我国柴油加氢脱硫催化剂的研究进展

在绿色低碳的新形势下,我国加快了汽柴油产品质量升级的步伐。目前我国炼油企业改善柴油产品质量主要依靠加氢脱硫工艺,而高活性柴油加氢脱硫催化剂的开发是加氢技术的关键。高活性柴油加氢脱硫催化剂具有原料适应性强、稳定性好、满足低硫清洁柴油生产需求的特点。本文介绍了国内柴油加氢脱硫催化剂的研究进展,对国产和进口加氢脱硫催化剂的性能进行了对比,并结合我国的实际情况提出了改善催化剂性能的建议。     

全球炼油加氢技术进展

对全球炼油加氢技术的进展进行了综述,并对我国炼油加氢技术发展方向进行了展望。指出今后我国需要加大低成本汽柴油加氢新技术研发,降低油品升级成本;加强渣油加氢裂化技术创新,并向工业化迈进。     

炼油加氢装置生产能力现状与分析

加氢技术是炼油企业生产清洁燃料的主要技术。从油品质量标准的发展趋势入手,综合分析了全球炼油加氢装置生产能力变化及扩能改造情况,重点论述了美国和西欧国家炼油加氢装置的应用场合,同时对未来发展趋势作了简要分析。指出加氢装置是未来炼油生产过程中必不可少的装置,国内加氢处理生产能力还有很大的上升空间。对于未来加氢处理技术的发展,开发出能够提高常规和非常规运输燃料质量和供应安全的方法,同时又能消除能耗增长和排放对环境的影响将极为重要。加氢裂化技术的应用将不断增多并更加灵活。高压加氢裂化技术仍为新建装置的首选;缓和/中压加氢裂化技术可更多地用于现有装置的改造项目,如生产超低硫柴油或用于FCC原料的加氢预处理等。     

加氢处理-催化裂化组合工艺的应用

加氢处理-催化裂化组合工艺适合加工劣质、重质原油的蜡油。劣质蜡油（减三线VGO、CGO、DAO等）经过加氢处理后甩作催化裂化原料，可优化FCC装置的操作条件，改善产品分布，降低催化裂化汽柴油硫含量，减少烟气中SOx、NOx排放。组合工艺的应用不仅提高了企业的劣质原油加工能力，同时还改善了产品结构，提高了炼油的主要技术指标。     

石油化工科学研究院开发的加氢技术与清洁燃料生产

综述了石油化工科学研究院开发的生产清洁燃料和石油产品的系列加氢催化剂和加氢技术.这些技术可以从ψ(烯烃)＞50%的FCC汽油生产ω(硫)＜30μg/g、ψ(烯烃)＜20%、抗爆指数损失小于2的汽油组分,和生产低硫、低芳烃柴油等优质的石油产品,为炼油企业提供了有效的技术支撑.     

炼油催化剂：未来市场看好

由于燃油新标准的推行，炼油商使用重质、劣质原料的增多，以及炼油能力的扩展，2007年是炼油催化剂用量强劲增长的一年。FCC催化剂市场将从供过于求更趋于平衡，而加氢催化剂的供需将比2006年稍有吃紧。     

渣油加氢技术的研究Ⅱ.渣油加氢与催化裂化双向组合技术(RICP)的开发

石油化工科学研究院在开发渣油固定床加氢技术（RHT）的基础上成功地开发了渣油加氢-FCC双向组合技术——RICP。该技术的特点是将加氢后的渣油作为FCC的原料，并将FCC的回炼油循环到渣油加氢反应器的入1：3，而不是自身循环。该技术可使渣油加氢装置进料粘度下降，掺入10％的FCC循环油，渣油加氢催化剂的脱硫率可提高5．1个百分点，脱残炭率提高10．9个百分点。当渣油掺入20％循环油时，FCC装置的汽、柴油收率可提高3．2个百分点，有利于进一步提高渣油加氢技术的经济性。     

FHUDS-8柴油超深度脱硫催化剂的反应性能和工业应用

为满足国内炼油企业柴油产品质量升级需要,提高加氢精制催化剂在国际市场的竞争力,中国石油化工股份有限公司抚顺石油化工研究院开发了FHUDS-8新一代低成本柴油超深度脱硫催化剂。中试试验结果表明,FHUDS-8催化剂具有优异的加氢脱硫、加氢脱氮和芳烃饱和活性,同时具有良好的活性稳定性和原料适应性。与上一代FHUDS-6催化剂相比,FHUDS-8催化剂不仅加氢活性略有提高,而且催化剂的堆积密度降低了20%,可大幅度降低催化剂的采购成本。该催化剂在多家炼油企业的柴油加氢装置上已有应用。工业应用结果表明,FHUDS-8催化剂具有优异的加氢活性,生产的柴油硫质量分数小于10μg/g,满足了企业生产国Ⅴ清洁柴油的需要。     

