煤化学-英语课件--chapter-1-coal-as-an-organic-sediment---a-copy

1、Chapter 1 Coal as an Organic Sediment,2,2009/08,Review:,Coal is a kind of sedimentary organic rock Coal had originated from ancient plant remains. Very complicatedly biochemical and physicochemical actions had worked in coal-forming process. Coal-formation had proceeded under certain climatic, biolo

2、gical, environmental and geological conditions.,A definition of Coal Coal is a kind of sedimentary organic rock originating from ancient plant remains undergone complicatedly biochemical and physicochemical changes under certain climatic, biological, environmental and geological conditions.,3,2009/0

3、8,Guide to new lecture,Prelude questions to Coal as an Organic Sediment Which plant remains could have been converted into coal? And what precursors had been experienced before coal had been formed ? How is the processes like from the origins to coal? Contents 1 Origins of coal 2 Precursors (先驱，前体，母

4、体) of coal 3 Coal-forming processes（成煤过程，成煤作用）,4,2009/08,1. The origins of coal,A brief description (please rehearse this paragraph) Coal was formed from partially decomposed (已降解的，已腐烂的）(and subsequently (后来，随后） metamorphosed (变质，变形）) plant debris (碎片，残骸） which collected in regions where waterlogged

5、 (浸满水的，涝的） or swampy (沼泽的，湿地的） conditions prevailed (流行，盛行，占优势）. These conditions prevented complete decay (腐烂，降解） of the debris as it accumulated and eventually(最后的） led to the material now as coal.,5,2009/08,In general terms, the debris consisted of trees, ferns（蕨类植物）, rushes （灯芯草，灌木）, lycopods （石

6、松属植物）, and several thousand plant species that have been identified in coal beds, but it appears that none of the species identified in many different coals originated in brackish-water （盐水） locales （区域）. Similar types of plant remains may be found in all types (ranks （煤阶）) of coal， but, of course,

7、the relative amounts （相对含量） vary considerably （相当地，非常地）. On this basis （由此）, it is not surprising that coal differs markedly （显著地） in composition from one particular seam are not uncommon, due not only to the wide variety of plant debris that could have formed the precursors （母体，前体） but also to the

8、many different chemical reactions that can occur during the maturation （成熟） process.,By the eyes of coal chemistry: plants-higher and lower plants. the lower : unicellular （单细胞的） or multicellular （多细胞的） fungoids （菌类） and algaes （藻类） without distinction （区分，分化） of roots, stems and leaves the higher :

9、 lichens （苔藓）, ferns （蕨类）, gymnosperm （裸子植物） and angiosperm （被子植物）,etc, and there is distinction of roots, stems and leaves,6,2009/08,Thus, once plant debris has accumulated under the “correct” conditions, the formation of peat（泥炭） gradually occurs （发生，出现）. Peat is not actually classified as coal bu

10、t it is, nevertheless （仍然，不过）, believed to be that material which is formed as the initial step in the process. However, to become coal, peat must progress （前进，进展，经历） through what is loosely termed “coalification” （煤化作用） process.,The coalification process is, in essence （本质）, the progressive （渐进的，累进

11、的） change in the plant debris as it becomes transformed from peat to lignite （褐煤） and then through the higher ranks （高阶） of coal （such as subbituminous （次烟煤） and bituminous （烟煤） coals） to anthracite （无烟煤）. The degree of coalification generally determines the rank of the coal, but the process is not

12、a series of straightforward （简单的，直截了当的） chemical changes. For example, the metamorphism （变质作用） of the plant debris not only relies on （depend on） geological time （地质年代） but also on temperature and pressure.,7,2009/08,Thus, when the organic debris (which may be identified as peat) is buried beneath （

13、在之下） overburden （过载，重压）, various physicochemical （物理化学的） processes occur as part of the metamorphosis （变质，变形）. The major influences are believed to be the resulting （由此引起的） heat and pressure developed because of the overlying （上面堆垛的） sedimentary cover (overburden).,This leads to changes in the const

