Field of the Invention

The present invention relates to an acylation coupling catalyst and acylation coupling method. In particular, but not exclusively, the present invention relates to the coupling of short chain carboxylic acids with aromatic molecules. Use of the acylation coupling catalyst in various acylation coupling methods including in catalytic fast pyrolysis, vapour phase upgrading of pyrolysis vapours and liquid phase upgrading of pyrolysis oil, as well as products derived from these applications of the acylation coupling catalyst, also form part of the present invention.

Background

Typically, pyrolysis oils are produced by condensing vapours of pyrolyzed biomass. Small carboxylic acids can be present in amounts up to 20 wt% in pyrolysis oils. These small carboxylic acids, which are predominantly formic acid and acetic acid, have little fuel value because of their low carbon number and high oxygen content. Small carboxylic acids such as formic acid, acetic acid and propionic acid in particular can be partially lost in the aqueous fraction of the pyrolysis oil, leading to reduced overall carbon efficiency. Further, the acidic and comparatively reactive nature of these molecules leads to difficulties with corrosion and stability of the pyrolysis oil. Therefore, it is generally desirable in the art to improve (upgrade) pyrolysis oils in order to minimise the above- mentioned problems.

It can be difficult to upgrade the initially-formed pyrolysis oil by typical methods such as fractionation because this involves a heating process that causes undesirable effects including carbon loss and polymerization.

The elimination of the carboxylic acids from the pyrolysis oil is also not a preferred solution, because their removal effectively reduces the number of carbon atoms available for oxidation and thereby reduces the maximum utility and/or efficiency as a fuel. It is generally considered to be beneficial to couple these short-chain carboxylic acids to other molecules within the pyrolysis oil. Coupling the carboxylic acids with aromatic molecules (acylation coupling) has been proposed, though a greater number of publications describe acid removal by esterification, hydrogenation or ketonisation. Acylation coupling is thought to be beneficial for at least two reasons. One reason is that the average molecular weight of the coupled product is greater than that of either the carboxylic acid or aromatic molecule by itself, thereby reducing the volatility and improving the efficacy of the pyrolysis oil. A second reason is that it generally leads to a decrease in acidity. The decrease in acidity provides a concomitant decrease in unwanted side-effects as set out above (Bridgwater, A. V., Czemik, S., Diebold, I, Meier, D., Oasma, A., Peackocke, C., Pizkorz, J., Radlein, D. Fast Pyrolysis of Biomass: A Handbook; CPL Press, Newbury Berkshire, UK, 1999).

Carbon-carbon coupling reactions through Friedel-Crafts reactions are known and well-studied. Several catalysts have been studied for e.g. acylation reactions, including for example HF, heteropolyacids and zeolites or zeotypes.

WO 2018/051070 discloses a method of producing hydrocarbons for use in making fuels, especially fuels from bio-derived sources such as wood. The process disclosed herein includes: pyrolysis of biomass to produce phenols and other aromatic molecules; separation of these molecules; hydrogenation of the phenolic molecules to aliphatic alcohols; and alkylation of the other aromatic molecules with the aliphatic alcohols using a zeolite catalyst. It is described there that a larger pore catalyst improved the alkylation step of this process.

Resasco et al. (ChemSusChem, 2017, 10, 2823-2832) disclose an investigation into the coupling of acetic acid with m-cresol. The authors reviewed the use of different kinds of zeolite and determined that large-pore zeolites (HY or H-Beta) provided improved acylation selectivity over a medium-pore zeolite (H-ZSM5).

Mante et al. (Fuel, 2014, 117, 649-659) disclose a fluid catalytic cracking ZSM-5-based additive as a co-catalyst to Y-zeolite based FCC catalysts in the catalytic pyrolysis of hybrid poplar. The authors concluded that the blends gave an increased organic liquid fraction and decreased coke/char and gas yields. Although acylation coupling is not described, the authors note that the ZSM-5 did not have a major effect on the pyrolysis product distribution.

It is desirable to develop new and improved catalysts to assist in the acylation coupling of carboxylic acids to aromatic molecules.

Preferred embodiments of the present invention seek to overcome one or more of the above disadvantages of the prior art. Preferred embodiments of the present invention seek to provide improved methods and catalysts for acylation coupling processes, in particular those which find application in the improvement of fuels and upgrading of pyrolysis oils and pyrolysis vapours.

Summary of the Invention

The present invention generally proposes the use of a mixture of solid acid zeolite catalysts to couple short-chain carboxylic acids with aromatic molecules to form acylated aromatic molecules such as ketones.

According to a first aspect of the invention, there is provided an acylation process comprising contacting a first molecule with a second molecule in the presence of a catalyst to produce an acylated second molecule, wherein the first molecule is an acylating molecule comprising a carboxy group; the second molecule has an aromatic group; and the catalyst comprises a zeolite mixture, the zeolite mixture comprising at least two zeolites, wherein the at least two zeolites comprise a first zeolite having medium-sized pores and a second zeolite having large-sized pores; and the second zeolite has a silica to alumina ratio of more than 5.

Particular advantages are found when the second zeolite has a silica to alumina ratio of between 12 and 100, and/or when the first zeolite has a silica to alumina ratio of between 5 and 300. In preferred embodiments of the methods of the first aspect, the second zeolite is present in an amount of at least 5 wt% based on the total weight of the first and second zeolites. Further advantages are found when the second zeolite is present in an amount of at least 10 wt% based on the total weight of the first and second zeolites, and preferably up to 50 wt% based on the total weight of the first and second zeolites.

In preferred embodiments, the process uses a zeolite mixture which has only first and second zeolites. That is, there is no third (or further) zeolite aside from the first and second zeolites present in such embodiments.

Suitably herein, the first zeolite comprises or is ZSM-5. Further suitably herein, the second zeolite comprises or is zeolite Y. Generally, these are in acid form and so these may alternatively be written herein as HZSM-5 and HY, respectively.

It is further preferred that the contacting is carried out at a temperature of between 300 and 700 °C.

Preferably, the first molecule comprises a carboxylic acid group. Typically, the first molecule may be a monocarboxylic acid, and preferably is a short-chain carboxylic acid so the first molecule may have the general formula R-COOH wherein R is H or Ci-io alkyl. In further preferred examples, the R group of the first molecule is H or C1-3 alkyl. In particularly exemplified embodiments, the first molecule is acetic acid or formic acid.

It is further preferred that the second molecule containing an aromatic moiety is an oxygenated aromatic molecule such as an oxygenated aromatic molecule that comprises an alcohol group. Preferably, the aromatic group of the second molecule comprises an aromatic ring whose ring atoms are all carbon. Where the second molecule has only one aromatic ring, it is therefore preferably not heteroaromatic.

