Effect of Cu loading content on the catalytic performance of Cu-USY catalysts for selective catalytic reduction of NO with NH3.

Series of Cu-USY zeolite catalyst with different Cu loading content were synthesized through simple impregnation method. The obtained catalysts were subjected to selective catalytic reduction of NOx with NH3 (NH3-SCR) performance evaluation, structural/chemical characterizations such as X-ray diffraction (XRD), N2 adsorption/desorption, H2 temperature-programmed reduction (H2-TPR), NH3 temperature-programmed desorption (NH3-TPD) as well as detailed in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments including CO adsorption, NH3 adsorption and NO+O2 in situ reactions. Results show that Cu-USY with proper Cu loading (in this work 5Cu-USY with 5 wt.% Cu) could be promising candidates with highly efficient NH3-SCR catalytic performance, relatively low byproduct formation and excellent hydrothermal stability, although its SO2 poisoning tolerability needs alleviation. Further characterizations reveal that such catalytic advantages can be attributed to both active cu species and surface acid centers evolution modulated by Cu loading. On one hand, Cu species in the super cages of zeolites increases with higher Cu content and being more conducive for NH3-SCR reactivity. On the other hand, higher Cu loading leads to depletion of Brønsted acid centers and simultaneous formation of abundant Lewis acid centers, which facilitates NH4NO3 reduction via NH3 adsorbed on Lewis acid centers, thus improving SCR reactivity. However, Cu over-introduction leads to formation of surface highly dispersed CuOx, causing unfavorable NH3 oxidation and inferior N2 selectivity.

Low-temperature VOCs oxidation performance of Pt/zeolites catalysts with hierarchical pore structure.

Different zeolites supported Pt catalysts with micro-mesoporous structure were prepared by organic base tetrapropylammonium hydroxide (TPAOH) treatment and their catalytic oxidation activity for various volatile organic compounds (VOCs) were evaluated. The results reveal that the synergistic effect between Pt nanoparticles and surface acid sites plays an important role in VOCs low-temperature removal. The small size and high dispersion of Pt nanoparticles on the surface of the zeolites would promote the catalytic oxidation of aromatics and alkanes over the Pt/zeolite catalysts, while strong acidity and abundant acid sites of catalysts are in favour of the oxidation of the VOCs containing N and O heteroatoms. In addition, it was found that Pt/ZSM-5 catalyst exhibits the highest oxidation activity for various VOCs low-temperature removal amongst all the catalysts due to the balance of both Pt dispersion and abundant acid sites in the catalyst. This comprehensive consideration should be very helpful when designing and preparing novel catalysts for the low-temperature removal of VOCs.

Trace CO elimination in H2-rich streams with a wide operation temperature window: Co deposited CuO-CeO2 catalysts.

This work provides a new strategy to eliminate trace CO in H2-rich gas in a wide operation temperature window for the application of hydrogen fuel cells. We engineered Co deposited CuO-CeO2 catalysts with a Co/(Cu + Ce) molar ratio of 1/1 that manages to maintain the CO level at below 100 ppm from 85 to 240 °C in the H2-rich reformate stream. CO-PROX and CO methanation reaction respectively occurred in the low and high temperature ranges. Multiple characterization techniques demonstrate that the molar ratio of Co/(Cu + Ce) significantly affects the synergistic interactions between the Cu, Co and Ce species, and ultimately the CO oxidation and CO methanation reactions. At low reaction temperatures, the Cu-Ce interaction mainly dominates the CO-PROX process, while at high reaction temperatures, CO methanation reaction takes place due to the reduction of Co3O4 to Co0 and the Co-Ce interaction takes charge of the CO methanation. Moreover, the increment of Co/(Cu + Ce) from 1/2 to 1 gives rise to the reprecipitation of the partially dissolved Cu species on Co3O4, which strengthens the Cu-Co interaction and stabilizes surface Cu+ and Co3+, thus promoting the low temperature CO-PROX catalytic performance.

Simultaneous Detoxification of Aflatoxin B1, Zearalenone and Deoxynivalenol by Modified Montmorillonites.

