Michael J. Watson

Upgrading biomass pyrolysis vapors over β-zeolites: role of silica-to-alumina ratio

The conversion of biomass primary pyrolysis vapors over several β-zeolites with silica-to-alumina ratios (SAR) varying from 21 to 250 was carried out in a flow microreactor to investigate the effect of number of acid sites on product speciation and deactivation of the catalyst. Experiments were conducted using a horizontal fixed bed semi-batch reactor in which up to 40 discrete 50 mg boats of biomass were pyrolyzed and the vapors upgraded over 0.5 g of the catalyst. Products were measured with a molecular beam mass spectrometer (MBMS). These studies were complemented using a tandem micropyrolyzer connected to a GCMS (py-GCMS) for speciation and quantifying the products. In the py-GCMS experiments, several 0.5 mg loads of pine were pyrolyzed sequentially and the vapors upgraded over 4 mg of catalyst. In all of these experiments, real-time measurements of the products formed were conducted as the catalyst aged and deactivated during upgrading. The results from these experiments showed that: (1) fresh catalyst for β-zeolites with lower SAR (more acid sites) produced primarily aromatic hydrocarbons and olefins with no detectable oxygen-containing species; (2) a suite of oxygenated products was observed from fresh catalysts with high SAR (few acid sites), indicating that 0.5 g of these catalyst materials did not have sufficient acid sites to deoxygenate vapors produced from pyrolysis of 50 mg of pine. This suite of oxygen containing products consisted of furans, phenol and cresols. The amount of coke deposited on each catalyst and the yield of aromatic hydrocarbons increased with the number of acid sites. However, while the catalysts were active, the biomass selectivity towards coke and hydrocarbons remained essentially constant on the catalysts of varying SAR.

Cortical ependymoma or monomorphous angiocentric glioma

Ependymoma is the third most common childhood intracranial tumor after medulloblastoma and pilocytic astrocytoma. Most ependymomas occur in the posterior fossa and spinal cord but only five cases confined to the cerebral cortex have been reported. The current case is a 5‐year‐old boy with a somewhat ill‐defined cortical tumor diagnosed as pilocytic astrocytoma on biopsy, and treated with radiotherapy. Nine years later, resection of the essentially unaltered tumor was performed for treatment of intractable seizures. Histologically, the tumor had some areas with the typical appearance of ependymoma as well other areas which contained piloid cells. There was also evidence of focal infiltrative growth. These findings bore resemblance to a recently described entity monomorphous angiocentric glioma/angiocentric neuroepithelial tumor, which combines features of ependymoma with pilocytic and diffuse astrocytomas. Both cortical ependymomas and angiocentric monomorphous glioma/angiocentric neuroepithelial tumor appear to be low‐grade tumors although their rarity makes accurate prognosis problematic. The current case has features of both entities, suggesting they may be closely related.

Catalytic fast pyrolysis of biomass: the reactions of water and aromatic intermediates produces phenols

During catalytic upgrading over HZSM-5 of vapors from fast pyrolysis of biomass (ex situ CFP), water reacts with aromatic intermediates to form phenols that are then desorbed from the catalyst micropores and produced as products. We observe this reaction using real time measurement of products from neat CFP and with added steam. The reaction is confirmed when 18O-labeled water is used as the steam source and the labeled oxygen is identified in the phenol products. Furthermore, phenols are observed when cellulose pyrolysis vapors are reacted over the HZSM-5 catalyst in steam. This suggests that the phenols do not only arise from phenolic products formed during the pyrolysis of the lignin component of biomass; phenols are also formed by reaction of water molecules with aromatic intermediates formed during the transformation of all of the pyrolysis products. Water formation during biomass pyrolysis is involved in this reaction and leads to the common observation of phenols in products from neat CFP. Steam also reduces the formation of non-reactive carbon in the zeolite catalysts and decreases the rate of deactivation and the amount of measured “coke” on the catalyst. These CFP results were obtained in a flow microreactor coupled to a molecular beam mass spectrometer (MBMS), which allowed for real-time measurement of products and facilitated determination of the impact of steam during catalytic upgrading, complemented by a tandem micropyrolyzer connected to a GCMS for identification of the products.

