WO2006090429A2

WO2006090429A2 - Removal of oxygen from hydrocarbons

Info

Publication number: WO2006090429A2
Application number: PCT/IT2006/000118
Authority: WO
Inventors: Cristian Landoni; Marco Succi
Original assignee: Saes Getters S.P.A.
Priority date: 2005-02-28
Filing date: 2006-02-28
Publication date: 2006-08-31
Also published as: WO2006090429A3; ITMI20050305A1

Abstract

A process for the activation of molecular sieves, alumina or mixtures thereof able to allow the removal of O2 from hydrocarbons is described, as well as a purifier for O2 removal from hydrocarbons comprising such activated material and a process for hydrocarbons purification.

Description

"REMOVAL OF OXYGEN FROM HYDROCARBONS"

The present invention relates to a process of activation of a purification material for oxygen removal form hydrocarbons, to a purifier for hydrocarbons comprising such a material, to a method for hydrocarbons purification employing such a material.

Recently, high purity hydrocarbons have found applications in various industrial processes, for example in microelectronics industry; it is widely known that in such processes the presence of gas impurities, even in the amount of traces, jeopardizes the efficiency of the processes themselves and the quality of the products. Both the use in new applications and the growing complexities and requirements of the industrial processes require increasingly greater purity levels for these gases, typically, water and oxygen concentrations of the hydrocarbons used in such processes must be lower than 10 ppb (parts per billion, i.e., one impurities molecule every 10⁹ gas molecules). The analysis of the state of the art about the problem of hydrocarbons purification, with particular reference to the abatement of the concentration of oxygen under 10 ppb, has failed to point out satisfactory solutions as these processes are complex and, in some cases, not completely efficient to grant the required purity levels.

The use of molecular sieves or alumina for the removal of water traces from gaseous means is known and widely documented; with the expression molecular sieves it is also referred to compounds identified in the field as zeolites, which are also often identified with the expression aluminum silicates.

In this regards, in patent US 4,286,611 a regenerable purifier for water removal made of a material comprising molecular sieves is described. Information about the ability of removing H₂O by molecular sieves can also be found in the products catalogue of suppliers of these materials, such as Sigma-Aldrich, Engelhard, CECA. Similarly, the ability of removing H₂O by activated alumina is known as well, related information being available in the commercial literature of the Axens group, the Fluid Energy Company, and in the article by R. Desai et al., "Adsorption of Water Vapor on Activated Alumina. I - Equilibrium Behavior", published on "The Canadian Journal of Chemical Engineering", Vol. 70, pages 699-706, year 1992. Also known is the fact that these materials have no significant oxygen removal ability.

In patent application JP 2004-148257 a system for producing acetylene 99,999% pure is described, i.e. with a total impurities residual content not greater than 10 ppm (parts per million). In addition to the fact of not achieving or ensuring a purity level compatible with the new requirements, the described process is complex and implies more phases since consisting in carrying out condensation cycles in a solvent in such a way to use the different solubility properties of acetylene with respect to impurities, thus improving the purity degree at every condensation cycle and subsequent evaporation. The acetylene produced according to this method is then passed through a purification system formed of a column of active carbons, which are intended to remove the solvent, and a molecular sieves column for the H₂O removal.

In patent US 4,404,118 a process of regeneration of adsorbing materials used for hydrocarbons purification through a thermal treatment in hydrogen is disclosed. Such a treatment takes place in order to regenerate an inherent capability of the adsorbers, i.e. the separation of different hydrocarbons, on the basis of the molecular dimensions or the sorption of polar species, with particular reference to ethers and alcohols. In this case the hydrogenation process is carried out after use of the material, in order to regenerate the same and to be able to use it again. In patent US 4,425,143 a purification process using a special class of natural zeolites able to remove H₂O and O₂ from gaseous flows is described. Such zeolites have the characteristic of having an iron content higher than similar compounds industrially manufactured. The technical solution described in this patent requires that, if the gas to be purified is not hydrogen or does not contain hydrogen at sufficiently high levels, H₂ is continuously added from an external source together with the gas to be purified, in order to convert the oxygen being present into water, which is then removed by the zeolites. This technical solution requires means and related safeties in order to add and manage the hydrogen to be continuously added to the gaseous fluid to be purified.

