**1. Introduction**

Researchers throughout the world are striving to develop alternate technologies for manufacturing chemicals and hydrocarbons from coal as crude oil sources becomedepleted [1,2]. Fischer–Tropsch Synthesis was invented by a German chemist (FTS). Syngas, a mixture of hydrogen and carbon monoxide produced from coal, natural gas, or biomass, is used in the FTS process [3]. There are two stages to the FT reaction. The catalyst is employed in the first stage to produce straight-chain hydrocarbons, as well as water and/or carbon dioxide [4]. Hydrocracking is employed in the second stage to create the products and split them into liquid fuel. To boost production, various catalysts (Fe, Co, Ru, and Ni) have been utilized [3]. Due to their better conversion and selectivity, as well as their ease of CO dissociation, metal catalysts are favored in the FTS process [5]. Due to their inexpensive cost, favorable reactional conditions, and high catalytic activity, iron (Fe) and cobalt catalysts are frequently selected and utilized in commercial FTS reactors [6].

Fe catalysts are less expensive than other catalysts, and provide more product distribution flexibility than other catalysts. The Fe-based catalyst is more appealing, since it

**Citation:** Amin, M.; Munir, S.; Iqbal, N.; Wabaidur, S.M.; Iqbal, A. The Conversion of Waste Biomass into Carbon-Supported Iron Catalyst for Syngas to Clean Liquid Fuel Production. *Catalysts* **2022**, *12*, 1234. https://doi.org/10.3390/ catal12101234

Academic Editors: Ainara Ateka and Javier Ereña

Received: 26 August 2022 Accepted: 8 October 2022 Published: 14 October 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

has a better water gas shift reaction with a lower H2/CO ratio [3]. For iron-based catalysts, there are two forms: supported and bulk, both of which are manufactured using the wet impregnation method. To prevent particle agglomeration, a supported iron catalyst requires the inclusion of metal support. In comparison to bulk iron catalysts, they can also have a higher mechanical strength [7]. Some support materials, such as SiO2, Al2O3, TiO2, and carbon, have been widely used in recent research to influence catalyst performance in the FTS process [8,9]. The FTS activity and selectivity are influenced by the physical and chemical features of the support. They have been used for a long time to help with the FTS process. Carbon compounds, such as carbon black and activated carbon, have been used for this purpose [10]. Supported iron FT catalysts provide a larger iron dispersion; therefore, research has shifted away from bulk iron FT catalysts in recent years. Supported iron catalysts improve the performance of iron species by optimizing the interaction of iron species with support catalysts [11].

An iron metal catalyst's support serves as a macromolecular ligand that either directly or indirectly increases the reactivity of the active site [7]. Carbon materials' catalytic performance is influenced by their electrical characteristics, surface chemistry, and porous structure [12]. Because activated carbons have a porous morphology, they havebeen used as a support material. In this study, activated carbon derived from "Lantana Camara" is used as a support. Selecting the right carbon support could affect the overall FTS process [13,14].

Lower activity is one of the key problems of iron-based catalysts, which can be improved by using the correct promoters, such as potassium, sodium, and copper, which are regarded as advantageous for Fe-catalysts. To improve selectivity and optimize the spatial organization of active iron species, a variety of promotors are utilized [3]. Researchers have recently focused their attention on promoters such as potassium, copper, sodium, and manganese [6]. Potassium (K) promoter has been widely used in carbon-supported iron catalysts to improve the selectivity of hydrocarbons. Potassium promoter reduces methane formation, and enhances the production of short olefins. The use of potassium promoter with carbon support showed a marginal effect on the reactivates of CO and CO2. The addition of potassium as a promoter creates effects on an optimized iron-carbide by donating electrons to an active surface of iron. That is why potassium is used as a promoter in this study. For this purpose, the incipient wetness impregnation method was used to produce the carbon-supported iron catalyst with potassium promoter for Fischer–Tropsch synthesis [14].

FTS reactions are classified into two types: low-temperature FTS reactions (200–280 ◦C) and high-temperature FTS reactions (300–350 ◦C). The low temperature FTS reactions have been used to make specific C5+ hydrocarbons. For the coproduction of liquid hydrocarbons, however, high temperature FTS reactions have been used. At a temperature of 270 ◦C, the synergistic effect of active co-sites and acidic sites has been deemed the best reaction temperature for gasoline synthesis [15]. Given the foregoing, the goal of this research was to look at FTS reactions at low temperatures (LT-FTS) of 200 ◦C and high temperatures (HT-FTS) of 350 ◦C to see how reaction temperature and catalyst type affected direct syngas conversion via Fischer–Tropsch synthesis. Potassium (K) was used as a "structural promoter" (Fe-C-K) to make the Fe-C catalyst more active and stable, and its effect on the next process will be looked into as well.

To the best of our knowledge, no study on the development of a carbon-supported iron catalyst by using *Lantana Camara* has been conducted. The oil nature of *Lantana Camara* enhanced the production of gasoline and diesel. Therefore, this article could be beneficial for researchers and industrialists for the preparation of a carbon-supported catalyst by using *Lantana Camara* as a carbon support.

#### **2. Results and Discussions**
