A PROCESS FOR PREPARATION OF 2, 5-FURAN DICARBOXYLIC ACID FROM 5-HYDROXYMETHYL FURFURAL FIELD OF THE INVENTION The present invention relates to a process of catalytic oxidation of 5-hydroxymethyl furfural (HMF) to 2, 5-Furan dicarboxylic acid (FDCA). More particularly, the invention provides a process for the synthesis of furan dicarboxylic acid (FDCA) from glucose or crude hydroxy methyl furfural (HMF) using non-noble metal catalyst. BACKGROUND AND PRIOR ART OF THE INVENTION 5-hydroxymethyl furfural (HMF) derived from cellulose via glucose formation is a very critical compound because of its active functional groups (-CHO and –CH2OH), which can be leveraged to synthesize various industrially important chemicals. HMF can be oxidized under aerobic conditions to yield 2,5-furan dicarboxylic acid (FDCA) which has a potential to replace Purified Terephthalic Acid (PTA) in polymer synthesis. As per the estimates, FDCA production in making PEF (Polyethylene Furanoate) is expected to have highest market potential in future, accounting for over 60% of global FDCA consumption. Considering the importance of the oxidation of HMF into FDCA, several researchers have demonstrated various catalytic pathways. Traditionally noble metals such as Ru, Pt, Au and Ag have been used for this process, making the process economically unviable, due to concerns of recyclability of these catalysts. Article titled, "Comparison of glucose conversion to 5-HMF using different modified mordenites in ionic liquid and biphasic media" by W. Mamo et al. published in Catalysis Science & Technology, 2016, 6(8) reports modified mordenites have been used in the direct conversion of glucose into 5-hydroxymethylfurfural (5-HMF) in two different media: the ionic liquid 1-butyl-3-methylimidazolium bromide ([BMIM]Br) and a biphasic system composed of water-acetone and ethyl acetate. In the prior arts US9321744B1 directly salts of Co (II), Mn (II), Ce (II) and corrosive bromide promoter is used. In the present invention, the inventor has given treatment to salts so as to remove free chlorides, acetates from the solution because these ions hinder the reaction process. The present system is efficient without using any promoter. Moreover, with metal salts system becomes homogeneous and present system by forming mixed metal oxides becomes heterogeneous. There are various reports available on leaching of Mg from MgO support. However, use of base while preparation of catalyst makes the system tedious and if proper washing is not done then this base contributes in the reaction. MgO is not a stable support under high temperature condition. In article titled," Selective oxidation of 5-hydroxymethylfurfural to 2, 5-furandicarboxylic acid over Au/CeO2 catalysts: the morphology effect of CeO2" by Qingqing Li et al. published in Catal. Sci. Technol., 2019,9, 1570-1580, gold (Au) catalyst is used while in present work, Co, Mn, Cu etc metals have been used. Additionally, Au is very expensive compared to metals. In the present work, ceria (Ce) has been used and have shown its contribution towards reaction. In this prior art ceria is used only as a support. Few other reports use dilute substrate solutions, which makes overall process energy intensive. In most of the reports, pure HMF (commercial) is used for the reactions and it is very well known that due to instability of HMF under ambient conditions, it is an economically unsustainable process when it needs to be produced on industrial scale. Therefore, there is a need or economically viable, industrial scale process for the synthesis of FDCA. Since the economics of the process is affected by the substrate i.e HMF and the catalyst and usually results in poor yields, the inventors have provided a process for synthesis of FDCA resolving all the above-mentioned issues in the prior arts. OBJECTIVES OF THE INVENTION: The main objective of the present invention is to provide a process for the synthesis of 2,5- furan dicarboxylic acid (FDCA) from crude 5-hydroxymethyl furfural (HMF) employing non noble metal catalysts. Another objective of the present invention is to provide catalysts for synthesis of 2,5-furan dicarboxylic acid (FDCA), which are synthesized by simple processes. SUMMARY OF THE INVENTION: Accordingly, the present invention provides a process for the synthesis of 2,5-furan dicarboxylic acid (FDCA) from crude 5-hydroxymethyl furfural (HMF) comprising the steps of: a) reacting a glucose with a zeolite catalyst in a solvent at a temperature in the range of 165°C-185°C for a period of 5-6 hrs to obtain crude 5-hydroxymethyl furfural; b) optionally, purifying the crude 5-hydroxymethyl furfural as obtained in step (a) with a solvent by extraction method to obtain pure 5-hydroxymethyl furfural; c) reacting the 5-hydroxymethyl furfural as obtained in step (a) or (b) with a mixed metal oxide catalyst in a solvent at a temperature in the range of 120°C-140°C for 1- 24 hrs under 10-20 bar O
2 /air pressure in the presence of a base to obtain 2,5-furan dicarboxylic acid. In another aspect of the invention, selectivity of the 2,5-furan dicarboxylic acid is in the range of 80 to 95 % with 50 to 80% of yield; and said crude 5-hydroxymethyl furfural used is with purity in the range from 80-90%. In another aspect of the invention, the zeolite catalyst used in said process step a) is selected from the group consisting of H-form of Mordenite, Faujasite, Beta zeolite, Mobil-type five and H-form of Zeolite Socony Mobil-5, and H-Beta type having Si/Al or Si/Heteroatom ratios in the range from 1 to 400, wherein the heteroatom is selected from Aluminum, Gallium and Boron. In another aspect of the invention, the solvent used in said process step (a) or (b) is selected from the group consisting of water, methyl isobutyl ketone, dichloromethane, methyl isobutyl ketone, ethyl acetate, diethyl ether, hexane, tetrahydrofuran, dimethyl sulfoxide, toluene alone or combination thereof. In another aspect of the invention, the mixed metal oxide catalyst used in said process step c) is selected from mixture of oxides of metals comprising of Cobalt, Cerium, Iron, Vanadium, Copper, Zirconium, Titanium, Lanthanum, Manganese and a mixture thereof, wherein said metals are supported on support selected from Cerium(IV) oxide, activated Carbon, Silicon dioxide, Zirconium dioxide, Aluminum oxide, Titanium dioxide, Magnesium oxide, Calcium oxide, Strontium oxide, Barium oxide, Lanthanum oxide, Samarium(III) oxide, Yttrium oxide, Zinc oxide, Molybdenum trioxide, Thorium dioxide, Zinc oxide-Aluminum oxide, Magnesium oxide- Titanium dioxide, Caesium/Aluminum oxide, Sodium oxide, Potassium oxide, Caesium oxide/Aluminum oxide, Caesium/Silicon dioxide, Caesium oxide/Silicon dioxide, Sodium oxide/Magnesium oxide, hydrotalcite (Mg6Al2(OH)16CO
3 ·4H2O), chrysolite (Mg
3 (Si
2 O
5 )O
3 (OH)4), sepiolite (Mg
4 Si
6 O
15 (OH)
