GB1574389A

GB1574389A - Catalyst activation process

Info

Publication number: GB1574389A
Application number: GB2974/77A
Authority: GB
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1976-02-02
Filing date: 1977-01-25
Publication date: 1980-09-03
Also published as: NL7701077A; BE850966A; DE2702327A1; AU514928B2; FR2339432B1; IT1080316B; JPS5294890A; BR7700626A; DE2702327C2; AU2149477A; FR2339432A1; JPS5939182B2; CA1080685A

Description

(54) CATALYST ACTIVATION PROCESS (71) We, EXXON RESEARCH AND ENGINEERING COMPANY, a Corporation duly organised and existing under the laws of the State of Delaware, United States of America, of Linden, New Jersey, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement :- The present invention relates to a process for activating a catalyst by reduction. The invention relates more particularly, but not exclusively, to the activation of catalysts comprising nickel, e. g. massive nickel catalysts.

Massive nickel hydrogenation catalysts having high nickel surface areas, for example, more than 70 m2/g, are known in the art. U. S.

Patent 3,868,332 teaches such a catalyst characterised as having a low sodium content, i. e. less than 0.2 wt. % based on total weight of catalyst. In U. S. Patent 3,859,370 the use of this catalyst in hydrogenation processes is claimed.

The present invention provides a process for activating a catalyst by reduction comprising the following steps in sequence: (a) reducing said catalyst by heating in the presence of hydrogen at a tempera ture sufficient partially to activate the catalyst; (b) contacting said partially activated catalyst in the presence of hydrogen with a reactive feed which undergoes exothermic reaction in the presence of said partially activated catalyst at conditions whereby said exothermic re action occurs, said conditions including a temperature greater than the temperature in step (a) at which the said catalyst is partially activated; and (c) continuing said contacting for a time sufficent to convert said partially acti vated catalyst to a more highly acti vated catalyst than the partially acti vated catalyst of step (a).

The catalyst may comprise nickel and may also comprise silica. The catalyst may comprise nickel and silica and have a nickel surface area in the range of from 50 to 100 m2/g and a total surface area in the range of from 150 to 300 m2/g.

The process of the invention may be employed for activating catalysts which are commonly activated by reduction at elevated temperatures, for example, at least 150 C.

The catalyst prior to this activation step may be prepared by any method known in the art.

For example, in preparing a supported catalyst which comprises a metal supported on an inert, porous support, a catalyst metal precursor will be impregnated or precipitated onto the support or, alternatively, the supported catalyst may be formed by coprecipitation, from solution, of the precursors of both the metal and the support. The solution may comprise any solvent in which the catalyst metal precursors are soluble, i. e., the solvent may be aqueous or nonaqueous. For example, a catalyst comprising nickel, copper and silica may be prepared by contacting a porous support (e. g. silica or kieselguhr), preferably a particulate support, with a solution of nickel, copper and silicate ions at such conditions that said ions are co-precipitated onto said support to yield a composite comprising nickel, copper and silica precursors supported on said porous support. The excess solvent is removed by methods known in the art, including heating and/or use of a vacuum. After solvent removal, if desirable, a calcination in air or an inert gas may be carried out.

The process of the invention is especially suitable for preparing hydrogenation catalysts which are activated by reduction at high temperature. Most especially, the process of the invention is useful for activating the massive nickel hydrogenation catalysts des cribed in the U. S. mentioned above. In its most preferred embodiment, the process of the invention is utilized to activate the catalysts which comprise nickel, copper and silica coprecipitated onto a porous support.

In one preferred embodiment, the importance of the invention arises from the fact that many commercial hydrogenation units are limited to a maximum temperature at the inlet of from 200 C to 250 C. It is noted that there are commercial hydrogenation units wherein a furnace is used to preheat the feed at the inlet. However, these units must be designed for temperatures of from 350 C to 400 C, since the nickel-silica catalyst must be reduced at a temperature of at least about 350 C for complete activation. Thus the catalyst is generally reduced and stabilized by the manufacturer. This requirement, however, increases the cost of the catalyst and makes in situ activation more attractive. Because of the above limitation on inlet temperature, prior to the discovery of the process of the instant invention, in situ techniques were not commonly available to the commercial users of nickel-silica hydrogenation catalysts.

In a preferred embodiment of the process of the instant invention the massive nickel catalyst, which is a high surface area nickel catalyst preferably containing copper, is charged into the hydrogenation reactor in a manner designed to minimize absorption of water from the atmosphere. The reactor may be purged with dry air or a dry inert gas to remove traces of water from both the reactor and the catalyst. The reactor is closed and then purged with an inert gas to remove oxygen.

