Hydrogenation of Styrene Oxide to 2-Phenylethanol Over Nanocrystalline Ni Prepared by Ethylene Glycol Reduction Method

Hindawi Publishing Corporation International Journal of Chemical Engineering Volume 2014, Article ID 406939, 6 pages http://dx.doi.org/10.1155/2014/406939 Research Article Hydrogenation of Styrene Oxide to 2-Phenylethanol over Nanocrystalline Ni Prepared by Ethylene Glycol Reduction Method Sunil K. Kanojiya,1 G. Shukla,1 S. Sharma,1 R. Dwivedi,2 P. Sharma,2 R. Prasad,2 M. Satalkar,3 and S. N. Kane3 1 IPCA Laboratories Ltd., Indore 452003, India 2 School of Chemical Sciences, DA University, Indore 452001, India 3 Magnetic Materials Laboratory, School of Physics, DA University, Indore 452001, India Correspondence should be addressed to R. Prasad; [email protected] Received 14 February 2014; Accepted 20 May 2014; Published 17 July 2014 Academic Editor: Moshe Sheintuch Copyright © 2014 Sunil K. Kanojiya et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Nanocrystalline nickel prepared by glycol reduction method and characterized by XRD and magnetic measurements has been used as a catalyst for hydrogenation of styrene oxide to 2-phenylethanol. Effect of process variables such as particle size of the catalyst, temperature, and pressure have been optimized to achieve a maximum conversion of 98% of styrene oxide with 99% selectivity towards 2-phenylethanol. The structure of the transition state has been computed employing density functional theory −1 and using Gaussian 09 suite. The enthalpy of reaction (Δ) and activation energy ()arecalculatedtobe85.3kcal⋅mol and −1 123.03 kcal⋅mol , respectively. A tentative mechanism for the reaction is proposed according to which atomized hydrogen and styrene oxide react together over the catalyst surface to produce 2-phenylethanol. 1. Introduction the sodium aluminate by repeated washing with water which is time consuming [10–13]. In the present work nanonickel 2-Phenylethanol (2-PEA) having smell of rose petals is a is prepared by glycol reduction process which is simple and material of commerce and finds applications as fragrance takes much less time compared to that required for Raney chemical [1–4] antimicrobial and antifungicidal agent [5, 6]. nickel preparation. Also particle size can be reduced to as low Many perfumes, cosmetics, and deodorant formulations are as 5 nm. basedonthiscompound.Itsesterssuchasphenylethyl Liquid phase [14–20]aswellasvapourphase[21, 22] acetate are equally important in perfumery industries. In con- processes have been used to convert styrene oxide (SO) into ventional process 2-phenylethanol is produced by reacting 2-PEA. Liquid phase reactions are performed under pressure benzene with ethylene oxide and using anhydrous AlCl3 as using either pure metal (Ni, Pd, Pt) or supported metals on acatalyst[7–9]. The process has the disadvantages of using carriers like Cao, SiO2,andMgO. ethylene oxide, which is an explosive chemical and requires There are reports on the production of 2-phenylethanol special care and license. AlCl3 canbeusedonlyonceand by reduction of styrene oxide with hydrogen in slurry phase creates disposal problem. The process leads to the formation 5usingPdsupportedoncarbon[4–6]. Recently, there of side products such as biphenyl which results into poor have been few reports on the hydrogenation of styrene selectivity towards 2-PEA. oxide employing alumina supported Pt catalyst [7]. In these Conventional catalyst used for many hydrogenation reac- processescostlymetalslikePdandPtareusedascatalyst. tions is Raney nickel (particle size of about 25 nm) which is There is a cursory report on reduction of styrene oxide to prepared by dissolving Ni-Al alloy in NaOH and removing 2-PEA by hydrogen over transition metals supported over 2 International Journal of Chemical Engineering ) 15 111 ( # 14 13 12 ) ) ) Intensity (a.u.) Intensity 220 11 Particle size (nm) Particle 111 ( ( # ∗ 220 ( ∗ 10 9 30 40 50 60 70 7 8 9 10 11 12 13 2 (deg) pH pH 7 pH 13 B pH 11 Figure 3: Effect of pH on particle size of catalyst. Figure 1: XRD pattern of nano Ni catalyst. ∗ =NiO,#=Ni. 1.0 0.5 max. 0.0 M/M −0.5 Intensity (a.u.) Intensity −1.0 −1500 −1000 −500 0 500 1000 1500 Magnetic ﬁeld (Oe) 20 30 40 50 60 70 80 N13 spent Raney Ni 2 (deg) N13 catalyst Figure 2: XRD pattern of spent catalyst. Figure 4: (a) Raney nickel (b), N13 catalyst, and (c) N13 spent catalyst. carbon [8]. To the best of our knowledge, there seems to condenser a 2% solution of anhydrous nickel acetate in be no report on the hydrogenation of styrene oxide using ethylene glycol was taken, pH adjusted with NaOH solution, nanonickel as catalyst prepared by glycol reduction process. and refluxed till whole of the nickel acetate was converted In view of this the present problem of reduction of styrene to Ni indicated by change of color from green to