Yutaka Dote

Recovery of liquid fuel from hydrocarbon-rich microalgae by thermochemical liquefaction

Liquefaction of Botryococcus braunii, a colony-forming microalga, with high moisture content was performed with or without sodium carbonate as a catalyst for conversion into liquid fuel and recovery of hydrocarbons. A greater amount of oil than the content of hydrocarbons in B. braunii (50 wt% db) was obtained, in a yield of 57–64 wt% at 300 °C. The oil was equivalent in quality to petroleum oil. The recovery of hydrocarbons was a maximum (>95%) at 300 °C.

CO2 fixation and oil production through microalga

Abstract As one way to prevent global warming due to carbon dioxide, microalgal oil production with secondarily treated sewage (STS) and thermochemical oil recovery from algal cells were studied. A hydrocarbon-rich microalga, Botryococcus braunii , produced hydrocarbons and consumed nitrate and phosphate in STS. Removal effects of the alga regarding As, Cd and Cr were observed during these experiments with an artificial medium. As for oil recovery from algal cells, the maximum yield of oil obtained by liquefaction was 64 wt% on a dry basis at 300°C with a catalyst of sodium carbonate.

Oil production from garbage by thermochemical liquefaction

Abstract Garbage was converted directly into oil by thermochemical liquefaction for the recovery of energy in the form of liquid fuel. The garbage with a moisture content of about 90 wt% was prepared by mixing cabbage, boiled rice, boiled and dried sardine, butter, and the shell of short-necked clam. The mixture was heated under pressurized nitrogen at 250°, 300°, or 340°C for 0.1, 0.5, or 2 h, with or without sodium carbonate as a catalyst (0 or 4% on a dry solid basis). Oil yield and its properties strongly depended on catalyst addition and reaction temperature, while holding time showed no marked effect. Oil was obtained in the highest yield of 27.6% on an organic basis under the following conditions: catalyst addition, 4 wt%; temperature, 340°C; pressure, 18 MPa; and holding time, 0.5 h. The oil had a calorific value of 36 MJ kg−1 and a viscosity of 53,000 mPas at 50°C. Its carbon content, hydrogen content, nitrogen content and oxygen content were 73.6, 9.1, 4.6 and 12.7%, respectively.

Analysis of oil derived from liquefaction of Botryococcus Braunii

Abstract Botryococcus braunii is a colonial green microalga that produces and accumulates oily hydrocarbons called botryococcenes (36% based on organics). It was reported that more oil was obtained than hydrocarbons in B. braunii when thermochemical liquefaction was applied to B. braunii for recovery of botryococcenes. In this paper, the properties of oil obtained by thermochemical liquefaction are clarified. The liquefied oil of B. braunii was fractionated into three fractions by silica gel column chromatography and analyzed to determine its composition. The yields of the three fractions based on organics were 5% of lower molecular weight hydrocarbons (MW, 197–281), 27.2% of botryococcenes (MW, 438–572) and 22.2% of polar substances (MW, 867–2209). The maximum recovery (78%) of botryococcenes in the liquefied oil was achieved at 200°C with the use of a catalyst.

Studies on the direct liquefaction of protein-contained biomass: The distribution of nitrogen in the products

In studies of the direct aqueous liquefaction of protein-contained biomass such as sewage sludge, nitrogen derived from proteins is distributed in both the oil and aqueous phases. The nitrogen in the oil is very difficult to remove by hydrotreatment over nickel/molybdenum catalysts. Egg albumin was used as a model protein in direct liquefaction studies of the nitrogen distribution in the products. The oil yield from albumin (10%) was much less than that obtained from actual feedstocks (typically in the range 30–40%). The nitrogen content of the oil (9%) represented less than 5% of the total nitrogen, while in the liquefaction of actual feedstocks, 30–50% of the nitrogen in the feedstock was found in the oil. No distribution of nitrogen to oil under 150°C occurred because of no oil yield. The majority of the nitrogen in albumin (80%) was distributed to the aqueous phase above 200°C. The distribution of nitrogen to oil was completed by 250°C. Sodium carbonate, used as a catalyst, prevented the distribution of nitrogen to oil. Albumin was decomposed to ammonia, not to amino acids.

