Study of a newly isolated thermophilic bacterium capable of Kuhemond heavy crude oil and dibenzothiophene biodesulfurization following 4S pathway at 60 °C

BACKGROUND: To meet stringent emission standards stipulated by regulatory agencies, the oil industry is required to bring down the sulfur content in fuels. As some compounds cannot be desulfurized by existing desulfurizing processes (such as hydrodesulfurization, HDS) biodesulfurization has become an interesting topic for researchers. Most of the isolated biodesulfurizing microorganisms are capable of desulfurization of refined products whose predominant sulfur species are dibenzothiophenes so biocatalyst development is still needed to desulfurize the spectrum of sulfur‐bearing compounds present in whole crude. RESULTS: The first desulfurizing bacterium active at 60 °C has been isolated, which reduces DBT concentration from 2 mmol L^?1 to 0.1 mmol L^?1 after 95 h, following the 4S pathway. Its DBT desulfurization pattern was represented by the Michaelis‐Menten equation. Various parameters such as V_max, K_m, µ_m, K_s and maximum specific DBT desulfurization rate were calculated which are 0.092 mmol L^?1 h^?1, 3.554 mmol L^?1, 0.157 h^?1, 3.722 mmol L^?1 and 0.192 mmol L^?1 DBT g^?1 DCW (dry cell weight) h^?1, respectively. It can desulfurize 50% of the sulfur content of Kuhemond heavy crude oil (KHC oil) with an initial sulfur content of 7.6%wt in 6 days. Its maximum specific desulfurization rate for KHC oil is equivalent to 0.005 g sulfur g^?1 DCW h^?1. The bacterium was isolated during a heavy crude oil biodesulfurization project initiated by PEDEC, a subsidiary of National Iranian Oil Company. CONCLUSION: The KHC oil sulfur removal efficiency of the bacterium is approximately five times that of BBRC‐9016 bacterium. It removes sulfur selectively without using sulfur‐containing compounds as its carbon source. By applying various media during its isolation, the probability of screening the correct microorganism is increased. Copyright © 2008 Society of Chemical Industry     

An integrated biodesulfurization process,including inoculum preparation,desulfurization and sulfate removal in a single step,for removing sulfur from oils

BACKGROUND: A single‐stage reactor, in which the growth of bacterial culture, induction of desulfurizing enzymes, and desulfurization reaction are carried out in a single step, was adopted to investigate desulfurization of dibenzothiophene (DBT) at high cell densities. Rhodococcus erythropolis, IGTS8 was used as the biocatalyst. Optimal conditions for bacterial growth and DBT desulfurization were investigated. RESULTS: Optimization of fermentation conditions was necessary to obtain high cell densities including controlling accumulation of acetate. Under optimal operating conditions, the maximum optical density at 600 nm (OD₆₀₀) was measured to be 26.6 at 118 h of cultivation. When biodesulfurization of DBT in model oil with a high cell density culture of IGTS8 was investigated, accumulation of sulfate was found to limit the extent of desulfurization. A sulfate removal step was added to obtain a single‐stage integrated biodesulfurization process. Sulfate removal was achieved via an aqueous bleed stream and use of a separation unit to recycle the organic phase. CONCLUSION: A proof of principle of a complete system capable of biocatalyst growth, induction, desulfurization and by‐product separation was demonstrated. This system enables simplification of the biodesulfurization process and has potential to lower the operating cost of the bioprocess. Copyright © 2008 Society of Chemical Industry     

GC-AED法研究催化裂化柴油中硫氮化合物

采用气相色谱-原子发射光谱（GC-AED）联用技术对FCC柴油中的含硫化合物、含氮化合物进行定性定量研究。结果表明：FCC柴油中硫化物的类型主要是噻吩类衍生物、苯并噻吩、苯并噻吩类衍生物、二苯并噻吩、二苯并噻吩类衍生物,其中苯并噻吩类衍生物、二苯并噻吩类衍生物的硫质量分数占总硫质量分数的93．6％以上。氮化物主要为碱性氮化物（Nb）和非碱性氮化物（Np）两大类型,其中碱性氮化物主要是苯胺及其衍生物,喹啉含量很低,约占总氮质量分数的0．1％,非碱性氮化物主要包括吲哚及其衍生物和咔唑及其衍生物,而咔唑类氮化物一般约占总氮质量分数的64％。不同来源的FCC柴油,其所含硫化物、氮化物的含量和分布不同。应根据其硫化物、氮化物的分布类型及规律,开发合适的柴油脱硫脱氮催化剂及相关工艺。     

Microbial desulfurization of coal and oil

Biotreatment of fossil fuels may be regarded as suitable technology for the desulfurization of oil and coal before combustion, especially for small-scale combustion plants where flue gas cleaning is too expensive.

