The reductive alkylation of Illinois No. 6 coal. Factors governing the reductive alkylation reaction in ethereal solvents

The reductive alkylation of Illinois No. 6 coal has been investigated to determine the experimental conditions that are most suitable for the conversion of the coal to an alkylated product that is soluble in tetrahydrofuran. Thermodynamic and kinetic factors influence the reactivity of the reducing agent; potassium is the most effective alkali metal. The reduction potentials of the aromatic hydrocarbons used as electron transfer agents dictate the effectiveness of these reagents; biphenyl and naphthalene are more suitable reagents than anthracene. The alkylation reaction is a kinetically controlled S_N2 process and reactive reagents such as primary alkyl iodides and sulphonates are necessary for complete alkylation reactions. Under the most suitable conditions, potassium, naphthalene, and straight-chain butyl iodide allow the conversion of almost 90 wt% of Illinois No. 6 coal to products that are soluble in tetrahydrofuran.     

Solid state magnetic resonance spectra of Illinois No. 6 coal and some reductive alkylation products

Illinois No. 6 coal and its reductive methylation and butylation products have been studied by magnetic resonance techniques. Conventional CP-MAS¹³Cn.m.r. spectroscopy indicates that 62% of the carbon atoms in the coal are aromatic and that about 6% of the carbon atoms are carbonyl. Esters are more abundant than carboxylic acids. The resonances of methoxy groups and other novel etheric carbon atoms are apparent in the high field region. Dipolar dephasing experiments suggest that methyl carbon atoms constitute no more than 16% of the carbon, methylene and methine carbon atoms about 14% and quaternary aliphatic carbon atoms about 2%. The dipolar dephasing experiments in conjunction with previous work also permit estimates of the hydrogen atom distribution. The THF-insoluble products obtained in the reductive alkylation reactions with¹³C-enriched alkylating agents contain paramagnetic and ferromagnetic substances that adversely influence the solid state n.m.r. spectra. However, good ¹³C n.m.r. spectra were obtained after these substances were extracted with aqueous hydrochloric acid. The O:C alkylation ratios are 1.2 and 1.0 for methylation and butylation, respectively. Dipolar dephasing experiments establish that the decay constants of functional groups in the whole coal and of C- and O-methyl-¹³C and C- and O-butyl-1 -¹³C nuclei in the labelled coal molecules are very similar to those of reference compounds. These findings suggest that the decay constants measured for the ¹³C nuclei in coals and coal-derived solids provide reliable information about their degree of substitution.     

Liquid-phase alkylation of Assam (Baragolai) coal

Liquid paraffin which consists of a large number of alkylated aliphatics and aromatics seems to be acting as an alkyl group transfer medium to receptive complexes like coal. The alkyl group receptive spots could be created in the coal complex by treatment with molten alkalis like sodium or potassium hydroxide. By repeating extractions of fresh coal with the same volume of liquid paraffin on a laboratory scale it was found that a stage was reached when liquid paraffin became rich enough in alkyl groups to become an alkyl group donor. This suggests a method for liquid phase alkylation of coal.     

Reductive alkylation of illinois No. 6 coal. 1H and 13C n.m.r. spectra of the 13C-enriched alkylation products

