Hydrocarbon Gas Production Research Articles

Synthesis of hydrocarbon gases from four different carbon sources and hydrogen gas using a gold-tube system by Fischer–Tropsch method

Several series of Fischer–Tropsch synthesis (FTS) experiments were conducted in a gold tube system with montmorillonite K-10 loaded with Fe3+ and Ni3+ as catalysts. Four different carbon sources: graphite, Na2CO3 solution (20%) and two types of CO2 gases with distinctive isotopic compositions were reduced in pure hydrogen gas at 400°C and 50MPa for 2–60h. The experimental results showed that the FTS reaction between liquid carbon and H2 could hardly occur. However, the reaction between gaseous phase carbon (CO2) and H2 gas was easier than that between solid phase carbon (graphite) and H2 gas; and the 13C depleted CO2 is more reactive than the 13C enriched CO2. Our results also show that the production of synthetic hydrocarbon gases from different carbon sources with H2 depends largely on the phases, and structural and thermal stability of carbon sources. In a relatively short reaction time at 400°C, the carbon isotope values of the synthesized alkane gases showed a full reversal trend with their molecular carbon numbers (δ13C1>δ13C2>δ13C3>δ13C4). However, with increasing reaction time, such a reversed isotopic distribution pattern disappeared. Our interpretation is that the final products were gradually replaced by cracking of the hydrocarbon products formed at the earlier stage of the synthesis process. Thus the 13C depleted gas from the thermal cracking was mixed with the 13C enriched residual gas, leading to the occurrence of a partial reversal or a normal isotopic distribution among C1–C4 alkane series (δ13C1<δ13C2<δ13C3<δ13C4), similar to the thermogenic alkane gases in nature. Under longer reaction time or/and higher reaction temperature (700°C), hydrocarbon gases would crack and generate monatomic carbon.The observed great discrepancy between the natural abiogenic gas and synthetic gas is likely due to the big difference in temperatures between geological settings and the laboratory experiment process. FTS experiments conducted under laboratory experimental condition are usually from low to high temperature and differ significantly from the abiogenic synthesis process for hydrocarbons in real geological settings, which is perceived as a cooling process from high to low temperature either under aqueous hydrothermal or volcanic intrusion conditions. Under certain (stable) geological temperature/pressure conditions, hydrocarbon gases generated might never suffer further decomposition, and thus might preserve a fixed “inverse” molecular isotopic fingerprinting as we observed in the laboratory. This has also been proven by a cooling FTS experiment.

Deep gases discharged from mud volcanoes of Azerbaijan: New geochemical evidence

This paper presents new geochemical data of hydrocarbon-rich gases released from some mud volcanoes of Azerbaijan. Methane is considerably the most abundant component of all the sampled gases, which show δD-CH4 and δ13C-CH4 values likely related to a dominant thermogenic source. These gases are characterized by the presence of more than 20 different cyclic compounds with concentrations up to several μmol/mol. A similar gas composition has recently been found to characterize many mud volcanoes of the Northern Apennines and Sicily (Italy). The data of the Azerbaijan mud volcanoes corroborate the notion that cyclic compounds can be considered reliable tracers for hydrocarbon gas production at considerable depths and temperatures up to 120–150 °C, which correspond to a 6.5–8.3 km depth range assuming an average geothermal gradient of 18 °C/km. This depth interval is consistent with both the depth of potential source rocks imaged seismically beneath some mud volcanoes, and the results of previous estimates that used the 13C/12C values of methane and ethane. Such deep-sourced gases and material (fluidized clayey mass and rock fragments) ascend into the core of anticlines and accumulate at shallower reservoirs, where fold-parallel outer-arc faults or fold-orthogonal fractures may penetrate and transfer the fluids to the surface. Finally, the basically equivalent composition of the different hydrocarbon groups (C2–C10 alkanes, aromatics and cyclic) determined in the gases sampled in both Azerbaijan and Italy manifests the lack of evident relationships between the chemistry of light hydrocarbons and the type of source rock.

