合成气制天然气甲烷化催化剂的研究进展

煤制天然气工艺主要包括煤气化和合成气甲烷化两个过程。综述了煤制天然气工艺中合成气甲烷化催化剂的研究进展,从活性组分、载体和助剂等方面介绍了国内外甲烷化催化剂的研究现状,并分析了甲烷化催化剂的失活原因。合成气甲烷化催化剂的发展方向是使催化剂具有更好的催化活性和热稳定性,以期开发出性能优异的具有自主知识产权的合成气甲烷化催化剂及配套技术。     

合成天然气Ni基甲烷化催化剂的研究进展

综述了合成天然气镍基甲烷化催化剂的研究进展,主要包括催化剂的活性组分、助剂和载体对催化剂性能的影响,引起甲烷化催化剂失活的因素,并对未来甲烷化催化剂的发展方向提出建议。     

白豹油田油井化学防蜡效果评价

进行了合成气完全甲烷化催化剂放大制备研究,对放大的催化剂进行了长周期的活性稳定性评价,并对催化剂的失活机理进行了探索性研究。研究结果表明,放大的催化剂经过1 000h的连续运行,CO平均转化率为99.9%,H2平均转化率为99.80%,CH4平均选择性为98.5%,放大的催化剂的反应性能基本达到小试催化剂的性能。对甲烷化催化剂失活的机理进行的研究发现,引起甲烷化催化剂长周期运行失活的原因主要是积炭和烧结,其中烧结是影响催化剂活性下降的主要因素。     

非晶态合金助剂在苯甲酸加氢中的工业应用

针对CO引起Pd/C催化剂活性的降低开发了非晶态合金甲烷化助剂,部分恢复了Pd/C催化剂的活性;通过增加旋液分离器和磁分离器,开发了以Pd/C催化剂和非晶态合金助剂为"复合"催化剂的苯甲酸加氢改进工艺。助剂结合新工艺已在工业装置上投入使用,取得良好的经济效益。工业应用结果表明,结合甲烷化助剂的新工艺有效解决了原工艺催化剂活性低、失活快、催化剂消耗量大的缺点。     

完全甲烷化催化剂失活原因分析

以Al_2O_3为载体,Ni(NO_3)_2·6H_2O,La(NO_3)_3·6H_2O为浸渍溶液,制备了完全甲烷化催化剂及相应的改性催化剂。以合成气为原料,研究了完全甲烷化催化剂失活的原因与机理。结果表明:催化剂失活是H2S中毒、CO中毒、催化剂积炭和烧结几种原因共同作用的结果。为了减少催化剂失活,合成气中H_2S体积分数应控制在1×10-6以下,甲烷化反应温度不低于300℃;在合成气中加入体积分数为10. 8%的水蒸气可抑制积炭。催化剂中引入MgO,La_2O_3对于提高催化剂的稳定性和抗烧结能力具有显著效果。     

甲烷转化制合成气的新型催化剂

在甲烷转化制合成气的蒸汽转化、干式转化或部分氧化工艺过程中,高比表面的碳化钼和碳化钨成为高效催化剂,这些碳化物的催化活性与铑、钌等重金属元素相当。转化率和产物分布与热力学平衡计算相一致。在常压条件下,因催化剂氧化为ＭＯ２,在所有工艺中催化剂都失活。在高压（８巴）下操作,碳化物表现稳定,在实验过程（７２ｈ）中,催化剂未失活。甲烷转化制合成气的新型催化剂@龙晓达     

水煤气直接甲烷化耐硫催化剂研究

用低硫原料气及含硫高、硫形态多的工业气体在改进后的钴系甲烷化催化剂上进行耐硫试验。结果证明,该催化剂既保持足够的甲烷化活性和选择性,且硫中毒失活速率常数小,耐硫性明显优于镍催化剂。     

甲烷无氧芳构化技术研究进展

综述了甲烷无氧芳构化技术的研究进展,对甲烷无氧芳构化技术(MDA)反应机理、催化剂积炭失活与再生、反应器的选择及工艺开发等方面做了讨论,并对MDA技术的发展提出了相应的建议。     

甲烷-CO_2重整制合成气研究进展

系统回顾和总结了当前甲烷和二氧化碳重整反应研究现状,分析了催化剂研究状况、反应机理和动力学行为及催化剂失活特性。探索抑制催化剂积碳失活的有效途径是ＣＯ２重整过程开发成功的关键。     

