V. N. Chulkov

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.

Formation of benzenediols upon electron-beam distillation of lignin mixtures with alkanes

In the process of the electron-beam distillation of lignin, its conversion into benzenediols increases in the presence of alkanes in the irradiated sample. An increase in the yield of benzenediols is accompanied by a decrease in the fractions of guaiacol, creosol, ethylguaiacol, and vinylguaiacol in the tar distilled off. It has been noted that alkanes serve as an additional source of atomic hydrogen and alkyl radicals, which, in turn, play a key role in the formation of benzenediols. In the presence of alkanes in the irradiated sample, guaiacol can be the main precursor of catechols; the proportion of guaiacol in the tar is almost three times below that in the case of distillation of individual lignin. It has been hypothesized that the chain decomposition of lignin can occur with the participation of •H and •CH3 radicals.

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.

Studies of physico-chemical properties of modified carbon nanomaterials for sorption extraction of radionuclides. II. Sorption properties of charcoal formed in electron-beam processing of plant materials

This work studies the effect of the porous structure of carbon adsorbent samples obtained using the method of electron-beam processing (EBP) on their physico-chemical properties and sorption properties in respect to Tc(VII). A complex study of the porous structure of the chosen samples was performed. The possibility is shown of developing a thinner porous structure in these carbon materials including micro- and mesopores by means of regulation of radiation exposure combined with treatment by different reagents. It is found that treatment by modifying agents (urea, thiourea, potassium rhodanide) of sorbing materials obtained by radiation processing of the initial plant material enhances their sorption properties in respect to the Tc(VII) anions.

Electron beam conversion of cellulose into liquid organic products

Cotton and pine cellulose was distilled under the heating with a beam of accelerated electrons (∼2 kGy/s) in a flow of gaseous alkanes. An organic liquid (∼60 wt %), gas (13–18 wt %), and charcoal were the products. Carbonyl compounds and furans dominate in the composition of the liquid. It is supposed that electron beam processing has a combined effect including preliminary radiolytic modification of cellulose, the initiation of its radical-chain destruction, and strong rapid warming-up within tracks.

Phenolic products of the high-temperature radiolysis of lignin

The products of the radiation-stimulated dry distillation of coniferous hydrolytic lignin at a residual pressure of 1–5 torr have been obtained and analyzed. The tar distilled off under irradiation conditions predominantly contains phenols, including about 33% benzenediols. Among the benzenediols, the fraction of catechols is 69%. Phenoxyl radicals are considered to be direct precursors of the phenolic products. It has been found that the formation of benzenediols can be due to the rupture of the ether bond in the methoxy group. Among secondary processes, the reactions of the addition of •H and •CH3 radicals to the benzene ring have been considered.

Electron-beam degradation of wood: 1. Dry distillation products

Electron-beam heating to ≥270°C initiates the process of dry (destructive) distillation of wood. Birch, aspen, alder, spruce, and pine wood is decomposed yielding liquid organic products (55–61 wt %), gas (13–18 wt %), and charcoal. The liquid largely consists of carbonyl compounds. The furan fraction makes up approximately one fifth. The liquid produced from softwood is heavier and is rich in phenolic compounds. The products of dry distillation upon wood irradiation in a stream of propane and butanes are enriched in liquid alkanes, alcohols, and ethers. The feasibility of conversion of the condensable products into regular liquid fuel is discussed.

Radiation-Induced Aggregation and Dehydration of Phytoplankton

Freshwater microalgae (phytoplankton) are worldwide in their distribution, and they play the most important role in the biological balance of internal water bodies. Because they are unpretentious with respect to ambient environment conditions, the microalgae can actively propagate thus bringing either harm or benefit. For example, in the period of their active growth, the microalgae substantially hamper the use of surface water for potable water and industrial water supply and complicate the operation of the open systems of water recycling [1]. On the other hand, microalgae can serve as a rich source of fodder and chemical raw materials. In particular, they are suitable for the production of thirdand fourth-generation biofuels [2]. The attractiveness of microalgae for fuel production is due to the fact that their cultivation does not require extensive land sections; in this case, a large volume of biomass is reproduced at a high rate.

A test facility for studying the radiolysis of gases and vapors

297 The experimental studies of the radiolysis of gas and vapor atmospheres are usually performed in the batch mode [1], when the sample is in a static or stirred state; in this case, additional inflow from without or the removal of a substance from the reaction vessel does not occur during the entire process of irradiation. Under these conditions, the probability of secondary transformations increases as the products of radiolysis are accumulated [2]; this inevitably affects the degree of conversion of the parent substance and the compo sition of end products. The industrial radiation chemical processing of gas and vapor atmospheres primarily implies irradiation in the flow regime. The removal of sulfur and nitrogen oxides from flue gases [3], the synthesis of liquid hydrocarbons from oil gases [4], and gas phase graft polymerization [2] can serve as the examples of these processes. Accordingly, a batch mode study of test samples should be supplemented with experiments performed in flow regimes at the stage of preproduc tion tests. Here, we describe a test facility for the elec tron beam conversion of gases and vapors under flow and circulating flow conditions. The composition and the construction of the units of this facility (see the figure) are oriented to perform operations at a pressure of ≤0.15 MPa and an average temperature of the irradiated atmosphere to 250°C. Depending on the problem to be solved, either a URT 1 frequency nanosecond electron accelerator, which generates a vertical electron beam (maximum energy, 1 MeV; pulse duration, 50 ns; and pulse repeti tion frequency, 1–50 Hz), or a LINS 02 500 linear accelerator, which generates a horizontal electron beam (maximum energy, 2 MeV; pulse duration, 4 μs; and pulse repetition frequency, 1–250 Hz), can be used as a radiation source. The facility is intended for testing the versions of conversion that do not change the phase composition of an atmosphere (the raw materials and products remain in a gas or vapor phase) and for studying gas to liquid or gas to solid conversions, that is, when the end products are released in a condensed state. The processed atmosphere can circulate about a closed path: the raw material is repeatedly exposed to irradi ation, and the loss of pressure caused by the condensa tion of products beyond the limits of a radiation zone is compensated due to the inflow of fresh raw material. The test facility consists of reactor 1, in which the gas or vapor is directly subjected to electron beam exposure, gas–liquid separation system 8–10, reac tant mixing unit 3–5, and gas supply regulation and control system 1, 2. The reactor is a cylindrical vessel made of stainless steel with flanges at the ends air tightly closed by steel end covers. One of the covers is supplied with a dia phragm of aluminum foil fixed between support grids. The diaphragm serves as the input window for an accelerated electron beam. The support grids prevent the foil from sagging under the action of an excess pressure or pressure reduction. The cover is supplied with water cooling channels and copper cooling coil 7 intended to decrease the gas temperature in the imme diate proximity of the inlet diaphragm. The tempera ture of water in the diaphragm cooling system is regu lated depending on a research task in order to prevent diaphragm overheating or vapor condensation on the inside of the diaphragm. The opposite end cover is supplied with detachable cylindrical copper vaporizer vessel 12 with a peripheral electric heater. The vaporizer vessel is air tightly fixed at the center of the cover; it is intended for the preheat ing of a reaction mixture and/or the evaporation of liq uids placed inside at a vertical orientation of the reac tor. In the case of a horizontal orientation of the reac tor, vaporizer vessel 12 can be connected to a special socket on the side of the reactor. Special inlet and outlet nipples are used for gas sup ply into the reactor, the removal of a reaction mixture SHORT COMMUNICATIONS RADIATION CHEMISTRY

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.