A preparation method of a polyester is provided. The method includes the following steps: allowing a raw material including a diacid and a diol to contact a monoclinic nano-TiO2 (namely, TiO2(B)) catalyst, and conducting an esterification reaction and a polycondensation reaction sequentially to obtain the polyester. The method can efficiently catalyze the synthesis of the polyester and avoid from yellowing of the polyester. Meanwhile, nano-TiO.sub.2(B) is polymerized in situ in the polyester, such that a structure of nano-TiO.sub.2(B) can adjust the structure and properties of a polyester matrix and effectively improve the mechanical, thermal, and barrier properties of the polyester.

A preparation method of a polyester is provided. The method includes the following steps: allowing a raw material including a diacid and a diol to contact a monoclinic nano-TiO2 (namely, TiO2(B)) catalyst, and conducting an esterification reaction and a polycondensation reaction sequentially to obtain the polyester. The method can efficiently catalyze the synthesis of the polyester and avoid from yellowing of the polyester. Meanwhile, nano-TiO.sub.2(B) is polymerized in situ in the polyester, such that a structure of nano-TiO.sub.2(B) can adjust the structure and properties of a polyester matrix and effectively improve the mechanical, thermal, and barrier properties of the polyester.

Embodiments of processes and multiple-stage catalyst systems for producing propylene comprising introducing a hydrocarbon stream comprising 2-butene to an isomerization catalyst zone to isomerize the 2-butene to 1-butene, passing the 2-butene and 1-butene to a metathesis catalyst zone to cross-metathesize the 2-butene and 1-butene into a metathesis product stream comprising propylene and C.sub.4-C.sub.6 olefins, and cracking the metathesis product stream in a catalyst cracking zone to produce propylene. The isomerization catalyst zone comprises a silica-alumina catalyst with a ratio by weight of alumina to silica from 1:99 to 20:80. The metathesis catalyst comprises a mesoporous silica catalyst support impregnated with metal oxide. The catalyst cracking zone comprises a mordenite framework inverted (MFI) structured silica catalyst.

Processes and multiple-stage catalyst systems are disclosed for producing propene by at least partially isomerizing butene in an isomerization reaction zone having an isomerization catalyst to form an isomerization reaction product, at least partially metathesizing the isomerization reaction product in a metathesis reaction zone having a metathesis catalyst to form a metathesis reaction product, and at least partially cracking the metathesis reaction product in a cracking reaction zone having a cracking catalyst. The isomerization catalyst may be MgO, and the metathesis catalyst may be a mesoporous silica catalyst support impregnated with a metal oxide. The metathesis reaction zone may be downstream of the isomerization reaction zone, and the cracking reaction zone may be downstream of the metathesis reaction zone.

An embodiment of the invention provides a method for forming a magnesium (Mg)-containing coating layer on the surface of a metal support, which comprises a first step of preparing a precursor solution containing a magnesium component, a second step of forming a precipitate on the surface of a metal support by immersing and aging the metal support in the precursor solution prepared in the first step, and a third step of forming a magnesium-containing coating layer on the surface of the metal support by calcinating the precipitate formed in the second step.

A zeolite has a CHA structure, a SiO.sub.2/Al.sub.2O.sub.3 composition ratio less than 15, and potassium in an amount of about 0.1% by mass to about 1% by mass in terms of K.sub.2O.

An exhaust gas purification catalyst or the like may inhibit poisoning of a noble metal component by a Si-containing compound generated or detached from silicon carbide, may inhibit degradation of exhaust gas purification performances over a long period, and may have excellent long-term durability. An exhaust gas purification catalyst may have a stacked structure including at least a substrate and a first and second coat layer, in that order. The substrate may be selected from a silicon carbide carrier including silicon carbide and a silicon carbide-covering carrier on which a coating layer including silicon carbide is provided. The first coat layer may include a compound including one or more alkaline-earth metals selected from Mg, Ca, Sr, and Ba. The second coat layer may includes one or more platinum group elements selected from Rh, Pt, and Pd.

The present disclosure features a method of making an engine aftertreatment catalyst, where the engine aftertreatment catalyst includes a metal oxide, a metal zeolite, and/or vanadium oxide when the metal oxide is different from vanadium oxide, each of which can be independently surface-modified with a surface modifier. The method includes providing a solution including an organic solvent and an organometallic compound; mixing the solution with a metal oxide, a metal zeolite, and/or a vanadium oxide to provide a mixture; drying the mixture; and calcining the mixture to provide a surface-modified metal oxide catalyst, a surface-modified metal zeolite catalyst, and/or a surface-modified vanadium oxide catalyst. The organometallic compound can be, for example, a metal alkoxide, a metal carboxylate, a metal acetylacetonate, and/or a metal organic acid ester.

A hollow cylindrical shaped catalyst body for gas phase oxidation of an alkene to an ,-unsaturated aldehyde and/or an ,-unsaturated carboxylic acid comprises a compacted multimetal oxide having an external diameter ED, an internal diameter ID and a height H, wherein ED is in the range from 3.5 to 4.5 mm; the ratio q=ID/ED is in the range from 0.4 to 0.55; and the ratio p=H/ED is in the range from 0.5 to 1. The shaped catalyst body is mechanically stable and catalyzes the partial oxidation of an alkene to the products of value with high selectivity. It provides a sufficiently high catalyst mass density of the catalyst bed and good long-term stability with acceptable pressure drop.

A zeolite has a CHA structure, a SiO.sub.2/Al.sub.2O.sub.3 composition ratio less than about 15, and an average particle size from about 0.1 m to about 0.5 m.