In some embodiments, the first and second molecules are each components of a process stream, such as a process stream derived from biomass. The process stream is typically a stream of molecules that forms during or after a process (e.g. a pyrolysis process) and may become a fuel after further upgrading or processing. Thus, in one embodiment, the product of the process (the process stream comprising acylated second molecule) is further processed to form a fuel. Such further processing can be done according to standard procedures known in the art. Where the process stream is derived from biomass, the process stream may be a pyrolysis-oil or pyrolysis vapours. In some embodiments, a product of the process comprises the one or more process streams comprising acylated second molecule, and the process includes further processing the one or more process streams comprising acylated second molecule to form a fuel.

In some embodiments, the method comprises providing a first stream comprising first molecule, and providing a second stream comprising second molecule, and carrying out acylation coupling between the first and second molecules of the respective streams in the presence of the catalyst.

In some embodiments, the method is carried out during a pyrolysis process. It has been found that particularly suitably the pyrolysis process is carried out in an inert atmosphere.

According to a second aspect of the invention, there is provided a composition prepared by a process according to the first aspect. The preferences set out there apply accordingly.

The composition of the second aspect may be any suitable composition. Specific compositions described herein include pyrolysis-oils, pyrolysis vapours, and fuels, particularly those originating from biomass. Thus, a pyrolysis-oil, pyrolysis vapour, or fuel may be prepared by a process including an upgrading process as described herein.

According to a third aspect of the invention, there is provided a use of a composition comprising a zeolite mixture in an acylation process, wherein the zeolite mixture comprises at least two zeolites, wherein the at least two zeolites comprise a first zeolite having medium-sized pores and a second zeolite having large-sized pores; and the second zeolite has a silica to alumina ratio of more than 5. In preferred embodiments, the use according to the third aspect is use in a process according to the first aspect. Further preferably, the use according to the third aspect produces a composition according to the second aspect. The preferences of the first and second aspects therefore apply equally to the third aspect.

A further aspect of the invention is a catalyst comprising a zeolite mixture, the zeolite mixture comprising two zeolites, the two zeolites comprising a first zeolite having medium-sized pores and a silica to alumina ratio of between 5 and 300; and a second zeolite having large-sized pores and a silica to alumina ratio of between 12 and 100; wherein the second zeolite is present in an amount of at least 5 wt% and up to 50 wt% based on the total weight of the first and second zeolites. In general, the catalyst of this aspect is particularly preferred for use in the process of the first aspect, or to prepare the composition of the second aspect, or in the use according to the third aspect. The preferences set out there apply accordingly.

It will be appreciated that features described in relation to one aspect of the invention may be equally applicable in another aspect of the invention. For example, features described in relation to the first aspect of the invention, may be equally applicable to the second or third aspects of the invention, and vice versa. Some features may not be applicable to, and may be excluded from, particular aspects of the invention, but this will be clear explicitly or from context.

Description of the Drawings

Embodiments of the present invention will now be described, by way of example, and not in any limitative sense, with reference to the accompanying drawings, of which:

Figure 1 shows an example of a reaction scheme between first and second molecules of the invention. According to the example scheme shown in (a), two products are possible: one is a C-C acylation product (2-hydroxy-4-methylacetophenone) and a C-0 esterification product (m-tolyl acetate). A catalyst composition of the invention can be used to provide a preferred C-C product. The example scheme shown in (b) indicates that the non-preferred C-0 product can undergo Fries rearrangement, to provide a preferred C-C product.

Figure 2 is a bar graph showing the effect of the silica to alumina ratio (SAR) of the HZSM-5 and HY zeolites, on the conversion (%) of m-cresol (leftmost set of bars) and on the selectivity (%) for the C-0 product (middle set of bars) and on the selectivity (%) for the C-C product (rightmost set of bars). From left to right on each set of bars, the zeolite mixture used was: 100% HZSM-5 (SAR = 30); 100% HZSM-5 (SAR = 50); 100% HY (SAR = 5); 100% HY (SAR = 12); 100% HY (SAR = 30); 100% HY (SAR = 60); 100% HY (SAR = 80). Reaction conditions are explained in Reference Example 1.

Figure 3 is a line graph showing the relative improvement in selectivity according to the relative proportion of HY included in a zeolite mixture comprising HZSM-5 (SAR 30) and HY (SAR 80). It can be seen that the relative improvement in selectivity is seen even at low %HY. Reaction conditions are set out in Example 2.

Figure 4 is a bar graph showing the selectivity of zeolite mixtures of HZSM-5 and HY for the C-0 and C-C products of the acylation reaction between acetic acid and m-cresol as shown schematically in Figure 1. The set of bars on the left shows the conversion (%) of m-cresol. The middle set of bars show the selectivity for the C-0 esterification product. The set of bars on the right show the selectivity for the C-C acylated product. From left to right on each set, the catalysts used to produce the respective bars are 100% HZSM-5 (SAR 30); 90% HZSM-5 (SAR 30) + 10% HY (SAR 5); 90% HZSM-5 (SAR 30) + 10% HY (SAR 12); 90% HZSM-5 (SAR 30) + 10% HY (SAR 60); 90% HZSM-5 (SAR 30) + 10% HY (SAR 80). Reaction conditions are set out in Example 3.

Figure 5 is a line graph showing the effect of %HY in zeolite catalytic mixtures containing HZSM-5 and HY on the residual solid (wt%) following the catalytic pyrolysis of biomass. In this example, the HY SAR was 80 and the HZSM-5 SAR 30. An increase in residual solid is seen between about 25 and about 50 wt% HY. Reaction conditions are set out in Example 4. Figure 6 corresponds with Figure 4 except that the SAR of the HZSM-5 is 50 instead of 30. Reaction conditions are set out in Example 5.

Figure 7 is a schematic diagram of an overview of a process of vapour phase upgrading. Figure 8 is a schematic diagram of an overview of a process of catalytic fast pyrolysis. Detailed Description

Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. The exemplary embodiments set forth herein are considered to be illustrative and nonlimiting, and various changes may be made without departing from the spirit and scope of the invention. The invention is not limited to the aspects and embodiments specifically described herein but is defined by the appended claims.

All documents mentioned in this text are incorporated herein by reference.

Definitions

For the avoidance of doubt, any theoretical explanations herein are provided for the purposes of improving the understanding of the skilled reader. The inventors do not wish to be bound by these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject-matter described.

Throughout and including the claims which follow, unless context requires otherwise, the word “comprise” and “include” and variations thereof are to be understood to imply the inclusion of the stated feature(s) but not the exclusion of any other feature(s).

As used in this specification and the appended claims, the singular forms “a”, “an” and “the” include plural forms unless context clearly dictates otherwise. Thus, for example, reference to “a molecule” means “one or more molecules” and the like. The term “about” means approximately and refers to a range that is optionally ± 25%, preferably ±10% and most preferably ±1% of the value with which the term is associated.

When a range, or ranges, for various numerical elements are provided, the range or ranges include the values unless provided otherwise. As the skilled person will appreciate, end points of specific ranges or particular values relating to the same feature can be combined to make new ranges.