Impact of hot fluid advection on hydrocarbon gas production and seepage in mud volcano sediments of thick Cenozoic deltas

Hydrocarbon seeps are ubiquitous at gas-prone Cenozoic deltas such as the Nile Deep Sea Fan (NDSF22NDSF:Nile Deep Sea Fan.) where seepage into the bottom water has been observed at several mud volcanoes (MVs33MV: mud volcano.) including North Alex MV (NAMV44NAMV: North Alex mud volcano.). Here we investigated the sources of hydrocarbon gases and sedimentary organic matter together with biomarkers of microbial activity at four locations of NAMV to constrain how venting at the seafloor relates to the generation of hydrocarbon gases in deeper sediments. At the centre, high upward flux of hot (70°C) hydrocarbon-rich fluids is indicated by an absence of biomarkers of Anaerobic Oxidation of Methane (AOM) and nearly constant methane (CH4) concentration depth-profile. The presence of lipids of incompatible thermal maturities points to mixing between early-mature petroleum and immature organic matter, indicating that shallow mud has been mobilized by the influx of deep-sourced hydrocarbon-rich fluids. Methane is enriched in the heavier isotopes, with values of δ13C∼−46.6‰VPDB and δD ∼−228‰VSMOW, and is associated with high amounts of heavier homologues (C2+) suggesting a co-genetic origin with the petroleum.On the contrary at the periphery, a lower but sustained CH4 flux is indicated by deeper sulphate–methane transition zones and the presence of 13C-depleted biomarkers of AOM, consistent with predominantly immature organic matter. Values of δ13C-CH4∼−60‰VPDB and decreased concentrations of 13C-enriched C2+ are typical of mixed microbial CH4 and biodegraded thermogenic gas from Plio-Pleistocene reservoirs of the region. The maturity of gas condensate migrated from pre-Miocene sources into Miocene reservoirs of the Western NDSF is higher than that of the gas vented at the centre of NAMV, supporting the hypothesis that it is rather released from the degradation of oil in Neogene reservoirs. Combined with the finding of hot pore water and petroleum at the centre, our results suggest that clay mineral dehydration of Neogene sediments, which takes place posterior to reservoir filling, may contribute to intense gas generation at high sedimentation rate deltas.

Conversion enhancement of tubular fixed-bed reactor for Fischer-Tropsch synthesis using static mixer

Recently, Fischer-Tropsch synthesis (FTS) has become an interesting technology because of its potential role in producing biofuels via Biomass-to-Liquids (BTL) processes. In Fischer-Tropsch (FT) section, biomass-derived syngas, mainly composed of a mixture of carbon monoxide (CO) and hydrogen (H2), is converted into various forms of hydrocarbon products over a catalyst at specified temperature and pressure. Fixed-bed reactors are typically used for these processes as conventional FT reactors. The fixed-bed or packed-bed type reactor has its drawbacks, which are heat transfer limitation, i.e. a hot spot problem involved highly exothermic characteristics of FT reaction, and mass transfer limitation due to the condensation of liquid hydrocarbon products occurred on catalyst surface. This work is initiated to develop a new chemical reactor design in which a better distribution of gaseous reactants and hydrocarbon products could be achieved, and led to higher throughput and conversion. The main goal of the research is the enhancement of a fixed-bed reactor, focusing on the application of Kenics™ static mixer insertion in the tubular packed-bed reactor. Two FTS experiments were carried out using two reactors i.e., with and without static mixer insertion within catalytic beds. The modeled syngas used was a mixed gas composed of H2/CO in 2: 1 molar ratio that was fed at the rate of 30 mL(STP)-min–1 (GHSV ≈ 136 mL. gca−1.h−1) into the fixed Ru supported aluminum catalyst bed of weight 13.3 g. The reaction was carried out at 180 °C and atmospheric pressure continuously for 36 h for both experiments. Both transient and steady-state conversions (in terms of time on stream) were reported. The results revealed that the steady-state CO conversion for the case using the static mixer was approximately 3.5 times higher than that of the case without static mixer. In both cases, the values of chain growth probability of hydrocarbon products (α) for Fischer-Tropsch synthesis were 0.92 and 0.89 for the case with and without static mixer, respectively.

Experimental investigation of hydrogen production through heavy naphtha cracking in pulsed DBD reactor

Abstract Cracking of heavy naphtha is studied experimentally in a nanosecond pulsed DBD plasma reactor. The system has been evaluated for instant production of light gaseous hydrocarbons in the range of C1–C3 and hydrogen via continuous hydrocarbons cracking at room temperature and atmospheric pressure. The effect of some process parameters such as reactor geometry/gap distance, carrier gas and feed flow rates have been considered on the reactor performance, experimentally. Results indicate that the less carrier gas and feed flow rates cause more energy efficiency. The maximum process efficiency is found for carrier gas and feed flow rates of 50 and 1 ml/min, respectively, which gets higher to 106.23 l/kWh for 11.50 W input power and 1.35 mm inner electrode diameter. Furthermore, results proof that for cracking process in DBD reactors there is an optimum diameter to maximize the process efficiency. For the reactor studied here, the optimum diameter of inner electrode is 2.68 mm. In this case energy efficiency of the process is 159.29 l/kWh. Results indicates that the hydrocarbon product distribution during the process is C2 > C1 ≫ C3 > C4.

