Explain, with reference to their structure, the great selectivity of zeolites as catalysts.

Nanocatalysts play an essential role in the manufacture of industrial chemicals.

(i) Describe the high pressure carbon monoxide (HIPCO) method for the production of carbon nanotubes.

(ii) Outline one benefit of using nanocatalysts compared to traditional catalysts in industry.

pores/cavities/channels/holes/cage-like structures

«only» reactants with appropriate/specific size/geometry fit inside/go through/are activated/can react

Accept “molecules/ions” for reactants.

i

iron«0»«penta»carbonyl/Fe(CO)₅ catalyst decomposes
OR
Fe(CO)₅ (g) → Fe(s) + 5CO(g)
OR
metal nanocatalyst/clusters/particles formed «in situ»

Accept “cobalt-molybdenum/Co-Mo/CoMo” as a catalyst

2CO(g) → CO₂(g) +C(s) 

Accept “conversion of CO molecules into CNTs/ SWNTs” for M2.

ii

higher efficiency per unit mass/volume of the catalyst «due to higher surface to mass/volume ratio»
OR
greater selectivity «due to metal nanoclusters/surface topology/pore size»
OR
higher stability of the catalyst «due to lower tendency to aggregation»
OR
reduced cost of the catalyst/product/chemicals «as precious metals can be replaced with nanocatalysts made of inexpensive materials»

Accept “high conversion efficiency”.

Accept specific examples such as use of nanocatalysts in fuel cells/catalytic converters «leading to reduced use of Pt/Rh/Pd».

Accept “nanocatalysts often operate under milder conditions «so less energy consumption involved/so promotes principles of green chemistry»”.

Accept “lower energy consumption” OR “reduced carbon footprint” OR “reduced global warming”.

Accept “nanocatalysts often have long lifetimes «so more economical».

Accept “some nanocatalysts have enzyme mimicking activities”.