“Cx-Cy” where x and y are integers refers to the number of carbon atoms in the hydrocarbon chain. For example, C1-C3 alkyl means an alkyl group having between 1 and 3 carbon atoms in the chain. It encompasses each of methyl, ethyl and propyl. It is not intended to limit the arrangement of atoms and so the hydrocarbon can be linear, branched or cyclic as appropriate.

“Heteroaromatic” refers to aromatic groups or compounds which contain a heteroatom in the ring i.e. an atom which is other than carbon. Typical heteroatoms include N, S and O.

In general, the catalysts described herein are used in conjunction with fluids including, for example, liquid phase fluids, such as pyrolysis-oils, or to vapours, such as pyrolysis vapours. In particular, the catalysts described herein are thought to find particular utility with fluids derived from biomass. The term “pyrolysis-oil” used herein refers to an oil, typically derived from a biological source, through the process of pyrolysis.

Where ranges are provided herein, the end-point of the range is included within the range unless explicitly stated otherwise.

As used herein, “zeolite” has the normal meaning in the art and refers to a particular kind of molecular sieve material. Zeolites are traditionally considered to be crystalline or quasi crystalline aluminosilicates. They usually have repeating tetrahedral units TO ₄ , where T is usually A1 and Si. Zeolites have defined arrangements of cavities, channels and/or pores typical of the individual material. They may be natural and synthetic. The label “zeotype” may alternatively be used. The terms “small-size pore”, “medium-size pore” and “large-size pore” are widely accepted terms of art in the field of zeolites. In particular, the pore size is defined by the number of tetrahedral coordinated atoms that make up (surround, form) the pores. Small pores are made up of 8 membered rings, medium pores 10 membered rings and large pores 12 membered rings. Ultra-large or extra-large pore sizes are known, with more than 12 rings. See for example Jacobs and Martens, Pure & Appl. Chem. (Vol. 58, No. 10, 1329, 1986), Ghosh et ah, “Nanoscale Materials in Chemistry” (2 ^nd Ed., Edited by Klabunde K.J. and Richard, R. M., John Wiley & Sons, 2009, Chapter 10, page 334, point 10.2.2) and Vinaches et ah, Molecules (2017, 22, 1307). The present application adopts these definitions as they are accepted in the art.

The number of tetrahedral coordinated atoms in a zeolite structure can be determined by any suitable method such as x-ray diffraction (XRD). The skilled person will be aware of suitable methods.

“Catalytic pyrolysis” includes catalytic upgrading, such as catalytic vapour-phase upgrading of the pyrolysis products, for example when the biomass is pyrolyzed non- catalytically and the products of the pyrolysis are upgraded using a catalytic upgrading process.

Detailed Description. Other Preferences and Embodiments

The present inventors have identified new and useful catalysts comprising zeolites for carrying out acylation reactions. They have surprisingly found that it is possible to provide unexpectedly high degrees of selectivity for desired acylation product by using a mixture of zeolites with different pore sizes and by controlling the silica to alumina ratio (SAR). In particular, they have found that by using a catalyst comprising a mixture of a first zeolite with a medium pore size and a second zeolite with a large pore size and a SAR within a defined range, unexpectedly high increases in selectivity for the desired C-C product result. The standard zeolite catalyst used in acylation coupling reactions in the art is presently HZSM-5, which has a medium pore size. Although previous studies (see e.g. Resasco et al, discussed above) have found that a large-pore zeolite such as HY or H-Beta by itself provides improvements in selectivity compared to HZSM-5, there are practical drawbacks to the use of 100% of the large-pore zeolite (e.g. 100% HY) in the applications described herein i.e. during vapor phase upgrading or catalytic fast pyrolysis. Specifically, 100% HY has been found to produce excessive coke formation in these applications, and this in turn leads to a reduced condensable oil yield. Therefore, 100% HY - although selective - does not afford all the advantages sought by the present inventors and cannot be used on a practical level to upgrade liquid or vapour-phase compositions such as pyrolysis-oils and pyrolysis vapours. Without wishing to be bound by theory, the inventors believe based on their studies that the greater coke formation from the HY is attributable to the large pore size of the zeolite.

The present inventors have unexpectedly found that the SAR of the first and/or second zeolite can also affect the selectivity of the acylation product. Therefore, the inventors believe that by tuning the amount of first and second zeolites used in the catalyst mixture, and by tuning the SAR of these zeolites (especially the SAR of the second zeolite), particularly high selectivity can be achieved.

Specifically, it has been found that mixing even a small amount (e.g. 10 wt%) of large pore zeolite having a relatively high SAR with the medium pore zeolite gives greater acylation selectivity than that of 100% medium pore zeolite as catalyst. This is demonstrated by e.g. Figs. 4 and 6 discussed elsewhere herein. The effect has been found to be especially pronounced when the SAR of the medium pore zeolite is higher - see e.g. Figure 6. That is, increasing the SAR of the medium pore zeolite decreases acylation selectivity. In contrast, increasing the SAR of the large pore zeolite increases acylation selectivity. It is surprising that the effect of the SAR is different for the different pore size zeolites. Especially, the inventors consider that the effect of the large pore zeolite SAR could not be predicted in advance, because the number of active sites would be expected to decrease as the SAR increases.

Accordingly, the present invention provides compositions comprising a mixture of zeolites, and their use in methods of acylation coupling, especially to upgrade fuels and fuel precursors such as pyrolysis-oils and pyrolysis vapours. The zeolite mixtures described herein comprise a first zeolite having medium-sized pores and a second zeolite having large-sized pores, the second zeolite having a SAR of more than 5.

The various features of the invention will now be described in detail. The preferences described in each section should be considered combinable with other preferences described elsewhere.

Catalyst

The processes of the invention use a catalyst comprising a zeolite mixture as described herein for acylation coupling reactions. Specifically, the catalysts discussed herein are used to assist in the formation of a new C-C bond between an acylating molecule and an aromatic molecule.

Zeolite Mixture

In general, the catalyst used in the invention comprises a zeolite mixture comprising first and second zeolites. Put differently, first and second zeolites are combined or mixed or blended together by any suitable means to form the zeolite mixture. The first zeolites have a medium pore size and the second zeolites have a large pore size. As discussed elsewhere, the nomenclature “small pore”, “medium pore” and “large pore” in relation to zeolites and zeotypes has a specific meaning to a person skilled in the art and so will be clearly understood.

There may be one or more types of first zeolites in the zeolite mixture. There may be one or more types of second zeolites in the zeolite mixture. Typical zeolite mixtures are expected to comprise a single type of first zeolite and a single type of second zeolite, e.g. for efficiency or cost reasons.

Typically and preferably, the first and second zeolites are acid zeolites. This is indicated by the prefix “H” in various parts of this disclosure. Bronsted acids are also expected to be typical. In general, aluminosilicates, silicoaluminophosphates and aluminophosphates are suitable zeolites. Pure silica zeolites are not preferred.