When the oxygen level is sufEiciently low, i. e. less than 1%, the purge gas is terminated and a reducing gas, preferably a hydrogen-rich gas is passed over the catalyst at a flow rate of from 1,000 V/Hr/V to 50, 000 V/Hr/V, pre- ferably 5, 000 V/Hr/V. The reducing gas is bled into the reactor with steadily increasing flow up until the point where full flow has been obtained. Then the temperature at the inlet is increased in increments of 10 C to 30 C at thirty minute intervals until a temperature of from 210 to less than 235 C is achieved within the catalyst bed. This temperature is maintained for a time sufficient to provide a partially activated catalyst composite, e. g., with 1v75% of the activity of a fully activated catalyst. The catalyst at this point is an active catalyst, although, due to the fact that much of the nickel exists in the nonmetallic (noncatalytically active) state, the catalyst is characterized as being partially activated. However, as will be further described below, it is critical that sufficient nickel exist in the metallic, i. e. catalytically active, state to yield a composite having some catalytic activity. The temperature at the inlet is then lowered to from about 100 C to 125 C and the flow of a reactive feed through the catalyst bed is commenced. The reactive feed when a hydrogenation catalyst is being activated by the process o, the instant invention is conveniently an unsaturated hydrocarbon, i. e., either an aromatic or olefinic hydrocarbon; or oxygenated derivatives thereof, e. g. alcohols, ethers, etc.

Examples of reactive feed which are useful in the process of the instant invention include: C2 to Czo olefins, C6 to Czo aromatic hydrocarbons, e. g. benzene, toluene, xylene hexene, butadiene, styrene, inter alia. The reactive feed may be 100% olefinic or aromatic or comprise mixtures of olefins and aromatics. Nonreactive components such as paraffins may also make up a portion of the reactive feedstream. Hydrogen is provided with the reactive feed since it is necessary as a reactant and to reduce the nickel to the metal. It is critical to the process of the instant invention that the reaction used to activate the partially activated catalyst composite must be exothermic since the purpose in contacting the catalyst with a reactive feed, at this point, is to utilize the heat of reaction to obtain a higher temperature at the surface of the catalyst than is available at the inlet or in the catalyst bed. Thus, the skilled artisan would adjust the reactive feed accordingly to obtain sufficient heat of reaction to convert the partially activated catalyst into a high activity catalyst, e. g., a catalyst with more than 75% of the activity of a fully activated catalyst.

The temperature during the contacting of the partially activated massive nickel hydrogenation catalyst with the reactive feed is raised, in increments of 10 C to 30 C per thirty minute interval, until the maximum temperature in the catalyst bed exceeds 235 C, preferably the temperature is raised to between 235 C and 275 C.

The ratio of the reactive fed to hydrogen and flow rates of both are adjusted to achieve a sufficient exotherm to raise the temperature of the catalyst in the bed to a level of 250- 275 C or more. The catalyst will be maintained at this temperature by means of the reaction occurring for a time sufficient to achieve, preferably full, i. e., 100%, activation of the catalyst, in approximately 2 to 20 hours.

The massive nickel catalysts activated by the process of the invention are useful in hydrogenation and may be used to hydrogenate aromatics, aldehydes, alcohols, olefins, including both straight and branched chain, and the various hydrocarbon double bonds found in edible fats and oils.

EXAMPLES The following examples best illustrate the process of the instant invention. The catalyst used in all the tests was prepared according to the following method: 8.75 gm of Cu (NO.,),. 3HO and 112 gm. of Ni (NO,),. 6H, O were dissolved in 500 ml of distilled water, then 39 gm. of Na2SiOs. 9H20 was dissolved ir. another 500 ml of water and 5 gm. ot acid washed kieselguhr was slurried in this second solution. The second solution with the kieselguhr slurried therein was stirred vigorously while the first solution containing the copper and nickel salts was added at a uniform rate over a 20 minute period. This mixture was then heated to the boiling point and 80 gm. of NH, HCO3 was added at a uniform rate over a 20 minute period. The mixture was kept at the boiling point for 3 hours while stirring continued. It was then filtered and washed 5 times with boiling water, each wash consisting of 500 ml of water. The filtercake was then dried at 120 C and calcined in air for 4 hours at 400 C. The catalyst contained by weight 45.0% nickel, 5.0% copper, and 50% silica (the impurities present in the acid washed kieselguhr being included in the weight of silica given).

