Julia A. Valla

Mesostructured zeolite Y—high hydrothermal stability and superior FCC catalytic performance

Controlled mesoporosity is successfully introduced into zeolite Y crystals through a surfactant templating approach. The mesoporous zeolite shows superb hydrothermal stability in the resulting mesostructure, while retaining strong acidity. Fluid catalytic cracking catalysts made from the mesostructured Y zeolites demonstrate significant improvement in product selectivity as a result of reduced limitation in reactant and product diffusion.

Characteristics and origin of char and coke from fast and slow, catalytic and thermal pyrolysis of biomass and relevant model compounds

Char and coke from biomass catalytic pyrolysis have different origins. They cannot be lumped as one since they occupy different locations on the catalyst surface and, thus, contribute differently to catalyst deactivation. In this study, catalyst (ZSM-5) deactivation in the perspective of comparison of char and coke from pyrolysis of different biomass types is investigated. Pine sawdust, glucose, and cellulose are used as feedstocks in the pyrolysis experiments. Biomass char and coke samples produced via slow and fast, thermal and catalytic pyrolysis are characterized with respect to their overall content, oxidation reactivity, catalyst surface area, pore size distribution changes, bonding groups and their effect on catalyst performance. In particular, it is shown that char forms as an external layer on the catalyst surface and in its macropores, whereas coke forms inside the zeolite micropores via hydrogen transfer and addition reactions. The catalyst effect on glucose and pine slow catalytic pyrolysis is minor compared with that on cellulose slow catalytic pyrolysis, due to macropore blocking by char formation. In fast catalytic pyrolysis, catalyst deactivation is mainly attributed to micropore blocking by coke formation. Char and coke are shown to coexist on the catalyst surface after fast catalytic experiments, with the char content after glucose fast catalytic pyrolysis being 30 wt% of the total solid residue. The origins of char and coke in the cellulose, hemicellulose and lignin components of pine are identified and mechanisms for their formation are proposed.

Catalytic pyrolysis of miscanthus × giganteus in a spouted bed reactor.

A conical spouted bed reactor was designed and tested for fast catalytic pyrolysis of miscanthus × giganteus over Zeolite Socony Mobil-5 (ZSM-5) catalyst, in the temperature range of 400-600 °C and catalyst to biomass ratios 1:1-5:1. The effect of operating conditions on the lumped product distribution, bio-oil selectivity and gas composition was investigated. In particular, it was shown that higher temperature favors the production of gas and bio-oil aromatics and results in lower solid and liquid yields. Higher catalyst to biomass ratios increased the gas yield, at the expense of liquid and solid products, while enhancing aromatic selectivity. The separate catalytic effects of ZSM-5 catalyst and its Al2O3 support were studied. The support contributes to increased coke/char formation, due to the uncontrolled spatial distribution and activity of its alumina sites. The presence of ZSM-5 zeolite in the catalyst enhanced the production of aromatics due to its proper pore size distribution and activity.

Investigation of in situ and ex situ catalytic pyrolysis of miscanthus × giganteus using a PyGC–MS microsystem and comparison with a bench-scale spouted-bed reactor

The objective of the present work is to explore the particularities of a micro-scale experimental apparatus with regards to the study of catalytic fast pyrolysis (CFP) of biomass. In situ and ex situ CFP of miscanthus × giganteus were performed with ZSM-5 catalyst. Higher permanent gas yields and higher selectivity to aromatics in the bio-oil were observed from ex situ CFP, but higher bio-oil yields were recorded during in situ CFP. Solid yields were comparable across both configurations. The results from in situ and ex situ PyGC were also compared with the product yields and selectivities obtained using a bench-scale, spouted-bed reactor. The bio-oil composition and overall product distribution for the PyGC ex situ configuration more closely resembled that of the spouted-bed reactor. The coke/char from in situ CFP in the PyGC was very similar in nature to that obtained from the spouted-bed reactor.

The effect of temperature, heating rate, and ZSM-5 catalyst on the product selectivity of the fast pyrolysis of spent coffee grounds

Spent coffee grounds (SCG) are a continuously produced and abundant biomass resource that is rich in fixed carbon and underutilized. In this study, fast pyrolysis was employed as a method of upgrading this waste product into higher value chemicals and commodities. The effect of catalytic upgrading via a ZSM-5 catalyst on the pyrolysis product was investigated at two heating rates and three different pyrolysis temperatures. The ZSM-5 catalyst was explored as the means to increase the selectivity to deoxygenated olefins and aromatic products. The liquid products from the pyrolysis of SCG were predominantly fatty acids, linear hydrocarbons, furans, phenols, ketones, and aromatic hydrocarbons. The ZSM-5 catalyst was seen to decrease selectivity to linear hydrocarbons and furans, and enhance selectivity to aromatic hydrocarbons and CO. Increasing the pyrolysis temperature was seen to decrease selectivity to fatty acids, and increase selectivity to aromatic and linear hydrocarbons.

Methanol Production from Natural Gas

Carbon dioxide (CO2) is widely recognized as a major greenhouse gas contributing to global warming. This greenhouse gas is produced in large quantities worldwide by the heavy industry, such as steel production, chemical and petrochemical manufacturing, cement production etc., including power generation from fossil fuel. In the past decades, the continuous and rapid development of such industries has caused considerable concern. Awakening to the CO2-mediated global warming problem has led to several international forums on climate change called by the United Nations. As a result all developed countries are called to regulate the CO2 emissions in order to eliminate the long term risk associated with climate change. Such a stipulation may adversely affect the development of a large number of industries in the near future. [1, 2]

A Bottle-Around-a-Ship Method to generate Hollow Thin-Shelled Particles Containing Encapsulated Iron Species with Application to the Environmental Decontamination of Chlorinated Compounds

Thin-shelled hollow silica particles are synthesized using an aerosol-based process where the concentration of a silica precursor tetraethyl orthosilicate (TEOS) determines the shell thickness. The synthesis involves a novel concept of the salt bridging of an iron salt, FeCl3, to a cationic surfactant, cetyltrimethylammonium bromide (CTAB), which modulates the templating effect of the surfactant on silica porosity. The salt bridging leads to a sequestration of the surfactant in the interior of the droplet with the formation of a dense silica shell around the organic material. Subsequent calcination consistently results in hollow particles with encapsulated iron oxides. Control of the TEOS levels leads to the generation of ultrathin-shelled (∼10 nm) particles which become susceptible to rupture upon exposure to ultrasound. The dense silica shell that is formed is impervious to entry of chemical species. Mesoporosity is restored to the shell through desilication and reassembly, again using CTAB as a template. The mesoporous-shelled hollow particles show good reactivity toward the reductive dichlorination of trichloroethylene (TCE), indicating access of TCE to the particle interior. The ordered mesoporous thin-shelled particles containing active iron species are viable systems for chemical reaction and catalysis.