Promotional effect of transition metals (Cu, Ni, Co, Fe, Zn)–supported on dolomite for hydrogenolysis of glycerol into 1,2-propanediol

Glycerol and Catalysis by Waste/Low-Cost Materials—A Review

The growing global demand for renewable energy sources can be reached using biofuels such as biodiesel, for example. The most used route to produce biodiesel is the transesterification reaction of oils or fats with short-chain alcohols, generating fatty acid esters (biodiesel) and a very important by-product, glycerol (Gly). Gly is widely used in different sectors of the industry, and in order to add value to this by-product, heterogeneous catalysis becomes a relevant tool, whether to transform glycerol into other chemical products of interest or even use it in the production of catalysts. Among the several studies found in the literature, the use of low-cost materials and/or wastes from the most diverse activities to prepare active catalytic materials for the transformation of Gly has been increasingly reported due to its valuable advantages, especially related to the cost of raw materials and environmental aspects. Thus, this brief review article presents the relationship between catalysis, low-cost materials, waste, and glycerol, through different studies that show glycerol being transformed through reactions catalyzed by materials produced from low-cost sources/waste or with the glycerol itself used as a catalyst.

Glycerol Hydrogenolysis to 1,2-Propanediol over Novel Cu/ZrO2 Catalysts

Glycerol is the main by-product of biodiesel production; its upgrading to more valuable products is a demanding issue. Hydrogenolysis to 1,2-propanediol is one of the most interesting processes among the possible upgrading routes. In this study, we propose novel copper/zirconia catalysts prepared by advanced preparation methods, including copper deposition via metal–organic framework (MOF) and support preparation via the sol–gel route. The catalysts were characterized by N2 physisorption, X-ray diffraction, Scanning Electron Microscopy, H2-TPR and NH3-TPD analyses and tested in a commercial batch reactor. The catalyst prepared by copper deposition via MOF decomposition onto commercial zirconia showed the best catalytic performance, reaching 75% yield. The improved catalytic performance was assigned to a proper combination of redox and acid properties. In particular, a non-negligible fraction of cuprous oxide and of weak acid sites seems fundamental to preferentially activate the selective pathway. In particular, these features avoid the overhydrogenolysis of 1,2-propanediol to 1-propanol and enhance glycerol dehydration to hydroxyacetone and the successive hydrogenation of hydroxyacetone to 1,2-propanediol.

Assessment on the Effect of Sulfuric Acid Concentration on Physicochemical Properties of Sulfated-Titania Catalyst and Glycerol Acetylation Performance

In this research, a solid acid catalyst was synthesized to catalyse glycerol acetylation into acetins. The sulphated-titania catalysts were prepared via the wet impregnation method at different sulfuric acid concentrations (5%, 10%, 15%, and 20%) and denoted as 5SA, 10SA, 15SA, and 20SA, respectively. The synthesized catalysts were characterized using FTIR, XRD, TGA, BET, NH3-TPD, XRF, and SEM-EDX. The synthesized catalysts were tested on glycerol acetylation reaction at conditions: 0.5 g catalyst loading, 100–120 °C temperature, 1:6 glycerol/acetic acid molar ratios, and 2–4 h reaction time. The final product obtained was analysed using GC-FID. An increment in sulfuric acid concentration reduces the surface area, pore volume, and particles size. However, the increment has increased the number of active sites (Lewis acid) and strong acid strength. 15SA catalyst exhibited excellent glycerol conversion (>90%) and the highest selectivity of triacetin (42%). Besides sufficient surface area (1.9 m2 g−1) and good porosity structure, the great performance of the 15SA catalyst was attributed to its high acid site density (342.6 µmol g−1) and the high active site of metal oxide (95%).

Catalytic Conversion of Glycerol into Hydrogen and Value-Added Chemicals: Recent Research Advances

In recent decades, the use of biomass as alternative resources to produce renewable and sustainable biofuels such as biodiesel has gained attention given the situation of the progressive exhaustion of easily accessible fossil fuels, increasing environmental concerns, and a dramatically growing global population. The conventional transesterification of edible, nonedible, or waste cooking oils to produce biodiesel is always accompanied by the formation of glycerol as the by-product. Undeniably, it is essential to economically use this by-product to produce a range of valuable fuels and chemicals to ensure the sustainability of the transesterification process. Therefore, recently, glycerol has been used as a feedstock for the production of value-added H2 and chemicals. In this review, the recent advances in the catalytic conversion of glycerol to H2 and high-value chemicals are thoroughly discussed. Specifically, the activity, stability, and recyclability of the catalysts used in the steam reforming of glycerol for H2 production are covered. In addition, the behavior and performance of heterogeneous catalysts in terms of the roles of active metal and support toward the formation of acrolein, lactic acid, 1,3-propanediol, and 1,2-propanediol from glycerol are reviewed. Recommendations for future research and main conclusions are provided. Overall, this review offers guidance and directions for the sufficient and economical utilization of glycerol to generate fuels and high value chemicals, which will ultimately benefit industry, environment, and economy.

On the application of 3d metals for C-H activation toward bioactive compounds: The key step for the synthesis of silver bullets

Several valuable biologically active molecules can be obtained through C-H activation processes. However, the use of expensive and not readily accessible catalysts complicates the process of pharmacological application of these compounds. A plausible way to overcome this issue is developing and using cheaper, more accessible, and equally effective catalysts. First-row transition (3d) metals have shown to be important catalysts in this matter. This review summarizes the use of 3d metal catalysts in C-H activation processes to obtain potentially (or proved) biologically active compounds.