Synthesis of Polycardanol Using BF3.O(C2H5)2 as Initiator: Influence of Polymerization Conditions on Reaction Products

Abstract

Cardanol acts to stabilize asphaltene particles in crude oil, but its derivative polycardanol, synthesized with BF3.O(C2H5)2 as initiator, exhibits divergent behavior, acting as both asphaltenes stabilizer and flocculant. This behavior could be related to structural differences in polycardanol samples. Therefore, in this work, we study the influence of some polymerization conditions (monomer purity, initiator concentration, and reaction time) on the structures and molar masses of the reaction products, and the reaction conversion. The materials were characterized by size‑exclusion chromatography and hydrogen and carbon nuclear magnetic resonance. When reacting with distilled cardanol, the conversion, the molar mass, and the homogeneity of structures increased as increasing initiator concentration in the range tested (1-3% m/m). For both monomers (different purity degrees), when using a lower initiator concentration (1% m/m), the product contained a larger amount of unreacted monomer and different structures were obtained due to the occurrence of rearrangements. The presence of triolefinic molecules in the monomer provoked crosslinked structures for higher initiator concentration (2-3% m/m). This study elucidated the differences among the reaction products of polycardanol.

Polycardanol's potential to deasphalt crude oil: Influence of polymer conversion degree, molar mass, and structure

“…The sample already available in the laboratory was named ACN (aged cardanol) and the newly distilled one was named DCN. [42] Commercialgrade toluene was supplied by Vetec Química Fina (Rio de Janeiro, Brazil), used after being distilled and dried on alumina at room temperature. n-Pentane and n-heptane with 99% purity were supplied by Isofar Ind.…”

“…The six polycardanol samples (Table 1) were previously synthesized and thoroughly characterized. [42] These materials were obtained from the reaction of cardanol using BF 3 Á O(C 2 H 5 ) 2 , and employed without purification (data are detailed in the Data S1). Material codes consist of four letters and two numbers.…”

“…[44] About 30.0 g of ASPR was placed in a bottle containing 1 L of the flocculant solvent and the system was submitted to constant mechanical stirring for 120 h. Then the precipitated material was filtered at 25 C and the filter paper containing all the solid material was folded and inserted in an extraction cartridge and processed in a Soxhlet device with the following steps: (i) washing the precipitate by employment of the respective flocculant solvent at a ratio of 1:40 g of precipitate/mL of solvent, at temperatures of $40 C and $100 C, respectively, for n-pentane and n-heptane, where the washing was stopped when the solvent presented a limpid aspect inside the compartment of the cartridge located in the extractor, and the solution contained in the roundbottom beaker was discarded; and (ii) solubilizing the asphaltenes, where the dry toluene was reintroduced in the system and the temperature was adjusted to $110 C, followed by cycling until the solvent presented F I G U R E 1 Structural representations of oligomers formed in each type of product generated in the polymerization of cardanol initiated with BF 3 Á O(C 2 H 5 ) 2 : (A) low-conversion product, (B) branched low-conversion product, and (C) high-conversion product. [42] a limpid aspect in the cartridge compartment, after which the solution of asphaltenes in toluene was poured into a Petri dish and placed under a fume hood until complete evaporation of the solvent. After drying, the asphaltene fractions were placed in amber flasks.…”

“…[10,41] In a recent study, our research group performed six reactions of cardanol in the presence of the initiator BF 3 Á O (C 2 H 5 ) 2 , under different conditions, and found that different structures, molar masses and conversion degrees could be obtained. [42] As pointed out by Bai et al, [43] the synthesis does not occur by the chain reaction between olefinic groups, but rather by the reaction of the hydrocarbon chain with the aromatic ring. The molecules differ by the position of inclusion of the aromatic ring in the aliphatic chain of the second monomer unit (Figure 1), in function of the reaction conversion degree.…”

“…Besides this, the products with low conversion can also contain smaller quantities of molecules with branches incorporated in the polymer chain (Figure 1B). [42] After detailed characterization of the six polymer products obtained, both regarding the structure and presence of unreacted cardanol, [42] the general objective of this work was to evaluate the influence of these products on the asphaltene precipitation onset, and to establish a relationship between the composition of each product and the phase behaviour of the asphaltenes. Besides this, one of the products was doped with different levels of cardanol to evaluate the influence of the unreacted monomer on the behaviour of the additive.…”