Raw Ca-based montmorillonite (MMT) was treated by H2SO4, calcination and organic compounds (hexadecyltrimethyl ammonium bromide (HTAB), cetylpyridinium chloride (CPC) and chitosan (CTS)), respectively. The modified montmorillonites were characterized by different methods and their adsorption performances for three mycotoxins (Aflatoxin B1 (AFB1), zearalenone (ZEA) and deoxynivalenol (DON)) were evaluated at pH = 2.8 and 8.0, respectively. The results indicate that surfactants (CPC and HTAB) intercalation is the most efficient modification, which obviously improves the adsorption performance of montmorillonite for mycotoxins, with adsorption efficiency of above 90% for AFB1 and ZEA whether under acid or alkaline conditions, due to the increase in basal spacing and the improvement of hydrophobicity. Moreover, the adsorption efficiencies of AFB1 and ZEA over CPC-modified montmorillonite (CPC-AMMT-3) coexisting with vitamin B6 or lysine are still at a high level (all above 94%). All modified montmorillonites, however, have low adsorption efficiency for DON, with somewhat spherical molecular geometry.

Synergistic effect of Pt nanoparticles and micro-mesoporous ZSM-5 in VOCs low-temperature removal.

Micro-mesoporous ZSM-5 zeolites were obtained by the post-treatment of tetrahydroxy ammonium hydroxide (TPAOH) solution with different concentration. The hierarchical pore structure formed during the desilication process facilitates the dispersion of Pt nanoparticles and Pt/ZSM-5 catalysts exhibit rather high catalytic activity for the deep oxidation of various VOCs at low temperature. The catalyst treated with TPAOH of 0.1 mol/L (Pt/ZSM-5(0.1)) shows the lowest degradation temperature (T90%) of 128 and 142°C, respectively for benzene and n-hexane. Compared with the untreated Pt/ZSM-5 catalyst, the abundant mesopores, small Pt particle size and finely dispersed Pt contribute to the superior catalytic activity and stability of the Pt/ZSM-5 catalysts for VOCs removal. More importantly, the existence of H2O in the feed gases hardly affected the activity of Pt/ZSM-5(0.1) catalyst at the low reaction temperature of 128°C, which is very important for VOCs low-temperature removal in the future practical applications.

Elucidating the structure, redox properties and active entities of high-temperature thermally aged CuOx-CeO2 catalysts for CO-PROX.

CuOx-CeO2 catalysts with different copper contents are synthesized via a coprecipitation method and thermally treated at 700 °C. Various characterization techniques including X-ray diffraction (XRD) Rietveld refinement, N2 adsorption-desorption isotherms, X-ray photoelectron spectra (XPS), UV-Raman, high-resolution transmission electron microscopy (HRTEM), temperature-programmed reduction (TPR) and in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) were adopted to investigate the structure/texture properties, oxygen vacancies, Cu-Ce interaction and redox properties of the catalysts. After the thermal treatment, the catalysts exhibited outstanding catalytic properties for the preferential oxidation (PROX) of CO (with the T50% of 62 °C and the widest operation temperature window of 85-140 °C), which provided a new strategy for the design of Cu-Ce based catalysts with high catalytic performance. The characterization results indicated that moderately elevating the copper content (below 5%) increases the amount of highly dispersed Cu species in the catalysts, including highly dispersed surface CuOx species and strongly bonded Cu-[Ox]-Ce species, strengthening the Cu-Ce interaction, increasing oxygen vacancies and promoting redox properties, but a further increase in copper content causes the agglomeration of crystalline CuO and decreases the highly dispersed Cu species. This work also provides evidence from the perspective that the catalytic performance of CuOx-CeO2 catalysts for CO-PROX at low and high reaction temperatures is dependent on the redox properties of highly dispersed CuOx species and strongly bonded Cu-[Ox]-Ce species, respectively.

One-pot synthesis of Fe/Cu-SSZ-13 catalyst and its highly efficient performance for the selective catalytic reduction of nitrogen oxide with ammonia.

Series of Fe/Cu-SSZ-13 catalysts with different Fe loading content were synthesized by simple one-pot strategy. The obtained catalysts were subjected to selective catalytic reduction (SCR) of NOx with NH3 and were characterized by various techniques. The results show that Fe0.63/Cu1.50-SSZ-13 catalyst with proper Fe content exhibits excellent catalytic activity with widest operation temperature window from 160 to 580°C, excellent hydrothermal stability as well as good resistance to sulfur poisoning when compared with Cu-SSZ-13, signifying its great potential for practical applications. Further characterizations reveal that the synthesized Fe/Cu-SSZ-13 catalysts present typical chabazite (CHA) structure with good crystallinity, while isolated Cu2+ and monomeric Fe3+ are revealed as the predominant copper and iron species. At low temperatures, isolated Cu2+ species act as primary active sites for SCR reaction, while monomeric Fe3+ species provide sufficient active sites for sustain the SCR activity at high temperature. Moreover, Fe over doping would lead to the damage of zeolite structure, destruction of isolated Cu2+ site, as well as the formation of highly oxidizing Fe2O3, thus causing deterioration of catalytic performances.

