The Chemistry and Processing of Hydrocarbons PDF

The Chemistry and Processing of Hydrocarbons Section 1 Masters in Energy UCD, Dublin Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Relevance of hydrocarbons About 50% of the world’s energy is consumed by manufacturing. More than 90% of this is fossil fuel or Hydrocarbon based. When...

The Chemistry and Processing of Hydrocarbons Section 1 Masters in Energy UCD, Dublin Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Relevance of hydrocarbons About 50% of the world’s energy is consumed by manufacturing. More than 90% of this is fossil fuel or Hydrocarbon based. When the amount of hydrocarbon based feedstock, used as manufacturing raw material, is added to this quantity the importance of hydrocarbon chemistry and processes will be evident. This importance is not going to change very much even if we shift to an economy less dependent on fossil fuels, since hydrocarbons from renewables will move in instead. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Fuel • What makes the fuel a fuel? • Fuel: a molecule • Fuel: Thermodynamic understanding • Fuel Molecule transformations Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Thermodynamics • • • • Gibbs and Helmholtz Free Energy Reversible transformations Useful work/energy Change in Free Energy, Enthalpy and Entropy • Activation Energy • Catalysis and Kinetics Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Thermodynamics vs Kinetics • Less stable Reactants • Stable Products • Driving Force and the Equilibrium of a reaction • Combustion • Oxidation • Reduction • Exo- and Endo- thermic Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Hydrocarbons • • • • • • CnH2n+2 alkanes (s two e- two centre bonds) CnH2n alkenes (olefins) CnH2n-2 alkynes Dienes two unsaturated bonds Polyenesmore unsaturated bonds Arenes aromatic (benzene parent, delocalized p system) • Cycloalkanes single, bridged, caged… Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Index of Unsaturation (2C + 2)- H i= 2 i = 0 for methane, 1 for ethene, 2 for ethyne H:C ratio highest for CH4, except for carbocations CH5+ and CH62+ For C60 or C70, H:C ratio can be as low as 0.03 Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy H:C ratio of natural hydrocarbon sources • • • • • • CH4 Natural gas (NG)* Crude Petroleum Tar sand bitumen Raw shale oil Bituminous coal 4.0 3.8 1.8 1.5 1.5 0.8 * >80-90% CH4 + C2-C6 alkanes Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Hydrocarbon sources • NG • CH4.nH2O • Crude Petroleum biological origin (gas hydrates) sea beds, Siberia biological*, abiogenic process originating from deep CH4 dating back from earth’s origin** • Coal low H, biological origin, types: lignite, sub-bituminous, bituminous and anthracite, same order for increasing aromaticity and decreasing volatiles. H:C = 0.8 for bituminous and 0.2 for anthracite * Presence of V and Ni porphyrins, low level of oxygenates, anaerobic microbes acting on moderate temperatures **Gold’s theory, not yet proven Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Hydrocarbon sources (continued….) • Heavy oils, shale and tar sands Heavy (bitumenous) oils of California, Venezuela and Canada Shale oil and tar sands of Canada Heavy oils are viscous to semi-solids with high levels of N, O, S, and relatively less HC. Usually contain V (as VO2+), Fe and Ni organometallics. These elements make processing complex and poison catalysts. Superacid catalysis is one possible solution? Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Coal formation process* • *Coalification is a deoxygenationaromatization process. It is a continuum of chemical, microbial and thermal changes, in which cellulosic wood and peat are converted over many millions of years. Severe geologic conditions also play a role. Aging increases aromaticity and decreases O content in coals. Lignite (brown) is young and bituminous is older and so on… Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Schematic of structural groups and bridges in bituminous coal Scheme of W.H. Wiser, University of Utah Note (CH2)n, and ether linkages, as well as sulphide and biphenyl bonds. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Coals to liquid Hydrocarbons (HC) Most bonds, except biphenyl, are readily scissible bonds. They undergo thermal and chemical cleavage reactions through which coals can be converted to liquid HC over a sequence of controlled reactions: - Breaking down of complex structures by hydrogenative cleavage reactions (increases solubility of organics) - Alkylation, hydrogenation and depolymerization, and their combinations - Extraction of products from reacted coals - Obtain clean liquid fuels, such as gasoline and heating oil Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Direct Coal liquefaction • High temperature solvent extraction - No catalyst, H donating solvent(s) H2 is added as a secondary H source • Catalytic liquefaction - a catalyst like ZnCl2, Friedel-Crafts catalysts like AlCl3, BF3-phenol catalyses depolymerizationhydrogenation of coals at 375 - 425 °C and 100-200 atmosphere pressure. Superacid HF-BF3 induced liquefaction involves depolymerization and ionic hydrogenation at 150 - 170°C. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Direct Coal liquefaction (continued) • Direct catalytic hydrogenation - a catalyst is intimately mixed with coal - Usually no solvent - H2 gas Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Fischer-Tropsch (F-T) chemistry • (Coal + O2 + steam) at 1100 °C giving CO, CO2 and H2 • Water-Gas (WG) shift reaction then allows optmization of CO:H2 ratio in the syn-gas • Syn-gas is then catalytically hydrogenated by F-T to hydrocarbons, or used for methanol synthesis. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy C1 Reactions relevant to both the fossil fuel based and the future renewable technologies K.R. Thampi in ‘Recent developments in catalysis’ B. Viswanathan and C.N. Pillai,( eds) Narosa Publishers, 1990. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Compositions (%) of typical crude petroleum types Fraction Light oil Heavy oil Saturates 78 17-21 Aromatics 18 36-38 Resins 4 26-28 Asphaltene Trace - 2 17 Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Petroleum Refining and Upgrading Crude petroleum is a dark viscous liquid, which contains hundreds of different HC. Distillation is used for separating the different fractions, which are used for different purposes. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Refining Process Oil refining separates crude mineral oil into groups or fractions of substances. The following steps are useful: The most common way to separate fractions is to do fractional distillation. Then, some of the fractions are processed to refined products. This conversion process, for example, can break longer chains into shorter ones. This allows a refinery to turn diesel fuel into gasoline depending on the demand for gasoline. Refineries also treat the fractions to remove impurities. Refineries combine the various fractions (processed, unprocessed) into mixtures to make desired products. For example, different mixtures of chains can create gasolines with different octane ratings. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Range of products from crude oil • • • • • Petroleum gas: for heating, cooking, feedstock for plastics, liquefied as LPG - C1 - C4 alkanes, b.p. = <40°C Naphtha or Ligroin: to be processed for gasoline - Mix of C5 - C9 alkanes, b.p. = 60 - 100°C Gasoline: liquid motor fuel - Mix of C5 - C12 alkanes and cycloalkanes; b.p. = 40 - 205°C Kerosene: fuel for jet engines and tractors, liquid, feedstock - Mix of C10 - C18 alkanes and aromatics; b.p. = 175 - 325°C Gas oil or diesel distillate: diesel fuel and heating oil; feedstock - Liquid > C12; b.p. = 250 - 350°C to continue…. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Range of products from crude oil (contd..) • • • Lubricating oil: motor oil, grease, lubricants - mix of long chain liquids (C20-C50), alkanes, cycloalkanes, aromatics; b.p. = 300 - 370°C Heavy gas or fuel oil: industrial fuel, feedstock - mix of long chain liquids (C20-C70), alkanes, cycloalkanes, aromatics; b.p. = 370 - 600°C Residuals: coke, asphalt, tar, waxes, feedstock - mix of long chain solids (>C70); multiple ringed compounds; b.p. = >600°C Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Refining and Upgrading Most fuel sources, irrespective whether they are fossil based or renewable types, require chemical processing to upgrade their fuel value, suitability to the end use, adaptability to technology, pricing and distribution. For eg., - Distillation of crude petroleum - Refining - Cracking - Reforming, etc. In addition, fuel materials are also used as chemical building blocks, for example in polymers, resins, etc. They are studied as PETROCHEMICALS. This also involves a variety of processing methods. Examples: Isomerization, Metathesis, Oligomerization, etc. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Petrochemicals Other uses Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy A refinery Source: Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Oil Refining Source: Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Distillation of crude Source: Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy HC refining and conversion processes - 1 - Cracking: to form lower Mol wt. Products and to supply alkenes for alkylation - Reforming (essentially dehydrogenation): increases Octane number of gasoline Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy HC refining and conversion processes - 2 Isomerization of alkanes and alkylaromatics: also for increasing the octane number of gasoline an to produce xylenes and so on… Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy HC refining and conversion processes - 3 • Alkylation: alkenes with alkanes and aromatics, to produce high octane gasoline, jet fuel, detergent alkylates, plastics, intermediates, etc. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy HC refining and conversion processes - 4 Metathesis Oligomerization and polymerization Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy HC refining and conversion processes - 5 • • • • • • • Other conversions are mostly functionalizations: Additions Carbonylative conversions Acylations Substitutions Oxidations Reductions Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Mineral hydrocarbons Synthetic hydrocarbons • This may become necessary as the petroleum reserves are getting exhausted. Coal as such is not adaptable to an economy tuned for dealing with liquid and gaseous fuels. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy HC synthesis methods Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy HC synthetic routes • Syngas based Fischer-Tropsch • CH3OH (MeOH) conversion - catalyst based, mainly zeolites - HBr based - Methyl halides based • CO2 conversion - photosynthetic, bacterial, catalytic, electrochemical • Direct CH4 conversion - condensation* - oxidative reactions, catalytic, superacids, halogens, Se, S, etc. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Thermodynamic and kinetic issues 2 CH4 ® C2H6 + H2; DH = 16kcal/mol *Any condensation of CH4 to C2H6 and then to higher HCs must overcome unfavourable thermodynamics. This can be achieved in condensation processes of oxidative nature, where H2 is removed by the oxidant. Kinetically low yields and poor selectivity to favoured products. Superacids cleave also longer chain alkanes. Hence C3 - C6 products predominate. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Nature of HC conversion reactions - 1 • Homolytic (free radical) reactions High temperature conversion processes of HCs fall in this category. Combustion of HCs itself is an example. Thermal cracking, cyclization, etc. are other examples. Low temperature examples are polymerization, and certain oxidation, substitution and addition reactions. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Nature of HC conversion reactions - 2 • Heterolytic (ionic) reactions In acid catalysed reactions of unsaturated HCs, trivalent carbocations are responsible for electrophilic conversions. CH3+ is the parent. Carbocations with five CH5+ parent also occurs. They are initiated by protolytic reactions. Both C-H and C-C bonds are susceptible. Base catalysed HC conversions are less common. When occurs, by proton abstraction intermediate carbanions are formed. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Heterolytic (ionic) reactions 1) 2) Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Heterolytic reactions (protolytic) 1) Not only C-H bonds but also C-C bonds…… 2) 3) Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Heterolytic reactions (acid catalyzed) Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Nature of HC conversion reactions - 3 • Base catalysed carbanionic alkylation, isomerization and polymerization are important. Base catalysed alkylation of alkylarenes, in contrast to acid catalyzed ring alkylation, leads to alkylation of the side chain in the benzylic position. An example is the alkylation of toluene to ethylbenzene required for styrene manufacture. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Heterolytic reactions (base catalyzed) Through carbanions: 1) 2) 3) Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Use of Hydrocarbons • Refined Petroleum Products – Transportation fuels – Fuels for space heating – Fuels for power generation – Feedstock for chemicals and plastics – Components for lubricants Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Main references used in our lessons • • • • • • ‘Hydrocarbon Chemistry’ by G.A. Olah and A. Molnar, 2nd Edition, John Wiley, 2003. ‘Petrochemicals in non-technical language’ by D.L. Burdick and W.L. Leffler, Pennnwell books, 1990. ‘Chemistry of catalytic processes’ by B.C. gates, J.R. Katzer and G.C.A. Schuit, McGraw-Hill, 1979. ‘Fundamentals of Industrial Catalytic Processes’ by C.H. Bartholomew, Wiley-Interscience, 2006. ‘Sustainable Strategies for the upgrading of natural gas’, edited by E.G. Derouane, V. Parmon, F. Lemos and F.R. Ribeiro, Springer, 2005. Plus various other sources acknowledged in the slides. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Exercise 1. Terms and names 1. Write down examples of: - Aliphatic, Cyclic, Saturated, Unsaturated, Alicyclic, Aromatic and Heterocyclic hydrocarbons. - Alkenes, arenes, n-alkane, i-alkane - Paraffins, Olefins, oxygenates, thiols, epoxides, cyclic oxides, anhydrides, ethers, nitriles, nitro-HC - O, m, p- xylenes, butylene Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Exercise 1 (contd…) 2. (CH3)2C=CH2 How do you call it? - isobutylene, 2-methyl propene or isobutene? 3. (CH3)3CH How do you call it? - isobutane, 2-methyl propane or butane? Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Exercise 1 (contd…) 3. What is: - a monomer, dimer, trimer, tetramer, oligomer, polymer and an isomer? - Give examples in each case. 4. What is Naphtha and Naphthene? Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Exercise 1 (contd…) 5. Why coal, tar sands and NG is less preferred (up till now) to crude oil? Give short answers. 6. Can you comment on why petroleum chemistry will still be very much relevant (or more) even if petroleum use is less favoured in future? Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Exercise 1 (contd…) 7. In petroleum processing, both thermal and catalytic conversions are widely used. For a given reaction and set of conditions, does the use of a catalyst change the equilibrium constant or heat of reaction compared to the situation in which no catalyst is used. Explain. (use your knowledge from other courses) Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Exercise 1 (contd…) 8. NH3 is an inorganic chemical. Then, why petroleum processing or C1 chemistry plays an important role in ammonia manufacture? (Hint: Answer lies in one of the slides covered in this class). Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Exercise 1 (contd…) 9. From coal to synthetic gasoline conversion, F-T reaction is an important route. Justify that this process is a depolymerization step followed by a polymerization reaction? Write relevant equations. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Exercise 1 (contd…) 10. When buying gas appliances, why do you have to specify whether you are using LPG or NG? Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Exercise 1-11. Oil Refinery Disaster: What went wrong? Get the reading material from your teacher, if you are interested to know Prof. K.R. Thampi, Hydrocarbon the details Processing, Masters in Energy Excercise 1-12 Study and familiarize with distillation principles, vapour-liquid equilibrium (VLE) and McCabbe-Thiele method. Use these principles when studying other courses dealing with process design and separation. Document Title: DISTILLATION Base Document URL: http://lorien.ncl.ac.uk/ming/distil/distil0.htm Author: Ming T. Tham (Email:[email protected]) Date: Oct. 1997 Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy Exercise 1-13 Refer to the slide, ‘HC refining and conversion processes - 2’. Use organic chemistry textbooks and references find out list a few examples of each of the reaction types given. List only hydrocarbon related transformations. Prof. K.R. Thampi, Hydrocarbon Processing, Masters in Energy