro-channel reactors are made by bonding plates (a) introducing the gaseous reactants through the inlet;
to form passages for the flow of the cooling medium. These (b) passing said reactants downwardly through said at least
reactors have to be fabricated by specialists and have to be 10 one tube to the upper surface of the, or the first, catalyst
contained in containment vessels. Thus the capital costs of carrier where they pass into the passage defined by the
these arrangements are substantial. A further problem is that inner perforated wall of the container before passing
there is a limit to the size at which modular units can be
radially through the catalyst bed towards the perforated
outer wall;
manufactured and the reactors Surprisingly have a high spe 15 (c) allowing reaction to occur as the synthesis gas contacts
cific weight per unit of production making them costly to the catalyst;
manufacture. (d) passing unreacted reactant and product out of the con
As high specific activity is required of the catalysts used in tainer though the perforated outer wall and then
micro-channel reactors, they tend to operate at higher tem upwardly between the inner surface of the skirt and the
peratures and produce products at the lighter end of the hydro outer wall of the annular container until they reach the
carbon chain spectrum. seal where they are directed over the end of the skirt and
A further problem associated with micro-channel reactors caused to flow downwardly between the outer surface of
relates to the risk of poisoning, to which as indicated above, the skirt and the inner surface of the reactor tube where
Fischer-Tropsch catalysts are particularly Susceptible. In a heat transfer takes place;
micro-channel reactor the relative amount of catalyst used is 25 (e) repeating steps (b) to (d) at any Subsequent catalyst
low and therefore if poisoning occurs, a significant reduction carrier, and
in performance will also be observed. If the catalyst becomes (f) removing product from the outlet.
deactivated, the developers have stated that it is necessary to The catalyst carrier is described in detail in PCT/GB2010/
return the reactor module to the factory to have the catalyst 0.01931 filed on 19 Oct. 2010 which is incorporated herein by
30 reference.
removed and replaced, resulting in high cost and significant
downtime unless costly reactors are maintained as spares. For the avoidance of doubt, any discussion of orientation,
Thus micro-channel reactors are generally only used in Small for example terms such as upwardly, below, lower, and the
capacity situations such as in so-called “flare busting duties like have, for ease of reference been discussed with regard to
where performance and costs are less than the problems asso the orientation of the catalyst carrier as illustrated in the
35 accompanying drawings. However, where the tubes, and
ciated with the disposal of inconvenient gas. hence the catalyst carrier, are used in an alternative orienta
An alternative arrangement is discussed in WO 2010/ tion, the terms should be construed accordingly.
069486 in which a number of adiabatic reactors are arranged The catalyst container will generally be sized such that it is
in series. Since the temperature rises described are Substan of a smaller dimension than the internal dimension of the
tial, this arrangement would not be expected to deliver good 40 reactor tube into which it is placed. The seal is sized such that
performance with conventional Fischer-Tropsch catalysts. In it interacts with the inner wall of the reactor tube when the
particular, the high temperatures would be expected to cause catalyst carrier of the present invention is in position within
rapid catalyst deactivation. In addition at areasonable overall the tube. The seal need not be perfect provided that it is
conversion, a high methane make would be expected. sufficiently effective to cause the majority of the flowing gas
Thus it will be understood that whilst the various 45 to pass through the carrier.
approaches to carrying out Fischer-Tropsch reactions each Generally, a plurality of catalyst carriers will be stacked
offer some advantages, they also each have their own disad within the reactor tube. In this arrangement, the reactants/
vantages. There is therefore still a need to provide an products flow downwardly between the outer surface of the
improved Fischer-Tropsch process which addresses one or skirt of a first carrier and the inner surface of the reactor tube
more of the problems of prior art arrangements. 50 until they contact the upper Surface and seal of a second
According to the present invention there is provided a carrier and are directed downwardly into the tube of the
process for the conversion of synthesis gas to higher hydro second carrier defined by the perforated inner wall of its
carbons by contacting a gaseous stream comprising synthesis annular container. The flow path described above is then
gas with a particulate Fischer-Tropsch catalyst, said process repeated.
