The conversion of pine pyrolysis vapors over fixed beds of HZSM-5 catalyst was studied as a function of deactivation of the catalyst, presumably by coking.

Mouse embryonic stem cells (mESCs) cultured in the presence of LIF occupy a ground state with highly active pluripotency-associated transcriptional and epigenetic circuitry. However, ground state pluripotency in some inbred strain backgrounds is unstable in the absence of ERK1/2 and GSK3 inhibition. Using an unbiased genetic approach, we dissect the basis of this divergent response to extracellular cues by profiling gene expression and chromatin accessibility in 170 genetically heterogeneous mESCs. We map thousands of loci affecting chromatin accessibility and/or transcript abundance, including 10 QTL hotspots where genetic variation at a single locus coordinates the regulation of genes throughout the genome. For one hotspot, we identify a single enhancer variant $10 kb upstream of Lifr associated with chromatin accessibility and mediating a cascade of molecular events affecting pluripotency. We validate causation through reciprocal allele swaps, demonstrating the functional consequences of noncoding variation in gene regulatory networks that stabilize pluripotent states in vitro. ll

Rapid coking and catalyst deactivation are significant problems during catalytic fast pyrolysis of biomass. Cellulose and lignin were found to coke via different mechanisms, resulting in two distinct types of catalyst deactivation. Lignin pyrolysis vapors cause coke formation mainly by external surface coking without limiting access to the active acid sites in the microchannels. Lignin deactivates the surface cracking capability of ZSM-5, resulting in unreacted primary vapors passing through while maintaining aromatization reactions. Cellulose pyrolysis vapors generate coke mainly as an extension of the aromatization reactions on the acid sites, which leads to occlusion of the internal acid sites. This deactivates the upgrading reactions, resulting in decreased aromatics formation, generation of oxygenated intermediates and increased alkylation of 1-ring aromatics and reduced multi-ring aromatics selectivity. The results indicate that the decrease in aromatics formation observed during catalytic pyrolysis of biomass is primarily caused by the coke generated from the polysaccharide components.

Three HZSM-5 catalysts with different binders (alumina, silica, and clay) were evaluated for upgrading of pine pyrolysis vapors. All catalysts were based on the same HZSM-5 with silica to alumina molar ratio of 30. Experiments in micro-scale analytical Py-GCMS/FID showed that fresh catalysts with silica and clay produced predominantly aromatic hydrocarbons at similar carbon yields. The catalyst with alumina gave lower vapor yields and produced both hydrocarbons and partially deoxygenated products, in particular furans. The catalyst with alumina also gave higher coke yields and exhibited faster deactivation than the catalysts with clay and silica binders. The low hydrocarbon yields and coke formation were attributed to the acidic sites provided by alumina and blocking of the zeolite sites. The catalysts with silica and clay as binders were further tested in a 2-inch fluidized bed system for ex situ catalytic pyrolysis of pine. Similar oils were produced over both catalysts with carbon yields of approximately 23 % and oxygen contents of 20-21 %.

Metal-impregnated (Ni or Ga) ZSM-5 catalysts were studied for biomass pyrolysis vapor upgrading to produce hydrocarbons using three reactors constituting a 100 000× change in the amount of catalyst used in experiments. Catalysts were screened for pyrolysis vapor phase upgrading activity in two small-scale reactors: (i) a Pyroprobe with a 10 mg catalyst in a fixed bed and (ii) a fixed-bed reactor with 500 mg of catalyst. The best performing catalysts were then validated with a larger scale fluidized-bed reactor (using ∼1 kg of catalyst) that produced measurable quantities of bio-oil for analysis and evaluation of mass balances. Despite some inherent differences across the reactor systems (such as residence time, reactor type, analytical techniques, mode of catalyst and biomass feed) there was good agreement of reaction results for production of aromatic hydrocarbons, light gases, and coke deposition. Relative to ZSM-5, Ni or Ga addition to ZSM-5 increased production of fully deoxygenated aromatic hydrocarbons and light gases. In the fluidized bed reactor, Ga/ZSM-5 slightly enhanced carbon efficiency to condensed oil, which includes oxygenates in addition to aromatic hydrocarbons, and reduced oil oxygen content compared to ZSM-5. Ni/ZSM-5, while giving the highest yield of fully deoxygenated aromatic hydrocarbons, gave lower overall carbon efficiency to oil but with the lowest oxygen content. Reaction product analysis coupled with fresh and spent catalyst characterization indicated that the improved performance of Ni/ZSM-5 is related to decreasing deactivation by coking, which keeps the active acid sites accessible for the deoxygenation and aromatization reactions that produce fully deoxygenated aromatic hydrocarbons. The addition of Ga enhances the dehydrogenation activity of the catalyst, which leads to enhanced olefin formation and higher fully deoxygenated aromatic hydrocarbon yields compared to unmodified ZSM-5. Catalyst characterization by ammonia temperature programmed desorption, surface area measurements, and postreaction temperature-programmed oxidation (TPO) also showed that the metal-modified zeolites retained a greater percentage of their initial acidity and surface area, which was consistent between the reactor scales. These results demonstrate that the trends observed with smaller (milligram to gram) catalyst reactors are applicable to larger, more industrially relevant (kg) scales to help guide catalyst research toward application.

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LOTUS domains are helix-turn-helix protein folds identified in essential germline proteins and are conserved in prokaryotes and eukaryotes. Despite originally predicted as an RNA binding domain, its molecular binding activity towards RNA and protein is controversial. In particular, the most conserved binding property for the LOTUS domain family remains unknown. Here, we uncovered an unexpected specific interaction of LOTUS domains with G-rich RNA sequences. Intriguingly, LOTUS domains exhibit high affinity to RNA G-quadruplex tertiary structures implicated in diverse cellular processes including piRNA biogenesis. This novel LOTUS domain-RNA interaction is conserved in bacteria, plants and animals, comprising the most ancient binding feature of the LOTUS domain family. By contrast, LOTUS domains do not preferentially interact with DNA G-quadruplexes. We further show that a subset of LOTUS domains display both RNA and protein binding activities. These findings identify the LOTUS domain as a specialized RNA binding domain across phyla and underscore the molecular mechanism underlying the function of LOTUS domain-containing proteins in RNA metabolism and regulation.

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