Method for adding an organic compound to a porous solid in the gaseous phase

Abstract

The invention relates to a process for adding an organic compound to a porous solid wherein the porous solid and the organic compound in the liquid state are brought together simultaneously, without physical contact between the solid and the organic compound in the liquid state, at a temperature below the boiling point of the organic compound and under pressure and time conditions such that a fraction of said organic compound is transferred gaseously to the porous solid.

Claims

1. A process for adding an organic compound to a porous solid comprising a) placing in proximity the porous solid and the organic compound in liquid state simultaneously and without physical contact between the solid and the organic compound in the liquid state, at a temperature below the boiling point of the organic compound and under pressure and time conditions such that a fraction of said organic compound is transferred gaseously to the porous solid, and after contact with the porous solid recycling gaseous effluent of the organic compound to either the organic compound in liquid state or to contact with the porous solid.

2. The process as claimed in claim 1, wherein a) is carried out by means of a unit for adding said organic compound comprising a first compartment and a second compartment that are in communication so as to allow the passage of a gaseous fluid between the compartments, the first compartment containing the porous solid and the second compartment containing the organic compound in the liquid state.

3. The process as claimed in claim 2, wherein the unit comprises a chamber that includes the first and second compartments, the two compartments being in gaseous communication.

4. The process as claimed in claim 2, wherein the unit comprises two chambers that respectively form the first and second compartments, the two chambers being in gaseous communication.

5. The process as claimed in claim 2, wherein a) is carried out in the presence of a stream of a carrier gas flowing from the second compartment into the first compartment.

6. The process as claimed in claim 1, wherein a) is carried out at an absolute pressure of between 0 and 1 MPa.

7. The process as claimed in claim 2, wherein, in a), a gaseous effluent containing said organic compound is withdrawn from the first compartment and the effluent is recycled to the first and/or the second compartment.

8. The process as claimed in claim 2, wherein, in a), a gaseous effluent containing said organic compound in the gaseous state is withdrawn from the first compartment, said effluent is condensed so as to recover a liquid fraction containing the organic compound in the liquid state and said liquid fraction is recycled to the second compartment.

9. The process as claimed in claim 1, wherein the porous solid is chosen from a catalyst support and a catalyst support further comprising at least one metal from group VIB and/or at least one metal from group VIII.

10. The process as claimed in claim 9, wherein the porous support is based on an oxide of a metal and/or of a metalloid.

11. The process as claimed in claim 10, wherein the porous support is based on alumina and/or silica.

12. The process as claimed in claim 1, wherein the organic compound is chosen from organic molecules containing oxygen and/or nitrogen and/or sulfur.

13. A process for preparing a catalyst comprising a porous support, at least one metal from group VIB and/or at least one metal from group VIII and at least one organic compound, the process comprising at least the following: i) depositing the organic compound on the porous support using the process as claimed in claim 1; ii) depositing at least one metal from group VIB and/or at least one metal from group VIII on the porous support by bringing the support into contact with the solution containing at least one precursor of said metal(s) from group VIII and/or at least one precursor of said metal(s) from group VIB; iii) drying the solid obtained at the end of ii), step i) being carried out before or after ii) and iii).

14. The process as claimed in claim 13, wherein the solution of ii) further comprises at least one additional organic compound different from the organic compound used in i).

15. The preparation process as claimed in claim 13, further comprising at least one impregnation of the porous support with a solution comprising an organic compound different from the organic compound used in i).

16. A process for treating a hydrocarbon feedstock wherein hydrogen, the hydrocarbon feedstock and a catalyst are brought into contact, at a temperature between 180° C. and 450° C., at a pressure between 0.5 and 30 MPa, with an hourly space velocity of between 0.1 and 20 h.sup.−1 and with a hydrogen/feedstock ratio expressed as volume of hydrogen, measured under normal temperature and pressure conditions, per volume of liquid feedstock of between from 50 l/l to 5000 l/l, said catalyst having been prepared by a process as claimed in claim 13 and subjected to at least one sulfiding process.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Other features and advantages of the invention will become apparent on reading the description of particular exemplary embodiments of the invention, given solely by way of illustration and without limitation, and with reference to the following figures:

(2) FIG. 1 is a diagram illustrating the principle of adding an organic compound according to standard practice known to a person skilled in the art;

(3) FIG. 2 is a diagram illustrating the process according to the invention for adding an organic compound according to a first embodiment;

(4) FIG. 3 shows a diagram of the process for adding an organic compound according to a second embodiment;

(5) FIG. 4 is a diagram of the process for adding an organic compound according to a third embodiment.

(6) Generally, similar elements are indicated by identical references in the figures.

(7) FIG. 1 corresponds to a block diagram presenting a known process for adding an organic compound to a porous catalyst support or a catalyst precursor as described previously that is denoted hereinbelow by the generic term “solid”.

(8) The batch of solid 1 is subjected to an optional pretreatment in a unit 2 for pretreatment of the solid intended, if need be, to condition the solid before the step of impregnation of the organic compound. This pretreatment step may, for example and depending on the desired effect, be a preliminary drying step in order to adjust the residual moisture content.

(9) This pretreatment may also be an addition by controlled addition of the same solvent, introduced through the line 3, as the one which is used during the impregnation of the organic compound in order to avoid too lively a reaction of the solid during the organic compound impregnation phase. The type of reaction that it is desired to avoid is for example a great release of heat linked to the sudden adsorption of the solvent (such as water for example) on the active sites of the solid.

(10) The batch of solid 4 resulting from the pretreatment step is sent to a unit 5 for impregnation of the organic compound. According to the prior art, this step uses a solution containing a solvent, for example water, in which the organic compound to be impregnated is dissolved. In FIG. 1, the impregnation solution is conveyed via the line 6. The impregnation is carried out according to any method known to a person skilled in the art and for example by a dry impregnation. In this impregnation method, the solid set in motion is subjected to a jet of the impregnation solution, the volume of solution sprayed generally being equivalent to the accessible pore volume of the solid to be impregnated. In accordance with prior art practice, the impregnated solid is discharged via the line 7 into a drying unit 8 in order to eliminate the solvent which was incorporated in the solid at the same time as the organic compound. The stream 9 represents the hot utility that is used to dry the solid, which is for example hot air. This results in a dried porous solid 10 comprising the chosen organic compound.

(11) Depending on the organic compound chosen and its solubility in the solvent used during the impregnation step, it is possible that the amount introduced is not sufficient at the end of a single impregnation step. In which case, use may be made of several impregnation and drying steps described above.

(12) After impregnation of the organic compound, the porous solid may undergo one or more steps of impregnation of one or more metals from group VIB and/or from group VIII in order to deposit an active metal phase. The step(s) of impregnation of the metal(s) may be followed, optionally after a maturing step, by a step of drying at a moderate temperature, generally below 200° C.

(13) FIG. 2 represents a block diagram of the process for adding the organic compound according to the invention which consists in bringing together, in a unit 11, the porous solid to be treated with the organic compound in the liquid state, the bringing together being carried out without physical contact between the porous solid and the liquid phase.

(14) With reference to FIG. 2, the porous solid 1 is optionally sent to a pretreatment unit 2 as mentioned above. The pretreatment may consist of a step of drying the solid for example when this porous solid is a catalyst precursor obtained by impregnation of a solution containing at least one metal from group VIB and/or at least one metal from group VIII. The porous solid 4 resulting from the pretreatment is conveyed to a unit 11 for bringing the solid together with the organic compound in the liquid state. With reference to FIG. 2, the unit 11 comprises a chamber divided into two compartments A and B which are separated from one another by a partition means 12, the two compartments being in communication so as to allow the passage of a gaseous stream of organic compound so that the compartments A and B share the same gaseous atmosphere. In this embodiment, compartment A is suitable for receiving the porous solid 4 whilst compartment B is suitable for receiving the liquid organic compound. In the embodiment from FIG. 2, the partition means 2 may be a perforated plate enabling the passage of the gaseous fluid.

(15) This bringing-together step is carried out in a controlled manner, at a temperature below the boiling point of said organic compound. Under these conditions, there is a vapor pressure of the organic compound which is generated by its liquid phase. Thus, a portion of the molecules of organic compound in the liquid state passes into gaseous form (vaporization) and is then transferred (gaseously) to the porous solid. Given that the organic compound vapor phase is gradually consumed by the solid, the liquid continues to vaporize. According to one embodiment, referred to as “batch” mode, the amount of liquid organic compound contained in compartment B is at least greater than the amount of the organic compound that it is desired to introduce into the porous solid. Alternatively, it is possible to continuously supply the organic compound in the liquid state as it is consumed by the porous solid or semi-continuously with a regular intermittent supply so as to maintain a minimum liquid level in compartment B. In FIG. 2, the makeup of organic compound in the liquid state is ensured via a duct 13.

(16) The bringing-together step according to the invention may be carried out by maintaining a stirring of the liquid in compartment B and/or by setting in motion the solid to be treated in compartment A.

(17) According to one preferred embodiment, the bringing-together step is carried out with a forced circulation of a stream of a gas, from compartment B containing the organic compound in the liquid state toward compartment A containing the porous solid to be additivated. As nonlimiting example, the stream of a gas may be carbon dioxide, ammonia, air with a controlled moisture content, an inert gas such as argon, nitrogen, hydrogen, natural gas or a refrigerant gas according to the classification published by IUPAC. The gas is either provided under pressure, or pressurized in order to overcome the pressure drops induced by the circuit by means of equipment for increasing the pressure of a gas such as a compressor or a fan. Preferably, the gas is injected via the line 14 into the liquid so as to ensure the stirring thereof in order to promote the saturation of the gas phase by the organic compound, increasing the gas/liquid exchange area.

(18) The bringing-together step is carried out under controlled time, temperature and pressure conditions so as to ultimately provide a solid 15 containing the organic compound. Without being bound to a particular theory, the introduction of the organic compound into the porous solid may result from a capillary condensation and/or adsorption process.

(19) As indicated in FIG. 2, the bringing together according to the invention may involve a recycling of the vapor phase extracted from compartment A via the line 16 leading into compartment A and/or into compartment B or optionally into the line 14. Alternatively, the gas phase 16 extracted from compartment A is cooled so as to condense the organic compound in liquid form which is thus recycled to compartment B via a line or optionally via the line 13.

(20) FIG. 3 is another embodiment of the process for adding the organic compound to a porous solid which differs from that of FIG. 2 in that the unit 11 for bringing the solid together with the liquid organic compound comprises two chambers 18 and 19 which are capable of containing, respectively, the optionally pretreated porous solid 4 and the organic compound in the liquid state, the two chambers being in communication by means of a duct 20 so as to enable solely the passage of a vapor phase containing the organic compound in the gaseous state.

(21) FIG. 4 is a variant of the process for adding an organic compound to a porous solid according to the invention in which the porous solid to be additivated undergoes a heat treatment at a temperature above that of the step of bringing together with the organic compound in the liquid state and in which a heated entraining gas is injected into the bringing-together unit 11.

(22) With reference to FIG. 4, the porous solid 1 undergoes a pre-treatment step which consists of a heat treatment at a temperature which is above the temperature applied in the step of bringing together in the unit 11. The process of FIG. 4 includes a thermal integration procedure that consists in using a carrier gas supplied by the line 21. This carrier gas 21 may be, for example and nonlimitingly, an effluent resulting from another process or a dedicated carrier gas. In the case of a dedicated carrier gas, this carrier gas may be, for example and non-limitingly, carbon dioxide, ammonia, air with a controlled moisture content, an inert gas such as argon, nitrogen, hydrogen, natural gas or a refrigerant gas according to the classification published by IUPAC. The gas is either provided under pressure, or pressurized in order to overcome the pressure drops induced by the circuit by means of equipment for increasing the pressure of a gas such as a compressor or a fan. If the temperature of the carrier gas is below the temperature applied in the step of bringing the solid together with the organic compound in the liquid state, it is advantageous to carry out a heat exchange, for example with an exchanger 22 of feed-effluent type in order to heat the carrier gas 21 with a gaseous effluent 17 resulting from the unit 11 which is described hereinbelow. As shown in FIG. 4, the reheated carrier gas stream 21 is sent via the line 26 into a heat exchanger 23 in which it exchanges heat with the heat-treated solid 4. This heat exchange may take place by direct or indirect contact between the gas and the solid. In the case of direct contact, the heat exchange takes place by contact of the carrier gas 21 with the porous solid 4, for example in a fluidized bed. In the case of indirect contact, it is possible to use a gas/solid exchanger comprising a set of tubes travelled through by the carrier gas which pass through the bed of porous solid. At the end of this heat exchange, there is a stream of cooled porous solid 24 and a stream of reheated carrier gas 25 which are sent to the bringing-together unit 11, respectively to compartment A and compartment B. The supplying of heated carrier gas 25 to the compartment containing the liquid organic compound may take place for example by means of a bubbling device. The role of this hot carrier gas 25 is two-fold: it provides heat as a replacement for or in addition to the temperature-maintaining device for the bringing-together step and it creates a movement of the gas phase of compartment B toward compartment A thus contributing to the transport of the organic compound in the gaseous state to the porous solid to be additivated.

(23) A gaseous effluent 17 which contains the carrier gas and optionally the organic compound in the gaseous state is discharged from compartment A to supply the heat exchanger 22 in order to reheat the carrier gas 21. The cooled gaseous effluent 17 leaving the exchanger 22 is either completely or partly recycled via the line 28 with the carrier gas 21, or is completely discharged from the unit 11 via the line 27.

(24) Besides the recovery of heat, the heat exchange 22 optionally makes it possible, when the cooling of the gaseous effluent 17 is sufficient, to condense a fraction of the organic compound which is entrained by the carrier gas. The condensate may then be recycled to compartment B containing the organic compound in the liquid state.

EXAMPLES

Example 1: Preparation of CoMoP Catalysts on Alumina Without Organic Compound C1 and C2 (Not in Accordance with the Invention)

(25) To an alumina support having a BET surface area of 230 m.sup.2/g, a pore volume measured by mercury porosimetry of 0.78 ml/g and a mean pore diameter of 11.5 nm defined as the volume median diameter by mercury porosimetry and which is in “extrudate” form, cobalt, molybdenum and phosphorus are added. The impregnation solution is prepared by dissolving, at 90° C., molybdenum oxide (21.1 g) and cobalt hydroxide (5.04 g) in 11.8 g of an 85 wt % aqueous solution of phosphoric acid. After dry impregnation, the extrudates are left to mature in a water-saturated atmosphere for 24 h at ambient temperature, then they are dried at 90° C. for 16 hours. The dried catalyst precursor thus obtained is denoted by C1. The calcination of the catalyst precursor C1 at 450° C. for 2 hours leads to the calcined catalyst C2. The final metal composition of the catalyst precursor C1 and of the catalyst C2 expressed in the form of oxides and relative to the weight of dry catalyst is then the following: MoO.sub.3=19.5±0.2 wt %, CoO=3.8±0.1 wt % and P.sub.2O.sub.5=6.7±0.1 wt %.

Example 2: Preparation of the CoMoP Catalyst on Alumina C3 (Not in Accordance with the Invention) by Co-Impregnation

(26) To the alumina support described above in example 1 and which is in the “extrudate” form, cobalt, molybdenum and phosphorus are added. The impregnation solution is prepared by dissolving, at 90° C., molybdenum oxide (28.28 g) and cobalt hydroxide (6.57 g) in 15.85 g of an 85 wt % aqueous solution of phosphoric acid. After homogenization of the mixture, 38 g of citric acid were added before adjusting the volume of solution to the pore volume of the support by addition of water. The (citric acid)/Mo molar ratio is equal to 1 mol/mol and the (citric acid)/Co molar ratio is equal to 2.7 mol/mol. After dry impregnation, the extrudates are left to mature in a water-saturated atmosphere for 24 h at ambient temperature, then they are dried at 120° C. for 16 hours. The dried catalyst additivated with citric acid thus obtained is denoted by C3. The final metal composition of the catalyst C3 expressed in the form of oxides and relative to the weight of dry catalyst is then the following: MoO.sub.3=19.6±0.2 wt %, CoO=3.7±0.1 wt % and P.sub.2O.sub.5=6.7±0.1 wt %.

Example 3: Preparation of the CoMoP Catalyst on Alumina C4 (Not in Accordance with the Invention) by Post-Impregnation

(27) 18 g of catalyst precursor C1 described above in example 1 and which is in the “extrudate” form are impregnated with an aqueous solution containing 3.2 g of 2-methoxyethyl 3-oxobutanoate and the volume of which is equal to the pore volume of the catalyst precursor.

(28) The amounts used are such that the amount of 2-methoxyethyl 3-oxobutanoate is 0.8 mol per mole of molybdenum (corresponding to 2.2 mol per mole of cobalt). The extrudates are left to mature in a water-saturated atmosphere for 16 h at ambient temperature. The catalyst precursor C4 is then dried at 120° C. for 2 hours to give the catalyst C4. The final metal composition of the catalyst C4 relative to the weight of dry catalyst is: MoO.sub.3=19.5±0.2 wt %, CoO=3.8±0.1 wt % and P.sub.2O.sub.5=6.7±0.1 wt %.

Example 4: Preparation of the CoMoP Catalyst on Alumina C5 (According to the Invention) by Introduction of an Organic Compound in the Vapor Phase After the Impregnation of the Metals

(29) Arranged in a closed chamber are 4 g of 2-methoxyethyl 3-oxobutanoate contained in a crystallizing dish. 12 g of the catalyst precursor C1 are introduced into the same closed chamber and arranged on a stainless steel grid so that the liquid 2-methoxyethyl 3-oxobutanoate is not in physical contact with the catalyst precursor C1. The closed chamber is placed in an oven at 120° C. for 6 hours. 14.1 g of catalyst C5 are thus obtained after the catalyst precursor C1 has been brought together with the 2-methoxyethyl 3-oxobutanoate compound in the gaseous state. The amount of 2-methoxyethyl 3-oxobutanoate thus transferred to the catalyst is such that the 2-methoxyethyl 3-oxobutanoate/Mo molar ratio is 0.8 mol per mole of molybdenum (corresponding to 2.2 mol per mole of cobalt). The final metal composition of the catalyst C5 relative to the mass of dry catalyst is: MoO.sub.3=19.5±0.2 wt %, CoO=3.8±0.1 wt % and P.sub.2O.sub.5=6.7±0.1 wt %.

Example 5: Preparation of the CoMoP Catalyst on Alumina C6 (According to the Invention) by Introduction of an Organic Compound in the Vapor Phase Before the Impregnation of the Metals

(30) Arranged in a closed chamber are 4 g of 2-methoxyethyl 3-oxobutanoate contained in a crystallizing dish. 8.4 g of the same support as the one used in example 1 are introduced into the same closed chamber and arranged on a stainless steel grid so that the liquid 2-methoxyethyl 3-oxobutanoate is not in physical contact with the support. The closed chamber is placed in an oven at 120° C. for 6 hours. 10.5 g of support additivated with 2-methoxyethyl 3-oxobutanoate are thus obtained. The amount of 2-methoxyethyl 3-oxobutanoate introduced on the support is fixed so as to obtain, after impregnation of the metals, a 2-methoxyethyl 3-oxobutanoate/Mo molar ratio of 0.8 mol per mole of molybdenum (i.e. again 2.2 mol per mole of cobalt).

(31) The modified support is then impregnated by an impregnation solution prepared by dissolving, at high temperature, molybdenum oxide (2.4 g) and cobalt hydroxide (0.6 g) in 1.4 g of an 85 wt % aqueous solution of phosphoric acid, taking care to adjust, by addition of water, the volume of the latter solution to the pore volume of the preceding modified support. After dry impregnation, the extrudates were left to mature in a water-saturated atmosphere for 24 h at ambient temperature, then dried at 120° C. for 16 hours to result in the catalyst C6. The final metal composition of the catalyst C6 relative to the weight of dry catalyst is the following: MoO.sub.3=19.8±0.2 wt %, CoO=3.9±0.1 wt % and P.sub.2O.sub.5=6.9±0.1 wt %.

Example 6: Evaluation in HDS of Diesel Fuel of the Catalysts C1, C2, C3 and C4 (Not in Accordance with the Invention) and C5 and C6 (in Accordance with the Invention)

(32) The catalysts C1, C2, C3 and C4 (not in accordance with the invention) and C5 and C6 (in accordance with the invention) were tested in HDS of diesel fuel.

(33) The features of the diesel fuel feedstock used are the following: density at 15° C.=0.8522 g/cm.sup.3, sulfur content=1.44% by weight. Simulated distillation: IP: 155° C. 10%:247° C. 50%:315° C. 90%:392° C. FP:444° C.

(34) The test is carried out in an isothermal crossed fixed-bed pilot reactor, the fluid circulating from bottom to top.

(35) The catalyst precursors are first sulfided in situ at 350° C. in the reactor under pressure by means of the diesel fuel of the test to which 2 wt % of dimethyl disulfide are added.

(36) The hydrodesulfurization tests were carried out under the following operating conditions: a total pressure of 7 MPa, a catalyst volume of 30 cm.sup.3, a temperature of from 330 to 360° C., with a hydrogen flow rate of 24 l/h and with a feedstock flow rate of 60 cm.sup.3/h.

(37) The catalytic performances of the catalysts tested are given in table 1. They are expressed in degrees Celsius relative to the (comparative) catalyst C2 chosen as a reference (C2): they correspond to the temperature difference to be applied in order to attain 50 ppm of sulfur in the effluent. A negative value signifies that the target sulfur content is attained for a lower temperature and that there is therefore an increase in activity. A positive value signifies that the target sulfur content is attained for a higher temperature and that there is therefore a loss of activity. The results obtained are reported in table 1.

(38) TABLE-US-00001 TABLE 1 Isovolumic relative activities in hydrodesulfurization of diesel fuel of the catalysts C1, C2, C3 and C4 (not in accordance with the invention) and C5 and C6 (in accordance with the invention) relative to the catalyst C2 (not in accordance). Catalyst Organic (comparative compound used Method of or according and introducing to the compound/Mo the organic invention) molar ratio compound HDS activity C1 (comp) none N/A Base + 1.0° C. C2 (comp) none N/A Base C3 (comp) Citric acid - Co- Base − 2.9° C. 1.0 mol/mol Mo impregnation C4 (comp) 2-methoxyethyl 3- Post- Base − 5.7° C. oxobutanoate - additivation 0.8 mol/mol Mo C5 (inv) 2-methoxyethyl 3- Gas phase Base − 6.8° C. oxobutanoate - after 0.8 mol/mol Mo impregnation of the metals C6 (inv) 2-methoxyethyl 3- Gas phase Base − 6.6° C. oxobutanoate - before 0.8 mol/mol Mo impregnation of the metals

(39) Table 1 clearly shows that the method of introducing the organic compound according to the invention makes it possible to avoid the use of a solvent and consequently to avoid a drying step while introducing the adequate amount of organic compound at a temperature far below its boiling point. Specifically, to prepare the catalysts C5 and C6, 2-methoxyethyl 3-oxobutanoate is used at 120° C. while its boiling point at atmospheric pressure is 254° C. Furthermore, the catalysts according to the invention are at least as efficient as those prepared according to the prior art. Specifically, the catalysts C5 and C6 according to the invention are more efficient than all the other comparative catalysts. The increase is very significant in comparison with catalysts that do not use an organic molecule (C1 and C2) or the citric acid (C3) commonly used by those skilled in the art. Furthermore, the catalysts C5 and C6 are more efficient than the catalyst C4 that uses the same organic molecule introduced according to a protocol well known to a person skilled in the art based on a post-additivation in aqueous solution. The organic compound may therefore be introduced according to the invention both before and after the impregnation of the metals forming the active metal phase. These examples therefore indeed showed the feasibility and the relevance of the method of introducing an organic compound according to the invention in particular for preparing catalysts that may have performances at least as high as those of the catalysts of the prior art.