Continuous catalytic upgrading of ethanol to n-butanol and >C4 products over Cu/CeO2 catalysts in supercritical CO2

n-Butanol (BuOH) often has superior properties as a bio-fuel compared to ethanol (EtOH). However finding sustainable sources of BuOH is proving difficult. In this paper, direct production of BuOH from EtOH is compared over custom-synthesized six Cu catalysts, supported on different solid acids. These catalysts were tested in a continuous flow supercritical CO2 (scCO2) reactor, and were found to catalyse the dehydrogenation, aldol condensation and hydrogenation steps of the so-called Guerbet reaction converting EtOH to BuOH. BuOH yields and selectivities were significantly different over the four catalysts. Cu on high surface area CeO2 showed the best activity for BuOH formation, with yields above 30% achieved with good selectivity. In addition high pressure CO2 is shown to have a positive effect on the reaction, possibly due to the redox cycle of Ce2O3 and CeO2.

Halogen exchange reactions for CFC alternatives.. The behaviour of fluorine-18 labelled hydrogen fluoride towards prefluorinated chromia containing nickel(II) or zinc(II)

Highly active catalysts are required for the conversion of CF3CH2Cl to the CFC-alternative refrigerant, CF3CH2F, by HF vapour under heterogeneous conditions. Chromia impregnated with a very low level of zinc(II) is a superior catalyst precursor to chromia alone. The behaviour of prefluorinated chromia and prefluorinated chromia containing zinc(II) or nickel(II) towards fluorine-18 labelled HF indicates that two types of labile surface fluoride are present, only one of which is catalytically active. Proposals are made to account for the role of ZnII and NiII.

Visualisation of single atom dynamics in water gas shift reaction for hydrogen generation

The water gas shift (WGS) reaction, CO + H2O → CO2 + H2, is the basis of heterogeneous catalysis important in the generation of clean hydrogen energy for fuel cells, transportation fuels and in ammonia manufacture. Ceria supported gold and related nanoparticles are potentially viable catalysts for the low temperature WGS reaction. The WGS catalytic reaction is a dynamic process and takes place on the solid catalyst surface at the atomic level. The current understanding of the reaction is inferred from studies of static catalysts and from indirect chemical studies without single atom sensitivity. Therefore the nature of dynamic atomic processes in the WGS reaction has remained inaccessible. Since the catalyst reaction site and atomic processes by which it activates and deactivates, change both in magnitude and mechanism with the reaction environment it is of fundamental importance to visualise the dynamic catalyst at the atomic level in WGS (CO + water mixture) environments, in real time. Novel environmental (scanning) transmission electron microscope with singe atom resolution is used herein to directly visualise and characterise, in real time, evolving atomic structures and processes in practical gold/ceria catalysts in controlled WGS environments. The in situ observations in WGS have revealed the formation of clusters of only a few gold atoms resulting from single atom dynamics and the catalytic effect of low coordination surface sites. The new insights have important implications for applications of nanoparticles in chemical process technologies including for transportation fuels and emission control.

Improving biomass pyrolysis economics by integrating vapor and liquid phase upgrading

