Patent Application
20240293795
Chemistry related to a zirconium-based metal organic framework for using as a heavy metal adsorbent in condensate and a preparation method thereof
In the petroleum exploration and production industry, the heavy metal contaminants, for example, arsenic (As) and mercury (Hg) can generally be found in a petroleum product which is a natural hydrocarbon compound obtained from the production process, including crude oil, natural gas, and natural gas liquid (NGL), also called condensate or natural gas condensate. These heavy metal contaminants cause disadvantages in terms of toxicity and corrosiveness which is a problem for performing next step where the petroleum product, especially the condensate, is used as a starting material, for example, in the petrochemical industry. The arsenic and mercury contained in a condensate may be in the form of various compounds, for example, mercury sulfide (HgS), mercury oxide (HgO), Arsenopyrite (AsFeS), etc.
Accordingly, to satisfy the needs to reduce or remove the heavy metal contaminants, especially arsenic and mercury compounds contained in the condensate, there is an attempt to develop methods and materials for using in the adsorption of those contaminants.
A metal-organic framework wherein the structure consists of a metal cluster and an organic linking ligand is deemed as a novel porous material which receives great attention and found in various applications, for example, gas storage, gas separation, chemical sensor, and heterogeneous catalysis, etc. Industrially, the metal-organic framework is another interesting option for using as an adsorbent with the adsorption property as required depending on the structure and porosity that can be adjusted according to the type of metal cluster and linking ligand selected.
Examples of invention related to the development of metal-organic framework for using as a contaminant adsorbent are shown below.
WO 2020/130953 A1 discloses the copper-based metal-organic framework for using in a removal of carbon dioxide (CO2) and other contaminants, for example, mercury, arsenic and hydrogen sulfide (H2S) from petroleum. The said copper-based metal-organic framework is obtained by a method comprising mixing copper (II) (Cu(II)) salt and 2,5-dibromobenzene-1,4-dicarboxylic acid, dimethylformamide (DMF) and methanol together, heating such mixture, and collecting the product.
WO 2020/130954 A1 discloses the copper-based metal-organic framework for using in a removal of carbon dioxide (CO2) and other contaminants such as Hg, As, and hydrogen sulfide (H2S) from petroleum. The said copper-based metal-organic framework is obtained by a method comprising the steps of mixing copper (II) (Cu(II)) salt and 1,2,4,5-tetrabromobenzene dicarboxylic acid, methanol and water together, heating such mixture, and collecting the product.
U.S. Pat. No. 10,260,148 B2 discloses a porous material including the metal-organic framework and a porous organic polymer for purifying electronic gas and removing mercury from the hydrocarbon stream.
The first aspect of the present invention relates to the zirconium-based metal organic framework for using as a heavy metal adsorbent in a condensate comprising at least a tetravalent zirconium ion (Zr4+) and a bidentate or tridentate linking ligand bonding the said tetravalent zirconium ion (Zr4+), wherein the zirconium-based metal organic framework according to the present invention may be subject to a surface treatment with a solution of alkali metal hydroxide to improve or enhance the efficiency in the heavy metal adsorption in the condensate.
The second aspect of the present invention relates to a method for preparing the zirconium-based metal organic framework for using as a heavy metal adsorbent in the condensate comprising the steps of:
Optionally, the method for preparing the zirconium-based metal organic framework according to the present invention may further comprise the step of (d) contacting the reaction product obtained from step (c) with an aqueous solution of alkali metal hydroxide at ambient temperature for 12-36 hours.
The third aspect of the present invention relates to a process for removing heavy metals in the condensate comprising contacting the condensate with the adsorbent comprising the zirconium-based metal organic framework according to the present invention.
An objective of the present invention is to provide the zirconium-based metal organic framework with the abilities to adsorb, remove, or reduce the contaminants which are heavy metal compounds, especially arsenic (As) and mercury (Hg) which may be in the form of compounds containing such heavy metals in the condensate.
Another objective of the present invention is to provide the method for preparing the zirconium-based metal organic framework where the framework's properties can be optimized for using as the aforementioned contaminant adsorbent in the condensate.
Moreover, the present invention is also aimed to provide the process for removing the aforementioned contaminants from the condensate by using an adsorbent which is a zirconium-based metal organic framework according to the present invention or an adsorbent comprising a zirconium-based metal organic framework according to the present invention.
