Process for producing dialkyl cycloalkanes

Abstract

A process for producing C10-C18 dialkyl cycloalkanes comprising : (i) subjecting a furfural compound, a furfuryl alcohol compound or a mixture of a furfural compound and a furfuryl alcohol compound to a reductive rearrangement reaction in the presence of water, hydrogen and hydrogenation catalyst comprising a supported transition metal to produce a reaction product comprising an active methylene-group containing cyclic ketone selected from cyclopentanone, substituted cyclopentanone, cyclohexanone or substituted cyclohexanone, and mixtures thereof; (ii) reacting the active methylene-group containing cyclic ketone obtained in step (i) with a furfural compound in an aldol condensation reaction in the presence of a catalyst to produce a reaction product comprising unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds; (iii) subjecting the unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (ii) to a hydrogenation reaction in the presence of hydrogen and a hydrogenation catalyst in order to produce saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds; and (iv) subjecting the saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (iii) to a hydrodeoxygenation step in the presence of hydrogen and a hydrodeoxygenation catalyst to produce a hydrocarbon product comprising C10-C18 dialkyl cycloalkanes, wherein the active methylene-group containing cyclic ketone is recovered from the reaction product produced in step (i) by subjecting the reaction product of step (i) to an azeotropic distillation step (ia) to produce a distillate stream comprising a major portion of the active methylene-group containing cyclic ketone and a bottom stream comprising a major portion of water and a minor portion of the active methylene-group containing cyclic ketone, wherein said distillate stream is used as feed in step (ii).

Description

[0001] PROCESS FOR PRODUCING DIALKYL CYCLOALKANES

[0002] Field of the invention

[0003] The present invention relates to a process for producing dialkyl cycloalkanes from furfural compounds. The dialkyl cycloalkanes produced by the process of the present invention are particularly useful as fuel components in sustainable aviation fuel (SAF) . Background of the invention

[0004] Long-chain alkanes (C8-C20) are important components of existing transportation fuels including distillate fuels such as diesel and aviation kerosene. In conventional fuels, long-chain alkanes have been obtained from petroleum sources or animal and vegetable oils. Petroleum sources are not renewable and animal and vegetable oils can be limited in supply .

[0005] Lignocellulose is a renewable carbon feedstock that exists widely in nature and can be obtained from biomass sources. It is therefore desirable to take advantage of lignocellulose to produce sustainable chemical and fuel components. Biomass-based furfural derivatives can be produced from lignocellulose feedstocks and such compounds can in turn be used to produce long-chain alkanes . This is discussed in review paper 'Furfuryl - a promising platform for lignocellulosic biofuels' ; by J.P. Lange, E. van der Heide, J. van Buijtenen, R.J. Price, ChemSusChem 2012, 5, 150-166.

[0006] Long-chain alkane fuels comprise cyclic structures that exhibit higher energy density. Dialkyl cycloalkanes are examples of such desired fuel components.

[0007] CN104045503A relates to a method for preparing C10-C18 long-chain cycloalkanes by using furfural compounds and cyclic ketones as raw materials. In a first step, a furfural compound is reacted with an active methylene-containing cyclic ketone in a Knoevenagel condensation reaction using basic substances as catalysts at a temperature of 20-120°C to produce a C10-C18 oxygen-containing cyclic organic compound. In a second step, the C10-C18 oxygen-containing cyclic organic compound produced in the first step is placed in a hydrogen environment and a hydrodeoxygenation treatment is performed to produce dialkyl cycloalkanes having a carbon chain length of between 10 to 18. However, the process taught in CN104045503A requires two different feedstocks, i.e. , furfural and the cyclic ketones, and proceeds through multiple reaction and separation steps. This all leads to high production costs .

[0008] It would be desirable to develop an improved process for producing dialkyl cycloalkanes wherein the various steps in the process are well integrated to minimize production costs. In particular, it would be desirable to avoid the need for foreign cyclic ketones as raw materials or other foreign chemicals, e.g. , for use as process solvent. Further, it would be desirable to provide a well streamlined process with minimum separation and purification steps between the various reaction steps.

[0009] Further, it would also be desirable to provide a process that provides increased yields and reduced manufacturing costs . Summary of the invention According to a first aspect of the present invention there is provided a process for producing C10-C18 dialkyl cycloalkanes comprising:

[0010] (i) subjecting a furfural compound, a furfuryl alcohol compound or a mixture of a furfural compound and a furfuryl alcohol compound to a reductive rearrangement reaction in the presence of water, hydrogen and hydrogenation catalyst comprising a supported transition metal to produce a reaction product comprising an active methylene group-containing cyclic ketone selected from cyclopentanone, substituted cyclopentanone, cyclohexanone or substituted cyclohexanone, and mixtures thereof;

[0011] (ii) reacting the active methylene group-containing cyclic ketone obtained in step (i) with a furfural compound in an aldol condensation reaction in the presence of a catalyst to produce a reaction product comprising unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds ;

[0012] (iii) subjecting the unsaturated C10-C18 oxygencontaining cyclic organic dimer and / or trimer compounds produced in step (ii) to a hydrogenation reaction in the presence of hydrogen and a hydrogenation catalyst in order to produce saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds; and

[0013] (iv) subjecting the saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (iii) to a hydrodeoxygenation step in the presence of hydrogen and a hydrodeoxygenation catalyst to produce a hydrocarbon product comprising C10-C18 dialkyl cycloalkanes, wherein the active methylene group-containing cyclic ketone is recovered from the reaction product produced in step (i) by subjecting the reaction product of step (i) to an azeotropic distillation step (ia) to produce a distillate stream comprising a major portion of the active methylene group-containing cyclic ketone and a bottom stream comprising a major portion of water and a minor portion of the active methylene group-containing cyclic ketone, wherein at least a portion of said distillate stream is used as feed in step (ii) • Advantageously, the process of the present invention can be carried out using only a furfural compound as starting material. If a furfuryl alcohol is used for step (i) it can be produced from furfural by simple hydrogenation. It is thereby not necessary to also purchase a separate ketone such as cyclopentanone or cyclohexanone as a starting material hence providing a simplified process for the production of C10-C18 dialkyl cycloalkanes.

[0014] In addition, the process of the present invention can advantageously make use of intermediates and products produced during the process itself as solvents and / or extractants which thereby avoids the need for external components, avoids the need for switching of solvents and avoids extra distillation steps that would be needed to recover solvent from the reaction intermediates or reaction product .

[0015] Further, the process of the present invention provides improved integration of the process steps, leading to increased productivity and reduced manufacturing costs.

[0016] The process of the present invention also recognizes that previously unreported by-products are potential SAF precursors, which increases the overall yield of the process. Brief Description of the Drawings

[0017] Figure 1 shows a simplified reaction scheme of one embodiment of the process of the present invention.

[0018] Figure 2 shows a process line-up of one embodiment of the present invention.

[0019] Figure 3 shows a process line-up of another embodiment of the present invention.

[0020] Figure 4 shows a process line-up of an alternative embodiment of the present invention.

[0021] Figure 5 shows a process line-up of an alternative embodiment of the present invention. Figure 6 shows the cyclopentanone conversion and trimer selectivity of the aldol condensation step (ii) using different solid and base catalysts at 40 bar N2 at 150°C for 5 hours in furfural with 4.3 wt% CPO and 1.8 wt% catalyst in furfural as per Example 1.3.

[0022] Figure 7 shows the hydrogenation intermediates produced in the adduct hydrogenation reaction of Example 1.4, identified by GCMS . (A) is the unsaturated trimer used as feed. (B) and (C) are the hydrogenation product obtained after reaction in decalin (B: 20 mL decalin, 3 g trimer, 0.1 g catalyst, 160°C, 120 bar H2, 2 hours) or in ethanol (C: 80 mL EtOH, 25 g trimer, 0.25 g catalyst, 160°C, 50 bar H2, 2 hours) .

[0023] Figure 8 shows the aldol adduct analysed using GCMC before hydrogenation, produced according to Example 1.3.

[0024] Figure 9 shows the product distribution analysed by GCMC for the hydrogenation of aldol adduct, dissolved in decalin and hydrogenation at constant pressure of 50 bar H2 at 150°C for 1.5 hours, as per Example 1.4.

[0025] Figure 10 shows the detailed reaction scheme of the rearrangement of furfural to cyclopentanol.

[0026] Figure 11 is a graphical representation of the data shown in Table 9.

[0027] Figure 12 shows the distribution of water soluble furanic oligomers analyzed by GPC after reductive rearrangement of furfural to CPO after the 4thdoses at pH 6.7 (A) , pH 3.5 (B) and pH 1.5 (C) (see Example 4.1) The grey areas represent the fraction of diesel and vacuum gasoil.