Pt-support interaction and nanoparticle size effect in Pt/CeO2-TiO2 catalysts for low temperature VOCs removal.

A series of Pt/CeO2-TiO2 catalysts (0.5 wt% Pt) with size-controllable Pt nanoparticles were prepared by a modified ethylene glycol reduction method and the Pt particle size effect of Pt/CeO2-TiO2 catalysts on benzene and 1,2-dichloroethane (DCE) degradation was investigated. It reveals that the metal-support interaction of PtOx species and CeO2-TiO2 mixed oxides is enhanced by the reduced Pt particle sizes. The formation of more Pt2+ species and stronger redox properties at low-temperature resulted by the enhanced metal-support interaction of Pt/CeO2-TiO2 catalysts both greatly promotes the deep oxidation for benzene and C2H3Cl byproduct during DCE degradation at low temperature. Pt/CeTi-11 with the smallest average Pt particle size (1.53 nm) exhibits the highest activity among all the catalysts for benzene degradation, with T90% of only 152 °C (1000 ppm, GHSV = 15,000 h-1). However, more acidic sites (especially the strong acid) were formed on the Pt/CeO2-TiO2 catalysts with bigger Pt nanoparticle (>2.95 nm), contributing to activate and convert DCE to C2H3Cl. More importantly, Pt/CeO2-TiO2 catalysts are extremely stable in DCE degradation reaction, and have been scarcely influenced by the presence of benzene and water in the feed gases.

The relation of structure and metal-support interaction with three-way catalytic performance of Rh/(Ce,Zr,La)O2 catalysts.

(Ce,Zr,La)O2 (CZL) mixed oxide-supported rhodium (Rh) catalysts were prepared by in situ synthesis method. Characterizations were adopted to investigate the relation of structure and metal-support interaction with catalytic behavior of catalysts. The results demonstrate that appropriate Ce/Zr ratio (2/1~1/4) could help to form more homogenous CZL ternary solid solution and promote the formation of more oxygen vacancies and defects (the lattice defects resulting from lattice distortion) in CZL supports, and thereby enhance oxygen storage/release performance. Meanwhile, it strongly affects the interaction between RhOx and CZL supports, which promotes the formation of more active Rh species (Rh0 + Rh3+) and the reduction of the oxygen species in Rh-Ce interface, leading to the enhancement of catalytic performance for HC, CO, and NOx eliminations. Rh/CZL-12 shows the best catalytic activity for HC and NOx eliminations. It could be attributed to the enhanced activation and oxygen mobility of lattice oxygen, which is verified by the results of DOSC measurement.

The crucial roles of guest water in a biocompatible coordination network in the catalytic ring-opening polymerization of cyclic esters: a new mechanistic perspective.

The ring-opening polymerization (ROP) of cyclic esters/carbonates is a crucial approach for the synthesis of biocompatible and biodegradable polyesters. Even though numerous efficient ROP catalysts have been well established, their toxicity heavily limits the biomedical applications of polyester products. To solve the toxicity issues relating to ROP catalysts, we report herein a biocompatible coordination network, CZU-1, consisting of Zn4(µ4-O)(COO)6 secondary building units (SBUs), biomedicine-relevant organic linkers and guest water, which demonstrates high potential for use in the catalytic ROP synthesis of biomedicine-applicable polyesters. Both experimental and computational results reveal that the guest water in CZU-1 plays crucial roles in the activation of the Zn4(µ4-O)(COO)6 SBUs by generating µ4-OH Brønsted acid centers and Zn-OH Lewis acid centers, having a synergistic effect on the catalytic ROP of cyclic esters. Different to the mechanism reported in the literature, we propose a new reaction pathway for the catalytic ROP reaction, which has been confirmed using density functional theory (DFT) calculations, in situ diffuse reflectance IR Fourier transform spectroscopy (DRIFTS), and matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS). Additionally, the hydroxyl end groups allow the polyester products to be easily post-modified with different functional moieties to tune their properties for practical applications. We particularly expect that the proposed catalytic ROP mechanism and the developed catalyst design principle will be generally applicable for the controlled synthesis of biomedicine-applicable polymeric materials.