2 , alkali ion-exchanged zeolites, alkali ion-added zeolites, lanthanide imide and nitride on zeolite, and metal oxynitrides. In another aspect of the invention, the base used in process step c) is selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide and potassium hydroxide. In yet another aspect of the invention, ratio of the 5-hydroxymethyl furfural: mixed metal oxide catalyst used in said process step c) is in the range of 0.1 – 10.0. In yet another aspect of the invention, the amount of said base used in said process step c) is 1-2 molar equivalent to complete 2, 5-furan dicarboxylic acid formation. In yet another aspect of the invention, the mixed metal oxide catalyst is selected from the group consisting of oxides of Cobalt-Manganese-Cerium, Cobalt-Manganese-Iron, Cobalt- Manganese-Iron-Zirconium and Cobalt-Manganese. The zeolite catalyst used at step a) is selected from the group comprising of H-form mordenite, faujasite, BEA, MFI, HMOR, HZSM-5, H Beta type having varying Si/Al or Si/Heteroatom ratios can vary from 1 to 400, wherein heteroatoms are selected from Al, Ga, B, which will retain zeolitic framework. The mixed metal oxide catalyst used at step c) is selected from the oxides of the metal group comprising of Co, Ce, Fe, V, Cu, Zr, Ti, La and Mn. Moreover, these metals also supported on various supports selected from CeO
2 , Activated Carbon, SiO
2 , ZrO
2, Al
2 O
3 , TiO
2, HT, MgO, NaY. The metal oxides comprising the catalyst are optionally supported on basic supports selected from the group consisting of: (1) Single component metal oxides – alkaline earth metal oxides (MgO, CaO, SrO, BaO etc.) – rare earth oxides (La
2 O
3 , Sm
2 O
3 etc.) – other oxides (Al2O
3 , ZrO
2 , Y2O
3 , ZnO, TiO
2 , MoO
3 , ThO
2 , etc.) (2) Double components metal oxide (ZnO–Al2O
3 , MgO–TiO
2 etc.) (3) Zeolites – alkali ion-exchanged zeolites: Na–X, Cs–X (where X stands for zeolite type) – alkali ion-added zeolites: Cs
2 O/Cs–X (where X stands for zeolite type) (4) Supported alkali metal compounds – alkali metal compounds on alumina (Na or K or Cs/Al
2 O
3 , Na
2 O or K
2 O or Cs
2 O/Al2O
3 etc.) – alkali metal compound on silica (Na or K or Cs/SiO
2 , Na
2 O or K2O or Cs
2 O/SiO
2 etc.) – alkali metal ions on alkaline earth oxides (Na
2 O/MgO etc.) (5) Clay minerals – hydrotalcite (for e.g. Mg
6 Al
2 (OH)
16 CO
3 ·4H
2 O with varying metal content) – chrysolite (for eg. Mg
3 (Si
2 O
5 )O
3 (OH)4 with varying metal content) – sepiolite (Mg
4 Si
6 O
15 (OH)
2 with varying metal content) (6) Non-oxide – KF supported on alumina (for e.g. KF/Al
2 O
3 etc.) – lanthanide imide and nitride on zeolite – metal oxynitrides: ALPON, VALPON etc. The selectivity of the product 2,5-furan dicarboxylic acid (FDCA) is >80%, preferably 80 to 95 % with >50%, preferably 50 to 80% yield. The HMF used is crude with purity in the range from 80-90%. Further, the present invention also provides a process for preparing the mixed metal oxide catalyst comprising mixing and grinding metal precursors in the range of 0.1- 1 molar ratio in presence of oxalic acid in the range of 0.5-0.75 at a temperature in the range of 25-35°C for time period of 10-20 minutes to obtain a paste; drying the grinded paste in hot air oven at a temperature in the range of 50°C to 150°C for time period of 2-16 hrs followed by calcination at temperature between 300-800°C in oven for a time period of 1-20 hrs in the presence of air to get the mixed metal oxide catalysts. In another aspect of the invention, the mixed metal oxide catalyst is synthesized by a simple, green process comprises grinding precursors with oxalic acid in a 1:0.75 ratio at 25-35°C for 10-20 