PROCESS FOR THE PREPARATION OF GAMMA-VALEROLACTONE BY CATALYTIC HYDROGENATION OF LEVULINIC ACID USING Ru-BASED CATALYSTS

Abstract

The present invention discloses a fast and selective process for the preparation of γ-valerolactone (Gvl) by catalytic hydrogenation of biomass-derived levulinic acid (LA) using recyclable ruthenium (Ru)-based heterogeneous catalysts in aqueous medium in stoichiometric yields (100%) under mild reaction conditions using nearly required amount of hydrogen.

Claims

1. A process for the preparation of γ-valerolactone comprising the following steps: (i) mixing levulinic acid or its esters with solvent in a Hastealloy reactor vessel at a temperature in the range of 24 to 28° C. to form a solution; (ii) adding catalyst to the solution obtained in step (i) to obtain a mixture and purging H.sub.2 into the mixture at 1-2 bar for three times after closing tightly the reactor vessel with the head assembly of the reactor; (iii) pressurizing the reactor vessel at the pressure in the range of 3 to 50 bar; (iv) heating the reactor vessel after attaining the specified pressure at a temperature ranging between 25 to 200° C. and stirring the reaction mixture after attaining the specified temperature for a period of time ranging between 2 min to 12 h; (v) cooling down the reactor vessel and release the unreacted H.sub.2 and separating the catalyst to get the product mixture; (vi) separating Gvl from the product mixture obtained in step (v) by extracting with dichloromethane (DCM) and removing DCM by rotary evaporation that can be reused.

2. The process as claimed in claim 1, wherein the catalysts are selected from the group consisting of Ru/NaY, Ru/MgAl-LDH, and hydrous ruthenium oxide (HRO) and its supported forms.

3. The process as claimed in claim 2, wherein the supports for HRO-C are selected from the group comprising cellulose, TiO.sub.2, Na-β, H-β, MCM-41, SBA-15, MgAl-LDH, and carbon.

4. The process as claimed in claim 1, wherein the Ru content used with respect to LA is 0.05 wt. % to 1 wt. %.

5. The process as claimed in claim 1, wherein LA concentration varied is in the range 1 to 50 wt. %.

6. The process as claimed in claim 1, wherein the conversion and yield are in the range of 0 to 100%.

7. The process as claimed in claim 1, wherein the solvents are selected from water, methanol, ethanol and isopropanol, THF, and 1,4-dioxane either alone or in combination thereof.

8. The process as claimed in claim 1, wherein the substrate are selected from LA or its esters such as methyl levulinate (MeL), ethyl levulinate (EtL) and butyl levulinate (BuL).

9. The process as claimed in claim 2, wherein the catalysts (HRO and supported HRO) are reusable with similar activity.

10. The process as claimed in claim 2, wherein the HRO catalysts either in neat or as supported form are used without any prior reduction and reduced in situ to Ru(0) under reaction conditions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1: Applications of Gvl in different industrial sectors

[0046] FIG. 2A: PXRD of HRO-C, HRO-N, HRO-SA and RuO.sub.2

[0047] FIG. 2B: PXRD of a. HRO-C before reaction b. HRO-C after reaction (1U-HRO-C)

[0048] FIG. 2C: PXRD of HRO-C, Na-β, H-β, HRO-C/Na-β and HRO-C/H-β

[0049] FIG. 2D: PXRD of a. HRO-C/Na-β before reaction b. HRO-C/Na-β after reaction (1U-HRO-C/Na-β) c. HRO-C/H-β before reaction d. HRO-C/H-β after reaction (1U-HRO-C/H-β).

[0050] FIG. 3A: TEM image of HRO-C

[0051] FIG. 3B: TEM image of HRO-C/H-β

[0052] FIG. 3C: TEM image of 2U-HRO-C

[0053] FIG. 4: TGA of catalysts (HRO-C, 2U-HRO-C and RuO.sub.2)

[0054] FIG. 5: FT-IR spectra of catalysts (HRO-C, 2U-HRO-C and RuO.sub.2)

[0055] FIG. 6A: .sup.1H-NMR spectra of synthesized Gvl using HRO-C/H-βcatalyst

[0056] FIG. 6B: .sup.13C-NMR spectra of synthesized Gvl using HRO-C/H-βcatalyst

[0057] FIG. 6C: FT-IR spectra of synthesized Gvl using HRO-C/H-β catalyst with Gvl sourced from M/s Sigma-Aldrich.