14、ituents （成分，组成） of the debris such as an increase in the carbon content, alteration （改变） of the functional groups （官能团）, alteration of the various molecular structures ultimately （finally） resulting in the loss of water , oxygen, and hydrogen with the increased resistance （阻力，阻抗，电阻） to solvents, hea

15、t, and oxidation.,8,2009/08,All theories about the formation of coal require that the original plant debris eliminate （去除，减少，消除） oxygen and hydrogen continuously under the prevailing （优势的） conditions, ultimately leading to a product containing approximately （大约） 90% w/w carbon, i. e., anthracite （无烟

16、煤）. In order for the maturation （成熟） to proceed, chemical principles （原理，法则） require that oxidation reactions be completely inhibited （禁止）.,However, in the early stages （早期阶段） of calcification, microorganisms （微生物） may play an important role and, somewhat paradoxically （看似矛盾而实际地）, they may interact

17、with the plant material under aerobic （需氧的） conditions as well as under anaerobic （厌氧的） conditions.,The formation of coal under the slow conditions generally referred to （指的是） as geological time （地质时期） may , nevertheless （不过，仍然）, be regarded as （被认为是） occurring in the absence of （缺少的） oxygen, thereb

18、y （因此） promoting （促进，提高，提升） the formation of highly carbonaceous （碳质的，高碳的） molecules through losses of oxygen and hydrogen from the original organic molecules.,9,2009/08,Summary,Plant remains,10,2009/08,2. Precursors of coal,Lignins （木质素） Carbohydrates （碳水化合物） Proteins （蛋白质） Lipoids （类脂） : Oils, fat

19、s, and waxes,The constituents （组成，组分） of the organic portion of the original plants, which ultimately （最终，最后） transformed （转化） into coal, has great influence on （对有极大影响） the finished coal structure and its composition. So it is necessary to make complete understanding of the constituents of the orga

20、nic portion of plants.,The makeup of the organic portion of plants consists of carbohydrates, lignin, proteins and lipoids.,Note that each of these compound types is a very broad classification, indicating the general complexity （复杂性） of the original plant debris. It is this fact alone which determi

21、nes the complexity of the “finished coal molecules”.,11,2009/08,The relative amount （相对量） of these constituents vary greatly with the particular species of plant as well as the relative stage of growth （生长阶段）. Nevertheless （不过）, it is possible (in an attempt to simplify （使简化） an already complex （复杂的

22、） situation) to acknowledge （承认，答谢） some generalities （共性，一般性）; the lignin content of plants may fall within （在之间） the range 10-35% w/w while in woody material the lignin may be within the narrower range of 25-30% w/w range. Thus, from these broad generalities alone, the original plant debris (depen

23、ding on location and the circumstances leading to the deposition （沉积）) is, indeed, increasing in complexity （复杂性）.,12,2009/08,Lignin （木质素） and cellulose （纤维素） are considered to be the major organic precursors （母体） to coal although there is little evidence （证据） to support （赞成，支持，证明） this theory. Neve

24、rtheless, laboratory （实验室） investigations （研究） into the nature of the transformation （变化，转化） have been carried out （实施，进行） for many years and perhaps a brief discussion is warranted （保证，授权，有理由） here not only to indicate the complexity of the problem but also to show the speculation （思考） involved in

25、（涉及） this concept （概念）. Indeed, the concept of a coal structure has continued for several decades （十年） and it is questionable （有争议的，可疑的） as to whether or even if there is a need to define coal in terms of （根据，按照） a distinct （clear） molecular structure.,13,2009/08,A. Lignin,Lignin（木质素） has been consi

26、dered one of the most important substances involved in the transformation of plant constituents（成分） into coal, and the molecular structure of lignin remains largely unknown and speculative （费解的）. ALignin is regarded as a polymer 。,14,2009/08,Aromatic polymers （芳香族聚合物）,Monomeric units: aromatic alcoh

27、ols （单体的单位）,Simplified representation of part of the lignin structure,(I) coniferyl alcohol （针叶树的） (II) sinapyl alcohol （芥子醇） (III)p-coumaryl alcohol （香豆醇）,These are the monomeric(单体) units found in lignin. Lignin is regarded as a polymer (or mixed polymer) of any one (or more) of these alcohols.,15