Oxygen mobility and microstructure properties-redox performance relationship of Rh/(Ce,Zr,La)O2 catalysts.

Rh/(Ce,Zr,La)O2 (CZL) catalysts with different Ce/Zr molar ratios of 1:0, 8:1, 4:1, 2:1, 1:1, 1:2, 1:4, 1:8 and 0:1 were prepared. The relationship of microstructure, dynamic oxygen mobility and the redox properties with catalytic activity for HC, CO and NOx eliminations were investigated. The results demonstrate that CZL mixed oxide with Ce/Zr ratio of 1:1 exhibits the largest OSC values as 904.3 umol·g-1 and structural defects. The increase of oxygen vacancies and structural defects would promote the interaction between Rh species and CZL mixed oxides, which further promotes the stabilization of RhOx particles and enhances the oxygen storage/release ability. Rh/CZLx catalysts with Ce/Zr molar ratio of 1:1-1:4 exhibit better catalytic activity and wider dynamic operation window due to their higher DOSC.

Effect of acid-treated and hexadecyltrimethylammonium bromide-modified montmorillonites on adsorption performance of mycotoxins.

A series of modified montmorillonites treated by acid and hexadecyltrimethylammonium bromide (HTAB) were prepared and characterized, and their adsorption performances for three mycotoxins (aflatoxin B1, zearalenone, and deoxynivalenol) were evaluated at pH 2.8 and 8.0, respectively. The results indicate that the layers of raw montmorillonite are exfoliated after acid treatment and more active sites for adsorption of weak polar mycotoxins are exposed. While the intercalation of HTAB leads to an obvious increase of the interlamellar spacing and hydrophobic character of montmorillonite. The HTAB-AMMT-3 modified by acid and HTAB exhibits excellent adsorption capacity towards aflatoxin B1 (AFB1) and zearalenone (ZEA) whether in acidic or alkaline conditions compared with raw montmorillonite (MMT). However, all modified montmorillonites have low adsorption capacity for DON due to its poor planarity preventing it from entering into interfacial layer of montmorillonite.

Doping effect of transition metals (Zr, Mn, Ti and Ni) on well-shaped CuO/CeO2(rods): nano/micro structure and catalytic performance for selective oxidation of CO in excess H2.

A series of CuO/CeM(rod) catalysts doped by transition metals were prepared and systematically characterized. The introduction of Mn and Ti plays a significant role in promoting the catalytic performance of the CuO/CeO2(rod) catalyst for the preferential oxidation of CO in H2-rich gas, while the doping with Zr basically maintains the same catalytic activity and Ni leads to a negative influence. Mn and Ti additives remarkably enrich the formation of defect structures and promote copper ion incorporation into the surface of CeM(rod), which greatly facilitates the generation of strong interfacial copper-ceria interaction in CuO/CeMn(rod) and CuO/CeTi(rod). In addition, CuO/CeMn(rod) possesses excellent surface oxygen mobility at low temperature due to the existence of manganese species with multiple valence states and todorokite species. The Ce-doped perovskite structure (Na0.5Ce0.5TiO3) further adjusts the oxygen vacancy in CuO/CeTi(rod) and anchors copper oxide species with strong interactions. Although a homogeneous solid solution is formed in CeZr(rod) with increased amounts of oxygen vacancies, the interaction between copper and ceria species in the interface of CuO/CeZr(rod) remains the same as with CuO/CeO2(rod). The addition of Ni impairs the dispersion of copper oxide and weakens the copper-ceria interaction, which damages the catalytic performance of CuO/CeNi(rod).

Promoting effect of Nb doping on catalytic performance for deep oxidation of 1, 2-dichloroethane over (Ce,Cr)xO2-Nb2O5 catalysts.

A series of Nb-doped (Ce,Cr)xO2-Nb2O5 mixed oxides with varying (Ce,Cr)xO2/Nb2O5 mass ratio were prepared by a co-precipitation method and evaluated for the catalytic performance of eliminating 1,2-dichloroethane (DCE). The results indicate that there exists a strong synergistic effect between acid sites and redox species in (Ce,Cr)xO2-Nb2O5 improving the catalytic activity for DCE oxidation. Appropriate Nb doping could promote the high dispersion and the interaction of metal oxides in the (Ce,Cr)xO2-Nb2O5 catalysts, resulting in the formation of more Cr6+ species with strong oxidizing ability and excellent mobility of oxygen species from bulk to surface to create more active sites for DCE deep oxidation. The (Ce,Cr)xO2-Nb2O5 catalysts with (Ce,Cr)xO2/Nb2O5 ratios of 2/1~1/2 exhibit excellent catalytic activity and durability for DCE degradation in dry air as well as benzene or water vapor, and less chlorinated byproduct is produced during the degradation of DCE.

