GB2607193A

GB2607193A - Adsorbent materials

Info

Publication number: GB2607193A
Application number: GB2207571.7A
Authority: GB
Inventors: David McDonnell William; William John Smith Andrew
Original assignee: Johnson Matthey PLC
Current assignee: Johnson Matthey PLC
Priority date: 2021-05-27
Filing date: 2022-05-24
Publication date: 2022-11-30
Also published as: GB202107524D0; WO2022248845A1; GB202207571D0

Abstract

A doped zeolite with the BEA framework and a silica to aluminium ratio of between 100:1 and 5:1. The beta zeolite is doped with palladium and bismuth. If any metals other than Al, Pd and Bi are present, they only comprise less than 0.5 wt% of the total weight of the doped zeolite. Preferably the material comprises between 0.1 and 5 wt% of the total weight of the doped zeolite, more preferably between 0.2 and 2 wt%. The material may preferably comprise between 0.05 and 2 wt% Bi and more preferably between 0.1 and 0.3 wt%. The doped zeolite may be used for the adsorption of ethylene. Preferably the doped zeolite may be used in a packaging insert wherein the doped zeolite is between two ethylene permeable layers. This packaging insert may optionally be used in a container containing perishable organic matter.

Description

Adsorbent Materials

Field of the Invention

The present invention relates to metal-doped zeolites and their use for adsorbing ethylene from perishable organic matter such as fruit, vegetables and cut flowers.

Background

The over-ripening or spoiling of fruit, vegetables and other organic matter during transit or storage can lead to significant produce loss and wastage. This is an increasing issue for those involved in fresh produce supply chains which may involve long transit times and variable climatic conditions. Modification of the atmosphere in which the organic matter is stored has been shown to be an effective strategy to prolong produce life. For example, alterations in oxygen and carbon dioxide levels within produce packaging can reduce produce respiration rates and therefore slow down the spoiling of fresh produce.

Other strategies involve the removal of volatile organic compounds (VOCs) from within, or surrounding, the produce packaging. VOCs are typically emitted by the produce itself, or may be present in the environment in which the produce is stored or transported. The presence of such VOCs can, for example, accelerate the spoiling of produce, lead to unwanted odours or tastes, or produce colour changes or other changes in appearance.

One such VOC is ethylene. Ethylene is a plant hormone and has a key role in many physiological processes in plants. For example, exogenous ethylene can initiate fruit ripening which in turn can lead to release of ethylene as the fruit ripens leading to high local concentrations. Other fresh produce types are also sensitive to ethylene even if their own ethylene production is low. The rate of ethylene generation can be a key factor in determining local ethylene concentrations, and this rate varies significantly between produce types. Excessive ethylene levels can lead to, for example, the premature ripening of fruit and vegetables, the wilting of fresh flowers, and the loss of green colour and an increase in bitterness of vegetables.

The control of ambient ethylene levels has been found to be effective in prolonging the shelf-life of many horticultural products, and various methods of ethylene control are utilised commercially. Methods include those based on ethylene adsorption and oxidation, for example the use of potassium permanganate.

Palladium-doped zeolites have been found to act as ethylene adsorbents. For example, it is described in W02007/052074 (Johnson Matthey Public Limited Company) that palladium-doped ZSM-5 may be used to adsorb VOCs, such as ethylene, which are derived from organic matter.

The rate of generation of ethylene by different types of organic matter can vary significantly, which can lead to high local ethylene concentrations. There remains a need to develop additional adsorbent materials with increased capacity and / or with different rates of adsorption, and therefore with the potential to enhance produce shelf-life.

Summary of the Invention

It has been surprisingly found that the addition of bismuth to palladium-doped zeolite materials with a BEA framework type can yield compositions with an enhanced ethylene adsorption profile, in particular for the adsorption of ethylene within fresh produce packages. Surprisingly, the addition of bismuth to palladium-doped zeolites with framework types other than BEA leads to only a minor improvement or a decrease in ethylene absorbing activity. The framework type BEA is also referred to as f3 in the literature.

In a first aspect the invention relates to a doped zeolite having the BEA framework type and a silica to alumina ratio (SAR) between 100: 1 and 5: 1, wherein the zeolite is doped with palladium and bismuth and wherein the content of any individual metal other than aluminium, bismuth and palladium is 0.5 wt% based on the total weight of doped zeolite.

In a second aspect the invention relates to the use of a doped zeolite according to the first aspect for the adsorption of ethylene. The materials described herein have particular utility for the adsorption of ethylene derived from perishable organic matter, such as fruit, vegetables or cut flowers.

In a third aspect the invention relates to a packaging insert for the adsorption of ethylene, wherein the insert is in the form of a sachet comprising: a first ethylene-permeable layer and a second ethylene-permeable layer sealed together at the edges of each layer; wherein a doped zeolite according to the first aspect is present between the layers..

A packaging insert is a material which is intended to be used in conjunction with packaging in order to adsorb ethylene from perishable organic matter held within the packaging.

Typically, perishable organic matter is stored and / or transported in a packaging structure, such as a crate, bag, box, tray, or punnet. Therefore, in a fourth aspect the invention relates to a packaging structure comprising a container, perishable organic matter and a packaging insert according to the third aspect. Particularly preferred contains are a crate, a bag, a bottle, a box, a tray or a punnet.

Description of the Fiqures

Figure 1 shows the ethylene removal by 1 wt% Pd BEA zeolite (SAR=28) samples doped with different amounts of bismuth.

Figure 2 shows the ethylene removal by 0.4 wt% Pd BEA zeolite (SAR=28) samples doped with different amounts of bismuth.

Figure 3 shows the ethylene removal by 1 wt% Pd or 1 wt% Pd 0.2 wt% Bi samples with framework types BEA, M Fl and CHA.

Figure 4 shows the results of a fruit trial of 1 wt% Pd / 0.2 wt% Bi / BEA zeolite (SAR=28) Figure 5 shows the results of a fruit trial of 0.4 wt% Pd /0.2 wt% Bit BEA zeolite (SAR=28) Detailed Description Preferred and/or optional features of the invention will now be set out. Any aspect of the invention may be combined with any other aspect of the invention unless the context demands otherwise. Any of the preferred and/or optional features of any aspect may be combined, either singly or in combination, with any aspect of the invention unless the context demands otherwise.

Any sub-headings are included for convenience only, and are not to be construed as limiting the disclosure in any way Zeolite The invention relates to zeolites which are doped with bismuth and palladium and their utility for adsorption of ethylene.

Zeolites are classified according to framework type, such framework types describing the connectivity of the tetrahedrally coordinated atoms of the framework in the highest possible symmetry. Three letter codes are assigned to each framework type in accordance with the "IUPAC Commission on Zeolite Nomenclature" and/or the "Structure Commission of the International Zeolite Association".

In all aspects of the present invention the zeolite has the beta (BEA) framework type and a silica to alumina ratio (SAR) between 100: 1 and 5: 1. It is preferred that the zeolite has a SAR of 10: 1 to 50: 1, such as 20: 1 to 40: 1.

US2009/0112006 (LyondellBasell Industries) describes a catalyst comprising palladium, lead, bismuth and a titanium or vanadium zeolite and their use as epoxidation catalysts.

Unlike the doped zeolites of the present invention, the zeolites described in these references are the titanium or vanadium counterparts of the aluminosilicate structure in which Ti or V units have replaced Al. The zeolites in this reference have a SAR » 100: 1.

CN101121132A (China Petroleum & Chemical Corporation) describes a catalyst for the transalkylation and dealkylation of aromatic hydrocarbons. The catalyst comprises a hydrogen type zeolite having a SAR of 12 to 70, 0.002-8 parts molybdenum oxide, 0.005- 8 parts of palladium or nickel oxide, 0.02-8 parts of an oxide selected from at least one of iron, bismuth, tin, platinum, rhodium, magnesium or titanium, and 10-60 parts of binder. Examples 2, 4 and 7 include 0.1-0.3 wt% palladium and 1.9-2.4 wt% bismuth, and in addition contain various other dopant metals, which are impregnated on a mixture of zeolite frameworks (13/MOR or pimOR/ZSM-5) In the present invention the content of any individual metal other than aluminium, bismuth and palladium is 0.5 wt% based on the total weight of the doped zeolite, such as 0.2 wt%, such as 0.1 wt%. It is preferred that the combined content of metals (other than aluminium, bismuth and palladium) is 0.5 wt%, such as 0.2 wt%, such as 0.1 wt%.

