Packed-bed tubular reactor for heterogeneous exothermic or endothermic catalytic reactions

Abstract

A reactor for Fischer-Tropsch reaction effected in a three-phase system essentially consisting of a gaseous reagent phase, a liquid reacted phase and a solid catalytic phase, wherein the solid catalytic phase is composed of packed bodies encaged in at least one open-cell foam structure with a high thermal conductivity.

Claims

1. A reactor, comprising: a substantially cylindrical container wherein a feeder and a discharger of a thermoregulation fluid for a chemical reaction are present; a top closing element and a bottom closing element placed at a top end and a bottom end of the container, respectively; a feeder of a reagent phase positioned in the top closing element or in the bottom closing element; a discharger of a product phase positioned in the top closing element or in the bottom closing element; a tubular element, arranged vertically inside the container between the top closing element and the bottom closing element, comprising in its interior a body having a structure of an open-cell foam, wherein: the open-cell foam has an average pore dimension ranging from 0.4 to 2.0 mm and a filling degree from 10% to 40%, and is made of a material having an intrinsic thermal conductivity higher than 10 W/m/K, and the body is configured to be filled with a catalyst in a form of particles, wherein a fill factor between a volume of the particles and a volume of a void space in the foam ranges from 0.4 to 0.7.

2. The reactor according to claim 1, wherein said reactor is arranged either vertically or horizontally or at any angle with respect to a ground.

3. The reactor according to claim 1, comprising at least five of said tubular element, which houses foams.

4. The reactor according to claim 3, wherein the at least five tubular elements form a tube bundle having a diameter substantially equal to or slightly smaller than an internal diameter of the cylindrical container, which occupies a volume ranging from 50 to 90% of a total volume of the cylindrical container.

5. The reactor according to claim 1, wherein said tubular element comprises open-cell foams having a relative density ranging from 3 to 70%.

6. The reactor according to claim 3, wherein the foams have an average pore dimension of from 0.5 to 1.0 mm.

7. The reactor according to claim 3, wherein the foams are rigid foams.

8. The reactor according to claim 5, wherein the catalyst in a form of a particulate is placed in said open-cell foams.

9. The reactor according to claim 8, wherein a fill ratio of (particulate volume)/(volume of void space available in the foams) ranges from 0.2 to 0.8.

10. The reactor according to claim 8, wherein a ratio between an average pore dimension of the foam and an average dimension of the catalytic particles ranges from 1.1 to 30.

11. A process for effecting an exothermic or endothermic catalytic reaction, the process comprising feeding reagents to the reactor according to claim 1, filled with the catalyst in a foam of a finely subdivided particulate.

12. The process according to claim 11, wherein the catalytic reaction is a Fischer-Tropsch reaction.

13. The process according to claim 11, wherein the catalyst is in a form of packed bodies.

Description

EXAMPLE

(1) A monotubular reactor is first prepared, having a length of 1.1 m, cooled externally, in which an open-cell and full trabeculae monolithic foam is inserted, metre long, made of aluminium, having an outer diameter substantially coinciding with the internal diameter of the reactor, equal to 28 mm, a filling degree of 15% and an average pore size of about 0.63 mm (density of 16 pores per centimetre). The surface per unit volume of said foam is 900 m.sup.2/m.sup.3.

(2) The trabeculae of said foam are coated (by means of slurry coating techniques) with a layer of catalyst for the Fischer-Tropsch synthesis, based on cobalt supported on alumina, having a thickness equal to 50 m. The quantity of catalyst charged into the reactor is 43.4 g.

(3) The reactor operates with a pressure at the head equal to 20 bar, feeding 4,000 Ncm.sup.3/h/g.sub.cat of a mixture of CO and H.sub.2 preheated to 234 C. and having a ratio between the two species equal to 2.1 moles of H.sub.2 per mole of CO. The coolant is kept at a constant temperature of 234 C.

(4) The total specific productivity of this reactor is equal to 44.5 kg/h/m.sup.3 and the pressure drops are negligible. The temperature profile inside the catalytic bed is practically flat and differs from the temperature of the coolant by less than 2 C. (T.sub.max=236 C.)

(5) An analogous monotubular reactor is then prepared, cooled externally, consisting of an open-cell monolithic foam, 1 meter long, made of aluminium, having an outer diameter equal to 28 mm, a filling degree of 15% and an average pore size of about 0.63 mm (density of 16 pores per centimetre).

(6) In this case, however, the trabeculae of the foam are not coated, but the foam cells are filled with catalytic particles packed with the same cobalt-based catalyst supported on alumina used in the previous test, having an average outer diameter of 300 m with a very narrow distribution obtained by means of selective sieving. In particular, the finely divided catalyst is simply poured into the tubular element containing the foam. In order to guarantee a homogeneous distribution of the catalytic particles in the foam cells, a vibratory motion of the tubular element is associated with the filling phase. The quantity of catalyst charged into the reactor is 454.8 g.

(7) The reactor operates with a pressure at the head equal to 20 bar, feeding 4,000 Ncm.sup.3/h/g.sub.cat of a mixture of CO and H.sub.2 preheated to 219 C. and having a ratio between the two species equal to 2.1 moles of H.sub.2 per mole of CO. The coolant is kept at a constant temperature of 219 C.

(8) The total specific productivity of this reactor is equal to 356 kg/h/m.sup.3 and the pressure drops, slightly higher than those of the previous case, are still tolerable, as they are lower than 1 bar. The temperature profile of the catalytic bed also has a temperature difference still maintained below 14 C. and differs from the temperature of the coolant by not more than 7 C. (T.sub.max=236 C.).

(9) By adopting a reactor loaded with foams packed with the catalytic particulate according to the present invention, instead of a reactor charged with washcoated foams, a productivity up to 8 times higher can therefore be obtained, with the same reactor volume, also guaranteeing the possibility of operating under modest pressure drop conditions and relatively insignificant temperature profiles.