蜡油加氢精制催化剂国内外研究现状

随着环保要求的日益严格和低硫汽柴油生产的要求,蜡油加氢处理技术将越来越显现其经济效益。从FCC原料加氢预处理的意义出发,介绍了国内外蜡油加氢处理工业催化剂的开发情况以及该类催化剂国内外研究进展。对生产厂家选择使用催化剂和开发新型高性能催化剂具有重要的参考价值。     

劣质柴油加氢改质催化剂的制备及其应用Ⅱ.共胶法加氢改质催化剂的应用

通过共胶法制备了一种非负载型加氢改质催化剂。采用X射线衍射、NH3-程序升温脱附、吡啶吸附红外光谱、扫描电子显微镜、N2吸附-脱附等手段对制备的催化剂进行表征。以中国石化青岛炼油化工有限责任公司(简称青岛炼化)和石大科技胜华炼油厂(简称胜华)两种劣质催化裂化(FCC)柴油为原料,考察催化剂的脱硫、脱氮、脱芳烃效果及其对高硫、高芳烃劣质柴油原料的适应性。结果表明,共胶法催化剂可在360℃下使青岛炼化FCC柴油硫质量分数由7 428μg/g降到14μg/g、胜华FCC柴油硫质量分数由5 114μg/g降到12μg/g,能够完全脱除两种劣质FCC柴油中的氮化物,且对FCC柴油的稠环芳烃脱除率达到99%以上。     

Effects of temperatures and storage time on resting populations of Escherichia coli O157:H7 and Pseudomonas fluorescens in vitro

Assessment of microbial interactions is crucial for documenting bacterial growth in pure and mixed cultures and their potential for biological applications. Pseudomonas fluorescens (non-plant pathogenic and non-pectinolytic) has been used as a biocontrol microbe for plant pathogens and food-borne bacteria. We determined the growth of Escherichia coli O157:H7 (Ec) and P. fluorescens(Pf) in monocultures and co-cultures in sterile distilled water (SDW), buffered peptone water (BPW) and trypticase soy broth (TSB). The effects of temperatures (5, 10, 15, 20, 25, 35, and 37 °C) and storage time (0, 2, 4, 6, 24, and 48 h) on bacteria populations were assessed. Bacteria counts in monocultures in SDW ranged from 2.14 to 3.03 and 2.54 to 3.31 Log CFU/ml for Ec and Pf; respectively. In BPW, mean bacteria counts (monocultures) ranged from 3.15 to 6.14 and 2.54 to 6.41 Log CFU/ml for Ec and Pf, respectively. Ec populations in co-culture varied with storage temperatures and time. After 48 h, Ec 43894 monocultures in TSB ranged from 2.17 to 8.75 and 2.31 to 8.85 Log CFU/ml at 20 and 35 °C; respectively. In co-cultures with Pf 2-79, Ec 43894 counts ranged from 1.71 to 5.83 (20 °C) and 1.90 to 9.03 Log CFU/ml (35 °C) in TSB. The reductions of Ec by Pf 2-79 varied among strains and generally ranged from 0.20 to 0.90, 0.63 to 1.18, and 0 to 0.56 Log CFU/ml in BPW (10 °C). Substrate availability, storage temperatures, and time significantly (P < 0.05) impacted Ec populations in co-culture. The liquid substrate experiments indicated suppressive conditions of Ec by Pf, however; the reduction of produce contamination by E. coli O157:H7 during transitory temperature abuse conditions such as the transportation of produce from fields needs further investigation.     