being carried out in a tubular reactor having an inlet and an
55 The catalyst carrier may be formed of any suitable mate
rial. Such material will generally be selected to withstand the
outlet, said outlet being located downstream of the inlet, said Operating conditions of the reactor. Generally, the catalyst
reactor comprising one or more tubes having located therein carrier will be fabricated from carbon steel, aluminium, stain
one or more carriers for said particulate catalyst and cooling less steel, other alloys or any material able to withstand the
medium in contact with said at least one tube: 60 reaction conditions.
wherein said catalyst carrier comprises: The wall of the annular container can be of any suitable
an annular container holding catalyst, said container hav thickness. Suitable thickness will be of the order of about 0.1
ing a perforated inner wall defining a tube, a perforated mm to about 1.0 mm, preferably of the order of about 0.3 mm
outer wall, a top Surface closing the annular container to about 0.5 mm.
and a bottom Surface closing the annular container, 65 The size of the perforations in the inner and outer walls of
a surface closing the bottom of said tube formed by the the annular container will be selected such as to allow uni
inner wall of the annular container, form flow of reactant(s) and product(s) through the catalyst
 US 8,906,970 B2
5 6
while maintaining the catalyst within the container. It will along the length of the carrier. The shaping of the upstanding
therefore be understood that their size will depend on the size skirt increases the surface area of the skirt and assists with the
of the catalyst particles being used. In an alternative arrange insertion of the catalyst carrier into the reaction tube since it
ment the perforations may be sized such that they are larger will allow any surface roughness on the inner Surface of the
but have a filter mesh covering the perforations to ensure 5 reactor tube or differences intolerances in tubes to be accom
catalyst is maintained within the annular container. This modated.
enables larger perforations to be used which will facilitate the Where the upwardly extending skirt is shaped, it will gen
free movement of reactants without a significant loss of pres erally be flattened to a smooth configuration towards the point
SUC. at which it is connected to the annular container to allow a gas
It will be understood that the perforations may be of any 10 seal to be formed with the annular container. The upstanding
suitable configuration. Indeed where a wall is described as skirt will generally be connected to the outer wall of the
perforated all that is required is that there is means to allow the annular container at or near the base thereof. Where the skirt
reactants and products to pass through the walls. These may is connected at a point above the bottom of the wall, the wall
be small apertures of any configuration, they may be slots, will be free of perforations in the area below the point of
they may beformed by a wire screen or by any other means of 15 connection. The upstanding skirt may be flexible.
creating a porous or permeable Surface. Generally, the upstanding skirt will stop at about 0.5 cm to
Although the top Surface closing the annular container will about 1.5 cm, preferably about 1 cm, short of the top surface
generally be located at the upper edge of the or each wall of of the annular container.
the annular container, it may be desirable to locate the top Without wishing to be bound by any theory, it is believed
Surface below the upper edge Such that a portion of the upper that the upstanding skirt serves to gather the reactants/prod
edge of the outer wall forms a lip. Similarly, the bottom ucts from the perforated outer wall of the annular container
surface may be located at the lower edge of the, or each, wall and direct them via the shapes towards the top of the catalyst
of the annular container or may be desirable to locate the carrier collecting more reactants/products exiting from the
bottom surface such that it is above the bottom edge of the outer wall of the annular container as they move upwardly. As
wall of the annular container such that the wall forms a lip. 25 described above, reactants/products are then directed down
The bottom Surface of the annulus and the Surface closing between the tube wall and the outside of the upstanding skirt.
