The process of converting methanol to hydrocarbons on the aluminosilicate zeolite HZSM-5 was originally developed as a route from natural gas to synthetic gasoline. Using other microporous catalysts that are selective for light olefins, methanol-to-olefin (MTO) catalysis may soon become central to the conversion of natural gas to polyolefins. The mechanism of methanol conversion proved to be an intellectually challenging problem; 25 years of fundamental study produced at least 20 distinct mechanisms, but most did not account for either the primary products or a kinetic induction period. Recent experimental and theoretical work has firmly established that methanol and dimethyl ether react on cyclic organic species contained in the cages or channels of the inorganic host. These organic reaction centers act as scaffolds for the assembly of light olefins so as to avoid the high high-energy intermediates required by all "direct" mechanisms. The rate of formation of the initial reaction centers, and hence the duration of the kinetic induction period, can be governed by impurity species. Secondary reactions of primary olefin products strongly reflect the topology and acid strength of the microporous catalyst. Reaction centers form continuously through some secondary pathways, and they age into polycyclic aromatic hydrocarbons, eventually deactivating the catalyst. It proves useful to consider each cage (or channel) with its included organic and inorganic species as a supramolecule that can react to form various species. This view allows us to identify structure-activity and structure selectivity relationships and to modify the catalyst with degrees of freedom that are more reminiscent of homogeneous catalysis than heterogeneous catalysis.

Methanol-to-olefin (MTO) conversion on microporous silico-aluminophosphates is particularly well-suited for the application of molecular-level concepts to the development of well-defined supported catalysts. The active site of a typical MTO catalyst is a nm-size inorganic cage with an essential organic component. Opportunities for altering the selectivity of such catalysts include tailoring the organic component and modification of the cage with additional inorganic material through ship-in-a-bottle synthesis. The latter possibility has already been realized experimentally by the development of a useful and practical phosphate-modified catalyst.

Using highly purified reagents and careful tests, we show that methanol and dimethyl ether are apparently unreactive on the two most important methanol-to-hydrocarbon catalysts, HZSM-5 and HSAPO-34. Thus, none of the "direct" mechanisms involving two to four carbon atoms in intermediates such as oxonium ylides, carbenes, carbocations, and free radicals are applicable. Only the "indirect" route (hydrocarbon pool) is an established mechanism for this chemistry. An active catalyst requires a hydrocarbon pool that typically begins with products from organic impurities in the feed, carrier gas, or the solid acid itself. Impurities may also play important roles in other reactions catalyzed by solid acids.

Pool view preferred: In agreement with recent theoretical work, a new line of experimental evidence was obtained in support of the controversial claim that direct mechanisms do not couple methanol to ethylene in the catalyzed methanol‐to‐olefin process. The results preclude carbene routes and oxonium ylide mechanisms, among others (see picture), in favor of the hydrocarbon pool mechanism.

Phosphorus modification of a HZSM-5 (MFI) zeolite by wet impregnation has long been known to decrease aromatic formation in methanol conversion chemistry. We prepared and studied a catalyst modified by introducing trimethylphosphine under reaction conditions followed by oxidation. Magic-angle spinning (MAS) NMR shows that extensive dealumination occurs, resulting in a catalyst with a much higher framework SiO2/Al2O3 ratio, as well as extraframework aluminum and approximately 1.4 equiv of entrained phosphoric acid (under working conditions) per aluminum. Upon dehydration or regeneration, the phosphoric acid is converted, reversibly, to entrained P4O10. The aromatic selectivity of the modified catalyst is significantly lower than that of an unmodified zeolite with a similar, increased framework SiO2/Al2O3 ratio. By comparing the rates of H/D exchange in propene under conditions similar to those in methanol conversion chemistry, we determined that the acid site strength is indistinguishable on modified and unmodified zeolites, and this is consistent with theoretical modeling. On the phosphorus-modified zeolite, the rate of propene oligomerization is greatly suppressed, suggesting that entrained phosphate is an impediment to sterically demanding reactions.