28、,2009/08,Thus, the carbon-carbon linkages are of the diphenyl type (I) as are a variety of aliphatic （脂肪族的） carbon-carbon linkages between the aromatic rings (II). In addition, the molecule of lignin contains various ether linkages (III; IV, and V;).,The chemical structure of lignin is still largely

29、 speculative, but it has been possible to make some general deductions (推论) about the nature of the linkage in this complex natural product.,Furthermore (此外，而且), investigations with lignin from conifers (松类，针叶树) have shown that diphenyl-type linkages (联苯型桥键) account for (占) approximately (about) 25%

30、 of carbon-carbon linkages. The remainder (其余，剩余) are connected by means of ether (醚) bonds. Thus, while (虽然) data of this type do not illustrate (阐明) the molecular structure of a complex molecule such as lignin, they do illustrate the bonds which either may remain intact(完整的) or may be ruptured (破裂

31、，打破) during the maturation process.,16,2009/08,Table 1-1 Methoxyl（甲氧基） and nitrogen contents (wt. %) of lignins from various sources,The extent of the amount of each particular alcohol has been presumed (推测) to be recognizable (可知的) from determinations (测试) of the methoxyl (-OCH3) content of various

32、 lignins，but the complication (复杂化) of nitrogen in the lignin is also evident .,This latter problem has not been fully resolved (解决) and therefore it is not known whether the nitrogen is inherent (内在的) in the lignin (i.e., chemically combined and part of the lignin substance) or whether the nitrogen

33、 arises (出现) by virtue of (由于) the presence (存在) of nitrogen-containing molecules that are difficult to separate from the lignin.,17,2009/08,Lignin（木质素） is the main substances in cell wall of the higher plants, and has been considered one of the most important precursors involved in the transformati

34、on of plant constituents（成分） into coal, and the molecular structure of lignin still remains largely unknown and speculative （费解的）.,18,2009/08,B. Carbohydrates,Sugars（糖）,Saccharides （糖）,Monosaccharides（单糖）,Polysaccharides（多糖）,Carbohydrates （碳水化合物）,Disaccharides （二糖）,Tetrasaccharides （四糖）,Trisaccharid

35、es （三糖）,Pentasaccharides （戊糖）,Celluloses （纤维素）,Starches （淀粉）,Carbohydrate，namely saccharide or sugar, is quite a broad type of constituents of plant, and was believed to have made a lot of contribution to coal formation.,Carbon Oxygen Hydrogen,19,2009/08,The monosaccharides(单糖), are the building blo

36、cks(构造单元) of the more complex carbohydrates. They are actually polyhydric(多羟基的) alcohols(醇) containing five to eight carbon atoms, and the five-and six-carbon sugars are the most common.,Table Structure and occurrence of the common five- and six-carbon atom sugars in plants,Their simple formulas ind

37、icate that they contain a carbonyl(羰基) (aldehyde(醛) or ketone(酮) function(官能), but this is not the actual case. The carbonyl functions usually occur in combination with (与一起)one of the hydroxyl functions (in the same molecule) to form a cyclic(成环的，环状的) hemiacetal(半缩醛) or a hemiketal(半酮缩醇),20,2009/08

38、,Although the monosaccharides (单糖)do occur as such in nature, it is more common to find the sugars occurring naturally in pairs (disaccharides(二糖) or in threes (trisaccharides(三糖) and , more likely, as the high molecular weight polysaccharides(多糖) It is the polysaccharides which most probably contri

39、bute to(贡献于) the source material(原始材料/物质) of coal, especially as the two well-known polysaccharides cellulose(纤维素) and starch(淀粉). The fibrous tissue in the cell wall of plants and trees contains cellulose and starch，and starch also occurs throughout the plant kingdom in various forms but usually as

