Value-Added Products from Urea Glycerolysis Using a Heterogeneous Biosolids-Based Catalyst

Abstract

Although thermal hydrolysis of digested biosolids is an extremely promising strategy for wastewater management, the process economics are prohibitive. Here, a biosolids-based material generated through thermal hydrolysis was used as a catalyst for urea glycerolysis performed under several conditions. The catalytic system showed remarkable activity, reaching conversion values of up to 70.8 ± 0.9% after six hours, at 140 °C using a catalyst/glycerol weight ratio of 9% and an air stream to remove NH3 formed during the process. Temperature played the most substantial role among reaction parameters; increasing temperature from 100 °C to 140 °C improved conversion by 35% and glycidol selectivity by 22%. Furthermore, the catalyst retained good activity even after the fourth catalytic run (conversion rate of 56.4 ± 1.3%) with only a slight decrease in glycidol selectivity. Thus, the use of a biosolids-based catalyst may facilitate conversion of various glycerol sources (i.e., byproduct streams from biodiesel production) into value-added products such as glycidol, and may also improve the economic feasibility of using thermal hydrolysis for treatment of biosolids.

Kinetics Modeling of Glycerol Carbonate Synthesis from Glycerol and Urea over Amberlyst-15 Catalyst

“…It was found that glycerol conversion increased from 56 to 95%. However, a slight decrease in glycerol carbonate selectivity was observed along with the increase of temperature to 433 K. The maximum selectivity of 98% was achieved at 413 K. Urea glycerolysis using biosolidsbased catalyst has been reported by Bartoli et al [21] and they showed that the influence of temperature is the key parameter for glycerol conversion. The glycerol conversion reached as high as 44% at 373 K after 6 h. However, by increasing temperature to 433 K, glycerol conversion as high as 44% was obtained only after 1 h. Hence, it could be seen that increasing temperature may accelerate the glycerol conversion.…”

“…The glycerol carbonate synthesis using MgO catalyst at the range of 0.015 to 0.045 found that the glycerol conversion could reach up to 71% with a selectivity of 100% at a temperature of 423 K [5]. In addition, urea glycerolysis using biosolids-based catalyst gave glycerol conversion of 70.8 % at 413 K after 6 h of reaction using 12 wt.% of catalyst loading [21].…”

Electrical and Microwave Characterization of Thermal Annealed Sewage Sludge Derived Biochar Composites

“…Nonetheless, several studies have used the treated sludge without removing metals for catalytic applications. Recently, thermally hydrolyzed sludge was used as an efficient catalyst for intra-and inter-molecular esterification processes [13,14]. Sludge catalytic activity could be magnified by pyrolytic processes that increase the inorganic content through a radical degradation of organic matter.…”

Glycerol Acetylation Mediated by Thermally Hydrolysed Biosolids-Based Material

“…Currently, producing refined glycerol from crude by-product streams is far more expensive than traditional processes [9][10][11] even if glycerol itself has many uses [12], such as an additive for cosmetic [13,14] and pharmaceutical [15] industries and as cattle feed [16,17]. Nonetheless, glycerol is an attractive feedstock for several conversion procedures, including oxidation [18], hydrogenolysis [19], etherification [20], esterification [21,22], glycerol carbonate synthesis [23][24][25] and biological conversions [24]. In particular, glycerol acetyl derivatives have received increasing attention due to their wide applications in many fields, from polymer production to fuel additive manufacturing [26][27][28][29][30].…”

“…Recently, Bartoli et al [23] described a novel catalyst derived from the solid residue recovered after the thermal hydrolysis of biosolids. Thermal hydrolysis of biosolids has been shown to dramatically improve settling rates, and thus offers a potential alternative to current disposal strategies that employ natural settling in large biosolids lagoons [53].…”