Distribution of nitrogen to oil products from liquefaction of amino acids

Nineteen different amino acids were liquefied by reaction at 300°C for 1 h to study distribution of nitrogen in amino acids and reaction products. Oil yields of the amino acids except tryptophan were less than 10%. Nitrogen contents of oil were less than 13%. All of the amino acids were unstable and most of the amino acid, except tryptophan, was converted to water soluble nitrogen compounds other than amino acids, so that the residue of nitrogen in feedstock amino acids in the oil was less than 7%. For tryptophan, oil yield was 66% and the distribution of nitrogen to the oil was 50%.

Methane production from cellulose by catalytic gasification

A water slurry of cellulose was directly gasified into methane using reduced nickel on kieselguhr and sodium carbonate as catalysts at 400 °C under pressure (about 13 MPa) for 1 h. In the absence of the catalysts, cellulose at about 20 wt% was converted into the gas which consisted mainly of carbon dioxide. Cellulose at about 40 wt% was converted into a char-like-material (residue), and 40 wt% was lost due to the formation of water promoted by the carbon balance (more than 90 %) and by the mole ratio (about 2) of hydrogen loss to oxygen loss. With increasing load of reduced nickel (from 0 to 20 wt% of the cellulose), the yield of residue and production of water decreased linearly (from 40 to 10 wt%) and gas yield increased linearly (from 20 to 80 wt%). The methane yield increased by the reduced nickel and mole ratio of CH4/CO2 approached unity with increasing load of reduced nickel. Reduced nickel would thus appear to catalyze the formation of methane and carbon dioxide through reaction of carbon and water. Sodium carbonate increased methane yield in the presence of reduced nickel, although the yield was negligible when sodium carbonate alone was added.

Thermochemical liquidization of dewatered sewage sludge.

Abstract Dewatered sewage sludge (approximately 80% moisture content) was liquidized by a heating process in order to be transported through a pipeline, and the pressure loss of liquidized sludge measured. The dewatered sludge could be liquidized at temperatures above 150–175°C, and the viscosity of the liquidized sludge could be reduced to that of concentrated sludge (approximately 98% moisture content). The liquidized sludge showed pseudoplasticity. Liquidized sludge, which has a high solid concentration, could be transported by pumping through a pipe with the same pressure loss as that of concentrated sludge. The pressure loss could be calculated using Fannings equation.

Liquefaction of barley stillage and upgrading of primary oil

Stillage from ethanolic fermentation of barley was converted directly into liquid fuel (primary oil) in the presence of sodium carbonate as a catalyst. The primary oil with a heating value of 36 MJ kg−1 was obtained in 38% yield at 300°C, N2 pressure of 12 MPa, a holding time of 0 min, and a catalyst loading of 2.5 wt%. To reduce high viscosity and oxygen, nitrogen, and sulfur content, the primary oil was hydrotreated with a NiMo/Al2O3 catalyst at an initial H2 pressure of 10 MPa. At 350°C and holding time of 4 h, the upgraded oil, competitive with petroleum oil, was obtained in 43% yield, and its properties were: heating value, 46 MJ kg−1; oxygen content, 0 wt%; nitrogen content, 3.6 wt%; sulfur content, 0.07 wt%; and viscosity, 62 cP@50°C).

Analysis of Oil Derived from Liquefaction of Sewage Sludge

Abstract The oil separated by steam distillation after liquefaction of sewage sludge was fractionated to strongly acidic, weakly acidic, basic, and neutral fractions by acid-base extraction. The total recovery of fractions was 77%. Each fraction was analysed by g.c.-m.s., and 71 types of compound were identified with reasonable certainty. No strongly acidic fraction was obtained. The weakly acidic fraction, comprising 2% of the oil, was exclusively composed of phenolic compounds. The basic fraction, comprising 20% of the oil, was exclusively composed of pyridines, pyrazines, quinolines, amines and methylphenylacetamide. The neutral fraction, comprising 56% of the oil, was exclusively composed of aliphatic compounds, alicyclic compounds, alcohols, ketones, aromatic compounds, sulphur-containing compounds, nitrogen-containing compounds and oxygen-containing heterocyclic compounds.