minutes. In yet another aspect of the invention, the said precursors used in said process of preparing the mixed metal oxide catalyst are selected from cobalt (II) acetate tetrahydrate, cereous nitrate hexahydrate, ferric nitrate nonahydrate, vanadium (III) chloride, copper (II) nitrate trihydrate, zirconyl nitrate,manganese (II) nitrate tetrahydrate and mixtures thereof. ABBREVIATIONS USED HMF: 5-hydroxymethyl furfural FDCA: 2, 5-Furan dicarboxylic acid MIBK: Methyl isobutyl ketone MgO: Magnesium oxide CaO: Calcium oxide SrO: Strontium oxide BaO: Barium oxide La
2 O
3 : Lanthanum oxide Sm2O
3 : Samarium(III) oxide Al
2 O
3 : Aluminium oxide ZrO
2 : Zirconium dioxide Y2O
3 : Yttrium oxide ZnO: Zinc oxide TiO
2 : Titanium dioxide MoO
3 : Molybdenum trioxide ThO
2 : Thorium dioxide Cs
2 O: Caesium oxide Na
2 O: Sodium oxide K2O: Potassium oxide SiO
2 : Silicon dioxide Mg
6 Al
2 (OH)
16 CO
3 · 4H
2 O:Hydrotalcite HMOR: H-form of mordenite zeolite in the range of Si/Al ratio can be 1-400 HZSM-5: H-form of ZSM-5 (Zeolite Socony Mobil #5) in the range of 1-400 MFI: Mobil-type five CeO2: Cerium(IV) oxide HT: Hydrotalcite NaY: Sodium form of Y zeolite (faujasite) MoO
3 : Molybdenum oxide ThO2: Thallium oxide ALPON: aluminophosphate oxynitride VALPON: aluminovanadatephosphate oxynitride BEA: Beta zeolite BRIEF DESCRIPTION OF THE DRAWINGS: Fig 1: SEM images of catalyst synthesized Fig 2: TEM images of catalyst synthesized Fig 3: XRD patterns for synthesized catalysts Fig 4: FT-IR spectrum for FDCA; FT-IR (ν, cm–1): 3151, 3125 (-OH); 1701 (C=O); 1572, 1424 (C=C); 1276, 1229 (C-O); 962, 852, and 763 (=CH) groups respectively. Fig 5:
1 HNMR (δ/ppm) spectrum for FDCA Fig 6: High Resolution Mass Spectroscopy analysis for FDCA. DETAILED DESCRIPTION OF THE INVENTION The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully understood and appreciated. In the current invention, the inventors have overcome several drawbacks of prior arts by developing an oxidation reaction in the presence of non-precious metal-based catalysts, which operate under milder conditions and use high substrate concentrations. Accordingly, to accomplish the objects of the invention, a process for the synthesis of 2, 5- furan dicarboxylic acid (FDCA) from crude 5-hydroxymethyl furfural (HMF) is provided; wherein the process comprising the steps of: a) synthesizing 5-hydroxymethyl furfural (HMF) from glucose by using a zeolite catalyst in a suitable solvent at a temperature in the range of 165°C-185°C for a period of 5-6 hr to afford crude 5-hydroxymethyl furfural (HMF); b) optionally, purifying the crude 5-hydroxymethyl furfural (HMF) with a suitable solvent obtained at step a) by extraction method to afford pure 5-hydroxymethyl furfural (HMF); c) reacting the 5-hydroxymethyl furfural (HMF) obtained at step b) with mixed metal oxide catalyst in a solvent at a temperature in the range of 120°C-140°C for 1-24 hr under 10-20 bar O
2 /Air pressure in the presence of a base to afford 2,5-furan dicarboxylic acid (FDCA). The process of the present invention is depicted below in scheme-1: Scheme-1 The zeolite catalyst used at step a) is selected from the group comprising of H-form mordenite, faujasite, beta, MFI, HMOR, HZSM-5, H-Beta type having varying Si/Al or Si/Heteroatom ratioscan vary from 1 to 400, wherein heteroatoms are selected from Al, Ga, B, which will retain zeolite framework. The suitable solvent used at step a) and step b) may include polar solvent, ketone solvent, ether solvent, ester solvent, non-polar