木质素在超临界甲醇和乙醇溶剂中液化过程分析

通过研究木质素分别在超临界甲醇和乙醇溶剂中的液化过程，分析反应温度（260～340℃）及反应时间（0～120min）对木质素在两种溶剂中的转化率、生物油收率及其组分差异的影响。实验表明，木质素在超临界乙醇中的转化率及产物收率均高于甲醇。当反应温度340℃，反应时间60min，木质素在超临界乙醇中的转化率和生物油收率比在甲醇中分别提高了16.23%和11.54%，残渣收率降低了16.23%。通过GC-MS和FTIR对生物油和残渣分析，发现生物油组分中芳香族化合物相对含量较高，在甲醇和乙醇溶剂中分别达到66.13%和58.84%；随着反应时间的延长，甲醇溶剂中残渣的醚键官能团逐渐增强，而在乙醇溶剂中则先增强后减弱。分析认为在木质素降解过程中，超临界乙醇和甲醇均可产生氢自由基作为供氢体，攻击木质素及其大分子片段中的官能团，同时使液化产物中的活性片段减活，减弱重聚合反应，从而更利于芳烃产物的生成。而甲醇在液化过程中容易与木质素断键产生的苯酚中间体发生脱氢缩合反应，通过醚键聚合产生长链芳香族化合物，形成残渣，降低生物油收率。     

Effects of solvent pretreatment and solvent incorporation on coal liquefaction

Yields of short-contact-time liquefaction product can be increased by pretreating the coal-solvent slurry at below normal liquefaction temperatures to permit solvent incorporation and/or swelling of the coal before liquefaction. An external pretreatment and an in situ pretreatment produce similar results. A coal-vehicle adduct was isolated from the pretreated coal and had liquefaction characteristics similar to the original coal. The beneficial effect of the solvent pretreatment is therefore believed to be the result of physical solvent incorporation with the coal, which causes solvent-aided liquefaction, in contrast with the thermal decomposition that can occur if some of the coal reaches liquefaction temperatures before it is contacted by vehicle. Pretreatment allows vehicle to be present (in contact with coal) at the reactive site in order to react with, and cap, coal free radicals.     

Non-isothermal liquefaction of liptobiolith coal in supercritical water flow and effect of zinc additives

The liquefaction of liptobiolith coal in water vapor and supercritical water (SCW) flow at uniform increase in temperature from 300 up to 470 °C and in SCW flow at 400 °C (30 MPa) with addition of zinc shavings to coal has been investigated. Temperature dependences of the yield of liquid and volatile products and kinetic parameters of the process have been obtained. The yields of oil, resin, asphaltene and volatile products in relation to the coal organic matter (COM) are 23.2, 16.1, 5.1 and 14.1%, respectively. CO₂, CO, H₂S and C₁–C₄ alkanes prevail in the composition of volatile products. The generation of oil, resin and asphaltene are found to have occurred in terms of the simultaneous chemical reactions of cleavage of the COM aliphatic CC bonds, while the volatile products result from the consecutive transformations of the COM components in the bulk and SCW solution. Participation of H₂O molecules in thermochemical transformations of COM leads to increase in the oxygen amount in the conversion products and residue by 13.2%. Hydrogen and heat evolution during zinc oxidation by SCW provides for the hydrogenation of COM in situ. Addition of zinc to coal results in increase in the volatile products yield up to 48.6% and decrease in the conversion residue yield up to 20.8%. Under these conditions the yield of resin does not change, while the yields of oil and asphaltene decrease up to 21.2 and 2.5%, respectively. Based on the sulfur balance it is revealed that ≈40% of sulfur atoms pass into ZnS owing to the reactions of H₂S with Zn and ZnO resulting in the removal of H₂S from the volatile conversion products.     

炼直接液化溶剂油的平均结构

对一种褐煤的直接液化加氢前、后溶剂油进行了1H核磁共振波谱、元素组成和分子量等性质的分析和平均结构参数的计算,研究了加氢前、后溶剂油分子的平均结构.结果显示:加氢处理前、后溶剂油的平均分子式为C17H23S0.004N0.09O0.12和C16H24S0.003N0.03O0.03,加氢前溶剂平均分子的芳碳率fa为0.46,平均分子结构含有2～3个环,其中芳香环为1～2个,环烷环为1个.经过加氢处理后溶剂油分子的平均结构发生较大的变化,溶剂平均分子芳碳率fa为0.37,平均分子结构中含有2个环,其中芳香环1个,环烷环1个,经加氢处理后,溶剂具备了较好的供氢性能.     