[0058] FIG. 6D: HR-MS of synthesized Gvl using HRO-C/H-β catalyst

ABBREVIATIONS

[0059] HRO: Hydrous ruthenium oxide

[0060] HRO-C: Hydrous ruthenium oxide prepared by precipitation method using RuCl.sub.3 with CaCO.sub.3

[0061] HRO-N: Hydrous ruthenium oxide prepared by precipitation method using RuCl.sub.3 with NaOH

[0062] HRO-SA: Commercial hydrous ruthenium oxide sourced from M/s Sigma-Aldrich

[0063] 1U-HRO-C: One time used HRO-C

[0064] 2U-HRO-C/H-β: Twice used HRO-C supported on H-β

DETAILED DESCRIPTION OF THE INVENTION

[0065] 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.

[0066] The present invention discloses a fast, mild and selective process for the preparation of γ-valerolactone (Gvl) by catalytic hydrogenation of biomass-derived levulinic acid (LA) using recyclable Ru-based heterogeneous catalysts in aqueous medium with maximum yield of Gvl (100%) while operating under mild reaction conditions.

[0067] In the present invention selective hydrogenation of LA to Gvl is achieved in excellent yield (100%) under mild reaction conditions in short reaction time in aqueous medium using recyclable Ru-based heterogeneous catalysts, in particular, hydrous ruthenium oxide (HRO) or its supported forms that does not require prior reduction and with lesser amount of Ru (with respect to LA), using nearly stoichiometrically required amount of H.sub.2. In comparison with the previous prior-art including those reported using Ru-based catalysts, the disclosed catalysts have improved activity, less energy demanding, conserving optimal utility of raw materials, needs shorter time and thus industrially more attractive.

[0068] The reactor was loaded with substrate (LA and LA esters), solvent, and catalysts at one time. The reaction was conducted at desired temperature and H.sub.2 pressure for a specified period of time. After completion of the reaction, reactor was cooled to room temperature and unconsumed hydrogen was released. The solid catalyst was separated by centrifugation and used for next cycle without any treatment. The liquid product mixture was quantified using ultra high-performance liquid chromatography (UHPLC). In the absence of catalyst, no conversion of LA was noted at 20 bar H.sub.2, 120° C. for 1 h and conversion of LA did not occur over HRO-C catalyst at 120° C. for 1 h in the absence of hydrogen. These two experiments showed that conversion of LA to Gvl requires both catalyst and H.sub.2.

[0069] The catalysts used in the invention are hydrous ruthenium oxide (HRO-C, HRO-N and HRO-SA), supported HRO-C, RuO.sub.2, Ru/MgAl-LDH and Ru/NaY. The HRO catalyst was prepared by using conventional precipitation method using NaOH or through a modified method using CaCO.sub.3. In addition, a commercially available HRO catalyst was also purchased from M/s Sigma-Aldrich and used. RuO.sub.2 catalyst was prepared by calcination of HRO-C in a muffle furnace at 550° C. for 3 h. Supported Ru catalysts (Ru/MgAl-LDH and Ru/NaY) were prepared by impregnation method using dilute RuCl.sub.3 solution (0.001 M). Supported HRO-C catalysts (supports used are cellulose, TiO.sub.2, Na-βzeolite, H-β zeolite, MCM-41, SBA-15, MgAl-LDH, and carbon) were prepared by precipitation followed by impregnation using dilute RuCl.sub.3 solution (0.001 M) and CaCO.sub.3 as precipitating agent.