solvent, and mixtures thereof. Polar solvents may include water, ammonia, sulfuric acid, deuterium oxide, ethanol, methanol, acetone, isopropanol, methyl ethyl ketone, n-propanol, acetonitrile, DMSO, and DMF and mixtures thereof. Nonpolar solvents may include chloroform, pentane, hexane, benzene, toluene, octane, decane, dimethyl ether, and dichloromethane, and mixtures thereof. Ketone solvent may include acetone, methyl ethyl ketone, methyl isobutyl ketone, and mixtures thereof. Ether solvents may include tetrahydrofuran, diethyl ether, 1,4-dioxane, methyl tert-butyl ether, and mixtures thereof. Ester solvents may include methyl acetate, ethyl acetate, isopropyl acetate, tert-butyl acetate, and mixtures thereof. The solvent used in step a) is mixture of water and methyl isobutyl ketone in the range of range 0.1:1 to 1:0.1 v/v. The solvent used in step b) is selected from dichloromethane, methyl isobutyl ketone, ethyl acetate, diethyl ether, hexane, tetrahydrofuran, dimethyl sulfoxide, toluene alone or combination therefrom. The mixed metal oxide catalyst used at step c) is selected from the oxides of the metal group comprising of Co, Ce, Fe, V, Cu, Zr, Ti, La and Mn. Moreover, these metals also supported on various supports selected from CeO
2 , Activated Carbon, SiO
2 , ZrO
2 , Al2O
3 , TiO
2 , HT, MgO, NaY. The metal oxides comprising the catalyst are optionally supported on basic supports selected form the group comprising of: (1) Single component metal oxides – alkaline earth metal oxides (MgO, CaO, SrO, BaO etc.) – rare earth oxides (La
2 O
3 , Sm2O
3 etc.) – other oxides (Al2O
3 , ZrO
2 , Y2O
3 , ZnO, TiO
2 , MoO
3 , ThO
2 , etc.) (2) Double components metal oxide (ZnO–Al
2 O
3 , MgO–TiO
2 etc.) (3) Zeolites – alkali ion-exchanged zeolites: Na–X, Cs–X (where X stands for zeolite type) – alkali ion-added zeolites: Cs
2 O/Cs–X (where X stands for zeolite type) (4) Supported alkali metal compounds – alkali metal compounds on alumina (Na or K or Cs/Al2O
3 , Na
2 O or K2O or Cs
2 O/Al
2 O
3 etc.) – alkali metal compound on silica (Na or K or Cs/SiO
2 , Na
2 O or K
2 O or Cs
2 O/SiO
2 etc.) – alkali metal ions on alkaline earth oxides (Na
2 O/MgO etc.) (5) Clay minerals – hydrotalcite (for e.g. Mg6Al2(OH)16CO
3 ·4H2O with varying metal content) – chrysolite (for eg. Mg
3 (Si
2 O
5 )O
3 (OH)4 with varying metal content) – sepiolite (Mg
4 Si
6 O
15 (OH)
2 with varying metal content) (6) Non-oxide – KF supported on alumina (for e.g. KF/Al2O
3 etc.) – lanthanide imide and nitride on zeolite – metal oxynitrides: ALPON, VALPON etc. The base used at step c) is selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide and potassium hydroxide. In particularly useful embodiment, sodium carbonate is used as a base at step c). The ratio of HMF:catalyst used at step c) is in the range of 0.1 – 10.0. The amount of base used at step c) is 1-2 molar equivalent to complete FDCA formation. The selectivity of the product 2,5-furan dicarboxylic acid (FDCA) is >80%, preferably 80 to 95 % with >50%, preferably 50 to 80% yield. In an embodiment of the invention, the HMF used is crude with purity in the range from 80- 90%. The mixed metal oxide catalyst is selected from Co-Mn-Ce, Co-Mn-Fe, Co-Mn-Fe-Zr, Cu- Mn. In an aspect of the invention, the mixed metal oxide catalyst is synthesized by a simple, green process comprises mixing metal precursors in the range of 0.1- 1 molar ratio and mixing with oxalic acid varying in the range of 0.5-0.75 at 25-35°C for 10-20 minutes; drying the