52K-1 composite additive to bring the quality of GShZ diesel fuel (DF) to the level of the requirements in GOST 305-82 for DF Z-45 and consequently to expand the area of its use was developed from domestic feedstock. Key words: composite additive, gas-condensate diesel fuel (GShZ), kinematic viscosity, cetane number.Urengoigazprom Ltd. gas-condensate GShZ DF developed according to TU 51-28-86 corresponds to petroleum Z-45 DF manufactured according to GOST 305-82 in quality. In particular, its low-temperature characteristics -cloud point and solid point -are the same as for Z-45 DF: maximum of -35 and -45°C, respectively, but the cetane number (CN) and viscosity at 20°C is lower than for Z-45 DF (Table 1).We attempted to bring the quality of GShZ DF to the level of Z-45 DF and in this way expand the area of its use.The low viscosity can negatively affect operation of the fuel system and can be the cause of increased wear. Polymeric thickeners are widely used to increase the viscosity of the oils and hydraulic fluids [1-3]. In our opinion, it is also expedient to bring GShZ DF up to the quality of Z-45 DF with additives of different kinds.The class of polymers (polymethacrylates or hydrocarbon copolymers) for increasing the viscosity of GShZ DF was selected based on a comparison of their thickening power. It was found that viscous hydrocarbon additives have 2-3 times better thickening power in oils than polymethacrylate additives in the same concentration in the oil. In consideration of the cost (Table 2) of the compared additives, we selected the domestic additive PRIMA-V according to TU 0257-001-48709481-99 for the study.For preparation of 5% polymer concentrate in GShZ DF, the polymer had to be swollen in the fuel for 5 h. The swollen polymer was mixed with GShZ DF at room temperature for 2 h. The additive solution obtained was added to GShZ DF in different concentrations by measuring the viscosity of the fuel.As Table 3 shows, a 0.2 wt. % concentration of copolymer in GShZ DF can be considered the working concentration, since the viscosity of the fuel at this concentration of the additive satisfies the requirements of GOST 305-82 for Z-45 DF with respect to this index: minimum of 1.8 mm 2 /sec. One of the important indexes in combustion of DF, the cetane number (CN), is determined as the volume concentration of cetane and a-methylnaphthalene in a standard mixture corresponding in ignitability to the tested DF [4, 5]. The value of the CN is a function of the hydrocarbon composition of the DF. For example, it decreases with an increase in the aromatic hydrocarbon residue and increases with an increase in the n-paraffin and olefin content. 665.733.035 and V. A. Vinokurov ____________________________________________________________________________________________________ I. M. Gubkin Russian State University of Oil and Gas.

A composite additive that decreases the cloud and solid points of GShZ gas-condensate diesel fuel, stable condensate "heavy" bottoms, to the values required by GOST 305-82 for grade "3-45" petroleum diesel fuel, was developed from domestic feedstock. This significantly improves the performance properties of gas-condensate diesel fuel..With stiffening of the requirements for the quality of diesel fuels (DT), additives with different functional applications are being increasingly widely used [1][2][3]. The quality of the GShZ DF processed at Urengoigazprom LLC totally corresponds to TU 51-28-86 and to the requirements of GOST 305-82 for winter Z -45 DF of petroleum origin on all indexes except for the cetane number (CN) and kinematic viscosity.