[0070] The Ru-based catalysts used in this invention were characterized by using various analytical techniques in particular by using powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Fourier-transformed infrared (FT-IR) spectroscopy, and transmission electron microscopy (TEM). The PXRD of HRO (HRO-C, HRO-N and HRO-SA) material did not show any diffraction peaks (FIG. 2A) suggests amorphous characteristic of this material. The TGA of HRO-C material showed weight loss in range of 150-350° C. (FIG. 4), attributed to weight loss of strongly adsorbed H.sub.2O molecules. The H.sub.2O molecules in HRO-C catalyst was also confirmed by FT-IR which showed broad band centred at 3440 cm.sup.−1 (FIG. 5) ascribed to O—H stretching. The particles of Ru in HRO-C catalyst are agglomerated as observed by TEM (FIG. 3A) probably due to both bonding and non-bonding (hydrogen bonding) interactions through oxygen atoms.

[0071] The present invention provides hydrogenation of LA to Gvl using Ru-based catalysts in presence of solvent selected from water, alcohols (methanol, ethanol and isopropanol), tetrahydrofuran (THF), and 1,4-dioxane either alone or in combination thereof. The invention concludes water alone as an excellent medium for the reaction (eco-friendly medium) that provided 100% yield of Gvl under optimized conditions.

[0072] The reaction was performed at a temperature in the range of 25-200° C. and with a hydrogen pressure in the range of 3-50 bar, the ruthenium loading in the range of 0.05-1 wt. % with respect to LA, the concentration of LA is in the range of 1-50 wt. % with respect to solvent.

[0073] The reaction progress was monitored at different time intervals in the range of 2 min to 12 h.

[0074] In particular, using HRO, HRO-C/H-β and Ru/MgAl-LDH as catalysts, the reactions were performed at temperature in the range of 25-200° C. and with a hydrogen pressure in the range of 3-10 bar, the ruthenium loading in the range of 0.1-0.5 wt. % with respect to LA, the concentration of LA is in the range of 1-25 wt. % with respect to solvent and the reactions were monitored in the time interval in the range of 2 min to 1 h. 100% conversion of LA with 100% yield of Gvl was achieved using HRO-C/H-β catalyst under mild reaction conditions viz., 50° C., 10 bar H.sub.2 for 45 min. Stoichiometric yield was achieved over Ru/MgAl-LDH under optimized reaction conditions 80° C., 10 bar H.sub.2 for 30 min. The invention provided quantitative and qualitative analysis of prepared Gvl wherein quantitative analysis was carried out by using UHPLC and the qualitative analysis was ascertained by using .sup.1H NMR (FIG. 6A), .sup.13C NMR (FIG. 6B), FT-IR (FIG. 6C) and HR-MS (FIG. 6D).

[0075] The selective preparation of Gvl was also observed in presence of HRO-C, supported HRO-C and Ru/MgAl-LDH catalyst using various levulinic esters namely methyl levulinate (MeL), ethyl levulinate (EtL) and butyl levulinate (BuL). The reactions were carried out under similar conditions that are used for LA. The hydrogenation of LA esters to Gvl were also carried out in presence of solvents selected from water, alcohols, THF, and 1,4-dioxane either alone or in combination thereof and preferably in water.

[0076] The active catalyst (HRO-C) was impregnated on different supports to widen the scope of the reaction window by varying parameters such as metal loading, temperature, pressure and time, besides easier recovery of the catalyst. Among the supports studied, the preferred supports for HRO-C with maximum dispersion are MCM-41, Na-β, and H-β, and more preferred support is Na-β or H-β (in terms of cost).

[0077] The active catalyst (HRO-C/H-β) was recycled and reused up to five reaction cycles without drop in its catalysts activity. The catalyst was recovered from the product mixture by simple centrifugation, the obtained solid was washed with water and dried at room temperature and used for the next cycle and the same procedure was repeated for five cycles and observed 100% yield of Gvl in all cases.

[0078] The catalytic activity of HRO-C was compared with other conventionally used catalysts such as RuCl.sub.3and 5% Ru/Al.sub.2O.sub.3 for this reaction. A set of the reactions were carried out at 100° C., 10 bar H.sub.2, and using 0.35 wt. % of Ru metal (with respect to LA) for 15 min. The HRO-C catalyst showed better catalytic activity (100% yield of Gvl) than conventional catalysts RuCl.sub.3 (10% LA conversion, 7% yield of Gvl) and 5% Ru/Al.sub.2O.sub.3 (30% LA conversion, 30% yield of Gvl).