The reductive alkylation of Illinois No. 6 coal has been carried out using potassium and naphthalene in tetrahydrofuran and methyl-¹³C and butyl-1 -¹³C iodides to alkylate the resultant polyanion. The soluble products of the reductive alkylation reaction were isolated by extraction and chromatography. Proton and carbon n.m.r. spectra were recorded. The intense resonance signal at δ3.95 which appears in the proton n.m.r. spectra of Illinois No. 6 coal butylated with unenriched butyl iodide is split into a doublet by the ¹³C nuclei. Similar results were obtained for the methylation products. The chemical shift and coupling interaction establish that aryl ethers are a very important constituent of the alkylated coal. The carbon n.m.r. spectra of the coal alkylated with ¹³C-enriched alkyl iodides are intense. The resonances of the C-alkylation products appear in a single broad band with a maximum intensity in spectral regions compatible with the formation of the reductive alkylation products of certain polynuclear aromatic hydrocarbons or the base-catalysed alkylation of certain benzylic carbon atoms. The resonances of the N -alkylation products appear in two distinct bands. These resonances are tentatively assigned to amines produced as a result of reductive alkylation of heterocyclic compounds. The resonances of the 0-alkylation products appear in three distinct bands which can be assigned to alkyl aryl ethers, alkyl aryl ethers with substituents at the adjacent positions, and to alkyl carboxylates. The ratio of ethers to carboxylates in the soluble alkylation products was determined to be 7.8 for butylation and 8.0 for methylation. The Chromatographic fractions contain different amounts of C-, N-, and 0-alkylation products. This finding suggests that the coal structure is not highly uniform.     

Oxidative weathering of Illinois No.6 coal

The exposure of freshly-mined Illinois No.6 bituminous coal (Monterey Mine No.1) to atmospheric oxygen at ambient conditions resulted in a slow oxidation reaction which appeared to be complete within two months to produce an oxidized coal product with ≈26% more organically bound oxygen than the fresh coal. An oxygen functional group analysis was performed to determine the carboxylic acid, hydroxyl and ether group content of the coal before, during and after the reaction. Infrared analysis showed no carbonyl production; however, ether functionality was being produced. O-methylation reactions which employed isotopically labelled methyl groups (both C-13 and deuterium) were used to identify and quantify O-H and CO₂H sites in the weathering coal samples. It was found that these acidic groups were not the products of oxidative weathering. Essentially all of the chemically incorporated oxygen eventually formed ether linkages. In a related study on this coal, hydroperoxide was detected as a transient intermediate in the early stages of the oxidation. A mechanism is proposed which involves the simultaneous formation under mild temperatures of a hydroperoxide and a carbon radical that undergoes a radical displacement producing the ether product directly. Solvent swelling studies revealed that these ethers act as cross-linking agents in the coal structure. The more highly cross-linked coal structure that resulted from weathering was responsible for the destruction of the plastic properties of this bituminous coal.     

Reductive alkylation of coals in liquid ammonia

The reductive alkylation of two different rank coals was investigated using metallic potassium and alkyl iodide in liquid ammonia. The reduction reaction alone increases the dissolution of the coals in dichloromethane only to a very small extent. However, the reduction process in conjunction with alkylation leads to readily dichloromethane soluble products. The solubilization of alkylated coals depends on the type of coal and the length of the substituent alkyl chain. The extracts were characterized by infra red spectroscopy, molecular mass, hydrocarbon class analysis and elemental analysis.     

Effects of coal cleaning on the short contact time liquefaction of Illinois No. 6 coal

This study was carried out to determine the effect of coal cleaning by oil agglomeration and sink-float methods on yields from short contact time liquefaction of Illinois No. 6 coal. The runs were made in a continuous unit using SRC-II distillates as process solvent. Measured yields included hydrogen (consumption), hydrocarbon gas, distillate oil, SRC (the pyridine-soluble portion of the residue) and insoluble organic matter, the pyridine-insoluble organic residue. The solubility of product SRC in hexane, toluene and pyridine was also determined. The principal finding was that coal cleaning by density methods reduced the yield of IOM obtained in subsequent liquefaction and this is attributed to the removal of inert components from the feed coal. In addition, cleaning which significantly reduced pyrite content of the feed coal also reduced the yield of distillate oil and tended to give a less soluble SRC during liquefaction. Deep cleaning by gravity methods gave the lowest IOM, but reduced pyrite content to the point where distillate oil was consumed rather than produced. Oil agglomeration reduced total ash to 50% of that in the run-of-mine coal, but left the pyrite level in the coal high. The relevance of these results to two-stage liquefaction is discussed.     