Although several patents, especially on the field of biodesulfurization of oil, already exist, successful application in a large scale could not be demonstrated until now. “Organic sulfur” is characterized by covalent C-S bonds and can be regarded as an element which is integrated in the macromolecular matrix of coal and in organic sulfur compounds present in oil. As for the results of more semi-empirical approaches no reproducibility and transferability to other oil qualities could be demonstrated when model compounds representing the organic sulfur species were used.

This research strategy resulted in a number of promising biochemical pathways for the degradation and/or desulfurization of such compounds. However, up to now the use of microorganisms able to degrade model compounds in a biotechnological process for coal or oil desulfurization does not meet the expectations.

Thus, it has to be concluded that additional research is needed which should be focussed on the development of biocatalysts with a broad substrate specificity and on methods to improve the availability of the organically bound sulfur in the molecular structure of oil and coal.     

Deep desulfurization of full range and low boiling diesel streams from Kuwait Lower Fars heavy crude

Information on feed quality and, in particular, various types of sulfur compounds present in the diesel (gas oil) fractions produced form different crudes and their HDS reactivities under different operating conditions are of a great value for the optimization and economics of the deep HDS process. This paper deals with deep desulfurization of gas oils obtained from a new heavy Kuwaiti crude, namely, Lower Fars (LF) which will be processed in the future at Kuwaiti refineries. Comparative studies were carried out to examine the extent of deep HDS, and the quality of diesel product using two gas oil feeds with different boiling ranges. The results revealed that the full range diesel feed stream produced from the LF crude was very difficult to desulfurize due to its low quality caused by high aromatics content (low feed saturation) together with the presence of high concentrations of organic nitrogen compounds and sterically hindered alkyl DBTs. The low-boiling range gas oil showed better desulfurization compared with the full range gas oil, however, deep desulfurization to 50 ppm sulfur was not achieved even at a temperature as high as 380 °C for both feeds. The desulfurized diesel product from the low-boiling gas-oil feed was better in quality with respect to the S, N and PNA contents and cetane index than the full-range gas-oil feed.     

Deep desulfurization of hydrodesulfurized diesel oil by Pseudomonas delafieldii R‐8

Biodesulfurization is a promising technology for deep desulfurization. The remaining alkylated DBTs (dibenzothiophenes) in the HDS‐treated (hydrodesulfurized‐treated) diesel oil could be selectively and efficiently desulfurized by resting cells of Pseudomonas delafieldii R‐8, a Gram‐negative bacterium. The desulfurization activities of resting cells were greatly affected by W/O ratio (the volume ratio of aqueous phase to oil phase) and cell concentration. The desulfurization activity increased with the increase in the W/O ratio. When the W/O ratio and cell concentration were 2 and 25 mg cm^?3, the desulfurization activity was as high as 0.41 mg(total sulfur) g^?1(dry cell weight, DCW) h^?1, ie higher than that reported previously. GC‐AED (gas chromatography with an atomic emission detector) analysis showed that the total reductions for all the C1DBTs and C2DBTs were approximately 100%, 94.63% for C3DBT, and 97.09% for C4DBT (designated CxDBT, where x is the number of alkyl groups attached). The rates of biodesulfurization relate to the number and position of alkyl groups attached to the DBT. Copyright © 2005 Society of Chemical Industry     

Simultaneous removal of sulphide and nickel by the compound of Chitosan Schiff Base from crude oil under microwave irradiation