These disadvantages are overcome by the invention, which in a first aspect consists in a process for the activation of a purification material comprising molecular sieves or alumina or mixtures thereof for the removal of oxygen from hydrocarbons, characterized in that such a material is subject to an activation process comprising the exposure to hydrogen or to gaseous mixtures containing hydrogen; in a second aspect the invention refers to a purifier for O₂ removal from hydrocarbons containing such activated material according to the process of the invention and, in a last aspect, it consists of a method for the purification of hydrocarbons using such purifier. The invention will be illustrated with reference to the figures in which:

- Figure 1 shows a flowchart representing an activation process for the purification material comprising the exposure of the material to hydrogen or to a gas containing hydrogen (process A); - Figure 2 shows a flowchart representing a simplified activation process for the purification material comprising the exposure of the material to a gas containing hydrogen (process B);

- Figure 3 shows a purifier for hydrocarbons containing the purification material activated according to the process of the invention; - Figure 4 shows a possible method for the purification of a fluid of hydrocarbons through a purification system;

- Figure 5 shows the results obtained with two small scale purifiers loaded with 3A type molecular sieves; and

- Figure 6 shows the results obtained with two small scale purifiers loaded with 13X type molecular sieves.

The inventors have discovered that by submitting a purification material comprising molecular sieves, alumina or mixtures thereof to an activation process with hydrogen or a gas containing hydrogen, such a process alters the characteristics of such purification material enabling its ability of removing oxygen from hydrocarbons. The activation process of the invention provides remarkable advantages with respect to what described in the above mentioned patent US 4,425,143 since in order to remove O₂ from hydrocarbons it is no more necessary to add hydrogen from an external source during hydrocarbons purification.

Unlike what disclosed in patent US 4,404,1-18, i.e. a process of reactivation of molecular sieves in hydrogen able to let the sieves themselves recover their functionality of removing alcohols and ethers, the activation process that is the object of the present invention can enable a new feature, unknown for a purification material comprising molecular sieves, alumina o mixtures thereof, that is oxygen removal from hydrocarbon streams.

The activation process of the invention, is applicable to different types of material, particularly molecular sieves, alumina or combinations thereof. Within the class of molecular sieves suitable for the realization of the invention there are zeolites indicated in the field with the names 3 A, 4A, 5 A, 13X.

The material activated according to the process of the invention can be used alone or in combination with other materials, for example particularly useful is its association with active carbons, which can remove solvents traces which can be present as a residual of the hydrocarbons production process.

Among the hydrocarbons for which the use of the purification material activated according to the process of the invention is advantageous, there are the aliphatic ones

(belonging to the alkane, alkene and alkyne families), with particular reference to methane, ethane, propane, butane, ethylene, propylene, butylenes, acetylene and propyne.

The purification material activated according to the method of the invention carries out its purifying function when used between 0 and 40 ⁰C.

The operations which will be herein described involve some steps or technical solutions that are widely known to the technicians in the field of gases purification, such as, for example, the introduction of the purification material inside a metal body provided with a gas inlet and an outlet, on which suitable connections are present in order to connect it to the gas line and, when necessary, to isolate it.

Other features which do not need any particular description as widely known in the field are the use of means for confining the purification material in the metal body, typically particle filters, or the use of shutoff valves upstream and downstream the metal body in order to ease the activation and installation methods.

Particularly useful for the purpose of testing the material is the presence of a bypass circuit in order to determine capabilities and characteristics of the purification material activated according to the process of the invention. Providing by-pass gas circuits through the use of shutoff valves or the so-called 3-ways valves is also widely known in the field of gases purification and will not be herein described.

Another operation which is commonly carried out in the field of gases purification and of the treatment of purification materials is the choice of the combination among the flows at which the purification material is to be activated, and the material quantity; for example, in the case of basic studies, wherein small quantities of material are used (10- 30 g), flows of gases between 0.1 1/min and some 1/min for the activation are indicatively used; such quantities of material and activation flows are also compatible with the use of small size purifiers usable, e.g., as purifiers for analytical instrumentation or for the so-called local purifiers, identified in the field with the expression "point of use" (POU) purifiers.

