An easy templateless method to synthesize porous carbon nanofibers (CNFs) having radially-oriented mesopores is reported, using selective gasification with nano-sized catalyst particles and hydrogen as the gasification reagent. The gasification generated pores whose size corresponds to that of the catalyst particle used for the drilling. The pores were formed along the graphitic layers, reflecting the structural alignment in the CNFs. The pore size and structure can be controlled by selection of catalyst and gasification conditions.

In the pretreatment of feeds for catalytic cracking and for HDA, the primary objective is to reduce the amount of organic sulfur and nitrogen compounds in the feedstock [Catal. Rev.-Sci. Eng. 36 (1994) 75] [1]. Organic nitrogen compounds have a significantly negative kinetic effect on hydrotreating reactions. The distribution of the organic nitrogen compounds in feed and hydrotreated products is discussed. Alkyl-substituted carbazoles are found to be the dominant and most refractive organic nitrogen compound in the feed. Our results show that indoles and quinolines are very reactive as compared with carbazoles. From the characterization of the pyrrole benzologues, it is concluded that the more the substituents, the lesser the reactivity. It is well known that conversion of organic sulfur occurs via two different mechanistic routes: the direct and the hydrogenation route [J. Catal. 61 (1981) 523; AIChE J. 27 (1981) 663; J. Catal. 97 (1986) 52; Catal. Today, in press; Polyhedron 16 (1997) 3213] [2], [3], [4], [5], [6]. The hydrogenation route converts the most refractive S-molecules and plays a very important role in the conversion of N-compounds. N-containing molecules often show a very low reactivity as compared with the analogous sulfur compounds. Several studies using model feedstocks show that nitrogen-containing molecules, and in particular, basic organic nitrogen compounds inhibit the HDS reaction [Appl. Catal. A 170 (1998) 1] [7]. In this study, real feed experiments have demonstrated that even though carbazoles are slow to react and are among the predominant N-compounds, it is the basic N-compounds that are the major inhibiting species in diesel fuels.

In this paper, we describe the investigation of chemical vapor deposition (CVD) of carbon from benzene and cyclohexane on a particular pitch-based active carbon fiber (ACF) at different deposition temperatures as a means of controlling the pore size of ACF in order to induce true molecular sieving capability and to discuss the mechanism of carbon deposition. This study showed that the specific temperature range 700-800 degrees C was very effective. In this range, deposition of amorphous carbon was restricted to the pore wall and became saturated at the level of 11% weight increase, as further deposition stopped. This treatment greatly enhanced the molecular sieve separation of CH4 from CO2. Reduction of pore size appeared to be limited by the thickness of the benzene plane, since no further carbon deposit took place when the pore could no longer accept benzene. Higher temperatures allowed deposition to occur on the outer surface of ACF, which plugged the pore completely on extended reaction time. Cyclohexane was found to be inferior to benzene as a carbon precursor, as it decomposed too rapidly in the gas phase at the temperature range used and precipitated the carbon plugging the pores. Thus, high molecular sieving selectivity was not obtained.

Model compound studies have shown that 1,2,3,4-tetrahydroquinoline is an exceptionally good coal solvent. In the pure compound, subbituminous coal conversion to THF-soluble products approaches 100% under relatively mild reaction conditions. The effectiveness of tetrahydroquinoline for coal conversion appears to be related to its concentration relative to coal. The unique behaviour of tetrahydroquinoline is ascribed to its being a highly active H-donor; the fact that it is regenerable under reaction conditions by the reaction of hydrogen and quinoline; and that its polarity allows penetration of the coal structure and aids in dispersion of the dissolved coal. It has been found that, during reaction with coal, tetrahydroquinoline and other nitrogen compounds undergo extensive condensation reactions which result in an increase in the nitrogen content of the high boiling and non-distillable liquefaction products.

The two-stage conversion of a subbituminous coal has been investigated using an autoclave reactor system. The overall performance of the reaction is found to be determined by the effectiveness of the first-stage operation and by the method of sequencing of the stages. The initial thermal products can undergo condensation reactions which render them unresponsive to subsequent catalytic conversion and which increase the light gas yield. This can occur during the first stage reaction, if there is limited capacity for free-radical stabilization, and upon storage and/or thermal cycling between stages. The latter effects are circumvented by operating the two stages in immediate sequence. Condensation is also reduced by increasing the solvent quality and the solvent:coal ratio. The presence of a catalyst during thermal decomposition of coal can greatly improve conversion and product stability even at short reaction time and can reduce constraints on solvent quality. The more feasible approaches to improving first-stage operation appear to be in controlling the solvent composition and in employing hydrogenation catalysts.

The liquefaction of a bituminous coal has been studied using distillate and non-distillable, coal-derived solvents. Different classes of solvent components can interact non-additively during reaction with coal to either promote or retard the process of coal dissolution. Above certain concentrations, polyfunctional compounds in heavy coal-derived liquids effect a measurable reduction in coal conversion and product selectivity by accentuating the degree of condensation reactions. Substantial removal of these compounds can be achieved by precipitation in a paraffinic solvent. Retrogressive reactions are reduced and positive synergistic interactions can be realized by the blending of heavy solvents with selected components, such as polycondensed aromatics, and with lower boiling, hydrogen-donor species.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Synthesis of Some Bicyclo[3.3.0]octane Derivatives1J. K. Stille, R. J. Sevenich, and D. D. WhitehurstCite this: J. Org. Chem. 1965, 30, 3, 938–940Publication Date (Print):March 1, 1965Publication History Published online1 May 2002Published inissue 1 March 1965https://pubs.acs.org/doi/10.1021/jo01014a506https://doi.org/10.1021/jo01014a506research-articleACS PublicationsRequest reuse permissionsArticle Views50Altmetric-Citations3LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOxirene. An Intermediate in the Peroxyacid Oxidation of AcetylenesJ. K. Stille and D. D. WhitehurstCite this: J. Am. Chem. Soc. 1964, 86, 22, 4871–4876Publication Date (Print):November 1, 1964Publication History Published online1 May 2002Published inissue 1 November 1964https://doi.org/10.1021/ja01076a029RIGHTS & PERMISSIONSArticle Views199Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (739 KB) Get e-Alerts Get e-Alerts