A study has been carried out for simultaneous desulfurization and demetalization by electric desalting from crude oil based on the oxidation of alkyl thiophene and nickel compounds with the compound of Chitosan Schiff Base under the condition of microwave irradiation (SDDM). Besides, an investigation has been made about the influence of Chitosan Schiff Base compound dose, initial temperature, and microwave time on desulfurization and demetalization. By using the optimized conditions for SDDM, up to 56% of sulfur and 82% of nickel removal rates were achieved for model compounds in crude oil samples. With the same conditions but without microwave the removal efficiency was lower than 56% for sulfur model compound and than 82% for nickel porphyrin in crude oil samples. Additionally, in order to develop a fundamental understanding of the SDDM mechanism of sulfides, a molecular simulation of sulfur compounds was performed with both the Hartree–Fock (HF) and second-order Moller–Plesset (MP2) levels of theory for the calculation of reaction kinetic rate by using Gaussian 03 program package. In comparison with conventional desulfurization and demetalization technology, the proposed SDDM process can accomplish the simultaneous removal of sulfur and nickel compounds from crude oil under relatively mild conditions.     

Hydrodesulfurization of hindered dibenzothiophenes: an overview

Hydrodesulfurization is a well-documented process which has been commonly used in the refining of crude oil for over 60 years. It is a process for which interest is frequently renewed due to the requirement to use new feedstocks and the application of more severe environmental legislation, for example, the need to reduce sulfur levels in fuels. Of particular importance in achieving low sulfur levels in fuels is the problem posed by a particular class of compounds, namely hindered dibenzothiophenes, e.g. dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene. Dibenzothiophenes demonstrate resilience to hydrodesulfurization using current catalyst formulations. This overview addresses the key area of hydrodesulfurization chemistry concerning the desulfurization of highly hindered sulfur containing molecules.     

Biodesulfurization of dibenzothiophene using recombinant Pseudomonas strain

BACKGROUND: The sulfur content in crude oil available from various sources ranges from 0.03 to values as high as 8.0 wt%. These high quantities of sulfur must be removed before the crude oil is processed because combustion of this oil would result in severe environmental pollution, such as acid rain. Due to high utility and operating costs, the conventional hydrodesulfurization process (HDS) is considered to be uneconomic. The biotechnological option, biodesulfurization (BDS) seems an attractive low cost, environmentally benign technology. RESULTS: This paper reports the development of a recombinant strain of bacteria designed by introducing desulfurizing, dsz genes containing plasmid pSAD 225‐32, which was isolated from Rhodococcus erythropolis IGTS8 into a gram negative solvent‐tolerant bacterium, Pseudomonas putida (MTCC 1194). This recombinant bacterium can desulfurize the dibenzothiophene (DBT) in the sulfur selective 4S‐pathway. It has been observed that for the same concentration of DBT, the recombinant strain's growth rate is greater than that of the parent strain. Increasing the concentration of DBT resulted in an increase of lag phase as well as decreased growth rate, which shows that the bacteria is following substrate inhibition type kinetics. This genetically modified bacterium can desulfurize 73.1% of 1.2 mmol L^?1 DBT (dissolved in ethanol) in 67 h of cultivation time using growing cells. CONCLUSIONS: It is concluded that further research in this area of biodesulfurization using genetically modified organisms may remove the bottlenecks presently in the way of commercialization of the BDS process. Copyright © 2007 Society of Chemical Industry     

Deep hydrodesulfurization of diesel fuel: Design of reaction process and catalysts

Deep hydrodesulfurization (HDS) of diesel fuel oil was designed based on the recognition that alkyl dibenzothiophenes such as 4-methyl-and 4,6-dimethyldibenzothiophenes were the main target for deep HDS. Multi-stage and fractional HDS were very effective to achieve satisfactory HDS in terms of both sulfur level and fluorescent color of desulfurized oil. Catalysts with the selective hydrogenation of refractory sulfur species in major aromatic partners and isomerization-disproportionation of their alkyl groups prior to HDS were also designed to promote the desulfurization of such sulfur species.     