负载型氮化物催化剂的性质及加氢精制性能

 采用N₂/H₂程序升温还原法制备了非负载型氮化钼(Mo₂N)和氮化镍钼(Ni₂Mo₃N)催化剂，并以Al₂O₃为载体制备了负载型氮化钼(Mo₂N/Al₂O₃)和氮化镍钼(Ni₂Mo₃N/Al₂O₃)催化剂。采用XRD、BET、H₂-TPR和NH₃-TPD等方法对制备的氮化物催化剂的性质进行了研究，并分别以含2%（质量分数，下同）噻吩和10%四氢萘的环己烷溶液为含硫、含芳烃的柴油模型化合物，考察了制备的负载型氮化物的加氢脱硫（HDS）及加氢脱芳烃（HAD）性能。结果表明，以金属氧化物为前驱物，采用N₂/H₂程序升温还原法制得的氮化钼为Mo₂N(γ型)、氮化镍钼为Ni₂Mo₃N；经钝化处理后，氮化物表面形成了金属氧化物保护层，其中Mo₂N/Al₂O₃和Ni₂Mo₃N/Al₂O₃表面氧化层的还原温度分别为350和300℃。Mo₂N/Al₂O₃和Ni₂Mo₃N/Al₂O₃催化剂的表面酸性以弱酸为主；二者均表现出较好的HDS性能，但Mo₂N/Al₂O₃的HDA性能很差，而Ni₂Mo₃N/Al₂O₃的HDA性能较Mo₂N/Al₂O₃有一定程度的提高，说明镍钼共存有利于提高金属组分的分散性及催化剂的加氢饱和性能。     

The Preparation of Wax Emulsions Stabilized by C5 Petroleum Resin

Wax emulsions were prepared by using paraffin wax and oxidized wax as raw materials, compound Wb-L as emulsifier, and C₅ petroleum resin as stabilizer. Its performance was studied. The results showed that when M _{C5 petroleum resin r}/M _{wax and oxidized wax} = 0.20, M _emulsifier/M _{wax and oxidized wax} = 0.50, M _water/M _{wax and oxidized wax} = 2.50, emulsifying time was 30 min, emulsifying temperature was 90–95°C, and stirring speed was 1,100 r/min, wax emulsions with good stability, dispersibility, and monodisperse particle size were obtained, giving a preservative solution in pencil board production.     

Inactivation of Staphylococcus saprophyticus in chicken meat and purge using thermal processing,high pressure processing,gamma radiation,and ultraviolet light (254 nm)

Staphylococcus saprophyticus is a common contaminant in meat and poultry, and causes urinary tract infections after colonization of the gastrointestinal tract, followed by accidental transfer of contaminated feces to the urethra. There is limited information regarding the inactivation kinetics of S. saprophyticus in meat and poultry. When S. saprophyticus was suspended in ground chicken meat (GCM) the thermal processing D₁₀ was 6.26, 0.60 and 0.09 min at 55, 60 and 65 °C, respectively. When S. saprophyticus was inoculated into GCM and subjected to high pressure processing (5 °C, 0–25 min) at 200, 300 or 400 MPa the HPP D₁₀ was 15.5, 9.43, and 3.54 min, respectively. When the S. saprophyticus cocktail was inoculated into GCM and irradiated (5 and −20 °C) the gamma radiation D₁₀ were 0.64 and 0.77 kGy, respectively. When S. saprophyticus was inoculated into chicken purge which was then placed on food contact surfaces including stainless steel, and high density polyethylene and polypropylene and treated with UV-C (0–60 mJ/cm²) the UV-C D₁₀ ranged from 14.9 to 18.5 mJ/cm². These results indicate the inactivation kinetics for S. saprophyticus are consistent with those for other foodborne pathogens and could be controlled in poultry meat and purge without difficulty.     

Histamine content and histamine-forming bacteria in mahi-mahi (Coryphaena hippurus) fillets and dried products

Forty-two mahi-mahi fillets and 17 dried products sold in retail markets in Taiwan were tested for histamine and histamine-forming bacteria. The levels of pH, salt content, water content, Aw, TVBN, APC, TC and Escherichia coli in mahi-mahi fillet samples ranged from 5.6 to 6.5, 0.05 to 2.44%, 70.9 to 82.8%, 0.95 to 0.99, 5.9 to 23.5 mg/100 g, 3.1 to 7.0 log CFU/g, <3 to 1650 MPN/g and <3 to 45 MPN/g, respectively. The levels of pH, salt content, water content, Aw, TVBN, APC, TC and E. coli in dried mahi-mahi samples ranged from 5.7 to 6.4, 0.63 to 20.13%, 7.1 to 42.9%, 0.51 to 0.85, 21.4 to 133.9 mg/100 g, 3.6 to 8.7 log CFU/g, <3 to 5900 MPN/g and <3 to 2500 MPN/g, respectively. The average content of various biogenic amines in fillets samples was less than 0.3 mg/100 g. Four of the 17 dried samples (23.4%) had histamine levels greater than the FDA guideline of 5 mg/100 g for scombroid fish and/or product with one of them containing 68.15 mg/100 g of histamine, which is greater than the 50 mg/100 g hazard action level. Eight histamine-producing bacterial isolates, capable of producing 12.6 ppm–562 ppm of histamine in trypticase soy broth supplemented with 1.0% l-histidine (TSBH), were identified as Raoultella ornithinolytica (three isolates), Pantoea agglomerans (two isolates), Proteus vulgaris (two isolates) and Enterobacter amnigenus (one isolate), by 16S rDNA sequencing with PCR amplification.     

