Yoshio Uemichi

Degradation of polyethylene to aromatic hydrocarbons over metal-supported activated carbon catalysts

Abstract The degradation of polyethylene to aromatic hydrocarbons on metal-supported activated carbon catalysts has been studied. The effect of the added metals was investigated in detail. Activated carbon impregnated with Pt, Fe, Mo, Zn, Co, Ni or Cu showed a higher catalytic activity for the formation of aromatics than that of the metal-free catalyst. The first three metals were the most effective. It was also found that the catalytic effects of Pt and Fe on the aromatic yield depended strongly on the support: activated carbon was most efficient, and silica-alumina and alumina were much less effective. Two active sites with different functions seemed to take part in the dehydrocyclization step involved in the degradation reaction. One was activated carbon surface sites, on which the abstraction of hydrogen atoms occurred predominantly. The other was metal sites which catalyzed the desorption of the hydrogen atoms. The desorption was a slow step of the dehydrocyclization on activated carbon, but was enhanced by the added metals, resulting in an increase in the yield of aromatics.

Degradation of polypropylene to aromatic hydrocarbons over Pt- and Fe-containing activated carbon catalysts

Abstract The degradation of polypropylene to aromatic hydrocarbons over activated carbon catalysts containing Pt and Fe has been investigated. The results obtained were compared with those for the degradation of polyethylene. The addition of Pt or Fe to activated carbon resulted in an increase in the yield of aromatics from polypropylene. However, the increase was less than that from polyethylene. Pt metal was more effective than Fe only when the reaction conditions involved a longer contact time. The formation of aromatics was explained by essentially the same mechanism as the case of polyethylene, in which an influence of methyl branching of polypropylene on the aromatization yield and a difference in catalytic activity of the catalysts containing Pt and Fe for a ring expansion reaction were considered.

Gas chromatographic determination of the products of degradation of polyethylene over a silica—alumina catalyst

Abstract The degradation products of polyethylene, especially a liquid fraction, formed over a silica-alumina catalyst were analyzed by glass capillary column gas chromatography. The liquid fraction contains large amounts of the same isoalkanes and aromatics as are present in the gasoline fraction of petroleum. Most of the isoalkanes are monobranched with a methyl group at the 2- or 3-position. The aromatics consist mainly of those with one or more methyl groups and are produced highly selectively at carbon numbers higher than 7. The degradation products are distributed in a narrow range of carbon number compared with those obtained by thermal degradation. The relative yield Of C 3 C- 5 fractions was greater than 70 wt. % at the initial stage of the reaction. Isomerization, aromatization and hydrogen transfer reactions seem to play an important role in the secondary degradation of the primary products of polyethylene.

Activity enhancement of mesoporous silica (FSM-16) by modification with iron (II) sulphate for the isomerization of 1-butene

Abstract The catalytic activity of mesoporous silica (FSM-16) for the isomerization of 1-butene was remarkably enhanced by modification with iron (II) sulphate. The enhancement of the activity of FSM-16 was attributed to the transformation of the silanol groups on FSM-16 into Bronsted acid sites by the inductive effect of FeSO4 and/or sulphate species formed by the decomposition of FeSO4.

Chemical recycling of poly(ethylene) by catalytic degradation into aromatic hydrocarbons using H-Ga-silicate

H-Ga-silicate exhibits excellent catalytic activity towards the formation of aromatic hydrocarbons, mainly benzene, toluene and xylenes (BTX), in the degradation of poly(ethylene), indicating its high potential as a catalyst for the advanced chemical recycling of polyolefins.

Promotive effect of H2S for hydrocarbon conversions over Na zeolites

H2S promotes remarkably the catalytic cracking of n-butane and the isomerization of cyclopropane over various Na zeolites, presumably because of the formation of new Brönsted acid sites on catalyst surface.AbstractH2S сильно промотирует каталитический крекинг н-бутана и изомеризацию циклопропана на различных Na-цеолитах, вероятно, вследствие образования новых брёнстэдовских кислых центров на поверхности катализатора.

Effects of Support on Formation of Active Sites and Hydrodesulfurization Activity of Rhodium Phosphide Catalyst

リン化ロジウム（Rh2P）触媒の活性点形成とその水素化脱硫（HDS）活性に対する担体の影響について検討した。担体には金属酸化物（MOx: SiO2，Al2O3，TiO2，MgOおよびZrO2）を用いた。いずれの担体の場合でも担持ロジウム－リン（Rh–P）触媒を水素還元するとRh2Pが生成した。一方，Rh2Pの生成温度は担体により異なった。このRh–P触媒のHDS活性は還元温度によって大きく変化した。最適な温度で還元したRh–P/MOx触媒のHDS活性の序列はSiO2～TiO2～Al2O3＞MgO＞ZrO2となった。また，還元温度を上昇させるとRh–P/MOx触媒のTOFは増加し，これはRh2Pが生成したためであることが分かった。Rh–P/MOx触媒のTOFの序列はTiO2＞ZrO2＞Al2O3＞SiO2＞MgOとなり，これはチオフェン転化率の序列とは一致しなかった。Rh–P/TiO2触媒が高いTOFを示した原因としては，部分的に硫化されたTiO2の生成が挙げられる。一方，Rh–P/MgO触媒のTOFが低かったのは，MgOは塩基性担体であり耐硫黄性が低かったためと考えられる。

Catalytic performance of noble metals supported on Al2O3-modified MCM-41 for thiophene hydrodesulfurization

Pt/4wt%Al2O3-MCM-41 catalyst showed high and stable activity for hydrodesulfurization of thiophene at 350°C and this activity was higher than that of commercial CoMo/Al2O3 hydrodesulfurization catalyst. Pt/4wt%Al2O3-MCM-41 catalyst has high hydrogenating ability in the hydrodesulfurization of thiophene. The Bronsted acid sites of Al2O3-MCM-41 and the spillover hydrogen formed on Pt particle in Pt/Al2O3-MCM-41 catalyst play an important role for the hydrodesulfurization of thiophene.

Catalytic performance of mesoporous silica SBA-15-supported noble metals for thiophene hydrodesulfurization

The Pt/AlSBA-15 catalyst showed high and stable catalytic activity for the hydrodesulfurization of thiophene at 350°C and this activity was higher than those of Pt/SBA-15 and commercial CoMo/Al2O3 catalysts. The Pt/AlSBA-15 catalyst has high sulfur-tolerant property toward hydrogen sulfide formed in hydrodesulfurization of thiophene. The Broensted acid sites of AlSBA-15 and the spillover hydrogen formed on Pt particle in Pt/AlSBA-15 catalyst play an important roles for the hydrodesulfurization of thiophene.

26-P-07-Hydrodesulfurization of benzothiophene over noble metals supported on mesoporous silica MCM-41

Publisher Summary This chapter discusses the hydrodesulfurization of benzothiophene over noble metals supported on mesoporous silica MCM-41. The Pt/MCM-41 catalyst shows high and stable catalytic activity for the hydrodesulfurization of benzothiophene at 350°C, and this activity is higher than that of commercial cobalt molybdenum/ alumina (CoMo/A1 2 O 3 ) catalyst. The Pt/MCM-41 catalyst has high sulfur-tolerant property toward hydrogen sulfide formed in the hydrodesulfurization of benzothiophene. The silanol group (Si–OH) of MCM-41 and the spillover hydrogen formed on platinum (Pt) particle in Pt/MCM-41 catalyst play important roles in the hydrodesulfurization of benzothiophene. Pt/MCM-41 might be a promising new hydrodesulfurization catalyst for bulky organic sulfur compounds in the petroleum feedstocks.