the bottom of the tube may beformed as a single unit or they By this method the heat transfer is enhanced down the whole
may be two separate pieces connected together. The two length of the carrier but as the heat exchange is separated from
Surfaces may be coplanar but in a preferred arrangement, they the catalyst, hotter or colder as appropriate heat exchange
are in different planes. In one arrangement, the Surface clos 30 fluid can be used without quenching the reaction at the tube
ing the bottom of the tube is in a lower plane than the bottom wall and at the same time ensuring that the temperature of the
surface of the annular container. This serves to assist in the catalyst towards the centre of the carrier is appropriately
location of one carrier on to a carrier arranged below it when maintained.
a plurality of containers are to be used. It will be understood The seal may be formed in any suitable manner. However,
that in an alternative arrangement, the Surface closing the 35 it will generally be sufficiently compressible to accommodate
bottom of the tube may be in a higher plane that the bottom the smallest diameter of the reactor tube. The seal will gen
Surface of the annular container. erally be a flexible, sliding seal. In one arrangement, an
Whilst the bottom surface will generally be solid, it may O-ring may be used. A compressible split ring or a ring having
include one or more drain holes. Where one or more drain a high coefficient of expansion could be used. The seal may be
holes are present, they may be covered by a filter mesh. 40 formed of any suitable material provided that it can withstand
Similarly a drain hole, optionally covered with a filter mesh the reaction conditions. In one arrangement, it may be a
may be present in the surface closing the bottom of the tube. deformable flange extending from the carrier. The flange may
Where the carrier is to be used in a non-vertical orientation, be sized to be larger than the internal diameter of the tube such
the drain hole, where present will be located in an alternative that as the container is inserted into the tube it is deformed to
position i.e. one that is the lowest point in the carrier when in 45 fit inside and interact with the tube.
SC. In the present invention, the annular space between the
One or more spacer means may extend downwardly from outer Surface of the catalyst container and the inner Surface of
the bottom surface of the annular container. The, or each, the tube wall is small, generally of the order of from about 3
spacer means may be formed as separate components or they mm to about 10 mm. This narrow gap allows a heat transfer
may be formed by depressions in the bottom surface. Where 50 coefficient to be achieved such that an acceptable temperature
these spacer means are present they assist in providing a clear difference of the order of about 10° C. to about 40° C.
path for the reactants and products flowing between the bot between the cooled exit gas and the coolant to be achieved.
tom surface of the first carrier and the top surface of a second The size of the annulus between the skirt and the catalyst
lower carrier in use. The spacer may be of the order of about wall and the skirt and the tube wall will generally be selected
4 mm to about 15 mm, or about 6 mm, deep. Alternatively, or 55 to accommodate the gas flow rate required while maintaining
additionally, spacer means may be present on the top surface. high heat transfer and low pressure drop. Thus the process of
The top surface closing the annular container may include the present invention may additional include the step of
on its upper Surface means to locate the container against a selecting the appropriate size of the annulus to meet these
catalyst carrier stacked above the container in use. The means criteria.
to locate the container may be of any suitable arrangement. In 60 The process of the present invention enables relatively
one arrangement it comprises an upstanding collar having large reactor tubes to be used. In particular, tubes having
apertures or spaces therein to allow for the ingress of reac diameters in the region of from about 75 mm to about 130 mm
tantS. or even about 150 mm can be used compared to diameters of
The upwardly extending skirt may be Smooth or it may be less than about 40 mm used in conventional systems. The
shaped. Any Suitable shape may be used. Suitable shapes 65 larger diameter tubes will allow capacity in the region of
include pleats, corrugations, and the like. The pleats, corru 10,000 US bbl/day to be achieved in a single reactor of less
gations and the like will generally be arranged longitudinally than 6 m in diameter and less than 700 tonnes in weight.
