Petros A. Pilavachi

In-situ upgrading of biomass pyrolysis vapors: Catalyst screening on a fixed bed reactor

In-situ catalytic upgrading of biomass fast pyrolysis vapors was performed in a fixed bed bench-scale reactor at 500°C, for catalyst screening purposes. The catalytic materials tested include a commercial equilibrium FCC catalyst (E-cat), various commercial ZSM-5 formulations, magnesium oxide and alumina materials with varying specific surface areas, nickel monoxide, zirconia/titania, tetragonal zirconia, titania and silica alumina. The bio-oil was characterized measuring its water content, the carbon-hydrogen-oxygen (by difference) content and the chemical composition of its organic fraction. Each catalytic material displayed different catalytic effects. High surface area alumina catalysts displayed the highest selectivity towards hydrocarbons, yielding however low organic liquid products. Zirconia/titania exhibited good selectivity towards desired compounds, yielding higher organic liquid product than the alumina catalysts. The ZSM-5 formulation with the highest surface area displayed the most balanced performance having a moderate selectivity towards hydrocarbons, reducing undesirable compounds and producing organic liquid products at acceptable yields.

Hydrotreating of waste cooking oil for biodiesel production. Part I: Effect of temperature on product yields and heteroatom removal.

Hydrotreating of waste cooking oil (WCO) was studied as a process for biofuels production. The hydrotreatment temperature is the most dominant operating parameter which defines catalyst performance as well as catalyst life. In this analysis, a hydrotreating temperature range of 330-398 degrees C was explored via a series of five experiments (330, 350, 370, 385 and 398 degrees C). Several parameters were considered for evaluating the effect of temperature including product yields, conversion, selectivity (diesel and gasoline), heteroatom removal (sulfur, nitrogen and oxygen) and saturation of double bonds. For all experiments the same commercial hydrotreating catalyst was utilized, while the remaining operating parameters were constant (pressure=1200 psig, LHSV=1.0 h(-1), H(2)/oil ratio=4000 scfb, liquid feed=0.33 ml/min and gas feed=0.4 scfh). It was observed that higher reactor temperatures are more attractive when gasoline production is of interest, while lower reaction temperatures are more suitable when diesel production is more important.

Catalyst hydrothermal deactivation and metal contamination during the in situ catalytic pyrolysis of biomass

Lignocellulosic biomass contains small amounts of alkali and alkaline earth metals, which may volatilize during the in situ catalytic pyrolysis of biomass and deposit on the catalyst, affecting its properties. In addition, due to the presence of steam in the process and exposure of the catalyst to high temperatures, hydrothermal deactivation also plays a key role to the catalysts life span. In this work we studied the effect of hydrothermal deactivation and deactivation by metal contamination of commercial ZSM-5 zeolite based catalyst formulations using two techniques. In the first technique, biomass metal nitrates were spray impregnated on the catalyst at different levels, followed by hydrothermal deactivation of the samples and characterization. In the second technique, hydrothermal deactivation and metal contamination were decoupled by using a hydrothermally stable ZSM-5 sample as a parent material for the preparation of catalyst samples that were exposed to different biomass amounts by carrying out biomass catalytic pyrolysis reaction–regeneration cycles in a bubbling fluidized bed reactor. During spray impregnation, the different metals accumulated on the catalyst at the same rate and increasing metal loading resulted in gradual loss of the surface area and pore volume of the catalyst, eventually leading to complete destruction of the zeolite after a certain threshold. During catalytic pyrolysis however, the biomass metals accumulated at different rates. Potassium accumulated very selectively on the catalyst, while sodium and calcium were less selective. Accumulation of magnesium and iron was not found to increase with increasing exposure to biomass. Cross section examination of the catalyst particles revealed that potassium was deposited evenly throughout the particles, while magnesium and calcium were only detected on the outer surface. Evaluation of the catalyst in pyrolysis tests showed that the presence of biomass metals on the catalyst altered the catalysts functionality, likely by introduction of some basic sites, which led to the deterioration of its catalytic performance.