The activation of greater quantities of material requires the use of higher flows, e.g., 1 kg of material can be activated by using a flow comprised between 1 and 100 1/min; generally, the greater is the quantity of the material, the higher must be the gas flow used for its activation. Figure 1 shows the activation process (process A) of the invention applied to a material comprising molecular sieves, alumina or mixtures thereof, able to trigger the removal OfO₂ from hydrocarbons capability.

According to this activation process, during phase 1 the heating of the purification material is carried out in a flow of purified inert gas. Li the remainder of the text and in the claims, by purified gas or purified gas mixture it will be meant a gas with an oxygen content less than 100 ppb, preferably with an oxygen content less than 10 ppb and event more preferably such gas is also anhydrous, so that the activated material will also be capable to remove moisture. With the term anhydrous it will be meant a gas with a moisture content less than 1 ppm. The starting activation temperature T_s, to which the purification material is raised in this phase of the process, is chosen within an interval comprised between 100 and 700 °C, preferably between 200 and 500 °C and even more preferably between 300 and 400 ⁰C. hi order to carry out the process in a controlled manner it is necessary to gradually raise the temperature, the material is brought to the starting temperature T_s in a time ti comprised between 0.1 and 6 hours, preferably between 0.2 and 2 hours and even more preferably between 0.5 and 1 hour. Subsequently (phase 2), the purification material is maintained in a flow of purified inert gas, brought to activation temperature T_ac and left in such conditions of flow and temperature for a time t₂, whose value is chosen in the range 1-48 hours, preferably between 12 and 24 hours. The ranges for the choice of the activation temperature T_ac are the same of the activation starting temperature T_s. In a preferred embodiment T_ac=T_s.

Typically, the passage of the material from temperature T_s to T_ac is not critical and does not need particular expedients concerning the time required for such thermal transition. Subsequently, the purification material is brought to the reduction temperature T_r and subject to a reduction treatment (phase 3) by flowing a gaseous reducing mixture formed of purified hydrogen or of a purified mixture of inert gas with hydrogen instead of a purified inert gas. The hydrogen percentage in such gaseous reducing mixture is greater or equal to 0.1% in volume, preferably greater or equal to 10% and even more preferably is made of hydrogen. The ranges of choice for the reducing temperature T_r are the same of the activation temperature T_ac and of the starting activation temperature T_s. In a preferred embodiment T_s=T_ac=T_r. Also in this case particular expedients are not needed for the thermal transition from T_ac to T_r.

The duration t₃ of phase 3 can have a value comprised between 1 hour and 24 hours, preferably between 3 and 20 hours. After this operation, the purification material is flowed with purified hydrogen or a purified mixture of inert gas with hydrogen (phase 4) and brought to the process inert gas switching temperature T_swj_tch; ^at which, the system is flowed with a purified inert gas (phase 5) until the process end temperature T_ep is reached and the purification material has been kept in a inert gas flow for a time t₄, wherein the duration t₄ of phase 5 can be comprised between 1 minute and 24 hours, preferably between 1 and 8 hours and even more preferably between 3 and 6 hours.

The process inert gas switching temperature T_SWj_tCh can have a value comprised between 20 ⁰C and up to T_ac.

The last process phase (phase 6) is the purification material isolation. The process end temperature T_ep can have a value comprised between 20 and 70

°C. If T_swi_tch is equal to T_ac the duration of phase 4 is almost instantaneous and is given by the time required to switch the gas supply from purified hydrogen or the purified mixture of inert gas with hydrogen; in all the other cases the phase 4 duration is given by the time required to cool down form T_ac to T_ep. The last phase of the process consists in isolating the activated purification material (phase 6). This operation is of simple accomplishment in the case shutoff valves are provided upstream and downstream the metal body, since it is sufficient to isolate firstly the downstream valve and then, after a while, the upstream valve. The procedure is more complex and requires a greater hand-ability when such valves are not provided; in this case the outlet of the metal body containing the material must be plugged up and then, after its disconnection from the gas line, the inlet must be also plugged up. Such a procedure can not keep the material pressurized with inert gas, but at least prevents its significant contamination by air.

