• Energy Research

Abstract Liquefaction of poly-isoprene based rubber (PIR) was performed using ethanol as a solvent for the production of liquid fuel and chemicals. An autoclave batch reactor was used to perform the ethanolysis of PIR at different temperature ranges (250–375 °C), with different ethanol to PIR ratio (0.5:1 to 4:1), and at different reaction times (15–75mins). The experimental results showed that a maximum yield of 86 wt % was achieved at temperature of 325 °C, ethanol to PIR ratio 1/1, and reaction time of 30 min. This liquid oil yield is about 14% higher than the yield obtained from the pyrolysis of PIR at 500 °C and about 10% higher than the yield obtained from hydrothermal liquefaction of PIR at 375 °C. Moreover, the utilization of ethanol in the process was also incorporated and product yields were redefined. Furthermore, ethanol contributed to enhance the quality of liquid-oil, particularly in term of viscosity, acidity, and energy density. Furthermore, the FTIR analysis showed methyl and methylene were most dominating functional groups found in the liquid product and GCMS analysis identified that they were presented by alkenes, aromatics, and alkyls.

This study aimed at the synthesis of heterogeneous acid catalysts by incorporating 12 tungstophosphoric acid (HPW) over mesoporous silica support KIT-6 via impregnation and sol-gel methods to improve the catalytic efficiency of the esterification reaction. The catalytic activity of the KIT-6 supported catalysts was investigated for esterification of oleic acid in the presence of MeOH. Synthesized catalysts were analyzed using scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) and Fourier transform infrared (FTIR) spectroscopy techniques. Characterization results showed the variation in porosity, roughness, presence of SiO2 and kegging structure after successful deposition of HPW over KIT-6 surface. Additionally, the textural property of synthesized catalysts was compared with highly active HPW and sulfated KIT-6. The ordered structure of mesoporous silica KIT-6 facilitated the dispersion of HPW resulting in better catalytic stability and activity. To evaluate the impact of synthesizing technique on catalytic activity and effectiveness of heterogeneous acid catalysts, loading of HPW over KIT-6 mesoporous silica was controlled between 10 to 30 wt%. Catalysts synthesized by impregnation and sol-gel methods showed the highest catalytic activity with 30-IM and 25-SG, respectively. The enhanced performance was ascribed to the improved textural property and amount of HPW, which led to higher activity, stability and reusability.

AbstractThere has been growing and recent interest in using non-edible feedstocks, such as waste animal fats, as an alternative to vegetable oils in biodiesel production to address the food versus fuel debate. Waste animal fats are cost effective and yield good quality biodiesel. Therefore, waste animal fats are appealing and excellent feedstocks to produce biodiesel. Commercially, the biodiesel is obtained by transesterification reaction of triglycerides present in oil/fat with alcohol in the presence of homogeneous base catalysts. However, free fatty acids found in low-quality oil feedstocks are particularly sensitive to homogeneous base catalysts, necessitating extra acid pretreatment and neutralization procedures that not only raise the overall expense of producing biodiesel but also create environmental contamination. Optimistically, the use of solid catalysts can offer an environmentally friendly, cost-effective and practical route for the manufacture of biodiesel from inexpensive oil feedstocks, including waste animal fat. The present review article covers catalyzed transesterification/esterification using various catalysts with particular focus on the use of heterogeneous catalysts when using waste animal fat as feedstock for biodiesel production. In particular, the properties of biodiesel obtained from waste animal fats are also compared to the biodiesel properties of standard organizations, such as the European Committee for Standardization (ISO) and the American Society for Testing and Materials (ASTM). Moreover, this paper also offers future research directions that can direct researchers to fill in knowledge gaps impeding the creation of efficient heterogeneous catalysts for long-term biodiesel generation. To the best of our knowledge, the valorization of waste animal fats from slaughterhouses is not feasible and has some techno-economic concerns. However, this technology is more desirable considering the environmental point of view to address the pollution problems caused by these wastes.