grinded paste in hot air oven at 50°C to 150°C for 2-16 h followed by calcination at 300-800degC temperature in oven for a period of 1-20 hr in the presence of air to get mixed metal oxide catalysts. Here, Oxalic acid was added for making material more porous. The precursors used are selected from Cobalt (II) Acetate Tetrahydrate, Cerous Nitrate Hexahydrate, Ferric Nitrate Nonahydrate, Vanadium (III) Chloride, Copper (II) Nitrate Trihydrate, Zirconyl Nitrate and Manganese (II) Nitrate Tetrahydrate. Metal precursors mixed in the range of 0.1-1 molar ratio and mixed with oxalic acid varying in the range of 0.5-0.75. Mixed metal precursor to oxalic acid ratio is 0.1:0.75M. In a comparative embodiment, supported metal catalysts using noble metals like Ru (0.25 to 3wt % loading) are prepared by wet impregnation method where mixed metal oxides are used as a support. In an optional aspect, the catalysts are synthesized by processes selected from sol-gel process or wet impregnation process or incipient wetness method, physical mixture of metal oxides etc. Several experiments have been conducted with different reaction parameters and by using different mixed metal oxides, solvents etc. Results from those experiments are summarized in the following tables. Table 1: The results obtained by using different mixed metal oxides on crude HMF (80 - 90%) oxidation. *Reaction condition: 0.5wt% solution of crude HMF (Purity 80-90%), catalyst (0.5 g), Water (30mL), Base (Na
2 CO
3 : 0.15 g). (MC= Mesoporous carbon, NG= Nitrogen doped graphene)
# 0.25 g catalyst. Note: When solid base is used in the reaction, homogeneous base is not used. Table 2: The data of effect of time on the HMF oxidation reaction. *Reaction condition: 0.5wt% solution of crude HMF (Purity 80-90%), catalyst (0.5 g), Water (30mL), Base (Na
2 CO
3 :0.15 g), Temperature (120
o C), O
2 Pressure (10-15 bar). Note: In case of Co-Mn-Ce (1:4:0.25) catalyst, reaction carried out at 6 bar oxygen and 140°C. Table 3: The data of effect of HMF purity on the oxidation. Purification of lab synthesized HMF was done in the lab by solvent extraction technique.
*Reaction condition: catalyst (0.5 g), solvent (water: 30 mL), Base (Na 2 CO 3 : 0.15 g) Table 4: Effect of reaction temperature on the HMF oxidation reaction. *Reaction condition: 0.5wt% solution of crude HMF (Purity 80-90%), catalyst (0.5 g), solvent (water: 30 mL), Base (Na 2 CO 3 : 0.15 g). Table 5: Recyclability of the catalyst is studied by conducting several experiments. *Reaction condition: 0.5wt% solution of crude HMF (Purity 80-90%), catalyst (0.5 g), solvent (water: 30 mL), Base (Na 2 CO 3 : 0.15 g), Temperature (120 o C), Pressure (10-15 bar). Note: In case of Co-Mn-Ce (1:4:0.25) catalyst, reaction carried at 6 bar oxygen and 140 o C. Table 6: The results obtained by HMF concentration study. *Reaction condition: Crude HMF (Purity 80-90%), catalyst (0.5 g), solvent (water: 30 mL), Base (Na 2 CO 3 : 0.15 g), Temperature (120 o C), Pressure (10-15 bar). Note: In case of Co-Mn- Ce (1:4:0.25) catalyst, reaction carried at 6 bar oxygen and 140 o C. Table 7: The results obtained by study experiments to check effect of O 2 and air oxidants against HMF purity. *Reaction condition: 0.5wt% solution of crude HMF, catalyst (0.5 g), solvent (water: 30 mL), Base (Na 2 CO 3 : 0.15 g), Temperature (120 o C). Note: In case of Co-Mn-Ce (1:4:0.25) catalyst, reaction carried at 6 bar oxygen and 140 o C. Reactions were also carried out in fixed bed reactor in a continuous mode with