David C. Dayton

Design and operation of a pilot-scale catalytic biomass pyrolysis unit

RTI International is developing an advanced biofuels technology that integrates a catalytic biomass pyrolysis step and a hydroprocessing step to produce infrastructure-compatible biofuels. At the current stage of development, the catalytic biomass pyrolysis process is being scaled-up in a 1 tonne per day (1 TPD) pilot plant based on a single-loop transport reactor design with continuous catalyst circulation and regeneration. The chemistry of biomass pyrolysis is manipulated by the catalyst and by controlling the pyrolysis temperature, vapor residence time, and biomass-to-catalyst ratio. The pilot unit has been successfully operated with a novel catalyst that produces a bio-crude intermediate with 24 wt% oxygen. Product yields and composition in the pilot plant are consistent with results obtained in a laboratory-scale 2.54 cm diameter bubbling fluidized bed reactor. The overall mass balance was 93%, while the carbon closure was 83%.

Integration of catalytic fast pyrolysis and hydroprocessing: a pathway to refinery intermediates and “drop-in” fuels from biomass

Single-stage hydrotreating (HDT) of loblolly pine biocrude produced from catalytic pyrolysis was conducted to gain insight to HDT performance in terms of product yields, liquid product quality, and hydrogen consumption. Tests were performed with a sulfided HDT catalyst at three different conditions. The longest continuous time onstream operation (365 h) was achieved at an average bed temperature of 290 °C, 138 bar pressure, H2/oil ratio of 3300 Nl l−1, and a liquid hourly space velocity (LHSV) of 0.25 h−1. The average carbon yield of the HDT liquids were 77%, 83%, and 89% for experiments 1, 2, and 3, respectively. Also, the biocrude carbon that ended up in the gas phase varied between 4.3% and 8.9%. The carbon in the aqueous phase fraction was negligible—less than 0.5% of the biocrude carbon. The average hydrogen consumed ranged from 0.04 g to 0.07 g per 1 g of dry biocrude. The highest carbon content measured for the HDT liquid products from all three experiments was 87.13 wt% and the lowest was 79.03 wt%. GC-MS analysis suggests that the HDT product with oxygen content less than 5 wt% contained mainly naphthenic hydrocarbons. On the other hand, HDT products with oxygen content greater than 5 wt% contained a higher concentration of simple phenols and aromatic hydrocarbons (mono- and poly-). Catalyst deactivation was evident in the quality of the HDT liquid collected over time; the density and viscosity increased, the H/C ratio and carbon contents decreased; also, the gasoline fraction decreased while the gas oil fraction increased. The results from this work suggest that HDT of biocrude produced by catalytic biomass pyrolysis can be successfully upgraded into hydrocarbon liquid fuels without a stabilization step.

Reactive catalytic fast pyrolysis of biomass to produce high-quality bio-crude

Reactive catalytic fast pyrolysis (RCFP) of biomass with atmospheric pressure hydrogen was investigated in a lab-scale fluidized bed reactor with varying reaction conditions (temperature and hydrogen concentration) and catalysts. Presence of atmospheric hydrogen with candidate RCFP catalysts was found to improve the yield and quality of bio-crude and minimize the char and coke formation. A molybdenum-based catalyst was the most effective at hydrodeoxygenating biomass pyrolysis vapors to produce a hydrocarbon-rich bio-crude intermediate with low oxygen content (<10 wt%). Higher hydrogen concentration and moderate reaction temperature (450 °C) favored higher bio-crude yields and quality. A yield of 43.2 C% in the C4+ organic fraction with as low as 6.2 wt% oxygen in the liquid was obtained under optimized reaction conditions. The resulting bio-crude contained primarily aliphatic and aromatic hydrocarbons, with small amounts of simple ketones, furans, and phenols. Up to 41.5% carbon in the biomass feed was converted into gas and condensable hydrocarbons with 29.7% in the condensable C4+ fraction. The improved bio-crude quality is expected to be more compatible with existing petroleum refining infrastructure.

Production and distillative recovery of valuable lignin-derived products from biocrude

Value-added chemicals present in liquid products from direct liquefaction of biomass can be recovered as bioproducts in an integrated biorefinery to enhance the economic viability of biomass-to-liquid fuel technologies and afford a higher return on investment. In recent efforts, RTI International is exploring and developing processes that could be used to produce bioproducts in addition to liquid fuel from biocrude intermediates. The present study focused on the production and recovery of high-value lignin-derived compounds from biocrude. Catalytic pyrolysis with a nonzeolite, alumina-based catalyst was used to produce the biocrude from loblolly pine in RTIs 1-tonne per day pilot-scale plant. Distillation was evaluated as a potential separation method given that the biocrude is relatively thermally stable and distillable compared to raw pyrolysis oils. The distillation studies were performed with a laboratory distillation unit (PETRODIST 300 CC) and the biocrude was fractionated into four distillate cuts: cut 1 (IBP-110 °C), cut 2 (110–200 °C), cut 3 (200–300 °C), and cut 4 (300–400 °C). In a case study, cut 3 was distilled further to concentrate the lignin-derived chemicals boiling between 200 and 270 °C. The results showed that a biocrude containing about 10 wt% guaiacols could be concentrated to about 35 wt% of guaiacols (representing 75% recovery) in the first distillation step. The second distillation step increased the concentration of guaiacols to about 53 wt% (representing 80% recovery). These findings suggest that it is possible to isolate and concentrate the lignin-derived products using a distillation column with a number of plates/trays. The yields, physicochemical properties, and chemical composition of the fractions, as well as the overall distillation separation efficiency, are reported.

CHAPTER 5:Catalytic Biomass Pyrolysis with Reactive Gases

Recent research and development efforts are focused on: (1) developing catalytic processes to modify the chemical and physical properties of direct liquefaction bio-oil intermediates to better match petroleum processes for biofuel production; and (2) developing new processes and catalysts to upgrade bio-oils into biofuels. Techno-economic analyses of these pathways highlight the importance of overall product yield for economic viability of biofuels process options. The objective of this chapter is to provide an overview of recent developments in the basic scientific understanding of and technical developments in direct biomass liquefaction processes that use reactive gases, like hydrogen and carbon monoxide, in combination with selective hydrodeoxygenation catalysts to produce low-oxygen-containing bio-crude. A review of hydrodeoxygenation using model compounds with a variety of catalysts at a range of process conditions provides a mechanistic understanding of deoxygenation pathways. Similar studies using real biomass as a feedstock in micropyrolyzers or small laboratory reactors investigate the impact of reactive gases on bio-crude yields and quality.