The content of metals within the doped zeolite can be measured by any suitable technique known to those skilled in the art, such as by Inductively Coupled Plasma (ICP) spectroscopy. For the avoidance of doubt, the content of each of bismuth and palladium may be 0.5 wt% or 0.5 wt%.

The zeolite framework may be counterbalanced by cations, such as by cations of alkali and/or alkaline earth elements (e.g., Na, K, Mg, Ca, Sr, and Ba), ammonium cations and/or protons. Where these are present, the content of each metal is 0.5 wt% based on the total weight of the doped zeolite. Preferably, the zeolite is in the hydrogen form.

The zeolite is doped with palladium, and typically comprises 0.1 to 5 wt% palladium based on the total weight of doped zeolite, preferably 0.2 to 2 wt%, 0.3 to 1.6 wt%, 0.3 to 1.4 wt%, more preferably 0.3 to 1.2 wt%.

It has been unexpectedly found that the addition of bismuth can lead to an enhanced ethylene adsorption profile. It should be noted that the term "adsorbent" and "adsorption" as used herein should not be construed as being limited to the uptake of ethylene to a particular route and includes the chemical conversion of ethylene into secondary compounds. As used herein, the term "adsorbent" is synonymous with "absorbent".

The zeolite typically comprises 0.05 to 2 wt% bismuth based on the total weight of doped zeolite, preferably 0.05 to 1%. A level of about 0.2 wt% bismuth has been shown to provide a particularly high ethylene scavenging rate, and it is therefore preferred that the zeolite comprises 0.1 to 0.3 wt% bismuth.

Typically, the zeolite comprises 0.2 to 2 wt% palladium and 0.05 to 1 wt% bismuth, preferably 0.05 to 0.5 wt% bismuth, more preferably 0.15 to 0.35 wt%. More preferably, the zeolite comprises 0.2 to 1.2 wt% palladium and 0.05 to 1 wt% bismuth, preferably 0.05 to 0.5 wt% bismuth, more preferably 0.15 to 0.35 wt% bismuth.

It is preferred that, if present, the content of molybdenum oxide in the doped zeolite is less than 0.002 vvt% based on the total weight of doped zeolite. Preferably the content of molybdenum oxide is less than 0.001 wt%. It is preferred that the zeolite is free of molybdenum oxide.

It is preferred that the zeolite is free from phases other than BEA. The presence of other zeolite phases can be determined by X-ray diffraction.

The zeolites as described herein may be advantageously used for the adsorption of ethylene, in particular ethylene originating from perishable organic matter, such as fruit, vegetables, cut flowers or other foodstuffs. In preferred embodiments the perishable organic matter is selected from avocados, bananas, broccoli, cabbage, cut flowers, kiwi fruits, nectarines, melons, onions, pears, potatoes, raspberries and strawberries.

Packaging insert A packaging insert is a material which is intended to be used in conjunction with packaging in order to adsorb ethylene from perishable organic matter held within the packaging.

A preferred packaging insert is a sachet. As used herein, a "sachet" means an article 20 comprising: a first ethylene-permeable layer and a second ethylene-permeable layer sealed together at the edges of each layer; wherein the doped zeolite is present between the layers.

A preferred material for the ethylene-permeable layer is a fibrous material, preferably a fibrous non-woven material. Exemplary and preferred material for the ethylene-permeable layer is TyvekTm which is a non-woven LOPE. An alternative exemplary and preferred material is glassine.

In some embodiments the sachet may be formed by folding a single ethylene-permeable material to provide a first ethylene-permeable layer and a second ethylene-permeable layer, providing doped zeolite between the layers, and sealing the remaining edges together to produce a sachet.

Packaging structure As used herein, the term "packaging structure" means an article comprising a container, perishable organic matter and a packaging insert.

Examples of suitable containers are a crate, a bag, a bottle, a box, a tray or a punnet. Typically, one or more packaging inserts will be included within the container, either loose or adhered to a surface of the container.