Compositional variabilities among crude oils from the southwestern part of the Qaidam Basin, NW China

A suite of crude oils have been analyzed by GC/MS in order to understand compositional heterogeneities in the oilfields located in the southwestern part of the Qaidam Basin, NW China. The oil samples investigated in this study can be grouped into two broad groups, A and B, based on the distributions of pentacyclic triterpanes. Group A oils predominately occurred in the northwestern part of the study area contain relatively high amounts of gammacerane and C₃₅ hopanes with the ratio of gammacerane to C₃₀ hopane (G/H) > 0.7 and the C₃₅/C₃₄ hopane ratio (C₃₅/C₃₄) > 1.2. In contrast, Group B oils mainly occurred in the southeastern part of the study area have relatively low values of G/H (~ < 0.7) and C₃₅/C₃₄ (< 1.2). Furthermore, Group A oils can be subdivided into three subgroups (A1, A2, and A3) by detailed investigation of molecular compositions of steranes, hopanes and aromatic sulfur compounds. Subgroup A1 oils, which mainly occurred in the westernmost corner, contain low amounts of dibenzothiophene (DBT) and methyldibenzothiophenes (MDBT) relative to C₃₀ hopane with the ratio of (DBT + MDBT)/C₃₀ hopane (DBT + MDBT/H) < ~ 0.25 and display high abundances of ααα20R C₂₈ sterane relative to C₂₉ compound with the C₂₈/C₂₉ sterane ratio > ~ 0.90. In contrast, subgroup A3 oils, which mainly occurred in depression areas, have relatively high values of (DBT + MDBT)/H (~ > 0.25) and relatively low ratios of C₂₈/C₂₉ sterane (~ < 0.90). Subgroup A2 oils, occurring in Gasikule and nearby oilfields, seem to have intermediate amounts of aromatic sulfur compounds and C₂₈ steranes relative to A1 and A3 oils, indicating a mixing signature of the two subgroups. The oil groups or subgroups revealed by the compositional heterogeneities and genetic affinities, as well as their regular occurrence in different oilfields, may indicate secondary petroleum systems existing within the Tertiary saline lacustrine petroleum in the southwestern Qaidam basin.     

Inhibition of Listeria monocytogenes in vitro and in goat milk by liposomal nanovesicles containing bacteriocins produced by Lactobacillus sakei subsp. sakei 2a

Lactobacillus sakei subsp. sakei 2a is a bacteriocinogenic lactic acid bacteria isolated from a Brazilian meat product, capable to inhibit Listeria monocytogenes in vitro and in foods. In this study, bacteriocin produced by this strain were encapsulated in phosphatidylcholine (FC) and 1,2-dioleoyloxy-3-trimethylammonium-propane (DOTAP) liposomes, separately and in combination, were characterized and evaluated for activity against L. monocytogenes in vitro and in experimentally contaminated UHT goat milk, during storage at 7 °C for 14 days and 30 °C for 24 h. The FC and DOTAP/FC (3:1) nanovesicles containing bacteriocins (12.800 AU mL⁻¹) presented zeta potential of −1.54 and + 38.13 mV, Entrapment Efficiency of 80.0% and 94.1%, and diameter of 91.19 and 81.49 nm, respectively. DOTAP/FC nanovesicle presented excellent stability, and maintained the same physicochemical characteristics over 28 days. Both free and encapsulated bacteriocins controlled L. monocytogenes growth in BHI medium and goat milk stored at 30 °C for at least 8 h, in a similar pattern. After 24 h in BHI medium, bacteriocins encapsulated in FC nanovesicles were more effective (p < 0.05) than free bacteriocins. However, in goat milk, no significant differences (p ≥ 0.05) were observed for the two types of nanovesicles. At 7 °C, both free and encapsulated bacteriocins retarded the L. monocytogenes growth, and after 5 days, counts were 5 log lower than in the controls, both in BHI and in goat milk. Encapsulation of bacteriocin in FC and DOTAP/FC nanovesicles did not affect the antimicrobial activity, but the advantages of their application for control of L. monocytogenes in goat milk based dairy products, when compared to free bacteriocins, remain unclear and more studies are needed.     

