Larry L. Anderson

Thermal and catalytic degradation of high density polyethylene and commingled post-consumer plastic waste

High density polyethylene (HDPE) and commingled post-consumer plastic waste (CP#2) were thermally and catalytically depolymerized in both a 27-cm3 tubing reactor and a 150-cm3 autoclave reactor at 400–435°C, 60 min. under N2 or H2, with or without TiCl3 or HZSM-5 as catalyst. For both HDPE and CP#2, no significant non-catalytic reactions occurred until the reaction temperature reached 430°C. For depolymerization reactions of HDPE and CP#2 in the autoclave reactor at 435°C, the optimum oil yields (88.7% for HDPE and 86.6% for CP#2) were obtained over TiCl3 catalyst, while the maximum gas yields (21.2% for HDPE and 17.6% for CP#2) were produced over HZSM-5 catalyst. HZSM-5 catalyzed cyclization and aromatization reactions while TiCl3 catalyzed recombination and disproportionation reactions. Detailed product analyses and characterization lead to a reasonable explanation of reaction pathways and mechanisms.

Carbon-13 magnetic resonance of coal-derived liquids

Abstract Carbon-13 Nuclear Magnetic Resonance Spectroscopy has been applied to coal-derived liquids in order to obtain additional information regarding molecular structure and composition. The data have demonstrated that, although the chemical structure is extremely complex, a significant amount of material is present in the form of normal paraffinic material both as free paraffins and alkyl substituents on aromatic and hydroaromatic materials. Semiquantitative estimates are made of the alkyl content of the liquids and the atom percentage of this material that must exist in the unprocessed coal.

New procedure for molecular-weight determination by vapour-phase osmometry

Abstract Inconsistent results on molecular weights determined by different methods reported in the recent literature prompted this study. A detailed investigation of the behaviour of benzil-chloroform solutions and fourteen other systems resulted in a major revision of the experimental procedure used in the VPO method for molecular-weight determination. The revision was based on a clear recognition of a ‘rectilinear region’ and a ‘curved region’ in the relation between the osmometer readout (ΔV) and non-volatile solute concentration. Only the rectilinear region shows a direct relation between ΔV and the number of solute molecules in an infinitely dilute concentration range, a fact which has not been clearly identified before. A method of determining a concentration range for the rectilinear region was devised and used to develop a simpler experimental procedure. Molecular weights of eleven model compounds were checked using the new procedure. Molecular weights of two coal-derived liquid fractions were also determined and the presence of association in their mixture was examined. Shortcomings in the present theory and two other experimental procedures are pointed out. Molecular weights of model compounds including those in the experiments quoted ranged from 122 to 1238.

Depolymerization of waste plastics with coal over metal-loaded silica-alumina catalysts

Abstract Catalytic effects of various hydrogenation-hydrocracking catalysts on the coliquefaction of coal with high-density polyethylene (HDPE) and commingled plastic were systematically investigated under typical liquefaction conditions: 430°C, 2000 psig H 2 for 1 h. Silica-alumina impregnated with Pt, Ni, Pd, or Fe showed higher catalytic activities for oil conversion than did metal-free catalysts. Apparently, the hydrogenation function was created on active metal sites while hydrocracking took place on active sites on silica-alumina. High total conversions were obtained even without a solvent added. Product analyses and characterization have assisted in the determination of reaction pathways and possible mechanisms. Ni K-edge extended X-ray absorption near-edge spectroscopy (EXANES) and extended X-ray fine structure spectroscopy (EXAFS) show that Ni is present as NiO with nanoscale particles. In this study, two-stage processing of coal with HDPE was also investigated. Very high total conversions (up to 92%) were obtained while using this technique.

Coprocessing waste rubber tire material and coal

Abstract Blind Canyon DECS-6 coal (BC6) was reacted with ground waste rubber tire (WRT) particles and pyrolyzed tire oil (PTO) recovered by vacuum pyrolysis of WRT in an investigation of the feasibility of coprocessing coal and waste tire materials to make transportation fuels. Reactions were carried out in tubing reactors under a 1000 psig (cold) hydrogen atmosphere at either 350 or 430°C for 1 h. Molybdenum catalyst was added in the form of ammonium tetrathiomolybdate, a catalyst precursor. The catalyst precursor was added to obtain a 1% by weight (NH4)2MoS4 loading of the reaction mixture. The amount of ground WRT mixed with BC6 was varied to determine the optimum ratio of reactants. A synergistic effect (beneficial effect of reacting coal and WRT together that is not observed when coal and WRT are reacted individually) was observed for most WRT BC6 reaction mixtures treated at 430°C with catalyst and for some mixtures without catalyst. Coprocessing at 430°C yielded greater total conversion to liquids than at 350°C, with the added advantage of diminishing the amount of carbon black found in the liquid products. BC6 coprocessed with PTO yielded the greatest synergistic effect when reacted at 430°C in the presence of the molybdenum catalyst. The synergism observed for PTO BC6 reactions may be related to the presence of polyaromatic hydrocarbons (PAHC) in the PTO. It was found that coprocessing coal with PTO is more beneficial than coprocessing coal with WRT, i.e. the BC6 PTO mixture yields more product liquids as well as diminished carbon black contamination of liquid products.