The zirconium-based metal organic framework prepared and characterized according to the present invention showed the great efficiency in adsorbing heavy metal compounds, especially arsenic and mercury in the condensate. It can remove up to about 85% of arsenic compound in the condensate and can remove up to about 99% of mercury compound in the condensate. Moreover, it was also found that the zirconium-based metal organic framework according to the present invention gave significantly higher percent removal of arsenic and mercury compounds in the condensate than other types of metal-organic framework commonly available.
Any aspects shown herein shall encompass the application to other aspects of the present invention as well, unless stated otherwise.
Technical terms and scientific terms used herein have meanings as understood by a person of ordinary skill in the art, unless specified otherwise.
Throughout the present invention, the term “about” is used to indicate that any values appearing or shown herein may be varied or deviate. Such variation or deviation may be caused by equipment error, or method used to determine the values.
The terms “consist(s) of,” “comprise(s),” “contain(s),” and “include(s)” are open-end verbs. For example, any method which “consists of,” “comprises,” “contains” or “includes” one component or multiple components or one step or multiple steps is not limited to only one component or one step or multiple steps or multiple components, but also encompasses components or steps that are not specified.
Tools, devices, methods, materials, or chemicals mentioned herein, unless specified otherwise, mean the tools, devices, methods, materials, or chemicals generally used or practiced by a person skilled in the art.
All components and/or methods disclosed and claimed in the present invention are intended to cover the aspects of the invention obtained from an action, a practice, a modification or a change of any factors which does not require any experiment that is substantially different from the present invention and gives properties and utility and provides the same effect as the aspects of the present invention according to the judgement of a person of ordinary skill in the art, although not specifically stated in the claims. Accordingly, substitutions or analogues of the aspects of the present invention and any slight modifications or changes that is clearly apparent to a person of ordinary skill in the art, are considered to be within the spirit, scope, and concept of the present invention as well.
The term “condensate” according to the present invention shall encompass the “condensate oil” or “natural gas liquid (NGL)” or “natural gas condensate” generally used in the art. As an example, the term “condensate” encompasses a mixture of liquid hydrocarbon having a molecular weight in a range of hydrocarbon containing from 1-14 carbon atoms, preferably 3-14 atoms.
The aspects of the present invention will now be described in more detail.
The first aspect of the present invention relates to the zirconium-based metal organic framework for using as a heavy metal adsorbent in a condensate comprising at least a tetravalent zirconium ion (Zr4+) and a bidentate or tridentate linking ligand bonding the said tetravalent zirconium ion (Zr4+).
In an alternative embodiment, the said zirconium-based metal organic framework is subject to a surface treatment with a solution of alkali metal hydroxide, especially subject to the surface treatment with the solution of alkali metal hydroxide with a controlled pH in a range of 7-12, preferably in a range of 7-8.
As an example, the surface treatment with such solution of alkali metal hydroxide may be conducted at ambient temperature for 12-36 hours.
The alkali metal hydroxide suitable for the surface treatment according to the present invention may be selected from a group consisting of sodium hydroxide, potassium hydroxide, and a mixture thereof.
Preferably, such alkali metal hydroxide solution is an aqueous solution of sodium hydroxide.
The linking ligand may be selected from a group consisting of 1,4-benzenedicarboxylic acid, 1,3,5-benzenetricarboxylic acid, But-2-enedioic acid, and a mixture thereof.
In a more specific embodiment, the tetravalent zirconium ion (Zr4+) is derived either from zirconium tetrachloride, zirconium oxychloride, zirconium oxychloride octahydrate, zirconium dioxide, zirconium tetrahydroxide, or a mixture thereof.
Preferably, the tetravalent zirconium ion (Zr4+) is derived from zirconium tetrachloride or zirconium oxychloride octahydrate.
The zirconium-based metal organic framework according to the present invention comprises a cluster node of 6 zirconium atoms (Zr6 cluster node) and 8 oxygen atoms partially linked to the linking ligand.
Preferably, the zirconium-based metal organic framework has a mole ratio of the tetravalent zirconium ion (Zr4+) to the linking ligand in a range of 1:1-3.
Moreover, the zirconium-based metal organic framework has an average BET surface area in a range of 300-1000 m2/g.
Preferably, the zirconium-based metal organic framework according to the present invention has an average pore volume in a range of 0.2-1.2 cm3/g and has an average pore diameter in a range of 3-5 nm.
Also preferably, the zirconium-based metal organic framework has a nitrogen adsorption-desorption isotherm type I or IV.