The activation process and its various phases can be automated through the use of automatic heating units, pneumatic valves and programmable controls for their driving.

With regards to this activation process, it is preferable to use purified gases in the process phase following the exposure to hydrogen (phase 6), while the first phases could be carried out also with a non purified gas. Also with regards to the gas quality employed in the latest phase it is possible to use a inert gas with an O₂ content not higher than 1 ppm; such an activation process is less reproducible respect a process employing purified gasses in the various phases, even if the activation material produced according to this variation can still exhibit the capacity to remove O₂.

Figure 2 shows a simplified process for the activation of molecular sieves, alumina or mixtures thereof (process B). hi particular, unlike the process A previously described, in this case the same gas is always used during all the activation phases of the material. Such a gas is made of a reducing gaseous mixture formed by a purified mixture of an inert gas with hydrogen. This reducing gaseous mixture has a hydrogen content comprised within the range 0.1% - 50%, preferably within 0.1% - 10% and even more preferably within 0.1% - 3%. It can immediately be observed that this second material activation process is simpler than the one previously described, as it consists of four phases instead of six. In particular, in phase 7 the purification material is heated from room temperature to the activation temperature T_ac. In this case a first simplification is given by having

A s^~~ -lac-

Similarly to process A, the activation temperature T_ac can be comprised between 100 and 700 °C, preferably between 200 and 500 °C and even more preferably between 300 and 400 °C.

Also in this case, in order to carry out the activation process in a controlled manner it is necessary to gradually raise the temperature; purification material is brought to the activation temperature T_ac in a time t₅, comprised between 0.1 and 6 hours, preferably 0.2 and 2 hours and even more preferably between 0.5 and 1 hour.

Subsequently, the system is kept at the activation temperature T_ac in a flow of a purified gaseous mixture made of inert gas containing H₂ for a time t₆ (phase 8). The time t₆ has a value comprised between 1 and 48 hours, preferably between 12 and 24 hours. In the penultimate phase of the process (phase 9) the purification material is cooled and flowed with the same gas for a time t₇. This time has a value comprised between 0.5 and 24 hours, preferably between 1 and 8 hours, and even more preferably between 3 and 6 hours.

Similarly to process A, also in this process the last phase (phase 10) consists of isolating the activated purification material, preferably leaving it under gas pressure through the use of the (optional) shutoff valves.

It is possible to observe that in this second process it is not necessary to change the gas according to the phase; this leads to a simplification and a reduction of the number of the phases (from six to four) in order to complete the activation process. Also in process B it is possible to automate the activation through the use of programmable heating units, pneumatic valves and related controls, which in this case, considering the easier activation process, would only serve to isolate the metallic body after the completion of the material activation process.

In a second aspect thereof, the invention relates to a purifier for O₂ removal from hydrocarbons, wherein the purification material contained in said purifier comprises molecular sieves, alumina or mixtures thereof and said molecular sieves, alumina or mixtures thereof have been subjected to an activation process comprising the exposure to hydrogen or to gaseous mixtures containing hydrogen; for example by employing one of the activation processes previously described (process A, process B).

The invention is applicable to hydrocarbons in the following states: gas, vapor, multiphase gases or liquids, such possible different states will generically be identified with the expression "fluid".

Figure 3 shows the purifier 30 object of the invention, in its most generic description, namely a metal, body 31 provided with an inlet 32 for the fluid to be purified and with an outlet 33 for the purified fluid. Suitable connection means are typically welded to the inlet 32 and the outlet 33 allowing an easy installation of the purifier on the transport line of the fluid to be purified. Such connection means are not indicated and are well known in the field, for example they can be of the type VCR^® by Cajon Company Corporation, and in some cases SWAGELOK^® by Crawford Fitting Company Corporation. Housing 31 contains the purification material of the invention 34 and a fluid permeable barrier 35 able to confine the purification material but allowing the purified fluid passage. Typically such a barrier is formed of a particle filter, which in this case carries out various functions; in particular:

- confines the purification material 34, - entraps possible particles released by the material itself,

- removes particles present in the fluid to be purified.

