ABSTRACT
The effect of reaction temperature and weight hourly space velocity (WHSV) on the reaction of 1-decene cracking to ethylene and propylene over H-ZSM-5 zeolite was investigated. Also, the thermal cracking reaction of 1-decene was studied by cracking over quartz sand as blank. It was observed that 1-decene undergoes a significant thermal cracking reaction above 600 °C over quartz sand. In the range of 500-750 °C, the conversion remained above 99% for 1-decene cracking over H-ZSM-5, and the catalytic cracking dominated even at 750 °C. With the increase in temperature, the yields of ethylene and propylene gradually increased, and the yields of alkanes and aromatics also increased. The low WHSV was favorable for the yield of light olefins. With the increase of the WHSV, the yields of ethylene and propylene decrease. However, at low WHSV, secondary reactions were accelerated, and the yields of alkanes and aromatics increased significantly. In addition, the possible main and side reaction routes of the 1-decene cracking reaction were proposed based on product distribution.
ABSTRACT
OBJECTIVES: To find whether Laparoscopic Roux-en-Y gastric bypass (RYGB) surgery was cost effective compared to conventional medical management (CMM) in Chinese patients with type 2 Diabetes(T2D) and obesity with a body mass index (BMI) ≥27.5 kg/m2 in four years. METHODS: A total of 106 obese T2D individuals who underwent RYGB and 106 T2D patients treated with CMM were enrolled from three academic medical centers. Total health related costs, Glycated Hemoglobin A1c (A1C) and BMI was recorded. Cost-Utility Analysis (CUA) was used. Utility values according to results of A1c were obtained from published studies. RESULTS: Improvements were observed in A1C (8.6% at baseline to 6.2% in the first year, p < 0.001) and BMI (30.7 kg/m2 at baseline to 24.3 kg/m2 in the first year, p < 0.001), and the effect lasted for 4 years after RYGB. In the CMM group, A1C fluctuated in four years. The health utility for RYGB group scores 3.756, whereas CMM group scores 3.594 in four years. The total healthcare costs decreased sharply from the second year after RYGB ($8,483 [¥52,596] in the first year to $672[¥4,164] in the second year, p < 0.001) and maintained for 3 years. In the CMM group, the total healthcare costs changed without significance. RYGB costs US$19,359 (¥125,836) per quality-adjusted life years (QALY) gained (incremental cost-utility ratio [ICUR]) compared to CMM, which was lower than a willingness-to-pay (WTP) of $20,277/QALY. CONCLUSIONS: Compared to CMM, RYGB is cost-effective for Chinese patients with type 2 diabetes and obesity 4 years after operation.