brown. oxide with hydrogen over nanonickel was undertaken with SampleswerepreparedatpH7,11,and13,andnamedas the objectives of (1) synthesizing the nanonickel by glycol N7,N11,andN13.Theanhydrousnickelacetatewasprepared reduction process (2) to characterize it by spectroscopic simply by drying laboratory grade nickel acetate in oven at ∘ and surface area measurement process (3) to evaluate its 105 C for few hours till a constant weight was achieved. Small performance as catalyst for hydrogenation of styrene oxide amount of the product was taken out for characterization. to 2-phenylethanol and (4) to predict a tentative mechanism The catalyst was always kept covered with ethylene glycol of the process. and taken out only when needed for characterization or for application as a catalyst. X-ray diffraction “XRD” (-2) 2. Experimental configuration patterns of the studied sample were obtained by Bruker D8 Advance diffractometer, with Cu-K radiation 2.1. Preparation of Catalyst and Its Characterization. In a ( =0.154nm).Roomtemperaturemagneticpropertiesof three necked flask fitted with a thermometer and a water the studied samples were measured using a digital hysteresis International Journal of Chemical Engineering 3 100 100 80 80 60 60 (%) (%) 40 40 20 20 0 0 320 330 340 350 360 370 380 Temperature (K) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 Duration (h) B D C E B D C E Figure 7: Effect of temperature on performance of catalyst. B = conversion, C = 2-PEA yield, D = others, and E = 2-PEA selectivity. Figure 5: Effect of duration of reaction. B = conversion, C = 2-PEA yield, D = others, and E = 2-PEA selectivity. 100 90 100 80 80 70 60 60 50 (%) 40 (%) 40 30 20 20 10 0 0 10 20 30 40 50 −2 0.0 0.2 0.4 0.6 0.8 1.0 Pressure (kg·cm ) Catalyst (wt%) B D B D C E C E Figure 8: Effect of pressure on catalyst performance. Temp. = 378 K, Figure 6: Effect of catalyst loading on the performance of the catalyst loading = 1%, duration = 4 hrs. B = conversion, C = PEA catalyst.B=conversion,C=2-PEAyield,D=others,andE=2- yield, D = Others, and E = Selectivity. PEA selectivity. The gas pressure decreases slowly with time and finally loop tracer employing conventional induction technique with becomes constant at completion of the reaction. After com- amaximumfieldof±1600 Oe. pletionofthereactionthereactorisopened,catalystis filtered, solvent is distilled, and product mixture is analyzed 2.2. Catalyst Evaluation. Catalytic performance of the pre- over a Chemito GLC machine using SE-30 column and FID pared catalyst for reduction of styrene oxide was evaluated detector. in a 2lt stainless steel pressure reactor supplied by Amar Engineering Mumbai. The reactor was fitted with a mechan- 3. Results and Discussion ical stirrer and pressure gauze. Heating was performed by circulating thermal fluid to the coil fitted internally to the 3.1. Catalyst Characterization. TheXRDpatternsofthe reactor. In a typical rum 50 g of styrene oxide in 500 mL of catalyst prepared at different pH are reproduced in Figure 1. methanol and 2.5 g of catalyst was charged to the reactor and ∘ The particle size was calculated from the 111 peak of the heated to 110 C. The reactor was pressurized through a hydro- powder employing Scherer’s formula [23]. Assignment of −2 gen gas cylinder to the desired pressure (40–100 kg⋅cm ). XRD peaks were made by comparing the reported pattern 4 International Journal of Chemical Engineering H3 H7 1 C C6 H9 H4 C2 C3 C5 H6 H8 C4 C8 H10 C7 H5 O1 H2 Ni1 H1 Ni2 (a) (b) (c) Figure 9: Structure of (a) reactant model, (b) product model, and (c) TS for hydrogenation of styrene oxide to 2-phenylethanol. is 0.7 Oe [25]. Observed change in the coercivity can be attributed to the different grain diameters in Raney Ni and in 150.0 bulk Ni. Magnetic measurements done on spent and fresh Ni- nanoparticlesrevealthattheyarehighlyanisotropic(whereas 125.0 TS Raney Ni is not that anisotropic), as can be seen in hysteresis 100.0 measurements (Figure 4). As the applied magnetic field is less P 75.0 than saturating field for the case of prepared Ni nanoparticles thesamplescouldnotbesaturated,sothecoactivitycould 50.0 123.03 not be estimated. An inspection of the hysteresis loops for 25.0 85.30 nano Ni suggests that its coercivity will be higher than that of Energy (kcal/mol) Raney Ni. This further suggests smaller size of the prepared 0.0 R nanoparticles compared to bulk and Raney Ni. 25.0 50.0 3.2. Effect of Duration of Reaction. Effect of duration of reaction was studied to have an idea of completion of the reaction. Results are shown graphically in Figure 5. Increasing duration Reaction process of reaction increased conversion of styrene oxide as well as yieldandselectivityof2-PEA.Itwasfoundthatduration of 4 hrs was enough for the completion of the reaction.

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