[0028] Figure 13 shows the molecular weight distribution of insoluble furanic oligomers collected by the acetone wash of the inside the autoclave reactor and analyzed by GPC after reductive rearrangement of furfural to CPO after the 4thdoses at pH 6.7 (A) , pH 3.5 (B) and pH 1.5 (C) (see Example 4.1) The grey areas represent the fraction of Diesel and vacuum gasoil.

[0029] Figure 14 is a graphical representation of the data shown in Table 10.

[0030] Detailed Description of the Invention

[0031] In a first aspect of the present invention the process comprises four steps (i) , (ii) , (iii) and (iv) , namely (i) a reductive rearrangement reaction, (ii) an aldol condensation reaction, (iii) a hydrogenation reaction, (iv) a hydrodeoxygenation reaction, and additionally contains an azeotropic distillation step (ia) .

[0032] As discussed below, it is also possible to integrate steps (iii) and (iv) into a single hydrodeoxygenation step (iiia) .

[0033] Reductive Rearrangement reaction

[0034] In step (i) of the process a furfural compound or a furfuryl alcohol compound is subjected to a reductive rearrangement reaction in the presence of water and hydrogen to produce an active methylene group-containing cyclic ketone. Step (i) produces an aqueous effluent wherein the active methylene group-containing cyclic ketone is present in the aqueous effluent.

[0035] Any furfural compound or furfuryl alcohol compound which can be used in a reductive rearrangement reaction is suitable for use in step (i) of the process. In a preferred embodiment, the starting material for step (i) is a furfural compound .

[0036] Examples of suitable furfural compounds as starting material for step (i) of the process include furfural, 5- methyl-2 -furfural , 4-methyl-2-f urf ural , 3-methyl-2-f urf ural , 5-chloromethylf urf ural, 4 -chloromethylf urf ural , 3- chloromethylf urf ural, 5-bromomethylf urf ural , 4- bromometylf urf ural , 3-bromomethylf urf ural , 5- iodomethylfurfural, 4-iodomethylfurfural, 3- iodomethylf urf ural , 5-hydroxymethyl furfural, 4-hydroxymethyl furfural, 3-hydroxymethyl furfural, 5-alkoxymethyl furfural, 4 -alkoxymethyl furfural, 3-alkoxymethyl furfural, 5- carboxymethylf urf ural , 4-carboxymethyl furfural, 3- carboxymethyl furfural, and mixtures thereof. A preferred furfural compound for use herein is furfural.

[0037] While a furfural compound is a preferred starting material for step (i) , it is possible to use a furfuryl alcohol compound as starting material for step (i) instead of or in addition to a furfural compound. Furfuryl alcohol versions of the furfural compounds listed above are suitable for use as a furfuryl alcohol compound. A preferred furfuryl alcohol compound for use in step (i) is furfuryl alcohol.

[0038] The reductive rearrangement reaction of step (i) is in itself well known to the person skilled in the art and details such as suitable process conditions, suitable catalysts, and the like, are taught in the prior art, for example, in Xiao, Catal Lett (2014) , 144:235, Xiao, Korean J. Chem. Eng. , 31 (4) , 593 (2014) , and Luque, Green Chemistry 2015, 17 (8) , 4183.

[0039] The reductive rearrangement reaction of step (i) is preferably carried out in the presence of a supported transition metal hydrogenation catalyst. A suitable supported transition metal hydrogenation catalyst for use herein contains copper, nickel, cobalt, or a noble metal, preferably copper, that is supported on a hydrothermally stable and non- basic support, particularly a support that contains carbon or a transition metal oxide compound selected from ZrC>2, TiCf, ZnO, and mixtures thereof. Preferred catalysts from the viewpoint of providing good yields of cyclopentanone include Cu on a ZrC>2 support, Cu on a 1102 support and Cu on a mixed ZrC>2 and TiC>2 support. A particularly preferred catalyst is Cu on a ZrC>2 support.

[0040] The reductive rearrangement reaction of step (i) is preferably carried out at a temperature in the range from 100°C to 300°C, more preferably from 150°C to 250°C and even more preferably in the range from 170°C to 200°C. In one embodiment, the reductive rearrangement reaction of step (i) is carried out at a temperature in the range from 100°C to 150°C since higher temperatures can lead to undesired consecutive hydrogenation of cyclopentanone to cyclopentanol. The reductive rearrangement reaction of step (i) is preferably carried out at a pressure of greater than 0.1 MPa, or greater than 0.3 MPa, or greater than 1 MPa, or greater than 3 MPa above the autogeneous pressure of water. For reference, the autogeneous water pressure in step (i) is 0.1 MPa at 100°C, 0.5 MPa at 150°C and 8 MPa at 300°C. The hydrogen partial pressure in step (i) is preferably in the range from 0.1 MPa to 10 MPa, more preferably from 0.5 MPa to 5 MPa and even more preferably from 1 to 2.5 MPa.

[0041] The reductive rearrangement reaction of step (i) is preferably carried out at neutral or acidic pH conditions. The pH of step (i) is preferably less than 7, but can be less than 6, even less than 5. The pH of step (i) is preferably greater than 1, more preferably greater than 2, even more preferably greater than 3.

[0042] Step (i) can be carried out in a standard reactor such as a batch reactor or a continuous flow reactor. In a preferred embodiment, step (i) is carried out in continuous stirred-tank reactor (CSTR) mode. It has been found that carrying out step (i) in CTSR mode advantageously leads to increased product yield and concentration, since the formation of oligomeric material is minimized while delivering the cyclic ketone at high concentration for more efficient recovery by azeotropic distillation.

[0043] The active methylene group containing-cyclic ketone produced in step (i) is selected from cyclopentanone, substituted cyclopentanone, cyclohexanone or substituted cyclohexanone. The substituents on the substituted cyclopentanone and substituted cyclohexanone are preferably selected from -OH, -CH3 and -CH2OH. In a preferred embodiment, the active methylene group-containing cyclic ketone is cyclopentanone.

[0044] Following an azeotropic distillation step (ia) described below, the active methylene group-containing cyclic ketone produced in step (i) is fed to step (ii) for reaction with a furfural compound in an aldol condensation reaction. Advantageously, this means that the process of the present invention can be carried out using only a furfural compound (or a furfuryl alcohol compound) as single starting material. It is not necessary to also purchase a separate active methylene-containing cyclic ketone as a starting material for the aldol condensation step (ii) , hence providing an overall simplified process for the production of C10-C18 dialkyl cycloalkanes . Aldol Condensation reaction

[0045] Step (ii) of the process of the present invention involves reacting the active methylene group-containing cyclic ketone obtained in step (i) with a furfural compound in an aldol condensation reaction to produce a reaction product comprising unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds.

[0046] Aldol condensation reactions in themselves are well known to those skilled in the art and details such as suitable process conditions, suitable catalysts, and the like, are taught in the prior art, for example, in Deng, Fuel Processing Technology, 148, 361, 2016; Javanshir, Current

[0047] Chemistry Letters, 3 (2) , 63, 2014; Babu, Synthetic Communications, 27 (21) , 3677 , 1997; Hashemi, Organic Chemistry: An Indian Journal, 2 (5-6) , 159, 2006; Esmaeili, Monatshefte fuer Chemie, 136 (4) , 571, 2005.

[0048] Step (ii) is carried out in the presence of a suitable catalyst. Catalysts for the aldol condensation reaction of step (ii) are well known to those skilled in the art. Preferably, the catalyst used in step (ii) is an acidic or basic catalyst, being homogeneous or heterogeneous, inorganic or organic. The selection of a homogeneous or a heterogeneous catalyst for step (ii) depends on the solvent used for step (ii) . Preferably, the catalyst for step (ii) is a heterogeneous, inorganic catalyst. Suitable heterogeneous, inorganic base catalysts include those containing zinc oxide, magnesium oxide, calcium oxide or a mixture thereof, optionally together with other metal oxides such as alkali metal oxides, alkaline earth metal oxides and lanthanide metal oxides, and mixtures thereof. Examples of suitable heterogeneous solid acid catalysts for step (ii) include alumina, amorphous and crystalline silica aluminas, including zeolites, supported heteropoly acids, niobia and other Group 4-6 transition metal oxides, and mixtures thereof, optionally with dopants. Examples of suitable homogeneous base catalysts for use in step (ii) include those containing hydroxides of alkali metals and hydroxides of alkaline earth metals, and N-containing organic molecules such as amines, pyridines and pyrroles. Examples of suitable homogeneous acid catalysts for use in step (ii) include HC1, H2SO4, H3PO4, heteropolyacids (for example, H3M012PO40) as well as carboxylic acids (for example acetic acid, lactic acid, formic acid, trichloroacetic acids, and the like) . Step (ii) is preferably carried out in the presence of a solvent. The solvent can be an aqueous solvent or an organic solvent or a mixture of an aqueous solvent and an organic solvent (a biphasic medium) . The aqueous solvent can be water or an aqueous alkaline solution (e.g. high pH NaOH solution) . The organic solvent is preferably a water- immiscible organic solvent, most preferably an organic solvent that solubilizes the unsaturated oxygen-containing organic dimer and / or trimer compounds. The organic solvent may comprise or consist of an organic component which is already produced as an intermediate product in the process, as described hereinbelow in the section entitled 'Integration of Process Steps' . For example, as explained below, a stoichiometric excess of furfural compound that is used as feed and which exists as unconverted (recycled) furfural, a portion of the saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (iii) , a portion of the dialkyl cycloalkane produced in hydrodeoxygenation step (iv) (or hydrodeoxygenation step (iiia) ) , or a mixture thereof, can be recycled to step (ii) for use as solvent.