催化裂化汽油脱硫技术进展

随着环保法规的日益严格,对汽油的质量要求越来越高,全世界都在为降低汽油硫含量而不懈努力。降低汽油硫含量是改善空气质量的有效手段。脱硫技术已经成为各炼油企业的关键技术。汽油中的硫化合物主要来自FCC(流化催化裂化)汽油,因此FCC汽油脱硫技术的研究与开发具有重要意义。目前,减少FCC汽油硫含量的技术主要有：FCC原料油加氢脱硫、FCC汽油加氢脱硫、溶剂萃取脱硫、催化裂化脱硫、氧化脱硫、生物脱硫和吸附脱硫等。笔者综述了国内外FCC汽油脱硫技术进展。     

Biocatalytic oxidation of fuel as an alternative to biodesulfurization

A biotechnological method for fuel desulfurization is described. The method includes the steps of biocatalytic oxidation of organosulfides and thiophenes, contained in the fuel, with hemoproteins to form sulfoxides and sulfones, followed by a distillation step in which these oxidized compounds are removed from the fuel. Straight-run diesel fuel containing 1.6% sulfur was biocatalytically oxidized with chloroperoxidase from Caldariomyces fumago in the presence of 0.25 mM hydrogen peroxide. The reaction was carried out at room temperature and the organosulfur compounds were effectively transformed to their respective sulfoxides and sulfones which were then removed by distillation. The resulting fraction after distillation contained only 0.27% sulfur. Biocatalytic oxidation of fuels appears as an interesting alternative to biodesulfurization.     

Oxidative processes of desulfurization of liquid fuels

Environmental concerns have introduced a need to remove sulfur‐containing compounds from light oil. As oxidative desulfurization is conducted under very mild reaction conditions, much attention has recently been devoted to this process. In this contribution, the developments in selective removal of organosulfur compounds present in liquid fuels via oxidative desulfurization, including both chemical oxidation and biodesulfurization, are reviewed. At the end of each section, a brief account of the research directions needed in this field is also included. Copyright © 2010 Society of Chemical Industry     

石油和煤微生物脱硫技术的研究进展

生物脱硫技术在能源工业发展和环境保护等方面显示出潜在的优势. 本文综述了应用于化石燃料生物脱硫的主要菌种及其脱硫原理、微生物的选育优化及微生物脱硫的动力学, 介绍了生物脱硫技术的工业化应用. 对生物脱硫技术的经济性进行了分析, 指出了进一步研究微生物脱硫技术存在的问题和在我国发展该技术的重要性.     

Medium optimization of <Emphasis Type="Italic">Rhodococcus erythropolis</Emphasis> LSSE8-1 by Taguchi methodology for petroleum biodesulfurization

High production of Rhodoccus erythropolis LSSE8-1 and its application for the treatment of diesel oils was investigated. Culture conditions were optimized by Taguchi orthogonal array experimental design methodology. High cell density cultivation of biocatalyst with pH control and fed-batch feeding strategies was further validated in a fermentor with the optimal factors. Cell concentration of 23.9 g dry cells/L was obtained after 96 h cultivation. The resting cells and direct fermentation suspension were applied for deep desulfurization of hydrodesulfurized diesel oils. It was observed that the sulfur content of the diesel decreased from 248 to 51 μg/g by two consecutive biodesulfurizations. It implied that the biodesulfurization process can be simplified by directly mixing cell cultivation suspension with diesel oil. The biocatalyst developed with the Taguchi method has the potential to be applied to produce ultra-low-sulfur petroleum oils.     

Enhancement of dibenzothiophene biodesulfurization using β-cyclodextrins in oil-to-water media

It has been reported that biodesulfurization (BDS) of dibenzothiophene (DBT) in oil-to-water emulsions is carried out by growing cells of the aerobic Rhodococcus erythropolis IGTS8 strain and developing the so-called 4S desulfurization pathway. On adding β-cyclodextrins, it is possible to improve the BDS yields, increase the diffusion of DBT into the aqueous phase or avoid the HBP accumulation. Moreover, by using greater biocatalyst initial concentrations and adding 15 ppm of β-cyclodextrin, a very high BDS yield has been observed, but the presence of mass transfer limitations and the inhibition effects were not satisfactorily avoided. The Haldane kinetic model agreed well with the experimental results obtained, and the values of the kinetic parameters were determined.     