Survival and inhibition of Staphylococcus aureus in commercial and hydrated tahini using acetic and citric acids

Tahini (sesame paste) is a low-moisture ready-to-eat food that has been linked to foodborne outbreaks and recalls. The objectives of this study were to investigate the behavior of Staphylococcus aureus in commercial and hydrated tahini at 10, 21 and 37 °C and to inhibit S. aureus in these products by 0.1, 0.3 and 0.5% acetic or citric acid. S. aureus was able to survive in commercial tahini with reductions of 3.3, 1.6 and 0.7 log₁₀ CFU/g at 37, 21 and 10 °C, respectively; while it grew in hydrated tahini with an increase of 3.9, 3.0 and 1.8 log₁₀ CFU/ml at 37, 21 and 10 °C, respectively, by 28d. Citric or acetic acid at ≤ 0.5% reduced S. aureus in commercial tahini by ≤ 2.3 log₁₀ CFU/ml by 28d compared to control at all of the tested temperatures. However, acetic and citric acid were more inhibitory at 37 and 10 °C, respectively. In hydrated tahini, viable S. aureus cells were not detected in the presence of 0.5 or 0.3% acetic acid after 7 and 14d, respectively, at both 21 and 37 °C; and after 14 and 28d, respectively at 10 °C. Acetic acid at 0.1% also reduced S. aureus numbers to undetectable levels after 14 and 28d at 21 and 37 °C, respectively. S. aureus cells were also not detected in the presence of 0.5% citric acid by 21d at all of the tested temperatures, or 0.1 and 0.3% citric acid by 28 and 21d, respectively at 21 °C. Acetic and citric acids could be used in tahini or tahini-based products to reduce the potential risk associated with S. aureus.     

Tenacity of Bacillus cereus and Staphylococcus aureus in dried spices and herbs

Numerous studies examined the antimicrobial effects of spice and herb extracts, whereas little is known about the effects of dry condiments on the survival of microorganisms. This study investigated the impact of dried condiments on the survival of Bacillus cereus and B. thuringiensis spores as well as Staphylococcus aureus cells. In addition, the survival variability between different strains was evaluated. Condiments (allspice, basil, cinnamon, nutmeg, oregano, paprika, parsley and pepper) were artificially contaminated by a dry spiking method using sand as carrier matrix and as control. The results show that counts of B. cereus and B. thuringiensis spores (initial spore count 5.6 ± 0.2 log₁₀ cfu/g and 6.7 ± 0.1 log₁₀ cfu/g, respectively) did not decline significantly in all condiments over a period of 50 weeks. In contrast, in some of the spiked test materials, cell counts of S. aureus (initial cell count 8.1 ± 0.5 log₁₀ cfu/g) were reduced below the detection limit of 10 cfu/g within 10 weeks of storage. D values for S. aureus ranged between 5 and 31 days depending on the strain, condiment and initial contamination level. In conclusion, dried condiments may not affect the survival of spores but can significantly affect the survival of non-spore forming bacteria. As strain variability can occur, tenacity studies should be conducted including a variety of strains.     

Occurrence of biogenic amines in beers from Chilean market

The presence of tryptamine, phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermidine and spermine was determined for the first time in beers commercialized in Chilean market. Dansylated amines were separated on a Zorbax-XDB C₁₈ column using a binary mobile phase composed of acetonitrile and 20 mmol L⁻¹ ammonium formate, pH 5.5. Chromatographic conditions were optimized using an experimental design, and validation was carried out following ICH recommendations. Calibration data fitted a linear regression model with R² > 0.996. Repeatability (n = 6) and intermediate precision (n = 3) in matrix showed RSD values lower than 5.00% and 5.21%, respectively. Recoveries at three different concentrations ranged from 75.50 to 96.48%. The proposed method was applied to determine the biogenic amines content in 101 beer samples produced by macro- (n = 65) and microbreweries (n = 36) using low (n = 63) and high fermentations (n = 38). Biogenic amines content in beer samples ranged from 0.53 to 85.04 mg L⁻¹, from which beers produced by microbreweries (19.13 ± 16.92 mg L⁻¹) showed a significant higher biogenic amines content (P = 0.0021) than beers produced by macrobreweries (9.65 ± 4.50 mg L⁻¹). Putrescine was the principal biogenic amine found in all kind of beers regardless origin, and the type of fermentation and brewery. Only 2 samples presented relevant levels of histamine and tyramine, but both below the limits reported by the European Food Safety Authority (EFSA). Thus, it can be concluded that beers commercialized in Chile are not a serious toxicological risk (e.g. hypertensive crisis) regarding the type and content of biogenic amines.