[0079] In another comparison, the most conventionally used commercial hydrogenation catalyst namely 5% Ru/C (M/s Sigma-Aldrich) was tested. The reaction was carried out using 2.5 wt. of LA 1(1 g of LA in 40 ml H.sub.2O) using 50 mg of catalyst at 10 bar H.sub.2 pressure and at 50° C. for 45 min. The yield of Gvl obtained was 39%. Under equivalent experimental conditions HRO-C/H-β showed 100%.

[0080] Increase in the wt. % of LA from 2.5 to 25 wt. % was studied for this reaction along with the extent of leaching of metal using inductively coupled plasma—optical emission spectrometry (ICP-OES). Negligible leaching was found up to 12.5wt. % of LA while beyond which high leaching of metal (Ru) was observed.

[0081] The reaction was scaled up for 20 g using 12.5 wt. % LA in water that showed 100% yield of Gvl demonstrates the scalability of the process. The product mixture was extracted with dichloromethane (DCM) for three times and observed that, the entire Gvl was extracted into DCM from the aqueous reaction mixture. The DCM was rotary evaporated to separate Gvl and the collected DCM was reused for subsequent product mixture extraction. Using this extractive separation technique, a maximum recovery of Gvl was realized (>95%) which is more energy efficient than distilling out water from the aqueous product mixture. The purity of Gvl as ascertained through HR-MS (FIG. 6D) and UHPLC was better than 99%.

[0082] The HRO catalyst used in the reaction is as such without any prior reduction and identified the occurrence of in situ reduction during the reaction. The in situ reduction of HRO catalyst during the reaction was confirmed by various analytical techniques namely PXRD, TEM, FT-IR and TGA. HRO, being an amorphous material (+3 and +4 oxidation state) did not show any diffraction peaks in PXRD while after the reaction the material showed an intense peak at 43.7° (101 plane; FIG. 2B) that can be indexed to hexagonal closed-packed (hcp) structure of ruthenium(0) (JCPDS: 06-0663). However, the extent of agglomeration of Ru particles of HRO-C catalyst (after the reaction) showed a decrease as inferred from TEM suggest disintegration of Ru nanoparticles from aggregated HRO-C particles (FIG. 3C). The TGA of fresh HRO-C showed a weight loss up to 24% in the temperature 150 to 350° C. (removal of strongly held H.sub.2O molecules) while the loss observed for the used HRO-C catalyst (after 2.sup.nd cycle) was 6% only (FIG. 4). This was also witnessed by FT-IR that showed a decrease in the intensity of O—H stretching band for the used HRO-C catalyst (FIG. 5). The catalyst Ru/MgAl-LDH and Ru/NaY have also underwent in situ reduction during the reaction.

[0083] We believe the invention preferred and claimed catalysts (HRO and Ru/Mg-Al LDH) have strongly adsorbed water molecules in their structure that are responsible for accessibility of LA molecules towards the active sites of the catalyst through hydrogen bonding and thus render high activity (Chem. Commun., 2014, 50, 12450-12453).

EXAMPLES

[0084] Following examples are furnished to support the feasibility of the invention but not to limit the scope of the invention

[0085] Catalysts Preparation

Example: 1

[0086] HRO—Hydrous ruthenium oxide (HRO) catalyst was prepared by both conventional precipitation method using NaOH (designated as HRO-N) and a modified precipitation method using CaCO.sub.3 as precipitating agent (designated as HRO-C). For HRO-C, 500 ml 0.001M of RuCl.sub.3 solution was added to CaCO.sub.3 solution (100 mg in 2L) and allowed to stand for 10 min with stirring at 25° C. The obtained precipitate was washed with water and dried at 100° C. for 6 h. The dried material was characterised by PXRD (FIG. 2A), FT-IR (FIG. 5) and TGA (FIG. 4). For HRO-N, to the stirred aqueous solution of ruthenium chloride (RuCl.sub.3.xH.sub.2O M/s Sigma-Aldrich; 200 ml of 0.001 M) a solution of 0.3 M sodium hydroxide was added dropwise at 25° C. until pH=7 and thereafter stirred the mixture for 12 h. The obtained precipitate was washed with water and dried at 100° C. for 6 h. The PXRD of the obtained HROs (HRO-C and HRO-N) matched well with commercial M/s Sigma-Aldrich sample (HRO-SA; FIG. 2A).