40、 a food reserve.,21,2009/08,The chemical composition of starch varies with the source but in any one starch there are two structurally different polysaccharides. Both usually consist entirely of glucose(葡萄糖) units but one is a linear(线型的) structure（amylose(直链淀粉)）whereas the other is a branched struc

41、ture (amylopectin(支链淀粉)，. Thus, in contrast to(相对于) the somewhat speculative chemistry of lignin, the structural chemistry of the polysaccharides （多糖） (cellulose and starch) is generally more well defined. For example, the molecular formula of cellulose is (C6H10O5)n, where n may be of the order of

42、several thousand.,22,2009/08,Fig. 1-6 Simplified structures for cellulose (I) and starch (II).,23,2009/08,1-7 A three-dimensional representation of the carbon skeleton of cellulose,24,2009/08,Fig. 1-8 A three-dimensional representation of the carbon skeleton of starch (amylose),Fig. 1-9 A three-dime

43、nsional representation of the carbon skeleton of branched starch (amylopectin),25,2009/08,C. Proteins,Proteins are those nitrogen-containing organic substances which occur in the protoplasm of all plant and animal cells. The element composition of proteins varies with the source, but a general range

44、 of protein composition is usually of the order:,With other elements, e.g., phosphorous (nucleoproteins) and iron (hemoglobin) also being present in trace amounts in certain proteins.,26,2009/08,The characteristic structural feature of proteins is a chain, or a ring, of amino acids(氨基酸) joined toget

45、her by amide linkages .,Simplified representation of part of a protein (peptide) chain of alanine,But the distinction between a protein and a peptide is not always clear. One arbitrary choice is to use a molecular weight of 10000 as a distinction between the two classes. That is: proteins have a mol

46、ecular weight in excess of 10000 while peptides below this value.,Amidogroup,Carboxyl group,The naturally occurring peptides have relatively short, flexible chains and, although hydrated in aqueous solution, can be reversibly dehydrated. On the other hand, proteins have very long chains which have d

47、efinite conformational character with water molecules filling the interstices.,Amino acids,Peptides,Proteins,27,2009/08,Proteins occur throughout nature in a wide variety of sizes and shapes and many proteins contain metals such as iron, zinc, and copper which, in turn, are intimately involved in th

48、e physiological (biological) functions of the molecules to which they are bound. They are believed to be the main contributors of the organic nitrogen-containing comounds.,28,2009/08,Fig. 1-11 Schematic representation of protein structure with indications of (a) atomic and (spatial arrangement of th

49、e helix.,29,2009/08,Table 1-4 Some commonly occurring proteins,30,2009/08,D. Lipoids,脂类化合物是指不溶于水而溶于醚、苯、氯仿等有机溶剂的有机化合物。在植物中脂类化合物主要有以下几种。 脂肪：属于长链脂肪酸的甘油酯。高等植物中含量少(1-2%)，低等植物含量高(20%左右)。在生化作用下在酸性或碱性溶液中分解生成脂肪酸和甘油，参与成煤作用。 蜡质：主要是长链脂肪酸与含有2426个碳原子的高级一元醇形成的脂类，化学性质稳定，不易受细菌分解。 树脂: 树脂是植物生长过程中的分泌物，当植物受伤时，胶状的树脂不断分泌出

50、来保护伤口。针状植物含树脂较多，低等植物不含树脂。树脂不溶于有机酸，不易氧化，微生物也不能破坏它，因此能很好地保存在煤中。 角质和木栓质、孢粉质：化学性质十分稳定，不溶于有机酸，微生物也难以作用，在成煤过程中能保存下来。,All the organic constituents in plants, which not soluble in the organic solvents such as ethers, benzene, chloroform, etc., fall within lipoid. They are: Oils and fats; Waxes; Resins; Cuti

51、ns, Seberins, sporins.,31,2009/08,Carbohydrates （碳水化合物） Lignins （木质素） Proteins （蛋白质） Lipoids （类脂） : Oils, fats, and waxes,Precursors of coal,包括纤维素、半纤维素及果胶质。 纤维素：在泥炭沼泽的酸性介质中，纤维素可以分解为纤维二糖和葡萄糖等简单化合物。半纤维素：比纤维素更易分解或水解为糖类和酸。果胶质为糖的衍生物，呈果冻状。在生物化学作用下，水解成一系列单糖和糖醛酸,木质素也是植物细胞壁的主要成分，在泥炭沼泽中，在水和微生物作用下发生分解，与其他化合物共同