轻质油品非加氢脱硫新工艺简介

随着环保法要求越来越苛刻，世界范围内对车用发动机燃料的硫含量要求日益严格。本文综述了近年来非加氢脱硫的新技术，包括生物脱硫、氧化脱硫、吸附脱硫、催化法和烷基化法脱硫。     

Desulfurization matching with coal poly-generation system based on dual gas resources

The coal poly-generation system for the production of alcohol and ether fuels as well as power is one of advanced coal utilization techniques. The team leaded by Professor Xie Kechang is carrying out the research on the poly-generation system to produce the syngas from the combination of gasified and pyrolyzed coal gas (dual gas resources) for the alcohol ether synthesis. Gas desulfurization is one of the key technologies for this system. The desulfurization matching with dual gas resources based poly-generation system for the production of alcohol and ether fuels as well as power is presented according to gas components, sulfur content, sulfur species and desulfurization accuracy in this technology. This matching desulfurization is classified into hot gas desulfurization, normal gas desulfurization, warm gas desulfurization and organic sulfur catalytic conversion. The preparation of H₂S removal sorbents, organic sulfur hydrolysis catalyst and the evaluation of their activities involved in the system were investigated. The H₂S removal efficiencies of the crude and fine desulfurization sorbents prepared for hot gas desulfurization are 90% and 99% at 500 °C in simulating coal gas, and their sulfur capacities are 21.85 wt.% and 24.91 wt.%, respectively. The organic sulfur catalyst shows the high hydrolysis activity, and the hydrolysis conversion of COS is more than that of CS₂ on the same catalyst. The research will provide necessary information for the matching desulfurization technology in the demonstration project on dual gas resources coal poly-generation system.     

Inhibition of nitrogen compounds on the hydrodesulfurization of substituted dibenzothiophenes in light cycle oil

The influence of nitrogen compounds on the hydrodesulfurization (HDS) activities of a series of substituted dibenzothiophenes in light cycle oil (LCO) was studied over a NiMo/Al₂O₃ commercial catalyst. Three types of light cycle oil with nitrogen compounds of different concentrations and chemical natures were used as feed—an original fluid catalytic cracking light cycle oil (LCO), LCO with most of its basic nitrogen removed, and an ultra-low nitrogen LCO. Experiments were conducted in a fixed-bed microreactor at a total pressure of 70 atm, temperatures between 330 and 400 °C, and liquid hourly space velocities (LHSV) in the range of 1.0 to 3.5 h⁻¹. The inhibition effects of nitrogen compounds on the HDS reactivity of the three sulfur groups—total sulfur, hard sulfur, easy sulfur—and 14 specific mono-, di- and tri-alkyl substituted dibenzothiophenes were investigated. The results showed that the HDS rate significantly increased using ultra-low nitrogen LCO. Pseudo first-order rate constants were estimated for the 14 mono-, di- and tri-alkyl substituted dibenzothiophenes. The HDS rates could be classified into three groups based on the position of the substituents. It was found that 4 and 6 substituted dibenzothiophenes had the lowest HDS rates. The HDS rate of the 14 substituted dibenzothiophenes were all increased when the ultra-low nitrogen feed was used. The improvement was greater for 4 and 6 substituted dibenzothiophenes than for those with one of the substituents at either the 4 or 6 positions. This finding indicates that the hydrogenation route is more strongly suppressed than hydrogenolysis route by nitrogen compounds since the hydrogenation route is believed to be the predominant reaction pathway for 4 and 6 alkyl-substituted dibenzothiophenes.     

Advanced distillation curve measurements for corrosive fluids: Application to two crude oils

We have recently introduced several important improvements in the measurement of distillation curves for complex fluids. The modifications include a composition-explicit data channel for each distillate fraction (for both qualitative and quantitative analysis) and corrosivity assessment of each distillate fraction. The composition-explicit information is achieved with a new sampling approach that allows precise qualitative as well as quantitative analyses of each fraction, on the fly. We have applied the new method to a variety of fluids, including simple n-alkanes, rocket propellant, gasoline, jet fuels, and a hydrocarbon fluid made corrosive with dissolved hydrogen sulfide. In the current contribution, we present the application of the advanced distillation curve method to two samples of crude oil. A primary motivation behind the work is to precisely measure the distillation curves of these oils using our advanced distillation apparatus; these low uncertainty measurements of true thermodynamic state points can be used for equation of state development and differentiation of crude oil samples. Then, the information content of each distillation was extended much further by use of the composition-explicit data channel: gas chromatography–mass spectrometry (GC–MS), infrared spectrophotometry (IR), gas chromatography with sulfur chemiluminescence detection (GC–SCD), and the copper strip corrosion test (CSCT) were used for each distillate volume fraction sampled. Consequently, for each volume fraction of crude oil distillate sampled, we can address the composition, quantitate the total sulfur content, and measure the corrosivity.