Prediction of Experimental Methanol Decomposition Rates on Platinum from First Principles

A microkinetic model for methanol decomposition on platinum is presented. The model incorporates competitive decomposition pathways, beginning with both O–H and C–H bond scission in methanol, and uses results from density functional theory (DFT) calculations [Greeley and Mavrikakis, J. Am. Chem. Soc. 124 (2002) 7193, Greeley and Mavrikakis, J. Am. Chem. Soc. 126 (2004) 3910]. Results from reaction kinetics experiments show that the rate of H₂ production increases with increasing temperature and methanol concentration in the feed and is only nominally affected by the presence of CO or H₂ with methanol. The model, based on the values of binding energies, pre-exponential factors and activation energy barriers derived from first principles calculations, accurately predicts experimental reaction rates and orders. The model also gives insight into the most favorable reaction pathway, the rate-limiting step, the apparent activation energy, coverages, and the effects of pressure. It is found that the pathway beginning with the C–H bond scission (CH₃OH→H₂COH→HCOH→CO) is dominant compared with the path beginning with O–H bond scission. The cleavage of the first C–H bond in methanol is the rate-controlling step. The surface is highly poisoned by CO, whereas COH appears to be a spectator species.     

煤制合成气低温甲醇洗配管总结

本文根据以煤为原料的合成氨工艺装置中低温甲醇洗涤净化系统的特点，对其配管在工程设计时的一些特殊要求进行总结，供工程设计人员参考。     

Preparation and characterization of a PtRu/C nanocatalyst for direct methanol fuel cells

PtRu/C nanocatalysts were prepared by changing the molar ratio of citric acid to platinum and ruthenium metal salts (CA:PtRu) from 1:1, 2:1, 3:1 to 4:1 using sodium borohydride as a reducing agent. Transmission electron microscopy analysis indicated that well-dispersed smaller PtRu particles (2.6 nm) were obtained when the molar ratio was maintained at 1:1. X-ray diffraction analysis confirmed the formation of PtRu alloy; the atomic percentage of the alloy analyzed by the energy dispersive X-ray spectrum indicated an enrichment of Pt in the nanocatalyst. X-ray photoelectron spectroscopy measurements revealed that 83.34% of Pt and 79.54% of Ru were present in their metallic states. Both the linear sweep voltammetry and chronoamperometric results demonstrated that the 1:1 molar ratio catalyst exhibited a higher methanol oxidation current and a lower poisoning rate among all the other molar ratios catalysts. The CO stripping voltammetry studies showed that the E-TEK catalyst had a relatively higher CO oxidation current than did the 1:1 molar ratio catalyst. Testing of the PtRu/C catalysts at the anode of a direct methanol fuel cell (DMFC) indicated that the in-house PtRu/C nanocatalyst gave a slightly higher performance than did the E-TEK catalyst.     

甲醇化工技术概述

随着石油资源的日益短缺,C1化学为解决石油化工原料及清洁燃料的技术链、产业链的接续问题探明了方向。甲醇是重要的有机化工原料,其深加工产品涉及到烯烃(乙烯、丙烯)、有机酸(甲酸、醋酸)、甲醛、二甲醚等多种有机化合物,而且甲醇还是优良的洁净燃料。煤制甲醇是现代煤化工极具影响的技术领域,应该充分利用我国相对比较丰富的煤炭资源,大力发展甲醇化工。     

苯基三甲氧基硅烷制备工艺

由苯基三氯硅烷（ＰｈＳｉＣｌ＿３）和甲醇（ＣＨ＿３ＯＨ）醇解制备苯基三甲氧基硅烷［ＰｈＳｉ（ＯＣＨ＿３）＿３〕过程中，采取及时驱除氯化氢（ＨＣｌ）的方法，控制副反应发生，可提高ＰｈＳｉ（ＯＣＨ＿３）＿３的质量，收率达８０％以上。     

半导体型Mo－Fe二元氧化物催化剂的研制

通过共沉淀法和进一步焙烧制得Ｍｏ－Ｆｅ二元氧化物。经ＸＲＤ定性分析表明，它们是由含量不同的Ｆｅ２（ＭｏＯ４）３和ＭｏＯ３所组成。利用固定床反应器研究了Ｍｏ－Ｆｅ氧化物／载体催化剂对甲醇氧化制甲醛的催化性能。对二元Ｍｏ－Ｆｅ氧化物进行了气体敏感性能测试，发现对甲醇具有较高的灵敏度，对氧气的灵敏度较低。其中，具有较高活性的催化剂对被测气体的灵敏度也较高     

High utilization platinum deposition on single-walled carbon nanotubes as catalysts for direct methanol fuel cell

This research aims to enhance the activity of Pt catalysts, thus to lower the loading of Pt metal in fuel cell. Highly dispersed platinum supported on single-walled carbon nanotubes (SWNTs) as catalyst was prepared by ion exchange method. The homemade Pt/SWNTs underwent a repetition of ion exchange and reduction process in order to achieve an increase of the metal loading. For comparison, the similar loading of Pt catalyst supported on carbon nanotubes was prepared by borohydride reduction method. The catalysts were characterized by using energy dispersive analysis of X-ray (EDAX), transmission electron micrograph (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectrum (XPS). Compared with the Pt/SWNTs catalyst prepared by borohydride method, higher Pt utilization was achieved on the SWNTs by ion exchange method. Furthermore, in comparison to the E-TEK 20 wt.% Pt/C catalyst with the support of carbon black, the results from electrochemical measurement indicated that the Pt/SWNTs prepared by ion exchange method displayed a higher catalytic activity for methanol oxidation and higher Pt utilization, while no significant increasing in the catalytic activity of the Pt/SWNTs catalyst obtained by borohydride method.     

Selectivities in methanol oxidation over silica supported molybdena

Selectivities in methanol oxidation over silica supported molybdenum oxide catalysts were investigated in relation with the phase distribution. The supported catalysts were prepared by impregnation with ammonium heptamolybdate. In addition to crystalline MoO₃, Mo containing cluster species of 1–2 nm size were observed by STEM even from a used catalyst with 13% catalyst loading. The percentage of Mo present as crystalline MoO₃ increases with the catalyst loading. An ESCA study indicates that part of surface Mo in the supported catalysts is reduced to Mo⁵⁺. The dimethyl ether selectivity increases with the catalyst loading and its formation occurs over the crystalline MoO₃ phase. The Selectivities to CO and methyl formate are greatly enhanced because of the presence of support, and are relatively independent of the catalyst loading and phase distribution. The dependence and independence of the Selectivities of different byproducts on the loading make the silica supported catalysts with high catalyst loadings less selective for the partial oxidation of methanol to formaldehyde.     

甲醇装置高效分醇技术及双"零"节能工艺

针对甲醇分离系统存在的普遍性问题 ,提出了“少醇无水”工艺技术并进行了工业实际应用。在“少醇无水”工艺的基础上 ,又提出双“零”工艺的构思。分别对该两种工艺进行了经济效益分析。结果表明 :“少醇无水”工艺可使入塔醇含量由0 .987%降至 0 .5 62 % ,装置能力提高 6.0 %～ 11.12 % ;双“零”工艺可使 10万t/a甲醇装置生产能力提高 2 2 .0 0 %。     

生产甲醇是山西焦炉气利用的有效途径

通过因地制宜的市场分析和技术经济分析 ,阐述了焦炉煤气制取甲醇是一条有效的化工利用途径