Examples of suitable first zeolites will be known to the skilled person and may include zeolites of the type (H)ZSM-5, (H)ZSM-ll (H)ZSM-22, (H)ZSM-35 and (H)ZSM-48.

Examples of suitable second zeolites will be known to the skilled person and may include zeolites of the type (H)Y, (H)ZSM-12, (H)-Beta, and mordenite.

Accordingly, the zeolite mixture may comprise any one or more of (H)ZSM-5,

(H)ZSM-l 1, (H)ZSM-22, (H)ZSM-25 or (H)ZSM-48 and any one or more of (H)Y, (H)ZSM-12, (H)-Beta, and mordenite. Exemplified herein are zeolite mixtures comprising HZSM-5 and HY, and these may be particularly preferred.

As used herein, the H in parentheses means that the zeolite may be in acid form or not. As mentioned elsewhere, acid form is preferred.

In the zeolite mixtures described herein, the first zeolite may be present in an amount of at least 5 wt%, preferably at least 10 wt%, more preferably at least 50 wt% and most preferably at least 70 wt% of the total weight of the first and second zeolites. The first zeolite may be present in an amount of at most 95 wt%, preferably at most 90 wt% and more preferably at most 85 wt% of the total weight of the first and second zeolites. The first zeolite may be present in an amount of between 5-95 wt%, preferably between 10- 95 wt%, more preferably between 50-95 wt% and most preferably between 75-90 wt% of the total weight of the first and second zeolites.

In the zeolite mixture, the second zeolite may be present in an amount of at least 5 wt%, preferably at least 7 wt% and more preferably at least 10 wt% of the total weight of the first and second zeolites. The second zeolite may be present in an amount of at most 90 wt%, preferably at most 50 wt%, and most preferably at most 25 wt% of the total weight of the first and second zeolites. The second zeolite may be present in an amount of between 1 and 90wt%, preferably between 5 and 50 wt%, more preferably between 10 and 25 wt% of the total weight of the mixture.

In instances where only first and second zeolite are present in the zeolite mixture, the amount of first and second zeolite together is 100 wt% of the zeolite mixture. In less preferred embodiments in which other zeolite components are present which are neither first nor second zeolite, the total amount of first and second zeolite together will be less than 100 wt% of the zeolite mixture.

Zeolite SAR

It has advantageously been found that by tuning the SAR of the second zeolite, improved selectivity for a product having a new C-C bond can be achieved. It has been found that when the second zeolite has a SAR of 5 or below, the desired selectivity may be lower compared to the use of a single, medium pore-size zeolite. Thus, in general, it is preferable if the second zeolite has a SAR of more than 5. Preferably, the second zeolite has a SAR which is more than 12, preferably more than 20, and most preferably more than 25. The second zeolite may have a SAR of at most 100, and preferably at most 90. The second zeolite may have a SAR of between 7 and 95, preferably between 12 and 90 such as between 25 and 85.

The inventors find that tuning the SAR of the first zeolite can also provide improved selectivity. In particular, the first zeolite preferably has a SAR of 5 or more, preferably of 10 or more and more preferably of 15 or more. Preferably, the first zeolite has a SAR which is up to 300, preferably up to 150 and more preferably up to 70. The first zeolite may have a SAR of between 5 and 300, preferably between 20 and 50 such as 30.

It can be seen from e.g. Figures 4 and 6 that even a small amount of HY mixed with HZSM-5 e.g. 10 wt% HY to 90 wt% HZSM-5, can give surprisingly good reactivity compared with the 100% HZSM-5 if the SAR is appropriately controlled. At relatively low SAR, such as 5, the C-C selectivity is relatively low. However, at higher SAR, especially e.g. 30 to 90, the C-C selectivity increases markedly. Indeed, at SAR of 30 to 90 as shown, the C-C selectivity is better than that of the HZSM-5 alone whether the HZSM-5 has SAR of 30 or 50.

Accordingly, in particularly preferred embodiments, compositions of the present disclosure comprise a zeolite mixture comprising one first zeolite which is (H)ZSM-5 and one second zeolite which is (H)Y, especially HZSM-5 and HY. The first zeolite is preferably present in an amount of between 75-95 wt% of the zeolite mixture. The remainder is second zeolite.

Most preferably, the second zeolite preferably has a SAR of between 25 and 85 and the first zeolite has a SAR of between 20 and 50.

Components other than the first and second zeolites (such as binders and other additives) may be present in the catalysts described herein, as discussed elsewhere herein. Generally, the first and second zeolites are present in an amount sufficient to produce effective acylation. Thus, in general, the first and second zeolites are expected to make up at least 10 mass%, preferably at least 15 mass% and most preferably 20 mass% or more of the total weight of the catalyst (as solids). Preferably, the total zeolite amount in the catalyst will be at most 97 mass%, preferably at most 95 mass% and most preferably at most 90 mass% of the catalyst. Typically, the total zeolite content will be between about 20 to 90 mass% of the catalyst. The remainder of the catalyst may include binders and other additives as discussed elsewhere.

The zeolite mixtures described herein can be used as catalysts for an acylation process, typically for an acylation process described elsewhere herein. That is, the catalysts are alternatively called acylation catalysts herein.

The mixture comprising first and second zeolites may be provided in any suitable form, and can be chosen according to the particular process conditions. For example, in vapour phase pyrolysis applications, fluid bed systems are typically used. However, fixed bed pyrolysis is also contemplated. Accordingly, the first and second zeolites may be supported, unsupported or monolithic. By way of further example, for liquid phase conversion, fixed bed or slurry phase processing may be used to achieve the acylation coupling. Accordingly, the first and second zeolites may alternatively be particulate.

Suitable first and second zeolites may be purchased from commercial sources or prepared using synthetic methods known in the art.

Optional Components

Other than the presence of the first and second zeolites in the zeolite mixture, the composition of the catalyst is not particularly limited. Other components may be present.

For example, a small-pore zeolite may be present in the zeolite mixture, though this is generally thought not to be preferable. A small-pore zeolite would typically be suitable for use in a process which is other than the acylation process described herein and may function simultaneously with or at a different time from, the first and second zeolites.

Further examples of other components that could be present in the catalyst if desired include additives. The additives that are selected would likely be chosen according to the specific application of the process of the invention. Additives that may be particularly suitable for use with zeolite mixtures for the applications described herein (e.g. catalytic fast pyrolysis, vapour phase upgrading and pyrolysis) include for example one or more of: inert materials like silica and alumina; basic materials like MgO, CaO and hydrotalcites, red mud - an alkaline product comprising mostly iron oxide - and binders. The binders are typical of those used in the art and include for example kaolin, silica and alumina.

Accordingly, preparation of the catalysts of the invention is not particularly limited and can be achieved by any suitable method.

For example, such preparation may include intimate mixing of first and second zeolites as described herein. Optional components such as binder may be added to the intimate mixture, or the intimate mixture may be added to optional components. The order or sequence of addition or combining is not particularly limited. In an alternative example, separate compositions comprising first and second zeolite (and containing optional components such as binder) may be mixed with one another to achieve the catalysts of the invention.

Mixing or combining of the first and second zeolites (and optional components if present) may be achieved by methods known to those skilled in the art. Process

During the processes of the present invention, a carbonyl-containing molecule (first molecule) which is an acylating molecule is attached to an aromatic molecule (second molecule). In general, the object of the acylation reactions of the invention are to promote carbon-carbon bond formation between the first and second molecules. The product is an acylated second molecule. When the first molecule is carboxylic acid, the reactions generally produce an aromatic ketone or an aromatic aldehyde. Effectively, this process lengthens the carbon chain length of the first molecules. This is advantageously achieved with a composition having a zeolite mixture as described elsewhere herein.

The catalyst used in the present invention includes zeolites, which are solid-phase materials. The reactants are generally either in the liquid or gas phase. Therefore, typically the process is heterogeneous.

The product of the process of the invention is an acylated aromatic molecule. That is, there is a new carbon-carbon bond formed between the first and second molecules. Specifically, the carbon of the carbonyl group of the first molecule is attached to one of the carbon atoms of the aromatic ring of the second molecule.

An example of this kind of reaction is shown schematically in Figure 1. The invention is not particularly limited to the specific molecules shown in Figure 1.

Figure 1 (a) shows an example of an acylation coupling process between m-cresol and acetic acid. The acetic acid is the acetylating molecule (first molecule). The m-cresol, with both a methyl substituent and a hydroxy substituent, is the aromatic molecule (second molecule). Under reaction conditions to be described elsewhere, two products may result. One is 2-hydroxy-4-methylacetophenone and one is m-tolyl acetate. The 2-hydroxy-4- methylacetophenone is the result of C-C acylation i.e. the reaction forms a new C-C bond. This is the desired product. The m-tolyl actetate is the result of a reaction which forms a new C-0 bond. This is not the preferred product in the present invention. Generally, and for the use of pyrolysis oils in transport fuels, a deoxygenation step is expected to follow the coupling process. Coupling via a C-C bond produces products that are more likely to retain the carbon content after this deoxygenation step than the C-0 coupled product. The lower resulting acidity is important particularly in fuel applications.

[It will be understood that non-oxygenated second molecules are not expected to suffer from the problem of formation of C-0 coupled products. Nevertheless, oxygenated aromatic molecules are common in pyrolysis oils, and so their production in preferred processes of the invention is taken into account by the inventors.]

Thus, where the present application describes or refers to a “C-C” product, or “C-C” selectivity, it is referring to acylation which results in the formation of a new C-C bond between acylating molecule and aromatic molecule. Where the present application describes or refers to a “C-O” product or “C-O” selectivity, it is referring to the formation of a new C-0 bond between acylating molecule and oxygenated aromatic molecule.

Figure 1 (b) shows that the m-tolyl acetate C-0 product exemplified in Figure 1 (a) can undergo a Fries rearrangement process. This leads to the desired C-C product shown in Figure 1 (a). These routes are believed to be possible using the catalyst compositions of the invention, and that various reaction conditions may promote or hinder them.

The present inventors have therefore attempted to provide compositions and reaction processes which maximise the production of C-C product and minimise the formation of C-0 product.

When the first and second molecules are components of a pyrolysis oil, an advantage of the process of the present invention is that it improves the retention of the available carbon atoms from the first and second molecules during subsequent processing steps, while providing a product molecule which is both more stable and less detrimental to the pyrolysis oil. That is, the disadvantages associated particularly with the presence of small- chain carboxylic acid molecules (see background section above) are removed. However, none of the carbon atoms are lost in the acylation process. Therefore, the pyrolysis oil retains its maximum fuel efficiency.

Sources of first and second molecules include biological sources such as agricultural waste, wood, straw, and municipal waste. Non-biological sources include coal tar and petrochemicals, particularly for the second molecules, and potentially plastics. Fermentation products may be a suitable source especially for first molecules. If desired, suitable first and second molecules can be purchased from commercial sources or prepared synthetically.

First Molecule

The first molecule is an acylating molecule. Thus, typically, it contains a carbonyl group (C=0). Accordingly, the first molecule has the general formula RCO-X. The nature of R is not particularly limited, but it is typically but not exclusively H or an optionally substituted alkyl or aryl group. Exemplary R groups are set out elsewhere. X is a leaving group. The term “leaving group” is a term of art and is understood by the skilled person.

In this case, it is a moiety whose bond to the carbonyl carbon can, under particular reaction conditions, be broken so that a new bond can be formed with the second molecule. In the present invention, it is preferred to form a new C-C bond. Accordingly, suitable leaving groups are capable of supporting electrons e.g. by having electronegative groups or electron delocalization. Exemplary groups X include but are not limited to OH, OR, halogen, and anhydride.

Preferably herein, the first molecule is a carboxylic acid. That is, X is OH.

Particularly for the applications envisaged herein, it is preferable for the carboxylic acid to be a mono-carboxylic acid. It is also preferable for the carboxylic acid to be a short-chain carboxylic acid, by which we mean a molecule of the general formula R-COOH, where R is H or an optionally substituted Ci-is alkyl and preferably H or an optionally substituted Ci- ₃ alkyl. In general, it is preferred that the alkyl is unsubstituted. The alkyl group may be cyclic, linear or branched, preferably linear or branched.

Particularly exemplified for the application of upgrading pyrolysis oils are carbonyl- containing molecules chosen from formic acid, acetic acid and propionic acid. Formic acid has the formula HCOOH. Acetic acid has the formula MeCOOH, so in the R-COOH formula above R is Ci alkyl. Propionic acid has the formula EtCOOH (Et is ethyl) so in the R-COOH formula above R is C2 alkyl.

The process of the invention may use one or more kinds of first molecule. For example, two or three or more kinds of first molecule can be used as acylating molecules during a process according to the claims. Suitably, each of formic acid and acetic acid may be acylating molecules using the zeolite mixtures described herein.

Second Molecule

The second molecules described herein are aromatic. That is, the second molecules contain one or more aromatic moieties (aromatic rings).

The present catalysts are expected to be capable of acylating aromatic molecules having more than one aromatic ring. Accordingly, the number and arrangement of aromatic rings of the second molecules is not especially limited and may include fused or non-fused ring systems. It is thought that the aromatic molecules which are typically most prevalent in the fuels and fuel precursors such as pyrolysis oils and pyrolysis vapours described herein generally have only one aromatic ring, though polyaromatic species such as those with 2 or 3 aromatic rings may also be present and may be used as the second molecule according to the invention.