Waste oils used as solvents for different ranks of coal

Abstract The effect of using different waste oils as solvent media for the liquefaction of lignite, subbituminous, and bituminous coals was investigated using tubing reactors. The waste oils utilized were waste automobile crankcase oil, oil produced by vacuum pyrolysis of waste rubber tires, and oil produced from vacuum pyrolysis of waste plastics. Reactions of coal and waste oils were carried out at 430°C under a hydrogen atmosphere for 1 h. Analysis of the waste automobile crankcase oil indicated the presence of heavy metals. Analyses of the oils derived from coprocessing coals of different rank with the automotive crankcase oil indicated that these oils were lower in overall trace metals compared with the trace metal content of untreated automobile crankcase oil. No coal rank dependence was observed for the removal of trace heavy metals (demetallation). Conversion yields indicated that all three solvents were similar for total gas + oil yields, asphaltene yields, and total conversion yields except for the vacuum pyrolyzed tire oil coprocessed with Illinois No. 6 coal. Coprocessing the vacuum pyrolyzed tire oil with Illinois no. 6 coal gave the best overall conversion. This was attributed to the presence of polyaromatic non-donor molecules present in the vacuum pyrolyzed tire oil and to the high pyrite content of the Illinois No. 6 coal.

A survey of methods of coal hydrogenation for the production of liquids

Abstract More than 60 coal hydrogenation-liquefaction processes are reviewed with respect to various process variables. These variables include temperature, pressure, residence time, catalyst type and percent, raw materials, liquid to coal ratio in the feed, percent product yield, space rate utilization, plant capacity, and references. The bibliography includes over 100 references covering the years 1910 to 1978. This reference section will help the reader to find additional information about an individual process. With most coal hydrogenation-liquefaction processes coal will have a residence time of about one hour in the reactor. This is especially true when these systems involve the reaction of coal mixed with a vehicle oil. However, those processes which involve the reaction of dry coal with hydrogen have reported residence times of a fraction of a second to several minutes. It is also apparent that those processes involving higher temperatures also have a higher gaseous yield. This is true even when the coal residence time is greatly shortened. In the past few years improvements have been made with catalysts. The improved catalysts have helped to decrease the necessary pressure of processes.

Activated extraction of coal using a hydrogen-donor solvent

Abstract The kinetics of the extraction of a high-volatile bituminous coal with 1,2,3,4-tetrahydronaphthalene (tetralin) under the influence of ultrasonic energy has been studied at five temperatures: from 47 to 87°C. The effects of intensity of ultrasonic energy, particle size, and hydrogen content of the coal were also recorded. Analysis of the results showed that a second-order reaction followed by a first-order reaction best describes the kinetics of the extraction process. The enthalpies of the second-order and first-order regions were respectively 8.7 and 2.5 kcal/mol, suggesting essentially physical control. The entropies were respectively −44 and −70 e.u. Auxiliary experiments and the kinetic data obtained suggest a model for the extraction process. The mechanism of the overall reaction is undoubtedly complex, but the data indicate that van der Waals and hydrogen-bonding forces are most affected by the ultrasonic energy, although stronger bonding is also affected giving much higher yields than would be expected. From the yields obtained in this study it is concluded that ultrasonic energy acts by rupturing bonds that are not affected by the solvent alone; the bonds affected are either strong hydrogen bonds or aliphatic covalent bonds, but not aromatic bonds.

Coliquefaction of coal and waste polymers

It has been shown that processing of coal to liquids can be done with high yields of liquids. Plastic materials. either pure as a commingled plastic waste containing different colors and impurities, can be processed with nearly 100% conversion to liquids and gases. Combinations of coal with plastic material can be processed to final products but with less conversion than expected fro interpolation of the data from processing coal alone and plastic alone. Polymerization catalysts such as Titanium compounds can be utilized to depolymerize plastic materials containing HDPE at temperatures above 420 Bifunctional hydrogenation/hydrocracking catalysts can improve the conversion of coal/plastic mixtures but the highest conversions and oil yields were obtained when a two step procedure was used with liquefaction of plastic done in one step and coprocessing of plastic-derived liquids and coal in a second step.

Catalysis of coal conversion at mild temperatures

Abstract Many materials have been used or tested as catalysts for the direct conversion of coal to liquids. However, the factors which determine whether a particular substance will be an excellent, fair or poor catalyst, or an inhibitor, are still not understood. Most of the catalyst studies have been of empirical nature and neither the specific catalytic mechanisms nor the exact forms responsible for the catalytic effects observed have been elucidated. In studies on the catalytic action of Lewis acids for the liquefaction of coal, many properties of these materials were correlated. After testing more than eighty catalysts, only one property was found to directly correlate with the yield of liquefaction products in coal conversion experiments. This property was found to be the electronic softness of the Lewis acids studied. Results from mild liquefaction experiments on bituminous coal have been obtained and give insight into the reactions taking place and the moieties involved in most of the liquefaction reactions.