Abstract Lignocellulosic biomass is an agricultural waste material abundantly produced in large quantities on earth. Rice husk (RH) is a type of lignocellulosic biomass and a huge byproduct of rice milling. Notably, the rice plant collects silica from the soil and stores the collected silica in the form of silicic acid inside the cellulose micro-compartments of the plant. Therefore, RH obtained from rice milling contains a significant quantity of amorphous silica, which can further be used for several other purposes. Furthermore, silica-rich RH can be employed as a raw material for the production of biofuels and biochars instantaneously via thermochemical processes such as pyrolysis and gasification. This article thoroughly explores a prospective method use to produce biosilica and energy from RH at the same time, which is currently under investigation. Moreover, this study also discusses current improvements in the synthesis of RH silica materials and their long-term use, particularly in energy and environmental functional materials. In terms of the environment, RH silica materials can remove heavy metals and organic pollutants in soil amendment, wastewater treatment, and gas purification via adsorption, catalysis, and integrative methods. In essence, there are numerous research and development obstacles to overcome in the production of biosilica and biofuels, respectively, from RH, and this review article highlights all of them.

Abstract Since decades, one of the major troublesome environmental issue to the society is Polystyrene waste. Thermal conversion method can be used to transform the plastic waste into useful energy source. In this study, liquefaction technique using ethanol as a solvent was used to produce liquid fuel from polystyrene. The experiments were performed at different temperatures (290–370 °C), ethanol to polystyrene ratios (0.25:1–4:1) and reaction times (15–75 min) in an autoclave batch reactor. After characterization, quantitative and qualitative evaluation of liquid products; results showed that at temperature of 350 °C, ethanol to polystyrene ratio of 0.5:1 and reaction time of 60 min, highest liquid yield of 84.7 wt% was achieved. The viscosity, density, pH, calorific value and flash point of the oil product at this condition was 0.36 cP, 0.88 g/mL, 6.86, 40.91 MJ/kg and 55 °C respectively. Through GC–MS analysis, it was found that the oil product was mostly composed of aromatics, alkenes and alkyls; which made the liquid oil suitable to be used as fuel. In addition, comparative study was conducted by replacing ethanol with water as solvent under same conditions. Based on results, study proved ethanol to be better solvent than water which is commonly used in liquefaction process. Lastly, the liquid fuel produced is suitable to be used as alternative energy source for conventional fossil fuels.

We evaluated the thermochemical properties and suitability of a variety of lignocellulosic biomass residues in Pakistan for energy production. Proximate, ultimate and calorific value analyses were performed to know the energy perspective, whereas thermogravimetric analysis was used to study the decomposition behavior of biomass samples under pyrolysis conditions. The moisture content, volatile matter, fixed carbon and ash content in the biomass samples were found within the range of 4.38–5.69%, 63.25–80.53%, 7.97–23.13%, and 7.12–14.35%, respectively. The range of carbon, hydrogen, and oxygen content was reported as 35.83–47.23%, 5.2–6.56%, and 45.6–58.55%, respectively. Lower values of sulfur and nitrogen content amongst the samples indicated that the biomass was environmentally friendly in terms of energy production. The heating value of the biomass was reported in the range of 15.20–18.44 MJ/kg. Fourier transform infrared spectroscopy showed the existence of hydroxyl, aldehydes, ketones, aromatic compounds, carbonyl compounds, ether, and halogen groups. Orange leaf biomass indicated a greater potential in producing bio-oil, whereas the horticulture biomass and mango leaves may have greater potential for biochar.

Abstract Pakistan’s current energy portfolio is problematic due to a lack of proper management and implementation of appropriate energy policies. This densely populated country has a high energy demand that rises yearly and is expected to increase three-fold by 2050. However, fossil fuel resources are continuously depleting by global overuse while negatively impacting the environment through increasing greenhouse gas emissions. This study reviewed the potential for agricultural residues to be used as renewable energy sources for bioenergy production in Pakistan to address the energy-related challenges that would also help in addressing the economic and environmental concerns. First, a comparison was made between the current energy situation, potential renewable energy scenarios, and global trends. Second, greenhouse gas (i.e., CO2) emissions in Pakistan were summarised and compared with other regions. Third, the thermochemical properties of different agricultural residues were reviewed along with varying the options of processing to produce renewable energy such as thermochemical conversion approaches (combustion, pyrolysis, gasification, and liquefaction) and biochemical conversion options (anaerobic digestion, and fermentation). Pakistan being an agricultural-based economy, produces vast quantities of agricultural residue biomass, which is mostly underutilized as animal feed, conventional fuel substitutes, left to rot in fields or burnt to get rid, resulting in the vast emissions of greenhouse gases causing severe environmental pollution and smog formation. A considerable share of Pakistan’s national energy demand can be fulfilled if these feedstocks are adequately managed and exploited through the energy sector and converted into large-scale bioenergy.