Bitumen Fractionation Using a Rugged and Economic Variant of ‘Si-SARA’ Method

Abstract

The chemical composition of bitumen is a reinvigorated aspect of looking into the origin of bitumen behavior. Diversification of crude sources, emphasizing high-value products of refining, and addition of rejuvenators, extenders, modifiers lead to unusual behavior of bitumen compared to unmodified bitumen. There are many cases where the integrity of bitumen as a chemical was understood to be compromised but not captured by usual lab tests. Therefore, the use of bitumen chemistry as a predictor of performance and quality control is being pursued in multiple research fronts. However, analysis of bitumen chemistry is challenging due to the need for specialized equipment and a protective environment. In a recent study, Sakib and Bhasin (2019) used a novel method called ‘Si-SARA’ for extracting bitumen chemical fractions on the scale of milligrams. The key elements of that procedure were (i) a syringe-filter-based separation to isolate asphaltene and (ii) pre-packaged silica cartridges (Solid Phase Extraction– SPE cartridges) for fractionation of maltene into saturates, aromatics, and resins using chromatography in a procedure similar to ASTM D4124 and IP469. The ‘SiSARA’ procedure is an order of magnitude speedier, cheaper, and more compact than that of other existing processes. This procedure leads up to the present work which offers a further refinement of the ‘Si-SARA’ procedure. Proposed modifications in the present paper make the procedure suitable for field labs and labs without a dedicated chemical handling facility, thereby offering even faster results and point-of-use quality control. xii The compact new process calls for an enclosed metallic chamber, a manual or motorized vacuum pump, an air pump, a magnetic stirring heating mantle, and a condenser setup. While the method uses syringe filters and SPE cartridges like the original method, this innovation removes two major and relatively expensive equipment; namely glass-made vacuum manifold and drying oven. The new process actually combines the vacuum manifold and drying oven chamber into a single metal ‘lunch box’-commercially available as a steel-made airtight food container- alternately used either as vacuum chamber or as drying chamber mode. When operated in vacuum manifold mode, the system is relatively basic with no flow control regulators though an off-on valve facilitates the elution process’ initiation and termination. A vacuum pump helps the liquid flow as shown in Sakib and Bhasin (2019). However, when operated under drying mode, a heating plate is placed under the box, which heats up and evaporates solvents. Solvent-rich gas inside the box then passes through a cold condenser coil with the help of an air pump. After condensation, the accumulated liquid is collected in a bottle, and gas/air is returned to the chamber to complete the iteration. This process offers a closed system and thus removes the necessity of a chemical hood. During drying, nitrogen or other inert gas blanket requires only a small amount of gas or is completely made redundant as the same volume of gas is iterated and thus the amount of oxygen is very limited. Additionally, the use of metal cans in place of glass vials to collect elute in the new process offers a quick-drying and rugged system regarding heating and transportation. To summarize, the newly proposed system uses the ‘Si-SARA’ method but utilizes more accessible and economic tools, which enables the chemical analysis of bitumen in limited resource labs, field labs, or labs previously not suitable for chemical testing