Suitable filters to carry out the above functions are characterized by a pores mean diameter comprised between 0.003 μm and 10 μm, supplied, for example, by Mott Corporation. Still referring to Figure 3, it is possible that an additional gas permeable barrier is provided immediately after the inlet 32 of the purifier before the purification material 34. This barrier can be identical or have different features with respect to barrier 35, e. g., it could be a particle filter having a pores diameter greater than barrier 35.

The purifier 30 can also comprise other optional components easing the installation and maintenance operations such as shutoff valves, 3 -ways valves or a bypass circuit, such elements and their use are widely known by a technician working in the field of gases purification and will not be indicated.

In Figure 3 the parts have not been illustrated in scale in order to simplify the description (with particular reference to the purification material representation).

The most diffused geometry in the field for the metal body 31 of the purifier is the cylindrical one, such specific geometry being not compulsory for the realization of the invention.

The above-described purifier can contain different materials, each of which can remove specific impurities, is characterized by the presence of a purification material comprising molecular sieves, alumina or mixtures thereof, which are activated through a process comprising the exposure to hydrogen or to a gas containing hydrogen, according to one of the processes previously described (A or B). This activation process can be carried out before introducing the molecular sieves, alumina or mixtures thereof inside the metal body of the purifier 31, or these can be introduced in non- activated form inside the purifier and subsequently be subjected to the activation process.

The first approach can be useful in the production of small size purifiers which typically use about 10-100 grams of material, in this case the activation of a greater quantity of material, e.g. 1 kg, allows to produce many purifiers of small dimensions; in the case of purifiers loaded with about 10 grams of material, it is possible to produce about 100 purifiers by carrying out a single activation process for the material.

This approach requires cautions in the purification material handling after the activation, in particular the process of introduction into the purifier body must take place by minimizing the exposure to air and ideally should be carried out in glove boxes flowed with inert gas. The purification material activated but not used should be stored in hermetic airtight containers filled with an inert gas atmosphere.

Another embodiment wherein the preceding method offers advantages is when the purifier has to contain two or more purification materials, wherein the other materials do not need the exposure to a gas containing hydrogen for their activation. A sample embodiment of this type is given, for example, by the combination of active carbons with molecular sieves, alumina or mixtures thereof activated according to one of the processes of the invention; the active carbons can remove solvent traces present as residuals of production of hydrocarbons, while the activated molecular sieves, alumina or mixtures thereof can remove O₂.

The advantage of the activation of the purification material after its introduction into the metal body of the purifier is that once the activation process is finished the means typically provided in a purifier, such as isolation valves, are used to prevent the activated material exposure to the air and its consequent degradation.

If the activation process (e.g. process A or process B) of molecular sieves, alumina or mixtures thereof does not negatively influence the characteristics of other purification materials optionally provided inside the purifier, it is anyway possible to carry out the activation process when the purifier is loaded and assembled.

In a third aspect thereof, the invention relates to a method of hydrocarbons purification characterized by the use of a purifier containing molecular sieves, alumina, or mixtures thereof and characterized in that such material is subjected to an activation treatment comprising the exposure to hydrogen or to a gas containing hydrogen. Examples of activation processes able to obtain such result are the ones previously described and identified as process A and process B.

If it is necessary to remove other impurities in addition to oxygen and water, it is possible that the purifier contains also other purification materials, e.g., a very advantageous combination provides for the use of active carbons for the removal of solvent traces.

The hydrocarbons purification method is applicable to hydrocarbons belonging to the alkane, alkene and alkyne families, with particular reference to methane, ethane, propane, butane, ethylene, propylene, butylenes, acetylene and propyne.

The hydrocarbons purification method is effective in a temperature interval comprised between 0 and 40 ⁰C.

In the purification method described above, if the industrial process in which such hydrocarbons are used would require it, it might be necessary to carry out a conditioning procedure in order to suppress gas residual levels contained in the purifier which may come from the last phase of the material activation process (comprising molecular sieves, alumina or mixtures thereof).

