z Catalysis Effect of Ru Precursors and Reduction Conditions on Catalyst Performance in Glycerol Hydrogenolysis Rasika B. Mane,* [a, b] Shivanand T. Patil, [a] Hanmant Gurav, [a] Sadhana S. Rayalu, [b] and Chandrashekhar V. Rode* [a] Catalyst precursors, their reduction protocols and reaction conditions integrally influenced the activity and selectivity pattern in glycerol hydrogenolysis. Ru prepared from chloride precursor (Ru(Cl)/CB) showed the maximum selectivity to CC cleavage products EG (56 %) and methanol (17 %) with 23 % selectivity to 1,2-PDO. While, that prepared from nitrosyl precursor (Ru(n)/CB) showed higher selectivity to 1,2-PDO (44 %) and lower to EG (42 %). The catalysts prepared either with chloride or nitrosyl precursors but reduced by H 2 showed lower glycerol conversion (10-11 %) than NaBH 4 reduced catalysts. For these catalysts, 1,2-PDO selectivity increased to 40–43 % along with the major formation of 2-propanol (48- 49 %) and very less selectivities to CC cleavage products. The lower activity of the H 2 reduced catalysts can be related to their lower acidity and the bigger Ru metal particle size (3-5 nm). For Ru(Cl)/CB catalyst, glycerol conversion increased from 28–97 % with a rise in temperature from 180 to 250 o C also favoring 1,2- PDO selectivity; indicating that CO bond cleavage was favoured in comparison to CC scission, at higher temperature. Introduction A decade ago, the concept of “Bio-refinery” was postulated by Ragauskas et al. which replaces fossil derived feed stock with renewable biomass to fulfill the ever growing demand of valuable fuels and chemical products. [1] More than 50 % growth in energy sector is projected by 2025, mostly anticipated from the fast developing countries of the world. Due to their finite nature and ecological impact, dependency on petroleum resources needs to be strategically reduced in future. [2] Biodiesel production through transesterification of triglycerides fits well into this concept of bio-refinery, as biodiesel is produced for fuel on one hand; and “bio-glycerol” being co- produced in this process can be converted further to various value added chemicals. Bio-glycerol availability has immensely increased due to increased biodiesel production (180 million tonnes in 2016) which cannot be absorbed by its conventional uses and ends up becoming a residue. Therefore, valorization of glycerol in several ways has become a persistent area of research. [3] In particular, a range of commercial products possible from the catalytic hydrogenolysis of glycerol include 1,2-propanediol (1,2-PDO), 1,3-propanediol (1,3-PDO) and ethylene glycol (EG), due to their wide spread applications in antifreeze formulations, unsaturated polyester resins, polymers, paints, plastics, pharmaceuticals etc. [4] However,1,2-PDO and EG at present are mainly produced from petroleum resources. Therefore the hydrogenolysis of bio-glycerol available from biodiesel industry, to 1,2-PDO and EG is a step forward towards realization of biorefinery concept. Catalytic hydrogenolysis of glycerol has been extensively studied which has been also summarized and discussed in several recent reviews. [4–6] In general, catalytic activity and product selectivity were found to be sensitive to the type of active (hydrogenation) metal and acid and/or base co-catalyst. [7] Among the reported catalysts, Ru is usually found to be the most efficient catalyst for glycerol hydrogenolysis under relatively low temperature and pressure conditions. [4] Never- theless, due to its intrinsic property for CC cleavage, formation of degradation products, such as ethanol, methanol, 1- propanol, 2-propanol and even methane is facilitated. [8] There- fore, several attempts have been made in order to improve the selectivity towards one of the desired products such as 1,2-PDO by using additives like, CaO, NaOH, [9] K, Cu, and Mo [10] sulphurised Ru catalysts, bimetal combinations with Pt, Au, Cu etc. [11–13] Several inorganic acidic and basic supports like SiO 2 , Al 2 O 3 , ZrO 2 , TiO 2 , [14] hydrotalicte, [15, 16] carbon nanotubes, [17] La 2 O 3 , MgO and CeO 2 etc. [18] for Ru also have been reported for directing the selectivity towards 1,2-PDO. More important factors controlling the activity and product selectivity are metal dispersion and particle size which in turn are governed by the type of metal precursors, catalyst reduction conditions and acidity (acid strength and acid density). Some of these studies include the work of Feng et al. in which smaller Ru particle size (Ru/TiO 2 ) showed maximum glycerol conversion of 90 % with simultaneous increase in EG selectivity (41 %) at the cost of 1,2-PDO (21 %). [19] For g-Al 2 O 3 [a] Dr. R. B. Mane, S. T. Patil, Dr. H. Gurav, Dr. C. V. Rode Chemical Engineering and Process Development Division CSIR-National Chemical Laboratory Pune 411-008 (India) E-mail: cv.rode@ncl.res.in rb.mane@ncl.res.in [b] Dr. R. B. Mane, Dr. S. S. Rayalu Environmental Materials Division CSIR-National Environmental Engineering Research Institute (CSIR-NEERI) Nagpur 440-020 (India) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/slct.201700049 Full Papers DOI: 10.1002/slct.201700049 1734 ChemistrySelect 2017, 2, 1734 – 1745 # 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim