Ways of enhancing oxidation of asphalts

Abstract

Increasing the quality of roofing and waterproofing materials involves developing new formulas for polymer-asphalt materials and technologies for adding the ingredients to composites [1][2][3][4][5][6][7]. However, in our opinion, the quality of the polymer-asphalt binders can be increased by improving the technology for production of high-melting roofing and waterproofing asphalts.Roofing asphalts BNK 40/180 and BNK 4/190 (GOST 9548) are usually finally oxidized in a battery of still reactors developed by VNIIPKneftekhim at the beginning of the 1960s. This technology did not spread to oil refineries (OR) due to the low output of these reactors and was used by consumers of asphalts for manufacturing small product lots [8].Production of high-melting asphalts in equipment of this type is characterized by a brief contact time of air with the oxidized mass and as a consequence, high concentration of oxygen in exhaust gases and coking of the gas space of the reactor [9, 10]. Oxidation of asphalts in reactors of this design can only be intensified by incorporating activating additives to the feedstock or reaction zone. Unfortunately, the information on the use of such additives only relates to technology for production of paving and construction asphalts.We will generalize the published data on enhancing oxidation of vacuum resids. The results of studies of this process can be transposed to final oxidation of roofing asphalts. One method of accelerating oxidation of heavy petroleum residues (HPR) is to incorporate additives containing different metal atoms in the oxidation zone. The results of an enormous number of studies in this 349 direction are generalized in monographs [11,12]. More than one hundred compounds capable of accelerating oxidation of vacuum resids into asphalts are known, for example: manganese dioxide; sodium carbonate; potassium chlorate; zinc, copper, aluminum sulfates; copper, lead, manganese, cobalt, iron, chromium naphthenates; some metal oxides [12]. Iron chlorides were industrially tested in [11]. Feeding them into the reaction zone caused instantaneous decomposition of the substance with formation of hydrogen chloride and an active hydrocarbon radical capable of carrying out a chain oxidation process. The asphaltenes formed have a molecular weight 2-2.5 times higher than the asphaltenes formed in traditional oxidation. The rate of the process increases and the quality of the construction asphalts are improved as a result [12].Iron chloride crystal hydrate, FeCl 3 ×6H 2 O, was tested in an industrial asphalt production unit [13]. The iron chloride was previously melted at 40-80°C in a steam-heated drum and then diluted with water to a concentration of 80% and fed into the oxidation tower by a plunger pump. Consumption of iron chloride was 0.1 wt. % in feedstock. Vacuum resid with a softening point of 30-31°C was used as the feedstock.The process was conducted at 265-270°C and air flow rate of 2700 m 3 /h. The reactor output in feedstock increased from 30 to 40 m 3 /h and the oxygen content in ...