Partial deoxygenation of bio-oil by catalytic fast pyrolysis with subsequent coupling and hydrotreating can lead to improved economics and will aid commercial deployment of pyrolytic conversion of biomass technologies. Biomass pyrolysis efficiently depolymerizes and deconstructs solid plant matter into carbonaceous molecules that, upon catalytic upgrading, can be used for fuels and chemicals. Upgrading strategies include catalytic deoxygenation of the vapors before they are condensed (in situ and ex situ catalytic fast pyrolysis), or hydrotreating following condensation of the bio-oil. In general, deoxygenation carbon efficiencies, one of the most important cost drivers, are typically higher for hydrotreating when compared to catalytic fast pyrolysis alone. However, using catalytic fast pyrolysis as the primary conversion step can benefit the entire process chain by: (1) reducing the reactivity of the bio-oil, thereby mitigating issues with aging and transport and eliminating need for multi-stage hydroprocessing configurations; (2) producing a bio-oil that can be fractionated through distillation, which could lead to more efficient use of hydrogen during hydrotreating and facilitate integration in existing petroleum refineries; and (3) allowing for the separation of the aqueous phase. In this perspective, we investigate in detail a combination of these approaches, where some oxygen is removed during catalytic fast pyrolysis and the remainder removed by downstream hydrotreating, accompanied by carbon–carbon coupling reactions in either the vapor or liquid phase to maximize carbon efficiency toward value-driven products (e.g. fuels or chemicals). The economic impact of partial deoxygenation by catalytic fast pyrolysis will be explored in the context of an integrated two-stage process. Finally, improving the overall pyrolysis-based biorefinery economics by inclusion of production of high-value co-products will be examined.

Renewable acrylonitrile production

A sweet source to make acrylonitrile Much of the attention directed toward displacing petroleum feedstocks with biomass has focused on fuels. However, there are also numerous opportunities in commodity chemical production. One such candidate is acrylonitrile, a precursor to a wide variety of plastics and fibers that is currently derived from propylene. Karp et al. efficiently manufactured this compound from an ester (ethyl 3-hydroxypropanoate) that can be sourced renewably from sugars. The process relies on inexpensive titania as a catalyst and avoids the side production of cyanide that accompanies propylene oxidation. Science, this issue p. 1307 Titania catalyzes efficient production of a commodity chemical using an ester sourced from sugars. Acrylonitrile (ACN) is a petroleum-derived compound used in resins, polymers, acrylics, and carbon fiber. We present a process for renewable ACN production using 3-hydroxypropionic acid (3-HP), which can be produced microbially from sugars. The process achieves ACN molar yields exceeding 90% from ethyl 3-hydroxypropanoate (ethyl 3-HP) via dehydration and nitrilation with ammonia over an inexpensive titanium dioxide solid acid catalyst. We further describe an integrated process modeled at scale that is based on this chemistry and achieves near-quantitative ACN yields (98 ± 2%) from ethyl acrylate. This endothermic approach eliminates runaway reaction hazards and achieves higher yields than the standard propylene ammoxidation process. Avoidance of hydrogen cyanide as a by-product also improves process safety and mitigates product handling requirements.

Tracking the structural changes in pure and heteroatom substituted aluminophosphate, AIPO-18, using synchrotron based X-ray diffraction techniques

We report the structural changes that occur during the thermal removal of organic template molecules that occlude the pores of small pore nanoporous zeolitic solids, AlPO-18, SAPO-18, CoAlPO-18, ZnAlPO-18 and CoSAPO-18. The calcination process is a necessary step in the formation of active catalysts. The studies performed using time-resolved High Resolution Powder Diffraction (HRPD) and High Energy X-ray Diffraction (HEXRD) techniques at various temperatures reveal that changes that take place are dependent on the type of heteroatom present in the nanoporous solids. While time-resolved HRPD shows clear changes in lattice parameters during the removal of physisorbed water molecules and subsequent removal of the organic template, HEXRD data show changes in various near neighbour distances in AlPO-18, SAPO-18, CoAlPO-18, CoSAPO-18 and ZnAlPO-18 during the calcination process. In particular HEXRD reveals the presence of water molecules coordinated to Al(III) ions in the as-synthesised materials. Upon removal of the template and water, these solids show contraction in the cell volume at elevated temperatures while first and second neighbour distances remained almost unchanged.

Far-Infrared Sounding of the Troposphere: Rational and the FIRST Instrument

The FIRST project shows the capabilities of an imaging FTS that covers the important long wavelength portion of the OLR. Here we describe the motivation behind the project, the prototype initial instrument, and results.