[0049] The temperature range used for step (ii) depends on the type of solvent used for step (ii) . When step (ii) is carried out in water using homogenous base, it is preferred to use mild temperature conditions, for example in the range from 25°C to 125°C, more preferably from 50°C to 100°C, even more preferably from 60°C to 80°C. When step (ii) is carried out in organic medium, higher temperatures may be needed, for example in the range from 50°C to 200°C, more preferably 75°C to 175°C, even more preferably from 100°C to 150°C.

[0050] Step (ii) is preferably carried out at a pressure that is at least the autogeneous pressure of the system. In the aldol condensation reaction of step (ii) , the molar ratio of furfural compound to active methylene group- containing cyclic ketone is preferably less than 10:1, more preferably less than 5:1, even more preferably less than 2.5:1. In the aldol condensation reaction of step (ii) , the molar ratio of furfural compound to active methylene group- containing cyclic ketone is preferably greater than 0.5:1, more preferably greater than 1:1, even more preferably greater than 2:1. In the aldol condensation reaction, a molar ratio of furfural compound to active methylene-group containing cyclic ketone of greater than 2 : 1 represents a molar excess of furfural compound. In a preferred embodiment, a small molar excess of furfural compound is desired in order to push the aldol condensation reaction to the trimer, but it is preferred to keep the excess furfural compound as small as possible in order to reduce the need to recover it. Any unconverted furfural compound that would be sent into hydrogenation step (iii) and hydrodeoxygenation step (iv) , (or into hydrodeoxygenation step (iiia) ) would then get converted to a C5 or C6 alkane which is too light for kerosene applications .

[0051] In one embodiment, the molar ratio of furfural compound to active methylene group-containing cyclic ketone is 2:1 which is the stoichometric amount needed for the aldol condensation reaction.

[0052] While a furfuryl alcohol compound can be used as a starting material in step (i) instead of or in addition to a furfural compound, for the aldol condensation reaction of step (ii) , it is necessary to use a furfural (i.e. aldehyde) compound as reactant rather than a furfuryl alcohol compound. Suitable furfural compounds for the aldol condensation reaction are the same as those listed above in relation to step ( i ) . The reaction product of the aldol condensation reaction of step (ii) comprises unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds. The reaction product can comprise dimers, trimers or a mixture of dimers and trimers. Preferably, the reaction product of step (ii) comprises a high concentration of the trimer, and preferably comprises greater than 50%vol. , more preferably greater than 60%vol. , even more preferably greater than 70%vol. of the trimer, based on the total reaction product of step (ii) . The dimer and trimer products of step (ii) can also be referred to as mono- and di-furfuryl cycloalkanone compounds. Hydrogenation

[0053] The unsaturated C10-C18 oxygen-containing cyclic dimer and / or trimer compounds produced in step (ii) are subjected to a hydrogenation step (iii) in the presence of hydrogen and a hydrogenation catalyst. The hydrogenation reaction produces saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds. Preferably, the reaction product of step (iii) comprises a high concentration of the saturated trimer, preferably comprising greater than 50%vol. , more preferably greater than 60%vol. , even more preferably greater than 70%vol. of the saturated trimer, based on the total reaction product of step (iii) .

[0054] Hydrogenation reactions are well known to those skilled in the art and details such as suitable process conditions, suitable catalysts, and the like, are taught in the prior art, for example in Hronec et al. , Fuel Processing Technology 138 (2015) 564-569 (in which f urf ural-c-pentanone coupling product is saturated (without deoxygenation) using noble metal / C catalysts at 130°C and 40 bar H2 in a variety of solvents) , Zhang et al. , Chem. Commun . , 2014, 50, 2572 (in which furfural is converted to bicyclic C10 hydrocarbon fuel by conversion to (1) cyclopentanone, (2) solvent-free aldol condensation (MgAl-HT at 150°C, wherein HT stands for hydrotalcite, the hydroxide form of MgAl or of Al-doped Mg (OH) 2) and (3) hydrodeoxygenation (Pd or Ni / SiO2 at 230°C) ) , and Corma et al. Angew. Chem. Int . Ed. 2011, 50, 2375 (in which methyl furan is trimerized to bisylvyl- penanone upon autoalkylation in water in the presence of pTSA at 50°C and then the trimer can subsequently be converted to diesel hydrocarbon upon hydrodeoxygenation over two consecutive beds of Pt / C + Pt / A12O3 at 350°C) .

[0055] The hydrogenation reaction of step (iii) is preferably carried out at a temperature in the range from 50°C to 200°C, more preferably in the range from 100°C to 150°C. The hydrogenation reaction of step (iii) is preferably carried out at a hydrogen partial pressure in the range from 0.1 MPa to 10 MPa, more preferably in the range from 0.2 to 2 MPa. The hydrogenation reaction is preferably carried out in a three-phase reactor (G / L / S) .

[0056] Suitable hydrogenation catalysts for use in step (iii) are known to those skilled in the art and include heterogeneous catalysts containing Ni, Co, a noble metal or a mixture thereof. The catalyst can consist of a skeleton metal catalyst such as Raney Ni, or a supported metal. In the latter case the support could contain carbon, e.g., active carbon, carbon nanotubes or carbon nanosheets, but it could also contain various metal oxides, e.g. SiC>2, AI2O3, ZrC>2, TiC>2, MgO, and mixtures thereof.

[0057] Hydrogenation step (iii) is preferably carried out at a lower temperature than hydrodeoxygenation step (iv) . If the unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (ii) are stable enough to support heating to the higher temperatures used in deoxygenation step (iv) without degrading and coking, then the lower temperature hydrogenation step (iii) can be integrated into deoxygenation step (iv) , and a separate hydrogenation step (iii) is not needed. Hence, in a second aspect of the present invention, step (iii) and step (iv) are integrated into a single step (iiia) by subjecting the unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (ii) to a hydrodeoxygenation step in the presence of hydrogen and a hydrodeoxygenation catalyst to produce a hydrocarbon product comprising C10-C18 dialkyl cycloalkanes.

[0058] Hence according to a second aspect of the present invention there is provided a process for producing C10-C18 dialkyl cycloalkanes comprising:

[0059] (i) subjecting a furfural compound, a furfuryl alcohol compound or a mixture of a furfural compound and a furfuryl alcohol compound to a reductive rearrangement reaction in the presence of water, hydrogen and a hydrogenation catalyst comprising a supported transition metal to produce a reaction product comprising an active methylene group-containing cyclic ketone selected from cyclopentanone, substituted cyclopentanone, cyclohexanone or substituted cyclohexanone, and mixtures thereof;

[0060] (ii) reacting the active methylene group-containing cyclic ketone obtained in step (i) with a furfural compound in an aldol condensation reaction in the presence of a catalyst to produce a reaction product comprising unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds; and

[0061] (iiia) subjecting the C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (ii) to a hydrodeoxygenation step in the presence of hydrogen and a hydrodeoxygenation catalyst to produce a hydrocarbon product comprising C10-C18 dialkyl cycloalkanes, wherein the active methylene group-containing cyclic ketone is recovered from the reaction produced in step (i) by subjecting the reaction product of step (i) to an azeotropic distillation step (ia) to produce a distillate stream comprising a major portion of the active methylene group- containing cyclic ketone and a bottom stream comprising a major portion of water and a minor portion of the active methylene group-containing cyclic ketone, wherein at least a portion of said distillate stream is used as feed in step (ii) . Preferably, said bottoms stream is recycled to step (i) • Obviously, the integration of hydrogenation step (iii) into step (iv) will not allow recycling of the saturated C10- C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (iii) as extractant and / or solvent. In that case, the final saturated C10-C18 dialkyl cycloalkane product can be recycled and used as extractant and / or solvent instead (see discussion on 'Integration of Process Steps' below) . Hydrodeoxygenation (step (iv) or step (iiia) )

[0062] In step (iv) of the process, the saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (iii) are subjected to a hydrodeoxygenation reaction in the presence of hydrogen and a hydrodeoxgenation catalyst to produce C10-C18 dialkyl cycloalkanes .