Naphtha cracking through a pulsed DBD plasma reactor: Effect of applied voltage, pulse repetition frequency and electrode material

In this study, a nano second pulsed dielectric barrier discharge plasma reactor has been investigated for conversion of heavy naphtha. Continuous liquid hydrocarbons cracking and instant production of hydrogen and light gaseous hydrocarbons in the range of C1–C3 have been studied at room temperature and atmospheric pressure by using argon as a carrier gas. The effect of applied voltage, pulse frequency and inner electrode material has been examined on the quantity and quality of products. Aluminum, copper, stainless steel, iron and brass have been selected to investigate the effect of electrode material. Results show that applied voltage, pulse repetition frequency and inner electrode material, affect the energy efficiency of the plasma cracking process. Stainless steel has been selected due to its high performance among all tested materials. The highest process efficiency has been obtained at 7kV and 18kHz which was 79.38lkWh−1 for 1mlmin−1 of feed injection and 24.70W input power. In this condition, the generation rate of hydrocarbon is 22.50mlmin−1. Results indicate that the hydrocarbon product distribution during the process is ethylene≫C2>C1≫C3.

The critical need to improve metrological assurance of tests of hydrocarbon gas products

Questions related to metrological assurance of tests of hydrocarbon gas products in the Russian Federation are considered. Drawbacks in the existing system of metrological assurance, in particular, the lack of a differential approach to types of hydrocarbon gases that differ in terms of composition, expressed both in regulatory documents as well as in the existing base of standard samples of composition, are noted.

Use of nanotechnology for the production of biofuels from butchery waste

Biodiesel can be used as a substitute for fossil fuels and successful studies have been carried out in different applications. The advantages with biodiesel are lower bulk, higher energy density, as well as more transportable and storable capability. We used butchery waste for the production of hydrocarbon gases and biodiesel. For this purpose we used nano catalyst and anatase form of titanium dioxide photocatalyst at room temperature. In the first experiment, butchery waste was cracked into low melting point oil, solid residue and hydrocarbon gases. In the second experiment, cracked oil was transesterified to biodiesel with NaOH at room temperature and atmospheric pressure. The results yielded best quality biodiesel. The economics of this novel process is much more cost competitive due to cheap raw material (butchery waste) that contains high levels of fatty acids. Photocatalysis gave hydrocarbons of prime importance. This study reports an interesting finding that butchery waste could be used for not only the production of biodiesel but also for hydrocarbons. This technology differs from others in that it uses low energy input, cheap and reusable catalyst, with low sulphur and nitrogenous waste gases than petro-diesel and is environment friendly. Key words: Butchery waste, photocatalyst, biofuel, cobalt nanoparticles, nickel nanoparticles, transesterification.

Results from Sleipner gravity monitoring: Updated density and temperature distribution of the CO2 plume