New insights into the effect of morphology on catalytic properties of MnO x -CeO2 mixed oxides for chlorobenzene degradation.

We synthesized four CeO2-MnO x mixed oxides with different morphologies using simple hydrothermal methods. The catalytic activity for chlorobenzene (CB) degradation decreases in the following order: rod-CeO2-MnO x > plate-CeO2-MnO x > polyhedra-CeO2-MnO x > cube-CeO2-MnO x . CeO2 and MnO x in the mixed oxides are highly dispersed and two new phases of both todorokite (S.G.: P2/m:b) and vernadite (S.G.: I4/m) with a special tunnel-like structure are found. Both rod-CeO2-MnO x and plate-CeO2-MnO x exhibit increased lattice microstrains generated from lattice distortion and defects; further, there are more oxygen vacancies and more MnO x (Mn4+ and Mn2+) species on the surface, particularly when compared to cube-CeO2-MnO x . Therefore, this promotes deeper oxidation activity for CB. Moreover, the strong interaction between CeO2 and MnO x also promotes the redox ability of CeO2-MnO x mixed oxides, while their oxygen storage capacity (OSC) properties are not only intrinsic to their structures but also limited to their surfaces and by their particle sizes.

Investigation on the structure-activity relationship of BaO promoting Pd/CeO2-ZrO2 catalysts for CO, HC and NOx conversions.

Four different synthetic routes (co-precipitation, oxidation-precipitation, citric acid sol-gel and reversed microemulsion) are adopted to prepare barium modified Pd/CeO2-ZrO2 catalysts and their catalytic activity towards CO, HC and NOx conversions is studied. The surface and bulk properties of these catalysts are characterized via XRD, N2 adsorption, XPS, UV-Raman, H2-TPR, and in situ DRIFTS. The catalyst prepared via the co-precipitation method exhibits the optimum three-way catalytic behavior, which is mainly due to its superior redox ability, whereas the oxidation-precipitation synthesis renders the catalyst with the best homogeneity and thermal resistance. However, for the catalyst prepared via the sol-gel route, its worst NOx reduction capacity is verified by the scarce appearance of negatively charged Pd0-N[double bond, length as m-dash]Oδ- species, which is related to the faster dissociation of NO based on in situ DRIFTS, and the abundance of surface CO-Pd+ species reveals its unsatisfactory deep oxidizability of the HC reactant.

Investigation on properties of Pd/CeO2-ZrO2-Pr2O3 catalysts with different Ce/Zr molar ratios and its application for automotive emission control.

Pd/CeO2-ZrO2-Pr2O3 (CZP) catalysts with different Ce/Zr molar ratios were synthesized and systematically investigated by XRD, N2 adsorption-desorption, XPS, H2-TPR, OSC and in situ DRIFTS techniques. The results of XPS, in situ DRIFTS, etc., show that the number of oxygen vacancies increases with the increasing Zr content and thus leads to the enhanced metal-support interaction and the accelerative formation rate of nitrate, formate, acetate and carbonate species, resulting in improving catalytic performance for HC and NO elimination, especially for Pd/CZP catalysts with Ce/Zr from 1/2 to 1/3. While Pd/CZP catalysts with higher OSC value (Ce/Zr=4/1-1/2) exhibit better catalytic activity of CO and NO2 elimination. An appropriate concentration of Zr facilitates the diffusion of Pr from the surface to the bulk of the CZP supports, thus forming more homogeneous CZP solid solution and improving the structure/textual stability, which promotes the thermal stability of catalysts. Pd/CZP catalysts with Ce/Zr from 2/1 to 1/2 exhibit good thermal stability.

Promoting effect of alkaline earth metal doping on catalytic activity of HC and NOx conversion over Pd-only three-way catalyst.