In general, the number of ring atoms of the aromatic moiety is not particularly limited. Typically, there will be 5-14 ring atoms. The aromatic moiety can comprise any suitable ring elements i.e. it may be carboaryl or heteroaryl. Heteroaryl moieties or molecules can comprise one or more heteroatoms such as nitrogen, oxygen and/or sulphur. Preferably in the present invention, the aromatic molecule comprises an aryl group such as a Cr _> aryl, Cio or Ci ₄ group, or an N-containing heteroaryl group such as pyrrole. The aromatic molecules which are typically most prevalent in the fuel and fuel precursors such as pyrolysis oils and pyrolysis vapours described herein generally have an aromatic ring which does not contain a heteroatom i.e. all the ring atoms are carbon.

Thus, it may be preferred to employ a process wherein the second molecules have one aromatic ring and/or wherein the second molecules have an aromatic moiety wherein all the ring atoms are carbon if only the most prevalent second molecules are present.

The aromatic ring may be substituted or unsubstituted by any suitable number and kind of substituent groups. The substitution pattern is not considered to be especially critical to the invention, though acylation may be more difficult if the molecule has especially large or bulky groups which hinder the formation of the C-C bond. At least one aromatic ring position is usually unsubstituted, so that C-C bond formation can take place directly.

It is believed that non-oxygenated aromatics such as benzene and toluene can be coupled with carboxylic acids according to the present methods. However, from the perspective of time efficiency, oxygenated aromatic molecules are particularly suitable for use in processes according to the invention. It is believed that oxygenated aromatic molecules are more electron rich than non-oxygenated aromatic molecules and capable of Fries rearrangements so that they may be more readily acylated in the processes herein.

Examples of oxygenated aromatic molecules include those with -0(C0)R ² substituents, where R ² is H, alkyl, alkylene or aryl group and the CO group in parentheses is optional. The R ² group may be H, Ci-30 alkyl, C6-10 aryl, C5-10 heteroaryl or C2-30 alkylene, preferably H, Ci- ₁₀ alkyl, Ce or Cio aryl, C _5-6 heteroaryl or C ₂ -ioalkylene. The alkyl may be straight, linear or branched. The alkylene group may be cis or trans. The heteroaryl group may have one or more heteroatoms selected from N, S or O.

Accordingly, in preferred embodiments, the aromatic molecules are oxygenated. Oxygenated second molecules are believed to be particularly receptive to being acylated by the first molecule, especially when preferred zeolite mixtures described herein are employed in the catalyst.

Examples of suitable aromatic molecules include benzene, toluene, xylene, phenol, m- cresol, and methoxyphenols.

Particularly preferred are second molecules having a phenolic moiety.

Further Options

In general, the zeolite mixtures according to the present invention are expected to be catalytically active and thus the composition comprising them is described herein as a catalyst. In particular, the catalytic activity should be useful for coupling first molecules, which are acylating molecules such as carboxylic acids, with second molecules, which are aromatic molecules. The catalysts described herein are for use with fluids, and thus the first and second molecules should be components of a fluid. The first and/or second molecules may independently be in the form of a liquid or a vapour (gas). That is, the compositions of the invention may be useful as applied to methods involving, by way of example only, catalytic fast pyrolysis, vapour phase upgrading of pyrolysis vapours which may or may not derive from a liquid oil, and/or liquid phase upgrading of a pyrolysis oil. Especially, fuels and fuel precursors such as pyrolysis oils and pyrolysis vapours which are derived from biological sources are contemplated. Alternative suitable applications for the catalysts described herein will be evident to the skilled person on reading this application.

The first molecules may form or form part of a first stream of first molecules. The second molecules may form or form part of a second stream of second molecules. The process described herein may use one or both first and second streams. In accordance with this description, the first and/or second streams may be in either a liquid or gaseous phase. In embodiments employing one or more of the first and or second streams, the first molecules form or form part of a first stream of first molecules and the second molecules form or form part of a second stream of second molecules and each of the first and second streams are in the same phase i.e. are either both liquid streams or both gaseous streams. The catalysts of the present invention can be used during catalytic fast pyrolysis to upgrade oils or vapours by coupling first and second molecules which are each component parts. Particularly preferred are pyrolysis-oils. The first and second molecules may be in the liquid phase. Alternatively, the first and second molecules of the fuel may be in the gaseous phase i.e. as a vapour or vapours. Alternatively, or additionally, the catalysts of the present invention can be applied after the catalytic fast pyrolysis process e.g. to vapours produced by the catalytic fast pyrolysis or to the resulting liquid that is formed from or comprised by the condensation product of the catalytic fast pyrolysis.

Process Conditions

The following describes particular aspects of the acylation processes of the invention. The options and preferences are intended to be combinable and not limiting. The skilled person will be aware of various suitable conditions for carrying out acylation processes particularly in relation to acylation of pyrolysis oils catalysed by zeolites.

Typically, and particularly with reference to pyrolysis oils, acylation takes place in an inert atmosphere. By “inert atmosphere” we mean substantially no oxidising gas is present.

That is, there is substantially no oxygen (including air) present. An inert atmosphere is preferred because it prevents the unintended and unwanted formation of oxidised products such as CO and CO2, or other kinds of undesirable reactions taking place during the acylation process. Suitable gases that provide an inert atmosphere will be known to the skilled person and include for example nitrogen, argon, helium, neon and hydrogen or mixtures thereof.

Typically, the pressure used during the acylation reaction is determined by the kind of reactor chosen. Acylation may typically be conducted under pressures of between about 0.1 and 1 MPa.

The present inventors have found that a suitable minimum temperature is around 150 °C, preferably around 200 °C and more preferably around 300 °C. The upper limit of the temperature is not particularly limited but will take account of factors including, but not limited to, the decomposition temperature of the reactants and products, and any change to the catalyst structure. Suitably, an upper temperature limit is around 1000 °C, such as 900 °C and preferably 700 °C. Preferably, the acylation process takes place at a temperature of between around 300 to 700 °C, preferably 400 to 600 °C.

Particularly in the case of oxygenated second molecule, the yield of C-0 product is found to be relatively unchanged by temperature. In addition, it is considered that e.g. rearrangement of C-0 products to C-C products, as well as general formation of C-C products, is promoted by higher temperatures, such as 200 °C or more.

Typical reaction times are dependent on the reactor technology used and thus could vary from the order of seconds to hours, such as 1 s to 10 hours. A number of kinds of reactors are available in the art and the process of the invention is adaptable to batch or continuous reactors as desired. Examples of suitable reactors might include, but are not limited to, a batch autoclave, fixed bed, trickle bed and fluidised bed.

Non-aqueous solvent such as a C6-20 alkane could be used in the process if desired, but is not considered necessary.

Zeolite materials may optionally be calcined before use if desired.

The processes of the present invention can be carried out as either batch or continuous processes according to requirements and is not particularly limited herein though generally it is thought continuous processes are slightly preferred in the art.

The concentration of reagents and products can be determined using any suitable method. Purely by way of example, a suitable chromatography technique may be used, such as a gas chromatograph (GC) fitted with an appropriate detector such as a flame ionisation detector (FID). Using such methods, quantification may be achieved by comparison of the response of the detector to a calibration curve, formed by measuring the detectors response at known concentrations of commercial samples. Compounds can be identified by comparison of retention times with that of commercial samples. Exemplary, non-limiting examples of processes that could be used according to the invention are set out below with reference to specific applications.

Liquid phase upgrading: Passing a liquid pyrolysis oil over the catalyst composition. This does not exclude re-vaporising the pyrolysis oil and passing over the catalyst composition.

Conditions:

Reactor type: Many e.g. fixed bed, trickle bed, batch autoclave

Temp: 100-400 °C, preferably 150-350 °C

Pressure: (dependent on the reactor type), 0.1 to 10 MPa Contact time: (dependent on the reactor type) minutes to hours

Solvent: A solvent is not needed but one could be used if desired (hydrocarbon, especially an alkane such as a C6-20 alkane)

Vapour phase upgrading: Passing pyrolysis vapours or vaporised pyrolysis oil over the catalyst composition before it is condensed into a liquid. See Figure 7. Conditions:

Reactor type: Most likely a fluidised bed (but a fixed bed cannot be excluded)

Temp: 300-700 °C, preferably 400-600 °C Pressure: (dependent on the reactor type), 0.1 to 1 MPa Contact time: short (FCC-type) Figure 7 is a schematic diagram of a vapour phase upgrading process in which the present invention could be applied. Biomass is fed in, and a fast pyrolysis process carried out. Resulting char and solids are typically removed following the fast pyrolysis, and vapour phase upgrading is subsequently carried out. A catalyst comprising first and second zeolite as described herein may be used in the vapour phase upgrading process. Subsequently, the upgraded vapours may be condensed and any non-condensable gases and any aqueous phase is typically removed. Subsequently, liquid phase upgrading may occur and a catalyst comprising first and second zeolites as described herein may be used at this stage also. Hydrogen is fed in at the liquid phase upgrading stage. The eventual products may include light gases, naphtha, hydrocarbon fuels and aqueous phase.

Catalytic fast pyrolysis: It is possible to combine the fast pyrolysis and vapour phase upgrading into one step by adding a catalyst as described herein into the fast pyrolysis reactor. The components of the pyrolysis oil are generated in situ and are upgraded by the catalyst. See Figure 8.

Conditions:

Reactor type: Most likely a fluidised bed (but a fixed bed cannot be excluded)

Temp: 300-700 °C, preferably 400-600 °C Pressure: (dependent on the reactor type), 0.1 to 1 MPa Contact time: short (FCC-type)

Figure 8 is a schematic diagram of a catalytic fast pyrolysis process in which the present invention could be applied. Biomass is fed in, and a catalytic fast pyrolysis process carried out. A catalyst comprising first and second zeolite as described herein may be used in the catalytic fast pyrolysis process. Resulting char and solids are typically removed, before condensation is carried out. At this stage, any non-condensable gases and any aqueous phase is typically removed. Subsequently, liquid phase upgrading may be carried out and a catalyst comprising first and second zeolites as described herein may be used at this stage also. Hydrogen is fed in at the liquid phase upgrading stage. The eventual products may include light gases, naphtha, hydrocarbon fuels and aqueous phase. Catalytic fast pyrolysis is a preferred pyrolysis process in which the processes of the invention can be used. The pyrolysis product stream may be produced directly from a pyrolysis process or from a process in which the direct product of a pyrolysis reaction is upgraded, usually by contact with a catalyst. In a particular embodiment the pyrolysis process includes a catalytic pyrolysis reaction. As noted above, a catalyst comprising first and second zeolites, most preferably ZSM-5 and Y, especially in their hydrogen form, may be used. Mukarakate et al. (Green Chem., 2015, 17, 4217) describe a process of catalytic fast pyrolysis of biomass over HZSM-5 in the presence of steam which increased the proportion of oxygenated aromatics, particularly phenols, in the product. In addition to phenolic products and aromatics, the pyrolysis product typically comprises olefins, carbonyl compounds, (hydroxy-) aldehydes, (hydroxy-) ketones, carboxylic acids, heterocyclic compounds such as furans and pyrans, and others.

The phenolic product may comprise phenol and/or substituted phenols, especially alkylphenols e.g. cresols. The phenolic product may be a mixture of phenol and substituted phenols. The phenolic product may contain higher aromatics such as naphthols.

Other aromatics products of the catalytic fast pyrolysis process may comprise mono aromatics and polycyclic aromatics, such as naphthalenes and anthracenes. The aromatics product may comprise hydrocarbons such as benzene, toluene, xylenes, ethylbenzene and other alkyl benzenes, alkyl naphthalenes etc.

Typically, the pyrolysis may be carried out at about 400-600 °C, under an inert atmosphere at atmospheric pressure or above and in the presence of a diluent such as sand. A short contact time (FCC type) is preferred. Catalytic pyrolysis can be carried out under similar conditions, in the presence of catalyst instead of sand. A catalyst comprising first and second zeolite as described herein can be preferentially used, because the inventors find it increases acylation coupling. Pyrolvsis oils

Where the first and second molecules are components of a pyrolysis oil, the source of the pyrolysis oil is not particularly limited. Examples of sources of pyrolysis oils include agricultural waste, wood, straw, and municipal waste. Preferred are agricultural waste, wood and straw. These are complex mixtures comprising many organic compounds including poly- and mono- aromatic molecules, hydrocarbons and oxygenates which may be cyclic or linear and may have a number of functional groups such as ether, carboxylic acid, alkoxy, alcohol, furan, ester, and carboxyl groups.

The process by which the pyrolysis oil is obtained is not particularly limited. Typically, a process of preparing a pyrolysis oil includes condensation of vapours formed by pyrolysis of biomass. The pyrolysis may be a catalytic fast pyrolysis.

Contemplated within the scope of the present invention is an acylation process which is conducted during the pyrolysis step of the upgrading/preparation of a pyrolysis oil. The inventors expect this to lead to greater efficiency as the pyrolysis oil should not require condensing before further heating.

Examples

The following examples demonstrate, but do not limit, aspects of the present invention. Reference Example 1 — Effect of Zeolite SAR

The effect of the SAR of the zeolite catalyst was investigated on the coupling of acetic acid with m-cresol. Five Zeolyst® HY materials, CBV 600 (SAR 5), CBV 712 (SAR 12), CBV 720 (SAR 30), CBV 760 (SAR 60) and CBV 780 (SAR 80) were chosen for investigation. Each has a similar surface area (660-780 nfg ¹ ). Two ZSM-5 material CBV3024E (SAR 30) and CBV5524G (SAR 50) are included for comparison and have a lower surface area (405-425 m ² g ') compared to the HY materials. All zeolite materials were calcined before use. The conditions were as follows: 10 L/min air flow; RT to 70 °C, l°C/min - hold for 4 h; 70 - 110 °C, l°C/min - hold for 4 h; 110 — 500 °C, l°C/min - hold for 4 h; cool to RT. RT = room temperature. Reasons for calcination include: ensure full conversion to protonated form of zeolite and remove any organic contaminates that may be present.

