Production of valuable chemicals from glycerol using carbon fiber catalysts derived from ethylene

Abstract

Ethylene was thermocatalytically transformed into carbon products via a CCVD process. The filamentous carbon obtained was further modified with concentrated sulfuric acid or 4‐benzenediazonium sulfonate (BDS) to produce acid-type catalysts. The as-prepared samples were characterized by SEM and TEM techniques to confirm their morphological features. TG, XRD, elemental, and porosity analyses were also performed to assess the quality of these materials. The fabricated carbons were tested in eco-friendly green synthesis of value-added fuel bio-additives, namely in glycerol esterification. The reaction of glycerol transformation was performed with acetic acid at 80 °C using different glycerol to acetic acid (Gly/AA) molar ratios. The samples functionalized with diazonium salt showed better performance in the above process than those modified with H2SO4, and this was found to be directly related to the degree of surface functionalization with acidic sites. BDS-modified carbon fibers allowed obtaining acceptable results within 6 h when the reaction was performed with a Gly/AA molar ratio of 1:6, however, the dominant products in this case were mono- and diacetins. Extended reaction time altered the distribution of products. Finally, the combined selectivity to the targeted acetins (i.e., DA and TA) was about 75.5%. A direct correlation between the content of –SO3H groups of CNFs and the yield of higher acetins was found.

SO3H-functionalized carbon fibers for the catalytic transformation of glycerol to glycerol tert-butyl ethers

“…Furthermore, in the DTG curve of CF et , an additional poorly separated signal can be distinguished (at about 750 °C). The above observations can suggest the presence of phases with a different number of defects in CF et , i.e., a slightly more defective phase (with a minimum at 640 °C), and the one more stable and well-organized (with a minimum at 750 °C) 28 , 57 . The absence of lower-temperature peaks excludes contamination of the samples with less thermally stable types of carbon, e.g., amorphous carbon (combustion temp.…”

“…This indicates that the methods used here for the modifications of CFs were successful. It should be stressed, however, that the degree of sample functionalization was not very high (the S contents between 0.4 and 1.4% were attained), which is not surprising taking into account a rigid and ordered structure of typical carbon fibers 28 , 33 . For comparison, our previous studies showed that modifications of carbon xerogels can produce samples with a 1.4—2.3% S content, while functionalization of carbon polymeric spheres can give materials with a sulfur content of 4.3% 34 .…”

“…Carbon fibers (CFs) were prepared by catalytic chemical vapor deposition (CCVD) using gaseous hydrocarbons such as isobutane or ethylene as carbon feedstocks, and nickel as a catalyst. The process was conducted under the optimized conditions established earlier 27 , 28 . Briefly, NiO (100 mg in the case of isobutane and 30 mg in the case of ethylene) was placed in a quartz boat in a horizontal tube furnace and heated under Ar flow to 550 °C.…”

A Green Approach to Obtaining Glycerol Carbonate by Urea Glycerolysis Using Carbon-Supported Metal Oxide Catalysts

“…In recent years, carbon materials such as carbon nanotubes and fibers (CNT and CNF, respectively), graphene, carbon dots (CD), hydrothermal carbons (HTC), and activated carbons (AC) have gained increasing attention in the field of catalysis. It has been found that adequately tailored carbons can be used as efficient heterogeneous catalysts for various catalytic processes, including the sustainable transformation of biomass or (bio)glycerol to value-added chemicals [ 19 , 20 , 21 ]. Carbons can also be applied as attractive supports for enzymes, metals, or metal oxide catalysts [ 22 , 23 , 24 ].…”