the employment of following reaction conditions: Substrate solution: 1 wt% HMF solution in water Flow: 1 mL/min Catalyst loading: 1 g Temperature: 150degC Oxygen pressure: 15 bar Conversion of HMF: 73% Yield of FDCA: 50% EXAMPLES: Following examples are given by way of illustration therefore should not be construed to limit the scope of the invention. Example 1: Preparation of mixed metal oxide catalyst Co-Mn-Ce (1:4:0.25) M: M: M ratio Typical synthesis procedure: added Cobalt (II) Acetate Tetrahydrate, Manganese (II) Nitrate Tetrahydrate and Cerous Nitrate Hexahydrate with molar ratio (1:4:0.25 M) given precursors mixed thoroughly and grind with the help of mortar-pestle till fine textured formation seen. Oxalic acid is added to desired precursor in 1:0.75M ratio and manually grind at 27°C for 20 min. Here, Oxalic acid was added for making material more porous. Then, the grinded paste was subjected for drying in hot air oven at 60°C for 16 h. After complete drying of powder, it was calcined at 300 o C for 3 hours in oven in presence of air to get mixed metal oxide catalysts denoted as Co-Mn-Ce. Example 2: Preparation of mixed metal oxide catalyst Co-Mn-Fe: (1:4:1) M: M: M ratio Typical synthesis procedure added Cobalt (II) Acetate Tetrahydrate, Manganese (II) Nitrate Tetrahydrate and Ferric Nitrate Nonahydrate with molar ratio (1:4:1 M) given precursors mixed thoroughly and grind with the help of mortar-pestle till fine textured formation seen. Oxalic acid is added to desired precursor in 1:0.75M ratio and manually grind at 27°C for 20 min. Here, Oxalic acid was added for making material more porous. Then, the grinded paste was subjected for drying in hot air oven at 60°C for 16 h. After complete drying of powder, it was calcined at 300 o C for 3 hours in oven in presence of air to get mixed metal oxide catalysts denoted as Co-Mn-Fe. Example 3: Preparation of mixed metal oxide catalyst Co-Mn-Fe-Zr (1:4:0.5:0.5) M: M: M: M ratio Typical synthesis procedure added Cobalt (II) Acetate Tetrahydrate, Manganese (II) Nitrate Tetrahydrate, Ferric Nitrate Nonahydrate and Zirconyl Nitrate with molar ratio (1:4:0.5:0.5 M) mixed thoroughly and grind with the help of mortar-pestle till fine textured formation seen. Oxalic acid is added to desired precursor in 1:0.75M ratio and manually grind at 27°C for 20 min. Here, Oxalic acid was added for making material more porous. Then, the grinded paste was subjected for drying in hot air oven at 60°C for 16 h. After complete drying of powder, it was calcined at 300 o C for 3 hoursin oven in presence of air to get mixed metal oxide catalysts denoted as Co-Mn-Fe-Zr. Example 4: Preparation of mixed metal oxide catalyst Cu-Mn: (1:4) M: M ratio Typical synthesis procedure added Copper (II) Nitrate Trihydrate and Manganese (II) Nitrate Tetrahydrate with molar ratio (1:4 M) given precursors mixed thoroughly and grind with the help of mortar-pestle till fine textured formation seen. Oxalic acid is added to desired precursor in 1:0.75M ratio and manually grind at 27°C for 20 min. Here, Oxalic acid was added for making material more porous. Then, the grinded paste was subjected for drying in hot air oven at 60°C for 16 h. After complete drying of powder, it was calcined at 500 o C for 17 hoursin oven in presence of air to get mixed metal oxide catalysts denoted as Cu-Mn. Catalyst Characterization Scanning Electron Microscopy Scanning electron micrograph images (Figure 1) show the morphology of prepared samples. Catalyst Co-Mn-Ce (1:4:0.25) (Figure 