Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

Summary

A convenient method for the synthesis of 2 nm supported bimetallic nanoparticle Pt-Cu catalysts for propane dehydrogenation is reported here. In situ synchrotron X-ray techniques allow for the determination of the catalyst structure, which is typically unobtainable using laboratory instruments.

Abstract

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are demonstrated here. The catalyst forms a substitutional solid solution structure, with a small and uniform particle size around 2 nm. This is realized by careful control over the impregnation, calcination, and reduction steps during catalyst preparation and is identified by advanced in situ synchrotron techniques. The catalyst propane dehydrogenation performance continuously improves with increasing Cu:Pt atomic ratio.

Introduction

Propane dehydrogenation (PDH) is a key processing step in the production of propylene, taking advantage of shale gas, the fastest growing source of gas in the country¹. This reaction breaks two C-H bonds in a propane molecule to form one propylene and molecular hydrogen. Noble metal catalysts, including Pd nanoparticles, exhibit poor selectivity for PDH, breaking the C-C bond to produce methane with a high yield, with the concomitant production of coke, leading to catalyst deactivation. Recent reports showed that selective PDH catalysts could be obtained by the addition of promoters like Zn or In to Pd^2,

Protocol

1. Synthesis of Supported 2 nm Pt-Cu Bimetallic Nanoparticle Catalysts

1. Preparation of metal precursor solution
   1. Dissolve 0.125 g of copper nitrate trihydrate (Cu(NO₃)₂·3H₂O) in 1 mL of water to achieve a sky blue solution.
      Caution: Use protective gloves when handling chemicals.
   2. Add ammonia dropwise to the copper nitrate solution, forming dark blue precipitates of copper hydroxide.
      Caution: Use a fume hood for handling bases and volatile chemicals.
   3. Keep adding ammonia until the dark blue precipitates dissolve to form a dark blue solution and the pH &....

Results

The propylene selectivity versus time for Pt and Pt-Cu catalysts measured at an initial propane conversion of about 20% is presented in Figure 1A. Pt catalyst has an initial selectivity of 61%, which increases to about 82% with time on-stream as the catalyst deactivates for 1h. The Pt-0.7Cu catalyst shows a better initial propylene selectivity of 72%. For Pt-2.3Cu and Pt-7.3Cu catalysts, their initial selectivity reach 90% and 96%, respectively, and are maint.......

Discussion

The Pt-Cu catalysts prepared in this work contain uniform nanoparticles around 2 nm in size, similar to heterogeneous catalysts qualified for industrial application. All the Pt and Cu precursors form bimetallic structures, as opposed to separate monometallic particles. This bimetallic interaction and small particle size are realized by careful control over the synthesis procedures. The impregnation process makes use of the Strong Electrostatic Adsorption (SEA) between metal ions and the surface of certain oxide supports<.......

Materials

Name	Company	Catalog Number	Comments
1 inch quartz tube reactor	Quartz Scientific	Processed by glass blower
drying oven	Fisher Scientific
calcination Furnace	Thermo Sciencfic
clam-shell temperature programmed furnace	Applied Test System	Custom made
propane dehydorgenation performance evaluation system		Homemade
gas chromatography	Hewlett-Packard	Model 7890
TEM grid	TedPella	01824G
pellet press	International Crystal Lab	0012-8211
die set	International Crystal Lab	0012-189
Linkam Sample Stage	Linkam Scientific	Model TS1500
copper nitrate trihydrgate	Sigma Aldrich	61197
tetraammineplatinum nitrate	Sigma Aldrich	278726
ammonia	Sigma Aldrich	294993
silica	Sigma Aldrich	236802
isopropyl alcohol	Sigma Aldrich
balance	Denver Instrument Company	A-160
spatulas	VWR
ceramic and glass evaporating dishes, beakers	VWR
heating plate
kimwipe papers
mortar and pestle
quartz wool
Swagelok tube fittings