Aggregation of CO2 and Organic Liquid Molecules at Near Critical and Supercritical Condition of CO2

In order to study the aggregation of CO₂ and organic liquid molecules in the binary systems of CO₂+ organic liquid at near critical and supercritical condition of CO₂, the radial distribution function of CO₂-organic liquid molecules and organic liquid–organic liquid molecules in the liquid phase of the CO₂+ organic liquid systems is calculated by molecular dynamic simulation in this work and compared with the results of our previous works. The results of the research show that the aggregates of CO₂–CO₂ molecules, CO₂-organic liquid molecules and organic liquid–organic liquid molecules are coexisted in the liquid phase of CO₂+ organic liquid system, respectively.     

CO2 Mobility and CO2/Brine Interfacial Tension Reduction by Using a New Surfactant for EOR Applications

The synthesis and use in enhanced oil recovery applications of a novel CO₂-philic surfactant derived from maleic anhydride and 2-butyl-1-octanol is reported. The synthesis involved the esterification of maleic anhydride to produce diester followed by sulfonation of the esterified product. The esterification reaction parameters were optimized for the maximum yield of 98.4%. By employing a silica sulfuric acid catalyst, the reaction kinetics of esterification were also investigated. The activation energy was found to be 45.58 kJ/mol. The sulfonation reaction of the esterified product was performed by using sodium bisulfite, and a yield of 82% of surfactant was achieved. The synthesized surfactant lowered the interfacial tension between CO₂/brine to 3.1 mN/m and effectively reduced the CO₂ mobility. This surfactant has a great potential to be used for CO₂ mobility control for CO₂?EOR applications.      

Synthesis of a New CO2 Philic Surfactant for Enhanced Oil Recovery Applications

The synthesis of CO₂ philic surfactant using maleic anhydride and 4-tert-butylbenzyl alcohol is reported. We reacted maleic anhydride with 4-tert-butylbenzyl alcohol to form bis(4-(tert-butyl)benzyl) fumarate and sulfonated the produced diester. The esterification reaction was optimized for a maximum yield of 98% of bis(4-(tert-butyl)benzyl) fumarate. First-order reaction kinetics with respect to acid was observed. The activation energy was found to be 55.62 kJ/mol. The sulfonated product of diester was obtained by the sulfonation reaction and the yield of 82% of surfactant was achieved. The in-house developed surfactant effectively lowered down the IFT between CO_2/brine to 4.2 mN/m. This surfactant is targeted for CO₂-EOR applications.     

Application of CO2-Triggered Switchable Surfactants to Form Emulsion with Xinjiang Heavy Oil

Owing to the high acid number of Xinjiang heavy oil and incomplete demulsification after pipelining, this article discusses the application of CO₂-triggered switchable surfactants to the emulsified transport of several Xinjiang heavy oils in the pipeline. Results show that CO₂-triggered switchable surfactants promote the formation and stabilization of oil-in-water (O/W) emulsion in the absence of CO₂ as a base. The property parameters of heavy oils fundamentally influence the indigenous emulsifying agents. The emulsion is stable when the heavy oil has a high acid number and low asphaltene content, which is also affected by some physical factors.     

Novel Surfactant for the Reduction of CO2/Brine Interfacial Tension

The synthesis of novel CO₂ philic surfactant using maleic anhydride and dipropylene tertiary butyl alcohol is reported. The synthesis involved the esterification of maleic anhydride to produce bis(2-(2-(tert-butoxy)propoxy)propyl) maleate and subsequent sulfonation of the esterified product. Para toluene sulfonic acid was employed as catalyst for the esterification reaction. The esterification reaction was optimized for the maximum yield of 98% of bis(2-(2-(tert-butoxy)propoxy)propyl) maleate. The esterification reaction kinetics employing heterogeneous catalyst were also studied. Although this is a bimolecular reaction, a first order reaction kinetics with respect to acid has been observed. The activation energy was found to be 58.71 kJ/mol. The diester was followed by the sulfonation process and a yield of 85% of surfactant was achieved. The synthesized surfactant successfully lowered down the IFT between CO_2/brine to 1.93 mN/m. This surfactant has a great potential to be used for CO₂-EOR applications.     