1b) and Co-Mn-Fe-Zr (1:4:0.5:0.5) (Figure 1d) shows agglomerated particles. Spherical and rounded shape particles are seen in case of Cu-Mn (Figure 1a) mixed oxides while flake shaped particles are observed in case of Co-Mn-Fe mixed oxide (Figure 1c). Transmission Electron Microscopy TEM images (Figure 2) show the morphological properties of Co-Mn-Ce (1:4:0.25) and Cu- Mn (1:4) (Figure 2a). It has been clearly seen the particle lattice fringes in case of Co-Mn-Ce (Figure 2b). The segregated particles with fringes are clearly visible in case of Cu-Mn (1:4) mixed oxide catalyst. All the synthesized catalysts were analysed by TEM and showed lattice fringes. XRD patterns for synthesized catalysts. The XRD pattern (Figure 3) of Cu-Mn (1:4) (Figure 3a) shows the characteristic peaks of the spinel CuMn2O4. Traces of CuO were also detected in the XRD pattern. Peaks for MnOx, along with Mn3O4 also has major contribution. In case of Co-Mn-Ce (1:4:0.25) (Figure 3b) the XRD pattern showed diffraction peaks of CeO 2 at 2θ = (28.6°, 33.1°, 47.6° and 56.5°). Peaks at 59.12° (222), 69.49° (400), and 76.82° (331) also contributes to CeO 2 . High intense peak of Mn 3 O 4 has seen at 2θ =36.1°. Figures 3c and 3d of Co-Mn-Fe (1:4:1) and Co-Mn-Fe-Zr, respectively clearly show the diffraction pattern of various phases like Fe2O 3 , Fe3O4, Co3O4, CoFe2O4, Mn2O 3 , CoMnO4, CoMnO 3 . From the data obtained, it seems reasonable to see the peak of tetragonal ZrO 2 at 2θ = 30.2°, 35.2°, 50.3,60.2° and 62.8°. Fe2O 3 , 2θ = 18°, 30.5°, 36°,49°,54° and 62.5° Fe 3 O 4 (Cubic), 2θ = 18°, 30.5°, 36°,,54° and 62.5° Co 3 O 4 (Cubic), 2θ = 33.5°, 38.5°, 41°, 54° CoFe2O4 (Cubic), 2θ = 30.5°, 36°, 41°, 62.5° Mn 2 O 3 (Cubic), , 2θ = 18°,33.5°, 36°, 41°,54° CoMnO 4 (Cubic) , 2θ = 38.5°, 61°, 62.5° CoMnO 3 (rhombohedral), 2θ = 41°, 54°, 65°. Example 5: synthesis of crude HMF Reactions were carried out in a batch mode reactor, with glucose or starch (10wt% with respect to water) as a substrate in the presence of HMOR (H-form mordenite) catalyst (0.143 g) at 175° C for 6 h. Water: methyl isobutyl ketone (MIBK) (1:5 v/v) was used as solvent (30 mL) and 41% yield of HMF with 53% selectivity and 77% HMF conversion was achieved. Example 6: purification of HMF A 20g of reaction mixture (HMF in organic solvent) was taken and solvent was evaporated to obtain semi-solid mass containing HMF. Water was added to this semi-solid mass and subsequently extraction of HMF with aforesaid solvent was done. If required to achieve higher purity of HMF, repeated extraction procedures were carried out to get highly purified 5-HMF (~purity±90%). Example 7: synthesis of FDCA In a batch mode reactor, 5-hydroxymethyl furfural (HMF), Solvent (Water) and catalyst (different mixed metal oxide) were added. Reactor was flushed and pressurized with O 2 /Air and desired pressure was filled. Then reaction mixture was stirred at desired temperature for definite time. Reactions are done in the temperature range of 120°C for 8 h using 10-20 bar O 2 /Air pressure. The reaction mixture was centrifuged and filtered through 0.22µm filter and analysed using HPLC equipped with a HC-75 H+ column (300*7.8 mm) and refractive index detector. ADVANTAGES OF THE INVENTION • Precious metals (like Au, Pt, Ag, etc.) avoided. • New combination of catalysts employed. • Lesser amounts of pressure required. • Crude HMF used. • Economically significant. • Environmental friendly process which avoids use of solvent, organic and mineral aids and mineral bases