Abstract To help monitor the evolution of stored CO 2 , we have made precision seafloor gravity measurements at 30 seafloor stations above the Sleipner CO 2 plume in the years 2002, 2005 and 2009. Each epoch of gravity data has an intra-survey repeatability of about 3 μGal (standard deviation), obtained using state-of-the-art instrumentation on top of pre-deployed seafloor benchmarks, with typically three visits on each location during a survey. We used three relative quartz-spring Scintrex CG-5 gravimeters in a unique offshore instrument package. Ocean tidal fluctuations and benchmark depths were determined using both pressure gauges on the gravity survey tool and stationary reference pressure gauges on the seafloor. We analyzed and accounted for multiple sources of changes in gravity to obtain an estimate of in situ CO 2 density. First, the injected CO 2 , 5.88 million tonnes during this time period, displaces denser formation water, causing a negative gravity change above the plume. This is the signal of interest for this study. At the same time, hydrocarbon gas production and water influx into the deep, nearby gas reservoir cause an increase in gravity of higher amplitude and longer wavelength. Finally, by observing vertical depth changes of the seafloor benchmarks between surveys to mm precision, we quantified vertical benchmark movements caused by sediment scouring. Some of the benchmarks have experienced more than 10 cm vertical movement over the 7 year duration of the experiment, and erosional topography can be seen in a >10 m broad area around some of the benchmarks. The shifting sediment can also cause a change in the observed vertical gravity gradient. We inverted the gravity changes for simultaneous contributions from: (i) injected CO 2 in the Utsira Formation, (ii) water flow into the Sleipner gas reservoir, and (iii) vertical benchmark movements. We estimate the part of the change in gravity caused by CO 2 injection to be up to 12 μGal. If we assume a geometry of the plume as seen in 4D seismic data, the best match to the 30 stations requires an average CO 2 density of 720±80 kg/ m 3 , neglecting dissolution of CO 2 into the formation water. While the CO 2 in the Utsira Fm. at Sleipner is supercritical, it is fairly close to the critical point; therefore only a slight increase in temperature could lower the density significantly. Density is also sensitive to impurities, which make up 1–2% of the injected material at Sleipner and reduce the density slightly. In the absence of down hole gauges in the injection well, we estimate the well-bottom CO 2 temperature to be 48 °C and pressure to be hydrostatic (∼105 bar). These conditions give a calculated density of 485±10 kg/ m 3 at the perforation. Density is expected to increase away from the well as CO 2 cools down from contact with the cooler formation, up to a maximum of about 710 kg/ m 3 . The distribution of temperature and density within the plume is difficult to model exactly, but most of the CO 2 is expected to cool down to initial reservoir temperature (∼35.5 °C at the perforation) except for a central high-temperature region where CO 2 is still near the injection temperature. Because the undisturbed formation temperatures and the injection temperature are fairly well known, the 2002–2009 gravity change can be used to constrain the rate of dissolution of CO 2 into the formation water. Dissolved CO 2 is invisible in seismic data. The contribution from gravimetric data could therefore be highly valuable for monitoring this process, which is important for long-term predictions of the CO 2 stored in the Utsira Fm. We give an upper bound on the dissolution rate of 1.8% per year.

Reaction of different carbonaceous materials in alkaline hydrothermal media for hydrogen gas production

Reactions of different carbonaceous materials in alkaline hydrothermal media have been studied in a batch reactor. In general, hydrogen gas production increased in the presence of sodium hydroxide for all samples. Based on experimental evidence, a chemical reaction model was developed for hydrogen gas production from these reactions. Evaluation of gaseous reaction products suggested that two main reaction types could have occurred with the samples. These were alkaline oxidation (degradation) leading to hydrogen gas and methane production, and thermal degradation (pyrolysis) leading to the production of tars and hydrocarbon gases. The carbohydrate-rich samples including glycerol, xylan and lignin produced more hydrogen gas via alkaline oxidation than coal, waste tyre and phenol. Pyrolysis was found to be the predominant reaction for coal and waste tyre. In the presence of NaOH, glycerol produced the highest hydrogen gas yield of 76%, while waste tyre produced the lowest yield of 8.2%. The proportions of hydrogen gas and methane in the gas product could be linked to the role of the stoichiometric reacting water during and after alkaline degradation. In addition, phenol was highly resistant to thermal degradation but less so to alkaline degradation. Results suggest that the chemical nature of the carbon atoms in the samples was crucial in influencing the dominant reaction type.

Study of the influence of pressure on enhanced gaseous hydrocarbon yield under high pressure–high temperature coal pyrolysis

The influence of pressure on the yield of gaseous hydrocarbon products derived from pyrolysis of Fushun and Xianfeng coals have been investigated in an anhydrous and confined system. Pyrolysis was performed in sealed gold tubes at 380 °C and under the pressures ranging from 50 to 250 MPa for 24 h. The results show that the effect of pressure on coal pyrolysis and product generation should not be ignored. For the Fushun and Xianfeng lignite, the yields of gaseous hydrocarbon generation increase by 9.1% and 12.7% when the pressure increases from 50 to 250 MPa, respectively. However, the yields of hydrogen gas decrease greatly with pressure. The hydrogen gas yields of Fushun and Xianfeng lignite decrease by 76.5% and 75.9%, respectively, when the pressure increases from 50 to 250 MPa. Yields of carbon dioxide gas of Fushun and Xianfeng coals were enhanced with increasing pressure by 7.4% and 8.9% respectively. Data of stable carbon isotope compositions reveal that the methane and ethane carbon isotope values are also affected by pressure, as they become heavier by approximately 1.2‰ (PDB) when the pressure is increased from 50 to 250 MPa. Simultaneously, the hydrogen isotope compositions of methane and ethane increase by 10.3‰ and 7.1‰, respectively. Our experimental results suggest that the increase in gaseous hydrocarbon yield is resulted from synthesis of carbon dioxide and hydrogen and pressure serves to facilitate the synthetic process.