[0063] Alternatively, in the second aspect of the present invention, in step (iiia) of the process, the unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (ii) are subjected to a hydrodeoxygenation reaction in the presence of hydrogen and a hydrodeoxygenation catalyst to produce C10-C18 dialkyl cycloalkanes . Hydrodeoxygenation reactions are well known to those skilled in the art and details such as suitable process conditions, suitable catalysts, and the like, are taught in the prior art, for example in Zhang et al. , Chem. Commun . , 2014, 50, 2572 (in which furfural is converted to bicyclic Cio hydrocarbon fuel by conversion to (1) cyclopentanone, (2) solvent-free aldol condensation (MgAl-HT at 150°C, wherein HT stands for hydrotalcite, the hydroxide form of MgAl or of Aldoped Mg (OH) 2) and (3) hydrodeoxygenation (Pd or Ni / SiO2 at 230°C) ) , and Corma et al. Angew. Chem. Int . Ed. 2011, 50, 2375 (in which methyl furan is trimerized to bisylvyl- penanone upon autoalkylation in water in the presence of pTSA at 50°C and then the trimer can subsequently be converted to diesel hydrocarbon upon hydrodeoxygenation over two consecutive beds of Pt / C + Pt / A12O3 at 350°C) .

[0064] The hydrodeoxygenation reaction of step (iv) (or step (iiia) ) is preferably carried out at a temperature in the range from 200 to 450°C, more preferably in the range from 300°C to 400°C. The hydrodeoxygenation reaction is preferably carried out at a hydrogen partial pressure in the range from 0.1 MPa to 10 MPa, more preferably in the range from 0.2 MPa to 2 MPa. When a separate hydrogenation step (iii) is present, preferably the hydrogen partial pressure in hydrodeoxygenation step (iv) is the same or slightly lower than the hydrogen partial pressure in hydrogenation step

[0065] (iii) •

[0066] The hydrodeoxygenation reaction of step (iv) (or step (iiia) ) is preferably carried out in a two-phase reactor (Gas / Solid) .

[0067] Suitable hydrodeoxgenation catalysts for use in step

[0068] (iv) (or step (iiia) ) are known to those skilled in the art and include heterogeneous catalysts containing Ni, Co, or noble metal or mixture thereof. The catalyst can consist of a skeleton or bulk metal catalyst such as Raney Ni, or a supported metal. In the latter case the support could contain carbon, e.g., active carbon, carbon nanotubes or carbon nanosheets, but it could also contain various metal oxides, e.g. Si02, A12O3, ZrO2, Ti02, MgO, and mixtures thereof. Azeotropic Distillation (step (ia) )

[0069] In addition to steps (i) , (ii) , (iii) and (iv) , the process of the present invention comprises an azeotropic distillation step (ia) . The active methylene group- containing cyclic ketone is present in the reaction product produced in step (i) which is in the form of an aqueous effluent. The aqueous effluent comprises water and active methylene-group containing cyclic ketone. The aqueous effluent of step (i) may also comprise a minor amount of oligomeric by-product and a minor amount of unconverted furfuryl alcohol. In particular, the active methylene group- containing cyclic ketone produced in step (i) is recovered from the reaction produced in step (i) in an azeotropic distillation step (ia) which comprises subjecting the reaction product of step (i) to azeotropic distillation to produce a distillate stream comprising a major portion of the active methylene-group containing cyclic ketone and a bottom stream comprising a major portion of water and a minor portion of the active methylene group-containing cyclic ketone, wherein at least a portion of said distillate stream is used as feed in step (ii) .

[0070] The bottom stream preferably comprises active methylene group-containing cyclic ketone at a concentration level below 2 wt%, more preferably below 0.5 wt%, and most preferably below 0.1 wt% by weight of the bottom stream. Preferably, said bottom stream is recycled back to reductive rearrangement step (i) . In one embodiment of the present invention, the reductive rearrangement reaction in step (i) further generates oligomeric by-products which are present in said bottom stream. In one embodiment of the present invention at least a portion of the oligomeric by-products is removed from the bottoms stream before it is recycled to reductive rearrangement step (i) .

[0071] In another embodiment of the present invention, said bottom stream is split into a first bottom stream and a second bottom stream wherein the first bottom stream is recycled to reductive rearrangement step (i) and wherein at least a portion of the oligomeric by-products are removed from the second bottom stream before it is recycled to reductive rearrangement step (i) .

[0072] Preferably, the azeotropic distillation step (ia) is carried out at a pressure in the range from 0.01 MPa to 5 MPa, more preferably in the range from 0.03 MPa to 3 MPa, even more preferably in the range from 0.1 MPa to 1 MPa.

[0073] Preferably, the distillate stream produced by the azeotropic distillation step (ia) comprises active methylene group-containing cyclic ketone at a concentration level above 40 wt%, more preferably above 60 wt%, by weight of the distillate stream.

[0074] Preferably the distillate stream produced in the azeotropic distillation step (ia) is passed to a condenser and subsequently a liquid / liquid separator to produce a first distillate stream that is enriched in the active methylene group-containing cyclic ketone, and a second distillate stream that is enriched in water. The first distillate stream preferably comprises greater than 70 wt%, more preferably greater than 80 wt%, even more preferably greater than 85 wt%, of active methylene group-containing cyclic ketone, based on the weight of the first distillate stream. The second distillate stream preferably comprises less than 45 wt%, preferably less than 40 wt%, even more preferably less than 35 wt%, of active methylene-group containing cyclic ketone, based on the weight of the second distillate stream. The first distillate stream is preferably used as feed for step (ii) . The second distillate stream is preferably recycled to the top of the azeotropic distillation step (ia) to further increase the quality of the azeotropic vapour.

[0075] In another less preferred embodiment of the present invention, the distillate stream produced by the azeotropic distillation step (ia) is condensed and a fraction is recycled back to the top of the azeotropic distillation step (ia) before it is sent to a liquid / liquid separator to be split into a first distillate stream and a second distillate stream as described above.

[0076] Further details of the azeotropic distillation of cyclopentanone in aqueous solution can be found in US-A- 2,623,072, incorporated herein by reference in its entirety. Cyclopentanone has a boiling point of 129-131° C which is higher than that of water. Distillative recovery of cyclopentanone from aqueous solution would therefore require evaporation of the water which constitutes the majority of the medium and thereby would require high energy and capex. As disclosed in US-A-2 , 623 , 072 , cyclopentanone forms a heterogeneous azeotrope mixture with water, which greatly facilitates its recovery from water. According to US Patent No. 2, 623,072, an azeotropic mixture of cyclopentanone / water of 63:37 vol / vol evaporates at 92.6 °C (740 mmHg) and then upon condensation splits into an organic and water phases with 53:47 vol / vol ratio, which contain 89 and 34 vol% of cyclopentanone, respectively. The formation of such azeotrope enables recovery of the cyclopentanone by distilling only a fraction of the water of the effluent of the reductive rearrangement step (i) . However, it does not allow recovery of any oligomeric product that would build-up upon recycling of the recovered water back to reductive rearrangement step (i) , which could deactivate the hydrogenation catalyst and deposit on its surface. This problem can be solved by allowing for some build-up of the oligomeric product until it naturally demixes from the aqueous phase and forms a dedicated organic phase upon cooling to near ambient temperature.

[0077] The combination of azeotropic distillation and liquid / liquid separation of the distillate fraction as described above can be combined with various modes of running the subsequent aldol condensation reaction in step (ii) . Examples of such various modes are further described below in the detailed description of the drawings.

[0078] Integration of Process Steps

[0079] It is recognised that the individual reactions of steps (i) , (ii) , (iii) and (iv) (or steps (i) , (ii) and (iiia) ) are well documented in the literature, however the present invention seeks to combine these steps in an integrated way in order to maximize overall product yield and minimize separation and purification between the various reaction steps to minimize capital and operational expenditure.

[0080] In addition to steps (i) , (ia) , (ii) , (iii) and (iv) (or steps (i) , (ia) , (ii) and (iiia) ) as described hereinabove, the process of the present invention can make efficient use of intermediates and products produced during the process itself as solvents and / or extractants which avoids the use of external components, switching of solvents and extra distillation steps .

[0081] In one embodiment, at least a portion of the saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (iii) or at least a portion of the hydrocarbon product comprising C10-C18 dialkyl cycloalkane produced in step (iv) or step (iiia) , or a mixture thereof, is recycled for use as solvent in aldol condensation step (ii) . Advantageously, the use of saturated oxygenated dimer and / or trimer as solvent in step (ii) offers the advantage of dissolving the unsaturated product of step (ii) and, thereby, avoiding its precipitation in the boiler of a distillation column when distilling off eventual excess furfural compound from the effluent of step (ii) prior to feeding it to step (iii) .

[0082] In another embodiment of the invention, at least a portion of the saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (iii) or at least a portion of the hydrocarbon product comprising C10-C18 dialkyl cycloalkane produced in step (iv) or step (iiia) , or a mixture thereof, is used as an extraction medium to remove the oligomeric by-products from the bottom stream and / or the second bottom stream prior to recycling the bottom stream and / or second bottom stream to the reductive rearrangement step (i) . The resulting organic stream that contains the extracted oligomeric by-products can then be fed to step (iii) , (iv) or (iiia) for hydrogenation and / or hydrodexoxygenation .