煤直接液化溶剂油的平均结构

对一种褐煤的直接液化加氢前、后溶剂油进行了1H核磁共振波谱、元素组成和分子量等性质的分析和平均结构参数的计算,研究了加氢前、后溶剂油分子的平均结构。结果显示：加氢处理前、后溶剂油的平均分子式为C17H23S0.004N0.09O0.12和C16H24S0.003N0.03O0.03,加氢前溶剂平均分子的芳碳率fa为0.46,平均分子结构含有2～3个环,其中芳香环为1～2个,环烷环为1个。经过加氢处理后溶剂油分子的平均结构发生较大的变化,溶剂平均分子芳碳率fa为0.37,平均分子结构中含有2个环,其中芳香环1个,环烷环1个,经加氢处理后,溶剂具备了较好的供氢性能。     

煤直接液化用溶剂的研究现状

对前人在煤直接液化研究中所使用的溶剂的种类、作用和优缺点进行综述,指出开发新的溶剂,使煤液化在较低温度和压力下完成并获得高的油收率是煤直接液化更容易实现和产业化的关键。     

Catalytic wood liquefaction using a hydrogen donor solvent

Direct wood liquefaction of pine sawdust (Pinus radiata) in a hydrogen donor solvent (tetralin), was studied in a 0.5 L autoclave using Co-Mo/γ-Al₂O₃ and Pt/γ-Al₂O₃ supported catalysts. Uncatalyzed as well as Raney Nickel catalyzed runs were also performed for comparison purposes. Reaction temperature was kept at 673 K and total system pressure at 10 MPa in all cases. Weight ratio of solvent to solid loaded was 2:1, the gas phase being either H₂ or N₂. Independent runs were also performed with cellulose and lignin which are the main wood constituents. Reaction products were characterized by means of gas chromatography and solvent fractionation using specific solvents.     

Improvement in coal liquefaction solvent quality by dewaxing

Recycle oils from the Integrated Two-Stage Liquefaction (ITSL), H-Coal and Solvent Refined Coal (SRC) processes were dewaxed by variants of commercial dewaxing processes—the ketone and the urea adduction techniques — yielding up to 47 wt % ‘wax’. Feed oils and product fractions were characterized by elemental analysis, ¹H n.m.r. and gas chromatography. The clean waxes were nearly pure mixtures of n-paraffins. The dewaxed oils were substantially better coal liquefaction solvents than the original (non-dewaxed) oils in batch liquefaction tests. For example, in one case, dewaxing improved the conversion of a bituminous coal to tetrahydrofuran-solubles under standard reaction conditions from 71 wt% (dafb) with the original oil to 87 wt % (dafb). These data provide a direct indication of the inimical effect of paraffinic components on solvent quality. The impact of solvent quality is particularly relevant to liquefaction processes in which thermal reactions proceed in a recycle solvent. In addition, the results indicate the technical feasibility of dewaxing coal liquefaction recycle oils by commercially available technology to improve solvent quality and to produce a useful by-product. Dewaxing could be applied in any liquefaction process that uses a deasphalted (preferably distillate) recycle stream.     

Catalytic close-coupled two-stage liquefaction process development with a bituminous coal

Catalytic close-coupled two-stage processing is the state-of-the-art direct liquefaction technology for converting coal into transportation and utility fuels. Three pilot plant runs were completed at the Wilsonville pilot plant using Illinois No. 6 coal and bimodal catalysts. Product yield and product quality data are presented. Appropriate comparisons are made with previous processes. The catalyst performance is discussed in terms of process-derived activity trends, catalyst analyses, and catalyst replacement rates. The effects of coal space velocity, concentrated coal slurry, the elimination of interstage separator, ground catalyst addition, and system pressure on process performance are discussed. Finally, process economics are discussed briefly.     