The presence of a palladium and bismuth-doped zeolite with the BEA structure may be used to control ethylene levels within such packaging structures.

The packaging structure may comprise a polymer film, such as a polyamide, polyethylene, polyethylene terephthalate, or polypropylene film, or blends or co-polymers thereof. The film may be used to seal the packaging structure, for example to seal a punnet or tray, or may, for example, form the majority of the packaging structure, such as in the case of a bag. The polymer film may be a single polymer layer, or may comprise a laminate structure of two or more layers which may be different materials.

The packaging structure may comprise a polymer film that is perforated, for example with holes or slits which are typically 50-500 pm in diameter or length as appropriate. Such perforations may be formed by laser perforation. In use, the degree of perforation may be used to control the gaseous composition within the packaging structure once produce has been placed inside, leading to a lower oxygen content. Such a packaging structure may be known as modified atmosphere packaging. In a preferred embodiment the atmosphere within the packaging structure comprises less than around 20% oxygen by volume, such as less than 18% oxygen by volume, for example 10-15% oxygen by volume.

The zeolites are typically used in the form of a powder or may be formulated, for example as granules.

The invention is now illustrated with the following non-limiting examples: 25 Examples Sample Preparation Palladium and bismuth doped BEA zeolite: Samples were prepared by incipient wetness impregnation. Solid Bi nitrate and Pd nitrate (--.8%) solution were weighed out to give the desired weight % of metal on the zeolite. The Bi nitrate was fully dissolved, by manual stirring, into the Pd nitrate solution. This solution was then diluted with water up to around 90-95% pore fill of the zeolite. The solution was added to the H-BEA zeolite (SAR 28) powder with stirring. The sample was then dried at 105°C (2-16 h) and then calcined at 500°C for 2 h with a 10°C/min ramp rate.

Samples of 1% Pd MFI, 1% Pd 0.2% Bi MFI, 1% Pd CHA and 1% Pd 0.2% Bi CHA were prepared according to the above method using MFI (SAR 23) and chabazite CHA (SAR 22) in place of H-BEA zeolite (BEA).

Sample Testing -Plug flow test The plug flow test gives an ultimate capacity for a sample by passing a known concentration of ethylene over it and measuring when ethylene is no longer adsorbed. A fixed bed of 0.2 g of sample pelletized to 250-355 pm was loaded into a quartz tube with an I.D. of 4 mm. The tube was fitted onto a plug flow reactor and a gas mixture of Ethylene/N2/02 was passed through a water bubbler to humidify it and over the sample.

Data was collected using a mass spectrometer and ethylene mass peaks 26 and 27 were recorded to give an ethylene breakthrough curve.

Effect of bismuth content on ethylene uptake at 1% Pd BEA A series of doped 1%Pd/#%Bi BEA zeolite samples were prepared and tested for ethylene uptake using the plug flow test (Figure 1). The results show ethylene uptake across the range of samples tested with the highest uptake at 0.2 and 0.3 wt% Bi.

Effect of bismuth content on ethylene uptake at 0.4% Pd BEA A series of doped 0.4%Pd/#%Bi BEA zeolite samples were prepared and tested for ethylene uptake using the plug flow test (Figure 2). The results show ethylene uptake across the range of samples tested with the highest uptake at 0.2 wt% Bi.

Effect of zeolite structure A series of doped zeolites having 1% Pd or 1% Pd /0.2% Bi with the framework BEA, MFI or CHA were prepared and tested for ethylene uptake using the plug flow test (Figure 3). The results show that there was a notable improvement in ethylene uptake in the case of BEA zeolite. Bi-doping only moderately improved the activity of 1% Pd MFI, and Bi-doping decreased the ethylene uptake of 1% Pd CHA.

Fruit trials A series of fruit trials were carried out using Pd / Bi doped BEA. Each zeolite sample was sealed with 1 kg of pears in a polyethylene bag containing mechanical perforations made using 700 micron diameter needles (XtendTM Bag). The bag was stored at 0°C. Ethylene levels in the fruit bag were measured every few days by taking a sample of the head space gas and measuring by gas chromatography. The steady state gas compositions achieved during the storage at 0°C are typically 18-20 vol% 02 and 0.5-1.0 vol% 002.