Solubility increase of coal by alkylation with various alcohols

A vitrinite concentrate of Taiheyio coat has been reacted with various alcohols using ZnCl₂ as a catalyst under nitrogen pressure. The reaction conditions such as the reaction time, reaction temperature, initial nitrogen pressure and the effect of other Lewis acids as catalysts have been examined using methanol. The product from the reaction with methanol at 400 °C is fully soluble in pyridine, 57% in benzene and 26% in straight-chain hexane. This result is similar to that obtained when coal is hydrogenated under 10 MPa hydrogen pressure. Higher temperature, higher initial nitrogen pressure and longer reaction times give increased solubility. ZnCl₂ and FeCl₃ are the best catalysts. Of the various alcohols, branched alcohols give better results.     

Supercritical toluene and ethanol extraction of an Illinois No. 6 coal

The effect of temperature, pressure, solvent/coal ratio and reaction time on supercritical toluene dissolution of an Illinois No. 6 are reported in this Paper. The experiments were conducted in a batch autoclave operating at temperatures ranging between 350 and 450 °C and pressures between 5.89 and 16 MPa. Low liquid yields in the range of 5–20% were obtained during toluene extraction. The liquid yields increase with temperature and total pressure, and only slightly with hydrogen partial pressure. Ethanol extraction gives better yields but significant solvent losses also occurred. The low liquid yield obtained can be attributed to the nature of the coal and the contacting batch mode used.     

Reactivity of O-methylated Illinois No. 6 coal towards alkyllithiums/methyl iodide

An O-methylated Illinois No. 6 vitrain was treated repeatedly with a series of C-H indicator bases of known pK_a and quenched with ^13,14C-methyl iodide. The extent of ¹⁴CH₃ incorporation depended strongly upon base strength, increasing in the order 9-phenylfluorenyllithium < fluorenyllithium < trityllithium. A significant number of methyl groups ($\text{0.7–1.2}\text{100}$ coal carbons) were introduced with fluorenyllithium and trityllithium as the base. Additional methyl groups were added upon a second and third treatment with base and alkylating agent. After three treatments, the number of added methyl groups had doubled. The extent of base reagent incorporation was established by parallel experiments using ¹⁴C-enriched bases. CP/MAS ¹³C n.m.r. of the first coal alkylation product using trityllithium and ¹³C-enriched methyl iodide was consistent with predominantly C-alkylation. From these results, a unified picture for coal structure emerges which contains a distribution of reactive C-H sites, distinguishable on the basis of their acid-base properties. Possible reactive sub-structures are considered.     

The preparation and pyrolysis of O- and C-benzylated Illinois No. 6 coal

Illinois No. 6 coal was modified by selective benzylation reactions and the O- and C-benzyl, benzyl-d₇ and benzyl-1-¹³C products were pyrolysed in a wire screen reactor at 500–1000 °C. The char, tar and gas yields were measured and the distribution of the isotopic labels in the lower molecular weight gaseous products was determined. The results suggest that the modified coals are more reactive than the natural coal. First, the modifications increase the concentration of reactive radicals and of hydrogen donor groups. Second, the exchange patterns also suggest that the energetically more favourable reactions occur reversibly and that radical addition and recombination reactions compete favourably with fragmentation and radical substitution reactions. Third, the non-random distribution of the isotopic labels in the products indicates that the reactions in the coal particle are kinetically controlled even at temperatures near 850 °C. Fourth, the distribution of the labels in the water and ethene implies that non-radical processes contribute. Thus, theories of pyrolysis that are based exclusively on radical processes may be seriously misleading.     

Catalytic upgrading of coal liquid vacuum residue derived from Illinois No. 6 coal

Two-stage hydrotreatment under appropriately optimized conditions, including the selection of catalysts and solvents, is very effective for the upgrading of heavy coal liquid residues. A catalyst of high hydrogenation activity and anti-coking nature is desirable for the first, lower temperature stage. Support is to be carefully designed in terms of pore structure and acidity. The coke produced during the hydrotreatment tends to plug intergranular pores of the extruded catalyst. Grinding enhances the activity of the extruded catalyst. The removal of coke precursor and minerals by solvent extraction is also helpful for maintaining catalyst activity.     

