Iron Fischer-Tropsch Catalysis

Application of Fe catalysts on a commercial scale using slurry bubble column reactors (SBCR) has been held back due to their poor attrition resistances. Recently, high attrition resistant catalysts have been successfully prepared using spray drying. Their improved physical strength was found to depend greatly on particle density, which was determined by type and concentration of SiO2 added to the catalysts. However, only Fe catalysts containing binder or binder + precipitated SiO2 were studied.To improve our understanding of the role of SiO2 on attrition properties of Fe catalysts, in general, attrition of spray-dried Fe catalysts prepared with only precipitated SiO2 was investigated. The amount of precipitated SiO2 that optimized catalyst performance (attrition resistance and activity) during an SBCR operation was suggested to be ca. 11 wt%. The strong relationship between catalyst attrition and particle density was consistent with the previous findings.Unlike high attrition resistant catalysts, whose physical and chemical attrition properties remained essentially unchanged after pretreatment, the physical strength of poor attrition-resistant catalysts was able to be improved significantly by pretreatment (CO or H2). This improvement was surprisingly decreased by the addition of water vapor during pretreatment. The presence of water vapor was found to prevent sintering of Fe pore structure but to provide no significant additional interaction between Fe and SiO2. The conventional CO-pretreatment was suggested as the best activation for Fe catalysts, since it results in high attrition resistance and reasonably high surface area.Different activation pretreatments (H2, CO, or syngas) result in different Fe phases, and the relationship of these phases with catalyst activity during FTS has been debated among researchers up to the present day. Steady-state isotopic transient kinetic analysis (SSITKA) was used to study at the site level the activity of differently activated Fe during CO hydrogenation. It was found that the H2-pretreated sample exhibited the highest concentration of surface reaction intermediates (NM) while those of CO- and syngas-pretreated ones were similar. The intrinsic site activity (kM) of differently pretreated catalyst samples was essentially identical. These results suggested that the active sites were on the surface of carburized Fe

All-solid-state polymeric screen printed and carbon paste ion selective electrodes for determination of oxymetazoline in pharmaceutical dosage forms

All-solid state potentiometric ion selective electrodes have the merits of being portable, small and suitable for small volume samples. Herein, disposable home-made screen printed polymeric ion selective electrode (SPE) is developed for determination of oxymetazoline (OXM) in pharmaceutical nasal drops and drug substance. Ion selective electrodes with optimal potentiometric response were achieved by careful selection of the ion exchanger and plasticizer. A screen printed electrode utilizing oxymetazoline-tetraphenyl borate (OXM-TPB) as an ion exchanger and dibutyl phthalate (DBP) as a plasticizer exhibited a Nernstian slope of 59.5±0.5 mV/decade (n=3) over the concentration range from 1×10-5 to 1×10-2 M OXM (r = 0.9999) with a detection limit of 5.0×10-6 M. The electrode is useful over a wide pH range from 4.0 to 8.0. The electrode showed a high selectivity for OXM against several common interfering ions. The potential interference from benzalkonium chloride was easily eliminated by treatment the sample with KI. Comparable potentiometric characteristics including linearity, detection limit, pH range and selectivity pattern were obtained with a carbon paste electrode (CPE) comprising same ion exchanger and plasticizer. The electrodes were successfully used for the assay of OXM in the drug substance and in the dosage form in presence of benzalkonium chloride with high accuracy (±2%) and precision (%RSD ˂2.5). The proposed method is simple, accurate and precise

ผลของการเย็นตัวต่ำกว่าจุดเยือกแข็งต่อความแข็งและออสเตไนต์เหลือค้างของเหล็กหล่อโครเมียมสูงที่มีปริมาณโครเมียม 16% และ 26%Effect Sub-zero Treatment on Hardness and Retained Austenite of High Cr Cast Irons with 16% and 26%Cr