[0083] In another embodiment of the invention, unconverted furfural following the aldol condensation step (ii) is recovered and recycled to step (ii) for use as solvent in the aldol condensation reaction. Hence, the furfural compounds have two functions in the present process, namely as reactants and as solvents, which requires careful dosing of the furfural compounds.

[0084] When integrating the individual steps of the process, it is desirable to take into consideration the desire to reach a furfural compound : ketone molar ratio for the aldol condensation step (ii) of less than 10:1, preferably less than 5:1 and preferably close to 2:1, the stoichiometric ratio that is needed for step (ii) .

[0085] In another embodiment herein, a portion of saturated oxygenated dimer / trimer and / or a portion of the final product produced in step (iv) or (iiia) can be recycled to the feed of step (iii) or (iiia) to dilute the unsaturated oxygenated dimer / trimer and, thereby, minimize undesired fouling and / or reduce the adiabatic temperature rise of step (iii) .

[0086] In another embodiment herein, the final product produced in step (iv) is recycled to the feed of step (iv) to dilute the saturated oxygenated dimer / trimer and, thereby, reduce the adiabatic temperature rise of step (iv) .

[0087] As already mentioned hereinabove, step (iii) and step (iv) can be integrated into a single step (iiia) . In one embodiment where step (iii) and step (iv) are integrated into a single step, a portion of the final product produced in step (iv) can be recycled to dilute the unsaturated oxygenated dimer / trimer from step (ii) to minimize undesired fouling and / or reduce the adiabatic temperature rise of the integrated hydrogenation-hydrodeoxygenation step. Step (iii) can be omitted by recycling a sufficient amount of dialkyl cycloalkane to step (iii) either directly by recycling it to step (iii) or indirectly by recycling it to step (ii) or even to step (i) .

[0088] The steps listed above serve to provide an improved process for producing dialkyl cycloalkanes, preferably C10- C18 dialkyl cycloalkanes, in which the process steps are much better integrated than the prior art process disclosed in CN104045503 by selecting suitable extraction methods, extraction media and solvent media to avoid expensive purification of intermediate, extractants and solvents, hence improving overall process efficiency and product yield. Fuel Products The hydrocarbon product emerging from step (iv) or step (iiia) of the present process comprises C10-C18 dialkyl cycloalkanes. The C10-C18 dialkyl cycloalkanes are selected from C10-C18 dialkyl cyclopentanes, C10-C18 dialkyl cyclohexanes, and mixtures thereof. In addition to the C10- C18 dialkyl cycloalkanes, said hydrocarbon product may also comprise some heavier products, for example, from the oligomeric by-product produced in step (i) , some monoalkyl cycloalkane coming from the dimer produced in step (ii) and treated in steps iii / iv (or iiia) , and also some acylic alkanes coming from ring opening or from the oligomeric byproduct from step (i) and treated in steps (iii) / (iv) (or iiia) . At least a fraction of the hydrocarbon product emerging from step (iv) or step (iiia) can be used as fuel components. Preferably, the C10-C18 dialkyl cycloalkanes are isolated from the hydrocarbon product as a separate fraction.

[0089] The CIO-18 dialkyl cycloalkanes produced according to the process of the present invention can be used as clean and low-carbon fuel components, especially as a kerosene fuel component in sustainable aviation fuel (SAF) . A preferred amount of C10-C18 dialkyl cycloalkanes for use in a sustainable aviation fuel (SAF) is from 0.1% vol to 100 vol%, more preferably from 5 vol% to 90 vol%, even more preferably from 10 vol% to 80 vol%, based on the sustainable aviation f uel .

[0090] The C10-C18 dialkyl cycloalkanes produced according to the process herein can also be used as clean and low-carbon diesel components. Their high degree of saturation will ensure good cetane, good cold flow properties and clean sootless burning, and hence are valuable for trucks and offroad vehicles used in mines and constructions sites .

[0091] Further, any acyclic alkanes present in the final hydrocarbon product produced in the process herein can also be used as a fuel component for use in a variety of fuel compositions, preferably for use in a sustainable aviation fuel (SAF) .

[0092] Detailed Description of the Drawings

[0093] Figure 1 is a simplif ied / ideal reaction scheme showing steps (i) , (ii) , (iii) and (iv) of the present invention, with furfural as feedstock and without eventual by-product. Step 1 of Figure 1 illustrates the reductive rearrangement reaction of Step (i) of the process of the present invention. In Step 1, furfural (or a furfural compound or furfural alcohol (not shown) ) undergoes a reductive rearrangement to produce a cyclopentanone (or a cyclohexanone (not shown) ) . Step 2 of Figure 1 illustrates the aldol condensation reaction of step (ii) of the process of the present invention. In Step (ii) , furfural (or a furfural compound (not shown) ) is reacted with cyclopentanone (or cyclohexanone) in an aldol condensation reaction to produce an unsaturated C10-C18 oxygen-containing cyclic organic trimer (and / or dimer (not shown) ) . Step 3 of Figure 1 illustrates the hydrogenation reaction of step (iii) of the process of the present invention. In Step (iii) , the unsaturated C10-C18 oxygen-containing cyclic organic trimer (and / or dimer (not shown) ) is hydrogenated to produce a saturated C10-C18 oxygen-containing cyclic organic trimer (and / or dimer (not shown) ) . Step 4 of Figure 1 illustrates the hydrodeoxygenation reaction of step (iv) of the process of the present invention. In Step 4, the saturated C10-C18 oxygen-containing cyclic organic trimer (and / or dimer (not shown) ) is hydrodeoxgenated to produce a C10-C18 dialkyl cyclopentane .

[0094] As discussed above, in one embodiment of the present invention it is possible to combine Step 3 and Step 4 into a single hydrodeoxygenation step (not shown in Figure 1) . The combination of azeotropic distillation and liquid / liquid separation of the distillate fraction as described above can be combined with various modes of running the subsequent aldol condensation reaction in step (ii) as follows : Mode 1: Aldol condensation in hydrogenated trimer and / or product (Figure 2)

[0095] In this embodiment, the azeotropic distillation step (ia) is carried out in distillation column SI and the first distillate stream (1) that is recovered from the liquid / liquid separator is fed to R2. Fresh furfural (2) is also fed to R2 preferably in a molar ratio of furf ural : cyclopentanone of slightly greater than 2:1, together with a portion of the hydrogenated trimer (3) and / or the final dialkyl cycloalkane product (4) as solvent. This mixture is then fed to the coupling reactor R2 to allow coupling of cyclopentanone with furfural to produce an unsaturated trimer. The resulting reactor effluent (5) from the aldol condensation step is then fed to a distillation column (S2) to recover excess of furfural and water as top stream (6) , and to recover the unsaturated trimer dissolved in hydrogenated trimer and / or product as bottom stream (7) . The resulting bottom stream can then be optionally mixed with at least a portion of the oligomeric product from Rl-Sl (8) and then fed to the dehydrodeoxygenation step (in R4 ) optionally via prior hydrogenation (in R3 ) to form dialkyl cyclopentane . Mode 2: Aldol condensation in excess furfural (Figure 3)

[0096] In this embodiment, the first distillate stream (1) that is recovered from the liquid / liquid separator is fed to coupling reactor R2. Fresh furfural (2) is also fed to R2 , preferably in a molar ratio of furf ural : cyclopentanone of greater than 2:1, to allow coupling of the cyclopentanone with furfural into an unsaturated trimer. The resulting reactor effluent (5) is then optionally mixed with a portion of the hydrogenated trimer (3) and / or the final dialkyl cyclopentane product (4) and fed to a distillation column S2 to recover excess of furfural and water as top stream (6) , and recover the unsaturated trimer dissolved in hydrogenated trimer and / or dialkyl cyclolalkane product as bottom stream (7) . The resulting bottom stream is then mixed with at least a portion of the oliogomeric product from Rl-Sl (8) and then fed to hydrodeoxygenation (in reactor R4 ) (optionally via prior hydrogenation (in reactor R3) ) to form dialkyl cycloalkane .

[0097] Mode 3: Aldol Coupling in excess biphasic medium (Figure 4)

[0098] In this embodiment, the first distillate stream (1) that is recovered from the liquid / liquid separator is mixed with fresh furfural in R2, preferably in a molar ratio of furf ural : cyclopentanone of slightly greater than 2:1, with a portion of the hydrogenated trimer (3) and / or the final dialkyl cycloalkane product (4) as solvent and with high pH aqueous stream (10) so that the reaction of CPO with furfural to produce an unsaturated trimer takes place in a biphasic medium. The resulting reactor effluent (5) from R2 is then split into a high pH aqueous stream (10) that is recycled to R2, and an organic stream that is fed to a distillation column S2 to recover excess of furfural and water as top stream (6) , and to recover the unsaturated trimer (dissolved in hydrogenated trimer and / or dialkyl cycloalkane product) as bottom product (7) . The resulting bottom product is then mixed with at least a portion of the oligomeric product from Rl-Sl (8) and then fed to hydrodeoxygenation (in reactor R4 ) (optionally via prior hydrogenation (in reactor R3) ) to form dialkyl cyclopentane.

