Dry reforming of CH4 over stabilized Ni-La@KCC-1 catalyst: Effects of La promoter and optimization studies using RSM
JOURNAL OF CO2 UTILIZATION
Authors: Abdulrasheed, A. A.; Jalil, A. A.; Hamid, M. Y. S.; Siang, T. J.; Abdullah, T. A. T.
Abstract
A bimetallic Ni-La catalyst supported on fibrous silica KCC-1 (KAUST Catalysis Centre 1) was prepared by in situ one-pot hydrothermal method. The catalyst was characterized by XRD, BET, FESEM-EDX, TEM, H-2-TPR, FTIRpyrrole, O-2 -TPO and XPS. The H-2 -TPR result revealed that the addition of La2O3 enhanced the reducibility of Ni2+, as observed by the 25.1 % increase in H-2 consumption. This is an evidence of improved dispersion as also indicated in the TEM images. Extra affinity for CO2 chemisorption and activation was provided by the La promoted catalyst with strong and intense basic sites to improve product selectivity. Therefore, the activity of catalyst was improved with significant enhancement in CO2 conversion and H-2/CO selectivity. As a result, the activation energy for CO2 and CH4 conversions were reduced by a margin of 10.4 kJ/mol and 2.2 kJ/mol respectively. Ni-La@KCC-1 catalyst showed no sign of deactivation throughout the 22 h time on stream while Ni@ KCC-1 deactivated after 15 h at a higher reactant feed composition. From ANOVA analysis, the reaction temperature is the most significant variable that influence CH4 conversion. The reaction operating condition was obtained that gives the optimum CH4 conversion. The model predicted response was 98.2 % fitted to the observed experimental values.
Correlation Between Hashimoto's Thyroiditis-Related Thyroid Hormone Levels and 25-Hydroxyvitamin D
FRONTIERS IN ENDOCRINOLOGY
Authors: Chao, Guanqun; Zhu, Yue; Fang, Lizheng
Abstract
Objective: The purpose of this study was to further clarify the association of Hashimoto's thyroiditis (HT) and vitamin D deficiency, and to seek the connection between them and related influencing factors. Methods: Data were obtained from subjects who underwent health examinations from January 2018 to December 2018. The diagnosis of HT was based on: antithyroid peroxidase antibody (TPO-Ab) levels >35 IU/ml and/or antithyroglobulin antibody (Tg-Ab) levels >40 IU/ml. Based on the Endocrine Society guidelines, 25-hydroxyvitamin D [25(OH)D] levels >= 30.0 ng/ml were classified as a vitamin D sufficiency; those between 20 and 29.9 ng/ml, as an insufficiency; and those <20 ng/ml, as a deficiency. All statistical analysis was performed by software R. Results: Of a total of 75,436 individuals who were physically examined, 5,656 of them had 25(OH)D levels tested at the same time; 5,230 were enrolled. The level of 25(OH)D in the non-HT group was higher than that in the HT group. Multiple regression analysis showed that HT was statistically significantly correlated with being male, body mass index (BMI), waist circumference, and thyroid-stimulating hormone (TSH). TSH levels in the insufficiency group and deficiency group were higher than those in the sufficiency group. Free triiodothyronine (FT3) and thyroxine (FT4) levels in the insufficiency group and deficiency group were lower than those in the sufficiency group. 25(OH)D increased by 1 ng/ml at the normal reference level, with an increase of 2.78 ng/dl in FT4 concentration and a decrease of 0.17 mIU/L in TSH. Conclusions: Patients with HT present with a reduced 25(OH)D level, and TSH is an independent risk factor for HT. TSH is negatively correlated with 25(OH)D level. FT3 and FT4 levels were positively correlated with 25(OH)D levels.