 US 8,906,970 B2
7 8
As discussed above the highly exothermic nature of the that is not occupied by catalyst. When the monolith is in use
Fischer-Tropsch reaction is a major factor in the design of a in a vertical reactor with downflow, the reactant(s) flow down
reactor in which the reaction can be carried out. The use of the wardly through the reactor tube, the reactant(s) first contacts
catalyst carrier in the process of the present invention, allows the upper face of the monolith catalyst and flows therethrough
tubes comprising a plurality of catalyst carriers to become, in 5 in a direction parallel to the axis of the cylinder. The seal of the
effect, a plurality of adiabatic reactors with inter-cooling. container prevents the reactant(s) from flowing around the
Any Suitable catalyst may be used in the process of the monolith and assists the direction of the reactants into the
present invention. Powdered, foamed, structured, or other catalyst. Reaction will then occur within the monolith cata
suitable forms may be used. lyst. The product will then also flow down through the mono
One benefit of the process of the present invention is that 10 lith in a direction parallel to the axis of the cylinder.
the carrier allows for the deployment of small diameter Fis Once the reactant(s) and product reach the bottom surface
cher-Tropsch catalysts to be used such as those having diam of the catalyst carrier they are directed towards the skirt of the
eters of from about 100 um to about 1 mm. Since these are carrier. To facilitate this flow, feet may be provided within the
used in a fixed bed, the mass transfer resistances can be carrier on the upper face of the bottom surface such that, in
greatly reduced over prior art arrangements. This will lead to 15 use, the catalyst monolith is Supported on the feet and there is
improved selectivity to the required products, particularly a gap between the bottom of the catalyst monolith and the
those having a carbon chain length of five and above. bottom surface of the catalyst carrier. The upwardly extend
Further, as these Small catalysts have a high Surface area ing skirt then directs the reactant(s) and product upwardly
and are located in the direct flow of the reacting gas, they are between the inner surface of the skirt and the outer surface of
maintained at a temperature which is very similar to that of the monolith catalyst until they reach the underside of the
the flowing gas. This will reduce the tendency to by-product seal. They are then directed, by the underside of the seal, over
formation. the end of the skirt and they then flow downwardly between
In one alternative arrangement, a monolith catalyst may be the outer surface of the skirt and the inner surface of the
used. In this arrangement, the structure of the catalyst con reactor tube where heat transfer takes place.
tainer may be modified. Full details of a catalyst container 25 In one alternative arrangement, the monolith catalyst has a
suitable for use with a monolith catalyst is described in GB channel extending longitudinally therethrough. Generally the
patent application no 1105691.8 filed 4 Apr. 2011 the con channel will be located on the central axis of the monolith
tents of which are incorporated herein by reference. catalyst. Thus where the reactor tube is of circular cross
Thus according to a second aspect of the present invention section, the monolith catalyst of this arrangement will be of
there is provided a process for the conversion of synthesis gas 30 annular cross-section. In this arrangement, in use, in a vertical
to higher hydrocarbons by contacting a gaseous stream com reactor with downflow, reactant(s) flow downwardly through
prising synthesis gas with a monolith Fischer-Tropsch cata the reactor tube and thus first contacts the upper surface of the
lyst, said process being carried out in a tubular reactor having monolith catalyst. The seal blocks the passage of the react
an inlet and an outlet, said outlet being located downstream of ant(s) around the side of the catalyst. Since the path of flow of
the inlet, said reactor comprising one or more tubes having 35 reactant(s) is impeded by the catalyst, it will generally take
located therein one or more carriers for said monolith catalyst the easier path and enter the channel in the monolith. The
and cooling medium in contact with said tubes; wherein said reactant(s) then enters the annular monolith catalyst and
catalyst carrier comprises: passes radially through the catalyst towards the outer Surface
a container holding a monolith catalyst, said container of the catalyst monolith. During the passage through the
having a bottom Surface closing the container and a skirt 40 catalyst monolith reaction occurs. Unreacted reactant and
extending upwardly from the bottom surface of said product then flow out of the monolith catalyst though the
container to a position below the location of a seal and outer surface thereof. The upwardly extending skirt then
spaced therefrom, said skirt being positioned such that directs reactant and product upwardly between the inner Sur
there a space between an outer surface of the monolith face of the skirt and the outer wall of the monolith catalyst
catalyst and the skirt; and 45 until they reach the seal. They are then directed, by the under
a seal located at or near a top Surface of the monolith side of the seal, over the end of the skirt and flow downwardly
catalyst and extending from the monolith catalyst by a between the outer surface of the skirt and the inner surface of
distance which extends beyond an outer surface of the the reactor tube where heat transfer takes place.
