Behavior of Titania Nanoparticles in Cross-linking Hydroxypropyl Guar Used in Hydraulic Fracturing Fluids For Oil Recovery

Abstract

Fluids pumped in hydraulic fracturing operations constitute highly viscous gels achieved via cross-linking of the polysaccharide derivative hydroxypropyl guar (HPG), e.g., with titanium or zirconium complexes. In this study, the mechanism underlying the cross-linking effect was clarified experimentally for the titanium system. It was found that the cross-linking effect is not based on a ligand exchange reaction with the cis-hydroxy functionalities present in HPG but instead relies on TiO2 nanoparticles resulting from hydrolysis of the Ti complexes. For example, 6 nm titania nanospheres (anatase polymorph) synthesized via acid hydrolysis of tetraisopropyl orthotitanate can increase the viscosity of a HPG solution by a factor of 25. However, this effect was observed only at pH = 2–4 where the nanoparticles are stable. At higher pH values, electrostatic repulsion between the nanoparticles decreases, resulting in agglomeration as was observed via zeta potential and pH-dependent particle size measurement. Such agglomerates exhibit a lower surface area and thus produce a weaker or no cross-linking at all. Similar effects were obtained from TiO2 particles when their diameter was increased stepwise from 6 to 14 nm. Minor additions of citric acid can stabilize the nanoparticles even at pH 5–11, thus allowing efficient cross-linking of HPG also in an alkaline environment while excessive amounts of citric acid (>5 mmol/g TiO2) retard the cross-linking process. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy revealed that the cross-linking mechanism is based on the formation of hydrogen bonds between OH groups present on the surface of titania and along the galactomannan chain of HPG. The study confirms that TiO2 nanoparticles represent the active species responsible for the cross-linking of HPG in fracturing fluids when titanium complexes are used.

Design and Fabrication of TiO2/Lignocellulosic Carbon Materials: Relevance of Low‐temperature Sonocrystallization to Photocatalysts Performance

“…Additionally, in Stage II, Ti precursor (TTiP) was added during the synthesis, and its cations were observed in the case of 20.4 wt.% TiO 2 /SWP700_48 mm and 20.4 wt.% TiO 2 /STARBON-800_48 mm (Table 3 and 4) by the presence of small at. [34,36] Additionally, the FT-IR bands in 700-900 cm À1 pointed out Ti-OÀTi bond in the TiO 2 anatase phase. It is well known that low frequencies ultrasound may induce oxygen vacancies and Ti 3 + which may be responsible for morphological, optical and surface changes in the prepared composite materials and may also help to control the course of sonocrystallization processes.…”

“…% of Ti 4 + and Ti 3 + which surface concentration increase further with the treatment steps. [30][31][32][33][34][35][36] Increase in the intensity of these bands was also attributed to the successful formation of titania nanoparticles on the lignocellulosic carbon surface. In Stage III, water was added during the synthesis, and its presence has been mainly observed in the case of 20.4 wt.% TiO 2 /SWP700_ 48 mm ( Figure 10) and 20.4 wt.% TiO 2 /STARBON-800_48 mm ( Figure 11) by a characteristic broad peak in the 3200-3600 cm À1 region (Figure 12).…”

“…In Stage III, water was added during the synthesis, and its presence has been mainly observed in the case of 20.4 wt.% TiO 2 /SWP700_ 48 mm ( Figure 10) and 20.4 wt.% TiO 2 /STARBON-800_48 mm ( Figure 11) by a characteristic broad peak in the 3200-3600 cm À1 region (Figure 12). Recent research [36] has suggested that free carboxylate anions of the crosslinked citric acid have high affinity towards the positive charges of Ti 4 + leading to the electrostatic linkages. It can be stated that the addition of water promote hydrolysis and condensation reactions and finally the formation of Ti-OÀTi chains, especially under sonication conditions where the reaction rates of hydrolysis and condensation can be increased by a better mass transfer and diffusion of reagents.…”

Applications of nanotechnology in oil and gas industry: Progress and perspective

“…High viscosity gels were prepared by cross-linking polysaccharide derivative hydroxypropyl guar (HPG) with titania nanoparticles. [59] Results indicated that the 6 nm titania nanospheres can increase the viscosity of a HPG solution by a factor of 25 due to the formation of hydrogen bonds between OH groups present on the surface of titania and on the galactomannan chain of HPG. Li et al [60] studied the effect of nanoparticles in enhancing CO 2 fracturing in unconventional gas reservoirs.…”

Comparison of Miniaturized and Conventional Asymmetrical Flow Field-Flow Fractionation (AF4) Channels for Nanoparticle Separations

“…For example, silver nanoparticles are used in textiles, fridges or washing machines, due to their antibacterial properties [2]. Titanium dioxide nanoparticles are used in sunscreens in order to achieve a better protection from UV radiation, and in hydraulic fracturing fluids for oil recovery [3]. Since data on toxicity are barely available, their increasing application in cosmetic products, food and their release in the environment might cause severe problems.…”