New 1,3,4-Oxadiazole Based Photosensitizers for Dye Sensitized Solar Cells (DSSCs)

1,3,4-Oxadiazole based photosensitizers with biphenyl, naphthalene, anthracene, and triphenylamine as the electron-donating moiety were synthesized for solar cell applications. In these photosensitizers, cyano groups were introduced as the electron acceptor and the anchor group because of their high electron-withdrawing ability and strong bonding to the semiconductor. Oxadiazole isomers were used as the π-conjugation system, which bridges the donor-acceptor systems. The electrochemical and optical properties of the sensitizers were investigated both in their native form and upon incorporation into dye sensitized solar cells. The results of UV-visible absorption spectroscopy, electrochemical impedance spectroscopic measurements, and photocurrent voltage characteristics indicate that 1,3,4-oxadiazole pi-spacer with the anthracene moiety has the highest efficiency of 2.58%. Density functional theory was employed to optimize the structures of the sensitizers and the TiO2 cluster

Development Of Eco-friendly Chitosan-g-polyacrylamide Preformed Particle Gel For Conformance Control In High-temperature And High-salinity Reservoirs

Oil and gas extraction has become challenging nowadays due to the accompanying amount of excess produced water that results in poor recoverability of hydrocarbon, besides other environmental and economic isues. A recent and efficient technology for conformance control is the injection of preformed particle gels (PPGs), which results in a more practical production process. Nevertheless, existing treatments fail in high-temperature reservoirs, are extremely sensitive to salinity, and are hazardous. The characteristics of the designed PPG, such as mechanical strength and thermal durability, is mainly depend on their crosslinking method. Polysaccharides-based gels prepared by physical crosslinking are weaker than the ones crosslinked by strong covalent bonding. This paper uses one of the polysaccharides and proposes an environmentally friendly PPG for water shutoff applications in reservoirs of high temperature (≤130 °C) and high salinity (200,000 ppm), named chitosan grafted polyacrylamide crosslinked with N, N′-methylene bisacrylamide, synthesized chemically by microwave assisted method. The PPG\u27s chemical compositions, grafting and crosslinking mechanism have been investigated by FTIR spectroscopy and SEM techniques. Swelling kinetics, swelling capacity, and mechanical strength measurements were conducted in different conditions to evaluate the influence of the reservoir conditions, such as salinity, temperature, and pH, on the PPG stability. TGA experiments were also performed to examine the thermal stability. Results have shown that the grafting method has produced a PPG with improved mechanical strength, thermal durability, and salt insensitivity. These results are consistent with the testing observations, where the swelling capacities and the storage modulusof Cs/PAMBA samples, with different MBA content, in deionized water were 2.72–11.64 g/g and 4272.1–22,687 Pa, respectively, while they are 2.52–13.82 g/g and 3699.6–22,910, respectively, in saline solution of TDS 67.2976 g/L. The PPGs are thermally stable and resist temperatures up to 130 °C. Besides being eco-friendly, the Cs/PAMBA showed good long-term thermal stability in high-temperature and high-salinity environments

Impact Of Composition And Salinity On Swelling And Gel Strength Of Poly (acrylamide-co-acrylic Acid) Preformed Particle Gel

The effects of various material compositions and reservoir environments on the ultimate strength and swelling kinetics of a commercial preformed particle gel (PPG) have been investigated. This study used different ratios of acrylamide and acrylic acid copolymers with a specific crosslinker concentration. Results have indicated that increasing the acrylic acid proportion enhances the PPGs\u27 ability to swell but weakens their network structure. In contrast, increasing the crosslinker content decreases the swelling ratio and increases the gel strength. The highest equilibrium swelling capacity among the six preformed particle gel samples was obtained for PPG2, which has the highest acrylic acid amount and the lowest crosslinker content, with a swelling ratio of 2400 g/g in deionized water and 59.8 g/g in brine 1 (67535.8 mg/l). On the contrary, PPG5, with the lowest acrylic acid and highest crosslinker content, has a swelling capacity of 239 g/g and more than 17 g/g in distilled and brine 1, respectively. Yet, PPG5 has the highest swollen gel strength of 615.5 Pa in deionized water and 3344 Pa in brine 1. The PPGs\u27 swelling ratios showed stepwise improvements along with increasing temperature, notably after 50 °C, yet the storage modulus (G′) was negatively affected. The PPGs revealed the highest swelling behavior in pH 6–8, decreasing dramatically in more acidic and basic conditions. The swelling ratios of the PPGs in brine 1 at 50 °C were between 12 and 32 g/g, having strengths in the range of 566–5508 Pa, depending on the crosslinker ratio. The PPGs also demonstrated the ability to compete with other commercial PPGs as they have shown physical and thermal stability when aging at 50 °C, specifically those with high crosslinker content (PPG5)

Application of various water soluble polymers in gas hydrate inhibition

Formation of hydrates in gas transmission lines due to high pressures and low temperatures is a serious problem in the oil and gas industry with potential hazards and/or economic losses. Kinetic hydrate inhibitors are water soluble polymeric compounds that prevent or delay hydrate formation. This review presents the various types of water soluble polymers used for hydrate inhibition, including conventional and novel polymeric inhibitors along with their limitations. The review covers the relevant properties of vinyl lactam, amide, dendrimeric, fluorinated, and natural biodegradable polymers. The factors affecting the performance of these polymers and the structure-property relationships are reviewed. A comprehensive review of the techniques used to evaluate the performance of the polymeric inhibitors is given. This review also addresses recent developments, current and future challenges, and field applications of a range of polymeric kinetic hydrate inhibitors. 2016 Elsevier Ltd. All rights reserved.This research is supported by Saudi Aramco through project # CPM 2297. Authors would like to thank the Center for Integrative Petroleum Research , King Fahd University of Petroleum & Minerals for supporting this research.Scopu

Chitosan/Polyacrylamide Green Gels for Water Control in High-Temperature Reservoirs

The rheology of a gel system composed of polyacrylamide (PAM) and chitosan is studied under typical reservoir conditions. The impacts of the degree of chitosan deacetylation, temperature, and salinity on the gelation behavior are assessed. The said system was prepared under ambient conditions and matured for 24 h at altered temperatures ranging from 50 up to 125 °C. An optimum formulation has been identified considering the rheological response and the initial viscosity constraints. The increase in the degree of syneresis with the degree of deacetylation indicates the long-Term thermal stability of the gels. Ammonium chloride was an effective retarder for the PAM/chitosan gelant, which delayed the gelation time from 60 to 210 min when 2 wt % is used; however, it compromised the final gel strength. The chitosan/PAM system showed a good rheological behavior and potential as a green plugging agent in high-Temperature oil and gas wells. Chitosan could be an alternative for commercial crosslinkers, such as polyethyleneimine

INFLUENCE OF BRANCH CONTENT OF ETHYLENE/1- HEXENE METALLOCENE –BASED LLDPE ON ITS MISCIBILITY WITH LDPE: A MOLECULAR DYNAMICS STUDY

The effect of branch content of hexene metallocene linear-low-density polyethylene (m-LLDPE) on its miscibility with low-density polyethylene (LDPE) was studied by molecular dynamics simulation. The branches of m-LLDPE were varied from 10 to 80 branches/ 1000 C, distributed uniformly on the chain. The LDPE was modeled as three long-chain branches with 22 short chain branches of different kinds. m-LLDPE and LDPE were blended at 500K and 450K. The results showed complete miscibility of blends for all the branch contents covered in this study. Lamellar structures in the melts of m-LLDPE and LDPE blends were detected up to a branch content of 40/1000 C