By anchoring metal complexes to supports, researchers have attempted to combine the high activity and selectivity of molecular homogeneous catalysis with the ease of separation and lack of corrosion of heterogeneous catalysis. However, the intrinsic nonuniformity of supports has limited attempts to make supported catalysts truly uniform. We report the synthesis and performance of such a catalyst, made from [Rh(C(2)H(4))(2)(CH(3)COCHCOCH(3))] and a crystalline support, dealuminated Y zeolite, giving {Rh(C(2)H(4))(2)} groups anchored by bonds to two zeolite oxygen ions, with the structure determined by extended X-ray absorption fine structure (EXAFS) spectroscopy and the uniformity of the supported complex demonstrated by (13)C NMR spectroscopy. When the ethylene ligands are replaced by acetylene, catalytic cyclotrimerization to benzene ensues. Characterizing the working catalyst, we observed evidence of intermediates in the catalytic cycle by NMR spectroscopy. Calculations at the level of density functional theory confirmed the structure of the as-synthesized supported metal complex determined by EXAFS spectroscopy. With this structure as an anchor, we used the computational results to elucidate the catalytic cycle (including transition states), finding results in agreement with the NMR spectra.

Background. While it is established that the incidence of cutaneous melanoma has risen over time in the United States, the incidence trend for mucosal melanoma of the head and neck (MMHN) is unknown. Methods. We used the Surveillance, Epidemiology, and End Results (SEER) database to determine incidence trends for MMHN from 1987 to 2009 in the United States. We determined annual percent change (APC) by weighted least squares and joinpoint regression analysis. Results. MMHN incidence increased from 1987 to 2009 (APC 2.4%; P < 0.01). Nasal cavity lesions increased in incidence (APC 2.7%; P < 0.01) over this duration, while the incidence of non-nasal cavity lesions remained stable. The highest rate of increase was in white females ages 55 to 84 (APC 5.1%; P = 0.01). Conclusions. The incidence of MMHN in the United States has been rising since 1987. This trend is driven primarily by increased incidence of nasal cavity melanomas.

BACKGROUND:The American Joint Commission on Cancer (AJCC) identifies five rare variants of prostate adenocarcinoma: mucinous, ductal, signet ring cell, adenosquamous and neuroendocrine including small cell. No prior study has comprehensively detailed incidence and outcomes for all AJCC variants of prostate cancer. METHODS: We used the Surveillance, Epidemiology and End Results (SEER) program to analyze prostate cancers diagnosed from 1973 to 2008. Cases of mucinous, ductal, signet ring cell, adenosquamous and neuroendocrine carcinoma were identified, along with cases of non-variant adenocarcinoma for comparison. Age-adjusted incidence rates (IRs) and overall survival (OS) were evaluated and stratified by race, age, stage and PSA. All IRs represent the number of cases per million people per year. RESULTS: Each variant is rare, with IRs between 0.03 (adenosquamous) and 0.61 (mucinous). There was a significant difference in incidence between Caucasian and African American patients with mucinous adenocarcinoma. Median OS varied ranged from 10.0 months in neuroendocrine carcinoma to 125.0 months in mucinous adenocarcinoma. In all, 5-year OS ranged from 12.6% in neuroendocrine carcinoma to 75.1% in mucinous adenocarcinoma. There was a significant difference in survival between Caucasian and African American patients for mucinous adenocarcinoma (median survival 144.0 vs 99.0 months, Po0.01). African American patients with mucinous adenocarcinoma also presented with more advanced stage disease compared with Caucasian patients. Multivariate analysis demonstrated that African American race was not associated with worse survival when corrected for stage. CONCLUSIONS: There are differences in IRs and OS among rare variants of prostate cancer. For mucinous adenocarcinoma, there are significant differences in incidence and survival between Caucasian and African American patients. These differences should be considered in clinical decision making for patients with these malignancies.