The Waterloo Fast Pyrolysis Process (WFPP) was used to determine the feasibility of extracting taxanes from needles, twigs and whole clippings of Taxus canadensis . Purification techniques developed for solvent extracts were not suitable for achieving analytic chromatographic separation of taxanes from pyrolytic lignins and other pyrolysis products as these materials are in much higher quantities in pyrolysis oil than in solvent extracts. A number of separation techniques were attempted including liquid–liquid partitioning, silica gel chromatography, adsorption and sodium phenoxide formation. Pretreatment of the feedstock by deionization was also attempted. Taxol® was identified in pyrolysis oils of needles and whole clippings with 20% recovery compared to solvent extraction. Other taxanes were most likely present in higher concentrations but could not be analyzed because of interference by phenolic substances.

An upgrading process for heavy oils and bitumens, based on the use of activated carbon catalysts, was investigated in a bench-scale plug flow reactor. Good results were obtained at pressures as low as 7.0 MPa at temperatures of 400-450 degreesC. The process required the presence of hydrogen gas and a hydrogen-rich solvent in a supercritical state. If the solvent was a highly saturated alkane, very little solvent decomposition occurred. A number of n-alkanes were tested as solvents, as well as paraffinic petroleum cuts and donor solvents such as tetralin and decalin. A range of values of other operating parameters was also investigated.With an Athabasca bitumen coker feed, bitumen conversions to distillable liquids of 82-88% by weight (95-105% vol%) were achieved, with 6-8 wt% (coke + pitch) yields. Demetallization was almost 100%, and hydrodesulfurization and hydrodenitrification levels of over 80% also resulted. Under similar conditions, a conventional Co/Mo hydrotreating catalyst gave higher hydrogen uptake but lower pitch conversion, supporting the concept that carbon-based catalysts may give a unique product distribution and utilize hydrogen more effectively.It is postulated that four conditions must be met to obtain the favorable results found in this work: there must be a significant level of supercritical fluid; there must be a highly saturated or paraffinic supercritical solvent present; hydrogen gas must be present; and there must be an activated carbon catalyst used which may also have incorporated in it a catalytically active metal. (C) 2001 Elsevier Science Ltd. All rights reserved.

Evidence is presented showing that it should be possible to depolymerize a purified cellulose to produce anhydro-oligosaccharides containing small numbers of glucosidic units if suitable reaction conditions are chosen. Experiments were carried out in a stream of nitrogen in a downflow cocurrent tubular reactor with a high temperature wall. Two sizes of particles of Avicel pH102 were used and two sizes of reactor tube with wall temperatures from 850 to 1200°C and residence times from 35 to 75 ms. From the solid residue of the reaction, a water soluble fraction was recovered which contained anhydrosugars. Yields of soluble solids of up to 44% of the cellulose fed were obtained in a small diameter tube, and up to 34% in a larger diameter reactor. Only a narrow window of reaction conditions exists which is optimal for maximum yields. Carbohydrate analyses showed significant yields of anhydro-oligosaccharides from G2 to G7, the limit of resolution for the HPLC column used. Normally, these compounds made up ∼50% of the soluble solids fraction. Substantial amounts of material >G7 were also produced but could not be identified. Tests were also done with pretreated Avicel, but only one method gave improved results (slow preheating) Given the probable high unit value of anhydro-ologosaccharides, it would appear that this method of flash pyrolysis may be worth further exploitation.

A hydrogenation process has been developed to recover carbon black from rubber crumbs prepared from scrap tires. A semi-batch 2 L autoclave was used, with hydrogen continuously bubbled through a slurry of rubber crumbs and a paraffinic dissolution oil under pressures from 300 to 1500 psig and temperatures of about 400 degrees C. The dissolution oil dissolved the rubber and allowed the carbon-black particles to be freed from the polymer matrix. The carbon black then acted as a hydrogenation/cracking catalyst. Under optimal reaction conditions, the yield of carbon black + inorganic additives was approximately 36%, the gas yield 1-2%, naphtha yield 8%, and the balance a product oil, part of which can be recycled as the dissolution reagent. The carbon-black product after filtering and drying had properties which were an average of those of the various grades added during tire manufacture. One-half of the inorganics could be removed by a simple acid wash if desired. The carbon black has a value more than twice that of the other products and could be the factor which would allow this process to be economically viable without subsidies.