The influence of alkaline earth metal (M=Mg, Ca, Sr and Ba) promoter on the structural/textural properties of Ce0.67Zr0.33O2 (designated as CZ) and the catalytic behavior of its supported Pd-only three-way catalyst (Pd/CZM) have been investigated. The results show that the modification with alkaline earth metal obviously improves the catalytic activity for hydrocarbon (HC) and nitrogen oxides (NOx) conversion, especially the introduction of Ba. Furthermore, the operation window of the promoted catalysts has also been widened. The doping of alkaline earth metal leads to the formation of more homogeneous Ce-Zr-M ternary solid solution with higher surface area and smaller crystallite size, and the corresponding Pd/CZM catalysts present improved reducibility of PdO species. The modification with Ca, Sr and Ba improves the thermal aging resistance, especially Ba. DRIFTS results reveal that the doping of alkaline earth metal enhances the oxygen and electron transfer ability and favors the dissociation of NO, which promotes the activation and storage capacity of the acidic atoms like NOx, and leads to enhanced catalytic activity performance.

[Relationship between anthropometric measures and the prevalence of diabetes in adults of Suzhou city, Jiangsu province].

OBJECTIVE: To explore the relationships between anthropometric measures as body mass index (BMI), percentage body fat, waist circumference (WC), hip circumference (HC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR) and the risks of diabetes. METHODS: We analyzed the baseline data of 53 260 participants who were aged 30-79 years and had been enrolled into the China Kadoorie Biobank (CKB) study from Suzhou city,Jiangsu province. Unconditional logistic regression analyses were conducted with adjustment for potential confounders. RESULTS: Overall, 5.3% of the participants had diabetes, with about a half of them being newly detected through on-site screening tests. The prevalence of diabetes increased with age, 61% higher (OR = 1.61, 95% confidence interval: 1.54-1.67) risk of diabetes, with 10 years increase of age. In both genders, all anthropometric measures were positively and significantly associated with diabetes, with the associations of measures in central adiposity stronger than those in general obesity, with WHR as the strongest. Each standard deviation (1- s) with greater WHR (<0.06 in men and 0.07 in women) was associated with 72% (61%-83%) higher risk of diabetes in men and 93% (83%-102%) in women. After adjusting for HC, each WC with 5 cm larger, showing 65% and 57% higher risks in men and women respectively. However, after adjusting for WC, every 5cm greater HC appeared and associated with respective 38% and 34% lower risks. CONCLUSION: Measures on adiposity including BMI, percentage body, WC, WHR and WHtR fat were all positively associated with the prevalence of diabetes. Measures of central obesity, particularly WHR, were more strongly associated with diabetes than measures of general obesity. When WC was under control, HC appeared inversely associated with diabetes.

Physical activity and sedentary leisure time and their associations with BMI, waist circumference, and percentage body fat in 0.5 million adults: the China Kadoorie Biobank study.

BACKGROUND: Few large studies in China have investigated total physical activity and sedentary leisure time and their associations with adiposity. OBJECTIVE: We investigated determinants of physical activity and sedentary leisure time and their associations with adiposity in China. DESIGN: A total of 466,605 generally healthy participants (age: 30-79 y, 60% female) in the China Kadoorie Biobank were included in this cross-sectional analysis. Self-reported information on a range of activities was collected by interviewer-administered questionnaire. Physical activity was calculated as metabolic equivalent task hours per day (MET-h/d) spent on work, transportation, housework, and nonsedentary recreation. Sedentary leisure time was quantified as hours per day. Adiposity measures included BMI, waist circumference, and percentage body fat (by bioimpedance analysis). Associations were estimated by linear and logistic regression. RESULTS: The mean physical activity was 22 MET-h/d, and the mean sedentary leisure time was 3.0 h/d. For each sex, physical activity was about one-third lower among professionals/administrators than among factory workers, with intermediate levels for other occupational categories. A 1-SD (14 MET-h/d) greater physical activity was associated with a 0.15-unit (95% CI: 0.14, 0.16) lower BMI (in kg/m(2)), a 0.58-cm (95% CI: 0.55, 0.61) smaller waist circumference, and 0.48 (95% CI: 0.45, 0.50) percentage points less body fat. In contrast, a 1-SD (1.5 h/d) greater sedentary leisure time was associated with a 0.19-unit higher BMI (95% CI: 0.18, 0.20), a 0.57-cm larger waist circumference (95% CI: 0.54, 0.59), and 0.44 (95% CI: 0.42, 0.46) percentage points more body fat. For any given physical activity level, greater sedentary leisure time was associated with a greater prevalence of increased BMI, as was lower physical activity for any given sedentary leisure time. CONCLUSIONS: In adult Chinese, physical activity varies substantially by occupation, and lack of physical activity and excess sedentary leisure time are independently and jointly associated with greater adiposity.