Analysis of solvent extracts from coal liquefaction in a flowing solvent reactor

Point of Ayr coal has been extracted using three solvents, tetralin, quinoline and 1-methyl-2-pyrrolidinone (NMP) at two temperatures 350 and 450 °C, corresponding approximately to before and after the onset of massive covalent bond scission by pyrolysis. The three solvents differ in solvent power and the ability to donate hydrogen atoms to stabilise free radicals produced by pyrolysis of the coal. The extracts were prepared in a flowing solvent reactor to minimise secondary thermal degradation of the primary extracts. Analysis of the pentane-insoluble fractions of the extracts was achieved by size exclusion chromatography, UV-fluorescence spectroscopy in NMP solvent and probe mass. With increasing extraction temperature, the ratio of the amount having big molecular weight to that having small molecular weight in tetralin extracts was increased; the tetralin extract yield increased from 12.8% to 75.9%; in quinoline, increasing extraction temperature didn't have an effect on the molecular weight of products but there was a big increase in extract yield. The extracts in NMP showed the enhanced solvent extraction power at both temperatures, with a shift in the ratio of larger molecules to smaller molecules with increasing extraction temperature and with the highest conversion of Point of Ayr coal among these three solvents at both temperatures. Solvent adducts were detected in the tetralin and quinoline extracts by probe mass spectrometry; solvent products were formed from NMP at both temperatures.     

Relative reactivity of hydrogen donor solvent in coal liquefaction

Hydrogen transfer from donor solvent to coal must involve reactions such as hydrogen donation to free radicals and hydrogenation of aromatic structures. The relative reactivities of five typical hydrogen donor solvents, more reactive than tetralin, were determined using a competing elimination reaction in the liquefaction of a bituminous coal at 400 °C and a brown coal at 350 °C. 9,10-Dihydroanthracene, 9,10-dihydrophenanthrene and 1,2,3,4-tetrahydroquinoline exhibited outstanding hydrogen donating ability. Further, the relative reactivities of five mild hydrogen donor solvents such as acenaphthene and indan were determined by a similar elimination reaction using a bituminous coal at 450 °C.     

Catalytic activity of iron compounds for coal liquefaction

The catalytic activity of pyrite and synthesized -FeOOH in coal liquefaction was investigated using batch autoclaves with the aim of developing an industrial iron catalyst. The results indicate that the presence of H₂S helps gaseous hydrogen transferring and prevents deactivation so that the catalyst promotes hydrocracking of coal and hydrogenation of the products. The activity converges with excess H₂S and sulfur addition equivalent to an S/Fe molar ratio of 2.0 being reasonable for the activation. The active site is located on the outer surface, with finely divided catalysts exhibiting high activity. Both pulverized pyrite and synthesized -FeOOH are sufficiently fine as to exhibit high activity in the process. Pulverized pyrite is an industrially feasible iron catalyst for coal liquefaction process, because it is inexpensive and does not require sulfur addition.     

Effect of solvent on molecular composition in coal liquefaction

The product from uncatalysed liquefaction of lignite using synthesis gas (CO-Steam process) was examined by column chromatography, high-resolution mass spectrometry, gas chromatography-mass spectrometry, and low-voltage mass spectrometry. The nature of the vehicle solvent affected the type and distribution of compounds in the product oil. Anthracene oil and recycle oil as solvents gave mainly aromatics and phenols. When tetralin was used as solvent, the product showed larger amounts of oxygen compounds, more hydroaromatic compounds, and a greater degree of alkylation in high-molecular-weight aromatics. Tetralin, therefore, appears to be a more powerful hydrogen donor than anthracene oil or recycle oil in stabilizing intermediate fragments that would otherwise repolymerize. Carbon-number analysis data for liquids prepared using three different solvents are presented.     

