BIOCHAR

Chemical industries increasingly rely on catalytic processes, and more than 90% of large scale chemical transformations depend on catalysts. Some of the commonly used homogeneous catalysts in Fridel Crafts alkylation reaction are; BF3, H2SO4, HF, AlCl3. Though, readily available at low cost, they have several limitations and these include toxicity, difficulty in separation and recovery and disposal problems. These limitations have intensified the demand for sustainable, efficient, and environmentally benign heterogeneous catalysts. This study focuses on the development of metal-doped coconut-shell biochars as robust heterogeneous catalysts for the Friedel Crafts benzylation of toluene. Biochars derived from the coconut shell produced at different pyrolysis temperatures (350, 400, 450, 500, 600 and 700 °C) were characterized in terms of their physicochemical and textural properties, surface oxygen functional groups and surface morphology using standard methods. The coconut shell biochar (CSB) sample with the optimal textural properties (CSB450) was then co-pyrolysed with Fe³⁺, Zn²⁺, and Fe³⁺/Zn²⁺ ions to produce metal doped biochars (Fe³⁺ - doped, Zn²⁺- doped, and Fe³⁺/Zn²⁺-doped biochar). Central Composite Design (CCD) of the Response Surface Methodology (RSM) was employed to optimize the process variables (metal loading, pyrolysis temperature and pyrolysis time) for the co-pyrolysis reaction. Similarly, RSM was used to optimized the process variables (mole ratio of toluene: benzyl chloride (T:BC), reaction temperature and reaction time) on benzyl chloride conversion to benzylated toluenes with the metal doped biochars. RSM-derived optimal conditions resulted in enhanced specific surface areas of 2098.04 m2 .g-1 for the Fe³⁺-doped biochar, 1721.40 m2 .g-1 for the Zn²⁺-doped biochar, and 2124.5 m2 .g-1 for the Fe³⁺/Zn²⁺-doped biochar. Compared with the pristine biochar (CSB450), the metal doped biochars (MBCs) showed improved physicochemical properties and textural properties. In addition, surface elemental analysis confirmed the successful incorporation of the Fe (10.09%), Zn (5.17%) and Fe/Zn (9.44/6.51%) on the MBCs. The results of the conversion process showed that the reaction temperature, mole ratio, and reaction time significantly affected benzyl chloride conversion with the metal doped biochar. Three novel models were developed for benzyl chloride conversion process. From the models, we predicted optimized process conditions; optimum benzyl chloride conversion of 93% was found for Fe3+/Zn2+ - doped biochar, with values of 87 and 81% for the Fe3+ - and Zn2+ - doped biochar respectively. This research established metal doped coconut shell biochar as an effective, low-cost, and environmentally friendly heterogeneous catalysts for organic transformations, presenting a viable alternative to conventional corrosive and non-recyclable catalysts in industrial alkylation processes.

Chemical industries increasingly rely on catalytic processes, and more than 90% of large scale chemical transformations depend on catalysts. Some of the commonly used homogeneous catalysts in Fridel Crafts alkylation reaction are; BF3, H2SO4, HF, AlCl3. Though, readily available at low cost, they have several limitations and these include toxicity, difficulty in separation and recovery and disposal problems. These limitations have intensified the demand for sustainable, efficient, and environmentally benign heterogeneous catalysts. This study focuses on the development of metal-doped coconut-shell biochars as robust heterogeneous catalysts for the Friedel Crafts benzylation of toluene. Biochars derived from the coconut shell produced at different pyrolysis temperatures (350, 400, 450, 500, 600 and 700 °C) were characterized in terms of their physicochemical and textural properties, surface oxygen functional groups and surface morphology using standard methods. The coconut shell biochar (CSB) sample with the optimal textural properties (CSB450) was then co-pyrolysed with Fe³⁺, Zn²⁺, and Fe³⁺/Zn²⁺ ions to produce metal doped biochars (Fe³⁺ - doped, Zn²⁺- doped, and Fe³⁺/Zn²⁺-doped biochar). Central Composite Design (CCD) of the Response Surface Methodology (RSM) was employed to optimize the process variables (metal loading, pyrolysis temperature and pyrolysis time) for the co-pyrolysis reaction. Similarly, RSM was used to optimized the process variables (mole ratio of toluene: benzyl chloride (T:BC), reaction temperature and reaction time) on benzyl chloride conversion to benzylated toluenes with the metal doped biochars. RSM-derived optimal conditions resulted in enhanced specific surface areas of 2098.04 m2 .g-1 for the Fe³⁺-doped biochar, 1721.40 m2 .g-1 for the Zn²⁺-doped biochar, and 2124.5 m2 .g-1 for the Fe³⁺/Zn²⁺-doped biochar. Compared with the pristine biochar (CSB450), the metal doped biochars (MBCs) showed improved physicochemical properties and textural properties. In addition, surface elemental analysis confirmed the successful incorporation of the Fe (10.09%), Zn (5.17%) and Fe/Zn (9.44/6.51%) on the MBCs. The results of the conversion process showed that the reaction temperature, mole ratio, and reaction time significantly affected benzyl chloride conversion with the metal doped biochar. Three novel models were developed for benzyl chloride conversion process. From the models, we predicted optimized process conditions; optimum benzyl chloride conversion of 93% was found for Fe3+/Zn2+ - doped biochar, with values of 87 and 81% for the Fe3+ - and Zn2+ - doped biochar respectively. This research established metal doped coconut shell biochar as an effective, low-cost, and environmentally friendly heterogeneous catalysts for organic transformations, presenting a viable alternative to conventional corrosive and non-recyclable catalysts in industrial alkylation processes.

The main goal of this research was to explore the effectiveness of slow pyrolysis of sawdust in generating high-quality biochar with beneficial characteristics for different uses, such as soil improvement and water purification. By adjusting the pyrolysis temperature and duration, the study sought to identify the ideal conditions for producing biochar with improved physicochemical properties. Sawdust, an abundant byproduct of the timber industry, underwent slow pyrolysis in a low-oxygen environment. The process was carried out at various temperatures, ranging from 400°C to 700°C, to evaluate how temperature affects both the yield and characteristics of the resulting biochar. The produced biochar was analyzed through several techniques, such as surface area measurement, pH analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett- Teller (BET) analysis, iodine number assessment, and yield percentage evaluation. The research revealed that slow pyrolysis of sawdust produced high-quality biochar with desirable characteristics. The biochar showed elevated carbon content, a porous structure, and an almost neutral pH, making it well-suited for use in agriculture and water purification. Both laboratory and field experiments confirmed that biochar effectively enhanced soil quality, boosted water retention, and improved nutrient availability. The research also showed that up to 55% of the material could be converted into solid biochar, while the rest was produced as bio-oil and syngas. These results emphasize the sustainable and versatile advantages of utilizing slow pyrolysis of sawdust for biochar production.