Example: 2

[0087] HRO-C/H-β—HRO-C supported on H-β zeolite was prepared using precipitation followed by impregnation method. 500 ml solution of 0.001 M of RuCl.sub.3 was added to precipitating agent which is 100 mg of CaCO.sub.3 solution (2 L) and 1 g of commercial Na-β zeolite, and the resulting mixture was stirred for 12 h at 25° C. The obtained precipitate was washed with water and dried at 100° C. temperature for 6 h. The PXRD profile of the dried material is given in FIG. 2C.

Example: 3

[0088] RuO.sub.2—20 mg of HRO-C (obtained from Example 1) was calcined at 550° C. for 3 h in a muffle furnace at a heating rate of 10° C./min. The solid obtained (15 mg) was RuO.sub.2 as confirmed by PXRD by comparing with standard diffraction pattern (FIG. 2A).

Example: 4

[0089] Ru/MgAl-LDH or Ru/NaY—Ru supported MgAl-LDH (LDH-layered double hydroxide) and NaY catalysts were prepared by impregnation method. To 100 ml of 0.001 M RuCl.sub.3 solution, lg of support material (MgAl-LDH and NaY) was added and stirred at 25° C. for 6 h. The solid obtained was collected by filtration and dried at 100° C. temperature for 6 h. The resulting material had 1 wt. % loading of Ru.

[0090] Catalytic Activity

Example: 5

[0091] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at temperature in the range of 24 to 28° C. To that, 3.5 mg of prepared HRO-C catalyst was added. The reactor vessel was pressurized with 5 bar H.sub.2 and heated at 50° C. for 90 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 6

[0092] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 25° C. To that, 3.5 mg of prepared HRO-C catalyst was added. The reactor vessel was pressurized with 5 bar H.sub.2 and heated at 25° C. for 12 h. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 48%.

Example: 7

[0093] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 27° C. To that, 3.5 mg of prepared HRO-C catalyst was added. The reactor vessel was pressurized with 5 bar H.sub.2 and heated at 50° C. for 30 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 40%.

Example: 8

[0094] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 26° C. To that, 3.5 mg of prepared HRO-C catalyst was added. The reactor vessel was pressurized with 10 bar H.sub.2 and heated at 100° C. for 15 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 9

[0095] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 28° C. To that, 3.5 mg of prepared HRO-N catalyst (prepared by NaOH precipitation method) was added. The reactor vessel was pressurized with 10 bar H.sub.2 and heated at 100° C. for 15 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 10

[0096] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 25° C. To that, 3.5 mg of prepared HRO-SA catalyst was added. The reactor vessel was pressurized with 10 bar H.sub.2 and heated at 100° C. temperature for 15 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 11

[0097] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 27° C. To that, 3.5 mg of prepared RuO.sub.2 catalyst was added. The reactor vessel was pressurized with 10 bar H.sub.2 and heated at 100° C. for 15 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. No yield of Gvl or conversion of LA was observed.

Example: 12

[0098] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 28° C. To that, 50 mg of prepared HRO-C/H-β catalyst was added. The reactor vessel was pressurized with 10 bar H.sub.2 and heated at 50° C. for 45 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 13

[0099] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 26° C. To that, 50 mg of prepared HRO-C/H-β catalyst was added. The reactor vessel was pressurized with 5 bar H.sub.2 and heated at 100° C. for 10 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 14

[0100] 1 g of LA was taken in mixture of solvents (20 ml of H.sub.2O +20 g of methanol (2.5 wt. % of LA)) in a 100 ml reactor vessel at 27° C. To that, 50 mg of prepared HRO-C/H-β catalyst was added. The reactor vessel was pressurized with 10 bar H.sub.2 and heated at 100° C. for 15 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 0%.

Example: 15

[0101] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 27° C. To that, 50 mg of prepared HRO-C/H-β catalyst was added. The reactor vessel was pressurized with 5 bar H.sub.2 and heated at 150° C. for 4 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 16

[0102] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 26° C. To that, 50 mg of prepared HRO-C/H-β catalyst was added. The reactor vessel was pressurized with 5 bar H.sub.2 and heated at 200° C. for 2 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 17

[0103] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 28° C.To that, 50 mg of prepared HRO-C/H-β catalyst was added. The reactor vessel was heated at 100° C. and pressurized with 3 bar H.sub.2; after attaining pressure, the reaction mixture was stirred for 30 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 18

[0104] 1 g of methyl levulinate (MeL) was taken in 40 ml of H.sub.2O (2.5 wt. % of MeL) in a 100 ml reactor vessel at 27° C. To that, 3.5 mg of prepared HRO-C catalyst was added. The reactor vessel was pressurized with 10 bar H.sub.2 and heated at 100° C. for 15 min. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 50% with 100% conversion of MeL.

Example: 19

[0105] 20 g of LA was taken in 160 ml of H.sub.2O (12.5 wt. % of LA) in a 300 ml reactor vessel at 28° C. To that, 1 g of prepared HRO-C/H-β catalyst was added. The reactor vessel was pressurized with 50 bar H.sub.2 and heated at 150° C. for 30 min. After completion of the reaction, the catalyst was separated by centrifugation. The obtained product mixture was extracted with DCM for three times, and further evaporated by using rotary evaporator and obtained 17 g of Gvl with 100% of purity as inferred by using UHPLC. The purity of recovered Gvl was also ascertained by 1H &13CNMR, IR and HR-MS (FIG. 6A-6D).

Example: 20

[0106] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 26° C. To that, 70 mg of prepared HRO-C/H-β catalyst was added. The reactor vessel was pressurized with 10 bar H.sub.2 and heated at 100° C. temperature for 10 min. After the reaction the catalyst was separated by simple centrifugation and it was used as such for next cycle without any pre-treatment and this procedure was followed for five subsequent cycles. The catalyst activity did not change and all cycles gave 100% yield of Gvl.

Example: 21

[0107] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 27° C. To that, 150 mg of prepared Ru/NaY catalyst was added. The reactor vessel was pressurized with 15 bar H.sub.2 and heated at 120° C. for 4 h. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 22

[0108] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 27° C. To that, 150 mg of prepared Ru/MgAl-LDH catalyst was added. The reactor vessel was pressurized with 10 bar H.sub.2 and heated at 80° C. temperature for 30 min. After completion of the reaction, the catalyst was separated by using centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 100%.

Example: 23

[0109] 1 g of LA was taken in 40 ml of H.sub.2O (2.5 wt. % of LA) in a 100 ml reactor vessel at 26° C. To that, 150 mg of prepared Ru/MgAl-LDH catalyst was added. The reactor vessel was pressurized with 5 bar H.sub.2 and heated at 120° C. for 1 h. After completion of the reaction, the catalyst was separated by centrifugation and the obtained clear product mixture was analyzed by UHPLC. The yield of Gvl obtained was 54% with 56% conversion of LA.

ADVANTAGES OF THE INVENTION

[0110] Reactions under mild conditions (50-100° C. and 5-15 atm. pressure of H.sub.2)

[0111] Nearly 100% conversion of LA

[0112] Excellent selectivity for Gvl (100%)

[0113] Lesser reaction time (2-30 min)

[0114] Using lesser weight % of precious metal, here Ru, content

[0115] Reactions using heterogeneous catalysts

[0116] No necessity of prior reduction of the active catalyst and is in situ generated

[0117] Active catalyst is recyclable

[0118] Reactions in aqueous medium

[0119] Requirement of nearly stoichiometric quantity of hydrogen thereby avoiding recycle operations

[0120] The active catalyst can be supported on inexpensive supports such as zeolites and LDHs for efficient recovery and reuse.