Co-gasification of coal and wastes in a pilot-scale installation 1: Effect of catalysts in syngas treatment to achieve tar abatement

Co-gasification of poor quality coals mixed with wastes has the advantage of diversifying energy resources and of decreasing the dependency on imported fossil fuels. However, the use of wastes like plastics increased the production of tar and gaseous hydrocarbons. Although, the correct adjustment of gasification experimental conditions, like temperature and air flow, may lead to some reduction of undesirable compounds, this procedure is not usually enough to accomplish effective reductions of tar and hydrocarbons, thus obliging to the use of further gas treatment. Co-gasification studies were undertaken in a pilot-scale installation. The syngas produced, after going through a cyclone to decrease particulates content, was further treated in two catalytic fixed bed reactors. In the first fixed bed reactor was used a low cost catalyst, like dolomite, to reduce H2S content in the gas and also to promote some tar destruction. In the second fixed bed reactor, Ni based catalysts were employed to achieve effective reduction of tar and other undesirable compounds. After the second fixed bed reactor, H2 content was much higher than that of the gas leaving the gasifier, values higher than 50% were obtained, while gaseous hydrocarbons contents were much lower, particularly CnHm contents were quite low, usually below the detection limit of the method used. The presence of tar was never detected after the second fixed bed reactor.

Where does all the helium that we use come from?

Helium occurs naturally in association with geological fluids and is regarded by economists as a mineral commodity. Commercially, helium is obtained as a by-product from natural gas reservoirs that typically have concentrations of up to 1% He by volume (STP). Existing sources of helium within the USA are expected to decline in parallel with declining natural gas production. Huge reserves of helium occur in Algeria, Qatar and Russia, which are likely to dominate production for the next several decades. In this context, political and economic factors that affect hydrocarbon gas production may influence the availability and price of helium.

Enhanced Production of α-Olefins by Thermal Degradation of High-Density Polyethylene (HDPE) in Decalin Solvent: Effect of the Reaction Time and Temperature

The thermal degradation of high-density polyethylene (HDPE) in decalin has been investigated as a method for the feedstock recycling of plastic wastes. The study is focused on the effects of the reaction time and temperature. The solvent increased the HDPE conversion and had a significant effect on the product distribution, which may be assigned mainly to the decalin participation on the reaction mechanism. Short reaction times and low temperatures in the presence of decalin contributed to an enhanced production of gaseous hydrocarbons. Longer reaction times and high temperatures in the presence of this solvent improved the production of C5−C55 hydrocarbons. The gaseous olefins and C5−C32 α-olefins increased with time and temperature; however, the best selectivity to olefins (96.5%) in the gaseous fraction was obtained at 5 h and 375 °C, whereas the higher selectivity to α-olefins (76%) within the C5−C32 fraction was achieved after 5 h and 425 °C.

Chemical catalysed recycling of waste polymers: Catalytic conversion of polypropylene into fuels and chemicals over spent FCC catalyst in a fluidised-bed reactor

Polypropylene (PP) was pyrolysed over spent FCC commercial catalyst (FCC-s1) using a laboratory fluidised-bed reactor operating isothermally at ambient pressure. The influence of reaction conditions including catalyst, temperature, and ratio of polymer to catalyst feed and flow rates of fluidising gas was examined. The yield of gaseous and liquid hydrocarbon products at 390 °C for spent FCC commercial catalyst (87.8 wt%) gave much higher yield than silicate (only 17.1 wt%). Greater product selectivity was observed with FCC-s1 as a post-use catalyst with about 61 wt% olefins products in the C 3–C 7 range. The selectivity could be further influenced by changes in reaction conditions. Valuable hydrocarbons of olefins and iso-olefins were produced by low temperatures and short contact times used in this study. It is also demonstrated that a post-use catalyst system under appropriate conditions the resource potential of polymer waste can be economically recovered and also can address the recycling desire to see an alternative to solve a major environment problem.