52、作用生成腐植酸类物质，这些物质最终转化成为煤。所以木质素是植物转变为煤的原始物质中最重要的有机组分。,蛋白质：高等植物中蛋白质含量少；低等植物中蛋白质含量高。在泥炭沼泽和湖泊的水中，蛋白质分解成氨基酸、喹啉等含氮化合物，参与成煤作用，但对煤的性质没有决定性的影响。是煤中硫、氮元素的来源之一。,脂类化合物是指不溶于水而溶于醚、苯、氯仿等有机溶剂的有机化合物。化学性质稳定，在成煤过程中能保存下来。,32,2009/08,. Coal formatting process,Question: what is the coal forming process like?,33,2009/08,Coal

53、-forming process peatification coalification The rank, type and grade of coal,Contents,34,2009/08,key terms and expressions,Diagenetic成岩的 Geophysical 地球物理的 Geochemical 地球化学的 tectonic 地质的，构造的 coal seam/strata煤层 Coalbed gas煤层气 depositional environment 沉积环境 temperature, time, and forces grade of coal煤级

54、 type of coal煤的类型 rank of coal煤阶,the range of impurities included,Acording to the coal-forming vegetation,the degree of metamorphism or coalification,Coal formation成煤作用 Coal forming process 成煤作用 Peatification泥炭化作用 Saprofication 腐泥化作用 Coalification煤化作用 metamorphism 变质作用 Peat泥炭 Lignite，brown coal褐煤 su

55、bbituminous coal 次烟煤 bituminous coal烟煤 Anthracite无烟煤 Hardcoal硬煤 Soft coal 软煤 stone-likecoal石煤,35,2009/08,1. Coal forming process,The complicated and far-lasting way had been undergone over millions and millions of years from ancient plant remains, which is called coal-forming process today. The proc

56、ess is also called coal-formation and is often expressed as followed:,Higher Plants lower plants,Peat sapropel,Peatification,Lignite sapropeliccoal,Bituminous coal,Anthracite stone-likecoal,Diagenisis or lignification,metamorphism,coalification,Bituminization,anthracization,saprofication,Diagenisis

57、or lignification,coalification,从远古植物遗体到煤，经历了复杂且慢长的历程，这个历程就是今天所说的成煤过程，也称为成煤作用（过程），常用下图来表述：,36,2009/08,Plant remains,peat,Peatification,lignite,Bituminous coal,Anthracite,Diagenisis or lignification,metamorphism,coalification,Coal forming process,Bituminization,anthracization,Including two stages: pea

58、tification and coalification.,高等植物死亡后，在生物化学作用下，变成泥炭的过程称为泥炭化作用。 在这一阶段，植物首先在微生物作用下，分解和水解为分子量较小的性质活泼的化合物，然后小分子化合物之间相互作用，进一步合成新的较稳定的有机化合物，如腐植酸、沥青质等。植物经泥炭化作用成为泥炭，在两方面发生巨大变化： （1）组织器官（如皮、叶、茎、根等）基本消失，细胞结构遭到不同程度的破坏，变成颗粒细小、含水量极大、呈胶泥状的膏状体泥炭；（2）组成成分发生了很大的变化，如植物中大量存在的纤维素和木质素在泥炭中显著减少，蛋白质消失，而植物中不存在的腐植酸却大量增加，并成为泥炭的

59、最主要的成分之一，通常达到40%以上。,Three processes: the microbiological degradation of the initial plant material, the conversion of the lignin of the plants into humic substances, and the condensation of these humic substances into larger coal molecules The kind of original plants, conditions of decay, depositional environment, and movements of the Earths crust are important factors in determining the nature, quality, and relative position of the coal seams.,The beginning of most coal deposits started with