A. K. Metreveli

Aromatic products of radiation-thermal degradation of lignin and chitin

Lignin and chitin degradation in the high-temperature radiolysis mode at ≤295°C has been investigated. Experimental conditions ensured the removal of low-molecular-weight products from the irradiation zone via volatilization. The formation of the low-molecular-weight aromatic products methoxyphenols and pyridine derivatives from lignin and chitin, respectively, has been shown. The yield of the distillable aromatic products was much higher than in the case of conventional dry distillation. It is noted that the mechanism of high-temperature radiolytic transformations of lignin and chitin differs from the mechanism of thermal transformations, which is due to the thermally stimulated degradation of radiation-induced radicals. It has been shown that high-temperature radiolysis opens a possibility for producing aromatic hydrocarbons at a lower dose rate and at lower temperature in comparison with conventional radiolysis and pyrolysis.

Radiation and postradiation distillation of biopolymers: Lignin and chitin

Lignin and chitin were decomposed in the regimes of postradiation dry distillation and distillation under conditions of radiation heating by accelerated electrons. The distilled off condensates consisted of two phases: brown viscous tar and lighter aqueous organic solution. The preliminary irradiation of lignin did not change the yield of distilled off tar, but it increased the fraction of alkoxyphenols in this tar. In the postradiation distillation of chitin, the yield of tar decreased with the dose. The effective distillation of biopolymers under radiation heating conditions was observed at dose rates higher than ∼1 kGy/s. The condensate distilled off at a dose rate of 1.5–2.5 kGy/s differed from the product of standard dry distillation in a higher yield of liquid organic products.

Effect of irradiation on aqueous dispersions of humic acids and lignin

The influence of electron-beam irradiation on the optical absorption of dilute aqueous solutions of lignin and humic acids has been studied. It has been shown that when the thickness of the irradiated layer of the solution is less than the electron range, preferential enlargement and precipitation of polyphenolic impurities observed. The most profound effect is achieved at doses of 5–15 kGy. When the irradiated-layer thickness is less than the electron range, the radiation-induced coagulation of impurities weakens. This effect can be due to the buildup of uncompensated charge of thermalizing electrons affecting the negatively charged micelles of polyphenolic impurities.

Electron-beam-induced conversion of gaseous and solid paraffins in the circulation regime

The following three regimes of the radiation-induced production of liquid hydrocarbon fuel have been compared: (1) the direct cracking of molten C17–C120 synthetic wax, (2) direct gas-phase synthesis from methane, and (3) the indirect initiation of the fragmentation of wax diluted with methane. It has been found that in contrast to the direct cracking, regime (3) afforded lighter products containing more saturated and isomeric components. In this case, the degree of methane binding is higher by a factor of almost 3 than that in regime (1).

Electron beam-assisted cracking of synthetic paraffins

The electron beam-initiated cracking of a mixture of C17–C120 paraffins at 350–370°C has been studied. The cracking regime implied simultaneous feedstock irradiation and rapid distillation of fragmentation products from the irradiation zone. The distillate was a mixture of 61.5 wt % alkanes and 38.5 wt % alkenes. The product molecule contained on average 13 carbon atoms. The gasoline fraction in the condensate was 32.3 wt %. It was demonstrated that the product composition can be changed depending on the geometric parameters of reaction equipment and temperature distribution at the reactor outlet.

Effect of absorbed dose on the postradiation dry distillation of cellulose and lignin

The postradiation dry distillation of cellulose and lignin has been studied. During the course of irradiation to 3 MGy, the weights of samples remained almost unchanged. The overpoints of lignin and cellulose irradiated at 2.2 MGy decrease by ∼80° and ∼100°, respectively. A third of the condensate from cellulose and almost a half that from lignin were distilled off at lower temperatures. Thermally unstable compounds are formed in cellulose; these compounds are predominantly converted into furans upon subsequent heating. The distillation of irradiated lignin affords a smaller amount of tar, but it is richer in methoxyphenols. The aqueous organic fraction distilled off has a higher concentration of soluble organic compounds.

Solid-to-liquid and gas-to-liquid transformation of alkanes under accelerated electron beam irradiation

A zero-waste method has been suggested for radiation-thermal cracking of Fischer–Tropsch waxes. The method is realized in the circulating mode and is based on the indirect action of radiation on the wax dissolved in methane or other gaseous hydrocarbons. The duration of exposure to irradiation of the feedstock components depends on their volatility. The method is characterized by the increased fixation yield of the gas. The major fraction of the final product is gasoline rich in isoalkanes.

Radiation-thermal transformations and distillation of lipids and disperse systems on their basis

The radiation-thermal transformations of rape oil under conditions of postradiation distillation, radiation heating, and electron-beam distillation with auxiliary heating were studied. Diesel hydrocarbons were predominant in the condensate distilled off upon combined heating. The concentration of oxygen atoms decreased as a result of radiation-induced decarboxylation and dehydration processes. The irradiation of oil as a constituent of disperse systems facilitated purposeful deoxygenation, a decrease in the viscosity, and an increase in the yield of the gasoline fraction.