skirt, said process comprising: In the arrangement in which the monolith catalyst includes
(a) introducing the gaseous reactants through the inlet; 50 the channel, the catalyst carrier may include a top Surface
(b) passing said reactants downwardly through said at least which will extend over the monolith catalyst but leave the
one tube to the upper surface of the, or the first, monolith channel uncovered. This top surface serves to ensure that the
catalyst where they pass through the monolith catalyst; reactant(s) do not enter the catalyst monolith from the top but
(c) allowing reaction to occur as the synthesis gas contacts are directed into the channel for radial flow.
the catalyst; 55 The discussion of the specific features of the catalyst car
(d) passing unreacted reactant and product out of the cata rier above in relation to the first embodiment applies equally
lyst and then upwardly between the inner surface of the in connection to the catalyst carrier for a monolith catalyst of
skirt and the outer surface of the monolith catalyst until the second embodiment insofar as the relevant features are
they reach the seal where they are directed over the end present.
of the skirt and caused to flow downwardly between the 60 Whichever type of carrier is used, in one arrangement more
outer surface of the skirt and the inner surface of the than 40 carriers, preferably more than 41 carriers are located
reactor tube where heat transfer takes place: within a single tube. More preferably, from about 70 to about
(e) repeating steps (b) to (d) at any Subsequent catalyst 200 carriers may be used. This will enable a reasonable tem
carrier; and perature rise of the order of from about 10°C. to about 20°C.
(f) removing product from the outlet. 65 to be maintained over each stage.
In one arrangement, the monolith catalyst is a Solid, in that The radial flow through the, or each, catalyst carrier within
there is substantially no space within the body of the monolith the tube means that the gas flow path length is also very low
 US 8,906,970 B2
10
when compared with prior art arrangements. Total catalyst FIG. 2 is a perspective view of the catalyst carrier from
depths of the order of about 2 meters may be achieved within below:
a tube of up to 20 meters of length at catalyst hourly space FIG. 3 is a partial cross section viewed from the side;
velocities of about 4000. The low flow path means that the FIG. 4 is a simplified diagram of the catalyst carrier of the
overall pressure drop achieved is an order of magnitude lower 5 present invention;
than that which would be experienced with the same catalyst FIG. 5 is a schematic illustration of a carrier of the present
in an axial tube not using the process of the present invention. invention from below when located within a tube:
One advantage of being able to achieve a low overall pres FIG. 6 is a schematic cross section of three catalyst carriers
Sure drop by the process of the present invention is that long located within a tube:
tubes with high Superficial gas Velocities, gases containing 10 FIG. 7 is an enlarged cross-section of Section A of FIG. 6;
high quantities of inerts or a gas recycle may be accommo FIG. 8 is a schematic representation of an alternative
dated without the pressure drop and potential for catalyst embodiment of the present invention, illustrating the flow
crushing disadvantages experienced with high flows through path;
current fixed bed systems. The ability to accommodate FIG.9 is a schematic representation of a third embodiment
recycle will enable overall conversion at lower per pass con 15 of the present invention, illustrating the flow path; and
versions to be achieved at high catalyst productivity and FIG. 10 is a schematic representation of the flow path
selectivity. between two stacked carriers of the kind illustrated in FIG.9.