提高甲烷化催化剂活性及延长寿命的探讨

本文目的在于分析合成氨装置甲烷化催化剂使用效果差的原因，建议采取相应的措施，提高甲烷化催化剂活性和寿命，从而提高经济效益。     

Inactivation of Bacillus subtilis spores by pulsed electric fields (PEF) in combination with thermal energy II. Modeling thermal inactivation of B. subtilis spores during PEF processing in combination with thermal energy

The application of pulsed electric fields (PEF) can be used to inactivate bacterial endospores if combined with thermal energy. A model was developed in the second part of the study aiming to separate thermal and PEF induced spore inactivation. Therefore thermal inactivation data of B. subtilis spores was obtained by glass capillary method and combined with temperature time profile of the PEF process. The PEF process can be separated in pre heating, PEF treatment and cooling phase. The temperature development in pre heating and cooling phase was simulated based on a theoretical numerical approach, the temperatures in the PEF unit were measured by fiber optic sensors. To evaluate the effect of pH on the inactivation the PEF treatment was performed in Ringer solution (4 mS/cm) at pH 4 and 7. The results of the developed model indicate a thermal and a PEF induced inactivation, where the temperature induced inactivation is slightly higher in acid Ringer solution. The impact of specific energy inputs up to 195 kJ/kg was evaluated, showing an increasing total inactivation of the spores, but also shift towards PEF induced inactivation. Applying an energy input of 195 kJ/kg an inactivation of 4.4 log was obtained in Ringer solution at pH 7, which could be separated in 1.15 log of thermal and 3.25 log of PEF related inactivation. The F-value, typically used to describe thermal spore inactivation processes was calculated for the combined PEF process based on the temperature time profile. The highest F-value determined for the maximum applied energy was 2.43 s, which confirms the low product heat load.     

Inactivation of Bacillus subtilis spores by pulsed electric fields (PEF) in combination with thermal energy – I. Influence of process- and product parameters

In addition to inactivation of vegetative microorganisms, PEF can be used to inactivate bacterial endospores when combined with thermal energy. In the first part of this study, the impact of the product parameters pH value (4 and 7), sugar level (5 and 10%) and conductivity (4 and 15 mS/cm) as well as the process parameters specific energy (up to 350 kJ/kg), electric field strength (6–11 kV/cm) and inlet temperature (56, 70 and 80 °C) on the inactivation of Bacillus subtilis spores were analyzed.The results of spore inactivation by PEF at different inlet temperatures indicated less energy requirements for sufficient inactivation at higher inlet temperatures. Comparing the inactivation at different pH values, the inactivation at acid pH value required less energy than at neutral pH value. A 1.6 log reduction using 167 kJ/kg was detected in Ringer solution at pH 4 compared to 0.6 log in neutral medium at an energy of 165 kJ/kg (inlet temperature of 80 °C and 9 kV/cm as electric field strength). Under the same process conditions (9 kV/cm and 80 °C inlet temperature), the addition of 10% sugar permitted to reduce the energy from 178 to 146 kJ/kg, require to reach a 3 log cycles inactivation of B. subtilis spores. The results showed a successful inactivation of B. subtilis spores by PEF in combination with thermal energy and represent therefore a promising process for spore inactivation with reduced heat load.     

Multiple regression model for thermal inactivation of Listeria monocytogenes in liquid food products

A multiple regression model was constructed for thermal inactivation of Listeria monocytogenes in liquid food products, based on 802 sets of data with 51 different strains and 6 cocktails of strains published from 1984 to 2010. Significant variables, other than inactivation temperature, were pH, sodium chloride content, sugar content, the temperature of growth or storage before inactivation, in addition to a heat shock before inactivation. The constructed model for thermal inactivation of L. monocytogenes has a reduced variability as these variables are known to influence the thermal resistance (and these are known or controllable in practice). Mean simulation results of inactivation of L. monocytogenes during pasteurisation (20 s, 76 °C) of raw milk (calculated mean level after growth 14 cfu/l) were comparable with results of a single regression model constructed from inactivation data found in experiments in milk only (175 data sets, 18 strains/cocktails). Both models predicted a probability of survival of less than 1 in a billion litres. The study shows that multiple regression modelling can be used to obtain a model from all data available, with a limited and realistic uncertainty level, while retaining the variability of heat resistance due to the 51 strains and 6 cocktails of strains (unknown and not controllable in practice).     