Mechanism of Produced Gas Reinjection During CO2 Flooding by Chromatographic Analysis

CO₂ flooding process has been a proven valuable method that could not only enhance oil recovery but also store greenhouse gas. However, CO₂ source greatly restrict its application in China. In this article, based on the produced oil and gas of Jilin oilfield, slim tube tests were conducted to study the feasibility of the produced gas reinjection without separation. In addition, according to the phenomenon of the experiment, displacement process was divided into three stages. Chromatographic analysis was conducted to study the mechanism of production gas reinjection during CO₂. Results indicate that components of the produced oil change along with CO₂ content, displacement pressure and production stages.     

Effects of CO2 Injection on Phase Behavior of Crude Oil

CO₂ flooding is a win-win technology, sequestrating greenhouse CO₂ while producing a significant amount of crude oil to help defray the cost of CO₂ sequestrating and enhancing oil recovery. However, due to the difference of sedimentary environment and poor properties of formations, physical properties of the crude oil and the effect of CO₂ flooding are not always satisfactory in most oilfields of China. Therefore, in this article, to improve the understanding of the oil recovery mechanisms and feasibility of CO₂ flooding in China, based on the oil and gas of Mao-3 oilfields, phase behavior of the CO₂ and crude oil system was investigated. Parameters like saturated pressure, volume factor, gas oil ratio, and viscosity were measured and their relationships analyzed. Results show that crude oil of Mao-3 reservoir and CO₂ has good mutual dissolution under reservoir conditions, and CO₂ could expand the oil and reduce the oil viscosity greatly. As a result, formation energy could be enhanced and flow characteristics of the oil could be improved by CO₂ flooding.     

Antioxidant Activity Degradation,Formulation Optimization,Characterization, and Stability of Equisetum Arvense Extract Nanoemulsion

Equisetum arvense supercritical CO₂ extracts (EAE) contained an initial antioxidant activity of 10.3 mM TEAC that suffered a sharp first order kinetics decay characterized by half-life time (t_1/2) of 1.05 ± 0.03 and 0.86 ± 0.03 weeks at 25 and 4°C, respectively. The aim of the present work was to develop a nanoemulsion formulation for providing EAE protection against deleterious environmental factors and extending its shelf-life functionality. The nanoemulsion area was identified by constructing pseudoternary phase diagrams and response surface methodology was used to optimize the preparation conditions. The best formulation achieved an EAE encapsulation efficiency of 97.5 ± 0.5% and antioxidant activity half-life time (t_1/2) was extended to 12.32 ± 0.40 and 14.56 ± 0.60 weeks at 25 and 4°C, respectively.      

Photocatalytic Degradation of Styrene in Aqueous Solution: Central Composite Design Optimization

In this study, the response surface methodology was first applied to optimize the photocatalytic degradation of styrene in aqueous phase under UV/TiO₂ system. Twenty experiments were done by adjusting three parameters (styrene concentration, TiO₂ dose, and pH) at five levels. Optimal experimental conditions for arbitrary aqueous styrene concentration (115 mg L^?1) were found: initial pH 7 and TiO₂ loading 2 g L^?1 with photocatalytic degradation efficiency of 79.2%. Furthermore, the main degradation intermediate produced was identified by GC/MS. The total organic carbon results revealed that the photocatalysis process could be effectively mineralized. Kinetics of the photocatalytic reaction followed a pseudo-first-order model.     

CO2-expanded bio-based liquids as novel solvents for enantioselective biocatalysis

For the first time, CO₂-expanded bio-based liquids were reported as novel and sustainable solvents for biocatalysis. Herein, it was found that by expansion with CO₂, 2-methyltetrahydrofuran (MeTHF), and other bio-based liquids, which were not favorable solvents for immobilized Candida antarctica lipase B (Novozym 435) catalyzed transesterification, were tuned into excellent reaction media. Especially, for the kinetic resolution of challenging bulky secondary substrates such as rac-1-adamantylethanol, the lipase displayed very high activity with excellent enantioselectivity (E value > 200) in CO₂-expanded MeTHF (MeTHF concentration 10% v/v, 6 MPa), whereas there was almost no activity observed in conventional organic solvents.     

Foaming Properties of CO2-Triggered Surfactants for Switchable Foam Control

Switchable surfactants, particularly those triggered by CO₂ used for switchable foam control, are relatively less documented. In this article, the foaming performance of 2-alkyl-1-hydroxyethylimidazolinium bicarbonate cationic surfactants (HEAIBs) was investigated for the first time. The foaming properties of these surfactants demonstrate that HEAIBs can generate foam with moderate stability, on demand, can be rapidly yet reversibly dissipated upon exposure to air. The results illustrated such a facile trigger, and the foam on/off transition would have huge potential to form a new class of stimuli-response foaming agents.