In Example A the catalyst was activated in H2, at a catalyst bed temperature of 245 C, with a nonreactive feed flow. In Example B, the catalyst was activated in H2, at a catalyst bed temperature of 245 C, with a reactive feed which contained 22.3% aromatics. In Example C, the catalyst was activated in H2, at a catalyst bed temperature of 245 C, with a reactive feed which contained 21.7% aromatics. In Example D, the catalyst was activated first with H2 at a catalyst bed temperature of 232 C, then with a reactive feed which contained 21.7% aromatics at 245 C.

TABLE I Example A Example B Conversion of aromatics at 100 hours on oil 60% 80% Run Conditions: Space Velocity-10-Volume feed/Hr/Volume Catalyst Pressure-600 psig Temperature-160 C H2-1000 Standard Cubic Feet/Barrel Feed-Mineral spirits* 22. 3% aromatics TABLE II Example C Example D Conversion of aromatics at 75 hours on oil 24% 34% Run : Space Velocity-30 Volume feed/Hr SVolume Catalyst Pressure-600 psig Temperature-160 C Ho-1000 Standard Cubic Feed/Barrel Feed spirits* 21.7% aromatics * The mineral spirits used was VARSOLTM ~3, from Exxon Chem. Co. U. S. A. which is a naphtha fraction with a boiling range of 310 F to 341 F, aromatics content of from about 21 to 23% on a wt. basis and 1.5 ppm sulfur or less."VARSOL"is a trade mark for the foregoing product.

In Table I, Example B shows significantly higher conversion than Example A. The data in Table II show how the added improvement obtained by the activation procedure described ir. this application. Example D shows sub santially more conversion than Example C which did not include a treatment with H2 prior to the high temperature activation with the reactive feed. Thus, the data in Tables I and II demonstrate the criticality of the two step activation process of the instant invention.

It should be noted, for purposes of definition, Example D represents a fully active catalyst composite, while Examples A, B and C, represent partially active catalyst composites, i. e., they have an activity (as measured by the reaction described in Example D and defining the catalyst activity of said catalyst composite as 10 ()/) from from to 75/,.

Claims

WHAT WE CLAIM IS :-

1. A process for activating a catalyst by reduction comprising the following steps in sequence: (a) reducing said catalyst by heating in the presence of hydrogen at a temperature sufficient partially to activate the cata lyst ; (b) contacting said partially activated cata lyst in the presence of hydrogen with a reactive feed which undergoes exo thermic reaction in the presence of said partially activated catalyst at conditions whereby said exothermic reaction occurs, said conditions includ ing a temperature greater than the temperature in step (a) at which the said catalyst is partially activated ; and (c) continuing said contacting for a time sufficient to convert said partially acti vated catalyst to a more highly acti vated catalyst than the partially acti vated catalyst of step (a).

2. A process according to claim 1 in which the catalyst comprises nickel.

3. A process according to claim 2 in which the catalyst comprises silica.

4. A process according to claim 3 in which the catalyst has a nickel surface area in the range of from 50 to 100m 2/g and a total surface area in the range of from 150 to 300 m'/g.

5. A process according to claim 3 or claim 4 in which the catalyst comprises copper.

6. A process according to claim 5 in which said catalyst is prepared by contacting a porous support with a solution of nickel, copper and silicate ions at conditions whereby said ions are co-precipitated onto said support to yield a composite comprising nickel, copper and silica precursors supported on said porous support.

7. A process according to claim 6 in which the said porous support is a particulate support.

8. A process according to claim 6 or claim 7 in which the said support is silica or kieselguhr.

9. A process according to any one of claims 1 to 8 in which the temperature in step (a) is less than 235 C and the temperature em ployed in step (b) is in the range of from 235 C to 275 C.

10. A process according to any one of claims 1 to 9 in which the temperature of the catalyst surface during step (b) exceeds the temperature of the catalyst bed.

11. A process according to any one of claims 1-10 in which step (a) is continued for a time sufficient to yield a catalyst with an activity of from 10 to 75% of the fully activated catalyst.

12. A process according to any one of claims 1-11 in which steps (b) and (c) are carried out at conditions sufficient to yield a catalyst with an activity of greater than 75% of the fully activated catalyst.

13. A process according to any one of claims 1 to 12 in which the said reactive feed comprises an unsaturated hydrocarbon or oxygenated derivative thereof.

14. A process according to claim 13 in which the said unsaturated hydrocarbon is a C4 to C2 aromatic hydrocarbon.

15. A process according to claim 13 in which the said unsaturated hydrocarbon is Cz to C20 olefinic hydrocarbon.

16. A process for activating a catalyst according to any one of claims 1 to 15 substantially as hereinbefore described.

17. A process for activating a catalyst sub stantially as hereinbefore described with reference to Example D.

18. A catalyst whenever activated in accordance with the process of any one of claims 1 to 17.