Geochemical evaluation of the hydrocarbon prospects of sedimentary basins in Northern Nigeria

Sedimentary basins of Northern Nigeria comprise the Middle and Upper Benue Trough, the southeastern sector of the Chad Basin, the Mid-Niger (Bida) Basin, and the Sokoto Basin. Organic geochemical and organic petrologic studies indicate the existence of potential source rocks in the Benue Trough and the Chad Basin, with coal beds constituting major potential source rocks in the whole of the Benue Trough. The generation and production of liquid and gaseous hydrocarbons from coal beds presently is world-wide indisputable. Although TOC values and liptinite contents are relatively high in the Mid-Niger (Bida) Basin, Tmax values and biomarker data show that hydrocarbons are probably just being generated in the basin and may not yet have been expelled nor migrated in large quantities.

A comparison of primary lignite structure as determined by pyrolysis techniques with chemical characteristics determined by other methods

Thermogravimetric-Fourier transform infrared (TG-FTIR) studies, using a ramp rate of 30 °C/min, have been used to determine the total acidity and carboxylic acid contents for a range of lignites from the Latrobe Valley coal fields, Vic., Australia, some of which were also studied in water- and acid-washed form. The results are compared with values determined by barium ion-exchange. Total acidities from barium ion-exchange showed good agreement with those determined from the total amount of CO+CO 2 evolved. The carboxylic acid content determined from the amount of CO 2 evolved in pyrolysis showed a good correlation with the concentration of stronger acid functional groups determined by barium ion-exchange, but was lower. The effect of ion-exchange with Na, Mg, Ca and Al on CO, CO 2, pyrolysis H 2O and hydrocarbon gas production, as well as on the relative yields of these different gases, was similar to that observed by earlier workers for pyrolysis over much longer run times.

Thermogravimetry-differential thermal analysis coupled with chromatography as a thermal simulation experimental method and its application to gaseous hydrocarbons from different source rocks

In this paper a thermogravimetry-differential thermal analysis method coupled with chromatography (TG-DTA-GC) has been adopted to simulate the generation of gaseous hydrocarbons from different hydrocarbon source rocks such as coals, mudstones, and carbonate rocks with different maturities. The temperature programming for thermal simulation experiment is 20°C/min from ambient temperature to 700°C. As viewed from the quantities and composition of generated gaseous hydrocarbons at different temperatures, it is shown that low-mature coal has experienced the strongest exothermic reaction and the highest loss of weight in which the first exothermic peak is relatively low. Low-mature coal samples have stronger capability of generating gaseous hydrocarbons than high-mature samples. The amounts and composition of gaseous hydrocarbons generated are closely related not only to the abundance of organic carbon in source rocks, but also to the type of kerogen in the source rocks, and their thermal maturity. In the present highly mature and over-mature rock samples organic carbon, probably, has already been exhausted, so the production of gaseous hydrocarbons in large amounts is impossible. The contents of heavy components in gaseous hydrocarbons from the source rocks containing type- I and -II kerogens are generally high; those of light components such as methane and ethane in gaseous hydrocarbons from the source rocks with III-type kerogens are high as well. In the course of thermal simulation of carbonate rock samples, large amounts of gaseous hydrocarbons were produced in a high temperature range.

Hydrocarbon prospectivity of Nigeria's inland basins: From the viewpoint of organic geochemistry and organic petrology

Hydrocarbon prospectivity of Nigeria's inland basins: From the viewpoint of organic geochemistry and organic petrology

Sonochemical Degradation of Sodium Dodecylbenzene Sulfonate in Aqueous Solutions

The sonochemical degradation of sodium dodecylbenzene sulfonate (SDBS) has been studied over a wide concentration range spanning the critical micelle concentration (CMC) of the surfactant. The rate of degradation of SDBS increased linearly with increasing concentration below the CMC of SDBS. Above the CMC, the degradation rate continued to increase but at a much slower rate compared with that below the CMC. It was found that the increasing rate of degradation of SDBS correlated closely with the decrease in the air/water surface tension of the surfactant solutions. The results of this study strongly suggest that the initial step in the degradation process is OH• radical attack onto SDBS molecules adsorbed at the cavitation bubble/solution interface. The sonication of SDBS solutions for extended periods of time (ca. 12 h) led to the generation of gaseous hydrocarbon products, such as methane, ethane, ethylene, and acetylene. It is concluded that further radical attack occurs on the intermediates produced from the initial degradation step. This further degradation pathway is responsible for producing both water-soluble species, and volatile products that are pyrolyzed within the cavitation bubbles.