UniversalPhase Transformation Mechanism and SubstitutedAlkyl Length and Number Effect for the Preparation of Overbased DetergentsBased on Calcium Alkylbenzene Sulfonates.

Overbased calcium sulfonate is oneof the largest commerciallyproduced nanomaterials; the phase transformation mechanism involvedin the key process of carbonation reaction for overbased detergentpreparation has not yet been fully understood. Following our previousinvestigation based on the heavy alkylbenzene sulfonate (HABS) surfactantof industrial byproduct, two commercial products with well-definedchemical compositions and structures, long-chain alkylbenzene sulfonate(LCABS) and comparative short-chain linear alkylbenzene sulfonate(SLABS), are employed in this study as model surfactants for furthermechanism study of this pivotal process by the combination of analyticaltechniques such as potentiometric titration, DLS, TEM, FTIR, and XRD.It has been demonstrated that amorphous calcium carbonate (ACC) isa prerequisite for the preserving and stabilization of the alkalinereserve, especially under thermal work environment. The phase transformationfrom ACC to crystalline vaterite polymorph rather than calcite hasbeen unambiguously confirmed as a universal mechanism for all thealkylbenzene sulfonate based systems. Furthermore, the length andnumber of alkyl tails of alkylbenzene sulfonate surfactants exhibita strong influence on characteristics of detergent products. The LCABSwith long-chain alkyl substituents or HABS with dialkyl substituentsplays an important role not only in inhibiting the agglomeration process,but also in protecting the metastable inorganic cores from fusionto avoid phase transformation. Such understanding should be of crucialimportance for guiding the preparation of overbased detergents andgreases. In addition, the study on the influence of the molar ratioof calcium oxide in the total alkaline calcium salts and the dosageof surfactant LCABS, promoter methanol, and catalyst anhydrous calciumchloride help to determine the suitable work window for detergentproduction, and moreover, the water content provides a handle forbetter understanding the reaction process and achieving good qualitycontrol for detergent manufacturing. [ABSTRACT FROM AUTHOR]