Ruthenium tetroxide catalysed oxidation of Illinois No. 6 coal: The formation of volatile monocarboxylic acids

Ruthenium tetroxide selectively oxidizes activated aromatic compounds under mild conditions and has been used for the catalytic oxidation of several different coals. The quantities of the volatile monocarboxylic acids with 2–6 carbon atoms have been determined by an isotope dilution technique. The amount of ethanoic acid ranges from 1 to 3mol/100C and the quantities of propanoic acid, and butanoic acid exceed 0.1 mol/100C. Methylpropanoic, pentanoic, 2-methylbutanoic, 3-methylbutanoicand hexanoic acid are formed in lesser amounts. The outcome of the experiment depends upon whether or not the coal has been extracted prior to oxidation. The results for Illinois No. 6 coal expressed in moles of ethanoic acid produced/l00C illustrate this feature: raw whole coal, 1.9; coal extracted by the method of Hayatsu and co-workers, 1.0. Dehydrogenation with benzoquinone prior to oxidation increases the yield of ethanoic acid to $\text{sol1.5mol}\text{100C.}$ The amounts of ethanoic acid obtained from the other extracted coals are 1.0 for Texas lignite, 1.2 for Rawhide subbituminous, 3.4 for Pittsburgh No. 8, 3.3 for a higher ranking bituminous coal (PSOC 726) and 0.7 for an anthracite (PSOC872). The results obtained in this study are compared with related information concerning the distribution of alkyl groups within coal by other methods.     

Electrolytic pretreatment of Illinois No. 6 coal

Electrolysis of Illinois No. 6 coal in acidic as well as basic electrolytes accomplishes significant amount of sulfur and ash removal under moderate reaction conditions. Electrolysis at 1.4 V vs. SCE (saturated calomel electrode) in 2 M NaCl + 9% HCl electrolyte accomplishes 62% sulfur removal and leaves behind a clean coal with the sulfur to heating value ratio of 1.44 lb S/million Btu (0.619 kg S/GJ) while coal slurry oxidation at 3.0 V vs. SCE results in 72% ash removal. Coal electrolysis in basic electrolytes accomplishes a clean residue with relatively low oxygen content. The sulfur to heating value ratio of 2.11 lb S/million Btu (0.907 kg S/GJ) is observed for coal electrolyzed in 2 M NaOH at 3.0 V vs. SCE. Impurity removal from coal is simultaneously accompanied by clean hydrogen gas production at the cathode at Faradaic coulometric efficiencies of over 95%. Hydrogen gas is produced by the depolarization of water by mineral impurities present in coal. A relatively small amount of H₂ is produced due to water splitting caused by the carbonaceous part of the coal. Model reaction pathways for coal cleaning are discussed. More work is in progress on the types of sulfur forms removed from coal.     

液体酸烷基化技术进展

介绍了氢氟酸烷基化、硫酸烷基化和离子液体烷基化等液体酸烷基化技术的研究现状,概述了世界主要液体酸烷基化技术供应商的技术创新和工艺改进。氢氟酸烷基化技术因催化剂是易挥发性剧毒物质,工艺改进主要侧重于工艺安全及减灾设备;硫酸烷基化工艺在低温下反应利于生产高辛烷值的烷基化油,该技术的工艺改进主要侧重于强化低温下的传质及反应热的及时移除;离子液体烷基化工艺催化剂的催化性能优于氢氟酸与硫酸,且对设备腐蚀小,对环境危害小,但是选择性和产率较低,其研发工作注重于开发高选择性及高产率的离子液体。烷基化油是高辛烷值汽油理想的调和组分,我国的地方炼厂出现烷基化热,投建的多为硫酸烷基化项目。但硫酸烷基化同样存在环境风险,已实现首次工业应用的离子液体法将迎来广阔的发展机遇。     