The reduced catalyst may be repeatedly and reliably A catalyst carrier 1 of the present invention is illustrated in
reduced and loaded into the carrier at a manufacturing facility FIGS. 1 to 3. The carrier comprises an annular container 2
and the balance of the container can be filled with wax. The which has perforated walls 3, 4. The inner perforated wall 3
containers may be assembled in connected units which will defines a tube 5. A top surface 6 is closes the annular container
simplify the loading of the reactor and in particular will mean at the top. It is located at a point towards the top of the walls
that the operators do not have to come into contact with the 3, 4 of the annular container 2 such that a lip 6 is formed. A
catalyst. The unloading procedure is also simplified since the bottom surface 7 closes the bottom of the annular container 2
carriers may be readily discharged before being taken for 25 and a surface 8 closes the bottom of tube 5. The surface 8 is
reprocessing. located in a lower plane that that of the bottom surface 7.
In one arrangement of the present invention, a plurality of Spacer means in the form of a plurality of depressions 9 are
reactors may be used in parallel. located present on the bottom surface 7 of the annular con
Liquid product stream separated from the stream exiting tainer 2. Drain holes 10, 11 are located on the bottom surface
the reactor will be recovered. In the process of the present 30 7 and the surface 8.
invention, unreacted gas exiting the outlet of the, or each, A seal 12 extends from the upper Surface 6 and an upstand
reactor may be further treated to remove heat. The removed ing collar 13 is provided coaxial with the tube 5.
heat may be reused and/or rejected to cooling. Liquid product A corrugated upstanding skirt 14 Surrounds the container2.
separated from the stream exiting the reactor will be recov The corrugations are flattened in the region Ltowards the base
ered. 35 of the carrier 1.
In one arrangement, two or more reactors may be located in A catalyst carrier 1 of the present invention located in a
series fluid communication with facilities located between reactor tube 15. The flow of gas is illustrated schematically in
each reactor to remove heat. The heat may be reused and/or FIG. 4 by the arrows.
rejected to cooling. In one arrangement, hydrogen and carbon When a plurality of catalyst carriers of the present inven
monoxide containing steam exiting the last stage of a series of 40 tion are located within a reactor tube 15 they interlock as
interconnected reactors may be recycled to any Suitable point illustrated in FIGS. 6 and 7. The effect on the flow path is
in the process. In one arrangement it will be recycled to the illustrated in the enlarged section shown in FIG. 7.
inlet of the first reactor. A catalyst carrier 101 of a second embodiment is illustrated
In one alternative arrangement, two or more groups of in FIG. 8. A bottom surface 102 closes the bottom of the
parallel reactors may be located in series. In this arrangement, 45 container 101. Feet 103 extend upwardly from the bottom
groups of parallel reactors are in series communication with Surface to support a monolith catalyst 104. An upstanding
facilities located between each group to remove heat. The skirt 105 extends from the bottom surface 102. The skirt may
heat may be reused and/or rejected to cooling. In one arrange be corrugated and may be flattened as in a region towards the
ment, liquid product may be removed between each stage bottom surface 103.
with hydrogen and carbon monoxide containing steam being 50 A seal 106 is provided to extend from the monolith catalyst
passed to a Subsequent reactor group in the series. Hydrogen 104 and interact with the wall of the reactor tube 107. Baffles
and carbon monoxide containing steam exiting the last stage 108 extend upwardly for the seal. These serve to direct flow
of a series of interconnected reactors may be recycled to any and to separate the carrier from the bottom surface of a carrier
Suitable point in the process. In one arrangement it will be located above the carrier. The flow of gas is illustrated sche
recycled to the inlet of the first reactor. 55 matically by the arrows.
Where the process includes a plurality of reaction stages, a An alternative embodiment of the present invention is illus
hydrogen rich stream may be fed to the second and/or one or trated in FIG.9. In this arrangement the monolith catalyst 104
more of any Subsequent stages. has a longitudinal channel 109 therethrough. In this arrange
Any suitable reaction conditions may be used. In one ment, the feet of the first embodiment may be omitted. This
arrangement, the reaction temperature will be from about 60 carrier is similar in arrangement to the first embodiment.