Impact of dissociation equilibrium shift on bacterial spore inactivation by heat and pressure

The shift of the dissociation equilibrium under pressure and temperature plays a decisive role in the inactivation of bacterial spores. To obtain the dissociation equilibrium shift in water and buffer systems, the thermodynamic dissociation constants in a wide range of pressure and temperature were modelled. Heat and pressure inactivation of Geobacillus stearothermophilus spores at different initial pH-values in ACES and phosphate buffer confirmed the modelled data. Thermal inactivation in both buffers at 114, 122 and 127 °C resulted in higher logarithmic reductions with ACES. Contrary, after pressure treatment at 500, 600 and 900 MPa with 80 °C phosphate buffer showed higher inactivation. These results indicated the different dissociation equilibrium shifts in buffer systems by heat and pressure.     

Modeling the inactivation of Neosartorya fischeri ascospores in apple juice by high pressure,power ultrasound and thermal processing

Neosartorya fischeri is a mould that spoils acid foods and can produce mycotoxins. In this work, the efficacy of high pressure processing (HPP, 600 MPa) and power ultrasound (24 kHz, 0.33 W/mL) in combination with 75 °C for the inactivation of four week old N. fischeri ascospores in apple juice was investigated and compared with 75 °C thermal processing alone. The HPP-75 °C process was the most effective technique for inactivating N. fischeri spores, resulting in 3.3 log reductions after 10 min vs. no inactivation for thermosonication (TS) and thermal processing. Unexpectedly, activation shoulders were observed during the TS process. Then, the effect of different temperatures on the ascospore inactivation in apple juice by HPP-thermal, TS and thermal processing was investigated, and the log survivors vs. time were modeled. Faster inactivation was achieved at higher temperatures for all the technologies tested, indicating the significant role of temperature for the spore inactivation, alone or combined with other processes. The Weibull model described the spore inactivation better by 600 MPa HPP-thermal (50, 60, 75 °C) and thermal (85, 90 °C), whereas Lorentzian was more appropriate for the TS treatment (65, 70, 75 °C). In conclusion, HPP is the best food preservation technology due to higher spore inactivation in apple juice at the same temperature.     

High pressure processing inactivation of Brettanomyces bruxellensis in seven different table wines

Brettanomyces bruxellensis (‘Brett’) is a major spoilage concern affecting many different wines worldwide, leading to undesirable sensory properties. Sulphur dioxide is the preferred method for wine production and preservation. However, this preservative can cause negative effects including allergic reactions. Therefore, in this study, the use of high pressure processing (HPP) technology to treat seven different types of table wines was investigated. The specific objectives were to determine the effect of wine variety, alcohol content and pH on the HPP inactivation of B. bruxellensis at 200 MPa for up to 3 min, and to estimate the Weibull model parameters of inactivation. Wine type was found to have a great effect on B. bruxellensis inactivation, with 200 MPa for 60 s leading to log reductions ranging from 1.1 (Dolcetto Syrah) to 5.1 (Rosé). Alcohol concentration had a significant effect on Brett inactivation when above 12.0% v/v, leading to increased inactivation from 3.1 to 4.2 after 200 MPa for 180 s in the 12.0 and 14.0% v/v wines, respectively. Wine pH had no significant effect. The inactivation followed a concave shape consistent with the Weibull model with n and b values from 0.376 to 0.731 and 0.07 to 1.09, respectively. As opposed to both Syrah wines and preservative free wine, HPP Brett. inactivation was very effective in Chardonnay (15 s for ≥7 log reductions), followed by Rosé and then Cabernet Sauvignon and Pinot Noir, achieving 6 log reductions in 180 s or less.     

Alternative approaches to predicting microbial behaviour: A probabilistic modelling approach for microbial inactivation and a revised web-tool,the Microbial Responses Viewer

An alternative predictive model for microbial inactivation and a novel web-based tool for the application of predictive microbiology are reviewed in this paper. The developed model, based on probabilistic concepts, enabled the identification of minimum processing conditions necessary to obtain a required log reduction, regardless of the underlying inactivation kinetics. The model also provides the probability distribution of the inactivation effect. The revised web-tool, the MRV (Microbial Responses Viewer), provides information concerning growth/no growth boundary conditions and the specific growth rates of queried microorganisms. The MRV enables users to retrieve microbial growth/no growth information intuitively. Using the MRV, food processors can easily identify appropriate food design and processing conditions.     