[0099] Mode 4: Aldol Coupling in aqueous phase (Figure 5) In this embodiment, the first distillate stream (1) that is recovered from the liquid / liquid separator is fed to reactor R2 and mixed with fresh furfural (2) , preferably in a molar ratio of furf ural : cyclopentanone of slightly greater than 2:1, and with a high pH aqueous stream (10) . Coupling of CPO with furfural into an unsaturated trimer takes place in aqueous medium in reactor R2. The resulting reactor effluent (5) is then split into a high pH aqueous stream (10) that is recycled to R2 , and an organic stream (11) that is fed to a distillation column S2 to recover excess of furfural and water as top stream (6) , and recover the unsaturated trimer (dissolved in hydrogenated trimer and / or dialkyl cycloalkane product) as bottom product (7) . The resulting bottom product is then mixed with at least a portion of the oligomeric product from Rl-Sl (8) and then fed to hydrodeoxygenation (in reactor R4 ) (optionally via prior hydrogenation (in reactor R3) ) to form dialkyl cyclopentane.

[0100] For all four modes described above, as alternative embodiments, the two or more streams which are fed to coupling reactor R2 can be pre-mixed before being fed to R2 or they can be fed as separate streams to R2 and then mixed together in R2. Furthermore, in the embodiments illustrated in Figures 2-5, a dotted line represents an optional recycle stream.

[0101] The invention is further illustrated by the following non-limiting Examples. Examples Experimental Procedures

[0102] Procedure 1 - Reductive rearrangement of furfural (step (i) )

[0103] The reductive rearrangement of furfural was performed in a 45 mL stainless steel autoclave equipped with a magnetic stirrer, pressure gauge and automated temperature control. Both nitrogen and hydrogen cylinders were attached to the reactor' s pressure gauge. Before each experiment, oxide-based catalysts (0.10 grams) were reduced in the reactor at 200 °C, 80 bar H2 for 1 hour. In a typical hydrogenation experiment, furfural (1 gram, 10.4 mmol) was dissolved into 20 mL of demineralized water that was acidified to the desired pH with H3PO4. The furfural solution was added to the reactor accommodating the reduced catalyst. The reactor was sealed and purged three times with nitrogen to remove most of the air. Thereafter, the reactor was flushed three times with hydrogen, loaded with hydrogen up to the desired pressure of 80 bar, then heated up to the desired temperature. Reaction time was set to start when the medium temperature reached the reaction temperature setpoint minus 5°C. When the reaction was finished, the reactor was cooled down to room temperature and the gas was released. Samples were collected at the start and end of each experiment and subsequently analysed by gas chromatography (GC) or high-pressure liquid chromatography (HPLC) to quantify the amounts of Furfuryl alcohol (FAlc) , cyclopentanone (CPO) and cyclopentanol (CPA) present in the samples. Saturated oxygenates such as tetrahydrofurfuryl alcohol, pentanediols and 2-methyltetrahydrof uran were lumped in 'others' . The yields were expressed in mole%, defined as

[0104] Yield = (mole of product found in the product) / (mole of furfural loaded into the reactor) .

[0105] The sum of yields of identified products and unconverted furfural is rarely close to 100 mol%. The missing products were found as heavier products by means of Gel permeation chromatography .

[0106] Procedure 2 - recovery of cyclopentanone (CPO) by azeotropic distillation

[0107] The recovery of the cyclopentanone (CPO) by azeotropic distillation step can be carried out according to the method disclosed in US-A-2 , 623 , 072. Procedure 3 - Aldol condensation (step (ii) )

[0108] A 45mL stainless steel autoclave was used for the aldol condensation reaction. The autoclave is equipped with a gas connected (loading and purging) , a pressure sensor, thermocouples, and an overhead hollow stirrer. The autoclave is placed in a heating mantle (oven) that is equipped with a water-cooling system. The autoclave was loaded with 0.35g of solid base or solid acid catalyst, 0.84 g (10 mmole) of cyclopentanone and either (1) 19.6 g (1880 mmol) of furfural or (2) a mixture of 16.5 mL saturated oxygenated trimer and 1.92 g (20 mmol) of furfural. The autoclave was closed, purged twice with 40 bars N2 gas under 1420 rpm stirring. The autoclave was loaded to 40 bars of N2 gas, stirring increased to 3050 rpm and the oven was turned on to the desired temperature . The reaction timer started when the autoclave reached the reaction temperature within 5 °C. The reaction ran either for 2 hours or 5 hours and was water cooled to room temperature afterwards, the pressure was released under 1420 rpm stirring. The reaction mixture was collected and together with a sample of the start mixture analysed by GCMS .

[0109] Procedure 4 - hydrogenation of the unsaturated oxygenated dimer and trimer (step (iii) )

[0110] The autoclave is typically loaded with 80 mL of solvent (decalin or ethanol) , 0.25g catalyst (Pd / C) and 60g of trimer produced from the aldol condensation, without any purification and drying steps, and closed properly. Under constant stirring, the autoclave was purged 3 times with N2 gas at 40 bar and twice with H2 gas at 50 bar. Finally, the autoclave was loaded to 50 bar of H2 gas, stirring was increased and the oven was set to 160 °C. The reaction was run at constant H2 pressure with H2 coming from H2 buffer vessel and supplied through mass flow controller to monitor the H2 consumption. The reaction was stopped when the hydrogen consumption, i.e. , the H2 supply through the mass flow controller, stopped. The catalyst was filtered out over a 45 pm filter and purified via a vacuum distillation procedure. The distillation was carried out stepwise, starting at 120°C, 1 atm and ended at 190°C, 10 mbar. The product was analysed by GCMS and GPC. The analysis confirmed that the product mainly consisted of saturated oxygenated trimer.

[0111] Example 1

[0112] Example 1.1 - reductive rearrangement (step (i) )

[0113] Procedure 1 above was followed using a variety of supported transition metal catalysts. All runs were carried out in a stainless steel autoclave reactor at a temperature of 160°C and a hydrogen pressure of 80 bar, using 5wt% furfural in aqueous solution at a pH of 3.5. The reductive rearrangement reaction from furfural (Fur) to cyclopentanone (CPO) proceeds via the furfuryl alcohol (FAlc) according to the mechanism in Reaction (I) below. Further hydrogenation results in formation of cyclopentanol (CPA) . It is desired to have maximum yields of CPO, not stopping at FAlc since FAlc would also be extracted together with the CPO) and not going all the way to CPA (since CPA does not reaction in step (ii) )

[0114] Reaction (I)

[0115] Table 1 shows the various catalysts used in the experiments of Example 1.1 and the mol% of cyclopentanone (CPO) , cyclopentanol (CPA) and furfuryl alcohol (FAlc) produced in each case. All yields are expressed in mol% of furfural intake; 'other' represents sum of byproducts such tetrahydrofurfuryl alcohols, 2 , 3-dihydro-5-methylf uran, pentanediol and cyclopentanediols that are detected and quantified by GCMS . As can be seen from the results in Table 1, the use of supported copper catalysts resulted in the conversion of furfural to cyclopentanone (CPO) in good yields. The catalyst which provided the best yield of cyclopentanone was Cu / Zr02 (copper on a zirconium dioxide support) , providing 43.3 mol% CPO. Cu / Ti02 catalysts also provided good yields of CPO (40.5 mol%) . When other types of supported metal catalysts were used the conversion of furfural to cyclopentanone was less effective, with a lower yield of cyclopentanone (22 mol% or less) . It should be noted that no unconverted furfural could be detected in all these runs.

[0116] Table 1

[0117] * "other" represent hydrogenated byproducts measured by GCMS .

[0118] Note that the yields of "CPO, CPA FALC and other" do not add up to 100%, the rest is oligomeric products

[0119] A further set of experiments were conducted to investigate the effect of solvent and temperature on CPO yields using Cu / ZrC>2 as catalyst. The solvents investigated were water, ethanol and decahydronaphthalene (decalin) at a reaction temperature of 160°C, a hydrogen pressure of 80 bar and a reaction time of 120 minutes. The results of these solvent experiments are shown in Table 2 below. The influence of temperature on the reductive rearrangement reaction was investigated by using three different reaction temperatures (140°C, 160°C, 180°C) at a hydrogen pressure of 80 bar, using a 5wt% aqueous solution of furfural for a reaction time of 120 minutes. The results of these temperature experiments are shown in Table 3 below.

