DE2038165C3 - Cylindrical catalyst pellets produced by compression for use in a gas phase process - Google Patents

Description

The invention relates to cylindrical, through Kat.tJysatorpelleis manufactured in compression for use in a gas phase process.

In some gas phase processes in which solid catalysts in the form of Kataiysatorpeiiets are used, the speed of the gas phase reaction is limited by the speeds which the reactants in the Kalalysatorpelleis in and with which the reaction products diffuse out of the catalyst pellets. Such gas phase reactions therefore preferably or mainly take place in the vicinity of the outer surfaces of the catalyst pellets, which is why it is advantageous to use Kataiysatorpeiiets in which the surface-to-volume ratio is high. This can be achieved by to make small catalyst pellets. However, in view of practical use, there is one Lower limit for the size of catalyst pellets, there the pressure required for pumping a gas through the catalyst bed or the pressure drop along the catalyst bed increases to the extent that in which reduces the size of the catalyst pellets. In addition, the production of very small Catalyst pellets are associated with higher costs. Using annular catalyst pellets can increase the ratio of Surface to volume and a reduction in the pressure drop can be achieved, but the manufacturing costs of annular Kaialysatorpcllcis are higher than with simple, cylindrical Kiitalysatorpellcis, and the practical usability of annular catalyst pellets is due to mechanical conditions iiiif limited to relatively large rings.

From DE-PS 5 52 5) 3 are ellipsoidal packing for adsorption and Kcaktionstürmc

known, which are provided with recesses and grooves to increase the effective surface and to achieve a sufficient passage cross-section or can have ribs. However, these packing bodies have the disadvantage that their production because of the complicated shape difficult and expensive and the transfer of this shape to catalyst pellets with the preferred, small size of a few millimeters is hardly possible

From US-PS 36 74 680 and 24 08 164 are catalyst pellets with enlarged, geometric Known surface that have very different shapes and are produced by extrusion can, if there is any simple method of making them, that extrusion process has however, the disadvantage that compacts are first formed which are not rigid and therefore their shape can change. In addition, these compacts must be cut, and it is not easy to get the length to keep the short pieces thus obtained constant.

Simple, cylindrical Kataiysatorpeiiets are also known, but these catalyst pellets have none optimal surface-to-volume ratio.

The object of the invention are therefore cylindrical, compression-produced catalyst pellets for Use in a gas phase process in which the ratio of surface area to volume is compared with the simple cylindrical catalyst pellets, which have a shape through which for one given case an optimal balance between surface increase and pressure drop in the catalyst bed and abrasion losses can be achieved and relatively low over a long period of use Cause pressure drop.

This object is achieved by the catalyst pellets characterized in claim I.

The catalyst pellets of the invention (hereinafter referred to simply as "pellets") have a better combination of properties than usual Catalyst pellets.

The pellets of the invention can be made almost as easily and cheaply as simple cylindrical ones Pellets. For this purpose, pelletizing devices are used, the two punches of which are complementary to the desired one Have the shape of the end faces of the pellets profiled or flat end faces.

The volume of an indented pellet is smaller and its outer surface area is larger than a cylindrical pellet with flat end faces and the same overall length and the same Diameter. When notched pellets according to the invention are placed in a reaction container for a Gas phase processes are charged is the weight required to fill the reaction vessel Pellets less than simple, cylindrical pellets with the same packing density, which is why the costs are lower. Since the surface area of the pellets according to the invention is increased in the reaction container, the efficiency of the reaction vessel for diffusion-limited gas phase reactions is also increased. When using the pellets according to the invention, the catalyst bed also has a greater permeability and therefore has a lower pressure drop ills a catalyst bed formed by cylindrical pellets with flat end faces.

The ratio of surface area to volume in a protruding pellet does not give way

depends significantly on the ratio for a cylindrical pellet with flat end faces. When inventive Pellets provided with a protrusion are filled into a reaction container, as a result however, an increase in permeability as the pellets i further apart due to the protrusions are kept, thereby reducing the weight and thus the cost of the catalyst, which is a unit volume of the Reaction container occupies are reduced.

The shapes are opposite to each other, with in a notch or a projection provided end faces of the pellets according to the invention need not be identical. Depending on the number of notches or projections on one or both end faces there are many possible configurations of the π pellets according to the invention. The notches or Projections can, for example, in the form of spherical segments, grooves (or beads in the case of Projections), annular grooves and rectangular prisms are present or conical or frustoconical be. Such a bead or such a groove can be linear or branched and, for example, in one three-pronged pattern.

To simplify the production and to increase the wear resistance, the notches or projections also have rounded edges or corners.

A very suitable pellet has a flat end face and an end face provided with a flat, conical notch, the depth of the notch m being between 0.2 and 0.5 of its diameter.

Le is preferably between 0.5 D and 1.5 D. To achieve a particularly advantageous improvement in the effectiveness of the catalyst, L / in the pellets according to the invention is between 0.05 D and 0.4 D, ti, however , where Li, as far as possible, is up to to 0.6 D. In the case of the pellets according to the invention, D is between 13 and 10 mm and preferably between 13 and 7 mm, since the production of annular pellets with these dimensions is generally not practical. Even with a larger diameter of the pellets according to the invention there are advantages, since the production of cylindrical pellets by compression is mechanically simpler than the production of annular pellets. ίί

When selecting the shapes of the notches and projections for the pellets according to the invention, the Ease of manufacture of punches for pelletizers. The main considerations which are to be employed in relation to the production of the "> <> pellets according to the invention exist in this,

(1) that the stamps should be profiled so that they are do not fix when they are used, ~> ->

(2) that the protrusions on the punches should not damage the pellets when the pellets are removed from the lower stamp to be removed, and

(3) that no part of the catalyst filled as a powder in the mold of the pelletizer is wi should be squeezed a little.

These manufacturing requirements are met by a variety of forms of the invention Pellets met, which is a possibility for <r> Offer optimization of the surface area to volume ratio. Hei pellets with grooves or beads can determine the relative orientation of the upper and lower punch of the pelletizing device so that grooves or beads are obtained in any desired relative orientation, or the Punches can be rotatable or rotated to give mutual alignment that is changes between the pellets of a catalyst charge.

Within the scope of the invention are slightly conical pellets in which the diameter D changes to a slight extent from one end face to the other.

To simplify production, it is advantageous if the pellets are flat and profiled Own end face. These pellets are formed by using a pelletizer with an upper, profiled stamp and a lower, flat stamp inserts. Pellets with rectangular notches or projections result in technical problems during manufacture, since rectangular stamps are involved their corners will soon be worn out.

All materials can be used for the production of the pellets according to the invention. ^- > 2n, which are usually used for the production of catalysts for gas phase reactions. Examples of these materials are support materials such as heavily reduced oxides of groups II to IV of the periodic table including hydraulic cements, catalytically active oxides such as silicon dioxide, aluminum dioxide and oxides of the Groups V to VIII of the periodic table and metals of group IB and VIII of the periodic table. Particularly advantageous catalysts which can be used in the form of pellets according to the invention are catalysts which contain cobalt and molybdenum oxides, as well as copper and zinc oxides. The constituents can all at the time of production of the pellets according to the invention by compression, or some of them can be added afterwards, for example by impregnation.

The invention is described below with reference to five advantageous forms of pellets according to the invention Explained in more detail with reference to the schematic drawings.

Fig. I shows a sectional view and a plan view of a pellet according to the invention which is provided with a conical notch on both end faces is.

Fig. 2 shows a sectional view and a plan view a pellet according to the invention, which is provided on both end faces with grooves that have a flat Have soil.

3 shows a sectional view and a plan view of a pellet according to the invention which is provided with V-shaped grooves on both end faces.

Fig. 4 is a sectional view and a plan view a pellet according to the invention, which is provided with a notch on the upper end surface, while the lower end face is flat.

F i g. 5 shows three views of an inventive Pellets, which is provided with a trapezoidal bead on its upper end face, while its lower end face has a trapezoidal notch, (i) a front view, (ii) a Side view and (iii) a top view of this i'cllet.

In the figures, X means the width of the notch or projection.

More detailed information on the in the F i g. I to 5 schematically illustrated pellets according to the invention are shown in Table I.

a he Ik · I

in Fig. I. IV-llcls around 2 ΚομοΙ- in the Pellets Ιοπιιιμαι Ι iiikcrluin- ten 11 ίμ. Ι i 111 O.d ) Dimensions of the 0.67 his 5 shown 0.07 (I., I.,) I) 0.5.1 0 8ΊΧ 11 l> 0.67 I ₁ I) 0.14 V /) 0 (ι1 ^ς

(2) Comparison

Relative volume per IVIIeI X ⁽ ) "

Relative outer space 105 '

pm IVIIeI

Relative weight of the IVIIeIs' M

per oleum unit

of the Keaklionsbehiillets

Relative outer surface 107 "

per unit

of the reaction container

Relative pressure drop X ¹ »'

IVIIcK mn
2 grooves groove
II. All
linden
Il ιμ. 21

115 '0.4'IX
0.44.1

0.I4X

IV-llcls mil
2 V-Iörmi- UCiI Nulcii (I II !. })

0.41
0. (i7

76 " X7.V .. 7 (i 107 " 105- 1 (1.1 Xl ". • '5.8. Ί2

84 "..

125 "

Xl "

IV-IIeIs mil one

Il ιμ. 4 |

0.1

0.17
0.72

IVIicls mn

I inkcrlninij and bulge (I 11; si

KM "..
i) I ""

0:47 0. ¹ M 0:47

0.2'M (zero 0.571 (Wulsli

0.075 (zero II.I7 «) (bead)

7 ')% 88 °.,

KM ",,

116%

<) 5 ""

The comparative diets given in Table I relate to the corresponding properties of cylindrical pellets with flat end faces, the same overall length L / and the same diameter D.

From Table I it can be seen that in the case of the pellets of FIG. I to 4 to fill a given volume of the Reaction container a lower weight of the pellets is required. what with a reduction in Costs associated with it. At the Feiieis eier F i g. ι to D lsi increases the external surface area of the pellets per unit volume of the reaction container, thereby increasing the activity of the in Form of the pellets used catalyst for a diffusion-limited gas phase reaction is increased. In addition, at the same speed for pumping through, it is the gaseous reactant reduced pressure drop to be overcome by the catalyst bed.

From Table I it can also be seen that by pellets with conical notches and with V-shaped grooves a maximum reduction in volume per Pellet is achieved. The maximum increase in the relative external area per pellet is given by one of the Pellets obtained with conical notches. The increase in the relative outer area is with this one Pellet with conical notches larger than pellets with V-shaped grooves, which is lost on the surface based on the ends of the grooves. The maximum increase in relative external area per unit volume of the reaction vessel (25%) is achieved by the pellets with V-shaped grooves.

For pellets with conical notches, the relative weight of the pellets per unit volume is smaller than with the pellets rr.it V-shaped grooves because the Pellets with grooves tend to interlock.

while the conical (jnkcrbiingcn not in cooperate with each other to a particular degree. The interlocking of grooves increases the number of the pellets per volume unit and thus the relative surface area per volume unit is increased. The maximal Reduction in pressure drop (23%) is achieved with one of the conical notches having pellets achieved.

at the vvahi between i'ciicis. the mil notches are provided, and pellets provided with protrusions, it must be decided which Property of greatest importance hai. when choosing a catalyst for a specific process, which is because neither of these two types of pellets according to the invention have all properties. namely an increased surface area, a decreased pressure drop and a decrease in the weight of the pellet 'pro Unit volume of the reaction vessel, shows to a desirable extent. The commonly achieved Values for the mean horizontal or vertical compressive strength are due to the different Packing style for cylindrical pellets with flat end faces is different from the mechanical behavior during the operation of the system correlates as with the pellets according to the invention.

On this basis, for a catalyst which contains expensive raw materials and is used for reaction vessels that are affected by the pressure drop are limited. Pellets with conical notches can be chosen, which have the greatest reduction in the Pellet weight and the pressure drop result. The grooved pellets that have the largest increase in Surface result and through this increase in area to a great extent increased activity

of the catalyst would be chosen for catalysts whose activity is high is diffusion-limited.

Example I.
Desulfurization of naphtha

One (2.8 ± 0.3)% CaO, (12 ± 0.1)% MoO, and Desulfurization catalyst containing (4.5 + 0.5)% MgO and aluminum oxide as a carrier was used in a pelletizer compressed to

(a) Pellets with flat end faces and

(b) notched pellets of the in Γ i g. 4 to produce the type shown.

The pellets all had a density of (0.8 ± 0.05) g / ml. The height /. Of the pellets was 3.6 mm. and the diameter O b ^p tru ° ^, A rnrn. The ΑΙ ^ί * Ι ^ν ' ¹ ^ ^{1 of} these pellets was compared under identical operating conditions, namely at a manometer pressure of 31.0 bar, at a temperature of 370 C. with a hydrogen / naphtha molar ratio of 0.25 and with a liquid Space velocity of lh ¹ . The feed material was desulphurized naphtha (boiling range 30 to 170 ° C). which was provided with thiophene up to a concentration of 100 parts by weight of sulfur per ΙΟ * ^{1 part by} volume of naphtha. In this test, the exit sulfur concentration was 0.4 parts per million (pellets of the invention) and 1.15 parts per million (pellets with flat end faces).

From these conditions, it can be seen that the desulfurization reaction is related to pore diffusion is limited and that the extent of removal of the sulfur with an increase in the geometric The surface of the pellets increases.

B L- is ρ ie I 2
Conversion of CO at low temperature

A catalyst consisting of 32% CuO, 54% ZnO and 14% AbO in the unreduced state was used for the Conversion of carbon monoxide and water vapor into hydrogen and carbon dioxide at temperatures of 200 to 250 ° C used.

Cylindrical pellets with flat end faces and three kinds of pellets of the present invention were prepared from the catalyst. The pellets according to the invention were pellets of the type shown in FIGS. 1 and 3 and pellets having a conical notch on one end face and a V-shaped groove on the other end face. All pellets had a diameter D of 5.4 mm and an overall length Li of 3.6 mm and a constant density of (1.4 ± 0.02) g / ml. Two tests were carried out in H / was

(a) each using a sample of 20 g and

(b) using one 25 ml sample each.

| Every pellet sample was taken in N? with 2% H ₂ at 230 ° C. and then tested for their activity at atmospheric pressure, a temperature of 230 ° C., a steam / dry gas ratio of 0.5 and under isothermal conditions in the reaction vessel of 15% CO _2, 5% CO and 80% II .. was passed over clic pellets at a rate of 300 l / h. Under these conditions, the various types of pellets exhibited the following activities: those in any degree of conversion of the gas per unit weight or unit volume of the catalyst bed can be expressed:

Table Il

IVIIcttyp

I i. it lic

t -.in: -u

Activity per unit weight of the catalyst bed ¹ U

Activity per unit volume of the catalyst bed 12.3

Bulk density OX ^;

12. ')

0.74

11.4
12.8

(1.75

Conical V-shaped groove

11.4
13.0
0.73

Obviously, even using a constant volume of catalyst, the activity is more advantageous Way, which is why the catalyst cost is very low.

Examples of other gas phase processes for which the Use of the catalyst pellets according to the invention is suitable. are hydrocarbon / steam gasification reactions, z. B. different types of steam reforming, the high temperature carbon monoxide conversion. the methanation of carbon oxide traces into hydrogen, the ammonia synthesis, the methanol synthesis. Hydrogenations and hydrocarbon isomerizations.

Example 3

At the third stage of a manufacturing process of hexamethylenediamine by hydrogenation of adip ns-'iiredinitril are from a gas mixture CO and CO ;. which act as catalyst poisons during hydrogenation, by practically complete conversion to CH ^ removed. This reaction takes place according to the following scheme:

CO + 3 H,

and CO- + 4 H-

Ni

Ni

CH ₄ + H ₂ O

CH ₁ + 2 H, O.

The third stage mentioned above became

(A) with Kataiysatorpeüets according to the invention, provided with notches on both end faces and

(B) with known, cylindrical catalyst pellets with flat end faces

carried out. The pellets were made by mixing nickel oxide, aluminum oxide and alumina cement with graphite (as a lubricant), pelletizing the dry mixture by compression in a flat cylinder shape with dimensions of 5.4 χ 3.6 mm and steaming to harden the cement. The ram pressure during pelletizing was much higher in the case of (B) than in the case of (A), around that in the table III to obtain mechanical values.

After each pellet was introduced into the reaction vessel, the nickel oxide became in both cases reduced to catalytically active, metallic nickel.

The inlet gas for the methanation reaction had the following composition:

CO: 0.3 volume%, CO ₂ : 0.3 volume%. H ₂ : 96.5% by volume and LH ₄ : 2M volume%.

The inlet temperature of the gas was 305 ° C. and the pressure was 18.1 bar.

Table III lists the relevant mechanical properties of the respective pellets prior to introduction into the reaction vessel and the resulting pressure drop after a certain use hazard listed.

IO

Table IM

Λ B. invention Hour of technology Medium Vertical Pound 22.7 57.2 load *) (kg per pellet) Medium Horizontal Pound 0.64 33.6 strength *) (kg per pellet) Abrasion loss *) (% by weight) 3.6 0.3 (Standard laboratory test) Useful life (years) 7.7 3.0 Pressure drop according to specified under 0.3 ner service life (kg cm ') 0.15

* \ Before

j-incat7

As can be seen from Table III, the pressure drop in the case of the inventive pellets (A) was after one much longer service life, almost half as large as in the case of the known pellets (B). in spite of a lot higher values for the crush resistance and the correspondingly lower abrasion losses with the known Pellets.

For this purpose 2 sheets of drawings

Claims (4)

Patent claims: 1. Cylindrical catalyst pellets produced by compression for use in a gas phase process, characterized in that they are provided on one or both end faces with at least one notch or a projection, the diameter D of the cylinder being between 1.5 and 10 mm, the total height of the catalyst pellets, ie the height of the cylinder including the projection or projections which may be present, is between 0.5 D and 2.0 D , the length L of the solidly filled volume, whose cross-sectional area perpendicular to the cylinder axis is 0.25 π D ² is between 0.05 D and 0.6 D and the ratio (L, -L ₁ ) ZD is greater than 0.25. 2. Catalyst pellets according to claim 1, characterized in that at least one notch is conical or frustoconical. 3. Kataiysatorpeiiets according to claim i, characterized in that a notch in the form of a Groove is provided 4. Catalyst pellets according to claim 1, characterized in that a projection in the form of a Bead is provided.