This conditioning procedure consists of the so-called "cycle purging", that is a series of pressurization cycles of the purifier, the number of such cycles being preferably comprised within the range 5-20. The cycle purge procedure is widely known in the field and therefore does not require any description; information about such a procedure can be found, for example, in the article "Evaluating electronics grade lines purging requirements" by Pearlstein et al., published on Media for Solid State Technology in March 2001, wherein such procedures are shown applied to the case of process gas distribution lines.

The method of the invention can be carried out, for example, by using the apparatus shown in Figure 4; on the transport line of the fluid to be purified 41 is mounted the purifier 30 containing the material activated according to one of the processes of the invention. Two shutoff valves 44, 46 are mounted respectively upstream and downstream of the purifier. Before the valve 44 a branch 42 with shutoff valve 45 is assembled allowing to by-pass the purifier, allowing a non-purified fluid to flow through the system 40. The presence of the three shutoff valves 44, 45, 46 makes the choice of which type of fluid (purified or not) to provide at the outlet 47 of the system very easy, in particular, with the valves 44 and 46 in the open state and valve 45 in the closed state a purified fluid will be obtained, whereas with valves 44 and 46 in the closed state and valve 45 in the open state a non-purified fluid will be obtained. Also the conditioning procedure results being very eased by the presence of such valves allowing an easy management of pressurization cycles for gaseous fluids or of emptying-filling cycles in the case of a fluid in the liquid phase thereof.

The embodiment of the purification system 40 shown in Figure 4 is only one of the possible embodiments of such system; variations thereof are widely known by the technicians working in the field and for this reason such a specific embodiment is not constraining for the realization of the invention.

The invention will be further illustrated with reference with the following examples.

EXAMPLE 1 A purifier metallic body provided with two shutoff valves is filled with 25 cc of molecular sieves, type 3 A, sold by CECA; two 10 μm particle filters are installed within the purifier to confine the purification material.

The purification material is then activated according to the following process:

- while flowed with 1.5 1/min of purified nitrogen, heating from room temperature to 350 °C in 2 hours (T_s=350 °C, t_x=2 hours), - once at 350 °C, the material is maintained in those conditions of temperature and flow for 8 hours (T_ac=350 °C, t₂=8 hours),

- while kept at 350 °C, the purifier material is then flowed with 1,5 1/ min of purified hydrogen for 8 hours (T_r=350 °C, t₃=8 hour),

- while flowed with purified hydrogen, the system is then cooled down until the temperature reaches 30 ⁰C (T_swi_tCh ⁼30 ⁰C). This condition is reached approximately in three hours,

- the material is then flowed with purified nitrogen for 1 hour (t₄=l hour, T_ep= 30 ⁰C) and then isolated by means of the two shutoff valves installed on the purifier body. EXAMPLE 2 (COMPARATIVE)

The same type and quantity of purification material used in example 1 is submitted to an activation process that does not include the exposure to hydrogen phase, as below shown:

- while flowed with 1.5 1/min of purified nitrogen, heating from room temperature to 350 ⁰C in 2 hours (T_s=350 °C, ti=2 hours),

- once at 350 °C, the material is maintained in these conditions of temperature and flow for 8 hours (T_ac=350 ⁰C, t₂=8 hours),

- the material is cooled down to 30 ⁰C (T_ep=30 °C) while flowing purified nitrogen and then isolated by means of the two shutoff valves installed on the purifier body. Such temperature condition is reached in approximately 1 hour.

EXAMPLE 3

The same process described in example 1 is applied to 25 cc of 13 X molecular sieves supplied by Grace.

EXAMPLE 4 (COMPARATIVE) The same process described in example 2 is applied to 25 cc of 13 X molecular sieves supplied by Grace. EXAMPLE 5

The purifiers, prepared as described in examples 1-4, are installed, one at a time, on a testing gas circuit with a purifier by-pass, as shown in figure 4. In this case at the end of line 47 is present a DELTA F Nanotrace II Oxygen gas analyzer, capable of measuring oxygen concentrations in the range 0.001-100 ppm.

