摘要:

Simply stated, a membrane is a barrier which is capable of redistributing components in a fluid stream through a driving force such as the difference in pressure, concentration, or electrical potential. When a concentration or electrical potential gradient provides the necessary driving force, this barrier separation process is called dialysis or electrodialysis. Most of the membrane processes are based on an applied pressure difference across the membranes.

ISSN:0161-4940    

DOI:10.1080/01614949108020296

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In a recent review on the influence of particle size on catalytic properties of supported metals [l], evidently a most important aspect of heterogeneous catalysis by any account, the authors end on a fairly discouraging note since they suggest doing even more work — with ever more sophisticated techniques and methods as well as normalized procedures — on top of an already formidable amount of literature. At such a state of the art it may be appropriate to reflect and to ask whether full pursuit of reductionism as scientific method needs fresh thinking in order to progress more effectively. Perhaps the difficulties are rooted in emphasis on mere data collection, the lack of a good empirical guiding principle, inappropriate models; in brief, the frequent simplification of a vastly complicated object — the real catalyst — into the sum of phenomena of better-understood idealized subsets. It might even be argued that a thorough knowledge of a well-characterized prototype or a particular model catalyst would be actually of little help in seeing the real world where catalysts are of irregular shape, suffer sintering, become poisoned; in other words, lose their ideal state after some time of operation. Also, we realize that a change in “quantity” often engenders a change in “quality”: For instance, a material with a BET area of hundreds of square meters per gram can hardly be considered to have a surface like a huge tennis court or ball field: it is rather “convoluted” in some very irregular fashion, having a shape that is difficult to realistically construct as a linear combination of planar portions.

ISSN:0161-4940    

DOI:10.1080/01614949108020297

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

It has been known for many years that it is possible to produce mixtures of methanol and higher alcohols from synthesis gas by alkali promotion of the methanol synthesis catalysts and by appropriate modification of the reaction conditions [l]. From 1927 to 1945 plants were in operation in the United States and Germany, that were dismantled with the coming of different feedstocks and the necessity of obtaining pure alcohols for chemical use. In the last decade the chemical and petroleum industry has shown a renewed and growing interest in the use of mixtures of methanol and higher aliphatic alcohols. The original goal in the late '70s was mainly to reduce oil dependence by producing synthetic components for gasoline blends. More recently the trend to lead phase-down due to environmental protection has focused the attention on the product performances of such alcohol mixtures as high octane blending stock for gasoline. It has been shown that the addition of higher alcohols to methanol increases the water tolerance in respect to phase separation, reduces the fuel volatility and the vapor lock tendency, and also results in higher volumetric heating values.

ISSN:0161-4940    

DOI:10.1080/01614949108020298

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

There is considerable interest in laboratories around the world in developing processes for the direct conversion of methane to higher valued products. Direct routes to useful chemicals would avoid the energy intensive steam reforming step used in existing technology [l]. Methane, however, is rather an inert substance and, apart from its ready reaction with oxygen, undergoes few reactions, the reaction between methane and halogens, carried out photochemically [2,3] or thermally [4], being an exception. Whilst patents have been issued for utilization of the thermal reaction between methane and chlorine to produce ethane [5,6], environmental concerns might prevent the large-scale commercial development of a process involving chlorine.

ISSN:0161-4940    

DOI:10.1080/01614949108020299

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0161-4940    

DOI:10.1080/01614949108020295

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor