Process for Limiting Self-Heating of Activated Catalysts

Abstract

The invention provides a process for limiting self-heating of activated particle catalysts wherein the catalyst particles are placed in motion inside a hot gas flow that passes through them and a liquid composition containing one or several film forming polymer(s) is pulverized onto the particles in motion until a protective layer is obtained on the surface of said particles containing said film forming polymer and having an average thickness of less than or equal to 20 ?m. The invention also provides the use of this process to reduce the quantities of toxic gases that may be emitted by the activated catalysts, as well as an activated catalyst for the hydroconversion of hydrocarbons covered with a continuous protective layer that are obtained by this process.

Claims

1. A process for limiting self-heating of activated catalyst particles, comprising: placing activated catalyst particles in motion in a fluidized bed within a hot gas flow passing continuously through the activated catalyst particles, wherein the gas has a temperature greater than 25? C.; and spraying onto the activated catalyst particles in motion a liquid composition comprising a solution or a dispersion of one or more film forming polymer(s) in a solvent, wherein the liquid composition contains 0.5% to 50% by weight of film-forming polymer(s) with respect to the total weight of the composition, wherein, upon evaporation of the solvent from the liquid composition, a protective layer containing said film-forming polymer(s) is formed on the surface of the activated catalyst particles, and wherein the protective layer has an average thickness lower than or equal to 20 ?m; thereby limiting self-heating of the activated catalyst particles.

2. The process according to claim 1, wherein the liquid composition contains from 0.5 to 25% by weight, with respect to the total weight of the composition.

3. (canceled)

4. (canceled)

5. The process according to claim 1, wherein the hot gas has a temperature ranging from 30 to 150? C.

6. The process according to claim 1, wherein the gas flows at a rate ranging from 5 to 100 m.sup.3 per hour per kilogram of catalyst.

7. The process according to claim 1, wherein the one or more film-forming polymer(s) forming the protective layer comprises from 50 to 100% by weight of the protective layer.

8. The process according to claim 1, wherein the one or more film-forming polymer(s) is (are) selected from the group consisting of: vinyl alcohol homo- and copolymer; polyvinyl alcohols and copolymers made up of vinyl alcohol and olefin(s) monomers ethylene and vinyl alcohol monomers (EVOH copolymers)-; partially hydrolyzed vinyl alcohol homo- and copolymers containing non-hydrolyzed vinyl acetate units-; polyethylene glycols-; collagen; polyethylene terephtalates (PET)-; polyethylene naphtalates (PEN)-; polyamides; polysaccharides; polyvinyl chlorides (PVC)-; polyvinylidene chlorides (PVDC)-; polyacrylonitriles (PAN)-; polyacrylate resins; copolymers of which at least one of the monomers is of the acrylate type; and mixtures thereof.

9. The process according to claim 1, wherein the film forming polymer is selected from the group consisting of polyvinyl alcohols, copolymers made up of vinyl alcohol and olefin(s) monomers.

10. The process according to claim 1, wherein the average thickness of the protective layer is less than or equal to 10 ?m.

11. The process according to claim 1, wherein the total amount of film-forming polymer used is within a range between 0.1 to 6% by weight with respect to the total weight of the initial activated catalyst particles.

12. The process according to claim 1, wherein the process further results in reducing emission of toxic gases by the activated catalyst particles.

13. An activated hydrocarbon hydroconversion catalyst obtained by a process as defined in claim 1, comprising activated catalyst particles which are each covered on their surface by a continuous protective layer having an average thickness ranging from 0.1 to 20 ?m and comprising from 50 to 100% by weight of one or several film forming polymer(s) chosen among: vinyl alcohol homo- and copolymers; partially hydrolyzed vinyl alcohol homo- and copolymers; polyethylene glycols-; collagen-; polyethylene terephtalates (PET)-; polyethylene naphtalates (PEN)-; polyamides-; polysaccharides; polyvinyl chlorides (PVC)-; polyvinylidene chlorides (PVDC)-; polyacrylonitriles (PAN)-; polyacrylates resins-; copolymers of which at least one of the monomers is of the acrylate type-; and mixtures thereof; wherein the total amount of film forming polymer represents from 0.1 to 0.4% by weight with respect to the total weight of the initial catalyst.

14-18. (canceled)

19. The process according to claim 1, wherein the liquid composition contains from 1 to 10% by weight of film forming polymer, with respect to the total weight of the composition.

20. The process according to claim 1, wherein the hot gas has a temperature ranging from 50 to 100? C.

Description

EXAMPLES

[0134] The examples below have been carried out using a commercial regenerated hydrotreatment catalyst, that contains 20% by weight of MoO.sub.3, and 5% by weight of CoO on alumina support, and which is made of cylindrical shaped extruded particles with an average diameter in number of 1.3 mm and an average length in number of 3.2 mm.

[0135] Activation of the catalyst: this catalyst has been introduced in a rotating oven fed with a gaseous sulfo-reduction mixture of hydrogen and hydrogen sulfide at partial pressures respectively of 0.8.Math.10.sup.5 and 0.2.Math.10.sup.5 Pa, with the gas and the solid circulating in counter-current flow. Sulfuration of the solid is achieved by a progressive increase of the temperature during the displacement of the solid matter inside the turning tube, up to a maximum temperature of 330? C., with a residence time inside the oven being about 4 hours. After cooling the solid at reactive atmosphere and nitrogen purge, it is placed in contact with nitrogen diluted air so that its temperature remains below 45? C.

[0136] The activated catalyst thus obtained is designated below as catalyst A. It has a sulfur content of 10.2% by weight, which corresponds to a sulfuration stoichiometry of the metal sites of 95%.

EXAMPLE 1 (AS PER THE INVENTION)

[0137] Catalyst A has been treated as follows:

[0138] 3 kg of catalyst A has been placed in a stainless steel perforated drum with a volume of 18 liters (useful volume of 5 L) at a rotation speed of 20 rotations/minute, through which passes in full a hot air flow of 160 m.sup.3/hr at 90? C. to keep the catalyst bed at 70? C. during pulverization. The hot air flow takes place in parallel to the pulverization jet, and in the same direction (descending flow).

[0139] 900 g of an EVOH polyethylene-poly vinyl alcohol copolymer solution (marketed under the name of EXCEVAL by the Kuraray company) at 5% by weight in water have been injected onto the catalyst particles by means of a two-fluid atomization nozzle with a solution flow rate of 7 g/min.

[0140] The water evaporates continuously which leads to the formation of a polymer layer or coating at the surface of the catalyst particles.

[0141] Following the full injection of the liquid, the catalyst is still stirred for 30 minutes at 70? C. to complete its drying, then cooled at ambient temperature.

[0142] In this way, catalyst B according to the invention has been obtained; the particles are covered with a continuous layer of poly ethylene-polyvinyl alcohol copolymer for which the average thickness is 5 ?m, as observed by scan electron microscopy.

[0143] Analysis of catalyst B shows that it contains 0.9% of carbon which corresponds to 1.5% by weight of polymer deposited on the catalyst with respect to initial catalyst A.

EXAMPLE 2 (COMPARATIVE)

[0144] Catalyst A has been treated as follows:

[0145] 3 kg of catalyst A have been placed in an unperforated stainless steel drum with a volume of 18 liters (useful volume of 5 L), at a rotation speed of 20 rotations/minute, and a hot air flow of 160 m.sup.3/hr at 95? C. is directed onto the surface of the catalyst bed to keep it at 55? C. during pulverization. The hot air enters through an inlet located inside the drum, and exits via the opening located in the front of the drum, without passing through the catalyst bed (leached bed), which explains that the heat exchange is not as good, and consequently the temperature is not as high inside the catalyst bed.

[0146] 900 g of an EVOH polyethylene-poly vinyl alcohol copolymer solution (marketed under the name of EXCEVAL by the Kuraray company) at 5% by weight in water have been injected onto the catalyst particles by means of an atomization nozzle with a solution flow rate of 5 g/min.

[0147] The water evaporates continuously which leads to the formation of a polymer layer or coating at the surface of the catalyst particles.

[0148] Following the full injection of the liquid, the catalyst is still stirred for 30 minutes at 55? C. to complete its drying, then cooled at ambient temperature.

[0149] In this way catalyst C has been obtained, which is not in accordance with the invention, for which the particles are covered with a non-continuous layer of polyethylene-poly vinyl alcohol copolymer for which the average thickness is 6 ?m as observed by scan electron microscopy, but which shows very considerable local thickness variations. In particular, we noticed the existence of points at the surface of the catalyst particles where the presence of a polymer layer was not detectable. At the points where a polymer layer is present, its thickness varies greatly, going from less than 0.1 ?m to about 15 ?m.

[0150] Analysis of catalyst C shows that it contains 0.8% by weight of carbon which corresponds to 1.4% by weight of polymer deposited on the catalyst with respect to initial catalyst A.

EXAMPLE 3 (COMPARATIVE)

[0151] Catalyst A has been treated as follows:

[0152] 3 kg of catalyst A have been placed in an unperforated stainless steel drum with a volume of 18 liters (useful volume of 5 L), at a rotation speed of 20 rotations/minute, and a hot air flow of 150 m.sup.3/hr at 80? C. is directed onto the surface of the catalyst bed to keep it at 50? C. during pulverization. The hot air enters through an inlet located inside the drum, and exits via the opening located in the front of the drum, without passing through the catalyst bed (leached bed).

[0153] A solution of 750 g of polyacrylate resin at 20% by weight in ethyl acetate has been injected onto the catalyst particles using an atomization nozzle with a solution flow rate of 4 g/min.

[0154] The solvent evaporates continuously which leads to the formation of a polymer layer or coating at the surface of the catalyst particles.

[0155] Following the full injection of the liquid, the catalyst is still stirred for 15 minutes at 50? C. to complete its drying, then cooled at ambient temperature.

[0156] In this way, catalyst D was obtained, which is not in accordance with the invention, for which the particles are covered with a non-continuous layer of polyacrylate resin for which the average thickness is 20 ?m as observed by scan electron microscopy, but which shows very considerable local thickness variations. In particular, we noticed the existence of points at the surface of the catalytic particles where the presence of a polymer layer was not detectable. At the points where a polymer layer is present, its thickness varies greatly, going from less than 0.1 ?m to about 50 ?m.

[0157] Analysis of catalyst D shows that it contains 3% by weight of carbon which corresponds to 5% by weight of polymer deposited on the catalyst with respect to initial catalyst A.

EXAMPLE 4 (AS PER THE INVENTION)

[0158] Catalyst A has been treated as follows:

[0159] 3 kg of catalyst A have been placed in a perforated stainless steel drum with a volume of 18 liters (useful volume of 5 L), at a rotation speed of 20 rotations/minute, with a hot air flow of 150 m.sup.3/hr running fully through it at 55? C. to keep the catalyst bed at 45? C. during pulverization. The hot air flow takes place in parallel to the pulverization jet, and in the same direction (descending flow).

[0160] A solution of 750 g of polyacrylate resin at 20% by weight in ethyl acetate has been injected onto the catalyst particles using an atomization nozzle with a solution flow rate of 4 g/min.

[0161] The solvent evaporates continuously which leads to the formation of a polymer layer or coating at the surface of the catalyst particles.

[0162] Following the full injection of the liquid, the catalyst is still stirred for 30 minutes at 45? C. to complete its drying, then cooled at ambient temperature.

[0163] In this way, catalyst E as per the invention was obtained, for which the particles are covered with a continuous layer of polyacrylate resin for which the average thickness is 18 ?m as observed by scan electron microscopy.

[0164] Analysis of catalyst E shows that it contains 3% by weight of carbon which corresponds to 5% by weight of polymer deposited on the catalyst with respect to initial catalyst A.

EXAMPLE 5 (COMPARATIVE)

[0165] In this example, a comparative catalyst F has been prepared, by applying to activated catalyst A a process identical to the one described in example 1 above, by replacing the polymer aqueous solution by deionized water (not containing any polymer):

[0166] 3 kg of catalyst A have been placed in a fully perforated stainless steel drum with a volume of 18 liters (useful volume of 5 L), at a rotation speed of 20 rotations/minute; a hot air flow of 160 m.sup.3/hr at 90? C. passes fully through it to keep the catalyst bed at 70? C. during pulverization. The hot air flow takes place in parallel to the pulverization jet, and in the same direction (descending flow).

[0167] Then, 900 g of deionized water have been injected onto the catalyst particles using a two-fluid atomization nozzle with a flow rate of 7 g/min.

[0168] The water evaporates continuously. Following the full injection of the liquid, the catalyst is still stirred for 30 minutes at 70? C. to complete its drying, then cooled at ambient temperature.

[0169] Consequently, comparative catalyst F has been obtained.

[0170] Analysis of catalyst F shows that it contains at least 0.1% by weight of carbon.

EXAMPLE 6: (COMPARATIVE)

[0171] In this example, a comparative catalyst F has been prepared by applying to activated catalyst A a process similar to the one described in example 5 above:

[0172] 3 kg of catalyst A have been placed in a fully perforated stainless steel drum with a volume of 18 liters (useful volume of 5 L), at a rotation speed of 20 rotations/minute, a hot air flow of 160 m.sup.3/hr at 130? C. passes fully through it to keep the catalyst bed at 100? C. during pulverization. The hot air flow takes place in parallel to the pulverization jet, and in the same direction (descending flow).

[0173] Then, 900 g of deionized water have been injected onto the catalyst particles using a two-fluid atomization nozzle with a flow rate of 7 g/min.

[0174] The water evaporates continuously. Following the total injection of the liquid, the catalyst is still stirred for 30 minutes at 100? C. to complete its drying, then cooled at ambient temperature.

[0175] Consequently comparative catalyst F has been obtained.

[0176] Analysis of catalyst F shows that it contains at least 0.1% by weight of carbon.

EXAMPLE 7 (COMPARATIVE)

[0177] In this example, a comparative catalyst G has been prepared by treating catalyst A as follows:

[0178] 1 kg of catalyst A has been placed in an unperforated stainless steel drum with a volume of 3 liters at a rotation speed of 12 rotations/minute, at a temperature of 120? C. under a nitrogen atmosphere.

[0179] Then, 200 g of mineral oil (marketed under the name of Lube Oil 600 Neutral by Total, with a viscosity at 40? C. of 120 cP) have been pulverized onto the catalyst, with a flow rate of 6 g/min.

[0180] Following full injection of the oil, the catalyst is cooled at ambient temperature.

[0181] In this way comparative catalyst G was obtained.

EXAMPLE 8

Characterization of the Obtained Catalysts

[0182] The properties of catalysts A to G described in examples 1 to 7 above have been assessed, by determining the following parameters for each:

[0183] Critical Self-heating TemperatureCSHT:

[0184] This parameter characterizes the self-heating properties of the activated catalyst, using a procedure similar to the UN standard (test described in the Recommendation on the transport of dangerous goods. Manual for Tests and Criteria, ISSN 1014-7160, Section 33.3 document). This CSHT test can be conducted according to two variants, for which only the volume of the sample varies. The test procedure is as follows:

[0185] Catalyst samples have been placed in a cubic metal grill box, which lets air pass through. A thermocouple is placed in the sample, and the box is placed in an oven equipped with thermostat.

[0186] If the temperature of the catalyst is not higher by more than 60? C. over that of the oven for a 24 hr period, the test is repeated with a new sample of the same catalyst and by increasing the oven temperature by 10? C.

[0187] This determines temperature T1 which corresponds to the highest oven temperature attained, for which the catalyst temperature is not higher than T1+60? C.

[0188] The critical Self-heating TemperatureCSHT is defined as follows:

CSHT(? C.)=T1(? C.)+5? C.

[0189] For the first variant of the test, the cubic box has a volume of 1 L and the temperature thus obtained was referred to as CSHT-1 L. For the second variant of the test, the cubic box has a volume of 15 mL and the temperature thus obtained was referred to as CSHT-15 ml.

[0190] Hydrosulfuration Activity:

[0191] Hydrosulfuration activity of each catalyst has been determined in a pilot unit.

[0192] The feedstock used is a straight run diesel fuel which has the following characteristics:

TABLE-US-00001 Sulfur content (ppm by weight) 11600 Nitrogen content (ppm by weight) 199 Density (g/mL) 0.859

[0193] For each sample, the catalyst volume used for the test is 10 mL.

[0194] When starting the hydrodesulfuration test, the diesel fuel feedstock is injected with a VVH=3 h.sup.?1 and the reactor is placed under hydrogen pressure (30.Math.10.sup.5 Pa), then the temperature is increased by 0.5? C./min up to 320? C. The 320? C. level is held for 5 hrs before proceeding with the test conditions. This standard startup stage for an activated catalyst is sufficient to deprotect the catalyst grains.

[0195] The test feedstock is then injected to start the actual test. The test conditions were as follows: pressure of 4 MPa (40 bars), H.sub.2/gazole (diesel fuel) ratio of 300, VVH=2h.sup.?1, temperature of 357 to 367? C., test duration of 6 days.

[0196] The sulfur content of the feedstock is measured at the outlet of the unit by means of a UV fluorescence analyser. The apparent constants of the desulfuration reaction have been calculated according to the E1 formula below:

[00001]$\begin{array}{cc}{K}_v=\left(\frac{1}{?-1}\right).Math.\left(\frac{1}{S^{?-1}}-\frac{1}{S_0^{?-1}}\right)*\mathrm{VVH}& \left(E.Math..Math.1\right)\end{array}$

where

[0197] K.sub.v=apparent reaction constant

[0198] ?=order of the reaction (considered equal to 1.2)

[0199] S=sulfur content of the effluents

[0200] S.sub.0=sulfur content of the feedstock

[0201] VVH=hourly volume speed of the liquid feedstock

[0202] The performances of each sample have been assessed with respect to that of a reference catalyst. For that, the Relative Volume Activity (RVA) has been calculated according to the E2 formula that follows:

[00002]$\begin{array}{cc}\mathrm{RVA}=\frac{\mathrm{Kv}?\left(\mathrm{sample}\right)}{\mathrm{Kv}?\left(\mathrm{reference}\right)}?100& \left(E.Math..Math.2\right)\end{array}$

[0203] As reference, the value K.sub.v of 100 has been assigned to activated catalyst A.

[0204] The Low Temperature SO.sub.2 Emissions:

[0205] A 25 g catalyst sample is weighed then placed in a 1 L container with air that is then sealed using a plug equipped with a septum. The container is then placed in a heat chamber with thermostat at 50? C. for 24 hrs. After 24 hrs, the container is removed and left to cool at ambient temperature. Then a SO.sub.2 analysis is made for the gas contained in the container, by sampling through the septum using a syringe. The gas analysis gives immediately the ppm result of SO.sub.2 emitted by the catalyst.

[0206] For each catalyst, immediately after its preparation the two critical self-heating temperatures (CSHT-1 L and CSHT-15 mL), the RVA activity and the SO.sub.2 formation were determined.

The results obtained for each catalyst are put together in Table 1 below:

TABLE-US-00002 TABLE 1 Protective CSHT CSHT Activity Emissions Catalyst layer Equipment 1 L 15 mL RVA SO.sub.2 A (initial 65? C. 115? C. 100 150 ppm catalyst) B EVOH Perforated 125? C. >220? C. 98 0.2 ppm (invention) drum C EVOH Unperforated 85? C. 155? C. 99 15 ppm (comparative) drum D Polyacrylate Unperforated 85? C. 145? C. 84 50 ppm (comparative) drum E Polyacrylate Perforated 105? C. 205? C. 88 4 ppm (invention) drum F Perforated 65? C. 115? C. 101 150 ppm (comparative) drum F Perforated 85? C. 145? C. 98 460 ppm (comparative) drum G Oil Unperforated 85? C. 145? C. 98 120 ppm (comparative) drum

[0207] The results above show that activated catalyst A has a low critical self-heating temperature (65? C.), typical for this type of catalyst at the newly activated state, then air-stabilized.

[0208] Protection provided with a layer of film forming polymer (catalyst B and catalyst E as per the invention), obtained with the process according to the invention, enables to reduce in a particularly efficient way the self-heating of the activated catalyst A: the critical self-heating temperature for box 1 L is increased considerably, since it is 125? C. for catalyst B and 105? C. for catalyst E.

[0209] In addition, these two catalysts show an SO.sub.2 emission well below initial catalyst A, and below the 5 ppm threshold.

[0210] In comparison, catalysts C and D which are not in accordance with the invention, for which the protection has been done in an unperforated drum, for which the air flow does not pass through the catalyst grains, have a self-heating feature that is quite higher, with CSHT-1 L temperatures of 85? C. In addition, the SO.sub.2 emission remains high in both cases (15 and 50 ppm). Consequently, these two examples show the importance of conducting the process according to the invention by having an air flow circulate through the catalyst particles during pulverization of the composition containing the film forming polymer.

[0211] Catalysts F and F correspond to blank tests, that permit to verify easily the impact of the coating conditions themselves (pulverization of water and hot air flow) on the properties of the catalyst. The self-heating properties of these two catalysts, for which the respective CSHT-1 L are 65 and 85? C., are coherent with the passivation methods by the active phase oxidation, already known by the prior state of the art. The SO.sub.2 emissions are greatly increased for catalyst F which can be explained by the relatively high oxidative stabilization of the active phase, when catalyst A has been placed at 100? C. under an air flow.

[0212] The use of mineral oil as protective material also leads to a moderate increase of the critical self-heating temperature and a small reduction of the SO.sub.2 emissions, at values that remain low in comparison with those reached for catalysts B and E according to the invention using film forming polymers.