The gas initially flowed to the analyzer is pure Nitrogen, supplied through the bypass circuit (valves 44 and 46 closed, valve 45 open), than at a time t_a, the gas source is switched from nitrogen to low grade acetylene (purity 99.996%, supplier SIAD of Bergamo). At a given time, referred as "time zero" the by-pass branch is isolated and the purifier is put on-line (valves 44 and 46 open, valve 45 closed) for the remainder of the experiment.

In the experiments it has been chosen to employ a "normalized test time", i.e. to employ a relative time scale defined on the basis of the most important testing event, the online switching of the purifier; therefore such time scale is simply obtained subtracting the time when the purifier is switched online.

Figure 5 shows the results obtained with sample 1 (line 51) and the results obtained testing sample 2 (line 52 - comparative test); it is possible to observe that when the gas source is changed from pure nitrogen to low grade acetylene, the analyzer readings goes to full scale, indicating that the oxygen concentration, although not precisely quantified, is higher than 100 ppm, that is the upper instrument reading.

When sample 1 is present few minutes after the "time zero" the oxygen reading drops almost to zero, while when sample 2 is present the measured oxygen concentration stays always above 100 ppm. This test shows the capability of the material activated according to the process of the invention to efficiently remove oxygen from hydrocarbons while the same material activated according to prior art process does not provide meaningful benefits.

Figure 6 shows the results obtained with sample 3 (line 63), while line 64 represent the comparative test (sample 4). Also this test shows that sample 4, activated according to the prior art, does not perform any meaningful oxygen removal action, while sample 3 exhibits satisfactory performances.

The experimental tests have been carried out with molecular sieves types 3A and 13X, that within the molecular sieves class represent the two opposite types of materials, more specifically molecular sieves 3A having the smallest average pore dimensions, molecular sieves 13 X the biggest one.

No tests have been carried out with regards to these materials H₂O removal capability since, as already discussed in the introduction, such capability is widely known in the technical field.

With regards to hydrocarbons, the tests have been carried out in acetylene since it is one of the most important hydrocarbons actually employed in manufacturing processes.

Claims

1. Process for the activation of a purification material comprising molecular sieves, alumina or mixtures thereof for the removal of oxygen from hydrocarbons, characterized in that said material is subject to an activation process comprising the exposure to hydrogen or to gaseous mixtures containing hydrogen.

2. Process according to claim 1 characterized by comprising the following phases:

- heating of said purification material from room temperature to the activation starting temperature T₅ under a purified inert gas flow for a time X_\ (phase 1),

- bringing said purification material to the activation temperature T_ac and maintaining said purification material in said purified inert gas flow for a time t₂ (phase 2),

- bringing said purification material to the reduction temperature T_r and flowing said purification material with purified hydrogen or a purified mixture of inert gas with hydrogen for a time t₃ (phase 3),

- flowing said purification material in a purified hydrogen gas flow or in a purified mixture of inert gas with hydrogen until the achievement of a inert gas switching temperature T_SWi_tCh (phase 4), - flowing said purification material with a purified inert gas for a time t₄ until the process end temperature T_ep is reached (phase 5),

- isolation of said purification material (phase 6).

3. Process according to claim 1 characterized by comprising the following phases: - heating of said purification material from room temperature to the activation starting temperature T₈ under an inert gas flow for a time t_\ (phase 1),

- bringing said purification material to the activation temperature T_ac and maintaining said purification material in said inert gas flow for a time t₂ (phase 2), - bringing said purification material to the reduction temperature T₁- and flowing said purification material with hydrogen or a mixture of inert gas with hydrogen for a time t₃ (phase 3),

- flowing said purification material in a hydrogen gas flow or in a mixture of inert gas with hydrogen until the achievement of a inert gas switching temperature T_swj_tch (phase 4), - flowing said purification material with a inert gas for a time t₄ until the process end temperature T_ep is reached (phase 5), wherein said inert gas has an oxygen content equal or less than 1 ppm,

- isolation of said purification material (phase 6).

