## 1 Introduction  
Liquid smoke as a result of pyrolysis of lignocellulosic biomass has driven research attention because of its constituents' potential as a substitute for fossil fuel, flavorings, colorings, antiseptics, and antioxidants and other value-added chemicals. [PERSON] et al. [1] reported liquid smoke obtained from coconut shells consists of phenol (16.4%), hydrocarbon (12.4%), phenolic (27.6%), and oxygenate compounds (53.6%), and acetic acid (3%). [PERSON] et al. [2] identified volatile compounds of coconut shell liquid smoke based on the percentage composition of each functional group as follows: phenol (90.75%), carbonyl (3.71%), alcohol (1.81%), and benzene (3.73%). However, the presence of reactive oxygenates and heavy molecular compounds leads to the instability of liquid smoke. Polymerizationand condensation reactions occur during its storage and accelerate easily by temperature increase or oxidation. The instability of liquid smoke generates difficulties in further processing, such as constituent separation or conversion. Hydrodeoxygation (HDO) is a promising process to remove oxygen that binds to hydrocarbons [3,4] through hydrodeoxygenation (removal of C-O), hydrogenation (saturation of C=O and aromatic rings), hydrogenolysis, and hydrocracking [5]. Moreover, HDO produces more stable hydrocarbons with higher energy content [6,7]. [PERSON] et al. [8] reported that HDO of _Saccharina japonica algae_ oil reduced the oxygen constituent, then improved the C/O molar ratio, which would be a benefit, resulting a higher heating value (HHV). In addition, [PERSON] et al. [9] reported the HDO of beech wood pyrolysis oil showed more than 50% oxygen and 80% water removed. Among the oxygen removal techniques, catalyzed HDO is believed to be the most efficient [10]. Zeolite has been developed as catalysts for HDO [10, 11, 12, 13, 14] due to their attractive characteristics, such as being hydrophobic, large size of pores, and being thermally stable [15,16]. A bifunctional catalyst such as metal-zeolite, which has active metal centers and acid sites of zeolite and synergetic function in hydrogenation and deoxygenation. Considering its low cost and availability, nickel is more attractive. Furthermore, nickel has been used as support towards its catalytic performance. [PERSON] et al. [17] stated that Ni load on zeolite has 12 times higher acidity and increases the crystalline degree by 7.40% compared to activated zeolite without metals. This catalyst increases the yield of bio-oil by 40.38% compared to natural zeolite. A bifunctional system has been reported to have significant effects towards the reaction routes to increase phenolic conversion [18]. [PERSON] et al. [19] reported a bifunctional catalyst, Ni\({}_{3}\)P/HZSM-5, that has hydrogenation sites and acid sites, showing the highest catalytic performance in the HDO of phenols to cycloalkanes. On the other side, based on the report by [PERSON] et al. [20], the addition of Ni metal to the oxide support decreases the surface area, the volume of mesopores, and the diameter of micropores, while mesopore diameter increases in contrast. HDO from the mixture of furfurilidene acetone (Fac) compounds and difurfurilidene acetone (F\({}_{2}\)Ac) compounds produces 100% product conversion with a selectivity of 8-octanol and 6-dodecene as 88.22% and 2.99%, respectively. Sarulla natural zeolite is considered as a potential catalyst in terms of its abundance and characteristics. It was reported that Sarulla natural zeolites contain mordenite and clinoptilolite minerals as mesoporous materials. Moreover, they possess high surface area and thermal stability after the activation and calcination treatment [21]. Currently, Sarulla natural zeolite has not been comprehensively evaluated as an HDO catalyst for liquid smoke stabilization. Therefore, this research aims to develop Sarulla natural zeolites as a catalyst with different Si/Al ratios along with Ni-loaded on zeolites.