The reaction conditions were as follows:

Zeolite catalyst (0.1 g) was added to 25 ml of a standard solution containing n-decane (0.200 mol dm ³ , 5.00 mmol), m-cresol (0.175 mol dm ³ , 4.38 mmol) and, acetic acid (0.525 mol dm ³ ml, 13.1 mmol) in dodecane solvent. Process conditions: 200 °C, 10 h, 20 bar N2, 800 rpm. The dodecane was used as a solvent to dilute the feed to simulate the presence of other components in the pyrolysis oil. Decane is an internal standard to allow product quantification which was measured using gas-chromatograph-flame ionisation detection. Table 1 below shows the properties of the catalyst used. The following general observations can be made. (1) Increased HY SAR increased the selectivity for the acylation product (excluding SAR 80). Without wishing to be bound by theory, the inventors believe that this indicates that stronger zeolite acid sites favour acylation, and that the total number of zeolite acid sites is less important than the relative strength of the acid sites.

The increased hydrophobicity of high SAR materials could also enhance acylation.

Without wishing to be bound by theory, the inventors think higher hydrophobicity could result in the presence of lower amounts of water in the zeolite pores. Since water reacts with reactive acylium ion intermediates, the expected lower amount of water leads to less unwanted side-reactions thereby leading to increased production of the desired acylated product.

(2) CBV 600 (HY, SAR 5) had poor selectivity for the desired acylation product (7%). Without wishing to be bound by theory, the inventors believe this could possibly be related to the comparatively higher Na content of CBV 600 which is likely bound to the strongest acid sites. This could in turn inhibit the availability of the strongest acid sites for the acylation reaction.

(3) The m-cresol conversion was highest for CBV 712 (HY, SAR 12) and CBV 720 (HY, SAR 30), (36-37%) compared to the other Zeolyst® materials (28-31%). The inventors believe that these materials have an advantageous balance of characteristics as explained above. The inventors note that the lack of correlation of desired product with the number of acid sites supports their theory that strong acid sites are important for acylation reactions using the present processes.

As seen in e.g. Figure 2, an opposite effect is seen for HZSM-5 SAR variation compared with the effect observed for HY SAR variation.

Example 2: Catalytic Zeolite Mixtures

In an effort to exploit the greater acylation selectivity observed with HY compared to

HZSM-5, ZSM-5 (SAR 30) was mixed with different quantities of HY (SAR 80). A total mass of 100 mg zeolite catalyst was used with 10-100% of the mass made up from HY as a physical mixture. The mixed HZSM-5/HY catalyst was applied to the coupling of acetic acid with m-cresol at 200 °C (see also Figure 3).

In Figure 3, C-0 = m-tolyl acetate, C-C = 2’-hydroxy-4’-methylacetophenone.

Conditions: Zeolite catalyst (mixed HZSM-5 SAR 30 (CBV 3024E) and HY SAR 80 (CBV 780), 0.1 g) was added to 25 ml of a standard solution containing n-decane (0.200 mol dm ³ , 5.00 mmol), m-cresol (0.175 mol dm ³ , 4.38 mmol) and, acetic acid (0.525 mol dm ³ ml, 13.1 mmol) in dodecane solvent. Process conditions: 200 °C, 10 h, 20 bar N2, 800 rpm. Using a combination of HZSM-5 and HY zeolites revealed the following trends (Figure 3):

• the conversion of m-cresol is approximately independent of the relative amount of HY; and

• the selectivity for the acylation product over the esterification product increases with the relative amount of HY, with the greatest relative increases in acylation selectivity seen at low %HY.

Example 3: Effect of SAR of Second Zeolite in Catalytic Zeolite Mixtures

Further investigations were carried out with 10 wt% HY based upon promising previous results. The SAR of the 10 wt% HY was varied between 5 and 80 and was used in combination with 90 wt% HZSM-5 (SAR 30). The 90/10 wt% HZSM-5/HY catalyst was applied to the coupling of acetic acid with m-cresol at 200 °C (see Figure 4).

As with Figure 3, C-0 = m-tolyl acetate, C-C = 2’-hydroxy-4’-methylacetophenone.

Conditions: Zeolite mixture (HZSM-5 SAR 30 (CBV 3024E), 0.09 g and HY SAR 5-80 (CBV 600, CBV 712, CBV 720, CBV 760, CBV 780), 0.01 g) was added to 25 ml of a standard solution containing n-decane (0.200 mol dm ³ , 5.00 mmol), m-cresol (0.175 mol dm ³ , 4.38 mmol) and, acetic acid (0.525 mol dm ³ ml, 13.1 mmol) in dodecane solvent. Process conditions: 200 °C, 10 h, 20 bar N2, 800 rpm. Varying the SAR of the HY co catalyst (10 wt%) between 5 and 80 revealed the following trends (Figure 4): • as the SAR of the HY co-catalyst increases, so does the m-cresol conversion; o there appears to be a synergistic effect of using a HZSM-5/HY mixture;

^■ 100% HY does not show linear relationship with between m-cresol conversion and SAR (Figure 2); · as the SAR of the HY co-catalyst increases so does the selectivity for the acylation product; o this is consistent with linear relationship between acylation selectivity and SAR exhibited by 100% HY (Figure 2); and

• it is thus considered possible to systematically tune the acylation selectivity by changing the SAR of the HY co-catalyst, even at just 10 wt% loading HY.

Example 4: HY Coke Formation Procedure:

1. Mixed ZSM-5 SAR 30 (CBV 3024E)/HY SAR 80 (CBV 780) catalysts (total 200 mg) was mixed with a biomass source (ARBOCEL CIOO) (100 mg) in a sample pot (C/B = 2)

2. 2 ± 0.01 mg catalyst/biomass mixture was loaded into a pyrolysis tube, using quartz wool as a stopper

3. Pyrolysis at 600 °C on CDS Pyroprobe 5250 T

4. The spent tube was collected upon discharge

5. Entire contents of tube (inc. quartz wool) were tipped into an alumina TGA pan

6. TGA analysis, RT 800 °C, 10 K min ¹ , 100 ml min ¹ air, alumina pan

7. Residual solid measured by mass loss measured between 200 - 750 °C

The results are shown in Figure 6. Example 5: Effect of changing SAR of First and Second Zeolite in Catalytic Zeolite Mixtures

Conditions: Zeolite mixture (HZSM-5 SAR 50 (CBV 5524G), 0.09 g and HY SAR 5-80 (CBV 600, CBV 712, CBV 720, CBV 760, CBV 780), 0.01 g) was added to 25 ml of a standard solution containing n-decane (0.200 mol dm ³ , 5.00 mmol), m-cresol (0.175 mol dm ³ , 4.38 mmol) and, acetic acid (0.525 mol dm ³ ml, 13.1 mmol) in dodecane solvent. Process conditions: 200 °C, 10 h, 20 bar N2, 800 rpm.

It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only, and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.