Trial 1 -The 1%Pd/0.2%Bi/BEA zeolite (SAR 28) sample was tested in a fruit trial alongside undoped 0.4%Pd/BEA zeolite (SAR 28). The examples used either 1 g of 0.4%Pd/BEA, 2 g of 0.4%Pd/BEA, or 1 g of 1%Pd/0.2%Bi/BEA. In each case, the materials were provided in a tray within the bag. The control was an XtendTM modified atmosphere bag with no ethylene absorber added. Ethylene levels were recorded and averaged over four bags running concurrently for every sample (Figure 4). The bag without an ethylene absorber was above desired ethylene levels within 1 day and quickly rose to levels above that displayed on Figure 1, reaching 7000 ppb in 15 days. As can be seen 1 g of the Bi-doped sample shows prolonged ethylene adsorption and remains effective after 47 days.

Trial 2 -The 0.4%Pd/0.2cYoBi/BEA zeolite (SAR 28) sample was tested in a fruit trial alongside undoped 0.4°/oPd/BEA zeolite (SAR 28). The samples were provided either in a tray within the bag or in Tyvek sachets (TyvekTm grade 1059B available from DuPont). 2 g of zeolite material was used in each case. Ethylene levels were recorded every few days (Figure 5). As can be seen 2 g of the Bi-doped samples showed significantly improved performance in comparison with the un-doped sample as a powder and in sachets. Sachets containing the Si-doped sample showed prolonged ethylene adsorption until the end of the study (-80 days).

Claims

Claims 1 A doped zeolite having the BEA framework type and a silica to alumina ratio (SAR) between 100: 1 and 5: 1, wherein: the zeolite is doped with palladium and bismuth, and the content of any individual metal other than aluminium, bismuth and palladium is 0.5 wt% based on the total weight of doped zeolite.
2. A doped zeolite according to claim 1, wherein the doped zeolite comprises 0.1 to 5 wt% palladium based on the total weight of doped zeolite.
3. A doped zeolite according to claim 1 or claim 2, wherein the doped zeolite comprises 0.2 to 2 wt% palladium based on the total weight of doped zeolite.
4. A doped zeolite according to any of claims 1 to 3, wherein the doped zeolite comprises 0.05 to 2 wt% bismuth based on the total weight of doped zeolite.
A doped zeolite according to any of claims 1 to 4, wherein the zeolite comprises 0.1 to 0.3 wt% bismuth based on the total weight of doped zeolite.
6 A doped zeolite according to any of claims 1 to 5, wherein, if present, the content of molybdenum oxide is less than 0.002 wt% based on the total weight of doped zeolite.
7 A doped zeolite according to any of claims 1 to 6, where the zeolite has a SAR of 10: 1 to 50:1.
8. A doped zeolite according to any of claims 1 to 7, where the content of any individual metal other than aluminium, bismuth and palladium is 0.2 wt% based on the total weight of doped zeolite.
9. A doped zeolite according to any of claims 1 to 7, where the content of any individual metal other than aluminium, bismuth and palladium is 5 0.1 wt% based on the total weight of doped zeolite.
A doped zeolite according to any of claims 1 to 9, where zeolite is free from phases other than BEA.
11. A doped zeolite according to any of claims 1 to 10, in the form of a powder.
12. Use of a doped zeolite according to any of claims 1 to 11 for the adsorption of ethylene.
13. A packaging insert for the adsorption of ethylene, wherein the insert is in the form of a sachet comprising: a first ethylene-permeable layer and a second ethylene-permeable layer sealed together at the edges of each layer; wherein a doped zeolite according to any of claims 1 to 11 is present between the layers.
14. A packaging insert according to claim 13, wherein the first and second ethylene-permeable layers are made from a fibrous LDPE.
15. A packaging structure comprising a container, perishable organic matter and a packaging insert according to claim 13 or claim 14.
16. A packaging structure according to claim 15, wherein the container structure is a crate, bag, bottle, box, tray or punnet.
17. A packaging structure according to claim 15 or claim 16, wherein the container is sealed with a polymer film.