Application of Polysaccharide Biopolymer in Petroleum Recovery.

Polysaccharide biopolymers are biomacromolecules derived from renewable resources with versatile functions including thickening, crosslinking, adsorption, etc. Possessing high efficiency and low cost, they have brought wide applications in all phases of petroleum recovery, from well drilling to wastewater treatment. The biopolymers are generally utilized as additives of fluids or plugging agents, to correct the fluid properties that affect the performance and cost of petroleum recovery. This review focuses on both the characteristics of biopolymers and their utilization in the petroleum recovery process. Research on the synthesis and characterization of polymers, as well as controlling their structures through modification, aims to develop novel recipes of biopolymer treatment with new application realms. The influences of biopolymer in many petroleum recovery cases were also evaluated to permit establishing the correlations between their physicochemical properties and performances. As their performance is heavily affected by the local environment, screening and testing polymers under controlled conditions is the necessary step to guarantee the efficiency and safety of biopolymer treatments.

Electro-deposition for asphaltene removal during heavy oil upgrading.

Blending crude oil with short-chain paraffins is a common method to improve the oil quality during heavy oil upgrading. The additional paraffins will cause precipitation of asphaltene that is removed by filtration or sedimentation; both processes are slow and inefficient. As a potential faster and more efficient removal method, an electric field can be applied in order to electro-deposit the asphaltene on the electrodes. Electro-deposition (E-D) experiments were conducted in a bench scale vessel while varying several process parameters such as the dilution ratio of paraffin to heavy oil, the paraffin used as the diluent, electric field strength, and the effect of resins on the E-D process. Increasing the dilution ratio resulted in more precipitated asphaltene and required a lower electric field strength for the E-D process. The electro-deposition process could affect the net charge of the asphaltene, and hence, both cathode and anode were closely observed: deposition onto the cathode was favored with higher dilution ratio and a lower electric field strength, while anode deposition occurred using a lower dilution ratio and higher electric field strength. This result is related to the higher resin content at low dilution ratio which adsorbs onto the asphaltene aggregate and shields or inhibits the effect of the electric field. To recover 1 kg of asphaltene, the energy input is estimated to be as low as 10 kJ. The process is relatively fast and requires low energy input, which can overcome the disadvantages of current filtration methods.

Cascade enzymatic reactions for efficient carbon sequestration.

Thermochemical processes developed for carbon capture and storage (CCS) offer high carbon capture capacities, but are generally hampered by low energy efficiency. Reversible cascade enzyme reactions are examined in this work for energy-efficient carbon sequestration. By integrating the reactions of two key enzymes of RTCA cycle, isocitrate dehydrogenase and aconitase, we demonstrate that intensified carbon capture can be realized through such cascade enzymatic reactions. Experiments show that enhanced thermodynamic driving force for carbon conversion can be attained via pH control under ambient conditions, and that the cascade reactions have the potential to capture 0.5 mol carbon at pH 6 for each mole of substrate applied. Overall it manifests that the carbon capture capacity of biocatalytic reactions, in addition to be energy efficient, can also be ultimately intensified to approach those realized with chemical absorbents such as MEA.

Biocatalytic carbon capture via reversible reaction cycle catalyzed by isocitrate dehydrogenase.

The practice of carbon capture and storage (CCS) requires efficient capture and separation of carbon dioxide from its gaseous mixtures such as flue gas, followed by releasing it as a pure gas which can be subsequently compressed and injected into underground storage sites. This has been mostly achieved via reversible thermochemical reactions which are generally energy-intensive. The current work examines a biocatalytic approach for carbon capture using an NADP(H)-dependent isocitrate dehydrogenase (ICDH) which catalyzes reversibly carboxylation and decarboxylation reactions. Different from chemical carbon capture processes that rely on thermal energy to realize purification of carbon dioxide, the biocatalytic strategy utilizes pH to leverage the reaction equilibrium, thereby realizing energy-efficient carbon capture under ambient conditions. Results showed that over 25 mol of carbon dioxide could be captured and purified from its gas mixture for each gram of ICDH applied for each carboxylation/decarboxylation reaction cycle by varying pH between 6 and 9. This work demonstrates the promising potentials of pH-sensitive biocatalysis as a green-chemistry route for carbon capture.