Exploratory work was carried out to develop a process for conversion of mixed plastic wastes into liquid transportation fuels or petrochemicals. The concept used is based on thermal depolymerization of the polymers in a suitable solvent followed by catalytic conversion of the resulting polymeric fragments into hydrocarbons with boiling points below 525 degrees C. The process is carried out batch-wise over a zeolite catalyst at temperatures from 350 degrees C to 450 degrees C and at atmospheric pressure. No hydrogen is used and volatile products formed are continuously removed from the reactor. Tests were carried out on polyethylene and polypropylene alone, and on mixtures of the two. Finally, a synthetic mixture of four different plastics was tested. From 90% to 98% of the plastic was converted to gases or distillable hydrocarbons. Of this yield, from 20% to 55% was gas, primarily propylenes and butylenes, and from 32% to 70% was a light hydrocarbon oil. Very little non-distillable coke or residue was formed. The use of mixtures did not affect the high conversions obtained, but the results could only be approximately predicted based on a pro-rating of results for the individual components.

Experiments are described which attempt to exploit the redox or oxygen transfer mechanism of iron-catalyzed coal gasification by periodically alternating between an oxidizing and a reducing gas environment. A low-rank, Canadian coal was used and carbon dioxide was the oxidizing gas. A 15% increase in the yield of CO based on CO2 supplied compared to the steady-state operation of the gasifier was observed at 800 degrees C for a coal loaded with 3 wt % Fe using a cycle period of 60 s, The advantage for the modulation operation decreased with increasing temperature and became negligible at 900 degrees C.

Use of a fluidized bed is an important design option if advantage is to be taken of the lower operating temperatures that catalytic coal gasification offers. Catalytic gasification, however, has been conducted with fixed bed systems whose performance is often quite different from that expected from fluidized beds. Experiments were performed in a microfluidized bed with continuous overflow to compare rates of coal gasification or pyrolysis, and rates of formation of the product gas components with and without an impregnated Fe catalyst. A Forestburg (Alberta) subbituminous coal was used. Variables were bed temperature, coal feed rate, and catalyst loading. The Fe catalyst becomes active above 750-degrees-C in the overflow fluidized bed regardless of catalyst loading, but the catalytic activity of the ash in the coal obscures the Fe contribution below 800-degrees-C. Coal pyrolysis occurs as the coal enters the bed so it is a devolatilized char that is gasified. Methane found in the product gas arises only from coal pyrolysis. Under the conditions used, methanation does not take place over Fe. For this high-ash coal, an optimum catalyst loading was observed at 3-5 wt % Fe based on the carbon in the coal.

Successive, alternating Pulses Of CO2 and N2 fed to beds of iron-impregnated coal char confirm the existence of a redox cycle with iron catalysts. Additional experiments with chars from raw and demineralized coals establish that the catalytic gasification dominates and that the coal ash also functions through a redox cycle. Extending the duration of the CO2 pulse leads to a plateau in the rate of CO formation that has not been previously observed. A redox cycle involving easily oxidized and reduced iron oxide species is proposed as the mechanism for gasification in this plateau region of the pulse.

Various kinds of catalysts are being developed and tested for the pyrolytic gasification of biomass using the Waterloo Fast Pyrolysis Process (WFPP) technology. The present report describes gasification tests with wood in a continuous bench scale fluidized bed reactor but with no added air or oxygen in the region of 500-700 degrees C and at short gas contact times, using a crystalline nickel aluminate catalyst. The objective was to determine the most appropriate operating conditions for this catalyst and its performance for the production of a synthesis gas in high yields. Experiments were carried out with this catalyst in both inert and reactive gasification media, but without any oxygen or air addition. The results show the influence of the catalyst on the nature of the gasification products and the effect of operating variables. Gas compositions are given for typical WFPP operating conditions. Evidence is presented which indicates that the gasification mechanism is a fast thermal pyrolysis followed by catalytic reforming of the vapors with a high yield of synthesis gas.

Experiments conducted in 0.15 m diameter bubble columns using water and non-aqueous liquids have shown that the gas velocity at which transition from the bubbly flow to the churn-turbulent flow regime occurs is a function of gas density. The transition velocity increased with increasing gas density. The direct effect of gas density on gas holdup in the bubbly flow regime is small with only a slight increase in holdup being observed at higher densities (epsilon(G) alpha rho(g) 0.04). In the churn-turbulent region a much greater effect of gas density on gas holdup was observed. These differences were found to be a direct function of the differences in holdup values at the transition points. Gas holdup was found to be a function of the gas phase momentum. In the bubbly flow regime holdup was directly proportional to momentum while in the chum-turbulent regime holdup was proportional to momentum to the one third power.Reasons for this behaviour are discussed, as well as the implied effects on liquid mixing in bubble column slurry reactors. The effects of gas density may offer an explanation for some apparently anomalous published results.