[0120] Table 2

[0121] Table 3

[0122] The results from Table 2 show the need for operating the reductive rearrangement step (i) in aqueous solution. The results from Table 3 show that high temperatures can lead to undesired consecutive hydrogenation of CPO to CPA. However, it is likely that the higher temperature experiments could be run for a shorter length of time to reduce CPA formation.

[0123] Example 1.2 - recovery of CPO by azeotropic distillation

[0124] The recovery of CPO by azeotropic distillation can be carried out according to Procedure 2.

[0125] Example 1.3 - aldol condensation of CPO in furfural (step (ii) )

[0126] The aldol condensation was run according to Procedure 3 above with furfural as co-reactant and solvent with various solid acids and bases as catalysts, namely:

[0127] Solid base: Mixed alumina / magnesia containing 20 (Mg20) , 30 (Mg30) and 70 wt% (Mg70) magnesia, supplied by Sasol

[0128] Solid acids: Gamma -Al umina , Y Zeolite and Amorphous silica-alumina (ASA) (denoted as 5545 in Figure 4) Both solid acids and bases catalysed the aldol condensation of CPO with furfural to unsaturated oxygenated trimer and dimer. Higher activity was observed for the solid acids, particularly the amorphous silica alumina.

[0129] Figure 4 shows the cyclopentanone conversion and trimer selectivity for the catalyst screening of different solid acid and base catalysts at 40 bar N2 at 150°C for 5 hours in furfural with 4.3 wt% CPO and 1.8 wt% catalyst in furfural.

[0130] The experiment using amorphous silica-alumina catalyst was run at 170°C for an extended reaction time to convert CPO to trimers with approximately 90 mol% yield after 5 hours (See Table 6 below) .

[0131] Table 6 below reports the weight ratios of cyclopentanone, dimer and trimer over time during the aldol condensation reaction of furfural and cyclopentanone at 170°C using an excess of furfural, i.e. with 4.3 wt% CPO and 1.8 wt% ASA as catalyst.

[0132] Table 6

[0133] Example 1.4 - hydrogenation of the unsaturated oxygenated dimer and trimer (step (iii) )

[0134] The unsaturated oxygenated dimer and trimer produced in Example 1.3 was used as feed for the hydrogenation step by dissolution in Decalin or Ethanol at 50 wt% in the presence of 10 wt% of Pd / C catalyst using method of Procedure 4. The reaction proceeded at a constant pressure of 50 bar H2 for 1.5 hours. The reaction conditions for the decalin and ethanol experiments are as follows: in decalin (B: 20 ml decalin, 3 g trimer, 0.1 g catalyst, 160°C, 120 bar H2, 2 hours) or in ethanol (C: 80 mL EtOH, 25 g trimer, 0.25 g catalyst, 160°C, 50 bar H2, 2 hours) .

[0135] The hydrogenation product shows a range of different products that result from stepwise hydrogenation, as indicated by GCMS (Figure 5) . The unsaturated oxygenated trimer has a molecular weight of 240.1 g / mol, whereas the fully hydrogenated product, still containing three oxygens, has a molecular weight of 252 g / mol. Figure 5 shows the identification of hydrogenated intermediates in the aldol adduct hydrogenation reaction identified by GCMS. Various intermediate products can be observed in the GCMS with molecular weights of 242 (+H2) , 244 (*+2H2) , 246 (+3H2) , 248 (+4H2) and 250 (+5H2) .

[0136] Figure 6 shows the aldol adduct analysed using GCMC, before hydrogenation.

[0137] Figure 7 shows product distribution for the hydrogenation of aldol adduct, dissolved in decalin and hydrogenation at constant pressure of 50 bar H2 at 150°C for 1.5 hours .

[0138] Table 7 shows the peak area percentage of each hydrogenation intermediate (peak area of intermediate products over the sum of all peak area) . Table 7 | 252 | 15.8% |

[0139] Example 1.5 - hydrodeoxygenation of the saturated oxygenated trimer

[0140] These experiments are run according to the methods documented in the literature references referred to above under the hydrodeoxygenation description.

[0141] Example 2

[0142] Example 2.1 - reductive rearrangement

[0143] The reductive rearrangement can be run as described in Example 1.1.

[0144] Example 2.2 - CPO recovery by azeotropic distillation

[0145] The CPO can be recovered following the reductive rearrangement reaction using the method of Procedure 2. Example 2.3 - aldol condensation in saturated oxygenated trimer

[0146] The aldol condensation is run in saturated oxygenated trimer by adding furfural to the CPO and saturated oxygenated trimer obtained from Example 2.2.

[0147] The aldol condensation proceeded significantly more slowly in saturated oxygenated trimer than in furfural, taking more than 20h to reach 50% CPO conversion and the production of dimer and trimer in a weight ratio of about 1:4. This was expected when considering the lower concentration of furfural in the medium, namely 10 wt% vs. 96 wt% .

[0148] Table 8 reports the aldol condensation of furfural and cyclopentanone measured in hydrogenated trimer at 170°C. Table 8

[0149] Examples 2.4 and 2.5. - hydrogenation and hydrodeoxygenation of the saturated oxygenated trimer.

[0150] Examples 2.4 and 2.5 are carried out in the same way as illustrated by Examples 1.4 and 1.5.

[0151] Example 3 - integrated scheme with aldol condensation in water .

[0152] According to this scheme, the reductive rearrangement is carried out as described in Example 1.1. The CPO can then be recovered by azeotropic distillation, as described in procedure 2.

[0153] The CPO and furfural is then contacted with the suitable amount of water that has been brought to pH between 8 and 14, e.g. , using NaOH or Ca (0H) 2. The reaction is run in biphasic conditions. The aldol condensation is then run as described in ' (2E, 5E) -2 , 5-Dif urf urylidenecyclopentanone , by Shi-Ying Ma and Ze-Bao Zheng, Acta Cryst . (2009) . E65, o3084 [doi : 10.1107 / S1600536809047278 ) . The precipitated unsaturated oxygenated trimer being insoluble in water, precipitates and is recovered by filtration or centrifugation prior to hydrogenation according to Example 1.4.

[0154] Example 4 -reductive rearrangement under CSTR operation

[0155] This example describes the operation of the reductive hydrogenation in fed-batch or CSTR (continuous stirred tank) mode to reduce the formation of heavy oligomeric products. For the sake of clarity, the reaction is operated with furfuryl alcohol as feed, in acidic aqueous medium and in absence of hydrogenation catalyst and hydrogen partial pressure. The desired reaction is thereby limited to the second reaction step of the detailed reaction scheme illustrated in Figure 10, i.e. , the rearrangement of furfuryl alcohol to 4-hydro-cyclopentenone (4-CHP) , which can't undergo reductive dehydration to 2-cyclopentenone . Procedure

[0156] The experiments were performed in a stainless steel 45 mL autoclave reactor that is loaded with an aqueous acidic solution of 0.5 wt% furfuryl alcohol and varying pH, without hydrogenation catalyst. Once loaded, the reactor was purged with nitrogen for three times, pressurised to 40 bar N2 at room temperature and heated up to the desired reaction temperature of 160 °C in around 15 minutes. Reaction time was set to start when the medium reached the reaction temperature setpoint minus 5°C. Once the reaction reached the desired reaction time, the reactor was cooled down to room temperature in around 15 minutes, a liquid sample was taken for analysis, a new dose of pure furfuryl alcohol was loaded in the reactor, the reactor was purged with N2, pressurised to 40 bar N2, and run for another period. Depending on the experiment, the dosing was repeated for "n" number of doses. Samples were taken before and after each dose and analysed accordingly .

[0157] The dosing experiment are then compared with reference experiments that dosed the final amount of FAlc in a single dose rather than spread over five doses.

[0158] Example 4.1

[0159] Figure 11 and Table 9 show the results of batch dosing experiments mimicking the working of a CSTR. After each dose the cumulative 4-HCP selectivity was determined. Reactions were performed in a stainless-steel autoclave, aqueous phase, pH control using H3PO4, 0.5 wt% FAlc per does, 160°C, nitrogen atmosphere of 40 bar Table 9: Cumulative 4-CHP concentration (mol / L) and selectivity (mol%) upon successive dosing of 0.3-0.5 wt% FALC into water at various pH Dosing experiments pH 1.5

[0160] Dosing experiments pH 3.5

[0161] Dosing experiments pH 6.8

[0162] Figure 11 (Table 9) shows the cumulative buildup of concentration and slow decrease in cumulative selectivity of 4-CHP after each 0.5 wt . % dose of FALC at various pH. It convincingly shows that the final concentration and selectivity of 4-CHP is higher after 5 doses of 0.5 wt% FAlc than a single dose of 2.5 wt%. For instance, it reaches 0.1 mol / L and 57 mol% vs. 0.09 mol / L and 50 mol% at pH 6.8. Similar trend is observed at pH 3.5, namely 0.085 mol / L and 45 mol% after 5 doses vs. 0.065 mol / L and 33 mol% after a single dose.

