The Study On Interactions Between Sulfur In Different Forms And Organic Matter

Sulfur is widely distributed in nature whose circulation is closely related to the life activities.Thus sulfur often occurred in various types of fossil fuels.Elemental sulfur and other sulfur-bearing compounds such as hydrogen sulfide and polysulphuric acid are either corrosive or toxic that they tend to disturb the mining,the development or utilization of fossil energy.A large part of our country's fossil fuels contain elemental sulfur: medium and high sulfur coal can accounts for more than a quarter of all coal resources;High-sulfur crude oil accounts for over 30% of the current production of crude oil and its proportion will be continuously increased in the near future along with the further exploitation of crude oil.The existed form and evolution process of sulfur in these fossil fuels are closely related to the thermal evolution of organic matter,thus the research on sulfur's role during the thermal evolution of organic matter should be carried on fundamentally in order to low the risk of using the sulfur-bearing fossil fuels.In this paper,a series of simulation experiments were conducted in sealed gold-tubes via different existed forms of sulfur and hydrocarbons in order to analyze the yields and the stable carbon isotopes of generated hydrocarbon gases and non-hydrocarbon gases.In addition,the solid products and liquid hydrocarbons were also examined qualitatively in this study.Through these simulation experiments,the hydrocarbon generation characteristics of kerogens and crude oils with different contents of sulfur were firstly studied;then the TSR between C7 hydrocarbons and MgSO4 were further investigated;Afterwards,the TSR of iron vitriol and the subsequent formation and evolution process of pyrite were traced;At last,the process and the reaction mechanism of sulfurization of 1-octene were explored in this study.Several conclusions can be drew as below:1.For the kerogen from the Youganwo Formation in the Maoming with relatively lower sulfur content(2.78 wt%)and the kerogen from the Qianjiang Formation in the Ban9 Well of the Jianghan Basin with higher sulfur content(14.28 wt%),their hydrocarbon generation characteristics were investigated and compared.Since they shared the similar gaseous hydrocarbons evolution process,thus,similar kinetic parameters are obtained for these two kerogens;The organic sulfur-containing compounds in the crude oil from the Yajiao 12-13 well with high sulfur content were composed by alkyl tetrahydrothiophenes,alkyl benzothiophenes and alkyl dibenzothiophenes.In comparison,the crude oil from the Changxie 9-1 well with lower sulfur content consisted of only two kinds of sulfur-containing compounds with alkyl benzothiophenes and alkyl dibenzothiophenes.As a result,large quantities of hydrogen sulfide were generated from the crude oil from the Yajiao 12-13 well while almost no hydrogen sulfide was yielded in the oil sample from the Changxie 9-1 well.We concluded that the content and form of sulfur in two series determined the different hydrogen sulfide yields.2.In three typical C7 light hydrocarbon compounds,n-heptane,toluene and methyl cyclohexane are all capable to be oxidized by MgSO4,resulting in the enrichment of 13 C in gaseous hydrocarbon products.During the TSR process,methane seems unable to directly participate in the TSR which its yields and stable carbon isotopic compositions were influenced through higher carbon numbered precursors.In addition,some labile sulfur compounds were formed at the low temperature period and decomposed at higher temperature during the whole TSR stage.It seems probably that those organic sulfur compounds might initiated and thus boosted the TSR.3.TSR with rather fast rate could be occurred between ferrous sulfate and n-octadecane which resulted in enhanced CO2 yields and relatively depleted stable carbon isotopes.No hydrogen sulfide was detected during the experiment because the existed ferrous ions would react with hydrogen sulfide leading to the formation of some ferrous sulphide compound.On the contrary,during the thermal simulation experiment between pyrite and n-octadecane under 450 ?,abundant H2 S will be generated since the produced elemental sulfur would react with the hydrocarbons which largely enhanced the occurrence of TSR.4.Element sulfur,pyrite and sodium bisulfide could be all sulfurized by 1-octene which lead to the formation of some organic sulfidic compounds.The polysulfides that only detected in the sulfur series might be the key intermediate products during the formation of octanethiol.Considering the fact of that 2-octanethiol are much more abundant than 1-octanethiol during the whole experimental stage,neither a free radical mechanism(selectivity of the sulfurization site)nor a formal Markovnikov addition which needs acid catalysis was involved in the reaction.On contrary,a concerted addition between the produced polysulfides and the double bonds could be associated in these reactions.