神华煤直接液化工艺供氢溶剂研究

就中国神华集团在煤直接液化供氢溶剂沸腾床制备加工工艺技术、国产化催化剂技术、工艺条件优化技术、专利技术等方面的研究进行了阐述,并对进一步精准开发高性能供氢溶剂技术提出建设性意见。     

神华煤直接液化工艺供氢溶剂研究

就中国神华集团在煤直接液化供氢溶剂沸腾床制备加工工艺技术、国产化催化剂技术、工艺条件优化技术、专利技术等方面的研究进行了阐述,并对进一步精准开发高性能供氢溶剂技术提出建设性意见。     

新型超临界水中煤气化制氢产物的CO2分离过程

目前CO₂的分离方式主要局限在常压条件下,在高压条件下分离CO₂的研究鲜有报道。本文为了解决这一问题,针对煤在超临界水中气化过程压力高的特点,构建了高压水吸收法分离CO₂系统,建立了高压多组分气液相平衡的能量分析模型和 分析模型;并对CO₂的分离过程进行分析,获得了高压吸收器中压力对各种气体产物摩尔分数和液相中气体吸收率的影响规律;针对高压水吸收法分离CO₂的流程,建立了CO₂分离过程中的能量分析模型和 分析模型,得到了高压吸收器中压力发生变化时,CO₂分离过程的能量效率、 效率以及CO₂分离能耗的变化规律,为超临界水中煤气化制氢新技术中分离器的设计提供了依据。     

Catalytic activity of various iron sulphides in coal liquefaction

Iron sulphides with various S-Fe atomic ratios, such as pyrite, iron(III) sulphide, pyrrhotite and troilite, were used as catalysts for coal liquefaction. Catalytic activities were compared on the basis of the temperature of the exothermic peak due to coal hydrogenolysis. Effects of hydrogen sulphide on catalytic activity of iron sulphides were also investigated. It is concluded that:

• 1.1. The catalytic activity of iron sulphides increases with increasing S-Fe ratio;
• 2.2. pyrite, with the highest catalytic activity, is converted to pyrrhotite before the onset of exothermic reactions from coal hydrogenolysis, this evidently being the reason for the high catalytic activity;
• 3.3. the catalytic activity of iron sulphides depends on the coal type;
• 4.4. the high catalytic activity of pyrite may be due to the creation of fresh pyrite surface during the reaction rather than to the presence of high concentrations of hydrogen sulphide.

     

Regulation of radicals by hydrogen-donor solvent in direct coal liquefaction

Radicals are important intermediates in direct coal liquefaction. Certain radicals can cause the cleavage of chemical bonds. At high temperatures, radical fragments can be produced by the splitting of large organic molecules, which can break strong chemical bonds through the induction pyrolysis of radicals. The reaction between the formation and annihilation of coal radical fragments and the effect of hydrogen-donor solvents on the radical fragments are discussed in lignite hydrogenolysis. Using the hydroxyl and ether bonds as indicators, the effects of different radicals on the cleavage of chemical bond were investigated employing density functional theory calculations and lignite hydrogenolysis experiments. Results showed that the adjustment of the coal radical fragments could be made by the addition of hydrogen-donor solvents. Results showed that the transition from coal radical fragment to H radical leads to the variation of product distribution. The synergistic mechanism of hydrogen supply and hydrogenolysis of hydrogen-donor solvent was proposed.     

Short contact time liquefaction of coal using hydrogen donor solvent

Liquefaction of coals to form benzene-soluble materials was studied at 400 °C under autogenous pressure conditions using tetrahydroquinoline (THQ), tetrahydroisoquinoline (THIQ) and tetralin (TL) as the hydrogen donating solvents. THQ was the best solvent with a conversion rate of 90% within 15 min for low rank coals (< 80% C). In contrast, it took 50 min to achieve a conversion of 80% when TL was used as the solvent, although both solvents could achieve almost complete conversion of coals into quinoline-soluble material within 10 min. THQ also showed excellent activity with blended coals. Some binary solvents exhibited activities which varied with the THQ content. A 1:3 by weight mixture of THQ and petroleum pitch produced the highest conversion of 100%.     

催化超临界水氧化苯胺

研究了在催化超临界水氧化体系中苯胺废水的处理(催化剂采用MnO2/CeO2),结果表明该催化剂有较高的催化活性,使苯胺彻底去除的温度、压力大大降低。实验得出了反应的最佳工艺条件为:温度380℃、压力26 MPa、停留时间5 s、氧气过量15倍,反应后的苯胺含量<1 mg/L、总有机碳(TOC)含量28.56 mg/L,二者均达到了国家的排放标准。