The zirconium-based metal organic framework according to the present invention is suitable especially for using as an arsenic and/or mercury adsorbent in the condensate.
Moreover, the present invention also relates to an adsorbent comprising the zirconium-based metal organic framework with the aforementioned characteristics according to the present invention.
The second aspect of the present invention relates to the method for preparing the zirconium-based metal organic framework for using as a heavy metal adsorbent in the condensate.
The method for preparing the zirconium-based metal organic framework for using as the heavy metal adsorbent in the condensate according to the present invention comprises the steps of:
The method for preparing the zirconium-based metal organic framework according to the present invention may further comprise the step (d) of contacting a reaction product obtained from step (c) with an aqueous solution of alkali metal hydroxide at ambient temperature for 12-36 hours.
Preferably, in step (d), pH of the aqueous solution of alkali metal hydroxide is controlled in a range of 7-12, preferably in a range of 7-8.
Such alkali metal hydroxide used in step (d) can be selected from a group consisting of sodium hydroxide, potassium hydroxide, and a mixture thereof.
Preferably, the aqueous solution of alkali metal hydroxide according to the method of the present invention is the aqueous solution of sodium hydroxide.
In a further aspect, the method for preparing the said zirconium-based metal organic framework further comprises step (e) of washing a product obtained from step (d) with the solvent and drying the product at a temperature ranging from 80-150° C. for 6-12 hours. Preferably, in step (e), the solvent is water.
In a specific embodiment, a mole ratio of the zirconium compound to the linking ligand in step (a) is in a range of 1:1-3.
Alternatively, a mole ratio of the zirconium compound to the modulating agent in step (a) is in a range of 1:4-6.
Optionally, a mole ratio of the zirconium compound to the modulating agent in step (a) is in a range of 1:300-400.
In a specific embodiment of the present invention, the method for preparing the zirconium-based metal organic framework comprises the steps of:
In a more specific embodiment of the present invention, the method for preparing the zirconium-based metal organic framework comprises the steps of:
In another specific embodiment of the invention, the method for preparing the zirconium-based metal organic framework comprises the steps of:
The preferred zirconium compound according to the method of the present invention may be selected from a group consisting of zirconium tetrachloride, zirconium oxychloride, zirconium oxychloride octahydrate, zirconium dioxide, zirconium tetrahydroxide, and a mixture thereof.
More preferably, the zirconium compound is zirconium oxychloride octahydrate or zirconium tetrachloride.
The preferred linking ligand according to the method of the present invention may be selected from a group consisting of 1,4-benzenedicarboxylic acid, 1,3,5-benzenetricarboxylic acid, But-2-enedioic acid, and a mixture thereof.
The preferred modulating agent according to the method of the present invention may be selected from a group consisting of formic acid, acetic acid, propionic acid, and a mixture thereof.
Even more preferably, the modulating agent is formic acid or acetic acid.
According to the method of the present invention, the solvent usable in steps (a) and (c) may be water and/or the organic solvent, e.g., acetone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), alcohol (alcohol) such as methanol, ethanol, etc.
Specifically, in step (a), the solvent may be selected from a group consisting of dimethylformamide, water, dimethyl sulfoxide, methanol, ethanol, and a mixture thereof.
Preferably, in step (a), the solvent is dimethylformamide or water.
Specifically, in step (c), the solvent may be selected from a group consisting of dimethylformamide, acetone, methanol, ethanol, water, and a mixture thereof.
The third aspect of the present invention relates to the process for removing heavy metals in the condensate comprising contacting the condensate with the adsorbent comprising the zirconium-based metal organic framework characterized according to the present invention or prepared according to the method of the present invention.
In a specific embodiment, the heavy metal removal process according to the present invention comprises contacting the condensate with the adsorbent which is performed at a temperature ranging from 18-80° C. and a pressure ranging from 1-30 bars.
Now, the invention will be described in more detail with reference to the examples of experiment and the accompanying drawings. However, these examples shall not be deemed to limit the scope of the present invention.
Prepare the examples of zirconium-based metal organic framework according to the present invention (Examples 1-3) using the chemicals, methods, and conditions as follows.