190° C. to about 250° C. The reaction pressure may be from However, additionally a top surface 110 is provided to cover
about 20 bara to about 80 bara. the upper surface of the monolith catalyst. The flow of gas in
The present invention will now be described, by way of the arrangement of FIG. 9 is illustrated schematically by the
example, by reference to the accompanying drawings in aOWS.
which: 65 When a plurality of catalyst carriers of the present inven
FIG. 1 is a perspective view from above of the catalyst tion are located withina reactor tube 107 the effect on the flow
carrier of the present invention; path is illustrated in the enlarged section shown in FIG. 10.
 US 8,906,970 B2
11 12
It will be understood that whilst the catalyst carriers have caused to flow downwardly between the outer surface of
been described with particular reference to a use in a tube of the skirt and the inner surface of the reactor tube where
circular cross-section the tube may be of non-circular cross heat transfer takes place;
section for example, it may be a plate reactor. Where the tube (e) repeating steps (b) to (d) at any Subsequent catalyst
is of non-circular cross-section, the carrier will be of the carrier, and
appropriate shape. In this arrangement, in the the embodi (f) removing product from the outlet.
ment described in which an annular monolith is used it will be 2. The process according to claim 1 wherein the catalyst
understood that the monolith will not be a circular ring and particles have a diameter of from about 100 um to about 1
this term should be construed accordingly. .
The present invention will now be discussed with reference 10
3. A process for the conversion of synthesis gas to higher
to the following example. hydrocarbons by contacting a gaseous stream comprising
EXAMPLE1 synthesis gas with a monolith Fischer Tropsch catalyst, said
process being carried out in a tubular reactor having an inlet
Conventional fixed bed reactors, currently in production 15 and an outlet, said outlet being located downstream of the
are capable of producing approximately 5833 US barrels/day inlet, said reactor comprising one or more tubes having
of Fischer-Tropsch liquids. Public disclosures indicate that located therein one or more carriers for said monolith catalyst
these reactors weight 1200 tonnes and have a diameter of 7.2 and cooling medium in contact with said tubes;
m and contain over 28000 tubes. A reactor for the process of wherein said catalyst carrier comprises:
the present invention processing feed gas containing hydro a container holding a monolith catalyst, said container
gen and carbon monoxide derived from natural gas with a having a bottom Surface closing the container and a skirt
diameter of 5.6 m will produce around 10000 US barrels/day extending upwardly from the bottom surface of said
of Fischer-Tropsch liquids and will contain approximately container to a position below the location of a seal and
2300 axial tubes each filled with about 80 catalyst carriers and spaced therefrom, said skirt being positioned Such that
will weigh approximately 700 tonnes. It will therefore be 25 there is a space between an outer surface of the monolith
understood that this represents an improvement of almost a catalyst and the skirt; and
factor of three in the specific weight installed per unit of a seal located at or near a top Surface of the monolith
production over the prior art arrangements. catalyst and extending from the monolith catalyst by a
The invention claimed is: 30
distance which extends beyond an outer surface of the
skirt, said process comprising:
1. A process for the conversion of synthesis gas to higher (a) introducing the gaseous reactants through the inlet;
hydrocarbons by contacting a gaseous stream comprising (b) passing said reactants downwardly through said at least
synthesis gas with a particulate Fischer Tropsch catalyst, said
process being carried out in a tubular reactor having an inlet one tube to the upper surface of the, or the first, monolith
and an outlet, said outlet being located downstream of the 35 catalyst where they pass through the monolith catalyst;
inlet, said reactor comprising one or more tubes having (c) allowing reaction to occur as the synthesis gas contacts
located therein one or more carriers for said particulate cata the catalyst;
lyst and cooling medium in contact with said tubes; (d) passing unreacted reactant and product out of the cata
wherein said catalyst carrier comprises: lyst and then upwardly between the inner surface of the
an annular container for holding catalyst in use, said con 40 skirt and the outer surface of the monolith catalyst until
tainer having a perforated inner wall defining a tube, a they reach the seal where they are directed over the end
perforated outer wall, a top surface closing the annular of the skirt and caused to flow downwardly between the
container and a bottom surface closing the annular con outer surface of the skirt and the inner surface of the
tainer, reactor tube where heat transfer takes place:
a surface closing the bottom of said tube formed by the 45 (e) repeating steps (b) to (d) at any Subsequent catalyst
inner wall of the annular container, carrier, and
a skirt extending upwardly from the perforated outer wall (f) removing product from the outlet.