Study of the changes in i.r. spectra bands of coal after reductive alkylation

Depolymerization reactions of a Spanish bituminous coal, such as reductive hydrolysis and alkylation, and O-alkylation, were investigated by Fourier transform infrared spectroscopy (FT-i.r.). The spectra show that the reductive hydrolysis increases the phenolic hydroxyl groups, whereas these decrease by alkylation. These changes in the OH group content were studied in relation to variations in the absorbances at 3800–2000, 1700, 1600 and 1112 cm⁻¹, and some linear correlations were found, which seem to indicate a clear contribution of the OH groups to the intensity of the broad band near 1600 cm⁻¹. The influence of the phenolic OH groups on the C=O vibration frequency at 1700 cm⁻¹ was also studied.     

Dihydroaromatic structure of Illinois No. 6 Monterey coal

Coal from the Monterey mine (Illinois No. 6 seam) has been oxidatively fragmented by trifluoroperoxyacetic acid. The major products were acetic, malonic, and succinic acids; benzene di, tri, tetra; and penta-carboxylic acids; and two compounds provisionally identified as the epoxides of ethylene tri- and tetra-carboxylic acids. These products are in best accord with a structure for Monterey coal in which dihydrobenzene units are frequently interspersed in a polymer composed of condensed aromatic chains and clusters. The methyl and hydroxyl substituents complete the dominant pattern.     

Carbonylation studies with Illinois No. 6 bituminous coal

Sodium metal and carbon dioxide were used to carbonylate Illinois No. 6 coal in a 1 l, high-pressure, autoclave in anhydrous tetrahydrofuran from 150 to 350 °C. Solubility of the reaction products in tetrahydrofuran and water, and the sodium uptake in the insoluble residue were determined. The reduction and subsequent carbonylation of coal produced a limited amount of solubility in these solvents, and the uptake of sodium in the insoluble residue reached a maximum of 6.29% at 250 °C with no carbon dioxide added. This corresponded to a ratio of sodium atoms per 1000 carbon atoms of 62.9, a 69-fold increase over the unreacted dried coal. Total acidity and carboxyl group content were calculated for the insoluble residues and unreacted bituminous coal. The per cent increase of carboxyl groups reached a maximum of 1.37 meq g^?1 at 2000 °C which represents a 174% increase over the unreacted coal.     

Biodesulfurization of dibenzothiophene sulfone by Arthrobacter sp. and studies with oxidized Illinois No. 6 coal

A bacterium identified as Arthrobacter sp. was grown on dibenzothiophene (DBT) sulfone as a sole source of sulfur, producing sulfite and sulfate. Sulfur in DBT sulfone (1.0 mM) was nearly quantitatively converted to sulfate by the organism. The organism could also use DBT sulfone as a sole source of carbon and energy. There was evidence for transient accumulation of benzoic acid in the culture medium after growth of the cells slowed. The DBT sulfoxide analogue 9-fluorenone was converted by resting cells to a product identified as 1,10-dihydroxy-1,10-dihydrofluoren-9-one, suggesting that DBT sulfone may be metabolized via an angular hydroxylation resulting in carbon- sulfur bond cleavage. This strain of Arthrobacter showed no ability to desulfurize oxidized Illinois No. 6 coal.     

在液氨环境中制备氨基钠的研究

氨基钠在化学工业及药物合成领域中有着广泛的应用。研究了以金属钠和液氨在氢气存在下制备氨基钠的方法,考察了反应温度、压力、原料配比等对产品质量的影响。将金属钠溶解在一定量的液氨中,然后转入高压反应釜密封,通入少量氢气吹出釜内空气,然后加热到50 ℃,搅拌反应1 h,可得到氨基钠质量分数为92%的产品。该方法方便快捷,合成周期短,无需催化,产品纯度高,色泽好,具有重要的应用前景。