Patrick A. Johnston

Soy-castor oil based polyols prepared using a solvent-free and catalyst-free method and polyurethanes therefrom

Bio-based polyols from epoxidized soybean oil and castor oil fatty acid were developed using an environmentally friendly, solvent-free/catalyst-free method. The effects of the molar ratios of the carboxyl to the epoxy groups, reaction time, and reaction temperature on the polyols’ structures were systematically studied. Subsequently, polyurethane films were prepared from these green polyols. Properties of the new, soy-castor oil based polyurethane films were compared with two other polyurethane films prepared from castor oil and methoxylated soybean oil polyol, respectively. Thermal and mechanical tests showed that the polyurethane films prepared from the new polyols exhibited higher glass transition temperatures, tensile strength, Youngs modulus, and thermal stability because of the higher degree of cross-linking in the new polyols. Moreover, the novel polyols, prepared using the solvent-free and catalyst-free synthetic route, were 100% bio-based and facilitate a more environmentally friendly and economical process than conventional soy-based polyols used for polyurethane production.

Comparison of in-situ and ex-situ catalytic pyrolysis in a micro-reactor system.

In this study, we compared ex-situ catalytic pyrolysis (CP) and in-situ CP of hybrid poplar in a micro-reactor system. When both pyrolysis and catalysis were performed at 700 °C, the carbon yield of olefins was greater for ex-situ CP than for in-situ CP (17.4% vs. 5.4%). On the other hand, in-situ CP produced more aromatic hydrocarbons than ex-situ CP (26.1% vs. 18.9%). The remarkably high yield of olefins from ex-situ CP indicates the potential of exploiting the process to preferentially produce olefins as a primary product from biomass, with aromatics being the secondary products. The carbon yield of carbonaceous residues from ex-situ CP was 18.6% compared to 31.3% for in-situ CP. Substantial carbon was deposited as char during ex-situ CP, which could be easily recovered as by-product, simplifying catalyst regeneration. The effects of catalyst loading, pyrolysis temperature and catalysis temperature on product distributions for ex-situ CP were also investigated. Our results showed that catalyst temperature strongly affected product distribution. While high catalyst temperature enhanced both olefin and aromatic production, yield of olefin increased to a greater extent than did aromatics. Neither pyrolysis temperature nor catalyst loadings had significant effect on product distribution for ex-situ CP.

Continuous production of sugars from pyrolysis of acid-infused lignocellulosic biomass

Although pyrolysis of carbohydrate-rich biomass should theoretically yield large amounts of sugar, the presence of alkali and alkaline earth metals (AAEMs) in most biomass prevents this from happening. Even in small amounts, AAEM strongly catalyzes the fragmentation of holocellulose to light oxygenates compared to the thermally-induced breaking of glycosidic bonds that yield anhydrosugars. The concept of AAEM passivation, by which the catalytic activity of AAEMs can be suppressed to enhance thermal depolymerization of lignocellulose to sugars, has been previously established at the microgram scale using batch reactors. The feasibility of increasing sugar yield via AAEM passivation has not been previously demonstrated at the kilogram scale in a continuous flow reactor. The goal of this research is to demonstrate the enhanced production of sugars from AAEM passivated feedstocks in a continuous auger pyrolyzer at the kilogram scale. Alkali and alkaline earth metal passivation prior to pyrolysis increased total sugars from red oak by 105% compared to conventional pyrolysis, increasing from 7.8 wt% to 15.9 wt% of feedstock. Light oxygenates and non-condensable gases (NCGs) simultaneously decreased 45%, from 27.1 wt% to 14.7 wt% of feedstock as a result of AAEM passivation. Similarly, AAEM passivation of switchgrass increased total sugars by 259%, from 4.5 wt% to 16.2 wt% of feedstock, while the light oxygenates and NCGs decreased by 48%, from 20.0 wt% to 10.5 wt% of feedstock. An undesirable outcome of AAEM passivation was an increase in char production, increasing by 65% and 30% for pyrolysis of red oak and switchgrass, respectively. Loss of lignin-derived phenolic compounds from the bio-oil can explain 67% and 38% of the increase in char for red oak and switchgrass, respectively. The remaining 33% char increase for red oak (3.1 wt% char) and 62% char increase for switchgrass (4.0 wt% char) appear to be from carbonization of sugars released during pyrolysis of acid-infused biomass.

Overliming detoxification of pyrolytic sugar syrup for direct fermentation of levoglucosan to ethanol.

The application of pyrolytic sugars for biofuel production through fermentation is challenged by inhibitory contaminant compounds. Inhibition is so severe that only 0.25% sugar syrup can be used. In this study, overliming was tested as a simple detoxification method, using the Escherichia coli KO11+ lgk to directly convert levoglucosan into ethanol. After treatment with at least 14.8 g/L of Ca(OH)2, fermentation with 2% (w/v) pyrolytic sugar syrup was observed with no inhibition of ethanol production. Further investigation of treatment time and temperature showed that 8-16 h of treatment at 20°C, and 1-4 h of treatment at 60°C are necessary to obtain consistent ethanol production. The samples treated with 18.5 g/L Ca(OH)2 at 60°C for 4 h showed no inhibition at 2.5%. Multiple contaminants removed by the overliming treatment were identified. This study demonstrates that overliming is a promising method for detoxification of pyrolytic sugars for fermentation.

Utilization of acetic acid-rich pyrolytic bio-oil by microalga Chlamydomonas reinhardtii: Reducing bio-oil toxicity and enhancing algal toxicity tolerance

This work was to utilize acetic acid contained in bio-oil for growth and lipid production of the microalga Chlamydomonas reinhardtii. The acetic acid-rich bio-oil fraction derived from fast pyrolysis of softwood contained 26% (w/w) acetic acid, formic acid, methanol, furfural, acetol, and phenolics as identified compounds, and 13% (w/w) unidentified compounds. Among those identified compounds, phenolics were most inhibitory to algal growth, followed by furfural and acetol. To enhance the fermentability of the bio-oil fraction, activated carbon was used to reduce the toxicity of the bio-oil, while metabolic evolution was used to enhance the toxicity tolerance of the microalgae. Combining activated carbon treatment and using evolved algal strain resulted in significant algal growth improvement. The results collectively showed that fast pyrolysis-fermentation process was a viable approach for converting biomass into fuels and chemicals.

Analysis of trace contaminants in hot gas streams using time-weighted average solid-phase microextraction: Proof of concept

Time-weighted average (TWA) passive sampling using solid-phase microextraction (SPME) and gas chromatography was investigated as a new method of collecting, identifying and quantifying contaminants in process gas streams. Unlike previous TWA-SPME techniques using the retracted fiber configuration (fiber within needle) to monitor ambient conditions or relatively stagnant gases, this method was developed for fast-moving process gas streams at temperatures approaching 300 °C. The goal was to develop a consistent and reliable method of analyzing low concentrations of contaminants in hot gas streams without performing time-consuming exhaustive extraction with a slipstream. This work in particular aims to quantify trace tar compounds found in a syngas stream generated from biomass gasification. This paper evaluates the concept of retracted SPME at high temperatures by testing the three essential requirements for TWA passive sampling: (1) zero-sink assumption, (2) consistent and reliable response by the sampling device to changing concentrations, and (3) equal concentrations in the bulk gas stream relative to the face of the fiber syringe opening. Results indicated the method can accurately predict gas stream concentrations at elevated temperatures. Evidence was also discovered to validate the existence of a second boundary layer within the fiber during the adsorption/absorption process. This limits the technique to operating within reasonable mass loadings and loading rates, established by appropriate sampling depths and times for concentrations of interest. A limit of quantification for the benzene model tar system was estimated at 0.02 g m(-3) (8 ppm) with a limit of detection of 0.5 mg m(-3) (200 ppb). Using the appropriate conditions, the technique was applied to a pilot-scale fluidized-bed gasifier to verify its feasibility. Results from this test were in good agreement with literature and prior pilot plant operation, indicating the new method can measure low concentrations of tar in gasification streams.

Quantitation of Sugar Content in Pyrolysis Liquids after Acid Hydrolysis Using High-Performance Liquid Chromatography without Neutralization

A rapid method for the quantitation of total sugars in pyrolysis liquids using high-performance liquid chromatography (HPLC) was developed. The method avoids the tedious and time-consuming sample preparation required by current analytical methods. It is possible to directly analyze hydrolyzed pyrolysis liquids, bypassing the neutralization step usually required in determination of total sugars. A comparison with traditional methods was used to determine the validity of the results. The calibration curve coefficient of determination on all standard compounds was >0.999 using a refractive index detector. The relative standard deviation for the new method was 1.13%. The spiked sugar recoveries on the pyrolysis liquid samples were between 104 and 105%. The research demonstrates that it is possible to obtain excellent accuracy and efficiency using HPLC to quantitate glucose after acid hydrolysis of polymeric and oligomeric sugars found in fast pyrolysis bio-oils without neutralization.

Process Development Unit for Integrated Studies of Syngas Cleaning

Gasification is among the most prominent thermochemical technologies for converting biomass into renewable fuels and chemicals. Raw syngas from biomass gasification contains several contaminates that must be removed before further processing or utilization. The objective of this research is to develop a process development unit suitable for integrated studies of gas cleaning, including removal of tars, hydrogen chloride (HCl), ammonia (NH3), and hydrogen sulfide (H2S). The approach to this project eliminates costly and hazardous waste streams that are sometimes associated with conventional gas stream clean-up. The tars and particulates are removed with heavy gas oil, which can then serve as additional feedstock in industrial refineries. Hydrogen sulfide is removed using hot fixed-bed adsorption. Water scrubbing is used to remove remaining NH3 and HCl. A final guard bed ensures residual contaminants reach target levels of 0.01g/m3 tar, 20 ppb sulfur, 2 ppb chlorine, 1 ppm ammonia and undetectable particulate matter. The process development unit constructed at Iowa State University employs a 20kg/h steam/oxygen gasification reactor to provide slightly pressurized (~15psig) syngas to the cleaning operations. Comprehensive on-line gas analysis is used to determine contaminant removal efficiency of individual cleanup stages.