Dissolved ZrOCl2·8H2O and 1,4-benzenedicarboxylic acid (the mole ratio of ZrOCl2·8H2O to 1,4-benzenedicarboxylic acid equal to about 1:1) in DMF. The resulting mixed solution (that is, the reaction mixture) was subject to sonication for 1 minute. Then, reacted by heating such mixed solution in an oven at a temperature of 120° C. for 24 hours. After completion, the resulting solid product was collected by centrifuging. The product was washed with DMF (3 times) and acetone (3 times), and then dried at a temperature of 150° C. under vacuum for 12 hours. Then, the dried product surface was treated by stirring in an aqueous solution of NaOH for 24 hours. After completion, washed with deionized water (DI) (3 times) and dried at a temperature of 150° C. under vacuum for 12 hours to obtain the final product as a white solid.
Dissolved ZrOCl2·8H2O and But-2-enedioic acid (the mole ratio of ZrOCl2·8H2O to But-2-enedioic acid equal to about 1:1) in a mixture between water and formic acid (the mole ratio of ZrOCl2·8H2O to formic acid equal to about 1:6). The resulting mixed solution (that is, the reaction mixture) was subject to sonication for 5 minutes. Then, reacted by heating such mixed solution in an oven at a temperature of 100° C. for 6 hours. After completion, the resulting solid product was collected by centrifuging. The product was washed with deionized water (3 times) and ethanol (3 times), and then dried at a temperature of 150° C. under vacuum for 12 hours to obtain the final product as a white solid.
Dissolved ZrCl4 and 1,3,5-benzenetricarboxylic acid (the mole ratio of ZrCl4 to 1,3,5-benzenetricarboxylic acid at about 1:3) in a mixture between DMF and formic acid (the mole ratio of ZrCl4 to formic acid at about 1:358). The mixed solution was subject to sonication for 20 minutes. Then, reacted by heating such mixed solution in an oven at a temperature of 130° C. for 48 hours. After completion, the resulting solid product was collected by centrifuging. The product was washed with DMF (3 times) and ethanol (3 times), and then dried at a temperature of 150° C. under vacuum for 12 hours. Then, such dried product surface was treated by stirring in an aqueous solution of NaOH for 24 hours. After completion, washed with DI water (3 times) and dried at a temperature of 120° C. under vacuum for 12 hours to obtain the final product as a white solid.
The above prepared examples of zirconium-based metal organic framework with different types of linking ligands (Examples 1-3) were further characterized using X-ray powder diffraction technique (XRD) to confirm the structure of the synthesized zirconium-based metal organic framework and nitrogen adsorption measurement technique (N2 adsorption) to characterize the porosity, the average BET surface area, and the pore volume of such examples.
The gel form of the material is one of the advantages as it is a vicious liquid with good stability. The material thus can be used conveniently compared to a powdered material which needs to be formed, for example, into granules before use.
Moreover, a small peak was also found at 2 theta of 6.5° which was a diffraction peak from the defect site in the structure of the metal organic framework of Example 1. The peak at this position would not be found in the simulated pattern of ideal UiO-66 crystal.
Moreover, from the XRD pattern of the three examples, the peaks were found at 2 theta of about 7°-9°, corresponding to the diffraction plane (111) and (200) of the 6-zirconium atom cluster (Zr6 cluster). This shows that the tetravalent zirconium ions (Zr4+) in the structure of Examples 1, 2 and 3 were in the form of 6-zirconium atom cluster.
The analysis results of the average BET surface area and the pore volume of Examples 1-3 and the comparative examples are as shown in Table 1, provided that Comparative Examples A and B are as follows:
According to the present invention, the efficiency in adsorbing the compounds of arsenic (As) and mercury (Hg) has been improved or enhanced by treating the surface of the material with the aqueous solution of alkali metal hydroxide, for example, sodium hydroxide, to increase the amount of hydroxy group (—OH) on the surface of the zirconium-based metal organic framework according to the present invention. Such increased amount of hydroxy group will increase the arsenic-specific active site due to the oxophilicity of arsenic which tends to form bonds with oxygen atoms.
The experiment was conducted to further study the effect of pH of the aqueous solution of sodium hydroxide used in the surface treatment step for the zirconium-based metal organic framework according to the method of the present invention by comparing the efficiencies in adsorbing arsenic compounds of the zirconium-based metal organic framework examples obtained by using the aqueous solution of sodium hydroxide with different pH, i.e., pH of 7, 8, 9, and 10, in the surface treatment step according to the method of the present invention. In the experiment, the pH of the aqueous solution of sodium hydroxide before being added to the dried zirconium-based metal organic framework example in step (c) (herein represented by pHNaOH aq before treatment) and the pH of parts of the aqueous solution of sodium hydroxide during surface treatment (herein represented by pHNaOH aq during treatment) were measured. The surface treatment is conducted at ambient temperature for 24 hours.