High pressure processing pretreatment enhanced the thermosonication inactivation of Alicyclobacillus acidoterrestris spores in orange juice

The spoilage of high acid fruit juices and nectars by Alicyclobacillus acidoterrestris is a major concern to juice manufacturers around the world since it is difficult to detect. In this study, thermosonication (ultrasound and heat, TS) and thermal inactivation of A. acidoterrestris spores in pretreated orange juice were carried out and resistance parameters were estimated. First, the effect of TS acoustic energy density (AED, 0.3–20.2 W/mL) on the inactivation at 75 °C was investigated. Then, the influence of TS temperature (70–78 °C) on the spore inactivation (AED = 20.2 W/mL) was studied. Next, we explored the effect of high pressure processing (HPP) pretreatment of juice on the 20.2 W/mL TS inactivation at the best temperature (78 °C). Lastly, the thermal inactivation of spores in juice heat shocked + 1 min sonicated vs. untreated juice was also investigated.Results of TS showed higher spore inactivation for higher AED (D_75°C-value of 49 min for 20.2 W/mL vs. 217 min for 0.33 W/mL). Lower D-values were obtained at higher temperatures (D_78°C-value of 28 min vs. D_70°C-value of 139 min at 20.2 W/mL). The TS D_78°C-value (at 20.2 W/mL) decreased further from 28 min to 14 min when the orange juice was previously submitted to 600 MPa for 15 min. Thermal treatment alone at 78 °C resulted in almost no spore inactivation, whereas the heat shock + ultrasound pretreatment of juice enhanced the thermal inactivation of spores (D_85°C-value decreased from 69 to 29 min). To conclude, HPP-assisted TS provided the best method for spore inactivation, indicating the benefit of high pressure and power ultrasound technology in addition to heat. TS required at least 8 °C lower temperatures than thermal treatments to achieve the same spore inactivation, which could enhance juice quality and energy savings.     

Improved process for decontamination of whey by a continuous flow-through pulsed light system

The effect of a continuous flow-through pulsed light (PL) system on the inactivation of Listeria innocua was evaluated in different liquid substrates: distilled water, whey, diluted whey and skimmed whey. Reductions in L. innocua counts increased with number of pulses and total fluence. For similar total fluence, treatments consisting of a higher number of pulses but lower voltage were more effective in L. innocua inactivation due to a higher probability to expose cells to the incident light. Microbial inactivation by PL depended on the quantity of light transmitted in the range 230–290 nm by liquid substrates. Regardless of the limited effectiveness of PL for decontamination of whey, its shelf life during storage at 4 °C was extended by at least 7 days. In order to improve the antimicrobial effectiveness of PL, this treatment could be carried out at mild processing temperatures (60 °C), which was shown to exhibit a synergistic effect on the inactivation of L. innocua. This combined process appears as a promising technique to decontaminate complex substrates such as whey or to reduce the intensity of individual treatments to achieve the required level of microbial inactivation.     

Effect of pressure,depressurization rate and pressure cycling on the inactivation of Escherichia coli by supercritical carbon dioxide

This work is focused on the use of supercritical carbon dioxide to inactivate the pathogenic Escherichia coli. For this purpose, the experimental design methodology was employed to evaluate the effects of pressure (8–28 MPa), depressurization rate (1–11 MPa min^?1) and pressure cycling (1–5 cycles) on the microorganism inactivation using the static-synthetic method in a variable-volume reactor. The number of pressure cycles and system pressure showed a significant influence on E. coli inactivation with supercritical CO₂, indicating that the increase in the number of pressure cycles and system pressure improve inactivation efficiency. Microbial inactivation followed first order reaction kinetics, where the rates increased with increasing pressure from 8 to 16 MPa. The decimal reduction times (D) ranged from 1.03 to 5.35 min. The pressure dependence of the E. coli specific inactivation rates can be described by the z value, which was found to be 11.4. The results reported here may be useful to provide an effective non-thermal sterilization of foods in pilot/industrial scale.