[0163] GPC analysis of the reaction product allowed to characterize the oligomeric product and its distribution over fictive fractions of gasoline, diesel, vacuum gasoil and vacuum residue, based on the molecular weight identified in GPC.

[0164] Figure 12 shows the distribution of oligomers that are soluble in the liquid phase at the end (dose 4, D4) while Figure 13 shows the insoluble oligomers that are deposited on the autoclave wall and stirrer and that were washed off by acetone. These figures clearly show the formation of diesel and vacuum gasoil (70-1000 Da; in the grey area) as well as vacuum residue products (at >1000 Da) . Upon assuming that the light gasoline-range are properly quantified by GCMS and the missing components correspond to the heavier products detected by GPC, we can complete the product breakdown as shown in Figure 14 (and Table 10) . Accordingly, the product obtained at pH 6.8 contains about 63% of gasoline product, 12% of diesel, 18% of VGO and 12% of vacuum residue. The Diesel fraction represents valuable product that can be fed to the hydrogenation and hydrodeoxygenation steps 3 and 4. Upgrading of the diesel components can proceeds via extraction with furfural (see Example 1.2) , feeding to the aldol condensation step 2 and subsequently feeding to step 3 and 4. The vacuum gasoil and vacuum residue are preferably recovered from the effluent and processed to distillate via hydrocracking or residue hydrocracking.

[0165] Table 10 - detailed product yield (reported in wt%) of the reductive arrangement obtained after the 4thfurfural dose of Example 4.1, based on GCMS for FALC, 4-CHP and gasoline and on GPC to distribute the missing components over diesel, VGO and VR fractions

Claims

C L A I M S1. A process for producing C10-C18 dialkyl cycloalkanes comprisin :(i) subjecting a furfural compound, a furfuryl alcohol compound or a mixture of a furfural compound and a furfuryl alcohol compound to a reductive rearrangement reaction in the presence of water, hydrogen and hydrogenation catalyst comprising a supported transition metal to produce a reaction product comprising an active methylene-group containing cyclic ketone selected from cyclopentanone, substituted cyclopentanone, cyclohexanone or substituted cyclohexanone, and mixtures thereof;(ii) reacting the active methylene-group containing cyclic ketone obtained in step (i) with a furfural compound in an aldol condensation reaction in the presence of a catalyst to produce a reaction product comprising unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds ;(iii) subjecting the unsaturated C10-C18 oxygencontaining cyclic organic dimer and / or trimer compounds produced in step (ii) to a hydrogenation reaction in the presence of hydrogen and a hydrogenation catalyst in order to produce saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds; and(iv) subjecting the saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (iii) to a hydrodeoxygenation step in the presence of hydrogen and a hydrodeoxygenation catalyst to produce a hydrocarbon product comprising C10-C18 dialkyl cycloalkanes, wherein the active methylene-group containing cyclic ketone is recovered from the reaction product produced in step (i)by subjecting the reaction product of step (i) to an azeotropic distillation step (ia) to produce a distillate stream comprising a major portion of the active methylenegroup containing cyclic ketone and a bottoms stream comprising a major portion of water and a minor portion of the active methylene-group containing cyclic ketone, wherein said distillate stream is used as feed in step (ii) .

2. A process according to Claim 1 wherein the reductive rearrangement reaction in step (i) further generates oligomeric by-products which are present in said bottoms stream produced in step (ia) .

3. A process according to Claim 1 or 2 wherein said bottoms stream is recycled to reductive rearrangement step (i) .

4. A process according to Claim 2 or 3 wherein at least a portion of the oligomeric by-products is removed from the bottoms stream before it is recycled to reductive rearrangement step (i) .

5. A process according to Claim 2 wherein said bottoms stream is split into a first bottoms stream and a second bottoms stream wherein the first bottoms stream is recycled to reductive rearrangement step (i) and wherein at least a portion of the oligomeric by-products are removed from the second bottoms stream before it is recycled to reductive rearrangement step (i) .

6. A process according to any of Claims 1 to 5 wherein the azeotropic distillation step (ia) is carried out at a pressure in the range from 0.01 MPa to 5 MPa.

7. A process according to any of Claims 1 to 6 wherein the distillate stream obtained after the azeotropic distillation is subjected to condensation and liquid / liquid separation to produce a first distillate stream and a second distillate stream wherein the first distillate stream comprises active methylene-group containing cyclic ketone at a concentration level of greater than 70wt%, based on the first distillate stream, andwherein the first distillate stream is fed to aldol condensation step (ii) .

8. A process according to any of Claims 1 to 7 wherein step (iii) and step (iv) are integrated into a single step (iiia) by subjecting the unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer produced in step (ii) to a hydrodeoxygenation step in the presence of hydrogen and a hydrodeoxygenation catalyst to produce a hydrocarbon product comprising C10-C18 dialkyl cycloalkanes.

9. A process according to any of Claims 1 to 9 wherein at least a portion of the saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (iii) or at least a portion of the hydrocarbon product comprising C10-C18 dialkyl cycloalkane produced in step (iv) or step (iiia) or a mixture thereof, is recycled for use as solvent in step (ii) .

10. A process according to Claim 4, 5 or 8 wherein at least a portion of the saturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (iii) or at least a portion of the hydrocarbon product comprising C10-C18 dialkyl cycloalkane produced in step (iv) or step (iiia) , or a mixture thereof, is used as an extraction medium to remove the oligomeric by-products from the bottoms streamand / or the second bottoms stream prior to recycling the bottoms stream and / or second bottoms stream to the reductive rearrangement step (i) .

11. A process according to any of Claims 1 to 10 wherein the furfural compound is selected from furfural, 5-methyl-2- furfural, 4 -methyl-2-f urf ural, 3-methyl-2-f urf ural, 5- chloromethylf urf ural, 4-chloromethylf urfural, 3- chloromethylf urf ural, 5-bromomethylf urf ural , 4- bromomethylf urf ural , 3-bromomethylf urf ural , 5- iodomethylf urf ural , 4-iodomethylfurfural, 3- iodomethylf urf ural , 5-hydroxymethyl furfural, 4-hydroxymethyl furfural, 3-hydroxymethyl furfural, 5-alkoxymethyl furfural, 4 -alkoxymethyl furfural, 3-alkoxymethyl furfural, 5- carboxymethylf urf ural , 4-carboxymethyl furfural, 3- carboxymethyl furfural, and mixtures thereof.

12. A process according to any of Claims 1 to 11 wherein the furfural compound is furfural.

13. A process according to any of Claims 1 to 12 wherein the hydrogenation catalyst used in step (i) comprises copper supported on a hydrothermally stable and non-basic support that contains carbon or a transition metal oxide compound selected from ZrO2, TiO2, ZnO, and mixtures thereof.

14. A process according to any of Claims 1 to 13 wherein the hydrogenation catalyst used in step (i) is selected from Cu on a ZrO2 support, Cu on a TiO2 support and Cu on a mixed ZrO2 and TiO2 support.

15. A process according to any of Claims 1 to 14 wherein the C10-C18 dialkyl cycloalkanes are selected from C10-C18dialkyl cyclopentanes, C10-C18 dialkyl cyclohexanes, and mixtures thereof.

16. A process for producing C10-C18 dialkyl cycloalkanes comprisin :(i) subjecting a furfural compound, a furfuryl alcohol compound or a mixture of a furfural compound and a furfuryl alcohol compound to a reductive rearrangement reaction in the presence of water, hydrogen and a hydrogenation catalyst comprising a supported transition metal to produce a reaction product comprising an active methylene-group containing cyclic ketone selected from cyclopentanone, substituted cyclopentanone, cyclohexanone or substituted cyclohexanone, and mixtures thereof;(ii) reacting the active methylene-group containing cyclic ketone obtained in step (i) with a furfural compound in an aldol condensation reaction in the presence of a catalyst to produce a reaction product comprising unsaturated C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds; and(iiia) subjecting the C10-C18 oxygen-containing cyclic organic dimer and / or trimer compounds produced in step (ii) to a hydrodeoxygenation step in the presence of hydrogen and a hydrodeoxygenation catalyst to produce a hydrocarbon product comprising C10-C18 dialkyl cycloalkanes, wherein the active methylene-group containing cyclic ketone produced in step (i) is recovered from the reaction product produced in step (i) by subjecting the reaction product of step (i) to an azeotropic distillation step (ia) to produce a distillate stream comprising a major portion of the active methylene-group containing cyclic ketone and a bottoms stream comprising a major portion of water and a minor portion ofthe active methylene-group containing cyclic ketone, wherein said distillate stream is used as feed in step (ii) .

17. A sustainable aviation fuel comprising the hydrocarbon product comprising the C10-C18 dialkyl cycloalkanes produced according to the process of any of Claims 1 to 16.

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