The initial removal of arsenic compounds in water was tested using the zirconium-based metal organic framework examples obtained by using the aqueous solution of sodium hydroxide at the different pH. The details are as follows.
The experiment result is shown in Table 2.
The experiment result in Table 2 shows that the zirconium-based metal organic framework examples prepared by treating with the aqueous solution of sodium hydroxide with pH of 7-10 had a good removal ability for the arsenic compounds, i.e., As(III) and As(V). The zirconium-based metal organic framework examples prepared by treating with the aqueous solution of sodium hydroxide with pH of 7 and 8 had the highest removal ability for arsenic.
Moreover, the initial adsorption efficiencies for the arsenic compounds, i.e., As(III) and As(V), in water of the zirconium-based metal organic framework examples according to the present invention and the comparative examples were compared according to the above test method. The experiment result is as shown in Table 3 below.
From the experiment result, when comparing between the structures with the same type of metal centres and linking ligands, it was found that surface treatment with the aqueous solution of sodium hydroxide with pH of 7-12 (Examples 1-3 and Comparative Example B) can significantly improve or enhance the ability to adsorb arsenic compounds, particularly As(III), of the zirconium-based metal organic framework, compared to the example that is not subject to surface treatment (Comparative Example A). However, Examples 1 and 2 prepared using chemicals, ratios, and particular steps according to the method of the present invention gave the higher percent removal of arsenic compounds, where Example 1 gave the highest percent removal of As(III) and As(V).
The efficiency in adsorbing arsenic and mercury compounds in the condensate examples obtained from two different sources was tested using the adsorbent, i.e., the zirconium-based metal organic framework examples prepared according to the method of the present invention (Examples 1-3) and Comparative Examples A-G which are the metal organic frameworks containing the different types of metal centres and linking ligands. The details are as follows.
The test result on the efficiency in adsorbing arsenic and mercury compounds in the condensate examples derived from Sources 1 and 2 using the different types of metal organic frameworks (Examples 1-3 and Comparative Examples aforementioned) as the adsorbent is shown in Table 4.
From the above experiment result, it was found that when comparing between the zirconium-based metal organic frameworks (i.e., Examples 1-3 and Comparative Examples A, C), the zirconium-based metal organic frameworks according to the present invention had the significantly superior efficiency in adsorbing the arsenic compounds in the condensate (from both Sources 1 and 2) than the comparative examples. That is, when contemplating the structures with the same type of inking ligands, it was found that Example 1 gave the percent removal of arsenic compounds in the condensate from Source 1 of up to about 85% and in the condensate from Source 2 of up to about 71%, while Comparative Example A gave the percent removal of arsenic compounds in the condensate from Source 1 of about 52% and in the condensate from Source 2 of about 54%. From such result, it clearly shows that the method for preparing the zirconium-based metal organic framework according to the method of the present invention can significantly improve the arsenic compound adsorption efficiency.
When contemplating the structures with different types of linking ligands, it was found that Comparative Example C gave the percent removal of arsenic compounds in the condensate from Source 1 of about 48% and from Source 2 of about 36%, while Examples 1-3 gave the percent removal of arsenic compounds in the condensate from Source 1 of about 85% (Example 1), 73% (Example 2), and 71% (Example 3) and in a condensate from Source 2 of about 72% (Example 1), 61% (Example 2), and 67% (Example 3).
Moreover, when comparing between the meta-organic frameworks with different types of metal centres and/or linking ligands (i.e., Examples 1-3 and Comparative Examples D, E), it was found that the zirconium-based metal organic frameworks according to the present invention (Examples 1-3) gave the significantly higher percent removal of arsenic compounds in the condensate from both Sources 1 and 2 than that of the comparative examples.
For example, when contemplating the structures having the same type of linking ligands but having different types of metal centres, it was found that Example 3 (metal centre being zirconium) gave the percent removal of arsenic compounds in the condensate from Source 2 of about 67%, while Comparative Example E (metal centre being iron) gave the percent removal of arsenic compounds in the condensate from Source 2 of about 45%. From such result, it clearly shows that the metal organic frameworks with zirconium metal centre according to the present invention had the significantly superior arsenic compound adsorption efficiency compared to that of the metal organic frameworks with other types of metal centres.
Best mode of the invention is as described in the detailed description of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2101003971 | Jun 2021 | TH | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2022/056061 | 6/29/2022 | WO |