of the annular container from a position at or near the 4. The process according to claim 1 wherein a plurality of
bottom surface of said container to a position below the catalyst carriers are stacked within the reactor tube.
location of a seal; and 50 5. The process according to claim 1 wherein the annular
a seal located at or near the top surface and extending from space between the outer Surface of the catalyst container and
the container by a distance which extends beyond an the inner surface of the tube wall is selected to accommodate
outer Surface of the skirt, said process comprising: the gas flow rate required while maintaining high heat transfer
(a) introducing the gaseous reactants through the inlet; and low pressure drop.
(b) passing said reactants downwardly through said at least 55 6. The process according to claim 1 wherein the annular
one tube to the upper surface of the, or the first, catalyst space between the outer Surface of the catalyst container and
carrier where they pass into the passage defined by the the inner surface of the tube wall is of the order of from about
inner perforated wall of the container before passing 3 mm to about 10 mm.
radially through the catalyst bed towards the perforated 7. The process according to claim 1 wherein the one or
outer wall; 60 more tubes have a diameter of from about 75 mm to about 150
(c) allowing reaction to occur as the synthesis gas contacts .
the catalyst; 8. The process according to claim 1 wherein more than 41
(d) passing unreacted reactant and product out of the con carriers are located within a single tube.
tainer though the perforated outer wall and then 9. The process according to claim 1 wherein from about 70
upwardly between the inner surface of the skirt and the 65 to about 200 carriers are located within a single tube.
outer wall of the annular container until they reach the 10. The process according to claim 1 wherein a plurality of
seal where they are directed over the end of the skirt and reactors are used in parallel.
 US 8,906,970 B2
13 14
11. The process according to claim 1 wherein unreacted 18. The process according to claim 13 wherein the heat is
gas exiting the outlet of the, or each, reactor is treated to reused and/or rejected to cooling.
remove heat. 19. The process according to claim 17, wherein liquid
12. The process according to claim 11 wherein the removed product is removed between each group of parallel reactors
unreacted gas is reused. with hydrogen and carbon monoxide containing stream being
13. The process according to claim 1 wherein two or more passed to a Subsequent reaction group in the series.
reactors are located in series.
20. The process according to claim 19 wherein hydrogen
14. The process according to claim 13 wherein the reactors and carbon monoxide containing stream exiting the last stage
located in series are in fluid communication with facilities
located between each reactor to remove heat. 10
of a series of interconnected reactors is recycled to any Suit
15. The process according to claim 13 or 14 wherein hydro able point in the process.
gen and carbon monoxide containing stream exiting the last 21. The process according to claim 20 wherein the stream
stage of the series of interconnected reactors is recycled to is recycled to the inlet of the first reactor.
any Suitable point in the process. 22. The process according to claim 9 wherein a hydrogen
16. The process according to claim 15 wherein hydrogen 15 rich stream is fed to the second and/or one or more of any
and carbon monoxide containing stream exiting the last stage Subsequent reactors.
of the series of interconnected reactors is recycled to the first 23. The process according to claim 1 wherein the reaction
reactOr. temperature is from about 190° C. to about 250° C.
17. The process according to claim 9 wherein groups of 24. The process according to claim 1 wherein the reaction
parallel reactors are in series communication with facilities pressure is from about 20 bara to about 80 bara.
located between each group to remove heat. k k k k k