เหล็กหล่อโครเมียมสูงเป็นกลุ่มเหล็กหล่อทนการสึกหรอแบบขัดสีใช้ทำลูกรีดสำหรับรีดเหล็กในอุตสาหกรรมเหล็กกล้า และหม้อบดในอุตสาหกรรมปูนซีเมนต์ เนื่องจากมีความต้านทานการสึกหรอแบบขัดสีสูง ในทางปฏิบัติต้องการความแข็งสูงและมีออสเตไนต์เหลือค้างน้อยที่สุดเพื่อเพิ่มอายุการใช้งาน งานวิจัยนี้ได้ศึกษาผลของการเย็นตัวต่ำกว่าจุดเยือกแข็งร่วมกับการทำกรรมวิธีทางความร้อนทั่วไปต่อความแข็งและปริมาณออสเตไนต์เหลือค้างของเหล็กหล่อโครเมียมสูงที่มีส่วนผสม 16% และ 26% โครเมียม ซึ่งเป็นส่วนผสมพื้นฐานในการใช้งาน ชิ้นงานอบอ่อนถูกชุบแข็งด้วยอุณหภูมิ 1,050 องศาเซลเซียส และเย็นตัวโดยใช้ลมเป่าตามด้วยการเย็นตัวต่ำกว่าจุดเยือกแข็งในน้ำแข็งแห้งผสมอะซิโตน ทำการอบคืนไฟชิ้นงานชุบแข็งที่อุณหภูมิ 400–550 องศาเซลเซียส พบว่า ความแข็งในสภาพชุบแข็งของเหล็กหล่อทั้งสองส่วนผสม หลังจากผ่านการเย็นตัวต่ำกว่าจุดเยือกแข็งสูงกว่ากรณีเย็นตัวโดยใช้ลมเป่า สัดส่วนเชิงปริมาตรของออสเตไนต์เหลือค้าง ลดลงอย่างมากเมื่อผ่านการเย็นตัวต่ำกว่าจุดเยือกแข็ง ความแข็งในสภาพอบคืนไฟแสดงการแข็งขึ้นทุติยภูมิจากการตกตะกอนของคาร์ไบด์ทุติยภูมิและการแปลงเฟสจากออสเตไนต์เป็นมาร์เทนไซต์ ค่าสัดส่วนเชิงปริมาตรของออสเตไนต์เหลือค้างลดลงเมื่ออุณหภูมิอบคืนไฟสูงขึ้น ชิ้นงานที่ผ่านการเย็นตัวต่ำกว่าจุดเยือกแข็งมีระดับการแข็งขึ้นทุติยภูมิน้อยกว่าชิ้นงานที่เย็นตัวโดยใช้ลมเป่า ความแข็งสูงสุดหลังอบคืนไฟพบที่อุณหภูมิ 450–500 องศาเซลเซียส ชิ้นงานที่ผ่านการเย็นตัวต่ำกว่าจุดเยือกแข็งจะมีค่าความแข็งสูงสุดมากกว่าชิ้นงานที่เย็นตัวโดยใช้ลมเป่า ค่าความแข็งสูงสุดลดลงเมื่อปริมาณโครเมียมเพิ่มขึ้น 26% โดยค่าความแข็งสูงสุด คือ 810 HV30 ในชิ้นงาน 16% โครเมียม และ 781 HV30 ในชิ้นงาน 26% โครเมียม ที่ผ่านการเย็นตัวต่ำกว่าจุดเยือกแข็งซึ่งมีค่าสัดส่วนเชิงปริมาตรของออสเตไนต์เหลือค้างน้อยกว่า 4%High chromium cast irons have been widely used as abrasive wear resistant materials. Their main and typical applications are for rolling mill rolls in the steel-making and pulverizing mills in cement industries because of excellent abrasive wear resistance. Practically, the required properties of the cast iron must be high hardness together with very less retained austenite for a long service life. In this research, the effect of sub-zero treatment on hardness and retained austenite of plain high Cr cast iron with 16% and 26%Cr was investigated. The annealed specimens were hardened at 1,050 °C and cooled by fan followed with sub-zero treatment by soaking in dry ice + acetone bath. Hardened specimens were tempered at a range of 400–550 °C. In the hardened state, the sub-zero treated specimens showed higher hardness than the fan air-cooled specimens. The volume fractions of retained austenite (Vγ) of sub-zero treated specimens were much lower than those of fan air-cooled specimens. In the tempered state, the tempered hardness curves showed a secondary hardening due to the precipitation of secondary carbides and the transformation of austenite to martensite. The Vγ value decreased as tempering temperature increased. Degree of secondary hardening was higher in the specimens tempered without sub-zero treatment. The maximum tempered hardness (HTmax) was obtained at 450–500 °C tempering. The HTmax value of sub-zero treated specimens was higher than that of fan air cooled specimens. The HTmax value decreased as Cr content increased to 26%.The highest values of HTmax, 810 HV30 in 16%Cr and 781 HV30 in 26%Cr specimens, were obtained in sub-zero treated specimens where the Vγ value were less than 4%

Catalyst Screening and Optimization Condition of Green Solvent for BHD Production using Ni-based Catalysts

The high production costs associated with bio-hydrogenated diesel (BHD) have posed a major challenge. Considering this, the present research focused on the production of green solvents at lower pressures as a potential solution. Specifically, the synthesis of various catalysts, namely Ni/γ-Al2O3, Ni/C, NiMo/γ-Al2O3, NiMo/SiO2TiO2, and NiMo/C, was conducted to facilitate the hydrodeoxygenation reaction of methyl laurate into cyclohexane, leading to conversion into dodecane. The resulting green solvent was analyzed using GC-FID and GC-TCD techniques. Among the five catalysts tested, NiMo/C demonstrated superior performance, achieving a conversion rate of 64.61%, selectivity of 62.46%, and yield of 44.98%. The gas analysis conducted using GC-TCD revealed the production of carbon monoxide, methane, and carbon dioxide, aligning with the dodecane pathway theory. Further analysis of the NiMo/C catalyst was conducted using SEM, BET, and XRD techniques, while the Design of Expert program was used to identify more favorable conditions for dodecane production. Through this optimization process, significant improvements were achieved, resulting in a conversion rate of 98.26%, selectivity of 66.82%, and yield of 65.66% at 320 °C and 28 bar, with a reaction time of 6 h