4. Process according to claim 1 characterized by comprising the following phases:

- heating said purification material from room temperature to activation temperature T_ac under a flow of a purified mixture of inert gas with hydrogen for a time t₅ (phase 7),

- maintaining said purification material in a flow of said purified mixture of inert gas with hydrogen during a time t₆ (phase 8),

- cooling and maintaining said purification material in a flow of said purified mixture of inert gas with hydrogen during a time t₇ (phase 9),

- isolation of said purification material (phase 10).

5. Process according to claim 2 or claim 4 wherein said purified inert gas, said purified hydrogen and said purified mixture of inert gas with hydrogen have an oxygen content less than 100 ppb.

6. Process according to claim 2 or claim 3 wherein said activation starting temperature T_s, said activation temperature T_ac and said reduction temperature T₁- are comprised between 100 and 700 ⁰C.

7. Process according to claim 2 or claim 3 wherein said activation starting temperature T_s, said activation temperature T_ac and said reduction temperature T_r are equal.

8. Process according to claim 2 or claim 3 wherein said inert gas switching temperature T_SWj_tch is comprised between 20 ⁰G and T_ac.

9. Process according to claim 2 or claim 3 wherein said process end temperature T_ep is comprised between 20 and 70 °C.

10. Process according to claim 2 or claim 3 wherein said heating time t\ from room temperature to said activation starting temperature T_s is comprised between 0.1 and 6 hours.

11. Process according to claim 2 or claim 3 wherein said time t₂ is comprised between 1 and 48 hours.

12. Process according to claim 2 or claim 3 wherein said time t₃ is comprised between 1 and 24 hours.

13. Process according to claim 2 or claim 3 wherein said time t₄ is comprised between 1 minute and 24 hours.

14. Process according to claim 4 wherein said time t₅ is comprised between 0.1 and 6 hours.

15. Process according to claim 4 wherein said time tg is comprised between 1 and 48 hours.

16. Process according to claim 4 wherein said time t₇ is comprised between 0.5 and 24 hours.

17. Process according to claim 2 wherein said phase 3 takes place flowing a purified mixture of inert gas with hydrogen, characterized in that the volume percentage of hydrogen in said mixture is greater than or equal to 0.1%.

18. Process according to claim 17 wherein said phase 3 takes place by flowing purified hydrogen.

19. Process according to claim 2 wherein said purified mixture of inert gas and hydrogen has a content of hydrogen in volume comprised between 0.1% and 50%.

20. Purifier for oxygen removal from hydrocarbons characterized in that the purification material contained in said purifier comprises molecular sieves, alumina or mixtures thereof activated according to one of the processes of claims 1 to 4.

21. Purifier according to claim 20 wherein said molecular sieves are chosen form the group 3 A, 4A, 5 A, 13X.

22. Purifier according to claim 20 wherein said molecular sieves, alumina or mixtures thereof are activated before the introduction in said purifier.

23. Purifier according to claim 20 wherein said molecular sieves, alumina or mixtures thereof are activated after the introduction in said purifier.

24. Purifier according to claim 20 comprising active carbons in addition to molecular sieves, alumina or mixtures thereof.

25. Purifier according to claim 20 comprising a metal body (31) containing said purification material (34), said metal body being provided with an inlet (32) and an outlet (33) and with a gas permeable barrier (35) arranged before said outlet (33).

26. Method for oxygen removal from hydrocarbons through a purifier containing therein molecular sieves, alumina or mixtures thereof, characterized in that said sieves, alumina or mixtures thereof are activated according to one of the processes of claims 1 to 4.

27. Method for oxygen removal from hydrocarbons according to claim 26 wherein after the installation of said purifier a conditioning procedure is carried out.

28. Method for oxygen removal from hydrocarbons according to claim 26 wherein the hydrocarbons to be purified belong to the alkane, alkene and alkine family.

29. Method for oxygen removal from hydrocarbons according to claim 26 wherein the hydrocarbons to be purified are methane, ethane, propane, butane, ethylene, propylene, butylenes, acetylene and propyne.

30. Method for oxygen removal from hydrocarbons according to claim 26 wherein said purifier operates at a temperature comprised between 0 and 40 °C.