658 Korean Chem. Eng. Res., 58(4), 658-664 (2020) https://doi.org/10.9713/kcer.2020.58.4.658 PISSN 0304-128X, EISSN 2233-9558 Blocking of Zeolite Pore by Loading Ni-Pt Nanoparticles for Maximization of Isomerization Selectivity A. Geetha Bhavani * ,† and N. Subba Reddy** *Department of Chemistry, Noida International University Research Innovation Centre, Noida International University, Gautama Buddha Nagar, Greater Noida-2013086, India **Department of Metallic & Materials Engineering, School of Materials Science and Engineering, Gyeongsang National University, 900 Gazwa-dong, Jinju, Gyeongnam, 52828, Korea (Received 10 January 2019; Received in revised from 3 June 2020; accepted 11 June 2020) Abstract - Zeolite HY is wet impregnated with Ni (0.1, 0.3, 0.4, 0.5 wt%), Pt (0.1 wt%) and reduced in presence of hydrogen to form nanosized particles of Ni and Pt. All the catalysts were characterized by XRD, TEM, ESCA, NH 3 -TPD, Pyridine adsorbed FT-IR and BET. Characterization results confirm that the Ni and Pt fractions effectively rehabilitated the physio-chemical properties of the zeolite HY catalysts. Further, all the reduced catalyst were screened with hydroisomerization of m-xylene at LHSV = 2.0 h -1 in the temperature range 250-400 ºC in steps of 50 ºC in hydrogen atmosphere (20 ml/g). The addition of Ni to Pt catalyst increases hydroisomerization conversion, as well as maximizes p-xylene selectivity by restricting the pore size. The increasing trend in activity continues up to 0.3 wt% of Ni and 0.1 wt% Pt addition over zeolite HY. The increasing addition of Ni increases the total number of active metallic sites to exposed, which increases the metallic sites/acid sites ratio towards the optimum value for these reactions by better balance of synergic effect for stable activity. The rate of deactivation is pronounced on monometallic catalysts. The results confirm the threshold Ni addition is highly suitable for hydroisomerization reaction for product selectivity over Ni-Pt bimetallic/support catalysts. Key words: Pore restriction, Ni and Pt nanoparticles, m-xylene reaction, Maximization of p-xylene selectivity. 1. Introduction The development of environmentally clean and cost-effective catalytic processes in fine and petrochemical industries has gained importance over the years due to improved environmental awareness. Catalytic processes of petrochemical industries using heterogeneous catalysts have advantageous features of their higher activity, reactant as well as product selectivity, ease of recovery and regeneration/reactivation for economic production. These advantageous features of heterogeneous catalysts also tailor to alter the various factors such as greater surface area, chemical composition, pore/channel size, geometry and distribution of the pores in the catalysts. Zeolites have an edge over the other metal oxides and sulfides because, unlike in the latter, the active sites in the zeolites are well defined and can also be tailored based on the end use application. In addition, they possess high surface area and large adsorption capacity, which can be controlled and varied. The size of the channels with the geometric constraints and intricate channel systems allows them to exhibit shape selectivity, with respect to reactant or product or transition state, in a catalytic reaction [1]. Shape selectivity of the zeolite catalysts has been well documented since it was first described by Weisz and Frilette [2]. In the absence of steric constraints imposed by the zeolite pores, the same selectivity as with liquid super acid is observed [3]. In particular, zeolites usually show specific selectivity in some reactions due to their microporous properties. It is generally believed that the majority of the active sites are located in the pores of zeolite. The major drawback of monofunctional catalyst is its less activity and selectivity in the transformation involving hydrocarbons such as hydrocracking, hydroisomerization and reforming reactions which require a metal function for hydrogenation/ dehydrogenation purposes. Further, due to coke formation during such reactions, the deactivation of monofunctional catalyst is faster. Scientists have introduced “bifunctional catalysts” which are composed of metal/metal ions for hydrogenation/dehydrogenation and acidic supports for acidity. Conventionally, noble metals like Pt, Pd, Re and Rh are loaded over acidic supports like γ-Al 2 O 3 , SiO 2 , clays, zeolites (ZSM-5, Y, β, MOR), aluminophosphate based molecular sieves (SAPO-5, SAPO-11, SAPO-41) and mesoporous materials like MCM- 41. Supported Pt, Pd catalysts are well known for their higher activity for hydrogenation, hydrocracking, hydroisomerization and naphtha reforming reactions. The principle behind the use of supported metal catalysts is to increase the effective surface area of metal particles and their dispersion over high surface area support material. In most cases, the metals are loaded by ion-exchange (IE) and incipient wetness impregnation (IWI) techniques. The present study carried out the hydroisomerization of C 8 hydrocarbons (m-xylene) over bimetallic catalysts of Ni-Pt loaded on different zeolite supports. The detailed effects of various physical parameters † To whom correspondence should be addressed. E-mail: gitabhavani_19@yahoo.co.in, geetha.bhavani@niu.edu.in This is an Open-Access article distributed under the terms of the Creative Com- mons Attribution Non-Commercial License (http://creativecommons.org/licenses/by- nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduc- tion in any medium, provided the original work is properly cited.