The depletion of fossil fuels has heightened research and utilization of renewable energy such as biodiesel. However, this has thrown up another challenge of significant increase in its byproduct, glycerol. In view of the characteristics and potentials of glycerol, efforts are on the increase to convert it to higher-value products, which will in turn improve the overall economics of biodiesel production. These high-value products include biofuels, oxygenated fuel additives, polymer precursors and other industrial bio-based chemicals. This review gives up-to-date research findings in the conversion of glycerol to the above high-value products, with a special focus on the performance of the catalysts used and their challenges. The specific products reviewed in this paper include hydrogen, ethanol, methanol, acetin, glycerol ethers, solketal, acetal, acrolein, glycerol carbonate, 1,3-propanediol, polyglycerol and olefins.

In this study, an optimized mesoporous sulfonated carbon (OMSC) catalyst derived from palm kernel shell biomass was developed using template carbonization and subsequent sulfonation under different temperatures and time conditions. The OMSC catalyst was characterized using acid-base titration, elemental analysis, XRD, Raman, FTIR, XPS, TPD-NH₃, TGA-DTA, SEM, and N₂ adsorption–desorption analysis to reveal its properties. Results proved that the OMSC catalyst is mesoporous and amorphous in structure with improved textural, acidic, and thermal properties. Both FTIR and XPS confirmed the presence of -SO₃H, -OH, and -COOH functional groups on the surface of the catalyst. The OMSC catalyst was found to be efficient in catalyzing glycerol conversion to acetin via an acetylation reaction with acetic acid within a short period of 3 h. Response surface methodology (RSM), based on a two-level, three-factor, face-centered central composite design, was used to optimize the reaction conditions. The results showed that the optimized temperature, glycerol-to-acetic acid mole ratio, and catalyst load were 126 °C, 1:10.4, and 0.45 g, respectively. Under these optimum conditions, 97% glycerol conversion (GC) and selectivities of 4.9, 27.8, and 66.5% monoacetin (MA), diacetin (DA), and triacetin (TA), respectively, were achieved and found to be close to the predicted values. Statistical analysis showed that the regression model, as well as the model terms, were significant with the predicted R² in reasonable agreement with the adjusted R² (<0.2). The OMSC catalyst maintained excellent performance in GC for the five reaction cycles. The selectivity to TA, the most valuable product, was not stable until the fourth cycle, attributable to the leaching of the acid sites.

Glycerol, a polyhydric alcohol, is currently receiving greater attention worldwide in view of its glut in the market occasioned by the recent upsurge in biodiesel production. The acetylation of glycerol to acetin (acetyl glycerol) is one of the many pathways of upgrading glycerol to fine chemicals. Acetin, which could be mono, di, and or triacetin, has versatile applications in the cosmetics, medicines, food, polymer, and fuel industries as a humectant, emulsifier, plasticizer, and fuel additive and so it is of high economic value. Given the critical role of catalysts in green chemistry, this paper reports the influence of the different heterogeneous catalysts used in glycerol acetylation. It also reviewed the influence of catalyst load, temperature, molar ratio, and the time on the reaction.

Biodiesel obtained from palm oil over an environmentally friendly catalyst is highlydesirable. For that matter, dolomite, a natural material was used as a catalyst in this work, and this included potassium oxide (K₂O)-doped dolomite, 5 wt% K/D, 10 wt% K/D, 15 wt% K/D, and 20 wt% K/D. X-ray diffraction analysis of dolomite revealed the CaO and MgO phases with high crystallinity, in which intensity reduced after doped with varying concentrations of K₂O. When the catalysts were evaluated, the K₂O-doped dolomite exhibited a better catalytic activity for palm oil transesterification. In the presence of K₂O, the methyl ester reached 98.7%, with the highest being displayed by 15 wt% K/D as compared to 87% over dolomite at reaction temperature of 60 °C, 12:1 methanol to palm oil ratio, 1 wt% catalyst amount and 1 h reaction time. SEM revealed that as more K₂O was doped on dolomite, the particles became more agglomerated, with a reduced BET surface area of 1.3 m²/g in 20 wt% K/D as opposed to homogeneously small-sized MgO and CaO particles in dolomite with a high BET surface area of 19.0 m²/g. However, the high activity of the doped catalyst was dictated by the high amount of basic site, as evidenced in TPD-CO₂ which showed an increase in the capacity of the basic site with an increased amount of K₂O. The catalyst was also reusable up to six times with a negligible decrease in activity due to K⁺ leaching.

Malaria remains one of the most prevalent diseases throughout tropics and subtropical areas and its effective chemotherapy remains a problem. Hence the need to continue to explore plants for their therapeutic potentials. In Nupeland, Lannea barteri (monkey’s faru), Piliostigma thonningii (camel’s foot tree or monkey’s bread), Clerodendrum aculeatum (haggar bush or garden quinine) and Crateva adansonii (Three leaved-caper) are some of the plants commonly used in the treatment of malaria. This study evaluated the phytochemical constituents and the acute toxicity of the methanolic extracts of these plants using standard procedures. Results of the qualitative phytochemical analysis showed that all the methanolic extracts of the plants tested positive to alkaloids, saponins, tannins, terpenoids and glycosides. While only P. thonningii shows the presence of anthroquinones. The analysis also shows the presence of flavonoids in all the plants extracts except C. adansonii root. Acute toxicity study of the extracts of L. barteri and P. thonningii leaves revealed an oral LD50 > 2500 mg/kg body weight, C. aculeatum leaf has LD50 >1500 mg/kg body weight and C. adansonii root has LD50 >2000 mg/kg body weight in mice. The presence of some of the phytochemicals in the plants’ extracts and the values of the LD50 recorded could explain their use traditionally for the treatment of wide array of illness including malaria. Key words: Malaria, Lannea barteri, Piliostigma thonningii, Clerodendrum aculeatum, Crateva adansonii, phytochemical, acute toxicity.