Effect of Different Metal Modified Dolomite Catalysts on Catalytic Glycerol Hydrogenolysis towards 1,2-Propanediol

Sains Malaysiana 51(5)(2022): 1385-1398 http://doi.org/10.17576/jsm-2022-5105-10

ABSTRACT A series of metal modified dolomite catalysts (10%Ni-20%Cu/Dol, 10%Co-20%Cu/Dol, 10%Fe-20%Cu/Dol, 10%Zn-20%Cu/DolNi) were synthesized via method of impregnation, later calcined at 500 ℃ and reduced by 5%H2 at 600 ℃. Those catalysts were formerly tested for their physico-chemical properties by BET, BJH, XRD, H2 - TPR, NH3 –TPD, CO2 -TPD and SEM, and followed by evaluation in catalytic performance of glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO). Among the examined catalysts, 10%Ni-20%Cu/Dol showed optimum hydrogenolysis activity owing to the good copper-nickel-dolomite interaction. The outcomes from the characterizations disclosed that the presence of nickel-copper species which principally enriched on dolomite surface thereby enhanced the properties of the catalyst in terms of good metal reducibility along with the presence of adequate catalyst acidity. All the good features of 10%Ni-20%Cu/Dol catalyst added to its high activity with 83.5% glycerol conversion (GC) and 75% 1,2- PDO with low methanol as side reaction product under 200 ℃, 4 MPa H2 and 10 h duration test, 1 g catalyst dosage and 20 wt% glycerol concentration.

INTRODUCTION It has been known that 1,2-propanediol (1,2-PDO) was used as a chemical additive in the manufacture of mainly pharmaceuticals, cosmetics, solvent in food, and as raw material for polyester resins (Gallegos-Suarez et al. 2015). The estimated global production of 1,2- PDO reached about 1.4 million tons yearly (Vasiliadou & Lemonidou 2011). Conventionally, its manufactured was via chlorination and hydration reaction process using propylene oxide derived petroleum (Bagheri et al. 2015; Rajkhowa et al. 2017). The concern of dwindling wealth of petroleum in addition to the environmental pollution topic, therefore, the production of 1,2-PDO from renewable bases could be necessitated as it could also substantively alter the market cost of 1,2-PDO. Meanwhile the excess of glycerol from biodiesel production could serve as an ideal material for the production of 1,2-PDO (Pandhare et al. 2016). Hydrogenolysis of glycerol to 1,2-PDO involves C=O bond activation on acid sites and hydrogenation of dehydrated intermediate product to form 1,2-PDO on metal sites (Balaraju et al. 2009; Gandarias et al. 2012; Mallesham et al. 2016; Zheng et al. 2015) (Scheme 1). Considerable efforts have been dedicated to glycerol hydrogenolysis using heterogeneous catalysts such as Ru and Ce and transition metal-based catalysts such as Cr, Co, Ni, Cu, Zn and Zr (Soares et al. 2016a; Xia et al. 2011; Yu et al. 2010). However, for a cost effective catalyst application, the use of economical metal-based catalysts are more look up since they also exhibited high in catalytic activity. Cu-based catalysts have been said to perform well in catalytic performance attributable to its efficiency towards C=O bond cleavage (C=O bond activation) rather than C-C bond cleavage (Freitas et al. 2018; Putrakumar et al. 2015). Further, a modification of Cu based-catalyst with co-catalysts or promoters (Ni, Co and Fe) have also been reported to improve and strengthen the interaction between the metals as high 1,2-PDO selectivity and glycerol conversion of > 60% over metal modified catalysts was attained (Gandarias et al. 2012; Jiang et al. 2016; Pudi et al. 2015; Soares et al. 2016b). The catalytic efficiency made known by metal modified catalyst was owing to the synergetic metals interaction which for that reason enhanced the crystallite size, metallic dispersion, acidity and metal reducibility of the catalyst (Jiang et al. 2016; Pandhare et al. 2016; Pudi et al. 2015; Soares et al. 2016a). For this work, dolomite with low-priced, highly abundance in Perlis, Malaysia and high acidic characteristic with mainly derived from calcium carbonate (CaCO3 ) and magnesium carbonate (MgCO3 ) has been selected as a catalyst support for the metal catalysts. The performance of the metal modified dolomite catalysts was then tested in glycerol hydrogenolysis to 1,2-PDO under 200 ℃, 10 h and 4 MPa H2 to relate the role of catalyst metal reducibility and catalyst acid capacity in the reaction performance. Meanwhile, impregnation method was preferred for catalyst preparation as it may control the catalyst metal size rather than by co-precipitation method (Azri et al. 2020). This could be attributed to during wet impregnation, an excess of solution containing the precursor of solid phase is used. The solid is then dried and the excess solvent is removed. It is the procedure whereby the maximum solubility of the precursor in the solution is limited. This method offers easy way to prepare a layer of active matter on the catalyst surface. This could be attributed to the solution transport from a capillary action process to a diffusion process, which is much slower. This feature made impregnation method as an effective process for the production of catalyst. 

Sains Malaysiana 51(5)(2022): 1385-1398 http://doi.org/10.17576/jsm-2022-5105-10